Final Report
REGIONAL AIR POLLUTION STUDY:
A PROSPECTUS
Part II - Research Plan
Prepared for:
THE ENVIRONMENTAL PROTECTION AGENCY
NATIONAL ENVIRONMENTAL RESEARCH CENTER
RESEARCH TRIANGLE PARK, NORTH CAROLINA
CONTRACT 68-02-0207
SRI Project 1365
STANFORD RESEARCH INSTITUTE
Menlo Park, California 94025 • U.S.A.
-------
Final Report
January 1972
REGIONAL AIR POLLUTION STUDY:
A PROSPECTUS
Part II - Research Plan
Prepared for:
THE ENVI RONMENTAL PROTECTION AGENCY
NATIONAL ENVI RONMENTAL RESEARCH CENTER
RESEARCH TRIANGLE PARK, NORTH CAROLINA
CONTRACT 68-02-0207
SR I Project 1365
R. T. H. COLLIS, Director
Atmospheric Sciences Laboratory (Project Director)
DON R. SCHEUCH, Vice President
Office of Research Operations
-------
FOREWORD
This Prospectus was prepared by Stanford Research Institute for the
Environmental Protection Agency under Contract No. 68-02-0207. While
this Prospectus has been reviewed by the Environmental Protection Agency
and approved for publication, approval does not signify that the contents
necessarily reflect the views and policies of the Environmental Protec-
tion Agency, nor is it intended to describe the Agency's program.
The complete Prospectus for the Regional Air Pollution Study is pre-
sented in four parts.
Part I
Part II
Part III
Part IV
Summary
Research Plan
Research Facility
Management Plan
A table of contents for all parts is provided in each of the four
parts to facilitate th~ use of the Prospectus.
iii
-------
ACKNOWLEDGMENT
This Prospectus was prepared at the Institute by a project team
representing the full range of disciplines necessary for the comprehensive
analysis of problems of air pollution. Research team members were drawn
from four of the eight Institute Research Divisions, including the fol-
lowing:
Electronic and Radio Sciences
Physical Sciences
Information Science and Engineering
Engineering Systems
Because of the interdisciplinary nature of the effort, the contributions
and research findings of many team members are distributed throughout this
Prospectus rather than concentrated in one or more specific chapters. Ac-
cordingly. contributions are acknowledged below by general areas associ-
ated with the study of air pollution problems.
This Prospectus was prepared under the supervision of R.T.H. Collis,
Project Director. The Project Leader was Elmer Robinson (now of Washing-
ton State University) until 15 January, when Richard B. Bothun, who had
been Deputy Project Leader, succeeded him.
The main contributions were as follows:
.
Elmer Robinson--Project leadership and the formulation of the
Research Plan
.
Richard B. Bothun--Project leadership and administrative man-
agement and the formulation of the Management Plan.
Technically, the principal contributions were:
.
Richard B. Bothun--Management, scheduling, costing, planning
.
Leonard A. Cavanagh--Air quality instruments, atmospheric
chemistry
v
-------
.
Ronald T. H. Collis--Meteorology, remote sensing, research
planning
.
Walter F. Dabberdt--Transport and diffusion modeling, mete-
orology, instrumentation
.
Paul A. Davis--Solar radiation, tracer studies
.
Roy M. Endlich--Meteorologital models, satellite systems
.
James L. Mackin--Helicopter and aircraft systems
.
Elmer Robinson--Meteorology, instrumentation, atmospheric
chemistry, research planning
.
Sylvin Rubin--Data processing systems
.
Konrad T. Semrau--Source inventory and emissions
.
Elmer B. Shapiro--Communication systems
.
James H. Smith--Atmospheric chemical transformation processes
.
Eldon J. Wiegman--Synoptic climatology
Valuable contributions were made in the latter stages of the project
by Dr. W. A. Perkins and Mr. J. S. Sandberg, consultants.
The Institute wishes to express its appreciation for the assistance
and provision of information by many staff members of the Environmental
Protection Agency. especially Charles R. Hosler, Contracting Officer's
Technical Representative; Dr. Warren B. Johnson, Jr., Chief, Model Devel-
opment Branch; Robert A. McCormick, Director, Division of Meteorology;
and Dr. A. P. Altshuller, Director; Division of Chemistry and Physics.
Additionally, the constructive criticism and comment provided by
members of the Meteorology Advisory Committee of the Environmental Pro-
tection Agency during the preparation of the Prospectus were of signifi-
cant value, and our indebtedness is hereby acknowledged.
vi
-------
CONTENTS
PART I - SUMMARY
FOREWO RD . . .
. . . . . . . . . . . . . . . . . . . . . . . . . .
ACKNOWLEDGMENT.
III
. . . .
. . . . . . . . . . . . . . . . . . . . .
I
THE BASIC PREMISE
. . . . . . . .
. . . . . . . . . . . . .
II
SCIENTIFIC AIR QUALITY MANAGEMENT
. . . .
The Basic Tool--The Mathematical Model. . . . .
The Processes To Be Modeled. . . . . . . . .
. . . . .
. . . .
Accuracy. . . . . . . . . . . . . . . . . . . . . .
Current Limitations of Modeling. . . . . . . . . . . . . .
Steps To Improve Models. . . . . . . . . . . .
The Regional Scale. . . . . . . . . . . . . . . . . . . .
THE REGIONAL AIR POLLUTION STUDY (RAPS)
. . (I .
. . . . . .
Concept. . . . . . . . . . . . . . . .
Purpose. . . .
Organization
Objectives. . . . . . . . . . .
. . . . . . .
. . . . . . . .
. . . . . . . . . . .
. . . .
. . . . . . .
. . . . .
. . . .
. . . . . . .
IV
SITE SELECTION
. . . . . . . . . . . . . . I . . . . . . .
V
THE RESEARCH PLAN.
. . . . . .
. . .. . . . .
. . . . . . .
Introduction . . . . . . . . .
Model Evaluation and Verification Program.
. . . . .
. . . . . . . .
Meteorological Factors. . . . . . . . . . . . . . . . .
Pollutant Source Estimates. . . . . . . . . . . . . . .
Air Quality Measurements. . . .
Atmospheric, Chemical, and Biological Processes. . . . . .
Human Social and Economic Factors
. . . . . . .
RAPS Technology Transfer
. . . . .
. . . . . .
vii
ii i
v
1
3
3
3
4
4
5
7
9
9
10
10
14
17
19
19
21
24
25
25
26
28
28
-------
CONTENTS
v
Continued
Schedules and Task Specifications for the Research Plan. .
Introduction. . . . . . . . . . . . . . . . . . . . . .
100 Model Verification. . . . . . . . . . . . . .
101 Boundary Layer Meteorology Program. . . . . .
102 Emission Inventory. . . . . . . . . . . . . . . . .
103 Air Quality Measurements. . . . . . . . . . .
104 Model Calculation and Verification. . . . . .
200 Atmospheric, Chemical, and Biological Processes
201 Gaseous Chemical Processes. . . . . . . . . . . . .
202 Atmospheric Aerosol Processes. . . . . . . . . . . .
203 Other Pollutant Related Atmospheric Processes.
204 Atmospheric Scavenging by Precipitation. . . . . . .
205 Air Pollutant Scavenging by the Biosphere. . . . . .
206 Atmospheric Processes. . . . . . . . . . . . . . . .
300 Human, Social, and Economic Factors. . . . . .
301 Human and Social Factors. . . . . . . . . . . . . . .
302 Economic Factors. . . . . . . . . . . . . . . . . .
400 Transfer of RAPS Technology for Control Agency
Applications and the Formulation of Control Strategies
401 Source Inventory Procedures. . . . . . . . . . . . .
402 Atmospheric Monitoring. . . . . . . . . . . .
403 Data Handl ing . . . . . . . . . . . . . . . . . . . .
404 Modeling Technology. . . . . . . . . . .
405 Other Significant Factors in Control Strategy
Formulation. . . . . . . . . . . . . . . . . . . . . . .
VI
THE FACILITY
. . . .
. . . . .
. . . .
. . . .
Rationale. . . . . . . . . . . . . . . . . . .
Basic Operations . . . . . . . . . . . . . . . . .
Basis for Monitoring Network. . . . . . . . . . . . . .
The St. Louis Regional Monitoring Network. . . . . . . .
viii
30
30
45
46
46
47
47
48
49
49
51
51
52
53
54
54
55
55
57
57
58
59
60
63
63
63
63
66
-------
VII
VIII
CONTENTS
MANAGEMENT AND SCHEDULING. .
. . . . .
. . . . . . . . . .
Introduction
. . . .
. . . . . . . . .
. . . . . . . . . .
Facility Activation Schedule. . . .
Permanent Management and Staffing. .
. . . . . .
. . . . .
. . . .
. . . .
COST SUMMARY
. . . . . . . . .
. . . . .
. . . . . .
Permanent Facilities and Staff. . . . . . . . . . .
Helicopter and Mixing Layer Observational Program. .
Research Plan. . . . . . . . . . . . . .
Personnel. . . . . . . . . . . . . . . . . . . . . . . .
Instrumentation and Equipment. . . . . . . . . . . . . .
Operations. . . . . . . . . . . . . . . . . . . . . . .
Total Cost of Research Plan. . . . . . . . . . . .
Total Costs of RAPS. . . . . . . . . . . . . . . . .
ix
71
71
71
73
77
77
80
80
81
83
85
86
86
-------
CONTENTS
PART II - RESEARCH PLAN
FOREWORD. . .
. . . . . . . . . . . . . . . . . . . . . . . . .
ACKNOWLEDGMENT. . . . . .
III
. . . . . . .
. . . . . . . . . . . .
I
INTRODUCTION TO THE RESEARCH PLAN
. . . . . . . .
. . . .
II
RESEARCH PLAN--OVERVIEW OF AIR POLLUTION MODELING
. . . .
Introduction. . . . . . . . . . . . . . . . .
Model Evaluation and Verification Program. . .
. . . . .
. . . . .
RESEARCH PLAN--METEOROLOGICAL PROCESSES
. . . . . .
Introduction. . . . . . . . . . . . . . . . . . . . . .
Atmospheric Dispersion Models. . . . . . . . . . . . . .
Gaussian Formulae. . . . . . . . . . . . . . . . . . .
Gradient Transfer Theory. . . . . . . . . . . . . . .
Other Model s . . . . . . . . . . . . . . . . . . . . .
Numerical Weather Prediction Models. . . . . . . . . . .
Model Sensitivity to Meteorological Variables. . . . . .
Experimental Meteorology Program. . . . . . . . . . . .
General. . . . . . . . . . . . . . . . . . . . .
Tracer Studies of Transport and Diffusion. . . . . . .
Urban and Rural Radiation Budget Studies. . . . . . .
The Role of Remote Probing T~chniques . . . . . .
Upper Air Sampling Program. . . . . . . . . . . . . .
Plume Dispersion Studies. . . . . . . . . . . . . . .
Studies of Spatial Variabilities . . . . . . . .
References. . . . . . . . . . . . . . . . . . . . . . .
IV
RESEARCH PLAN--ATMOSPHERIC CHEMISTRY AND TRANSPORTATION
PROCESSES. . . . . . . . . . . . . . .
Introduction
. . . .
. . . . .
. . . .
x
iii
v
1-1
II-l
-1
-3
III-l
-1
-4
-4
-11
-24
-27
-30
-46
-46
-48
-62
-67
-74
-79
-81
-84
IV-l
-1
-------
CONTENTS
IV
Continued
The S02 Cycle. . . . . . . .. .... . . . . .
Emission Sources of Sulfur Compounds. . . . . . . . .
Chemical Reactions of Importance to the SO -Cycle Model
2
Removal Mechanisms for Sulfur Compounds. . . . .
The Research Program. . . . . . . . . . . . . . . . .
The Photochemical Cycle--Hydrocarbons:Nitrogen Oxides:
Oxidant. . . . . . . . . . . . . . . . . . . . . . . . .
Sources of Nitrogen Oxides. . . . . . . . . . .
Reactions of Nitrogen Oxides in the Absence of
Hydrocarbons. . . . . . . . . . . . . . . . . . . . .
Hydrocarbon Sources and Removal Processes. . . . . . .
The Hydrocarbon-Nitrogen Oxides Reactions.
The Research Program . . . . . . . . . . . . . .
The Particulate Cycle. . . . . . . . . . . . . . . . .
Background Haze. . . . . . . . . . . . . . . . .
Natural Backgrpund Aerosols. . . . . . . . . . . . . .
Particulate Emissions Inventory. . . . . . . . .
The Chemistry of Particulate Formation in the
Atmosphere. . . . . . . . . . . . . . . . . . . . . .
The Research Program. . . . . . . . . . . . . . . . .
Development of Continuous Rainfall pH Measurement and
Sequential Precipitation Collection. . . . .
Carbon Monoxide Cycle. . . . . . . . . . . .
Source of CO . . . . . . . . . . . . . . . . . . . . .
Important Chemical Reactions of CO . . . . . . . . . .
CO Sinks. . . . . . . . . . . . . . . . . . . .
The CO Research Program. . . . . . . . . . . . . . .
The Chemical Research Program Schedule
Aerosol Research Program . . . . . . . . . . .
The S02 Flux Measurement. . . . . . . . . . . . . . .
The HC:NO Research Program. . . . . . . . . . . . . .
x
The CO Research Program.
. . . . . .
References
. . . .
. . . . .
. . . . . .
. . . . . . .
xi
IV-2
-3
-5
-8
-9
-12
-14
-15
-17
-18
-20
-24
-25
-27
-28
-30
-32
-34
-35
-37
-39
-40
-41
-42
-44
-46
-47
-51
-53
-------
CONTENTS
v
RESEARCH PLAN--EMISSION ESTIMATES. . . . . . .
. . . . .
Requirements of the Emission Inventory System. . .
Classification of Emission Sources . . . . . . . .
Source Processes . . . . . . . . . . . . . .
Source Uni t s . . . . . . . . . . . . . . . . . . .
Stationary Sources. . . . . . . . . . . . . . . . . .
Mobile Sources . . . . . . . . . . .
Po 11 u t ant s . . . . . . . . . . . . . . . . . . . .
Factors Affecting Emission Levels . . . . . . . . .
Stationary Sources. . . . . . . . . . . . . . . . . .
Mobile Sources. . . . . . . . . . . . . . . . .
Inventory Procedures and Accuracy. . . . . . . . . . . .
Accuracy of Estimates . . . . . . . . . . . . . .
Procedures. . . . . . . . . . . . . . . . . . . . . .
Emission Model. . . . . . . . . . . .
Control Strategy Studies. . . . . . . . . . . . . . . .
Inventory Schedu~e . . . . . . . . . . - . . . . .
VI
RESEARCH PLAN--ECONOMIC AND SOCIAL IMPACT STUDIES. . . .
Introduction. . . . . . . . . . . . . . . . . . .
Human and Social Factors. . . . . . . . . . . . . . . .
Economic Factors. . . . . . . . . . . . . . . . .
VII
RESEARCH PLAN--TECHNOLOGY TRANSFER
. . . .
. . . .
Introduction . . . .
Technology Transfer Program.
. . . . . .
. . . . . .
" . . .
. . . . . . . . . .
VIII
OTHER AGENCY RESEARCH PROGRAMS
. . . . .
. . . . .
METROMEX . . . . . . .
NCAR Fate of Pollutants
NOAA's MESOMEX . . . .
. . . . .
Study (FAPS)
. . . . . . .
. . . . . . . .
APPENDIX
SCHEDULES AND TASK SPECIFICATIONS FOR THE RESEARCH
PLAN . . . . . . . . . . . . . . . . . . . . . . . .
xii
V-l
-1
-2
-5
-5
-5
-7
-7
-8
-8
-10
-11
-11
-13
-17
-18
-18
VI-l
-1
-2
-5
VII-l
-1
-1
VI II -1
-2
-3
-4
A-I
-------
CONTENTS
PART III - RESEARCH FACILITY
FOREWORD. . .
. . . . . . . . . . . . . . . . . . . . . . . . .
ACKNOWLEDGMENT. . . .
. . . . . . . . . .
. . . . . .
. . . . .
IX
INTRODUCTION TO FACILITY DESIGN AND OPERATIONS
. . . . .
X
ST. LOUIS SITE SELECTION
. . . .
. . . .
. . . . .
Summary. . . . . . . . . . . . . . . . . . . . . . . . .
Si te Selection Criteria. . . . . . . .
Method of Analysis . . . . . . . . . . . . .
National Summary Analysis. . . . . . . . . .
Meteorology. . . . . . . . . . . . . . . . . . . . . .
Foss il Fuel s .. . . . . . . . . . . . . . . . . . . .
Regional Isolation. . . . . . . . . . . . . . .
Results. . . '. . . . . . . . . . . . . . . . . .
General Analysis of Standard Metropolitan Statistical
Areas. . . . . . . . . . . . . . . . . . . .
Pollutants. . . . . . . . . . . . . . . . . . .
Manufacturing. . . . . . . . . . . . . . . . . .
Geographical Separation. . . . . . . . . . . . .
Sunshine. . . . . . . . . . . . . . . . . . . . . . .
Space Heating. .
Results. . .
Agriculture.
. . . . .
. . . .
. . . .
. . . . . .
. . . . . . . . .
. . . . . . . .
. . . .
XI
NEAR-SURFACE ATMOSPHERIC RESEARCH FACILITY
. . . . . . .
General Considerations. . . . . . . . . . . . . . . . .
Horizontal Extent of the Network. . . . . . . . . . . .
Network Orientation. . . . . . . . . . . . . . . . . . .
Characteristics of Stations. .
Meteorological Instrumentation. . . . . . . . . .
. . . .
. . . . . .
xiii
iii
v
IX-l
X-l
-1
-4
-7
-8
-8
-9
-11
-12
-12
-15
-17
-21
-22
-22
-23
-24
XI-l
-1
-1
-14
-23
-27
-------
CONTENTS
XII
AIR QUALITY SAMPLING
. . . . . . . .
. . . .
Introduction. . . . . . . . . . . . . . . . . . . . . .
Permanent Network Monitoring Stations for Pollutants
Semipermanent Monitoring Station. . . . . . . . .
Pollutants To Be Monitored for Establishment of Air
Qual it Y . . . . . . . . . . . . . . . . . . .
Carbon Monoxide. . . . . . . . . . .
Methane, Nonmethane Hydrocarbons, and Total Hydro-
carbons. . . . . . . . . . . . . . . . . . . . . . . .
Ni trogen Oxides. . . . . . . . . . . . . . . . . . . .
Sulfur Oxides and Hydrogen Sulfide and Total Sulfur. .
Ozone. . . . . .
. . . . . . . . . . . .
. . . . . . .
Suspended Particulate Material. . . . . . . . . . . .
Other Pollutants of Interest Not Measured by Network
Pollutant Monitoring Techniques. . . . . . .
Carbon Monoxide, Methane, and Total Hydrocarbon.
Nitric Oxide,. Total Nitrogen Oxides. . . . . . .
Sulfur Dioxide, Hydrogen Sulfide, Total Sulfur. . . .
Ozone. . . . . . . . . . . . . . . . . . .
Suspended Particulate Material. . . . . . . . . . . .
Summary of Pollutant Instruments. . . . . . . . . . .
Instrument Calibration. . . . . . . . . . .
Local Calibration. . . . . . . . . . . . . . . . . . .
Calibration Vans for Primary Calibration. . . . . . .
Role of Research Programs. . . . . . . . . .
XIII
DATA ACQUISITION AND HANDLING.
. . . .
. . . . . .
Introduction. . . . . . . . . . . . . . . . . . . . . .
Policies and Principles. . . . . . . . . . . . . . . . .
S Y stem Ov erv i ew . . . . . . . . . . . . . . . . . . . . .
Instruments. . . . . . . . . . . . . . . . . . . .
Data Acquisition Equipment at Stations. . . . . . . . .
Data Formats. . . . . . . . . . . . . . . . . . . . . .
The Central Data Collection Facility. . . . . . . . . .
Overview
. . . .
. . . . .
. . . .
. . . . . . .
Functional Tasks. . . . . . . . . . . . . . . . . .
Equipment Complement. . . . . . . . . . . . . . . . .
xiv
XII-l
-1
-1
-4
-7
-8
-8
-8
-8
-9
-9
-9
-10
-12
-13
-15
-17
-18
-20
-21
-21
-23
-23
XIII-l
-1
-1
-2
-6
-8
-13
-15
-15
-16
-18
-------
XIII
XIV
CONTENTS
Continued
The Central Data Collection Facility (cont.)
Disk File Organization. . . . . . . . . . . . . . .
Manual Data Entry. . . . . . . . . . . . . . . . . .
Reliability Considerations and Maintenance. . . . .
Communications for the Data Collection Network. . . .
The Telephone Companies. . . . . . . . . . .
Facil it ies . . . . . . . . . . . .
Cost s . . . . . . . . . . . . . . .
Alternative Communication Approaches. . . . . . . .
MIXING LAYER OBSERVATION PROGRAM
. . . . .
. . . . .
Introduction. . . . . . . . . . . . . . . . . .
General Mixing Layer Observation Methods. . . .
Primary Aircraft Support for the Regional Study.
Helicopter Support Function. . . . . . . . . . .
Schedule of Operations. . . . . . . . . . . . . . .
Cost s . . . . . . . . . . . . . . . . . . . . . . . .
