United States
Environmental Protection
Agency
Environmental Research
Laboratory
Athens GA 30605
EPA 600 3 82-023
July 1982
Research and Development
Exposure Analysis
Modeling System (EXAMS)
User Manual and System
Documentation
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EPA-600/3-82-023
EXPOSURE ANALYSIS MODELING SYSTEM (EXAMS):
User Manual and System Documentation
by
Lawrence A, Burns
David M. Cline
Ray R. Lassiter
Environmental Research Laboratory
U.S, Environmental Protection Agency
Atnens, Georgia 30613
ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
ATHENS, GEORGIA 30613
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DISCLAIMER
This report has been reviewed by the Environmental Research
Laboratory, U.S. Environmental Protection Agency, Athens,
Georgia, and approved for publication. Mention of trade names or
commercial products does not constitute endorsement or
recommendation for use.
ii
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FOREWORD
Environmental protection efforts are increasingly directed
toward preventing adverse health and ecological effects
associated with specific compounds of natural or human origin.
As part of this Laboratory's research on the occurrence,
movement, transformation, impact, and control of environmental
contaminants, the Environmental systems Branch studies complexes
of environmental processes that control the transport,
transformation, degradation, fate, and impact of pollutants or
other materials in soil and water and develops models for
assessing exposures to chemical contaminants.
Concern about environmental exposure to synthetic organic
compounds has increased the need for techniques to predict the
behavior of chemicals entering the environment as a result of the
manufacture, use, and disposal of commercial products. The
Exposure Analysis Modeling System (EXAMS), which has been under
development at this Laboratory for more than 3 years, provides a
convenient tool to aid in judging the environmental consequences
should a specific chemical contaminant enter a natural aquatic
system. Because EXAHS requires no chemical monitoring data, it
can be used for new chemicals not yet introduced into commerce as
well as for those whose record of use is known. EXAMS and other
exposure assessment models should contribute significantly to
efforts to anticipate potential problems associated with
environmental pollutants.
David w. Duttweiler
Director
Environmental Research Laboratory
Athens, Georgia
ill
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ABSTRACT
The Exposure Analysis Modeling System (EXAMS) was designed
for rapid evaluation of the behavior of synthetic organic
chemicals in aquatic ecosystems. From the chemistry of a
compound, and the relevant transport and physical/chemical
characteristics of the ecosystem, EXAMS computes:
1) Exposure: the ultimate (steady-state) expected environmental
concentrations (£ECs) resulting from a specified pattern of
(long term, time-invariant) chemical loadings,
2) Fate: the distribution of the chemical in the system and the
fraction of the loadings consumed by each transport and
transformation process, and
3) Persistence: the time required for effective purification of
the system (via export/transformation processes) once the
chemical loadings terminate.
EXAMS is an interactive program; it allows a user to specify and
store the properties of chemicals and ecosystems, modify the
characteristics of either via simple English-llJce commands, and
conduct efficient, rapid evaluations and sensitivity analyses of
the probable aguatic fate of synthetic organic chemicals,
EXAMS combines loadings, transport, and transformations into
a set of differential equations by using the law of conservation
of mass as an accounting principle. This law accounts for all
the chemical mass entering and leaving a system as the algebraic
sum of (1) external loadings, (2) transport processes that export
the compound fron the system, and (3) transformation processes
that convert the parent compound to daughter products. EXAMS'
fundamental equations describe the rate of change of chemical
concentrations as a balance between increases originating from
external and internally recycled loadings, and decreases
resulting from transport and transformations. The set of unit
process models that compute the dynamic behavior of a compound is
the central core of EXAMS. These are all "system-independent"
models, that is, each formulation includes a direct statement of
the interactions between the chemistry of a compound and the
environmental forces that shape its behavior in aauatlc systems.
EXAMS' environmental data are contained in a file composed
of concise descriptions of the aguatic systems of interest to a
user. Each water body is represented via a set of N compartments
or distinct zones in the system. EXAMS has been designed to
accept standard water-quality and limnological parameters. EXAMS
also includes a descriptor language for specification of system
geometry and connectedness. The code has been written in a
general (Ni-comparttnent) form. The software is available in 10-,
50-, or 100-compartment versions. The code will support larger
versions, up to a limit of 999 environmental compartments*
This report covers a period from June 1, 1978 to January 30,
1981 and woric was completed as of January 30, 1981.
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CONTENTS
Foreword Hi
Abstract • lv
Acknowledgement ........ x
1. introduction 1
1,1 Background 1
1.2 Exposure Analysis in Aquatic systems 1
1.2.1 Exposure 2
1.2.2 Persistence ......... 2
1.2.3 Fate 2
1.3 The EXAMS Program 3
1.4 Sensitivity Analysis and Error Evaluation ...... 5
1.5 EXAMS Process Models ......... 6
1.5.1 lonization and Sorption , 7
1,5.2 Transformation Processes . 8
1,5.3 Transport Processes 9
1.5.4 Chemical Loadings 9
1,6 Ecosystems Analysis and Mathematical -Systems Models . 10
1.6,1 EXAMS Design strategy ..... 10
1,6.2 Temporal and Spatial Resolution ,,,12
1,6.3 Model Assumptions 14
2, Fundamental Theory ........... 16
2,1 Compartment Models and Conservation of Mass 16
2,2 Equilibrium Processes .......*..*.....17
2.2.1 lonization Reactions 19
2,2.2 Sediment Sorption 21
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2.2.3 Blosorption 25
2.2.4 Equilibrium Distrioution Coefticients 26
2.3 Kinetic Processes 33
2.3.1 Transport .......... 33
2,3.1.1 Hydrology and advection 36
2.3.1.2 Advected water flows ... .... 40
2.3.1.3 Advective sediment transport ... 45
2.3.1.4 Dispersive transport ..............49
2.3,1.5 Transport of synthetic organic chemicals .... 63
2.3.2 Volatilization 65
2.3.2.1 Chemical data entry 71
2.3,2,2 Exchange constants for water vaoor 71
2.3.2.3 Exchange constants for molecular oxygen .... 72
2.3,2,4 Example applications ..............74
2.3.2.4.1 Radon in small lakes in the Canadian Shield , 74
2.3.2,4,2 t,4-dicniorobenzene in Lake Zurich 77
2.3.3 Direct Photolysis , 82
2.3,3.1 Direct photolysis in aquatic systems ...... 83
2.3.3.2 Light attenuation in natural waters ...... 89
2.3.3.2.1 Distribution functions CD) in natural waters 89
2.3,3.2.2 Absorption coefficients (a) in natural waters 91
2.3.3.3 Reaction quantum yields (QUAMS) 92
2.3.3.4 Absorption spectra (ABSG) ...........95
2.3.3.5 Effects of sorption to suspended sedinents
and biota .98
2.3.3,5.1 Simulation analysis of sorption effects on
direct photolysis 100
2.3.3.6 iMear-surface solar oeam and sky irradiance
(input irtLAMG) 104
2,3,3.7 Input data and computational mechanics --
Summary .......,, .« 106
2.3.4 Specific Acid, Specific Base, and Neutral
Hydrolysis , 111
2.3.4.1 Temperature effects ....... 114
2.3.4.2 lonization effects , 117
2.3.4.3 Sorption effects 119
2.3.5 Oxidation 123
vi
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2.3.6 Microblal Transformations 1?6
2.4 Input Pollutant Loadings 134
2.5 Data Assembly and Solution of Equations 138
2.5.1 Exposure 138
2.5.2 Fate 142
2.5.3 Persistence . 143
3. User's Guide 149
3.1 Introduction and Sample Run 149
3.1.1 Introduction 149
3.1.2 Sample Run 151
3.1.3 Sample Data Entry Forms 162
3,2 Interactive System Commands and Keywords . 173
3.3 Tutorial interactive Sessions ........... 187
3.3.1 Basic Familiarity with EXAMS 188
3.3.2 Entering New Data; Analyzing Persistence .... 198
3.3.3 Sensitivity Analysis 207
3.3.4 Sample Application Study ............ 217
3.4 Preparing Batch Input Data ............. 231
3.4.1 Format Codes ............ 237
3.4.2 Creating or Changing the User Pun Information * . 240
3.4.3 Creating or Changing the Chemical Data 241
3.4.4 Crea-ting or Changing the Environmental Data . . . 247
4. Programmer's Supplement ......... 251
4.1 System Documentation ................ 251
4.1.1 System Overview ..... .... 251
4.1,2 Resource Requirements .............. 254
4.1,3 System Architecture ........ 254
4,1.4 Overlay Structure ......... . . 256
4,1.5 File Organization . 259
4.1,5.1 Environmental file 259
4.1.5.2 Chemical file ..... 260
4.1,5,3 Online assistance file ............ 263
4.1.5,4 Labeled COMMON variables file 263
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4.1.6 Organization of EXAMS' Labeled COMMONS 264
4.2 Implementation Notes ..... 271
4.2.1 POP 11/70, IAS, Batch Version 271
4.2.2 POP 11/70, IAS, Interactive Version ....... 271
4.2.3 IB" 370, QS/MVS, Batch Version 272
4.2.4 IBM TSC Interactive 10-Compartment Version . . . 273
4.3 Special Installations ..... 273
4.3.1 EXAMS at NCC-IBM 273
References ............ 275
Glossary for EXAMS' Computational Subroutines ...... 2B8
Glossary for Labeled Common UNITS 319
Glossary for Labeled Common INPAR 321
Appendices
A . Documentation of Computational Subroutines ...... 327
DATAIN 330
BLOCK DATA . 332
GHOST 334
PRCHEM 335
PRENV 337
DISTPB 339
FLOWS 342
fcATADV 344
SEDADV 345
DISPER 347
PRFLOw 349
CKLOAO ....... 351
FIRORD 353
PHOT01 '..... 356
PHOT02 ....... 357
VOLAT 359
STEADY . 361
AVEOUT 363
FLXOUT , 365
DRIVER 366
FCT 369
FDER 370
OUTP . 371
SUNUP 372
viii
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EXAMS was created in response to the needs of program
offices of the U.S. Environmental Protection Agency for exposure
evaluation tools, several persons in these program offices made
valuable suggestions and comments during development of the
program; we are especially grateful to ^ichael W. Slima* of the
Office of water Planning and Standards for his intelligent
interest and ability to articulate desirable properties of
computerized analytical tools.
The system-independent process models used in EXAMS are its
central core, ^e were critically dependent upon cooperation and
advice provided by specialists in the environmental chemistry of
transformation and sorption processes. we are particularly
grateful to fi.L. Baughnan, D.S. Brown, S.W. Karickhoff,
D.F. Paris, W.C, Steen, N.L. wolfe, and R.G, Zepp for fruitful
discussions and reviews of EXAMS.
EXAMS was originally released for testing in October of
1979. A number of users have detected "bugs" in the program and
advised us of their findings. Assuredly additional problems will
surface as EXAMS receives wider usage; we are always grateful
for any information that can be used to improve the proaram.
The discussion of EXAMS* batch input data (Section 3.4) was
prepared,by Felice 0. Burchfield.
we are grateful to Bruce Bartell, Steven Hodge, Honnie Moon,
and Caroline Phillips for their assistance in preparing the
illustrations and typescript of this report.
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SECTION 1
INTRODUCTION'
1.1 Background
Industrial production of agricultural chemicals, plastics,
and Pharmaceuticals has steadily increased over the past three
decades. More recently, growth of the chemical industry has been
accompanied by increasing concern over the effects of synthetic
chemicals on the environment. The suspicion has arisen that, in
some cases, the benefits gained by using a chemical may not
offset the cost of incidental damage to man's natural
life-support systems. The toxicity of a chemical does not of
itself indicate that the environmental risks associated with its
use are unacceptable, however. A rational evaluation of the risk
posed by the use and disposal of synthetic chemicals must begin
from a knowledge of the exposure, persistence, and fate of
chemicals in the environment.
The Exposure Analysis Modeling System (EXAMS), developed at
the Athens Environmental Research Laboratory, is an interactive
computer program intended to give decision-makers in industry and
government access to a responsive, general, and controllable tool
for readily deriving and evaluating the behavior of synthetic
chemicals in the environment. Initial work has focused on the
development of the interactive command language and user aids
that are the core of EXAMS, and on the genesis of the first EXAMS
mathematical model. This model was designed primarily for the
rapid screening and identification of synthetic organic chemicals
likely to adversely impact aguatic systems. This report is
intended to acguaint potential users with the underlying theory,
capabilities, and use of the system.
1.2 Exposure Analysis in Aquatic Systems
EXAMS was conceived as an aid to those who must execute
hazard evaluations solely from laboratory descriptions of the
chemistry of a newly synthesized toxic compound. EXAMS estimates
exposure, fate, and persistence following release of an organic
chemical into an aguatic ecosystem. Each of these terms was
given a formal operational definition during the initial design
of the system.
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1.2.1 Exposure
When a pollutant is released into an aauatic ecosystem, it
is entrained in the transport field of the system and begins to
spread to locations beyond the original point of release. During
the course of these movements, cheroical and biological processes
transform the parent compound into daughter products. In the
face of continuina emissions, the receiving system evolves toward
a "steady-state" condition. At steady state, the pollutant
concentrations are in a dynamic equilibrium in which the loadings
are balanced by the transport and transformation processes.
These residuals can be compared to the concentrations posing a
danger to living organisms. The comparison is one indication of
the risk entailed by the presence of a chemical in natural
systems or in drinking-water supplies. These "expected
environmental concentrations" (EF.Cs), or exposure levels, In
receiving water bodies are one component of a hazard evaluation,
1.2.2 Persistence
lexicological and ecological "effects" studies are of two
kinds: investigations of short-term "acute" exposures, as
opposed to longer-term "chronic" experiments. Acute studies are
often used to determine the concentration of a chemical resulting
in 50% mortality of a test population over a period of hours.
Chronic studies examine suo-lethal effects on populations exposed
to lower concentrations over extended periods. Thus, for
example, an EEC that is 10 times less than the acute level does
not affirm that aguatic ecosystems will not be affected, because
the probability of a "chronic" impact increases with exposure
duration. A computed EEC thus must be supplemented with an
estimate of "persistence" in the environment. (A compound immune
to all transformation processes is oy definition "persistent" in
a global sense, but even in this case transport processes will
eventually reduce the pollutant to negligible levels should the
input loadings cease.) The notion of "persistence" can be given
an explicit definition in the context of a particular
contaminated ecosystem: should the pollutant loadings cease,
what time span would be reguired for dissipation of most of the
residual contamination? (For example, given the half-life of a
chemical in a first-order system, the time reguired to reduce the
chemical concentration to any specified fraction of its Initial
value can be easily computed.) with this information in hand, the
appropriate duration and pollutant levels for chronic studies can
be more readily decided.
1.2.3 Fate
The toxicologist also needs to know which populations in the
system are "at risk." These can to some extent be deduced from
the distribution or "fate" of the compound, that is, by an
estimate of EECs in different sectors of the ecosystem. EXAMS
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reports a seoarate EEC for each compartment, and each local
population, used to define the system.
The concept of the "fate" of a chemical in an aquatic system
has an additional, equally significant meaning. Each transport
or transformation process accounts for only part of the total
behavior of the pollutant. The relative importance of each
process can be determined from the percentage of the total system
loadings consumed by the process. The relative importances of
the transformations indicate which process is dominant in the
system, and thus in greatest need of accuracy and precision in
its kinetic parameters. Overall dominance oy transport processes
•nay imply a contamination of downstream systems, loss of
significant amounts of the pollutant to the atmosphere, or
pollution of ground-water aguifers.
t.3 THE EXAMS Proaram
The need to predict chemical exposures from limited data has
stimulated a variety of recent advances in environmental
modeling. These advances fall into three general categories:
i. Process models giving a guantitative, often
theoretical, basis for predicting the rate of
transport and transformation processes as a
function of environmental variables.
2. Procedures for estimating the chemical parameters
reguired by process models. Examples include
linear free energy relationships, and correlations
summarizing large bodies of experimental chemical
data.
3. Systems models that combine unit process models
with descriptions of the environmental forces
determining the strength and speed of these
orocesses in real ecosystems.
The vocabulary used to describe environmental models
includes many terms, most of which reflect the underlying
intentions of the modelers. Models may be predictive,
stochastic, empirical, mechanistic, theoretical, deterministic,
explanatory, conceptual, causal, descriptive, etc. The EXAMS
program is a deterministic, predictive systems model, based on a
core of mechanistic process equations derived from fundamental
theoretical concepts. The EXAMS computer code also includes
descriptive empirical correlations that ease the user's burden of
parameter calculations, and an interactive command language that
facilitates the application of tne system to specific problems.
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EXAftS "predicts" In a somewhat limited sense of the term,
Many of the predictive water-quality models currently in use
include site-soecific parameters that can only be found via field
calibrations. After "validation" of the iiodel by comparison of
its calibrated outputs with additional field measurements, these
models are often used to explore the merits of alternative
management plans. EXAMS, however, deals with an entirely
different class of problem. Because newly synthesized chemicals
must be evaluated, little or no field data may exist.
Furthermore, EECs at any particular site are of little direct
interest. In this case, the goal, at least in principle, is to
predict EECs for a wide range of ecosystems under a variety of
geographic, morphometric, and ecological conditions, EXAMS
includes no direct calibration parameters, and its input
environmental data can be developed from a variety of sources.
For example, input data can be synthesized from an analysis o'f
the outputs of hydrodynamic models, from prior field
investigations conducted without reference to toxic chemicals, or
from the appropriate limnological literature. The EECs generated
by EXAMS are thus "evaluative" (Lassiter, Baughman, and Burns
1978) predictions designed to reflect typical or average
conditions, EXAMS' environmental data case can be used to
describe specific locales, or as a generalized description of the
properties of aquatic systems in broad geographic regions,
EXAMS relies on mechanistic, rather than empirical,
constructs for its core process equations. Mechanistic
(physically determinate) models are more robust predictors than
are purely empirical models, which cannot safely be extended
beyond the range of prior observations. EXAMS contains a few
empirical correlations among chemical parameters, but these are
not invoked unless the user approves. For example, the partition
coefficient of the compound on the sediment phases of the system,
as a function of the organic carbon content of its sediments, can
be estimated from the compound's octanol-water partition
coefficient. A direct load of the partition coefficient (KOCG,
see Glossary) overrides the empirical default estimate, however.
(Because EXAMS is an interactive program in which the user
has direct access to the input data base, much of this
documentation has been written using the computer variables
(e.g., KOcG above) as identifiers and as quantities in the
process equations. Although this approach poses some
difficulties for the casual reader, it allows the potential user
of the program, to see the connenctions between program variables
and the underlying process theory. The Glossary section of this
document includes an alphabetical listing and definitions of
EXAMS' input variables.)
EXAMS is a deterministic, rather than a stochastic, model in
the sense that a given set of inputs will always produce the same
output. Uncontrolled variation is present both in ecosystems and
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in chemical laboratories, and experimental results from either
milieu are often reported as mean values and tneir associated
variances. Probaoilistic modeling techniques (e.g. fonte-Carlo
simulations) can account, in principle, for this variation and
attach an error pound or confidence interval to each important
output variable. Monte-Carlo simulation is, however, very
time-consuming (i.e., expensive), and the statistical
distributions of chemical and environmental parameters are not
often known in the requisite detail. The objective of this kind
of modeling, in the case of hazard evaluations, would in any case
be to estimate the effect of parameter errors on the overall
conclusions to be drawn from the model. This goal can be met
less expensively and more efficiently by some form of sensitivity
analysis.
1.4 Sensitivity Analysis and Error Evaluation
EXAMS does not provide a formal sensitivity analysis among
its options: the number of sub-simulations needed to fully
account for interactions among chemical and environmental
variables Is prohibitively large (Benrens 1979). When, for
example, the second-order rate constant for alkaline hydrolysis
of a compound is described to EXAMS via an Arrhenius function,
the rate constant computed for each compartment in the ecosystem
depends on at least six parameters. These include the frequency
factor and activation energy of the reaction, the partition
coefficient of the compound (KOCG), the organic carbon content of
the sediment phase, the temperature, and the concentration of
hydroxide ion. The overall rate estimate is thus as dependent
upon the accuracy of the system definition as it is upon the
skill of the laboratory chemist; in this example, the rate could
vary six orders of magnitude as a function of differences among
ecosystems. In order to fully map the parameter interactions
affecting a process, all combinations of parameter changes would
have to be .simulated. L'ven this (simplified) example would
require 63 simulations ((2**n) - 1, where n is the number (6) of
parameters) merely to determine sensitivities of a single
component process in a single ecosystem compartment.
Sensitivity analysis remains an attractive technique for
answering a crucial question that arises during hazard
evaluation. This question can be simply stated: "Are the
chemical data accurate enough, and precise enough, to support an
analysis of the risk entailed by releases of the chemical into
the environment?" Like many simple questions, this question does
not have a simple, definitive answer. It can, however, be broken
down into a series of explicit, more tractable questions whose
answers sum to a reasonably complete evaluation of the
significance that should be attached to a reported error bound or
confidence interval on any input datum. Using the output tables
and command language utilities provided by EXAMS, these questions
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can be posed, and answered, in the following order.
1. which geographic areas, and which ecosystems,
develop the largest chemical residuals? EXAMS
allows a user to load the data for any environment
contained in his files, specify a loading, and run
a simulation, through a simple series of one-line
English commands.
2. Which process is dominant in the most sensitive
ecosystemCs)? The dominant process, i.e., the
process most resoonslble for the decomposition of
the compound in the system, is the process
requiring the greatest accuracy and precision in
its chemical parameters. EXAMS produces two
output tables that indicate the relative
importance of each process. The first is a
"kinetic profile" (or frequency scaling), which
qives a compartment-by-compartment listing with
all processes reduced to equivalent (/hr) terms.
The second is a tabulation of the overall
steady-state fate of the compound, giving a
listing of the percentage of the load consumed by
each of the transport and transformation processes
at steady state.
Given the dominant process, the input data affecting this
process can be varied over the reported error bounds, and a
simulation can be executed for each value of the parameters. The
effect of parameter errors on the EECs and persistence of the
compound can then be documented by compiling the results of these
simulations.
This sequence of operations is, in effect, a sensitivity
analysis, but the extent of the analysis is controlled and
directed by the user. In some cases, for example, one process
will always account for most of the decomposition of the
compound. When the data base for this dominant process is
inadequate, the obvious answer to the original question is that
the data do not yet support a risk: analysis. Conversely, if the
dominant process is well defined, and the error limits do not
substantially affect the estimates of exposure and persistence,
the data may be judged to be adequate for the exposure analysis
portion of a hazard evaluation.
1.5 EXArtS Process Models
In EXAMS, the loadings, transport, and transformations of a
compound are combined into differential equations by using the
mass conservation law as an accounting principle. This law
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accounts for all the compound entering and leaving a system as
tne algebraic sun ot (1) external loadings, (2) transport
processes exporting the compound out of the system, and (3)
transformation processes within the system that degrade the
compound to its daughter Products. The fundamental equations of
the model describe the rate of change in chemical concentrations
as a balance between increases due to loadings, and decreases due
to the transport and transformation processes removing the
chemical from the system.
The set of unit process .models used to compute the kinetics
of a compound is the central core of EXAMS. These unit models
are all "second-order" or "systerc-independenfmodels: each
process equation includes a direct statement of the interactions
between the chemistry of a compound and the environmental forces
that shape its behavior in aquatic systems. Most of the process
equations are based on standard theoretical constructs or
accepted empirical relationships. For example, light intensity
in the water column of the system is computed using the
Beer-Lambert law, and temperature corrections for rate constants
are computed using Arrhenius functions. Detailed explanations of
the process models incorporated in EXAMS, and of the mechanics of
the computations, are presented In section 2,
1,5.1 lonization and sorption
lonization of organic acids and bases, and sorption of the
compound with sediments and biota, are treated as thermodynamic
properties or (local) equilibria that constrain the operation of
the kinetic processes. For example, an organic base in the water
column may occur in a number of molecular species (as dissolved
ions, sorbed with sediments, etc.), but only the uncharged,
dissolved species can be volatilized across the air-water
interface. EXAMS allows for the simultaneous treatment of up to
15 molecular species of a chemical. These include the parent
uncharged molecule, and singly- or doubly-charged cations and
anlons, each of which can occur in a dissolved, sediment-sorbed,
or biosorbed form. The program computes the fraction of the
total concentration of compound that is present in each of the 15
molecular structures (tne "distribution coefficients," ALPHA).
These values enter the kinetic equations as multipliers on the
rate constants. In this way, the program accounts for
differences in reactivity that depend on the molecular form of
the chemical. For example, the lability of a particular molecule
to hydrolytic decomposition may depend on whether it is dissolved
or is sorbed with the sediment phase of the system. EXAMS makes
no intrinsic assumptions about the relative transformation
reactivities of the 15 molecular species. These assumptions are
under direct user control through the way the user structures the
input data describing the chemistry of the compound.
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1,5.2 Transformation Processes
EXAMS computes the kinetics of transformations attributable
to direct photolysis, hydrolysis, biolysis, and oxidation
reactions. The incut chemical data for hydrolytic, biolytic, and
oxidative reactions can t>e entered either as single-valued
second-order rate constants, or as a pair of values definina the
rate constant as a function of environmental temperatures. For
example, the input data for alkaline hydrolysis of the compound
consists of two computer variables: KBHG, and EBHG. When EBHG
is zero, the program interprets KBHG as the second-order rate
constant. when EBHG is non-zero, &6HG is interpreted as the
activation energy of tne reaction, and KBHG is re-interpreted as
the pre-exponential (frequency) factor in an Arrhenius equation
giving the second-order rate constant as a function of the
environmental temperature (TCELG) in each system compartment,
(KBHG and EBHG are botn actually matrices with 15 elements; each
element of the matrix corresponds to one of the 15 possible
molecular species of the compound.)
EXAMS includes two algorithms for computing the rate of
photolytic transformation of a chemical. These algorithms were
structured to accommodate the two more common kinds of laboratory
data and chemical parameters available to describe photolysis
reactions. The simpler of the algorithms (suoroutine PHOTni)
requires only an average first-order rate constant (KDPG)
applicable to near-surface waters under cloudless conditions at a
specified reference latitude (RFLATG). In order to give the user
control of reactivity assumptions, KDPG is coupled to
user-supplied (normally unit-valued) reaction quantum yields
(QUANTG) for each molecular species of the compound. The more
complex algorithm (subroutine PHOT02) computes photolysis rates
directly from the absorption spectra (molar extinction
coefficients, A8SG) of the compound and its ions and measured
values of the reaction quantum yields.
The total rate of hydrolytic transformations is computed by
EXAMS as the sum of three contributing processes. Each of these
processes can be entered as simple rate constants or as Arrhenius
functions of temperature. The rate of specific-acid catalyzed
reactions is computed from the pH (PHG) for each sector of the
ecosystem, and specific-base catalysis is computed from the
environmental pOH (POHG). The rate data for neutral hydrolysis
of the compound are entered as a set of pseudo-first-order rate
coefficients for reaction of the 15 molecular species with the
_water molecule.
EXAMS allows the user to compute biotransformation of the
compound in the water column, and in the bottom sediments, of the
system as entirely separate functions. Both models are
second-order equations that relate the rate of biotransformation
to the size of the oacterial population actively degrading the
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compound. The second-order rate constants (
column, KBACSG for bentnic sediments) can be
single-valued constants or as functions of
non-zero value Is entered for the 0-10 of
(parameters QTBAWG and QTBASG, respectively),
as the rate constant at 20 degrees C, and the
each sector of the ecosystem is adjus
temperature
KBACwG for the water
entered either as
temperature, fohen a
a oiotransf oriration
KBAC is interpreted
biolysis rate in
ted for the local
Oxidation reactions are computed from the chemical input
data and the total environmental concentrations of reactive
oxidizing species (allcylperoxy and alkoxyl radicals, etc.)
specified by the user. The chemical data can again be entered
either as simple second-order rate constants or as Arrhenius
functions.
1.5,3 Transport Processes
Internal transport
via advective
sediment-sorbed,
losses at the
vectors (JFRADG,
both advective
water through the
and export of a chemical occur in EXAMS
and dispersive movement of dissolved,
and biosorbed materials and by volatilization
air-water interface. EXAMS provides a set of
etc.) that specify the location and strength of
and dispersive transport pathways. Advection of
system is then computed from the water balance,
using hydroloqic data (rainfall, evaporation rates, streamflows,
groundwater seepages, etc.) supplied to EXAMS as part of the
definition of each environment. Dispersive interchanges within
the system, and across system boundaries, are computed from the
characteristic length (CHARLG), cross-sectional area (XSTUFG),
and dispersion coefficient (DSPG) specified for each active
exchange pathway. EXAMS can compute transport of a toxicant via
whole-sediment bedloads, suspended sediment wash-loads, exchanges
with fixed-volume sediment beds, ground-water infiltration,
transport through the thermocline of a lake, losses in effluent
streams, etc. Volatilization losses are computed using a
two-resistance model. This computation treats the total
resistance to transoort across the air-water interface as the sum
of resistances in the liguid and vapor phases immediately
adjacent to the interface.
1,5.4 Chemical Loadings
External loadings of
point sources (STRLDG),
or aerial drift (DRFLDG),
ground-water seepage (IFLLDG) entering the system,
load can be entered for any system compartment, but
will not implement a loading that is inconsistent with the system
definition. For example, the program will automatically cancel a
a toxicant can enter the ecosystem via
non-point sources (NPSLDG), dry fallout
atmospheric wash-out (PCPLDG), and via
Any type of
the program
-------
PCPLD entered for the hypolimnion or benthic sediments of a lake
ecosystem, dhen this type of corrective action is executed* the
change is reported to the user via an error message.
1.6 ecosystems Analysis and Mathematical Systems Models
The EXAMS program was constructed from a systems analysis
perspective. Systems analysis begins by defining a system's
goals, inputs, environment, resources, and the nature of the
system's components and their interconnections. The system goals
describe the outputs produced by the system as a result of
operating on its input stream. The system environment comprises
those factors affecting system outputs over which the system has
little or no control. These factors are often called "forcing
functions" or "external driving variables." Examples for an
aquatic ecosystem include runoff and sediment erosion from its
watershed, insolation, and rainfall. System resources are
defined as those factors affecting performance over which the
system exercises some control. The resources of an aquatic
ecosystem include, for example, the ph throughout the system,
light intensity in the water column, and dissolved oxygen
concentrations. The levels of these internal driving variables
are determined, at least in part, by the state of the system
itself. In other words, these factors are not necessarily
single-valued functions of the system environment, Fach of the
components or "state variables" of a system can be described in
terms of Its .local input/output behaviors and its causal
connections with other elements of the system. The systems
approach lends itself to the formulation of mathematical systems
models, which are simply tools for encoding knowledge of
transport and transformation processes and deriving the
implications of this knowledge in a logical and repeatable way,
A systems model, when built around relevant state variables
(measurable properties of system components) and causal process
models, provides a method for extrapolating future states of
systems from knowledge gained In the past. In order for such a
model to be generally useful, however, most of its parameters
must possess an intrinsic interest transcending their role in any
particular computer program. For this reason, EXAMS was designed
to use chemical descriptors (Arrhenius functions, pKa, vapor
pressure, etc.) and water quality variables (pH, chlorophyll,
biomass, etc.) that have been independently measured for many
chemicals and ecosystems.
1,6,1 EXAMS Design strategy
The conceptual view adopted for EXAMS begins by defining
aquatic ecosystems as a series of distinct subsystems,
interconnected by physical transport processes that move
10
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synthetic chemicals into, through, and out of the system. These
subsystems include the epilimnion and hypolinnion of lakes,
littoral zones, benthic sediments, etc. the basic architecture
of a computer model also depends, however, on its intended uses.
EXAMS was designed for use by toxicologists and decision-makers
who must evaluate the risk cosed by use of a new chemical, based
on a forecast from the model. The EXA^s program is itself part
of a "hazard evaluation system," and the structure of the program
was necessarily strongly influenced by the niche perceived for it
in this system.
Many intermediate technical issues arise during the
development of a systems model. Usually these issues can be
resolved in several ways; the modeling "style" or design
strategy used to build the model guides the choices taken among
the available alternatives. The strategy used to formulate EXAMS
begins from a primary focus on the. needs of the intended user
and, other things being equal, resolves most technical issues in
favor of the more efficient computation. For example: all
transport and transformation processes are driven by internal
resource factors (pH, temperature, water movements, sediment
deposition and scour, etc.) in the system, and each deserves
separate treatment in the model as an individual state variable
or function of several state variables. The strategy of model
development used tor EXAMS suggests, however, that the only state
variable of any transcendent interest to the user is the
concentration of the chemical itself in the system compartments.
EXAMS thus treats all environmental state variables as
coefficients describing the state of the ecosystem, and only
computes the implications of that state, as residual
concentrations of chemicals in the system.
Although this approach vastly simplifies the mathematical
model, with corresponding gains in efficiency and speed, the
system definition is now somewhat improper. System resources
(factors affecting performance that are subject to feedback
control) have been redefined as part of the system environment.
In fact, the "system" represented by the model is no longer an
aquatic ecosystem, but merely a chemical pollutant. Possible
failure modes of the model are immediately apparent. For
example, introduction of a chemical subject to alkaline
hydrolysis and toxic to plant life into a productive lake would
retard primary productivity. The decrease in primary
productivity would lead to a decrease in the pH of the system
and, conseguently, a decrease in the rate of hydrolysis and an
increase in the residual concentration of the toxicant. This
sequence of events would repeat itself Indefinitely, and
constitutes a positive feedback loop that could in reality badly
damage an ecosystem. Given the chemical buffering and functional
redundancy present in most real ecosystems, this example is
inherently Improbable, or at least self-limiting. More
importantly, given the initial EEC, the environmental
11
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toxicologist could anticipate the potential hazard.
There is a more telling advantage, moreover, to the use of
environmental descriptors in preference to dynamic environmental
state variables. Predictive ecosystem models that include all
the factors of potential importance to the Kinetics of toxic
Pollutants are only now being developed, and will require
validation before any extensive use. Furthermore, although
extremely fine-resolution (temporal and spatial) models are often
considered an ultimate ideal, their utility as components of a
fate model for synthetic chemicals remains suspect. Ecosystems
are driven by meteorological events, and are themselves subject
to internal stochastic processes. Detailed weather forecasts are
limited to about nine days, because at the end of this period all
possible states of the system are equally probable. Detailed
ecosystem forecasts are subject to similar constraints (Platt e't
al. 1977), For these reasons, F.XAMS was designed primarily to
forecast the prevailing climate of chemical exposures,, rather
than to give detailed local forecasts of E'ECs in specific
locations.
1.6.2 Temporal and Spatial Resolution
When a synthetic organic chemical is released into an
aquatic ecosystem, the entire array of transport and
transformation processes begins at once to act on the chemical.
The most efficient way to accommodate this parallel action of the
processes is to combine them into a mathematical description of
their total effect on the rate of change of chemical
concentration in the system. Systems that include transport
processes lead to partial differential equations, which usually
must be solved by numerical integration. The numerical
techniques in one way or another break up the system, which is
continuously varying in space and time, into a set of discrete
elements. spatial discrete elements are often referred to as
"grid points" or "nodes", or, as in EXAMS, as "compartments,"
Continuous time is often represented by fixing the system driving
functions for a short interval, integrating over the interval,
and then "updating" the forcing functions before evaluating the
next time-step. At any given moment, the behavior of the
chemical is a complicated function of both present and past
inputs of the compound and states of the system,
EXAMS is .oriented toward efficient screening of a multitude
of newly invented chemicals. Ideally, a full evaluation of the
possible risks posed by manufacture and use of a new chemical
would begin from a detailed time-series describing the expected
releases of the compound into aquatic systems over the entire
projected history of its manufacture. Given an equivalently
detailed time-series for environmental variables, machine
integration would yield a detailed picture of EECs in the
12
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receiving water body over the entire period of concern. The
great cost of this approach, however, militates against its use
as a screening tool. Fine resolution evaluation of synthetic
chemicals can probably be used only for compounds that are
singularly deleterious and of exceptional economic significance.
The simplest situation is that in which the chemical
loadings to systems are Known only as single estimates pertaining
over indefinite periods. This situation is the more likely for
the vast majority of new chemicals, and was chosen for
development of EXAMS. It has an additional advantage. The
ultimate fate and exposure of chemicals often encompasses many
decades, making detailed time traces of EFCs feasible only for
short-term evaluations. In EXAMS, the environment is represented
via long-term average values of the forcing functions that
control chemical's behavior. By combining the chemistry of the
compound with average properties of the ecosystem, EXAMS reduces
the screening problem to manageable proportions. These
simplified "first-order" eguations are solved algebraically to
give the ultimate (i.e., steady-state) EECs that will eventually
result from the input loadings.
Transport of a chemical from a loading point into the bulk
of the system takes place by advected flows and by turbulent
dispersion. The simultaneous transformations presently result in
a continuously varying distribution of the compound over the
physical space of the system. This continuous distribution of
the compound can be described via partial differential eguations.
In solving the eguations, the physical space of the system must
be broken down into discrete elements, EXAMS is a compartmental
or "box" model. The physical space of the system is broken down
into a series of physically homogeneous elements (compartments)
connected by advective and dispersive fluxes. Each compartment
is a particular volume element of the system, containing water,
sediments, biota, dissolved and sorbed chemicals, etc. Loadings
and exports are represented as mass fluxes across the boundaries
of the volume elements; reactive properties are treated as point
processes within each compartment.
In characterizing aguatic systems for use with EXAMS,
particular attention must be given the grid-size of the spatial
net used to represent the system. In effect, the compartments
must not be so large that internal gradients have a major effect
on the estimated transformation rate of the compound. In other
words, the compartments are assumed to be "well-mixed," that is,
the reaction processes are not slowed by delays in transporting
the compound from less reactive to more reactive zones in the
volume element. Physical boundaries that can be used to delimit
system compartments include the air-water interface, the
thermocline, the benthic interface,, and perhaps the depth of
bioturbatlon of sediments. Some processes, however, are driven
by environmental factors that occur as gradients in the system,
13
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or are most active at Interfaces, For exarr-ple, irradiance is
distributed exponentially throughout the water column, and
volatilization occurs only at the air-water interface. The rate
of these transformations may be overestimated in, for example,
quiescent lakes in which the rate of supply of chemical to a
reactive zone via vertical turbulence controls the overall rate
of transformation, unless a relatively fine-scale segmentation is
used to describe the system. Because compartment models of
strongly advected water masses (rivers) introduce some numerical
dispersion into the caluiations, a relatively fine-scale
segmentation Is often advisable for highly resolved evaluations
of fluvial systems. In many cases the error induced by highly
reactive compounds will be of little moment to the probable fate
of the chemical in that system, however. For example, it makes
little difference whether the photolytic half-life of a chemical
is 4 or 40 minutes; in either case it will not long survive
exposure to sunlight.
1.6.3 Model Assumptions
EXAMS, lifce all models, is based upon a number of
assumptions. The program has been designed to evaluate
long-term, steady loadings of chemicals that result in
trace-level EECs in aquatic systems. EXAMS generates a
steady-state, average flow field for the ecosystem. The program
cannot evaluate the transient concentrated EECs that arise, for
example, from spills of toxic chemicals. This limitation arises
from two factors: First, a steady flow field is not always
appropriate for evaluating the spread and decay of a major pulse
(spill) input. Second, the assumption of trace-level EECs, which
can be violated by spills, has been used to design the process
equations used in EXAMS. The following assumptions were used to
build the model.
(1) A first-order evaluation can be executed
Independently of the chemical's actual effects on
the system. In other words, the chemical does not
Itself radically change the environmental
variables that drive its transformations. Thus,
for example, an organic acid or base is assumed
not to change the pH of the system, the compound
Is assumed not to Itself absorb a significant
fraction of the light entering the system, and
oacterial populations do not grow (or decline)
simply due to the presence of the chemical,
(2) EXAMS uses linear sorption isotherms, and
second-order (rather than Michaelis-Menten-Monod)
expressions for biolysis. This approach Is known
to be valid for low concentrations of pollutants;
Its validity at high concentrations is less
14
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certain. EXAMS controls its computational range
to ensure that this assumption is not arossly
violated. The program *iil not report FECs for
loadings that result in aqueous-phase chemical
residuals greater than 50% of the aqueous
solubility of the compound, or l.t>5 to in the
dissolved neutral (uncharged) torn of the
compound. This restraint incidentally allows the
model to ignore precipitation ot the compound from
solution, and precludes inputs ot solid particles
of the chemical.
(3) Sorption is treated as a thermodynamic or
constitutive property of each compartment in the
system, that is, sorption/desorption kinetics are
assumed to be rapid compared to other processes.
The adequacy of this assumption is partially
controlled by properties of the compound and
system oeina evaluated. Fxtensively sorbed
chemicals tend to be sorbed and desorbed more
slowly tnan weakly sorbed compounds? desorption
half-lives may approach 40 days for the most
extensively bound chemicals, Experience with the
program has indicated, however, that strongly
sorbed chemicals tend to oe captured by benthic
sediments, where their release to the water column
is controlled by benth.ic exchange processes. This
phenomenon overwhelms any accentuation of the
speed of processes in the water column that may be
caused by the assumption of local equilibrium.
15
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SECTION 2
THFOHY
Many excellent books, revie* articles, and journal reports
have been written on the subject of the fate and transport of
chemicals in the environment. This report is not intended as an
exhaustive summary of the ideas and factual information available
from the literature. EXAMS is a distillation of that literature,
encoded in a computer program. This section of the report is a
summary of the fundamental ideas that were used to construct the
EXAMS program. The references cited represent only the key
findings or papers that directly influenced the FXAMS code.
Additional detail and background Information can be found in the
works listed in the bibliography for this report.
2,1 Compartment Models and Conservation of v'ass
EXAMS' environmental data are contained in a file (the
"canonical environments file") that includes a series ot concise
descriptions of the aquatic systems of interest to a user. (The
term "canonical" simply means that the data in the file includes
only those quantities bearing directly on the fate and transport
of synthetic organic chemicals.) Each water-body is represented
via a set of N compartments or distinct zones in the system. The
program is based on a series of mass balances, which give rise to
a single differential equation for each compartment. Working
from the transport and transformation process equations, EXAMS
compiles an equation for the net rate of change of chemical
concentration in each compartment. The resulting system of N
differential equations describes a mass balance for the entire
ecosystem. These equations have the general form of Equation
2.1:
Eq. 2.1
where:
V (dlCJ/dt) = Le
Li - (V)(K)[C)
V is the volume
[CJ is the total
Le is the total
Li is the total
resulting
compartments,
in the compartment (liters),
concentration as ivq/liter of V,
loading on the compartment (rag/hr),
(m g / h r )
of water
chemical
external
internal loading on the compartment
from contaminated flows among
and
system
16
-------
K is an overall pseudo-first-order C/hr) loss constant that
expresses the combined effect of transport and trans-
formation processes that decrease chemical concentration.
The "canonical environments file" currently supplied with
the £XAMS computer program is intended solely as a series of test
values to establish that the program is operating correctly.
Althouqh the data supplied in this file are within the range of
observed values, this file is not intended for production runs of
the program. EXAMS has been designed to accept standard
water-quality parameters and system characteristics that are
commonly measured by limnologists throughout the world, EXAMS
also includes a descriptor language (parameters JFRADG, JTURBG,
etc.) that simplifies the specification of system geometry and
connectedness. The procedure for defining an FXAMS environment
is illustrated in section 3. The EXAMS code has been written in
a general (N-compartment) form; the program can be modified and
recompiled to handle up to 999 compartments. The program is
available in 10-, 50-, and 100-compartment versions.
The Chemical data base supplied with the program includes 11
compounds investigated by Smith and coworfcers (1978). As with
EXAMS' nominal environmental data base, these data should not be
regarded as immutably fixed. In many instances the data of Smith
et al. (1978) were augmented in order to illustrate EXAMS' data
entry capabilities, and the assumptions used to fill gaps in the
chemical data base are open to revision as additional
experimental data become available.
2.2 Equilibrium Processes
The Kinetic properties of organic chemicals are often
strongly influenced by the molecular state of the compound.
Consider, for example, a compound that can both ionize, and sorb
to suspended sediments. In this case, the compound will be
present in the water column in ionized, unionized, and sorbed
states. In inland waters, where aerosol formation can be
neglected, only the unionized, unsorbed molecule can be
volatilized across the air-water Interface. An accurate
evaluation of the tendency of the compound to volatilize thus
cannot be obtained until ionization and sorptlon are incorporated
in the estimation method. Ionization and sorption also affect
the reactivity of chemicals to transformation processes, but the
magnitude of the changes cannot be as readily predicted.
Laboratory determinations of kinetic rate constants are
often limited to homogeneous phase (clean water) investigations.
Modeling the behavior of a compound in real systems requires some
knowledge, or some assumptions, about the effects of sorption and
ionization on a chemical's behavior in the environment. EXAMS
does not contain "hard-wired" assumptions that sorption either
17
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"protects" the compound, enhances its reactivity, or has no
effect. Instead, the input chemical data include separate rate
constants for each molecular form of the compound. This data
array allots a user to include unique rate constants for ions and
sorbed molecules when these are known. *hen heterogeneous phase
(or PH dependent) chemical data are not available, the necessary
assumptions are left to the user's discretion.
lonization and sorption of synthetic chemicals are treated
as thermodynamic or constitutive properties of each ecosystem
compartment in EXft^S. EXAMS treats these processes as local
(within-compartment) equilibria, rather than calculating a qlobal
(system-wide) partitioning of the compound atrong its possible
molecular snecies. The alternative of global partitioning or
full system-wide equilibria has also been used in the context of
evaluative models (e.q., Mackay 1979). As noted by their
authors, this assumption neqlects effects of intra-systerr
transport and environmental heterogeneity.
lonization equilibria are usually achieved within a very
short tine, compared to the time-scale of transport and
transformation processes, so a (local) equilibrium assumption is
usually justified in natural systems. Desorption of neutral
molecules bound to sediments, however, is relatively slow for
compounds that are extensively bound (large partition
coefficients). EXAMS' evaluations do not explicitly include the
effects of sorption/desorption kinetics on transport or
transformation processes. The program does, however, compute
some major kinetic effects of slo* desorptlons, as an implicit
function of interactions between benthic sediments and the
overlying water column.
Extensively sorbed compounds are usually predominantly
captured by the bottom sediments (benthic compartments) in an
aquatic systen. Release of the compound to the water column is
then limited by the turnover rate of the bottom sediments
themselves. The turnover times of benthic sediments are usually
longer than the desorption half-lives of organic chemicals.
Consequently, the major kinetic limitations imposed by residence
in bottom sediments qenerally exceed those attributable to
desorption kinetics as such.
EXAMS allows for the existence of four ionized species, in
addition to the parent unionized molecule. Each of these can
partition onto the sediment phase, and the biota» in an ecosystem
compartment. The program computes the fraction of the total
chemical concentration present in each molecular structure.
These distribution coefficients (ALPHA) are used as multipliers
on the user-specified transformation rate coefficients for each
decomposition process.
18
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2.2.1 lonization Reactions
According to the Hronsted-Lowry concept of ionization
reactions, acids and bases react *Jth solvent (water) to form a
conjugate acid-base pair (Stumm and Morgan 1970). The EXAMS
program regards any synthetic organic as potentially capable ol
acting as an ampholyte, and forcing both singly and doubly
charged cations and anions in an aqueous Tedium. The unionized
molecule is taKen as the parent compound, and is denoted in the
program documentation as "SH2." The potential acid-base
reactions are then:
(1) Basic reactions:
Eg. 2,2 (a) (SH2) + (H2U) <--> (SH3+) * (OH-)
Eq. 2.3 (b) (SH3+) + (H20) <--> (SH4++) + (OH-J
(2) Acidic reactions:
Eg. 2.4
Eq. 2.5
(a)
(b)
(SH2)
(SH-)
(H20) <--> (SH-) +- (H30+)
(H20)
(S=) t (H3D+)
This set of chemical reactions describes the simultaneous
existence of five chemical species of the compound. These
species are: (1) tne unionized parent molecule SH2, (2) a singly
charged cation SK3t, H) a doubly charged cation SH4t+, (4) a
singly charged anion SH-, and (5) a doubly charged anion S=,
(Again, because EXAf's is an interact!
user has direct access to the input
documentation has been written using the
identifiers and as quantities in the proce
this approach poses some difficulties for
allows the potential user of the program
between program variables and the underlyi
Glossary section of this document con
listing and definitions of EXAMS' input
cases, direct input data are named
("Global"), and variables internal to the
are named with a terminal "L" ("Local").
be specified by the user; "KPvSL" is its 1
ve program in which the
data base, much of this
computer variables as
ss equations. Although
the casual reader, it
to see the connenctions
ng process theory. The
tains an alphabetical
variables. In most
with a terminal "G"
EXAMS program itself
For example, "KPSG" can
nternal equivalent.)
Most compounds do not exhibit the full range of behaviors
given in Equations 2.2--2.S. EXAMS' chemical input data stream
carries, for each chemical, a vector (SPFLG) of 5 flags that
tells the program which of the ionization reactions are
appropriate for that compound. (A "flag" in this usage means a
signal used to control execution of the program.) Setting an
element of the SPFLG vector to "1" indicates that the
corresponding chemical species in fact exists; setting an
19
-------
element of SPFLG to "0" (zero) indicates the chemical species
does not exist. SPFLG(l) should usually oe set to indicate the
existence of the parent molecule. *nen, for example, the
remaining flags (SPFLG(2), (3), (4), and (S)) are all zero, EXAMS
treats the chemical as a neutral (unionizaole) organic compound.
Again, when SPFLGC2") is set ( = 1), and sm.G(3), (4), and (5) are
0, the comoound is taken to be an organic base forming only a
singly charaed cation (SH3+).
The equilibrium constants for the ionization reactions
provide a measure of the strength of the organic acid/base
relative to *ater. The basicity constants corresponding to
Equations 2.? and 2.3 are:
Eg. 2.2.1 KDl = [SH3 + HQH-} / [SH2HH20)
Eg. 2.3.1 *b2 = fSH4*tJ«JH-} / ISH3+]
The acidity constants corresponding to Equations 2.4 and 2.5 are:
Eq.'2.4.1 Kal = rSH-J(H+} / (SH2HH20}
Eq. 2.5.1 Ka? = tS=J(H+> / [SH-]
These ionization constants
Morgan 1970:8?), which tafce
activity, TUPAC convention),
concentration units. (Salt
are "nixed" constants (Sturr-m and
pH = -log{h+> ( Off) is hydrogen ion
and the compound is expressed in
effects on pK values, and changes in
pKw *ith temperature, are currently neglected in EXAMS.)
In dilute aqueous solutions (unit water activity, {H20}=1),
the water terms in the equilibrium constants can be neglected.
In benthic sediments, however, much of the compartment volume is
occupied by solids, and the decreased activity of water roust be
considered. In EXAMS, this problem is overcome by referring all
concentrations to the aqueous phase of the compartir-ent (note
dimensions of variables in Equation 2.1),
Basicity and acidity constants are entered to EXAMS as the
negative of their Briagsian logarithms, that is, as pK values.
The computer variables are PKBG(l) and PRRG(2) for the first and
second basicity constants (generating SH3+ and SH4f,
respectively) and PKAG(l) and PKAG(2) for the first and second
acidity constants (generating SH- and S=, respectively). The
equilibrium constants can be entered either as single
(temperature-independent) pK values or as functions of
temperature. Temperature dependencies of the equilibrium
constants are computed from an integrated form of the
Gibbs-Helmholtz equation (Castellan 1964:215-217). Each computer
input datum (PKBG, PKAG) has a corresponding enthalpy variable
20
-------
(EPKBG, EPKAG). when the enthalpy term (FPK) is zero, the PK
datum is ta
-------
a vector of partition coefficients (KPSG) *hose elements apply to
each of the corresoondina chemical species. That is, KPSG(l) is
tne partition coefficient for neutral orcianics or the unionized
molecule (SH2), KPSGC2) applies to the Sh3+ molecule, etc.
EXAMS uses linear isotherms for all sorption computations,
rather than the non-linear Freundlich or f.anamuir formulations.
(A linear isotherm is equivalent to a partition coefficient.)
Linear isotherms are usually an adequate descriptor of the
capture of neutral orqanics by sediments, at least up to 50% of
their rfater solubility or l.E-S M (Karickhoff 1980 (oral comm.)).
EXAMS restricts its operating range to ensure that this
assumption is not violated. These restrictions are imposed by
evaluating the external loadings to ensure that the inputs to the
system are not excessive, and by a pre-outout evaluation of the
computed P:F:CS in all compartments. Excessive loadings are
reduced to one-half their maximum permissible value in the inlet
carrier flow (see section 2.4).
The uotaKe of neutral organic chemicals by soils and aquatic
sediments apparently involves dissolution of the compound into
the organic matrix of the soil/sediment, rather than a pure
physical (surface) adsorption (see, for example, Chiou, Peters,
and Freed 1979). Sorption of this class of chemical probably
takes place by a nydroonobic mechanism, in *?hich the compound (or
more generally the SH2 molecule of acids and bases) is driven
from the *ater phase of the system hy a large fugacity. This
process is conceptually similar to the extraction and recovery of
an organic pollutant from *?ater using an organic solvent.
The partition coefficent (KPSG) for a particular compound
can be normalized to the organic content of soils (Chiou, Peters,
and Freed 1979) or, equivalently, to the organic carbon content
of aquatic sediments (Karickhoff, Brown, and Scott 1979). The
resulting parameter (KOCG) is a relatively stable,
system-independent measure of an instrinsic property of organic
compounds. KOCG can be used to compute a partition coefficient
(KPSL) for sediment phases of an aquatic system, as a function of
the organic carbon content (FROCG, organic carbon as fraction of
dry weight) of the sediment phase of each compartment.
KQCG is strongy correlated with the octanol-water partition
coefficient (KOi"G) (Karicichof f, Brown, and Scott 1979). For
whole sediments, as used in EXAMS, KOCG can be reliably estimated
as 41% of KCMG (Karicichoff, in orep.).
EXAMS computes the SH2 partition coetficent (KPSL(l)) for
each system compartment via an hierarchical evaluation of these
input data (KPSG(l), KOCG, KOWG). KOCG is the preferred datum,
and if it is non-zero, a local (compartment-specific) KPSL(l) is
computed from KOCG and the organic carbon content (FROCG) of the
sediment phase of each compartment, when KOCG is zero, but the
22
-------
entry Is non-zero, xpsL(l) is computed as 0.4l*KO*G*FPOCG.
The KPSG datum is used as a systeii-*ide partition coefficient
only when both KDCG and KU*G are zero entries. Thus when an
observed KPSG is preferred for some user application, both KOCG
and KO*/G should be omitted from the input data (that is, set to
zero) because, otherwise, the oreferred computations will
override tne user's intentions.
Organic ions can exchange with the normal soil ions, to an
extent probably governed by the ion exchange capacity of a
sediment. Tne particle-size distribution of the sediment,
however, apparently also governs the ability of the sediment to
take up organic ions (KaricKhoff and Bro*n 1978). The complexity
of this process has hindered tne development of robust,
system-independent analogs of KOCG for organic ions.
EXAMS includes a series of (admittedly sorrewhat speculative)
"system-independent" measures of ion sorption that can be invoked
at the user's option. These parameters relate the KPSL for the
organic ions to the ion exchange capacities of sediment phases ir,
each system compartment. me computer variables are:
HCECC1 )
KCEC(2)
KAEC(l)
KAEC(2)
for
for
for
for
sorbt
sorpt
sorpt
sorot
ion
ion
ion
ion
of
of
of
of
SH3
SH4
SH-
s=;
•»•;
+ + ;
*
r
KPSL
KPSL
KPSL
KPSL
(2)
(3)
(4)
(b)
computed
confuted
computed
computed
from
from
from
from
CFCG
CLCG
AECG
AECG
The units of KCFC and KAEC are ((mg/kg)/ (,mg/L)/(meq/l 00 q dry
weight); the cation (CECG) and anion (AECG) exchange capacities
of system sediments are entered as millieguivalents (meq) per 100
grams dry weight of the sediment, when a measured partition
coefficient is preferred for all sediments in the system, it
should be loaded via the appropriate element of the KPSG vector
and the corresponding element in KCEC or KAEC should be set to
zero.
EXAMS uses tne partition coefficient (KPS) for each chemical
species, nowever computed, to calculate tne equilibrium sediment
sorption of each species on each particulate sediment phase (P)
in the system. The chemical eguations and equilibrium
expressions are similar for each chemical species:
Eg. 2.7 (SH2) + (P)< XSH2P) KPS(l) = [SH2PJ/CSH2][P]
Eq. 2.8 (SH3+) + (P)< XSH3P + ) KPS(2) = [SH3P+]/[SH3+][P]
Eq. 2.9 (SH4++) + (P)< XSH4P + +) KPS(3) = [SH4P++]/[SH4++J[P]
Fq. 2.10 (SH-) t (PX---XSHP-) KpS(4) = (SHP-J / [SH-) [P]
Eg. 2.11 (S=) -f (P)< XSP=) KPS(5) = [SP = 1 / [S = ) [P]
23
-------
Sediment partition coefficients are usually reported as a
ratio of the concentration of soroed chemical (t>g compounc/g ory
weight of sediment) to the residual anueous phase concentration
(mq/liter), in "dimensionless" units ((Tig/kg)/ (mq/i.)). The
sorption equilibrium constants are equivalent to conventional
partition coefficients only so lonq as the concentration of
particulate -natter [PJ is expressed as a "sediment-water ratio"
«g dry weight/ liter of *ater), and the cnemical concentrations
(e.q., fSH2P] and [SH2J) are referred to the aqueous pnase of the
system ani expressed as (mq compound/liter of *ater). FXA^S
adheres to this convention for its internal computations. EXAvs'
output taoles, however, are convertea tc conventional reportirq
units. For example, concentrations of sedirent-sorbed chemicals
are reported to the user as mq/kg dry *eiaht of sediirent, hut are
carried internallv as (soroed mq)/(iiter of water).
The need tor strict adherence to this convention arises frorr
the very larae sedi~nent/*ater ratios of tenthic sediments,, mater
column compartments can oe assumed to have a *ater volume
essentially the sa^e as their environmental volume (VOLG). For
these compartments, KXAVS' internal variaole (Sf-DCOL, the
sediment/water ratio (kg/I)) is simply computed as l.t-6 times
the input datuir. (SDCHHG, suspended sediments in mq/L).
Because the solid phase occupies a significant fraction of
the total environmental volume of Ped sediments, SFDCOL is
computed quite differently for benthic (TVPBE "P") compartments.
For benthic compartments, trie input datum SDCHPG is the bulk
density of the sediment (g/cc environmental volume). The
sediment/water ratio is computed from the bulk density and *ater
content CP3Ti«AG, 100 * the fresh weight/dry weight ratio) of the
sedimentr and the total environmental volume (VOLS, cubic meters)
of the compartment. (The computation takes the density of water
as t g/cc.) The equations are:
fcq. 2.12 SEDCOl- = SFDMSL/* ATVOL, *nere
Eq. 2.12.1 TOTMAS = SDChRG*VOLG*l000.
£q. 2.12.2 SEDMSL - TOTMAS/(PCT*AG/100.), and
Eq. 2.12.3 ftATVQL ~ TOTMAS - SEDM5L
In these equations, TUT^AS is the total compartment mass (ka),
SEDMSL is the mass of sediment in the compartment (kg), and
wATVOL is the volume of *ater contained in the compartment
(liters).
The sediment/water ratio can also be computed directly from
the water content of the sediment (Equation 2.13).
Ed. 2.13 SEDCOL = 1/((Pd*AG/100) - 1)
24
-------
another natter altoqetner (see Section 2.3.6).) EXAVS
nevertheless accounts, to some extent, for tne physical transport
of biosorbed chemical. Tne oiomass in each ecosystem compartment
is segregated into a resident (fixed ir place), and a
transportable (olan (SH-) f (H30+)
Eq. 2.21 (SH-) * (H20) <---> (S=) + (H30+)
In order to evaluate the effects of ionization on transformation
and transport of the chemical, EXAMS requires three concentration
ratios (R):
26
-------
Eq. 2.22 (I) the fraction present as Sh2, or Ml) = lSH2J/[Stl
Eq, 2.23 (2) the fraction present as SH-, or R(2) = [SH-J/[St]
Eq. 2.24 (3) the fraction present as S=, or P(3) = lS=J/[StJ
The equilibrium constants for the chemical equations 2.20 and
2.21 are:
Fq. 2.25 Kal = [SH-]{Ht>/[SH21
Eq. 2.26 Ka2 = [S=]{H +>/[SH-J
As has already been mentioned, EXAMS computes {H + } as
10.**(-PHG). The equilibrium expressions, together with a
concentration condition, provide enough information for computing
the desired concentration ratios P (Stumm and Morgan 1970:102).
The concentration condition is simply a statement of the law of
conservation of mass:
Eq. 2.27 [StJ = CSH2J + [SH-J + [S=]
The concentration condition (Eq. 2.27) and the definition of the
first concentration ratio H(l) (Eq. 2.22) combine to give:
Eq. 2.28 R(l) = [SH21 / ( ISH2J + tSH-J + tS=) )
The equilibrium expressions can now be solved for [SH-J and tS=J
in terms of [SH2J. To wit, Fq. 2.25 can be rearranged to give:
Eq. 2.29 I SH-J = KaltSH2]/
and, from eq. 2.26,
Eq. 2.30 tS=] = Ka2[SH-]/{H+>
Substituting Eq. 2,29 into Eq. 2.30 yields:
Eq. 2.31 [S=l = (Kal)(Ka2)[SH2J/(Ht}{Ht>
Substituting Fq. 2.29 and Eq. 2.31 into Fa. 2.28, and cancelling
[SH2] from numerator and denominator, yields the desired result:
Eq. 2.32 R(l) = 1/(1 + Kal/{H^> 4 (Kal)(Ka2)/ )
The second distribution coefficient R(2) can be computed in
an analogous fashion. From the definition of R(2) in Eq 2.23,
and the concentration condition (Eq. 2.27),
Eq. 2.33 R(2) = [SH-]/[StJ = [SH-J / (tSH2) f tSH-] + IS=])
Solving Eq. 2.25 for [SH2], and Eq. 2.26 for IS=J, yields the
27
-------
required exoressions in [sH-]:
F.q. 2.34 tSH2] = (SH-J(H+>/Ka1
Ea. 2.35 [S = J = Ka2[SH-]/{H4>
Suostitutini Eqs. 2.34 and 2.35 into tq. 2.33, and cancelling
[SH-3 froTt numerator and denominator, then gives an expression
for R(2):
Eq. 2.36 R(2) = 1 / ( ) / (1 + Kal/
Eq. 2.38 R(3) =
1 + Kal/ f (Kal) (Ka2)/(H+> {H+}
Eq. 2.38 is equivalent to the expression for R(3) obtained via
substitution of expressions for CSH2] and [SB-] (in terms of
CS=]) into the formula for R(3) given oy:
Eq. 2.39 R(3) = [S=]/(StJ = [S = ] / ( [SH2] 4- [SH-J + tS = ] )
Rearranging Eq. 2.26 gives [SH-] in terms of [S=J :
Eq. 2.40 [SH-] = [S=]{H+>/Ka2
and Eq. 2.25 gives:
Eq. 2.41 CSH2] = [SH-J
-------
or, substituting F.q. 2.40 into F.q. 2.41,
Fq. 2.42 (SH21 = (S=HH+Mh + > / (fal)(Ka2)
Substituting Fiqs. 2.40 and 2.42 into Kg. 2.39, and cancelling
(S-] front numerator and denominator, then yields:
Kq. 2.43 R(3) = 1 / ( < H-t-> { H+ } / (Kal ) ( Ka2 ) + /Ka2 + 1)
which is equivalent to Eq. 2.38.
This example demonstrates that an algorithm for computing
the distribution coefficients (ALPHA) of any multi-species
mixture can be constructed in the following way.
(1) ^rite a concentration condition for [Stl that expresses the
law of conservation of mass (Eq. 2.27).
(2) Define the distribution coefficient for the parent molecule
(SH2) as [SH?J/[St] (Eq. 2.28).
(3) Solve the equilibrium expressions for the full system
(Eq. 2.25 and Eq. 2.26) for each molecular species,
expressing each species in terms of tSH2] (Fq, 2.29 and
Eq. 2.31).
(4) Cancel CSH2J from each of these expressions (Eq. 2.29 and
2.31), thereby obtaining the contribution of each species
(DISFCTU)) to the denominator of Eq. 2.32.
(5) Compute a total denominator (SU^FCT) as ( 1 + these terms),
as in Eq. 2. 32 (that is, DISFCTU) = [SH21/ISH2) = 1).
(6) Compute each distribution coefficient (ALFHA(I)) as
DISFCT(l-)/SUMFCT, v*here DISFCTU) = 1 and, in this example,
DISFCK2) = Kal/(H-f> and DISFCK3) s (Kal ) (Ka2)/
-------
denominator of (SH21/ [Stl are:
(1) Contribution of [SH2] :
Eq. 2.4-S DISFCTU) = ISH21/ISH2J = 1.0
(2) Contribution of sediment-soroed SH2, that is, tSH2P] : froir
Eq. 2.7,
Eq. 2.46 [SH2P] = [SH2HPJ (KPSU ) J , and DISFCT(2)=(KPS(1))CPJ
(Recall that [P] is the sediment/water ratio, SEDCOL. )
(3) Contribution of oiosorbed SH2, that is, [SH2B]: fro*
Eq. 2.14,
tq. 2.47 fSH2BJ = [SH2J IBJ(KPFK1)), and DIStCT(3)s(KPB(1))(BJ
(Recall that [B] is the nioT.ass/^ater ratio, BlOTni,.)
(4) Contribution of singly charged cation, [SH3+J: FXAMS
computes as 10.**(-POHG), and, fron Ka. 2.2.1,
Eq. 2.4R [SH3 + J= (Kb I)[SH2J/
(Recall that all computations are referenced to the
aqueous phase of a given compartment, so (H20> can
be taKen as 1.}
(5) Contribution of sediTent-soroed singly charged cation,
[SH3P+] ; fro-n Ea. 2.8,
Eq. 2.49 [SH3P + J = (KPS(2)) [SH3 + J [P]
Substituting Eq. 2.48 into Ea. 2.49 yields
Eq. 2.50 (SH3+P] = UPS(2) ) (Kbl ) IPJ [SH2J/{OH-} , and
DISFCT(5) = (KPS(2))(Kbl)tP]/{OH-}
(6) Contribution of oiosorbed singly charged cation, tSH36tj:
from Eq. 2.15,
Eq. 2.51 [SH3B+J = (KPB(2))tSH3f][B]
Substitution of Eq. 2.48 into Eq. 2.51 yields:
30
-------
Substituting F.q. 2.59 into F.q. 2.60 yields:
Eq. 2.61 [SHP-] = (KPS(4) MKal ) [SH2J (P]/OH} , and
niSFCT(ll) = (*al)(KPS(4)HP]/{M}
(12) Contribution of blosorbed singly charged anion, ISHB-l:
rearranging Eg. 2.17 qives:
Eq. 2.62 ISHB-] = ( KPB( 4) ) [SH-H 6J
Substitution of F.Q. 2.59 into Eq. 2.62 yields:
Eq. 2.6* fSHB-J = ( KPB ( 4) ) ( Ka 1 HSH2 ] I B] / < H + } , and
DTSFCTU2) = (Kal)(KPR(4) IBJ/{Ht>, and
DISFCTU3) = (Kal) (Ka2)/{H-»> {H+}
(14) Contribution of sediment-sorbed doubly charqed anion,, ISP = 3 :
rearranqinq tq. 2.11 qives:
Eq. 2.66 ISP = J = (KPS(5)) [S = J I PJ
SUbStitutina Eq. 2.65 into Fq. 2.66 yields:
Eq. 2.67 (SP = J = (Kal)(Ka2)(KPS(5))ISH2] [PI/(H + >
, and
DISFCr(lS) = (Kal)(Ka2)(KPB(5))lBJ/
-------
Finally, the total denominator is:
SUMFCT = DISFCTU) + DISFCK2) 4 ... 4 DISFCTU5)
and the distribution coefficient, that is, the traction of the
total concentration of compound CStJ present in each molecular
form, can be simply computed as:
AL.PHAU) a DISFCT(I)/SUMFCT
The subroutine containing this section of the EXAMS code
(DISTRB) also computes the fraction of [Stl present in all
dissolved, sediment-sorbed, and biosorbed species combined,
ALPHAC16), for example, is the total dissolved fraction; it is
the sum of ALPHA(l), (4), (7), (10), and (13). These summary
coefficients are used with the transport equations. ALPHA(16) is
coupled to the water motions to compute the transport of
dissolved materials, ALPHAU?) is coupled to sediment transport
to compute the transport of sediment-sorbed compound, and
ALPHA(IB) is coupled to the transport of plankton to compute the
transport of biosorbed compound.
2.3 Kinetic Processes
"Kinetic" processes, unlike rapid (local) equilibrium
processes such as ionization and sorption, occur on time scales
that make their time-dependent behavior of direct concern in a
hazard evaluation, (very slow processes, at the further extreme
of the temporal spectrum, are usually treated by modelers as
absolute constants. For example, changes in the emission of
light by the sun (the solar "constant") are usually modeled only
oy astrophysicists.) The kinetics of the transport regime in
aquatic syst-ems, and the kinetics of the transformation processes
that degrade a chemical to innocuous forms, are the primary
constituents of EXAMS' evaluative capabilities.
2.3.1 Transport
EXAMS includes a simple calculation of steady-state average
transport of water, sediments, and planktonic organisms
throughout the system. The flows of water, sediments, and
Plankton act as simple carriers for the dissolved (ALPHAU6)),
sediment-sorbed (ALPHA(17)), and biosorbed (ALPHAU8)) forms of
the synthetic organic chemical. These carrier flows are
ultimately reduced to coefficients that express the effects of
transport processes on the kinetics of the chemical; the vector
of concentrations of the synthetic organic chemical itself is the
only true time-dependent state variable in EXAMS.
33
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A hydrologic sub-program was created for F'XA^S in order to
minimize the labor necessary to specify, or modify, the physical
transport section of KXAMS* environmental aata base. This data
base is composed primarily of readily available and easily
comprehended parameters, such as tne volume, nean depth, and
surface area of the system compartments. Any of these parameters
can be modified by the user as desired. fcXAHS then recomputes
the exchanges of materials among compartments, and the net
transport of materials through the system, in effect creating a
new physical model according to the user's laodifications.
The hydrologic subroutine operates on three sub-sets of
EXAMS' environmental data base. The first sub-set is a
description of the volumes of water entering each zone of the
system from external sources. The second data sub-set
categorizes the geometry of the system, and the properties and
distribution of biomass and sediments. The third sub-set
contains structural properties of the ecosystem itself. This
last (variables JFRADG, JTURBG, etc.) specifies the direction and
strength of the flow pathways Interconnecting the system
compartments. The flow of water through the system compartments
is computed from a mass balance on water entering and leaving
each segment.
EXAMS' flow pathways can oe specified via advective or
dispersive equations, or both. (Advection is like a freight
train, dispersion is like a drunken walk.) The program uses
conventional eguations for both processes. Since the volume of
the compartments is constant, the law of conservation of mass
demands that the nydrologic inputs to a compartment be balanced
by advected flows leaving the compartment. The expresssion used
for dispersive or turbulent exchanges across compartment
boundaries is, as usual:
(DSPGHXSTURG)
(CHAPLG)
where XSTURG is the cross-sectional area of the exchange boundary
(in square meters), CHARLG is the "characteristic length"
(meters) along the flow path (that is, the average length of the
compartments or the distance between compartment centers,
measured along the exchange axis), and DSPG is the eddy
dispersion coefficient (sguare meters/hour). For example, in a
simple model of a stratified lake, when XSTURG is the area of the
thermocline and CHARLG is one-half the mean depth of the lake,
this expression describes the rate of exchange of water between
the epilimnion and hypolimnion.
EXAMS also computes sediment transport via the general
advective and dispersive equations, but an additional set of
transport rules is superimposed on the sediment equations. For
34
-------
example, an advective pathway between *ater column compartments
Is permitted to carry along suspended sediments (ana plankton)
from one compartment to the next. An advective pathway from trie
water column into a benthic sediment is not allowed to carry
sediment with it, however: This fcind of pathway is reserved for
water seepaae into the sediment, and ground-water recnarae
leaving the system. The sediment transport rules give EXAtfS the
ability to include riverine sediment wash-loads and bed-loads,
groundwater seepage and recharge, and complex exchanges between
the water column and benthic sediment deposits driven by physical
and biological processes dominant in non-fluvial systems.
EXAMS does not explicitly represent seguential deposition
and scour of benthic sediment zones, nor does it allow for a
secular accumulation of bottom sediments with consequent burial
of sorbed chemicals. In one sense, this limits EXAMS' utility.
For example, run-of-the-river flood control reservoirs are very
common in the USA, and many of them rapidly accumulate sediments
and bury chemicals in their depths. The bottoms ot many, if not
most, free-flowing rivers and larger lakes accumulate sediments
quite slowly, however. In addition, the synthetic chemicals
captured by benthic sediments prooably are frequently re-exposed
to the overlying water column via water turbulence, physical
disturbance by demersal fishes, and the internal stirring of
sediments by benthic organisms (bioturbation). EXAMS therefore
treats benthic sediments as bottom zone compartments with a fixed
volume, subject to continual (albeit slow) exchanges with the
overlying water column. At least for evaluation and screening
purposes, it seemed unwise to suppose that buried synthetic
chemicals will never reappear.
where appropriate, however, net sedimentation and burial of
synthetic chemicals can be readily evaluated, for the burial
process can be represented via a first-oraer disappearance of the
compound from benthic sediments. For example, given an active
sediment depth of 10 cm, and a net burial of 1 mm/yr, the loss
coefficient for a synthetic compound in the sediment would be
0.1/10 = 0.01 /vr with a half-life of 69 years.
EXAMS was designed for evaluative purposes, rather than for
detailed site-specific applications. For this reason, EXAMS'
transport algorithms were written in a very general form that
uses an input description of the transport conditions in the
system, rather than attempting to compute hydraulics and solids
transport from first principles. Several cautions to the user
defining an ecosystem for entry to the program are therefore in
order.
First, because EXAMS is a compartment model, the
representation of advected flows necessarily introduces some
numerical dispersion into the computations. Although this poses
little problem for general evaluations, it should be recognized
35
-------
that the concentrations computed by the erograir for a particular
location are to a decree dependent OP the spatial resolution used
to represent the system. For example, FXA^S computes the average
concentrations in a river reach, rather than the details of the
(usually decreasing) profile of concentrations within the reach.
As the number of compartments used to describe tne reach
increases, tne compartmentalized representation begins to
approach the more detailed profile predictable from an analytic
solution to the governing partial differential eguations. In
general, for site-specific applications simplified transport
representations can oe adjusted or "calibrated" to more
faithfully depict transport detail, via initial matchinu of
program outputs to a conservative tracer substance. Chloride
concentration is often used as a calibration tracer in estuaries;
temperature and dissolved substances can be used for calibration
studies in lacustrine systems. Of course, if desired, t'XAMS
could be loaded via an analysis of the outputs of detailed
hydraulic and sediment transport models.
Secondly, EXA^S does not impose a segment-by-segment mass
oalance on the solid phases (sediments and biota) that transport
sorbed chemicals through the system. In some instances, sediment
(detrital materials) and biota are subject to significant
creation and destruction in some areas of aguatic systems, so
that, unlike water, these guantities cannot be treated as simple
mass-conservative entities in a generalized algorithm. Thus, for
example, mass balances for suspended sediments in fcXA^S are left
to the user's discretion. The F.XAPS program, however, does not
permit a failure to conserve sediment mass to perturb the mass
balance for synthetic organic chemicaJs.
Exchanges with sediment beds are Described primarily via a
dispersive exchange term (Section 2.3.1.4), This approach
involves a statistical summary of a multitude of physical and
biological transport mechanisms that have not been fully
characterized in tne literature. It has disadvantages in that
the appropriate magnitudes for the input parameters (e.g., DSPG)
are only approximately known. Unfortunately, the magnitudes of
the descriptive parameters needed for a more mechanistic
characterization of these multiple physical and biological
transport pathways are still less perfectly icno»n. In general,
the sensitivity of EXAMS' outputs to variation in
seditnent*water column exchange parameters should probably be
routinely examined, at least for extensively soroed compounds.
2,3.1.1 Hydrology and advection
Hydrologic inputs are specified in tXAXS' environmental data
base via four variables: STFLOG (stream flow), NPSFLG
(non-point-source flow), INTFLG (ground-water inflows), and MING
(rainfall). After subtracting evaporative water losses (KVAPG),
3b
-------
the sum. of these terms is the total water flow enterinq a
compartment from external sources. EXAMS adds to this sum the
advected flows enterinq the compartment via other compartments in
the system. This grand sum is the total amount of water advected
into the compartment from all (internal and external) sources
combined. The total advective flow through the compartment is
then distributed among the flow paths specified for that
compartment in the JFRADG and ITOAPG structural vectors.
Three of the nydrologic input variables (STFLOG, NPSFLOG,
and INTFL3) are vectors that include a separate entry for each
compartment of the aquatic system described by the data base.
The STFLur, vector is used to enter point sources, tributary
flows, stream flows entering a latce, and the discharge enterinq
the uppermost reach of a river system. The NPSFLGs are used to
enter non-point-flows and overland runoff flowing into the
compartments. Ground-water seepage or subsurface flows are
entered via TNTFIG. STFLOG, NPSFLG, and IMFLG all have units of
cubic meters per hour; EXAMS allows each compartment to receive
an entry from each category.
Rainfall (RATNG) is a scalar variable in EXAMS, that is, the
environmental descriptor is a single value rather than a
compartment-specific vector, RAING has units of mm/month. EXAMS
converts this climatological aatum to a quantity of water
entering each compartment having an air-water interface. The
conversion is simply:
Eq. 2.70 PAIMFL = (PAING)(AREAG)/(730.5)
where RAINFL is in liters/hour (based on 730.5 hours/month).
EXAMS detects the air-water interface, and decides whether to
admit rainfall into the compartment, from the structure of the
system. Rainfall is not permitted to enter compartment types
(TYPEE) "R" (benthic) or "H" (hypolimnion). The decision
mechanism for L(ittoral) and E(pillrcnion) compartments is
slightly more complex. For these compartment types, EXAMS checks
the compartment numbered one less than the compartment under
consideration (that is, if the current compartment is J, the
decision is based on the properties of compartment (J-l) ). If
tne preceding compartment is another element of the water column,
rainfall is not allowed to enter the current (Jth) compartment.
At first glance, this decision seems trivial: after all,
rain only falls on the water surface, therefore only these
compartments can receive rainfall. The problem is complicated,
however, by the fact that EXAMS was designed to allow a user to
interactively modify any variable in the environmental data base.
EXAMS therefore tiust be able to detect any change in the system
structure and accurately recompute, in this case, a new
hydrologic regime. Changes in system structure affect a number
of other processes as well. For example, in computing vertical
37
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light extinction through the water column, EXAMS must detect the
top of the water column, compute the light levels in eacn
successively deeper water-column con.par ttient, and then restart
the computation for each adjacent vertical section.
The problem, then, is somewhat more general than it first
appears, and is not entirely trivial: EXAMS must decode trie
three-dimensional structure of the system as an implicit function
of the inout environmental aata. The decoded structure then
serves as a guide for computina the Kinetics of the transport and
transformation processes. The decoding proDlem could, of course,
be eliminated by requiring that the environmental data include a
more complete set of structural descriptors. This approach,
however, leaves the user in the uncomfortable position of having
to memorize a large set of arbitrary, model-specific compartment
descriptors of little intrinsic interest.
EXAMS instead relies on a set of simple conventions for
numbering and naming the compartments used to describe an aquatic
system. These conventions can be stated as 4 definition rules:
(1) Compartments can be named (TYPFJE) either "LM (littoral), "E"
(epilimnJon), "H" (hypolimnion), or "P" (oenthic). These
names carry their usual implications: ar. "HH compartment
lacks an air-water interface, a "BH compartment is a bottom
sediment, etc. The water column ot the littoral cannot be
suodivided; all other system zones can be entered as
vertical stacks of the same TYPEE.
(2) Compartment number 1 must be part of a water column and must
be of TYPEE "E" or "I".
(3) Each vertical segment must be numbered in increasing order
with increasing depth. That is, when a vertical segment is
divided into, say, 4 compartments, if the topmost compart-
ment is numbered 5, the bottom coirpartment will be number 8.
(4) Every vertical segment must terminate in at least one bottom
sediment ("R") compartment.
EXAMS' computations are somewhat more efficient if one more rule
is observed:
(5) Vertical bloctcs of compartments are arranged, and numbered,
along the main advective flow paths in the system.
EXAMS' internal decoding of the (implied) system structure
thus avoids the problem of multiple model-specific parameters,
but at some cost: EXAMS must assume that the user has
scrupulously adhered to these rules. Suppose, for example, that
a 10-miie stretch of river were described as 10 successive "LM
compartments, and the benthic sediments were omitted: EXAMS
would suppose the system to be a vertical, 10-mile-deep column of
water. Again, should a surface-water compartment be designated
"H", EXAMS will not allow rain to fall, nor chemicals to
volatilize, from the compartment. Examples of proper and
improper segmentations of a small river and lake system are given
in Figure 2.1.
38
-------
a. Improper segmentation and numbering: compartment number 1 is
(B)enthic, benthic sediments are incomplete, and numbering is
horizontally rather than vertically organized.
..
A
1
V
b.
—
A
1
V
->| 2 L I— ->l
j. _____________ j. i
1 3
V
1 i B I
is vertical exchange
Proper segmentation:
vertical segments incl
number l is of surface
->l 1 1 I— >l
! 3
V
12 81
IA
*
is vertical exchange
!--->! |— >l 5 L |« — >
L 1 1 1
,mmmmm± 1 A fp 1 1
1 17 B 1
1 1
1 i
1 1
16 HI
1
V
18 81
vertically organized numbering, all
ude a bottom sediment, and compartment
water type ("L" or "E").
|--->| !--->! 8 L |— — >
L 1 1 1
v 1 19 B I
1 1
1 1
16 HI
A
1
V
17 B 1
Figure 2.1 Example of compartmental system structure.
39
-------
EXAMS' final hydrological input quantity is a
compartment-specific vector of evaporative water loss rates*
EVAPG, with units (mm/month). A value of EVAPG can be entered
for any compartment, out EXAMS ignores inappropriate entries,
that is, evaporation is allowed only for compartments with an
air-water interface.
EXAMS can be operated with very generalized descriptions of
aquatic systems typical of broad geographic regions, or with more
detailed descriptions of particular sites and locales. The
mechanics of EXAMS' transport computations can best be
appreciated via a specific example. This example will be
developed in considerable (site-specific) detail, so as to
illustrate methods for preparing environmental data for EXAMS,
computational mechanics, and the range of transport processes
that can be accommodated by the program.
2.3.1.2 Advected water flo*s
EXAMS' advective flow computations are fundamentally nothing
more than a direct application of the law of conservation of
mass. Because changes in storage volumes are not permitted, the
total inputs to each compartment must be balanced by advected
outflows. The advective transport regime thus can be computed by
imposing a water (mass) balance on the hydrologic inputs to the
system. The logic of these computations can best be seen within
the context of a specific example:
a 9-compartment model of a portion of a slowly
moving slough or river system. Upstream discharge into
compartment 1 is 10 cubic meters/hr. The flow is split by an
and 5; 75% of the flow goes to
compartment 5, Compartment 3
also receives a tributary
meters/hour. Each segment is loo n long and 2
3 is
Figure 2.2 is
island into compartments 3
compartment 3, the remainder to -.^,„?.•-•• ^...-..v -. v~...r-—«.-•••-••-- „
" ' discharge of an additional 10 cubic
__ 100 it long and 2 m deep. The
segment widths are 10 m for 1 and 7, but compartment
and compartment 5 is 2
8 m,
m, wide. The rate of evaporative water
loss (EVAPG) is 146.1 mm/mo for all segments; no rain falls on
the system. EXAMS' hydrologic input data, thus far, looks like
this:
COMP. STFLOG
1
3
5
7
10
10
AREAG
1000
800
200
1000
EVAPG
146.1
146.1
146.1
146.1
VOLG
2000
1600
400
2000
DEPTHG
2
2
2
2
40
-------
EXAMS now converts STFLOG and EVAPG (via AKEAG, as in
Eq. 2.70) to the net liters/hour entering each compartment from
external sources (WATINL), and sums the total available flow
(TOT1N), arriving at the hydrologic analysis shown in Table 2,1.
10 I
->l 3 L l\
/I I \
/ 4.........4. \
/ +.-......+ \
/ 14 B | \
/ 4.-......4 \
-<
10 I
/ I
I
12 31
\ I ! /
->l 5 LI/
I 8
4...
4...
I 9
B I
...4
...4
B I
16 B I
+--....._+
Figure 2.2 Nine-compartment model of Noname Slough ecosystem.
Table 2,1, Advective inputs to Noname Slough
ICOMP.
1
3
5
7
STRMFL
10000
10000
0
0
EVAPL
200
160
40
200
TOT IN
WATINLI
9800
9840
- 40
- 200
s 19400
The structure of the advective flow field is given by
parameters JFRADG, ITOADG, and ADVPRG. These names are acronyms
41
-------
for J FRom ADvection
ADvection PRoportion
merely indicates that
they are available
(JFRADG), I TO ADvection (ITOADG), and
(ADVPRG), respectively, (The terminal "G"
these are "Global" parameters, that is,
to the user for interactive modification.)
Vector JFRADG is a list of the source compartments for each flow.
The corresponding member of ITOADG holds tne number of the
compartment receiving the flow, and ADVPRG gives the fraction of
the total flow through compartment JFRADG that follows the path
to ITOADG. A zero (0) entered in ITOADG denotes an export frorr
the system, EXAMS' report of the (partial) structure given for
the slough system in Figure 2.2 would appear as in Table 2.2,
Table 2.2, EXAMS output -- partial advective structure, Noname Slough.
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: Unspecified Chemical
ECOSYSTEM: Noname Slough - Advection test data
mmmmtemmmmmm»mmmmmmmm
-------
which can receive, deliver, or exchange advected flows with any
or all of the other compartments in the system. The N
input/output equations are solved by a Gaussian elimination
algorithm (Stuart 1970:304-311), This algorithm is a matrix
solution of a normalized form of the input/output equations. The
matrix (AMAT) is loaded in three stages: First, each value of
WAT1NL is divided (normalized) by TQTIN, and loaded on the (N-H)
column of AMAT, Next, the coefficients on the output (X) terms
(which are always unity (1)) are loaded on the diagonal of AMAT,
Finally, the AOVPR values are entered into AMAT with a row index
given by ITOADG and a column index given by JFRADG, (The system
export terms (ITOADG = 0) are not required for this part of the
analysis.) Leaving aside Noname Slough's benthlc compartments,
the coefficient matrix would be:
Table 2,3, Normalized coefficient matrix, advection equations
JFRAD
I
T
0
A
D
•<
1
1
3
5
7
1 1
1
-.75
-.25
0
3
0
1
0
-1.0
5
0
0
1
-1.0
7
0
0
0
1
WATFL/TOTIN
0.505155
0.507216
-0.002062
-0.010309
The solution of this system of equations is:
X(l) s 0.505155
X(3) * 0.886082
X(5) = 0.124227
X(7) = 1.000000
where "X" is now the fraction of TOTIN passing through each
compartment.
For each compartment, EXAMS computes the actual discharges
along each flow path as the product of X, TOTIN, and the ADVPBG
for the pathway. This information is entered in a matrix (WATFL)
of flows among segments. The row and column indices of WATFL are
43
-------
the same as those of AMAT, that is, the i*ATFf< indices give the
source and destination compartment number for each flow. Exports
from the system (in liters per hour) are entered into a vector
(WATQUL) of exports from each compartment. The exports from each
(JFRADG) compartment are computed as the product of X, TQTIN, and
ADVPRG for those pathways having ITOAOG = 0.
In the Noname slough example, the discharges from segment
number 1 are:
and
WATFL(3,1) * (0.505155)(19400)(0.75) = 7350,
WATFL(5,J) = (0.505155M19400M0.25) s 2450.