Helicopter Instrumentation Package. . . . . . . . .
Balloon Tracking System. . . . . . . . . . . . .
System Design Concept. . . . . . . . . .
Activation Schedule. . . . . . . . . . . .
Costs. . . . . . . . . . . . . . . . . . . . . . . .
Special Aircraft-Based Meteorological Observations
General Concepts. . . . . . . . . . . . . . . . . .
Instrumentation Considerations . . . . . . . . .
Special Aircraft-Based Air Quality Observations.
Western Environmental Research Laboratory (WERL)
Selection of Parameters. . . . . . . . . . . . . . .
Selection of Surveillance Techniques. . . . . . . .
XV
GENERAL CLIMATOLOGY OF ST. LOU IS
. . . . . .
. . . . .
Introduct ion. . . . . . . . . . . . . . . . . . . . .
Principal Seasonal Meteorological Characteristics
Cold Season (Mid-October to Mid-April) ... .
Warm Season (Mid-April to Mid-November) . . . . . .
xv
XIII-19
-20
-20
-21
-21
-22
-23
-24
XIV-l
-1
-1
-3
-4
-4
-9
-9
-14
-14
-17
-17
-18
-18
-19
-24
-24
-26
-26
XV-l
-1
-3
-3
-8
-------
CONTENTS
xv
Continued
Meteorological Parameters Relating to Pollution. . . . .
Stagnating Anticyclones. . . . . . . . . . . . .
Wind. e , . . . . . . . . . . . . . . . . . . . . . .
XVI
LAND AND BUILDING REQUIREMENTS
. . . . .
. . . .
. . . .
Central Facility. . . . . . . . . .
Selection Criteria. . . . . .
Interior Space Requirements.
Outdoor Facilities
Instrument Station Sites
Selection Criteria
Implementation. . . . . . . . .
. . . . .
. . . . .
. . . . . .
. . . .
. . . . .
. . . . . . . .
. . . . .
. . . .
. . . . . . . .
xvi
XV-9
-9
-13
XVI-l
-1
-1
-4
-6
-7
-7
-9
-------
CONTENTS
PART IV - MANAGEMENT PLAN
FOREWORD. . .
. . . . . . . . . . . . . . . . . . . . . . . . .
ACKNOWLEDGMENT. . . . . . .
X-ITII
XVIII
. . . . . . . . . . . . .
. . . . .
INTRODUCTION TO THE REGIONAL STUDY SCHEDULING,
STAFFING, AND COST. . . . . . . . . . . . . . .
Introduction. . . . . . . . . . . . . . . . . . . . .
The St. Louis Facility . . . .
Facility Activation Schedule. . . . . . . . . . . . .
Permanent Management and Staffing. . . . . . . . . . .
Cost s . . . . . . . . . . . . . . . . . . . . . . . . .
Permanent Facility and Staff. . . . . . . . .
Helicopter and Mixing Layer Observational Program. . .
Research Plan. . . . . . . . . . . . . .
Total Costs. . . . . . . . . . . . . . . . . . . . .
iii
v
XVII -1
-1
-2
-5
-7
-9
-9
-12
-12
-14
IMPLEMENTATION SCHEDULE OF THE ST. LOUIS FACILITY. . . XVIII-l
Int roduction . . . . . . . . . . . . . . . . . .
Prototype Instrument Station and Central Facility. . .
Schedule Network and Estimated Activity Durations. .
Activity Descriptions. . . . . . . . . . . . . . . .
Network Critical Path. . . . . . . . . . . . . . . .
Activation Schedule of Class A and Class B Stations. .
Uni t Schedules. . . . . . . . . . . . . . . . . . .
Sequential Station Activation Schedule and Mainte-
nance Requirements. . . . . . . . . . . . . .
Full Facility Implementation . . . . . . . . . .
General Scheduling Conditions. . . . . . . . . . . .
Class A and B Station Activation with Prior Proto-
type Station Acceptance. . . . . . . . . . . .
Class A and B Station Activation Without Prior
Prototype Station Acceptance. . . . . . . . . . . .
Class C Station Activation Schedule. . . . . .
Aggregate Facility Activation Schedule. . . . . . .
xvii
-1
-3
-3
-17
-27
-33
-33
-36
-44
-44
-53
-55
-59
-63
-------
CONTENTS
XIX
PERMANENT MANAGEMENT AND STAFFING
. . . . .
Introduction. . . . . . . . . . . . . . . . . . . . .
Regional Study Management. . . . . . . . . . . .
Research Triangle Park Staff. . . . . . . . . .
St. Louis EPA Operating Staff with EPA Operation
St. Louis EPA Staff with Prime Contractor Operation. .
St. Louis Facility Implementation . . . .
Staff Scheduling . . . .
XX
ST. LOUIS FACILITY INITIAL COSTS AND ANNUAL OPERATING
COSTS. . . . . . . . . . . . . . . . . . . . . .
Introduct ion. . . . . . . . . . . . . . . . . . . . .
Ini t ial Costs of the St. Louis Facil i ty . . . . .
Air Quality and Meteorological Instruments. . . . .
Instrument Station Preparation, Facilities, and
Appurtenances. . . . . . . . . . . . . . . . . . . .
Ditigal Data Terminal and Communication Equipment. .
Central Faci 1 i ty and Equipment. . . . . . . . . . .
Vehicular Support Facilities. . . . . . . . .
Total Initial Costs. . . . . . . . . . . . . . . . .
Annual Operating Costs. . . . . . . . . . . . . . . .
Personnel. . . . . . . . . . . . . . . . . . .
Instrument Replacement and Spare Parts. . . .
Telephone Communication System. . . . . . . .
Motor Vehicles. . . . . . . . . . . . . . . . . . .
Building and Land Rental. . . .
Miscellaneous. . . . . . . . . . . . . . . . . . . .
Total Estimated Annual Operating Costs
. . . .
XXI
RESEARCH PLAN COSTS. . . . .
. . . . . . . . .
. . . .
Introduction. . . . . . . . . . . . . . . . . .
Personnel. . . . . . . . . . . . . . . . . . . . . . .
Requirements. . . . . . . . . . .
Cost s . . . . . . . . . . . . . . . . . .
Instrumentation and Equipment. . . . . . . . . . . . .
Operations. . . . . . . . . . . . . . . . . . .
Total Cost . . . . . . . . . .
xviii
XIX-l
-1
-1
-6
-13
-25
-26
-32
XX-I
-1
-1
-3
-5
-6
-9
-11
-13
-15
-17
-17
-19
-20
-21
-22
-23
XXI-l
-1
-2
-2
-5
-6
-10
-11
-------
II-l
III-l
-10
-11
VI-l
ILLUSTRATIONS
PART II - RESEARCH PLAN
Model Verification Program. . . .
. . . . . .
Vertical Profiles of Wind and Eddy Diffusivity .
. . . .
-2
Peak Surface Concentration as a Function of Distance
from an Elevated Source. . . . . . . . . . . . . . . .
-3
Peak Surface Concentration as a Function of the Radial
Distance from the Source. . . . . . . . . . . . . . . .
-4
Sources of Input Errors and Uncertainties in Variables
Utilized in Air Quality Simulation Models. . . . . . .
-5
Effect of Wind Direction on Concentrations Computed
for the Washington, D.C., Camp Station. . . . . . .
-6
Effect of Moving Receptor Point
. . . . .
. . . .
-7
Normalized Concentration as a Function of Stability
and Mixing Depth. . . . . . . . . . . . . . . . . . . .
-8
Hypothetical Lateral-Longitudinal and Vertical-
Longitudinal Cross Sections Showing Envelopes for
Plumes Generated Simultaneously by Identical Point
Source at Two Elevations. . . . . . . . . . . . . . .
-9
Hypothetical Lateral-Longitudinal and Vertical-
Latitudinal Cross Sections Showing Envelopes for
Plumes Generated Simultaneously by Identical Point
Sources Displaced Crosswind Along Y-Axis. .
Hypothetical Surface, Vert ical-Longi tudinal and Vert ical-
Latitudinal Cross Sections for Plumes Generated Simulta-
neously by Identical Point Sources at Different Upwind
Ranges from Crosswind and Vertical Samplers at x
o
Program Elements of Tracer Experiments
. . . . . . . . .
Interrelationship of Models Pertaining to Air Quality
xix
II-5
III-34
-35
-36
-41
-42
-44
-45
-54
-57
-58
-63
VI-3
-------
III-l
-5a
-5b
1V-l
V-l
TABLES
PART II - RESEARCH PLAN
Sensitivity Analysis of the Gifford and Hanna (1971)
Dispersion Model. . . . . . . . . . . . . . . . . . . .
-2
Calculated Values of the Mean and Standard Deviation
of [(Xy - XE)/XyJ as a Function of Systematic Errors
in the Lateral Diffusion Coefficient 0y' after Hilst . .
Calculated Values of Mean and Standard Deviation of
(;~ - XE)/XT as Function of Systematic Errors in
Vertical Diffusion Coefficient 0 , after Hilst . . . . .
z
-3
-4
Calculated Values of Mean and Standard Deviation of
(Xr - XE)/~ as Function of Systematic Errors in Wind
Direction (a); Hilst . . . . . . . . . . . .
Atmospheric Conditions. .
" " " . "
. . " .
Pollutants.
" . . . .
. . . . "
. . . " " . " . "
-6
Vector Error of Wind (m/sec) at 5 km as a Function of
Tracking System and Ratio (Q) of Mean Wind to Ascent
Rate. . . . . . . . . . . . . . . . . . . . . . . . . .
Chemical Reactions of Importance to the S02-Cycle
'-2
The 14-Step SAI Model
. " . " "
. . . " " . .
. " . " "
-3
Hydrocarbon Reactivity in NO Photooxidation
-4
Chemical Reactions of Importance to the Particulate
Cycle. . . . . . . . . . . . . . . . . . . . . .
Average Particulate Chemical Analyses (~g/m3)
-5
" . " " .
-6
Particulate Emissions Inventory of St. Louis
. . . " . .
-7
The Chemical Research Program
" " " .
. " . . . " . .
Classification of Sources for Emission Inventory
" . " .
xxi
II 1-32
-38
-39
-39
-69
-70
-77
IV-4
-21
-22
-26
-27
-29
-43
V-3
-------
Chapter I
INTRODUCTION TO THE RESEARCH PLAN
Part II of this Prospectus presents the Research Plan of the
Regional Study. Two methods of presentation of the Research Plan are
used. The first method provides a comprehensive overview of the three
principal components contained in the process of air pollution: meteor-
ological processes, atmospheric chemistry and transformation processes,
and the emission sources. The second method defines specific research
tasks to be carried out during the study.
In the first presentation, the general state of the art of these
components is discussed, and the major problem areas on which the Regional
Study should be most strongly focused are identified.
The considerations of meteorological processes in Chapters II and
III cover their general involvement and effects on relationships of their
magnitudes to air pollution and the manner in which these processes are
treated in several mathematical models having a relatively advanced
degree of development~ Several of these models are likely to be the
subject of detailed analysis during the Regional Study.
The discussion of atmospheric chemistry and transformation processes
in Chapter IV covers the atmospheric pollutant cycles of the principal
pollutants, including sulfur oxides, nitrogen oxides, hydrocarbons,
particulate matter, photochemical oxidants, and carbon monoxide. The
atmospheric cycles of most of these pollutants are not well understood,
and recommendations are presented for improvement in the state of knowl-
edge of these cycles in their most critical sectors. The function of
both particulate material as a scavenger for many pollutants is addressed,
along with the role of precipitation in removing both gaseous and par-
ticulate material from the atmosphere.
Chapter V presents the need for, and the procedures necessary to
develop and maintain, a source inventory. A general classification
scheme of a source inventory is presented that first divides the inven-
tory into stationary and mobile sources. These categories are divided,
respectively, into area and point sources and area and line sources. A
further breakdown for all is made into combustion and noncombustion
sources. The concepts and general rules by which sources can be assigned
I-I
-------
to these groups are provided and the methods of data acquisition are
treated.
Whereas the foregoing chapters of Part II treat the main scientific
and technical aspects of the Regional Study, the latter chapters address
important primary derivatives of the scientific effort. Chapter VI
addresses companion research efforts that could be carried forward in
the area of economic and social implications of air pollution and pro-
grams for its control and abatement. Air quality data acquired by the
instrument system, the source inventory, and perhaps the scientific
programs, together with independently gathered data on the area's popu-
lation, land use, manufacturing operations, and other factors, should
lay the base for sorely needed development and improved understanding
of the economic and social problems entailed in air pollution.
Chapters VII and VIII generally cover the interaction of the
Regional Study with other organizations. Chapter VII--Technology
Transfer--advances the concept that the Regional Study will indeed
include developments and advances in the state of the art of instrument
systems, data handling and processing, model verification, and many
other areas that can be profitably adapted for use in similar or quite
different areas of research as well as operation. The general content
of a research program to cover these activities is suggested.
Chapter VIII covers the need for the Regional Study to interact with
a number of other ongoing research efforts in the St. Louis area. These
efforts are described and anticipated points of interaction are iden-
tified. These seven chapters, as noted, provide an overview and dis-
cussion of the Research Plan.
The second presentation of the Research Plan is provided in the
Appendix of Part II. This appendix consists of a set of specific
research tasks drawn from the broader discussion, along with estimates
of the scheduling and personnel requirements for each task. The tasks
are placed within four principal groups and assigned a numerical iden-
tifier. The four principal groups are shown below.
100
Model verification
200
Atmospheric chemical and biological processes
300
Human, social, and economic factors
400
Transfer of RAPS technology.
1-2
-------
Each group in turn is divided into between four and six components,
with the 100 group, for example, divided into 101, 102, 103, and 104.
Each of these are further divided into specific tasks using a decimal
notation, 101.1, 101.2, and so on. Scheduling and personnel estimates
are shown at the decimal level.
1-3
-------
Chapter II
RESEARCH PLAN--OVERVIEW OF AIR POLLUTION MODELING
Introduction
The scope of research efforts in the field of boundary layer simula-
tion modeling centers on the need to understand, describe, predict, and
ultimately control air quality in the lowermost stratum of the atmosphere.
Simulation modeling provides the necessary link between inferences gleaned
from air quality data obtained at isolated, single-point monitoring sta-
tions and the broad, yet detailed, picture of air quality that is required
over an entire urban region; it also permits assessment of the ramifica-
tions of actual or projected growth (zoning) patterns and emission con-
trol (proportional versus selective) procedures. Neiburger (1969) pre-
sents a detailed discussion of the application of modeling in the study
and control of air pollution.
Simulation modeling of the boundary layer refers precisely to phys-
ical or mathematical modeling of the atmospheric planetary boundary layer--
the lowermost stratum-of the atmosphere (on the order of 1 km depth) in
which the effect of surface friction on the wind field is manifested.
From a more practical standpoint, it is also the layer in which atmo-
spheric pollutants are generally emitted, transported, diffused, and
transformed. Mathematical models include, generally, gradient-transfer,
similarity, Gaussian plume and puff, and statistical formulations, while
physical modeling is done with the aid of wind or water tunnels. The
utility of the mathematical models lies in their ability to describe and
parameterize the physics of the problem over a large region and to predict
meteorological and air quality changes that may occur either in time (as
a result of the progression or development of weather systems) or from
the alteration of emission patterns. Ideally, mathematical models are
capable of achieving arbitrary degrees of temporal and spatial resolution
to solve specific problems. High resolution, for example, may be neces-
sary when considering pollutant concentration in urban core areas, whereas
relatively low spatial resolution may be required for the study on the
mesoclimatic scale. Physical models are perhaps less flexible, yet are
Soc., 50(12), 957-965 (1969).
Neiburger, M., Bull. Amer. Meteorol.
11-1
-------
ideal for evaluating the gross features of, for example, pOllutant distri-
butions in extremely inhomogeneous or complex locations.
It is highly desirable that the RAPS program evaluate the ability of
the more promising models to simulate the atmospheric environment on both
the micro- and mesoscales. In this regard, the models should be evaluated
according to the specific function that they may serve. Specifically,
evaluation programs are recommended for the following three functional model
types: (1) diagnostic, (2) predictive, and (3) climatic. The primary
emphasis at this time should be placed on diagnostic (descriptive) models,
because the current or steady-state distribution of pollutants on the
mesoscale must be described before detailed prognostic models can be
developed. Prognostic or predictive models in this sense do not include
diagnostic models which may be input with anticipated meteorological
and emissions data to simulate an expected condition. Rather, predictive
models use current initial conditions to predict (on the order; say, of
one or two days) meteorological and perhaps emission fields, thereby
predicting the level of air quality for some time in the future. Moreover,
emphasis must be given to the development and evaluation of dynamic
climatological models which have the ability to describe the mesoclimate
and changes that may result from mesoscale urbanization.
Toward the achievement of these goals, it is essential that the
various models be evaluated (and refined, as appropriate) with "real"
data collected in the field. Such data collection will further our abil-
ity to understand and 'simulate the lower atmosphere on the mesoscale (on
the order of 250 km). But unless one is able to observe the process he
is attempting to describe, simulation modeling may be little more than
an esoteric exercise. A vast amount of effort has been expended in the
development of the various mathematical models and in their subsequent
evaluation. In almost no case have the observed data been obtained on
a scale compatible with the resolution of the model computation. Virtually
all meteorological and air quality data collected on a routine basis for
purposes other than model verification are the result of single point
measurements (or, at the very best, several adjacent points). As such,
the observation is a representation of very localized conditions and, in
perspective, is a measure of the integrated effect of various scales of
motion: micro, meso, and macro. In many cases, it is the microscale
phenomena that predominate and there can be little surprise at the inabil-
ity of numerical models to simulate the observation when the model may, in
fact, predict only average conditions over a broad area, say a one kilo-
meter square or larger. Another objective of the program should therefore
be the definition of the spatial variability of ambient air quality as well
as the spatial resolution of the simulation models. In practice, a feed-
back between observations and computations should result whereby the
II-2
-------
observations define the appropriate time and space scales that the models
need to achieve, and eventually the models are used to describe spatial
and temporal variations on the basis of a few representative measurements.
Federal air quality guidelines define levels of air quality on several
time scales: hourly, eight-hourly, daily, and annually. On the basis of
results from the observation/modeling programs, spatial criteria may also
need to be established. It appears equally necessary to define criteria
where the air quality is evaluated in parallel, over various length (or
area or volume) and time scales. In this regard and in consideration of
the requirements of model verification, the data collection program must
also concern itself with the potential of remote (long-path) observation
techniques where a particular contaminant can be measured on the appro-
priate spatial scale.
In summary, an extensive air monitoring network is required to define
the scope of the problem and to evaluate and refine the mathematical
models that are to simulate the level of air quality over a broad region.
As such, the network should be not only extensive, but also flexible so
that it will serve the many purposes of the simulation program. It must
be capable of providing data from the substreet microscale to the regional
mesoscale. The observations will also be used to evaluate these models
on a variety of temporal scales: simulation of existing conditions (diag-
nostic requirement), prediction of short-term changes (prognostic require-
ment), and evaluation of potential mesoclimatic alterations (extended
prognosis). Physical modeling techniques should be employed to supple-
ment the field observation program in urban core areas where the complexi-
ties of building structures may severely limit routine in situ measure-
ments on a practical basis.
Model Evaluation and Verification Program
The evaluation of the various simulation models can be accomplished
most efficiently by considering the models in terms of the functions that
they may be expected to serve. For convenience, these functions may be
divided into three parallel types: (I) the time frame and resolution of
the model, (2) the spatial frame and resolution, and (3) the class of con-
taminants to be considered. The models may therefore be classified
according to whether they simulate the quality of the air in terms of the
concentration distribution of inert, reactive, or particulate contaminants
over either localized or expansive regions for current or forecasted con-
ditions. Accordingly, there are on the order of a dozen functions that a
model or models may be expected to fulfill; that is, there may be local-
ized, diagnostic models for inert pollutants which have application in
11-3
-------
planning and evaluation studies (such as in the study of expected carbon
monoxide concentrations resulting from highway development) or regional,
prognostic models of reactive contaminants required for emissions control
procedures. Figure 11-1 illustrates this concept, as well as the sub-
sequent steps in a model evaluation and verification program. It may be
further desirable to test the various models under a variety of distinct
meteorological conditions. One such stratification could be the separa-
tion of low and moderate-to-high wind speed cases (isolation of stagna-
tion conditions); other distinctions may be made between near steady-state
and strong advective conditions, or strong versus weak insolation.
At this point, the purpose of the simulation will have been defined
and certain forcing physical criteria established; specific models falling
within this framework can then be introduced for evaluation and subsequent
verification. It is strongly recommended that initially the performance
of the models be evaluated against both observed measures of air quality
and the predictions of a simple standard (or reference) model or models.
The simple model used by Hanna (1971) or a relatively simple box or
Gaussian formulation (see Chapter III) should be considered. Quantitative,
statistical techniques should then be applied to test the model against
the reference and the observations. If the test model cannot show signif-
icant superiority to the reference, then it can be safely excluded from
the later, detailed evaluation program. Emphasis should also be placed
on a qualitative assessment of the extent and nature of the required
input data. If a given model performs well, but requires input data that
may not be readily available at the present or in the foreseeable future,
then alternative formulations or parameterization may be necessary for
further consideration.
Having initially demonstrated its feasibility, the model should be
evaluated in detail in order to define both its strong and weak points so
that refinements may be made. This detailed model evaluation program
should include both fundamental and applied research tasks for the testing
of the basic components of the model; namely, meteorological, emissions,
and transformation processes. The applied tasks are, in effect, individual
evaluation programs for the three process areas (or submodels). Submodel
predictions of wind, turbulence, stability, emissions, plume rise, reaction
rates, and so forth would be compared with routine observations from the
research network (which may not be strictly routine for nonresearch pro-
grams). The sensitivity of each model and submodel should be evaluated
Hanna, S. R., "Simple Methods of Calculating Dispersion from
Sources," paper presented at the Conference on Air Pollution
Raleigh, N.C., Sponsored by Amer. Met. Soc., April, 1971.
Urban Area
Meteorology.
11-4
-------
I MODEL FUNCTION I
!
+
t
TIME SCALE.
1.
2.
3.
DIagnostic
Prognostic
Climatic
SPATIAL SCALE:
1.
2.
Local (micro)
Regional (meso)
POLLUTANT CLASS.
1. Inert
2. Reactive
3. Partlcu late
ELEMENTARY METEOROLOGICAL STRATIFICATION:
1.
2.
3.
4.
Wind speed-stagnation versus dIlutIOn
Statlonanty-steady-state versus time variant
Insolation-strong versus weak
Etc.
MODELISI
OBSERVATIONS
OF AIR QUALITY
ROUTINE, DETAILED
OBSERVATIONS
FINAL VERSION
OF MODEL
FIGURE B-1
. "II
INITIAL MODEL
EVALUATION
..... -
---.
EMISSIONS
INPUT DATA
I
I
...-_J
AIR QUALITY
SIMULATION,
"SIMPLE" MODEL
UNACCEPTABLE
SPECIAL STUDIES
REVISION TO
MODEL
SA-1365-52
MODEL VERIFICATION PROGRAM
II-5
-------
with regard to the response of the output (model prediction) to variations
of the input parameters. In addition to these direct or applied tasks,
there is an acknowledged need for complementary research programs of a
more fundamental nature. These would be directed toward providing a
better understanding of the physical nature of the various physical proc-
esses so that the models may be revised accordingly and in conjunction
with the requirements resulting from the applied program. Many of these
fundamental programs can be anticipated; others, however, will result
only as output requirements of the initial, detailed evaluations. The
fundamental programs or special studies are given in detail in later
sections.
11-6
-------
Chapter I I I
RESEARCH PL~~--~lliTEOROLOGICAL PROCESSES
Introduction
~Iost mathematical air quality simulation models may be classified
conveniently in four major categories according to atmospheric disper-
sion theory: (1) gradient-transfer, (2) Gaussian (puff and plume),
(3) similarity, and (4) statistical. In each type, the procedure is
generally similar. An emissions field is specified (strength and spa-
tial distribution), and then the field is redistributed and transformed
accordiGg to the transport and diffusion characteristics of the atmo-
sphere together with the consideration of reactions or deposition of
the various contaminants. The manner in which the emissions, transport,
diffusion, and transformations are specified varies a great deal among
the various model types and indeed also among specific models of a given
type. Perhaps the most important and certainly the most striking dif-
ference is in the treatment of diffusion.
The gradient-transfer method has as its basis the analog with the
classical Fickian-type diffusion where the flux of mass or momentum is
taken to be directly proportional to the gradient and where the factor
of proportionality is the so-called eddy diffusivity. The simpler gra-
dient models assume diffusivity profiles, while others either compute
the variation on the basis of observations or through parameterization
techniques. Diffusion in the Gaussian models is given by lateral and
vertical standard deviation functions; these are usually proportional
to travel distance from the source and the degree of atmospheric sta-
bility. Similarity models treat diffusion as occurring with a finite
propagation rate determined from the characteristic turbulent length
scale of similarity theory and are strictly applicable only in the at-
mospheric surface layer--that stratum adjacent to the earth's surface
(on the order of 10 m depth) where height variations of the turbulent
fluxes of mass, momentum, heat, or water vapor (as examples) are negli-
gible in comparison with the magnitude of the surface flux and in con-
sideration of measurement inaccuracies. In statistical theory, the dif-
fusion is determined from consideration of the root-mean-square Lagrallgian
velocity fluctuations (measured, however, at a fixed point) and a char-
acteristic autocorrelation function, usually under the assumptions of
homogeneity and stationarity of the flow properties and coincidence be-
tween mass and momentum transport.
III-l
-------
The essential objective of an evaluation and validation program for
any of the various model types should be the development of a suitable
model or models that will simulate meteorological and/or air quality con-
ditions that are representative: (1) over a specified averaging period,
(2) with the necessary spatial resolution, and (3) for the desired time
frame, i.e., current conditions or predicted (short or long term) changes.
Less tangible objectives of the program also must be considered.
The applicability of the various models must be evaluated in terms of
both the immediate and future ability of air pollution control and plan-
ning personnel to utilize them. In this regard, the capability and ac-
cessibility of the required computational facilities must be evaluated.
One must also weigh the input requirements of the various models in terms
of the type of meteorological and emissions data that are currently avail-
able or can be anticipated. Compromises may be necessary to produce use-
ful, workable, and tested models within the RAPS program. Attention must
also be devoted to the more sophisticated and complex models that may be
less suited for day-to-day operation but that serve a real need in the
evaluation of the simpler models and in planning and impact studies.
Also, techniques that will be required to process and analyze both mea-
sured and computed data must not be overlooked.
The large volume of data will require computer processing for all
routine operations. Fortunately, there have been major developments in
meteorological objective analysis that may be applied to this problem.
Typical approaches to objective analysis have been given by Cressman
(1959), Sasaki (1971), Stephens (1970), and Endlich and Mancuso (1968).
In general, grid point values of a property of interest are determined
from the measured values at surrounding stations, with higher weighting
given to observations closer to the grid point. Variable importance may
be assigned to different types of data, depending on sizes of random ob-
servational errors or other factors.
The general tendency of atmospheric properties to arrange themselves
along the flow direction is included in the weighting scheme of Endlich
and Mancuso. Stations are given a higher weighting if they are upwind
or downwind than if they are crosswind at the same distance from the
grid point. The determination of the flow direction is based on the ob-
served wind directions. All these analysis techniques were derived for
synoptic scale phenomena, but with suitable modifications they can be
applied to regional boundary layer observations. Determinations of op-
timal weighting functions for regional analysis and other detailed mat-
ters can be made from the various data obtained early in the observa-
tional program.
111-2
-------
The objective analysis methods currently in use are sufficiently
flexible that they can be used with a variety of grids. For example,
in using observed data spaced more densely in a central area in the
manner discussed in Chapter XI, more than one grid spacing may be de-
sirable. A fine-scale square grid could be used in the central area,
surrounded by a grid of doubled spacing, with a third even larger grid
near the extremity of the area of interest. Alternatively, analyses
could be made on a grid of regularly increasing spacing away from a
central point. These decisions on grids can be made in concert with
decisions concerning the diffusion models that will be applied to air
quality properties. It is worth noting also that analysis rules for
air quality properties (such as ozone concentration) probably can be
quite similar to those used for meteorological properties, since meteor-
ological factors tend to control the dispersion of pollutants.
Meteorological quantities that would be analyzed include wind com-
ponents (u, v, w), temperature, humidity, pressure, cloud cover and type,
precipitation, and incoming and outgoing radiation. From these proper-
ties, other important factors would be calculated such as mixing layer
depth and Richardson number. Sources of data would include the towers,
surface stations, and upper-air facility of the regional network, sur-
face and rawinsonde reports from standard networks, satellite cloud pic-
tures in the visible and infrared, and radar measurements of precipita-
tion. Satellite data with one-half mile resolution will probably be
obtainable via telephone lines from a satellite readout station, which
we understand is planned for installation at Kansas City by NOAA. Other
standard data can be obtained in conventional ways.
From an objective analysis, values of any property can be obtained
at any desired point by simple interpolation schemes. However, it is
important to realize that the accuracy of the analyzed values (and in-
terpolated ones) depends on the data coverage in that immediate vicinity.
The highest reliability exists at the place and time of the greatest con-
centration of observations, regardless of whether analyses are done by
hand or by computer.
The computer that assembles, processes, and analyzes these data
should also be used to control one or more display devices. Rapid dis-
play of analyses will permit operational and research personnel to as-
similate and assess changing events with minimal delay. This will be
necessary eventually for real-time control of air quality. Considera-
tion should be given to cathode-ray-tube displays; automatic line drawing
equipment; video disk storage of maps, charts, and satellite pictures;
and the software needed to operate these devices.
111-3
-------
The various applications of objective analyses could be used in:
(1)
Diffusion and air quality models and computations.
(2)
Improved descriptions of small scale meteorological variables
using spectral analysis techniques, leading to better objec-
tive analysis methods.
(3)
Comparison of observed and predicted profiles of meteorological
properties.
(4)
Determination of trade-offs between space and time aspects of
meteorological observations.
(5)
Description of mesophenomena associated with cities such as
the heat island effect and local thunderstorm occurrences.
(6)
Research on boundary layer dynamics.
(7)
Comparison of analyzed meteorological properties to cloud
behavior shown by satellite data.
(8)
Delineation of initial conditions for fine-mesh prediction
models for the air quality control region.
The following sections will serve to present the structure, input
requirements, and potential of several model types that appear capable
of meeting some of the requirements stated earlier in this discussion.
Atmospheric Dispersion Models
Gaussian Formulae
Introduction
The most widely used simulation model at the current time is
based on the Gaussian diffusion formulation. It is assumed that the
downwind distribution of pollutant concentration (X, M L-3) from indi-
vidual, instantaneous point sources of strength Q(M) is Gaussian-shaped
in all directions,
111-4
-------
X (x,y,z,t)
=
Q
(2TT)3/2 a a a
x y z
~ [(x::t)" + (:;)2 J
exp [- ~ to:h)" J + exp [- ~ ta-z")2 ]
exp
(III-I)
where x is distance along the mean wind direction from the source (height
h) and y is the horizontal and z the vertical crosswind directions. The
variances (a2, L2) are usually specified as a function of meteorological
conditions and travel distance. Equation (III-I) is termed the Gaussian
"puff" formula. If steady-state conditions are assumed, the time inte-
gration of the puff equation results in the so-called plume formula,
where
x(x,y,z)
=
2ncr :a z a exp [- ~ ~y )2J exp [- ~ ~a-z")2]
+ exp [- ~ ta+:YJ
(III-2)
The height h is treated more appropriately as an effective
source height where both the physical height of the emitter and the rise
of the plume must be considered. Briggs (1969) has given a definitive
analysis of the treatment of the effects of efflux velocity and buoyancy.
Ostensibly, the puff formula is more rigorous, since it can
allow for the inclusion of departures of the flow field from the usually
assumed straight motion, as well as for temporal variations of the emis-
sions, transport, and diffusion characteristics. However, this is ac-
complished with a substantial increase in computation time and expense
and with questionable improvement of the results. pasquill (1971) has
aptly pointed out that acceptance of the superiority of the puff method
implies an ability to adequately describe trajectories and the growth
of individual elements. However, the wide variability of the wind field
over the spatial scale of the calculations suggests the use of an ensemble
average, which is equivalent to the plume method. Previous studies
(Islitzer and Slade, 1968) have shown that the assumptions explicit in
the plume formulation are satisfactory for averaging times on the order
of one-half hour and longer, although temporal changes of the mesoscale
wind field may limit application for the longer averaging periods.
II 1-5
-------
The basic Gaussian plume formulation can be applied to both
point and area sources; in practice, the usual procedure is to represent
an area source by an effective uniform emission strength and height and
to consider anomalous sources by the addition of specific point source
calculations. Various numerical integration techniques for the represen-
tation of the continuous area source have been evaluated by Shieh and
Halpern (1971), while an analytical method has been used, for example,
by Stanford Research Institute (Ludwig et al., 1970).
The SRI Model--an Example
The SRI model can be used conveniently to discuss Gaussian
models in general; unlike some of the more extensive formulations that
may be expected to be evaluated in the Regional Study (see, for example,
the numerous Gaussian models presented at the Symposium on Multiple-
Source Urban Diffusion Models [Stern, 1970J and the Conference on Air
Pollution Meteorology [American Meteorological Society, 1971J), the SRI
model has been well tested in an extensive field program (Johnson et al.,
1971). Unlike other evaluation programs, the field experiment was spe-
cifically designed to collect data that would test all components of the
model. As such, it did not suffer the limitations imposed by relying on
available data--usually collected for some purpose other than model eval-
uation.
The fundamen'tal theme of the SRI model is the simulation of
the distribution of chemically inert, vehicle-generated pollutants in
an urban area from existing or easily obtainable meteorological and emis-
sions data. The model can be used in two ways: (1) in the synoptic mode,
in which hourly concentrations are calculated from meteorological and
traffic data; and (2) in the climatological mode, in which concentration
frequency distributions are calculated on the basis of long term sequences
of input data. The only input data required are airport weather observa-
tions and city traffic information. Because wind is the only input that
is directly measured, submodels have been developed to estimate the emis-
sions, atmospheric stability, variances, and mixing depth from the mea-
sured quantities.
The model is receptor-oriented, and the concentration at that
point is determined by the atmospheric conditions and emissions from
logarithmically spaced angular segments aligned upwind of the receptor
along the mean transport wind. The innermost sector extends from the
receptor to 125 m (comparable to a city block); the four inner sectors
have a width of 45° to allow for large initial dispersion, while the
outer six sectors are 22.5° in width (~ 2a) in accord with Gifford's
II 1-6
-------
(1961) findings of plume spread under slightly unstable conditions.
Emissions are assumed uniform within each segment but may vary between
segments. The smaller sectors near the receptor provide the higher
resolution required for nearby sources.
Equation (111-2) is integrated over x and y to permit appli-
cation on an area-source basis,
x
0.8 N~l -
- . 1 Q.
u 1= 1
[ l-bj l_bj]
x - x
i+l i
a .(1 - b.)
J J
(111-3)
where i is the number of the segment (i = 1, N) and j is the stability
class. The parameters a and b are functions of atmospheric stability
and result from the formulation for the variation of 0z' the vertical
standard deviation of the pollutant distribution,
Gz1
=
a x
j
b
j
(111-4)
Equation (111-4) is based on an examination of experimental data on ver-
tical diffusion in urban areas (Pooler, 1966; McElroy and Pooler, 1968;
and Leighton and Dittmar, 1952, 1953 a-e).
Model predictions were compared initially with measured data
from Continuous Air Monitoring Program (CAMP) stations; calculated and
observed values often differed significantly in magnitude, although trends
were similar. The failure of the model to predict observed values ac-
curately resulted, in part, from the fact that the basic model treated
only the diffusion process on the urban scale, while observations are
greatly influenced by street-scale effects. A simple street effects
submodel was subsequently developed and has greatly improved the per-
formance of the model. The street effects submodel is based on "box-
model" reasoning and predicts the contribution of very local sources to
the total concentration as a function of roof-level wind direction, wind
speed, street width, street traffic, and height and street side (e.g.,
windward, leeward). Field experiments were conducted in San Jose, Cali-
fornia, and st. Louis, Missouri, for the purpose of model evaluation,
refinement, and validation.
111-7
-------
The SRI program serves to illustrate, in part, the basic na-
ture and scope of the proposed RAPS program. The objectives of the SRI
study were the refinement and validation of a practical, multipurpose
regional (urban mesoscale to street microscale) dispersion model from
the results of detailed field measurements. The measurement program
was designed not only to evaluate the validity of the computed concen-
trations but also to test the degree to which the various model compo-
nents (submodels) were able to simulate the input requirements of the
basic model (in this case, Eq. [III-2J). The following discussion serves
to expound on the nature of the input data requirements and their simu-
lation to prescribe requirements that an observational network must sa-
tisfy for the total evaluation of Gaussian-type dispersion models.
The input requirements for virtually all classes of pollution
simulation models may be classified conveniently into one of two types,
emissions and meteorological. According to the manner in which the
various models have been classed (i.e., by the nature of diffusion simu-
lation), the problem of the input of emissions data is common to all
models. The problem of the simulation of emissions may be further struc-
tured into three subelements: specification of the strength and spatial
and temporal variations of the emissions field. The strength of emis-
sions implies the fractionation into pollutant types as well as the rate
with which they are emitted. Furthermore, modeling of the spatial and
temporal variations must appreciate the nature of the emission-generating
process together with the desired model resolution. For example, the
modeling of daily concentrations of a pollutant may require specifica-
tion of subday emissions when the basic emitting period is shorter than
one day. The emissions problem is further complicated when considering
mobile rather than stationary sources where both the strength and spa-
tial distribution may be some temporal function.
In its model, SRI was concerned with the emission of carbon
monoxide (CO) by automobiles. The strength of the emission of CO is a
function of the number of vehicles and, more directly, of their speed
and age. San Jose has an extensive computer-based traffic monitoring
network that provides detailed traffic information for the central busi-
ness district (CBD). Spatial and temporal distributions in the outer
region are obtained from historical traffic data. With the available
traffic information, evaluation of the emissions submodel was reduced
to a check of the empirical equation that quantified the effect of vehi-
cle speed and age. The evaluation of the emission of CO from the CBD
was made from a CO mass budget analysis using surface (van) and aerial
(helicopter) measurements around the area. The difficulties of effec-
tively evaluating the simulation of a complex emission field--such as
CO, S02' and NO--are large and accentuate the need for a major program
111-8
-------
of emission inventory design and simulation; the SRI verification program
resulted in the conclusion that its submodel was not invalid. Although
only a qualified success, its verification program is a pioneering effort
for area source emissions modeling. Additional work in this important
area is required and will most probably include the use and development
of suitable, remote monitoring systems; a discussion of the task of emis-
sions modeling is given in Chapter V.
Meteorological inputs to the model are required to describe
atmospheric transport and diffusion; for the Gaussian models, this is
done by the mean wind and the variance of the vertical pollutant dis-
tribution (see Eq. [III-2J or [III-3J). A time-averaged, low-level wind
speed and direction are the only routine observations that may be used
directly in the model. No definitive guidelines exist for the height at
which this measurement should be made; in practice, available winds are
often used with little regard for the height, location, sensor-type, and
other factors. However, the results may not reflect these inaccuracies
because of similar limitations in the emissions, diffusion, and concen-
tration (observed) values, as well as the empirical nature of the model
itself. Smith and Singer (1966) provide insight into the interpretation
and use of the term in the equation. It is an indicator of the mean
speed and direction with which dispersion is occurring. Because of the
horizontal transport and vertical diffusion of a plume, it will encounter
changes in the mean wind speed and direction. This effect is usually
most pronounced as the plume grows vertically because of the well-known
variation of wind with, height, but it can also occur in the horizontal
plane because of either temporal changes or horizontal variations in the
wind field. To incorporate these effects in the Gaussian models, they
suggest the use of a variable "mean equivalent wind" corresponding to
the speed at the height of the vertical center of mass of the plume.
There are five basic methods for estimating the lateral and
vertical standard deviation functions required in the Gaussian-type
formulations; the development and evaluation of the various methods have
been summarized by Slade (1968). The first method was developed by
Sutton (1953) and follows from dimensional analysis of the proposed de-
pendence of the Lagrangian single-particle autocorrelation function on
only the intensity of turbulence and the eddy viscosity. The standard
deviation functions can be estimated analytically from a knowledge of
the turbulence intensity and the shape of the wind profile. Because of
the widespread use of the Sutton formulation, algorithms have been de-
veloped to estimate his so-called virtual diffusion coefficients (which
are proportional to cry and crz) from available observations of: (1) the
shape of the wind profile or (2) magnitude of the wind speed together
with an estimate of atmospheric stability. A second method for esti-
mating the lateral and vertical standard deviation functions is through
III-9
-------
their functional relation to the lateral and vertical eddy diffusion
coefficients. The application is somewhat questionable because of the
practical (and theoretical) difficulties in determining the eddy diffu-
sivity and in treating its height variation in view of the constancy of
the standard deviation functions. The last three methods are more at-
tractive (as evidenced by their popularity), since they parameterize the
sigma functions on the basis of directly measurable atmospheric values.
The method of Cramer (1957) relates crz and cry to the standard deviation
of wind direction fluctuations and travel distance. Hay and pasquill
(1959) and pasquill (1961) also estimate vertical and lateral spread
from wind-direction fluctuation measurements. They further present,
together with Gifford (1961), a parameterization technique for estimat-
ing stability and hence crz and cry from wind speed and insolation data,
together with travel distance. Smith and Singer (1966) and Singer and
Smith (1953) relate the standard deviation functions to wind direction
spread (gustiness), as well as to travel distance in a form similar to
Equation (111-4). Their gustiness classification is well known and in-
herently incorporates the effects of stability and wind speed.
The SRI model uses a modified form of the Hay and Pasquill
method. During the San Jose program, the stability algorithm was evalu-
ated (and slightly modified) on the basis of a comparison with a bulk
stability coefficient computed from measured vertical profiles of tem-
perature and wind. The dependence of crz on travel distance (x) and
stability was also revised on the basis of recently available urban
diffusion data (Leighton and Dittmar, 1952, 1953 a-e). The data for
the Pasquill-Gifford formulations were based on measurements taken in
England over rolling, wooded countryside containing small towns and so
may not be strictly applicable for use in urban areas. Another question
that therefore must be answered is the degree and nature of the depen-
dence of cry and crz on the aerodynamic roughness of the interface boundary.