The only non-zero outlet flow is
WATOULO) = (1.0)(19400)(1.0) = 19400.
The WATFL matrix and the WATOUL vector for these sections of
Noname Slough are shown in Table 2,4. EXAMS' outputs include a
"transport profile" of the system, showing the advected flows
through each segment, EXAMS also computes a (local) turnover or
"water renewal" time (tne volume/discharge ratio) for each
compartment. EXAMS' transport profile for Noname Slough, as
defined thus far, is given in Table 2.5.
Table 2,4. Example WATFL matrix and foATQUL vector (liters/hour)
JFRAO
I
T
0
A
D
1
1
3
5
7
1
0
7350
2450
0
3
0
0
0
17190
5
0
0
0
2410
7 1
0
0
0
0
WATOUL: I
+.„-+,
19400
44
-------
Table 2.5, Partial transport profile for Noname Slough
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: Unspecified Chemical
ECOSYSTEM: Noname siougn - Advection test data
TABLE 9. TRANSPORT PROFILE OF ECOSYSTEM.
CP T* VOLUME SEDIMENT WATER FLOW SED, FLOW RESIDENCE TIME (DAYS)
Y (CUBIC M) MASS (KG) (CU. M/DAY) (KG/DAY) WATER SEDIMENTS
1L
2B
3L
4B
5L
6B
7L
8B
9B
2.0000E+03
1.600E+03
400.
2.000E+03
235.
413.
57.8
466.
8.50
3.88
6.92
4.30
* COMP. TYPE: »L"=LITTORAL; "E"=(EPi) AND MHHS(HYPO)LIMNIQN; MB**BENTHIC
2,3.1.3 Advective sediment transport
Sedimentary materials (detritus) can be produced and
destroyed biogenically within an aquatic ecosystem. Sediment
transport thus is not computed in EXAMS via the simple mass
balance constraints used to compute the transport of advected
water masses, EXA.MS instead treats advected sediment as a
non-conservative substance whose transport is simply driven by
the hydrodynamics of the system. The point* (STFLOG) and
non-point- (NPSFLG) external hydrologic inputs do contain coupled
sediment loads (STSEDG and NPSEDGf icg/hr). These variables are
only used, however, to evaluate the chemical loadings (see
Section 2.4); they do not enter the chemical transport
equations.
EXAMS computes advective sediment transport as the product
of the rates of water transport and the sediment/water ratio
(SEDCOL, Eq, 2.12) of the source compartments. WATFL and WATOUL
load an analogous sediment flow matrix (SEDFL) and
(SEDOUL), both having units of kg sediment
are used to
export vector
transported per hour. The equation for advective sediment
transport among compartments iss
Eq. 2.71 SEDFL(I,J) * WATFL(I,J) * SEDCOL(J),
and the equation for advected sediment export is
45
-------
Eq. 2.72 SEDOUL(J) = WATOUKJ) * SEDCOL(J).
These equations are not blindly executed for the entire system,
however.
The execution of the sediment transport equations (Eqs.
2.71 and 2.72) Is constrained by a series of special conditions.
These conditions can be expressed as a set of 5 sediment
transport rules:
(1) An advected water mass leaving any water column compartment
carries an entrained sediment washload, unless the flow
enters a benthic compartment. A flow from the water column
into a benthic sediment is an infiltration flow that does not
transport sediments.
(2) Benthic sediment ("B") compartments can always export water
across system boundaries, and can advect water to any other
compartment in the system.
(3) A benthic compartment can export sediment (in addition to
water) only when it occupies the sediment-water interface
(that is, the (j-1) compartment is not of TYPEE "B").
(4) sediment cannot be advected from a benthic compartment to any
element of the water column.
(5) When benthic compartments are not vertically adjacent
(actually, when their compartment numbers differ by 2 or
more), sediments can be advected from one to another (for
example, alonq a bedload transport path).
These sediment transport rules allow EXAMS to include
sediment washloads and bedloads, and seepage of groundwater both
into and out of the system. One additional system definition
rule must be observed, however, when a groundwater recharge is
portrayed: The groundwater flow path must include at least 2
vertical benthic sediment compartments. If this definition rule
is ignored, EXAMS will interpret the export flow leaving the
benthic compartment as a bedload (rule 3) rather than as a
groundwater recharge.
These concepts can be illustrated by expanding the
definition of Noname Slough (Figure 2.3). In the expanded
definition, one segment receives a groundwater input (INTFLG) of
0.2 cubic meters/hour. The groundwater seep passes through
benthic compartment 6 and is advected into the overlying water
(rule 2); by rule 4 the water flow does not entrain a sediment
flow. The downstream segment (7) loses water to a groundwater
recharge. The infiltration flow is 2% of the total advected flow
through compartment 7 (ADVPRG = 0.02). By rule 1, the
46
-------
infiltration does not entrain the suspended sediments. The
groundwater recharge must be carried on from compartment 8 Into
compartment 9 before it can be exported from the system, however,
or tXAMS would Interpret the export as a bedioad
than as a flow of water only (rule 2).
(compartment 2 to 4 to 8), e>y rule 5, carries
sediments downstream. The bedioad export at
enabled under rule 3. The washload (compartments
(rule 3) rather
The bedioad path
both water and
compartment 8 is
1 to 3, 5 to 7)
moves through the
downstream transport
system under rule 1; EXAMS computes
of suspended sediment from Eq, 2,71.
the
10
I I
->l 3 L |\
/I IV
4..... ...+ / .» 4 & |\ \ +...... — «.
I | / / +- ----- --+ \ \ | I
--->| 1 L !--< / \ >->! 7 L |
10 I I \ / \ / i I
+........+ x X f.......-4
+......„.+ / \ / \ f........+
--- >| 2 8 |«- \ +---..... + / -->j 8 B I-
+ .- ...... 4 \ | | / +........4
->| 5 LI/ + ---- ...-4
I I I 9 B I
->
6 B
0.2 -»-
12%
V
Fig. 2.3 Moname Slough bedioad, washload, and groundwater flows.
To complete this example, some additional properties of the
sediments must be specified. Let, therefore, Noname Slough have
a suspended sediment concentration (washload, SDCHRG) of 100 ppm,
and stream-borne sediment loadings (STSEOG(l) and (3)) of 1.0
fcg/hr, (Note that this treatment imposes a mass balance on
suspended sediments.) The depth of the surficial sediments
(compartments 2, 4, 6, and 8) is 5 cm; each has a bulk density
(SDCHRG) of 1.2 g/cc, and a water content (PCTWAG) of 180%.
Segment 9 is a 30 cm layer of sand with a bulk density of 1.95
g/cc, and a water content of 115%,
47
-------
The bedload is, of course, another measuraale property of
the Slough, Suppose, for example, the measured bedload leaving
the downstream segment of the Slough were 100 kg/hr. The ADVPPG
for the crossed infiltration and bedload transport through
compartment 8, and the upstream bedload inputs, can be developed
from this datum and an assumed solids balance for the system.
The sediment/water ratio for the surficial sediments is 1.25
kg/liter (F,q. 2.13); the water export associated with the
bedload is, therefore, (100)/(1.25) = 80 liters per hour = 0.08
cubic meters/hr. The groundwater infiltration was given as 2% of
the available discharge passing through segment 7 (Figure 2.3).
The total segment 7 discharge is 19.4 cubic m/hr (Table 2.4),
plus the groundwater seep entering via segment 6 (Figure 2.3), or
19.6 cubic meters/hour. The 2% infiltration is therefore
(0.02M19.6) = 0.392 cubic m/hr, and the total flow through
compartment 8 is 0.392 + 0.08 = 0.472 cubic m/hr. The ADVPRG for
the throughput of infiltrated water is therefore (0.392)/(0.472)
= 0.83; the ADVPRG for the bedload is 0.17.
Finally, presuming the bedload originates in egual measure
from the influent flows to compartments 2 and 4, the bedload
inflows to both segments are 0.04 cubic meters of water per hour
(STFLOG(2) and (4)), with a parallel sediment load (STSEDG) of 50
kg-Xhr. EXAMS' retrieval of the full advective specifications is
shown in Table 2.6, and EXAMS' computed advective "transport
profile" is reprinted in Table 2.7.
Table 2.6. Full advective structure of Nonarne Slough
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: Unspecified Chemical
ECOSYSTEM: Noname Slough - Advective transport regime
TABLE 8. INPUT DATA DESCRIBING ENVIRONMENT: TURBULENT INTERCONNECTIONS,
COMP. NO.
CONNECTED
ADVECTION
COMP. NO.
CONNECTED
ADVECTION
COMP. NO.
CONNECTED
ADVECTION
(JFRAD)
(ITOAD)
(ADVPR)
(JFRAD)
(ITOAD)
(ADVPR)
(JFRAD)
(ITOAD)
(ADVPR)
0
2
0
1
3
.750
7
8
.OOOE-02
8
9
.830
1
5
0.250
2
4
1.00
8
0
0.170
3
7
1 .00
4
8
1.00
5
7
1.00
6
5
1.00
7
0
0.980
9
0
1.00
48
-------
Table 2.7. Advective transport regime in Nonage slough
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: Unspecified Chemical
ECOSYSTEM: Noname Slough - Advective transport regime
TABLE 9. TRANSPORT PROFILE OF ECOSYSTEM.
CP T* VOLUME SEDIMENT WATER FLOW SED. FLOtf RESIDENCE TIME (DAYS)
Y (CUBIC M) MASS (KG) (CU. M/DAY) (KG/DAY) WATER SEDIMENTS
1L
2B
3L
4B
5L
6B
7L
8B
9B
2.000E+03
50.0
1.6QOE+03
40,0
400,
10.0
2.000E+03
50.0
300.
200.
3.333E-»-04
160.
2.667E+04
40.0
6.667E+03
200.
3.333E+04
5.087E+05
235.
0.960
413.
1.92
62,6
4.80
470.
11.3
9.40
23.5
1.200E+03
41.3
2.400E+03
6.26
0,000
46.1
2.407E+03
0.000
8.50
27.8
3.88
11.1
6.39
1.11
4.25
2.35
8.12
8.50
27.8
3.88
11.1
6.39
4,34
13,8
* COMP, TYPE: "LM=LITTORAL; "E"=(EPI) AND "H"=(HYPO)LIMNION; "B"*BENTHIC
2.3.1,4 Dispersive transport
The mean advected flow is not the only process governing the
transport of synthetic chemicals in aquatic systems. Turbulence
and shear flow in rivers, for example, combine to generate a wide
spectrum of meso-scale advective processes. Similarly, in
stratified lakes exchange across the thermocline is driven by
molecular diffusion, wind-induced mixing, storm surges, and
internal waves and seiches. These meso-scale processes can
usually be described via a statistical summary (the dispersion
equation) of their effects on the average transport of dissolved
substances (see, for example, Fischer et al. 1979), EXAMS'
environmental data base includes 5 vectors that specify the
direction (JTURBG, ITURBG), and strength (DSPG, XSTUPG, CHARLG)
of dispersive transport pathways in an aquatic system.
The corresponding members of the JTUPBG and ITURBG vectors
specify the pair of compartments that are exchanging materials
via each dispersion pathway. For example, the 4th entry in the
vectors could be used to specify an exchange between compartments
7 and 10, by setting JTURBG(4) = 7, and 1TURBGC4) = 10. Because
dispersion, unlike advection, is a symmetrical process, this
pathway could also be specified as JTURBGC4) c 10 and ITURBGC4) c
7, Boundary conditions (dispersive exchanges with the external
world) are specified by a 0 setting on either vector. In other
words, the vectors can specify a turbulent exchange of, for
example, compartment 10 (an embayment), with an external
reservoir, via either (JTURBG = 10; ITURBG * 0) or (JTURBG • Of
49
-------
ITURBG = 10). EXAMS computes the boundary exchanges as a simple
displacement of contaminated, by chemical-free, water and
sediments. Non-zero chemical boundary conditions are loadings,
and thus would interfere with EXAMS' estimates of persistence
(defined as the time to cleanse the system after all loadings
terminate). Non-zero (dispersive) chemical boundary conditions
can, of course, always be introduced via an artificial
point-source or non-point-source advective input, coupled with a
symmetrical advective export from the compartment, or via a
DRFLDG (see Section 2.4).
The conventional dispersion equation used in EXAMS describes
the rate of exchange of environmental volume across a boundary
between two compartments. EXAMS' formula is:
(DSPGMXSTURG)
Eq. 2.73 F = — —
(CHARLG)
In this equation, XSTURG is the cross-sectional area of the
pathway (in square meters), CHARLG is the "characteristic length"
of the path (m), and DSPG is the dispersion coefficient or eddy
diffusivity (square meters/hour). F is then a flow of
environmental volume, with dimensions of cubic meters per hour.
Equation 2,73 is homologous with the mathematics of simple
Fickian molecular diffusion. The dispersion equation, however,
is a statistical summary of the large-scale effects of meso-scale
advective processes; it is used when the meso-scale processes
are so complex or sporadic that a detailed treatment is
intractable. The net result of the meso-scale processes is
similar to molecular diffusion in that dissolved constituents are
transported along the gradients of concentration in the system.
The apparent rate of transport of materials from areas of high,
to areas of low, concentration is much faster than rates of
molecular diffusion, however. For this reason, the kinetic
parameter in Eg. 2.73 (OSPG) is usually called a "dispersion
coefficient," "turbulent diffusivity,", or "eddy diffusivity,"
rather than a "diffusion" constant (Bird, Stewart/ and Lightfoot
1960:629). The events described by dispersion are not fully
homologous with Fickian diffusion, however, and the use of
dispersion terms to depict chemical transport in sediments
requires careful adjustment for effects of porosity, tortuosity,
sorption, and ion exchange (Berner 1976).
From the dispersion equation (2.73), EXAMS computes a flux
of water and sediments along the pathway specified by JTUPBG and
ITURBG. The fluxes between compartments are added to the
advective flows in matrices WATFL and SEDFL, thereby completing
EXAMS' description of the system's internal flow field. The
boundary fluxes are added to the appropriate elements of WATOUL
and SEDOUL? the exchange brings in a replacement volume of
uncontaminated water and sediments.
50
-------
The "characteristic length" (CHARLG) of a pathway
conventionally represents the distance between compartment
centers, measured along the axis of the exchange, A single
segment thus may have several characteristic lengths, depending
on the geometric orientation of its linkages to adjoining
segments. The cross-sectional area (XSTURG) for the exchange
path also depends upon the orientation of the compartments. For
a vertical exchange, as for example transport across the
thermocline of a lake, XSTURG is usually the AREAG of the
hypolimnion compartment. Longitudinal dispersion in a river
conventionally takes the flow, cross section as XSTURG, however,
and this does not correspond to any value of AREAG. Adherence to
these conventions is left to the user's discretion. EXAMS does
not attempt to evaluate the geometry of the system, but simply
inserts the user's entries for CHARLG and XSTUPG into Eq. 2.73.
Although EXAMS does not evaluate the orientation of the
dispersive exchange pathways, the program does adjust its
computations according to the nature (that is, the TYPEE) of the
exchanging compartments. These adjustments are primarily
important for the exchanges across the benthic boundary layer,
because of the very different physical properties of the water
column and a sediment bed. In this case, a simple symmetric
exchange of environmental volumes would transport very different
sediment masses and volumes of water. EXAMS allows for the
possibility of biogenic production and decay of detrital
sedimentary materials, and thus generally does not impose
explicit internal mass-balance constraints on the transport of
sediments in the system. In this case, however, the massive
injection of bed sediments into the water column, with little or
no resettlement, would amount to a gross distortion of sediment
transport dynamics beyond the realm of biogenic possibility, Tae
simple dispersion equation (2.73) thus requires situational
adjustments. EXAMS therefore divides its dispersion computations
into 3 distinct cases: (1) dispersion between water column
compartments, (2) dispersion between benthic compartments, and
(3) dispersion between a benthic sediment and the overlying water
column.
(1) Dispersion within the water column:
The volumetric displacement of suspended sediments can
almost always be neglected, so the water volumes and
environmental volumes of water column compartments can be assumed
not to differ. For example, a 15000 mg/L washload with a density
of 1,5 g/cc would perturb this assumption by only 1%. EXAMS
therefore computes the exchange flow of water between
water-column compartments (in liters/hour) as:
UOOOMDSPGHXSTURG)
Eq, 2.74 FLOW = —....—....-......•
(CHARLG)
51
-------
This value is added to the advective flows already in WATFL(I,J)
and WATFLCJ,!). (I is the compartment number held in ITUPBG; J
is the compartment number held in JTURBG.) The dispersive
exchange is equivalent to a symmetric pair of advected (pseudo)
flo*s between the compartments, if FLOW is a boundary condition,
it is added to WATOUL(J), where J is the compartment number held
by the non-zero member of the (JTURBG, ITURBG) couple.
The SEDFL matrix is updated via
Eq, 2.75 SEDFL(I,J) <— SEDFL(I,J) + (FLOW)*(SEDCOL(J))
and
Eq. 2.76 SEOFL(J,1) <--- SEDFL(J,I) + (FLOW)*(SEDCOL(I) )
The SEDOUL vector is updated via
Eq. 2,77 SEDOUL(J) <—- SEDOULCJ) + (FLOW)*(SEDCOUJ))
(SEDCOL is the sediment/water ratio, F,q. 2.13). In this case,
sediment mass need not be conserved. when the exchanging
compartments have differing concentrations of suspended
sediments, EXAMS permits a net tlo* of sediments along the
concentration gradient. EXAMS assumes that biogenic production
and decay of detrital materials within the compartments serves to
maintain the gradient.
EXAMS computes lateral, vertical, and horizontal dispersion
via this procedure. The equations thus account for several
rather different processes. The effects of shear flow in rivers
are computed via a "longitudinal dispersion coefficient."
Depending upon tne geometry and slope of the channel, riverine
longitudinal dispersion coefficients can vary from 2700 (Yuma
Mesa A Canal, Schuster 1965) to 5.4E6 (Missouri River near Blair,
Nebraska; Yotsukura et al, 1970) square meters per hour (cited
from Fischer et al. 1979:126). Some small lakes develop nearly
uniform vertical density gradients that inhibit vertical
exchange, while allowing rapid lateral dispersion, at all depths
in the lake. Usually, however, the most important barrier to
vertical transport in lakes is a localized region (the
metalimnion or thermocline) with a steep temperature (density)
gradient. The exchange of epilimnetic and hypolimnetic water
masses is driven by wind-induced eddies, storm surges, and
Internal seiches (see, for example, wetzel 1975:89-122), The net
effect of these processes can usually be summarized via a
dispersion equation. For example, Snodgrass (1977) used a
"vertical diffusivity coefficient" to "integrate the effects of
molecular diffusion, eddy diffusion, internal waves, seiches,
standing waves, [andj hypolimnetic entrainment ... into a net
transport process" across the thermocline of Lake Ontario. The
52
-------
average DSPG during tne stratified period (April to November)
ranged from 1.0 to 4.1 square meters per day, over 6 years of
measurements.
(2) Dispersion within the bottom sediments;
In some cases, exchanges among benthic compartments require
adjustment for strongly differing properties of the exchanging
segments. The surficial sediments of Noname Slough (Figure 2.3)
are laterally homogeneous, for example, but the deeper sandy
layer (compartment 9) differs substantially from the surficial
layers in bulk density, water content, and organic carbon
content. The sediment/water ratios of these layers can be
compared by inserting their water contents (PCTWAG) into
Eq. 2.13. In the surficial sediments, the given water content is
180%, and SEDCQL = 1.25 kg sediment per liter of water. The
sandy layer has a water content of 115%; its SEDCOL (6,67
kg/liter) is 5 times that of the surficial layers. Dispersion
between benthic compartments therefore must allow for exchanges
between segments of very different physical properties.
Furthermore, the water volume and the environmental volume
of a benthic sediment are by no means the same. The surficial
sediments of Noname Slough, to continue the example, have a given
bulk density of 1,2 g/cc. The volumetric (liter/liter) water
content ("porosity") can be computed via Eq. 2.12-2.12.3; the
surficial sediments contain only 0.53 liters of water per liter
of environmental volume. The porosity of the sandy layer (bulk
density 1.95 q/cc) is only 0.25 L/L. Equation 2.74 thus cannot
be used for a direct computation of dispersive transport of a
synthetic chemical between benthic sediment compartments.
The distribution of chemicals within lacustrine and marine
sediments has been successfully modeled via a vertical
one-dimensional treatment of transport and chemical dynamics in
this subsystem (Berner 1976, Imboden and Lerman 1978, Jones and
Bowser 1978). These one-dimensional ("diagenetic") equations
include the usual dispersive, advective, and reaction terms. The
advective terms in these equations are often used to describe the
net deposition of sedimentary materials, and the effective
vertical flow of interstitial waters produced by compaction of
the deposits. EXAMS precludes deposition and permanent burial of
synthetic organic chemicals as inappropriate to an evaluative
model, so its advective terms (Section 2.3.1.3) represent
ground-water flows and, where appropriate, irrigation of benthic
deposits by burrowing organisms.
The activities of burrowing organisms (bioturbation),
physical disturbance by demersal fishes, and intermittent strong
water turbulence tend to physically mix solids deposited on the
sediment surface to appreciable depths. These actively mixed
zones generally extend from about 2, to as deep as 50,
53
-------
centimeters in natural systems CJones and Bowser 1978 and
references therein). This physical reworking modifies observed
concentration profiles in sediments, and has led Schink and
Guinasso (1977) to propose the use of explicit solids mixing
terms in the one-dimensional treatment of early diagenesis in
sediments.
EXAMS makes use of a compartmentalized realization oil these
one-dimensional equations, but does not permit explicit mixing of
sediment solids between benthic compartments. The deptn of the
sediment compartments used to describe a system is taken to be a
depth through which the sediment can be regarded as "well-mixed,"
The mixing of solids is thus implicity incorporated into the
specifications of the structure of the system, rather than as
direct terms in the simulation equations. In effect, therefore,
EXAMS assumes that vertical concentration gradients within the
benthic compartments do not greatly disturb the results of its
evaluations.
There is some experimental evidence that the speed of
internal mixing processes in surficial sediments is sufficiently
rapid to justify EXAMS' discretized treatment. For example,
McCall and Fisher (1977, quoted from Jones and Bowser 1978) have
shown that typical population densities of tubificid oligochaetes
can completely rework the top 5 cm of sediments every 2 weeks in
a laboratory setting, vanderborqht and i*ollast (1977) found that
the upper 3 cm of marine (North Sea) sediments exhibited an
internal dispersion coefficient of l.E-4 square cm/sec? this
value implies a reworking time of only 25 hours,
when a dispersion term (lateral or vertical) is specified
for exchange between benthic compartments, EXAMS computes a
symmetrical exchange of water (only) between the compartments.
This exchange flow is used to update the WATFL matrix. Generally
the input dispersion coefficient in such a case should be
corrected only for tortuosity; the program itself corrects for
the average porosity of the 2 compartments involved, and for
sorption of the chemical to solid phases. EXAMS imposes no
limitations on the magnitude of DSPG, irrigation of deep
sediment zones by burrowing organisms can thus be represented via
dispersion terms, if desired, A boundary condition for a bottom
sediment compartment is computed in much the same way, except, of
course, the porosity of the specified compartment is the only
datum available for correction of the nominal DSPG,
(3) Exchanges between bed sediments and overlying waters:
Capture of organic chemicals by sediment beds can occur via
several processes, A dissolved phase can sorb directly to the
surface of the bed, with the sorbed material being then subducted
into the bed via bioturbation. Irrigation of the sediments by
tube-dwelling animals can directly entrain a flow of contaminated
54
-------
water through the bed? the sediment solids will then tend to
strip chemical from the water flow. Filter-feeaing organisms can
aggregate compounds sorbed with suspended fine particles and add
material to the bed, as may the sequential deposition, internal
mixing, and scour events characteristic of riverine systems. In
lakes and oceans, sediment "bursting" (Heathershaw 1974} results
in frequent saltation of bed solids, leading to
sorption/desorption events an-d entrapment of free boundary waters
in the redeposited sediment matrix.
Although direct sorption/desorption to the sediment surface
is a continuous process, many of the interactions between the
water column and benthic sediments are highly intermittent. For
example, Heathershaw (1976) has estimated that, in well-mixed
areas of the Irish Sea, as much as 70% of the Reynolds stress in
the benthic boundary layer results from events occupying only 5%
of the total time of record. Interactions mediated by the biota
are presumably also intermittent and highly variable in their
intensity. The most practical and efficient means of
representing this array of interactions between the water column
and benthic sediments is to use a statistical summary of their
macro-scale effects, that is, a dispersion equation (Berner
1976). This strategy was adopted for EXAMS.
A dispersive exchange between a water column (L, E, or H)
and a benthic (B) compartment is described to EXAMS via
specification of a characteristic length (CHARLG),
cross-sectional area (XSTURG), and dispersion coefficient (DSPG)
for the water column -- benthic element exchange pathway. The
volumetric exchange given by FLOW (Eq. 2.74) can be regarded
(heuristically) as the saltation of a unit volume of the bed
(containing water and solids), followed by equilibration with the
water column and resettlement on the bed, EXAMS thus separates
the rate of exchange of environmental volume given by
(DSPG)(XSTURG)/(CHARLG) into distinct water and solids exchange
components. The porosity of the benthic sediment is coupled to
the dispersion equation to give a water-exchange term, via the
expression:
WATVOL (DSPG)(XSTURG)
...... * ..............
VDLG CHARLG
This water flow term (units of liters/hour) is then used to
update symmetric locations in the WATFL matrix, giving an
apparent rate of exchange of fluids between the water column and
the interstitial pore waters of the benthic sediment compartment.
Chemical transport can then be computed by treating these water
flows as simple carriers for the dissolved fraction resident on
either side of the benthic boundary layer.
In some cases, exchanges across the benthic boundary layer
55
-------
can be treated as oeing driven by gradients in dissolved chemical
concentrations alone. Many synthetic organic chemicals, however,
have very high partition coefficients, so that sorption onto the
surface of the bed followed by bloturbational subduction is
probably a significant mechanise of chemical transport for these
compounds. The remaining exchange volume is therefore taken to
represent a direct interaction of the bed solids with the water
column compartment. First, an apparent "resuspension" or
"bursting" term for the exposure of the bed solids to the water
column is computed as the product of the sediTienttwater ratio
(SEDCOL) of the benthic zone and the fluid exchange rate. The
SEDFL matrix is thus updated by an apparent flow of bed sediments
(TEMSEO, units leg/hour) into the water colutin via the expression:
WATVQL (DSPGHXSTURG)
Eq. 2,78 TEMSED = SEDCOL * --.--- * --. ........
VOLG CHARLG
Strictly speaking, a "solids balance" now reguires that an
equal mass of sediment resettle on the bed, in order to maintain
the notion of a stable (steady-state) bed thickness. The
transport of a chemical across the benthic boundary layer can
then be computed by regarding the solid phase as a simple carrier
of sorbed chemicals, using sorbed concentrations (mg/kg solids)
on either side of the boundary.
The foregoing is, for the most part, conventional
compartment modeling. still, because a multitude of processes
have been summarized in a single kinetic expression, a careful
independent trial of the approach seemed warranted. Although a
number of experimental tests of the equations can be imagined,
initial tests were conducted by comparing the output from the
EXAMS program to a example situation constructed on theoretical
grounds alone. This test was conducted on a reduced subsystem of
the Noname slough ecosystem. Consider, for example, the vertical
segment of Noname Slough that includes a 2 m water column
underlain by a 5 cm mud deposit and a 30 cm layer of sand (Figure
2.3). If the transport characteristics of this subsytem are
redefined to eliminate the bedload and groundwater infiltration,
the dispersion equation can be used to describe vertical movement
of a chemical in the subsystem.
Retaining the physical sediment characteristics CSDCHPG,
PCTWAG) developed in section 2.3.1.3, the sorptive properties of
the sediments must now also be specified. For the example, let
the organic carbon content of the washload be 2% (FROCG * 0.02),
that of the mud layer 5%, and let the sand contain only 0.1%
organic carbon. The characteristic length (CHARLG) and exchange
cross section (XSTURG) for the dispersive exchanges can in this
instance be developed directly from the geometry of the system.
These values, along with the kinetic exchange coefficients (DSPG)
are given in Table 2.8. Vanderborght and wollast (1977), working
56
-------
with rhodamine dye in North Sea sediments, found that physical
turbulence induced benthic boundary layer exchange coefficients
of 2.9E-6 to 6.2E-4 square cm/sec. The test DSPG for Noname
Slough were selected from this range of values.
Table 2.8, Dispersive Interconnections for Noname Slough test subsystem
AEPL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: Unreactive test chemical: Koc = 3.E5
ECOSYSTEM: Noname Slough - Dispersion equation test data
TABLE 8. INPUT DATA DESCRIBING ENVIRONMENT: TURBULENT INTERCONNECTIONS.
COM?. NO. CJTURB) 7 8
CONNECTED (ITURB) 8 9
X-SECTION (XSTUR) l.OOOE+03 i.OOOE+03
CHAR. LN. (CHARL) 1.02 0.175
EDDY DISP. (DSP) 1.500E-04 3.600E-05
In order to test the dispersive transport alogorithm in
isolation, the test chemical can be specified as a completely
unreactive, non-volatile neutral compound, with a Koc of 3.E5.
When the test chemical is introduced into the system, an
equilibrium state could be rapidly generated by suspending the
benthic layers in the water column, and thoroughly agitating the
mixture. At equilibrium, this 4-phase system would exhibit a
single aqueous concentration, and sorbed-phase concentrations
differing as the ratio of their partition coefficients (i.e., in
proportion with the' organic carbon contents of the sediment
phases). If the bed solids were then allowed to resettle, the
simple separation of the materials would not result in any change
in the dissolved (mg/L of water) or sorbed (mg/Jcg dry solids)
concentrations. The environmental concentrations (mg/L of total
environmental volume) could, of course, differ between the water
column and the (restored) bed layers.
This situation also applies to an open system in a dynamic
equilibrium or steady state. Suppose, for example, that water
contaminated to a level of 1 ug/L (ppb) with the test chemical
flows continuously through the Noname Slough subsystem. The
dispersion equation controls only the rate of exchange of
chemical between the water column and the benthic subsystem. At
steady state, no concentration gradient remains to drive further
net chemical exchange. In this instance of an unreactive
compound, the final dynamic equilibrium is equivalent to the
static case.
The resulting computer output is shown in Table 2,9a, The
computations lead to a steady-state end point of equal sorbed
57
-------
concentrations for the washload and the mud layer, rather than
equal dissolved concentrations. Although the concentration
distribution between the bed sand and mud layers follows the
theoretical expectations, this result for the washload and the
mudlayer is exactly opposite the expected outcome of the test.
Table 2.9a. EXAMS test of dispersive exchange equations.
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: Unreactive neutral compound — Koc = 3.E5
ECOSYSTEM: Noname Slough -- Dispersion equation test data
•mm»mmm>mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm»
-------
coefficients (Kp). in this way, for example, if the Kp of the
bed sediment were 5 times that of the suspended sediment, the
rate of capture of chemical by the bed would be proportionally
larger than that suggested by Eq. 2.78 simply coupled to the
concentration on the washload, and conversely.
Although organic carbon content governs the ability of a
sediment to sorb neutral (uncharged) molecules, an organic acid
or base will occur as both neutral and charged species, with a
speciation governed by the pH of the system. The sorptive
capacity of a sediment may thus depend on its carbon content, ion
exchange capacity, and the pH of the compartment. Thus when
necessary, the relative sorptive capacity of sediment phases can
be computed via the distribution coefficients (ALPHA) and
sediment:water ratios (SEDCOL) of the water-column and benthic
compartments specified for an exchange pathway. Given
ALPHA(16,w) and ALPHA(16,b) as the total dissolved fraction in
the water column (w) and benthic (b) compartments, respectively,
and ALPHA(17,w) and (17,b) as the sediment-sorbed fractions, the
return "flow" (SEDFL) of suspended sediment across the benthic
boundary layer to the sediment compartment can be computed as:
ALPHA(16,w) * SEDCOL(w) ALPHA(l7,b)
TEMSEO * .-•• — ..-.-......-•••• * ....................
ALPHA(17,w) ALPHA(16,b) * SEDCOL(b)
This calculation yields the ratio of the sorptive capacity
(overall partition coefficient, Kp) of the benthic sediment, to
that of the washload. Thus for example, if the benthic sediments
have a Kp twice that of the washload, the rate of capture of
chemical by the bed (that is, the apparent pseudo-settlement rate
of saltatory bed materials) must occur at twice the rate that
would be inferred directly from the properties of the washload
itself.
The effect of this revision can now be tested by execution
of the test case described above; the results are given in
Table 2.9b. The consequences of the calculation are now quite
satisfactory: The calculated dissolved concentrations are
uniformly 0.625 ppb, and the sorbed concentrations reflect the
differences in organic carbon content of the system sediments.
Note, however, that this computation is valid within the context
of the EXAMS program only because sediment transport is not an
explicit state variable in the program, i.e., the SEDFL matrix is
not a description of sediment transport per se, but merely a
computational device for computing the exchange of synthetic
organic chemicals across the benthic boundary layer. "Solids
balances" and stable bed thicknesses are the responsibility of
the user when assembling an environmental description to drive
the program; EXAMS simply processes this data (via the SEDFL
matrix) to arrive at a proper characterization of chemical
transport in the system.
59
-------
Table 2.9b. F.XAMS test ot modified dispersive exchange equations
AEFL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: Unreactive neutral compound —• KOC = 3.E5
ECOSYSTEM: Noname Slough -- Dispersion equation test data
TABLE 13. DISTRIBUTION OF CHEMICAL AT STEADY STATE: IN THE WATER COLUMN:
COMP STEADY-STATE RESIDENT MASS **** TOXICANT CONCENTRATIONS ****
2 TOTAL DISSOLVED SEDIMENTS BIOTA
G/M KILOS % MG/* MG/L MG/KG UG/G
7 2.000E-03 2.0000E-03 100.00 l.OOOE-03 6.250E-04 3.75
SUBTOTAL: 2.ooooE-03 0.49
AND IN THE BOTTOM SEDIMENTS:
8 0.313 0.3125 76.61 9.38 6.250E-04 9.38
9 9.543E-02 9.5428E-02 23.39 0.188 6.250E-04 0.188
SUBTOTAL: 0.4079 99.51
TOTAL MASS (KILOGRAMS) s 0.4099
* TOTAL CONCENTRATION AS MG/L IN WATER COLUMN, AS MG/KG IN SEDIMENTS.
A fuller test of EXAMS' transport algorithms can be executed
by specifying the ion exchange capacities and organic carbon
content ot all sediment phases in Noname Slough (Table 2.10), and
by coupling the advective transport characteristics (Table 2.6)
to a full specification of exchange properties across the benthic
boundary layer (Table 2.11). Given a test chemical that is an
organic base with, say, a pKb of 7.4, and a KCECG of 250., while
retaining the Koc of 3.E5, EXAMS computes the Kp of sediment
phases as a function of the pH in each sector of the ecosystem.
Given a pH of water
Noname Slough muds of
column compartments of 8,0, a pH in the
6.0, and a pH of 7,0 in the sand
(compartment 9), EXAMS transport profile of the system is given
in Table 2.12, Note that the transport profile reflects both
physical characteristics of the ecosystem, and interactions of
the compound with the chemistry of the system. The residence
times in EXAMS' transport profiles, which indicate the local
strength of transport processes in each compartment, are thus an
amalgam of chemical and physical properties and will, therefore,
differ for compounds of differing sorptive properties. In other
words, these residence times should not be interpreted in terms
of sediment dynamics or hydraulics; they refer to the kinetics
of transport of the synthetic organic compounds forming the
subject matter of EXAMS,
60
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Table 2.10. Properties of Noname Slough sediments
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: Unreactive organic base: Koc = 3.E5, Kcec * 250
ECOSYSTEM: Noname Slough - full transport regime
TABLE 5. INPUT DATA DESCRIBING ENVIRONMENT: SEDIMENT CHARACTERISTICS.
TY
1L
2B
3L
4B
5L
6B
7L
8B
98
SDCHR
(1)
100.0
1.200
100,0
1.200
100.0
1.200
100.0
1.200
1.950
PCTWA
(2)
180.0
180.0
180.0
180.0
115.0
FROC
(3)
2.0000E-02
5.0000E-02
2.0000E-02
5.0000E-02
2.0000E-02
5.0000E-02
2.0000E-02
5.0000E-02
l.OOOOE-03
CEC
(4)
15.00
10.00
15.00
20.00
15.00
20.00
15.00
25.00
0.1000
AEC
(4)
12.00
12.00
12.00
14.00
12.00
16.00
12.00
18,00
0,1000
DOC
MG/L
(1) UNITS: MG/L SUSPENDED SEDIMENT IN L, E, H; BULK DENSITY (G/CC) IN B
(2) 100 * F.W./D.tf. IN B,
(3) DIMENSIONLESS.
(4) MEQ/100 GRAMS DRY WEIGHT.
Finally* the exposure concentrations resulting from a load
of the organic base that contaminates the first sector of Noname
Slough to a level of 1 ppb is given in Table 2.13, The dilution
effects of bedload transport, groundwater entry (at compartment
6), and the tributary inflow (at compartment 3) can be seen in
these results. In this case, the advectlve flows through the
system result in steady-state exposures that differ substantially
from a simple chemical equilibrium state. The dispersive
exchange terms are nonetheless necessary for a complete
description of the system: These terms serve as the only
available descriptors of interactions between the bedded
sediments of compartments 2, 4, and 6 with their overlying water
columns.
61
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Table 2.11. Dispersive transport specifications for Noname Slough
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: Unreactive organic base: KOC = 3.E5, Kcec = 250
ECOSYSTEM: Moname Slough - full transport regime
TABLE 8. TNPUT DATA DESCRIBING ENVIRONMENT: TURBULENT INTERCONNECTIONS.
COMP. NO.
CONNECTED
X-SECTION
CHAR. LN.
EDDY DISP.
(JTURB)
(ITURB)
(XSTUR)
(CHARL)
(OSP)
7
8
i.oooE+03
1.02
1.500E-04
1,
0,
8
9
OOOE+03
175
3.600E-05
1
2
l.OOOE+03
1.02
1.500E-04
3
4
800.
1.02
1.500E-04
5
6
200.
1.02
1.500E-04
Table 2.12. Complete transport profile of organic base in Noname Slough
AEPL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: Unreactive organic base: KOC = 3.E5, Kcec = 250
ECOSYSTEM: Noname Slough - full transport regime
TABLE 9. TRANSPORT PROFILE OF ECOSYSTEM.
CP T*
Y
1L
2B
3L
4B
5L
6B
7L
8B
9B
VOLUME
(CUBIC M)
2.000E+03
50.0
1.600E+03
40.0
400.
10.0
2.000Et03
50.0
300.
SEDIMENT WATER FLOW SED. FLOW
MASS (KG) (CU. M/DAY) (KG/DAY)
200.
3.333E+04
160.
2.667E+04
40.0
6.667E+03
200.
3.333E+04
5.087E+05
237.
2.83
414.
3.42
63.0
5.17
472.
15.1
11.3
2.007E+03
3.541E+03
2.261F+03
4.273E+03
561.
468.
3.216E+03
4.749E+03
0.000
RESIDENCE TIME (DAYS)
WATER SEDIMENTS
8.44
9.41
3.86
6.24
6.35
1.03
4.23
1.76
6.72
9.966E-02
9.41
7.077E-02
6.24
7.128E-02
14.2
6.219E-02
7.02
* COMP. TYPE: "L"sLITTORAL; "E"*(EPI) AND "HBs(HYPO)LJMNION; "B"*BENTHIC
62
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Table 2.13. Exposure concentrations of organic base in Noname Slough
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: Unreactive organic base: Koc = 3.E5, Kcec = 250
ECOSYSTEM: Noname slough - full transport regime
TABLE 13. DISTRIBUTION OF CHEMICAL AT STEADY STATE: IN THE WATER COLUMN:
COMP STEADY-STATE RESIDENT MASS
2
G/M KILOS %
**** TOXICANT CONCENTRATIONS ****
TOTAL DISSOLVED SEDIMENTS BIOTA
MG/* MG/L MG/KG UG/G
1 2.
3 5.
5 1.
7 4.
OOOE-03
039E-04
877E-03
442E-04
SUBTOTAL:
AND I
2 6.
4 3.
6 0.
8 3.
9 1.
2.0000E-03
4.0315E-04
3.7547E-04
4.4420E-04
3.2228E-03
62.
12.
11.
13.
1.
06
51
65
78
79
1
2
9
2
•
*
*
•
OOOE-03
520E-04
387E-04
221E-04
6.
1.
5.
1.
284E-04
583E-04
898E-04
396E-04
3
0,
3
0.
.72
936
.49
825
N THE BOTTOM SEDIMENTS:
939E-02
570E-02
138
641E-02
539E-02
SUBTOTAL:
TOTAL
MASS (K
6.9387E-02
2.8560E-02
2.7519E-02
3.6411E-02
1.5394E-02
0.1773
ILOGRAMS) a
39.
16.
15.
20.
8.
98.
0
14
11
52
54
68
21
.1
3
805
2
1
4
1
•
.08
.07
.13
.09
026E-02
4.
1.
5.
1.
1.
155E-04
528E-04
890E-04
364E-04
364E-04
2
1
4
1
3.
.08
.07
.13
.09
024E-02
* TOTAL CONCENTRATION AS MG/L IN WATER COLUMN, AS MG/KG IN SEDIMENTS.
2.3.1.5 Transport of synthetic organic chemicals
EXAMS uses the transport field defined by WATFL, SEDFL,
WATOUL, and SEDOUL to compute first-order coefficients that
describe transport of chemical through the ecosystem. These
coefficients describe the export of chemicals from the system,
and the internal transport of the compound among the compartments
used to define different pnysical sectors of the system.
The WATOUL and SEDOUL vectors are used to compute exports
from each compartment. A value of EXAMS' internal vector EXPQKL,
with dimensions of (liters/hour) , is calculated for each
compartment as EXPOKL *
SEDOUL
ALPHA(16)*WATOUL t ALPHA( 17)*
ALPHA( 18 )*WATOUL*PLRAG
SEDCOL
where ALPHAU6), (17), and (18) are the total fractions of the
chemical in dissolved, sediment-sorbed, and biosorbed states,
respectively. The transport of biosorbed material is restricted
to the planktonic fraction (user input datum PLRAG). Planktonic
63
-------
organisms are by definition subject to transport by water flows.
EXAMS' computations therefore assume that this fraction of the
chemical is free to move along all water-transport pathways,
rather than imposing a set of special transport rules akin to the
sediment transport rules of Section 2.3,1.3.
Pollutants also leave each compartment via water and
sediment flow pathways that connect the compartment to other
sectors of the ecosystem. F'rom the perspective of the donor
compartment, these flows can be represented as a pure export of
chemical across the boundaries of the compartment, despite the
fact that the material may be returned from the receptor
compartment at some later time. Each row of the WATFL and SEDFL
matrices gives tne flows of water and sediments leaving a
compartment, and tne row sums are the total local (that is,
within-system) outflows from the compartments. F'or each
compartment, EXAMS computes a value of an internal variable
(INTOUL, liters/hour) analogous to the export vector EXPOKL.
This computation can be represented as INTOUL =
SUMSED
ALPHA(16)*SUMWAT + ALPHA(17)*•----- 4 ALPHA( 1 8 ) *SUMKAT*PLRAG
SEDCOr,
where SUMriAT and SUSSED are the appropriate row sums in the WATFL
and SEDFL matrices, and SEDCOL and PLRAG are the sediment:water
ratio and planfctonic biomass fraction for the donor compartment.
These transport terms (EXPOKL and INTOUL) must now be
converted to pseudo-first-order coefficients that express tJheir
effect on the concentration of chemical in the source (donor)
compartment. This coefficient (CONOUL, dimensions /hour) is
computed as:
EXPOKL f INTOUL
Eq. 2.79 CONOUL =
WATVOL
where WATVOL is the volume of water (liters) present in the donor
compartment. This coefficient (CONOUL) is the contribution of
transport processes to the overall loss constant HK" of Eq. 2.1.
Intra-system transport also imposes chemical loadings on the
compartments receiving the contaminated flows (factor "Li" in
Eg. 2.1). EXAMS combines the WATFL and SEDFL matrices into a new
matrix (JNTINL, dimensions liters/hour) needed for computing the
internal loadings (Li) on each compartment. Each element of
INTINL is first calculated from the sum of corresponding elements
in WATFL and SEDFL via the expression:
64
-------
SEDFL
ALPHA(16)*WATFL t ALPHAU7) *------ + ALPHAC18)*WATFL*PLRAG
SEDCOL
using values of ALPHA, SEDCOL, and PLRAG for the donor
compartment.
Multiplication of each element of INTINL in a given row, by
the concentration of chemical in the donor compartment given by
the successive column indices of the row, yields the magnitude of
the loadings passed to the receptor compartment by each of the
donors. The sum of these loadings is the internal load (Li,
mg/hr) on the receiving compartment. Li must also be divided by
the aqueous volume of the receptor ("V" in Eq. 2.1), in order to
express the effect of the internal loadings on the concentration
of chemicals in the receptor. EXAMS therefore divides each
element of INTIML by the volume of the receiving compartment:
INTINL <—• INTINL/WATVOL
and retains the resulting matrix of pseudo-first-order
(dimensions /hr) coefficients for subsequent use in its
steady-state and kinetic simulation equations (Section 2.5).
2.3.2 Volatilization
EXAMS uses a two-resistance model to compute export of
synthetic organics across the air-water interface. The
two-resistance or "two-film" models, although originally
developed for industrial applications (Whitman 1923), have
recently been successfully adapted to environmental problems by
Liss (1973), Liss and Slater (1974), Mackay and Leinonen (1975),
and Macfcay (1978). For its derivation, whitman (1923) pictured
the air-water interface as being composed of "stagnant films" of
air and water, bounded by well-mixed bulk phases on either side
of the interface (Figure 2.4, redrawn from Liss and Slater 1974).
The flux of compound (F, moles/ma/hour) through the aqueous film
can be described using Pick's first law:
Eq. 2.80 F = D(dC/dZ)
where D is the aqueous diffusion constant of the chemical in the
film (m2/hr), C is the concentration of unionized, unsorbed
compound (mol/cubic m), and dC/dZ is the concentration gradient
In the film. The flux of chemical through the stagnant
atmospheric layer is, similarly, given by:
Eq. 2.81 F s D/RT (dP/dZ)
where D is now the diffusion constant of the compound in the air
layer, dP/dZ is the partial pressure (atmospheres) gradient in
65
-------
Increasing C and P
Connective
transport
Psg
Gas film
Molecular
diffusion
I
I Air
I
Interface /
I
I Water
I
v
Liquid film
Molecular
diffusion
Csl
Z i
I
I
I
I
Cl
Convective
transport
Figure 2.4. Whitman (1923) two-resistance or two-film model of a
gas-liquid interface. Cl is concentration (mol/cubic m) in bulk
water, Pg is partial pressure (atm) in bulfc air, Csl is aqueous
concentration in liquid at the interface, Psg is partial pressure
on atmospheric side of interface (after Liss and Slater 1974).
66
-------
the film, R is the gas constant (8.206E-5 cubic fl - atm/ mol K),
and T is Kelvin temperature.
Environmental gas exchange processes are often formulated in
terms of an "exchange constant" k, which expresses the
conductivity of the film to gas transport. The exchange constant
has dimensions of velocity (m/hr); it is also known as the "mass
transfer coefficient," "permeability coefficient,"
"adsorption/exit coefficient," and "piston velocity." The flux of
gas through the stagnant layers is given as
Eq. 2.82 F = (kl) dC (liquid phase), or (kg) dP/RT (gas phase)
where dC (dP) is the concentration (partial pressure) difference
across the film, and k = D/z, z the film thicknesses. The
reciprocals (r * 1/k) of the exchange constants give the
transport resistances of the aqueous and atmospheric interface
zones.
Given a steady-state transport of gas through the interface,
the flux through the stagnant layers of air and water (Figure
2.4) must be the same. Therefore, Eq. 2,82 implies that
Eq. 2.84 F = kl (Csl - CD = fcg/PT (Pg -Psg)
where kl is the liquid phase, and kg the gas phase, exchange
coefficient. The partitioning of the exchanging (unionized)
substance across the air-water interface is given by Henry's Law:
Eq. 2.85 Psg * H (Csl)
where H is the Henry's Law constant (atm - cu. *n/mol). Csl and
Psg can be eliminated between Eqs. 2.84 and 2.85, yielding an
equation relating the transport flux to the bulk phase
concentrations only:
Eq, 2.86 F « Kl (Pg/H - CD , where
Eq. 2.87 1/K1 = 1/kl * RT/(H*kg)
The total resistance to transfer of a gas across the
air-water interface (Ri s 1/KD is thus the sum of the series
resistances in the liquid (l/ki) and gas (RT/(H*kg)) phases of
the interface. The two-resistance model assumes that transport
resistance at the interface can be neglected; although generally
this is the case, under very turbulent conditions or in the
presence of surface-active contaminants this assumption is less
tenable (Bird, Stewart, and Lightfoot 1960:652).
The "two-film" picture of the air-water interface (Figure
2.4) is physically unrealistic, although events at molecular
scales undoubtedly have an effect on interphase transport. Both
67
-------
atmospheric and hydrodypamic eddy turbulence must often extend to
the air-water interface, however, and the notion of a
discontinuous transition from turbulent flow to a stagnant film
near the air-water interface cannot be seriously entertained.
The supposition that the interface is composed of stable, uniform
films is still less plausible. The two-resistance models do,
however, explicitly recognize that transport resistance occurs
both in the aqueous and in the atmospheric regions of the
air-water interface. There is ample precedent (see, for example,
Fischer et al. 1979) for amalgamating the effects of intermittent
turbulent and advective transport events occurring in the
interfacial zone, into an effective dispersion coefficient D or
exchange constant k. Furthermore, predictions derived from
two-resistance models usually differ very little from the
predictions of more complex (e.g., surface-renewal theory) models
(Danckwerts 1970). Laboratory studies of the volatilization of
chlorohydrocarbons from dilute aqueous solution Dilling 1977;
Dilling, Tefertiller, and Kallos 1975) have provided further
evidence that two-resistance models are good predictors of fluxes
of organic chemicals across the air-water interface.
A two-resistance model has been used to compute the
transport of atmospheric contaminants (sulfur dioxide, carbon
tetrachloride, etc.) into the world ocean (Liss and Slater 1974).
Such an application requires a Knowledge of Pg, the bulk
atmospheric partial pressure. Lacking a measured value of Pg, it
can in some circumstances (global models, plume (stack gases)
dispersion models) be calculated and coupled to a two-resistance
interphaSe transport model. Usually, however, bulk atmospheric
transport of organic pollutants volatilized froir> aquatic systems
is so rapid that Pg can be neglected (Mackay and Leinonen 1975,
Mackay 1978). This approach was adopted for EXAMS, resulting in
a simplification of Eg. 2.86, yielding
Eq, 2.88 F a -Kl (CD
Because EXAMS was designed, among other things, for
pre-manufacture evaluation of new chemicals, there was, in any
case, little likelihood that measured values of Pg would be
readily available for use in the model. EXAMS does not entirely
preclude atmospheric inputs, however. EXAMS' loading functions
allow for entry of spray drift (DRFLDG), and for rain-out
(PCPLDG) loadings, where these can be computed (see Section 2,4
for a discussion of pollutant loadings in EXAMS).
For use in EXAMS, Eg. 2.88 must be rephrased to give the
effect of volatilization on the concentration of pollutant in
each sector of the ecosystem (compartment) having an air-water
interface. EXAMS* concentration variable ([C], Eq. 2.1) is the
total concentration of pollutant in units of mg/liter of aqueous
volume. Multiplication of both sides of Eq. 2.88 by
MWTG*AREAG/VOLG, where MWTG is the gram molecular weight of the
68
-------
compound, AREAG is the area of the air-water interface (square
meters), and VOLG is the volume (cubic meters) of the
compartment, gives
Eq. 2.89 dCC]/dt = -(K1*AREAG/VOLG) * (ALPHA(i)) * ICJ
The additional factor ALPHA(l) is the fraction of the total
pollutant concentration tCJ present as a volatilizable
(unionized, unsorbed) chemical species (Section 2.2.4). The
group (K1*AREAG/VOLG)*(ALPHA(1)) is a pseudo-first-order rate
constant with units /hr. This rate constant is computed in
EXAMS' subroutine "VQLAT;" it is the volatilization contribution
to the total pseudo-first-order rate constant given as parameter
"K" in EQ. 2.1.
EXAMS' two-resistance model reduces at this point to a
computation of the transport resistances (or exchange constants)
of chemical pollutants in the liquid (1/<1) and atmospheric
(RT/(H*kg)) zones of the air-water interface. These transport
resistances are governed by the intensity and duration of
physical turbulence and convective motions in the interface
zones. Following a suggestion of Liss and Slater (1974), EXAMS
indexes the transport resistance of chemical pollutants against
the exchange properties of well-studied environmental substances.
The transport of oxygen across the air-water interface of aquatic
systems (reaeration) has been studied for -nany years. Oxygen
transport is controlled by resistance in the liquid phase (Liss
1973). The exchange constant for dissolved oxygen thus provides
a measure of turbulence on the liquid side of the air-water
interface, water itself, as the solvent for chemical pollutants
in aquatic systems, has no transport resistance in the liquid
phase of the interface: its transport is controlled by events in
the atmospheric zone of the interface.
Given exchange constants for oxygen and for water vapor
(note that the latter is not the same as the evaporation rate),
it remains to index the transport resistances of the pollutant to
those of the environmental referents. Several Indexing methods
have been proposed. Kinetic theory suggests that the average
molecular Kinetic energies of all chemicals present in a given
zone of the Interface are the same, and, therefore, that average
molecular velocities in a multi-component mixture should
distribute in proportion to the square root of the molecular
weights of the components. Liss and Slater (1974) suggested this
form of Indexing. EXAMS uses this method for relating the
exchange constant for water vapor to the vapor-phase
volatilization resistance of pollutants. The temperature of the
vapor is assumed to be the same as the water temperature
specified for the appropriate aquatic compartment. EXAMS thus
computes the vapor-phase transport resistance (RESGAS) from the
equation:
69
-------
Eq. 2.90 RESGAS = (TKEL*8. 206E-5) / UAT*H£NRY*SQRT (18 . /MWTG) )
where TKEL is Kelvin temperature, MI is the water vapor exchange
constant, HENRY the Henry's Law constant, and the molecular
weight of water is taken as 18.
Reasoning from the Stokes-Einstein equation, Tsivoglou
(1967) suggested that the (liquid-phase dominated) exchange
constants for molecular oxygen vs. the normal atmospheric gases
(Kr, Ra, He, etc.) are linearly related to their relative
molecular diameters or, equivalently, their molecular diffusion
constants in water. A literal interpretation of the Whitman
"two-film" derivation gives much the same result. Models based
on surface-renewal theories suggest, however, that relative
exchange constants should vary as the square root of
diffusivities (DancKwerts 1970:100). Doboins (1964) constructed
an elegant hybrid of film and surface-renewal theory that
collapses to a Whitnan model under quiescent conditions, and to a
surface-renewal model under more turbulent conditions. He also
found, via laboratory studies, that the appropriate root of the
diffusivity ratio for the nitrogen/helium gas pair tended from
0.985 to 0.648 with increasing water turbulence, as expected from
his theoretical equations. Given the uncertainties in estimating
or averaging oxygen exchange constants, however, a full
development of the Dobbins model for inclusion in EXAMS seemed
unwarranted.
The molecular diffusivity of a new organic chemical is not
often known, although it frequently can be estimated from other
chemical properties (Reid, Prausnitz, and Sherwood 1977). The
molecular weight of an organic compound is almost always
available, however, so EXAMS uses Liss and Slater's (1974)
molecular weight corrector as its default technique for relating
the liquid-phase transport resistance of a pollutant to exchange
constants of dissolved oxygen (parameter K02G). The liquid-phase
transport resistance (RESLiQ) is then simply:
Eq. 2.91 RESLIQ = l./(K02 * SORT[32./MWTGJ)
where K02 is the oxygen (molecular weight 32) exchange constant.
EXAMS, however, also provides a user-specified input parameter
(KVOG) that overrides the default procedure when it is non-zero,
A user can thereby specify the oxygen exchange index as a simple
ratio of diffusivities, a diffusivity ratio to any fractional
power, or via an experimental value meausured by the technique of
Hill et al, (1976), corrected as appropriate for differences
between laboratory and field turbulence conditions. When KVOG is
non-zero, EXAMS computes the liquid-phase transport resistance
as:
Eq. 2,92 RESLIQ = 1,/(K02*KVOG)
70
-------
The total transport resistance of the pollutant Is the
simple sum of the individual phase transport resistances. The
exchange constant of the pollutant (EXAMS' parameter "COND"
(conductivity)) is the reciprocal of that sum (Ki » COND =
l./(RESLIQ + RESGAS)). EXAMS computes the pseudo-first-order
volatilization rate constant as:
COMD * ALPHA(l) * AREAG / VOLG
as the final computational step in subroutine VOLAT.
2.3.2.1 Chemical data entry
The chemical parameters governing volatilization of a
pollutant from aquatic systems can be entered into EXAMS'
chemical data base in several ways. The gram molecular weight of
the pollutant (MWTG) is required, for computation of the
vapor-phase transport index (Eq, 2.90). The Henry's Law constant
(HENRY) can be loaded, however, either as a single value of
HENRYG (atm-m3/mol), or as a funtion of temperature, fehen
parameter EHENG is loaded as a non-zero value, EXAMS computes the
Henry's Law constant at local temperatures TCELG from the
relationship:
Eq, 2.93 log(HENRY)= HENRYG - {[1000*EHENGJ/[4.58(TCELG+273.15)J>
Given a zero value for HENRYG, but a non-zero value for the vapor
pressure of the compound, EXAMS Internally computes the Henry's
Law constant from the vapor pressure/solubility ratio (Macfcay and
wolKoff 1973, Macicay and Leinonen 1975). If either the vapor
pressure or the solubility of the compound have been entered as
functions of temperature, these data are adjusted to local
(TCELG) temperatures (via Eq. 2,94 and/or Eq, 2,95), prior to
computation of HENRY,
Eq, 2,94 log(VAPR)* VAPPGM[1000*EVPRG) / [4,58(TCELG+273,15)1}
Eq, 2.95 SOL * 1000*MWTG*{10**[SOLG -
UlOOO*ESOLG)/[4.58(TCELG+273.15)J> ])
Note that, although a simple (temperature invariant) pollutant
solubility Is entered in units of mg/L (ppm), EXAMS expects
solubility as a function of temperature to be entered via the
ideal solubility law, that is, as the dependence of molar
solubility on temperature.
2,3.2,2 Exchange constants for water vapor
The water vapor exchange constant (WAT, Eq, 2,90) used to
compute the vapor-phase transport resistance of pollutants is not
71
-------
itself a direct user input to felXAMS. Liss (1973), in a series of
wind-tunnel experiments, found the piston velocity of water vapor
to be a linear function of windspeed. EXAMS takes, as its user
input variable, the average windspeed at a height of 10 cm above
the water surface (input variable MNDG, m/s). The exchange
constant for water vapor (WAT) is computed separately for each
compartment from these data. Liss' results can be represented
via a linear regression equation that includes the shift in units
from m/s tor wind speed to m/hour for the *ater vapor exchanqe
constant!
Eq. 2.96 WAT = 0.1857 + 11.36 * wlNDG
in which changes in wind velocity at 10 cm above the water
surface (WI^DG) account for 98.3% of the variance in the exchange
constant for water vapor («AT, m/nr) over a range of windspeeds
from 1.6 to 8.2 m/s.
windspeeds observed at other heights can be converted to
windspeed at 10 cm via the usual assumption of a logarithmic wind
profile (Israelsen and Hansen 1962). The numerical result of the
conversion depends to some extent on the unit of measurement used
for height. More exactly, windspeeds Ul and U2 at heights Zl and
Z2 are related by:
U1/U2 = log(Zl/Zo)/log(Z2/Zo)
where Zo, is the "effective roughness height." The roughness
height is generally on the order of one millimeter; wind
measurement heights thus should be expressed in mm in order to
achieve a vertical translation of an observed windspeed datum.
For example, many terrestrial USA weather stations measure
windspeeds at 18-20 feet (6 m) above ground level, windspeed at
10 cm can be estimated by multiplication of this datum by (log
100)/(log 6000), that is» by reducing the observation by a factor
of 1.89. The standard observational height for windspeed data in
oceanographic investigations is 10 m, in this case requiring
reduction of the data by a factor of 2, to generate values of
WINDG for EXAMS.
2.3.2.3 Exchange constants for molecular oxygen
Hydrodynamic turbulence near the air-water interface is
generated by a variety of mechanisms. In swiftly flowing streams
and rivers, bed shear stress on the moving waters generates eddy
turbulence that can keep the entire water column in a state of
constant agitation. Where rivers widen into coastal estuaries,
advection velocities decrease, but the motion of the tides tends
to maintain strong turbulence in the surface waters. In lakes
and in the open ocean, wind stress is a primary force producing
turbulent motions in the upper part of the water column,, Wind
72
-------
waves travel far beyond the storm systems producing them in the
largest laices and in the oceans, and tne great ocean currents and
upwelling zones generate upper water turbulence beyond that
attributable to the winds alone. In smaller lakes, wind stress
may be directly responsible for most of the hydrodynamic motion
in the system.
EXAMS requires an oxygen exchange constant as an input datum
for each compartment from which a pollutant can volatilize. The
input datum (KQ2G, cm/hr) is assumed to be the exchange constant
measured at 20 degrees C, or corrected to that temperature.
EXAMS uses the conventional engineering correction Cequivalent to
an Arrhenius expression) for converting K02G to the temperature
(TCELG) of each compartment (Kramer 1974):
Eq. 2.97 K02L * (K02G/100.) * (1.024)**(TCELG - 20.)
(K02G is also divided by 100 to convert cm/hr to »/hr).
Reaeration rates can be measured in the field in a number of
ways, including tracer techniques (Tsivoglou, McClanahan, and
Sanders 1972) and oxygen release into a nitrogen-sparged dome
(Copeland and Duffer 1964, Hall 1970). Lacking measured values,
oxygen exchange constants can in many instances be estimated from
other properties of the system. Kramer (1974) has briefly
reviewed the available predictive equations for estimating oxygen
exchange coefficients in streams and rivers. Most of these
contain terms for flow velocities and depth. Many also include
longitidunal dispersion coefficients, energy grade lines, and
channel widths. Although predictive equations have been
successfully used for riverine systems, generally these equations
significantly undef-predict reaeration in estuarine systems.
Oxygen exchange constants in rivers are generally on the order of
5 to 20 cm/hr. In estuaries, exchange constants of 4 to 25
cm/hr, and as large as 100 cm/hr, have been observed. Liss and
Slater (1974) estimated an average exchange constant for the open
sea of 20 cm/hr.
In laices and ponds, reaeration may be primarily determined
by the local winds. Banks (1975, Banks and Herrera 1977) showed
that the effect of wind on reaeration rates can be separated into
two distinct zones* At windspeeds (at 10 m height) less than
about 5.5 m/s, exchange constants correlate with the square root
of windspeed. At higher windspeeds, the exchange constant
increases as the square of the wind velocity. Banks (1975)
gives:
Eq. 2.98 KL * (4.19E-6) SQRT(U) for U < 5.5 a/s
Eq. 2.99 KL » (3.2E-7) U**2 for U > 5.5 m/s
where KL is the oxygen exchange constant (in m/s) and U Is
73
-------
windspeed (m/s) at 10 m above the water surface. Over a range of
windspeeds from 1 to 30 m/s, the oxygen exchange constant thus
would change from 1.5 to 104 cm/hr.
2.3.2.4 Example applications
A number of reports on volatilization from natural water
bodies have been published. These studies provide good
illustrations of of the general utility and level of reliability
of the two-resistance model used for EXAMS.
2.3.2.4.1 Radon in small lakes in the Canadian Shield
Emerson (1975) conducted an experimental investigation of
the loss of radon gas (Rn 222) from snail lakes in Canada's
Experimental Lakes Area (ELA). He reported his results in terms
of exchange constants for Rn gas; the "best estimate" was 0,16
to 0.40 m/day. Average wind velocities, measured 1 m
water surface, were about 1,5 m/s. Summer
temperatures in these lakes are about 20 degrees C
1971), Windspeed and temperature suffice, given the
constant for Rn, to derive an independent estimate
exchange constant from EXAMS' two-resistance model.
was
above the
epilimnion
(Schindler
Henry's Law
of the Rn
EXAMS computes both a gas- and liquid-phase transport
resistance. Rn transport is usually controlled by the
liquid-phase resistance. Under a sufficiently stagnant airmass,
however, gas-phase resistance can be greatly magnified. In this
instance, computation of the gas-phase resistance serves to
illustrate EXAMS* procedure, and to demonstrate that Rn transport
is controlled by events in the liquid phase of the air-water
interface of these lakes.
Wilhelm, Battino,
solubility of radon gas
pressure. The Henry's
between 0 and 50 degrees
and Wilcock (1977) give the aqueous
as the mole fraction under 1 atm partial
Law constant (atm-m3/mol) of Rn gas
C can be computed from their data:
T(deg. C): 0 5 10 15 20 25 30 35 40 45 50
mol frXE4: 4.24 3.40 2.77 2.31 1.95 1.68 1.46 1,29 1.16 1,05 0.96
HENRYX100; 4.25 5.31 6.50 7,81 9.24 10.8 12.3 14.0 15.6 17.2 18.8
Regression of these data on the model
HENRY s A exp(-B/RT)
74
-------
where R is the gas constant (1.9872 cal/deg mol) and T is Kelvin
temperature, yields A s 660,5 and B/R = 2615, accounting for 99%
of the variation in HENRY with temperature. EXAMS' input data
thus could include;
HENRYG = log A = 2.82
and
KHENG * (B/R) * R * 0.001 (kcal/cal) = 5.197 kcal/mol
EXAMS would then compute local (compartment-specific) values of
the Henry's Law constant for Radon, as a function of
environmental temperatures (TCELG), via Eq. 2.93. In what
follows, the Henry's Law constant at 20 degrees C will be taken
as 0.09239 atm-m3/mol.
A piston velocity for water vapor (foAT, Eq, 2.96) can be
computed from the observed windspeed datum (1.5 m/s at 1000 mm
height). EXAMS' input datum (WINDG) is referenced to a 10 cm
height above the water surface. The observed windspeed can be
corrected to a 10 cm height by assuming a logarithmic wind
velocity profile:
WINDG a 1.5 (log 100 / log 1000) = 1.0 m/s
The water vapor exchange constant (Eq.2,96) is then:
WAT * 0.1857 t (U.36H1.0) * 11.5 rn/hr
and the gas-phase transport resistance (RESGAS, here Rg,
Eq. 2.90) is:
Rg * (293.15*8.206E-5) / (11.5*0.09239*SQRT[18/2221) = 0,079 hr/m
Emerson's (1975) investigations were conducted in small
(3.6-5.6 ha), shallow (mean depth 3,6-5.6 m) dimictic lakes with..
relatively long hydraulic residence times (3.2-4,2 yr) (Brunskill
and Schindler 1971). The hydrodynamics of these lakes are
clearly dominated by wind stress, and Banks' (1975) equations
(Eqs. 2.98 and 2.99) can be used to estimate an exchange
constant for molecular oxygen. The input datum for these
equations should be referenced to a height of 10 ra above the
water surface. The observed datum thus must be translated to
10-m height via:
U * 1.5 (log 10000 / log 1000) » 2.0 m/s
U is less than 5.5 m/s; Eq. 2.98 therefore applies and KL 9
4.19E-6 SQRT(2.0) * 5.93E-6 m/s. EXAMS' input datum (K02G) has
dimensions of cm/hr; the units conversion yields K02G = 2.13
cm/hr.
EXAMS' default technique for estimating the liquid-phase
75
-------
transport resistance uses the molecular weight of the pollutant
as an indexing factor. The temperature ot the epilironlon (20
degrees C) in this case Deviates the need for conversion of K02G
to a differing value at the temperature of the environment
(Eq. 2.97). The liquid-phase Rn transport resistance (RESLIQ In
Eq. 2.91, here designated Rl) can be computed as:
Rl = I/CO.0213 * SQRTC32/222J ) = 123.66 hr/m
Resistance in the liquid phase thus amounts to 99.9% of the total
Rn transport resistance (Rt = Rg + PI = 123.74 hr/m). The
estimated exhange constant for Rn gas is therefore 1/Rt = 8.08E-3
m/hr = 0.19 m/day, which value can be compared to Emerson's
(1975) experimental estimate of 0.16 - 0.40 m/day.
EXAMS also allows for the entry of a user-specified
liquid-phase transport index (KVGG, Eq. 2.92), where this
parameter has been measured experimentally, or has been estimated
from the aqueous diffusivity of the pollutant. Emerson (1975,
citing Rona (1918) via Peng (1973)) gives a diffusion constant
for Rn of 1.37E-5 cnr\2/s at 25 degrees C, The diffusion constant
of molecular oxygen in water at 25 degrees is 2.41E-5 cm2/s
(Vivian and King 1964, cited from Reid, Prausnitz, and Sherwood
1977:576). The diffusivity ratio (KVOG = 0(Rn)/D(02)) is thus
1.37/2.41 a 0.568. Application of Eg. 2.92 then yields a
liquid-phase transport resistance in these small lakes of:
Rl = 1/[(0,0213)CO.568)1 s 82.6 hr/m
and a Rn exchange constant (i/(Rl*Rg)) of 0.29 m/day. Tsivoglou
(1967) measured simultaneous exchange constants for oxygen and Rn
in laboratory experiments, arriving at a value of KVOG * 0,70,
(This value corresponds to the 0.63 root of the diffusivity
ratio.) Application of Eq, 2.92 in this case yields Rl »
l/(.0213)(0.70) = 67.1 hr/m, and a Rn exchange constant of 0.36
ro/day,
EXAMS' estimates of the Rn exchange constant (0.19, 0.29,
and 0,36 m/day) thus encompass essentially the same range as
Emerson's (1975) experimental "best estimates" of 0.16 to 0,40
m/day. The critical element in an accurate application of EXAMS
to this situation is obviously, therefore, the selection of
appropriate values for the environmental driving variables (WINDG
and K02G), rather than the choice of a method of indexing Rn
transport against EXAMS' environmental descriptors, Liss and
Slater (1974) have estimated average exchange constants for
oxygen (20 cm/hr) and water vapor (3000 cm/hr) applicable to the
surface ot the open sea. These values have on occasion been used
to estimate the volatilization of pollutants from inland waters.
For Rn transport in these small ELA lakes, use of Liss and
Slater's (1974) oceanic exchange constants would give:
76
-------
Rg s (293.15*8.206E-5)/(30,0*0.09239*SQRTtlB/222J) = 0.0305 hr/m
Rl ~ 1/(0.2*SQRT132/222J) a 13.17 hr/m
Rt = Rg + Rl = 13.2 hr/m
and a Rn exchange constant (1/Rt) of 1.8 m/day. The fallacy of
an uncritical extrapolation of environmental driving forces (in
this case the reaeration rate) between systems is apparent: The
ELA Rn exchange constant, estimated from oxygen and water vapor
transport in the open sea, is an order of magnitude too large, as
compared with either the measured values, or to estimates from
EXAMS' two-resistance models parameterized via windspeed and
Banks' (1975) compilation of reaeration rates as a function of
wind velocity.
2.3.2,4.2 1,4-dichiorobenzene in Lake Zurich
Schwarzenbach and coworkers (1979) conducted a one-year
study of the fate and transport of 1,4-dichlorobenzene (DCB) in
Lake Zurich, Switzerland. Contaminated effluents from
waste-water treatment plants are the primary source of DCB
loadings entering the laice. The concentration of DCB in these
effluents is relatively constant among treatment plants and over
time, providing an opportunity for a case-history trial of EXAMS'
steady-state evaluative capabilities.
DCB is not subject to appreciable degradation by chemical or
biochemical processes in aquatic systems (Callahan et al. 1979);
its behavior is governed by volatilization, transport, and
sorption phenomena.' EXAMS in this instance requires 4 chemical
descriptors: the molecular weight (MWTG), solubility (SOLG),
octanol-water partition coefficient (KOWG), and Henry's Law
constant (HENRYG). The molecular weight of DCB (C6H4C12) is
147.0. The aqueous solubility and octanol-water partition
coefficient of DCB have been measured by Banerjee and coworkers
(1980). DCB is soluble to 0.502 mM in water at 25 degrees C
(SOLG SB 73.8 ppm). its octanol-water partition coefficient
(KOWG) is 2340.
The Henry's Law constant of DCB has not been measured, but
it can be estimated (for 25 degrees C, the temperature of the
solubility observation) from the vapor pressure/solubility ratio
(Mackay and Wolfcoff 1973, Mackay and Leinonen 1975). Para-DCB Is
a solid at normal environmental temperatures (mp 53.1 degrees C
(Weast 1971)). The vapor pressure (Pv) of solid 1,4-DCB at 10,
30, and 50 degrees C is 0.232, 1*63, and 8.435 torr, respectively
(Darkis, Vermiillon, and Gross 1940). Regression of these data
on the model Pv s A exp(-BXT) yields A 9 9.63E11, B » 8223, and
accounts for 99.99% of the variation in Pv with temperature.
EXAMS could be loaded with the results of this regression
77
-------
analysis. I.e., VApRG = log A = 11.98, and EVPRG = (B)CR)(0.001)
s 16.34 Real/Tide. Alternatively, the Henry's Law constant can
be estimated via interpolation of the observed vapor pressure to
25 degrees C. The latter procedure was used for this analysis of
DCB in Lake Zurich. The interpolated value of Pv is 1.011 torr
at 25 degrees C. The Henry's Law constant is therefore
(1.011/760)70.502 = 2.66E-3 atm-m3/nr>0l.
EXAMS also requires environmental input data describing Lake
Zurich, In this case, a "canonical" data set need only include
information relevant to transport, sorption, and volatilization
of neutral organics. Schwarzenbach and coworkers (1979)
restricted their investigation to the central basin of Lake
Zurich. Both the upper and the central basins receive
DCB-contaminated waste-water effluents. The central basin can be
modeled in isolation, however, by treating inputs from the upper
basin as advected loadings to the (downstream) central basin.
Except as noted otherwise, the environmental description given
below was drawn from Schwarzenbach et al. 1979,
The central basin has an average hydraulic residence time of
1.2 yr. Banks' (1975) method for estimating K02G from windspeed
thus seems most appropriate, lacking extensive direct field
measurements of the oxygen exchange constant. The annual mean
windspeed for the period 1955-63, 65-69 was 2.6 m/s (5.1 kt)
(unpublished data for Zurich, Switzerland/ Kloten, summarized by
USAF £TAC, supplied courtesy of NOAA), Although a station
history was not available, these data were in all probability
collected at the conventional meteorological screen height. (6 m).
windspeed at 10 m height would be 2.6(log 10000/log 6000) * 2.75
m/s. Computation of K02G via Eq, 2.98 then gives:
K02G = (4.19E-6) (SQRTL2.75]) (3600 s/hr) (100 cm/m) = 2.5 cm/hr
Average windspeed at 10 cm height (EXAMS' input parameter WINDG)
would be 2,6(log 100/log 6000) » 1.38 m/s.
The mean depth of the central basin is 50 m, and the surface
area is 68 km2, giving a total volume of 3.4E9 m3. The lake
stratifies during the summer (May through September); the
thermocline sets UP at a depth of 10 m by early May and remains
at about that depth until fall turnover (Li 1973). A simple
"box" model of the lake can be constructed for EXAMS by dividing
the lake into 3 vertical zones, each with an area (AREAG) of 68
km2 or 6.8E7 m2. For the epilimnion segment (compartment 1,
TYPE(l) * "E"), DEPTHG(l) * 10 (m), and VOLG(l) » 6.8E8 (m3).
The hypolimnion ( 2, TYPE(2) s "H") then has DEPTHG(2) * 40, and
VOLG(2) * 6,8E7*40 = 2.72E9 m3. Assuming a 2 cm depth of active
benthic sediments ( 3, T¥.PE(3) = "B") gives DEPTHGO) * 0.02, and
VOLG(3) * 1.36E6 m3.
Li (1973) computed the vertical eddy diffusion coefficient
78
-------
In Lake Zurich, as a function of depth and season, from observed
monthly temperature profiles averaged over 10 years of record.
The annual mean temperature of the epilinnion (0 - 10 m depth,
TCELG(D) was 11 degrees C; the mean hypolimnion temperature was
5.6 degrees C (TCELG(2)). The eddy dispersion coefficient at 10
m depth averaged 0.058 cm2/s during the stratified period and was
about 1 cm2/s during the balance of the year. The annual mean
value (DSPG for parameterizing average transport between the
epilimnion and hypolimnion) was 0.6 cm2/s; EXAMS' input value of
DSPG = 0.2 sq m/hr. The dispersion coefficient for exchange
between the hypolimnion and-benthic sediments (Section 2.3.1.4)
was taken as l.E-4
-------
m3/hr. The total load of DCB on the central basin was 88 kg/yr,
of which 25 teg derived from the upper basin, 62 kg from treatment
plant effluents discharged into the central basin, and 1 kg/yr
from other minor sources. For the EXAMS simulation, these
loadings were summed to give a STRLDG(l) to the epilimnion of the
central basin of 0.010 kg/hr. (Section 3.3.4 demonstrates the
entry of this data into EXAMS, and the command sequences used to
conduct the analysis.)
EXAMS' resulting output tables (Tables 2.15 and 2.16)
predict a flux of DCB to the atmosphere of 59.4 kg/yr,
water-borne exports of 28.2 kg/yr, and a total mass of 36.5 kg
DCB resident in the water column (DCB concentration 10.7 ng/L).
By comparison, Schwarzenbach et al. (1979) estimated a resident
mass of 38 kg (11.2 ng/L) in the lake, and, from a mass balance
tor DCB, estimated the flux to the atmosphere to be 60 kg/yr,
with a water-borne export of 28 kg/yr.
Table 2.15. Predicted concentration and resident mass of DCB
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: I^-DICHLORQBENZENE
ECOSYSTEM: LAKE ZURICH - CENTRAL BASIN (UNTERSEE)
^^m**mmmmmmmm*m~m^^~mm9*^mmmmm*tmf9nmm~mmm~mmmm9*m*mm»»m^m9mm~mmmmmmmmmmmmmmmm*
TABLE 13. DISTRIBUTION OF CHEMICAL AT STEADY STATE: IN THE WATER COLUMN
COMP STEADY-STATE RESIDENT MASS
2
G/M KILOS %
**** TOXICANT CONCENTRATIONS ****
TOTAL DISSOLVED SEDIMENTS BIOTA
MG/* MG/L MG/KG UG/G
1 1.074E-04 7.302 20.00 1.074E-05 1.074E-05 2.060E-04 0.000
2 4.295E-04 29.21 80.00 1.074E-05 1.074E-05 2.060E-04 0.000
SUBTOTAL: 36.51 99.22
AND IN THE BOTTOM SEDIMENTS:
3 4.228E-06 0.2875 100.00 2.114E-04 1.074E-Ob 2.060E-04 0.000
SUBTOTAL: 0.2875 0.73
TOTAL MASS (KILOGRAMS) = 36.80
^^mmmtmmmm9fmmmmm»»mmmm»^mi»^»m*mm9*mmm9**»m^mmmmm*m9mm9*mm^m^»m>mmmmfmmimmmmmmi
* TOTAL CONCENTRATION AS MG/L IN WATER COLUMN, AS MG/KG IN SEDIMENTS.
During the stratified period, contaminated treatment plant
effluents spread laterally through the iietalitmion of the lake
and mix with both the hypolimnion and the epilimnion
(Schwarzenbach et al. 1979). Assuming that the summertime
loadings nix upward and downward in equal measure, EXAMS'
loadings can be modified to account for this phenomenon. The
summer (5 nonth) DCS load to the hypolimnion would amount, to
(5/12)(62)/2 kg/yr, which can be entered to EXAMS as a "drift"
load (DRFLDG(2)) of 1.5E-3 kg/hr. Proportionate reduction of the
DCB load on the epilimnion gives STRLDG(l) s 8.5E-3 kg/hr. Given
80
-------
this modification, EXAMS predicted a larger concentration of DCB
in the hypolinmion (13.5 ng/L), and a resident mass of 44.0 kg
DCB; the predicted fluxes and DCB concentration in the
epilimnion (10.7 ng/L) were unchanged.
Table 2.16. Summary of EXAMS' results for DCB in Lake Zurich
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: I^-DICHLOROBENZENE
ECOSYSTEM: LAKE ZURICH - CENTRAL BASIN (UNTERSEE)
TABLE 17. EXPOSURE ANALYSIS SUMMARY.
EXPOSURE:
A. MAXIMUM CONC. IN WATER COLUMN: 1.07E-05 MG/L DISSOLVED, 1.07E-05 TOT
MAX. CONC. IN BOTTOM SEDIMENT: 1.07E-05 MG/L DISSOLVED IN POPE WATER
B. BIOSORPTION - MAX. CONCENTRATION - PLANKTON: o.oo UG/G
BENTHOS: 0.00 UG/G
C. MAXIMUM TOT. CONC. IN SEDIMENT DEPOSITS: 2.11E-04 MG/KG (DRY WEIGHT)
FATE:
A. TOTAL STEADY-STATE ACCUMULATION: 37. KG; 99.22% IN WATER COL.,
0.78% IN BOTTOM SEDIMENTS.
B. TOTAL LOAD: 0.24 KG/DAY - DISPOSITION: 0.00% VIA CHEMICAL
TRANSFORMATIONS, 0.00% BIOTRANSFORMED, 67.79% VOLATILIZED,
32.21% EXPORTED VIA OTHER PATHWAYS.
PERSISTENCE:
A. AT THE END OF A 216. DAY RECOVERY PERIOD, THE WATER COLUMN HAD
LOST 50.51% OF ITS INITIAL TOXICANT BURDEN; THE SEDIMENTS HAD
LOST 19.54% OF THEIR INITIAL BURDEN ( 50.26% REMOVAL OVERALL).
B. SYSTEM SELF-PURIFICATION TIME IS ROUGHLY 36. MONTHS.
A test o* other transport indices requires Knowledge of DCB
diffusivity. The aqueous dlffusivlty of DCB can be estimated
from eoiar volume at the normal boiling point (Vb), and Vb can
itself be estimated fro* Vc, molar volume at the critical
temperature (Reid, Prausnitz, and Sherwood 1977). Vc for p-DCB
is 372 cc/g-mol; Vb = 0.285(Vc**1.048) (Tyn and Calus method) *
140.9 cc/g-mol. The aqueous diffusivlty of p-DCB at 25 degrees
Cf computed via the Hayduk-Laudie revision of the Othmer-Thakar
relationship, is (13.26E-5)(0.8904**(-1.4))(140.9**(-.0589)) s
8.46E-6 c*2/s, taking the viscosity of water at 25 degrees C as
0.8904 cp (Weast 1971:F-36). The diffusivity ratio D(DCB)/D(02),
given the diffusivity of molecular oxygen D(02) as 2.41E-5 cm2/s,
is 0,35; its square root is 0.59.
Substituting these values (via KVOG) for EXAMS' default
molecular weight transport index (SQRT(32/147) c 0.47) gave
estimated resident DCB masses of 43.8 kg (12.9 ng/L), and 31.0 kg
(9.1 ng/L), respectively. Simulation using Liss and Slater's
81
-------
(1974) open-sea transport parameters (»ith the molecular weight
transport index) predicted a resident mass of only 6.6 kg (2.0
ng/L). These comparisons are summarized in Table 2.17. The
default molecular weight transport index provided the most
accurate prediction of the volatilized flux of DCB from Lake
Zurich. As was tne case for Rn transport in ELA lakes, however,
the selection of proper values for environmental driving forces
seems to be more critical, than is the choice taken among methods
of indexing pollutant transport across the air-water interface
against its environmental referents.
Table 2.17. Results of EXA^S simulations of the behavior of DCB
(1,4-dichlorobenzene) in Lake Zurich, Switzerland. Predicted
concentration, resident mass in water column, and fluxes vary as
a function of load routing, method used to index interphase
transport against its environmental referents, and environmental
transport parameters.
Method Concentration, Mass, Volatilization, Elxport,
ng/L kg kg/yr kg/yr
Measured
SQRT(32/147)
Partial load
to Hypolimnion
D(DCB)/D(02)
11.2
10.7
10.7(E)
13.5(H)
12.9
38.
3b.5
44.0
43.8
60.
59.4
59.4
53.7
27 * 1
28.2
28.2
33.9
D(DCB)
SQRT ----- 9.1 31.0 63.7 24.0
D(02)
SQRT(32/147),
K02=20cm/hr, 1.95 6.64 82.5 5.13
WAT=30*/hr
2.3.3 Direct Photolysis
EXAMS includes two entirely separate subroutines that
coapute rates of direct photolysis. These subroutines are
82
-------
mutually exclusive, and accept different Kinds of input data.
The first subroutine, PHOT01, begins from a pseudo-first-order
rate constant (KDPG) respresentinq the photolytic decomposition
rate in near-surface waters under cloudless conditions at a
specified latitude (RFLATG). The second subroutine, PHOT02,
works from measured light absorption spectra and reaction quantum
yields of the compound. EXAMS selects the appropriate routine
via an audit of the structure of the chemical input data. For
each existing ionic species (SH2, SH-, s=, SH3 + , SH4++; see
SPFLG and Section 2,2.1), a positive value of KDPG invoices
execution of PHQT01, When an- entry for KDPG is zero, but at
least one value of ABSG, the light absorption spectrum of the
molecule, is non-zero, EXAMS calls on subroutine PHOT02 to
compute the photolysis rate. (Technically this test is executed
on a summation of the ABSG vector of the ionic species; a
positive value of this sun (internal variable ABSTOL) and a zero
KDPG invoke the call to PHOT02.) Note .that the structure of this
decision in effect gives KDPG a higher computational priority
than ABSG, that is, if both KDPG and ABSG are positive, EXAMS
will use PHOTOl and KDPG for its computations, and will ignore
the absorption spectrum, if PHOT02 is the preferred
computational mechanism, the KDPG vector must contain zero values
in the data base.
The techniques used within EXAMS for computing rates of
direct photolysis have been derived from the work of Zepp and
coworkers (Zepp 1978; 1980; Miller and Zepp 1979a, 1979b; Zepp
and Baughman 1978; Zepp and Cline 1977; Zepp et al. 1975, 1976,
1977). Zepp (1980), and Zepp and Baughman (1978) have recently
summarized techniques for predicting direct photolysis in natural
waters; a computer code for evaluating this transformation
pathway has been described by Zepp and Cline (1977).
2.3.3.1 Direct photolysis in aquatic systems
Direct photochemical reactions are a consequence of the
absorption of electromagnetic energy by a pollutant molecule. In
this "primary" photochemical process, absorption of a photon
promotes the molecule from its ground state to an electronically
excited state. The excited molecule then either reacts to yield
a photoproduct, or decays via some other mechanism (fluorescence,
phosphorescence, etc.) back to the ground state. The efficiency
of each of these energy conversion processes is called its
"quantum yield;" the law of conservation of energy requires that
the primary quantum efficiencies sum to 1.0, These ideas are
expressed by two fundamental laws of photochemistry. The first,
the "Grotthus-Draper" law, states: "Only the light which is
absorbed by a molecule can be effective in producing
photochemical change in the molecule." Simple irradiation of a
system does not necessarily result in photochemical reactions;
the light must be of wavelengths that can be absorbed by the
83
-------
chemical. Conversely, laboratory Irradiation of a chemical with
wavelengths that are not found in natural waters «29Q nm) is of
diminished value for predicting the behavior of the compound in
the environment. The second law of ohotochemistry, the
"Stark-Einstein" law, was formulated after the discovery that
interactions of light and matter are restricted to discrete
(quantized) events. This second law in its modern form CCalvert
and Pitts 1966:20) states: "The absorption of light by a
molecule is a one-quantum process, so that tne sun of the primary
process quantum yields must be unity."