The recent SRI field program in st. Louis was directed toward providing
additional information in this area. Continuous measurements of wind
direction fluctuations and vertical profiles of wind and temperature
(for the computation of stability coefficients) were made in the urban
center; results of the program are not yet available.
The SRI model also treats the effects of a limited mixing depth
due to the presence of elevated inversions. Under these conditions. pol-
lutants tend to become uniformally distributed in the vertical after suf-
ficient travel time has taken place. Therefore, the model reverts to a
simple "box" type when the surface concentrations of the two formulations
first become equal. The afternoon (maximum) mixing depth is computed
from the morning sounding of the nearest radiosonde station and is taken
as the height where the potential temperature of the sounding is equal
III-IO
-------
to the afternoon maximum surface potential temperature. Estimation of
the nighttime mixing depth over a city is based on Summers' (1966) model
of the urban heat island and an empirical relationship (Ludwig, 1968,
1970) between rural lapse rates and the intensity of the heat island
effect. Hourly mixing depths are estimated by interpolation based on
surface temperature during the day and on time for the evening. Evalua-
tion of the mixing depth submodel was based on helicopter temperature
profiles and the lidar, remote probing technique.
other investigators have examined the problem of treating the
effect of a limiting mixing depth in the Gaussian model. Meade (1959)
suggests the cessation of vertical spreading when cr = 0.456 H, but this
z
has the undesirable feature of a substantial vertical concentration gra-
dient below the lid. pasquill (1962) has proposed that crz should become
a constant after reaching H, and is based on the desire to maintain a
near-constant concentration profile at this point. Smith and Singer
(1966) have suggested what is essentially the procedure used in the SRI
model; they have proposed that crz = 0.8 H in the limit with a lid such
that the ground level concentration given by their model would be con-
sistent with the value for a uniform vertical distribution (box model).
Finally, the effects of pollutant transformation and removal
processes must be considered in the model. This includes the deposition
of particles and gases, the effects of precipitation scavenging, and the
transformations of chemical and photochemical reactions. These are com-
mon to all model types, and are discussed at greater length in Chapter IV.
In summary, the direct atmospheric inputs to the Gaussian-type
models are the effective transport wind speed and direction, mixing depth,
and standard deviation (diffusion) functions. None of these parameters
are either easily or routinely measurable, and they require submodels
for their evaluation. Various formulations have been discussed, and the
SRI model has been presented to illustrate the structure of a Gaussian
model, together with the type of field program that is necessary for its
evaluation. Specific research tasks required for the refinement and
evaluation of Gaussian (and other) models are presented later in this
chapter.
Gradient Transfer Theory
General
The gradient transfer or so-called K-theory is based on the
solution of the equation for the diffusion of mass postulated by Fick,
in analogy with similar governing equations of other disciplines: Darcy's
111-11
-------
law for groundwater flow, Fourier's law for heat
law of electrostatics, and Ohm's law for current
sical form for these equations is
conduction, Maxwell's
conduction. The clas-
dq
dt
=
02-
K~
2
OX
(I II-5)
where q is the mean value of the particular variable and K is a constant
diffusion coefficient--the eddy diffusivity for the atmospheric case.
Equation (111-5) can be reexpressed in a more general form where the dif-
fusion is treated in three dimensions and the coefficients are not neces-
sarily equal and can vary in space,
dq oq oq Oq oq d ~x ~:)
= u - + v + w dZ + dt =
dt dX dY dX
a( 00) o( 00) (I II-6)
+-K-+-K-+S
Oy y dY oz Z dZ q
where Sq is the source/sink term of the parameter q. It may be worth-
while at this time, in view of the discussion of the preceding section,
to point out that the solution of Equation (111-5) for a stationary
medium with a point sowrce of q is a Gaussian function.
The applicability of the concept of an effective or eddy coef-
ficient for the determination of the diffusion of mass, momentum, or
energy in the atmosphere is open to some question. The eddy diffusivity
for momentum has its physical basis in the mixing length hypothesis of
Prandtl; its application to mass and energy diffusion may be conjectured,
considering two points: (1) if the scale of the diffusive action is suf-
ficiently small to permit representation by the mean gradient and (2) to
what degree a diffusion coefficient for mass (or energy) can be determined
from observed properties of the eddy (wind) field, as is the usual pro-
cedure. These points have been the subject of considerable discussion
over the years, and pasquill (1971) has presented a recent synopsis.
The general acceptance of the practical utility of the method may be
judged by the wealth of papers that treat the diffusion process in this
manner (see, for example, the review given in Slade, 1968) and the many
useful results achieved. A quotation attributed to Corrsin (1959) aptly
sums up the situation: "... K theory is not useful in principle but only
in practice."
IIl-12
-------
In practice, solutions of various forms of the general equation
(III-6)--cornrnonly referred to as the conservation equation--usually fol-
low three procedures for the treatment of the wind and diffusion terms.
In the simplest case, a priori knowledge of the distribution of wind and
diffusivity components is assumed known. A second and more general type
specifies the wind field and then computes the diffusion coefficients
from a suitable model relating flux and gradient. The third and ultimate
model generates all dependent variables.
An alternative, yet related, classification scheme is through
consideration of the various specific approaches used to solve the con-
servation equations. Generally, this latter approach classifies the
models as either Eulerian (fixed coordinate system) or Lagrangian (moving-
cell concept); Roth et al. (1971) have given a fairly comprehensive eval-
uation of models in these terms. Model differences are reflected pri-
marily in the mathematics of the solutions, while the classification of
the transport and diffusion processes is secondary.
The moving-cell approach traces the trajectory of a hypothet-
ical air parcel across an airshed. The model assumes that the parcel
maintains its integrity throughout its movement, thereby neglecting
horizontal transport or diffusion across the lateral boundaries of the
parcel and the height variation of the wind. This approach greatly sim-
plifies the solution and provides an assessment of the effect of specific
sources along the traj~ctory. Aside from the simplification of the at-
mospheric process, the results are limited to the given trajectory. The
Eulerian (fixed coordinate) approach is subdivided into: (1) conven-
tional finite difference solutions, (2) the so-called particle-in-cell
(PIC) method, and (3) the well-mixed cell model. The PIC method is char-
acterized by representing the continuous concentration field by a finite
number of mass points. The third Eulerian method represents the airshed
by a three-dimensional array of uniformly mixed cells where intercellular
transport, but not diffusion, is permitted.
Roth, et al. (1971) conclude that the various models are only
now reaching a state of development where direct comparisons may be made.
In view of the various simplifications and mathematical approaches that
the models encompass, it seems desirable to approach an assessment of
K-theory modeling through examination of the most general type in terms
of the treatment of the atmospheric process. A finite difference model
of transport and diffusion in the urban planetary boundary layer by
Pandolfo et al. (1971) perhaps best illustrates the current state of the
art of regional K-theory modeling. As such, it will be used to illus-
trate some of the various features of the K-theory models with the ob-
jective of examining its potential for application and, subsequently,
111-13
-------
its evaluation and validation within the proposed RAPS program.
tive formulations will be cited where appropriate.
Alterna-
A Complex Numerical Prediction Model
The model developed by Pandolfo and his associates (1971) at
the Center for the Environment and Man (CEM) is a numerical integration
of the K-theory forms of the conservation equations for mass. momentum,
heat, and water vapor. The procedure incorporates generation of the
wind and diffusivity fields from initial and boundary conditions and is
generally applicable to any environment as a result of the parameteriza-
tion of the various fluxes in terms of geophysical parameters (e.g.,
latitude, solar hour angle, albedo, aerodynamic roughness). Because of
the simultaneous solution of the five conservation equations, feedback
loops between, for example, the pollutant and temperature or wind fields
can be considered.
The CEM model is in reality a family of models with different
degrees of sophistication and objectives. The model can be applied in
the predictive as well as the diagnostic mode and has been used to eval-
uate the three-dimensional structure of the mesoscale planetary boundary
layer, as well as to analyze height and temporal variations at a single
station.
When the equations of motion for the planetary boundary layer
are considered together with the gradient transfer assumption, the equa-
tions for the conservation of horizontal momentum are given as
au au a (Km ~~)
- + u - = - + f(v - v )
at OX oz g
ov Ov a (K ov) - f (u
- + v- = - u )
at oy oz m OZ g
(III-7)
(I II-8)
where u and v are the wind components (LT-1) in x and y, respectively;
the subscript g refers to the geostrophic value which represents the
acceleration due to the horizontal pressure field, f is the Coriolis
parameter (T-1). and it is assumed Ku Z = K = K . The contribution
- v-z m
by the terms for the horizontal diffusion of momentum can be assumed to
be negligibly small in comparison with the vertical component, i.e.,
I ~ (K oCu,v] )1» I ~ (K oCu,v]) + ~ (K oCu,vJ)
OZ z oz OX x ox dY Y Oy
III-14
-------
Alternately, the effects of horizontal diffusion may be treated implicitly
in the computational scheme.
The equation for the conservation of heat follows in a similar
fashion from (111-6),
aT aT aT aT
-+u-+v-+w-
at ox oy OZ
=
~
OZ
~ ) oK
aT H
K - +f-
H OZ OZ
+fw+S
s
+ S
L
(III-9)
KH is the eddy diffusivity for heat, T is temperature (D), and f is the
adiabatic lapse rate. The first term on the right-hand side of Equa-
tion (111-9) expresses the vertical diffusion of heat without the effects
of adiabatic warming or cooling while the second and third terms describe
the adiabatic effects resulting from turbulent and mean vertical exchanges,
respectively. The last two terms describe the sources (or sinks) of heat
due to solar (subscript s) and terrestrial (subscript L) radiation, re-
spectively.
Moisture conservation is expressed by
* * * *
oq oq oq oq
~ + u ox + v oy + w ~
=
a
OZ
~ *)
K aq s
w oz + W
(III-10)
*
where q is the specific humidity (n.d.) and Sw describes the internal
sources or sinks of moisture.
Finally, the mass conservation equations for the various pol-
lutants are of the form
oP.
l
oP.
l
oP.
l
cP.
l
a ( OPi)
az Km ~
+ (S ). + R.
p l l
(Ill-ll)
at
+u-+v-+w-
ox Oy oz
and where Pi is the concentration (ML-3) of the pollutant species, i,
Sp represents the pollutant source or sink term (ML-3T-l), and Ri is the
rate of generation or depletion (ML-3T-l) of species i by chemical reac-
tions or fallout.
Exclusion of the horizontal diffusion terms cannot be as easily
justified for the treatment of pollutant dispersion as it often can be
III-15
-------
for momentum, for example. However, proven quantitative formulations for
horizontal diffusion in the planetary boundary layer are not available.
Pandolfo (1971) goes on to state that, in view of this limitation, the
relative accuracy of various finite difference schemes is rather academic
at this time, provided the diffusive component of the inaccuracy is known.
Therefore, the CEM model uses the diffusive computational error of the
upwind differencing scheme to implicitly simulate the gross characteris-
tics of the horizontal diffusion.
The simultaneous solution of Equations (111-7-11) which is based
on a knowledge of the initial and boundary conditions, together with the
diffusivity and source terms, would ideally permit both the description
and prediction of the three-dimensional fields of mass, momentum, and
energy within the limitations of computer technology and the applicabil-
ity of the gradient-transfer theorem. The multitude of K-type dispersion
models that have been formulated within the last decade are numerical
solutions using varying simplifications and computational techniques of
the general, composite problem as formulated above. For example, if the
wind and diffusivity fields are specified rather than computed (see, as
examples, Sklarew, 1970; and Seinfield, 1971), the dispersion model is
reduced to the solution of Equation (111-11) alone. However, the pro-
cedure implicitly ignores the potentially significant feedback mecha-
nisms between moisture, pollutants and temperature (and hence stability,
wind, and diffusivity). In practice, the limitations imposed by these
restrictions are not too severe, since the effects are likely second
order.
However, use of the model is generally restricted to what con-
veniently may be classified as a planning or evaluation role where it is
desired to examine the effects of: (1) a given or projected meteorologi-
cal situation on the pollutant concentration field resulting from a speci-
fied emissions field or (2) conversely, a variable emissions field under
given meteorological conditions.
There is indeed much to be said of the need for this particular
application of the model. Aside from the practical requirements that have
been cited, this form of the model provides a reliable test of the poten-
tial of the more complex (and expensive), interacting predictive models.
For surely, if the simple model can only attain a certain degree of suc-
cess in simulating a concentration field given an adequate set of meteo-
rological conditions, then the potential of the complex model is similarly
limited. Unfortunately, a completely adequate set of input meteorological
data may only be available from extensive research programs such as the
RAPS, and therefore the need arises to generate the necessary conditions
111-16
-------
from limited data, together with an appropriate procedure for extension
through parameterization by readily available geophysical data. Along
these lines, the research program must evaluate the parameterization
scheme and specify the necessary spatial and temporal resolution (scales)
that are required to model the physical atmospheric processes correctly.
The CEM model incorporates a horizontal grid mesh on the order
of 10 X 10 with up to 30 levels; the finer vertical resolution is neces-
sary to describe properly the large meteorological variations through
the planetary boundary layer. The height variation of the eddy diffusiv-
ity is computed with the aid of the results of surface layer similarity
theory. Although the surface layer is commonly considered as the shallow
stratum adjacent to the earth's surface, it may be defined alternately
as any layer in the planetary boundary layer where the height variation
of the turbulent flux of momentum (or mass or heat) is negligibly small
in comparison with the absolute value. The mean eddy diffusivity of heat
and momentum thereby are computed for each layer from the slope of the
wind, temperature, and moisture profiles through the gradient Richardson
number and the stability regime, i.e., stable conditions, or forced or
free convection. The vertical wind, temperature, and moisture profiles,
in turn, are computed simultaneously. The enormity of the computational
task is readily apparent on consideration of the fact that there are 17
independent variables (for the single pollutant case) in Equations (111-7-
11). Therefore, additional independent equations (or submodels) are re-
quired to specify all the variables.
A thorough evaluation of a model of this type would require the
examination of the performance of each of the submodels. The formulations
for the diffusivities and the equations for the atmospheric heat source
and sink terms due to solar and terrestrial radiative exchange in the
presence of various particulates and gases are two specific cases where
such evaluation is necessary. In short, evaluation would ideally require
information on the three-dimensional and temporal structure of the dis-
tribution of mass, momentum, and energy in the planetary boundary layer
on a regional scale.
Aside from the problems and complexities of realistically simu-
lating the physics of the overall problem, the restrictions imposed by
computer storage and computational time and expense must be considered.
The latter two considerations can vary according to the type and purpose
of the computations. A real time diagnostic or short term predictive
model will require a minimal turnaround time, whereas use of the model
for long range planning or evaluation purposes may impose little or no
restriction on the time of the computation.
111-17
-------
The limitation set by the finite storage capacity of the com-
puter will implicitly affect the time problem, but more importantly, it
will limit the spatial extent and/or resolution of the model. The CEM
model, as an example, more than adequately provides the vertical resolu-
tion required but does not permit sufficient horizontal resolution for
many purposes. The horizontal extent of a typical mesoscale region is
on the order of 200 km for air quality considerations; the CEM model
has been tested for the Connecticut area with a horizontal resolution
of 24 km. This scale of resolution is probably adequate to describe the
mesoscale features of the wind, temperature, and moisture fields over
substantially homogeneous terrain, but it is not sufficient to model the
effects of variations in the aerodynamic, thermal, and evaporative char-
acteristics of the terrain that may arise from the presence of large
towns and cities. The City of St. Louis occupies an area of 158 km2
while the county is 1300 km2. The problem of scaling is even more acute
when considering the emissions field. Therefore, an objective of the
RAPS should be the definition of the spatial (and temporal) scales ap-
propriate to the various meteorological variables and pollutants. It
may be necessary to consider nesting of the scales used in the solution
of the model. For example, to simulate air quality conditions charac-
teristic of a horizontal length scale of 1 km, it may be necessary to
consider, say, the radiative and moisture fluxes on a 20 km scale, wind
on the 5 to 10 km scale, and emissions on a scale of 1 km.
The CEM three-dimensional simulation test used historical winter
data for the initial and boundary conditions. The grid extended over Long
Island Sound and therefore tested the response of the model to the influ-
ence of extreme difference in surface conditions (topographic effects have
not yet been incorporated in the CEM model). Pollution source data were
obtained from the Connecticut source inventory of Hilst et al. (1967).
Sulfur dioxide was the only pollutant considered in the test; unfortu-
nately, chemical reactions have not yet been included in the model. The
results really permit only a qualitative assessment of the model, but
they do show the gross horizontal patterns expected from the varied
(urban, rural, and water) surface characteristics. Systematic conver-
gence patterns result over the urban areas and are reflected in the
deeper mixing layers. Lower rural nocturnal temperatures are also
predicted.
Although the three-dimensional form of the model is attractive
in principle, it is not yet sufficiently developed to permit evaluation
with existing or anticipated air quality data owing to weaknesses in the
treatment of the following areas: (1) chemical and photochemical reac-
tions, (2) horizontal advection, (3) topographic effects, and (4) hori-
zontal resolution.
111-18
-------
A more rigorous test of the model entailed the use of a single
station, neglecting horizontal gradients and mean vertical motions. In
this manner, the sensitivity of the model to a variety of external con-
ditions was considered. Specifically, three single-station experiments
were conducted: (1) estimation of the effects of surface characteristics
on the interface temperature and atmospheric stability, (2) examination
of the effects of varied source heights, and (3) examination of the ef-
fect of pollutants on the temperature structure and the feedback effects
on the pollutant concentrations. The single-station model predicts real-
istic urban-rural differences of the near-surface temperature: winter
daytime maxima are similar while the nocturnal minimum is lOoK lower for
the rural case. The warmer urban nocturnal temperatures are attributed
primarily to anthropogenic heating, with the effect of the thermal admit-
tance of the substratum being secondary. The depth of the mixing layer
is shown to be highly correlated with surface temperature; near-surface
pollutant concentrations vary by a factor of five over the day with mini-
mum concentrations occurring in the afternoon.
The effect of a fixed profile of pollutant concentration on the
surface temperature was a 2°K decrease in both the amplitude and absolute
value of the diurnal cycle. Another simulation evaluated the feedback
between the pollutants and the temperature structure through the effect
on the eddy diffusivity; the results projected a 25% change in pollutant
concentration.
A Simple Model of Numerical Prediction
The numerical simulation model of Roth and his associates (1971)
at Systems Applications (SA) is another example of a finite-difference
solution to the gradient transfer form of the equation for mass conserva-
tion; the distribution (x, y, z, t) of the momentum and energy fields are
specified on the basis of observations and empirical formulations. As
such, the model is only prognostic in the sense that it predicts the
ground level concentration field given a forecast of the horizontal wind
field and vertical temperature profile. Unlike the CEM model, it does
incorporate photochemical reactions and interactions of the contaminants
as well as the effects of terrain irregularities. However; horizontal
diffusion is ignored.
The SA model was tested initially to predict the distribution
of carbon monoxide (CO) in the Los Angeles Basin. CO was chosen for the
test, because it is inert and permitted the evaluation of the meteorologi-
cal, emissions, and computational aspects of the model without the com-
plexities of the reaction terms. The sensitivity of predictions of the
111-19
-------
average surface CO concentration for the two-mile square grid areas could
be considered as a result of variations (both at the surface and aloft)
in the: (1) wind field, (2) eddy diffusivity, (3) mixing depth, (4) com-
putation scheme, (5) grid size, and (6) the integration time interval.
Comparison of predicated concentrations with observations at 11 scattered
monitoring stations shows generally good agreement for a 13-hour period
of one test day (correlation coefficient of 0.65); a second period with
light winds (and subsequently, high surface concentrations of CO) gave
poorer results.
Results of the sensitivity tests are given only qualitatively.
Roth et al. (1971) report that "modest" variations in the wind field and
mixing depth have" significant" effects on the concentrations. Sensi ti v-
ity to the vertical profile of diffusivity has not yet been evaluated.
The finite difference method is accurate except when large concentration
gradients are encountered. Finally, the emissions formulation has not
been thoroughly evaluated, although considerable effort has been expended
in obtaining an accurate traffic data base.
Emissions of CO in the Basin are mainly from automobiles (96%),
with minor contributions from aircraft (3%). Automotive emissions are
treated as a constant per vehicle-mile with higher values assigned to
early morning hours because of "cold starts." Locally important emis-
sions from power generating stations and refineries are also considered.
Specification of the temporal and spatial distribution of the
mixing depth (H) over the Basin is based on the studies of the Los Angeles
marine layer by Edinger (1959) and Edinger and Helvey (1961). Temporal
variations are provided by 20 temperature profiles obtained over the two-
day period at a total of four locations. The spatial distribution of H
for 625 grid squares is given by Edinger's works. An evaluation of ob-
served and predicted values showed good agreement for the morning hours
and poor results in the afternoon.
The surface wind field was reconstructed from observations taken
each hour at 34 locations by four different organizations. Streamline and
isotach patterns were subjectively analyzed and then digitized over the
grid. Little or no upper air wind data were available, and two gross
assumptions were tested for the determination of the three-dimensional
wind field. The first assumption considered the horizontal wind field
as invariant with height; the second assumption specified the shape of
the vertical profile of the vertical component of the wind. The verti-
cal structure of the horizontal wind was then computed for the latter
case, with certain restrictions placed on the magnitude of the wind speed
and the amount of veering permitted.
II 1-20
-------
The eddy diffusivity was not explicitly coupled to the wind
field, but rather was specified empirically according to the work of
Eschenroeder and Martinez (1969). According to their synthesis, the
vertical profile of the diffusivity is given by the value of the sur-
face wind speed and the height of the inversion lid where the diffusiv-
ity at the lower boundary is constant (30 m2jsec) for all conditions.
It is somewhat surprising in view of the coarse treatment of
the meteorological variables that the agreement between prediction and
observation is so encouraging. The reasons may hinge on the predomi-
nance of the surface emission sources. During the morning hours, the
level of surface concentrations is strongly controlled by the height
of the inversion; the SA results show that application of the Edinger
work is most suitable during this period. With these shallow mixing
depths, contaminants become rather uniformly distributed up to the lid,
and the surface wind is a good approximation to the transport wind for
the layer. For afternoon conditions, the lid may be expected to be
quite high, and subsequent inaccuracies in its computation contribute
relatively little to the predicted surface concentrations. Because of
the large diffusive capability of the atmosphere, errors in the winds
aloft may be less significant. Equally important in the success of the
model is the accuracy of the emissions field,
A Simple Analytical Model
A simple analytical method for calculating dispersion from ur-
ban area sources has been presented in a recent series of papers by re-
searchers from the Atmospheric Turbulence and Diffusion Laboratory (ATDL)
of NOAA (Gifford, 1970; Gifford and Hanna, 1970; and Hanna, 1971). The
work is a welcome addition to the numerous papers on dispersion modeling,
since it presents a simple method for calculating the area surface con-
centration that can be used to test the results of the more complex and
expensive numerical models. In so doing, the authors stress an impor-
tant point: "The usefulness of any. . area source diffusion model
depends on its performance compared with other area source models. In
the past, as new models appeared in the literature, there was no com-
parison with other models. Clearly, if the concentrations predicted by
a complicated model are not significantly better than the predictions
of. . simple. . model [sJ of diffusion, then there is no practical
justification for the new model," The ATDL model, together with other
simple formulations such as the box model or the SRI Gaussian model, can
provide for such evaluations.
III-21
-------
The ATDL model is an analytical solution of the gradient trans-
fer form of the mass conservation equation under the following assumptions:
(1) conditions are steady-state, (2) horizontal diffusion is relatively
insignificant, and (3) chemical reactions and deposition are ignored.
When the x-axis is aligned with the tranJbort wind, the area concentra-
tion (X ) from a surface area source is determined from
A
OXA a [ OXAJ
u ox = oz Kz ~
(I II-12)
The vertical profiles of wind and vertical eddy diffusivity are assumed
to be represented by power laws, where
m ~
u = u ( z/ z )
1 1
j (III-13)
n
K = K ( z/ z )
z 1 1
On introducing a similarity transformation of the independent variables,
Equation (111-12) reduces the solution of two ordinary differential equa-
tions through the separation of variables. With the area-source distribu-
tion given over a horizontal grid (N x N), the solution at z = 0 is eval-
uated over N equal intervals of x:
(XA)
o
zm (lix)l-s
1
c u
1 1
(Q, + ~
i=2
[ l-s l-sl}
Ql i - (i - 1) J
(I II-l4)
where s = (m + 1)/(2 + m-n) and x = N6x. If the vertical distribution
of concentration is assumed to be Gaussian, the vertical standard devia-
tion can be given by a = axb (see Eq. 111-3) and Eq. (111-14) becomes
z
( XA)
o
"Vi
I-b
(6x/2)
u a (1 - b)
1
h"
N
L:
i=2
[ l-b
Q. (2i + 1) - (2i -
1 ~
U'-bJ}
(III-15)
III-22
-------
This simplification appears justified, since Gifford and Hanna (1970) have
shown that the form of the vertical distribution of concentration has
"little impact" on the surface value. However, it should be pointed out
that this form of the ATDL model--Equation (III-15)--is virtually identi-
cal to the SRI Gaussian model--Equation (IV-3).
Hanna (1971) proceeds to further simplify (15) in view of the
relative weight of the area source-strengths on the concentration at the
receptor; if the source strength is uniform in x, the innermost area con-
tributes 220% more to the receptor concentration than does the second
sector, 420% more than the third, and so forth. Therefore, Equation (111-
15) is reduced to its most simple form,
( XA)
o
= C-
Ql
u
1
, and
C
:i [(2N2+ 1) "rb
1
a (l - b)
(III-16)
An exponential form for Q(x) is also considered in the paper. Equa-
tion (111-16) was compared with results of more complex models as re-
ported by Lamb (1968) for natural gas in the Los Angeles Basin and
Roberts et al. (1969, 1970) for sulfur dioxide in Chicago.
Lamb's model incorporates a numerical solution to the mass con-
servation equation and is quite flexible, with such features as time-
variable sources, space-variable wind, and ground absorption and simple
chemical reactions of the pollutants. However, the model is restricted
to a uniform vertical wind distribution and constant eddy diffusivities.
Gifford and Hanna (1970) and Hanna (1971) compared the results of Lamb's
model for a 16-hour period over 4-mile square sectors with those obtained
using Equation (111-15). The results compare favorably in a qualitative
sense, but no correlation statistics are presented. It is unfortunate
that the ATDL computations were made using the annual average wind direc-
tion frequency distribution, together with a single value for the mean
wind speed chosen on the basis of Lamb's wind speed data. It would ap-
pear that in limiting the representativeness of their data, the authors
have severely restricted the value of the comparison.
1II-23
-------
The comparison with Roberts' results for Chicago is a better test
of the ATDL argument. Roberts' is an integrated puff model consisting of
" 11 .
a series of algorithms assembled around a kernel that represents the dlS-
persion of contaminants from point and area sources as a three-dimensional
Gaussian distribution. The kernel represents a three-dimensional puff and
is integrated according to a time series of piecewise constant wind vectors
and atmospheric stability parameters to "simulate the transient behavior
of a continuous smoke plume."
Hanna (1971) refers to the model as "the most complex in the
business." Hanna used Equation (111-16) to compute surface concentrations
of S02 using the emissions and meteorological data given by Roberts. Hanna's
predictions are about twice the magnitude of Roberts', although the former
are highly correlated with observations of surface S02 concentration. In
all cases presented by Hanna, results from the simple model provided cor-
relations that overlapped those of Roberts within the 95% confidence in-
terval; in a few cases, the simple model was superior.
The case presented by Hanna is not significantly conclusive to
even consider the abandonment of the development of sophisticated models
at this time. However, it does present a yardstick that may serve to
measure the merits of the various complex models. As such, the evalua-
tion of all models within the RAPS should be made against the output of
a simple model (or models), in addition to field observations of pollu-
tant concentrations.
Other Models
The discussion of the preceding two sections focuses on two practical
approaches to the problem of simulation of atmospheric dispersion of mass
(and momentum). The Gaussian models may be considered quasi-empirical,
having some basis in the theory of atmospheric dynamics, while the gradient-
transfer models seem to be quasi-theoretical, relying on empirical formula-
tions for the description of wind and eddy diffusivity. The latter are
appealing, since they provide a basis for examining the interrelationships
or feedbacks between energetic and mass- or momentum-transfer processes.
Another work that also incorporates the atmospheric feedback mechanisms
is the dynamic climatology ("climatonomy") model of Lettau (1952, 1969,
1970). The work is particularly attractive in that it is centered on an
analytical solution to the energy budget equations through the parameteri-
zation of the various energy transfer processes in terms of geophysical
parameters; as such, feedbacks are inherent in the formulation. Lettau
(1970) has applied the concept to a study of the physical and meteoro-
logical aspects and bases of urban diffusion modeling. In a practical
1II-24
-------
application (1969), he investigated the nature of the radiation balance
for urban areas in contrast to a rural environment.
Another type of diffusion model that should be mentioned is the ap-
plication of surface-layer similarity theory. This approach has its
foundation in the specification of the Eulerian characteristics of tur-
bulent flow by the friction velocity together with the Monin-Obukhov-
Lettau stability length. In contrast to K-theory, similarity theory
treats the diffusion process as occurring with a finite velocity. Al-
though physically appealing, this concept may not be of prime importance
when compared with the complexities introduced by marked wind shears,
irregular terrain, nonsteady conditions, and so forth. Application of
similarity models seems to be further limited by the difficulties in ob-
taining solutions to diabatic conditions.
The statistical theory of relative atmospheric motion offers addi-
tional physical insight of the diffusion process. The original statisti-
cal theory of Taylor (1921) considered the motions of fluid particles over
some diffusion time to be completely independent. Particles that thus
find themselves infinitely close at some point in time must forever remain
so. The relative diffusion theory provides an alternate approach in which
the rate of spreading of nearby particles is considered relative to their
mutual center of mass. Gifford (1968) summarizes the distinction by con-
sidering relative diffusion as the treatment of the spreading out of a
cloud of fluid particles or the spreading of a plume from its instanta-
neous center line through joint Langrangian statistics of two dispersing
particles. Single-particle Lagrangian statistics treat the average
spreading of a plume about a fixed axis. The relevance of the distinc-
tion may be minimal when, for example, the objective of the computation
is the prediction of hourly concentrations as in the previously discussed
comment by Pasquill (1971) on the merits of the puff versus the plume
formulation.
Another model based on physical principles is the vorticity-transfer
formulation introduced by Lettau in 1964 and subsequently refined in a
series of papers over the next five years. The theory treats the eddy
displacements of fluid particles as three-dimensional, reflecting the
coexisting tendencies of the fluid to conserve its initial properties
while adapting to its new environment (entrainment). Additionally, the
importance of the longitudinal length-scale of turbulence is considered
in conjunction with the classical (Prandtl) lateral length scale. Ex-
pressions for the variances and covariances of velocity and temperature
fluctuations are given in terms of the length scales and mean fluid flow
properties. Non-Newtonian stress-strain (a gradient transfer) relation-
ships result that permit eddy fluxes in nonshear regions as well as
111-25
-------
countergradient fluxes. Lettau (1964, 1966, 1967, 1968) has applied the
theory to an extensive list of problems: (1) wall turbulence, (2) sur-
face layer structure, (3) turbulent free jet, (4) Karman's similarity
principle, (5) nature of eddy diffusivities for heat and momentum, and
(6) heat transfer. Dabberdt (1969) has extended the theory to the case
of bidirectional mean shear flow in the planetary boundary layer. The
theory may provide a rational basis for prescribing the nature of the
horizontal eddy diffusivity.
Moses (1969) discusses a tabulation prediction scheme developed at
the Argonne National Laboratory. The method consists of developing an
ordered set of combinations of meteorological variables and presenting
the distribution of surface concentrations of a particular contaminant
for each element in the set. In the tabulation, the independent vari-
ables are wind direction and speed, time of day, temperature, and sta-
bility; various percentile values are presented in addition to maxima
and minima. The procedure is purported to have the following advantages
over other receptor-oriented methods: (1) ease of use, (2) speed,
(3) presentation of percentile distribution of concentration (fore-
cast application), and (4) implicit consideration of nonlinear rela-
tionships of the independent variables.
The disadvantages of the method are: (1) an extensive observa-
tional data base (reported to be a 2-year minimum) is required at each
forecast (receptor) point, (2) a large digital computer is required for
the initial tabulation,' (3) changes in the emissions grid degrade the
results, and (4) the model cannot account for aerodynamic effects of
construction. However, the method appears attractive for regions where
continuous records of meteorological, emissions, and air quality data
are available. It would seem to have application in the quantification
of a normalized prediction of the spatial distribution of contaminants
from analytical or numerical models.
Finally, a very recent multibox model developed by MacCracken et al.,
(1972) at the University of California should also be mentioned. The model
is simple and flexible. First, observed time- and space-dependent values
of surface wind and inversion height are put into a meteorological data
model that incorporates topographic effects and develops a mass-consistent
horizontal wind field and diffusion coefficients (vertical and horizontal)
for the region. These are then used together with a time- and space-
varient emissions field in the multibox model to compute time-varying
pollutant concentrations in each box. Box-size resolution is variable
and photochemical reactions are incorporated in the model. Preliminary
verification tests have been conducted for the simulation of CO concen-
trations in the San Francisco Bay Area with some encouraging results.
111-26
-------
Additional work will concentrate on refinements to the photochemical as-
pects, as well as on an evaluation of the sensitivity of the model to
input data representation.
The models and types presented are not intended to provide an ex-
haustive survey of air quality simulation methods. Rather, the intent
has been to supplement the two basic types--Gaussian and gradient-
transfer--with representative alternatives that possibly have less gen-
eral application to the overall modeling problem but that can provide
varying degrees of insight or utility.
Numerical Weather Prediction Models
The use of currently available, numerical weather prediction models
should be considered to provide predictions of the meteorological vari-
ables for use as input data to the regional atmospheric dispersion models.
Their application to air pollution problems can make use of the tre-
mendous advances that have been achieved in numerical weather forecasting
in the last 15 years. On the other hand, special problems exist in mak-
ing detailed forecasts for areas of limited size. These problems are
discussed briefly below.
The numerical models that are in operational use for weather predic-
tion encompass either fhe Northern Hemisphere or the entire globe. In
the United States, such models are in use at the National Meteorological
Center, NOAA; at the Air Force Global Weather Central, Offutt Air Force
Base, Omaha; and at the Navy's Fleet Numerical Weather Facility, Monterey,
California. These models represent the atmosphere using 6 to 10 levels
in the vertical and a horizontal mesh with points separated by 300 to
400 km. The atmospheric boundary layer structure and dynamics are treated
in only a rough and approximate manner. These models are used primarily
for synoptic scale forecasting for periods up to three days in advance.
To obtain more detailed forecasts, the Air Force uses a mesoscale
model (Kerlin, 1970) for North America, which is similar to the hemi-
spheric model except that the horizontal grid spacing is only half as
large. This horizontal spacing (~150 km) is considerably smaller than
the average distance between radiosonde stations, so that further re-
duction would not be beneficial, unless additional radiosonde observa-
tions became available. However; it is possible to obtain additional
vertical resolution within the atmospheric boundary layer from radio-
sonde data. This is done in the Air Force boundary layer model (Hadeen,
1970) which uses the same horizontal grid as the mesoscale model for an
111-27
-------
area covering the contiguous 48 states. The boundary layer model has
seven layers (or eight levels) between the surface and 1600 meters and
provides forecasts of winds, temperature, moisture, and pressure for
periods of 12 to 24 hours in advance. This is made possible because the
boundary layer model is controlled to a considerable degree by informa-
tion at its upper level (about 1600 m aboveground) produced by the meso-
scale forecast model mentioned above. The winds and pressure at this
level predicted by the mesoscale model control the forecast positions
of features such as highs, lows, and fronts in the boundary layer.
The mesoscale model also provides forecasts of clouds for layers
above 1600 m. The boundary layer model has internal dynamics that pro-
duce temperature forecasts based on advection, diurnal heating effects,
and cloudiness. These temperatures give thermal winds that are used to
determine surface winds from the upper level values provided by the meso-
scale model. The intervening winds are then fit to a Blackadar type of
Ekman spiral. The model follows work originally done by Gerrity (1967).
The equations also include terms for eddy diffusivity and conductivity,
the effect of cloudiness on diurnal heating, and changes of state of water
substance. In spite of certain simplifications and assumptions, the Air
Force boundary layer model is by far the most complete model for low level
meteorology that is now available on an operational basis. The informa-
tion from the model is used in forecasting ceilings and visibility at air-
ports, low-level turbulence, severe thunderstorm occurrences, and so forth.
It is strongly recommended that EPA consider obtaining forecasts
from this model for the four (or more) grid points that are nearest to
St. Louis. It is our understanding that the Air Force Global Weather
Central is willing to make the forecasts available to other government
agencies. Similar boundary layer forecasts are not expected to become
available from NMC for two years or more. One of the major research
tasks proposed for the Regional Study concerns the use of these boundary
layer forecasts in controlling air quality within a region. This will
be an entirely new line of research.
Further development of even more detailed boundary layer numerical
models most logically would introduce much finer horizontal grids (~10 km
instead of the ~150 km of the present Air Force model), more vertical
levels, and more complete and complex dynamics. Work in this direction
has been done by Pandolfo (1965 and 1971). In addition to purely scien-
tific problems, some serious practical obstacles would be encountered in
applying such a model for operational purposes. These entail the diffi-
culty of obtaining initial conditions for the entire mesh and also the
necessity of specifying upper and lateral mathematical boundary condi-
tions as the prediction proceeds. This can be understood from the con-
siderations discussed below.
111-28
-------
To obtain detailed initial conditions for a fine-mesh regional model
covering an area of 100 km on a side would be quite feasible using a dense
network of observations. However, under moderate or strong winds, air will
cross such an area within a few hours. After the original air has passed
out of the region, the conditions predicted within the region are controlled
to a large degree by assumptions made concerning the time history of meteor-
ological properties at the inflow boundaries. This tends to limit the pre-
dictability of the model to a few hours, unless accurately predicted con-
ditions at the upper and lateral boundaries of the fine mesh are available
from some other source, such as the mesoscale numerical forecast.
At this time we do not envision a realistic method for obtaining such
detailed lateral conditions, since the desired information is beyond the
resolution of the mesoscale model. The natural alternative is to expand
the area of the fine-mesh model and of the observations needed for its
initial conditions. However, to encompass air that could reach the area
of interest within a longer period such as 12 hours, one would have to
expand the dimension of a side of the fine mesh to at least 500 km. Ob-
taining detailed data over a region this large would probably be prohibi-
tively expensive. Thus, it does not seem likely that operational fore-
casts for a finer mesh than that used by the Air Force can be achieved
within the next few years for this reason alone.
Another anticipated difficulty with fine-mesh boundary layer predic-
tions is that the fini~e difference methods in current use have the general
property of tending to smooth the smaller scale features of the weather
patterns as the prediction proceeds. Therefore, wanted details tend to
be lost as the period of prediction increases.
A final point about fine-scale predictions for a region concerns the
computational requirements. These depend on the number of grid points in
the mesh, the number of variables carried, the efficiency of iteration
schemes for relaxation or similar processes, and the length of the time
step. It is instructive to compare a possible regional model to a known
global model. For example, Manabe et al. (1971) used a horizontal mesh
of 9200 points (~250 km spacing) at 9 levels, giving approximately 80,000
points for the globe. We assume that that their dynamical equations and
those of a fine-mesh regional model are of similar nature and complexity.
Their time step was 5 minutes. Obtaining a 24-hour global prediction
required 27 hours of computation using a Univac 1108 computer. A re-
gional fine mesh model of, say, 100 horizontal points (~10 km spacing)
at 10 levels would give only 1000 points. However, the time step for
computational stability would have to be reduced to 5 (10/250) or
111-29
-------
0.2 minutes because of the smaller mesh size. Thus, the computational
requirements for a fine-mesh regional model are about (1000/80,000)
(5/0.2) = 0.3 times as large as those required by Manabe. These require-
ments are still considerable and would entail large computer costs and
a sizable staff to man the operation.
The difficulties and costs enumerated above would have to be sur-
mounted to obtain a fine-scale regional prediction of boundary layer
meteorological conditions. A continuing research program should be di-
rected to this subject. However, we believe that for the next few years
main reliance should be placed on forecasts provided by the present Air
Force boundary layer model.
Model Sensitivity to Meteorological Variables
It is particularly important to assess the sensitivity of the various
models to variations in the input meteorological variables; evaluation of
the sensitivity to emission and reaction factors is equally important, but
discussion will be deferred to subsequent sections in keeping with our
modular approach to modeling theory. The basic objective of evaluating
the sensitivity of model calculations is to assess the importance of the
various atmospheric processes in determining concentration levels and
to simultaneously permit the refinement of model formulations based on
suitable observations of the relevant parameters. The interchange be-
tween observations and 'simulation is reciprocal, and it will be particu-
larly important that the observing network not retard simulation develop-
ment. However, in designing the field system, it will be necessary to
be guided by available modeling results, as well as by the experience
of past observation programs.
Specifically, it is important to know the effects in output values
caused by changes in the inputs. If a very small change in a certain
input results in a large change in the output, then the model--and pre-
sumably the physical system--is very sensitive to that input and it will
be necessary to provide values of the input that are very accurate to
avoid large errors in the output. On the other hand, if large changes
in an input have little effect on the output, then little effort need be
expended to achieve high input accuracy for that particular variable.
Sensitivity is not likely to remain constant over the whole range of val-
ues that a particular variable can assume. Thus it is possible that for
certain combinations of parametric values, the model output will be to-
tally independent of the changes in one or more inputs.
independent of the changes in one or more inputs.
III-3D
-------
Of the dispersion models discussed in the preceding sections, the
gradient-transfer types have the greatest potential for describing the
atmospheric dynamics and energetics on the regional scale. The exten-
sive and complex numerical solutions are adaptable to synthesizing the
intricacies of the four-dimensional meteorological fields, but their
sensitivity can be evaluated only through a systematic variation of the
inputs (either singularly or in combination). The process is tedious
and expensive, and no systematic evaluations have been reported to date.
Several limited tests have been made (see, for example, Roth et al.,
1971, and Pandolfo et al., 1971), but the results are given only in
qualitative terms.