The rate of photolytic transformations in aquatic systems
depends upon botn the light intensity in the medium (in other
words, the dose rate), and on the response of the irradiated
pollutant. The chemical response is composed of two factors:
the pollutant's absorption spectrum (EXAMS' variable ABSG), and
its quantum efficiency for pnotochemical transformations
(reaction quantum yield, QUANTG). The logic of the situation can
be developed in terms of monochromatic light, with spectral
effects subsequently incorporated via integration or summation
across the solar spectrum. in EXAMS, the solar spectrum is
subdivided into 39 wavelength intervals (Taole 2.18), and the
total rate constant is computed as the sum of contributions from
each spectral interval. In what follows, however, the spectral
subscripts have in most cases been omitted, in the interest of
notational simplicity.
Light intensity decreases exponentially with depth in any
absorbing medium. This phenomenon is known as the Beer-Lambert
law, and can be stated mathematically as:
Eq. 2.100 d(Eo)/dz = -K(Eo)
where Eo » photon scalar irradiance, photons/cm2/sec
z = depth, m (DEPTHG)
K = diffuse attenuation coefficient for irradiance, /m, and
Eq. 2.101 K = Da t (Bb) (Smith and Tyler 1976),
where D is the mean optical path per unit z (dircensionless), a is
the absorption coefficient for the medium (/m), and (Bb) is the
back-scattering coefficient. Although seldom measured in
freshwater systems, back-scattering is generally very small in
marine waters and can be neglected (Jerlov 1976).
Photon scalar irradiance (Eo) is the sum of two contributing
light fields in natural waters, the downwelling (Ed) and
upwelling (Eu) irradiances. Field measurements, although for the
most part restricted to marine systems, have In almost all cases
resulted in measured values of Eu of only 2% or less of Ed.
Upwelling irradiance can contribute significantly to Eo at
84
-------
Table 2.18. Spectral Intervals used in EXAMS (Zepp and Cllne
1977), and spectral absorption coefficients of water (Smith and
Baker 1980), chlorophylls t pheophytins (Smith and Baker 1978b),
(humlc) dissolved organic carbon (unpublished data of B.C. Zepp),
and suspended sediments (Miller and Zepp 1979a)
Waveband
NO.
1
2
3
4
5
6
7
8
9
10
li
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
Center,
nm
297.5
300.0
302.5
305.0
307.5
310.0
312.5
315.0
317.5
320.0
323.1
330.0
340.0
350.0
360.0
370.0
380.0
390.0
400.0
410.0
420.0
430.0
440.0
450.0
460.0
470.0
480.0
490.0
503.75
525.0
550.0
575.0
600.0
625.0
650.0
675,0
706.25
750.0
800.0
Width,
nm
2.5
H
n
*
n
N
M
M
N
2.5
3.75
10.0
n
N
H
M
H
II
H
II
M
H
N
n
m
n
N
10.0
17.5
25.0
H
N
II
H
II
25.0
37.5
50.0
50.0
Spectral Light Absorption Coefficients
water
/m
(WATETA)
0.160
0.141
0.133
0.126
0.119
0.105
0.0994
0.0952
0.0903
0.0844
0.0793
0.0678
0.0561
0.0463
0.0379
0.0300
0.0220
0.0191
0.0171
0.0162
0.0153
0.0144
0.0145
0.0145
0.0156
0.0156
0.0176
0.0196
0.0295
0.0492
0.0638
0.0940
0.244
0.314
0.349
0,440
0.768
2.47
2.07
Pigments
/m/(mg/L)
(PIGETA)
...
...
...
...
...
. ..
...
...
...
...
...
...
...
55.
55.
51.
46.
42.
41.
39.
38.
35.
32.
31.
28.
26.
24.
22.
19.
14.
10.
8.
6.
5.
8.
13.
3.
2.
0,
DOC
/m/(mg/L)
(DOCETA)
6.30
6.12
5.94
5.76
5.57
5.39
5.22
5.06
4.90
4,74
4.56
4.17
3.64
3.15
2.74
2.34
2.00
1.64
1.39
1,19
1.02
0.870
0,753
0.654
0,573
0.504
0.444
0.396
0.357
0.282
0.228
0.188
0.158
...
...
...
...
...
...
Sediments
/m/(mg/L)
(SEDETA)
0,34
N
«
M
N
II
N
II
II
n
N
II
N
tt
H
N
M
II
n
m
H
*
N
ii
ii
n
N
II
N
•
M
It
II
II
H
N
M
•
0.34
85
-------
visible wavelengths in the clearest ocean waters, however, where
molecular bacK-scattering can be significant, and over white
sandy bottoms of high albedo (Jerlov 1976). In the following
discussion, photon irradiance is designated "E" and is treated as
being identical with Ed or Eo; Eu is assumed to be
insignificant.
Integration of Eq. 2.100 yields an expression for the
residual irradiance after transmission through a homogeneous
layer of depth z:
Eq, 2.102 E(z) = ECO) exp(-Kz) = E(0) exp(-Daz)
where E(0) is the irradiance at the top of the layer. The rate
of light absorption in the layer, Ew (photons/cm2/s), is (ECO) -
ECz)), or
Eq. 2.103 Ew = ECO) C 1 - expC-Kz) )
For photochemical purposes, it is most convenient to express
light absorption on a volumetric molar basis CBailey et
al. 1979:223) Cone mole of photons is an Einstein, E). The rate
of light absorption Iw, in E/liter/s, is:
Ew
Eq, 2.104 Iw = — * CiOOO cm3/l) * CO.01 m/cm)
CAMz)
where A = 6.023E23 photons/mole (Avogadro's number). Denoting
ECO)/A as lo CE/cm2/s), the volumetric absorption rate Iw is:
Eq, 2.105 Iw (E/liter/s) = 10 CIo/z) C 1 - exp(-Kz) )
The electronic absorption spectra of synthetic organic
chemicals are usually reported as Cdecadic) molar absorptivites
or extinction coefficients, with units /cm/Cmole/liter) or /cm/M
(EXAMS' input variable ABSG). The defining equation is:
Eq. 2.106 ABSG = Ab/(l*[Pl)
where Ab is the absorbance measured in a spectrophotometer, 1 is
the pathlength in cm, and CP] is the molar concentration of the
chemical. The presence of the chemical in a natural water body
increases the absorption coefficient Cunits /m) of the water from
(a) to (a + (100 cm/m)(ln 10)(ABSG)tPJ). The total rate of light
absorption in the water body then becomes, by substitution into
Eq. 2.105,
Eq. 2.107 Iw = (10)(Io/z)U-exp( -D
where D is the relative optical path in the water body
(Eq. 2,101). The fraction of this light absorbed by the
86
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pollutant Itself is:
(2.303)(100)(ABSG)m
a + (2.303)UOO)(ABSG) tP]
and the rate of light absorption by the pollutant la, in
E/liter/s, is:
(2303.)(Io)U-exp(-Dz)> (ABSG) IP]
Eq. 2.108 la = —.--—-—--—.- --- ........... ---- ...... --- . ---- ...
{a + 230.3(ABSGHP] > z
At trace levels of the pollutant (EXAMS' operating range), by
definition the quantity (230. 3( ABSG) [P] ) « a, and (a +
230.3(ABSG) [P] ) can be approximated by the natural absorption
coefficient of the water body, a. Equation 2.108 in these
circumstances reduces to:
(1000)(2.303)(A8SG) Io ( l-exp(-Daz) )
Eq. 2.109 la = — --------- -- ---- ........... ........ [pj
(a)(z)
The quantity Ia/[P) is called the "specific sunlight absorption
rate" of the pollutant, Ka (Zepp 1980).
Ka can also be computed from the average light intensity in
any layer of the water body (Miller and Zepp 1979a). In this
approach, the average light intensity Em (photons/cm2/s) is found
by integration of Eq. 2,102 over the depth of the layer z,
followed by division of the resulting integral by z:
E(0) (l-exp(-Daz))
Eq. 2.110 Em = - --- - --- ..........
(D)(a)(z)
where E(0) is the intensity at the top of the layer. Em
(photons/cm2/s) can be converted to molar units dm, E/cm2/s) via
division by Avogadro's number:
Em E(0) (l-exp(-Daz))
Eq. 2, Hi Im a — - = — — * .............
A A (D)(a)(z)
which, talcing Io « E(0)/A,
1 lod-exp(-Daz)
D
The term Io(l-exp(Daz)/az in this equation is embedded in
Eq. 2.109; la and Ka can thus be computed from the average light
87
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intensity Im via the equivalent expressions:
Eg, 2.112 la » 2.303 * 1000 (cti3/liter) * (ABSG) Jm D [p] ,
and
Eq. 2.113 Ka = 2303. (ABSG) Im D
Light absorption is a one-quantum process, thus la
(E/liter/s) also gives the rate of electronic activation of the
pollutant (M/s). Ka, the specific sunlight absorption rate, thus
has units /s. If each photon absorbed oy the chemical pollutant
resulted in photochemical transformation of one molecule, Ka
would amount to a pseudo-first-order rate constant for photolysis
of the pollutant. This is seldom the case in solution-phase
systems, however. The efficiency of the (secondary)
photochemical transformation process is called the "reaction
quantum yield" (EXAMS input parameter QUANTG), with
(dimensionless) units of moles/Einstein. (Zepp (1978) has
described procedures for measuring QUANTG of organic chemicals in
dilute air-saturated aqueous solutions.) The rate of
photochemical transformation of a pollutant is given by:
Eq. 2.114 dtPJ/dt = (QUANTG) la = (QUANTG) Ka tP]
The quantity (QUANTGHKa) is the pseudo-first-order photolysis
rate constant. Multiplication of this quantity by 3600 s/hr
gives the photolytic contribution to the overall transformation
rate constant K in £q. 2.1.
Although the foregoing discussion has been phrased in terms
of monochromatic light, the effect of spectral differences can be
readily incorporated via integration or summation (in discrete
wavebands) across the solar spectrum. The rate of photolysis of
a synthetic organic compound thus can be computed from the
absorption spectra and reaction quantum yields of the several
ionic species of the chemical, via a coupling of these parameters
to the (spectrally-dependent) behavior of light in natural waters
(EXAMS' subroutine PHOT02). Often, however, the absorption
spectrum of a compound has not been quantified (although the
spectral position of absorption maxima may be known). EXAMS
provides an additional subroutine, PHOT01, designed to accept
measured photolysis rate constants as its primary input data.
For example, Smith and coworkers (1978b) attempted to measure the
absorption spectrum of Mirex, but the absorptivity was below the
detection limit of their instrument (0.1 /cm/M). Experimental
studies, conducted via continuous exposure of an aqueous solution
of Mirex to ambient sunlight at Menlo Park, CA for a period of 6
months, showed that Mirex is photochemically reactive in aqueous
solution with a pseudo-first-order rate constant of 3.7E-3 /day.
(A pseudo-first-order rate constant determined via a brief
experiment, for example at midsummer local noon, should be
88
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adjusted for annual mean intensity and daylength prior to entry
in EXAMS.)
So long as the reaction mixtures absorb a negligible
fraction of the ambient light dm = lo), this observed rate
constant (KDPo) is equivalent to:
KDPo = (QUANTG) Ka = 2303. (QUAMG) (ABSG) lo D
integrated across the solar spectrum. The average photolysis
rate constant in a layer of appreciable depth (KDPz) is then
1 - exp(-Daz)
Eq. 2.115 KDPz = KDPo * —. ——— —
(DHaMz)
where the absorption coefficient (a) for the water body is some
appropriate single value. PHOT01 also computes a correction term
for effects of cloudiness and geographic latitude. EXAMS' input
variable (KDPG, units /hr) is taken as the near-surface
pseudo-first-order photolysis rate constant under cloudless
conditions at a specified latitude RFLATG. PFLATG is expressed
in degrees * tenths. For example, Menlo Park, California, is at
37 deg 27* N; EXAMS' input would be RFLATG = 37.4.
2,3.3.2 Light attenuation in natural waters
The attenuation of irradiance in natural waters is described
by the diffuse attenuation coefficient or "K-function," K
(Eq. 2.101), with units /m. The numerical value of K depends
upon both the absortoance of the medium (a), and upon the relative
optical path in the water body (D). The absorbance of a natural
water body results from absorption of light by the water itself,
plus absorption by green plants, dissolved organic matter
(primarily humic materials), and suspended sediments. The
optical path parameter D depends on the angle of Incidence of the
light source(s), and on forward scattering of the light within
the water body itself.
2,3,3.2.1 Distribution functions (D) in natural waters
The optical parameter D is the mean optical path per unit
vertical depth in the system; D may be called a "distribution
function" as proposed by Prlesendorfer (1958a, 1958b? quoted
from Smith and Tyler 1976), or an "inverted value of an average
cosine" where the average cosine is defined as a/K (Jerlov 1976).
(The term "average cosine" originated from a generalization of
the fact that the path length of the solar beam is given by the
secant (I/cos) of the angle of refraction of the beam.) In the
case of a colllmated light beam incident normal to the water
89
-------
surface, D = 1.0. In the case of a completely diffused light
field, D reaches its maximum value of 2.0 (Leiqhton 196l:24ff).
In the clearest natural waters, the distribution function is
dominated to appreciable depths by the geometry of incident sky
radiation and the solar beam. When the sun is in the zenith, the
solar D = 1.0; D increases with increasing zenith angle, when
the sun is near the horizon, D reaches a Uniting value of about
1.5, because of refraction of the solar beam as it crosses the
air-water interface. At low solar elevations, however, the
underwater light field in the photochemically significant portion
of the solar spectrum is dominated by contributions from diffuse
skylight.
The collimating effect of transmission across the air-water
interface reduces the distribution function for diffuse skylight
from a D of 2.0 in the atmosphere, to a submarine value of about
1.19 (Poole and Atkins 1926, quoted from Hutchinson 1957:391).
This value corresponds to an equivalent solar elevation of about
44 degrees. The total incident photochernically active irradiance
(wavelengths < 370 nm) is dominated by skylight at solar
altitudes less than 45 degrees, and irradiance at wavelengths <
330 nm is dominated by sky radiation at all solar elevations
(Leighton 1961:23). A distribution function of 1.19 is thus
probably an adequate approximation for the clearest natural
waters.
In most natural waters, and in the deeper parts of clear
waters, the radiance distribution approaches an asymptotic value
in which forward scattering by suspended particles is balanced by
light absorption, and the distribution coefficient attains a
stable value. At shallow depths in natural waters containing
scattering particles, D is usually larger than the value
suggested by the solar elevation. For example, in the Baltic Sea
and in tne Mediterranean, D has been measured at 1.40 and 1.25,
respectively (Hojerslev 1973, 1974; Jerlov and Liljequist 1938;
quoted from Jerlov 1976:88). The corresponding solar beam D
values were only 1.14 and 1.04 respectively, indicating a strong
effect of particle scattering in these waters. Miller and Zepp
(1979a) measured light scattering by 6 natural sediment
suspensions. The distribution function ranged from 1.3 to 2.0,
but showed little correlation with the suspension concentrations
of the sediments (17 - 105 mg/L).
The distribution function for each element of the water body
Is an (environmental) input parameter to EXAMS, These parameters
(DFACG) can be set at any value between 1.0 and 2.0. If an input
value is 2, however, EXAMS resets the distribution
function of the offending compartment to DFACG = 1.19.
90
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2,3.3,2.2 Absorption coefficients (a) in natural waters
EXAMS computes separate values of the spectral absorption
coefficients (a) for each sector of the water body. Absorption
is computed from the sum of the contributions of water Itself,
plant pigments, dissolved organic carbon (primarily attributable
to humic materials of molecular weight > 1000 (Mickle and Ketzel
1978)), and suspended sediments. Absorption coefficients for
water itself, and the specific absorption coefficients for the
other absorbing species, are given in Table 2,18, These values
are not available for modification by the interactive user. The
absorption coefficients can be modified by editing EXAMS' BLOCK
DATA and recompiling the program,
EXAMS computes the total absorption coefficient (a, units
/m) for each spectral interval in each water column compartment
via Eq. 2.116:
Eq. 2.116 asWATETA-KPIGETA) (CHLG)-KDOCETAHDOCG)+ (SEDETA)(SDCHRG)
The spectral specific absorption coefficients supplied with the
program CPIGETA, OOCETA, SEDETA) are given in Table 2.18, The
environmental concentrations of the absorbing species (CHLG,
DOCG, and SDCHRG) are entered as part of the environmental data
base for each water-column compartment of each ecosystem. These
variables have dimensions (mg/L); they can be modified
interactively.
Absorption by plant pigments is keyed to the concentration
of total chlorophyll-like pigments (chlorophylls + pheopigments)
in each sector of the water column (input varible CHLG, units
mg/L). Under very eutrophic conditions, Chi "a" can attain 2
mg/L (Tailing et al, 1973, quoted from wetzel 1975:337). in
ollgotrophic alpine and arctic lalces, pigment concentrations can
be as low as 0,001 mg/L (Wetzel 1975:334), Smith and Baker
(1978b) determined the contribution of total chlorophyll-like
pigments (CHLG) to the K-function of marine systems via
regression analysis; the resulting spectral K values differed
little from spectrophotometrically determined absorbance of
phytoplankters, EXAMS' specific absorption coefficients (PIGETA
in Eq. 2.116 and Table 2.18) were developed by division of Smith
and Baker's (1978b) "k2" by an assumed average distribution
function of 1.20,
EXAMS' specific absorption coefficients for DOC (DOCETA)
were supplied by R,G. Zepp (unpublished data). These values
(Table 2,18) were determined via analysis of samples from the
Aucilla River, Florida, a natural water receiving stained
drainage from freshwater wetlands. The Aucilla River data are
probably fairly typical of the humic materials found as dissolved
organic carbon (DOCG) in natural waters.
91
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Light absorption by suspended sediments may vary across the
solar spectrum, but interference by particle scattering has
hampered investigation of this phenomenon. Miller and Zepp
(1979a) determined both D- and K-functions for 331 nm light, via
actinometer experiments conducted on a series of 6 natural
sediment suspensions. The specific absorbance coefficient (
(D/K)/[S), where CS] (i.e., SDCHRG) is the concentration of
suspended sediments in mg/L) varied from 0.19 to 0.59, with a
mean value of 0.34, /m/(mg/L). EXAMS includes a 39-element
vector of specific sediment absorption coefficients; this vector
is currently uniformly filled with a value of 0.34.
In the case of subroutine PHOT01, the absorption spectrum of
the compound is not available for coupling to the absorption
spectrum of the water body. Subroutine PHOT01 requires
appropriate single absorption coefficients "a" (input parameter
CMPETG), These values can be entered as part of the
environmental data base. Each compartment of the ecosystem is
then described by an individual element of EXAMS' vector CMPETG,
with units /m. Alternatively, CMPETG can include (or be filled
with) zero values; EXAMS then computes a value (or values) of
CMPTEG via Eq, 2.116. The wavelength interval selected for this
computation depends on the chemical data describing the compound.
The chemical data base includes a variable (LAMAXG, nm) that can
be used to specify the desired wavelength interval for computing
"a" (i.e., CMPETG). The region of greatest overlap of the
absorption spectrum of the chemical with the solar spectrum Is
perhaps the most appropriate value tor LAMAXG. In many
instances, however, only the spectral location of peak absorbance
is Known, in which case this value can be used for LAMAXG. If
LAMAXG is outside the solar spectrum (that is, <296.25 nm or >825
nm), EXAMS computes CMPETG via Eq. 2.116 at 300 nm (interval 2 in
Table 2.18), Input values of LAMAXG need not be restricted to
the centers of the wavebands in Table 2.18; EXAMS selects the
specific absorption coefficients for computing CMPETG via a
matching of LAMAXG to the appropriate spectral intervals in the
Table. For example, if LAMAXG = 306,5, EXAMS selects absorption
coefficients from waveband 5 in Table 2.18; a LAMAXG of 442,2
selects waveband 23; etc.
2.3.3.3 Reaction quantum yields (QUANTG)
A photoactivated organic molecule can undergo a variety of
secondary (thermal) transformations, including photoaddition and
substitution reactions, cycloadditlons, isomerizations and
rearragements, and photofragmentations and eliminations (Turro
1978). The efficiency of photochemical processes is expressed in
terms of the "quantum yield," that is, the number of moles of
photochemical activity per mole of photons (Einsteins) absorbed.
Photoactivated molecules are subject to numerous physical and
chemical processes, and the efficiency of each of these processes
92
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can be expressed as a quantum yield (examples include the
fluorescence quantum yield, phosphorescence quantum yield,
quantum yield for formation of a specific product molecule, etc,)
The quantum yield of significance for EXAMS is the
"disappearance" quantum yield (input parameter QUANTG), that is,
the number of moles of parent compound transformed to daughter
products per mole of photons absorbed.
The (secondary) transformation processes often involve
thermal reactions, and the disappearance quantum yield therefore
can be somewhat teiperature dependent. These thermal reactions
are very fast, however, as they must be in order to compete with
thermal reversion of the unstable intermediates to the original
pollutant molecule. The activation energies of the thermal
transformation reactions are on the order of only 1-2 kcal/mple,
so EXAMS does not include an option for description of
temperature effects on disappearance quantum yields.
Unlike vapor-phase photochemical reactions, the
disappearance quantum yields of organic molecules in aqueous
solution are usually independent of the wavelength of incident
radiation, at least within the environmentally significant
portion of the solar spectrum. This difference arises from the
enhanced opportunity for energy transfer to the solvent in
condensed-phase systems. In solution-phase irradiation, the
rapid (radlationless) decay of excited molecules from second or
higher electronic states, to their first excited state* normally
precludes reaction from the higher states (Zepp 1978). Some
organic dyes* stable under visible light but photochemically
labile under UV, are notable exceptions to this rule. This
phenomenon should be suspected when a 100+ nm gap is present in
the compound's absorption spectrum. In such a case the assumed
lack of wavelength dependence of QUANTG should be tested by
experiments conducted in both absorbing regions of the spectrum.
If necessary,- the photochemically inactive section of the
compound's absorption spectrum can be omitted from the input data
(ABSG). Very small organic molecules, and some coordination
compounds, can exhibit a wavelength dependence of QUANTG. The
Photochemistry of iron (II) cyanide complexes is one example of
this phenomenon (Balzani and Carassitl 1970, quoted from Zepp
1978), Most small organic molecules in aqueous solution are
photochemically unreactive in sunlight, however. The
disappearance quantum yields used as input to EXAMS should in all
cases be derived from experiments using wavelengths that are part
of the environmentally relevant portion of the solar spectrum,
rather than far UV « 290 nm).
QUANTG can also be affected by the chemistry of the water
solution itself. The quantum yields of the ionic species of an
organic acid or base generally differ. This phenomenon leads to
an apparent dependence of QUANTG on the pH of the medium. EXAMS
allows for the entry of a separate value of QUANTG for each ionic
93
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species of the compound. This information can be deduced from a
Knowledge of the PK(S) of the compound, absorption spectra of its
ionic species, and quantum
pHs, For example, Zepp
determining disappearance
rate of transformation of
reference compound R, of
yield QUANTG(R).
slopes of the
yield experiments conducted at several
(1978) has described methods for
quantum yields via comparison of the
a test pollutant P to that of a
tcnown absorptivity ABSG(R) and quantum
The method depends on a comparison of the
(pseudo-first-order) In [P3 and In [R]
disappearance curves over time, under irradiation at a selected
wavelength (e.g., 313 nm). The reference compound serves to
normalize the experiment for light Intensity and the geometry of
the photochemical apparatus. For a neutral molecule,
Eq. 2.117
SLOPE(P) ABSG(R) * QUANTG(R)
QUANTG(P) = ------- * ...................
SLOPE(R) ABSG(P)
The apparent OUANTG of an organic acid or base will depend on the
pH of the system. For a fixed pH, Eq. 2.117 can be rewritten to
include the ionization equilibria and separate absorptivites and
quantum yields of the various ionic species of the pollutant P.
For example, a monoprotic organic acid will distribute between
its uncharged (SH2) molecule and its anion (SH-) (see Section
2.2.4) as:
Eq. 2.118
Eq. 2,119
ALPHA(SH2) *
ALPHA(SH-) s
(Ka)/)
»/(l + (Ka)/
-------
(0.76)(5000)(QUANTG(SH2)) + (0.24)(10000)(QUANTG(SH-)) a 10
(0.50)(50QO)(QUANTG(SH2)) t (0.50)(10000)(QUANTG(SH-)) * 20
giving a reaction quantum yield for the uncharged molecule of
1.5E-4, and QUANTG(SH-) s 3.9E-3.
Zepp and Baughman (1978) have discussed the effect of other
dissolved species on the direct photolysis of synthetic organic
molecules. Dissolved oxygen in some instances "quenches"
photochemical reactions via energy transfer from a pollutant
molecule to the oxygen molecule at the expense of transformation
pathways. Disappearance quantum yields should be determined in
air-saturated pure water to allow for this effect? EXAMS does
not include an explicit algorithm to make allowances for varying
dissolved oxygen concentrations. (Sunlit waters are very rarely
anaerobic.) Photochemical reactions with dissolved nucleophilic
species such as hydroxide, chloride, bromide, and sulfide can
change the reaction quantum yield of a pollutant from the value
determined in in pure water system. The concentrations of these
species in natural fresh waters are, however, typically much too
small for them to compete with nucleophilic displacements by
water itself. In marine systems, chloride and bromide occur at
concentrations (0,6 and 0.001 Molar, respectively) high enough to
compete, in principle, with water.
Some organic compounds that are not photoreactive in pure
water are photoactive when complexed with metal ions. For
example, NTA and EDTA are photochemically activated by
compiexation with iron (III). Photoactive co-dissolved
substances (e.g., dissolved humic materials) can also mediate
photoreactions of pollutant chemicals via direct energy transfer
to the pollutant molecule, or by generation of reactive
intermediates (e.g., singlet oxygen). These phenomena are
properly termed "indirect" or "sensitized" photolyses, however,
as opposed to the "direct" phototransformations that are the
subject of this Section.
2,3,3,4 Absorption spectra (ABSG)
The absorbance of organic acids and bases in aqueous
solution varies with pH, as a result of differential light
absorption by the neutral molecule and its ions. The rate of
photolytic transformation of an organic acid or base in natural
waters thus depends on the pH of the system, EXAMS' computations
(in Subroutine PHOT02) are keyed to the species-specific
absorption spectra of the pollutant chemical (uncharged parent
molecule and its ionic species), measured in pure water. Sub-
routine PHOT02 links the average spectral solar intensities in
each layer of the water body to the absorption spectra of the
compound, and thereby computes a value of Ka (Eg, 2.113) for each
95
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dissolved molecular species. Subroutine PHOT02 is invoiced by
another subroutine (FIRORD) whose primary task is to merge
environmental and chemical data into the final pseudo-first-order
format (Eq. 2.1) needed for efficient computations.
EXAMS' only dynamic state variable is the total
concentration of pollutant in each ecosystem segment, referred to
the aqueous phase of the compartment. The fraction of this total
concentration present as each molecular species is computed via
the equilibrium ionization and sorption distribution coefficients
ALPHA (Section 2.2.4). Subroutine FIRORD, once in possession of
Ka values for the several ionic species, computes the
contribution of each to the total pseudo-first-order direct
photolysis rate constant via the expression (compare Eq. 2,114):
AI,PHA(I) * QUANTG(I) * Ka(I)
where the subscript (I) refers in turn to each of the ionic
species.
This computational loop is actually iterated 3 times for
each ionic species, because EXAMS incorporates the effects of
sorption to sediments and biota via a set of 3 values of QUANTG
for each ionic species. In other words, for each ionic species
I, EXAMS computes the total contribution of that species to the
overall direct photolysis rate constant by fixing the value of I,
and summing the expression:
ALPHA(I,K) * QUANTG(1,K) * Ka(I)
over the K=l (dissolved), K=2 (sediment sorbed), plus K=3
(biosorbed) forms of the compound in each sector of the
ecosystem. The mechanics of this computation allow the user to
control the photoreactivity of sorbed molecules via the entries
in the QUANTG chemical input vectors.
Sorption of the pollutant to suspended sediments and to
biota can induce complex changes in both the light absorption
spectra and the reaction quantum yields of the compound, and can
"protect" the molecule from exposure to sunlight via migration or
dissolution into the (darkened) interior of sediment particles.
EXAMS' first-order evaluations use the quantum yield parameter
(QUANTG) as a mechanism for approximating the effects of sorption
on the photoreactivity of pollutant chemicals; the phenomena
involved are discussed in greater detail in Section 2.3.3.5.
In order to compute the effects of pH on light absorption
and on photolytic rate constants, EXAMS requires a specific
absorption spectrum (ABSG vector) for each (dissolved) molecular
species of the pollutant chemical. These absorption spectra can
be deduced from the pK(s) of the compound and the absorption
spectra of aqueous solutions of the chemical, measured at several
96
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pHs. The procedure is analogous to that described for QUANTG in
Section 2.3.3.3. For example, Smith and coworkers (1978b)
measured the absorption spectrum of p-Cresol at pH 5.1, 7.0, and
8.9 (Table 2,19). Para-cresol Is a weak organic acid (pKa =
10.2); at pH 5,1, 7,0, and 8,9 the anion is present as only
0.00079, 0.063, and 4.77 percent of the total concentration. The
observed spectra (Table 2.19) clearly indicate that the anion is
the more stronaly absorbing species.
Table 2.19, Absorption spectra of p-Cresol in pure water
mmm*>mmmm**+immmmmmmmm~mmm***mm^mmmmm9*mmmmmmi**mmmmmmv*mmmmm**mm4
Waveband Spectral Absorption Coefficients (/cm/M)
»**+•»-!
nm pH 5,1 pH 7,0 pH 8,9 (SH2) (SH-) pH 7.0
297.5 14
300.0 3.8
302.5 2.4
307,5 0
310.0
312.5
315.0
317.5
320.0
323.1
330,0
18
7.2
3.8
2
2
1
0
193
173
150
92.6
63.5
40.3
24.1
13.0
6.2
3.8
0
14 3767
3.8 3551
2.4 3097
0 1941
1331
845
505
272
130
80
16
6.0
4.4
1.2
0.8
0.5
0.3
0.2
0.08
0.05
* Spectra measured at pH 5,1, 7.0, and 8.9 by Smith et al. 1978b
+ Spectra of uncharged (SH2) molecule and p-Cresol anion derived
via Eg. 2.121
I Absorption at pH 7.0 predicted via Eq, 2.121, pKa of 10.2, and
absorption coefficients of (SH2) and (SH-) molecular species.
97
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The observed absorption coefficient at any fixed wavelength
is the sum of absorbance attributable to the uncharged (SH2)
molecule* plus that attributable to the anionic (SH-) species.
Denoting the observed absorption coefficient as ABSf this sum can
be expressed algebraically:
Eq. 2.121 ABS = ALPHA(SH2) * ABSGCSH2) + ALPHA(SH-) * ABSG(SH-)
This equation can be used to estimate the separate absorbances of
the SH2 and SH- molecules. For example, at 297.5 nm, for pH 7,0;
18 = (0.999369) ABSG(SH2) f (6.31E-4) ABSG(SH-)
and at pH 8,9,
193 = (0.952) ABSG(SH2) 4 (0.0477) ABSG(SH-)
Simultaneous solution of these equations yields ABSG(SH2) s 15.6
and ABSG(SH-) = 3734.
The uncharged molecule is present as 99.9992% of the total
concentration at pH 5.1, so the pH 5.1 spectrum is perhaps the
best experimental measure of ABSG(SH2). Tafcing this to be so,
the absorption spectrum of the (SH-) anion can be calculated from
the pH 8.9 spectrum via Eq. 2.121. For example, at 297.5 nm,
193 = (0.952)(14) + (0.0477) ABSG(SH-)
gives ABSG(SH-) = 3767. The accuracy of this procedure can be
tested by using Eq. 2.121 to predict absorbance of the solution
at pH 7.0:
(0.999369X14) + (6.31E-4) (3767) = 16 (/cro/M)
as compared to the experimental value of 18 /cm/M. The computed
absorption spectra of the uncharged SH2 molecule and the SH-
anion of p-Cresol are also shown in Table 2,19, with the
projected absorption coefficients at pH 7.0, The absorption
spectra of the individual molecules are the appropriate data for
entry into EXAMS' chemical data base (input vectors ABSG),
2.3,3.5 Effects of sorption to suspended sediments and biota
The effects on direct photolysis of sorption to suspended
sediments and biota are incorporated into EXAMS via separate
disappearance quantum yields (QUANTG) for the sorbed forms of
each dissolved species (SH2, SH-, etc.) of the compound.
Although sorption can produce subtle and complex changes in the
photochemistry of pollutants, light extinction by suspended
particulate matter, and capture of sorption-prone chemicals by
bottom sediments, relegate the effects of sorption to a secondary
98
-------
role. It cannot simply be assumed, however, that sorption
Inevitably "protects" a chemical from direct interaction with
solar radiation, so EXAMS allows for alternatives to this
assumption via the QUANTG chemical input vector.
The "sorption" process includes adsorption of a chemical
onto particle surfaces, dissolution of uncharged species into
suspended organic materials, and migration into the interior of
particles via diffusion along pore channels. The particle
microenvironment is often very different from that of the
surrounding aqueous milieu. For example, the surface acidity of
clay minerals can result in protonation of organic bases beyond
that predicted by solution-phase pH and PK (Kariclchoff and Bailey
1976). This effect can, at least in principle, be represented
via EXAMS' separated partition coefficients for the ionic species
of a pollutant (Section 2.2.2). The extent of the
sorptlon/protonation process is influenced, however, by particle
size, interactions with the solution-phase carbonate system, and
inorganic cations adsorbed on the clay surface. These
complexities, and the fact that mineral clays constitute a
varying proportion of natural sediments, restrict EXAMS to the
phenomenological approach described in Section 2.2.2. The
photoreactivlty of an organic acid or base can be affected by
ionic speciation at the surface of adsorbent particles. Bailey
and Kariclchoff (1973) demonstrated this effect via its converse:
these authors showed that UV spectroscopy can be used to monitor
surface acidity of clay minerals via the shift in the absorption
spectrum of adsorbed organic bases from that of the uncharged, to
the protonated, molecular species.
The dissolution of neutral organic pollutants into suspended
organic matter or surface organic films also removes the chemical
from aqueous solution to a very different microenvironraent. This
organic microenvironment may alter the absorption spectrum,
quantum yields, and photochemical reactions of a sorbed molecule,
for organic sorbents usually differ from water in both refractive
index and polarity. A change in the refractive index of the
absorbing medium Implies changes in spectral radiation density
(erg/cm3/unit frequency range) in the medium, and therefore in
the apparent absorption spectrum of a pollutant chemical.
Although the effects of such phenomena can be computed in some
cases (Strickler and Berg 1962), the heterogeneity of natural
suspended organic matter defies description. Particle size
distribution (i.e., light extinction in the interior of the
particle) would also affect the average radiation density
experienced by a sorbed-phase pollutant.
In addition, reaction conditions within a suspended particle
microenvironment must differ from those of aqueous solution?
these differences can alter the reaction quantum yields and the
kinds of photochemical products that result from irradiation of
the system (Miller and Zepp 1979b). Suspended sediments may also
99
-------
retard sorbed-phase photoreactions by quenching excited states of
the molecule, and may enhance photoreaction via indirect
processes or "sensitized" reactions. Possible indirect reactions
include the production of excited states or free radicals via
irradiation of the organic matrix of the suspended particles, and
photoelectric excitation of semiconductors, such as Ti02, which
are a common constituent of many natural sediments (Oliver,
Cosgrove, and Carey 1979).
A few phenomenological investigations of the effects of
natural suspended sediments on photochemical kinetics have
appeared in the literature; the complexity of the phenomena has
led their authors to describe their findings via apparent effects
on reaction quantum yields. Oliver, Cosgrove, and Carey (1979)
compared the effect of ourlfied Ti02 semiconductor to the
photochemical efficacy of Ti ores (ilmenite and rutile) and
natural river suspensoids. Although ourified Ti02 was an
efficient photochemical catalyst, the Ti ores and the natural
sediments alike simply suppressed the photochemistry of the test
materials via competitive light absorption. Miller and Zepp
(1979b), from studies of the photolysis of DDE and
m-trifluoromethylpentadecanophenone (TPP) in natural suspended
sediments, concluded that the sediment microenvironcnent is
similar to a saturated hydrocarbon solvent. These authors
reported an apparent increase in the disappearance quantum yield
of sorbed DDE to 1,5 times its value in aqueous solution, and a
factor of 2 to 6 decrease in the apparent quantum yield of TPP.
Both results were consistent with the behavior of these compounds
in organic solvents. Miller and Zepp (1979a) concluded that the
competitive absorption of light by suspensoids is nonetheless the
dominant effect of suspended particles on photolysis in natural
waters.
2.3.3.5.1 Simulation analysis of sorption effects on direct
photolysis
Photolytic transformation of pollutant chemicals is an
important process in many aquatic systems, most especially when
photochemical transformation is the only degradation process
capable of limiting organism exposures under environmental
conditions. This process is critically dependent on competitive
light absorption by suspended materials, and on the effects of
sorption on the availability of a pollutant to photochemical
processes.
In a natural water body, capture of a pollutant by benthic
sediments removes the compound to a photochemically inactive
(dark) sector of the ecosystem. The net photochemistry of a
pollutant chemical thus depends on solution- and sorbed-phase
photoreactivity, competitive light absorption by suspensoids, and
capture of the pollutant by the benthic subsystem. The
100
-------
interactions among these processes can be explored via EXAMS.
For the example simulations, the ecosystem was a small (1 ha)
static pond, 2 m deep, with a 1 cm active benthic subsystem of
bulk density 1.75 g/cc and water content 150%. The example
compound had a near-surface halflife of 1 hour in solution (KDPG
= 0.6931, QUANTGCl,!) * 1.0), but was a full order of magnitude
more photoreactive when sorbed with suspended sediments
(QUANTG(2,1) = 10.0), The distribution function (DFACG) was
taken as 1.20; EXAMS used the sum of light absorption by water
itself (at 300 nm), plus the absorbance attributable to suspended
sediments, to compute the average light intensity in the water
column (Eq. 2.115). Systematic changes in the partition
coefficient of of the chemical (KPS) and the concentration of
suspended sediments (SDCHRG) then were used to elucidate their
net effect on the photochemistry of the compound, under
conditions most favorable for enhancement of phototransformation
kinetics by sorption.
The results of simulations using a suspended sediment
concentration of 10 mg/L and varying partition coefficients (0 -
1.E6 L/kg) are given in Table 2.20. These results are given in
terms of pseudo-first-order halflives for the water column
subsystem alone, and for the entire pond ecosystem, (The
whole-system halflives assume that the rate of transport from the
benthic subsystem into the water column does not limit the rate
of photochemical transformation of the compound.) Under these
environmental conditions, less than 1% of the compound in the
water column is in the sorbed state for a partition coefficient
less than 1000 L/kg. when the partition coefficient is greater
than 1000, however, more than 85% of the resident material is
captured by the (dark) benthic subsystem. The system-level
halflife of the cdmpound increases steadily with increasing Kp,
despite the greater photoreactivity of the sorbed material.
The effect of competitive light absorption by suspended
materials was examined by fixing the partition coefficient at 100
L/kg, and systematically increasing the concentration of
suspended sediments from 0 to 10,000. mg/L (Table 2.21). In
this case, light absorption by the suspended sediments rapidly
increased the photochemical halflife of the compound. This
effect overwhelmed the enhanced photoreactivity of the sorbed
material, despite the fact that more than half of the total
compound in the system resided in the water column (at steady
state).
101
-------
Table 2.20, Effect of partition coefficient Kp (liters/kg) on net
photoreactivity «*hen suspended sediment concentration = 10 mg/L*
Kp,
L/fcg
0.
1.
10.
100.
1000.
10000.
100000.
1000000,
Percent
dissolved
In water
100.
100.
100.
99.9
99.0
90.9
50.0
9.09
Percent
captured
by benthos
0.29
0.87
5.8
36.9
85.2
98. 2
99.7
99.8
Pseudo-Fi
Half live
tfater Column
8.50
8.50
8.49
8.42
7.80
4.68
1.55
0.93
rst-order
s, hours
Whole system
8 ,,52
8 ,,57
9.01
13,4
52.9
253,
452.
492.
* Average liqnt Intensity in water column 11.8% of surface value
Table 2.21. Effect of suspended sediroent concentration CSJ on
net photoreactivity when partition coefficient KP » 100 uters/kg
CSJ,
mg/L
0.
1.
10.
100.
1000,
10000.
Percent
dissolved
in water
100.
100.
99.9
99.0
90.9
50,0
Percent
benthic
capture
36.96
36.96
36.93
36.73
34.77
22.67
I(z)/I(0) Pseudo-First-Order
(Average) Halflives, hours
% water Column Whole System
84.8
59.3
11.8
1.22
0.12
0.012
1.18
1.68
8.42
75.2
449.
1484.
1.87
2.67
13.4
119.
688.
1918.
102
-------
The system-level pseudo-first-order halflife indicates the
outcome of the interaction between competitive light absorption
by suspended materials/ capture of tne compound by bottom
sediments, and enhanced photoreactivity in the sorbed state.
Table 2.22 gives the systen-level photochemical halflife of a
compound that is 100 times more reactive in the sorbed, than in
the dissolved, state, for a range of Kp and sediment
concentrations unlikely to be exceeded in nature. As compared
with the 1.18 hour halflife of the unsorbed, clean-water
baseline, an increase in sorptlon leads to a net suppression of
the rate of photochemical transformation of the compound in all
cases, despite the uniquely (and unrealistically) favorable
conditions assumed for the analysis. In sum, the effects of
residence in the sorbed state on photoreactivity are of secondary
importance, and can be adequately summarized via a simple
descriptive parameter (QUANTG), in the context of a first-order
evaluation.
Table 2.22. Effect of suspended sediment concentration (mg/L)
and partition coefficient (Kp, liter/leg) on system-level
pseudo-first-order photochemical halflife (hours) when sorbed
chemical is 100 times more reactive than dissolved species
Kp,
liter/kg
0.
1.
10.
100.
1000.
10000.
100000.
1000000.
Suspended
0 1
1.18
1.19
1.25
1.87
8.06
69.9
689.
6876.
1.69
1.70
1.79
2.65
10.5
50.0
89.6
97.4
Sediment Concentration, mg/L
10 100 1000 10000
8.52
8.57
8.93
12.3
29.1
45.9
49.2
49.6
82.2
81.8
79.1
65.4
51.7
49.0
48.6
48,6
819.
749.
437.
125.
63.3
56.6
55.9
55.8
8182.
4157.
861.
209.
137.
130.
129.
129.
The effects of sorption to organic slicks at the air-water
interface are not included in EXAMS for similar reasons;
103
-------
Although the concentration in the slick can be large, the total
fraction of the pollutant resident in the film is probably too
small to have much effect on the system-wide kinetics of
pollutant chemicals (Zepp and Baughman 1978).
EXAMS represents the photochemical effects of sorption to
suspended sediments, and to biota, via separate entries in the
QUANTG vectors. Note that these vectors represent the effect of
residence in the oiosorbed state on the direct photolysis of the
pollutant; they are not intended to represent photosensitization
or photobiological transformation of pollutants by phytoplanlcton.
Although qualitive studies have indicated that this pathway
exists, as yet a quantitative basis for predicting its magnitude
and importance in natural systems has not been developed (Zepp
1980).
2.3.3.6 Near-surface solar beam and sky irradiance (input WLAMG)
The spectral light field is entered into EXAMS as a vector
("WLAMG") of 39 photon irradiances. WLAMG is the total (solar
beam plus skylight) irradiance under clear (cloudless)
conditions, just below the air-water interface (that is, after
subtracting reflected light from the light incident on the
surface). EXAMS corrects the input irradiance for effects of
cloud cover via Buttner's (1938, cited from Zepp 1980) empirical
relationship:
Eq. 2.122 WLAMG <-— WLAMG * (1 - 0.056*(CLOUDG) )
The cloudiness (EXAMS' input scalar CLOUDG) term is the average
sky cover in tenths, with a range from 0 (clear sky) to 10 (full
cover).
Clear-sky irradiance at the earth's surface depends on
latitude, site elevation, atmospheric turbidity and water vapor
content, and the ozone content of the stratosphere (Leighton
1961). EXAMS' environmental («LAMG vector can be developed via
site-specific measurements, or via estimates appropriate to the
regional geography of an evaluative ecosystem type.
Computational methods for estimating spectral irradiance have
been explored by a number of authors (e.g., Leighton 1961;
Green, sawada, and Shettle 1974; Green, Cross, and smith 1980;
Green and Schippnick 1980; Dozier 1980). Irradiance spectra are
often computed or measured in energy units. These spectra can be
converted to photon irradiances via Planck's law. For example,
given an energy spectrum ("Es") in uWatts/cn»2/nm, WLAMG in
photons/cm2/sec/N nm can be computed from:
Eq. 2.123 WLAMG = Es * 5.047E9 * LAM(nm) * N(nm)
where LAM is the wavelength of the incident radiation, and
104
-------
J/s l.E-9 (m/nm)
l.E-6 ..... * ............................. = 5.047E9
uWatt 6.6262E-34 (J s) * 2.99 (m/s)
At 297.5 nm, for example, the appropriate conversion factor is:
WLAMG(l) * ES * 5.047E9 * 297.5 * 2.5 « 3.754E12 * Es
Zepp and Cline (1977), using a computer program ("SOLAR")
available on request from those authors, calculated photon scalar
irradiance ("w") at the 39 wavelength intervals adopted for
EXAMS. Their report gave "midseason," "midday" spectral
irradiance at 40 degrees N latitude. For EXAMS, these values
must be reduced by a daylength factor and via sinusoid averaging
over the photoperiod (i.e., multiplied by 2/3.14), Summer . and
winter photon irradiances ("W values quoted from Zepp and Cline
1977), and yearly mean values, are shown in Table 2.23. The
WLAMG vector given in this table is supplied with the nominal
environmental definition distributed with the EXAMS software.
Note that the bandwldths of the input wavebands, for wavelengths
longer than 323.1 n-n, are all per 10 nm. This waveband size does
not correspond to the computational wavebands for Intervals 29-39
(i.e., wavelengths > 490 nm; see Table 2.18). EXAMS expands the
wavebands to their full computional bandwidth internally. For
example, the input datum for interval 39, centered at 800 nm, is
Increased by a factor of 5 to expand the input WLAMG (/10 nm) to
the full 50 nm computational bandwidth.
Subroutine PHOT01 begins from near-surface precomputed
photolysis rate constants (KDPG), and thus does not use the
spectral irradiance vector WLAMG in its computations. PHOTOl
adjusts KDPG via a cloudiness correction (Eq. 2,122), and also
corrects KDPG for the geographic translation from the latitude at
which each KDPG was measured (RFLATG) to the latitude of the
ecosystem (LATG), The correction term is computed from the total
annual solar + sky radiation received at latitudes RFLATG and
LATG, Ground-level radiation was computed as a function of
latitude at 10 degree intervals via procedures described by List
(1966) using an atmospheric transmission coefficient of 0.90.
Estimated total radiation increased from 1.038E5 cal/cm2/yr at
the pole, to 2.744E5 ly/yr at the equator. Regression of the (8)
estimates on:
Y s a * b cos(2L)
where L is the latitude in radians, yielded a * 1.917E5, b *
8.705E4, and accounted for 99.7% of the variation in total
irradiance (Y) with latitude. In subroutine PHOTOl, the
correction term for KDPG is computed as:
105
-------
KDP <--- KOPG *
a -I- b COS (0.0349 LATG)
a + b cos (0.0349 RFLAT3)
For example, for a rate constant measured at the equator and a
polar ecosystem,
KDP <--- KOPG *
a + b cos (0.0349 * 90)
m**m~*mm»*m»mm»mmtmfmm~^**mmmm
a + b cos (0.0349 * 0)
= 0.38(KDPG)
This procedure is based on total solar energy input, and thus may
underestimate the latitude dependence of photochemical
transformation of pollutants that absorb sunlight most strongly
at wavelengths < 320 nm.
2.3.3.7 Input data and computational mechanics -- Summary
Subroutine PHOT01 was designed to evaluate chemicals whose
absorption spectrum has not been quantified. Its primary input
datum, KDPG, is a vector of pseudo-first-order photolysis rate
constants. A separate value of KDPG can be entered for each
existing ionic species (SH2, SH3+, etc.). KDPG is assumed to
apply to near-surface waters, under cloudless conditions and
full-day average solar irradiance. EXAMS adjusts the rate
constant for light extinction in the water column , effects of
cloud cover, and deviation of the latitude of the system (LATG)
from the latitude at which the rate constant was measured
(RFLATG).
Each value of KDPG is paired to 3 elements of the QUANTG
matrix of disappearance quantum yields. QUANTG(l,k) is the
disappearance quantum yield of the aqueous dissolved molecule(s)
("k" the number of the ionic species, where k s 1 denotes the
uncharged (SH2) molecule, k = 2 is the
(SH4+-O, 4 is (SH-), and 5 is (S*)).
parameter is set to a dummy unit value,
quantum yield of the compound be known, a near-surface Ka (Eq.
2.113) can be loaded via KDPG, and the observed quantum yield(s)
can be entered via QUANTG. QUANTG(2,k) and QUANTG(3,k) specify
the quantum yields of the sediment-sorbed and biosorbed forms of
each ionic species of the compound. These parameters allow for
entry of known sorption effects on photolysis rate constants, and
in any case allow the user to relax the assumption that sorption
"protects" the compound from photoreactions.
(SH3+) cation, 3 is
Usually for PHOTOl this
but should the true
106
-------
Table 2.23. Sample input spectral irradiance (WLAMG) for EXAMS
NO.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
waveband
Center,
nm
297.5
300,0
302.5
305.0
307.5
310.0
312.5
315.0
317,5
320.0
323.1
330.0
340.0
350.0
360.0
370.0
380.0
390.0
400,0
410.0
420.0
430.0
440.0
450.0
460.0
470.0
480.0
490.0
503,75
525.0
550.0
575.0
600.0
625.0
650.0
675.0
706.25
750.0
800.0
Input
Widtn
N, nm
2.5
N
M
N
H
H
ft
n
H
2.5
3.75
10.0
N
N
n
N
H
N
N
N
N
H
n
M
N
If
H
N
n
H
*
H
H
H
N
N
H
N
10.0
Spectral Irradiance, photons/cm2/sec/N nm
Sumnier*
6.47E+11
2.19E-H2
6.57E+12
1.63E+13
2.74E+13
4.44E+13
6.43E+13
8.36E+13
1.03E+14
1.21E+14
2.26E+14
7.62Etl4
8.75E+14
9.38E-H4
l.OOE+15
1.12E+15
1.24E+15
1.48E+15
2.12E-U5
2.79E+15
2.87E+15
2.77E+15
3,27Etl5
3.68E-H5
3.72E+15
3.84E-^15
3.94E+15
3.72E-H5
3.80Etl5
4.01E-H5
4.18Efl5
4.23E-H5
4.27E+15
4.28E+15
4.29E-H5
4.27E+15
4.22E+15
4^,04E-H5
3.87E+15
Winter*
O.OOEfOO
6.01E+10
3.00Etll
1.39E+12
3.69E+12
6.98E*12
1.45E+13
2.22E-H3
2.96E+13
4.08E*13
7.40E+13
2.79E+14
3.41E+14
3.63E*14
3.83E+14
4.18E414
4.50E+14
6,46E-»-14
9.31E+14
1.23E-H5
1.27E+15
1.23E+15
1.46E+15
1.64E+15
1.67E+15
1.72E+15
1.77E+15
1.68E-H5
1.71E+15
1.81Etl5
1.88E-H5
1.90E+15
1.92E
-------
The computations executed by subroutine PHOT01 are
inherently less precise than wavelength-specific computations
based on the chemical's absorption spectrum (PHOT02), because
PHOT01 cannot evaluate the effects of spectrally differentiated
light extinction in the water column. PHOTOl is, however, useful
for photoreactive compounds with absorbances too small to measure
using current techniques.
Subroutine PHQT02 couples the absorption spectra of the
compound (A8sG(1-39,k)) to the irradiance spectrum incident on
the water body (WLAMG). The QUANTC matrix in this case contains
measured disappearance quantum yields; its use in EXAMS is in
all other respects (effects of sorption, etc.) identical to the
use described for subroutine PHOTOl.
Both photolysis subroutines operate on the incident light
field to compute the average light intensity in each compartment
of the ecosystem. (In PHOTOl, the incident light field has a
nominal value of 1.0, because KDPG has built into it the
clear-stcy irradiance at latitude RFLATG.) PHOTOl uses a spectral
composite light absorption coefficient for each sector of the
water body (CMPETG); PHOT02 computes the absorption coefficient
for each spectral waveband (Table 2.18) from the pigment (CHLG),
dissolved organic carbon (DOCG), and suspended sediment (SDCHRG)
concentrations in each compartment (Eg. 2.116).
The water column ("E" and "HH compartment types) can be
subdivided into as many horizontal slices as seems appropriate
for a particular water body. EXAMS traces light extinction
vertically through the slices by computing irradiance at the
bottom of each compartment, as well as the average irradiance
used for computing photolysis rate constants. When the (J-l)
compartment is another Fl or H segment, irradiance at the bottom
of the (J-l) compartment is taken as the starting point for
irradiance computations in the current (J) sector. This scheme
will fail, however, if the system definition rules given in
Section 2.3.1.1 are disregarded.
An example of a logical, but improper, segmentation scheme
is shown in Figure 2,5a. Calls to EXAMS' Photolysis subroutines
are executed in compartment order. For this ecosystem, the first
call computes photolysis in compartment 1, a (Dittoral water
column compartment. The incident light field at the air-water
interface is identified as the light intensity at the top of the
compartment, and EXAMS computes both average light intensity and
irradiance at the bottom of compartment 1. Compartment 2 is a
(B)enthic compartment;
108
-------
I I
I L 1 I
4. ...... 4
I B 2 l\
4.. .....4 \
B 4
4.. ....
|\
4 \
I \
\ \
\ \
\ 4
\
4.
H 5
...
B 6
a. improper segmentation: incomplete vertical definition.
1 1
1 L 1 1
4. ......4 E 3
1 B 2 |\
4.. .....4 \
\ B 4
E 5
l\
....4 \
I \
\ \ H 6
\ \
\ 4........................
\ B 7
b. Proper segmentation: complete vertical definition.
Figure 2.5. Examples of proper and improper vertical structure.
109
-------
EXAMS simply sets tne photolysis rate to 0 and does not call a
photolysis subroutine. Upon reaching compartment 3, EXAMS checks
the compartment type of the (J-i) compartment. As compartment 2
is neither E nor H, the incident light field is used to start the
computations. (Note that the test is based on compartment types
"E" and "H" only; (L)ittoral water column compartments thus
should not be horizontally subdivided.) A photolysis subroutine
is not invoiced for (B)enthic compartment 4. When EXAMS now calls
for irradiance computations for the (H)ypolimnion compartment
(5), an error occurs. EXAMS inspects (J-l) compartment 4, finds
it to be (B)entnic, and starts its computations for the
hypolimnion using the surface incident light field, rather than
intensity at the bottom of the epilimnion.
The proper system definition is shown in Figure 2.5b. In
this case, upon initiation of computations for the hypolimnion
(now numbered 6), EXAMS finds that the (J-l) compartment (5) is
an (E)pilimnion segment. The light intensity at the bottom of
compartment 5 (internal variable BOTLIT in PHOT01, BOTLAMU-39)
in PHOT02) is retrieved and used to start the irradiance
computations for the hypolimnion.
EXAMS reports the average light Intensity in each sector of
the ecosystem as part of its "canonical profile" of the system.
These reports are given as a percentage of the light field
incident on the water body. The numerical value of this quantity
can vary with the chemistry of the compound. For a chemical for
which photolysis is computed via the KDPG vector (PHOTOi), the
average light intensity is governed by CMPETG alone, but CMPETG
can vary with LAMAXG, For a chemical for which photolysis is
computed via the absorption spectrum (PHOT02), the reported
average light intensity is based only on that portion of the
solar spectrum in which the compound absorbs radiation.
Different chemicals thus experience a different reduction in
total radiant intensity within the same waterbody.
For organic acids and bases, the apparent average light can
be variously reported, depending upon which ionic species is
evaluated at the first call to PHOTOI or PHOT02. For example,
given a chemical with non-zero ABSG vectors for SH2 and SH-, the
reported average intensity would be based upon the SH2 (first
called) absorption spectrum, although a fuller (or reduced)
portion of the solar spectrum might be used to compute photolysis
of the SH- anion. For an amphoteric compound, If the SH2
molecule were described via KDPG, and the SH4+ and SH* ions were
described via their absorption spectra, EXAMS would report
average light levels based on the absorption spectrum of SH4+.
This phenomenon arises from an interaction among the photolysis
subroutines. In this case, the uncharged (SH2) molecule is
evaluated first via subroutine PHOTOI, and EXAMS' internal
variable (LIGHTD that is reported in the "canonical profile" is
computed from CMPETG. When PHOT02 is called for evaluation of
liO
-------
SH4+, however, LTGHTL Is recomputed over the part of the solar
spectrum In which SH4+ absorbs light. During the third set of
computations (SH- in PHOT02), LIGHTL is not recomputed. If an S=
(k=5) anion had been described via KDPG, the call to PHOT01 would
not reset LIGHTL, for PHOT01 would have already executed this
computation for the current compartment and will not repeat it.
In sum, it should be recognized that the average light
intensity reported in EXAMS' "canonical profile" of the ecosystem
results from interaction between the chemistry of the synthetic
compound and properties of the ecosystem. This output provides a
sense of the effect of competitive light absorption in the water
body on Photolysis of the compound, but it usually should not be
interpreted as an intrinsic property of the ecosystem itself.
2.3.4 Specific Acid, Specific Base, and Neutral Hydrolysis
Many organic compounds react directly with water in the
aqueous solvent system. In addition, water dissociates into
hydronium and hydroxide ions, and the concentrations of these
subsidiary species often affect the rates of chemical
transformations. EXAMS includes kinetic constants for three
kinds of hydrolytic pathways: specific-acid (H3CH) catalyzed,
neutral hydrolysis, and specific-base (OH-) catalyzed
transformations*
The breakdown of esters to yield a carboxylic acid and an
alcohol is a convenient example of hydrolytic transformations.
The overall reaction is:
Eq. 2.124 RCODR' + H20 —> RCOOH 4- R'OH
where R and R* can be any alkyi or acyl moiety. Although this
equation accurately depicts the stoichiometry of ester
hydrolysis, it does not serve as a defining equation for
computing the velocity of the reaction. The rate of
transformation of any specific ester is fundamentally dependent
on its chemical structure. The speed of the reaction often
depends on the pH of the medium as well, however, because ester
hydrolysis can proceed via three distinct pathways (acid/base
catalysis, neutral) with identical net stoichiometry.
Because chemical reactions involve shifts in electronic
bonding orbitals, organic compounds are most readily attacked by
groups that can donate or accept electrons from the target
molecule. Electron-deficient chemical species (e.g., hydrogen
ions) are called "electrophiles." Electrophiles are particularly
attracted to atoms with negative charge, to a lone pair of
electrons, and to the electron-dense region of a double bond.
Chemical groups with extra non-bonding electrons are called
"nucleophiles." The electronegative hydroxide ion is a relatively
ill
-------
strong nucleophile. The water molecule is itself nucleophilic,
because the oxygen atom of this "polar" molecule has a lone pair
of electrons.
The mechanisms of the formation and hydrolysis of organic
esters have been reviewed by Kirby (1972). Tinsley (1979:105 ff)
has summarized the routes and mechanisms of ester hydrolysis
under environmental conditions, where in all probability only the
"A(AC)2" and "B(AC)2" mechanisms are significant. Although all
three routes of ester hydroysis Involve nucleophilic phenomena,
the mechanism of the pathway is somewhat different in each case.
Acid-catalyzed ester hydrolysis is a true "catalysis"
reaction in that hydronium ion participates in the reaction but
is not consumed by the reaction sequence. In the first step of
this pathway, the electrophilic hydronium ion protonates the
carbonyl (C=0) oxygen. The protonated ester then undergoes a
nucleophilic addition of water to give a tetrahedral
intermediate; this step is catalyzed by a second water molecule
acting as a general base. Finally, the tetrahedral intermediate
breaks down via two additional (fast) steps to yield the product
carboxylic acid and alcohol, and to regenerate the catalytic
hydronium ion.
Because two water molecules are involved in the formation of
the tetrahedral intermediate, the specific-acid catalyzed
hydrolysis of the ester bond is "second-order" in water. With
water as the solvent medium for the dissolved phase of the
compound, however, the water concentration does not change during
the course of the reaction and need not be incorporated in the
kinetic expression. The observed rate constants are nonetheless
subject to solvent effects and should be measured using pure
water as the solvent whenever possible. The direct involvement
of the water molecule in the reaction also imposes a need tor
care in the extrapolation of hydrolysis rate constants (measured
in pure water) to compounds sorbed with sediments.
In EXAMS, all concentrations are referenced to the water
phase of each compartment (Eq. 2.1). The total pollutant
concentration c (units mg/liter of water), when multiplied by the
appropriate distribution coefficient ALPHA, gives the dissolved
concentration of pollutant in the aqueous phase of each
compartment, including that in the interstitial pore water of a
benthic sediment. This fraction of the pollutant hydrolyzes at
the rate measured via a homogeneous phase (pure water)
experiment. EXAMS computes the effects of residence in a sorbed
state (where water concentration can be quite small) on the
reactivity of the compound via an additional set of input
parameters (Section 2.3.4.3).
Neutral hydrolysis of organic esters proceeds via a
mechanism similar to that of the second stage of the
112
-------
acid-catalyzed pathway. Two molecules of water are again
involved in the formation of a tetrahedral intermediate, with one
molecule of water acting as the nucleophile and a second water
acting as a general base catalyst. Although the neutral reaction
is usually treated as a simple first-order process (Wolfe 1980),
it is in fact technically second-order in water concentration.
For this reason, the reaction is subject to solvent effects, and
requires the same caution in extrapolation to sorted states as
was described above for acid-catalyzed hydrolysis.
Alkaline hydrolysis, the third hydrolytic mechanism
considered in this Section, is not strictly speaking a
hydroxide-"catalyzed" reaction, for hydroxide ion is consumed in
the reaction sequence, yielding the ester's constituent alcohol
and the anion of its carboxylic acid. At trace concentrations of
the ester in buffered natural waters, however, this distinction
is of no practical significance. As in the neutral and
acid-catalyzed pathways, a tetrahedral intermediate species is
probably involved in alkaline hydrolysis. In this case, however,
the intermediate is usually envisioned as resulting from a direct
nucleopnilic attack of hydroxide ion on the carbonyl carbon, with
formation of the tetrahedral intermediate as the rate-limiting
step in the reaction pathway. The tetrahedral intermediate then
breaks down via release of an R'O- anion, and rapid proton
transfer (to R'O-), to yield the products of the reaction (R'OH
and RCOO-).
The overall rate of hydrolytic transformation is thus the
sum of three competing reactions, and the observed rate constant
(Kobs, units /hr) can be computed as the sum of contributions
from acid-catalyzed (KAH), neutral (KNH), and base-catalyzed
(KBH) reactions (Wolfe 1980):
Eq. 2.125 KobS = (KAHMH+J t KNH + (KBHHOH-J
Kobs is a pseudo-first-order (/hr) rate constant under the
specified environmental conditions (pH, pOH) in pure water.
After incorporation of the effects of ionization and sorption on
reactivity, Kobs becomes the hydrolytic contribution to the
overall pseudo-first-order rate constant K of Eq. 2.1. The
second-order transformation rate constants are part of EXAMS'
input chemical data base. KAH and KBH have units of reciprocal
molarity and reciprocal hours (/M/hr). KNH, the neutral
hydrolysis rate constant, has units /hr. The environmental data
for this computation is entered as a separate pH and pOH for each
sector (compartment) of the ecosystem; the EXAMS variables are
"PHG" and "POHG," respectively.
The utility of this approach is not, of course, United to
chemical transformations of carboxylic acid esters. For example,
amides, carbamates, and organophosphates break down via
hydrolytic mechanisms (Tinsley 1979). Also, many haiogenated
113
-------
compounds are subject to unimolecular and bimolecular
nucleophilic substitution (SN1 and SN2) or elimination (El and
E2) reactions whose kinetics can be represented via Eq. 2.125.
Experimental studies of the rate of hydrolysis in buffered
aqueous solution can be used to determine Kobs at fixed pH
levels. In many cases KAH and KBH can be determined at low and
high pH, respectively, where only one reaction pathway is
significant. The pH-rate profile, a plot of log Kobs vs. pH,
then includes a descending (acid catalyzed) and ascending
(alkaiirve) limb, with slopes of -1.0 and +1.0, respectively
(Figure 2.6). These lines intersect at the theoretical rate
minimum, giving the best pH for an experimental determination of
any neutral contribution (KNH). One or more of the reaction
pathways may be undetectably slow for a particular compound,
resulting in a simplified pH-rate profile. (The use of pH-rate
profiles for calculating hydrolysis rate constants has been
described in more detail be Kirby (1972:153) and by Mabey and
Mill (1978).)
Reported chemical rate constants are often based on the
second or minute as the unit of time. For use in EXAMS, such
data must be converted to units based on the hour. For example,
the neutral hydrolysis rate constant of phenyl acetate is 6.6E-8
/sec (Figure 2.6). EXAMS' chemical input parameter (KNHG, units
/hr) would be
6.6E-08 (/sec) * 3600 (sec/hr) = 2.38E-4 /hr.
2.3.4.1 Temperature effects
Each hydrolytic rate constant in EXAMS' chemical data base
(KAHG, KNHG, KBHG) has a paired input parameter that allows for
alternative entry of the chemical information as an (Arrhenius)
function of temperature. The pairings are KAHG - EAHG, KNHG -
ENHG, and KBHG - EBHG, respectively. The rate constant variables
(KAHG etc.) are interpreted as the (Brlggsian logarithm of the)
"pre-exponential" or "frequency* factor in an Arrhenius function,
only when the parallel activation energies (EAHG etc.) are
non-zero. When the input energy parameter is set to zero, EXAMS
accepts the kinetic parameter (KAHG, etc.) as the rate constant
itself (compare Section 2.3.2.1). For example, an activation
energy (Ea) for the neutral hydrolysis of phenyl acetate (ENHG)
of, say, 20,000. cal/mole would imply a frequency factor A of:
A = KNH / exp(-Ea/RT)
(T in Kelvin) or, given KNH = 2.38E-4 /hr at 25 degrees C (Figure
2.6),
A » 2.38E-4 / exp(-20000./(1.99*298.15)) * 1.04EU /hr
114
-------
CD
-i-J
ed
-f->
w
cd rt
JH O
I O
L; cu
ffi S 'C
CD
CV2
115
-------
and log A, the EXAMS input (KNHG) would = 11.02 /hr,
in this instance, if EXAMS were loaded with KNHG = 2.38E-4
and ENHG s 0.0, KNHG would be used as the rate constant for
neutral hydrolysis irrespective of the temperature (environmental
input parameter TCELG) obtaining in the system compartments.
Alternatively, EXAMS could be loaded with KNHG * 11.02 and ENHG =
20.0. In the latter case EXAMS would compute local (compartment
specific) values of the neutral hydrolysis rate constant KNH via:
log KNH a KNHG - ( (1000.*ENHG) / 4.58 (TCELG * 273,15) )
or, at TCELG = 25 degrees C,
log KNH = 11.02 - (1000)(20)/(4.58)(298.15) = -3,626
and
KNH « 2.36E-4 /hr.
In many cases the temperature dependence of a chemical rate
constant is reported in terms of transition state theory, that
is, as an enthalpy (H) and entropy (S) of activation. Given H in
calories/mole and S in cal/deg/mole (also called "entropy units,"
e.u,), data reported under this convention can be converted to
Arrhenius functions via (Bunnett 1961):
Eq. 2.126 Ea a H •»• RT (calories/mole)
and
Eq, 2.127 log A * S/4.58 + log T + 14.319 (/hr)
(Because the RT term is only about 600 cal/mol at room
temperature, however, in many cases reported values of H are in
fact uncorrected Arrhenius activation energies (Ea).) For
example, wolfe and coworkers (1977) found that malathion
(0,0-dimethyl-S-(l,2-dicarbethoxy)ethylphosPhorodithioate) breaks
down via an acid catalyzed degradation with an enthalpy of
activation (H) of 22.3 kcal/mol and an entropy of activation (S)
of -4.1 eu. Using 15 degrees C as the temperature for
conversion, Eq. 2.126 gives
Ea a 22300 + (1.987)(288.15) = 22872. cal/mol
and an EXAMS input of EAHG » 22,87 kcal/mol. The frequency
factor A (Eq, 2.127) would be:
log A * -4.1/4.58 + log(288.15) t 14.319
yielding log A * 15,88 /hr = KAHG,
When a compound is subject to more than one degradation
pathway, the rate constants must be combined prior to entry in
116
-------
EXAMS' chemical data base. For example, malathion undergoes an
alkaline carboxyl ester hydrolysis plus an E2 elimination
reaction kinetlcally dependent on hydroxide ion concentration
tQH-J (Wolfe et al. 1977), These authors computed entropies and
(uncorrected) enthalpies of activation for both reactions; this
information could be used to generate an Arrhenius approximation
for the total alkaline disappearance rate constant KBH via the
transition state theory eguation
Eq, 2.128 KHB C/hr) = (7.5018E13)(T) exp (-H/RT) exp (5/R)
where H * Ea - RT, as in Eg. 2.126. Whenever possible, however,
it is probably better to rely on experimental determinations of
the total disappearance rate constant, measured at
environmentally relevant temperatures. In this case, the total
(second-order) disappearance rate constant was measured at 0 and
at 27 deg. C; it was 0.067 and 5.5 /M/s, respectively. The
activation energy and frequency factor can be easily computed
from this data, giving KBHG • 23,67 /hr and EBHG * 26.6
kcal/mole.
2.3.4.2 lonization effects
Anions and cations of organic acids and bases can hydrolyze
at rates differing greatly from those of the parent unionized
species. This phenomenon can give rise to pH-rate profiles very
unlike the archetypal example of phenyl acetate (Figure 2,6),
including an apparent kinetic dependence on fractional powers of
CH30+] or fOH-]. In order to encompass these phenomena, each of
EXAMS' input kinetic parameters (and parallel activation
energies) was set' up as a 3X5 matrix of variables. The second
index of these parameter matrices specifies the ionic species for
which a particular rate constant applies. (The first index
allows for -specification of the effects of sediment* and
bio-sorption .on reactivity; this aspect of EXAMS' input data is
discussed in Section 2.3.4,3.)
Consider, for example, the hydrolysis of the series of
substituted 2-phertyl-l ,3-dloxanes studied by Bender and Silver
(1963), All the acetals in the series showed the usual
acid-catalyzed hydrolyses, but those members containing an o- or
p-phenolic substituent were reactive at alkaline pH as well. The
pH-rate profile for one member of this series,
2-(4-hydroxy-5-nitrophenyl)-l,3-dioxane ("HND"), is shown in
Figure 2.7, This profile includes a descending limb of slope
-1.0 at low pH, a zone of little change in Kobs suggestive of a
neutral mechanism, followed by a second descending limb in the
alkaline pH range, which begins in the vicinity of pH = pKa.
From a comparison of the kinetics of o- and p-phenollc
substituted acetals, and from the effect of deuterium oxide on
117
-------
o
0>
w
-4
-6
-8
= 0.15
130
pKa 6.63
2-(4-Hydroxy-5-Nitrophenyl)
1,3-Dioxane
8
PH
Figure 2.7. Hydrolysis pH-rate profile
for a substituted 2-Phenyl-l,3-Dioxane.
Data from Bender and Silver 1963.
118
-------
these kinetics, Bender and Silver (1963) concluded that the
hydrolysis of these compounds does not proceed via a neutral
mechanism. Instead, the initial descending limb is the result of
the usual acid-catalyzed hydrolysis of the unionized species, and
the descending limb in the alkaline pH region results from a
similar acid-catalyzed hydrolysis of the phenolate anion (Figure
2.7). The anion is 860 times more reactive than the unionized
species. The uniformity of Kobs at intermediate pH results from
the increasing importance of the phenolate anion, as a fraction
of the total concentration, in this pH range.
The hydroiytic kinetics of HNO can be completely specified
in EXAMS' chemical data base via the pKa of the compound and the
rate constants for acid hydrolysis (KAHG) of the uncharged and
the anionic species. The existence of the unionized species and
the phenolate anion is signalled by setting SPFLG(l) and SPFLG(4)
to 1 (Section 2.2.1), and the pKa of HND is specified via PKAG(l)
^ 6.63. The second-order rate constants are 540. and 4.68E5
/M/hr for the parent compound and the anion respectively (Figure
2.7), This information is loaded to EXAMS by setting KAHG(l,l)
to 540, and KAHG(1,4) to 4.68E5. The first index (Section
2.3.4,3) simply denotes the form of the compound (1 = dissolved).
The second index specifies the ionic species to be transformed.
Subscript (t,l) thus specifies the unionized dissolved HND as
reacting at rate (540HH3Q+] /hr, and subscript (1,4) specifies
the phenolate anion as reacting at rate (4.68E5)[H3Q+3 /hr.
2,3.4.3 Sorption effects
Sorption of a compound either with sediment phases or with
living biomass removes the compound to a microenvironment that
can be very different from the free water phase of the system,
For example, Miller and Zepp (1979b) found that the daughter
product yields resulting from photolysis of DDE shifted from
p,P'-dichlorobenzopnenone toward DDMU (1,l-bis(p-chlorophenyl)-
2-chloroethylene) when the parent DDE was sorbed with suspended
sediments. Photolysis of DDE dissolved in hexane also gave
enhanced yields of DDMU. The authors concluded that the sorbed
compound experienced a microenvironment similar to that of an
organic solvent, and very different from that of the aqueous
phase.
Similar effects can be postulated for the majority of modes
of chemical reaction of organic compounds in the environment.
Presumably reactions like the neutral hydrolysis of carboxylic
acid esters, in which the water molecule participates in the
reaction, would be substantially inhibited by residence of the
target molecule in a sorbed state. An El or SNl reaction might
be little affected, however. Furthermore, the possibility of
accelerated (sediment "catalyzed") reactions cannot be
disregarded. Although no definitive studies on the effects of
119
-------
residence in a sorbed state on chemical reactivity have appeared
in the literature, such exploratory experiments as have been
undertaken indicate that sorption "protects" many compounds from
hydrolytic transformation. This is not a universal phenomenon,
however, for in some cases the reactivity of compounds was not
affected by residence in a sorbed state (wolfe 1980 (in prep.)).
Obviously, then, the differences between the sorbed form of
an organic compound and its dissolved phase can be as profound as
the differences between, for example, an organic acid and its
anions (Section 2.3.4.2). EXAMS therefore provides for the entry
of rate constants (or Arrhenius functions) that specify the
kinetics of sorbed forms completely independently of the
reactivity of the aqueous dissolved phase of the compound. Each
named kinetic parameter is a matrix with 15 elements, allowing
*«i. ,.„ f« K i««4f- ena/.
-------
Given that the assumption of a rapid local sorption
equilibrium holds good, however,
Eq. 2.132 Cw s ALPHA(l) Ct , and
Eq. 2.133 R Cs = ALPHA(2) Ct , where
Eq. 2.134 ALPHA(l) = 1/(1 + (Kp)(R)) , and
Eq. 2.135 ALPHA(2) = (Kp*R)/(l + (Kp)(R))
(Kp the partition coefficient), as described in Section 2.2.4.
Substitution of Eq. 2.132 and Eq. 2.133 into Eq. 2.131 gives:
Eq. 2.136 d(Ct)/dt » ( ALPHAUHKw) + ALPHA(2)(Ks) ) Ct
Equation 2.136 is (a simplified form of) the defining equation
used to build EXAMS' algorithm for combining the reactivity of
dissolved and sorbed forms into a single pseudo-first-order rate
constant.
The simplicity of this model makes the conversion of
experimental observations into a form suitable for EXAMS
relatively straightforward. Suppose, for example, that a neutral
organic compound ("NOC"), subject to a pH-independent
transformation, is observed to have a half-life in pure water of
33 hours. The rate constant describing this process is:
Kw s -(In 0.5)/33 « 0.021 /hr
This rate constant enters EXAMS' chemical data base via KNHG(1,1)
* 0.021. The first subscript of KNHG denotes the dissolved form
(1) of the compound; the second denotes an uncharged molecule.
(As NOC is a neutral compound, only SPFLG(l) is set (i.e., * 1),
and SPFLG(2), (3), (4), and (5) are 0, denoting the non-existence
of any ionic species.)
Suppose, now, that NOC has a partition coefficient on a
particular sediment of 90000 (mg/kg)/(mg/L), and an experimental
determination is made of the half-life of the compound after
sorption equilibration on a 100 mg/L suspension of the sediment,
(So long as local sorption equilibrium is maintained, the
half-life can be ascertained by following either Cw or Cs over
time.) The fraction of Ct present as dissolved and as sorbed NOC
can be computed via Eqs. 2.134 and 2.135. The sediment/water
ratio R is (100 mg/L) * (l.E-6 Kg/ml) « l.E-4 kg/L; the
dissolved fraction is:
Eq, 2,137 ALPHA(l) « 1 / (U(90000)(1,E-4) ) * 0,10
and the fraction sorbed 1st
121
-------
Eq. 2.138 ALPHA(2) = (90000)(1,E-4) / (1+(90000)(1.E-4)) s 0.90
This experiment has three obvious possible outcomes. First,
sorption may have no effect on the reactivity of the compound.
Second, the observed half-life may be increased in strict
proportion with ALPHA(l), that is, sorption may "protect" the
compound. Finally, an altered half-life may be indicative of an
altered, but non-zero, reactivity of the sorbed phase of the
compound.
In the first case, when the presence of the sediment
suspension has no effect on the rate of transformation of the
compound, Ks is identically the same as Kw. EXAMS could then be
loaded with KNHG(2,1) = 0.021. The subscript "2" denotes the
sediment-sorbed form of NOC.
When residence in a sorbed state Inhibits the transformation
reaction, the observed rate constant Kobs will decrease in
proportion with the residual water concentration of the compound.
From Eg. 2.136,
KobS = ALPHA(1)*KW t ALPHA(2)*KS
In this example, ALPHA(l) = 0.10, and, if Ks = 0 then
Kobs * (0.10M0.021) s 0.0021 /hr.
The possibility that sorption "protects" the compound can thus be
evaluated via the compound's half-life in a sediment suspension.
Here, given Kobs * 0.0021, the half-life Tau is given by;
Tau = -(In 0.5)/(0.0021) * 330 hours.
In other words, an observed half-life that was not significantly
different from 330 hours would be a clear indication that Ks 9 0,
and EXAMS could be loaded with KNHG(2,1) s 0.
Finally, the observed half-life may be neither 33 nor 330
hours, indicating that the sorbed state, while reactive, does not
transform at the same rate as the aquueous-phase dissolved
compound. (In the event that the observed half-life were longer
than 330 hours, Ks would be negative. The most probable
explanation of such an event, however, is that either the
sediment was contaminated with the study compound prior to the
experiment, or that the assumption of rapid local equilibrium has
been violated.) Any half-life between 0(+) and 330 hours can be
converted to a value of Ks via Eq. 2.136. if the half-life were
less than 33 hours, the transformation must have been accelerated
in the sediment phase and Ks > Kw. Suppose, however, that the
half-life of NOC in the 100 mg/L sediment suspension was 150
hours. The first-order rate constant Kobs is then:
122
-------
KobS
-(In 0.5)/(150,) * 4.621E-3.
Given Kobs = ALPHA(l) KW + ALPHA(2) Ks,
4.621E-3 = (O.DC0.021) + (0.9) KS
then
and Ks s 2.80E-3. The rate of reaction of NOC in the sorbed
state was thus 13.3% of that of the dissolved phase of the
compound. This information could now be entered into EXAMS via
KNHG(2,1) = 2.8E-3.
Second-order pH-mediated reactions ocurring on sediments are
accommodated in EXAMS in a wholly analogous way. EXAMS uses the
solution-phase pH and pOH to compute rates of reaction, so of
course the input data must also be developed from this
perspective. The full 15-element matrices of KAHG, KNHG, and
KBHG allow for the specification of effects of both sediment- and
bio-sorption on first-order, tH30+) mediated, and tOH-] mediated
reactions. In addition, any of these rate parameters can
alternatively be specified via an Arrhenius function, as
described in Section 2.3.4.1.
2.3.5 Oxidation
Direct photolysis is not the sole pollutant transformation
process driven by the solar flux in aquatic systems. The
simultaneous occurrence of plant decomposition products ("humic
materials"), dissolved oxygen, and sunlight often results in an
acceleration of the rate of transformation of organic pollutants.
Zepp and coworlcers (1977), for example, found that methoxychlor,
with a direct photolysis halflife of more than 300 hours, had a
halflife of as little as 2.2 hours under irradiation in natural
waters containing dissolved humic materials. Further, Ross and
Crosby (1975) found that a solution of aldrin in water from a
taro paddy can be photochemically converted to dieldrin, despite
the fact that aldrin does not absorb sunlight.
These Kinds of reactions are usually termed "indirect" or
"sensitized" photolysis. Indirect photolysis can be subdivided
into two general classes of reactions. First, "sensitized
photolysis" per se involves sunlight absorption and electronic
excitation of a sensitlzer (humic) molecule, followed by direct
chemical interaction between the excited state of the sensitizer
and a pollutant molecule. Possible chemical reactions include a
direct energy transfer to the pollutant molecule, hydrogen atom
transfer from pollutant to sensitizer to give free radicals, and
union of sensitizer and pollutant yielding an excited-state
complex or "exciplex" (Zepp and Baughman 1978). The resulting
free radicals or exclplexes can then react with dissolved
molecular oxygen, a process termed "type I sensitized
photooxidation" by these authors.
123
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The second class of indirect photolysis involves the
formation of chemical oxidants in natural waters, primarily via
the interaction ot sunlight, humic materials, and dissolved
oxygen (type II sensitized photooxidation of Zepp and Baughman
1978). The primary oxidants (cnown to occur in natural waters are
hydroxyl and peroxy radicals (Mill, Hendry, and Richardson 1980),
and singlet oxygen (Zepp et al. 1977), Alkoxy radicals and
diradicals may also contribute to environmental oxidation of some
compounds, but their presence in natural waters has not been
conclusively demonstrated (Mill 1980),
EXAMS represents the oxidative transformation of pollutants
via a purely phenomenological coupling of a second-order rate
constant (KOXG, units /M/hr) to user entries for the molar
concentration (OXRADG, moles/liter) of oxidants in each ecosystem
compartment. The pseudo-first-order contribution of oxidation
processes to the overall transformation rate constant K of
Eg, 2,1 is computed for each (I) compartment via:
Eg. 2.139 K (/hr) = KOXG * OXRADG(I)
The input parameter KOXG is again a 3X5 matrix, allowing for
separate entry of rate constants of ionic species and for control
of the effects of sorption on reactivity. The subscripts have
the same significance and use as described for KAHG etc. in
Section 2.3,4, Effects of temperature are entered via a parallel
matrix of Arrhenius activation energies EOXG (iccal/mole), again
as described in Section 2,3,4 for hydrolytic reactions.
The occurrence and concentration of oxidants in natural
waters has been investigated via the irradiation of chemical
"probes" in a laboratory setting. Zepp and coworkers (i977)
studied the generation of singlet oxygen using solutions of
2,5-dimethylfuran (DMFN) in natural waters. DMFN gives
1,2-diacetylethylenes via 1,4-addltion of singlet oxygen. The
speed of this reaction upon irradiation of the solution gives a
quantitative measure of the steady-state concentration of singlet
oxygen in the solution. Similarly, Mill and coworfcers (1978,
1980) have used cumene (isopropylbenzene) and pyridine as
chemical probes for the steady-state concentrations of peroxy and
hydroxyl radicals in irradiated natural waters.
Some results of these studies are given in Table 2.24,, The
average steady-state molar concentrations of oxidants were on the
order of l.E-13 for singlet oxygen, l.E-9 for peroxy radicals,
and i.E-17 for hydroxyl radicals.
124
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Table 2.24, Steady-state concentrations (moles/liter) of
oxidants in some natural waters*
Source
Singlet Oxygen Peroxy Radical Hydroxyl Radical
13
X 10 M
9
X 10 M
17
X 10 M
Aucilla River,
FL
Okefenofcee
Swamp, GA
Mississippi
River, LA
18.
22.
5.
2.8
1.8
Coyote Creefc,
CA
Boronda Lake,
CA
9.1
5.0
9.5
0.45
1.6
0.15
Data from Mill, Hendry, and Richardson 1980; zepp et al. 1977
These concentra'tions were determined via photolysis of thin
layers of solution, and are presumably dependent on the intensity
and spectral distribution of the solar flux in the solution.
Because light extinction in the water column reduces the
volumetric average solar flux below that at the air-water
Interface, the oxidant concentrations given in Table 2.24 apply
only to the surface zone of natural bodies of water* The effect
of light extinction can be computed from the equation:
Eq. 2.140
I/Io * (1 - exp(-kZ)) / kZ
where I/Io is the average light intensity as a fraction of Its
surface value do), k is a diffuse attenuation coefficient (/n),
and z is the depth of the compartment (m). The factor I/Io can
be used to generate depth-corrected oxidant concentrations for
use In EXAMS. Alternatively, the program itself can be used to
generate correction factors, using the input variables and
program outputs described in Section 2.3.3.
EXAMS allows for the entry of environmental concentrations
of only one kind of oxidant. For a compound reactive with More
125
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than one oxldant species, the rate constant and environmental
concentration giving the most significant transformation rate can
be entered, or a composite rate constant and environmental
oxidant concentration can be computed and loaded in the data
bases.
Although the mechanism of generation of oxidants of course
precludes their occurrence in benthic sediments, EXAMS does not
preclude the entry of a non-zero value of OXRADG for a "B"-type
compartment. If OXRADG for a benthic compartment is non-zero,
EXAMS simply computes a reaction rate via coupling to KOXG, and
adds the result to the overall pseudo-first-order transformation
rate constant (K in Eg. 2.1). This feature allows OXPADG and
KOXG to be used as "free parameters" for evaluation of processes
not explicitly respresented in EXAMS. For exairple, Mulk:ey and
Burns (1980), in a simulation study of the effects of small
reservoirs on pollutant dynamics, loaded data describing
reductive dechlorination of toxaphene into EXAMS. This was
accomplished by setting OXRADG to 1.0 for benthic compartments
and to 0,0 for all water column compartments, and then using the
KOXG matrix to load pseudo-first-order rate constants for
reductive dechlorination of the compound in bottom sediment
zones.
2.3.6 Microbial Transformations
Microbial communities are a ubiquitous constitutent of
almost all aquatic ecosystems. The microbiota play a central
role in the remineralization of plant and animal debris; they
have evolved the capacity to transform and harvest energy from an
immense array of naturally occurring organic compounds. The
optimistic hope that "the solution to pollution is dilution" to
some extent had its origin in a naive faith in the ability of
saproblc microbes to utilize any and all synthetic organic
compounds in their metabolic mills.
Total faith in the ability of natural systems to absorb and
detoxify synthetic chemicals was, of course, shaken by the
discovery of the world-wide dispersal (and bioconcentration) of
synthetic biocldes, notably DDT and the related compounds DDE and
DDD. It is now "axiomatic that micro-organisms are fallible and
that many synthetic organic compounds are recalcitrant ... and
accumulating in some environments" (Alexander 1979a). In
consequence, qualitative "biodegradability" tests (Swisher 1970)
are now routine in the detergent industry, and "sludge" tests
have been suggested (Buzzell, Thompson, and Ryckman 1969) as a
routine procedure for evaluating industrial synthetic organic
compounds. The latter tests can also provide some assurance that
the compound will not destroy the microbial communities that
serve nan in sewage treatment plants, as well as providing an
evaluation of the biodegradability of the compound (e.g., Baird
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et al. 1974).
The discovery of microbial fallibility has led to a more
critical and quantitative view of microbial metabolism of
synthetic organics? it no longer suffices to know that a
compound is "biodegradable." Instead the rates, products,
microbial populations, and environmental conditions surrounding
an observed biodegradation are of increasing interest to the
microbiological and ecological community. Given that the natural
microbial substrates can massively accumulate in special
circumstances (e.g., peat bogs and swamps), a degree of
skepticism is obviously warranted toward any claim of universal,
unconditional biodegradability of a synthetic organic compound.
The rates at which a compound is biodegraded must depend upon
both the structure of the compound, and on the metabolic capacity
of the microbial community resident in the ecosystem receiving
the compound.
Microbial communities derive energy for metabolism and
growth from the breakdown of organic compounds, and the kinetics
of growth and substrate utilization have been of interest to
microbiologists for many years. Both population growth and
substrate utilization rate have been described via Monod's (1943)
analogy with Michaelis-Menten enzyme kinetics (Slater 1979), In
this approach, the growth of a microbial population in an
unlimiting environment is described by:
Eq, 2,141 dN/dt « u N
where u is called the "specific growth rate" and N is microbial
biomass or population size. The Monod equation modifies
Eq, 2,141 via the recognition that consumption of resources in a
finite environment must at some point curtail the rate of
increase (dN/dt) of the population. This fact was incorporated
into Eq. 2.141 via:
[si
Eq. 2.142 u » u(max) -—••- —
Ks + [SJ
in which CS1 is the concentration of the growth limiting
substrate, u(max) is the "maximum specific growth rate" obtaining
when (S3 is present in excess (i.e., non-limiting), and Ks, the
"saturation constant" is that value of CSJ allowing the
population to grow at rate u(max)/2. An equation describing the
behavior of the growth substrate (SJ over time, and thus by
implication the dynamics of a biodegradable synthetic compound,
follows via a simple derivation (Slater 1979): Assuming that a
fixed amount of growth results from metabolism (and therefore
loss from solution) of a unit quantity of 5, then
Eq. 2.143 dN s -Y dS
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where ¥ is the "yield coefficient" in cells or bioroass produced
per unit S metabolized. Talcing
dS dS dN
Eq. 2.144 —— = —- - —
dt dN dt
gives
Eq. 2.145 dS/dt s -(U/Y) N
or, substituting Eq. 2.142 for u,
dS u(max) [S]
Eq. 2.146 — — s - — — - .......... N
dt Y Ks + [S]
The observed microbial growth yield Y is often calculated
from the amount of microbial biomass produced during the course
of transformation of a measured quantity of substrate. Because a
microbial population must satisfy maintenance requirements before
any growth can occur, the apparent yield Y can fall quite
drastically at low concentrations of S. Expressions with
separated growth and maintenance yields have been developed by
Pirt (1975), and it is possible to compute the separate
magnitudes of growth and maintenance yields from microbial growth
experiments (Slater 1979).
The Monod formulation (Eq. 2.146) has been successfully
applied to biotransformation of synthetic chemicals in a
laboratory setting. These studies have demonstrated that a Monod
analysis need not be restricted to single-species populations,
that is, the Monod equations can serve as adequate descriptors of
substrate transformation by "mixed" or "heterogeneous* (i.e.,
multi-species) microbial populations. In one example, Paris,
Lewis, and Wolfe (1975) isolated a 4-species consortium of
organisms able to use malathion as its sole source of carbon.
Analysis of the growth response of the population and of
concurrent malathion transformation rates then gave the Monod
parameters u(max) * 0.37 /hr, Ks = 2.17 UM/L (0.716 mg/L), and Y
* 4.1E10 cells/uM (1.2E11 cells/mg). In a similar study, Smith
and coworfcers (1978) investigated the degradation of p-cresol by
mixed microbial cultures able to use the compound as a sole
carbon source. These authors expressed their results in terms of
Monod parameters, finding u(max) = 0.62 /hr, Y = 1.8E9 cells/mg,
and Ks * 0.84 mg/L.
Unfortunately, these elegant applications of classical
microbiological methods to the biotransformation or "biolysis" of
synthetic organic compounds are difficult to apply in a broader
ecological context. The first difficulty, which has received
some attention in the microbiological literature, is primarily
128
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mechanical: The Monod formulation (Eq. 2.146) is non-linear In
its parameters, and thus imposes a high cost in computation time
when used in a computer program or mathematical model. For trace
concentrations of pollutants (i.e., CS3 « Ks), however, the term
(Ks * tS]) in the denominator of Eq. 2,146 can be approximated
by Ks, giving the linear approximation:
dtSJ u(max)
Eq. 2.147 -— = - ...... N [S]
dt Y Ks
This formulation is similar to the "second-order" equations used
to describe the Kinetics of chemical reactions, and the term
u(max)/(Y Ks) can by analogy be termed a second-order biolysis
rate constant Kb2, with units /hr/(cells/l) when population sizes
N are expressed in cells/1.
The propriety of this substitution can be readily evaluated.
For malathion, u(max)/(Y Ks) « 0.37/(4.1E10*2,17) »4.16E-12
/hr/(cells/l). Paris et al. (1975) also computed values of Kb2
from microbial population sizes and malathion transformation
rates in their experimental studies, finding a mean value for Kb2
of (2.6+Q.7)E-12 (95% confidence interval) /hr/(cells/l) for a
series of 8 experimental determinations spanning a concentration
range from 0.0273 to 0,33 uM in malathion. The measured Kb2
differed from u(max)/(Y Ks) by less than a factor of 2,
suggesting that simplified kinetic experiments could be used to
develop second-order rate constants, in lieu of a detailed
elaboration of u(max), Y, and Ks, when the region of concern is
restricted to levels of compound « Ks,
Furthermore, dissolved pesticide concentrations in surface
waters are often very low Indeed. For example, dieldrin,
llndane, and DDT have been found primarily at ng/L levels both in
the USA (M-atsumura 1972) and in Britain (Brooks 1972). For
industrial chemicals, however, the situation can be somewhat
different. For example, the release of phenolic wastes into the
St. Lawrence River results in riverine concentrations of 0.01 to
0.15 mg/L (Visser et al. 1977). Although these high
concentrations are restricted to a dispersion cone immediately
downstream of the effluents, Ks for p-cresol (0.84 mg/L) is
uncomfortably close to the highest measured concentrations.
The need for a thorough evaluation of the propriety of
Eg, 2.147 as an adequate approximation to the Monod formula
(Eq, 2.146) disappears, however, upon examination of the
conceptual difficulties standing in the way of the application of
either equation to environmental situations, A natural microbial
community derives its energy from a large variety of organic
detrital materials. A microbial species restricted to a
trace-level synthetic compound as its sole carbon source would be
at a severe competetive disadvantage; there is no way of
129
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predicting a priori the population densities the degrader could
attain in real systems. Even when a synthetic compound is
sufficiently similar to natural substrates that it can be
indifferently degraded by the microbial community as a whole, the
presence of multiple energy-yielding substrates in the
environment violates a fundamental assumption underlying the
Monod approach, that is, that CS], the synthetic compound, limits
growth. In many instances, moreover, a compound may be
transformed or degraded in an energy-reguiring detoxification
process, making the concept of cell yield (¥) of dubious utility.
When the compound, for whatever reason, is degraded in the
absence of a change in population size, the apparent zero yield
forces abandonment of Eg, 2.146 and 2.147 alike, (This
phenomenon is sometimes called "cometabolism," e.g., Alexander
1979b; Jacobson, D'Mara, and Alexander 1980.)
Despite these difficulties, the rate of transformation of
organic pollutants must depend on the structure of the compound
and the metabolic capacity of microbial communities. The
simplest expression of this duality is the second-order equation:
Eg. 2.148 dtSJ/dt = - Kb2 B [S3
which asserts that the rate of biolysis (dtSJ/dt) is first-order
in compound concentration [SJ and in microbial activity B, and in
which the identification of Kb2 with u(max)/(Y Ks) is discarded.
This approach reguires that the second-order rate constant be
determined via laboratory studies of relatively undisturbed
samples drawn from natural microbial communities. It also
reguires demonstration that dCSJ/dt is linearly proportional to
CS] for fixed levels of B, and that appropriate measures of B be
found.
One conventional microbiological technlgue for
characterizing microbial populations is simple population size,
measured, for example, by colony counts on pour-plate agars (APHA
1976). To the extent that population size is an adeguate measure
of community metabolic capacity, simple microbiological
technigues could serve to characterize the rate of
biotransformation of synthetic compounds in natural environments.
This hypothesis has been explored for three compounds
(butoxyethyl ester of 2,4-D (2,4-DBE), malathion, and
chlorpropham) by Paris and coworkers (Baughman, Paris, and Steen
1980; Paris et al. 1981). These authors investigated
biotransformation of their study compounds in samples of natural
waters drawn from 40 locations in the continental USA. Ambient
water temperatures at the collection points ranged from 1 to 29
degrees C, and the laboratory studies were conducted at the
observed ambient temperature of the sampled environments.
Ambient bacterial populations, as measured by 48-hour incubation
on TGE (tryptone glucose extract) agar at 22 degrees C, ranged
from 4.E2 to 9.E5 cells/ml (Paris et al. 1981). Biolysis of
130
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these chemicals was demonstrable first-order in compound
concentration and in population size, and was relatively
independent of temperature. The 95% confidence intervals (based
on between-site variation) for Kb2 (/hr/Ccell/L)) and number of
sites for these compounds were (5.42+0.97)E-10 (2,4-DBE, 31
sites), (4.54+0.74)E-ll (malathlon, 14 sites), and
(2.63+0.72)E-14 (chlorpropham, 11 sites).
Evaluation of biolysis in such "river die-away" studies is
particularly difficult when a combination of small populations
and slow rates of biodegradation leads to inconveniently long
biolysis halflives. In such cases population densities must be
augmented via centrifugation or supplemental nutrient broth. The
latter procedure can have the disadvantage of favoring
opportunistic heterotrophs at the expense of organisms better
equipped to degrade more recalcitrant compounds. For example,
the second-order biolysis rate constant (Kb2) for chlorpropham is
unaffected when population densities are augmented via nutrient
broth supplementation, but the measured Kb2 for phenanthrene
decreases in approximate proportion with the the population
increase (Paris, oral comm.).
Baughman, Paris, and steen (1980) also reported second-order
rate constants for biotransformation of synthetic chemicals by
populations derived from aquatic sediments. The observed rate
constants for 2,4-OBE and lalathion were consistent with the rate
of degradation by water-column populations, at Kb2 of 2.3E-10 and
4.0E-11 /hr/(celi/L) respectively. Aerobic biolysis of
chlorpropham by the sediment-derived populations was almost an
order of magnitude faster (Kb2 a 1.42E-13) than biolysis by the
water-column populations (Kb2 s 2.4E-14 /hr/(cell/L)). By
varying the sediment/water ratio, these authors also demonstrated
that chlorpropham, methoxycnlor, and several phthaiate esters
were unavailable to biolytic organisms when sorbed to suspended
sediments.
Plate-count estimates of bacterial population densities are
extremely selective and can underestimate total populations sizes
by 3 or more orders of magnitude (wetzel 1975:571, Fletcher 1979,
Jannasch and Jones 1959), Furthermore, although increases in
pollutant flux (that is, mg/L/time or mass degraded/time) with
increasing chemical concentration (consonant with
pseudo-first-order Kinetics) have been observed in nature (e.g.,
Sherrill and Sayler 1980), it is also true that, at elevated
pollutant concentrations, both a reduction in the apparent
first-order rate constant (Tinsley 1979:l49ff), and zero-order
Kinetics (Visser et al. 1977) have been observed. The latter
phenomena are consonant (mathematically) with Eq. 2,146, it is
not clear, however, whether these kinetics are a reflection of
the maximum growth rate of a specialized sub-population of
degraders or result from toxic effects of elevated concentrations
on the microbial community.
131
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In any case, it is clear that the studies of second-order
kinetics cited above are a useful beginning in the detailed
quantitative study of rates of biotransformation of pollutant
chemicals. Little more extrapolative power can be developed
until such time as the environmental coupling variables that
govern the metabolic capacity of natural and laboratory microbial
populations have been rigorously determined and measured In both
Kinds of systems.
As a first appoximation, EXAMS utilizes a simple
second-order equation (F,q. 2.148) to compute the rate of
biotransformation of pollutant chemicals. Microbial population
densities for each sector of the ecosystem enter EXAMS'
environmental data base via the BACTOG vector. For water column
compartments, BACTOG has units of cells/ml; BACTOG for benthic
compartments has units cells/100 g dry weight of sediment. (A
useful summary of observed bacterial population densities in
aquatic systems can be found in Wetzel 1975: 571-596.)
Second-order biolysis rate constants enter EXAMS' chemical data
base via separated parameters for water-column (KBACWG) and
benthic (KBACSG) populations. The nominal units are
/hr/(cell/ml) in both cases. EXAMS internally converts benthic
microbial population densities to units (cells/ml of water)
commensurate with the units of the rate constants KBACSG. This
conversion is executed via the expression:
(BACTOG * SEDMSD/UOO. * WATVOL)
where SETDMSL is the mass of sediment in the compartment (kg),
WATVOL is the volume of water contained in the compartment
(liters) (Eq. 2.12 et seq.), and the numerical factor (100) is a
units conversion term (1000 (ml/L) / 10 (decagrams (cwt)/kg).
Finally, EXAMS also includes a dimensionless environmental
parameter (ACBACG, nominal range 0.0 - 1.0) that can be used to
specify the proportion of the total population that actively
degrades the compound. This parameter can be used to modify rate
constants developed from sole-carbon-source studies via an
estimate of the representation of the degrader species in the
microbial subsystem of each sector of the ecosystem.
Despite the ruthless parsimony imposed on EXAMS'
representation of biolysis kinetics, the degree of chemical
detail provided by EXAMS' allowance for ionic and sorptive
speciation leads to fairly substantial opportunities for the
inclusion of biolytic kinetic detail. Both KBACWG and KBACSG are
3X5 element matrices; each element represents a separate rate
constant for the ionic and sorbed species of the pollutant. (The
use of the matrix indices to specify chemical species is
described in Section 2.3.4.) In addition, biolysis rate constants
can be entered either as temperature-independent single values,
or as functions of environmental temperatures. The effective
average environmental temperature governing a biolysis rate
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(environmental input parameter BIOTMG) Is separated from the
temperature variable governing chemical reactions (TCELG),
because a Q-10 function (rather than an Arrhenius function) is
used to depict the effects of temperature on biolysis rates.
The Q-lOs (i.e., increase in biolysis rate per 10 degree C
change in temperature) for KBACWG and KBACSG occur as the
parallel matrices QTBAWG and QTBASG, respectively. When the
value of parameter QTBAWG or QTBASG is non-zero, EXAMS takes the
corresponding member of KBACWG or KBACSG as the biolysis rate
constant at 20 degrees C, and recomputes the second-order rate
constant via the 0-10 equation:
(BIOTMG - 20)/10
Eq. 2.149 KBAC <— KBAC * QTBA
(20)
The (compartment-specific) environmental temperature variable
(BIOTMG) used in this computation has units of Celsius degrees;
it is separated from the temperature variable (TCELG) used for
chemical reactions in order that, if desired, Q-10 weighted
averaging can be used to summarize observed environmental data.
Because mlcrobiai communities frequently adapt their metabolic
capacity to keep pace with slow secular (e.g. seasonal) changes
in environmental temperatures, temperature responses measured in
a laboratory setting do not always apply to environmental
conditions. This limitation should be recognized when
interpreting the results of EXAMS simulations that include
temperature effects on biolysis rate constants.
Although the nominal units of BACTOG and KBAC include
bacterial population densities expressed as numbers/ml, clearly
these variables can in both Instances be redefined to encompass
any environmental coupling variable of utility in estimating
blodegradatlon rates in aquatic ecosystems. It is, however,
especially important that these units be commensurate: For
example, if the rate constants were determined via viable plate
counts, and the natural population estimated via direct counts,
biolysis rates would probably be grossly overstated.
Furthermore, the simple second-order equation allows for a
multiplicity of estimators of microbial capacity. For example,
Neely (1980: H7ff) lists 7 commonly used estimators of
microbial biomass or activity, including counting techniques, ATP
and DMA analyses, and oxygen uptake. By suitable (user)
redefinition of the nominal units of KBAC and BACTOG, EXAMS can
be used to compute pseudo-first-order rate constants as a
function of environmental variation in the presumed governing
variable, so long as KBAC and BACTOG are entered into EXAMS' data
bases In commensurate units.
The mechanics of EXAMS' conversion of second-order biolysis
rate constants and the compartment-specific environmental
133
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coupling variables to pseudo-first-order forir are completely
homologous with trie equations used for chemical reactions. The
total pseudo-first-order biolysis rate constant is accumulated as
the sum of expressions of the form:
Eq. 2.150 Kb = ALPHA * KBAC * BACTO * ACBAC
where ALPHA is the fraction of the total pollutant concentration
present in each existing ionic or sorbed chemical species, KBAC
is the appropriate element of matrix KBAO or KBACS (corrected as
needed for environmental temperatures), and (BACTO * ACBAC) is
the degrader population density or metabolic capacity of the
microbial community in each ecosystem compartment. The sum of
these pseudo-first-order (/hr) expressions then becomes the
biolysis contribution to the overall (compartment-specific)
pseudo-first-order rate constant K of Eq. 2.1.
2.4 Input Pollutant Loadings
The flux of a pollutant chemical entering an ecosystem (term
"Le" in Eq. 2.1) is a primary determinant of the ultimate
exposure experienced by resident organisms. EXAMS does not
compute pollutant loadings. Loadings may be developed via
projected or measured Industrial effluent fluxes, agricultural
runoff, landfill seepages, etc., but these computations must be
executed externally to EXAMS.
EXAMS provides input vectors for 5 kinds of loadings to each
compartment of the system. These are: point-source or
stream-borne loadings (STRLDG), non-point-source loadings
(NPSLDG), contaminated ground-water seepage entering the system
(IFLLDG), precipitation washout from the atmosphere (PCPLDG), and
spray-drift (or miscellaneous) loadings (DRFLDG). The loadings
have units of leg (of chemical)/hour in all cases. These loadings
are taken as time-invariant constants in EXAMS' steady-state
computations. Generally, therefore, the input loads should be
developed (at least nominally) as long-term average values,
although EXAMS can be adapted (at the user's discretion) to
evaluate, for example, the consequences of shorter-term heavy
loadings of kinetically labile compounds.
Each non-zero pollutant loading must conform to the
hydrologic definition of the ecosystem, or EXAMS will not
implement the loading. Thus EXAMS will cancel a STRLDG, NPSLDG,
or IFLLDG for a given compartment, if that compartment does not
receive an appropriate carrier flow STFLOG, NPSFLG, or INTFLG
respectively. (Definition and entry of the hydrologic variables
is discussed in Section 2.3.1.1.) Precipitation (RAING) is a
scalar variable in EXAMS; a PCPLDG is therefore allowed only for
compartments possessing an air-water Interface. Non-zero PCPLDGs
are automatically cancelled in the case of B (benthic) or H
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(hypolimnion) compartments. A PCPLDG is unconditionally
permitted for compartment number I, which will always have an
air-water interface if the system definition rules discussed in
Section 2.3.1.1 are followed. For all other water-column
compartments, EXAMS simply looks back at the (J-l) compartment.
If this (J-l) compartment is also part of the water column, it is
assumed to be directly above the current (J) compartment and any
non-zero PCPLDG is removed. Compartments with an air-water
interface are always preceded by a benthic (B) compartment when
EXAMS' system definition conventions (Section 2.3.1.1) are
observed.
EXAMS' subroutine CKLOAD evaluates the propriety of the four
kinds of loadings that enter via carrier flows. These loadings
are evaluated against the volume of the carrier flows and the
water quality characteristics of the target compartment. These
evaluations were designed to prevent a user inadvertently
specifying a loading outside EXAMS' operating range. In
particular, EXAMS makes no provision for crystallization of the
compound fron solution, nor does the program allow for a gradual
dissolution of chemical from a condensed (solid or liquid) phase.
In addition, the non-linearities potentially present at high
chemical concentrations (non-linear sorption isotherms,
appreciable light absorption by the compound, zero-order
biolysis* etc.) are not incorporated in the code. EXAMS' loading
check computations are divided into two groups: checks based on
carrier flows of water alone (PCPLDG and IFLLOG), and checks
based on carrier flows of water plus an entrained sediment
loading (STRLDG and NPSLDG).
Ground-water seep and rainfall loadings are simply
constrained to the lesser of 50% of the aqueous solubility of the
pollutant or l.E-5 M in SH2, In these computations, the
temperature (TCELG) and pH (PHG and POHG) of the target
compartment receiving the load are used to compute (as
appropriate) the solubilities of each ionic species of the
compound, and the distribution of the pollutant among its ionic
species (distribution coefficients ALPHA, computed as described
in Section 2.2). EXAMS then computes the concentration of
pollutant in the carrier flow, if the solubility criterion is
exceeded, EXAMS reduces the load to the extent necessary to
conform to one-half the upper limit of EXAMS' operating range,
and notifies the user of the modification(s). The loadings are
simply recomputed as the product of one-half the limiting
concentration and the carrier flow rate, that is,
Eq. 2.151 LOAD(kg/hr) = 0.5 * LIMIT(kgXL) * INFLOW(LXhr) / BETA
where LIMIT is one-half the solubility of the least soluble
chemical species or l.E-5 M in SH2 (whichever is less), and BETA
is the fraction of the total concentration present in the least
soluble dissolved form.
135
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Each streamflow (STFLOG) or non-point-source water flow
(NPSFLG) entering a compartment may have an associated stream
sediment (STSEDG) or non-point-source sediment (NPSEDG) loading
(kg sediment/hr) to the compartment. STSEDG and NPSEDG are not
used in transport computations (see Section 2.3.1.3). In the
course of evaluating stream-borne and non-point-source pollutant
loadings, EXAMS computes a sorption equilibrium for capture of
the pollutant by entrained sediments in the stream or
non-point-source flows entering each compartment. These
computations use the temperature, pH, and sediment partitioning
parameters (e.g., organic carbon content (FROCG) and ion exchange
capacities (AECG and CECG)) of the target compartment. From the
sediment/water ratio of the carrier flow, EXAMS computes the
distribution coefficients (ALPHA) of the chemical in the carrier
flow. If the residual aqueous concentration of any dissolved
species exceeds its concentration limit, the offending loading is
reduced via Eg. 2,151. Note that this reduced loading is less
than the maximum permissible loading for the inlet stream,
After checking the loadings and making any necessary
modifications, summing all external loads and units conversion
from kg/hr to mg/hr yields term Le of Eg. 2,1.
"Drift" loadings (DHFLDG) are initially implemented without
modification. If EXAMS' steady-state computations result in
final chemical concentrations above EXAMS' operating range (i.e.,
residual agueous dissolved concentrations greater than 50% of
solubility or l.E-5 M in SH2), any DRFLDGs are then sequentially
reduced until the computationally invalid estimates are
corrected. These computations are executed in subroutine STEAD*.
(If no drift loads were specified and the results are outside the
operating range, EXAMS aborts the run and returns control to the
user for corrective action.)
The DRFLDG vector can be used to specify miscellaneous
loadings not encompassed in EXAMS' four other loading types.
EXAMS, for example, does not allow for entry of pollutant across
the air-water interface from a polluted atmosphere (Section
2,3,2). The impact of a polluted atmosphere can, however, be
computed from the bulk atmospheric partial pressure of the
contaminant, and entered into EXAMS via the DRFLDG vector. The
net flux of pollutant across the air-water interface (F,
moles/m2/hr) is given (Eg. 2,86) by:
F = Kl (Pg/H - CD
where Kl is the exchange constant (m/hr), and both (Pg/H) and Cl
have units of (moles/m3). By assuming the bulk atmosphere to be
uncontaminated (Pg = 0,0), the term (Pg/H) was discarded in the
development of EXAMS' algorithm for computing volatilization
losses of pollutants from aguatic systems. In much the same way,
the gross pollutant loadings imposed by a contaminated atmosphere
136
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can be computed by talcing Cl = 0.0, EXAMS computes and reports a
contaminant-specific pseudo-first-order exchange constant (/hr)
for each sector of the ecosystem. These values, representing (Kl
* AREAG / VOLG) for each compartment, can be read off from EXAMS'
output table "Kinetic Profile of Organic Toxicant" during a
preliminary run of the program. The gross flux (F, moles/m2/hr)
entering the system from a polluted atmosphere is
F s Kl (Pg/H)
Given the partial pressure of the compound in the bulk
atmospnere, the loadings on the system (Icg/hr) can thus be
computed via:
DRFLDG
icg/hr
Kl * AREAG
—....——
VOLG
/hr
1
* VOLG * MWTG * 0.001 * Pg *
HENPYG
m3
g/mol kg/g atm mol/(atm m3)
After computing DPFLDs for each sector of the system, EXAMS can
be run again to evaluate the impact of the contaminated
atmosphere. When interpreting EXAMS' outputs, however, it must
be remembered that EXAMS' estimates of volatilization halflives
and persistence assume that the atmosphere has been
decontaminated.
Non-zero boundary conditions can also be loaded into EXAMS
via the DRFLDG vector. EXAMS' environmental input data can
include a characteristic length (CHARLG), cross-sectional area
(XSTURG), and dispersion coefficient (DSPG) at any boundary of
the system (by setting either JTURBG or ITURBG to zero, as
described in Section 2.3.1.4). The exchange flow of water across
the boundary is given by (Eq. 2.74):
FLOW (liters/hr)
UOOOHDSPGHXSTURG)
(CHARLG)
If the inlet exchange flow is contaminated to a level of CCJ
mg/L, the loading (kg/hr) on the system of Interest is simply:
LOAD s FLOW * 1C] * i.E-6 (kg/Big)
This load can be Imposed of the receptor compartment via the
appropriate element of the DRFLDG vector. Remember, however,
that the loading will be removed for EXAMS' persistence
simulation.
The final term in Eq. 2.1 Is "Li," the sun of the internal
loadings on the system compartments. These loadings arise from
flows of contaminated water, sediments, and plankton among the
137
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physical
magnitudes
distribution
sectors (compartments) of the ecosystem. Their
can be computed from the magnitudes of the flows, the
of the compound among its dissolved and sorbed
species, and the concentration of the pollutant in the source
compartments (expressed as mass/unit aqueous volume). EXAMS uses
matrices (see Section
loading factors (EXAMS'
the compartment number
the WATFL (r,/hr) and SEDFL (kg/hr) flow
2.3.1.5) to compute a matrix of internal
internal variable INTINL). Taking "S" as
(index) of the source compartment, ano
target comprtment, each element of INTINL
MT" as the index of
is computed from:
the
Eq. 2.152 iNTINLs WATFL(T,S)*ALPHA(16,S)
SEDFL(T,S)*ALPHA(17,S)
SEDCOL(S)
+ WATFL(T,S)*ALPHA(18,2)*PLPAG(S)
where the total dissolved, sediment-sorbed, and biosorbed
distribution coefficients of the source compartment are given by
ALPHA(16,S), (17,S)f and (18,S) respectively
This computation results in terms which, when
total concentration of pollutant in the source
(mg/L), yield the mass loadings Li (mg/hr)
compartments, the final term in Eq. 2.1.
(Section 2.2.4).
multiplied by the
(S) compartments
on the target (T)
2.5 Data Assembly and Solution of Equations
2.5,1 Exposure
After computing all terms in Eq. 2,1, the resulting system
of mass-balance equations can be divided through by the volume of
the compartments to give a set of equations describing the rate
of change of chemical concentration over time:
Eq. 2.153
dCCJ
»*•• *
dt
Le
..
V
Li
..
V
[CJ
As time passes, the system evolves toward an ultimate
"steady-state" condition at which the concentrations achieve
stable values. This endpoint is defined by the condition dtCJ/dt
s 0,0 for every compartment. At steady state, then, the
concentration of pollutant in each sector of the ecosystem is
given by
Eg. 2.154
[CJ
(Le/V + Li/V)/K
EXAMS' subroutine STEADY was designed to solve the equations for
these concentrations, which define the exposure levels of the
pollutant.
138
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The logic of the situation can be illustrated via an
elementary example. For the example, consider the behavior of a
non-sorbing chemical, subject to neutral hydrolysis as its sole
transformation process, in a static one-hectare pond. The pond
is 1 meter deep, with VOLG therefore 10000 m3. The benthic
subsystem consists of a 5 cm active depth of material with a bulk
density (SDCHRG) of 1.5 g/cc and a water content (PCTWAG) of
150%. The environmental volume of the benthic zone (VOLG) is 500
m3; its aqueous volume is 250000 liters of water (Eq. 2.12).
Defining exchange between the benthic subsystem and the water
column via XSTURG = 10000 m2, CHARLG * (1.05/2) = 0.525 m, and
DSPG * l.E-4 m2/hr, the rate of exchange of fluid volume between
the water column and the interstitial pore water (Section
2.3.1.4) is
250000 (l.E-4)(10000)
WATFL = ---—- * ......*....... = 952.4 liters/hr
500 0.525
This exchange flow of water can be reduced to its
pseudo-first-order effect on chemical concentrations (Kt) in the
water column (w) and the benthic (b) subsystem via:
Kt(W) a 952.4/1,E7 a 9.524E-5 /hr
and
Kt(b) = 952.4/250000 = 3.810E-3 /hr
As the compound does not sorb, transport of sediment and plankton
can in this instance be ignored.
The internal loadings on the system arise from pollutant
contamination of the 952,4 L/hr exchange flow between the system
compartments. All the compound is present in dissolved form,
thus giving ALPHA(16) s 1.0 by definition, EXAMS computes its
internal load factors Li/V by dividing the elements of INTINL
(Eq. 2,152) by the volume of the target compartment. In this
instance, the load factor on the benthic subsystem resulting from
contamination of the water column is
INTINL(b,w) <— (952.4 * 1.00)/250000 « 3.810F-3 /hr
and the load factor on the water column resulting from
contamination of the benthic interstitial water is
INTINL(w,b) <— (952,4 * 1.00)/1.E7 s 9.524E-5 /hr
(INTINL and Kt are equal in this much simplified example; this
is not usually the case,)
Finally, given an external load on the water column (here a
DRFLDG) of, say, 0,02 kg/hr, and a neutral hydrolysis rate
constant of 0,01 /hr, the behavior of the chemical in the system
139
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Is given by:
Eq. 2.155 d£CwJ/dt = (0.02E6/l ,E7)+9.524E-5(Cb)-(0.01 + 9.524E-5)Cw
Eq. 2.156 d[Cb)/dt= 3.810E-3(Cw) - (0.01 t 3.810E-3)Cb
where Cw Is the aqueous concentration In the water column and Cb
is the aqueous concentration in the interstitial pore water
(mg/L). At steady state, d[Cwj/dt = dtCb]/dt = 0.0, resulting In
2 equations in 2 unknowns:
Eq. 2.157 - 0.01009524 Cw + 0.00009524 Cb s - 0.002
Eq. 2.158 0.00381 Cw - 0.01381 Cb * 0.0
This elementary example can be easily solved to give Cw = 0.1986
and Cb = 0,0548 mg/L. EXAMS' subroutine STEADY solves the
simultaneous linear equations that describe steady-state
concentrations by use of the Gaussian elimination algorithm
discussed in Section 2.3.1.2. EXAMS' output for the example
system described above is given in Table 2.26.
Table 2.26. EXftMS' output tabulation of steady-state concentrations.
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: Unsorbed chemical subject to neutral hydrolysis
ECOSYSTEM: Static 1-hectare pond, 1 meter deep
TABLE 13. DISTRIBUTION OF CHEMICAL AT STEADY STATE: IN THE WATER COLUMN:
COMP STEADY-STATE RESIDENT MASS **** TOXICANT CONCENTRATIONS ****
2 TOTAL DISSOLVED SEDIMENTS BIOTA
G/M KILOS % MG/* MG/L MG/KG UG/G
1 0.199 1,986 100.00 0.199 0.199 0.000 0.000
SUBTOTAL: 1.986 99.32
AND IN THE BOTTOM SEDIMENTS:
2 1.370E-03 1.3699E-02 100.00 2.740E-02 5.479E-02 0.000 0,000
SUBTOTAL: i,3699E-o2 0.68
TOTAL MASS (KILOGRAMS) a 2.000
* TOTAL CONCENTRATION AS MG/L IN WATER COLUMN, AS MG/KG IN SEDIMENTS.
As Gaussian elimination is not an infallible mechanism for
executing these computations, EXAMS' subroutine STEADY includes a
second technique for computing the solution to the system of
equations (Eq, 2.154), This algorithm is an iterative method
140
-------
that applies Eq. 2.154 to each compartment In turn* and then
repeats the entire process until such time as the successive
estimates for each compartment change by less than 0.0001%. This
alternative algorithm is invoiced in those cases for which
Gaussian elimination fails.
EXAMS allows for up to 100000 interations of the full
"linear cascade" computation. If the linear cascade terminates
without full convergence, EXAMS aborts the run; this event
generally can be taken as an indication that steady-state
concentrations are unbounded. For example, a non-transformable
chemical in a static pond without any export pathways will
accumulate indefinitely; in this situation no "steady-state"
condition can be computed. The user can check on the degree of
convergence achieved by EXAMS for the full ecosystem by examining
the mass balance check printed as the final entry ("Residual
Accumulation Rate") in EXAMS' output table entitled "Analysis of
Steady-State Fate of Organic Toxicant."
In the elementary example given above, the linear cascade
solution would proceed:
Iteration 1, step 1: solve for Cw (compartment number 1)
Cw a (Le/V 4 Li/V)/K = (0.002 + 9.524E-5(Cb)) / 0.01009524
giving, as Cb at the moment = 0.0,
Cw * 0.002/0.01009524 * 0.19811
Iteration 1, step 2: solve for Cb (compartment number 2)
Cb a (Le/V + Li/V)/K « 0.00381(Cw)/0.01381
a (O.OT)381*0.19811)/0,01381 « 0.05467
From the initial estimates, the second iteration proceeds to
compute a refined estimate of Cw and Cb:
Cw a (0.002 + (9.524E-5*0.05467))/0.01009524 « 0.19863
Cb a (0.00381*0.19863)/0.01381 s 0.054799
The convergence test Is computed for each compartment by
calculating the relative change in the estimate. The change in
Cw was
1 - 0.19811/0.19863 * 0.0026 "
and the change in Cb was
1 - 0.05467/0.054799 « 0.0026
141
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As these
criterion
test values are greater than EXAMS' convergence
(l.E-6), EXAMS continues with a
linear cascade.
/ f w *» n < -• w wvuvr.A.iFViiVk7 fi *. w 11
EXAMS judges convergence
when the relative change in every "
tnird iteration of the
to be complete only
compartment is less than l.E-6,
2.5.2 Fate
After computing the ultimate exposure concentrations that
will be produced in the system, EXAMS executes an evaluation of
the impact of each transport and transportation process on the
behavior of the compound. During the course of reducing its
input data to pseudo-first- order form, EXAMS preserves the value
of each process' contribution to the overall pseudo-first-order
rate constant K (Eq. 2.1) tor each compartment. The flux of
chemical transformed or transported under steady-state conditions
(mass/time) is then given by the product of the process rate
constant, the steady-state concentrations, and the agueous volume
of each conpartment. In the instance under review, the chemical
fluxes attributable to neutral hydrolysis are
Fw = Khyd * Cw * WATVOL(w) * l.E-6 (Kg/mg)
= (0.01)(0.1986)(l.E7)(l.E-6) = 0.01986 Xg/hr
in the water column, and
Fb = (O.Ol)(0.05479)(2.5E5)U.E-6) = 0.000137 Jcg/hr
in the benthic subsystem.
EXAMS sums the fluxes (by process) over the entire system,
and computes the significance of the process via division of the
process flux by the sum of the external loadings on the system,
followed by conversion of this result to a percentage basis. In
the example, the total flux is (0.01986 t 0.000137) kg/hr, the
total loading was 0.02 icg/hr, thus hydrolytic transformation
accounts for 100(0.01986 + 0.000137)/0.02 ~ 100% of the input
loadings, as of course it must in this elementary example,
EXAMS* output table containing the results of the flux
analysis, entitled "Analysis of Steady-State Fate of Organic
Toxicant," also Includes estimated halflives for removal or
dissipation of the chemical from the system. These halflives are
computed under the assumption that internal transport delays are
insignificant and, thus, are intended solely as a supplemental
view of the general significance of each process. The halflife
computations are executed via division of the total process
fluxes by the total mass of pollutant resident in the system to
give a system-wide pseudo-first-order rate constant Kpr. The
halflife is then simply
142
-------
Tp • - ln(0.5)/Kpr
In the example case, the total resident mass (computed as the sum
of volumes and concentrations) is 2.00 kg (Table 2.26), and the
projected hydrolytic halflife is therefore
Tp = (0.69315 * 2.00)/(0.01986 + 0.000137) * 69.3 hours.
EXAMS does not always and inevitably report fluxes and
halflives in hours, for irj many instances the hour is an
inconveniently small reporting unit, instead, the program makes
a preliminary evaluation of the total transport and
transformation flux through the ecosystem, and computes a
first-order estimate of the total halflife of the compound. This
preliminary estimate is then used to select the most appropriate
(hours, days, months, or years) time scale for reporting the
results of all succeeding time-depehdent computations. This
estimate of the "system-level" halflife is also used to set the
time intervals for EXAMS' "persistence" computations, as
described in Section 2.5.3.
EXAMS' flux computations, along with its table of
compartment- specific pseudo-first-order rate constants (output
table "Kinetic Profile of Organic Toxicant") were designed to
serve as a "sensitivity analysis" of the behavior of the
pollutant in the particular ecosystem Involved. These tables
indicate the relative strength of the transformation processes,
and thereby indicate which processes are in need of the most
scrupulous and exact experimental determinations of rate
constants. In addition, EXAMS interactive capabilities allow a
user to vary the input data over a reported error bound, and thus
determine, for example, the degree of uncertainty implied for
steady- state exposure concentrations.
2.5.3 Persistence
EXAMS' final round of computations deal directly with a
third (after exposure and fate) aspect of pollutant evaluation in
aquatic systems, that of the "persistence" of the compound. It
should perhaps be emphasized that EXAMS computes local, rather
than global, persistence, that is, EXAMS' computations address
the persistence of compounds in the specific ecosystem under
review, and do not address the global issue of the persistence of
a compound after it leaves the local ecosystem. Thus, for
example, a compound that is not subject to any transformation
processes is (globally) totally persistent by definition, foithin
the more limited context of a particular ecosystem, however,
export processes will ultimately result in a "cleanup" of the
system, and the time required for this cleanup process can be
computed. (As the ultimate exposure concentrations for a
143
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transformationally persistent chemical in a static (closed)
system are unbounded, EXAMS never encounters the resulting
infinite cleanup times.)
EXAMS begins its persistence computations by using the
steady-state concentrations of pollutant in the system as a set
of starting values or "initial conditions." These initial
conditions are presented to a numerical integration package
(subroutine DRIVER et seq.). The relevant set of differential
equations, describing the oehavior of the pollutant over time, is
essentially Eq, 2,1 with the external loadings (Le) set to zero
or struck from the equations:
Eq. 2.159 d[CJ/dt a Li/V - K[CJ
EXAMS computes the dissipation of the compound over time, talcing
the time required to encompass 2 (estimated) system-level
haifllves as the endpoint of the simulation. The results of this
simulation are summarized in EXAMS' output table entitled
"Simulation of system Response after Load Ceases."
EXAMS' subroutine DRIVER has two integration packages
available to it; these routines nave been described by
Malanchuk, Otis, and Bouver (i960). DRIVER initially calls upon
a 4th-5th order variable time-step Runge-Kutta integrator. In
the event that the equations are mathematically "stiff," the
partially complete integration is returned to DRIVER, which then
invokes an alternate package that integrates stiff equations by
Gear's method.
EXAMS limits the expense incurred in the integration via a
limitation on the total number of steps which these routines are
permitted to execute, EXAMS writes out the secular dissipation
of the compound at 12 equally spaced times, up to the endpoint
(TFINAL) defined by 2 estimated system-level halflives. If the
integrators exceed their alloted expense allowance prior to
integration to TFINAL, control is returned to DRIVER for
evaluation fo the situation. If the integrators have failed to
reach the first output point (TFINAL/12), EXAMS aborts all
further peristence computations and so notifies the user. If at
least one output point has been passed, EXAMS uses the latest
point reached by the integrators in its persistence computations,
and notifies the user that the dissipation simulation was
abbreviated.
In the vast majority of cases, EXAMS' dissipation
simulations conclude with a successful integration to TFINAL.
EXAMS' output summary of the time course of dissipation via
neutral hydrolysis in the static pond used as an example in
Section 2,5.1 is given in Table 2,27,
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Table 2.27. Sample EXAMS output for dissipation of chemical
after removal of external loadings
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICALS Unsorbed chemical subject to neutral hydrolysis
ECOSYSTEM; static 1-hectare pond, 1 meter deep
TABLE 16. SIMULATION OF SYSTEM RESPONSE AFTER LOAD CEASES.
OT OT 4V •> •§ • W • (P * • <• Ml •> V W Ml *•> • V V • * M ** •* *• W W •* l0 <• iP Ml •••*•§ Ml HI • •* •• • Vp • fll VP 9 Vl IV • • V W fli •• I
TIME AVERAGE POLLUTANT CONCENTRATIONS MASS OF POLLUTANT
HOURS
WATER COLUMN
BOTTOM SEDIMENTS
WATER COL SEDIMENTS
FREECMG/L) SEDCMG/KG) PORECMG/L) SED(MG/KG) TOTAL KG
0.
12.
24,
36.
48.
60.
72.
84.
96.
108.
120.
132.
144,
0.199
0.176
0.156
0.138
0.123
0.109
9.627E-02
8.533E-02
7.563E-02
6.704E-02
5.943E-02
5.268E-02
4.670E-02
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
5.479E-02
5.430E-02
5.298E-02
5.107E-02
4.875E-02
4.616E-02
4.341E-02
4.060E-02
3.778E-02
3.500E-02
3.232E-02
2.974E-02
2.728E-02
0,000
0,000
0.000
0.000
0,000
0,000
0,000
0.000
0,000
0.000
o.ooo
0.000
0,000
1.986
1.760
1.560
1.383
1.225
1.086
0.9627
0.8533
0.7563
0.6704
0.5943
0.5268
0,4670
TOTAL KG
1.370E-02
1.357E-02
1.324E-02
1.277E-02
1.219E-02
1.154E-02
1.085E-02
1.015E-02
9.444E-03
8.751E-03
8.079E-03
7.434E-03
6.820E-03
EXAMS' subroutine SUMUP prints a summary of the exposure and
fate information generated by the program and also estimates and
reports the length of time required for cleanup of the ecosystem,
EXAMS reports, in the first instance, the percentage of the
initial chemical masses in the entire water column and benthlc
subsystem that had been dissipated by time TFINAL. EXAMS then
weights these dissipations according to the initial distribution
of the chemical in the system, and reports a first-order estimate
of the time required for the system to cleanse itself of the
chemical mass accumulated at steady state. This estimate is
computed as 5 (pseudo-first-order, weighted) halflives; in a
true first-order system this would correspond to dissipation of
97% of the mass of chemical initially present in the system.
(The actual (mathematical) "order" of the system is defined by
the number of compartments used to describe the ecosystem. For
example, wnen a water-body is described to EXAMS via 20 segments,
EXAMS compiles 20 linked first-order differential equations, and
145
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solves this system of equations to generate its outputs. The
data used in EXAMS' persistence time computations is generated by
summing the residual chemical masses over compartments, thereby
following the dissipation of the chemical in the entire system.
The computations are in this sense reduced order approximations;
thus EXAMS reports are given as "rough" estimates (e.g., Table
2.28).)
This computation can DC illustrated via the results of the
sample simulation given in Table 2.27. At the expiration of 144
hours, the resident pollutant mass had fallen from 1.986 to 0.467
kg in the water column. This dissipation of the pollutant
represents a loss of
100 (1 - (0.467/1.986)
or 76.5% of the original material. Similarly, the benthic
subsystem has lost (1.37E-2 - 6.82E-3) = 6.88E-3 leg or 50.2% of
its original mass of chemical. (The benthic sediment exhibits a
slower loss of chemical as a result of continuing recontamination
(Li, Eq. 2.159) of this subsystem from the water column.)
In a first-order system, the decrease of an initial mass of
material Qo over time is given by
Q(t) a Qo exp(-(c * t)
or
ln(p(t)/Qo) * -let
where K Is the first-order rate constant and t is time. The
halflife is defined as the time required for Q(t) to reach Qo/2
or for Q(t)/Qo = 0.5, that is,
H « -ln(0.5)/ic
The first-order haiflives (H) for these water-column (Hw) and
benthic (Hb) subsystems are, therefore:
Hw * (0.69315H144) / ln(. 467/1.986) = 69.0 hrs
and
Hb s (0.69315H144) / ln(6.82E-3/l.37E-2) * 143,4 hrs
At steady state, 99.32% of the compound was present in the
water column, and only 0.68% was in the benthic subsystem (Table
2.26). EXAMS thus estimates the tine required for dissipation of
the chemical as:
Td * 5 (0.9932 (Hw) + 0.0068 (Hb))
s 5 (0.9932 (69.0) + 0.0068 (143.4)) * 347.5 hrs
146
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or 14.5 days. EXAMS output summary for this example is given in
Table 2.28.
Table 2.28. Sample EXAMS summary output table, analysis of unsorbed
compound subject to neutral hydrolysis, in static 1 hectare pond
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: Unsorbed chemical subject to neutral hydrolysis
ECOSYSTEM: Static 1-hectare px>nd, 1 meter deep
TABLE 17. EXPOSURE ANALYSIS SUMMARY.
EXPOSURE:
A. MAXIMUM CONC. IN WATER COLUMN: 0.20 MG/L DISSOLVED, 0,20 TOT
MAX. CONC. IN BOTTOM SEDIMENT: 5.48E-02 MG/L DISSOLVED IN PORE WATER
B. BIOSORPTION - MAX. CONCENTRATION - PLANKTON: 0.00 UG/G
BENTHOS: o.oo UG/G
C. MAXIMUM TOT. CONC. IN SEDIMENT DEPOSITS: 2.74E-02 MG/KG (DRY HEIGHT)
FATE:
A. TOTAL STEADY-STATE ACCUMULATION: 2.0 KG; 99.32% IN WATER COL.,
0.68% IN BOTTOM SEDIMENTS.
B. TOTAL LOAD: 2.00E-02 KG/HOUR - DISPOSITION: 100.00% VIA CHEMICAL
TRANSFORMATIONS, 0.00% BIOTRANSFORMED, 0.00% VOLATILIZED,
0.00% EXPORTED VIA OTHER PATHWAYS.
PERSISTENCE:
A. AT THE END OF A 144. HOUR RECOVERY PERIOD, THE WATER COLUMN HAD
LOST 76.49% OF ITS INITIAL TOXICANT BURDEN; THE SEDIMENTS HAD
LOST 50.21% OF THEIR INITIAL BURDEN ( 76.31% REMOVAL OVERALL).
B. SYSTEM SELF-PURIFICATION TIME IS ROUGHLY 14. DAYS.
If the majority of the chemical had been present in the benthic
zone, EXAMS would of course have given computational precedence
to dissipation in the sediment subsystem for its estimate of
decontamination time.
A more detailed evaluation of the persistence of the
chemical can be executed via a graphical analysis of the time
course of pollutant dissipation, plotted from the results of
EXAMS' numerical simulation of this phenomenon (Table 2,27). In
interpreting EXAMS' estimate of the time required to dissipate
the chemical, it should be remembered that EXAMS' estimate
represents five halflives, or about 97% removal of the initial
mass. If this removal suggests that the chemical would still
occur at unacceptable concentrations, a first-order evaluation of
the time required to achieve a specified reduction can be
computed from EXAMS' outputs. Suppose, for example, that the
time to reduce the chemical to 0.01% of its initial value were
the time of interest. This time is given by the expression
147
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C-ln(Q/Qo)/K), where Q/Qo is in this case 0.0001. EXAMS'
estimate of decontamination time is computed as (5)(0.69315)/K,
where K can be regarded as a weighted whole-system first-order
decay constant. KXAMS* estimate of dissipation time Td can thus
be expanded via the approximation:
- ln(Q/Qo) Td
Eq, 2.160 T = .............
(5)(0.69315)
In this instance, O/Oo = 0.0001, -ln(Q/Qo) z 9.21, and the time
to reduce the chemical to 0.01% of its steady-state value is
approximately
(9.21H14)
T = ............ s 37 days
(5)(0.69315)
Note, however, that a continued first-order decay of
chemical in the benthic subsystem would, at 37 days (888 hours),
result in a residual of
100 exp(888 ( In 0.5 / Hb) )
or 1.4% of the original benthic pollutant mass. The system-wide
dissipation of the chemical may leave pocKets of higher
concentration in zones of restricted physical transport.
extrapolations of EXAMS' results beyond the designed
operating range of the program are probably ill-advised. If
necessary, however, a plot of the results of EXAMS' dissipation
simulation should be used to evaluate the propriety of a
first-order extrapolation of system self-purification times.
148
-------
SECTION 3
USER'S GUIDE
3.1 Introduction and Sample Run
This Section is an introduction to the use of the EXAMS
interactive language and system. It is designed to familiarize
users with the structure of the command language that gives
access to the computer system, to describe the kinds of input and
output used by the system, and to provide some sample sessions
that serve as tutorials and as examples of EXAMS applications.
Sample data input forms for organizing and preparing chemical and
environmental data for entry into the program can be found at the
end of Section 3.1.
3.1.1 Introduction
This version of EXAMS was designed to evaluate the ultimate
or "steady-state" behavior of organic chemicals in aquatic
ecosystems. EXAMS is not a "model" of aquatic ecosystems, for it
contains but a single state variable •- a vector of
concentrations of chemical pollutants. The properties of aquatic
ecosystems that govern the behavior of synthetic organic
chemicals are- presented to EXAMS via an n-compartment set of
input data. EXAMS uses these data to compute the behavior of
chemical pollutants in the ecosystem. The environmental
descriptors encompass only those variables having a direct
bearing on pollutant behavior; they can thus be termed a
"canonical" description of the environment. Each environmental
variable is constrained to a single value within a given area
(compartment) of the ecosystem, and thus must be regarded as an
average or "typical" value over some relevant period.
EXAMS couples the canonical characteristics of the
environment to the properties of a given organic chemical, using
process models (mathematical relationships) appropriate to each
aspect of chemical behavior considered Tsection 2). EXAMS'
process models include the icinetics of volatilization, transport,
direct photolysis, hydrolysis (specifIc-acid/base and neutral),
oxidation, and bacterial transformations in the water column and
bottom sediments of the ecosystem, as well as equilibrium
149
-------
partitioning of the chemical into las many as five) ionic
species, each of wnich may occur as a dissolved, sediment-sorbed,
or biosorbed molecule.
The process models are assembled into a set of ordinary,
first-order differential equations that describe the kinetics of
the chemical in the n-compartment system under investigation,
EXAMS then analyzes this set of differential equations in several
ways. EXAMS produces a series of output tables that provide
information on the fate, exposure, and persistence of the
chemical, and provide some guidance for exploring the degree to
which conclusions drawn from the data are affected by error or
uncertainty in the input data (sensitivity).
A number of operational definitions can be attached to the
notions of "fate," "exposure," etc. For EXAMS' purposes, the
"fate" of a pollutant means its ultimate (steady-state) relative
distribution within the ecosystem (percent captured by bottom
sediments, etc.), and the percentage of the total system loading
that is consumed by each kinetic process (photolysis, export,
etc.) at steady state. "Exposure" is taken to mean the final
residual concentration of chemical present in each compartment at
steady state. Exposure concentrations are presented in four
forms: the total concentrations (mg/L in the water column, mg/kg
in bottom sediments), concentrations of dissolved species (mg/L),
sediment-sorbed concentrations (mg/kg), and biosorbed
concentrations (ug/g) associated primarily with planktonic or
sessile organisms that form the base of the food chain.
The "persistence" of the chemical is evaluated via an
additional set of operations. The input loadings are set to zero
(removed) and the system of equations is passed to a numerical
integration subroutine with the steady-state concentrations as
initial values. The integrator then computes the disappearance
of the chemical from the ecosystem over a period corresponding to
about 2 system half-lives, i.e., the time needed to remove about
75% of the chemical accumulated in the ecosystem. The outcome of
this integration is reported to the user, and a "system self-
purification time" is estimated from the results.
EXAMS does not undertake any formal sensitivity analyses of
the systen. Sufficient information is provided, however, to
allow a user to derive the probable magnitude of uncertainties in
conclusions that are implied by a given range or error bound for
any of the input data. The computer outputs include a "Kinetic
Profile" (or frequency scaling) of the chemical, with all
processes reduced to equivalent (/hr) units, and a tabular
presentation of toe steady-state fate of the chemical (i.e., the
percentage of the load consumed in each process). These tables
indicate the relative importance of each transformation process
within the ecosystem of concern. EXAMS' interactive capabilities
allow the user to select the dominant process(es) and vary the
150
-------
relevant input data over a reported error range. In this way the
effect, for example, of error in chemical rate constants on
exposures and persistence can be readily evaluated.
3.1.2 Sample Run
A simple example EXAMS session is given below, including the
initial LOGIN and LOGOUT sequences on the Athens Environmental
Research Laboratory's DEC PDF 11/70 computer. The example shows
the selection of benzotf]quinoline and a eutrophic lake as the
compound and ecosystem of concern, specification of chemical
loadings, retrieval of a hard-copy of the results, and the
computer output from the run. (The input data used for this
example is also supplied with the batch version of the program.)
A series of sample data entry forms follow the output tables
from the sample run. These forms (pp. 162-172) can be removed
from the manual and duplicated; they provide a means of
organizing and assembling input data for the EXAMS program.
PDS> PT50
User TSO UIC1250,203J TT13: 14:50:50 ll-JAN-81
PDS> RUM EXAMS
14:51:34
welcome to EXAMS
Exposure Analysis Modeling System
Athens Environmental Research Laboratory
Released for field trials Jan-81
The ATHENS collection of compounds is available for your use.
EXAMS > COMPOUND IS BFQ
Compound selected > BENZOtfJQUINOLINE
EXAMS > ENVIRONMENT IS EUTROPHIC LAKE
selected environment is: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE
TEST DEFINITION
EXAMS > CHANGE STRLD(l) TO 0.5
EXAMS > CHAN PCPLDGU) TO 6.4E-03
EXAMS > CH PCPLC3) TO .032
151
-------
EXAMS > CH PCP(6) TO 0.0064
EXAMS > CH IFLL(2) TO .02
EXAMS > CH IFLLDGO) TO .02
EXAMS > CH NPSL(l) TO .16
EXAMS > CHANGE NPSLDGC6) TQ 0.16
EXAMS > RUN
Simulation beginning for:
Compound: BENZOCfJQUINOLINE
Environment: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST
DEFINITION
with a load of (icg/hr) > 0.904800
Run complete.
EXAMS > PRINT ALL
Requested report has been spooled to printer.
EXAMS > STOP
Job433 — STOP
14:57:19 size: 32K CPU: 22.35 status: SUCCESS
PDS> LOGOUT
User TSO UIC C250,203J TT13: 14:48:00 ll-JAN-81
CONNECT TIME 07 M SYSTEM UTILIZATION 43 MCTS
The seventeen output tables generated by this sample session are
given on the following nine pages.
152
-------
AFRL-ESB iMODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: BENZOUJQUINOLINE
ECOSYSTEM: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
mmm»mmmmmmmmmmmmmmmmm»mmmmmmm~mmmmmmmmmmmmmm>mmmmmmmmmmmmmmmmmmmmtmif»>
TABLE 2. INPUT DATA DESCRIBING ENVIRONMENT: GLOBAL PARAMETERS.
KOUNT= 7
IRRADIANCE
2.9900E+1
2.8100E-H
2.6800E+1
6.8800E-M
9.3000E+1
l.OSOOEtl
RAIN(MM/MO)s
(WLAM,P/SQ
2
3
4
4
4
5
5
5
2
8
9
1
.4000E+1
,2100Etl
.9400E+1
.1400E+1
.4900E+1
.OSOOEf 1
105.0
CM/SEC/N NM):
2 8.
3 1.
4 3.
4 9.
4 1.
5 1.
8400E+1
8100E+1
6600E+1
1700E+1
OOOOE+1
OSOOEtl
2
4
4
4
5
5
8
1
2
5
9
1
1
CLOUDdOTHS
.9100E+10
.3800E-U3
.1100E+14
.2600E-H4
.2700E-H4
.0500E-H5
.0700E-H5
)
3
1
2
6
9
1
1
= 5.0
.3800E+11
.8500E-H3
.2600E+14
.9200E-H4
.5900E-H4
.0600Etl5
.0300E-H5
LAT= 40.00
1.1100E+12
2.3300E413
2.4100E-H4
7.1200E+14
9.8300E+14
1.0700E+15
9.8800E-H4
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: BENZomouiNOLiNE
ECOSYSTEM: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
mmmmmmmmm**mmmmmmmmmmmm^mmmmmmmmmmmmmmm"m»mmmmm»mmmmmmmmmmmm»mmmmmmf*
TABLE 3. INPUT DATA DESCRIBING ENVIRONMENT: BIOLOGICAL PARAMETERS.
TY
1L
2B
3E
4H
SB
6L
7B
BIOMS
(1)
51.00
250.0
2.200
0.7500
10.00
51.00
250.0
PLRA
(2)
2.0000E-02
0.0000
1.000
1.000
0.0000
2.0000E-02
0.0000
BIOTM
DEG C.
20.00
20.00
20.00
5.000
5.000
20.00
20.00
BACTO
(3)
l.OOOOE+05
2.0000E+07
l.OOOOE+04
1000.
2.0000E+06
l.OOOOE+05
2.0000E+07
ACBAC
(2)
1.000
1.000
1.000
1.000
1.000
1.000
1.000
CHL
MG/L
4.0000E-03
4.0000E-03
5.0000E-04
4.0000E-03
(1) UNITS: MG/L IN WATER COLUMN (L,H,B); G (D.W.)/SQUARE METER IN (B).
(2) DIMENSIONLESS NUMBERS.
(3) UNITS: CELLS/ML IN L, E, H; CELLS/100 G D.W. IN B.
154
-------
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: BENZOtfJQUINOLINE
ECOSYSTEM; EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE
TY
1L
2B
3E
4H
5B
6L
7B
4. INPUT DATA DESCRIBING ENVIRONMENT: DEPTHS AND INFLOWS.
DEPTH STFLO
M CU M/HR
5.000 485.0
5.0000E-02
10.00
10.00
5.0000E-02
5.000
5.0000E-02
STSED NPSFL
KG/HP CU M/HR
40.00 48.50
48.50
NPSED
KG/HR
97.00
97.00
INTFL
CU M/HR
130.0
130.0
130,0
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: BENZomouiNOLiNE
ECOSYSTEM: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE
TY
1L
2B
3E
4H
5B
6L
7B
5, INPUT
SDCHR
(1)
0.5000
1.850
0.5000
0.5000
1.850
0.5000
1.850
DATA DESCRIBING ENVIRONMENT: SEDIMENT CHARACTERISTICS.
PCTWA
(2)
137.0
137.0
137.0
FROC
(3)
3.8000E-02
3.8000E-02
3.8000E-02
3.8000E-02
3.8000E-02
3.8000E-02
3.8000E-02
CEC
(4)
25.00
25.00
25.00
25.00
25.00
25.00
25.00
A EC
(4)
25.00
25.00
25.00
25.00
25.00
25.00
25.00
DOC
MG/L
2.500
2.500
0.5000
2.500
(i) UNITS: MG/L SUSPENDED SEDIMENT IN L, E, H; BULK DENSITY (G/co IN B
(2) 100 * F.W./D.W. IN B.
(3) DIMENSIONLESS.
(4) MEQ/100 GRAMS DRY WEIGHT.
155
-------
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: SENzntfJQUINOLINE
ECOSYSTEM: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE
TY
1L
2B
3E
4H
5B
6L
7B
6. INPUT
K02
CM/HR 320
5,000
10.00
0.0000
5.000
DATA DESCRIBING ENVIRONMENT: AERATION, LIGHT, MISC.
WIND
M/S 310 CM
1.500
2,000
0.0000
1.500
CMPET
/M
2.000
2.000
1.000
2.000
DFAC
M/M
1.190
1.190
1.190
1.190
EVAP
MM/MON
90.00
85.00
0,0000
90,00
AREA
SQ M
5.0000Et04
5.0000E+04
2.5000E+05
2.5000E+05
2.5000E+05
5.0000E+04
5.0000E+04
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: BENZQC£)O.UINOLINE
ECOSYSTEM: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 7.
COMP. NO.
CONNECTED
ADVECTION
COMP, NO,
CONNECTED
ADVECTION
AERL-ESB
CHEMICAL:
ECOSYSTEM;
TABLE 8.
COMP. NO,
CONNECTED
X-SECTION
CHAR. LN.
EDDY DISP,
COMP. NO,
CONNECTED
I
NPUT DATA
DESCRIB
ING
ENVIRONMENT
•
*
ADVECTIVE
INTERCONNECTIONS.
CJFRAD) 13625
(ITOAD) 36014
(ADVPR) 1.00 1.00 1.00 1.00 1,00
(JFRAD) 7 4
(ITOAD) 6 3
(ADVPR) 1,00 1.00
MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
BENZOtf JQUINOLINE
EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
INPUT DATA
(JTURB)
(ITURB)
(XSTUR) 5
(CHARD
(DSP) 4
(JTURB)
(ITURB)
DESCRIBING
1
2
.OOOE+04 2.
2,53 1
.676E-05 0,
3
6
ENVIRONMENT
3
4
SOOEtOS 2.
0.0 5
398 9.
: TURBULENT
4
5
500E+05 5.
.03 2
306E-05 4.
INTERCONNECTIONS.
6 1
7 3
OOOE+04 2.500E+03
.53 300,
676E-05 1.196E+03
X-SECTION (XSTUR) 2.500Et03
CHAR. LN. (CHARL) 300,
EDDY DISP. (DSP) 1.196E+03
156
-------
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: BENzomouiNOLiNE
ECOSYSTEM; EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE
CP T*
Y
1L
2B
3E
4H
5B
6L
7B
9, TRANSPORT PROFILE
VOLUME
(CUBIC M)
2.500E+05
2.500E+03
2.500E+06
2.500E+06
1.250E+04
2.5QOE+05
2.500E+03
SKDIMENT
MASS (KG)
125.
3.376E+06
1.250E+03
1.250E+03
1.688E+07
125.
3.376E+06
OF ECOSYSTEM.
WATER FLOW
(CU. M/DAY)
2.552E+05
3.131E+03
7.367E+05
2.423E+05
3.176E+03
2.628E+05
3.131E+03
SED. FLOW
(KG/DAY)
2.902E+04
3.001E+04
368,
1.451E+05
1.500E+05
2.902E+04
3.001E+04
RESIDENCE
WATER
0.980
0.399
3.39
10.3
1.97
0.951
0.399
TIME (DAYS)
SEDIMENTS
4.308E-03
112.
3.39
8.613E-03
112.
4.307E-03
112.
* COMP. TYPE: ML"=LITTOPAL; WEMS(EPD AND "H"S(HYPO)LIMNION; "B"=BENTHIC
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: BENzomouiNOLiNE
ECOSYSTEM: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 10. KINETIC PROFILE OF ORGANIC TOXICANT. RATE CONSTANTS DERIVED
FROM COUPLING OF TOXICANT CHARACTERISTICS TO ECOSYSTEM PROPERTIES.
CP T*
Y
1L
2B
3E
4H
SB
6L
7B
HYDROLYSIS PHOTOLYSIS
0.000
o.ooo
0.000
0.000
0.000
0.000
0,000
3.925E-03
0,000
2.010E-03
1.690E-28
0.000
3.925E-03
0.000
RST-ORDER
RATE CONSTAN
OXIDATION BIOLYSIS
0.000
0,000
0.000
0.000
0.000
0.000
0.000
3.508E-03
5.750E-06
3.594E-04
1.271E-05
2.036E-07
3.508E-03
5.750E-06
VOLATILITY
1.374E-06
o.ooo
1.192E-06
0.000
0.000
1.374E-06
0.000
TRANSPORT
4.758E-02
4.006E-04
1.228E-02
7.161E-03
3.765ET-04
4.882E-02
4.006E-04
* COMP. TYPE: "L"sLITTORAL? "E"*(EPD AND "H"*(HYPO)LIMNION; "B"*BENTHIC
157
-------
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: BENzotfJQUINOLINE
ECOSYSTEM: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE
CP T*
Y
P
1L
2B
3E
4H
SB
6L
7B
11.
PH
8.00
6.50
8.00
7.40
6.50
8.00
6.50
CANONICAL PROFILE OF ECOSYSTEM.
POH
6.00
7.50
6.00
6.60
7.50
6.00
7.50
TEMP
DEG.
w *
20.0
20.0
20.0
5.0
5.0
20.0
20.0
REAERATION
COEFF.
COMPOSITE
LIGHT AVE
BACTERIAL
POP. SIZE
M/HR % C
5.
0.
0.
0.
0.
5.
0.
OOOE-02
000
100
000
000
OOOE-02
000
2.24
0.000
1.12
2.124E-28
0.000
2.24
0.000
1
2
1
1
2
1
2
ELLS/**
.OOOE+05
.OOOE+07
.OOOE+04
.OOOE+03
.OOOE+06
.OOOE+05
.OOOE+07
1
0
1
5
0
1
0
OXIDANT
CONC.
(MOLAR)
.OOOE-09
.000
.OOOE-09
.OOOE-10
.000
.OOOE-09
.000
DISSOLVED
PERCENT
*
97.5
2.955E-02
99,8
99.9
2.959E-02
97.5
2.955E-02
* COMP. TYPE: "L"=LITTORAL; "E"S(EPI) AND "H"S(HYPQ)LIMNION; WB"=BENTHIC
** ACTIVE BACTERIAL POPULATIONS AS CELLS/ML IN WATER COLUMN,
CELLS/100 G (DRY WEIGHT) OF SEDIMENTS IN BOTTOM SEDIMENTS.
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: BENZQUJQUINOLINE
ECOSYSTEM: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 12. TOXICANT LOADINGS (KG/HR) BY SYSTEM ELEMENT.
ELEMENT STREAM FLOW RAINFALL INTERFLOW NFS LOAD DRIFT LOAD
1 0.5000 6.4000E-03 0,1600
2 2.0000E-02
3 3.2000E-02
4
5
6 6.4000E-03 0.1600
7 2.0000E-02
158
-------
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: BENZOLJQUINOLINE
ECOSYSTEM: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 13. DISTRIBUTION OF CHEMICAL AT STEADY STATE: IN THE WATER COLUMN:
COMP STEADY-STATE RESIDENT MASS
2
G/M KILOS %
**** TOXICANT CONCENTRATIONS ****
TOTAL DISSOLVED SEDIMENTS BIOTA
MG/* MG/L MG/KG UG/G
1 0.590
3 0.763
4 0.750
6 0.401
SUBTOTAL:
AND IN THE
2 9.84
5 6.22
7 7.00
SUBTOTAL:
TOTAL MASS (
29,51
190.7
187.5
20.05
427.8
BOTTOM SEDI
491.8
1555.
349.9
2397.
KILOGRAMS)
6.
44.
43.
4.
15.
MENTS:
20.
64.
14.
84.
s
90
57
84
69
15
52
88
60
85
2824
0
7
7
8
*
.11
8
.626E-02
.50
.01
146
92.
104
1E-02
9E-02
.
1
*
0
7
7
7
0
7
8
.115
.613E-02
.494E-02
.815E-02
.116
.367E-02
.277E-02
149.
98.8
96.9
101.
145.
92.1
103.
57
38
37
39
55
35
39
.4
.0
.3
.0
.9
.4
.8
* TOTAL CONCENTRATION AS MG/L IN WATER COLUMN, AS MG/KG IN SEDIMENTS.
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: BENzotfJQUINQLINE
ECOSYSTEM: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 14. AVERAGE, MAXIMUM, AND MINIMUM CONCENTRATIONS AT STEADY STATE.
1
CP)TOTAL
MG/*
CP)
DISSOLVED
MG/L
CP)
SEDIMENTS
MG/KG
CP)
BIOTA
CP)
UG/G
MASS
2
G/M
WATER COLUMN:
AV
MA
MI
8.738E-02
1) 0.118
4) 7.501E-02
1)
4)
8
0
7
.606E-02
.115
.494E-02
1)
4)
112.
149.
96.9
1)
4)
42.
57.
37.
9
4
3
3)
6)
0.63
0.76
0.40
BOTTOM SEDIMENTS:
AV
MA
MI
114.
2) 146.
5) 92.1
2)
5)
9
0
7
.093E-02
.116
.367E-02
2)
5)
114.
145.
92.1
2)
5)
43.
55,
35.
7
9
4
2)
5)
7.7
9.8
6.2
1 NUMBER IN HALF-PARENS CP) INDICATES COMPARTMENT WHERE VALUE WAS FOUND.
* TOTAL CONCENTRATION AS MG/L IN WATER COLUMN, AS MG/KG IN SEDIMENTS.
159
-------
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: BENZOE*JQUINOLINE
ECOSYSTEM: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 15. ANALYSIS OF STEADY-STATE
PROCESS
HYDROLYSIS
OXIDATION
PHOTOLYSIS
ALL CHEMICAL PROCESSES
WATER COLUMN (BACTERIA)
BOTTOM SEDIMENTS (BACTERIA)
TOTAL BIOLYSIS
VOLATILIZATION
WATER-BORNE EXPORT
TRANSFORMATION AND TRANSPORT
TOTAL SYSTEM LOAD
RESIDUAL ACCUMULATION RATE:
FATE OF ORGAN
MASS FLUX
KG/DAY
0.0000
0.0000
13.87
13.87
5.874
0.1237
5.998
7.0866E-03
1.842
21.72
21.72
5.7220E-06
1C TOXICANT.
% OF LOAD
0.00
0.00
63.86
63.86
27.05
0.57
27.62
0.03
8.48
100.00
0.00
HALF-LIFE*
DAYS
141.2
141.2
50.47
1.3424E+04
326.4
2.7625E+05
1063,
* HALF-LIVES ARE ESTIMATES BASED ON A FIRST-ORDER RATE APPROXIMATION,
160
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AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL; BENZOC*JQUINOLINE
ECOSYSTEM: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 16. SIMULATION OF SYSTEM RESPONSE AFTER LOAD CEASES.
TIME AVERAGE POLLUTANT CONCENTRATIONS MASS OF POLLUTANT
DAYS WATER COLUMN BOTTOM SEDIMENTS WATER COL SEDIMENTS
FREE(MGXL) SED(MGXKG) PORECMG/L) SED(MG/KG) TOTAL KG
0.
15.
30.
45.
60.
75.
90.
105.
120.
135.
150.
165.
180.
8.606E-02
4.802E-02
4.068E-02
3.723E-02
3.483E-02
3.280E-02
3.095E-02
2.923E-02
2.762E-02
2.612E-02
2.471E-02
2.339E-02
2.214E-02
112.
62.3
52.8
48.3
45.2
42.5
40.1
37.9
35,8
33.9
32.0
30.3
28.7
9.093E-02
8.613E-02
8.024E-02
7.454E-02
6.925E-02
6.439E-02
5.994E-02
5.585E-02
5.210E-02
4.865E-02
4.548E-02
4.255E-02
3.985E-02
114.
108.
100.
93.2
86.6
80.5
74.9
69.8
65.1
60.8
56.8
53.2
49.8
427.8
285.6
242.8
223.3
210.1
198.9
188.7
179.1
170.0
161.5
153.4
145.7
138.5
TOTAL KG
2.397E+03
2.323E+03
2.211E+03
2.095E+03
1.984E+03
1.878E+03
1.779E+03
1.686E+03
1.598E+03
1.515E+03
1.437E+03
1.363E+03
1.293E+03
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: BENZocfJQUINOLINE
ECOSYSTEM: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 17. EXPOSURE ANALYSIS SUMMARY.
EXPOSURE:
A. MAXIMUM CONC, IN WATER COLUMN: 0.12 MG/L DISSOLVED, 0,12 TOT
MAX. CONC. IN BOTTOM SEDIMENT: 0.12 MG/L DISSOLVED IN PORE WATER
B. BIOSORPTION - MAX. CONCENTRATION - PLANKTON: 57. UG/G
BENTHOS: 56. UG/G
C. MAXIMUM TOT. CONC. IN SEDIMENT DEPOSITS: 1.46E+02 MG/KG (DRY WEIGHT)
FATE:
A. TOTAL STEADY-STATE ACCUMULATION: 2.82E+03 KG; 15,15% IN WATER COL.,
84.85% IN BOTTOM SEDIMENTS.
B. TOTAL LOAD: 22. KG/DAY - DISPOSITION: 63.86% VIA CHEMICAL
TRANSFORMATIONS, 27,62% BIOTRANSFORMF.D, 0,03% VOLATILIZED,
8.48% EXPORTED VIA 0-THER PATHWAYS,
PERSISTENCE:
A, AT THE END OF A 180. DAY RECOVERY PERIOD, THE WATER COLUMN HAD
LOST 67.63% OF ITS INITIAL TOXICANT BURDEN; THE SEDIMENTS HAD
LOST 46.04% OF THEIR INITIAL BURDEN ( 49.31% REMOVAL OVERALL).
B, SYSTEM SELF-PURIFICATION TIME IS ROUGHLY 31. MONTHS.
161
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Data Entry series 1. Chemical Input Data.
AERL-ESB MODEL OF FATE OF ORGANICS IN AQUATIC ECOSYSTEMS
CHEMICAL NAME: .^-~._.^..
SPFLG VECTOR (SH2, SH3+, SH4++, SH-, S):
TABLE 1.1. SH2 (NEUTRAL MOLECULE, SPECIES »1) INPUT DATA, SPFLG(1)=1
MWTa «««... SOL a .... VAPR= .. HENRY= .
KVOa
KPS=
KAH2a _,
KAH3= „,
KBHla __,
KBH2= _.
KBH3a .^..
KBACW1* ..
KBACW2a „
KBACW3a w
QUANT1:
KPB
EAH2a
EAH3a ...
EBHls .^
EBH3a ___
QTW3a
RFLATs _
EVPR =
KOC =
KNHla ....
KOW
KNH3
.. ENH3« r
KBACS2a ^.
LAMAX* 0.00
QUANT3= -..
ABSORPTION SPECTRUM (ABS):
162
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AERL-ESB MODEL OF FATE OF ORGANICS IN AQUATIC ECOSYSTEMS
CHEMICAL NAME; __„—.—-..—-
TABLE 1,4. SH-
(SINGLY CHARGED ANION, SPECIES #4) INPUT DATA. SPFLG(4)sl.
PKAlB
MWT =
KAH1 =
KAH2s
KAH3=
KBH1 =
KBH2=
KBH3=
KPS s
EBH2s
EBH3S
KBACW1= ......
KBACW2* ..
KB AC W 3= -.—-. QTW3= ..
KDP= ...„,.. RFLAT* ......
QUANT1= ..„_«. OUANT2B _
ABSORPTION SPECTRUM (ABS):
SOL» ..
KPB» .,
KNH1= w.
KNH2= ...
KNH3s
KOXls _..
KOX2s «^
KAEC8 .,
KOX3* «..««.
KBACSls ——
KBACS2s _._
KBACS3s ».«^.
QUANT3« ..
QTSli
165
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AERL-ESB MODEL OF FATE OF ORGANICS IN AQUATIC ECOSYSTEMS
TABLE 1
(DOUBLY
PKA2= .
MWT = .
KAH1= .
KAH2= -
KAH3= .
KBH1= .
KBH2= .
KBH3= .
KBACW1=
KBACW2=
KBACW3=
KDP= ..
QUANT1=
ABSDRPT
.5. SH=
CHARGED ANIQN, SPECIES »5) INPUT DATA. SPFLG(5)si.
__ EPKA2= .... SOLs . .. ESOLs ,-„•..- -a
— — KPS = _„_ KPBs ...... KAEC« — «»«.
GT ft M *7 S KMH^S F N H ? S
«-„.. EAH3= KNH3= ..«. ENH3= .«.
STAMPS Kny2s P*DX?B
... - F,RH?= ™-...— K^xis ....^. F^y^r .......
.__ OTW2S .. KBACS2= . QTS2* .-
OTW3= ..^^. KBACS3= «.. QTS3« 1L... r^
-. Rff.ATs ,,-.„...
_. QUANT2= ._ QUANT3=
ION SPECTRUM (ABS):
166
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Data Entry Series 2. Specification of Environment
Number of Compartments (KOUNT):,
Environment
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Type of compartment:
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
SKETCH OF ECOSYSTEM COMPARTMENTS AND INTERCONNECTIONS:
TABLE 2. INPUT DATA DESCRIBING ENVIRONMENT? GLOBAL PARAMETERS.
RAIN(MM/MO)* __~..._ CLOUDC 10THS)» ..«_ LAT= _,__»_
IRRADIANCE (WLAM,P/SQ CM/SEC/N NM): «.^«J+W. _.„£*"„_ ..^«E+—
167
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Type of compartment, "L," "E," "H," "B"
Compartment NO. .«„»«..
Geometry of Compartment:
SDCHR = .. . VOL =
AREA s ...... DEPTH = ......
STFLO = ._-.„„ STSED = ...„,.
NPSFL = ...... NPSED s ......
INTFL = ... EVAP = . *
WIND * ...... * PCTWA s ...... **
(TYPEE):
Specifications of Compartments
FROC =
AEC c
PH a
OXRAD * «.
PLRA « .
BACTO s
K02 =
DOC a
CHL 3
* -- This datum for water column compartments only
** .. This datum for benthic compartments only
...... CEC =
...... TCEL s .
...... RIOMS a
—~~. BIOTM = m
ACBAC s m
— * DFAC = .
*
— .. *
*
168
-------
Type of compartment , "L," "E," "H," "B"
Compartment NO. JJ.T-.,^^^^^^-!-^
Geometry of Compartment!
SDCHR = ...... VOL = _^_.-
AREA * .. .. DEPTH * —^.—
STFLO s ..-«„ STSED s ,._««.-
NPSFL « ,^_ NPSED s «~~~-
* —— EVAP « ....... *
* .««««. * PCTWA s ~-~— **
(TYPEE)
specifications of Compartment:
FROC
PH s
OXRAD s
PLRA =
BACTO s
DOC *
CHL «
CEC
POH
BIOMS
*
*
*
DFAC *
*
*
* « This datum for water column compartments only
** .. This datum for benthic compartments only
169
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3.2 Interactive System commands and Keywords.
This Section describes the functioning of EXAMS' interactive
commands and the response options for the commands. The text is
also available to an interactive user via the HELP command.
BASE (i.e., EXAMS' response to a simple EXAMS > HELP)
EXAMS is an interactive computer language and modeling
system for analyzing exposure, fate, distribution, and
persistence of synthetic organic chemicals in aquatic ecosystems.
The EXAMS command language allows a user to select chemicals
(COMPOUND and RECALL commands) and ecosystems (ENVIRONMENT and
RECALL) from external data bases, specify (CHANGE) the chemical
loadings on the system, conduct an exposure analysis (RUN),
retrieve the results (LIST, PLOT, PRINT), modify (CHANGE) any of
the input data and reRUN the system, and STORE new data for later
RECALL.
When entering commands and response options, any EXAMS
vocabulary word can be abbreviated to the characters needed for
EXAMS to decode the word. For example, a RUN command can be
entered as RUN or as RU. To get HELP for a particular keyword,
type HELP , HELP is available for the name of any input
VARIABLE, and for the keywords:
ADVECTION
ENVIRONMENT
LIST
QUALITY
STOP
AUDIT
ERASE
LOADS
QUIT
TURBULENCE
CHANGE
EXIT
PLOT
RECALL
CHEMISTRY
GEOMETRY
POINT
RUN
COMPOUND
GLOBALS
PRINT
SHOW
DESCRIBE
HELP
PROFIL
STORE
ADVECTION
The ADVECTION option of the SHOW command returns the input
data characterizing the advective interconnections among
compartments of the current ecosystem. Up to NCOH
interconnections can be specified; inactive pathways are not
displayed. Syntax is
EXAMS > SHOW ADVECTION
The index vectors contain the source (JFRAD, J FRom ADvection)
and receiving (ITOAD, I TO ADvection) compartments in homologous
locations. Parameter ADVPR gives the proportion of the total
advective flow through compartment JFRAD that leaves via the
173
-------
(ITPAD,JFRAD) pathway,
Advective interconnections can be re-specified (CHANGEd) at
will. Export pathways are designated by loading a "0" in ITOAD.
Should the new definition fail to adhere to the principle of
conservation
simulation.
of mass, however, EXAMS will decline to RUN the
AUDIT
The AUDIT command makes a record of all subsequent commands
entered into EXAMS, The syntax of the command is:
EXAMS > AUDIT
After receiving an AUDIT command, EXAMS copies each
following user command and/or response to the output data file
defined by FORTRAN logical unit AUDOUT. After leaving EXAMS >,
this file can be retrieved and used as a record of the session.
CHANGE
The CHANGE command alters the value of any input datum. The
syntax of this command is
EXAMS > CHANGE TO
where is the name of the variable and is its new
value, EXAMS variables may be scalars, vectors, or matrices.
(The meaning of the vector and matrix indices (subscripts) is
explained under , For example, the command
EXAMS > CHANGE PH(4) TO 7,6
would alter the pH of compartment 4 to 7,60, EXAMS also allows
the use of "wild cards" <*> for vector and matrix indices. For
example, the command
EXAMS > CHANGE PH(*) TO 7,6
alters the pH of ALL compartments to 7,60. In using the CHANGE
command, it is important that matrix indices be specified in the
proper (row, column) order. For example, CHANGEing ENH(3,1) is
not equivalent to CHANGEing ENH(i,3): the former refers to the
biosorbed form of a neutral molecule (SH2); the latter to the
dissolved form of an SH4++ cation! The outcome of a CHANGE can
174
-------
always be checked by invoicing the appropriate SHOW option,
CHEMISTRY
The CHEMISTRY option of the SHOW command returns the
chemical data currently available to EXAMS for simulation RUNS.
Syntax is:
EXAMS > SHOfo CHEMISTRY
For convenience, ail MATRIX variables include the row index of
the datum as a suffix; the column index (chemical SPECIES #) is
given in the table header. The latter quantity is also the
proper index for VECTOR variables. Thus for example, a reference
to KBACW3 in the chemical data for SPECIES #1 gives the value for
KBACW(3,1), the 2nd-order rate constant for biolysis of the
biosorbed form of a neutral (SH2) molecule in the water column.
This datum can be altered by:
EXAMS > CHANGE KBACW(3,1) TO
All input data can be CHANGEd; the DESCRIBE and HELP commands
can be used to ascertain the dimensions and attributes of the
input variables.
COMPOUND
COMPOUND is used as a stand-alone command AND as a keyword
in the SHOW, STORE, RECALL, and ERASE commands. (Type , , etc. for a description of these useages.)
The stand-alone COMPOUND command has two distinct functions: it
can be used either to SELECT a chemical from the fixed data base,
or to reNAME the current chemical. The syntax for the SELECT
option is:
EXAMS > COMPOUND IS
where "aaa" is the abbreviation of an available chemical. (Type
for a table of contents.) The syntax for the
NAME option is:
EXAMS > COMPOUND NAME IS
after which "bbb" (up to 60 characters permitted) will be entered
as part of the title for all output tables produced by EXAMS.
For example, the command:
175
-------
EXAMS > COMPOUND IS DBC
loads the data base describing 7H-dibenzo[c,g)carbazole, a
(carcinogenic) nitrogen heteroclycic compound found in
energy-related effluents. The command:
EXAMS > COMPOUND NAME IS <7H-dibenzo[c,g]carbazole with high biolysis>
would result in the text <7H- ... > being printed as part of the
title of EXAMS' subsequent outputs.
DESCRIBE
The DESCRIBE command returns the attributes of a specific
input datum. Command syntax is
EXAMS > DESCRIBE
where is the name of an input variable.
For example, EXAMS > DESCRIBE WLAMG
returns: wLAM is a REAL VECTOR with 39 rows.
Or: EXAMS > DES ENH
returns: ENH is a REAL MATRIX with 3 rows and 5 columns.
The information returned by DESCRIBE is needed when SHOWing or
CHANGEing an input datum.
ERASE
The ERASE command clears a selected location if the user
chemical or environmental data base (UDBs). The syntax of the
command is:
EXAMS > ERASE COMPOUND *
or
EXAMS > ERASE ENVIRONMENT *
where "#" is the location in the UDB to be cleared. This command
can be used to help protect the confidentiality of chemical or
environmental data.
176
-------
ENVIRONMENT
ENVIRONMENT is used as a stand-alone command AND as a
Keyword In the SHOW, STORE, RECALL, and ERASE commands. (Type
, etc. for a description of the latter useages.) The
stand-alone ENVIRONMENT command has two distinct functions. It
is used either to SELECT an ecosystem from the fixed data file,
or to reNAME the current system. The syntax for the SELECT
option is
EXAMS > ENVIRONMENT IS
where "aaa" Is the name of an available ecosystem. Type ENVIRONMENT NAME IS
after which "bbb" (up to 60 characters permitted) will be used as
part of the title for all of EXAMS' subsequent ouput tables. For
example, the command:
EXAMS > ENVIRONMENT IS POND
loads the fixed data base describing a pond ecosystem. The
command:
EXAMS > ENVIRONMENT NAME IS Southeastern Pond with pH of 6>
would result in the text being printed as part of the
title of EXAMS' subsequent outputs.
EXIT
The EXIT command is used to terminate use of EXAMS and
return to the operating system, e.g., PDS>. The syntax of the
command is
EXAMS > EXIT
The EXIT command is also used to abort a coiffmand sequence when
the command has been inadvertantly initiated. For example, given
the input
EXAMS > COMPOUND , EXAMS will return the prompt:
177
-------
SELECT or NAME a compound or EXIT >
Responding to this prompt with will return you to the
EXAMS > prompt with no action taken on the COMPOUND command.
GEOMETRY
The GEOMETRY option of the SHOW command returns a
compartment-by- compartment listing of environmental data
describing the current ecosystem. The compartment number given
with each block of data is the appropriate vector index for
CHANGEing the variables listed in the block. The attributes and
dimensions of each parameter can be inspected via the DESCRIBE
and HELP commands. Command syntax is
EXAMS > SHOW GEOMETRY
GLOBALS
The GLOBALS option of the SHOW command returns the values of
global (i.e., not specific to any single compartment)
environmental descriptors. The attributes and dimensions of each
parameter can be accessed via DESCRIBE and HELP. CLOUD, LAT, and
WLAM are used to calulate photolysis rates of the chemical; RAIN
is part of the input hydrologic data. Each input datum can be
CHANGEd to any desired value.
HELP
The HELP command is used to obtain information about the use
of EXAMS vocabulary words (commands and response options) and to
obtain definitions and physical dimensions of the chemical and
environmental input data. Input data can be CHANGEd from the
nominal values held in the data bases to any desired number.
Syntax of the HELP command is:
EXAMS > HELP
where can be the name of a command (e.g., SHOW), an
optional response word (e.g., ADVECTION), or the name of an input
variable (e.g., KBACW), For example, typing
EXAMS > HELP HELP invoked this message,
178
-------
The structure of the input data is described under the
VARIABLES, but VARIABLES is not a part of the formal
EXAMS vocabulary.
LIST
The LIST command issues reports (based on simulation
studies) that describe the exposure, distribution, fate, and
persistence of a chemical in a particular ecosystem/load
situation. The reports include the input data describing the
chemical and the ecosystem, fate and exposure data at
steady-state, pseudo-first-order half-lives by process, and a
system self-cleansing time based on all processes acting in
concert. The command sytax is
EXAMS > LIST
where H#" can be any of the integers U,2,3, ..., 17) or "ALL".
Alternatively, issuing the command
EXAMS > LIST
generates the EXAMS prompt
Table >
Typing (rather than <»>) in response to "Table >" will
elicit a numerical listing and description of the available
output tables.