Gifford and Hanna (1971) have evaluated the response of the
dieted concentration from their K-model to normalized changes of
input parameters (P),
pre-
the
6( X )
A
o
(XA)
o
6p
= k-
P
(III-17)
using an alternate form of Equation (111-14):
(XA)
o
m (t.x/2)1-s
zl
c u (BO - s)
1 1
{Q +.~l Q.
o 1= 1
[ I-s
(2i + 1) - (2i -
1) 1- s] J
(I II-18)
Where the parameter B depends on the shape of vertical concentration pro-
file. The results of the analysis are given in Table III-I. The model
is shown to be fairly sensitive to variations of the stability parameter
(I-b) under stable conditions; otherwise, small changes in the input
parameter produce only small changes in the surface concentration.
III-31
-------
Table 111-1
SENSITIVITY ANALYSIS OF THE GIFFORD
AND HANNA (1971) DISPERSION MODEL
Parameter Range 62,n(x) =k62,nP k
A
0
-1 6u/u -1
u I-30m sec -
I:::.x 5-50 km 6I:::.x (I-b) (I-b)
I:::.x
6(1-b) I-b I-b
I-b .09 - .29 (I-b) (l-b)x 2, nx (I-b)x 2,n x
(for Ql = Q )
0
N 5 - 10 6(N+l) (I-b) (I-b)
(2N+l)
Q 6Qo N Q -1
0 for type D
Many orders -e+L: i Fi) ""'0.6
(Central Qo 1 Q and Q = Q
source box) 0 i 0
Qj Many order~ 6Q F (Qo ~ .10 to .15 for type D and
j j ,- +
(j'th Qj Q = Q
N Qi Firl i 0
source box) + L:
i=l Qj
B 0.4 1 - 6B/B -I
f .01 1 6f If I
i i i
I-b
In the above, Fi = (2i + 1) - (2i -
obtained, assuming for simplicity that
form of Equation (111-18).
I-b
1) . The result for (1 - b) was
Qi = Qo = constant, from the continuous
X
AO
(2/TT)1/2 Q /-b [a(I-b)Url
o
In view of the small variability of a(l-b) over the expected range, from un-
stable to type-D conditions (neutral stability), this product was assumed con-
stant in evaluating the effect of (I-b).
1II-32
-------
On the basis of this analysis, Gifford and Hanna conclude that sur-
face concentrations resulting from area-source emissions are relatively
insensitive to the form of the vertical concentration distribution (B),
and they "are not inclined to regard uncertainty about the precise form
of this quantity as being much of a problem." This hypothesis should be
tested with other models that incorporate vertical profiles of diffusiv-
ity that ~re nonmonotonical and wind that is bidirectional, as well as
the important case of elevated sources.
Michael (1971) has evaluated the effects of the shape of the boundary
layer wind and diffusivity profiles on the center-line distribution of sur-
face concentration from an elevated point source. The form of the mass
conservation equation used is:
oX oX o2x a
u-+v-=K -+-
ox oy y oy2 oz
(K z ;~)
(III-19)
The wind and diffusivity profiles were not determined uniquely but are
assumed to have the shapes illustrated in Figure 111-1. The lateral dif-
fusivity was assumed to be independent of height. The results of various
combinations of diffusivity and unidirectional wind profiles are given in
Figure 111-2; the source height h was taken to be 100 m. The important
point shown by these graphs is that fall-off of the peak surface concen-
tration at large dista~ces from the source is determined by the shape of
the profile of diffusivity and not velocity (however, it must be kept in
mind that the diffusivity profile is controlled in part by the velocity
profile). The velocity profile, in turn, affects the location and magni-
tude of the maximum and close-in distribution.
The effect of directional shear on the ground-level concentration
is illustrated in Figure 111-3. The downwind distribution of relative
concentration is controlled by the shear to a significant extent at long
travel distances but minimally near the source.
On the other hand, Gaussian models have been rather extensively
evaluated with regard to their sensitivity to parameter variations. A
thorough treatment of the problem has been given by Hilst (1970), using
the Travelers Research Corporation (TRC) regional model where the effects
of both random and systematic input errors were examined. The sources of
error and uncertainty were grouped into four classes: (1) pollutant dif-
fusion and distribution estimates, (2) positional errors, (3) source
strength estimates and (4) pollutant decay and loss estimates. The spe-
cific sources of errors that constitute the four classes are shown later
in Figure 111-4; taken from Hilst.
1II-33
-------
100
N
...:
::!
I-
J:
..... c.:J
.....
..... w
I J:
c,.)
~
10
0.2
V(z)
- U(z)
0.4
0.6
1000
N
o
0.2 0.4 0.6 0.8 1.0 1.2 1.4
NORMALIZED WIND VELOCITY, U(zl!U(1OO1
(a)
~ 220
~ 200
I-
a 180
~ 160
140
380
360
340
320
300
280
260
240
120
100
80
60
40
20
o
o 0.4 0.8 1.2 1.6 2.0 2.4
KiKz (100) NORMALIZED DIFFUSIVITY COEFFICIENT
(bl
SA-1365-21
FIGURE 111-1
VERTICAL PROFILES OF WIND AND EDDY DIFFUSIVITY (MICHAEL, 1971)
-------
z
o
i=
<{
:: 1.0
z
w
U
Z
o
U
w
>
i=
<{
...J
W
a:
5.0
CURVE U V KZ
1 L 0 I
2 N 0 I
3 L 0 III
4 N 0 III
0.1
0.1
1.0
10
KZ (100) x
U (100) h2 DIMENSIONLESS DISTANCE FROM SOURCE
SA-1365-22
FIGURE 111-2
PEAK SURFACE CONCENTRATION AS A FUNCTION OF
DISTANCE FROM AN ELEVATED SOURCE (MICHAEL, 1971)
II 1-35
-------
z
o
i=
4:
a::
I-
~ 1.0
u
Z
o
U
w
>
I-
4:
~
w
a::
5.0
CURVE U V(100)h KZ
KZ(100)
1 M 0.0 III
2 M 1.6 III
3 M 3.2 III
4 M 6.5 III
5 M 13.0 III
0.1
0.1
1.0
10
KZ(100)r
U(100)h2 DIMENSIONLESS DISTANCE FROM SOURCE.
SA-1365-23
FIGURE 111-3
PEAK SURFACE CONCENTRATION AS A FUNCTION OF
THE RADIAL DISTANCE FROM THE SOURCE (MICHAEL, 1971)
II 1-36
-------
The distinction between the effects of random and systematic errors
is particularly interesting. For example, random errors are to be expected
in the preparation of source inventories, but these are likely to be com-
plemented in some cases by a systematic underestimate through the neglect
of singularly unimportant--yet collectively significant--sources. Errors
in diffusion estimates will tend to be primarily random for short averaging
times but systematic for longer periods. Positional errors can also be
of both types; surveying errors will usually be random, but the result on
the positioning of sources or receptors with respect to a given trajectory
may be systematic (especially for small source-receptor separation). Re-
sults of Hilst's sensitivity analyses for the meteorological parameters
follow, with only the systematic errors actually evaluated. The effects
of systematic and random errors in the source field are given in the emis-
sions section.
The TRC model uses a receptor-oriented Gaussian
Contributions to the concentration at a receptor are
along the air trajectory (not necessarily straight);
fields are treated as steady over two-hour periods.
the State of Connecticut.
plume formulation.
made from sources
wind and dispersion
The test region was
The effect of the lateral diffusion coefficient on the concentration
resulting from a multiple-source field is minimal, because the effect of
lateral diffusion from a distributed source field is to rapidly produce
a uniform crosswind cOQcentration. This is reflected in Table 111-2
where values of the mean and standard deviation of the normalized dif-
ference between predictions of concentration with and without a sys-
tematic lateral diffusion error are given as a function of the latter.
Sensitivity of the predicted concentration to systematic errors
in the vertical diffusion coefficient is significant, as shown in
Table 111-3. This is particularly true when the coefficient is under-
estimated [(0 T - 0 E)/0 T-+IJ. The effect is less significant for
z- z- z-
overestimates partially because of the predominance of the effects of
local sources.
The effects of positional errors (e.g., mislocation of sources,
receptors, and trajectories) affect the nature of the errors of the other
parameters. Hilst used systematic variations of the wind direction for
the assessment of the interrelated, positional errors. The mean errors
are comparable with those associated with the vertical diffusion coeffi-
cient, while the variances are even larger as shown in Table 111-4.
111-37
-------
Table I II-2
CALCULATED VALUES OF THE MEAN AND STANDARD
DEVIATION OF [(XT - XE)/XTJ * AS A FUNCTION
OF SYSTEMATIC ERRORS IN THE LATERAL
DIFFUSION COEFFICIENT 0y, AFTER HILST (1970)
(0 - 0) (r ~ X.) 0
Y-~ Y-E X(T,E)
Y-T
-0.2 -0.003 :If).02t 0.105 < 0.122 < 0.139t
+0.2 0.007 :If). 03 0.130 < O. 151 < 0.172
-0.5 -0.018 :If). 03 0.138 < 0.161 < 0.183
+0.5 0.012 :If). 03 0.138 < 0.161 < 0.183
-0.7 -0.032 :If).04 0.170 < O. 197 < 0.224
+0.7 0.014 :If). 03 0.141 < 0.164 < O. 187
"true" concentration (no error)
* "X.r=
~=
"estimated" concentration (with error)
t
Limits are assessed at the 95% confidence level.
III-38
-------
Table III-3
CALCULATED VALUES OF MEAN AND STANDARD DEVIATION
OF (Xr 1E)/Xy AS FUNCTION OF SYSTEMATIC ERRORS
IN VERTICAL DIFFUSION COEFFICIENT 0z' AFTER
HILST (1970)
(Limits Assessed at 95% Confidence Level)
( 0 z~ zT ° ZE) (~~~) 0X(T,E)
-0.2 0.055 :!: 0.03 0.112 < O. 130 < 0.148
+0.2 -0.071 :!: 0.03 0.143 < 0.164 < O. 187
-0.5 0.120 :!: 0.03 0.133 < 0.155 < O. 177
+0.5 -0.236 :!: 0.05 0.206 < 0.240 < 0.276
-0.7 0.151 :!: 0.03 0.145 < 0.168 < 0.191
+0.7 -0.429 :!: 0.15 0.669 < 0.776 < 0.885
Table III-4
CALCULATED VALUES OF MEAN AND STANDARD DEVIATION
OF (Xy - Xr)!Xy AS FUNCTION OF SYSTEMATIC ERRORS
IN WIND DIRECTION (8); HILST (1970)
(Limits Assessed at 95% Confidence Level)
e - e E' (~~ ~) °
T X(T,E)
degrees
+10 -0.134 :!: 0.04 0.191 < 0.222 <0.253
-10 -0.124 :!: 0.04 0.193 < 0.218 < 0.248
+20 -0.436:1: ? -
-20 -0.232 :I: 0.26 1.14 < 1.32 < 1.51
+40 -0.152 :I: 0.22 0.93 < 1. 08 < 1.23
-40 -0. 524 :!: 0.33 1.45 < 1. 68 < 1.92
III-39
-------
As a result of the TRC study, the sensitivity of the calculations
to variations of the input meteorological factors may be summarized by
considering the mean and standard deviations of the prediction error
resulting from normalized variations of fD.5 of the input parameters
(x 20, 40° for wind direction):
Type of Error
Mean Error
Individual Errors
Wind direction
(x 20°)
(x 40°)
~ ~ -25% -200 to +150%
~ -50% -275 to +175%
~x2~ ~ x 50%
~ x 5% ~ x 20%
Wind direction
Vertical diffusion coefficient
Lateral diffusion coefficient
It should be recognized that while the TRC work is extensive, it is
still a case study for a given emissions network and meteorological field.
As such, these results generally may not be applicable, yet they do illus-
trate the manner in which the concentrations can respond to variations of
the appropriate pollution variables within a given model design. However,
the model does not explicitly consider the effects of a limited mixing
depth.
The SRI dispersio~ model has also been evaluated (Ludwig et al.,
1970) for its sensitivity to variations in the meteorological and posi-
tional factors (as well as in the emissions field) in terms of: (1) wind
speed, (2) wind direction, (3) stability and mixing depth, and (4) re-
ceptor location. The first-order response of predicted concentrations
to wind speed changes by the SRI model is directly proportional to the
inverse of that parameter. This is the case with both the general
Gaussian formulation and the specific box model used with limiting mix-
ing depths. A second-order response occurs in the effect of wind speed
on the determination of the stability category and is considered in
terms of sensitivity to variations of the latter.
The ramifications of wind direction errors are illustrated in Fig-
ure 111-4 and are seen to be closely related to sensitivity with regard
to the source field. Figure 111-5 is an example of the changes that can
result and is based on sample calculations for the Washington, D.C.,
CAMP station under two sets of meteorological conditions. Calculations
were made at 22.5° increments, and the largest difference between adja-
cent directions is about 60%. The effects of receptor location are
111-40
-------
1. SOURCE MISPLACED
2. SOURCE STRENGTH MISESTIMATED
3. WIND SPEED AT SOURCE IN ERROR .- - 1/
4. TRAJECTORY MISCALCULATED ;.r'~ 1/
5. VERTICAL DIFFUSION MISESTIMATED - 8
6. HORIZONTAL DIFFUSION MISESTIMATED ,.,~ ~-;.~:,~,~~
7. LOSSES MISESTIMATED ~.' ~oPO--;:~'>,
8. RECEPTOR MISPLACED ~~ "~Y:'~4'(:;: 5;7'
(~ ~~~~S~'<::~<.' .6::;;>.
T~~~::~'~"~.I;' .--:-'. ~F:----~-'---;-
.r.. 1 .." 7 :~
. . . ~ -
~" :.)r-"""'" -' -~;r' ---.~
~--.~-~~ '=-~,"'-
..,..,.- ~ ~._~ -~ 7 /
SA-1365-24
FIGURE III-4
SOURCES OF INPUT ERRORS
AND UNCERTAINTIES IN VARIABLES
UTILIZED IN AIR QUALITY SIMULATION
MODELS (HILST, 1970).
III-41
-------
5
E
a.
a.
Z 4
o
I-
«
a::
I-
~ Z
w 3
~ u
~ Z
I 0
~ U
N 0
U
2
7
6
o
o
,', -~
, ,-
I \
I \
I \
I \
, \
I \ -"
/', I \,'
2 m/s / '...' " //
100 m / '/
"
",,--~ /
\ /
\ I
\ /.. ",,/
\ I
\ I
\ I
---.I
4 m/s
200m
50
100
1 50 200 250
WIND DIRECTION - degrees from N
300
TA-7874--6R2
FIGURE III-5
EFFECT OF WIND DIRECTION ON CONCENTRATIONS COMPUTED FOR
THE WASHINGTON, D.C., CAMP STATION. (0700-0800 LST, Neutral
Stability, Wind Speeds and Mixing Depths as Shown).
350
-------
closely related to those of wind direction, i.e., moving the receptor re-
lative to the source alters the relative location of the sources (or the
wind direction). To study the effects, the receptor location was dis-
placed by 0.1 mile increments; Figures III-6(a) and 6(b) show the changes
in calculated concentrations arising from both lateral and longitudinal
displacements. The initial location again corresponds to the CAMP sta-
tion. In this area, the street network is dense, and concentrations are
quite sensitive to the location of the receptor relative to the streets.
Stability and mixing depth interact in the SRI model to determine
which of the two submodels (Gaussian or box model) is used for the cal-
culation of the contribution of emissions from a given upwind segment.
To determine the effects on the model output of variations in stability
and mixing depth, calculations were made using two different configura-
tions of sources. In the first case, source strengths were assumed to
be the same in all segments. It was assumed that there were no emissions
beyond the outer boundary of the last segment, 32 km from the receptor.
The results of calculations for this source configuration and for various
combinations of stability and mixing depth are shown in Figure III-7(a).
The results are essentially the same for low values of mixing depth, re-
gardless of stability. For very shallow mixing layers, the box model is
used for almost the entire distance upwind of the receptor. Since the
box model results are independent of stability, it is to be expected that
the results converge at small mixing depths.
The neutral and slightly unstable cases are unaffected by mixing
depth for the larger values of the parameter. This also is quite reason-
able, because the mixing of the emitted material proceeds rather slowly
under the more nearly stable conditions and the mixing is uninhibited by
the top of the mixing layer, if it is sufficiently high. In such cases,
the Gaussian model is used for the concentration calculations throughout
the entire 32-km upwind distance. The results of Gaussian model calcula-
tions are independent of mixing depth.
For the moderately unstable and extremely unstable cases, the box
model is used in the calculations, for at least some segments, for mixing
depths to 3000 m. However; the number of segments for which the box model
is applicable decreases with increasing mixing depth, so that calculated
concentrations become less dependent on mixing depth as that parameter
increases. This is reflected in the continual approach of the slope of
the curves toward zero.
The SRI sensitivity analysis
calculated with a source strength
ceptor to zero 32-km upwind. The
for mixing depth and stability was re-
that decreased linearly from the re-
results of these calculations are shown
111-43
-------
5
4
E
0.
0.
z 3
o
I-
«
a:
I-
Z
w
u 2
z
o
u
o
u
o
-1.0
-0.5 0 0.5
RECEPTOR lOCATION DISPLACEMENT, 'X - mi
(a) ALONG-WIND
1.0
5
4
E
0.
0.
z 3
o
~
«
a:
I-
Z
w
~ 2
o
u
o
u
o
-1.0
~~ 0 O~
RECEPTOR LOCATION DISPLACEMENT, Y - mi
(b) CROSS-WIND
1.0
TA-7574-5A
FIGURE III-6
EFFECT OF MOVING RECEPTOR POINT (Washington, D.C., CAMP Station;
0700-0800 LST, Wind 2700/4 ms-1, Neutral Stability, Mixing Depth 200 m)
II 1-44
-------
1000
800
600
H
H
H
I
~
CJl
d
-
U 100
:J
80
60
400
NEUTRAL
200
40
MODERATELY UNSTABLE
20
(a) UNIFORM SOURCE STRENGTH
10
50
500
1000
50
MIXING DEPTH - m
1000
100
FIGURE III-7
NEUTRAL
MODERATELY UNSTABLE
(b) SOURCE STRENGTH DECREASING
LINEARLY FROM RECEPTOR
100
500
NORMALIZED CONCENTRATION AS A FUNCTION OF STABILITY AND
MIXI NG DEPTH. Normalized for average source strength over 32-km upwind sector.
-------
in Figure 1II-7(b). Qualitatively, the two source configurations produce
similar results. However, the dependence on mixing depth is less for all
cases for the latter.
Evaluation of model sensitivity is clearly a difficult task. The
models discussed exemplify the complexities that arise as a result of the
method of solution of the equations, as well as of the representation of
the variables. Further complicating the problem are the discontinuities
that exist, for example, in given emissions and topographic (urban-rural
differences) fields, as well as in the variations between regions. The
effects of relatively small-scale horizontal wind variations « 5 km) must
also be defined.
Experimental Meteorology Program
General
The experimental meteorology program will cover field experiments
that are directed toward understanding and subsequently describing the
relationships between atmospheric dynamic, kinematic, and energetic
processes and the resultant transport and diffusion of effluents in
the lower atmosphere. A basic concept behind these experimental stud-
ies in RAPS is that they will be conducted both over an extended period
of time and intensively during specified periods; thus the data will
serve to show not only 'the nature of atmospheric processes for specific
periods but also the range of variability of conditions that can be ex-
pected. This latter feature is extremely important, because in many
air pollution situations not only the long term average contributes to
the problem but also the infrequent, short term departures. The RAPS
program will be especially designed to document the frequency and magni-
tude of these situations.
Tracer studies anticipated for the RAPS program for the study of
transport and diffusion processes will use both gaseous and particle
tracers in addition to neutral-density balloons. Techniques that in-
clude a significant amount of automatic operation will fit best into
this program, because they can be used more readily on a semiroutine
basis for extended periods with minimum manpower. For gaseous tracer
studies, tracers such as sulfur hexafluoride (SF6) are preferred, be-
cause the analysis is automated more readily and can be undertaken at
a field laboratory soon after the test. This is not the case with in-
soluble fluorescent pigments, which generally require visual counting
111-46
-------
using a microscope. Soluble pigments and dyes have some uses as tracers
and can be analyzed rapidly in the field. Additional gaseous tracers
should be developed and tested to augment SF6 because of increasing back-
ground levels of SF6 and to permit dual or multiple point releases as
discussed later.
The RAPS experimental meteorology program should include a facility
for the mapping of horizontal wind trajectories using constant-level
balloons at one or more altitudes. The operational facility should per-
mit target balloons to be followed for distances of at least 150 km at
levels as low as 150 m. Two systems, in particular, are potentially
available for these experiments: (1) conventional radar tracking and
(2) a new radio-locating system using Doppler principles.
The radar system has been developed to a high degree of sophistica-
tion, principally by the Atmospheric Sciences Laboratory at NOAA, and
its advantages and limitations are fairly well known. The system uses
a van-mounted M-33 radar to track one or more transponder-equipped
balloons. Radar position data are recorded on magnetic tape and sub-
sequently processed by computer. NOAA has tested and refined the tech-
nique in a series of field programs over the past decade. Limitations
are in the operating costs of the system and the current inability to
provide real-time, quantitative wind data.