LOADS
The LOADS option of the SHOW command returns a tabulation of
the chemical loadings on the ecosystem. The first column of this
table gives the number of the compartment receiving the load;
these numbers are the appropriate vector indices for entering or
CHANGEing loads. Command syntax is:
EXAMS > SHOW LOADS
The internal variable names (used for CHANGE) for each type of
load listed in the columns of the tabulation are:
STREAM FLOW --- STRLD
RAINFALL — PCPLD
INTERFLOW --- IFLLD
179
-------
NPS LOAD -— NP5LD
DRIFT LOAD —- DRFLD
Each time a new COMPOUND or ENVIRONMENT is selected, all chemical
loads are reset to zero. If a given loading is found (during a
simulation RUN) to violate assumptions of the model (e.g., by
supersaturating an inlet carrier flow), or is found to be
inappropriate (e.g., a PCPLD to a (B)enthic compartment), that
load is modified as necessary. These new loadings are stored in
the LOADS matrix and returned to the user, i.e. the erroneous
loadings are discarded and the new values are retained.
PLOT
The PLOT command produces a graphic display of selected
results from the most recent simulation. PLOT contains 3 levels
of subcommands;
(1) - the type of PLOT desired « or
(2) - the concentration variable — , ,
, , or
(3a) - the "statistical" variable -- (under
POINT)
(3b) - the environmental zone « (under PROFIL)
PLOT requires that each of these options be specified in the
order given above. An example of the syntax of this command is
EXAMS > PLOT
Enter POINT, PRQFIL, HELP or EXIT >
Enter TOTAL, DISSOLVED, PARTICULATE, BIOTA, «ASS, HELP or EXIT >
Enter AVE, MAX, MIN, MINMAX, HELP, or EXIT >
The HELP option produces a definition of each of the available
options; the EXIT option will abort PLOT and return to the
EXAMS > prompt.
The PLOT command can also be executed via a single line,
i.e., the PLOT requested in the example given above could also be
entered as:
EXAMS >
180
-------
(Remember that you need enter only enough letters
word to make It distinct.)
of any EXAMS
POINT
POINT is a type of PLOT (c.f.) available through EXAMS
graphics. Specifically, the response to:
EXAMS > PLOT
Enter POINT, PROFIL, HELP, or EXIT >
produces a vertical profile of chemical concentration in the
ecosystem. EXAMS then requires that a concentration variable
(TOTAL, DISSOLVED, PARTICIPATE, BIOTA, or MASS) and a
"statistical" variable (AVE, MAX, WIN, or MINMAX) be specified.
Plots of maximum and minimum values Include the compartment
number where that concentration occurs.
The concentration (TOTAL, DISSOLVED, PARTICIPATE, BIOTA,
MASS) and "statistical" (AVE, MAX, MIN, MINMAX) variables are
defined in the Internal HELP responses of the PLOT command.
PRINT
The print command performs the same function as the LIST
command, but the output is routed to a line printer. Syntax is
EXAMS > PRINT
where is any of the numbered output tables (1 through
t7). The command routes all 17 tables to the
printer.
PROFIL
PROFIL is a type of PLOT (c.f.) available through EXAMS
graphics. Specifically, the response to:
EXAMS > PLOT
Enter POINT, PROFIL, HELP, or EXIT >
181
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produces a longitudinal PROFILe of chemical concentrations in the
ecosystem. EXAMS then requires that a concentration variable
(TOTAL, DISSOLVED, PARTICIPATE, BIOTA, or MASS) and an
environmental zone CWATER or SEDIMENTS) be specified. The
abscissa of the resulting PLOT is organized according to
downstream progression in the ecosystem (i.e., by ascending
compartment number). In the case of ecosystems that are
vertically inhomogeneous, the PLOT will show separate entries
for, e.g., the epilimnion and hypolimnion. These can be
distinguished by noting the compartment number and letter codes
given on the plots (e.g., E for epilimnion and H for
hypolimnion).
The concentration variables (TOTAL, DISSOLVED, PARTICIPATE,
BIOTA, MASS) and environmental zones (WATER, SEDIMENT) are
defined in the internal HELP responses of the PLOT command.
QUALITY
The QUALITY option of the SHOW command returns a
compartment-by- compartment listing of canonical water quality
data describing the current ecosystem. The compartment number
given with each block: of data is the appropriate vector index for
CHANGEing the variables listed in the block. The attributes and
dimensions of each parameter can be inspected via the DESCRIBE
and HELP commands. Command syntax is
EXAMS > SHOW QUALITY
QUIT
The QUIT command is used to terminate use of EXAMS and
return to the operating system, e.g., PDS>. The syntax of the
command is
EXAMS > QUIT
RECALL
The RECALL command retrieves chemical or environmental data
from the user data bases (UDBs) for use in EXAMS. Command syntax
iss
182
-------
EXAMS > RECALL COMPOUND *
or
EXAMS > RECALL ENVIRONMENT «
where "*M is the location of the data in the UDB, The table of
contents of the UDBs can be generated via a SHOW command, that
is,
EXAMS > SHOW USER COMPOUNDS
or
EXAMS > SHOW USER ENVIRONMENTS
RUN
The RUN command instructs EXAMS to execute a simulation and
create the output tables describing the results.
Command syntax is EXAMS > RUN
where is a carriage return, .Simulation RUNS cannot be
executed until a COMPOUND and an ENVIRONMENT have been selected,
and at least one non-zero LOAD has been specified. If any of
these steps has not been completed when the RUN command is
issued, EXAMS prints a reminder and aborts the RUN.
SELECT
SELECT is not an EXAMS user keyword. EXAMS uses SELECT as a
prompt when a COMPOUND or ENVIRONMENT command is issued without a
complete command sequence. For example,
EXAMS > COMPOUND
elicits
SELECT or NAME a compound or EXIT >
EXAMS will now recognize either
-------
EXAMS > STORE ENVIRONMENT I
where "*" is an available location in the UDB. If the selected
location in the UDB is already in use, EXAMS will report the fact
and require confirrigation that the existing data are to be
overwritten and destroyed.
TERMINAL
The TERMINAL command identifies your terminal for EXAMS'
plotting routines. The syntax of the command is:
EXAMS > TERMINAL IS
The available options are: (1) -- a DEC terminal equipped
for graphics, (2) <4010> — any Tectronlx series (4010, 4012,
4014, etc.) with graphics capability, and (3) for all other
alphanumeric terminals lacking an internal graphics package.
EXAMS should have this information prior to initiation of the
PLOT command, if it does not, EXAMS will execute a TTY plot.
TURBULENCE
The TURBULENCE option of the SHOW command returns the input
data characterizing the dispersive interconnections among
compartments of the current ecosystem, up to NCON
interconnections can be specified; inactive pathways are not
displayed. Syntax is
EXAMS > .SHOW TURBULENCE
Homologous pairs in the index vectors (JTURB, ITURB) serve to
define the system exchange pathways (a "0" in either vector,
paired with a non-zero compartment number in the homologue,
defines a boundary condition). XSTUR is the crossectional area
for pathway (JTURB, ITURB); CHARL is its characteristic length
(mean of mixing lengths or compartment dimensions along the flow
path); DSP is the eddy dispersion coefficient.
Dispersive interconnections can be re-specified (CHANGEd) as
desired. If the new definition Includes non-existent
compartments (e.g., a JTURB ,GT, KOUNT) -or compartments not
connected to the main system, however, EXAMS may in some cases
decline to RUN simulations.
185
-------
USER
USER is a subpart of the SHOW command. USER directs EXAMS
to the chemical and environmental user data bases (UDBs). The
commands:
EXAMS > SHOW USER COMPOUNDS
and
EXAMS > SHOW USER ENVIRONMENTS
generate tables of contents for these UDBs.
VARIABLES
The chemical and environmental data used for EXAMS*
computations are continually available for inspection and
alteration by the interactive user. The data can be inspected in
tabular form (type for a description), or the current
value of any single datum can be SHQWn. For example,
EXAMS > SHOW PHC4)
will return:
PH IS 7.000
when the pH of compartment number 4 is 7.0. A description of
each blOCK of data (ADVECTIQN, CHEMISTRY, GEOMETRY, GLOBALS,
LOADS, QUALITY, TURBULENCE) is given under is the name of one of these blocks. Typing is the name of an input datum will elicit a
definition of the variable (e.g., . When CHANGEing or SHOWing a variable, the
vector/matrix indices must be entered in the proper (row, column)
order (because is by no means equivalent to
). In a system that can handle 10-compartment
ecosystems, the dimensions of variables include the values: (5),
(3,5), (10), (30), (5,39), and (39). Dimension (5) refers to the
ionic species of the chemical (c.f. ); dimension (3)
refers to physical forms (1: dissolved, 2: sediment-sorbed, 3:
blosorbed); dimension (3,5) to matrices of molecular
configurations amalgamating (3) and (5) (e.g., refers
to a blosorbed neutral molecule); dimension (10) to ecosystem
compartments; dimension (30) to compartment interconnections;
and dimension (39) refers to irradiance and light absorption
intervals (see Table 2.18).
186
-------
3.3 Tutorial Interactive Sessions
This Section contains four sample fc'XAMS sessions designed to
introduce the user to the EXAMS facility. Although each session
has underlying pedagogical objectives, the nominal user
objectives are:
3.3.1. To enter the EXAMS system, execute runs of a selected
chemical in selected ecosystems, secure selected plots and output
listings of the results, and terminate the session.
3.3.2. To analyze the persistence of a new chemical in a
particular ecosystem, given meager input data.
3,3.3. To execute a sensitivity analysis defining the need for
accuracy in rate constants for a particular chemical/environment
situation.
3.3,4. To enter a new set of chemical and environmental data,
evaluate the behavior of the chemical, and store the data in the
UDBs.
The on-line help file can be used as a reminder of the
syntax of any command; its use is illustrated in Session 1.
Once a command has been invoiced, in general a carriage return
will cause EXAMS to return a prompt that includes a listing
of the available response options.
EXAMS' interactive capabilites can be used to enter both
chemical and environmental data. New chemicals and new
environments can be specified (via the CHANGE command), given
distinctive names up to 60 characters long (NAME command), and
stored in user data bases (STORE command, either as STORE
COMPOUND or STORE ENVIRONMENT). The User Data Bases can be
inspected Via and ,
which elicit a table of the current contents.
When entering new chemical data, the UNS (unspecified)
compound is available as a template. UNS is a neutral compound,
but the template can be expanded by CHANGES to the SPFLG vector
(see Glossary). Similarly, the UNS environment serves as a
template for entering new environmental data. In this case, UNS
has but a single compartment. The first step in entering a new
ecosystem is therefore to CHANGE parameter KOUNT to the desired
number of compartments, followed by a specification of the TYPEE
of each sector of the system.
Environmental and chemical data in the User Data Bases are
permanently stored and can be retrieved for use in subsequent
sessions via the RECALL command. Unlike the COMPOUND command,
RECALL tafces a numerical location for its data retrieval. For
example,
EXAMS > RECALL ENV 34
loads data at position 34 in the data base into current memory.
187
-------
3,3.1 Tutorial session »1: Basic Familarity with EXAMS
Objectives: basic familiarity with EXAMS, use ot command
statements (SHOW, COMPOUND, ENVIRONMENT, HUN, HELP, CHANGE, LIST,
PLOT) and response options (CHEMISTRY, LOADS, POINT, PROFIL,
etc.).
PDS> RUN EXAMS
17:37:59
welcome to EXAMS
Exposure Analysis Modeling system
Athens Environmental Research Laboratory
Released for field trials Jan-81
The ATHENS collection of compounds is available for your use,
EXAMS > SHOW COMPOUNDS
CHEMICAL NAME COMMON NAME
1 UNSPECIFIED CHEMICAL UNS
2 9H-CAR8AZOLE CAR
3 BENZOtflQUINQLINE BFO
4 7H-DlBENZO[c,qJCARBAZQLE DBC
5 BENZOCbJTHIQPHENE BT
6 DIBENZOTHIOPHENE DBT
7 BENZCalANTHRACENE BA
8 p-CRESOL PCR
9 BENZOtaJPYRENE BAP
10 MIREX MIR
11 METHYL PARATHION Mp
12 QUINOLINE QUI
EXAMS > COMPOUND IS PCR
Compound selected > p-CRESOL
EXAMS > SHOW CHEMISTRY
Compound characteristics for > p-CRESOL
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: P-CRESOL
ECOSYSTEM: Unspecified Environment
188
-------
EXAMS > 5HO ENVIRON
1 UNSPECIFIED ENVIRONMENT
2 POND
3 OLIGOTROPHIC LAKE
4 EUTROPHIC LAKE
5 RIVER
EXAMS > EMV IS OLIGOTROPHIC LAKE
Command not recoqnized. Enter help for command info.
EXAMS > ENV IS OLIG
Selected environment is: OLIGOTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST
DEFINITION
EXAMS > RUN
No load specified.
Simulation not performed.
EXAMS > HELP LOAD
The LOADS option of the SHOW command returns a tabulation of the
chemical loadings on the ecosystem. The first column of this table
gives the number of the compartment receiving the load; these numbers
are the appropriate vector indices for entering or CHANGEing loads.
Command syntax is
EXAMS > SHOW LOADS
The internal variable names (used for CHANGE) for each type of load
listed in the columns of the tabulation are:
STREAM FLOW
RAINFALL
INTERFLOW
NPS LOAD
DRIFT LOAD
STHLD
PCPLD
IFLLD
NPSLD
DRFLD
Each time a new COMPOUND or ENVIRONMENT is selected, all chemical loads
are reset to zero. If a given loading is found (during a simulation
RUN) to violate assumptions of the model (e.g. by supersaturating an
inlet carrier flow), or is found to be inappropriate (e.g, a PCPLD to a
(B)enthic compartment), that load is modified as necessary. These new
loadings are stored in the LOADS matrix and returned to the user, i.e.
the erroneous loadings are discarded and the new values are retained.
EXAMS > CHANGE STRLD(l) TO 0.5
EXAMS > CH NPSLD(6) TO .05
190
-------
EXAMS > SHOW LOADS
Environment: OLIGOTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
Compartments (KOUNT): 7
1234567
Type of compartment (TYPEE): L B E H B L B
TABLE 12. TOXICANT LOADINGS (KG/HR) BY SYSTEM ELEMENT.
ELEMENT STREAM FLOW RAINFALL
1 0.5000
2
3
4
5
6
7
INTERFLOW NPS LOAD DRIFT LOAD
5.0000E-02
EXAMS > RUN
Simulation beginning for:
Compound: p-CRESOL
Environment: OLIGOTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
with a load of (Icg/hr) > 0.5500000
Hun complete.
EXAMS > LIST
Table > HELP
1 Input chemistry
2 Input data describing environment: GLOBAL parameters
3 Input data describing environment: BIOLOGICAL parameters
4 Input data describing environment: DEPTH and INFLOWS
5 Input data describing environment: SEDIMENTS characteristics
6 Input data describing environment: AERATION, LIGHT, MISC.
7 Input data describing environment:
8 Input data describing environment:
9 Transport profile of ecosystem
10 Kinetic profile of organic toxicant
11 Canonical profile of ecosystem
12 Toxicant loadings
13 Distribution of toxicant at steady-state
14 Average, maxima and minima at steady-state
15 Analysis of fate of toxicant
16 Post-load decay kinetics
17 Exposure analysis summary
ALL ENTIRE REPORT
ADVECTIVE INTERCONNECTIONS
TURBULENT INTERCONNECTIONS
Table > 15
191
-------
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: P-CRESOL
ECOSYSTEM: OLIGOTROPHIC LAKE, AEHL DEVELOPMENT PHASE TEST DEFINITION
TABLE 15, ANALYSIS OF STEADY-STATE FATE OF ORGANIC TOXICANT,,
PROCESS MASS FLUX % OF LOAD HALF-LIFE*
KG/DAY DAYS
HYDROLYSIS 0.0000 0.00 ---
OXIDATION 2.944 22.30 442.6
PHOTOLYSIS 0.3858 2.92 3378.
ALL CHEMICAL PROCESSES 3.330 25.22 391.3
WATER COLUMN (BACTERIA) 1.660 12.57 776,2
BOTTOM SEDIMENTS (BACTERIA) 2.0953E-03 0.02 7155.
TOTAL BIOLYSIS 1.662 12.59 784.2
VOLATILIZATION 0.2547 1.93 5115.
WATER-BORNE EXPORT 7.954 60.26 163,8
TRANSFORMATION AND TRANSPORT 13.20 100.00
TOTAL SYSTEM LOAD 13.20
RESIDUAL ACCUMULATION RATE: 2.5749E-05 o.oo
* HALF-LIVES ARE ESTIMATES BASED ON A FIRST-O.RDER RATE APPROXIMATION.
EXAMS > LIST 17
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: P-CRESOL
ECOSYSTEM: DLIGOTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 17. EXPOSURE ANALYSIS SUMMARY.
EXPOSURE:
A. MAXIMUM CONC. IN WATER COLUMN: 0.36 MG/L DISSOLVED, 0.36 TOT
MAX. CONC, IN BOTTOM SEDIMENT: 0.11 MG/L DISSOLVED IN PORE WATER
B. BIOSORPTION - MAX. CONCENTRATION - PLANKTON: 7.2 UG/G
BENTHOS: 2.2 UG/G
C. MAXIMUM TOT. CONC. IN SEDIMENT DEPOSITS: 1.2 MG/KG (DRY WEIGHT)
FATE:
A. TOTAL STEADY-STATE ACCUMULATION: 1.88E+03 KG; 98.85% IN WATER COL,,
1,15% IN BOTTOM SEDIMENTS,
B. TOTAL LOAD: 13, KG/DAY - DISPOSITION: 25.22% VIA CHEMICAL
TRANSFORMATIONS, 12.59% BIOTRANSFORMED, 1.93% VOLATILIZED,
60.26% EXPORTED VIA OTHER PATHWAYS,
PERSISTENCE:
A. AT THE END OF A 192. DAY RECOVERY PERIOD, THE WATER COLUMN HAD
LOST 72.72% OF ITS INITIAL TOXICANT BURDEN; THE SEDIMENTS HAD
LOST 63,21% OF THEIR INITIAL BURDEN ( 72,62% REMOVAL OVERALL),
B. SYSTEM SELF-PURIFICATION TIME IS ROUGHLY 17. MONTHS.
192
-------
EXAMS > PLOT
Enter POINT, PROFIL, HELP or EXIT > HELP
The following options are available:
POINT - vertical profile of the TOS concentration
PROFILE - Longitudinal profile of the TOS cone.
HELP - This message
EXIT - Return to the Exams prompt.
Enter POINT, PROFIL, HELP or EXIT > POI
Enter TOTAL, DISSOLVED, PARTICIPATES, BIOTA, MASS, HELP or EXIT > HE
The following concentration options are available:
TOTAL - mg/1 in water column,
mg/kg in benthic sediments.
dissolved mg/l.
sediment-sorbed mg/kg
biosorbed ug/g.
toxicant mass as grams/sq. meter AREA.
This message.
Return to the Exams prompt.
Enter TOTAL, DISSOLVED, PARTICIPATES, BIOTA, MASS, HELP or EXIT > DISS
Enter AVE, MAX, MIN, MINMAX, HELP or EXIT > HELP
The following statistical options are available:
MAX - For maximum concentration.
MIN - For minimum concentration.
AVE - For average concentration.
MINMAX • For simultaneous plot of maxima and minima.
HELP - This message.
EXIT - Return to the Exams prompt.
Enter AVE, MAX, MIN, MINMAX, HELP or EXIT > MAX
DISSOLVED
PARTICIPATE
BIOTA
MASS
HELP
EXIT
0.4000
-I
I
I
I
11111111111
C
0
N
M C
A E
X N
I T
M R
A A
T
I
0
N
0.3200
0.2400
0.1600
I 1
-I 1
I 1
I 1
I 1
I 1
-I i
I 1
I 1
I 1
1
1
i
1
1
1
D
I
S
S
0
L
V
E
D
M
G
1
1
i
1
1
i
1
1
i
1
D
I
S
S
0
L
V
E
D
M
G
/
55555L55555
0.8000E-01 -+.11111 ill111-55555555555
WAT COL BOT SED
193
-------
EXAMS > PLOT PROF DISS
Enter WATER, SEDIMENTS, HELP or EXIT > HELP
The following options are available:
WATER - Water column concentrations.
SEDIMENTS - Bottom sediment concentrations*
HELP - This message.
EXIT - Return to the Exams prompt.
Enter WATER, SEDIMENTS, HELP or EXIT > WATER
0.3650
0.3570
0.3490
D C
I 0
S N
S C
0 E
L N
V T
E R
D A
T
M I
G 0 0.3410
/ N
0.3330
-I
I
I
I
I
-I
I
I
I
I
-I
I
I
I
I
-I
I
I
I
I
LLLLLLLLLLL
EEEEEEEEEEE
3 3
3 3 LLLLLLLLLLL
33 66
-•••.11111111111.33333333333.44444444444.66666666666
WATER COLUMN
194
-------
EXAMS > ENV IS EUTR
Selected environment is: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST
DEFINITION
EXAMS > RUN
No load specified.
Simulation not performed,
EXAMS > CH STRLD(l) TO 0.5
EXAMS > CH NPSLD(6) TO .05
EXAMS > RUN
Simulation beginning for:
Compound: p-CRESQL
Environment: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
with a load of (kg/hr) > 0,5500000
Run complete.
EXAMS > LIST 15
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: P-CRESOL
ECOSYSTEM: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 15. ANALYSIS OF STEADY-STATE FATE OF ORGANIC TOXICANT.
PROCESS MASS FLUX % OF LOAD HALF-LIFE*
KG/HR HOURS
HYDROLYSIS 0,0000 0.00 —-
OXIDATION 4.7950E-03 0.87 7893.
PHOTOLYSIS 1.0320E-04 0.02 3,667lEt05
ALL CHEMICAL PROCESSES 4.8982E-03 0.89 7726.
WATER COLUMN (BACTERIA) 0.5381 97.83 69.79
BOTTOM SEDIMENTS (BACTERIA) 4.3094E-04 0.08 684.3
TOTAL BIOLYSIS 0.5385 97.91 70.28
VOLATILIZATION 3.6674E-04 0.07 1.0319E+05
WATER-BORNE EXPORT 6.2519E-03 1.14 6053*
TRANSFORMATION AND TRANSPORT 0.5500 100.00
TOTAL SYSTEM LOAD 0.5500
RESIDUAL ACCUMULATION RATE: 1.1921E-07 0.00
* HALF-LIVES ARE ESTIMATES BASED ON A FIRST-OPDER RATE APPROXIMATION,
EXAMS > PRINT 15
Requested report has been spooled to printer.
195
-------
EXAMS > LIST 17
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: P-CRESOL
ECOSYSTEM: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 17. EXPOSURE ANALYSIS SUMMARY.
EXPOSURE:
A. MAXIMUM CONC. IN WATER COLUMN; 2.51E-02 MG/L DISSOLVED, 2.52E-02 TOT
MAX. CONC. IN BOTTOM SEDIMENT: 2.26E-03 P>G/L DISSOLVED IN PORE WATER
B. BIOSORPTION - MAX. CONCENTRATION - PLANKTON: 0.50 UG/G
BENTHOS: 4.52E-02 UG/G
C, MAXIMUM TOT. CONC. IN SEDIMENT DEPOSITS: 2.35E-02 MG/KG (DRY WEIGHT)
FATE:
A. TOTAL STEADY-STATE ACCUMULATION: 55. KG; 99.22% IN WATER COL.,
0.78% IN BOTTOM SEDIMENTS.
B. TOTAL LOAD: 0.55 KG/HOUR - DISPOSITION:
TRANSFORMATIONS, 97.91% BIOTPANSFORMED,
1.14% EXPORTED VIA OTHER PATHWAYS.
PERSISTENCE:
A. AT THE END OF A 132. HOUR RECOVERY PERIOD, THE WATER COLUMN HAD
LOST 46.42% OF ITS INITIAL TOXICANT BURDEN; THE SEDIMENTS HAD
LOST 5.74% OF THEIR INITIAL BURDEN ( 46.11% REMOVAL OVERALL).
B. SYSTEM SELF-PURIFICATION TIME IS ROUGHLY 33. DAYS.
EXAMS > PRINT 17
Requested report has been spooled to printer.
EXAMS > PLOT PROF DIS WAT
0.89% VIA CHEMICAL
0.07% VOLATILIZED,
D C
I 0
S N
5 C
0 E
L N
V T
E R
D A
T
M I
G 0
/ N
L
0.2600E-01
0.2100E-01
0.1600E-01
0.1100E-01
0.6000E-02
-I
I
I
I
I
-I
I
I
I
I
-I
I
I
I
I
-I
I
I
I
I
- +
LLLLLLLLLLL
1
1
1
1
1
1
1
1
1
1
1
1
t
1
1
1
1
1
-11
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
111111111,
1 EEEEEEEEEEE
3 3 HHHHHHHHHHH
3 34 4
WATER COLUMN
196
-------
EXAMS > LIST 13
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: P-CRESOL
ECOSYSTEM: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 13. DISTRIBUTION OF CHEMICAL AT STEADY STATE: IN THE WATER COLUMN:
COMP STEADY-STATE RESIDENT MASS
2
G/M KILOS %
**** TOXICANT CONCENTRATIONS ****
TOTAL DISSOLVED SEDIMENTS BIOTA
MG/* MG/L MG/KG UG/G
1 0.126 6.291
3 9.559E-02 23.90
4 8.956E-02 22.39
6 3.190E-02 1.595
SUBTOTAL: 54.1?
AND IN THE BOTTOM SEDIMENTS:
2 4.660E-04 2.3298E-02 5.48
5 1.585E-03 0.3963 93.14
7 1.181E-04 5.9065E-03 1.39
SUBTOTAL: 0.4255 o.?8
11,
44,
41,
2,
99,
.61
,11
,33
,94
,22
2.517E-02 2.514E-02 0.258 0.501
9.559E-03 9.558E-03 9.798E-02 0.191
8.956E-03 8.955E-03 9.012E-02 0.179
6.380E-03 6.374E-03 6.533E-02 0.127
6.901E-03
2.348E-02
6.603E-04
2.261E-03
6.608E-03
2.263E-02
1.320E-02
4.522E-02
1.750E-03 1.674E-04 1.675E-03 3.348E-03
TOTAL MASS (KILOGRAMS) =
54.60
* TOTAL CONCENTRATION AS MG/L IN WATER COLUMN, AS MG/KG IN SEDIMENTS.
EXAMS > QUIT
JOB11 — STOP
17:44:02 SIZE: 31K CPU: 50.63 STATUS: SUCCESS
PDS > LOGOUT
197
-------
3,3.2 Tutorial Session #2; Entering New Data;
Analyzing Persistence
Objectives: Use of CHANGE, COMPOUND, and STORE commands to enter
chemical data, investigating properties of chemicals with EXAMS.
The compound is "XXX", a chemical that has recently been
synthesized but has seen no use in commerce. Its molecular
weight is 263.4, it is soluble in water to 0.15 ppm, has a vapor
pressure of 0.02 Torr, and has an apparent partition coefficient
on sediments of about 1000. The results of partitioning experi-
ments, however, were not entirely satisfactory; in fact the
partition coefficient may be as low as 100 or as high as 10,000.
The objective of this EXAMS run is to determine, for this
"persistent" (by definition, at least for the moment, as no
indication of degradability is available), the actual degree to
which the material would persist in lafce ecosystems, and the
magnitude of volatilization losses to be expected given a unit
loading. Furthermore, the uncertainty in the partition
coefficient is of unknown significance to the conclusions, so
EXAMS interactive capabilities win be called upon to perform a
sensitivity analysis of this question.
PDS> RUN EXAMS
22:36:12
Welcome to EXAMS
Exposure Analysis Modeling System
Athens Environmental Research Laboratory
Released for field trials Jan-81
The ATHENS collection of compounds is available for your use.
EXAMS > SHOW COMPOUNDS
CHEMICAL NAME COMMON NAME
1 UNSPECIFIED CHEMICAL UNS
2 9H-CARBAZOLE CAR
3 BENZOtflQUINOLINE BFQ
4 7H-DIBENZO[c,g)CARBAZOL£ DEC
5 BENZOCblTHIOPHENE BT
6 DIBENZOTHIOPHENE DBT
7 BENZ[a]ANTHRACENE BA
8 p-CRESOL PCR
9 BENZOtaJPYRENE BAP
10 MIREX MIR
11 METHYL PARATHION MP
12 QUINOLINE QUI
198
-------
EXAMS > COMP IS UNS
Compound selected > Unspecified Chemical
EXAMS > HELP VARIABLES
The chemical and environmental data used for EXAMS' computations are
continually available for inspection and alteration by the interactive
user. The data can be inspected in tabular form (type for a
description), or the current value of any single datum can be SHOfcn,
For example, EXAMS > SHOW PH(4) will return: PH IS 7.000 when
the pH of compartment number 4 is 7.0. A description of each block of
data (ADVECTION/CHEMISTPY/GEOMETRY/GLOBALS/LOADS/QUALITY/TURBULENCE) is
given under is the name of one of these
blocks. Typing is the name of an input datum
will elicit a definition of the variable (e.g. . when CHANGEing or SHOWing a variable, the vector/matrix
indices must be entered in the proper (row,column) order (because
is by no means equivalent to ). In a system
that can handle 10-comparttnent ecosystems, the dimensions of variables
include the values: (5), (3,5), (10), (30), (5,39), and (39). Dimension
(5) refers to the chemical species of the toxicant (c.f. );
dimension (3) refers to physical forms (1: dissolved, 2: sediment-
sorbed, 3: biosorbed); dimension (3,5) to matrices of molecular
configurations amalgamating (3) and (5) (e.g. refers to a
biosorbed neutral molecule); dimension (10) to ecosystem compartments?
dimension (30) to compartment interconnections; and dimension (39)
refers to irradiance and light absorption intervals (see Table 2.18).
EXAMS > HELP SOL
SOL is a REAL VECTOR with 5 rows.
Aqueous solubility of toxicant chemical species. If the corresponding
value in vector ESOL (c.f.) is zero, SOL(K) is interpreted as an
aqueous solubility in mg/liter. If ESOL(K) is non-zero, SOL(K) is
interpreted as the base-10 logarithm of the pre-exponential factor in
an equation (Eq. 2.95) describing the molar solubility of the toxicant
species as a function of environmental temperature (TCEL), The vector
indices for SOL are given in the text describing ESOL. Solubilities
are used (inter alia) to limit the permissible external loadings of
the toxicant on the system to values consonant with model assuptions.
Units: mg/liter
EXAMS > HELP ESOL
ESOL is a REAL VECTOR with 5 rows.
Enthalpy term for describing solubility of the
toxicant as a function of temperature.
ESOL(l) - datum for solubility of SH2
ESOL(2) - datum for solubility of SH3+
ESOLC3) " " " " SH4-H-
ESOL(4) " " " " SH-
ESOL(5) " " " " S=
Unitst kcal/mole
EXAMS > CHANGE SOL(l) TO 0.15
199
-------
EXAMS > CH MrfT TO 263.4
EXAMS > SHQ MWT
MWT IS 263.4
EXAMS > DESCRIBE VAPP
VAPR is a REAL SCALAR.
EXAMS > CH VAPR TO 2.E-2
EXAMS > HELP KPS
KPS is a REAL VECTDR with 5 rows.
Partition coefficients for computing sorption of toxicant on
compartment sediments. The chemical species signified by each
of the values entered in the vector Is defined in the text for
parameter ESOL.
Units: (mg/icg)/(mg/iiter)
EXAMS > CHAN KPS(l) TO 100.
EXAMS > COMPOUND NAME IS XXX WITH KPS=100.
EXAMS > SHOW CHEMISTRY
Compound characteristics for > XXX *ITH KPS=100,
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: xxx WITH KPSSIOO,
ECOSYSTEM: Unspecified Environment
TABLE 1.1.
MWT= 263.4
KVO* 0.0000
KPS= 100.0
KAHla 0.0000
KAH2= 0.0000
KAH3= 0.0000
KBH1= 0.0000
KBH2= 0.0000
KBH3s 0.0000
KBACWls 0.0000
KBACW2* 0.0000
KBACW3* 0.0000
KDP= 0.0000
QUANT1= 0.0000
SH2 (NEUTRAL MOLECULE, SPECIES 1) INPUT DATA.
SOL = 0.1500
ESOL= 0.0000
KPB 9 0.0000
EAH1= 0.0000
EAH2= 0.0000
EAH3= 0.0000
EBH1= 0.0000
EBH2= 0.0000
EBH3= 0.0000
QTW1= 0.0000
QTW2= 0.0000
QTW3= 0.0000
VAPR= 2.0000E-02 HENPY= 0.0000
RFLAT= 0.0000
OUANT2= 0.0000
ABSORPTION SPECTRUM (ABS): 0.0000
0.0000 0.0000 0.0000
0.0000 0.0000 0.0000
0,0000 0.0000 0.0000
0.0000 0.0000 0.0000
0.0000 0.0000 0,0000
0.0000 0.0000 0.0000
EVPRs 0.0000
KOC = 0.0000
KNHls 0.0000
KNH2» 0.0000
KNH3= 0.0000
KOX1= 0.0000
KOX2= 0.0000
KOX3= 0.0000
KBACS1= 0.0000
KBACS2s 0.0000
KBACS3= 0.0000
LAMAX= 0.00
QUANT3= 0.0000
0.0000
0.0000 0.0000
0.0000 0.0000
0.0000 0,0000
0.0000 0,0000
o.oooo o.oooo
0.0000 0.0000
EHEN = 0.0000
KOW = 0.0000
ENHls 0.0000
ENH2« 0.0000
ENH3s 0.0000
EOX1= 0.0000
EOX2= 0.0000
EOX3= 0.0000
QTSls 0.0000
QTS2= 0.0000
QTS3s 0.0000
0.0000
0.0000
0.0000
0,0000
0.0000
0.0000
o.oooo
200
-------
EXAMS > ENVIR IS EUTR
Selected environment Is: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST
DEFINITION
EXAMS > CH STRLD(l) TO 1.0
EXAMS > RUN
Simulation beginning for:
Compound: XXX WITH KPSslOO,
Environment: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
with a load of (fcg/nr) > 1.000000
STREAM LOADING EXCEEDED SOLUBILITY LIMIT IN ELEMENT 1.
LOAD HAS BEEN ADJUSTED.
Run complete.
EXAMS > SHO LOADS
Environment: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
Compartments (KOUNT): 7
1234567
Type of compartment (TYPEE): L B E H B L B
TABLE 12. TOXICANT LOADINGS (KG/HR) BY SYSTEM ELEMENT.
ELEMENT STREAM FLOW RAINFALL INTERFLOW NPS LOAD DRIFT LOAD
1 1.8337E-02
2
3
4
5
6
7
EXAMS > SHOW USER COMP
No user defined compounds in the library.
EXAMS > STORE COMP 7
Compound stored > XXX WITH KPS=100.
201
-------
EXAMS > LIST 17
AEPL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AOUATIC ECOSYSTEMS
CHEMICAL: xxx WITH KPS=IOO.
ECOSYSTEM: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 17. EXPOSURE ANALYSIS SUMMARY.
EXPOSURE:
A. MAXIMUM CONC. IN WATER COLUMN: 2.91E-03 MG/L DISSOLVED, 2.91E-03 TOT
MAX. CONC. IN BOTTOM SEDIMENT: 1.43E-03 MG/L DISSOLVED IN POPE WATER
B. BIOSORPTION - MAX. CONCENTRATION - PLANKTON: 0.00 UG/G
BENTHOS: o.oo UG/G
C. MAXIMUM TOT. CONC. IN SEDIMENT DEPOSITS: 0.14 MG/KG (DRY WEIGHT)
FATE:
A. TOTAL STEADY-STATE ACCUMULATION: 11. KG; 75.36% IN WATER COL.,
24.64% IN BOTTOM SEDIMENTS.
B. TOTAL LOAD: 0.44 KG/DAY - DISPOSITION: 0.00% VIA CHEMICAL
TRANSFORMATIONS, 0.00% RIOTPANSFORMED, 92.57% VOLATILIZED,
7.43% EXPORTED VIA OTHER PATHWAYS.
PERSISTENCE:
A. AT THE END OF A 36.0 DAY RECOVERY PERIOD, THE WATER COLUMN HAD
LOST 73.23% OF ITS INITIAL TOXICANT BURDEN; THE SEDIMENTS HAD
LOST 17.29% OF THEIR INITIAL BURDEN ( 59.45% REMOVAL OVERALL).
B. SYSTEM SELF-PURIFICATION TIME IS ROUGHLY 8. MONTHS.
EXAMS > LIST 15
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: xxx WITH KPSSIOO.
ECOSYSTEM: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 15, ANALYSIS OF STEADY-STATE FATE OF ORGANIC TOXICANT.
PROCESS MASS FLUX % OF LOAD HALF-LITE*
KG/DAY DAYS
HYDROLYSIS 0.0000 0.00 - —
OXIDATION 0.0000 0.00 - —
PHOTOLYSIS 0,0000 0.00 ---
ALL CHEMICAL PROCESSES 0.0000 0.00 ---
WATER COLUMN (BACTERIA) 0,0000 0.00 - —
BOTTOM SEDIMENTS (BACTERIA) 0,0000 0,00 ---
TOTAL BIOLYSIS 0.0000 0,00
VOLATILIZATION 0,4074 92,57 19,51
WATER-BORNE EXPORT 3.2680E-02 7,43 243,3
TRANSFORMATION AND TRANSPORT 0,4401 100.00
TOTAL SYSTEM LOAD 0.4401
RESIDUAL ACCUMULATION RATE: 4.4703E-08 0.00
* HALF-LIVES ARE ESTIMATES BASED ON A FIRST-ORDER RATE APPROXIMATION.
202
-------
EXAMS > CH KPS(l) TO 1000.
EXAMS > COMP NAME IS XXX WITH KPSMOOO.
EXAMS > RUN
Simulation beginning for:
Compound: XXX WITH KPSMOOO.
Environment: EUTROPHic LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
with a load of (kg/hr) > 0.1833750E-01
Run complete.
EXAMS > LIST 17
203
-------
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: xxx WITH KPS=IOOO.
ECOSYSTEM: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 17. EXPOSURE ANALYSIS SUMMARY.
EXPOSURE:
A. MAXIMUM CONC. IN WATER COLUMN: 2.91E-03 MG/L DISSOLVED, 2.92E-03 TOT
MAX. CONC. IN BOTTOM SEDIMENT: 2.64E-03 MG/L DISSOLVED IN PORE WATER
B. BIOSORPTION - MAX. CONCENTRATION - PLANKTON: 0.00 UG/G
BENTHOS: o.oo UG/G
C. MAXIMUM TOT. CONC. IN SEDIMENT DEPOSITS: 2.6 MG/KG (DRY WEIGHT)
FATE:
A. TOTAL STEADY-STATE ACCUMULATION: 47, KG; 18.52% IN WATER COL.,
81,48% IN BOTTOM SEDIMENTS.
B. TOTAL LOAD: 0.44 KG/DAY - DISPOSITION: 0.00% VIA CHEMICAL
TRANSFORMATIONS, 0.00% BIOTRANSFORMED, 92.57% VOLATILIZED,
7.43% EXPORTED VIA OTHER PATHWAYS.
PERSISTENCE:
A. AT THE END OF A 144. DAY RECOVERY PERIOD, THE WATER COLUMN HAD
LOST 69.81% OF ITS INITIAL TOXICANT BURDEN; THE SEDIMENTS HAD
LOST 42.38% OF THEIR INITIAL BURDEN ( 47.46% REMOVAL OVERALL).
B. SYSTEM SELF-PURIFICATION TIME IS ROUGHLY 27. MONTHS.
EXAMS > LIST 15
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: xxx WITH KPSSIOOO.
ECOSYSTEM: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 15, ANALYSIS OF STEADY-STATE FATE OF ORGANIC TOXICANT.
PROCESS MASS FLUX % OF LOAD HALF-LIFE*
KG/DAY DAYS
HYDROLYSIS 0.0000 0.00
OXIDATION 0.0000 0.00 - —
PHOTOLYSIS 0.0000 0.00 ---
ALL CHEMICAL PROCESSES 0.0000 0.00 ---
WATER COLUMN (BACTERIA) 0.0000 0.00 -—
BOTTOM SEDIMENTS (BACTERIA) 0.0000 0.00 —
TOTAL BIOLYSIS 0.0000 0.00
VOLATILIZATION 0.4074 92.57 79.43
WATER-BORNE EXPORT 3.2696E-02 7.43 989.7
TRANSFORMATION AND TRANSPORT 0.4401 100.00
TOTAL SYSTEM LOAD 0.4401
RESIDUAL ACCUMULATION RATE: 4.4703E-08 o.oo
* HALF-LIVES ARE ESTIMATES BASED ON A FIRST-OflDER RATE APPROXIMATION.
204
-------
EXAMS > STORE COMPOUND 8
Compound stored > XXX WITH KPSslOOO.
EXAMS > CH KPS(l) TO 10000,
EXAMS > COM? NAME IS XXX WITH KPS=10000.
EXAMS > RUN
Simulation beginning for:
Compound: XXX WITH KPS»10000.
Environment: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
with a load of Ocg/hr) > 0.1833750E-01
PLEASE BE PATIENT; THE KINETIC EQUATIONS ARE STIFF.
Run complete.
EXAMS > LIST 17
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: xxx WITH KPS»IOOOO.
ECOSYSTEM: EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 17. EXPOSURE ANALYSIS SUMMARY.
EXPOSURE:
A. MAXIMUM CONC. IN WATER COLUMN: 2.91E-03 MG/L DISSOLVED, 2.92E-03 TOT
MAX, CONC. IN BOTTOM SEDIMENT: 2.88E-03 MG/L DISSOLVED IN PORE HATER
B. BIOSORPTION - MAX. CONCENTRATION - PLANKTON: 0,00 UG/G
BENTHOS: o.oo UG/G
C. MAXIMUM TOT. CONC. IN SEDIMENT DEPOSITS: 29. MG/KG (DRY WEIGHT)
FATE:
A. TOTAL STEADY-STATE ACCUMULATION: 4.06E+02 KG; 2.14% IN WATER COL.,
97.86% IN BOTTOM SEDIMENTS.
B. TOTAL LOAD: n. KG/MONTH • DISPOSITION: 0.00% VIA CHEMICAL
TRANSFORMATIONS, 0.00% BIOTRANSFORMED, 92.54% VOLATILIZED,
7.46% EXPORTED VIA OTHER PATHWAYS.
PERSISTENCE:
A. AT THE END OF A 36.0 MONTH RECOVERY PERIOD, THE WATER COLUMN HAD
LOST 61.54% OF ITS INITIAL TOXICANT BURDEN; THE SEDIMENTS HAD
LOST 55.13% OF THEIR INITIAL BURDEN ( 55.26% REMOVAL OVERALL).
B. SYSTEM SELF-PURIFICATION TIME 18 ROUGHLY 13. YEARS.
EXAMS > STORE COMPOUND 9
Compound stored > XXX WITH KPSslOOOO.
205
-------
EXAMS > LIST 15
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: xxx WITH KPSMOOOO,
ECOSYSTEMS EUTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 15. ANALYSIS OF STEADY-STATE FATE OF ORGANIC TOXICANT.
PROCESS MASS FLUX % OF LOAD HALF-LIFE*
KG/MONTH MONTHS
HYDROLYSIS 0.0000 0.00
OXIDATION 0.0000 0.00 • —
PHOTOLYSIS 0.0000 0.00 —
ALL CHEMICAL PROCESSES 0.0000 0.00
WATER COLUMN (BACTERIA) 0.0000 0.00 —
BOTTOM SEDIMENTS (BACTERIA) 0.0000 0.00
TOTAL BIOLYSIS 0.0000 0.00 —
VOLATILIZATION 12.40 92.54 22.68
WATER-BORNE EXPORT 0.9999 7,46 281.1
TRANSFORMATION AND TRANSPORT 13.40 100.00
TOTAL SYSTEM LOAD 13.40
RESIDUAL ACCUMULATION RATE: 2.7213E-06 0.00
* HALF-LIVES ARE ESTIMATES BASED ON A FIRST-ORDER RATE APPROXIMATION.
EXAMS > STOP
JOB32 — STOP
22:44:48 Size: 31K CPU: 58.40 status: SUCCESS
In summary:
KPS VOLATILIZED FLUX
100. 0.41 kg/day
1000. 0.41 Kg/day
10000. 0.41 kg/day
REMOVAL TINE
0.7 year
2.2 years
13, years
The available data for "xxx" have been stored under 3 descriptive
names in EXAMS' User Data Base. Upon re-entering the system,
these data can be retrieved via the RECALL conr-and, for example:
EXAMS > RECALL COMP 8
206
-------
3,3.3. Tutorial session *3: Sensitivity Analysis
Objectives; using EXAMS tor evaluation of rate constant data,
and altering ecosystem properties via the CHANGE command. The
EXAMS run is designed to elicit the primary degradation pathway
of methyl parathion in a 1-hectare pond, investigate the effects
of pH (i.e. alkaline hydrolysis) and biolysis rate constants on
pollutant Kinetics, and run a comparative baseline of methyl
parathion behaviour in an oligotrophic lake.
PDS> RUN EXAMS
23:50:51
Welcome to EXAMS
Exposure Analysis Modeling System
Athens Environmental Research Laboratory
Released for field trials jan-81
The ATHENS collection of compounds is available for your use.
EXAMS > CQMP IS MP
Compound selected > METHYL PARATHION
EXAMS > ENV IS POND
Selected environment is: POND, AERL DEVELOPMENT PHASE TEST DEFINITION
EXAMS > CHANGE STRLDU) TO 0.02
EXAMS > COM? NAME is Methyl Parathion - Baseline
EXAMS > RUN
Simulation beginning for:
Compound: Methyl Parathion - Baseline
Environment: POND, AERL DEVELOPMENT PHASE TEST DEFINITION
with a load of (kg/nr) > 0.2000000E-01
Run complete.
EXAMS > LIST 15
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: Methyl Parathion - Baseline
ECOSYSTEM; POND, AERL DEVELOPMENT PHASE TEST DEFINITION
207
-------
TABLE 15. ANALYSIS OF STEADY-STATE FATE OF ORGANIC TOXICANT.
PROCESS MASS FLUX % OF LOAD HALF-LIFE*
KG/DAY DAYS
HYDROLYSIS 7.3110E-03 1.52 666.7
OXIDATION 0.0000 0.00 -•-
PHOTOLYSIS 4.6392E-03 0.97 1051,
ALL CHEMICAL PROCESSES 1.1950E-02 2.49 407.9
WATER COLUMN (BACTERIA) 0.3498 72.87 6.318
BOTTOM SEDIMENTS (BACTERIA) 1.6757E-02 3.49 159.0
TOTAL BIOLYSIS 0.3665 76.36 13.30
VOLATILIZATION 9.1247E-05 0.02 5..3415E+04
WATER-BORNE EXPORT 0.1014 21.13 48.05
TRANSFORMATION AND TRANSPORT 0.4800 100.00
TOTAL SYSTEM LOAD 0.4800
RESIDUAL ACCUMULATION RATE: 4.4703E-08 0.00
* HALF-LIVES ARE ESTIMATES BASED ON A FIRST-ORDER RATE APPROXIMATION.
EXAMS > SHOW CHEM
Compound characteristics for > Methyl Parathion - Baseline
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: Methyl Parathion - Baseline
ECOSYSTEM: POND, AERL DEVELOPMENT PHASE TEST DEFINITION
SH2 (NEUTRAL MOLECULE, SPECIES 1)
SOL s 50.00
ESOLs 0.0000
KPB
371.5
EAHls 0.0000
EAH2s 0.0000
EAH3* 0.0000
22.00
EBH2s 0.0000
EBH3« 0.0000
TABLE 1.1.
MWT= 263,1
KVOs 0.0000
KPSs 50,00
KAHls 0.0000
KAH2s 0.0000
KAH3= 0.0000
KBHlx 17.69
KBH2* 0.0000
KBH3s 0.0000
KBACWla 4.6000E-08 QTW1= 0,0000
KBACW2* 0.0000 QTW2= 0,0000
KBACW3S 0.0000 QTW3* 0.0000
KDPs 0.0000 RFLATs 40.00
QUANTls 1.7000E-04 QUANT2= 0.0000
ABSORPTION SPECTRUM (ABS): 6040.
4310. 3700. 3210.
1630. 1310, 933.0
145.0 82.00 45,00
0.0000 0.0000 0.0000
0.0000 0,0000 0,0000
0,0000 0,0000 0,0000
VAPRr 14.37
EVPRs 26.11
KOC * 0.0000
KNHls 13.66
KNH2s 0.0000
KNH3 = 0,0000
KOXls 0.0000
KOX2= 0.0000
KDX3s 0.0000
KBACSls 4.
KBACS2= 0,
KBACS3* 0,
LAMAXs 0.
QUANT3* 0
5460
2760,
568.0
9.000
0.0000
0,0000
0,0000
INPUT DATA,
HENRY" 0.0000
EHEN * 0,0000
KOW * 0,0000
ENH1= 23.40
ENH2» 0.0000
ENH3» 0,0000
EOXlJ
EOX2>
EOX3J
0.0000
0.0000
0.0000
6000E-08 QTS1:
0000
0000
00
,0000
2290.
374.0
0.0000
0,0000
0.0000
0.0000
QTS2s
0.0000
0.0000
QTS3s 0.0000
4930,
1920,
244.0
0,0000
0,0000
0.0000
0,0000
208
-------
EXAMS > SHOW
Enter one of the following options:
COMPOUNDS,
CHEMISTRY,
ENVIRONMENT,
GEOMETRY,
ADVECTION,
TURBULANCE,
QUALITY,
GLOBALS,
LOADS,
USER,
HELP or
EXIT > QUALITY
Environment: POND, AERL DEVELOPMENT PHASE TEST DEFINITION
Compartments (KOUNT): 2
1 2
Type of compartment (TYPEE): L B
Compartment No, 1
FROC
AEC
PH
OXRAD
PLRA
BACTO
K02
DOC
CHL
x
s
s
X
s
X
s
s
s
0,1000
25.00
8.000
l.OOOOE-09
3.1000E-02
l.OOOOE+05
8,000
0.5000
2.0000E-03
CEC
TCEL
POH
BIOMS
BIOTM
ACBAC
CMPET
DFAC
s
s
9
S
s
S
S
r
25.00
15.00
6,000
12.90
15.00
1.000
2.000
1.190
Would you like information for compartment No. 2
Enter (Y, N o-r Q to quit) > Y
Environment: POND, AERL DEVELOPMENT PHASE TEST DEFINITION
Compartments (KOUNT): 2
1 2
Type of compartment (TYPEE): L B
Compartment No. 2
FROC * 0.1000 CEC = 25,00
AEC • 25,00 TCEL s 15.00
PH s 6.000 POH * 8.000
OXRAD * 0.0000 BIOMS s 50.01
PLRA * 1.2000E-04 BIOTM s 15.00
BACTO » 2.0000E+07 ACBAC = 1.000
EXAMS > CHANGE PH(») TO 10.
209
-------
EXAMS > HELP POH
POH Is a REAL VECTOR with 10 rows.
The negative value of the power to which 10 is raised in order to
obtain the temporally averaged concentration of hydroxide COH-1 ions
in gram-molecules per liter.
Units: pOH units
EXAMS > CH POH(*) TO 4
EXAMS > ENVIR NAME IS Alkaline Pond - enhanced hydrolysis
EXAMS > STORE ENVIRON 5
Environment stored: Alkaline Pond - enhanced hydrolysis
EXAMS > RUN
Simulation beginning for:
Compound: Methyl Parathion • Baseline
Environment: Alkaline Pond - enhanced hydrolysis
with a load of (kg/hr) > 0.2000000E-01
Run complete.
EXAMS > LIST 15
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: Methyl Parathion - Baseline
ECOSYSTEM: Alkaline Pond - enhanced hydrolysis
TABLE 15. ANALYSIS OF STEADY-STATE
PROCESS
HYDROLYSIS
OXIDATION
PHOTOLYSIS
ALL CHEMICAL PROCESSES
HATER COLUMN (BACTERIA)
BOTTOM SEDIMENTS (BACTERIA)
TOTAL BIOLYSIS
VOLATILIZATION
HATER-BORNE EXPORT
TRANSFORMATION AND TRANSPORT
TOTAL SYSTEM LOAD
RESIDUAL ACCUMULATION RATE:
FATE OF ORGAN
MASS FLUX
KG/DAY
7.4498E-02
0.0000
3.98HE-03
7.8479E-02
0.3002
1.4240E-02
0.3144
7.8304E-05
8.7048E-02
0.4800
0.4800
4.4703E-08
1C TOXICANT,
% OF LOAD
15.52
0.00
0.83
16.35
62,53
2.97
65.50
0.02
18.13
100.00
0.00
HALF-LIFE*
DAYS
55.85
1045.
53.01
6.318
159.0
13.23
5.3131E+04
47.79
HALF-LIVES ARE ESTIMATES BASED ON
210
A FIRST-OflDER RATE APPROXIMATION,
-------
EXAMS > ENV IS POND
Selected environment is: POND, AERL DEVELOPMENT PHASE TEST DEFINITION
EXAMS > CHANGE SRTLD(l) TO 0.02
Unrecognized variable name.
EXAMS > CH STRLD(l) TO 0.02
EXAMS > RUN
Simulation beginning for:
Compound: Methyl Parathion - Baseline
Environment: POND, AERL DEVELOPMENT PHASE TEST DEFINITION
with a load of (icg/hr) > 0.2000000E-01
Run complete.
EXAMS > LIST 17
AERL-ES8 MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: Methyl Parathion - Baseline
ECOSYSTEM: POND, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 17. EXPOSURE ANALYSIS SUMMARY.
EXPOSURE:
A. MAXIMUM CONC. IN WATER COLUMN: o.ib MG/L DISSOLVED, 0.16 TOT
MAX. CONC. IN BOTTOM SEDIMENT: 0.11 MG/L DISSOLVED IN POPE WATER
B. BIOSORPTION - MAX. CONCENTRATION - PLANKTON: 59. UG/G
BENTHOS: 42. UG/G
C. MAXIMUM TOT. CONC. IN SEDIMENT DEPOSITS: 5.7 MG/KG (DPY WEIGHT)
FATE:
A. TOTAL STEADY-STATE ACCUMULATION: 7.0 KG; 45.34% IN WATER COL.,
54.66% IN BOTTOM SEDIMENTS.
B. TOTAL LOAD: 0.48 KG/DAY - DISPOSITION: 2.49% VIA CHEMICAL
TRANSFORMATIONS, 76.36% BIOTRANSFOPMED, 0.02% VOLATILIZED,
21.13% EXPORTED VIA OTHER PATHWAYS.
PERSISTENCE:
A, AT THE END OF A 24.0 DAY RECOVERY PERIOD, THE WATER COLUMN HAD
LOST 90.03% OF ITS INITIAL TOXICANT BURDEN; THE SEDIMENTS HAD
LOST 25.72% OF THEIR INITIAL BURDEN ( 54.87% REMOVAL OVERALL).
P. SYSTEM SELF-PURIFICATION TIME IS ROUGHLY 6. MONTHS.
EXAMS > CHA KBACW(1,1) TO 4.6E-7
EXAMS > COM? NAME IS Methyl Parathion with HIGH biolysis.
211
-------
EXAMS > STORE COMP 3
Compound stored > Methyl Parathion with HIGH biolysis.
EXAMS > RUN
Simulation beginning for:
Compound: Methyl Parathion with HIGH biolysis.
Environment: POND, AERL DEVELOPMENT PHASE TEST DEFINITION
with a load of (fcg/hr) > 0.2000000E-01
Run complete.
EXAMS > LIST 17
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: Methyl Parathion with HIGH biolysis.
ECOSYSTEM: POND, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 17. EXPOSURE ANALYSIS SUMMARY.
EXPOSURE:
A. MAXIMUM CONC. IN WATER COLUMN: 2.10E-02 MG/L DISSOLVED, 2.11E-02 TOT
MAX. CONC. IN BOTTOM SEDIMENT: 1.49E-02 MG/L DISSOLVED IN PORE WATER
B. BIOSORPTION - MAX. CONCENTRATION - PLANKTON: 7.8 UG/G
BENTHOS: 5.5 UG/G
C. MAXIMUM TOT. CDNC. IN SEDIMENT DEPOSITS: 0.75 MG/KG (DRY WEIGHT)
FATE:
A. TOTAL STEADY-STATE ACCUMULATION: 0.93 KG; 45.34% IN WATER COL.,
54.66% IN BOTTOM SEDIMENTS.
B. TOTAL LOAD: 2.00E-02 KG/HOUR - DISPOSITION: 0.33% VIA CHEMICAL
TRANSFORMATIONS, 96.87% BIOTRANSFORMED, 0.00% VOLATILIZED,
2.80% EXPORTED VIA OTHER PATHWAYS.
PERSISTENCE:
A. AT THE END OF A 60.0 HOUR RECOVERY PERIOD, THE WATER COLUMN HAD
LOST 93.05% OF ITS INITIAL TOXICANT BURDEN? THE SEDIMENTS HAD
LOST 3.04% OF THEIR INITIAL BURDEN ( 43.85% REMOVAL OVERALL).
B. SYSTEM SELF-PURIFICATION TIME IS ROUGHLY 5. MONTHS.
EXAMS > CH KBACW(1,1) TO 4.6E-9
EXAMS > COMP NAME IS Methyl Parathion with LOW biolysis.
EXAMS > STORE COMP 4
Compound stored > Methyl Parathion with LOW biolysis.
212
-------
EXAMS > RUN
Simulation beginning for:
Compound: Methyl Parathion with LO* oiolysis.
Environment: POND, AERL DEVELOPMENT PHASE TEST DEFINITION
with a load of (kg/hr) > 0.2000000^-01
Pun complete.
EXAMS > LIST 17
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: "ethyl Parathion #ith LOW biolysis.
ECOSYSTEM: POND, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 17. EXPOSURF ANALYSIS SUMMARY.
EXPOSURE:
A. MAXIMUM CONC. IN WATER COLUMN: 0.46 MG/L DISSOLVED, 0.46 TOT
MAX. CONC. TN BOTTOM SEDIMENT: 0.33 MG/L DISSOLVED IN POPE rfATER
B. BIOSORPTION - ^AX. CONCENTRATION - PLANKTON: 1.71E+02 UG/G
BENTHOS: 1.21E+02 UG/G
C. MAXIMUM TOT. C3NC. IN SEDIMENT DEPOSITS: 17. MG/KG (DRY HEIGHT)
FATE:
A. TOTAL STEADY-STATE ACCUMULATION: 20. KG? 45.34% IN WATER COL. ,
54.66% IN BOTTOM SEDIMENTS.
B. TOTAL LOAD: 0.48 KG/DAY - DISPOSITION: 7.23% VIA CHEMICAL
TRANSFORMATIONS, 31.31% BIOTRANSFORMED, 0.06% VOLATILIZED,
61.40% EXPORTED VIA OTHER PATHWAYS.
PERSISTENCE:
A. AT THE FND OF A 60.0 DAY RECOVERY PERIOD, THE WATER COLUMN HAD
LOST 82.20% OF ITS INITIAL TOXICANT BURDEN; THE SEDIMENTS HAD
LOST 44.62% OF THEIR INITIAL BURDEN ( 61.66% REMOVAL OVERALL).
B. SYSTEM SELF-PURIFICATION TIME IS ROUGHLY 8. MONTHS.
Summary (not a machine output) -- Pond biolysis analysis
Rate Constant Exposure Concentration
(mg/L)
LOW 0.46
BASELINE 0.16
HIGH 0.021
213
-------
Restart computations for oligotrophic lake comparison:
EXAMS > COMP IS HP
Compound selected > METHYL PARATHIDN
EXAMS > COMPOUND NftME IS Methyl Parathion - Baseline.
EXAMS > ENV IS OLIG
Selected environment is: OLIGOTPOPHIC LAKE, AERL DEVELOPMENT PHASE TEST
DEFINITION
EXAMS > CHA STRLD(l) TO 1.0
EXAMS > RUN
Simulation beginning for:
Compound: Methyl Parathion * Baseline.
Environment: OLIGOTROPHIC LAKE, AEPL DEVELOPMENT PHASE TEST DEFINITION
with a load of (kg/hr) > 1.000000
Run complete.
EXAMS > LIST 15
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: Methyl Parathion - Baseline.
ECOSYSTEM: OLIGOTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 15. ANALYSIS OF STEADY-STATE
PROCESS
HYDROLYSIS
OXIDATION
PHOTOLYSIS
ALL CHEMICAL PROCESSES
WATER COLUMN (BACTERIA)
BOTTOM SEDIMENTS (BACTERIA)
TOTAL BIOLYSIS
VOLATILIZATION
WATER-BORNE EXPORT
TRANSFORMATION AND TRANSPORT
TOTAL SYSTEM LOAD
RESIDUAL ACCUMULATION RATE:
FATE OF ORGANI
MASS FLUX %
KG/DAY
1.861
0.0000
16.26
18.12
0.1717
8.4649E-04
0.1725
1.4732E-02
5.688
24.00
24.00
8.5831F-06
C TOXICANT.
OF LOAD
7.75
0.00
67.77
75.52
0.72
0.00
0.72
0.06
23.70
100.00
0.00
HALF-LIFE*
DAYS
572.5
•»•»•§
65.49
58.77
5499,
1.4300E+05
6174,
7.2304E+04
187,3
* HALF-LIVES ARE ESTIMATES BASED ON A FIRST-ORDER RATE APPROXIMATION.
214
-------
EXAMS > LIST 10
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: ^ethyl Parathion - Baseline.
ECOSYSTEM: OLIGOTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 10. KINETIC PROFILE OF ORGANIC TOXICANT. RATE CONSTANTS DERIVED
FROM COUPLING OF TOXICANT CHARACTERISTICS TO ECOSYSTEM PROPERTIES.
CP T*
Y
1L
26
3E
4H
SB
6L
7B
HYDROLYSIS
8.36RE-05
6.077E-07
8.573E-05
1.983E-05
1.438F.-07
8.368E-05
6.077E-07
• PSEUDO-FIPST-OKDEP FATE CONSTAN
PHOTOLYSIS OXIDATION BIOLYSIS
5.205E-04
0.000
7.857E-04
1.611E-04
0.000
7.683E-04
0.000
0,000
0.000
0,000
0.000
0.000
0.000
0.000
4.514E-05
1.778E-06
4.598E-06
4.600E-07
9.127E-09
4.514E-06
8.890E-08
VOLATILITY
1.326E-06
0.000
6.752E-07
o.ooo
0,000
1.326E-06
0,000
TRANSPORT
4.200E-02
1 .105E-03
1.228E-02
4,163E-03
5.230E-04
4.324E-02
1.105E-03
* COMP. TYPE: "L"=LITTORAL; ME"=(EPI) AND HH"=(HYPO)LIMNIQN; "BM=BENTHIC
EXAMS > LIST 11
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: Methyl Parathion - Baseline,
ECOSYSTEM: OLIGOTROPHIC LAKE, AERL DEVELOPMENT PHASE TEST DEFINITION
TABLE 11. CANONICAL PROFILE OF ECOSYSTEM.
CP T*
Y
P
1L
2B
3E
4H
5B
6L
78
6
5
6
7
5
6
5
PH
.50
.70
.90
.00
.70
.50
.70
POH
7
8
7
7
8
7
8
.50
.30
.10
.00
.30
.50
.30
TEMP
DEC.
w *
15.0
15.0
15.0
5.0
5.0
15.0
15.0
REAERATION
COEFF.
M/HR
4.441E-02
0.000
8.882F-02
0.000
0.000
4.441E-02
0.000
COMPOSITE BACTERIAL
LIGHT AVE POP. SIZE
% CELLS/**
43.1
0.000
59.0
20.3
0.000
59,9
0,000
1.
2.
1
1
1.
1
1.
OOOE+03
OOOE+05
00.
0.0
OOOE+03
00.
OOOE*04
OXIDANT
CONC,
(MOLAR)
l.OOOE-09
0.000
1 .OOOE-09
5.000E-10
o.ooo
l.OOOE-09
0,000
DISSOLVED
PERCENT
*
98.1
0.715
100.
100.
0.734
98.1
0.715
* COMP, TYPE: "L"=LITTORAL; "EM=(EPD AMD "H"SCHYPO)LIMNION; "BB=BENTHIC
** ACTIVE BACTERIAL POPULATIONS AS CELLS/ML IN WATER COLUMN,
CELLS/100 G (DRY WEIGHT) OF SEDIMENTS IN BOTTOM SEDIMENTS,
215
-------
EXAMS > PRINT ALL
Requested report has been spooled to printer,
EXAMS > PLOT PROF TOT WAT
0.3600
C
T 0
0 N
T C
A E
L N
T
M R
G A
/ T
L I
0
N
0.3200
0.2800
0.2400
0.2000
•I
I
I
I
I
•I
I
I
I
I
•I
I
I
I
I
•I
I
I
I
I
LLLLLLLLLLL
1
1
1
1
1
1
1
1
1
I EEEEEEEEEEE
1 3 3
1 3
1 3
1 3
1 3
3 HHHHHHHHHHH 6
34 46
34 46
34 46
LLLLLLLLLLL
6
6
6
6
, 111111111_33333333333_44444444444«66666666666
WATER COLUMN
EXAMS > EXIT
JOB254 -- STOP
00:02:07 size: 31K CPU: 58:03 status: SUCCESS
PDS > LOGOUT
216
-------
3.3.4 Tutorial Session »4: Sample Application Study
Objectives: entry of new chemical and environmental data,
exploration of alternative process models. This session
duplicates the analysis of volatilization of I,4-dichlorobenzene
discussed in Section 2.3.2.4.2. Note that the environmental data
are not a complete canonical description of Lake Zurich; they
are restricted to a simple aeometry plus those parameters needed
to construct volatilization models on EXAMS.
PDS > RUN EXAMS
20S27:10
welcome to EXAMS
Exposure Analysis Modeling System
Athens Environmental Research Laboratory
Released for field trials Jan-81
The ATHENS collection of compounds is available for your use,
EXAMS > COMP IS UNS
Compound selected > Unspecified Chemical
EXAMS > COMP NAME IS 1,4-DICHLOROBENZENE
EXAMS > CHANGE MWT TO 147.0
EXAMS > CHANGE SOL(l) TO 73.8
EXAMS > CH KOW TO 2340
EXAMS > CH HENRY TO 2.66E-3
EXAMS > SHO USER COMP
Directory of user defined compounds
NO. COMPOUND NAME
3 Methyl Parathion with HIGH biolysis
4 Methyl Parathion with LOW biolysis.
7 XXX WITH KPS=100.
8 XXX WITH KPSslOOO.
9 XXX WITH KPSxlOOOO.
EXAMS > STORE COMP 1
Compound stored > 1,4-DICHLOROBENZENE
217
-------
EXAMS > ENV IS UNS
Selected environment is: Unspecified Environment
EXAMS > ENV NAME IS LAKE ZURICH - CENTRAL BASIN (UNTERSEE)
EXAMS > CHA KD2GU) TO 2.5
EXAMS > CHA WIND TO 1.38
Subscript out-of-range.
EXAMS > HELP WIND
WIND is a REAL VECTOR With 10 TOWS,
Average wind velocity at a reference height of 10 cm, above the
water surface. Parameter is used to compute a piston velocity
for water vapor (Liss 1973, Deep-Sea Research 20:221) in
the 2-film treatment of volatilization losses.
Units: meters/second
EXAMS > CH WIND(I) TO 1.38
EXAMS > SHOW KOUNT
KOUNT IS 1
EXAMS > CHANGE KOUNT TO 3
EXAMS > CH TYPE(l) TO E
EXAMS > CH TYPE(2) TO H
EXAMS > CHA T¥PE(3) TO B
EXAMS > CH DEPTH(l) TO 10.
EXAMS > CH VOLG(l) TO 6.8E8
EXAMS > CH DEPTH(2) TO 40
EXAMS > CH VOLG(2) TO 2.72E9
EXAMS > CHA DEPTHO) TO 0.02
EXAMS > CHA VOLGC3) TO 1.36E6
EXAMS > CHAN AREA(*) TO 6.8E7
EXAMS > CH TCEL(i) TO 11
EXAMS > CH TCELC2) TO 5.6
EXAMS > CHA TCELGC3) TO 5.6
218
-------
EXAMS > CH DSP(l) TO 0.2
EXAMS > CH DSPC2) TO l.E-4
EXAMS > CH XSTURGO) TO 6.8E7
EXAMS > CH JTUR(l) TO 1
EXAMS > CH ITUP(l) TO 2
EXAMS > CH JTURC2) TO 2
EXAMS > CH ITUR(2) TO 3
EXAMS > SHO TUR
Environment: LAKE ZURICH - CENTRAL BASIN (UNTERSEE)
Compartments (KOUNT): 3
1 2 3
Type of compartment (TYPEE): E H B
AERL-ES8 MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: I^-DICHLOROBENZENE
ECOSYSTEM: LAKE ZURICH - CENTRAL BASIN (UNTERSEE)
TABLE 8. INPUT DATA DESCRIBING ENVIRONMENT: TURBULENT INTERCONNECTIONS.
COMP. NO. (JTURB) 1 2
CONNECTED (ITUPB) 2 3
X-SECTION (XSTUR) 6.800E+07 6.800E+07
CHAR. LN. (CHARD 1.00 0.000
EDDY DISP. (DSP) 0.200 l.OOOE-04
EXAMS > HELP CHARL
CHARL is a REAL VECTOR with 30 rows.
Characteristic length (average of compartment dimensions or mixing
lengths) for the dispersive exchange pairing given by the corresponding
compartment numbers of JTURB and ITURB. A given compartment may have
different mixing lengths in different exchange pairings.
Units: meters
EXAMS > CHA CHARL(l) TO 25
EXAMS > CHA CHARL(2) TO 20,01
219
-------
EXAMS > SHQ TUR
Environment: LAKE ZURICH - CENTRAL BASIN (UNTEFSEE)
Compartments (KOUNT): 3
1 2 3
Type of compartment (TYPEE): E H B
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: I^-DICHLOROBENZENE
ECOSYSTEM: LAKE ZURICH - CENTRAL BASIN CUNTERSEE)
mmmmmmmm~mmmmmmmmmmmm~m~mmmmmm~mmmmmmmmmmmmmmmmmmmmmmm»mmmmmm*mmmm»mmm CHAN SDCHRGC*) TO 5
EXAMS > CH SDCHRGC3) TO 1.5
EXAMS > CH PCTWAGC3) TO 150.
EXAMS > CHAN FROCC*) TO .02
EXAMS > CH STFLG(l) TO 3.E5
Unrecognized variable name.
EXAMS > HELP STFL
STFLO is a REAL VECTOR with 10 rows.
Stream flow entering ecosystem compartments. Stream flows
include base flow into head reach of river or estuary,
tributaries, creeks entering a lafce or pond, etc.
Units: cubic meters/nour
EXAMS > CHAN STFLOCD TO 3.E5
EXAMS > CHAN STRLD(l) TO 0.01
EXAMS > RUN
Simulation beginning for:
Compound: 1,4-DICHLOROBENZENE
Environment: LAKE ZURICH - CENTRAL BASIN (UNTERSEE)
with a load of Ocg/hr) > 0.1000000E-01
220
-------
HYDROLOGIC DEFINITION OF COMPARTMENT 1 IS IMPROPER.
THERE IS A NET ADVECTED FLOW LEAVING THIS COMPARTMENT,
BUT THE FLOW PATHWAY HAS NOT BEEN SPECIFIED.
SIMULATION ABORTED.
Run complete.
EXAMS > CHANGE JFRAD(l) TO 1
EXAMS > CHA ADVPR(l) TO 1.0
EXAMS > SHO AD
Environment: LAKE ZURICH - CENTRAL BASIN (UNTERSEE)
Compartments (KOUNT): 3
1 2 3
Type of compartment (TYPEE): E H B
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: I^-DICHLOROBENZENE
ECOSYSTEM: LAKE ZURICH - CENTRAL BASIN (UNTERSEE)
mmmm»mmmmmmm'*mmm~mmm~mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm*r~mm'*mmmmtmmmmm~mmi
TABLE 7. INPUT DATA DESCRIBING ENVIRONMENT: ADVECTIVE INTERCONNECTIONS,
COMP. NO. (JFRAD) 1
CONNECTED (ITOAD) 0
ADVECTION (ADVPR) 1.00
EXAMS > RUN
Simulation beginning for:
Compound: 1,4-DICHLOROBENZENE
Environment: LAKE ZURICH - CENTRAL BASIN (UNTEPSEE)
with a load of (Kg/hr) > 0.1000000E-01
Run complete.
EXAMS > LI 13
221
-------
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: I^-DICHLOROBENZENE
ECOSYSTEM: LAKE ZURICH - CENTRAL BASIN (UNTERSFE)
TABLE 13. DISTRIBUTION OF CHEMICAL AT STEADY STATE: IN THE WATER COLUMN:
COMP STEADY-STATE RESIDENT MASS **** TOXICANT CONCENTRATIONS ****
2 TOTAL DISSOLVED SEDIMENTS BIOTA
G/M KILOS % MG/* MG/L MG/KG UG/G
1 1.074E-04 7.302 20.00 1.074E-05 1.074E-05 2.060E-04 0.000
2 4.295E-04 29.21 80.00 1.074E-05 1.074E-05 2.060E-04 0.000
SUBTOTAL: 36.51 99.22
AND IN THE BOTTOM SEDIMENTS:
3 4.228E-06 0.2875 100.00 2.114E-04 1.074E-05 2.060E-04 0,000
SUBTOTAL: 0.2875 0.78
TOTAL MASS (KILOGRAMS) = 36.80
* TOTAL CONCENTRATION AS MG/L IN WATER COLUMN, AS MG/KG IN SEDIMENTS.
EXAMS > LI 15
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: I^-DICHLOROBENZENE
ECOSYSTEM: LAKE ZURICH - CENTRAL BASIN (UNTERSEE)
TABLE 15. ANALYSIS OF STEADY-STATE FATE OF ORGANIC TOXICANT.
PROCESS MASS FLUX % OF LOAD HALF-LIFE*
KG/DAY DAYS
HYDROLYSIS 0.0000 0.00 —
OXIDATION 0.0000 0.00 —
PHOTOLYSIS 0.0000 0.00
ALL CHEMICAL PROCESSES 0.0000 0.00 -—
WATER COLUMN (BACTERIA) 0.0000 0.00
BOTTOM SEDIMENTS (BACTERIA) 0.0000 0.00 ---
TOTAL BIOLYSIS 0.0000 0.00 - —
VOLATILIZATION 0.1627 67.79 156.8
WATER-BORNE EXPORT 7.7315E-02 32.21 329.9
TRANSFORMATION AND TRANSPORT 0.2400 100.00
TOTAL SYSTEM LOAD 0.2400
RESIDUAL ACCUMULATION RATE: 2.2352E-08 0.00
* HALF-LIVES ARE ESTIMATES BASED ON A FIRST-ORDER RATE APPROXIMATION.
EXAMS > LI 17
222
-------
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: i^-DICHLOROBENZENE
ECOSYSTEM: LAKE ZURICH - CENTRAL BASIN CUNTF.RSEE)
TABLE 17. EXPOSURE ANALYSIS SUMMARY.
EXPOSURE:
A. MAXIMUM COHC. IN WATER COLUMN: 1.07E-05 «G/L DISSOLVED, 1.07E-05 TOT
MAX. CQNC. IN BOTTOM SEDIMENT: 1.07E-05 MG/L DISSOLVED IN POPE WATER
B. BIOSQRPTION - MAX. CONCENTRATION - PLANKTON: 0.00 UG/G
BENTHOS: o.oo UG/G
C. MAXIMUM TOT. C3NC. IN SEDIMENT DEPOSITS: 2.11E-04 MG/KG (DRY WEIGHT)
FATE:
A. TOTAL STEADY-STATE ACCUMULATION: 37. KG; 99.22% IN WATER COL.,
0.78% IN BOTTOM SEDIMENTS.
B. TOTAL LOAD: 0.24 KG/DAY - DISPOSITION: 0.00% VIA CHEMICAL
TRANSFORMATIONS, 0.00% BIDTRANSFOPMED, 67.79% VOLATILIZED,
32.21% EXPORTED VIA OTHER PATHWAYS,
PERSISTENCE:
A. AT THE END OF A 216. DAY RECOVERY PERIOD, THE WATER COLUMN HAD
LOST 50.51% OF ITS INITIAL TOXICANT BURDEN; THE SEDIMENTS HAD
LOST 19.54% OF THEIR INITIAL BURDEN ( 50.26% REMOVAL OVERALL).
B. SYSTEM SELF-PURIFICATION TIME IS ROUGHLY 36. MONTHS.
EXAMS > SHOW USER ENV
Directory of user defined ENVIRONMENTS
No. ENVIRONMENT NAME
5 Alkaline Pond - enhanced hydrolysis
EXAMS > STOR ENV 1
Environment stored: LAKE ZURICH - CENTRAL BASIN (UNTERSEE)
EXAMS > PRINT ALL
Requested report has been spooled to printer.
EXAMS > SHO USER ENV
Directory of user defined ENVIRONMENTS
No. ENVIRONMENT NAME
1 LAKE ZURICH - CENTRAL BASIN (UNTERSEE)
5 Alkaline Pond - enhanced hydrolysis
EXAMS > CHA DRFLDC2) TO 1.5E-3
EXAMS > CH STRLD(l) TO 8.5E-3
EXAMS > ENV NAME IS LAKE ZURICH WITH PARTIAL LOAD TO HYPOLIMNION
EXAMS > RUN
223
-------
Simulation beginning for:
Compound: 1,4-DICHLOROBENZENE
Environment: LAKE ZURICH WITH PARTIAL LOAD Ta, HYPOLIMNION
with a load of (kg/hr) > 0.1000000E-01
Run complete.
EXAMS > LI 13
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: I^-DICHLOROBENZENE
ECOSYSTEM: LAKE ZURICH WITH PARTIAL LOAD TO HYPOLIMNION
TABLE 13. DISTRIBUTION OF CHEMICAL AT STEADY STATE: IN THE WATER COLUMN:
COMP STEADY-STATE RESIDENT MASS **** TOXICANT CONCENTRATIONS ****
2 TOTAL DISSOLVED SEDIMENTS BIOTA
G/M KILOS % MG/* MG/L MG/KG UG/G
1 1.074E-04 7.302 16.59 1.074E-05 1.074E-05 2.060E-04 0.000
2 5.398E-04 36.71 83.41 1.350E-05 1.349E-05 2.589E-04 0.000
SUBTOTAL: 44.01 99.19
AND IN THE BOTTOM SEDIMENTS:
3 5.313E-06 0.3613 100.00 2.657E-04 1.349E-05 2.589E-04 0.000
SUBTOTAL: 0,3613 o.ei
TOTAL MASS (KILOGRAMS) a 44.37
*mmmm*mmmmmmmmmmmmmmmmm*mmmmmmmmmmmmmmmmmmmmm*mmmmmmitmm~m**m*mmmt,mm — mm'
* TOTAL CONCENTRATION AS MG/L IN WATER COLUMN, AS MG/KG IN SEDIMENTS.
EXAMS > LI 15
224
-------
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: I^-DICHLOROBENZENE
ECOSYSTEM: LAKE ZURICH WITH PARTIAL LOAD TO HYPOLIMNIQN
TABLE 15. ANALYSIS OF STEADY-STATE FATE OF ORGANIC TOXICANT.
PROCESS MASS FLUX % OF LOAD HALF-LIFE*
KG/DAY DAYS
HYDROLYSIS 0.0000 0.00 ---
OXIDATION 0.0000 0.00
PHOTOLYSIS 0.0000 0.00
ALL CHEMICAL PROCESSES 0.0000 0.00 ---
WATER COLUMN (BACTERIA) 0.0000 0,00 ---
BOTTOM SEDIMENTS (BACTERIA) 0.0000 0.00 ---
TOTAL BIOLYSIS 0.0000 0.00 - —
VOLATILIZATION 0.1627 67.79 189,1
WATER-BORNE EXPORT 7.7315E-02 32.21 397.8
TRANSFORMATION AND TRANSPORT 0.2400 100.00
TOTAL SYSTEM LOAD 0.2400
RESIDUAL ACCUMULATION RATE: 2.2352E-08 0,00
* HALF-LIVES ARE ESTIMATES BASED ON A FIRST-ORDER RATE APPROXIMATION,
EXAMS > LI 17
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: I^-DICHLOROBENZENE
ECOSYSTEM: LAKE ZURICH WITH PARTIAL LOAD TO HYPOLIMNION
TABLE 17, EXPOSURE ANALYSIS SUMMARY.
EXPOSURE:
A, MAXIMUM CONC. IN WATER COLUMN: 1.35E-05 MG/L DISSOLVED, 1.35E-05 TOT
MAX. CONC, IN BOTTOM SEDIMENT: 1.35E-05 MG/L DISSOLVED IN POPE WATER
B, BIOSORPTION - MAX, CONCENTRATION - PLANKTON: 0,00 UG/G
BENTHOS: o.oo UG/G
C, MAXIMUM TOT. CONC. IN SEDIMENT DEPOSITS: 2.66E-04 MG/KG (DRY WEIGHT)
FATE:
A. TOTAL STEADY-STATE ACCUMULATION; 44. KG; 99.19% IN WATER COL.,
0.81% IN BOTTOM SEDIMENTS.
B. TOTAL LOAD: 0.24 KG/DAY - DISPOSITION: 0,00% VIA CHEMICAL
TRANSFORMATIONS, 0.00% BIOTRANSFOPMED, 67.79% VOLATILIZED,
32,21% EXPORTED VIA OTHER PATHWAYS,
PERSISTENCE:
A. AT THE END OF A 252. DAY RECOVERY PERIOD, THE WATER COLUMN HAD
LOST 54.35% OF ITS INITIAL TOXICANT BURDEN; THE SEDIMENTS HAD
LOST 25.70% OF THEIR INITIAL BURDEN ( 54.11% REMOVAL OVERALL),
B, SYSTEM SELF-PURIFICATION TIME IS ROUGHLY 37. MONTHS.
225
-------
EXAMS > CHA KVQG TO 0.35
EXAMS > COMP NAME IS 1,4-DCB WITH DIFFUSIVITY TRANSPORT INDEX
EXAMS > RECALL ENV 1
Selected environment is: LAKE ZURICH - CENTRAL BASIN (UNTERSEE)
EXAMS > CHAN STRLD(l) TO 0.01
EXAMS > RUN
Simulation beginning for:
Compound: 1,4-DCB WITH DIFFUSIVITY TRANSPORT INDEX
Environment: LAKE ZURICH - CENTRAL BASIN (UNTERSEE)
with a load of (Kg/hr) > 0.1000000E-01
Run complete.
EXAMS > LI 13
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: i,4-DCB WITH DIFFUSIVITY TRANSPORT INDEX
ECOSYSTEM: LAKE ZURICH - CENTRAL BASIN (UNTEPSEE)
m»m»mmmmmmmmmmmmmmmmm9m»mmmmmmma>mm»mmmmmmmmmm*mmmmmmmmmmmmmmmmmmmmmmmmmi
TABLE 13. DISTRIBUTION OF CHEMICAL AT STEADY STATE: IN THE WATER COLUMN!
mmm9mmmm^mmmm»mmmm»»mm»m»mm»^mmmmmm
* TOTAL CONCENTRATION AS MG/L IN WATER COLUMN, AS MG/KG IN SEDIMENTS.
EXAMS > LI 15
226
-------
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: 1,4-oce *IITH DIFFUSIVITY TRANSPORT INDEX
ECOSYSTEM: LAKE ZURICH - CENTRAL BASIN (UNTERSEE)
TABLE 15. ANALYSIS OF STEADY-STATE
PROCESS
HYDROLYSIS
OXIDATION
PHOTOLYSIS
ALL CHEMICAL PROCESSES
WATER COLUMN (BACTERIA)
BOTTOM SEDIMENTS (BACTERIA)
TOTAL BIOLYSIS
VOLATILIZATION
HATER-BORNE EXPORT
TRANSFORMATION AND TRANSPORT
TOTAL SYSTEM LOAD
RESIDUAL ACCUMULATION PATE:
FATE OF ORGANIC
MASS FLUX %
KG/DAY
0.0000
0.0000
0.0000
0.0000
o.oooo
0.0000
0.0000
0.1471
9.2869E-02
0.2400 1
0.2400
2.2352E-08
TOXICANT.
OF LOAD
0.00
0.00
0.00
0.00
0.00
0.00
0.00
61.30
38.70
00.00
0.00
HALF-LIFE*
DAYS
...
• ••
208.2
329.9
* HALF-LIVES ARE ESTIMATES BASED ON A FIRST-ORDER RATE APPROXIMATION.
EXAMS > CH KVOG TO 0.59
EXAMS > COMP NAME is 1,4-ocs WITH SORT(DIFFUSIVITY) TRANSPORT INDEX
EXAMS > RUN
Simulation beginning for:
Compound: 1,4-DCB rflTH SQRT(DIFFUSIVITY) TRANSPORT INDEX
Environment: LAKE ZURICH - CENTRAL BASIN (UNTEPSEE)
with a load of (kg/hr) > 0. 1000000E-01
Run complete.
EXAMS > LIST 13
227
-------
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: i,4-DCB WITH SQRT(DIFFUSIVITY) TRANSPORT INDEX
ECOSYSTEM: LAKE ZURICH - CENTRAL BASIN (UNTERSEE)
TABLE 13. DISTRIBUTION OF CHEMICAL AT STEADY STATE: IN THE WATER COLUMN:
COMP STEADY-STATE RESIDENT MASS **** TOXICANT CONCENTRATIONS *»**
2 TOTAL DISSOLVED SEDIMENTS BIOTA
G/M KILOS % MG/* MG/L MG/KG UG/G
1 9.131E-05 6.209 20.00 9.131E-06 9.130E-06 1.752E-04 0.000
2 3.652E-04 24.84 80.00 9.131E-06 9.130E-06 1.752E-04 0.000
SUBTOTAL: 31.05 99.22
AND IN THE BOTTOM SEDIMENTS:
3 3.595E-06 0.2445 100.00 1.798E-04 9.130E-06 1.752E-04 0.000
SUBTOTAL: 0.2445 o.78
TOTAL MASS (KILOGRAMS) = 31.29
* TOTAL CONCENTRATION AS MG/L IN WATER COLUMN, AS MG/KG IN SEDIMENTS.
EXAMS > LI 15
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: i,4-DCB WITH SQRTCDIFFUSIVITY) TRANSPORT INDEX
ECOSYSTEM: LAKE ZURICH - CENTRAL BASIN (UNTERSEE)
TABLE 15. ANALYSIS OF STEADY-STATE FATE OF ORGANIC TOXICANT.
PROCESS MASS FLUX % OF LOAD HALF-LIFE*
KG/DAY DAYS
HYDROLYSIS 0.0000 0.00 ---
OXIDATION 0.0000 0.00 -•-
PHOTOLYSIS 0.0000 0.00 --»
ALL CHEMICAL PROCESSES 0.0000 0.00 - —
WATER COLUMN (BACTERIA) 0.0000 0.00 —
BOTTOM SEDIMENTS (BACTERIA) 0.0000 0.00 - —
TOTAL BIOLYSIS 0.0000 0.00 ---
VOLATILIZATION 0.1743 72.61 124.5
WATER-BORNE EXPORT 6.5743E-02 27.39 329.9
TRANSFORMATION AND TRANSPORT 0.2400 100.00
TOTAL SYSTEM LOAD 0.2400
RESIDUAL ACCUMULATION RATE: 0.0000 0.00
* HALF-LIVES ARE ESTIMATES BASED ON A FIRST-ODDER RATE APPROXIMATION.
228
-------
EXAMS > SHOW USER COM?
Directory of user defined compounds
No. COMPOUND NAME
1 1,4-DICHLOROBENZENE
3 Methyl Parathion with HIGH biolysis
4 Methyl Parathion with LOW biolysis.
7 XXX WITH KPS=100.
8 XXX WITH KPS=1000.
9 XXX WITH KPS=10000.
EXAMS > RECALL COMP 1
Compound selected > 1,4-DICHLOROBENZENE
EXAMS > ENV NAME IS LAKE ZURICH WITH OCEANIC WIND AND REAERATION
EXAMS > SHOW K02C1)
K02 IS 2.700
EXAMS > CHANGE K02U) TO 20.
EXAMS > SHOW WIND(l)
WIND IS 1.600
EXAMS > CHANGE WTND(l) TO 2.6245
EXAMS > RUN
No load specified.
Simulation not performed.
EXAMS > CHA STRLDC1) TO 0.01
EXAMS > RUV
Simulation beginning for:
Compound: 1,4-DICHLOROBENZENE
Environment: LAKE ZURICH WITH OCEANIC WIND AND REAERATION
with a load of (Kg/hr) > 0.1000000E-01
Run complete.
EXAMS > LIST 13
229
-------
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: I^-DICHLOPOBENZENE
ECOSYSTEM: LAKE ZURICH WITH OCEANIC WIND AND REAERATION
DISTRIBUTION OF ORGANIC TOXICANT AT STEADY-STATE: IN THE WATER COLUMN:
COMP STEADY-STATE RESIDENT MASS **** TOXICANT CONCENTRATIONS ****
2 TOTAL DISSOLVED SEDIMENTS BIOTA
G/M KILOS % MG/* MG/L MG/KG I'G/G
1 1.952E-05 1.328 20.00 1.952E-06 J.952E-06 3.746F-05 0.000
2 7.810E-05 5.311 80.00 1.952E-06 1.952E-06 3.746E-05 0.000
SUBTOTAL: 6.638 99.22
AND IN THE BOTTOM SEDIMENTS:
3 7.687E-07 5.2273E-02 100.00 3.844E-05 1.952E-06 3.746E-05 0.000
SUBTOTAL: 5.2273E-02 0.78
TOTAL MASS (KILOGRAMS) = 6.691
* TOTAL CONCENTRATION AS MG/L IN WATER COLUMN, AS MG/KG IN SEDIMENTS.
EXAMS > LIST 15
AERL-ESB MODEL OF FATE OF ORGANIC TOXICANTS IN AQUATIC ECOSYSTEMS
CHEMICAL: IM-DICHLOROBENZENE
ECOSYSTEM: LAKE ZURICH WITH OCEANIC WIND AND REAERATION
ANALYSIS OF STEADY-STATE FATE OF ORGANIC TOXICANT
PROCESS MASS FLUX % OF LOAD HALF-LIFE*
KG/DAY DAYS
HYDROLYSIS 0.0000 0.00
OXIDATION 0.0000 0.00 —
PHOTOLYSIS 0.0000 0.00
ALL CHEMICAL PROCESSES 0.0000 0.00 —
HATER COLUMN (BACTERIA) 0.0000 0.00 —
BOTTOM SEDIMENTS (BACTERIA) 0.0000 0.00 —
TOTAL BIOLYSIS 0.0000 0.00 —
VOLATILIZATION 0.2259 94.14 20.53
HATER-BORNE EXPORT 1.4058E-02 5.86 329.9
TRANSFORMATION AND TRANSPORT 0.2400 100.00
TOTAL SYSTEM LOAD 0.2400
RESIDUAL ACCUMULATION RATE: 0.0000 0.00
* HALF-LIVES ARE ESTIMATES BASED ON A FIRST-ORDER RATE APPROXIMATION.
EXAMS > QUIT
JOB104 •* STOP
20:44:10 size: 31K CPU: 1:9.78 status: SUCCESS
230
-------
3.4 Preparing Batch Input Data
EXAMS* batch input data are arranged as diagramed below.
The input stream includes three data sets: user run information,
chemical parameters, and environmental parameters.
/ Environment Parameter Data
/ Chemistry Parameter Data
t
User Run Information
/ JCL
/
Job Card
This section contains four subsections:
3.4.1 Fornat Codes
3.4.2 Creating or Changing the User Run Information
3.4.3 Creating or Changing the Chemical Data
3,4.4 Creating or Changing the Environmental Data
231
-------
Section 3,4,1 is a detailed list of format codes. Sections
3.4.2, 3.4.3, and 3.4,4 describe the parameters for user run
information, chemical data and environmental data, respectively.
Figures 3.1, 3.2, and 3.3 are sample data sets with parameter
names and format codes.
To maice a change in the input data, locate the parameter in
the parameter index, Table 3.1, On the indicated page, find the
description of the parameter to be changed and its format code.
The format code refers to the detailed description of the
parameter layout in Section 3.4.1. The sample data sets in
Figures 3,1, 3,2, and 3,3 show the relative position and sequence
of the parameters.
For example, to change the pH of compartment »5 in the
environmental data:
1, The parameter index refers PHG to page 249.
2. Page 249 defines the parameter and gives its format
code as "5,"
3, In Section 3,4,1, format code 5 describes records
as "8F10.0." This field width must be preserved
when the data base is altered.
4, Locate PHG in the sample environmental data input
(Figure 3,3) for the relative position of the
parameter in the input data stream.
To create an entirely new set of input data, all parameters
must be present as described in Sections 3.4.2, 3.4.3, and 3.4.4.
232
-------
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235
-------
3,4.1 Format Codes
In the example datasets, Figures 3.2 and 3.3, following the '...'
(columns 81-83) are the variable name, record number for that
format (if applicable), and format code. The narrative
associated with each database also references the format codes.
Code
1
2
3
4
5
Format
60 characters, left justified. Format: (60A1)
Columns 1-5 right justified. Format: (2015)
Column 1, one character/record. The maximum
number of records is equal to the number of
compartments. Format: (Al)
Columns 1-10. Format: (F10.0)
Each record contains 8 10-column fields, maximum
2 records per variable. Format: (8F10.0)
Record 1
Record 2
(if needed)
Columns
1-10
11-20
1-10
11-20
Compartment
1
2
9
10
Five record layout containing 39 values. Four
records contain eight 10-column fields; the
fifth contains seven. Format: (8F10.0)
Record 1
Columns
1-10
11-20
Value
1
2
Record 2
71-80
1-10
8
9
71-80
237
-------
Record 5
1-10
33
61-70
39
The number of records is equal to NSPEC1 or
NSPEC2 divided by 16. Each record contains
16 five column fields. For JFRADG and ITOADG
use NSPECl and for JTURBG and ITURBG use
NSPEC2. Each field is right justified.
Format: (2015)
Record 1
Columns
1-5
6-10
1
2
Record 2
76-80
1-5
16
17
Record n
41-50
51-60
29
30
Format: (5(11,IX))
Column Flag
1 1
3 2
5 3
7 4
9 5
Format: (8F10.0)
Columns value
1-10 1
11-20 2
21-30 3
238
-------
10 Fomnat: (8F10.0)
Columns Value
1-10 1
11-20 2
21-30 3
31-40 4
11 Format: (8FIO.O)
Columns value
1-10 1
11-20 2
12 The number of records Is equal to NSPEC1 or
NSPEC2 divided by eight. Each record contains
eight 10-column fields. For ADVPRG use NSPEC1
and for XSTURG, CHARLG, and DSPG use NSPEC2.
Format: (8F10.0)
Columns Value
Record 1 1-10 1
11-20 2
71-80
Record 2 .
Record n 41-50 29
51-60 30
239
-------
3,4.2 Creating or Changing the User Run information
This sequential file contains chemical name, ecosystem name, and
loads.
Record 1: (CHEM1
Record 2: (EC01)
Record 3: (NLOAD
Record 4,.
Chemical name - three characters maximum.
Format: (A3)
Ecosystem name - three characters maximum.
Format: (A3)
Number of loadings.
Format: (15)
.,,NLOAD+3: (I,STRLDG,NPSLDG,PCPLDG,DRFLDG,IFLLDG)
Each of NLOAD records contain the load
number and the Ith STRLDG, NPSLDG, PCPLDG,
DRFLDG, IFLLDG.
Format: (I5,5F10.0)
STRLDG - Stream loadings.
NPSLDG - Non-point source loadings.
PCPLDG - Precipitation loadings.
DRFLDG - Drift loadings.
IFLLDG - Interflow loadings.
Record 4
Columns
1-5
6-15
16-25
26-35
36-45
46-55
Field
I
STRLDG(I)
NPSLDG(I)
PCPLDG(I)
DRFLDG(I)
IFLLDG(I)
240
-------
3.4.3 Creating or Changing the Chemical Data
Locate the CHEM2 record in the chemistry data. This record acts
as a header/delimiter for the associated parameters. The
chemical parameter data are located in the following sequential
record layout. (The format code list provides the detailed
format specifications.)
Record: (CHEMNA) Chemical name. Format: 1
Record: (SPFLG) Flags denoting which species occur. Five
flags: 1 denoting occurrence, 0 denoting
nonexistence. Format: 8
•If SPFLG(l)=l;
Record: (MWTG,SOLG(1),ESOLGU))
Molecular weight of the toxicant, aqueous
solubility of the toxicant chemical species,
and exponential term for describing
solubility of the toxicant as a function of
temperature. Three values per record.
Format: 9
Record: (KPSG(l),KPBG(1),KOCG,KOWG)
Partition coefficient of toxicant on
compartment sediment. Partition coefficient
of toxicant on compartment biomass (BIOHSG).
Multiplication of KOCG by the fractional
organic carbon content (FPOCG(J)) of each
system sediment yields the partition
coefficient. Octanol-water partition
coefficient of toxicant. Four values per
record. Format: 10
Record: (KVOG,HENRYG,EHENG,VAPRG,EVPRG)
Measured experimental value for
(volatilization) liquid-phase transport
resistance, expressed as a ratio to the
reaeration rate. Henry's Law constant of
the toxicant. Used to compute Henry's Law
constant as a function of temperature. Used
to compute Henry's Law constant if the
latter input datum (HENRY.G) is zero, but
VAPRG is non-zero. Molar heat of
vaporization for vapor pressure described as
a function of temperature. Five values per
record. Format: 10
241
-------
Record; (QUANTGC1,1),QUANTG(2,1),QUANTGC3,1))
Reaction quantum yield in photolytic
transformation of toxicant. Separate values
are provided for each molecular
configuration of the toxicant. Three values
per record. Format: 9
Record: (ABS1) Absorption spectrum for uncharged molecule
(SH2). The following list explains the
correspondence between array element and
wavelength: 1:297.5, 2:300.0, 3:302.5,
4:305.0, 5:307.5, 6:310.0, 7:312.5, 8:315.0,
9:317.5, 10:320.0, 11:323.1, 12:330.0,
13:340.0, 14:350.0, 15:360.0, 16:370.0,
17:380.0, 18:390.0, 19:400.0, 20:410.0,
21:420.0, 22M30.0, 23:440.0, 24:450.0,
25:460.0, 26:470.0, 27:480.0, 28:490.0,
29:503.75, 30:525.0, 31:550.0, 32:575.0,
33:600.0, 34:625.0, 35:650.0, 36:675.0,
37:706.25, 38:750.0, 39:800.0. Format: 6
Record: (KDPG(l),RFLATG(1),LAMAXG)
A near-surface photolytic rate constant for
the Kth chemical species of the toxicant.
Reference latitude for corresponding direct
photolysis rate constant (c.f. KDPG).
Wavelength for computing zenith light
extinction coefficient. Three values per
record. Format: 11
Record: (KAHG(1,1)KAHG(2,1),KAHG(3,1))
Second-order rate constants for
specific-acid catalyzed hydrolysis of
toxicant. Three values per record. Format:
9
Record: (EAHG(1,1),EAHG(2,1),EAHG(3,1))
Arrhenius activation energy of specific-acid
catalyzed hydrolysis of the toxicant.
Matrix indices allow entry of the data as
separate value for each chemical
species/physical form configuration of the
toxicant molecule. Three values per record.
Format: 9
Record: (KNHGU,1),KNHG(2,1),KNHG(3,1))
Rate constants for neutral hydrolysis of
organic toxicant. Three values per record.
Format: 9
Record: (ENHG(1,1),ENHG(2,1),ENHG(3,1))
Arrhenius activation energy of neutral
242
-------
hydrolysis of the toxicant. Three values
per record. Format: 9
Record: (KRHGU , 1 ) ,KBHG(2,1),KBHG(3,1))
Second-order rate constants for
specific-base catalyzed hydrolysis of
toxicant. Three values per record. Format:
9
Record: (EBHGC1,1),EBHG(2,1),EBHG(3,1))
Arrhenius activation energy of specific-base
catalyzed hydrolysis of the toxicant. Three
values per record. Format: 9
Records (KOXG(1,1),KOXGC2,1),KOXG(3,1))
Second-order rate constants for oxidative
transformation of toxicant. Three values
per record. Format: 9
Record: (EOXG(1,1),EOXG(2,1),EOXG(3,1))
Arrhenius activation energy of oxidative
transformation of the toxicant. Three
values per record. Format: 9
Record: (KBACWG(1,1),KBACWGC2,1),KBAC*G(3,1))
Second-order rate constants for water column
bacterial biolysis of the organic toxicant.
Three values per record. Format: 9
Record: (OTBAWG(1,1),QTBAWGC2,1),QTBAWG(3,1))
Q-10 Values for bacterial transformation
(c.f. KBACWG) of toxicant in water column
of the system. Three values per record.
Format: 9
Record: (KBACSG(1,1),KBACSG(2,1),KBACSG<3,1))
Second-order rate constants for benthic
sediment bacterial biolysis of the organic
toxicant. Three values per record. Format:
9
Record: (QTBASGU,1),QTBASG(2,1),QTBASG(3,1))
Q-10 Values for bacterial transformation
(c.f. KBACSG) of organic toxicant in
benthic sediments. Three values per record.
Format: 9.
•If SPFLG(2),SPFLG(3);K=2,3-
Record: (PKBGC1),EPKBG(1),SOLG(K),ESOLG(K))
Negative base-10 logarithm of first (K=2)
and second (K=3) base dissociation constants
243
-------
of organic toxicant. Exponential term for
base dissociation constant of toxicant (Kb)
as a function of temperature. Aqueous
solubility of toxicant chemical species.
Exponential term for decribing solubility of
the toxicant as a function of temperature.
Four values per record. Format: 10
Record: (KPSG(K),KPBG(K),KCECGCK-1))
Partition coefficient of toxicant on
compartment sediment. Partition coefficient
of toxicant compartment biomass (BZOMSG).
Multiplication of the cation exchange
capacity of system sediments by KCECG gives
the partition coefficient for sorption of
the SH3+ cation (KCECG(D). Three values
per record. Format: 9
Record: (QUANTGU,K),QUANTG(2,K),QUANTG(3,K))
Reaction quantum yield in photolytic
transformation of toxicant, separate values
are provided for each molecular
configuration of the toxicant. Three values
per record. Format: 9
Record: (ABS2) Absorption spectrum for singly charged
cation (SH3+). See ABS1. Format: 6
Record: (KDPG(K),RFLATG(K))
A near-surface photolytic rate constant for
the Kth chemical species of the toxicant.
Reference latitude for corresponding direct
photolysis rate constant (c.f. KDPG). Two
values per record. Format: 11
Record: (KAHGU,K),KAHG(2,K),KAHG(3,K))
Second-order rate constants for
specific-acid catalyzed hydrolysis of
toxicant. Three values per record. Format:
9
Record: (EAHGC1,K),EAHG(2,K),EAHG(3,K))
Arrhenius activation energy of specific-acid
catalyzed hydrolysis of the toxicant.
Matrix indices allow entry of the data as a
separate value for each chemical
species/physical form configuration of the
toxicant molecule. Three values per record.
Format: 9
Record: (KNHG(1,K),KNHG(2,K),KNHG(3,K))
Same as SPFLG(l)
244
-------
Record! (ENHGd,K),ENHG(2,K),ENHG(3,K))
Same as SPFLG(l)
Record; (KBHG(1,K),KBHG(2,K),KBHG(3,K))
Same as SPFLG(l)
Record: (EBHGU fK),EBHG(2,K),EBHG(3,K))
Same as SPFLG(l)
Record: (KDXGU,K),KQXG(2,K),KOXG(3,K))
Same as SPFLG(l)
Record: (EOXGCl,K),EOXG(2,K),EOXG(3,K))
Same as SPFLG(l)
Record: (KBACWGU,K),KBACfcG(2,K),KBAC*G(3,K))
Same as SPFLG(l)
Record: (QTBAWGd,K),QTBAWG(2,K),QTBAI*G(3,K))
Same as SPFLG(l)
Record: (KBACSG(1,K),KBACSG(2,K),KBACSG(3,K))
Same as SPFLG(l)
Record: (QTBASGU,K),QTBASG(2,K),QTBASGC3,K))
Same as SPFLG(l)
•If SPFLG(4)fSPFLG(5);L=4,5-
Record: (PKAGd ) ,EPKAGC1 ) ,SOLG(L) ,ESOLG(D)
Negative base-10 logarithm of first (L*4)
and second (L=5) acidity constant of organic
toxicant. Exponential term for acid
dissociation constant of toxicant (Ka),
Aqueous solubility of toxicant chemical
species. Exponential term for describing
solubility of the toxicant as a function of
temperature. Four values per record.
Format: 10
Record: (KPSG(L),KPBG(L),KAECGU))
Partition coefficient of toxicant on
compartment sediment. Partition coefficient
of toxicant on compartment biomass (BIOHSG).
Multiplication of the anion exchange
capacity of the system sediments by KAECG
gives the partition coefficient on the
sediment. Three values per record. Format:
9
Record: (QUANTG(1,L),QUANTG(2,L),QUANTG(3,D)
Same as SPFLG(l)
245
-------
Record: (ABS4) Absorption spectrum for singly charged anion
(SH-). See ABS1. Format: 6
Record: (KDPG(L),RFLATG(D)
Same as SPFLG(l)
Record: (KAHGU ,L) ,KAHG(2,L) ,KAHG(3,D)
Same as SPFLG(l)
Record: (EAHG(1,L),EAHG(2,L),EAHG(3,D)
Same as SPFLG(l)
Record: (KNHGC1,L),KNHG(2,L),KNHG(3,L))
Same as SPFLG(l)
Record: (ENHGU ,L) ,ENHG(2,L) ,ENHG(3,D)
Same as SPFLG(l)
Record: (KBHGU ,L),KBHG(2,L) ,KBHG(3,D)
Same as SPFLG(l)
Record: (EBHGU,L),EBHG(2,L),EBHG(3,L))
Same as SPFLG(l)
Record: (KOXGU ,L) ,KOXG(2,L) ,KOXG(3,D)
Same as SPFLG(l)
Record: (EOXGU,L),EOXG(2,L),EOXG(3,L))
Same as SPFLG(l)
Record: (KBACWG(1,L),KBACWG(2,L),KBACWG(3,U)
Same as SPFLG(l)
Record: (QTBAWGU ,L),QTBAWG(2,L),QTBAWG(3,D)
Same as SPFLG(l)
Record: (KBACSG(1,L),KBACSG(2,L),KBACSG(3,L))
Same as SPFLG(l)
Record: (OTBASGCl,L)fQTBASG(2,L),QTBASG(3,D)
Same as SPFLG(i)
246
-------
3.4.4 Creating or Changing the Environmental Data
Locate the EC02 record in the environmental data. This
record acts as a neader/deiirniter for the associated
parameters. The compartment parameter data are located in the
following sequential record layout. (The format code list
provides detailed format specifications.)
(SYSTYP)
(KOUNT)
Record:
Record:
Record:
Record: (I,ATG)
Ecosystem name, maximum
Format: 1
60 characters.
Dumber of compartments, maximum number of
compartments is NPX, which is fixed for a
particular installation. Format: 2
The next KOUNT records each contain a one
character compartment code, KOUNT the
number of compartments. Format: 3
Ecosystem latitude, columns 1-10, degrees
and seconds as whole number and decimal
fraction, e.g. 10.15. Format: 4
Record:
Record:
Record:
Record:
Record:
Record:
Record:
Record:
(WTN'OG)
(VOLG)
(AREAG)
(DEPTHG)
CSTFLOG)
(STSEDG)
(NPSFLG)
(NPSEDG)
Kind velocity per cotrpartment , eight per
record. Format: 5
Total environmental volume per
compartment. Format: 5
Area of each ecosystem compartment.
Format: 5
Average depth of each compartment.
Format: 5
Stream flow entering ecosystem
compartments. Format: 5
Stream-borne sediment load entering
ecosystem compartments. Format: 5
Non-point-source water flow entering
ecosystem compartments. Format: 5
Non-point-source sediment loads entering
ecosystem compartments. Format: 5
247
-------
Record; (INTFOG) Interflow (groundwater seepage) entering
each ecosystem compartment. Format: 5
Record: (PAING) Average rainfall in geographic area of
system. Columns 1-10, Format: 4
Record: (CLOUDG) Average cloudiness in tenths of full sky
cover. Columns 1-10. Format: 4
Record: (WLAMG) Temporally averaged spectral irradiance
immediately below the water surface. This
is a five record layout containing 39
values, ten columns per value, eight
values per record. Format: 6
Record: (DFACG) Distribution function (optical path) for
each compartment. Format: 5
Record: (EVAPG) Evaporative water losses from ecosystem
compartments. Format: 5
Record: (SDCHRG) For water column compartments the
suspended sediment concentration? for
benthic sediment compartments the bulk
density of the bottom sediment. Format:
5
Record: (PCTWAG) Percent water in bottom sediments of
benthic compartments. Elements
corresponding to water column compartments
are not used (dummy values). Format: 5
Record: (NSPECl) Number of active advective transport
pathways. Format: 2
Record: (JFRADG) Source compartment (J) for advective flow.
Format: 7
Record: (ITOADG) Receiving compartment (I) for advective
flow. Format: 7
Record: (ADVPRG) Proportion of total advective flow from
compartment J that flows to compartment I.
Format: 12
Record: (NSPEC2) Number of active dispersive transport
pathways. Format: 2
Record: (JTURBG) Source compartment for dispersive flow.
Format: 7
Record: (ITURBG) Receiving compartment for dispersive flow.
248
-------
Format:
Record:
Record:
Record:
Record:
Record:
Record:
Record:
Record:
Record:
Record:
Record:
Record:
Record:
Record:
(XSTUFG)
(CHAPLS)
(DSPG)
(FROCG)
(CECG)
(AECG)
(TCELG)
(PHG)
Cross-sectional areas
exchanges. Format: 12
for
Characteristic lengths of
exchange pairings. Format: 12
dispersive
dispersive
Kddy dispersion coefficients for
dispersive exchange pairings. Format: 12
Organic carbon content of compartment
sediments. Format: 5
Cation exchange capacity of sediments in
each compartment. Format: 5
Anion exchange capacity of sediments in
each compartment. Format: 5
Average temperature of
compartments. Format: 5
ecosystem
Record: (POHG)
Record: (OXRADG)
(BIOMSG)
(PLRAG)
(BIOTMG)
(BACTOG)
(ACBACG)
(K02G)
Negative value of log of temporal average
of tH+J concentration for each
compartment. Format: 5
Negative value of log of temporally
averaged [OH-] concentration for each
compartment. Format: 5
Molar concentration of environmental
oxidants in each ecosystem compartment.
Format: 5
Total actively sorting biomass in each
compartment. Format: 5
Planktonic fraction of total biomass in
each compartment. Format: 5
Biotemperature in
Format: 5
each compartment.
in each
Bacterial population density
compartment. Format: 5
Proportion of bacterial population that
actively degrades toxicant. Format: 5
Rearation parameter in each compartment.
Format: 5
249
-------
Record: (CMPETG) Single-valued zenith lignt extinction
coefficient for water columns, dummy
variable for benthic compartments.
Format: 5
Record: (DOCG) Dissolved organic carbon concentration in
water column compartments, dummy variable
in benthic compartments. Format: 5
Record: (CHLG) Concentration of chlorophyll and
chlorophyll-lilce pigments in water column
compartments, dummy variable in benthic
compartments. Format: 5
250
-------
SECTION 4
PROGRAMMER'S SUPPLEMENT
4.1 System Documentation
4.1.1 system Overview
EXAMS is a collection of FORTRAN routines that supports
batch and interactive modes of operation. The batch version uses
a driver routine to process the user's inputs and invoke the
simulation program. The interactive version replaces the driver
routine with routines that allow the user to interactively
specify and alter inputs to the simulation program, invoke the
simulation code, and review the results. Both implementations of
EXAMS use the same simulation code. Figures 4.1 and 4.2 show the
block structure of the batch mode and the interactive mode of
operation, respectively.
The batch mode requires a single input stream, e.g. a card
reader, and a single output stream, e.g. a line printer. The
interactive version communicates with the user via a computer
terminal. This version requires a mass storage capability for
the chemical and environmental libraries, the online assistance
file, the variables description file, the tabular output file,
the kinetics output file, and the steady-state output file and,
optionally, a line printer for selected outputs.
EXAMS was designed and implemented with the aim of providing
a portable code. The code was written in American National
Standard FORTRAN X3.9-1966 with only one extension, the DEFINE
FILE option. This option provides rapid access to information
stored in external files; random access files significantly
reduce input/output (I/O) time over that required by sequential
access files. The DEFINE FILE option is supported by the
majority of minicomputer implementions of FORTRAN, and by most
recent versions of FORTRAN on mainframes.
The interactive version of EXAMS executes extensive
character string manipulations; the 1966 FORTRAN standard does
not support this feature. To ensure portability of EXAMS'
character string storage and manipulations, the character strings
are stored in an unpacked format, that is, one character per
INTEGER location.
251
-------
Input
Simulation
Output
Figure 4.1. EXAMS Block Structure for Batch
Mode of Operation.
252
-------
in
a
d
253
-------
4,1,2 Resource Requirements
EXAMS has been implemented in FORTRAN IV as defined by the
ANS FORTRAN X.39-1966 report. The DEFINE FILE extension of the
standard is used for file manipulation, but standard sequential
I/O can be substituted with some sacrifice in speed of execution.
An overlay capability is required to implement EXAMS on small
computers such as the PDP-11 or HP 3000, The batch version
requires 64K bytes (overlaid) of memory (for aquatic systems of
up to 10 compartments); this version does not require mass
storage capabilities. The interactive version also requires 64K
bytes (overlaid) of memory, plus an additional mass storage
requirement. The interactive version of EXAMS requires 100K
bytes of mass storage for utility tiles, 2K bytes for each
chemical in the active files and 2.5K bytes for each active
defined environment. Execution times range from a few seconds to
several minutes depending on the problem to be solved. The
software is distributed on magnetic tape; the source code
consists of about 16,000 card images.
4,1,3 System Architecture
The batch version of EXAMS uses a driver routine to process
the input stream and invoice the simulation. The input stream
defines the simulation to be performed by specifying the name of
a compound, the name of an environment, and chemical loadings on
the selected environment. The input stream also includes the
chemical (compound) database and the environmental database.
After the names of the compound and environment and the chemical
loadings have been read, the driver sequentially searches the
remainder of the input stream (the chemical and environmental
databases) for the parameters associated with the compound and
environment specified in the input. Because the search is
sequential, the order of the data in the input stream is very
Important, that is, the name of the compound must precede the
name of the environment, and the chemical database must precede
the environmental database.
When the chemical and environmental data have been extracted
from the databases, the driver routine invokes the simulation
driver that controls program execution until the simulation is
complete. At the conclusion of the simulation, the main driver
regains control and execution ends. The main driver routine can
be rewritten to execute multiple runs, incorporate plotting and
statistical routines, etc. The simulation code need not be
•odlfied to support these enhancements,
The elements of a batch input stream occur in the following
254
-------
order (see section 3.4).
1. Name of compound
2. Name of environment
3. Loadings
4. Chemical dataoase
5. Environmental database
In the interactive version of EXAMS, the irain driver routine
used with the batch version is replaced with an executive
routine, utility routines, and a mass storage database. The
executive communicates with the user, deciphers the user's
inputs, and takes appropriate action based on these inputs. A
user can select compounds and environments, specify chemical
loadings, alter parameter values, invoice the simulation program,
store and retrieve user-defined chemical and environmental
parameters, request online assistance, print inputs and results,
and plot the results.
EXAMS acquires input from the user's terminal in the form of
a string of characters and deciphers the intent expressed in that
string. If the intent is recognized, the action is performed.
If it is not recognized, an appropriate message is printed on the
terminal. EXAMS' lexical analyzer deciphers the input string by
isolating groups of characters into lexical entities called
"tokens." The tokens are tested to determine whether they are
members of appropriate tables, A table may contain character
strings that represent the names of compounds, the names of
environments, keywords, etc., depending upon the relative
position of the token in the input string. For example, the
string
CHANGE MWT TO 437
has 4 tokens: CHANGE, M*fT, TO, and 437. CHANGE is compared with
a table of valid EXAMS commands, WT is compared with a table of
names of variables that can be CHANGEd. The token TO makes the
expression more readable; it is a necessary portion of the
command. The token 437 is converted to a floating point number
that is assigned to MWT.
Data elements in the recognition process include: a table
of tokens for matching the input string, the total number of
tokens, a vector containing the length of each token, and a
vector that contains the minimum length of each token required to
make it unique. For example, consider:
255
-------
TABLE x RUNSTOPPLOTCOMPOUNDSHQW
LEN a 3,4,4,8,4
MIN = 1,2,1,1,2
NUMBER x 5
Five tokens are in the recognition table: "TABLE" "RUN,"
"STOP," "PLOT," "COMPOUND," and "SHOW"; with corresponding
lengths of 3, 4, 4, 8, and 4 characters. The minimum lengths
required for uniqueness are 1, 2, 1, 1, and 2, respectively.
The recognition alogrithra first compares the length of the
input string with the length of each toicen in the recognition
table. If the length of the input string is greater than the
length of the toicen, the token is ignored. The length of the
next toicen is then tested; this process continues until all
entries in the recognition table are exhausted. If the length of
the input string is less than or equal to the length of the
current toicen, the toicen is a possible match. If the minimum
length required for uniqueness is less than or equal to the input
string, the input string is then compared against the token. If
the input string and the toicen agree, then the input string has
been recognized. If they do not agree, then the next toicen is
tested. This procedure continues until a match is made or until
all entries in the recognition table nave been exhausted. If no
match is made, the input string was not recognized.
Consider, for example, an input of "RU." The input string
has a computed length of 2. The input length is compared with
the length of the first entry in the recognition table (3) and
meets the criterion for length. The minimum length for this
entry is 1, and this test is also successful. Finally, the
character test is performed and a match is established.
4,1.4 Overlay structure
An overlay structure for the batch version of EXAMS is shown
in Figure 4.3 and an overlay structure for the interactive
version of EXAMS is shown in Figure 4.4.
256
-------
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257
-------
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258
-------
4.1.5 File Qrqanization
4.1,5.1 Environmental file
Environmental data are held in a single random access file.
The data are segregated into two Kinds of environmental
definitions: fixed or unCHANGEable data, and a user-defined
database available for interactive modification. Both datasets
in the file have the same structure, but they are created,
stored, and retrieved via different mechanisms.
The "fixed" environmental definitions are included with the
EXAMS distribution package. Their names are specified in the
BLOCK DATA portion of the code, in the variable "ECONAM." The
number of fixed definitions is stored in NOECOS, the vector
ECOLEN holds the lengths of the names, and the vector MINECO
holds the minimum length required to m.alce each name unique.
The fixed environment definitions are created by a utility
routine included in the EXAMS distribution. This utility
transfers the definitions from a sequential file to a random
access file. These fixed definitions can be retrieved by the
user, but these records cannot be altered from an interactive
terminal. This restriction was established to forestall
inadvertent modifications. The "fixed" database is accessed via
a reference to the name of the environment in an "ENVIRONMENT"
command.
User-defined environments can oe created, stored, retrieved,
and erased interactively. A fixed environment definition can be
retrieved, altered, and stored in the user-defined portion of the
database. "Fixed" databases (especially "UNS," the "unspecified"
environment) can be used as templates for loading new
environmental definitions (see Section 3.3.4).
User-defined environments are referred to by number, rather
than by name. The command "SHOW USER ENVIRONMENTS" displays a
table of contents of the user-defined environmental database.
All data associated with a user-defined environment can be
eliminated via the ERASE command. The cownand "ERASE ENVIRONMENT
N," where N is the number of the environment to be erased, sets
all numeric data to zero and all alphabetic data to blanks in the
Nth sector of the database.
The size of records in the database is a function of the
maximum number of compartments available to a particular
installation of EXAMS, This size is defined when EXAMS is
compiled. When the size is changed, the da»ta base must be
rebuilt. This database is built by a stand-alone utility routine
that is included with EXAMS, The data are arranged in the record
with the floating point (REAL) quantities first, followed by the
integer (INTEGER) quantities. The parameters NPX and NCON are
259
-------
used to define the system size of EXAMS and the layout and size
of the records in this file. The location assignments are shown
in Table 4.1. The position parameters used in this table (N, M,
K, and L) are related to NPX and NCON by: N=4*NCON, M=N+29*NPX,
K=L*N, and L
4.1.5.2 Chemical file
Chemical data are held in a single random access file. The
data are segregated into two Kinds of chemical definitions:
fixed or unCHANGEable data, and a user-defined database available
for interactive modification. Both datasets in the file have the
same structure, but they are created, stored, and retrieved via
different mechanisms.
The "fixed" chemical definitions are included with the EXAMS
distribution package. Their names are specified in the BLOCK
DATA portion of the code, in the variable "CMPNAM." The number of
fixed definitions is stored in NQNAME, the vector NAMLEN holds
the lengths of the names, and the vector MINCMP holds the minimum
length required to make each name unique.
The fixed chemical definitions are created by a utility
routine included in the EXAMS distribution. This routine
transfers the definitions from a sequential file to a random
access file. These fixed definitions can be retrieved by the
user, but these records cannot be altered from an interactive
terminal, This restriction was established to forestall
inadvertent modifications. The "fixed" database is accessed via
a reference to the name of the chemical in a "COMPOUND" command.
user-defined chemicals can be created, stored, retrieved,
and erased interactively. A fixed chemical definition can be
retrieved, altered, and stored in the user-defined portion of the
database. "Fixed" databases (especially "UMS," the "unspecified"
chemical} can be used as templates for loading new chemical
definitions (see Section 3.3.4).
User-defined chemicals are referred to by number, rather
than by name. The command "SHOW USER COMPOUNDS" displays a table
of contents of the user-defined chemical database. All data
associated with a user-defined chemical can be eliminated via the
ERASE command. The command "ERASE COMPOUND N," where N is the
number of the chemical to be erased, sets all numeric data to
zero and all alphabetic data to blanks in the Nth sector of the
database.
This database is built by a stand-alone utility routine that
is included with EXAMS. The data are arranged in the record with
the floating point (PEAL) quantities first, followed by the
integer (INTEGER) quantities. The location assignments are shown
in Table 4.2.
260
-------
Table 4.1, Location assignments for environmental file
Starting Ending Length Name Type
Position Position
1
NCON+1
3*NCONtl
N+NPX+1
N-H31NPX + 1
N+15*NPX+1
N+19*NPX+1
N + 2HNPX+1
N+23*NPX+1
N+24*NPX+1
N + 27*NPX-H
>X + 1
Mf 1
M + 42
L + l
L+NCON+1
K+l
K+NPX+2
NC3N
2*NCON
N+NPX
Nt4*NPX
N-»-8*NPX
N+10*NPX
N+11*NPX
N+12*NPX
Ntl4*NPX
N-»-24*NPX
N+26*NPX
Nf27*NPX
N-»-28*NPX
N+29*NPX
Mt39
M-^40
M-»-41
M + 42
L+NCON
Lf4*NCON
K+l
K-l-NPX-H
KtNPX+61
NCON
NCON
NCON
NCON
NPX
NPX
NPX
NPX
NPX
NPX
NPX
NPX
NPX
NPX
NPX
NPX
NPX
NPX
NPX
NPX
NPX
NPX
NPX
NPX
NPX
NPX
NPX
NPX
NPX
NPX
NPX
NPX
NPX
39
1
1
1
NCON
NCON
NCON
NCON
1
NPX
60
XSTUPG
CHAPLG
DSPG
ADVPRG
SDCHRG
FROCG
CECG
AECG
PCTWAG
TCELG
PHG
POHG
OXRADG
BIOMSG
PLPAG
BIOTMG
BACTOG
ACBACG
K0.2G
CMPETG
VOLG
AREAG
DEPTHG
EVAPG
STFLOG
STSEDG
NPSFLG
NPSEDG
1NTFLG
DFACG
DOCG
CHLG
WLAMG
CLOUDG
PAING
LATG
JFRADG
ITOADG
JTUPBG
ITURBG
KOUNT
TYPEE
SYSTYP
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
PEAL
REAL
REAL
REAL
PEAL
REAL
PEAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
INTEGER
261
-------
Table 4,2. Location assignments for chemical file
Starting I
Position P<
1
2
7
12
14
16
18
20
25
30
31
32
34
36
37
38
39
40
55
60
75
90
105
120
135
150
165
180
195
210
225
240
245
440
441
442
447
Ending
jsition
1
6
11
13
15
17
19
24
29
30
31
33
35
36
37
38
39
54
59
74
89
104
119
134
149
164
179
194
209
224
239
244
439
440
441
446
506
Length
1
5
5
2
2
2
2
5
5
1
1
2
1
1
1
1
1
1
5
15
15
15
15
15
15
15
15
15
15
15
15
5
195
1
1
5
60
Name
MWTG
SOLG
ESQLG
PKBG
EPKBG
PKAG
EPKAG
KPSG
KPBG
KO.CG
KOWG
KCECG
KAECG
KVOG
HENRYG
VAPRG
EVPRG
QUftNTG
KDPG
KAHG
EAHG
KNHG
ENHG
KBHG
EBHG
KOXG
EOXG
KBACWG
QTBAWG
KBACSG
OTBASG
RFLATG
ABSG
LAMAXG
EHENG
SPFLG
CHEMNA
Type
REAL
REAL
REAL
REAL
REAL
PEAL
REAL
REAL
REAL
REAL
REAL
PEAL
REAL
REAL
REAL
REAL
REAL-
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
INTEGER
INTEGER
262
-------
4.1,5.3 Online assistance file
The online assistance database is a sequential file; it is
organized oy keywords. Tnese keywords are designated by a M$" in
the first position of a record, information for a given keyword
continues until the next occurrence of a record with "$" in
position 1. The records are 80 characters long and a record with
"SEND" signals the end of the file.
4.1.5.4 Labeled COMMON variables file
This file is accessed in response to the HELP command. The names of the variables are specified in the
BLOCK DATA portion of the EXAMS code in the variaole "MODS." The
number of descriptions is stored in NOMQD, the vector MODLEN
holds the lengths of the names, and the vector MODMIN holds the
minimum length required to make each of the names unique.
The database is organized as a random access file. Each
record of the database corresponds to the name of a labeled
common variable and is 800 characters long. The database records
are created by a utility routine included in the EXAMS
distribution. This routine transfers the descriptions from a
sequential file to a random access file.
263
-------
4.1.7 Organization of EXAMS* Labeled COMMONS
EXAMS labeled COMMONS are described in Tables 4.3 through 4.23,
Table 4.3 Labeled COMMON BACTG sorted by name and by position,
Name
KBACSG
KBACWG
QTBASG
QTBAWG
Table 4.4
Name
EVAPG
LATG
RAING
W1NDG
Table 4.5
Name
SPFLG
Table 4.6
Name
ABSG
KDPG
LAMAXG
QUANTG
RFLATG
Position
31-45
1-15
46-60
16-30
Length
15
15
15
15
Labeled COMMON CLIMG
Position
2-11
12
1
13-22
Length
10
1
1
10
Labeled COMMON CQNTRG
Position
1
Length
5
Labeled COMMON DPHOTG
Position
26-220
16-20
221
1-15
21-25
Length
195
5
1
15
5
Name
KBACSG
QTBAWIG
KBACSG
QTBASG
sorted by
Name
PAING
EVAPG
LATG
tolNDG
sorted by
Name
SPFLG
sorted by
Name
QUANTG
KDPG
RFLATG
ABSG
LAMAXG
Position
1-15
16-30
31-45
45-60
name and by
Position
1
2-11
12
13-22
name and by
Position
1
name and by
Position
1-15
16-20
21-25
26-220
221
Length
15
15
15
15
position.
Length
1
10
1
10
position.
Length
6
position.
Length
15
5
5
195
1
264
-------
Table 4.7 Labeled COMMON FLOWG sorted by name and by position,
Name
INTFLG
NPSEDG
NPSFLG
STFLOG
STSEDG
Position
41-50
31-40
21-30
1-10
11-20
Length
10
10
10
10
10
Name
STFLOG
STSEDG
NPSFLG
NPSEDG
INTFLG
Position
1-10
11-20
21-30
31-40
41-50
Length
10
10
10
10
10
Table 4.8 Labeled COMMON GEOMT sorted by name and by position,
Name
AREAG
DEPTHG
VOLG
Position
11-20
21-30
1-10
Length
10
10
10
Name
VOLG
AREAG
DEPTHG
Position
1-10
11-20
21-30
Length
10
10
10
Table 4.9 Labeled COMMON HYDROG sorted by name and by position,
Name
EAHG
EBHG
ENHG
KAHG
KBHG
KNHG
Position
16-30
76-90
46-60
1-15
61-75
31-45
Length
15
15
15
15
15
15
Name
KAHG
EAHG
KNHG
ENHG
KBHG
EBHG
Position
1-15
16-30
31-45
46-60
61-75
76-90
Length
15
15
15
15
15
15
265
-------
Table 4.11 Labeled COMMON IONG sorted cy nase and by position.
Name
EPKAG
EPKBG
PKAG
PKBG
Table 4.12
Position Lengt
7-8
3-4
5-6
1-2
Labeled COMMON
h
2
2
2
2
*iaire
PKBG
EPKBG
PKAG
EPKAG
LOADSG sorted
Position
1-2
3-4
5-6
7-8
oy narce and by
Length
2
2
2
2
posit
Name
Position Length
K' a in e
Position Length
DPFLDG
IFLLDG
NPSLDG
PCPLDG
STRLDG
31-40
41-50
11-20
21-30
1-10
10
10
10
10
10
STRLDG
NPSLDG
PCPLDG
DPFLDG
IFLLDG
1-10
11-20
21-30
31-40
41-50
10
10
10
10
10
Table 4,13 Labeled COMMON NAME1G sorted by name and by position.
Name
«*•••»•*!
CHEMNA
Position Length
»mmmmmmm~*mmm
-------
Table 4.15 Labeled COMMON OXIDG sorted by na*e and by position.
Mane
EOXG
KOXG
Table 4.16
Name
KAECG
KCECG
KOCG
KOWG
KPBG
KPSG
Table 4.17
Name
ESOLG
MWTG
SOLG
Table 4.18
Name
CHLG
CLOUDG
CMPETG
OGACG
DOCG
WLAMG
Position
16-30
1-15
Labeled
Position
15-16
U-14
11
12
6-10
1-5
Labeled
Position
7-11
1
2-6
Length
15
15
COMMON PART
Length
2
2
1
1
5
5
Name
KOXG
EOXG
G sorted by
Nasre
KPSG
KPBG
KOCG
KOrtG
KCECG
KAECG
COMMON PCHEMG sorted by
Length
5
1
5
Labeled COMMON PHOG
Position
21-30
70
1-10
71-80
11-20
31-69
Length
10
1
10
10
10
39
Name
MfcTG
SOLG
ESOLG
Position
1-15
16-30
name and by
Position
1-5
6-10
11
12
13-14
15-16
name and by
Position
1
2-6
7-11
Length
15
15
position.
Length
5
5
1
1
2
2
position.
Length
1
5
5
sorted by name and by position.
Name
CMPETG
DOCG
CHLG
WLAMG
CLOUDG
DFACG
Position
1-10
11-20
21-30
31-69
70
71-80
Length
10
10
10
39
1
10
268
-------
Table 4.22 Labeled COMMON UNITS sorted by name and by position,
Name
Position Length
Na*e
Position Length
AUDOUT
INCOMP
INDEF
INCNVR
INHLP
KINOUT
RPTOUT
SSOUT
TIYIN
TTYOUT
6
7
8
10
9
3
1
2
4
5
1
1
1
1
1
1
1
1
1
1
RPTOUT
SSOUT
KINOUT
TTYI*
TTYOUT
AUDOUT
INCOMP
INDEF
INHLP
INENVR
1
2
3
4
5
6
7
8
9
10
1
1
1
1
1
1
1
1
1
1
Table 4.23 Labeled COMMON VOLATG sorted by nave and by position,
Mane
Position Length
Nave
Position Length
EHENG
EVPRG
HENRYG
KVOG
VAPRG
3
5
2
1
4
1
1
1
1
1
KVOG
HEWRYG
EHENG
VAPRG
EVPRG
1
2
3
4
5
1
1
1
1
1
270
-------
4.2 Implementation Notes
4.2.1 PDP-11/70, IAS, Batch version
1. Mount the Files-11 tape, e.g.,
MOUNT/NOOP/DEN:1600 MMO: EXAMS
2. COPY MMO:*.*?* *.*;*
3. Execute the command files FOTOX.C*D and LNTOX.CMD to compile
and task-build EXAMS.
4, Run EXAMS as follows.
PDS> RUN EXAMS
The results should be compared with the sample output listing
supplied with the distribution package (Section 3.1) to verify
that EXAMS has been installed correctly.
4.2.2 PDP-11/70, IAS, Interactive Version
1. Mount the Files-11 tape, e. g.,
MOUNT/NDOP/DEN:1600 MMO: EXAMS
2. COPY MMO: [*,*]*.*;* *.*;*
3. Edit file BUILD.BIS TO REFLECT YOUR USER IDENTIFICATION ON
THE "$JOBM CARD.
4, SUBMIT FILE BUILD.BIS to the batch stream. BUILD.BIS creates
the necessary random access files used by EXAMS and the EXAMS
task image. When the batch job finishes EXAMS is ready for use
and may be invoiced by entering the following command.
PDS> RUN EXAMS
271
-------
4,2,3 IBM-370, os/MVS, Batch Version
1. Because of the wide variety of IBM 360/370/3032/3033
configurations, a specific instruction for the installation of
EXAMS is not provided. The JCL that was used to install EXAMS on
EPA's IBM computer is provided as a guide, however.
Installation dependent JOB card
//S EXEC FORTHCLG
//FORT.SY5IN 00 *
File No. 6 of the distribution tape,
//LKED.SYSLMOD DD DlSPs(NEW,CATLG)
// VOL*SER=USERXX,
// UNIT=3330-1,SPACE=(TRK,20,20,1),RLSE),
// DCB=BLKSIZE=13030,
// DSNsAESOP(AESOP)
//GO.FT03F001 DD DUMMY,DCB=BLKSIZE=1000
//GO.FT04F001 DD DUMMY,DCBsBLKSlZE=1000
//GO.SYSIN DD *
File Mo. 7 of the distribution tape
File No, 8 of the distribution tape
File NO, 9 of the distribution tape
Note: Either the *G' or the 'H' level FORTRAN compiler can be
used. The results should be compared with the enclosed sample
output listing (Section 3,1) to verify that EXAMS has been
installed correctly,
2, The following JCL is used to execute EXAMS from the stored
load module.
Installation dependent JOB card
//GO EXEC PGM=AESOP
//STEPLIB DD DISP*SHR,DSNsAESOP
//GO.FT03F001 DD DUMMY,DCB=BLKSIZEslOOO
//GO.FT04F001 DD DUMMY,DCB*BLKSIZE*1000
//GO.FT06F001 DD SYSOUTsA,DCB»(LRECLsl33,RECFM*FBA,BLKSIZE»1330)
//GO.FT05F001 DD *
FILE NO. 7 OF THE DISTRIBUTION TAPE
FILE NO, 8 OF THE DISTRIBUTION TAPE
FILE NO, 9 OF THE DISTRIBUTION TAPE
272
-------
4.2.4 IBM TSO Interactive 10-Compartment version
File 1 contains a sample run stream that can be used to build the
compound and environment files. The run stream:
1. Creates a skeletal random access file for the chemical data.
The file that is created ("COMPOUND.DATA,") is accessed by EXAMS
via Logical Unit Number (LUN) 7. In order to accommodate 506
REAL variables, the record length for this file is 2024 bytes.
2. Creates a skeletal random access file for environmental data.
The file that is created ("ENVIRO.DATA,") is referred to by EXAMS
as LUN 10. In order to accommodate 643 REAL variables, the
record lenqth for this file is 2572 bytes.
3. Transfers the information stored in the sequential datasets
defined by FORTRAN units 1 and 2 to the random access datasets
created in steps 1 and 2,
The run stream should be modified to conform with your
installation policies.
File 2 contains a sample run stream used to build the sequential
file required to support the on-line HELP utility. The file,
HELP.DATA, is 80 characters long and is referred to by EXAMS as
LUN 9.
File 3 contains a sample run stream used to build the random
access file, DESDEF.DATA, that supports the on-line "HELP
variable" and "DESCRIBE variable" commands. The records in the
file are 800 characters long; the file is accessed by EXAMS via
LUN 8.
File 4 contains the EXAMS source code without any job control
language. The code consists of 9619 source images and 6052
comment images. The code should be compiled and linked into a
dataset that is accessible by TSO.
File 5 contains a sample TSO CLIST that can be used to allocate
the datasets necessary to execute EXAMS.
4.3 Special Installations
4.3.1 EXAMS at NCC-IBM
To use the interactive version of EXAMS at NCC-IBM, the
following steps should be issued while logged on to TSO.
273
-------
> This first step need be executed only once. It
copies the necessary datasets to your account;
these datasets assume permanent residence on your
account.
EXEC 'CN.EPADMC.A324.COPyiO.CLIST'
EXAMS, by entering
> Thereafter, execute
following command:
the
EXEC EXAMS10
An introductory message will be printed at your terminal,
followed by the EXAMS prompt:
EXAMS >
A listing of dataset, EXAMS10.CLIST, follows.
USING(INPUT)
FREEALL
ATTRIB INPUT RECFM(F) LRECL(BO)
ALLOCATE DATASETC*) FILE(FT05F001)
DATASET(*) FILE(FT06F001)
DATASETeCOMPOUND.DATA) FILE(FT07FOOi) SHR
DATASET(ENVIRO.DATA) FILE (FTlOFOOi) SHR
DATASET(DESDEF.DATA) FILE(FT08FOOi) SHR
DATASET(HELP.DATA) FILECFT09F001) SHR
RECFM(F) LRECL(SO) BLKSIZE(SOO)
RECFM(V S) LRECL(80) BLKSIZE(800)
ALLOCATE
ALLOCATE
ALLOCATE
ALLOCATE
ALLOCATE
ATTRIB FT02
ATTRIB FT03
ATTRIB FT04 RECFM(V S) LRECL(SO) BLKSIZE(800)
ALLOC DA(TEMPi) F(FT02F001) NEW DELETE USINGCFT02)-
BLOCKC800) SPACE(50,50)
ALLOC DA(TEMP2) F(FT03F001) NEW DELETE USINGCFT03)-
BLOCK(800) SPACE(50,50)
ALLOC DA(TEMP3) F(FT04F001) NEW DELETE USING(FT04)-
BLOCK(SOO) SPACE(50,50)
CALL EXAMSIO(EXAMSIO)
The load module for the batch version of EXAMS
cataloged and named:
CN.EPAOMC.A324.EXAMS10B.LOAD(EXAMS10B)
is
274
-------
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287
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GLOSSARY FOR EXAMS' COMPUTATIONAL SUBROUTINES
This glossary contains an alphabetical listing of all COMMON
variables of EXAMS' computational subroutines. For each
variable, this glossary gives:
Logical (L)
(V), or Matrix
(39,5))
(M)
> Name of the variable
> Location (e.g., labeled common XXXX)
> Data type: Real (R), Integer (I), or
> Dimension type: scalar (S), vector
> Numerical size of dimensions (e.g.,
> Definition of the variable
> Units (as a separate line in the case of input variables)
> List of computational subroutines requiring the variable
Input variables can also be identified by the terminal letter in
the variable name (G for Global, e.g., VOLG). All variables that
include a vector dimension determined by the maximum number of
compartments available to define a system are designated "NPX."
ABSG(39,5) in labeled common DPHOTG (R,M)
Absorption spectrum (molar extinction coefficients) for each (of
5 possible) ionic species of the chemical, average values over
each of 39 wavelength intervals. The 39 wavelength intervals are
defined in Table 2.18 (Section 2.3.3).
ABSGU,!) —
ABSG(I,2) -
ABSGU,3) -
ABSGU,4) —
ABSGU,5) —
absorption spectrum of neutral molecule (SH2)
absorption spectrum of singly charged cation (SH3+)
absorption spectrum of doubly charged cation (SH4++)
absorption spectrum of singly charg&i *nion (SH-)
absorption spectrum of doubly charges anion (S«)
Units: /cm/(mole/Liter) (decadic)
Subroutines: FIRORD, PHOT02, PRCHEM
ACBACG(NPX) in labeled common QUALG (R,V)
Proportion of bacterial population that actively degrades
synthetic organic chemical. If the biolysis rate constants are
not based on natural mixed bacterial populations, the total
bacterial populations (BACTOG) given for each compartment can be
modified (via ACBACG) to give the size of the population that is
actively degrading the chemical.
288
-------
Units: dimensionless ratio, nominal range 0.0 to 1,0
Subroutines: FIRQRD, PRENV
ADVPRG(3*NPX) in labeled common SETUPG (R,V)
Proportion of total advective flow leaving compartment JFRADG
that is delivered to compartment ITOADG. Although usually 1.0,
this feature allows for downstream branching, loop flows, etc.
An error condition is raised if the ftDVpRSs for a given
compartment sum to neither o nor 1.
Units: dinensionless
Subroutines: PPEMV, WATADV
AECG(IPX) in labeled common SED*G (R,V)
Anion exchange capacity of sediments in each compartment. This
parameter is useful in relating sediment sorption (partitioning)
of anions to a variable characteristic of system sediments.
Units: milliequivalents/100 grams dry weight
Subroutines: DISTRB, PRENV
ALPHA(18,MPX) in labeled common PAPT1L CP,M)
The 18 values of ALPHA are distribution coefficients (fraction of
total concentration of chemical (Y) present as a particular
species/form configuration of the molecule), for each ecosystem
compartment. Each ALPHA vector allows for partitioning among 5
chemical species (neutral molecule, singly or doubly charged
anions and cations), with each species potentially partitioned
among 3 physical forms (dissolved, sediment-sorbed, biosorbed).
The 3 regaining elements in the vector are used for the total
dissolved, sedimen.t-sorbed, and bio-sorbed distribution
coefficients.
ALPHA(1,J) •• fraction of chemical present as the neutral
molecule (SH2) dissolved in the water phase of the compartment.
ALPHA(2,J) -- fraction present as neutral molecule sorbed with
sediment phase of compartment.
ALPHA(3,J) -- fraction present as neutral molecule sorbed with
compartment bloirass.
ALPHA(4,J) -- fraction of chemical present as dissolved singly
charged cation generated by base dissociation or
SH2 -f H20 <---> SH3* + OH-
in the water phase of the compartments.
ALPHA(5,J) ** fraction of chemical present as SH3+ sorbed with
sedinent phase of compartment.
289
-------
ALPHA(6,J) -- fraction of chemical present as biosorbed SH3 + .
ALPHA(7,J) -• fraction of chemical present as a dissolved, doubly
charged cation (SH4++) via base dissociation or
SH3+ + H20 <-«> SH4 + t + OH-
in the water phase of each compartment.
ALPHA(8,J) •» fraction of chemical present as SH4+ + sorbed with
sediment phase of compartment J.
ALPHA(9,J) »- fraction of chemical present as biosorbed SH4+ + in
compartment J.
ALPHA(10,J) — fraction present as singly charged anion (SH-)
produced from organic acid via
SH2 «• H20 <— -> H30+ + SH-
dissolved in water phase of compartment J.
ALPHA(11,J) -- fraction present as SH- sorbed with sediments
ALPHA(12,J) -- fraction present as oiosorbed SH-.
ALPHA (1 3, J) -• fraction of chemical concentration present as
doubly charged anion dissolved in water phase of compartment J,
produced by
SH- * H20 <-— > H30+ + S«
ALPHA(14,J) -- fraction present as s= sorbed to sediment phase J.
ALPHA(l5,J) »* fraction present as biosorbed S=.
ALPHA(16,J) -- fraction of total concentration .present in
dissolved for* in the water phase of compartment J, Sum of
ALPHA(1,J) + ALPHA(4,J) + ALPHA(7,J) + ALPHA(10rJ) + ALPHA(13,J).
ALPHA(17,J) — fraction of total concentration present as
sedlment-sorbed Molecules in compartment J. Sui of ALPHA(2,J) +
ALPHA(5,J) + ALPHA(8rJ) + ALPHA(11,J) 4 ALPHA(14,J).
ALPHA(18rJ) ** fraction of total concentration present as
biosorbed species of the chemical. Sum of ALPHAU3, 6, 9, 12,
15), J).
subroutines: AVEOUT, DISPER, DISTRB, FIROBD, OUTP, STEADY
AREAG(NPX) In labeled common GEOMT (F,V)
Area of ecosystem elements (compartments). This variable is used
290
-------
(inter alia) to convert steady-state masses of chemical captured
in each compartment to a grams/square meter basis. For
(E)pilimnion and (L)ittoral compartments, AREAG(J) is the area of
the air-water interface; for (H)ypolinrnion compartments AREAG is
the area of the tnermocline; for (B)enthic compartments it is
the surface area of the bottom. In the latter case APEAG may
differ from XSTURG in a dispersive exchange pair because of a
reduction in exchanging area due to rock outcrops, etc.
Units: square meters
Subroutines: AVEQUT, DISTRB, FLOWS, OUTP, PRENV, VOLAT
B in labeled common SETUPL (I,S)
Letter code for detecting (B)enthic compartments.
subroutines: BLOCK DATA, DISTRB, GHOST, FIRORD, FLOWS, PRENV
BATCH in labeled common SETUPG (I,S)
Flag for indicating batch vs. interactive control. Batch mode is
denoted by BATCH set to 1; interactive mode by BATCH set to 0.
Computational subroutines: BLOCK DATA, PRCHEM, PRENV, STEADY
Interactive subroutines: LISSTP, MAIN, SHOW
BACTOG(NPX) in labeled common QUALG (R,V)
Bacterial population density in each compartment.
Units: Water column compartments: cells/milliliter
Benthic compartments: cells/100 grams dry weight of sediment
Subroutines: FIRORD, PRENV
BIOLKL(NPX) in labeled common CHEM1L (R,V)
Total pseudo-first-order degradation rate constant (/hr) for
bacterial biolysis in each compartment.
Subroutines: FIRORD, FLXOUT
BIOMSG(NPX) in labeled common QUALG (R,V)
Total actively sorbing biomass in each ecosystem compartment.
This parameter is used in computation of sorption of the chemical
with plant/animal material in the ecosystem compartments. The
parameter is interpreted differently for the water column vs.
the benthic compartments. For a water column compartment, total
biomass must be expressed as mg (dry weight)/Liter of water in
the compartment, and it may include all biomass subject to
biosorptive exchange with that water -- i.e., plankton plus
benthic algae, macrophyte leaves, etc. Parameter PLRAG (the
PLankton RAtio) gives the fraction of this total .biomass that is
passively transported by advective and dispersive water movement.
In the case of benthic compartments, BIOKSG is the total biomass
of the benthic infauna etc. in grams (dry weight) per square
meter of bottom. Once again the PLRAG for each (B)enthlc
291
-------
compartment Indicates that fraction of the biomass that is not
firmly fixed in the bottom, but can be transported by turbulent
and advective motions -- thus distinguishing, for example, plant
roots and bivalves from smaller creatures such as planaria or
amphipods.
Units: water column compartments: tig (dry weight)/Liter
Benthic compartments: grams (dry weight)/square meter
Subroutines: DISTRB, PRENV
BIOPCT in labeled common RESLT (R,5)
Percentage of total chemical load on the system that is consumed
via biolysis at steady state.
Subroutines: FLXOUT, SUMUP
BIOTMG(NPX) in labeled common QUALG (R,V)
Biotemperature in each ecosystem compartment, i.e., temperature
to be used in conjunction with Q-10 expressions for biolysis rate
constants. This parameter is separated from the physical
temperature input data (TCELG) in order that the input data can
reflect Q-10 averaging of an observed temperature time-series.
Units: degrees C.
subroutines: FIRORO, PRENV
BIOTOL(NPX) in labeled common MASSL (R,V)
Compartment biomasses converted to internal units (kg (dry) per
liter of water content).
Subroutines: AVEOUT, DISTRB, OUTP
BOTLAM(39) in labeled common ENPARL (R,V)
On entrance to subroutine PHOT02, BOTLAM holds the spectral
irradiance at the bottom of the last previous ecosystem
compartment evaluated by the routine. On exit from PHOT02,
BOTLAM contains the spectral irradiance at the bottom of the
current water column compartment.
Subroutines: PHOT02
BOTLIT in labeled common ENPARL (R,S)
On entrance to subroutine PHOTOl, BOTLIT contains the relative
(to surface light) light intensity at the bottom of the last
previous water-column compartment evaluated by the routine. On
exit from PHOTOt, BOTLIT contains the relative light intensity at
the bottom of the current compartment.
Subroutines: PHOTOl
CECG(NPX) in labeled common SEDMG (R,V)
Cation exchange capacity of sediments in each compartment. This
292
-------
parameter is of utility in relating sediment sorption
(partitioning) of cations to a variable characteristic of system
sediments.
Units: milliequivaients/100 grams dry weight of sediment
Subroutines: DISTRB, PRENV
CHARLG(3*NPX) in labeled common SF.TUPG (R,V)
Characteristic length (average of compartment dimensions or
mixing lengths) for the dispersive exchange pairing given by the
corresponding compartment numbers of JTUPBG and 1TURBG. A given
compartment may have different mixing lengths in different
exchange Pairings.
Units: meters
subroutines: DISPER, PRF.NV
CHEMNA(60) in labeled common NAME1G (input data) (I,V)
CHEMNA holds the name of the synthetic organic chemical, with up
to 60 characters permitted. CHEMNA is used in the headings for
the data written to the output files of the program.
Units: Alphameric characters
Subroutines: AVEOUT, FIRORD, FLXOUT, GHOST, PRCHEM, PRENV
CHEMPC in labeled common RESLT (R,S)
Percentage of total chemical load on the system that is consumed
via all chemical transformation processes at steady state.
Subroutines: FLXOUT, SUMUP
CHLG(NPX) in labeled common PHOG (R,V)
Concentration of chlorophyll and chlorophyll-liice pigments in
water column compartments. (Dummy variable in benthic
compartments.-)
Units: milligrams/Liter
Subroutines: PHOT02, PRENy
CLOUDG in labeled common PHOG (R,S)
Average cloudiness in tenths of full sky cover.
Units: dimensionless, range of 0,0 to 10.0
Subroutines: PHOioi, PHOT02, PRENV
CMPETG(NPX) in labeled common PHOG (R,V)
Single-valued zenith light extinction coefficient for water
columns, dummy variable for benthic compartments.
Units: /meter
Subroutines: PHOTOI, DATAIN
293
-------
CONLDl(NpX) in labeled common MISCL (R,V)
Numerical rate of Increase (mg/L/hr) of chemical concentration in
each compartment as a result of external loadings.
subroutines: FIRORD, STEADY
DEPTHG(NPX) in labeled common GEOMT (R,V)
Average depth of each compartment.
Units: meters
Subroutines: PHOT01, PHOT02, PRENV
DFACG(NPX) in labeled common PHOG (R,V)
Distribution function (ratio of optical path length to vertical
depth) for each compartment. (Dummy variable for benthic
sediments.)
Units: dimensionless, values constrained to range of 1.0 to 2,0
Subroutines: PHOTOi, PHOT02, PRENV
DOCETAO9) in labeled common DPHOTL (R,V)
Spectral light absorption coefficients ( /m/(mg/D) for dissolved
organic carbon. Values and data sources given in Section 2.3.3,
subroutines: BLOCK DATA, PHOT02, PRENV
DOCG(NPX) in labeled common PHOG (R,V)
Dissolved organic carbon concentration in water column
compartments. (Dummy variable for benthic compartments.)
Units: mg/Liter
Subroutines: PHOT02, PRENV
DOMAX(IO) in labeled common RESLT (P,V)
Storage locations for maximum values at steady-state.
DOMAXU) -« maximum value of Z(ll) in the water column
DOMAX(2) -- maximum value of Z(7) in the water column
DOMAX(3) -- maximum value of Z(8) in the water column
DOMAX(4) -- maximum value of Z(9) in the water column
DOMAX(S) -- maximum value of Z(10) in the water column
DOMAXC6) — Maximum value of Z(ll) in the bottom sediments
DOMAX(7) •- maximum value of Z(7) in the bottom sediments
DOMAX(8) — maximum value of Z(8) in the bottom sediments
DOMAXC9) — maximum value of Z(9) in the bottom sediments
DOMAX(IO) •• maximum value of ZUO) in the bottom sediments
subroutines: AVEOUT, SUMUP
DOMIN(IO) in labeled common RESLT (R,V)
Storage locations for Minimum values at steady-state.
294
-------
DOMIN
DOMIN
DOMIN
DOMIN
DOMIN
DOMIN
DOMIN
DOMIN
DOMIN
DOMIN
(
(
(
I
(
(
(
(
(
(
1
2
3
4
5
6
7
8
9
1
)
)
)
)
)
)
)
)
)
0
m
)
m
m
niniflnu:n
minimiiT
minimuTi
minimum
minimum
m i n i m u T!
TinimuT!
minimum
-Ti i n i m u T>
- minimum
value
value
value
value
value
value
value
value
value
value
of
of
of
of
of
of
of
of
of
of
Z
Z
Z
Z
Z
Z
Z
Z
Z
;il) in the water column
;7) in the water column
;3) in the water column
;9) in the water column
;iO) in the *ater column
!11) in the oottom sediments
.7) in the bottom sediments
!8) in the bottorr sediments
;9) in the bottom sediments
U10) in the bottom sediments
Subroutines: AVEOUT
DRFLDG(NPX) in labeled common LOADSG (R,V)
Drift loadings (aerial drift, direct applications,
etc.) of chemical on eacn system element.
Units: leg/hour
Subroutines: CKLOAD, STEADY
stack fallout,
DSPG(3*NPX) in labeled common SETUPG CP,V)
Eddy diffusivity to be applied to the dispersive exchange pairing
given by the corresponding compartment numbers of JTURBG and
ITURBG. In the case of horizontal mixing DSPG is the
longitudinal dispersion coefficient, for vertical mixing it may
represent exchange across the thermocline or exchanges with
bottoin sediments. In the latter case DSPG is a composite of
direct sorption to the sediment surface, mixing of the sediments
oy benthic animals, stirring by demersal fishes, etc.
units: square meters/hour
Subroutines: DISPER, PRENV
E in labeled common SETUPL (I,S)
Letter code for detecting (E)pilimnion compartments.
Subroutines: BLOCK DATA, DISTRB, FLOWS, GHOST, PHOT01, PHOT02
EAHG(3,5) in labeled common HYDROG (R,M)
Arrhenius activation energy of specific-acid-catalyzed hydrolysis
of the chemical. Matrix indices allow entry of the data as
separate values for each chemical species/physical form
configuration of the molecule.
EAHG(1,1)
EAHGC2,!)
EAHG(3,1)
EAHG(1,2)
EAHG(2,2)
EAHG(3,2)
EAHGC1,3)
datum
datum
datum
datum
datum
datum
datum
applicable
applicable
applicable
applicable
applicable
applicable
applicable
to dissolved SH2
to sediment-sorbed SH2
to biosorbed SH2
to dissolved SH3+
to sediment-sorbed SH3+
to biosorbed SH3+
to dissolved SH4++
295
-------
EAHG(2,3) — datum
EAHG(3,3) — datum
£AHG<1,4) -- datum
EAHG(2,4) -- datum
EAHG(3,4) — datum
EAHG(1,5) — datum
EAHG(2,5) -- datum
EAHG(3,5) — datum
applicable
applicaole
applicable
applicable
applicable
applicable
applicable
applicable
to sedlment-sorbed SH4++
to bibsorbed SH4*t
to dissolved SH-
to sediment-sorbed SH-
to biosorbed SH-
to dissolved S=
to sediment-sorbed S=
to biosorbed S*
Units: kcal/gram mole
Subroutines: FIRORD, PRCHEM
EBHG(3,5) in labeled common HYDROG (R,M)
Arrhenius activation energy of specific-base-catalyzed hydrolysis
of the chemical. Matrix indices allow entry of the data as
separate values for eacn chemical species/physical form
configuration of the molecule. The IS species/form indices are
given as part of the definition of EAHG above.
Units: fccal/gram mole
Subroutines: FIRORD, PRCHEM
EHENG in labeled common VOLATG (R,S)
Parameter used to compute Henry's law constants as a function of
environmental temperatures (TCELG). When EHENG is non-zero, the
Henry's law constant is computed as follows:
log HENRY -s. HENRYG-((1000.*EHENG)/(4.58*(TCELG+273.15)))
Units: kcal/gram mole
Subroutines: PRCHEM, VOLAT
ENHG(3,5) in labeled common HYDROG (R,M)
Arrhenius activation energy of neutral hydrolysis of the
chemical. Matrix indices allow entry of the data as separate
values for each chemical species/physical form configuration of
the molecule. The 15 species/form indices are given as part of
the definition of EAHG above.
Units: Kcal/gram mole
Subroutines: FIRORD, PRCHEM
EOXG(3,5) in labeled common OXIDG (R,M)
Arrhenius activation energy of oxidative transformation of the
chemical. Matrix indices allow entry of the data as separate
values for each chemical species/physical forn configuration of
the molecule. The 15 species/form indices are given as part of
the definition of EAHG above.
Units: fecal/gram mole
Subroutines: FIRORD, PRCHEM
296
-------
EPKAG(2) in labeled common IONG (K,V)
Exponential term (see PKAG) for acid dissociation
chemical (Ka). EPKAGU) is datum for generation of
EPKAGC2) is datum for generation of S= fron SH-.
Units: kcal/gram nole
Subroutines: DISTR8, PPCHEM
constants of
SH- from SH2;
EPKBG(2) in labeled common IONG (R,V)
Exponential term (see PKBG) for base dissociation constants of
chemical (Kb). EPK8GU) is datum for generation of SH3+ from
SH2; EPK8G(2) is datum for generation of SH4++ from SH3 + .
Units: Kcal/gram mole
Subroutines: DISTPB, PRCHE*
ESOLG(5) in labeled common PCHEMG (R,V)
Exponential term for describing solubility of
function of temperature (see SOLG).
the chemical as
ESOLG(i) -
ESOLG(2)
ESOLGC3)
ESQLG(4)
ESOLG(5)
- datum for solubility of SH2
datum for solubility of SH3+
datum for solubility of SH4++
datum for solubility of SH-
datum for solubility of S=
Units: fccal/gram mole
Subroutines: CKLOAD, PRCHEM, VOLAT
EVAPG(NPX) in labeled common CLIMG (P,V)
Evaporative water losses from ecosystem compartments.
Units: nsillinjeters/month
Subroutines: FLOWS, PRENV
EVAPL(MPX) in labeled common FLOWSL (R,V)
Evaporative water losses converted to internal units (L/hr)
Subroutines: FLOWS
EVPRG in labeled comnon VDLATG (R,S)
Molar heat of vaporization for vapor pressure
function of temperature (see VAPRG).
Units: kcal/gram mole
Subroutines: PRCHEM, VOLAT
described as a
EXPOKL(NPX) in labeled common CHEP1L (P,V)
Pseudo-first-order rate constant (/hr) expressing rate of
decrease of chemical concentration in each conpartaent resulting
fro* entrained exports of chemical leaving the system.
297
-------
subroutines: FIRORD, FLXOUT
EXPPCT in labeled common RESLT (R,S)
Percent of total chemical load that is exported from the system
at steady state.
Subroutines: FLXOUT, SUMUP
FROCG(NPX) in labeled common SEDMG (R,V)
Organic carbon content of compartment sediments as fraction of
dry weight. Parameter is coupled to KDCG to generate the
sediment partition coefficient for SH2 as a function of a
property (FROCG) of the sediment.
Units: dimensionless weight ratio
Subroutines: DISTRB, PRENV
H in labeled common SETUPL (I,S)
Letter code for detecting (H)ypolimnion compartments.
subroutines: BLOCK DATA, DISTRB, FIRORD, FLOWS, GHOST, PHOTOI,
PHOT02
HENRYG In labeled common VOLATG (R,S)
Henry's la* constant of the chemical. If parameter EHENG is
non-zero, HENRYG is used as the pre-exponential factor in
computing the Henry's law constant as a function of environmental
temperatures (TCELG).
Units: atmosphere-cubic meters/mole
Subroutines: FIRORD, PRCHEM, VOLAT
HYDRKL(NPX) in labeled common CHEM1L (R,V)
Total pseudo-first-order rate constant (/hr) for hydrolytic
transformations of the chemical in each compartment.
subroutines: FIRORD, FLXOUT
ICALL in labeled common SETUPL (I,S)
ICALL is an internal flag used in subroutine PHOT02 to Indicate
that the surface light field has been filled out to full
wavelength Intervals and pre-multiplied by a numerical conversion
factor.
Subroutines: GHOST, PHOT02
IFLAG in labeled common TIHEL (internal variable) (I,S)
IFLAG is an internal program monitoring flag. It is used to
control subsequent operations when any of a number of error
conditions are encountered.
Subroutines: CKLOAD, DISTRB, DRIVER, FLOWS, GHOST, PRENV,
298
-------
SEDADV, STEADY, SUMUP,
IFLLDG(NPX) in labeled common L3ADSG (R,V)
Chemical loadings entering the system via interflows (all
subsurface water flows entering via a sediment compartment).
units: kilograms/hour
Subroutines: CKLOAD, STEADY
INDEXS(NPX) in labeled common SETUPL (I,v)
INDEXS is a vector of flags designating oenthic compartments.
1NDEXS is 1 for (B)enthic sediments, 0 otherwise.
Subroutines: AVEOUT, DISPER, D1STRB, FIRORD, FLXOUT, OUTP,
SEDADV
INDEXW(NPX) in labeled common SETUPL (J,V)
INDEXW is a vector of flags designating water column
compartments. It tafces a value of 1 for E, H, and L compartments
and a value of 0 for 8 compartments.
Subroutines: AVEOUT, DISPER, DISTRB, FIRDRO, FLOWS
INTFL(NPX) in labeled common FLQwSf, (F,V)
Compartment interflows converted to internal units (liters/hr).
Subroutines: CKLOAO,
INTFLG(NPX) in labeled common FLOfcG (R,V)
Interflow (subsurface water flow) entering each ecosystem
compartment. Assumed to involve a flow of water only, usually
entering the system via a sediment compartment.
Units: cubic meters/hour
Subroutines: FLOWS, PRENV
INTINL(NPX,NPX) in labeled common CHEM1L (R,M)
Matrix of pseudo-first-order coefficients (/hr) expressing rate
of increase of chemical concentration in receiving compartments
due to internal flows of water, sediments, and plankton among
ecosystem compartments.
Subroutines: FCT, FDER, FIRORD, STEADY
ITOADG(3*NPX) in labeled common SETUPG (I,V)
Index vector containing compartment numbers designating the
compartments to receive advective flow from the compartment
occupying the corresponding position in vector JFRADG (i.e.,
ITOADG(K) and JFRADG(K) define an advective transport pathway of
the system). (0,0) pairs are interpreted as empty storage
locations, i.e., inactive pathways. 1TOADG can contain a 0
299
-------
paired with a non-zero value in JFRADG to indicate an export
pathway. If the program encounters a compartment number greater
than KOUM (the number of compartments used to define the
system), an error condition is raised. (see also ADVPRG,
JFRADG.)
Units: dimensionless integer number
subroutines: WATADV, PRENv
ITUHBG(3*NpX) in labeled common SETUPG (I,V)
Index vector containing compartment numbers that, with the
compartment number found at the corresponding location of JTURBG,
define a dispersive transport pathway of the system. (0,0) pairs
are interpreted as inactive pathways. A 0 in ITURBG paired with
a non-zero compartment number in JTURBG is interpreted as a
boundary condition with a clean (zero synthetic chemical)
water-body. If the program encounters a compartment number
greater than KOUNT (the number of compartments used to define the
system), an error condition is raised. (See also CHARLG, DSPG,
JTURBG, and XSTURG.)
Units: dimensionless integer number
Subroutines: DISPER, PRENV
JFRADG(3*NPX) in labeled common SETUPG (I,V)
Index vector containing compartment numbers designating the
compartments that export via advective flows to the compartment
occupying the corresponding position in vector ITOADG (i.e.,
ITQADG(K) and JFRADG(K) define an advective transport pathway of
the system). (0,0) pairs are interpreted as empty storage
locations, i.e., inactive pathways. JFRADG must not contain any
zeros paired with non-zero compartment numbers in vector ITOADG,
since chemical loadings to the system are handled explicitly as
stream loads (STRLOG), non-point-source loadings (NPSLDG), etc.
If the program encounters a compartment number greater than KOUNT
(the number of compartments used to define the system), an error
condition is raised. (See also ADVPRG, ITOADG.)
Units: dimensionless integer number
Subroutines: FLOWS, WATADV, PRENV
JSAVl in labeled common SETUPL (I,S) Flag used in subroutine
PHOT01 to Indicate that light extinction in the current
compartment has already been computed.
Subroutines: GHOST, PHOTQl
JSAV2 in labeled common SETUPL (I,S)
Flag used in subroutine PHOT02 to indicate that average spectral
irradiance in the current compartment has already been computed.
Subroutines: GHOST, PHOT02
300
-------
JTURBG(3*NPX) in labeled common SETUPG (I,V)
Index vector containing compartment numbers that, with the
compartment number found at the corresponding location of ITURBG,
define a dispersive transport pathway of the system, (0,0) pairs
are interpreted as inactive pathways. A 0 in JTURBG paired with
a non-zero compartment number in ITURBG is interpreted as a
boundary condition witn a clean (zero synthetic chemical)
water-body. If the program encounters a compartment number
greater than KOUNT (the number of compartments used to define the
system), an error condition is raised. (See also CHARLG, DSPG,
and XSTURG.)
Units: dimensionless integer number
Subroutines: DISPER, PRENy
KAIL(NPX) in labeled common CHEM2L (R,V)
Local (computed) value of first acid dissociation constant (as a
function of temperature when input data permits) of chemical in
each system compartment,
subroutines: CKLOAO, DISTRB
KA2L(NPX) in labeled common CHEM2L (R,V)
Local (computed) value of second acid dissociation constant (as a
function of temperature when input data permits) of chemical in
each system compartment,
Subroutines: CKLOAD, DISTRB
KAECG(2) in labeled common PARTG (R,V)
Multiplication of the anion exchange capacity of system sediments
by KAECG gives the-partition coefficient for sorption of the SH-
anion (KAECG(D) and the S= anion (KAECG(2)) to system sediments
as a function of a property of the sediment. Inclusion of this
feature is somewhat speculative at this time, but sorption
characteristics of chemical ions can alternatively be loaded via
KPSG.
Units: ((mg/kg)/(mg/L))/(meq/100 g dry weight)
Subroutines: DISTRB, PRCHEM
KAHG(3,5) in labeled common H5TDROG (R,M)
Second-order rate constants for specific-acid-catalyzed
hydrolysis of chemical. If the corresponding entry in the
Arrhenius activation energy matrix (EAHG) for this reaction is
zero, the value entered in KAHG is taken as the second-order rate
constant. If the corresponding entry in the activation energy
matrix (EAHG) is non-zero, the value entered in matrix KAHG is
interpreted as the base-10 logarithm of the frequency factor in
an Arrhenius function for the reaction, and local values of the
second-order rate constant are computed as a function of
temperature (TCELG) in each system compartment. The matrix
301
-------
Indices for each of the 15 possible chemical species/physical
form configurations of the molecule are given in the text
describing matrix EAHG.
Units: /mole[H+3/hour
Subroutines: FIRORD, PRCHEM
KBIL(NPX) in labeled common CHEM2L (R,V)
Local (computed) value of first base dissociation constant (as a
function of temperature when input data permits) of chemical in
each system compartment.
subroutines: CKLOAD, DISTRB
KB2L(NPX) in labeled common CHEM2L (R,V)
Local (computed) value of second base dissociation constant (as a
function of temperature when input data permits) of chemical in
each system compartment.
Subroutines: CKLOAD, DISTRB
KBACSG(3,5) in labeled common BACTG (R,M)
Second-order rate constants for benthic sediment bacterial
biolysis of the organic chemical. If the corresponding entry in
the Q-10 matrix (QTBASG) for this process is zero, the number
entered in matrix KBACSG is taken as the second-order rate
constant* If the corresponding entry in the 0-10 matrix is
non-zero, the value entered in matrix KBACSG is interpreted as
the numerical value of the second-order rate constant at 20
degrees C«, and local values of the rate constant are computed as
a function of temperature (BIOTMG) in each ecosystem compartment.
The matrix indices for each of the 15 possible chemical
species/physical form configurations of the molecule are given in
the text describing matrix EAHG.
units: ral/celi/nour
Subroutines: FIRORD, PRCHEM
KBACWG(3,5) in labeled common BACTG (R,M)
Second-order rate constants for water column bacterial biolysis
of the organic chemical. If the corresponding entry in the Q-10
matrix (QTBAWG) for this process is zero, the number entered in
matrix KBACWG is taken as the second-order rate constant. If the
corresponding entry in the 0-10 matrix is non-zero, the value
entered In matrix KBACWG is interpreted as the numerical value of
the second-order rate constant at 20 degrees C., and local values
of the rate constant are computed as a function of temperature
(BIOTMG) in each ecosystem compartment. The matrix indices for
each of the 15 possible chemical species/physical form
configurations of the molecule are given in the text describing
matrix EAHG,
Units! ml/cell/hour
302
-------
subroutines: FiRORD, PRCHEM
KBHG(3,5) in labeled common HYDROG (R,M)
second-order rate constants for specific-base-catalyzed
hydrolysis of chemical. If the corresponding entry in the
Arrhenius activation energy matrix (EBHG) for this reaction is
zero, the value entered in KBHG is taken as the second-order rate
constant. If the corresponding entry in the activation energy
matrix (EBHG) is non-zero, the value entered in matrix KBHG is
interpreted as the base-10 logarithm of the frequency factor in
an Arrhenius function for the reaction, and local values of the
second-order rate constant are computed as a function of
temperature (TCELG) in each system compartment. The matrix
indices for each of the 15 possible chemical species/physical
form configurations of the molecule are given in the text
describing matrix EAHG.
Units: /moleCOH-]/hour
subroutines: FIRORO, PRCHEM
KCECG(2) in labeled common PARTG (R,V)
Multiplication of the cation exchange capacity of system
sediments by KCECG gives the partition coefficient for sorption
of the SH3 + cation (KCECG(D) and the SH4++ cation (KCECG(2)) to
system sediments as a function of a property of the sediment.
Inclusion of this feature is somewhat speculative at this time,
but sorption characteristics of chemical ions can alternatively
be loaded via KPSG.
Units: ((Tjg/kg)/(5ng/L))/(meq/100 g dry weight)
Subroutines: DISTRB, PRCHEM
KDPG(5) in labeled common DPHOTG (P,V)
KDPG(K) is a near-surface photolytic rate constant for the Kth
ionic species of the chemical. The ionic species denoted by each
value of K is given in the text describing parameter ESOLG. Each
value of KDPG represents the outcome of an experiment conducted
in natural sunlight. The parameter is a temporally averaged
(e.g., over whole days, seasons, etc.) first-order photolytic
transformation rate constant pertaining to cloudless conditions
at some reference latitude RFLATG.
units: /hour
Subroutines: FIRORD, PHOT01, PRCHEM
KDTIME in labeled common TIMEL (I,S)
Internal flag indicating appropriate temporal reporting units
(hours, days, months, or years).
Subroutines: DRIVER, FLXOUT, GHOST, SUMUP
303
-------
KNHG(3,5) in labeled common HYDROG (R,M)
Rate constants for neutral hydrolysis of organic chemical. If
the corresponding entry in the Arrhenius activation energy matrix
(ENHG) for this reaction is zero, the value entered in KNHG is
taken as the rate constant. If the corresponding entry in the
activation energy matrix (ENHG) is non-zero, the value entered in
matrix KNHG is interpreted as the base-10 logarithm of the
frequency factor in an Arrhenius function for the reaction, and
local values of the rate constant are computed as a function of
temperature (TCELG) in each system compartment. The matrix
indices for each of the 15 possible chemical species/physical
form configurations of the molecule are given in the text
describing matrix EAHG,
Units: /hour
Subroutines: FIRQRD, PRCHEM
K02G(NPX) in labeled common QUALG (R,V)
Reaeration parameter at 20 degrees C, in each ecosystem
compartment.
Units: centimeter/hour
Subroutines: FIRORD, PRENV, VOLAT
K02LCNPX) in labeled common FLOWSL (R,V)
Reaeration parameters in each compartment (m/hr) after
temperature adjustment and units conversion.
Subroutines: FIRQRD, VOLAT
KOCG in labeled common PARTG (R,S)
Multiplication of KOCG by the fractional organic carbon content
(FROCG(J)) of each system sediment yields the partition
coefficient for sorption of unionized (SH2) compound to the
sediment.
Units: ((mg/kg)/(mg/L))/fraction organic carbon
Subroutines: DISTRB, PRCHEM
KOCL in labeled common PART1L (R,S)
Computed (or transferred from KOCG) value of KOC (c.f. KOCG}*
If KOCG is zero, but KOWG is non-zero, KOCL is computed from
KOWG.
Subroutines: DISTRB
KOUNT in labeled common SETUPG (input variable) (I,S)
Number of compartments used to define current ecosystem.
Units: dimensionless integer
Subroutines: AVEOUT, CKLOAD, DISPER, DISTRB, DRIVER, FCT, FDER,
FIRORD, FLOWS, FLXOUT, GHOST, OUTP, PRENV, PRFLOW, SEDADV,
STEADY, WATADV
304
-------
KOUNTS in labeled common SETUPL (R,S)
Internal count of number of sediment co-npartments in current
ecosystem.
Subroutines: AVEQUT, DISTRB, OUTP
KOUNTW in labeled common SETUPL (R,S)
Internal count of number of water column compartments
current ecosystem definition.
Subroutines: AVEOUT, DISTRB, OUTP
used in
KO«G in labeled common PARTG (R,S)
Octanol-water partition coefficient of chemical. Used to compute
carbon-normalized partition coefficients of neutral species (SH2)
when neither Koc nor Kp have been entered in che-nical data base.
Units: (mg/L)/(mg/L)
Subroutines: DISTRB, PRCHEM
KQXG(3,5) in labeled common OXIDG (P,M)
Second-order rate constants for oxidative transformations. If
the corresponding entry in the Arrhenius activation energy matrix
(EOXG) for this reaction is zero, the value entered in KOXG is
taken as the second-order rate constant. If the corresponding
entry in the activation energy matrix (EOXG) is non-zero, the
value entered in matrix KOXG is interpreted as the base-10
logarithm of the frequency factor in an Arrhenius function for
the reaction, and local values of the second-order rate constant
are computed as a function of temperature (TCELG) in each system
compartment. The matrix indices for each of the 15 possible
chemical species/physical form configurations of the molecule are
given in the text describing matrix EAHG.
Units: /(mole environmental oxidants/Liter) /hour
Subroutines: FIRORD, PRCHEM
KPBG(5) in labeled common PARTG (R,V)
Partition coefficient for computing sorption of chemical with
compartment biomass (BIOMSG). The chemical species signified by
each of the values entered in the vector is defined in the text
for parameter ESOLG.
Units: (ug/gram)/(mg/Liter)
Subroutines: DISTRB, PRCHEM
KPSGC5) in labeled common PARTG (R,V)
Partition coefficients for computing sorption of chemical on
compartment sediments. The chemical species signified by each of
the values entered in the vector is defined in the text for
parameter ESOLG. Also see KPSL.
Units: (ng/lcg)/(rag/Liter)
305
-------
Subroutines: DISTRB, PRCHEM
KPSL(5,NPX) in labeled common PART1L (R,M)
Local computed values of sediment partition coefficients defining
sorption of chemical to system sediments. In computing the KPSL,
the input data are treated in an hierarchical fashion.
Parameters that describe a dependence of KPS on properties of the
environment take first precedence. Specifically, a non-zero KOCL
(correlation of KPS with organic carbon content of sediments) is
used to compute KPSL for the neutral species (SH2) of the
molecule, giving KPSL(1,J) for the Jth compartment. If a zero
value for KOCG is entered in the input data, but KOWG is
non-zero, then KOCL is computed from KOWG and KOCL is used to
generate KPSLU,J). Only if KOCG and KOWG are both zero is the
explicit partition coefficient for the neutral molecule (KPSG(l),
which can be zero) utilized for direct computation of KPSL(1,J).