The radio-locating system has been designed and given preliminary
field testing as a proprietary system by Control Data Corporation (Belmont,
1971) under the trade name METRAC. The CDC system provides position loca-
tion using Doppler radio techniques and a multistation network, together
with transponder-equipped balloons. The data are transmitted to a central
computer for recording ~ real-time processing and display. METRAC is a
flexible and attractive system, and the feasibility of incorporating it
or an equivalent system as an integral part of the Regional Study is
strongly encouraged; operational details follow in a subsequent dis-
cussion.
Additional experimental meteorology programs and studies will also
complement and supplement the basic research network. As discussed later,
these include radiation studies, supplemental aerial sampling, and poten-
tial satellite applications.
111-47
-------
Tracer Studies of Transport and Diffusion
Purpose and Scope
An obvious goal of the overall field program is the development
of the capability to use operational meteorological observations for the
assessment of the dilution capabilities of the atmosphere over an urban
and adjacent rural area. As work progresses toward this goal, a system
for the routine collection of essential meteorological data will be es-
tablished for estimating pollutant transport and diffusion and eventually
for pollution forecasting. Such a system, while retaining several spe-
cial observations at key points, might include deployment of standard
instrumentation over a subsynoptic scale no larger than one-half degree
of latitude.
Over areas free of unusual irregularities in terrain, it is
assumed that with the observational data it is possible to describe rele-
vant atmospheric characteristics that also account for the transport and
dispersion of atmospheric pollutants. To test the validity of this as-
sumption so as to check numerical models and to aid in the design of an
optimum system of meteorological observation, it is considered necessary
to conduct field studies to directly observe atmospheric dispersion.
Tracer studies are one technique in which known amounts of identifiable
materials (gases and particles) are released and sampled downstream at
other positions and times. The release of balloons that float at a con-
stant altitude and thus serve to track the transport wind is another
technique for tracing. The introduction of tracers enables the analyst
to start with a known source at a specific location and to avoid confu-
sion with other sources in subsequent measurements downstream. During
the proposed tracer studies for the RAPS program, measures of the tracer
dispersion (in terms of standard deviations of integrated concentrations)
and its variations would be related to measures of atmospheric turbulence
and transport; atmospheric indices in turn would be related to meteoro-
logical analyses based on observations that are feasible for routine ac-
quisition.
A good review of the meteorological aspects of diffusion and
of experimental tracer studies is given by Slade (1968); other good re-
views covering studies into the late 1960s are also available (Stern,
1968, and WMO, 1970). Past studies have provided the background infor-
mation required for the RAPS program. In fact, the St. Louis Dispersion
Study of McElroy and Pooler (1968) during 1963-65 may serve as a proto-
type tracer study. Other tracer work was carried out in the early 1950s
by Leighton and Ditmar (1952). With the exception of the programs re-
ported by Hilst and Bowne (1966), and the tetroon experiments of Pack and
111-48
-------
Angel (1963), most of the tracer experiments have not dealt directly with
the urban environment. Many of the previous field studies, as a result
of economic limitations, were conducted without sufficiently detailed
meteorological measurements and without adequate modeling of existing
and changing atmospheric states. Since different tracers and instruments
were used in different environments, it usually has not been possible to
combine data in a form most suitable for intercomparison. Furthermore,
the degree of feedback between atmospheric properties that influence the
disposition of pollutants and the variable pollutant loading that in-
directly influences subsequent atmospheric properties has not been clearly
defined.
It is hoped that tracer studies performed during the RAPS pro-
gram will provide a standard basis for reducing or eliminating the costs
of extensive future tracer studies for similar urban environments. For
more complicated topographic regions or for the study of very localized
behavior of pollutants, special tracer studies will still be required in
the future, but even then the information on meaningful measurements and
analyses acquired during the RAPS program for a variety of meteorological
conditions will be useful. To achieve this objective, the tracer studies
during RAPS will be conducted extensively as well as selectively to en-
compass representative meteorological conditions associated with pollu-
tion, including day-night and seasonal differences. Although periods of
stormy or severe weather probably will be avoided during the tracer ex-
periments, operations will be performed during mesoscale meteorological
regimes with distinct differences in stability, wind speed, and wind
direction during each season to include significant land use and energy
budget variations for the urban and surrounding rural environments.
Each series of experiments will be planned to span a period of
24 hours of longer. During a 24-hour period, it is anticipated that
tracer observations generally would be conducted during four periods
of up to one hour each, but allowance should be made for a variety of
release and sampling times. Over the year, the collection of data
during approximately 24 different days should provide an extensive
data bank. However; balloon tracers could be used routinely under all
weather conditions, with or without other tracer experiments. Up to
four observations per day during each midseason month would establish
a good data set for comparison with other meteorological observations.
111-49
-------
More
tion
from
frequent observations could be
periods or during periods when
satellite photographs.
taken during interesting precipita-
low-level cloud motions are determined
General Requirements
The basis for a study of pollutant levels is conservation. With-
in any defined atmospheric volume, the totality of sources will equal the
buildup or storage rate of the pollutant plus the divergence of the trans-
port of pollutants over the volume. Consider a volume of atmosphere con-
taining continuous internal sources of pollutants, with no upwind sources,
that is sufficiently large to encompass any lateral spread of pollutants.
If deposition at the lower boundary is negligible and if some upper
boundary such as a thermal inversion exists, across which negligible
vertical transport occurs, then the rate of buildup or loss of the total
pollutant load within the volume will depend on the rate of transport
by the wind across the downwind face of the volume. Thus, with the
product of the estimated mixing depth and the mean flow rate through-
out the atmospheric volume as a crude index, it is possible to assess
the dilution potential of the atmosphere. Frequently, this sort of
idealized assessment is based on information on the atmospheric flow
rate at a single level.
To describe the potential rates of change of pollutant levels
locally within the volume and to arrive at a more reliable estimate of
total downwind transport, it is also necessary to describe the mixing
capability (horizontally and vertically) of the atmosphere. The dif-
fusive ability can be described in terms of the intensity of turbulence
that is usually expressed by the normalized variance of the fluctuations
of components of the wind velocity- Alternatively, the fluctuations of
horizontal and vertical wind directions can be used as indices of tur-
bulence. Because of the local and sometimes inconvenient nature of
turbulence measurements, it is customary to describe the mixing capa-
bility of the atmosphere in terms of the stability, say, as a gradient
Richardson number, which includes measures of the vertical gradients
of temperature and horizontal wind speed. A somewhat better option
is to obtain measures of both the stability and the related intensity
of turbulence.
III-50
-------
In summary, the essential meteorological ingredients in a pol-
lution assessment program are simply (1) the depth of the mixing layer,
(2) the distribution (especially vertical) of the wind velocity within
the mixing layer, and (3) the mixing capability within the atmospheric
volume. All three factors are related to the thermodynamic stability
and the surface roughness, both geometric and aerodynamic. Inasmuch
as steady state conditions usually are not realized in the boundary
layer, it is essential also to obtain information on (4) the rates of
change of stability, flow rate, and associated turbulence. The latter
quantities, when not governed by larger scale synoptic changes, are re-
lated to local advection and the spatial distribution of the time-varying
surface heat budget. Characteristic synoptic parameters include the
gradient wind velocity at the top of the mixing layer, the large-scale
stability and vertical motion, and cloudiness. The importance of all
these factors must be considered in a complete analysis of data collected
during the tracer and transport experiments; deposition and scavenging
must be considered also where they apply to specific experiments.
Prime interest is in the ground level concentrations of pollu-
tants, arising both from surface and elevated (tall stack) sources, at
locations within the urban area and at rural locations at long distances
(up to 150 km) downrange from urban sources. For the dispersion of
pollutants from elevated sources and the long range transports, it is
important to consider vertical dispersion rates and their changes.
Furthermore, it is the vertical dispersion rate that the urban envir-
onment influences the most, but only limited information on vertical
dispersion rates is available from previous studies. In fact, conclu-
sive evidence of significant urban influences on atmospheric disper-
sion rates has not been documented except for enhanced dispersion at
short ranges (less than about one-half mile). On the other hand,
changes in meteorological conditions over the urban area have been ob-
served consistently. Most notable are the changes in the temperature
distribution and the stability, especially at night. These changes
can be attributed largely to the increased storage of energy during
the daytime (in addition to manmade heat sources) within the urban
subsurface, with subsequent increases in thermal emission and verti-
cal exchange at night.
III-51
-------
The most commonly used dispersion model is the Gaussian plume
formulation,
x
Q
1
2m 0 11
Y z
exp (- 2:;) ! exp [-
2 2 {
(z-h) J [(Z+h) J
+ exp -
2 2 )
20 20
z z
(I II-20a)
When sampling receptors are located at height Z = 0 this expression re-
duces to
x
- =
Q
1
TT00U
Y z
exp [ -
2
-L -
2
20
Y
2
2:2J
z
(I II-20b)
where Q is the continuous source strength, X is the average concentra-
tion, u is the mean plume transport wind, y is the lateral departure
from the time mean axis (x) of the traveling plume, h is the elevation
of the source above the receptor plane, 0y is the standard deviation
of the horizontal (lateral) concentration distribution within the con-
tinuous plume, and 0z is the standard deviation of the vertical concen-
tration distribution within the plume. Although this model implicitly
assumes for a given atmospheric stability and surface aerodynamic rough-
ness that 0y and 0z are only functions of x, it would be instructive,
under different conditions, to examine the possible variability of 0y
with z and the variability of 0z with both hand y.
Important factors to consider when checking models of computed
concentrations are the variations in 0y and 0z and the relationship
between them. Accordingly, these factors have been given emphasis
in the recommended design considerations for tracer studies during
RAPS.
III-52
-------
Experimental Design Considerations
Gaseous and Particle Tracers (Short Range)--With occurrence of
meteorological conditions considered to be favorable for a tracer experi-
ment, the deployment and preparation of tracer sources and sampling array
are conducted on the basis of an initial low-level tetroon trajectory ob-
tained about six hours in advance. Continuous point sources will be posi-
tioned near the surface and at one or more levels up to a height corres-
ponding to a tall stack. A suitable platform for the elevated source(s)
might be a stack itself, an available tower, or a mast mounted on the roof
of a building (if no serious problem exists with local circulation anoma-
lies). When surface and elevated sources are operated together, they will
be located at the same position.
Downwind sampling of concentrations of tracer material arriving
at the surface, either from surface or elevated sources, will be conducted
over sampler arrays distributed in equal azimuth increments along cross-
wind arcs at several ranges. (A maximum range for fluorescent particle
tracers will probably be restricted to distances of less than 15 km.)
It is highly desirable that two or more distinguishable tracers (e.g.,
particles with different fluorescent colors) be released simultaneously
from two or more elevations or locations and also sampled simultaneously
at the same receptor location.
The most general set of tracer runs will yield data on the
variation of cr with range x and height z (see Eq. III-I). For this
y
experiment, various tracers will be released simultaneously from a
surface and an elevated source(s)j surface receptors downwind will sample
the tracers simultaneously along crosswind arcs at different ranges (as
shown in Figure 111-8). Measures of the standard deviation of the cross-
wind distribution (from the various sources) at the several arc locations
describe the variation of cry with x and h for the existing meteorological
and surface conditions along the plume trajectory over the urban area.
Differences in the actual dosages from the two sources will depend on
the vertical dispersion rates.
With measurements of the appropriate mean transport winds, it
is possible to use measurements of cry to determine the crz's for each source
from Equation 111-1. Results could be assessed with the aid of observed
vertical and temporal variations in stability. Differences in the meas-
ured cr 's for each source would be attributable primarily to vertical
y
variations in cry' Since cr is normally considered to be independent of
height, these measurementsYshould be extremely valuable, especially when
samples are compared at several arcs sufficiently distant so that both
III-53
-------
y
x
FROM
ELEVATED
SOURCE
FIRST SAMPLING RANGE
z
'/
~
///~//..
----------- ~ .
... x
xA
SA-1365-25
FIGURE III-a
HYPOTHETICAL LATERAL-LONGITUDINAL AND VERTICAL-LONGITUDINAL
CROSS SECTIONS SHOWING ENVELOPES FOR PLUMES GENERATED
SIMULTANEOUSLY BY IDENTICAL POINT SOURCES AT TWO ELEVATIONS.
Plume axes parallel to x axes.
II I-54
-------
plumes are within regimes for which range variations of 0z are likely to
be equal. Observed differences in the horizontal variations in the 0z'S
inferred for each plume would be documented for further evaluation.
The standard deviation of the vertical distribution of material
in a plume is of special interest, because it is most likely to be in-
fluenced by the urban environment. It is anticipated that pronounced
changes in vertical dispersion parameters are very responsive to changes
in stability and roughness. However, it is a difficult quantity to meas-
ure; in many previous experiments, it was estimated from other data rather
than measured directly. The basic problem with measurements of 0z (or
with direct measurements of vertical variations in ° ) is the difficulty
y
of sampling in a vertical array from the surface to some distances above
tall stacks and in the appropriate downwind position from a continuous
source. In this critical region of the urban environment, aircraft can-
not be used for sampling even if they did not influence the dispersion
measurements themselves. At higher elevations in the boundary layer,
meaningful dispersion data can be acquired more simply from series of
tetroon flights (as described below).
Another problem with measurements of vertical dispersion near
the ground is the necessity of correction for boundary "reflections."
In the simplified model, a hypothetical mirror-image source is assumed
to be operating below a uniformly smooth ground surface that is treated
as being completely transparent. Thus, when the actual plume intercepts
the surface, downwind concentrations above the lower boundary are en-
hanced by an amount equivalent to the additional effluent from the hy-
pothetical source. This model (see Eq. III-I) does not allow for local
irregularities in surface roughness or flow characteristics; furthermore,
scavenging and settling processes are not considered in Equation III-I.
A local range study of the vertical dispersion could be con-
ducted at and near one of the basic 30-meter observation towers. Wind,
temperature, and component wind fluctuation measurements on the tower
would be provided at the three standard heights and at two or more ad-
ditional levels. Also, the tower could be rigged for tracer sampling
along the vertical. A semimobile tower of the same height and type
would be situated downwind with a dense vertical array of receptors.
If the plume sources from two heights are located sufficiently close
so that the towers extend through the plume tops, measurements of X(z)
and 0z can be obtained conveniently at the two ranges. This arrange-
ment would permit evaluation of the mean transport wind concept. Meas-
ures of ° could be obtained from the crosswind sampling arcs near the
y
III-55
-------
surface, and ° 's could be computed for comparison with the measured
z
° 's as a function of source height h. Finally, the ° 's could be
Z ' Z
compared with the observed Richardson numbers, whereas both the oz's
and the Richardson numbers could be compared with the measurements of
the component wind velocity fluctuations.
Direct sampling of the vertical distribution of tracers on
the larger scale can be accomplished (with difficulty) from an array
of samplers at different heights along the cable of a barrage balloon.
The barrage balloon would be located near the center of the plume, per-
haps on the basis of initial sampling at the surface along a crosswind
arc. Some mobility of the barrage balloon along the arc may be desira-
ble. Alternatively, a very tall tower, such as the KMOX TV tower, could
be used as the platform for the vertical sampling array. The use of the
tower requires flexibility in locating the sources upwind. On the other
hand, if it were possible to instrument the tower, it would be simpler
to conduct the vertical sampling there than from the barrage balloon.
From the point of view of both vertical sampling position and
computational models of the dispersion, it is important to ascertain
whether ° varies with y, i.e., crosswind within the plume. Suppose
z
that for the fixed vertical sampling array two identical sources are
positioned at the same upwind range but displaced crosswind with re-
spect to each other as shown in Figure 111-9. Different tracers would
be released simultaneously from the sources and sampled simultaneously
along the vertical array. If the 0z determined from one tracer differed
significantly from 0z for the other tracer; then it would appear that
0z in Equation 111-1 could not be considered to be independent of the
crosswind direction. In addition, as with the small scale measurements,
0z could be determined by simultaneous sampling along the vertical axis
of simultaneous releases at two different elevations from the same range.
Results would be useful for assessing the possible influence of the lower
boundary on oz' Therefore, this experiment actually constitutes an addi-
tion to the first experiment described in conjunction with Figure 111-9.
More generally; the variation of 0z with range or with travel
time is desired. Again, for a fixed single vertical array of samplers,
identical sources could be located near the surface at different ranges
upwind, as shown in Figure 111-10. Different tracers would be released
at the same rate from each source and sampled along the vertical array.
The 0z determined empirically for each tracer would provide a descrip-
tion of ° with range X. In some situations it might be possible to
z
determine ° from the altitude range above the plume core only. While
z
this tracer experiment to define ° as a function of range is being
z
conducted, sampling can be carried out along the surface arcs so that
III-56
-------
y
z
CONSTANT
---
--
--
--
---
--
--
---
-
-
-----
--
--
x
x
a
XA
x
z (Sampling Axis)
~
--
.........
"-
'\
\
\
I
I
/
/
,/
---
--
y
SA-1365-26
HYPOTHETICAL LATERAL-LONGITUDINAL AND VERTICAL-LATITUDINAL
CROSS SECTIONS SHOWING ENVELOPES FOR PLUMES GENERATED
SIMULTANEOUSLY BY IDENTICAL POINT SOURCES DISPLACED
CROSSWIND ALONG Y-AXIS
FIGURE III-9
III-57
-------
y
I z = 0 I --- --/..... PLUME ENVELOPES
--
--
///---- ,~
x (Plume Axes)
"-,,-
-
-......
/---
--
--
POINT SOURCES - - ---
z
z
SAMPLING
PLANE
, x = Xol /-
/
/
I
I
-
"-
"-
\
\
I
x
y
x
o
SA-1365-27
FIGURE IlI-10
HYPOTHETICAL SURFACE, VERTICAL-LONGITUDINAL, AND VERTICAL-
LATITUDINAL CROSS SECTIONS FOR PLUMES GENERATED
SIMULTANEOUSLY BY IDENTICAL POINT SOURCES AT DIFFERENT
UPWIND RANGES FROM CROSSWIND AND VERTICAL SAMPLERS AT X
o
III-58
-------
simultaneous measures of 0y as a function of range can be obtained (as
required by Eq. 111-1). At the same time it might be desirable to use
two vertical sampling arrays, say, the TV tower and one barrage balloon
system located appropriately at a greater downwind distance. Ideally,
separate surface sampling arcs would include each of the vertical sampling
arrays.
With a vertical sampling array, it is also possible to determine
o from a series of elevated instantaneous line sources released repeat-
z
edly upwind from a helicopter.5 However, it is not possible to make meas-
urements of lateral dispersion with the line source. Nevertheless, the
technique should be used to enable comparisons with 0 's determined from
z
the continuous point source experiments and with 0z'S computed from
meteorological data.
Long Range Tracers--For examining the transport and dispersion
of a plume along trajectories extending to about 100 km, SF6 can be used
as the tracer. This gaseous tracer will be useful for observations over
the rural area downwind from the city. An elevated source might be
situated in the upwind portion of the urban area in such a manner that
its plume will encompass the TV tower (if it is equipped with a verti-
cal sampling array). A vertical sampling array attached to the cable
of a barrage balloon could be situated much farther downwind in the
rural area, near the center of a crosswind arc of surface receptors.
The vertical array probably would be necessary for very stable condi-
tions. Measurements of 0 and 0 would be obtained over the rural area;
y z
these results would be compared with corresponding measurements in the
urban area and with computations based on the meteorological conditions
along the trajectory.
Balloon Studies--Superpressured constant-level tetroons with
attached transponders can be tracked by radar or radio position finding
techniques for considerable distances to provide a good representation
to the three-dimensional trajectory of an air parcel (Hass, et al., 1967)
for distances exceeding 100 km. The observed trajectories can provide
considerable detail on the existing wind field and can be used to extend
and check trajectories computed by an objective analysis of wind measure-
ments available by conventional methods. Since tetroons actually are
tracers, they also can be used to derive estimates of the diffusive
capability of the atmosphere. If the release level is a few hundred
meters above the ground, the resulting trajectories provide useful in-
formation, as described earlier, for positioning sampling arcs for lower
level tracer studies over the urban area. In addition, each tetroon can
III-59
-------
be considered to be a platform for procuring other data. The latter con-
cept could be easily introduced to practice by adoption of the METRAC
system proposed by Control Data Corporation (1971). In this system,
radio signals are transmitted from the lightweight, expendable tetroon
package to an established network of receivers over the area of interest
(radars are not required). The METRAC ground stations consist of a
readily transportable receiving station and a simple antenna. For tar-
get positioning, a minimum of four stations must be within line-of-
sight, but some redundancy in the system is strongly recommended by
CDC. Within the RAPS area, it would be necessary to have receiver
sites to cover adequately the longer distance transport and the several
prevailing wind directions. The METRAC network could be used both for
constant level wind trajectories including turbulence structure, tem-
perature, and other compatible sensor data and for profile measurements
of wind, turbulence characteristics, temperature, and other parameters
using rising balloons. Accurate positioning of the tetroon as a func-
tion of time is accomplished by Doppler radio techniques, and as many
as four additional measurements could be obtained and radioed separately
to the receivers. Temperature and perhaps relative humidity and pres-
sure measurements could be accommodated.
It has been demonstrated (Islitzer and Slade, 1968) that esti-
mates of atmospheric dispersion can be obtained from individual tetroon
trajectories, from successive tetroon trajectories, and from lateral dis-
tances between pairs of tetroons released nonsimultaneously. In the
latter case, the time separation can be varied to obtain useful data
in terms of varying atmospheric conditions. Relative diffusion esti-
mates also can be obtained from the simultaneous release of two or more
tetroons.