Similarly, a non-zero KCEC (correlation of KPS to cation
exchange capacity of sediments) is preferentially used to compute
sorption of cations to system sediments. (KCECG(l), for the
singly charged cation SH3 + , generates KPSL(2,J); KCECGC2), for
the doubly charged cation SH4++, generates KPSL(3,J).) A
non-zero KAEC is preferentially used to compute sorption of
anionlc species of the chemical. (KAECG(l), for the singly
charged anion SH-, generates KPSL(4,J); KAECG(2), for the doubly
charged anion s=, generates KPSL(5,J).) Only when KCEC or KAEC
values are zero is the explicit value of the partition
coefficient (KPSG) used to generate KPSL(*,J) for the ionic
species of the chemical.
When KPSG values are used directly, KPSG(l) pertains to the
neutral (SH2) molecule, KPSG(2) to SH3+, KPSGC3) to SH4++,
KPSGC4) to SH-, and KPSG(5) to SB.
subroutines: CKLOAD, DISTRB
KVOG in labeled common VOLATG (R,S)
Measured experimental value for (volatilization) liquid-phase
transport resistance, expressed as a ratio to the reaeration
rate.
Units: dlmensionless ratio
Subroutines: PRCHEM, VOLAT
L In labeled common SETUPL (I,S)
Letter code for detecting (Dittoral compartments.
Subroutines: BLOCK DATA, DISTRB, GHOST
LAMAXG in labeled common DPHOTG (R,S)
Wavelength used to calculate single-valued zenith light
306
-------
extinction coefficient (CMPETG) for use in subroutine PHOTOl.
LAMAXG is only used when OPETGCJ) is zero/ i.e., at the user's
option (Section 2.3.3.2.2).
Units: nm
Subroutines: PRCHEM,
LATG in labeled common CLIMG (R,S)
Geographic latitude of ecosystem.
Units: degrees and tenths Ce.g., 37.24)
Subroutines: PHOTOl, PRENV
LIGHTL(NPX) in labeled common ENPARL (R,V)
In subroutine PHOTOl, LIGHTL(J) is computed as the average light
intensity in the current (J) compartment, as a fraction of the
near-surface light intensity (tatcen as 1.0 or 100%). In
subroutine PHQT02, LIGHTLCJ) is computed as the average total
irradiance in the current (J) compartment, as a fraction (%) of
the total irradiance at the water surface, for that region of the
solar spectrum within which the chemical absorbs light.
Subroutines: FIRORD, PHOTOl, PHOT02
MAXPT(IO) in labeled common RESLT CI/V)
Stores compartment number where the corresponding DOMAX was
found*
Subroutines: AVEOUT
MINPTUO) in labeled common RESLT (I,V)
Stores compartment number where the corresponding DOMIN was
found.
Subroutines: AVEOUT
MWTG in labeled common PCHEMG (R,S)
MWTG is the gram molecular weight of the chemical.
Units: grams/mole
Subroutines: CKLOAD, FIRORD, PRCHEM, VOLAT
NCON in labeled common SETUPL (I,S)
Maximum number of compartment interconnections available.
Subroutines: BLOCK DATA, DATAIN, DISPER, FLOWS, PRENV, WATADV
NPRINT in labeled common TIMEL (I,S)
Counter on calls to subroutine OUTP,
Subroutines: DRIVER
307
-------
NPSCOL(NPX) in labeled common FLOWSL (R,V)
Computed concentration of sediment (kg/L) in non-point-source
inputs to system compartments.
Subroutines: CKLOAD, FLOWS
NPSEDG(NPX) in labeled common FLOWG (R,V)
Non-point-source sediment loads entering ecosystem compartments.
Units: kg/hour
Subroutines: FLOWS, PRENV
NPSFL(NPX) in labeled common FLOWSL (R,V)
Local value of non-point-source water flow (L/hr) entering
compartments.
Subroutines: CKLOAD, FLOWS
NPSFLG(NPX) in labeled common FLOWG (R,V)
Non-point-source water flow entering ecosystem compartments.
Units: cubic meters/hour
Subroutines: FLOWS, PRENV
NPSLDG(NPX) in labeled common LOADSG (R,V)
Chemical loadings entering compartments via non-point sources.
Units: leg/hour
Subroutines: CKLOAD, STEADY
NPX in labeled common SETUPL (I,S)
Maximum number of ecosystem compartments available.
Subroutines: BLOCK DATA, DATAIN, DISTRB, GHOST
OXIDKL(NPX) in labeled common CHEM1L (R,V)
Pseudo-first-order rate constants (/hr) for oxidative
transformation of chemical in each compartment.
Subroutines: FIRORD, FLXOUT
OXRADG(NPX) in labeled common QUALG (R,V)
Molar concentration of environmental oxidants (e.g., peroxy
radicals, singlet oxygen) in each ecosystem compartment.
Units: moles/Liter
Subroutines: FIRORD
PCPLDG(NPX) in labeled common LOADSG (R,V)
Chemical loadings entering each compartment via rainfall.
Units: kg/hour
Subroutines: CKLOAD, STEADY
308
-------
PCTWAG(NPX) in labeled common SEDMG (R,V)
Percent water in bottom sediments of bentnic compartments.
Elements of this vector that correspond to water column
compartments are not used (dummy values), PCTWAG should be
expressed as the conventional soil-science variable
(100.*fresn/dry weight); all values must be be .GE. 100. An
entry in PCTWAG that is less than 100.0 for a benthic compartment
raises an error condition, and program control is returned to the
user for correction of the input data.
Units: ditiensionless
Subroutines: DISTRB, PRENV
PHG(NPX) in labeled common QUALG (R,v)
The negative value of the power to which 10 is raised in order to
obtain the temporally averaged concentration of hydronium ions
[H30t] in gram-molecules per liter (-log[H+J).
Units: PH units
Subroutines: CKLOAD, DISTRB, FIPOPD
PHOTKKNPX) in labeled common CHEM1L (R,V)
Pseudo-first-order rate constant (Xhr) for photolytic
transformation of the chemical in each ecosystem compartment.
Subroutines: FIRQRD, FLXOUT
PIGETA(39) in labeled common DPHOTL (R,V)
Spectral light absorption coefficients (/m/(mg/D) for
chlorophyll and chlorophyll-like pigments. Values and data
sources in section 2.3.
Subroutines: BLOCK -DATA, PHOT02, PRENV
PKAGC2) in labeled common IONG (R,V)
Negative base-10 logarithm of first and second acid dissociation
constants of organic chemical. If the corresponding values of
EPKAG are nonzero, however, the acidity constants are computed
directly:
log Ka = PKAG - (1000. * EPKAG / (2.303 * R * (TCELG + 273.15)))
PKAG(l) refers to generation of SH- from SH2? PKAG(2) refers to
generation of S= from SH-.
Subroutines: DISTRB, PRCHEM
PKBGC2) in labeled common IONG (RrV)
Negative base-10 logarithm of first and second base dissociation
constants of organic chemical. If the corresponding values of
EPKBG are non-zero, however, the basicity constants are computed
from:
309
-------
log Kb = PKBG - (1000. * EPKBG / (2.303 * R * (TCELG + 273.15)))
PKBG(l) refers to generation of SH3 + from SH2; PKBG(2) refers to
generation of SH4++ from SH3+.
Subroutines: DISTRB, PRCHEM
PLRAG(NPX) in labeled common QUALG (P,V)
Fraction of total biomass (BIOMSG, c.f.) in each compartment that
is planfctonic, i.e., subject to passive transport via
entrainment.
Units: dimensionless
Subroutines: FIRORD, PRENV
POHG(NPX) in labeled common QUALG (R,V)
The negative value of the power to which 10 is raised in order to
obtain the temporally averaged concentration of hydroxide IOH-]
ions in gram-molecules per liter (-logCOH-J).
Units: POH units
subroutines: CKLOAD, DISTRB, FIRORD
QSSAV In labeled common RESULT (R,S)
Total mass of chemical (teg) resident in benthic sediments of
ecosystem at steady-state.
Subroutines: GHOST, SUMUP
QTBASG(3,5) in labeled common BACTG (R,M)
0*10 values for bacterial transformation (c.f. KBACSG) of
organic chemical in benthic sediments. The 0-10 is the increase
in the second-order rate constant resulting from a 10 degree C
temperature Increase. The matrix indices for each of the 15
possible chemical species/physical form configurations of the
molecule are given in the text describing matrix EAHG.
Units: dimensionless
Subroutines: FIRORD, PRCHEM
QTBAWG(3,5) in labeled common BACTG (R,M)
0-10 values for bacterial transformation (c.f. KBACWG) of
chemical in the water column of the system. Q-10 is the increase
in the second-order rate constant resulting from a 10 degree C
temperature Increase. The matrix indices for each of the 15
possible chemical species/physical form configurations of the
•olecule are given in the text describing matrix EAHG.
Units: dimensionless
subroutines: FIRORD, PRCHEM
310
-------
QTSAV in labeled common RESULT (R,S)
Total mass of chemical resident in system at steady state.
Subroutines: GHOST, SUMUP
QUANTG(3,5) in labeled common OPHOTG (R,«)
Reaction quantum yield in photolytic transformation of chemical.
The quantum yield is the traction of total quanta absorbed by the
chemical resulting in transformations. separate values are
provided for each molecular configuration of the chemical in
order to malce assumptions concerning their relative reactivities
readily available to the user. The matrix indices for each of
the 15 possible ionic species/sorbed form configurations of the
chemical molecule are given in the text describing matrix EAHG.
Units: dimensionless
Subroutines: FIRORD, PRCHEM
QWSAV in labeled common RESULT (R,S)
Total mass of chemical resident in water column of system at
steady state.
Subroutines: GHOST, SUMUP
RAINFL(NPX) in labeled common FLOrtSL (R,V)
Rainfall entering each ecosystem compartment afte.r conversion to
internal units (L/nr).
Subroutines: CKLOAD,
RAING in labeled common CLIMG (R,S)
Average rainfall in geographic area of system.
Units: millimeters/month
Subroutines: FLOWS, PRENV
RFLATGC5) in labeled common DPHOTG (R,V)
Reference latitude for corresponding direct photolysis rate
constant (c.f. KDPG). see text describing parameter ESOLG for
chemical species specified by the vector index of RFLATG.
Units: degrees and decimal fraction (e.g., 40.72)
Subroutines: PHOTOl, PPCHEM
SDCHRG(NPX) in labeled common SEDMG (P,V)
The interpretation given this parameter depends on the type ot
compartment involved. For water column compartments ((L)ittoral,
(E)pilimnion, and (H)ypolimnion compartments), SDCHRG is the
suspended sediment concentration. For (B)enthic sediment
compartments, SDCHRG is the bulk density of the bottom sediment.
Units: Water column compartments: mg/Liter
Benthic compartments: grams/cubic centimeter
311
-------
Subroutines: DISTRB, PHOT02, PRENV
SEDCOL(NPX) in labeled common MASSL (R,V)
Sediment concentration after conversion to internal units
(kg/Liter of water) in each compartment.
Subroutines: AVEOUT, DISPER, DISTRB, FIPQRD, FLOtrfS, OUTP, SEDADV
SEDETAO9) in labeled common DPHOTL (R,V)
Spectral light absorption coefficients (/m/(mg/L) of suspended
sediments. Values and data sources given in Section 2.3.3,
Subroutines: BLOCK DATA, PHOT02, PRENV
SEDFL(NPX,NPX) in labeled common FLOWSL (R,M)
Matrix of sediment flows (icg/hr) among compartments.
Subroutines: DISPER, FIRORD, PRFLOW, SEDADV, WATADV
SEDMSL(NPX) in labeled common MASSL (R,V)
Mass of sediment (leg) resident in each compartment.
Subroutines: AVEOUT, DISTRB, FIRORD, PRFLOW
SEDOUL(NPX) in labeled common FLOWSL (R,V)
Export rate of sediment (kg/hr) from each compartment.
Subroutines: DISPER, FIRORD, PRFLOW, SEDADV, WATADV
SOLG(5) in labeled common PCHEMG (R,V)
Aqueous solubility. If the corresponding value in vector ESOLG
(c.f.) is zero, SOLG(K) is interpreted as an aqueous solubility
in mg/Liter. If ESOLG(K) is non-zero, SOLG(K) is used in an
equation describing the molar solubility of the chemical species
as a function of environmental temperature (TCELG), I.e.,
SOL (mg/L) =
1000,*MWTG*10.**(SOLG-UOOO.*ESOLG/(2,303*R*(TCELG+273.15))))
Solubilities are used (inter alia) to limit the permissible
external loadings of the chemical on the system to values that
generate final residual concentrations ,LE. 50% of aqueous
solubility (or 1.E-5M). This constraint is imposed in order to
help ensure that the assumption of linear sorption isotherms is
not seriously violated. The vector indices denote the following
chemical species:
SOLG(l) — solubility of neutral molecule (SH2)
SOLG(2) — solubility of singly charged cation (SH3+)
SOLG(3) — solubility of doubly charged cation (SH4++)
SOLG(4) — solubility of singly charged anion (SH»)
312
-------
SOLG(5) -- solubility of doubly charged anion (S=)
Units: mg/Liter
subroutines: CKLOAD, PRCHEM, VOLAT
SPFLG(S) in labeled common CONTRG (I,V)
Vector containing flags that indicate which chemical species of a
chemical actually exist and are thus to be considered by the
program. The flags control the number of blocks (1*5) of
chemical data to be recorded in the output file; the chemical
data for species that do not exist is necessarily assumed to be
non-existent.
SPFLG(l) set (=1) indicates the neutral molecule (SH2) exists
SPFLG(2) set indicates existence of SH3 +
5PFLGC3) set indicates existence of SH4++
SPFLGC4) set indicates existence of SH-
SPFLGC5) set indicates existence of S=
Units: dimensionless
Subroutines: CKLOAD, DISTRB, FIRORD, PRCHEM, STEADY
STFLOG(NPX) in labeled common FLOWG (R,V)
Stream flow entering ecosystem compartments. Stream flows
include base flow into head reach of river or estuary,
tributaries, creeks entering a lake or pond, etc.
Units: cubic meters/hour
Subroutines: FLOWS, PRENV
STRLDG(NPX) in labeled common LOADSG (R,V)
Chemical loadings entering ecosystem compartments
flow.
Units: )cg/hou.r
Subroutines: CKLOAD, STEADY
via stream
STRMFL(NPX) in labeled common FLOWSL (R,V)
Stream flows converted to internal units (L/hr).
Subroutines: CKLOAD, FLOWS
STSCOL(NPX) in labeled common FLOWSL (R,V)
Internal stream sediment concentrations Ocg/L) for compartments.
subroutines: CKLOAD, FLOWS
STSEDG(NPX) in labeled common FLOWG (R,V)
Stream-borne sediment load entering ecosystem compartments.
Units: kg/hour
313
-------
Subroutines: FLOWS, PRENV
SYSLDL In labeled common MISCL (R,S)
Total chemical loading (kg/hr) on the ecosystem.
subroutines: CKLOAD, FLXOUT, STEADY, SUMUP
SYSTYP(60) in labeled common NAME2G (input data) (I,V)
SYSTYP holds the name of the ecosystem being considered, with up
to 60 characters permitted. SYSTYP is written in the headings
for all data written to program output files.
Units: alphameric characters
Subroutines: AVEOUT, FIRORD, FLXOUT, GHOST,PRCHEM, PRENV
T in labeled common TIMEL (R,S)
Time (hrs) in numerical integration subroutine.
Subroutines: DRIVER
TCELG(NPX) in labeled common QUALG (R,V)
Average temperature of ecosystem compartments for use (as needed)
in exponential functions describing chemistry of synthetic
organic compounds. (The averaging method may use exponential
functions.)
Units: degrees C.
Subroutines: CKLOAD, DISTRB, FIRORD
TFACTR in labeled common TIMEL (R,S)
Internal numerical factor for converting internal time (hours) to
units written in output files (hours, days/ months, or years).
Subroutines: FLXOUT, OLITP, SUMUP
TFINAL in labeled common TIMEL (R,S)
End point for numerical integration subroutine. TFINAL is
estimated as 2 system half-lives in subroutine FLXOUT.
Subroutines: DRIVER, FLXOUT, SUMUP
TINCR in labeled common TIMEL (R,S)
Tine increment between data output times in numerical integration
subroutine. Computed in subroutine FLXOUT.
Subroutines: DRIVER, FLXOUT
TOTETAC39) In labeled common ENPARL (R,V)
Total spectral light absorption coefficients (/n) for ecosystem
compartments.
Subroutines; PHOT02
314
-------
TOTKL(NPX) in labeled common CHE^IL (R,V)
Pseudo-first-order rate constants (/hr) for all loss processes
combined, In each compartment.
Subroutines: FCT, FOER, FIRORD, STEADY
TOTLDL(NPX) in labeled common MISCL (R,V)
Total external cnemlcal loading (icg/hr) on each ecosystem
compartment.
subroutines: CKLQAD, FIRORD, STEADY
TPRINT in labeled comi\on T1MEL (R,S)
Times at which integrator writes to output files.
Subroutines: DRIVER
TYPEE(NPX) in labeled common NAME2G (input data) (1,V)
Letter codes designating compartment types used to define
ecosystem. Available types: (L)ittoral, (E)piliitmion,
(H)ypolimnion, and (B)enthic.
Units: dif-nensionless
Subroutines: AVEQUT, DISTRB, FIPORD, FLOWS, PHOT01, PHOT02,
PRENV, PRFLOd
VAPRG in labeled common VOLATG (R,S)
Vapor pressure of compound. Used to compute Henry's law constant
if the latter input datum (HENRYG) is zero, but VAPRG is
non-zero. If EVPRG is non-zero, VAPRG is used in an equation
describing vapor pressure (Pv) as a function of temperature
(TCELG) in the ecosystem compartments, i.e.,
log PV = VAPRG - (1000. * EVPRG / (2.303 * P * (TCELG + 273.15)))
Units: Torr
Subroutines: FIRORD, PRCHEM, VOLAT
VOLG(NPX) in labeled common GEQMT (R,V)
Total environmental volume of ecosystem compartments.
Units: cubic meters
Subroutines: DISPER, DISTRB, PRFLOW, VOLAT
VOLKL(NPX) in labeled common CHEM1L (R,V)
Pseudo-first-order rate constants (/hr) for volatilization losses
from compartments.
Subroutines: FIRORD, FLXOUT
VOLPCT in labeled common RESLT (R,S)
315
-------
Percent of total load exported via volatilization at steady
state.
Subroutines: FLXOUT, SUMUP
WATETAC39) in labeled common DPHOTL (R,V)
Spectral light absorption coefficients for pure water (/m),
Values and data sources given in Section 2.3.3.
Subroutines: BLOCK DATA, PHOT02, PRENV
WATFL(NPX,NPX) in labeled common FLOWSL (R,M)
Internal matrix of water flows (L/hr) among system compartments,
Subroutines: DISPER, FIRQRD, FLOWS, PRFLOW, SEDADV, WATADV
WATINL(NPX) in labeled common FLOWSL (R,V)
Total water inflow (L/hr) to compartments.
Subroutines: FLOWS, WATADV
WATOUL(NPX) in labeled common FLOWSL (R,V)
Total water export (L/hr) from compartments,
Subroutines: DISPER, FIRORD, PRFLOW, SEDADV, WATADV
WATVQL(NPX) in labeled common MASSL (R,V)
Volume of water (liters) in each compartment. /BR Subroutines:
AVEOUT, DISPER, DISTRB, FIRORD, FLXOUT, OUTP, PRFLOW, STEADY
WAVELO9) in labeled common ENPARL (R,V)
Average spectral irradiance in compartment.
Subroutines: PHOTQ2
WINDG(NPX) in labeled common CLIMG (R,V)
Average wind velocity at a reference height of 10 centimeters
above the water surface. Parameter is used to compute a piston
velocity for water vapor (Liss 1973, Deep-Sea Research 20:221) in
subroutine VOLAT,
Units: meters/second
Subroutines: FIRORD, PRENV, VOLAT
WLAMG(39) in labeled common PHOG (R,V)
Temporally averaged spectral irradiance (solar beam + sJcy light)
immediately below the water surface (i.e., after accounting for
reflection from the water surface). The 39 wavelength intervals
are given in Table 2.18 of section 2,3. An example of
appropriate input data is given in Table 2.23 of section 2,3.3,6
(cf. Zepp and dine 1977). The input data (WLAMG) wavebands are
316
-------
not Identical with the full wavelength intervals used for
averaging; the data are expanded to the full intervals in
routine PHOT02. For wavelength intervals 1 to 10 (covering
295-322.5 nm) N in tne input unit is a 2.5 nm waveband. For
wavelength interval 11 (center at 323.1 nm) the input data
waveband is 3.75 nm. For wavelength intervals 12 to 39 (covering
the spectral region from 325 nm through 850 nm), N in the input
data (width of WLAMG waveband) is 10 nip.
Units: photons/(square cm)/second/(N nanometers)
Subroutines: PHOT02, PRENV
WLAMLO9) in labeled common ENPARL (R,V)
Local values of spectral irradiance after expansion
wavelength intervals and pre-inultipllcation by
computation factors.
Subroutines: PHOTQ2
to full
numerical
XSTURG(3*NPX) in labeled common SETUPG (R,V)
Cross-sectional area to be applied to the dispersive exchange
pairing given by the corresponding compartment numbers in vectors
JTURBG and ITURBG (c.f.).
Units: square meters
Subroutines: DISPER, PRENV
Y(NPX) (R,V)
State variable vector passed through argument lists.
Subroutines: AVEOUT, DRIVER, FCT, FDER, FLXOUT, GHOST,
STEADY
OUTP,
YSATL(5,NPX) in labeled common FLQWSL (R,M)
Local values f-or aqueous solubility of 5 chemical species of
chemical (c.f. SQLG) in each ecosystem compartment,
subroutines: CKLOAD, STEADY
the
ZC18) in labeled common RESULT (R,V)
Intermediate variable used for program outputs,
Z(l) — average concentration (rag/L) of dissolved chemical in
aqueous phase of water column,
Z(2) -- average concentration (mg/kg) of chemical sorbed with
suspended sediments in water column.
Z(3) «- average concentration (mg/L) of chemical dissolved in
interstitial water of bottom sediments.
Z(4) — average concentration (nig/kg) of chemical sorbed with
benthic sediments.
Z(5) *- total pollutant mass in water column of ecosystem (kg)
2(6) »- total pollutant mass in benthic sediments of ecosystem
317
-------
(Kg)
Z(7) -- total concentration (mg/L in water column, mg/kg in
benthic sediments).
Z(8) «•- dissolved chemical concentration, mg/Liter of water
Z(9) •- concentration of sorbed chemical .(mg/icg of sediment)
Z(10) -- concentration of biosorbed chemical, ug/g
Z(ll) «- mass of chemical in compartment (g/square meter of
AREAG)
Z(12) •- total kg mass of chemical in compartments
Z(13) -• average g/sguare meter in water column compartments
Z(i4) — average total concentration in water column (mg/L).
Z(15) -- average concentration biosorbed in water column (ug/g)
Z(16) -- average g/square meter in benthic compartments.
Z(17) -• average total concentration (mg/kg) in benthic
compartments
Z(18) -- average chemical biosorbed in bottom sediments (ug/g),
subroutines: AVEOUT, GHOST, FLXOUT, OUTP, SUMUP
318
-------
GLOSSARY FOR LABELED COMMON UNITS
This glossary contains an alphabetical listing of all
variables used in the interactive and simulation code of EXAMS
for I/O operations. The glossary gives:
> The name of the variable
> Definition of the variable
> List of subroutines requiring the variable
All variables are of the INTEGER SCALAR type.
The program Is supplied with the following assignments (set in
BLOCK DATA):
UNIT NUMBER
AUDOHT
INENVR
1NCOMP
INDEF
IMHLP
KINQUT
RPTOUT
SSOUT
TTYIN
TT¥OUT
01
10
07
08
09
04
02
03
05
05 (06 for
IBM's TSO)
AUDOUT - Logical unit number for writing the user's Inputs
when the AUDIT option is In effect.
Interactive subroutines: MAIN, 1NREC
INENVR - Logical unit number for reading and writing
information to and from the environmental database.
Interactive subroutines: BLDCMD, ENVIRO, ERASE, . MAIN, RECALL,
STORE, USROPT
INCOMP - Logical unit number for reading and writing
319
-------
information to and from the chemical database.
Interactive subroutines: BLDCMD, COMPND, ERASE, MAIN, RECALL,
STORE, USROPT
JNDEF - Logical unit number for reading the description of
variables used with the SHOW and DESCRIBE commands.
Interactive subroutines: BLDCMD, HELP
INHLP «• Logical unit number for reading the text available
via the HELP command.
Interactive subroutines: BLDCMD, BLDHLP, HELP
KINOUT - Logical unit number for writing results of
numerical Integration to Kinetics plotting file.
Computational subroutines: BLOCK DATA, FLXOUT, GHOST, OUTP
Interactive subroutines: BLDCMD
RPTOUT - Logical unit number for data written to output
report file.
Computational subroutines: AVEOUT, BLOCK DATA, DRIVER, FIRORD,
OUTP, FLXOUT, GHOST, PRCHEM, PRENV, PRFLOW, STEADY, SUMUP
Interactive subroutines: BLDCMD, LISSTR, SHOW
SSOUT - Logical unit number for data written to plotting
file containing EXAMS' steady-state chemical concentrations.
Computational subroutines: AVEOUT, BLOCK DATA, GHOST
Interactive subroutines: BLDCMD, PLOTX, PONDAT, PRODAT
TTYIN • Logical unit number for interactive input commands.
Computational subroutines: BLOCK DATA, PRCHEM, PRENV
Interactive subroutines: BLDCMD, COMPND, DESCRI, ENVIRO, ERASE,
GETNUM, IFIND, INREC, NEWNAM, RECALL, STORE, TERMAL
TTYOUT - Logical unit number for output error messages and
warnings, and for EXAMS' interactive responses.
Computational subroutines: BLOCK DATA, CKLOAD, DISPER, DISTRB,
DRIVER, FLOWS, GHOST, PRCHEM, PRENV, SEDADV, STEADY, WATADV
Interactive subroutines: BLDCHA, BLDCMD, BLDECO, BLDHLP, BLDMOD,
BLDNAM, COMPND, DATOPT, DESCRI, DESOUT, ENVIRO, ERASE, GETNUM,
HEDSHO, HELP, IFIND, LISSTR, LIST, MAIN, MNLN, MODIFY, NEWNAM,
PLOTX, PONDAT, PRTPRM, RECALL, RUNIT, SHOENV, SHOW, STAOPT,
STORE, TERMAL, TYPOPT, USROPT, WHTCMD, ZONOPT
320
-------
GLOSSARY FOR LABELED COMMGM 1NPAR
This glossary contains an alphabetical listing of COMMON
variables that are used in the interactive code of EXAMS. For
each variable, the glossary gives:
> The name of the variable
> Dimension type ( Scalar, Vector)
> Numerical size of dimensions
> Definition of the variable
> List of subroutines requiring the variable
All variables are of the INTEGER type.
AUDIT (Scalar) - allows an audit trail of user inputs to be
recorded. When set to 0, no audit trail is produced; when set
to 1, an audit trail is written to the dataset defined by FORTRAN
unit AUDOUT.
Interactive subroutines: MAIN, INREC
CMDLEN (Vector (20)) - Is used to store the lengths of the
primary commands used by the executive. The Ith element of the
vector contains the length of the Ith command.
Interactive subroutines: BLDCMD, WHTCMD
CMPNAM (Vector (210)) - stores the chemical (compound) names
in successive elements, 1 character per element.
Interactive subroutines: BLDNAM, COMPND, SHOW
COMVAR (Vector (20)) - holds the number of variables in each
labeled COMMON that can be modified via the CHANGE command. The
relationship between the elements of COMVAR and the labeled
COMMON is:
i - NAME1G 11 - LOAOSG
2 - CONTRG 12 - NAME2G
3 - PCHEMG 13 - SETUPG
4 - IONG 14 - SEDMG
5 - PARTG 15 - QUALG
6 - VOALTG 16 - PHOG
7 - DPHOTG 17 - GEOMT
321
-------
8 - HYDROG 18 - CLIMG
9 • OXIDG 19 - FLOWG
10 - BACTG 20 - UNITS
Interactive subroutines: BLDMOD, MODIFY
ECOLEN (Vector (20)) - is used to store the lengths of the
ecosystem names. The Ith element contains the length of Ith
ecosystem name.
Interactive subroutines: BLDECO, ENVIRO, SHOENV
ECONAM (Vector (100)) - holds the ecosystem
successive elements, 1 character per element,
Interactive subroutines: BLDECO, ENVIRO, SHOENV
names in
HELEN (Vector (50)) - holds the lengths of the online
assistance keywords. The Ith element of the vector contains the
length of the Ith assistance keyword.
Interactive subroutines: BLDHLP, HELP
HELPS (Vector (300)) - holds the online assistance
in successive elements, one character per element.
Interactive subroutines: BLDHLP, HELP
keywords
IENV (scalar) - holds the database record number of the
currently selected ecosystem. If 1, then the "Unspecified"
ecosystem has been selected.
Interactive subroutines: MAIN, ENVIRO, ERASE, RUNIT, SHOW,
RECALL, USROPT
INPUT (Vector (80)) - contains the most recent input string
received (subroutine INREC).
Interactive subroutines: BLDCMD, BLDECO, BLDHLP, BLDNAM, COMPND,
DESCRI, ENVIRO, ERASE, GETNUM, HELP, IFIND, LIST, MATCH, MODIFY,
NEWNAM, PRTPRM, RECALL, SCAN, STORE, TERMAL, WHTCMD
MINCMD (Vector (20)) - holds the lengths of strings required
to make each string in the primary command set unique. The Ith
element of the vector holds the minimum length of the Ith command
string.
Interactive subroutines: BLDCMD, WHTCMD
MINCMP (Vector (60)) * holds the lengths of strings required
to make each string In the set of chemical names unique. The Ith
322
-------
element of the vector holds the minimum length of the Ith string.
Interactive subroutines: BLDNAM, COMPND
MINECO (Vector (20)) - holds the lengths of strings required
to malce each ecosystem name unique. The Ith element of the
vector holds the minimum length of the Ith ecosystem name string.
Interactive subroutines: BLDECO, ENVIRO
MINHLP (Vector (50)) - holds the lengths of strings required
to malce each online assistance Keyword unique. The Ith element
of the vector holds the minimum length of the Ith online
assistance Keyword.
Interactive subroutines: BLDHLP, HELP
MODLEN (Vector (120)) - holds the lengths of the names of
variables available to the CHANGE command. The Ith element of
the vector contains the length of the Ith name.
Interactive subroutines: BLDMOD, DESCRI, HELP, MODIFY, PRTPRM,
SHOW
(Vector (120)) - holds the lengths of strings
required to make each variable available to the CHANGE command
unique. The Ith element of the vector holds the minimum length
of the Ith string.
Interactive subroutine: BLDMOD, DESCRI, HELP, MODIFY, PRTPRM
MODS (Vector (500)) - holds the names of variables used by
the CHANGE command in successive elements, one character per
element.
Interactive subroutines: BLDMOD, DESCRI, HELP, MODIFY, PPTPRM,
SHOW
NAMLEN (Vector (60)) - holds the lengths of the names of the
compounds. The Ith element of the vector contains the length of
the Ith string.
interactive subroutine: BLDNAM, COMPND, SHOW
NCMDS (Scalar) - holds the number of primary commands
available.
Interactive subroutines: BLDCMD, MAIN,
NOCOM (scalar) - holds the number of labeled COMMON areas
available to the CHANGE command.
Interactive subroutines: BLDMOD, MODIFY, PRTPRM
323
-------
NOCREC (Scalar) - holds the maximum number of records
available for the chemical data file. This value includes both
user and system defined compounds.
Interactive subroutines: BLDCMD, ERASE, RECALL, STORE USIROPT
NOECOS (Scalar) - holds the number of ecosystems available.
Interactive subroutines: BLDECQ, ENVIRO
NOEREC (Scalar) - holds the maximum number of records
available for the environmental data file. This value includes
both user defined and "fixed" environments.
Interactive subroutines: BLDCMD, ERASE, RECALL, STORE, USROPT
NOHELP (Scalar) - holds the number of Keywords available for
use with the online assistance utility.
Interactive subroutines: BLDHLP, HELP
NOMOD (Scalar) - holds the number of variables available for
use with the CHANGE command. Interactive subroutines: BLDMOD,
DESCRI, HELP, MODIFY, PRTPRM, SHOb
NONAME -(Scalar) holds the number of "fixed" chemical
datasets.
Interactive subroutines: BLDNAM, COMPND, ERASE, RECALL, SHOW,
STORE, USROPT
POUND (Scalar) - holds the database record number of the
currently, selected compound. If 1, then the "Unspecified11
compound has been selected.
Interactive subroutines: COMPND, LISSTR, MAIN, RECALL
PRICMD - (Vector (200) ) - is used to store the primary
command strings in successive elements of the vector, one
character per element.
Interactive subroutines: BLDCMD, WHTCMD
START (Scalar) * points to the starting position for scans
of vectors that contain strings.
Interactive subroutines: BLDCMD, BLDECO, BLDHLP, BLDNAM, COMPND,
DESCRI, ENVIRO, ERASE, GETNUM, HELP, IFIND, LIST, MATCH, MODIFY,
NEWNAM, PRTPRM, RECALL, SCAN, STORE, TERMAL, WHTCMD
324
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ition for the scans
STOP (Scalar) - points to the ending pos:
of vectors that contain strings.
Interactive subroutines: BLDCMD, BLDECO, BLDHLP, COMPND, DESCPI,
ENVIRO, ERASE, GETNUM, HELP, IFIND, LIST, MATCH, MODIFY, PRTPRM,
RECALL, SCAN, STORE, TERMAL, WHTCMD
TCOL (Vector (120) ) - holds the nutnoer of columns of the
matrix variables that can be modified via the CHANGE command.
The Ith element contains the length of the Ith matrix variable.
If the variable is not a matrix, then the Ith value of TCOL is
set to 0.
Interactive subroutines: BLDMOD, DESOUT, MODIFY, PRTPRM
TD (Vector (120) ) - holds the data type of variables that
can be modified via the CHANGE command. The type codes are:
1 - COMPLEX
2 - DOUBLE PRECISION
3 - REAL
4 - INTEGER
5 - LOGICAL
The Ith element of the vector contains the designation for the
Ith CHANGEable variable.
Interactive subroutines: BLDMOD, DESCPI, DESOUT, HELP, MODIFY,
PRTPRM
TERMTY (Scalar) - holds the type of
present only TTY is-supported.
terminal in use,
At
TERMTY
VALUE
TERMINAL
TYPE
1
2
3
DEC VT55
Tektronix 4010 series
TTY compatible
Interactive subroutines: MAIN, INREC, TERMAL
TROW (VECTOR (120) ) - holds the number of rows in a matrix,
or the length of a vector, of variables that can be modified via
the CHANGE command. If the variable is a scalar, TROW(I) a o.
The Ith element of the vector contains the vector length or
matrix row size of the Ith CHANGEable variable.
Interactive subroutines:BLDMOD, DESOUT, MODIFY, PRTPRM
325
-------
T5 (VECTOR (120) ) - holds the storage type of variables
that can be modified via the CHANGE command. The storage codes
are:
1 - Scalar
2 - vector
3 - Matrix
The Ith element of the vector contains the code for the Ith
element of CHANGEable variables.
Interactive subroutines:BLDMOD, DESOUT, MODIFY, PRTPRM
TYPE (Scalar) - holds a code denoting the delimiter that was
encountered by the SCAN subroutine.
Interactive subroutines; BLDCMD, BLDECO, BLDHLP, BLDNAM, COMPND,
DESCRI, ENVIRO, ERASE, GETNUM, HELP, IFIND, LIST, MODIFY, NEWNAM,
PRTPPM, RECALL, SCAN, STORE, TERMAL, WHTCMD
326
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APPENDIX A
DOCUMENTATION OF COMPUTATIONAL SUBROUTINES
EXAMS' computational subroutines are executed in the following
order.
GHOST. GHOST is primarily a program control module. It performs
few computations aside from preserving intermediate variables and
initializing run-control parameters. GHOST opens the files for
program output, writes information to the files for identifying
the run, calls subroutines, and checks for error flags that may
be set by the subroutines.
PRCHEM. PRCHEM records the chemical characterization of the
synthetic organic (input data) in the output file defined by
FORTRAN unit RPTOUT.
PRENV, PRENV records the canonical characterization of the
ecosystem (input data) in the output file defined by FORTRAN unit
RPTOUT.
DISTRB. DISTRB partitions the chemical among its ionic species
(up to 5), with each of the ionic species further partitioned
into dissolved, sediment sorbed, and biosorbed forms. The
resulting distribution coefficients are used as multipliers on
the (input) homogeneous-phase reaction coefficients.
FLOWS, FLOWS computes the advective and dispersive transport
field that moves the chemical through the ecosystem compartments.
After conversion of the input hydrologic data to a form suitable
for further computations, FLOWS calls four subsidiary routines:
WATADV, SEDADV, DISPEP, and PRFLOW.
WATADV. WATADV uses Gaussian elimination to calculate the
total advection of water among system compartments and the
magnitude of net advective exports,
SEDADV. SEDADV uses the outcome of WATADV to compute chemical
transport due to movement of suspended sediments, sediment
exports, and bedioads.
DISPER. DISPER evaluates the turbulent transport field
(including boundary conditions) for water and sediments, and
327
-------
generates the total chemical transport field as a sun of
advective and turoulent motions.
PRFLOW. PRFLQrf writes a profile of the transport
characteristics of the ecosystem to the output file defined by
FORTRAN unit RPTOUT.
CKLOAD. Subroutine CKLOAD accumulates the total loadings to
system elements, cheocs to ensure that none of the loadings (via
rainfall, interflow, point (stream) or non-point sources) are at
aqueous concentrations (after accounting for partitioning in the
input flows) greater the 50% of the aqueous solubility at the
temperature specified for the system element loaded by the flow.
(This constraint is imposed to maintain the linear sorption
isotherms used in the model within their proper range and to
prevent loadings of condensed-phase chemical,)
FIRORD. FIRORD reduces the kinetics of the chemical to
pseudo-first-order form by coupling characteristics of the
chemical and the environment. If the input data permit, the
properties of the chemical are adjusted to reflect the effect of
temperature in each physical element of the system. The
pseudo-first-order reaction rate constants are computed from the
interactive effects of partitioning, temperature, and other
characteristics of the environment for each species or form,
FIRORD also converts the input loadings and advective and
dispersive flow field to pseudo-first-order effects on chemical
concentrations, and writes both a Kinetic profile of the chemical
and a canonical profile of the ecosystem to the output data set
defined by FORTRAN unit RPTOUT. FIRORD calls three subroutines
(PHOTOl, PHOT02, and VOLAT) that evaluate photolysis and
volatility, (PHOTOl and PHOT02 are mutually exclusive
computations; FIRORD selects the appropriate routine based on
the structure of the input data.)
PHOTOl. PHOTOi accepts a measured (clear day) photolysis rate
constant at a specified reference latitude as input data,
PHOTOl corrects this rate constant for deviation of the
latitude of the ecosystem from the reference latitude, effects
of cloud cover, and light extinction in the water column based
on a single-valued zenith light extinction coefficient entered
as part of the canonical environmental data,
PHOT02, PHOT02 computes the photolysis rate constant by
coupling the absorption spectrum of the chemical to the ambient
light field. Light intensity in the water column is computed
by assembling a total light absorption coefficient from the
input data (DOC, chlorophyll, suspended sediment
concentrations) and coupling this information to an
input-specified near-surface spectral irradiance and
distribution coefficient.
328
-------
VOLAT. voijAT computes volatilization rate constants using a
two-resistance model of movement of chemical across the
air-water interface,
STEADY. STEADY computes the steady-state concentrations of
chemical in all system elements (using either Gaussian
elimination, or, should this fail, an iterative first-order
cascade technique) including the effects of internal transports
among compartments.
If solubility criteria are violated as a result of drift
loadings, these loads are reduced and the computations are
re-evaluated, STEADY then writes a final profile of the loads to
the output data set defined by FORTRAN unit RPTOUT.
AVEOUT. AVEOUT computes and reports the average, maximum, and
minimum steady-state concentrations of chemical. AVEOUT also
gives an element by element listing of the concentrations and
distribution of chemicals throughout the ecosystem. AVEOUT
writes to the output data sets defined by FORTRAN units RPTOUT
and SSOUT; the latter are used for plotting the results of
EXAMS' steady-state computations,
FLXOUT, FLXOUT analyzes and reports the steady-state fate of the
chemical. The information reported for each process includes the
mass flux (kg/time) attributable to the process, the percentage
of load consumed in the process, and a projected half-life that
would result from each process acting in isolation. The
processes are also summed by category (chemical, biological,
transport), and a total system half-life is estimated from the
total flux in order to specify a time-frame for the integration
routine ("DRIVER").
DRIVER. DRIVER is a dispatching and error checking routine that
calls the Rurfge-Kutta or Gear's method (the latter is invoiced for
stiff equations) integration routines (RKFINT, STFINT, et seq.).
The integration is carried out over two (estimated) half-lives,
using the steady-state concentrations as initial conditions, in
order to evaluate persistence of the chemical after the external
loadings cease. The time-course of disappearance of the compound
is summarized in the output data set defined by FORTRAN unit
RPTOUT, and a detailed compartment-by-compartment time trace is
written to the ouput data set defined by FORTRAN unit KINOUT.
SUMUP. SUMUP writes a single-page summary of the prior analyses
to the output data set defined by FORTRAN unit RPTOUT, along with
an estimate of the ecosystem's self-cleansing time derived from
an analysis of the chemical dissipation results computed by
DRIVER.
Each of EXAMS* computational subroutines is described In a
separate section of this appendix. The format used for these
329
-------
descriptions includes the purpose of the routine, restrictions on
its use, normal usage, and, where appropriate, a brief
description of the algorithm or method used in the routine.
I. IDENTIFICATION
A. TITLE: DATAIN
8. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: L.A. Burns, Aug. 1979
D. REVISION: Jan. 1981
II. PURPOSE: DATAIN serves as a root segment for the batch
version of EXAMS. Routine DATAIN pre-zeros the variables
and acquires run parameters, input chemical data, and
input environmental data from the appropriate files.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: GHOST
C. COMMON STORAGE!
ABSG(39,5) in labeled common DPHOTG
ACBACG(NPX) in labeled common QUALG
ADVPRG(NCON) In labeled common SETUPG
AECG(NPX) in labeled common SEDMG
AREAG(NPX) in labeled common GEOMT
BACTOG(NPX) in labeled common QUALG
BIOMSG(NPX) in labeled common QUALG
BIOTMG(NPX) in labeled common QUALG
CECG(NPX) in labeled common SEDMG
CHARLG(NCON) in labeled common SETUPG
CHEMNA(60) in labeled common NAME1G
CHLG(NPX) in labeled common PHOG
CLOUDG in labeled common PHOG
CMPETG(NPX) in labeled common PHOG
OEPTHG(NPX) In labeled common GEOMT
DFACG(NPX) in labeled common PHOG
330
-------
DOCG(NPX) In labeled common PHDG
DRFLDG(NPX) In labeled common LOADSG
DSPG(NCON) In labeled common SETUPG
EAHG(3,5) In labeled common HYDROG
EBHG(3,5) in labeled common HYDROG
EHENG in labeled common VOLATG
£NHG(3,5) in labeled common HYDROG
EOXG(3,5) in labeled common OXIDG
EPKAGC2) in labeled common IONG
EPKBG(2) in labeled common IONG
ESOLGC5) in labeled common PCHEMG
EVAPG(NPX) in labeled common CLIMG
EVPRG in labeled common VOLATG
FROCG(NPX) in labeled common SEDMG
HENRYG in labeled common VOLATG
IFLLDG(NPX) in labeled common LOADSG
INTFLG(MPX) in labeled common FLOwG
ITOADG(NCON) in labeled common SETUPG
ITURBG(NCON) in labeled common SETUPG
JFRADG(NCON) in labeled common SETUPG
JTURPG(NCON) in labeled common SETUPG
KAECGC2) in labeled common PAPTG
KAHG(3,5) in labeled common HYDROG
K6ACSG(3,5) in labeled common BACTG
KBACWG(3,5) in labeled common BACTG
KBHG(3,5) in labeled common HYDROG
KCECGC2) in labeled common PARTG
KDPGC5) in labeled common DPHOTG
KNHG(3,5) in labeled common HYDROG
K02G(NPX) in labeled common OUALG
KOCG in labeled common PAPTG
KOUNT in labeled common SETUPG
KOWG in labeled common PARTG
KOXG(3,5) in labeled common OXIDG
KPBG(S) in labeled common PARTG
KPSG(5) in labeled common PARTG
KVOG in labeled common VOLATG
LAMAXG in labeled common DPHOTG
LATG in labeled common CLIMG
M«TG in labeled common PCHEMG
NCON in labeled common SETUP2
NPSEDG(NPX) in labeled common FLOWG
NPSFLG(NPX) in labeled common FLOWG
NPSLDG(NPX) in labeled common LOADSG
NPX in labeled common SETUP2
OXRADG(NPX) in labeled common QUALG
PCPLDG(NPX) in labeled common LOADSG
PCTWAG(NPX) in labeled common SEDMG
PHG(NPX) in labeled common QUALG
PKAG(2) in labeled common IONG
PKBGC2) in labeled common IONG
PLRAG(NPX) in labeled common OUALG
331
-------
POHG(NPX) In labeled common QUALG
QTBASG(3,5) in labeled common BACTG
QTBArfG(3,5) in labeled common BACTG
QUANTG(3,5) in labeled common DPHOTG
RAING in labeled common CLIMG
RFLATG(S) in labeled common DPHOTG
SDCHRG(NPX) in labeled common SEDMG
SOLGC5) in labeled common PCHEMG
SPFLG(S) in labeled common CONTRG
STFLOG(NPX) in labeled common FLOWG
STRLDG(NPX) in labeled common LOADSG
STSEDG(Npx) in labeled common FLOWG
SYSTYP(60) in labeled common NAME2G
TCELG(NPX) in labeled common QUALG
TTYOUT in labeled common UNITS
TYPEE(NPX) In labeled common NAME2G
VAPRG in labeled common VOLATG
VOLG(NPX) in labeled common GEOMT
wiNDG(NPX) in labeled common CLIMG
WLAMGC39) in labeled common PHOG
XSTUPG(NCON) in labeled common SETUPG
IV. USAGE
A. ENTRY POINT: DATAIN
B. CALLING SEQUENCE: None
C. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS: If the requested chemical or
environmental data cannot be
found, the run is aborted.
V. ALGORITHM OR METHOD — not applicable
I. IDENTIFICATION
A. TITLE: BLOCK DATA
B. SOURCE LANGUAGE: FORTRAN IV
332
-------
C. AUTHOR, DATE: L.A. Burns, Aug. 1979
D. REVISION: Oct. 19RO
II. PURPOSE: BLOCK DATA is used to load constant input data.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
c. COMMON STORAGE:
B in labeled common SETUPL
BATCH in labeled common SETUPG
DOCETAO9) in labeled common DPHQTL
E in labeled common SETUPL
H in labeled common SETUPL
KlNOUT in labeled common UNITS
L in labeled comnmon SETUPL
NCON in labeled common SETUPL
NPX in labeled common SETUPL
PIGETAO9) in labeled common DPHOTL
RPTOUT in labeled common UNITS
SEDETAO9) in labeled common DPHOTL
SSOUT in labeled common UNITS
TTYIN in labeled common UNITS
TTYOUT in labeled common UNITS
WATETAO9) in labeled common DPHOTL
IV. USAGE
A. ENTRY POINT: None
B. CALLING SEQUENCE: None
C. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS: NOne
E. ERROR CONDITIONS AND RETURNS: None
V. ALGORITHM OR METHOD -- not applicable
333
-------
I. IDENTIFICATION
A. TITLE: GHOST
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: L.A. Burns, Aug. 1979
D. REVISION: Jan. 1981
II. PURPOSE: GHOST is a program control module that dimensions
the state variable(s) (Y), sets error criteria, calls
subroutines, preserves intermediate variables, and checks
for error flags (IFLAG) that may be set by its subroutines.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: AVEOUT
CKLOAD
DISTRB
DRIVER
FIRORD
FLOWS
FLXOUT
PRCHEM
PRENV
STEADY
SUMUP
C. COMMON STORAGE:
CHEMNAC60) in labeled common NAME1G
ICALL in labeled common SETUPL
IFLAG in labeled common TIMEL
JSAV1 in labeled common SETUPL
JSAV2 in labeled common SETUPL
KINOUT in labeled common UNITS
KOUNT in labeled common SETUPG
NPX in labeled common SETUPL
QSSAV in labeled common RESULT
QTSAV in labeled common RESULT
QWSAV in labeled common RESULT
RPTOUT in labeled common UNITS
SSOUT in labeled common UNITS
SYSTYP(60) In labeled common NAME2G
TTYOUT In labeled common UNITS
Z(18) in labeled common RESULT
334
-------
IV. USAGE
A. ENTRY POINT! GHOST
8. CALLING SEQUENCE: CALL GHOST
C. INPUT ARGUMEMTS: None
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS:
Returns to calling program if the number of ecosystem
compartments requested by the user exceeds the maximum
number available (NPX), or if any subroutine returns with
IFLAG .GE. 8.
V. ALGORITHM OR METHOD — not applicable
I. IDENTIFICATION
A. TITLE: PRCHE*
8. SOURCE LANGUAGE: FORTRAN iv
C. AUTHOR, DATE: L.A. Burns, Aug. 1979
D. REVISION: Jan. 1981
II. PURPOSE: PRCHEM records input chemical data in an output
file.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: INREC
c. COMMON STORAGE:
ABSG(39f5) in labeled common DPHOTG
335
-------
BATCH in labeled common SETUPG
CHEMNAC60) in labeled common NAME1G
EAHG(3,5) in labeled common HYDROG
EBHG(3,5) in labeled common HYDROG
EHENG in labeled common VOLATG
ENHG(3,5) in labeled common HYDROG
EQXG(3,5) in labeled common OX1DG
EPKAGC2) in labeled common IQNG
EPKBG(2) in labeled common IONG
ESOLG(5) in labeled common PCHEMG
EVPRG in labeled common VOLATG
HENRYG in labeled common VOLATG
KAECGC2) in labeled common PARTG
KAHG(3,5) in labeled common HYDROG
KBACSG(3,5) in labeled common BACTG
KBACWG(3f5) in labeled common BACTG
KBHG(3,5) in labeled common HYDROG
KCECGC2) in labeled common PARTG
KDPG(5) in labeled common DPHOTG
KNHG(3,5) in labeled common HYDROG
KOCG in labeled common PARTG
KOWG in labeled common PARTG
KOXG(3,5) in labeled common OXIDG
KPBG(5) in labeled common PARTG
KPSG(5) in labeled common PARTG
KVOG in labeled common VOLATG
LAMAXG in labeled common DPHOTG
MWTG in labeled common PCHEMG
PKAG(2) in labeled common IONG
PKBG(2) in labeled common IONG
QTBASG(3,5) in labeled common BACTG
QTBAWG(3,5) in labeled common BACTG
QUANTG(3,5) in labeled common DPHOTG
RFLATGC5) in labeled common DPHOTG
RPTOUT in labeled common UNITS
SOLG(S) in labeled common PCHEMG
SPFLG(5) in labeled common CONTRG
SYSTYP(60) in labeled common NAME2G
TTYIN in labeled common UNITS
TTYOUT in labeled common UNITS
VAPRG in labeled common VOLATG
IV. USAGE
A. ENTRY POINT: PRCHEM
B. CALLING SEQUENCE! CALL PRCHEM
C. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS: None
336
-------
E. ERROR CONDITIONS AND RETURNS:
Returns to calling program with IFLAG set to 8 if SPFLG(l)
.EQ. 1 .AND. MWTG.LE.O.
V. ALGORITHM OR METHOD
Subroutine PRCHEM records the chemical characterization of
the compound (input data) in the output file defined by
FORTRAN logical unit PPTOUT.
I, IDENTIFICATION
A. TITLE: PRENV
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: L.A. Burns, Aug. 1979
D. REVISION: Nov. 1980
II. PURPOSE: PRENV records input environmental data in an
output file and executes several data evaluation and
augmentation sequences.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: INREC
c. COMMON STORAGE:
ACBACG(NPX) in labeled common QUALG
ADVPRG(NCON) in labeled common SETUPG
AECG(NPX) in labeled common SEDMG
AREAG(NPX) in labeled common GEQMT
B in labeled common SETUPL
BACTOG(NPX) in labeled common QUALG
BATCH In labeled common SETUPG
BIOMSG(NPX) in labeled common QUALG
337
-------
BIOTMG(NPX) in labeled common QUALG
CECG(NPX) In labeled common SEDMG
CHARLG(NCON) in labeled common SETUPG
CHEMNA(60) in labeled common NAME1G
CHLG(NPX) in labeled common PHOG
CLOUDG in labeled common PHOG
CMPETG(NPX) in labeled common PHOG
DEPTHG(NPX) in labeled common GEOMT
DFACG(^PX) in labeled common PHOG
DOCETAO9) in labeled common OPHOTL
DOCG(NPX) in labeled common PHOG
DSPG(NCON) in labeled common SETUPG
EVAPG(NPX) in labeled common CLIMG
FROCG(NPX) in labeled common SEDMG
IFLAG in labeled common TIMEL
INTFLG(NPX) in labeled common FLOfcG
ITOAOG(NCON) in labeled common SETUPG
ITURBG(NCON) in labeled common SETUPG
JFRADG(NCON) in labeled common SETUPG
JTURBG(NCON) in labeled common SETUPG
K02GCNPX) in labeled common QUALG
KOUNT in labeled common SETUPG
LAMAXG in labeled common OPHOTG
LATG in labeled common CLIMG
NCON in labeled common SETUPL
NPSEDG(NPX) in labeled common FLOWG
NPSFLG(NPX) in labeled common FLOWG
PCTWAG(NPX) in labeled common SEDMG
PIGETA(39) in labeled common DPHOTL
PLPAG(NPX) in labeled common QUALG
RAING in labeled common CLIMG
RPTOUT in labeled common UNITS
SDCHRG(NPX) in labeled common SEDMG
SEDETAO9) in labeled common DPHOTL
STFLOG(NPX) in labeled common FLOWG
STSEDG(NPX) in labeled common FLOWG
SYSTYPC60) in labeled common NAME2G
TTYIN in labeled common UNITS
TTYOUT in labeled common UNITS
TYPCC(NPX) in labeled common NAME2G
NATETAO9) in labeled common DPHOTL
HINDG(NPX) in labeled common CLIMG
WLAMGO9) in labeled common PHOG
XSTURG(NCON) in labeled common SETUPG
IV. USAGE
A. ENTRY POINT: PRENV
B. CALLING SEQUENCE: CALL PRENV
338
-------
c. INPUT ARGUMENTS: None
D, OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS:
Returns to calling program with IFLAG set to 8 if the water
content (PCTwAG) or bulk density (SDCHPG) of any benthic
segment is zero.
V. ALGORITHM OR METHOD
Subroutine PRENV records the characteristics of the
environment (input data) in the output file defined by
FORTRAN logical unit RPTOUT. Several data evaluation and
augmentation sequences are also executed by this
subroutine:
1. Absolute zeros for FROCG, CECG, AND AECG are replaced
with reasonable lower bounds (0,001, 0.01, and O.Oi
respectively).
2. Absolute zeros for suspended sediments (SDCHRG of
water column segments) are replaced with a value of 0,001
mg/L.
3, If CMPETG(J) is zero, LAMAXG is used to locate the
corresponding spectral light absorption coefficients and
compute the needed value(s) of C^PETG.
I. IDENTIFICATION
A, TITLE: DISTRB
B, SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: I.A. Burns, Aug. 1979
D, REVISION: May 1980
II. PURPOSE: DISTPB calculates distribution coefficients
(fraction of total concentration present as a particular
molecular species) for charged and uncharged chemical
339
-------
species (up to 5), each in a free (dissolved),
sediment-sorbed, and biosorbed form.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
c. COMMON STORAGE:
AECG(NPX) in labeled common SEDMG
ALPHA(18,NPX) in labeled common PART1L
AREAG(NPX) in labeled common GEOMT
8 in labeled common SETUPL
BIOMSG(NPX) in labeled common QUALG
BIOTOL(NPX) in labeled common MASSL
CECG(NPX) in labeled common SEDMG
E in labeled common SETUPL
EPKAG(2) in labeled common IONG
EPKBG(2) in labeled common IONG
FROCG(NPX) in labeled common SEDMG
H in labeled common SETUPL
IFLAG in labeled common TIMEL
INDEXS(NPX) in labeled common SETUPL
INDEXW(NPX) in labeled common SETUPL
KAIL(NPX) in labeled common CHEM2L
KA2L(NPX) in labeled common CHEM2L
KAECG(2) in labeled common PARTG
KBIL(NPX) in labeled common CHEM2L
KB2L(NPX) in labeled common CHEM2L
KCECG(2) in labeled common PARTG
KOCG in labeled common PARTG
KOCL in labeled common PART1L
KOUNT in labeled common SETUPG
KOUNTS in labeled common SETUPL
KOUNTW in labeled common SETUPL
KOWG in labeled common PARTG
KPBG(5) in labeled common PARTG
KPSG(5) in labeled common PARTG
KPSL(5,N?X) in labeled common PART1L
L in labeled common SETUPL
NPX in labeled common SETUPL
PCTWAG(NPX) in labeled common SEDMG
PHG(NPX) in labeled common QUALG
PKAGC2) in labeled common IONG
PKBGC2) in labeled common IONG
POHG(NPX) in labeled common QUALG
SEDCHRG(NPX) In labeled common SEDMG
SEDCOL(NPX) in labeled common MASSL
SEDMSL(NPX) in labeled common MASSL
340
-------
SPFLGC5) in labeled common CONTRG
TCELG(NPX) in labeled common QUALG
TTYOUT in labeled common UNITS
TYPEE(NPX) in labeled common NAME2G
VOLG(NPX) in labeled common GEOMT
WATVOL(NPX) in labeled common MASSL
IV. USAGE
A. ENTRY POINT: DISTRB
B. CALLING SEQUENCE: CALL DISTRB
C. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS! None
E. ERROR CONDITIONS AND RETURNS:
Returns to calling program with IFLAG set to 8 if any
compartment type (TYPEE) is improper.
V. ALGORITHM OR METHOD
Subroutine DISTRB partitions the chemical among its ionic
species (up to 5), with each of the ionic species further
partitioned into dissolved* sediment-sorbed, and biosorbed
forms. The resulting distribution coefficients (ALPHA) are
subsequently (subroutine FIRORD) used as multipliers on the
(input data) 'homogeneous-phase reaction rate coefficients.
The (DISTRB) input data for ionization Includes the pKa of
organic acids and pKb of organic bases. These data may be
loaded either as single values or as temperature functions;
in the latter case the temperature (TCELG) of each
compartment is used to compute a local value of the
ionization constant. Sorption to biomass and to whole
sediments are also treated as equilibrium processes. For
biomass sorptlon, the equilibrium constant (partition
coefficient) is loaded as a single value for each chemical
species (KPBG). The partition coefficient for whole
sediments can be loaded in several ways; this feature is
described in the glossary for EXAMS under "KPSL" and in
Section 2.2.2,
The fraction of the total concentration (Y state
variable) present in each of the 15 possible molecular
configurations (dissolved neutral molecule, etc.) is loaded
to the ALPHA matrix. ALPHA contains as many columns as
there are ecosystem segments, and also includes the tnt-ai
dissolved, sediment-sorbed, and biosorbed fractions
341
total
(as
-------
ALPHA 16, 17, and 18).
The chemical equations for the pK of ionic species and
the partitioning coefficients of each ion, together with
the conservation condition (sum of all species/forms *
total concentration) give a set of 15 equations in 15
unknowns for the 15 distribution coefficients (ALPHA). The
(pre-computed) solution to this system of equations is the
heart of the code for subroutine DISTRB. For each
ecosystem compartment, the contribution of each
species/form configuration (DISFCT(I)) is computed, their
sum is taken, and then each ALPHA is computed as the ratio
of DISFCT(I) to that sum.
I. IDENTIFICATION
A. TITLE: FLOWS
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: L.A. Burns, Aug. 1979
D. REVISION: May 1980
II, PURPOSE: FLOWS computes advective and dispersive transport
fields for water and sediments in a steady-state aquatic
ecosystem.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: DISPER
PRFLOW
SEDADV
HATADV
c. COMMON STORAGE:
AREAG(NPX) in labeled common GEOMT
B In labeled common SETUPL
EVAPG(NPX) in labeled common CLIMG
EVAPL(NPX) in labeled common FLOHSL
342
-------
H in labeled common SETUPL
IFLAG in labeled common TIMEL
INDEXW(NPX) in labeled common SETUPL
INTFL(NPX) in labeled common FLOWSL
INTFLG(NPX) in labeled common FLOWG
JFRADG(NCON) in labeled common SETUPG
KOUNT in labeled common SETUPG
MCON in labeled common SETUPL
NpSCOL(NPX) in labeled common FLOwSL
NPSEOG(NPX) in labeled common FLOfcG
NpSFL(NPX) in labeled common FLOWSL
NPSFLG(NPX) in labeled common FLrmG
RAINFL(NPX) in labeled common
RAING In labeled common CL1MG
STFLQG(NPX) in labeled common
STRMFL(NPX) in labeled common FLOWSL
STSCOL(NPX) in labeled common FLOWSL
STSEDG(NPX) in labeled common FLO*G
TTYOUT in labeled common UNITS
TYPEE(NPX) in labeled common NAME2G
WATFL(NPX,NPX) in labeled common FLOWSL
in labeled common FLO^SL
IV, USAGE
A. ENTRY POINT: FLOWS
B. CALLING SEQUENCE: CALL FLOWS
C. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS:
Returns to calling program with IFLAG set to 8 if:
1) any compartment is completely disconnected from the
main body of the system, or
2) subroutine ftATADV sets IFLAG to 8.
V. ALGORITHM OR METHOD
Subroutine FLOWS is primarily a dispatching routine. FLOWS
converts the global (input) parameters describing the
hydrology, geometry, and sediment loads in the ecosystem to
their internal dimensions, computes the net advective flow
in each compartment, checks for erroneous input data, and
calls on four additional subroutines to compute the
343
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advectlve (WATAPV, SEDADV)
transport fields, and to print
and dispersive (DISPER)
the results (PRFLOW),
I. IDENTIFICATION
A. TITLE: WATADV
B. SOURCE LANGUAGE: FORTRAN iv
C. AUTHOR, DATE: L.A. Burns, Aug. 1979
D. REVISION: Jan. 1981
II. PURPOSE: WATADV calculates the total advection of water
among ecosystem compartments, and the magnitude of
advective exports.
net
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
C. COMMON STORAGE:
ADVPRG(NCON) in labeled common SETUPG
IFLAG in labeled common TIMEL
ITOADG(NCON) in labeled common SETUPG
JFRADG(NCON) in labeled common SETUPG
KOUNT in labeled common SETUPG
NCON in labeled common SETUPL
SEDFL(NPX,NPX) in labeled common FLOWSL
SEDOUL(NPX) in labeled common FLOWSL
TTYOUT in labeled common UNITS
WATFL(NPX,NPX) in labeled common FLOWSL
WATINL(NPX) in labeled common FLOWSL
WATOUL(NPX) in labeled common FLOWSL
IV. USAGE
A. ENTRY POINT: WATADV
344
-------
B. CALLING SEQUENCE: CALL WATADV(TOTIN)
C. INPUT ARGUMENTS: TOTIN - total water flow entering system
fro* all sources, less total
evaporation.
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS:
Returns to calling program with IFLAG set to 8 if:
1) flows through any compartment have been defined in a
way that violates mass conservation,
2) the nominal (input) water budget for the whole system
fails to conserve mass, or
3) the Gaussian elimination processor fails.
V. ALGORITHM OR METHOD
The mass-conservative equations for hydrologic transport
through an n-compartment system are solved by Gaussian
elimination.
I. IDENTIFICATION
A. TITLE: SEDADV
B. SOURCE LANGUAGE: FORTRAN IV
c. AUTHOR, DATE: L.A. Burns, Aug. 1979
D. REVISION: May i960
II. PURPOSE: SEDADV computes transport of synthetic organics
via an evaluation of transport of suspended sediments among
system compartments, sediment exports, and bedload sediment
transport In an aquatic ecosystem.
III. RESTRICTIONS
345
-------
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
c. COMMON STORAGE:
IFLAG in labeled common TIMEL
INDEXS(NPX) In labeled common SETUPL
KOUNT in labeled common SETUPG
SEDCOL(NPX) in labeled common HASSL
SEDFL(NPX,NPX) in labeled common FLOWSL
SEDOUL(NPX) in labeled common FLOfcSL
TTYOUT in labeled common UNITS
WATFL(NPX,NPX) in labeled common FLOWSL
WATOUL(NPX) in labeled common FLQWSL
IV. USAGE
A. ENTRY POINT: SEDADV
B. CALLING SEQUENCE: CALL SEDADV
C. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS: Returns to calling program
with IFLAG=8 if compartment
#1 is a bottom sediment.
V. ALGORITHM OR METHOD
Subroutine SEDADV uses the advective flow field for water
(computed by subroutine WATADV) to compute the entrained
transport of suspended sediments, sediment exports, and
bedloads. This treatment of sediment flows of necessity
assumes that the system compartments have been numbered in
a logical way. Compartment II must be a water column. The
system block diagram must then be numbered in vertical
order, proceeding along the main advective flow path. For
example, for a river system with two vertical sediment
compartments in each reach, compartment li would designate
the water column of the first reach, 12 the shallow
sediment of the first reach, 13 its deeper sediment; 14
the water column of the second reach, 15 its shallow
sediment, 16 its deeper sediment, etc.
Given this numbering scheme, advected flows among
sediment compartments are permitted, so that bed-loads can
346
-------
move along the advective flow patncs) of the system.
Advective flows from the water column into the sediments
(and vice versa), however, are taken to involve a flow of
contaminated water only (as in groundwater seepage or
recharge).
Because either sediment genesis or degradation
(remineralization) can occur within system elements, the
system sediments are treated as a non-conservative
constituent. Thus the sediment concentrations in the
system compartments (in-put data loaded by the user) are
used directly in the computations, and no attempt is made
to construct a sediment budget froti the input (stream,
non-point-source) sediment loadings. The latter are simply
used to constrain chemical loadings to more-or-less
reasonable values (see subroutine CKLOAD).
The program provides for exchanges of sediments with
external sources and sintcs (i.e., boundary condition
dispersive exchanges), so the total sediment budget cannot
be explicitly determined.
Thus in summary, exports of water across system
boundaries carry an entrained sediment flow except in the
case where the outflow is from a bottom sediment
compartment AND the (J-i) compartment is also a sediment.
Intra-system transport of entrained sediment is subject to
three constraints: First, advective flows between water
columns carry a sediment load determined by the sediment
concentration in the source compartment. Second, advective
flows involving a sediment--water column pair are
constrained to a water flow only (ground water seepage and
recharge). Third, advection between sediments entrains a
parallel sediment flow only when the compartment numbers
indicate that the sediments are not vertically connected
(i.e., the compartment numbers differ oy more than one
digit). (See Section 2.3.1.3.)
I. IDENTIFICATION
A. TITLE: DISPER
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: L.A. Burns, Aug. 1979
347
-------
D. REVISION: JUl. 1980
II. PURPOSE: DISPEP calculates a dispersive transport field
(including boundary conditions) for water and sediments in
an aquatic ecosystem, and generates a total transport field
as the sum of advective and dispersive components.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
c. COMMON STORAGE:
ALPHA(18,NPX) in labeled common PART1L
CHARLG(NCON) in labeled common SETUPG
DSPG(NCON) in labeled common SETUPG
INDEXSCNPX) in labeled common SETUPL
INDEXW(NPX) in labeled common SETUPL
ITURBG(NCON) in labeled common SETUPG
JTURBG(NCON) in labeled common SETUPG
KOUNT in labeled common SETUPG
NCON in labeled common SETUPL
SEDCOL(NpX) in labeled common MASSL
SEDFL(NPX,NPX) in labeled common FLOWSL
SEDOUL(NPX) in labeled common FLOWSL
TTYOUT in labeled common UNITS
VOLG(NPX) in labeled common GEOMT
WATFL(NPX,NPX) in labeled common FLOWSL
WATOUL(NPX) in labeled common FLQWSL
WATVOL(NPX) in labeled common MASSL
XSTURG(NCON) in labeled common SETUPG
IV. USAGE
A. ENTRY POINT: DISPER
B. CALLING SEQUENCE: CALL DISPER
c. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS: None
V, ALGORITHM OR METHOD
348
-------
Computation of dispersive flows: In this series of
computations, the chemical transport arising from
dispersive mass transport is computed from Input data for
dispersive compartment pairings (JTURBG and ITURBG),
cross-sectional area (XSTURG, square meters),
characteristic length (CHAPLG, meters), and eddy
diffusivity (DSPG, square meters per hour) specified for
the exchange pairing. All boundary conditions for
dispersive exchange across system boundaries are taken as
zero in chemical concentration because, otherwise, the
estimates of persistence of the chemical (after loads are
removed) become Intractable.
The processes occurring in the water column are rather
different from those occurring within the sediments or at
the sediment-water interface, even though the computational
treatment is similar. The basic computation (DSPG * XSTUFG
/ CHAPLG) results in a quantity with dimensions of cubic
meters per hour, and nominally refers to transport of a
cubic meter of environmental volume. For transport among
water column compartments this presents no difficulty --
the water flow is given directly, and (given the
non-conservative treatment of sediment used in the program)
the parallel sediment flows are computed from the suspended
sediment concentrations in the source compartments.
Chemical exchange involving bed sediments must also account
for differences in the sorptive capacity of the bed layers
and the washload. EXAMS' treatment of this process is
discussed in Section 2.3.1.4.
I. IDENTIFICATION
A. TITLE: PRFLOW
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: L.A. Burns, Aug. 1979
D. REVISION: Jui. 1980
II. PURPOSE: PRFLOW writes a profile of the chemical transport
characteristics of an aquatic ecosystem to an output file.
349
-------
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
8. OTHER ROUTINES REQUIRED: None
C. COMMON STORAGE:
KOUNT In labeled common SETUPS
RPTOUT in labeled common UNITS
SEDFL(NPX,NPX) in labeled comnon FLOWSL
SEDMSL(Npx) in labeled common MASSL
SEDOUL(NPX) in labeled common FLOWSL
TYPEE(NPX) in labeled common NAME2G
VOLG(NPX) in labeled common GEOMT
MATFL(NPX,NPX) in labeled common FLOWSL
WATOUL(NPX) in labeled common FLOwSL
WATVOL(NPX) in labeled common MASSL
IV. USAGE
A. ENTRY POINT! PRFLOW
B. CALLING SEQUENCE: CALL PRFLOW
c. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS: None
V. ALGORITHM OR METHOD
Subroutine PRFLOW writes a compartment-by-compartment
summary of chemical transport characteristics of the
ecosystem to the output file defined by FORTRAN logical
unit RPTOUT.
The variables reported Include: compartment volumes,
total sediment masses, water and sediment flows, and
residence (turnover) times for water and sediments. The
compartment volumes are Input data (VOLG); the sediment
•asses are computed in subroutine FLOWS. Subroutine PRFLOW
computes the total chemical movement associated with water
and sediment transport through the compartments by summing
the advectlve plus dispersive flows loaded in matrices
wATFL and SEDFL and vectors HATOUL and SEDOUL (these
variables are loaded by subroutine DISPER). Residence
times are then computed as the ratio of water volume or
350
-------
sediment mass to the appropriate flow quantity. The value
loaded to the SEDFL matrix via dispersive processes can
vary if the sorptive capacity of the sediments differs,
i.e., the computed residence times can differ as a function
of properties of the chemical (see Section 2.3.1.4).
I. IDENTIFICATION
A. TITLE: CKLOAD
B. SOURCE LANGUAGE: FORTRAN iv
C, AUTHOR, DATE: L.A. Burns, Aug. 1979
D. REVISION: Jan. 1981
II. PURPOSE: CKLOAD constrains chemical loadings to values that
do not exceed 50% of the aqueous solubility or l.E-5 M
(after accounting for sorption), checics that input carrier
flows exist for each posited loading, and accumulates the
total compartment loadings,
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
C. COMMON STORAGE:
DRFLDG(NPX) in labeled common LOADSG
ESOLG(5) in labeled common PCHEMG
IFLAG in labeled common T1MEL
IFLLDG(NPX) in labeled common LOADSG
INTFL(NPX) in labeled common FLQfoSL
KAIL(NPX) in labeled common CHEM2L
KA2L(NPX) in labeled common CHEM2L
KBIL(NPX) in labeled common CHEM2L
KB2L(NPX) in labeled common CHEM2L
KOUNT in labeled common SETUPG
KPSL(5,NPX) in labeled common PART1L
MWTG in labeled common PCHEMG
NPSCOL(WPX) in labeled common FLOWSL
351
-------
NPSFL(NPX) in labeled common FLONSL
NPSLDG(NPX) in labeled common LOADSG
PCPLPG(NPX) in labeled common LOADSG
PHG(NPX) in labeled common QUALG
POHG(NPX) in labeled common OUALG
RAINFL(NPX) in labeled common FLOWSL
SOLG(5) in labeled common PCHEMG
SPFLG(5) in labeled common CQNTRG
STRLDG(NPX) in labeled common LOADSG
STRMFL(NPX) in labeled common FLOWSL
STSCOL(NPX) in labeled common FLObSL
SYSLDL in labeled common MISCL
TCELG(NPX) in labeled common OUALG
TOTLDL(NPX) in labeled common MISCL
TTYOUT in labeled common UNITS
YSATL(5,NPX) in labeled common FLOWSL
IV. USAGE
A. ENTRY POINT: CKLOAD
B. CALLING SEQUENCE: CALL CKLOAD
C. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS: If no positive loadings
remain, IFLAG is set to 8,
V. ALGORITHM OR METHOD
Subroutine CKLOAD accumulates the total loadings to
system elements (compartments), removes loadings that lack
an associated input carrier flow, and checks to ensure that
none of the loadings (via rainfall, interflow (ground-water
seepage), point (stream), or non-point sources are at
aqueous concentrations (after accounting for partitioning
to sediments in the input flows) greater than 50% of
aqueous solubility at the temperature specified for the
system element receiving the load, or l.E-5 M in SH2.
(This constraint is imposed to ensure that the simulation
run is in accord with the Intrinsic assumptions used to
develop the program, e.g., that linear sorption isotherms
are proper, and that the chemical loadings do not include
solid particles.)
The computational scheme used in CKLOAD is, in
principle, the same as that used in subroutine DISTRB,
352
-------
i.e., the code contains the solution to systems of linear
equations describing the distribution coefficients (local
variable BETA for the 5 or 10 possible molecular species).
Those cases requiring water quality data (e.g., water
temperature or pH) use input data for the target
compartment of the loading under review, tfhen the residual
concentration exceeds the concentration limit, the load is
reduced and an informative message is written to the user
in the output data set defined by FORTRAN logical unit
TTYOUT.
I. IDENTIFICATION
A. TITLE: FIRORO
B. SOURCE LANGUAGE: FORTRAN iv
c. AUTHOR, DATE: L.A. Burns, Aug. 1979
D. REVISION: NOV. 1980
II. PURPOSE: FIRORD merges environmental data and chemical
characteristics of an organic compound to yield a
pseudo-first-order description of the chemical's kinetic
behavior.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: PHOT01
PHOT02
VOLAT
c. COMMON STORAGE:
ABSG(39,5) in labeled common DPHOTG
ACBACG(NPX) in labeled common QUALG
ALPHA(18,NPX) In labeled common PAPT1L
B in labeled common SETUPL
BACTOG(NPX) in labeled common QUALG
BIOLKL(NPX) in labeled common CHEMiL
BIOTMG(NPX) in labeled common QUALG
353
-------
CHEMNA(60) in labeled common NAME1G
CONLDL(NPX) in labeled common MISCL
EAHG(3,5) in labeled common HYDROG
EBHG(3,5) in labeled common HYDROG
ENHG(3,5) in labeled common HYDROG
EOXG(3,5) in labeled common OXIDG
EXPOKL(NPX) in labeled common CHEMIL
H in labeled common SETUPL
HENRYG in labeled common VOLATG
HYDRKL(NPX) in labeled common CHEMIL
INDEXS(NPX) in labeled common SETUPL
INDEXW(NPX) in labeled common SETUPL
INTINL(NPX,NPX) in labeled common CHEMIL
KAHG(3,5) in labeled common HYDROG
KBACSG(3,5) in labeled common BACTG
KBACWG(3,5) in labled common BACTG
KBHG(3,5) in labeled common HYDROG
KDPG(5) in labeled common DPHOTG
KNHG(3,5) in labeled common HYDPOG
K02(NPX) in labeled common QUALG
K02LCNPX) in labeled common FLOWSL
KOUNT in labeled common SETUPG
KOXG(3,5) in labeled common OXIDG
LIGHTL(NPX) in labeled common ENPARL
MWTG in labeled common PCHEMG
OXIDKL(NPX) in labeled common CHEMIL
OXRADG(NPX) in labeled common QUALG
PHG(NPX) in labeled common QUALG
PHOTKL(NPX) in labeled common CHEMIL
PLRAG(NPX) in labeled common QUALG
POHG(NPX) in labeled common QUALG
QTBASG(3,5) in labeled common BACTG
QTBAWG(3,5) in labeled common BACTG
QUANTG(3,5) in labeled common DPHOTG
RPTOUT in labeled common UNITS
SEDCOL(NPX) in labeled common MASSL
SEDFL(NPX,NPX) in labeled common FLOWSL
SEDMSL(NPX) in labeled common MASSL
SEDOUL(NPX) in labeled common FLOWSL
SPFLG(5) In labeled common CONTRG
SYSTYP(60) in labeled common NAME2G
TCELG(NPX) in labeled common QUALG
TOTKL(NPX) in labeled common CHEMIL
TOTLDL(NPX) in labeled common MISCL
TYPEE(NPX) In labeled common NAME2G
VAPR6 in labeled common VOLATG
VOLKL(NPX) in labeled common CHEMIL
MATFL(NPX,NPX) in labeled common FLOWSL
HATOUL(NPX) in labeled common FLOWSL
WATVOL(NPX) In labeled common MASSL
WINDG in labeled common CLIMG
354
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IV. USAGE
A. ENTRY POINT: FIRQRD
B. CALLING SEQUENCE: CALL FIRORD
C. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS: None
V, ALGORITHM OR METHOD
This routine reduces system-independent process models
describing the kinetics of a synthetic organic chemical to
pseudo-first-order form by coupling characteristics of the
chemical and of the environment. Insofar as the input data
permits, the chemical properties of the compound are
adjusted (via Arrhenius functions) to reflect the effect of
temperature in each physical element (compartment) of the
system. The pseudo-first-order reaction rate constants are
calculated from the interactive effects of partitioning,
temperature, and other relevant charateristics of the
environment (pH, pOH, irradiance, advectlon, bacterial
population sizes, etc.) for each ionic species/sorbed form
of the chemical present; the reactivities of the several
varieties are summed to give a total pseudo-first-order
rate constant. The routine accounts for the potential
existence of five ionic species (neutral molecule, singly
and doubly charged cations and anions), each of which may
occur in three sorbed forms (dissolved, sediment-sorbed,
bio-sorbed.
The processes evaluated include photolysis,
volatilization, hydrolysis, oxidation, bacterial biolysis,
transport, and ionization and sorption equilibria. Routine
FIRORD also converts the external input loadings and the
advective and dispersive flow field into pseudo-first-order
effects on chemical concentrations and writes both a
kinetic profile of the compound and a canonical profile of
the ecosystem to the file defined by FORTRAN logical unit
RPTOUT, Routine FIRORD also calls three subroutines
(PHOTO!, PHQT02, and VOLAT) that evaluate photolysis and
volatility. (PHOT01 and PHOT02 are n-utually exclusive
computations; FIRORD selects the appropriate routine based
on the structure of the input data.)
355
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I, IDENTIFICATION
A. TITLE: PHOTOI
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: L.A. Burns, Aug. 1979
D. REVISION: Oct. 1980
II. PURPOSE: PHOTOI corrects an experimental pseudo-first-order
rate constant for photolytic decomposition of a synthetic
organic chemical in the water column of an aquatic
ecosystem for effects of cloud cover, water depth, and
deviation of the latitude of the ecosystem from that of the
location where the experiment was executed.
Ill, RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
c. COMMON STORAGE:
BOTLIT in labeled common ENPARL
CLOUDG in labeled common PHOG
CMPETG(NPX) in labeled common PHOG
DEPTHG(NPX) in labeled common GEOMT
DFACG(NPX) in labeled common PHOG
E in labeled common SETUPL
H in labeled common SETUPL
JSAVl in labeled common SETUPL
KDPG(S) in labeled common DPHOTG
LATG in labeled common CLIMG
LIGHTL(NPX) in labeled common ENPARL
RFLATG(S) in labeled common DPHOTG
TYPEE(NPX) in labeled common NAME2G
IV. USAGE
A, ENTRY POINT: PHOTOI
B. CALLING SEQUENCE: CALL PHOTOI(RATEK,K,J)
C. INPUT ARGUMENTS: K - index value for chemical species
J - index value for ecosystem compartment
D. OUTPUT ARGUMENTS: RATEK: pseudo-first-order photolysis rate
356
-------
constant
E. ERROR CONDITIONS AND RETURNS: None
V. ALGORITHM OR METHOD
The basic unit of input to PHOT01 is a first-order
photolysis rate constant of a synthetic chemical, generated
via experimental studies. This rate constant is assumed to
represent a temporally averaged value applicable under
cloudless conditions in near-surface waters at some
reference latitude (RFLATG). Distinct values of the rate
constant (KDPG(K)) and reference latitude (RFLATG(K)) may
be entered for each of five possible ionic species of the
chemical (neutral molecule, singly and doubly charged
cations and anions). PHOT01 applies the Beer-Lambert law
to compute the reduction in rate due to light absorption in
the water column of the system. Light intensity at the
water surface is taken as unity, and the average (relative)
light intensity in the water column is computed as a
function of depth (DEPTHG(J)), a single-valued zenith light
extinction coefficient (CMPETG(J)), and a distribution
function (DFACG(J)) for the current (J) compartment. If
the current (J) compartment has an overlying water mass,
the relative intensity at the bottom of this overlying
water (computed on a previous call to PHOT01) is used as
the starting point for computations in the current (J)
compartment.
An additional reduction in rate is calculated to
account for cloud cover, and the rate constant for the
current (K) chemical species is finally adjusted for the
difference in latitude between the location of the
ecosystem and the experimental studies. The latitude
correction is based on a cosine function describing total
annual light input (solar beam + sJcy light) at sea level
(data from Smithsonian Meteorological Tables (List 1966)).
I. IDENTIFICATION
A. TITLE: PHOT02
B. SOURCE LANGUAGE: FORTRAN IV
357
-------
C. AUTHOR, DATE; L.A. Burns, Aug. 1979
D. REVISION: Sep. 1980
II, PURPOSE; PHOT02 calculates the rate of light absorption by
a chemical in a water column compartment of an aquatic
ecosystem. The value returned by the routine can be
multiplied by a reaction quantum yield to give a
pseudo-first-order rate constant for photolytic
decomposition of the chemical.
Ill, RESTRICTIONS
A. MACHINE DEPENDENCY; None
B. OTHER ROUTINES REQUIRED; None
C» COMMON STORAGE;
ABSG(39,5) in labeled common DPHOTG
BOTLAM(39) in labeled common ENPARL
CHLG(NPX) in labeled common PHOG
CLOUDG in labeled common PHOG
DEPTHG(NPX) in labeled common GEOMT
DFACG(NPX) in labeled common PHOG
DOCETAC39) in labeled common DPHOTL
DOCG(NPX) in labeled common PHOG
E in labeled common SETUPL
H in labeled common SETUPL
ICALL in labeled common SETUPL
JSAV2 in labeled common SETUPL
LIGHTL(NPX) in labeled common ENPARL
PIGETAC39) in labeled common DPHOTL
SDCHRG(NPX) in labeled common SEDMG
SEDETAC39) in labeled common DPHOTL
TOTETAC39) in labeled common ENPARL
TYPEE(NPX) in labeled common NAME2G
WATETAC39) in labeled common DPHOTL
WAVELC39) in labeled common ENPARL
WLAMGC39) in labeled common PHOG
WLAMLO9) in labeled common ENPARL
IV. USAGE
A. ENTRY POINT: PHOT02
B. CALLING SEQUENCE: CALL PHOT02(RATEK,K,J)
C, INPUT ARGUMENTS; K - index value for chemical species
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J - index value for ecosystem compartment
D. OUTPUT ARGUMENTS: RATEK - rate of absorption of light by
synthetic organic chemical
£. ERROR CONDITIONS AND RETURNS: None
V, ALGORITHM OR METHOD
This routine adjusts the near-surface spectral irradiance
(WLAMG) for effects of cloud cover, fills out wavelength
intervals (e.g., for interval 39, the input data has
dimensions /10 nm, but the full width of the interval is 50
nm), and pre-multiplies all data by a units conversion
FACTOR, with the outcome stored in w'LAML, For each water
column, a (spectral) total light absorption coefficient is
assembled as the sum of contributions from water itself,
suspended sediments (SDCHRG), dissolved organic carbon
(DOCG), and chlorophyll and chlorophyll-like pigments
(CHLG). The Beer-Lambert law is then used to compute light
absorption and average spectral irradiance within the water
column compartment. If the current (J) compartment has an
overlying water-mass, spectral irradiance at the bottom of
this overlying water (comouted on a previous call to
PHOT02) is used as a starting point for computations in the
current (J) compartment. Light absorption by the current
(K) ionic species of a chemical is computed by coupling the
average spectral irradiance in the water column, the
absorption spectrum of the compound, and the distribution
function of the current (J) compartment. The routine
assumes that the chemical itself does not contribute
significantly to the total light absorption coefficient.
The algorithm is described in detail in Section 2.3.3.
I. IDENTIFICATION
A. TITLE: VOLAT
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: L.A. Burns, Aug. 1979
D. REVISION: Jul. 1980
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II, PURPOSE: VOLAT computes a pseudo-first-order rate constant
describing the export of a synthetic organic chemical
across the air-water interface of an aquatic ecosystem.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
c. COMMON STORAGE:
AREAG(NPX) in labeled common GEOMT
EHENG in labeled common VQLATG
ESOLG(5) in labeled common PCHEMG
EVPRG in labeled common VOLATG
HENRYG in labeled cotimon VOLATG
K02G(NPX) in labeled common QUALG
K02L(NPX) in labeled common FLDWSL
KVOG in labeled common VOLATG
MWTG in labeled common PCHEMG
SOLG(5) in labeled common PCHEMG
TCELG(NPX) in labeled common QUALG
VAPRG in labeled common VOLATG
VOLG(NPX) in labeled common GEOMT
WINDG(NPX) in labeled common CLIMG
IV. USAGE
A. ENTRY POINT: VOLAT
B. CALLING SEQUENCE: CALL VOLATCK,BETA,RATEK)
C. INPUT ARGUMENTS: K - index value for ecosystem compartment
BETA - fraction of total concentration of
chemical that is present as neutral
(uncharged), dissolved species.
D. OUTPUT ARGUMENTS: RATEK - pseudo-first-order rate constant
for volatilization
E, ERROR CONDITIONS AND RETURNS: None
V. ALGORITHM OR METHOD
VOLATG uses a two-resistance model (Whitman 1923) to
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compute a pseudo-first-order rate constant for
volatilization losses of a synthetic organic chemical
across the air-water interfaces of an aquatic ecosystem.
The bulk air concentration of the chemical is assumed to be
negligible. The first-order rate constant is computed as
the total transport conductivity (reciprocal of the sum of
resistances to transport in the liquid and gas phases)
multiplied by the fraction of the total concentration of
the chemical present in transportable (i.e., unsorbed,
uncharged) form (input argument BETA), times the surface to
volusne ratio of the current (K) compartment. The routine
corrects the input reaeration parameter (cm/hr at 20
degrees C.) for the temperature of the current (K)
compartment. Liquid phase resistance is computed either
from an experimentally determined ratio to the reaeration
rate, or, if this parameter (KVOG) is entered as a zero,
resistance is estimated from the square root of the ratio
of molecular weights of oxygen and the chemical. Gas phase
resistance is estimated from the Henry's law constant of
the chemical, temperature, the molecular weight ratio of
the chemical to the molecular weight of water, and a piston
velicity for water vapor computed from the input values for
windspeed (Liss 1973). If a zero value is loaded for the
Henry's law constant, this parameter is estimated from the
vapor pressure/solubility ratio.
I. IDENTIFICATION
A. TITLE: STEADY
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: L.A. Burns, Aug. 1979
D. REVISION: Jan. 1981
II. PURPOSE: STEADY computes the steady-state concentration of
synthetic organic chemicals in all active ecosystem
compartments.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
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B. OTHER ROUTINES REQUIRED: None
C. COMMON STORAGE:
ALPHA(18,NPX) in labeled common PART1L
BATCH in labeled common SETUPG
CONLOL(NPX) in labeled common MISCL
DRFLDG(NPX) in labeled common LOADSG
IFLAG in labeled common TIMEL
IFLLDG(NPX) in labeled common LOADSG
INTINL(NPX,NPX) in labeled common CHEM1L
KOUNT in labeled common SETUPG
NPSLDG(NPX) in labeled common LOADSG
PCPLDG(NPX) in labeled common LOADSG
RPTOUT in labeled common UNITS
SPFLGC5) in labeled common CONTRG
STRLDG(NPX) in labeled common LOADSG
SYSLDL in labeled common MISCL
TOTKL(NPX) in labeled common CHEM1L
TOTLDL(NPX) in labeled common MISCL
TTYOUT in labeled common UNITS
WATVOMNPX) in labeled common MASSL
YSATL(5,NPX) in labeled common FLOWSL
IV. USAGE
A. ENTRY POINT: STEADY
B. CALLING SEQUENCE: CALL STEADY(Y)
C. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS: Y - steady-state concentration vector
C. ERROR CONDITIONS AND RETURNS:
Returns to calling program with IFLAG set to 8 if final
concentrations exceed solubility criteria.
V. ALGORITHM OR METHOD
The steady-state concentration vector (Y) Is computed
by Gaussian elimination. The processor matrix is loaded
with INTINL (transport), (-TOTKL) on the diagonal, and
(normalized) zero-order loadings expressed in terns of
their effect on concentration (-CONLDL). For those cases
in which Gaussian elimination fails, a linear cascade
technique is invoiced to compute Y. In this algorithm, the
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algebraic solution
Y(J) =
-------
BIOTOL(NPX) In labeled comuon MASSL
CHEMNA(ftO) in labeled common NAMEJ.G
DOMAX(IO) in labeled common RESLT
DOMIN(IO) in labeled common RESLT
INDEXS(NPX) in labeled common SETUPL
INDEXWCNPX) in labeled common SETUPL
KOUNT in labeled common SETUPG
KOUNTS in labeled common SETUPL
KOUNTW in labeled common SETUPL
MAXPT(NPX) in labeled common RESLT
MINPT(NPX) in labeled common RESLT
RPTOUT in labeled common UNITS
SEDCOL(NPX) in labeled common MASSL
SEDMSL(NPX) in labeled common MASSL
SSOUT in labeled common UNITS
SYSTYP(60) in labeled common NAME2G
TYPEE(NPX) in labeled common NAME2G
WATVOL(NPX) in labeled common MASSL
Z(18) in labeled common RESULT
IV. USAGE
A. ENTRY POINT: AVEOUT
B. CALLING SEQUENCE! CALL AVEOUT(Y)
C. INPUT ARGUMENTS: Y - steady-state concentration vector for
synthetic organic chemical
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS: None
V. ALGORITHM OR METHOD
Output concentration variables are computed as the
product of the appropriate distribution coefficient (ALPHA)
and the total concentration of chemical (Y) in each
compartment. Average values are found by summing over
compartments followed by division by the number of
compartments involved. Concentration maxima and minima are
found by simple magnitude testing.
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I. IDENTIFICATION
A. TITLE: FLXOUT
B, SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: L.A. Burns, Aug. 1979
D, REVISION! Jan, 1981
II. PURPOSE: FLXOUT analyzes and reports the steady-state fate
of synthetic orqanlc chemicals.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
c. COMMON STORAGE:
BIOLKL(NPX) in labeled common CHEMlL
BIOPCT in labeled common RESLT
CHEMNA(60) in labeled common NAME1G
CHEMPC in labeled common RESLT
EXPOKL(NPX) in labeled common CHEMlL
EXPPCT in labeled common RESLT
HYDRKL(NPX) in labeled common CHEMlL
INDEXS(NPX) in labeled common SETUPL
KDTIME in labeled common TIMEL
KINOUT in labeled common UNITS
KOUNT in labeled common SETUPG
OXIDKL(NPX) in labeled common CHEMlL
PHOTKL(NPX) in labeled common CHEMlL
RPTOUT in labeled common UNITS
SYSLDL in labeled common MISCL
SYSTYPC60) in labeled common NAME2G
TFACTR in labeled common TIMEL
TFINAL in labeled common TIMEL
TINCR in labeled common TIMEL
VOLKL(NPX) in labeled common CHEMlL
VOLPCT in labeled common RESLT
WATVOL(NPX) in labeled common MASSL
Z(18) in labeled common RESULT
IV. USAGE
A. ENTRY POINT: FLXOUT
365
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B. CALLING SEQUENCE: CALL FLXOUTU)
C, INPUT ARGUMENTS: Y - steady-state concentration vector
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS: None
V. ALGORITHM OR METHOD
Subroutine FLXOUT analyzes and reports the
steady-state fate of synthetic organic chemicals. The
information reported for each process includes the mass
flux (leg/time) attributable to the process, the percentage
of the total load consumed in the process, and a projected
(first-order) half-life that would result from each process
acting in isolation absent internal transport limitations.
The processes are also summed by category (chemical,
biological, transport), and a total system half-life is
estimated from the total flux. The latter is used to
specify a time-frame for the numerical integration routines
(RKFINT and STFINT).
The fluxes are computed as the sum over compartments
of the product of concentration (Y(J)) and the
pseudo-first-order rate constant of each process in the
compartment (computed in FIRORD). Halflives are estimated
as 0.69 times the resident chemical mass divided by the
flux. The appropriate time-frame for reporting results
(hours, days, months, or years) is computed from the
(estimated) overall system halflife of the chemical. An
overall mass balance is struck: as the residual loading not
accounted for by process fluxes. The fate of the chemical
(process fluxes, mass balance, etc.) is written to the
output file defined by FORTRAN logical unit RPTOUT.
I. IDENTIFICATION
A. TITLES DRIVER
B. SOURCE LANGUAGES FORTRAN IV
C, AUTHOR, DATES I*.A, Burns, Oct. 1979
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D. REVISION: May 1980
II. PURPOSE: dispatching routine for EXAMS' integrators.
III. RESTRICTIONS:
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: FCT
FDER
OUTP
RKFINT
STFINT
c. COMMON STORAGE:
IFLAG in labeled common TIMEL
KDTIME In labeled common TIMEL
KOUNT in labeled common SETUPG
NPRINT in labeled common TIMEL
RPTOUT in labeled common UNITS
T in labeled common TIMEL
TFINAL In laoeled common TIMEL
TINCR in labeled common TIMEL
TPRINT in labeled common TIMEL
TTYOUT in labeled common UNITS
IV. USAGE
A. ENTRY POINT: DRIVER
B. CALLING SEQUENCE: CALL DRIVERCY)
C. INPUT ARGUMENTS: Y — steady-state concentration vector
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS: Returns with IFLAG = 9 if
integrators fail.
V. ALGORITHM OR METHOD
Subroutine DRIVER is primarily a dispatching routine that
calls the EXAMS numerical integration subroutines RKFINT
and STFINT. DRIVER initially calls RKFINT to integrate the
kinetic equations from t = 0.0 to TFINAL. If RKFINT
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returns with IFLAG=6 (stiff equations), DRIVER calls STFINT
to continue the integration from the current value of t to
TFINAL. If either integrator returns abnormally (e.g.,
T.LT.TFINAL), DRIVER checks for the existence of partial
results that can be used to calculate the persistence of
the chemical (computed in subroutine SUMUP).
The integration routines have been described by
Malanchuk, Otis, and Bouver (1980). EXAMS uses both a
Runge-Kutta and a Gear's (stiff equation) routine from this
publication, including: RKFINT, RKFS; STFINT, STIFF,
GINTRP, GEAR, DECOMP; and the user-supplied (i.e.,
problem-specific) routines FCT, FDER, and OUTP.
Several minor modifications of these routines were
implemented to enable their use In EXAMS:
1. For both RKFINT and STFINT:
a. three parameters (TT, I1FLAG, and TPRINT) were
added to the calling sequence in order to return
the current values of T, IFLAG, and TOUT to
subroutine DRIVER.
b. a counter (NPRINT in labeled common TIMED was
added to track the number of calls to OUTP -- this
counter is used (in DRIVER) to determine whether a
successful partial integration has been executed,
i.e., whether sufficient data is available to
compute persistence despite failure of the
integrators to reach a normal completion.
c. program STOPs were converted to RETURNS.
2. RKFINT returns immediately to DRIVER if the kinetic
equations are "stiff"; DRIVER then invokes STFINT to
continue the integration from the current value of T
toward TFINAL.
3. In order to control the expense of the Job,
a. counter MAXNFE in RKFS was reduced from 6000 to
3000.
b. counter NBLFE was added to STFINT; integration is
terminated at the expiration of 2 blocks of MAXNFE.
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I. IDENTIFICATION
A. TITLE: FCT
B. SOURCE LANGUAGE: FORTRAN iv
C. AUTHOR, DATE: L.A. Burns, Aug. 1979
D. REVISION: Oct. 1980
II. PURPOSE: FCT evaluates derivatives YP(J) = DY(J)
III. RESTRICTIONS
A, MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
c. COMMON STORAGE:
INTINL(NPX,NPX) in labeled common CHEM1L
KOUNT in labeled common SETUPG
TOTKL(NPX) in labeled common CHEM1L
IV. USAGE
A. ENTRY POINT: FCT
B. CALLING SEQUENCE: CALL FCTCTIME,Y,DY)
C. INPUT ARGUMENTS: TIME - Independent variable
Y - solution vector at TIME
D. OUTPUT ARGUMENTS: YP - rate of change of Y at TIME
E. ERROR CONDITIONS AND RETURNS: None
V. ALGORITHM OR METHOD
FCT computes the rate of change of chemical concentration
(Y) in each ecosystem compartment from the relationship:
DY(J)/DT s -TOTKL(J)*Y(J) + {Sum [Y(I)*INTINL(I,J)]>
where TOTKL is the first-order loss coefficient and the
INTINL are first-order coefficients expressing the effects
of internal transport on chemical concentrations.
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I. IDENTIFICATION
A. TITLE: FDER
8. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR,DATE: L.A. Burns, Oct. 1979
D. REVISION: Jul. 1980
II. PURPOSE: FDER computes Jacobian matrix for EXAMS.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
c. COMMON STORAGE:
INTINL(NPX,NPX) in labeled common CHEM1L
KOUNT in labeled common SETUPG
TOTKL(NPX) in labeled common CHEM1L
IV. USAGE
A. ENTRY POINT: FDER
B. CALLING SEQUENCE: CALL FDER(TIME,Y,*,YP,DER)
C. INPUT ARGUMENTS: TIME - current value, independent variable
Y * solution vector at TIME
YP - derivatives DY/DT at TIME
DER - dummy subroutine name
D. OUTPUT ARGUMENTS: w - Jacobian matrix
E. ERROR CONDITIONS AND RETURNS: None
V, ALGORITHM OR METHOD
The Jacobian matrix for the EXAMS chemical disappearance
integration is constant. Subroutine FDER transfers *TOTKL
to the diagonal of working matrix M, and loads the
remainder of H from matrix INTINL.
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I. IDENTIFICATION
A. TITLE: OUTP
B. SOURCE LANGUAGE: FORTRAN iv
C. AUTHOR, DATE: L.A. Burns, Aug. 1979
D. REVISION: Oct. 1980
II. PURPOSE: OUTP records results ot time-trace computations
in output files.
Ill, RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
C. COMMON STORAGE:
ALPHA(18,NPX) in labeled common PAPT1L
AREAG(NPX) in labeled common GEOMT
BIOTOL(NPX) In labeled common MASSL
INDEXS(NPX) in labeled common SETUPL
KINOUT in labeled common UNITS
KOUNT in labeled common SETUPG
KOUNTS in labeled common SETUPL
KOUNTW in labeled common SETUPL
RPTOUT in labeled common UNITS
SEDCOL(NPX) in labeled common MASSL
TFACTR in labeled common TIMEL
WATVOL(NPX) in labeled common MASSL
Z(18) in labeled common RESULT
IV. USAGE
A. ENTRY POINT: OUTP
B. CALLING SEQUENCE: CALL OUTP(TIME,Y,W)
C. INPUT ARGUMENTS: TIME - current value, independent variable
Y - solution vector at TIME
W - 1st derivatives of Y at TIME
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS: None
371
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V. ALGORITHM OR METHOD
Subroutine OUTP transforms EXAMS' internal state variable
(Y) to the concentration variables used for output, and
writes the current values of the independent and dependent
variables to the output files defined by FORTRAN logical
units RPTOUT and KINOUT.
I. IDENTIFICATION
A. TITLE: SUMUP
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: L.A. Burns, Aug. 1979
D. REVISION: NOV. 1980
II, PURPOSE: SUMUP estimates ecosystem self-cleansing time and
writes a summary of all analyses executed by EXAHS.
III. RESTRICTIONS
A, MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
c. COMMON STORAGE:
BIOPCT in labeled common RESLT
CHEMPC in labeled common RESLT
DOMAX(IO) in labeled common RESLT
EXPPCT in labeled common RESLT
IFLAG in labeled common TIMEL
KDTIME in labeled common TIMEL
QSSAV in labeled common RESULT
OTSAV in labeled common RESULT
QWSAV in labeled common RESULT
RPTOUT in labeled common UNITS
SYSLDL in labeled common MISCL
TFACTR in labeled common TIMEL
TFINAL in labeled common TIMEL
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VOLPCT In laoeled common RESLT
Z(18) in labeled cominon RESULT
IV, USAGE
A. ENTRY POINT: SUMUP
B. CALLING SEQUENCE: CALL SUMUP
C. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS: None
V. ALGORITHM OR METHOD
Subroutine SUMUP is primarily a data summary routine; it
writes a single-page summary of all prior analyses
conducted by EXAMS to the output file designated by LUN
RPTOUT. Subroutine SUMUP also estimates the persistence of
the chemical from the outcome of numerical integration of
the equations describing transformation and transport
losses. An overall "system self-purification time" is
estimated as the weighted mean of five halflives
(first-order approximation) for removal of the chemical
from the water column and bottom sediments of the
ecosystem. These halflives are weighted according to the
initial steady-state distribution of the chemical, that is,
a rapid loss of chemical from the water column is heavily
discounted it 99.9% of the material resides in bottom
sediments, and conversely.
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APPENDIX B
DOCUMENTATION OF INTERACTIVE USER INTERFACE SUBROUTINES
EXAMS' Interactive subroutines are executed as a function of
user input •• not in a fixed sequence. The executive routine
MAIN calls WHTCMD to determine the intent of the user. After a
valid command has been identified, the executive passes control
to the subroutine responsible for the desired action.
Utilities Group
The utilities group of subroutines is co-resident with
EXAMS' executive routine* Utility routines execute unit
operations for the functional subroutines described below.
GETNUM, GETNUM scans the input string and returns the numerical
equivalent of the characters encountered.
IHELP. IHELP determines whether either the keyword "HELP," or
the keyword "EXIT," is contained in the input string "INPUT."
INREC. INREC reads a single record from logical unit "UNIT." The
result is transmitted to the calling program in the variable
"INPUT." End-of-file is indicated by "EOF," which is 0 if no
end-of-file Is encountered and i if end-of-file is found. An
audit trail is produced, if requested by the user.
IMBED. IMBED locates the first non-blank character in a
character string.
LRAIL. LRAIL searches for the last non-blank character
proceeding from the end of the string toward the beginning.
MATCH. MATCH tests whether an input string "INPUT" is a member
of the table of strings "NAME." There are "NUMB" strings in
•NAME," each having a length defined by "LENS."
MATCHC. MATCHC determines where the string "STR2" is imbedded in
string "STRING."
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SCAN, SCAN examines a character string for specified delimiters
and returns the index of the first delimiter encountered.
SHOENV. SHOENV lists the system-defined names from the
environmental database on the terminal.
VALUE. VALUE converts a character string to a numerical value.
The only acceptable characters are the digits 0, l, 2, 3, 4, 5,
6, 1, 8, and 9, plus the delimiters -, + , ., E, and D.
Functional Groups
The functional group that decodes the user's input contains
a single subroutine, WHTCMD.
WHTCMD. foHTCMD prompts the user for a command, accepts the
command and returns to the calling program.
The functional group that executes the STORE and ERASE
commands includes subroutines ERASE, PACK, PAKENV, and STORE.
ERASE. ERASE replaces the information stored in the selected
record of the chemical or environmental database with null
values. Any information in the selected record prior to
execution of the ERASE command is destroyed.
PACK. PACK copies the data contained in the labeled COMMONS
associated with the descriptions of the chemical, to a single
vector. The resulting vector is written to the chemical
database. Conversion to a single vector minimizes I/O time.
PAKENV. PAKENV copies data contained in the labeled COMMONS
associated with the currently selected environment, to a single
vector. The vector is written to the environmental database.
Conversion to a single vector minimizes 1/0 time.
STORE. STORE loads the current environment or chemical into the
user database, for permanent storage and later retrieval via the
"RECALL" command.
The functional group that executes the -CHANGE command
includes the subroutines CHANGE and MODIFY.
CHANGE. CHANGE either assigns a value to a variable or transfers
the value of a variable to a temporary location.
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MODIFY. MODIFY changes variables of the computational model.
The functional group that executes the HELP and DESCRIBE
commands includes subroutines DESOUT, DESCRI, and HELP.
DESCRI. DESCRI lists the attributes of a variable, including the
data and storage type and the number of row and columns.
DESOUT. DESOUT transmits the attributes of a variable contained
in labeled COMMON to the user's terminal,
HELP. HELP provides on-line assistance to the user.
The functional group that executes the TERMINAL command
consists of a single subroutine, TERMAL.
TERMAL. TERMAL sets TERMTY to a code that represents the
user-specified terminal type.
The functional group that executes the SHOW command includes
subroutines CHANGE, HEDSHO, IFIND, LISSTR, PRCHEM, PRENV, PRTPPM,
SHOW, STEADY, and USROPT.
CHANGE. CHANGE either assigns a value to a variable or transfers
the value of a variable to a temporary location.
HEDSHO. HEDSHO is called by subroutine SHOW to list table
headings.
IFIND. IFIND gets the next input token, calls subroutine MATCH
to determine whether the token is contained in the table of
strings ("NAME"), and returns the table index of the identified
token. the parameter "MSG" is used to prompt for more input if
the input token is not identified.
LISSTR. LISSTR lists the ecosystem number--name pairs,
PRCHEM. PRCHEM is discussed in Appendix A.
PRENV, PRENV is discussed in Appendix A.
PRTPRM. PRTPRM is called in response to the SHOW
command and prints the the requested value on the terminal.
SHOW. SHOW implements the SHOW command, and displays any of the
following Information on the terminal when selected: available
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compounds and environments, chemical parameters describing the
currently selected compound, and environmental parameters of tne
currently selected environment. In addition, any of the labeled
COMMON variables associated with the currently selected compound
or environment can be displayed.
STEADY. STEADY is discussed in Appendix A.
USROPT. USROPT lists user-defined compounds and environments.
The functional group that executes the RUN, PRINT, and LIST
commands includes the subroutines LIST and PUNIT.
LIST. LIST compiles all or selected portions of the output
report file. The file is accessed via FORTRAN unit RPTOUT.
RUNIT. RUNIT is called in response to the run command to ensure
that a compound and environment have been selected, that the
aqueous solubility is greater than 0.0, and that at least one
load has been specified.
The functional group that executes the PLOT command includes
Subroutines DATOPT, IFIND, PLOTX, PONDAT, PRODAT, SCALE, STAOPT,
TYPOPT, VSTR, XBAR, and ZONOPT.
DATOPT. DATOPT identifies the kind of data to be plotted.
IFIND. IFIND gets the next input token, calls subroutine MATCH
to determine whether the token is contained in the table o£
strings ("NAME"), and returns the table index of the identified
token. The parameter "MSG" is used to prompt for more input if
the input token is not identified.
PLOTX. PLOTX plots the steady-state results on the terminal. It
is an interim product and will be replaced with an enhanced
version. The current version can be used as a guide for
extracting parameters from the output files.
PONDAT. PONDAT retrieves specific records from the plot file.
Statistical information about the simulation is collected. These
data are available in two different forms: water column, and
bottom sediments. Each of the forms has three parts: average,
maximum, and minimum.
PRODAT. PRODAT retrieves data from the steady-state output file
to be used for plotting profiles.
SCALE. SCALE is the equivalent of routines that are supplied
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with digital incremental plotters. The routine scans the input
data and computes a starting value and a scaling factor. These
values are used to scale the input data to ensure that it will
fit in the user-defined plotting area.
STAOPT. STAOPT identifies the statistical option to be plotted.
TYPOPT. TYPOPT determines the type of plot requested.
VSTR. VSTR moves the LEN characters stored in the vector
"STRING" into the uppermost positions ot column "X" of the matrix
"AREA." The matrix has MAXY rows.
XBAR. XBAR inscribes a vertical bar on the plotting area,
"AREA."
ZONOPT. ZONOPT identifies the zone that is to be plotted.
The functional group that executes the COMPOUND,
ENVIRONMENT, and RECALL commands includes subroutine COMPND,
ENVIRO, NEWNAM, RECALL, UNPACK, and UNPENV.
COMPND. COMPND allows the user to select a compound or to change
the name of the currently selected compound.
ENVIRO. ENVIRO allows the user to select an environment or to
change the name of the currently selected environment,
NEWNAM. NEWNAM obtains a user-defined name.
RECALL. RECALL retrieves a selected record from the
environmental or chemical database. This routine Implements the
"RECALL" command.
UNPACK. UNPACK reads a record from the chemical database. This
information is then copied to the labeled COMMON variables
associated with the descriptions of chemicals. The data are read
as a single vector to minimize I/O time.
UNPENV. UNPENV reads the specified environmental record and
transfers the information to the variables used to describe the
environment.
Action for the AUDIT, STOP, EXIT, and QUIT commands is
performed internally by the executive.
After the user-entered RUN command has been validated by the
378
-------
RUNIT subroutine, the subroutines described
invoiced. Subroutine DATAIN is not included in
version of EXAMS.
in Appendix A are
the interactive
I. IDENTIFICATION
A. TITLE: CHANGE
B. SOURCE LANGUAGE: FORTRAN iv
C. AUTHOR, DATE; D. Cline, Aug. 1979
D. REVISIONS: None
II. PURPOSE: CHANGE either assigns a value to a variable or
transfers the value of a variable to a temporary location.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
c. COMMON STORAGE:
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
All
variables
variables
variables
variables
variables
variables
variables
variables
variables
variables
variables
variables
variables
variables
variables
variables
variables
variables
in
in
in
in
in
in
in
in
in
in
in
in
in
in
in
in
in
in
labeled
labeled
labeled
labeled
labeled
labeled
labeled
labeled
labeled
labeled
labeled
labeled
labeled
labeled
labeled
labeled
labeled
labeled
common
common
common
common
common
common
common
common
common
common
common
common
common
common
common
common
common
common
NAME1G
CONTRG
PCHEMG
IONG
PARTG
VOLATG
DPHOTG
HYDHOG
OXIDG
BACTG
NAM&2G
SETUPG
SEDf*G
QUALG
PHOG
GEOMT
CLIMG
FLOfcG
379
-------
All variables In labeled common UNITS
All variables in labeled common H23456
IV. USAGE
A. ENTRY POINT: CHANGE
B. CALLING SEQUENCE: CALL CHANGE
c. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS: None
V. ALGORITHM OR METHOD:
The variables to be changed are organized as a function of
the labeled COMMON in which they are defined. A computed
GO TO statement using the variable ICOM directs the program
flow to the desired location. When the labeled COMMON area
is reached, another computed GO TO statement using the
variable IVAR directs the program flow to the section of
code where the selected variable is changed. The variable
RDWR determines whether the variable is to read or changed.
If RDWR=0, the variable is set to the quantity provided by
the calling program. If RDWR is set to "1," the data are
copied to a temporary variable for use by the calling
program.
I. IDENTIFICATION
A. TITLE: DATOPT
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. dine, Aug. 1979
D. REVISIONS: None
II. PURPOSE: DATOPT identifies the kind of data to be plotted.
380
-------
in. RESTRICTIONS:
A. MACHINE DEPENDENCY:
Initialization of the vector DATMSG requires 8 characters
per data element. This dependency can be overcome by
providing a vector that will accomodate 80 characters and
by redefining the DATA statement.
B. OTHER ROUTINES REQUIRED: IFIND
C. COMMON STORAGE:
TTYOUT in labeled common UNITS
IV. USAGE
A. ENTRY POINT: DATOPT
B. CALLING SEQUENCE: CALL DATOPT(IDAT)
c. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS:
IDAT (Scalar, Integer) — receives the option:
1: Total, ug/L in water column
rag/kg in benthic sediments
2: Dissolved, mg/L
3: Particulate, sedlment-sorbed, tug/leg
4: Biota, biosorbed, ug/g
5: Mass, chemical mass as grams/mZ area
E. ERROR CONDITIONS AND RETURNS:
IDAT is set to -1 if an end-of-file is encountered.
V. ALGORITHM OR METHOD:
Calls subroutine IFIND to determine the type of data
requested.
381
-------
I. IDENTIFICATION
A. TITLE: DESCRI
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. Cline, Aug. 1979
D. REVISIONS: None
II. PURPOSE: DESCRI lists the attributes of a variable,
including the data and storage type and the number of row
and columns.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: DESOUT
IMBED
INREC
MATCH
SCAN
c. COMMON STORAGE:
INPUT in labeled common INPAR
MODLEN In labeled common INPAR
NODMIN In labeled common INPAR
NODS in labeled common INPAR
NOMOD in labeled common INPAR
START in labeled common INPAR
STOP in labeled common INPAR
TD In labeled common INPAR
TTYIN In labeled common INPAR
TTYOUT In labeled common INPAR
TYPE in labeled common INPAR
IV. USAGE
A, ENTRY POINTS DESCRI
B. CALLING SEQUENCE: CALL DESCRI
C. INPUT ARGUNENTS: None
D. OUTPUT ARGUMENTS: None
C, ERROR CONDITIONS AND RETURNS:
382
-------
If an end-of-file is encountered, the name of the variable
is not identified, or a COMMON name is specified, an error
message is printed and control returns to the calling
program.
V. ALGORITHM OR METHOD:
The input string, "INPUT," is scanned for the name of a
variable. It the input is null, the user is prompted for
the name of a variable. Once the name of a variable is
found, subroutine MATCH is called to determine the validity
of the name. If invalid, an error message is printed and
control returns to tne calling progra-n. If valid, the full
variable name is copied to the vector, "OUT." Subroutine
DESOUT is then called to print the attributes at the
terminal.
I. IDENTIFICATION
A. TITLE: DESOUT
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. Cline, Aug. 1979
D. REVISIONS: None
II. PURPOSE: DESOUT lists the attributes of a variable
contained in labeled COMMON, at the user's terminal
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
c. COMMON STORAGE:
TCOL in labeled common INPAR
TD in labeled common INPAR
TROW in labeled common INPAR
TS in labeled common INPAR
383
-------
TTYOUT in labeled common INPAR
IV. USAGE
A. ENTRY POINT: DESOUT
B. CALLING SEQUENCE: CALL DESOUTUNDX,NAME,LEN)
c. INPUT ARGUMENTS:
INDX (Scalar, Integer) - holds the table offset that
points to the attribute codes
held in the TCOL, TD, TROW, and
TS vectors.
NAME (Vector, Integer) - holds the name of the variable,
one character per element.
LEN (Scalar, Integer) - holds the number of characters
in NAME,
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS: None
V. ALGORITHM OR METHOD:
The name of the variable held in NAME and the string "IS A"
are copied to the vector "OUTPUT," one character per
element. The codes for the data type, that is, REAL,
INTEGER, LOGICAL, etc., are held in TD, The codes for
storage mode, that is SCALAR, VECTOR, or MATRIC are held in
TS. The number of rows is held in TROW, and the number of
columns is held in TCOL. INDX is used as an index to
retrieve the codes in TD, TCOL, TS, and TROW. The codes
for data type, data storage, number of rows and number of
columns are converted to characters and copied to OUTPUT.
OUTPUT is transmitted to the user's terminal via FORTRAN
unit TTYOUT.
384
-------
I. IDENTIFICATION
A. TITLE: ENVIRO
B. SOURCE LANGUAGE; FORTRAN IV
C. AUTHOR, DATE: D. Cline, Aug. 1979
D. REVISIONS: None
II. PURPOSE: ENVIRO allows the user to select an environment or
to change the name of the currently selected environment.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: IHELP
IMBED
INREC
MATCH
NEMAN
SCAN
SHOENV
UNPENV
c. COMMON STORAGE:
DRFLDG(Npx) in labeled common LOADSG
ECOLEN(64) in labeled common INPAR
ECONAM(800) in labeled common INPAR
IENV in labeled common INPAR
IFLLDG(N"PX) in labeled common LOADSG
INENVR in labeled common UNITS
INPUT in labeled common INPAR
MINECO(64) in labeled common INPAR
NOECOS in labeled common INPAR
NpSLDG(Npx) in labeled common LOADSG
PCPLDG(NpX) in labeled common LOADSG
START in labeled comion INPAR
STOP in labeled common INPAR
STRLDG(NPX) in labeled common LOADSG
SYSTYP(60) in labeled common NAME2G
TTYIN in labeled common UNITS
TTYOUT in labeled common UNITS
TYPE in labeled common INPAR
IV. USAGE
385
-------
A. ENTRY POINT: ENVIRO
B. CALLING SEQUENCE: CALL ENVIRO
c. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS:
If errors are detected during the execution of this
routine, appropriate messages are printed on the user's
terminal before returning to the calling routine.
V. ALGORITHM OR METHOD:
Subroutine ENVIRO is called in response to the the
ENVIRONMENT command. The input string "INPUT" is scanned
for the keywords "IS" or "NAME IS." If invalid input is
encountered, then an error message is printed and control
returns immediately to the calling routine. If the input
proves to be null, or the input is incomplete, the user is
prompted with a message appropriate to the situation. When
the keyword "IS" is detected and followed by a valid name
of an environment, IENV is set to the database record
number that holds the environmental information. The data
are read via FORTRAN unit INENVR.
If the keyword "NAME IS" is detected, the name of the
environment is changed to that entered by the user.
If the keyword "EXIT" or the keyword "HELP" is detected
during the execution of this routine, one of the following
occurs:
EXIT • causes an immediate return to the calling routine.
HELP - prints a short message informing the user of
possible responses.
I. IDENTIFICATION
A. TITLE: ERASE
386
-------
B. SOURCE LANGUAGE: FORTRAN iv
C. AUTHOR, DATE; D. CUne, May 1980
0. REVISIONS: None
II. PURPOSE: ERASE replaces the information stored in the
selected record of the chemical or environmental database
with null values. Any information that in the selected
record prior to the execution of the ERASE command is
destroyed.
Ill, RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED:
GETNUM
IHELP
IMBED
INREC
MATCH
SCAN
c, COMMON STORAGE:
in labeled common UNITS
INENVR in labeled common UNITS
INPUT in labeled common INPAR
NQCREC in laoeled common INPAR
NOECOS in labeled common INPAR
NOEREC in labeled common INPAR
NONAME in labeled common INPAR
START in labeled common INPAR
STOP in labeled common INPAR
TTYIN in labeled common UMTS
TTYOUT in labeled common UNITS
TYPE in labeled common INPAR
IV. USAGE
A. ENTRY POINT: ERASE
B. CALLING SEQUENCE: CALL ERASE
c. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS: None
387
-------
E. ERROR CONDITIONS AND RETURNS:
If the selected record exceeds the range of allowable
record numbers established for the user, an error message
is printed on the user's terminal.
V, ALGORITHM:
The input string "INPUT" is scanned for the keywords
"COMPOUND" or "ENVIRONMENT" to determine which database
contains the input record to be erased. GETNUM is called
to extract the record number. The record number is tested
to ensure that it is in the range of user-defined record
numbers. A vector with an appropriate number of blanks and
zeroes is written to the selected database. If the
"COMPOUND" option was specified, the information is written
to the chemical database via FORTRAN unit INCOMP; FORTRAN
unit INENVR is used to transmit the information to the
environmental database when the "ENVIRONMENT" option is
specified.
I. IDENTIFICATION
A. TITLE: GETNUM
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE; D. dine, Aug. 1979
D. REVISIONS: None
II. PURPOSE: GETNUM scans the input string and returns the
numerical equivalent of the characters encountered.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: IMBED
SCAN
VALUE
388
-------
c. COMMON STORAGE:
INPUT in labeled common INPAR
START in labeled common INPAR
STOP In labeled common INPAR
IV. USAGE
A. ENTR* POINT: GETNUM
B. CALLING SEQUENCE: CALL GETNUMCERR,RESULT)
c. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS:
ERR (Scalar, Integer) is used as an error indicator.
RESULT (Scalar, Real) receives the converted numerical
quantity.
E. ERROR CONDITIONS AND RETURNS:
0: No errors detected
1: Nun input
2: Non-numeric character encountered
V, ALGORITHM OR METHOD:
The characters are isolated in the input string "INPUT,"
and subroutine VALUE is called to convert the characters to
a numerical quantity.
I, IDENTIFICATION
A. TITLE: HEDSHO
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. Cline, Aug. 1979
D. REVISIONS: None
389
-------
II. PURPOSE: HEDSHO is called by the SHOW subroutine to list
table headings.
Ill, RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
C. COMMON STORAGE:
KOUNT in labeled common SETUPG
SYSTYPC60) in labeled common NAME2G
TTYOUT in labeled common UNITS
TYPEE(NPX) in labeled common NAME2G
IV. USAGE
A. ENTRY POINT: HEDSHO
B. CALLING SEQUENCE: CALL HEDSHO
C. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS: None
V. ALGORITHM OR METHOD
The names of the currently selected environment and
chemical are printed, followed by the compartment type
codes CL, H, etc.).
I. IDENTIFICATION
A. TITLE: HELP
390
-------
B. SOURCE LANGUAGE: FORTRAN iv
C. AUTHOR, DATE: 0. Cline, Aug. 1979
D. REVISIONS: Mone
II. PURPOSE: HELP provides on-line assistance to the user,
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: DESOUT
IMBED
INREC
LRAIL
MATCH
SCAN
C. COMMON STORAGE:
HELP in labeled common INPAP
HELEN (50) in labeled common INPAP
HELPS (300) in labeled common INPAP
INDEF in labeled common UNITS
INHLP in labeled comnon UNITS
INPUT (80) in labeled common INPAP
MINHLP (50) in labeled common INPAR
MQDLEN (120) in labeled common INPAP
MODMIN (120) in labeled common INPAR
MODS (500) in labeled common INPAR
NOHCLP in labeled common INPAR
NOMOD In labeled common INPAR
START in labeled common INPAR
STOP in labeled common INPAR
TD (120) in labeled common INPAR
TTYOUT in labeled coinnon UNITS
TYPE in labeled common INPAR
IV. USAGE
A. ENTRY POINT: HELP
B. CALLING SEQUENCE: CALL HELP
C, INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS: None
391
-------
E, EPROR CONDITIONS AND RETURNS: None
V. ALGORITHM OR METHOD
The input string "INPUT" is scanned for a keyword or the
name of a variable in the labeled COMMONS reserved for the
chemical and environmental parameters. If no input is
encountered, then a list of available keywords is printed
on the terminal. If a token is found in the input stream,
MATCH is called to determine whether it is contained in the
table of keywords. If a match is made, text is read from
the file connected to FORTRAN unit INHLP and the text is
printed on the terminal. In the event that the MATCH
routine falls to identify the token, MATCH is called again
with a table of the labeled COMMON variables mentioned
above to determine whether assistance was requested for one
of them. If a match is made, text is then read via FORTRAN
unit INDEF and printed at the terminal. If the match
fails, a list of available keywords is printed at the
terminal.
I. IDENTIFICATION
A. TITLES IFIND
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. Cline, Aug. 1979
D. REVISIONS: None
II. PURPOSE: IFIND gets the next input token, calls subroutine
MATCH to determine whether the token is contained in the
table of strings (NAME), and returns the table index of the
identified token. The parameter "MSG" is used to prompt
for more input if the input token is not identified.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: IMBED
392
-------
INPEC
MATCH
SCAN
:OMMON STORAGE:
INPUT in labeled common INPAR
START in labeled common INPAR
STOP in labeled common INPAR
TTYIN in labeled common UNITS
TTYOtiT in labeled common UNITS
TYPE in labeled common INPAR
iv. USAGE:
A. ENTRY POINT: IFIND
B. CALLIMG SEQUENCE:
IsIFIND(NUMB,LENS,NAME,MINS,MSG,PROMPT)
c. INPUT ARGUMENTS:
NUMB (Scalar) - number of entries in the tables
LENS (Vector) - lengths of "NAME" entries
NAME (Vector) - table of names in successive elements,
1 character per element.
M1NS (Vector) - minimum lengths of "NAME" entries
required for uniqueness.
MSG (Vector) - holds object-time FOPMAT specifications.
Used when prompting is requested.
PROMPT (Scalar) - denotes whether or not prompting is
required when the user's input is
missing or invalid.
D. OUTPUT ARGUMENTS:
Returned as IFIND(NUMB,LENS,NAME,MINS,MSG,PROMPT)
E. ERROR CONDITIONS AND RETURNS:
IFIND » 0 — if no user input or the input cannot
t>e identified and PROMPT = i.
IFIND a i •• an index that points to the entry In the
393
-------
table that matched the input provided by
the user. 1=1, if the first table entry
matched the user's input. 1=2, for the
second table entry, etc.
V. ALGORITHM OR METHOD
The input string "INPUT" is scanned for a token. If a
token is found, subroutine MATCH is called to determine
whether the token matches any of the entries in the table
NAME.
If an invalid or null response is provided when PROMPT is
set to 0, the user is asked for more input. When PROMPT is
set to 1, control returns immediately to the calling
program.
I, IDENTIFICATION
A. TITLE: IHELP
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. Cline, Aug. 1979
D. REVISIONS: None
II. PURPOSE: IHELP determines whether the keyword "HELP," or
the keyword "EXIT," Is contained in input string "INPUT."
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: MATCH
c, COMMON STORAGE: None
IV. USAGE
A. ENTRY POINT: IHELP
394
-------
B. CALLING SEQUENCE: CALL IHELPUT)
C. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS:
IT (Scalar, Integer) - is coded as follows:
IT Description
0 Neither -"HELP" nor "EXIT" found
1 "HELP" found
2 "EXIT" found
E. ERROR CONDITIONS AND RETURNS: None
V. ALGORITHM OR METHOD
Subroutine MATCH is called to determine whether either HELP
or EXIT is present.
I. IDENTIFICATION
A. TITLE: IMBED
B. SOURCE LANGUAGE: FORTRAN iv
C. AUTHOR,DATE: Cline, D. M. Aug 1979
D. REVISIONS: None
II. PURPOSE: IMBED locates the first non-blank character in a
character string.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
C. COMMON STORAGE: None
395
-------
IV. USAGE
A. ENTRY POINT: IMBED
B. CALLING SEQUENCE: J=IMB£D(STRING,ISTRT)
c. INPUT ARGUMENTS: STRING, ISTRT
STRING (Vector) holds the string to be scanned,
one character per element
ISTRT (Scalar) denotes the position in STRING
where the scan is to begin,
D. OUTPUT ARGUMENTS: I a IMBED(STRING,ISTPT)
E. ERROR CONDITIONS AND RETURNS:
The value of IMBED is the index of the first non-blanK
character found in an 80 character string. If the line
contains no non-blanK characters, then IMBED is set to 100.
V. ALGORITHM OR METHOD
The string "STRING" is scanned for the first occurrence of
a blank or horizontal tab, starting at the position given
by index ISTRT, up to its 80th character. The position in
the string where the blank occurs is returned in IMBED,
1, IDENTIFICATION
A. TITLE: INREC
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. Cline, Aug. 1979
D. REVISIONS: None
II. PURPOSE: INREC reads a single record from logical unit
UNIT. The result is transmitted to the calling program in
396
-------
the variable "INPUT." End-of-file is indicated by "EOF,"
which is 0 it no end-of-file is encountered and 1 if
end-of-file is found. An AUDIT trail is produced, if
requested by the user.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
C. COMMON STORAGE
AUDIT in labeled common INPAR
INPUT in labeled common INPAR
TTYIN in labeled common UNITS
IV. USAGE
A. ENTRY POINTI INREC
B. CALLING SEQUENCE: CALL INREC(EOF,UNIT)
C. INPUT ARGUMENTS:
UNIT (Scalar, Integer) holds the FORTRAN logical unit
number used to read the input record.
D. OUTPUT ARGUMENTS:
EOF (Scalar, Integer) is used as an error indicator.
E. ERROR CONDITIONS AND RETURNS:
EOF -- 0: no end-of-file encountered
EOF -- 1: end-of-file encountered
v. ALGORITHM:
The next record is read from the file accessed via FORTRAN
logical unit UNIT and the first 80 characters are stored in
INPUT. If AUDIT is equal to 1 and UNIT is equal to TTYIN,
the record is echoed to the audit trail file via FORTRAN
logical unit AUDOUT.
397
-------
I. IDENTIFICATION
A. TITLE! LISSTR
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. Cline, Aug. 1979
D. REVISIONS: None
II. PURPOSE: LISSTR lists the ecosystem number--name pairs.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: PRCHEM
C. COMMON STORAGE:
BATCH in labeled common INPAR
CHEMNA (60) in labeled common NAME2G
POUND in labeled common INPAR
RPTOUT in labeled common UNITS
TTYOUT in labeled common UNITS
IV. USAGE
A. ENTRY POINT: LISSTR
B. CALLING SEQUENCE: CALL LISSTR(NUMB,LENGTH,NAMES,COL)
C. INPUT ARGUMENTS: All integers
NUMB (Scalar) - Number of names of compounds
LENGTH (Scalar) - Vector that holds the lengths
of the chemical names
NAMES (Vector) - holds the names of compounds,
1 character per element
COL (Scalar) • flag to determine the action
to be taken.
* 1, list the system database
chemical names.
* 1, lists the parameters describing
398
-------
the currently selected compound,
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS:
If COL is outside the valid range of values, an error
message is printed at the terminal.
V. ALGORITHM OP METHOD:
The input parameter "COL" is tested to determine what
action is to be taken. For COL a 1, the names of chemicals
are extracted from the input parameter NAMES and listed on
the terminal. The first column is the full name used on
output tables and the second column is the abbreviated
name, when COL=2, subroutine PRCHF.M is called and the
parameters decribing the currently selected chemical are
listed on the terminal. Before PHCHEM is called, BATCH is
set to 1 and the output unit RPTOUT is set to TTYOUT. Upon
return from PPCHEM, BATCH and RPTOUT are reset to their
original values.
I. IDENTIFICATION
A. TITLE: LIST
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. Cline, Aug. 1979
D. REVISIONS: None
II. PURPOSE: LIST compiles all or selected portions of the
output report file. The file is accessed via FORTRAN unit
RPTOUT.
III. RESTRICTIONS
A, MACHINE DEPENDENCY: None
B, OTHER ROUTINES REQUIRED: GETNUM
399
-------
IMBED
INREC
LPA1L
MATCH
MATCHC
SCAN
c. COMMQ.N STORAGE:
INPUT in labeled common INPAR
RPTOUT in labeled common UNITS
START in labeled common INPAP
STOP in labeled common INPAR
TTYIN in labeled common UNITS
TTYOUT in labeled common UNITS
TYPE in labeled common INPAR
IV. USAGE
A. ENTRY POINT: LIST
B. CALLING SEQUENCE: CALL LISTCOUTUNT,SPOOL)
C. INPUT ARGUMENTS: Botn integers
OUTUNT (Scalar) - FORTRAN unit for printing output report.
SPOOL (Scalar) - if 0, output is not spooled
if 1, output is spooled
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS:
An error message is printed when end-of-file is
encountered, the entry is out-of»range, or when simulation
results are not available for listing.
V. ALGORITHM OR METHOD:
The input string "INPUT" is scanned for a tofcen,
is present, the user is prompted with the options
and requested to enter his choice. When a choice
subroutine MATCH is called to determine the
request; "ALL," "HELP," or "EXIT." If one of
found, the appropriate action is performed. If
is not recognized, subroutine GETNUM is called to
whether a numeric argument has been specified
numeric response causes a selected portion of the
400
If none
available
Is made,
type of
these Is
the choice
determine
. A valid
file to
-------
be listed on the terminal. It the response is not
recognized or is out-of-range, the user is notified and
prompted for more input.
I. IDENTIFICATION
A. TITLE: LRAIL
B. SOURCE LANGUAGE: FORTRAN iv
C. AUTHOR, DATE: D. dine, Aug. 1979
D. REVISIONS: None
II, PURPOSE: LRAIL searches for the last non-blank character
proceeding from the end of the string toward the beginning,
III, RESTRICTIONS
A. MACHINE-DEPENDENCY: None
8. OTHER ROUTINES REQUIRED: None
C, COMMON STORAGE: None
IV, USAGE
A. ENTRY POINT: LRAIL
B, CALLING SEQUENCE: L=LRAILCSTRING,LEN)
C. INPUT ARGUMENTS: Both integers:
STRING (Vector) - text to be searched
LEN (Scalar) - search starts in this position
D, OUTPUT ARGUMENTS: L = LRAIL(STRING,LEN)
E, ERROR CONDITIONS AND RETURNS:
The position of the last non-blanic character in the
character string is returned in LRAIL(STRING,LEN). if no
401
-------
non-blanic character is found, then the function sets LRAIL
to 1.
V. ALGORITHM OR METHOD
The string "STRING" is scanned from the position given by
index LEN to position i. LRAIL is set to the position in
the string where the first non-blank character occurs.
I. IDENTIFICATION
A. TITLE: MATCH
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. dine, Aug. 1979
D. REVISIONS: None
II. PURPOSE: MATCH tests whether an input string "INPUT" is a
member of the table of strings "NAME." There are "NUMB"
strings in "NAME," each having a length defined by "LENS."
Ill, RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
c. COMMON STORAGE:
INPUT in labeled common INPAR
START in labeled common INPAR
STOP in labeled common INPAR
IV. USAGE
A. ENTRY POINT: MATCH
B. CALLING SEQUENCE: M * MATCHCNUMB,LENS,NAME,MINS)
402
-------
C. INPUT ARGUMENTS: All integers
NUMB (scalar) - number of table entries
LENS (Vector) - lengths of the NAME entries
NAME (Vector) - table of names in successive elements
(one character per element)
MINS (Vector) - minimum lengths of NAME entries
required for uniqueness
D. OUTPUT ARGUMENTS: Returned as MATCH(NUMB,LENS,NAME,MINS)
E. ERROR CONDITIONS AND RETURNS: None
ALGORITHM OR METHOD
This routine determines whether a token in the input string
"INPUT" is contained in the table of strings, "NAME." The
token begins at position START and ends at position STOP*!.
The length is computed as (STOP - START). MATCH is
normally set to the index of of the table entry that
matched the token. If the token is not identified, MATCH
is set to 0.
I. IDENTIFICATION
A. TITLE: MATCHC
8. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. Cline, Aug. 1979
D. REVISIONS: None
II. PURPOSE: MATCHC determines where the string "STR2" ii
imbedded in string "STRING."
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
403
-------
B. OTHER ROUTINES REQUIRED: None
c. COMMON STORAGE: None
IV. USAGE
A. ENTRY POINT: MATCHC
B. CALLING SEQUENCE: M = MATCHC(STRING,START,LENGTH,STR2,LEN2)
C. INPUT ARGUMENTS:
STRING (Vector, Integer) - the primary string
START (Scalar, integer) - the search begins at
STRING(START)
LENGTH (Scalar, Integer) - number of characters in STRING
to be searched from START
STR2 (Vector, Integer) - the secondary string
LEN2 (Scalar, Integer) - length of STR2
D. OUTPUT ARGUMENTS: M = MATCHC(STRING,START,LENGTH,STR2,LEN2)
E. ERROR CONDITIONS AND RETURNS:
If string "STR2" is found In "STRING," then the position in
"STRING" where the match begins is returned. Otherwise,
strings do not match and a value of zero is returned.
V. ALGORITHM OR METHOD:
The search begins in position START in string, STRING. The
strings are compared, character for character, until any
two characters that are not equivalent are encountered or
the entire LEN2 characters are tested without error.
I. IDENTIFICATION
A. TITLE: MNLN
404
-------
B. SOURCE LANGUAGE: FORTRAN iv
C. AUTHOR, DATE: D. Cline, Aug. 1979
D. REVISIONS: None
II. PURPOSE: MNLN determines the minimum number of characters
required to uniquely identify a string among a set of
strings of varying lengths.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
c. COMMON STORAGE:
TTYOUT in labeled common UNITS
IV. USAGE
A. ENTRY POINT: MNLN
B. CALLING SEQUENCE: CALL MNLN(NUMB,LKNS,STRING,MINS)
C. INPUT ARGUMENTS:
NUMB (Scalar, Integer) - number of strings
LENS-(Vector, Integer) - length of each string
STRING (Vector, Integer) - contains the strings
(one character per element)
D. OUTPUT ARGUMENTS:
MINIS (Vector, Integer) - receives the minimum lengths
E. ERROR CONDITIONS AND RETURNS:
If duplicate strings are encountered, a message is printed
on the terminal and execution stops immediately.
V. ALGORITHM OR METHOD:
Each string is compared against all other strings in the
405
-------
set to determine the minimum number of characters required
to uniquely identify each string.
I. IDENTIFICATION
A. TITLE: MODIFX
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. Cline, Aug. 1979
D. REVISIONS: None
II. PURPOSE: MODIFY dynamically changes variables of the
computational sector of EXAMS (Appendix A).
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: CHANGE
INREC
MATCH
MATCHC
SCAN
VALUE
c. COMMON STORAGE:
COMVAR in labeled common INPAR
INPUT in labeled common INPAR
MODLEN in labeled common INPAR
MOOMIN in labeled common INPAR
MODS in labeled common INPAR
NOCOM in labeled common INPAR
NOMOD in labeled common INPAR
START in labeled common INPAR
STOP in labeled common INPAR
TCOL in labeled common INPAR
TD in labeled common INPAR
TROW in labeled common INPAR
T5 in labeled common INPAR
TTYIN in labeled common UNITS
406
-------
TTYOtJT in laoeled common UNITS
TYPE in labeled common INPAR
IV, USAGE
A. ENTRY POINT: MODIFY
B. CALLING SEQUENCE: M=MODIFY(IT)
C. INPUT ARGUMENTS:
IT (Scalar, Integer) - used as a durrmy argument to
satisfy the requirements of a
FUNCTION definition.
D. OUTPUT ARGUMENTS:
I=MOOIFY(IT)
F. ERROR CONDITIONS AND RETURNS:
ERROR CODE CONDITION FOUND
-3
-2
-1
0
+ 1
+ 2
+ 3
4-4
•f5
+ 6
+ 7
COMMON group not found
Invalid name
End-of-flie
O.K.
wull input
Imbedded DlanK, systeti error
COMMON name specified
Only one argument allowed
for vectors
NO "TO"
Subscript out-of-range
scalars cannot have arguments
V. ALGORITHM OR METHOD
The name of the variable is isolated from the input string
"INPUT," and subroutine MATCH is used to identify the
variable. If defined, subscripts are decoded. The value
to be assigned to the selected variable is isolated and
converted to a numerical value via the function VALUE.
407
-------
I. IDENTIFICATION
A. TITLE: NEWNAM
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. Cline, Aug. 1979
D. REVISIONS: None
II. PURPOSE: NEWNAM obtains a user-defined name.
Ill, RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: IMBED
INREC
c. COMMON STORAGE:
CHEMNA in labeled common INPAR
INPUT in labeled common INPAR
START in labeled common INPAR
SYSTYP in labeled common NAME2G
TTYIN in labeled common UNITS
TTYOUT in labeled common UNITS
IV. USAGE
A. ENTRY POINT: NEWNAM
B. CALLING SEQUENCE: CALL NEWNAM (IT)
c. INPUT ARGUMENTS:
IT (Scalar, Integer) - 0: replace the name of the
currently selected compound
1: replace the name of the
currently selected environment
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS: None
V. ALGORITHM OR METHOD:
408
-------
The name is isolated froir the input strinq
stored in CHEMNA if IT=O or in SYSTYP if IT=I
"INPUT" and
I. IDENTIFICATION
A. TITLF: PACK
B. SOURCE LANGUAGE: FORTRAN iv
C. AUTHOR, DATE: D. dine, Aug. 1979
D. REVISIONS: None
II. PURPOSE: PACK copies the data contained in the labeled
COMMONS associated with the descriptions of the chemical to
a single vector. The resulting vector is written to the
chemical database. Using a single vector minimizes 1/0
time.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
c. COMMON STORAGE:
All
All
All
All
All
All
All
All
All
All
variables
variables
variables
variables
variables
variables
variables
variables
variables
variables
in
in
in
in
in
in
in
In
in
in
labeled
labeled
labeled
labeled
labeled
labeled
labeled
labeled
labeled
labeled
common
common
common
common
common
common
common
common
common
common
NAME1G
CONTPG
PCHEMG
IONG
PAPTG
VOLATG
DPHOTG
HYDROG
OXIDG
BACTG
IV. USAGE
A. ENTRY POINT: PACK
409
-------
B. CALLING SEQUENCE: CALL PACK(RECORD,UNIT)
c. INPUT ARGUMENTS:
RECORDCScalar, Integer) - holds record number to be written
UNIKScalar, Integer) - holds the FORTRAN unit number
that Is connected to the chemical
database.
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS: None
V. ALGORITHM OR METHOD
The labeled COMMON variables are copied into a single
vector. The resulting vector is written to the chemical
database via FORTRAN unit UNIT.
I. IDENTIFICATION
A. TITLE: PAKENV
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. Cline, Aug. 1979
D. REVISIONS: None
II. PURPOSE: PAKENV copies data contained in the labeled COMMON
associated with the currently selected environment into a
single vector. The vector is written to the environmental
database. Use of a single veetor minimizes I/O tine.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
c. COMMON STORAGE:
410
-------
All variables in labeled common NAME2G
All variables in labeled common SETUPG
All variables in labeled common SEDMG
All variables in labeled common QUALG
All variables in labeled common PHOG
All variables in labeled common GKOMT
All variables in labeled common CLIMG
All variables in labeled common FLQWG
IV. USAGE
A. ENTRY POINT: PAKENV
B. CALLING SEQUENCE: CALL PAKENV(RECOBD,UNIT)
c. INPUT ARGUMENTS:
RECORD (Scalar, Integer) holds numoer of record to be
written
UNIT (Scalar, Integer) holds the FORTRAN unit number
connected to the environmental
database
D. OUTPUT ARGUMENTS: None
£. ERROR CONDITIONS AND RETURNS: None
V. ALGORITHM OR METHOD:
The labeled COMMON variables are copied into a single
vector. The resulting vector is written to the to the
requested file via FORTRAN unit "UNIT."
I. IDENTIFICATION!
A. TITLE: PLOTX
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. Cline, Aug. 1979
411
-------
D. REVISIONS: None
II. PURPOSE: PLOT* plots the steady-state results on the termi-
nal. It is an interim product and will be replaced with an
enhanced version. This version can be used as a guide for
extracting parameters from the output files.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: DATOPT
PONDAT
PRODAT
SCALE
STAOPT
TYPOPT
VSTR
XBAR
ZONOPT
c. COMMON STORAGE:
SSOUT in labeled common UNITS
TTYOUT in labeled common UNITS
IV. USAGE
A. ENTRY POINT: PLOTX
B, CALLING SEQUENCE: CALL PLOTX
c. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS: None
V. ALGORITHM OR METHOD
The plot is created in the matrix "AREA" which has MAXY
rows and 61 columns. MAXY is presently set to 21 so that
the plot can be accommodated on a DEC VT52/VT55 terminal.
After "AREA" has been blanked, the remainder of the
plotting options are determined. IOPT is set to 1 for
point plots and to 2 for profile plots-. The concentration
type is coded in IDAT:
412
-------
IDAT Concentration type
1 Total
2 Dissolved
3 Particulate
4 Biota
5 Mass
If point plots are selected, the statistical type is
determined and coded in IVAL.
IVAL statistic
1
2 Minimum
3 Average
Data to be plotted are collected via subroutine PONDAT and
subsequently plotted. If profile plots are selected, the
zone type is determined and coded in IZON.
IZON Zone
1 water column
2 Bottom sediments
Data to be plotted are collected via subroutine PRODAT and
subsequently Plotted. The online assistance (HELP) utility
provides a fuller explanation of the plotting options,
including concentration units. The tutorial also provide
examples of usage.
I. IDENTIFICATION
A. TITLE: PONDAT
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. dine, Aug. 1979
D. REVISIONS: None
II. PURPOSE: PONDAT retrieves specific records from the plot
file. Statistical information about the simulation is
413
-------
collected. These data are available in two different
forms: water column, and bottom sediments. Each of the
forms has three parts: average, maximum, and minimum.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
C, COMMON STORAGE?
TTYOUT in labeled common UNITS
SSOUT in labeled common UNITS
IV. USAGE
A. ENTRY POINT: PONDAT
B. CALLING SEQUENCE: CALL PONDAT(EOF,WATBOT,NOTE,Y,IVAD
C. INPUT ARGUMENTS:
IVAL (scalar, Integer) denotes the statistical
type to be plotted.
WATBOT (Scalar, Integer) holds selection code:
1: water column,
2: bottom sediments
D. OUTPUT ARGUMENTS:
NOTE (Vector» Integer) - the compartment numbers
Y (Real, Vector) - contains the requested data
EOF (Scalar, Integer) - end-of-file indicator
0 -- no eof,
1 — eof
E. ERROR CONDITIONS AND RETURNS:
See EOF above
V. ALGORITHM OR METHOD
Records are read via FORTRAN unit SSOUT until the second
occurrence of an asterisk Is found in the second element of
a record. Information for the water column precedes the
414
-------
Dottoip sediment data in the file. Records are read and the
selected data and co-npartment number are transferred to the
Y and NOTE variables.
I. IDENTIFICATION
A. TITLE: PRODAI
p. SOURCE LANGUAGE: FORTRAN iv
C. AUTHOR, DATE: D. ciinef Aug. 1979
D. REVISIONS: None
II. PURPOSE: PRODAT retrieves data from the steady-state output
file to be used for plotting profiles.
Ill, RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
C. COMMON STORAGE:
SSOUT in labeled common UNITS
IV. USAGE
A. ENTRY POINT: PPODAT
B. CALLING SEQUENCE:
CALL PRODAT(EOF,Y1,Y2,N1,N2,MOTE11,NOTE12,NOTE21,NOTE22,IDAT)
c. INPUT ARGUMENTS:
EOF (Scalar, Integer) - end-of-file indicator:
0 •- no eof, 1 -• eof
IDAT (Scalar, Integer) denotes the concentration
types to be plotted
415
-------
D. OUTPUT ARGUMENTS:
Yl (vector, Real)
Y2 (Vector, Real)
Nl (scalar, integer)
N2 (Scalar, Integer)
NOTE11 (Vector, integer)
NOTE12 (Vector, integer)
NOTE21 (Vector, integer)
NOTE22 (Vector, integer)
the water column data
the sediment data
number of water compartments
numoer of sediment compartments
the water column compartment
number
the water column compartment
type
the sediment compartment
number
the sediment compartment
type
E. ERROR CONDITIONS AND RETURNS: None
V, ALGORITHM OR METHOD:
The file accessed via FORTRAN unit SSOUT contains the
steady-state water column and sediment concentrations. The
water column records precede the sediment records and are
marked by an asterisk in the second element of the ending
record. This record contains no useful output data; it is
used only as a flag to indicate the end of the water column
or sediment data. IDAT is used to compute the subscript of
the reguired concentration type.
I. IDENTIFICATION
A. TITLE: PRTPRM
B. SOURCE LANGUAGE: FORTRAN iv
416
-------
C. AUTHOR, DATE: D. Cline, Aug. 1979
D. REVISIONS: None
II. PURPOSE: PRTPRM is called in response to the SHOW command and prints the the requested value on the
terminal.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: CHANGE
MATCH
SCAN
VALUE
c. COMMON STORAGE:
COHVAR in labeled common INPAR
INPUT in labeled common INPAR
MODLEN in labeled common INPAP
MODMIN in labeled common INPAR
MODS in labeled common INPAR
NOCOM In labeled common INPAR
NOMOD in labeled common INPAR
START in labeled common INPAR
STOP in labeled common INPAR
TCOL in labeled common INPAR
TD in labeled 'common INPAR
TROW in labeled common INPAR
TS in labeled common INPAP
TTYOUT in labeled common UNITS
TYPE in labeled common INPAR
IV. USAGE
A. ENTRY POINT: PRTPRM
B. CALLING SEQUENCE: CALL PRTPRMUT)
c. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS:
IT (Scalar, Integer) returns the condition code.
E. ERROR CONDITIONS AND RETURNS:
417
-------
IT Condition Code
-3 * COMMON group not found
-2 * name not identified
-1 * E-O-F (End of file)
0 * 0. K.
+1 * E-O-L for argument 1
+ 2 * E-O-L for argument 2
+3 * argument out-of-range
+4 * null input
+5 * wild card specified
+6 * COMMON name specified
+7 * scalar name with dimensions specified
4-8 * vector name with more than one dimension
V. ALGORITHM OR METHOD
The name of the variable is extracted from the input string
"INPUT" and MATCH is called to determine whether it is a
valid name. In the event that the input is not identified
or null, control returns to the calling program. When a
valid name of a variable encountered, its current value is
fetched and an object time FORMAT statement is invoked to
transmit the name and its value to the terminal.
I. IDENTIFICATION
A. TITLE: RECALL
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. dine. May 1980
D. REVISIONS: None
II. PURPOSE: RECALL retrieves a selected record from the
environmental or chemical database. This routine
implements the "RECALL* command.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
418
-------
8. OTHER ROUTINES REQUIRED:
GETNUM
IHELP
IMBED
INREC
MATCH
SCAN
UNPACK
UNPENV
C. COMMON STORAGE:
in labeled common NAME1G
DRFLOG in labeled common LOADSG
IENV in labeled common INPAR
IFFLDG in labeled common LOADSG
INCQMP in labeled common UNITS
INENVR in labeled common UNITS
INPUT in labeled common INPAR
NOCREC in labeled common INPAR
NOECQS in labeled common INPAR
NOEREC in labeled common INPAR
NONAME in labeled common INPAR
NPSLDG in labeled common LOADSG
PCPLOG in labeled common LOADSG
POUND in labeled common INPAR
START in labeled common INPAR
STOP in labeled common INPAR
STRLDG in labeled common LOADSG
SYSTYP in labeled common NAME2G
TTYIN In labeled common UNITS
TTYOUT in labeled common UNITS
TYPE in labeled common INPAR
IV, USAGE
A. ENTRY POINT: RECALL
B. CALLING SEQUENCE: CALL RECALL
c. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS: None
E, ERROR CONDITIONS AND RETURNS: None
v. ALGORITHM:
The input string "INPUT" is scanned for the Keywords
419
-------
"COMPOUND" or "ENVIRONMENT" to determine which database
contains the input record. GETNUM is called to extract the
number of the record to be read. If the "COMPOUND" option
was specified, subroutine UNPACK reads the selected record
via FORTRAN unit INCOMP, and transfers the information to
the parameters used to describe chemicals. If the
"ENVIRONMENT" option was specified, subroutine UNPENV reads
the selected records via FORTRAN unit INENVR, and transfers
the information to the parameters used to describe
environments. If missing input is encountered, or invalid
information is detected, the user is prompted for
additional input, or messages describing the error are
printed on the terminal.
I. IDENTIFICATION
A. TITLE: RUNIT
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. Cline, May 1980
D. REVISIONS: None
II. PURPOSE: RUNIT is called in response to the RUN command to
ensure that a compound and an environment have been
selected, that the aqueous solubility is greater than 0.0,
and that at least one load has been specified.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
C. COMMON STORAGE:
DRFLDG In labeled common LOADSG
IENV in labeled common INPAR
IFFLDG in labeled common LOADSG
KOUNT in labeled common SETUPG
NPSLDG in labeled common LOADSG
PCPLDG in labeled common LOADSG
420
-------
POUND in labeled common INPAR
SOLG in labeled common PCHEMG
STRLDG in labeled common LOADSG
TTYOUT in labeled common UNITS
IV. USAGE
A. ENTRY POINT: RUNIT
B. CALLING SEQUENCE: CALL RUNIKIRUN)
C. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS:
IRUN (Scalar, Integer) receives the test status:
0 -- one of the tests failed
1 -- all tests passed
E. ERROR CONDITIONS AND RETURNS:
Messages are printed on the terminal if a test failed.
V. ALGORITHM OR METHOD:
The parameters "POUND," "IENV," "SOLGU)," and the
summation of all variables contained in the labeled COMMON
LOADSG, are tested to ensure that they all exceed 0,0.
I. IDENTIFICATION
A. TITLE: SCALE
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. dine, April 1981
D. REVISIONS: None
II, PURPOSE: SCALE is the equivalent of routines supplied with
digital incremental plotters. The routine scans the input
data, and computes a starting value and a scaling factor.
421
-------
These values are used to scale the input data to assure
that it will fit in the user defined plotting area.
Ill, RESTRICTIONS:
A. MACHINE DEPENDENCY: None
B, OTHER ROUTINES REQUIRED: SCALE2 (Lewart 1971)
C, COMMO.N STORAGE: None
IV. USAGE
A. ENTRY POINT: SCALE
B. CALLING SEQUENCE: CALL SCALEURRAY,AXLEN,NPTS,INO
c. INPUT ARGUMENTS:
ARRAY (Vector, Real) - values to be scaled
AXLEN (Scalar, Real) - length of the plotting area
in inches
NPTS (Scalar, Integer) - number of values to be scaled
INC (Scalar, Integer) - not used, but required for
compatibility
D, OUTPUT ARGUMENTS:
The NPTS+1 element of the input vector contains the
starting value. The NPTS+2 element of the input
vector contains the scaling value.
E, ERROR CONDITIONS AND RETURNS: None
V, ALGORITHM OR METHOD:
Lewart, C. 1971. Algorithms SCALE1, SCALE2, and SCALE3
for determination of scales on computer generated plots.
Algorithm 463 In: Collected Algorithms from ACM, Vol. II.
Association for Computing Machinery, inc., New York, New
Yoric.
422
-------
I.
A. TITLE: SCAN
B. SOURCE LANGUAGE: FORTRAN iv
C. AUTHOR, DATE: D. Cline, Aug. 1979
D. REVISIONS: Mone
II. PURPOSE: SCAN examines a character string for specified
delimiters and returns the index of the first delimiter
encountered.
Ill, RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
C. COMMON STORAGE: None
IV. USAGE
A. ENTRY POINT: SCAN
B. CALLING SEQUENCE:
CALL SCAN (STRING,START,STOP,TYPE,DELIM,NDELIM)
C. INPUT ARGUMENTS:
STRING (Vector, Integer) - input string
START (Scalar, Integer) - tne index of the first
character to oe scanned
DELIM (Vector, Integer) - delimiters
NDELIM (scalar, Integer) - number of entries in DELIM
D. OUTPUT ARGUMENTS:
STOP (Scalar, Integer) - index of delimiter found
TYPE (Scalar, Integer) - type of delimiter
E. ERROR CONDITIONS AND RETURNS:
423
-------
If start is greater than 80, or no delimiter is found,
null line, then TYPE is set to 100 and returned.
or
V. ALGORITHM OR METHOD:
Each character in "STRING" is compared with each of the
characters stored in "DELIM;" it a match is made, the
position of the character is returned in "STOP" and "TYPE"
is set to the index of the matching character in
"DELIM." If a match is not made, the scan continues until
a match is made or column 80 is exceeded. This condition
causes "TYPE" to be set to 100 and control is returned to
the calling program.
I, IDENTIFICATION
A. TITLE: SHOENV
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. Cline, Aug. 1979
D. REVISIONS: None
II. PURPOSE: SHOENV lists the system-defined names from the
environmental database at the terminal.
III. RESTRICTIONS:
A. MACHINE-DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
c. COMMON STORAGE:
ECOLEN in labeled common INPAR
ECONAH in labeled common INPAR
NOECOS in labeled common INPAR
TTYOUT in labeled common INPAR
424
-------
iv. USAGE
A. ENTRY POINT: SHOENV
B. CALLING SEQUENCE: CALL SHOENV
c. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS: None
V. ALGORITHM OP METHOD:
The names of environments are extracted from the vector
"ECONAM," one character per element. The vector "ECOLEN"
holds the length of each of the names, and "NOECOS" denotes
the number of names available.
I. IDENTIFICATION
A. TITLE: SHOW
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. dine, Aug. 1979
D. REVISIONS: None
II. PURPOSE: SHO* implements the SHOW command, and displays
information on the terminal when one of the following
options is selected:
Keyword
- Function listed
COMPOUNDS
CHEMISTRY
ENVIRONMENTS
USER
additional
ENVIRONMENT
names of chemicals
chemical parameters describing the
currently selected compound
names of environments
names of user-defined compounds and
environments, requires an
qualifier on COMPOUND or
425
-------
For the currently selected environment,
GEOMETRY
ADVECTION
TURBULANCE
QUALITY
GLOBAL
LOADS
system geometry
advective Interconnections
turbulent interconnections
water quality parameters
global parameters
chemical loadings by system element
In addition, any of the labeled COMMON variables associated
with the currently selected chemical or environment may be
displayed.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED:
HEDSHO
IFIND
INREC
LISSTR
USROPT
PREXV
PRTPRM
SHOENV
STEADY
C. COMMON STORAGE:
BATCH in labeled common INPAR
IENV in labeled common INPAR
INPUT In labeled common INPAR
MODLEN in labeled common INPAR
MOOS in labeled common INPAR
NAMLEN in labeled common INPAR
NOMOD In labeled common INPAR
NONAME In labeled common INPAR
TTYOUT In labeled common UNITS
All
All
All
All
All
All
All
All
All
All
All
variables
variables
variables
variables
variables
variables
variables
variables
variables
variables
variables
in
in
In
In
In
in
In
In
In
In
In
labeled
labeled
labeled
labeled
labeled
labeled
labeled
labeled
labeled
labeled
labeled
cowmon
coBBon
coBBon
common
coBBon
CORBOn
coBBon
coBBon
COBBOn
COBBOn
COBBOn
NAME1G
CONTRG
PCHE«G
IONG
PARTG
VOLATG
DPHOTG
HYDROG
OXIDG
BACTG
NAME2G
426
-------
All
All
All
All
All
All
All
All
variables
variables
variables
variables
variables
variables
variables
variables
in
in
in
in
in
in
in
in
labeled
labeled
labeled
labeled
labeled
labeled
labeled
labeled
common
common
condition
common
common
common
common
common
SETUPG
SEDWG
OUALG
PHOG
GEOMT
CLIMG
FLObG
LOADS
IV. USAGE
A, ENTRY POINT: SHOW
B. CALLING SEQUENCE: CALL SHOw
C. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS:
Errors are detected and appropriate messages are printed on
the terminal.
V, ALGORITHM OR METHOD:
Subroutine IFIND is called to determine whether one of the
options in the keyword table "SHQNAM" has been entered. If
so, the requested information is printed. If a keyword is
not identified, the input is assumed to be a variable name
and subroutine PRTPRM is called to identify and list Its
current value. If no input is received, a list of options
is printed on the terminal and the user is requested to
enter his choice. in the event that an error is
encountered, an appropriate error message Is printed and
control Is returned to the calling program.
I. IDENTIFICATION
A. TITLE: STAOPT
8. SOURCE LANGUAGE: FORTRAN IV
427
-------
C. AUTHOR, DATE: D. dine, Aug. 1979
D. REVISION; None
II. PURPOSE: STAOPT identifies the statistical option to be
plotted.
in, RESTRICTIONS:
A. MACHINE DEPENDENCY:
Initialization of the vector DATMSG requires 8 characters
per data element. This dependency can be overcome by
providing a vector that will accomodate 80 characters and
by redefining the DATA statement.
8. OTHER ROUTINES REQUIRED: IFIND
c. COMMON STORAGE:
TTYOUT in labeled common UNITS
IV. USAGE
A. ENTRY POINT: STAOPT
B. CALLING SEQUENCE: CALL STAQPTUVAD
C, INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS:
IVAL (Scalar, Integer) receives the statistical code:
1 -- maximum
2 -- minimum
3 « average
E, ERROR CONDITIONS AND RETURNS:
•
IVAL is set to -1 if an end-of-file is encountered.
V. ALGORITHM OR METHOD:
Calls subroutine IFIND to identify the statistical option
requested.
428
-------
I. IDENTIFICATION
A. TITLE: STORE
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. Cline, May, 1980
D. REVISIONS: None
II. PURPOSE: STORE transfers the current set of environmental
or chemical descriptors into the user data base for
long-term storage and subsequent retrieval via the "RECALL"
command.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: GETNUW
IHELP
IMBED
INREC
MATCH
PACK
PAKENV
SCAM
C. COMMON STORAGE:
CHEMNA in labeled common NAME1G
1NCOMP in labeled common UNITS
INENVR in labeled common UNITS
INPUT in labeled common INPAR
NOCREC in labeled common INPAR
NOECOS in labeled common INPAR
NOEREC in labeled common INPAR
NONAME in labeled common INPAR
START in labeled common INPAR
STOP in labeled common INPAR
SYSTYP in labeled common NAME2G
TTYIN in labeled common UNITS
TTYOUT in labeled common UNITS
TYPE in labeled common INPAR
IV. USAGE
A. ENTRY POINT! STORE
429
-------
8. CALLING SEQUENCE: CALL STORE
C. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS: None
V. ALGORITHM OR METHOD:
The Input string "INPUT" Is scanned for the keywords
"COMPOUND" or "ENVIRONMENT" to select the database to use
when writing the output record. The record number used in
the write operation is contained in the input string, and
subroutine GETNUM is used to obtain this quantity. If the
"COMPOUND" option was specified, information describing the
currently selected chemical is passed to subroutine PACK
for writing to the chemical database via FORTRAN unit
INCOMP. if the "ENVIRONMENT" option was specified,
information describing the currently selected environment
is passed to subroutine PAKENV, which writes to the
environmental database via FORTRAN unit INENVR. If input
is missing or invalid information is detected, the user is
prompted for additional input or appropriate error messages
are printed on the terminal.
I. IDENTIFICATION
A. TITLE: TERMAL
B. SOURCE LANGUAGE: FORTRAN iv
C, AUTHOR, DATE: D. Cline, Aug. 1979
0. REVISIONS: Jan., 1981
II. PURPOSE: TERMAL sets TERMTY to a code that represents the
user specified terminal type.
Ill, RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: IREC
430
-------
MATCH
SCAN
COMMON STORAGE:
INPUT in labeled common 1NPAP
START In labeled common INPAR
STOP In labeled common INPAR
TERMTY in labeled common I^PAR
TTYIN in labeled common UNITS
TTYQUT in laoeled common UNITS
TYPE in labeled common INPAP
XV. USAGE
A. ENTRY POINT: TERMAL
B. CALLING SEQUENCE: CALL TERMAL
C, INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS: None
V. ALGORITHM OR METHOD:
The input string "INPUT"
If a toKen is found,
determine its validity.
incomplete, the user
before MATCH is called.
is scanned for a terminal type.
subroutine MATCH is called to
If the input string is absent or
is prompted for additional input
when a valid terminal type is
found, TERMTY is set as follows:
TERMT*
VALUE
TERMINAL
TYPE
1 DEC VT55
2 Tektronix 4010 series
3 TTY compatible
Any other response will leave TERMTY unchanged.
431
-------
I. IDENTIFICATION
A. TITLE: TYPOPT
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR,DATE: O. Cline, Aug. 1979
D. REVISION: None
II. PURPOSE: TYPOPT determines the type of plot requested.
in, RESTRICTIONS:
A. MACHINE DEPENDENCY:
Initialization of the vector DATMSG requires 8 characters
per data element. This dependency can be overcome by
providing a vector that will accomodate 80 characters and
by redefining the DATA statement.
B. OTHER ROUTINES REQUIRED: IFIND
c. COMMON STORAGE:
TTYOUT in labeled common UNITS
IV. USAGE
A. ENTRY POINT: TYPOPT
B. CALLING SEQUENCE: CALL TYPOPT(ITYP,IOPT)
C. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS:
ITYP (Scalar, Integer) used as follows:
ITYP Function
-1 End-of-file encountered
4 User selected, "EXIT"
Any other value indicates an error free return,
IOPT (Scalar, Integer) -- l: Point plots selected
2: Profile plots selected
432
-------
E. ERROR CONDITIONS AND RETURNS:
ITYP is used as an error flag as described above.
V. ALGORITHM OR METHOD:
Subroutine IFIND determines the type of plot requested is
point or profile.
I. IDENTIFICATION
A. TITLE: UNPACK
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. Cline, Aug. 1979
D. REVISIONS: None
II. PURPOSE: UNPACK reads a record from the chemical database.
This information is then copied to the labeled COMMON
variables associated with the chemical descriptions. The
data are read as a single vector to minimize I/O time.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
C. COMMON STORAGE:
All variables in labeled common NAME1G
All variables in labeled common CONTRG
All variables in labeled common PCHEMG
All variables in labeled common IONG
All variables in labeled common PARTG
All variables in labeled common VOLATG
All variables in labeled common PPHUTG
All variables in labeled common HYDROG
All variables in labeled common OX1DG
433
-------
All variables in labeled common BACTG
IV. USAGE
A. ENTRY POINT: UNPACK
B. CALLING SEQUENCE: CALL UNPACK(RECORD,UNIT)
c. INPUT ARGUMENTS:
RECORD (Scalar, Integer) holds record number to be read.
UNIT (Scalar, Integer) holds the FORTRAN unit number that
is connected to the chemical data-
base.
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS: None
V, ALGORITHM OR METHOD
Information is read as a single vector from the chemical
database via FORTRAN unit UNIT. The results are copied to
the labeled COMMON variables used to decribe chemicals.
I. IDENTIFICATION
A. TITLE: UNPENV
B. SOURCE LANGUAGE: FORTRAN iv
C. AUTHOR, DATE: D. Cline, Aug. 1979
D. REVISIONS: None
II. PURPOSE: UNPENV reads the specified environmental record
and transfers the information to the variables used to
describe the environment.
III. RESTRICTIONS
434
-------
A. MACHINE DEPENDENCY:
B. OTHER ROUTINES REQUIRED; None
c. COMMON STORAGE:
All
All
All
All
All
All
All
All
variables
variables
variables
variables
variables
variables
variables
variables
in
in
in
in
in
in
in
in
labeled
labeled
labeled
labeled
labeled
labeled
labeled
labeled
common
common
common
common
common
common
common
common
NAME2G
SETUPG
SEDMG
QUALG
PHOG
GEOMT
CLIMG
KLOKG
IV. USAGE
A. ENTRY POINT:
B. CALLING SEQUENCE: CALL UNPF,NV(RFCOPD,UNIT)
C. INPUT ARGUMENTS:
RECORD (Scalar, Integer) holds record number to be read.
UNIT (Scalar, Integer) holds the FORTRAN unit number that
is connected to the environmental
database.
D. OUTPUT ARGUMENTS: None
E, ERROR CONDITIONS AND RETURNS: None
V. ALGORITHM OR METHOD:
The environmental information contained in record "RECORD"
is read into a single vector via FORTRAN unit UNIT. The
information is then copied from the vector to the
appropriate labeled COMMON variables used to describe the
environment. A single vector is used to minimize I/O time.
435
-------
I, IDENTIFICATION
A. TITLE: USROPT
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. dine, May 1980
D. REVISIONS: None
II. PURPOSE: USROPT lists user-defined chemicals and
environments.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
8. OTHER ROUTINES REQUIRED: None
C. COMMON STORAGE:
INCOMP in labeled common UNITS
INENVR in labeled common UNITS
TTYOUT in labeled common UNITS
IV. USAGE
A. ENTRY POINT: USROPT
B. CALLING SEQUENCE: CALL USROPTCWHICH)
C. INPUT ARGUMENTS:
WHICH (Scalar, Integer) - I, select compounds
2, select environments
D. OUTPUT ARGUMENTS: None
E. ERROR CONDITIONS AND RETURNS: None
V. ALGORITHM OR METHOD:
The starting record number in the selected database is
computed for the value of WHICH. Then, as each record is
read, the name of the chemical or environment, as
appropriate, is tested to determine whether It is all
blank. If not, the record number and the name are printed
on the terminal. In the event that all records are blank
436
-------
for a given database, a message to that effect is printed.
I. IDENTIFICATION
A. TITLE: VALUE
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: Cline, D. M. Aug. 1979
D. REVISIONS: None
II. PURPOSE: VALUE converts a character string to a numerical
value. The only acceptable characters are the digits 0, 1,
2, 3, 4, 5, 6, 7, 8, 9, plus tne delimiters -, + , ., E, and
D.
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
c. COMMON STORAGE: None
IV. USAGE
A. ENTRY POINT: VALUE
B. CALLING SEQUENCE: V = VALUE(DIGIT,LEN)
C. INPUT ARGUMENTS:
DIGIT (Vector, Integer) - characters to be converted
LENGTH (Scalar, Integer) - number of characters in DIGIT
D. OUTPUT ARGUMENTS: Returned as VALUE(DIGIT,LENGTH)
E. ERROR CONDITIONS AND RETURNS:
If a non-numeric character is encountered, VALUE is set to
437
-------
-0.123456E38.
V. ALGORITHM OR METHOD
Each character is converted to its numerical equivalent and
then multiplied by a power of ten, dependent upon its
position relative to an existing or implied decimal point.
Other characters such as, +, -, E and D are handled in an
appropriate fashion.
I, IDENTIFICATION
A. TITLE: VSTR
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. Cline, Aug. 1979
D. REVISIONS: None
II, PURPOSE: VSTR moves the LEN characters stored in the
vector "STRING" into the upper-most positions of column "X"
of the matrix "AREA." The matrix has MAXY rows.
III. RESTRICTIONS
A, MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
C. COMMON STORAGE: None
IV. USAGE
A, ENTRY POINT: VSTR
B. CALLING SEQUENCE: CALL VSTRCX,LEN,MAXY,AREA,STRING)
C. INPUT ARGUMENTS: All integers
X (Scalar) denotes the column of matrix "AREA"
438
-------
that is to receive the data.
LEN (Scalar) denotes the number of characters
to be copied to the matrix.
STRING (Vector) holds the characters to oe transferred
to the matrix, 1 character per element.
MAXY (Scalar) denotes the number of rows in the matrix.
D. OUTPUT ARGUMENTS:
AREA (Matrix) is the matrix that receives the characters.
E. ERROR CONDITIONS AND RETURNS: None
V. ALGORITHM OR METHOD:
The offset for upper-Tost Justification is computed as:
(Yl = MAXY - LEN - l). The characters are moved to column
x from "STRING," one character at a
I. IDENTIFICATION
A. TITLE: r*HTCMD
B. SOURCE LANGUAGE: FORTRAN iv
C. AUTHOR, DATE: D. dine, Aug. 1979
D. REVISIONS: None
II. PURPOSE: KHTCMD prompts the user for a command, accepts the
command and returns to the calling program.
III. RESTRICTIONS:
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: IMBED
INREC
MATCH
439
-------
SCAN
c. COMMON STORAGE:
CMDLEN In labeled common INPAR
INPUT in labeled common INPAR
MINCMD in labeled common INPAP
NCMDS in labeled common INPAR
PRICMD in labeled common INPAR
START in labeled common INPAR
STOP in labeled common INPAR
TTYIN in labeled common UNITS
TTYOUT in labeled common UNITS
TYPE in labeled common INPAR
IV. USAGE
A. ENTRY POINT: *HTCMD
B. CALLING SEQUENCE: CALL WHTCMDCCMD)
c. INPUT ARGUMENTS: None
D. OUTPUT ARGUMENTS:
CMD (Scalar, integer) - index of the command to be executed
E. ERROR CONDITIONS AND RETURNS: None
V. ALGORITHM OR METHOD:
The input string "INPUT" is scanned until a token is
detected, or until the end of the string is encountered.
If a token is found, subroutine MATCH is called to
determine whether a valid command has been entered. A
valid entry causes CMD to be set to an index that
represents this command. If the token Is not a valid
command, then the user is prompted for additional input.
I, IDENTIFICATION
A. TITLE: XBAR
440
-------
B. SOURCE LANGUAGE: FORTRAN IV
C. AUTHOR, DATE: D. CUne, Aug. 1979
D. REVISIONS: None
II. PURPOSE: XBAR inscribes a vertical bar on the plotting
area, "AREA."
III. RESTRICTIONS
A. MACHINE DEPENDENCY: None
B. OTHER ROUTINES REQUIRED: None
c. COMMON STORAGE: None
IV. USAGE
A. ENTRY POINT: XBAR
B. CALLING SEQUENCE:
CALL XBAR(X,HGT,WIDTH,MAXY,AREA,NOTE,NOTE1)
c. INPUT ARGUMENTS:
X (Scalar, integer) - mid-point of the bar on the
horizontal axis
HGT (Scalar, Integer) - magnitude of bar, in print lines
WIDTH (Scalar, integer) - width, in print positions
MAXY (Scalar, Integer) - maximum number of print lines in
the plotting area
NOTE (Scalar, integer) * character used to form the left
and right vertical lines of the
bar
NOTEl (Scalar, Integer) - character used to form the top
line of the bar
D. OUTPUT ARGUMENTS:
AREA (Matrix, Integer) - the plotting area of size
441
-------
MAXY by 61 used as print
image buffer.
E. ERROR CONDITIONS AND RETURNS: None
V. ALGORITHM OR METHOD:
The characters are transferred to the plotting matrix,
"AREA," one character per element.
I. IDENTIFICATION
A. TITLE: ZONOPT
B. SOURCE LANGUAGE: FORTRAN iv
C. AUTHOR,DATE: O. Cline, Aug. 1979
D. REVISION: None
II. PURPOSE: ZONOPT identifies the zone to be plotted.
III. RESTRICTIONS:
A. MACHINE DEPENDENCY:
Initialization of the vector DATMSG requires 8 characters
per data element. This dependency can be overcome by
providing a vector that will accommodate 80 characters and
by redefining the DATA statement.
B. OTHER ROUTINES REQUIRED: IFIND
c. COMMON STORAGE:
TTYOUT in labeled common UNITS
IV. USAGE
A. ENTRY POINT: ZONOPT
442
-------
B. CALLING SEQUENCE: CALL ZONOPTUZON)
c. INPUT ARGUMENTS; None
D. OUTPUT ARGUMENTS:
IZON (Scalar, Integer) - receives the zone code:
1: water column
2: bottom sediments
E. ERROR CONDITIONS AND RETURNS:
IZON is set to -1 if an end-of-file is encountered.
V, ALGORITHM OR METHOD:
Subroutine IFIND is called to identify the zone option
requested.
443
« US GOVERNMENT PRINTING OFFICE 1982-559-092/0409