For the RAPS program, it would appear most profitable to oper-
ate with pairs of tetroons transmitting at different radio frequencies.
The pairs could be released simultaneously at two different altitudes,
and successive releasing of pairs could be performed at desired inter-
vals. In this way it would be possible to obtain lateral and vertical
dispersion estimates over the urban area and at the same time acquire
measurements of stability (e.g., the gradient Richardson number) along
the actual trajectory, both over the urban and rural areas. In fact,
this system of observation may be the most beneficial of all tracer
studies in the RAPS program.
111-60
~
-------
Transformation Processes and Deposition--The source and sampling
systems for the gaseous or particle tracers also will be used to conduct
special observations that are designed to provide empirical data on the
significance of transformation or deposition processes. For example, at
select times, measurements of dispersion from specific sources using non-
reactive tracer gases, i.e., SF6' will be compared with the dispersion
associated with reactive emissions, e.g., S02 or NO. In addition, dis-
persion measurements from the source using the nonreactive tracer gas
(i.e., SF6) will be compared with measurements from either unique iden-
tifiable particle emissions, e.g., heavy metals or a unique particulate
tracer such as fluorescent pigment. Both types of experimental programs
will be conducted during a variety of meteorological conditions.
Special Observations--It is safe to assume that most meteorologi-
cal parameters that are relevant to the tracer studies will be acquired
from the planned program of objective analysis of meteorological obser-
vations from surface, tower, balloon, and aircraft platforms. These will
include measures of turbulence intensity in the lower 30 meters, as well
as in the boundary layer above the urban structures. In addition to
routine data collection techniques, remote sensing techniques will be
applied to measurements of profiles of temperature, wind, turbulence,
and particulate loading. Correlation spectrometer measurements of
columnar variations in S02 and N02 concentrations, and lidar measure-
ments of mixing depth are also possibilities. As described above, the
recommended tetroon tracer program would itself provide valuable wind
and stability data. However, additional special observations are de-
sired to evaluate the tracer programs.
It is recommended that, at each source and at the center of
each tracer sampling arc during the period of tracer release and sam-
pling, additional measurements be made of temperature, wind speed, and
lateral wind direction fluctuations. Not only will these observations
complement other observations, but they also will provide a means for
evaluating the applicability of simpler meteorological measurements to
the techniques for estimating transport and diffusion.
The only other area requiring additional observation and/or
analysis deals with the effective urban surface itself. Both the geo-
metric and aerodynamic surface roughness (including a zero-plane wind
displacement level) should be determined as a function of wind direc-
tion and range increments. This would enable evaluation of the in-
fluence of roughness variations on the wind characteristics and sta-
bility downwind. Finally, more data are required on the thermal
111-61
-------
influence of the urban surface on changes in stability. This will re-
quire representative data on the thermal forcing function (primarily
solar radiation) at the surface and data on the distribution of the
thermal response in terms of variations in the effective surface tem-
perature. Such data are discussed in the following section on urban
and rural radiation budget studies.
Summary
It is clear that successful tracer experiments must be correctly
interfaced with the deployment of other measuring facilities, the collec-
tion and processing of other measurements, and the analysis of pertinent
meteorological quantities. Ample meteorological data will be available.
Figure 111-11 summarizes all the basic program elements that have been
recommended for the tracer experiments. Although the outline is self-
explanatory, no reference is made to the extensive data analyses that
are required, to the evaluation of results in terms of the meteorologi-
cal parameters, or to model predictions.
The continuous point sources will be operated in the lower por-
tion of the mixing layer, whereas the tetroons will operate generally in
the middle or upper portions of the mixing layer. Of the point source
plume studies near the ground, the key experiments entail the simultaneous
release of individually distinguishable tracers at different heights with
simultaneous sampling along the same crosswind arrays of surface receptors,
and direct simultaneous measures of vertical dispersions of distinguishable
plumes released simultaneously from different positions. The key tetroon
tracer experiments use two tetroons released simultaneously at two alti-
tudes with temperature sensors and radio transmission, thereby enabling
the measurement of stability along the trajectory in addition to disper-
sion characteristics.
Urban and Rural Radiation Budget Studies
Existing observational data have revealed differences in the radia-
tion and heat budget of the urban area with respect to the neighboring
rural area. As the land use varies, differences in the radiation budgets
also vary. The pollutants and differences in the boundary conditions
that are responsible for the changes in the radiation budget influence
the dynamics and heat budget of the lower atmosphere; in turn, feedback
mechanisms exist to influence the distributions of pollutants, tempera-
ture, water vapor; and cloudiness. The effect of the urban environment
111-62
-------
METEOROLOGICAL DATA
Synoptic Conditions
Mesoscale Structure
Turbulence Meausrements
INSTANTANEOUS SOURCES
(~ 200 m above surface)
I
SuccesSive Simultaneous Releases
of Pairs of Instrumented Tetroons
at Two Altitudes (Radio Telemetry)
and Network Tracking)
Transport Speed and Trajectory
Stability (e.g., Richardson No.)
Along Trajectory
DisperSion Data {a and Ozl Along
Trajecrory
i------------l
I I
I Series of Instantaneous Lme I
I Sources (released by he! Icopter) at I
I Several Ranges from Vertical r - - - +-
I Sampling Array (0 z versus XI I
I I
L______--_J
INITIAL TETROON TRAJECTORY
SPECIAL SURFACE DATA
ALONG TRAJECTORY
Deployment and Preparation of
Tracer Sources and Sampling Arrays
Roughness Dlstnbutlons
IrradIation (downward)
TemperatUre (from aircraft)
-
CONTINUOUS POINT SOURCES
(~ 100 m above surface)
~
SF 6 Tracer (1009 range)
,
Distinguishable Gaseous or PartIcle
Tracers (short range)
o and u (Inferred) versus h and X
V z
Two or More DIstinguishable Tracers
Released Simultaneously at Several
Elevations and Sampled
Simultaneously Along CrosswInd
arcs With Surface Receptors
Surface Crosswind Sampling (Oy)
And Vertical Sampling Along Barrage
Balloon Cable (Oz) Over Downwind
Rural Areas
o and 0 versus h and X
v z
Same as Above But With Local Scale
Sampling Along VertIcal Array of
Receptors on 30 m Tovver
Comparison With 0 and 0 Over
V z
Urban Area With EmphasIs On
Changes in Stability and Roughness
-----------
Same as Above But With Vertical
Sampling Array Rigged On A Radio
Or TV Tower Or Along Barrage
Balloon Cable
Sources Located At Variable Range
o z versus y
Two DIstinguishable Tracers Released
SImultaneously From T.....o Sources
At Same Elevation But Displaced
CrosswInd; Single Vertical Sampling
Array (TV tower or barrage
balloon Cable)
SA-1365-28
FIGURE III-11
PROGRAM ELEMENTS OF TRACER EXPERIMENTS
II 1-63
-------
on its own climate and the climate of surrounding rural areas, as well
as the significance to the larger-scale climatology, are of particular
concern in future planning. Basic objectives of this portion of the
experimental program are to:
(1)
Document differences in urban and rural radiation budgets for
the surface and boundary layer along with differences in pollu-
tant concentrations, temperature, water vapor, and cloudiness.
(2)
Provide radiation data required for the formulation of direct
input into applied mathematical models of the boundary layer.
( 3)
Enable testing and revision of relevant radiative components
currently used in mathematical models.
An observational program to document surface and near-surface dif-
ferences in the radiation budgets over urban and rural areas must be con-
ducted in conjunction with observations of temperature and water vapor
profiles, careful observations of cloudiness, and measures of pollution
concentrations. Because of the pronounced radiative effects of clouds,
it is especially important to document differences between rural and
urban cloudiness as a function of local solar time, especially if the
effects of pollutants are to be deduced. As for the radiation measure-
ments, precision instruments (Drummond, 1970) should be used because of
the small relative differences to be expected.
The most important component of the surface heat budget is the
available total solar radiation (a forcing function), The most sig-
nificant response function is the surface temperature and the asso-
ciated thermal emission from the surface. Sizable heat storage in the
urban area can result from daytime solar absorption, supplemented by
space heating within structures and may lead to excessive nocturnal
emission. In the boundary layer above the surface, both infrared cool-
ing and daytime solar heating influence the radiation budget; they are
linked to the atmospheric stability and to the diurnally varying trans-
port processes.
Meaningful surface measurements of the upward hemispheric flux are
difficult to obtain because of the complicated surface inhomogeneities
and, for the solar measurements, by complex shadowing patterns that are
related to variations in sun angle. As the altitude of observation of
upward flux is increased, the size of the heterogeneous surface area
contributing to the measurement increases rapidly. Therefore, low al-
titude measurements of upward flux profiles must include spatial in-
tegration to be compatible with higher altitude measurements. On the
II 1-64
-------
other hand, representative measurements of downward flux can be acquired
from relatively few locations with instruments situated near the upper
boundary of surface structures. Since the upward flux measurements at
the surface must be integrated spatially, the upward and downward flux
measurements at the stations in a surface network should be obtained
separately from carefully located sensors. Measurements of downward
flux should be free of surface obstructions; measurements of upward
flux should include representative sampling of surface materials and
structures, as well as typical shadowing patterns for different sun
angles.
Two quantities that are critical to a detailed analysis of the sur-
face radiation budget are the surface albedo (as a function of sun angle)
and the surface emissivity (longwave). Useful estimates of these quanti-
ties can be postulated initially on the basis of special emissivity and
reflectance data for known surface materials. These estimates must be
supplemented by special low-level airborne observations (and/or labora-
tory simulations of the surfaces with controlled sources).
The measurements of the solar irradiance at the surface should in-
clude total solar radiation (direct plus diffuse) as well as the sky
(diffuse) radiation only. The latter observation will be helpful in
estimating the fraction of extinction due to absorption (Lettau and
Lettau, 1969). In addition, two or three spectral observations should
be included to aid in subsequent analyses of observed variations. The
spectral breakdown should at least include a portion of the visible
spectrum that is free of molecular absorbers and a portion of the in-
frared spectrum that includes water vapor absorption. At the same sur-
face sites, observations would include upward shortwave fluxes, and
both upward and downward total irradiances (i.e., hemispheric fluxes,
including the atmospheric or surface thermal emission). Alternatively;
the longwave fluxes could be measured separately with suitably filtered
radiometers.
At several key solar hour angles, aircraft observations of downward
and upward solar fluxes and downward and upward total radiation (longwave
fluxes included) should be made both at low level (e.g., 500 ft) and just
above the boundary layer (e.g., 5000 ft). Nocturnal measurements would
yield only the infrared fluxes. Although the airborne observations would
not necessarily be conducted routinely over many days, sufficient flights
would be conducted under differing meteorological conditions to (1) pro-
vide direct information on solar heating and infrared cooling rates for
the boundary layers over urban and rural areas and (2) provide a relative
111-65
-------
measure (at the lower flight level) of the spatial distribution of the
surface albedo and the thermal emission. The latter data would be used
to extend the surface measurements of upward flux. During tracer ex-
periments, the flight paths could be directed along pertinent plume
trajectories. Furthermore, the aircraft data should be useful for es-
tablishing estimates of coefficients or ratios of coefficients pertain-
ing to the aerosol scattering and absorption. (Molecular scattering
and absorption components can be computed.)
It is difficult to estimate the true surface infrared emission (up-
ward flux) from downward-looking radiometric platforms above the surface
because of the absorption and emission of the intervening atmosphere.
An alternative approach is to acquire airborne data on the spatial dis-
tribution of the effective surface temperature from downward-looking
radiometric measurements in the 11 ~m window region of the infrared
spectrum and to compute a representative upward flux. Standard obser-
vations of temperature and relative humidity would enable corrections
for residual absorption-emission from the atmosphere in the window re-
gion. However, since the infrared correction may depend on the concen-
tration of particles, it might be useful to acquire infrared window
measurements at the surface looking upward to note variations in at-
mospheric emission with variations in particle loading. Also, with
the effective surface temperature for the nonhomogeneous surface area
and with the observed temperature and water vapor profiles, it is pos-
sible to compute the infrared cooling distribution through the surface
layer. If the radiometrically-inferred surface temperature is discon-
tinuous with the surface temperature deduced by extrapolation of tem-
perature profiles, the discontinuity should be maintained during the
computations (unless there are obvious instrumental errors). Represen-
tative measurements of the downward infrared flux will be available near
the surface, and representative measurements of both downward and upward
fluxes above the boundary layer will be available occasionally from air-
craft. Of particular note would be differences between observations and
computations, especially when the latter are performed by neglecting the
influence of particles.
The surface radiation measurements over both rural and urban areas
should be conducted routinely at about the same heights above sea level,
with prime consideration given to representativeness near the average
height of urban structure. In general, the program outlined herein is
similar to that being conducted in the Raleigh, North Carolina, area by
111-66
-------
Flowers and Peterson. Briefly, the possible breakdown of measurements
can be summarized as follows:
Surface Radiation Measurements
(l)
Total direct plus diffuse solar downward
(2)
Total diffuse solar downward
( 3)
Spectral direct plus diffuse solar downward (visible and
near-infrared)
(4) Total solar upward
(5) Total thermal (long wave) downward
(6) Total thermal upward
(7) Photometer turbidity measurements
Aircraft Radiation Measurements (occasional, at two heights)
Items (1), (4), (5), and (6) above, plus measurements of
effective surface temperature in the 11 ~m infrared window
region.
Supporting Measurements
(1)
Temperature and water vapor profiles
(2)
Cloudiness
( 3)
Pollution concentrations (near surface)
The Role of Remote Probing Techniques
Ground-based Techniques
The capability of detecting, observing, or measuring various
atmospheric conditions remotely is valuable if (1) such data cannot be
obtained otherwise or (2) if they can be obtained more efficiently and
economically by such a capability. The basic factors are the accessi-
bility of the portion of the atmosphere observed and the nature of the
III-67
-------
information required. Thus, although it is readily possible to measure
atmospheric temperature at a height of 1000 feet given a tower, regular
radiosonde, tethered balloon, or aircraft facilities, much more conve-
nient and economical techniques of making such a measurement remotely
from the surface are desirable. On the other hand, the measurement of
some parameters is feasible only with remote, or at least extended path,
techniques. Atmospheric transmission is a case in point, and mean con-
centrations of, say, CO, over extended volumes or the mean air flow
across an area, are other examples.
In the present context, then, we consider what techniques of
remote probing should be considered in terms of their ability to provide
information more effectively and economically on (1) meteorological fac-
tors and (2) pollutants than is possible with point or in-situ measure-
ments.
Regional
the more
The information required is that serving both the needs of the
Study's objectives, such as research and model verification, and
general need of the real-time assessment and forecasting problems.
In addition to the distinction between meteorological and pol-
lutant measurements, it is convenient to consider the possibilities under
two headings:
(1)
Data collection at a Regional Study facility
(2)
Research activities as part of the Regional Study.
Under (1), it is apparent that remote techniques could make very
valuable contributions to the data collection networks of the Study facil-
ity. Particularly since much of the data required in studying the trans-
port and diffusion of pollutants on the regional scale are best considered
in broader and more comprehensive terms than are easily acquired by point
measurements, many forms of remote measurements (e.g., long path) would
provide data on the appropriate form. Again, since the three-dimensional
aspects are so important it would be valuable to have more comprehensive
data (in time and space) of the stability conditions and wind structure
of the lower 3 km or so, than can be provided even by radiosonde and air-
craft technique (or even the towers at the lowest levels). Similarly,
it would be most useful to be able to determine directly the broad dis-
tribution of gaseous pollutants and their flux within an extended area
rather than to have to infer such information from point measurements.
(Tables 1II-5a and 5b show the range of such techniques.)
111-68
-------
Type of Observation
Vertical temperature profile
~
~
~
I
0'1
(!)
Vertical humidity profile
Vertical turbidity profile (here con-
sidered as an indication of mixing depth
and stability)
Horizontal turbidity profiles or path
transmittances
Wind velocity, vertical profile
Vertical turbulence profile
Mean horizontal wind flow over extended
path
Mean path turbulence
Table III-5a
ATMOSPHERIC CONDITIONS
Purpose
To assess and predict mixing depth -
i.e., the depth of the neutral or unstable
layer in which pollutants are usually
mixed.
This entails:
Identifying the presence of
Assessing the height of the
base and the thickness and
of such inversions
inversions
inversion
intensity
Measuring lapse rates in the boundary
layer
To aid in forecasting changes in stabil-
ity and mixing depth (see vertical tem-
perature profile)
To assess and predict mixing depth and
monitor mixing processing
To assess "visibility" as a meteorologi-
cal parameter and pollution state
Input to transport and diffusion models
Input and transport and diffusion models
Input
(as a
point
to transport and diffusion
more representative sample
readings)
models
than
I npu t
(as a
point
to transport and diffusion models
more representative sample than
readings)
Candidate Techniques
Microwave or IR radiometry
Acoustic sounding
Raman lidar
Differential lidar absorption spectroscopy
Raman lidar
Microwave or IR radiometry
Lidar
Lidar and laser transmissiometry
Acoustic sounding
Lidar correlation anemometry--Doppler
radar, and Doppler lidar
Acoustic sounding Doppler lidar
Lidar correlation anemometry
Optical and microwave propagation
analysis
-------
Table 1II-5b
POLLUTANTS
Data Required
Candidate Technique
Particulate
centrations
vertical)
distributions and con-
(both horizontal and
Lidar
Transmissiometry (limited
resolution and generally
tal only)
Long path spectroscopy (mainly IR)
spatial
horizon-
Gaseous concentrations (with
spatial variation in vertical or
horizontal, ~ over extended
sample path)
.
Using fixed point--point paths
(absorption)
Using fortuitous distant re-
flectors (absorption and
emission)
.
Passive spectroscopy (absorption
and emission)
Lidar using Raman, Resonant Raman,
or fluorescence principle
Unfortunately, however, despite the considerable interest in
this subject for so long, the possibility of incorporating remote sensing
techniques in the basic data collection facility of the Regional Study
is, with a few exceptions, probably unlikely until the latter stages of
the project--i.e., after another three to four years. This follows from
the fact that although a number of techniques and devices are under de-
velopment at the present time, few are within range of being at the pro-
totype trial stage. With the inevitable time lags entailed in manufac-
turing and marketing complex instrumentation, it thus is unlikely that
fully tried, routine product devices will be available for procurement
and installation as part of the basic data collection network in the
main period of the study.
The few exceptions that are at a fairly advanced stage (nota-
bly, microwave radiometry [ThermasondeJ, lidar, acoustic sounders, and
passive spectroscopic ~echniques) can probably be expected to make use-
ful contributions to the data collection facility on an experimental
basis and will become more routinely useful and effective as the Regional
Study proceeds. Other techniques can be considered only as embryonic in
111-70
~
-------
terms of the main objectives of the Regional Study at this time. The in-
vestigation and trial of such techniques (and even those already in a
more advanced stage) thus logically fall under the heading of research
activities within the Regional Study, and programs to compare and evaluate
such techniques, both between competing systems and between the conven-
tional basic data collection facility, would be included as topics in the
Research Plan.
Therefore, it is recommended that research into the use of re-
mote sensing techniques in RAPS be considered in two stages:
(1)
Experimental--in which devices that have already been pro-
cured and are under study within the current EPA monitoring
research programs are made available to the RAPS program
on a trial and evaluation basis. These instruments are:
(a)
SRI/EPA Mark VIII Lidar--capable of mapping particu-
late concentrations
(b)
At least one advanced model Thermasonde (microwave
radiometer--capable of measuring thermal profiles
and determining the height of the surface inversion)
(c)
COSPEC II Barringer Correlation Spectrometer--capable
of determining S02 and N02 either over an extended
path or in terms of total burden in the vertical
To these should be added
(d)
A vertical acoustic sounder (of which a number of
prototypes have been built)--capable of monitoring
the depth of the mixing layer and identifying in-
version levels. (An approach that is very attrac-
tive for operational use because of its relatively
low cost.)
All these techniques have been sufficiently well developed and
demonstrated to indicate that they could early provide useful inputs into
RAPS observational programs--especially those concerned with special proj-
ects. The further trials and experience gained in such experimental col-
laborations would hopefully qualify them for more routine use in later
stages of RAPS, beside providing a valuable input to the technology of
remote probing in general.
(2)
Research--in which devices that are less well developed at
the present time or have yet to be well tested are used in
111-71
-------
research programs to investigate their potential for more
routine use. These include:
(a)
Long path absorption spectrometers already procured
or under procurement:
(ii)
(iii)
(i)
General Dynamics IR grating spectrometer (for
various species over a path length of 2 miles)
Bendix UV variable filter spectrometer (for
03 over path lengths of 0.25 to 1.5 miles)
General Electric C02 Laser (ILAMS) long path
absorption spectrometer (for ammonia and
ethylene and other gases over a 2-mile path)
Other devices and techniques not yet procured or de-
veloped but that are likely to become available dur-
ing the RAPS period:
(b)
(ii)
(iii)
(iv)
(vi)
(i)
Other types of long path or passive spectrom-
eters
Acoustic sounding systems for measuring tem-
perature, humidity, and wind profiles
Advanced microwave or IR radiometers capable
of measuring temperature profiles (using angu-
lar scanning and multifrequency techniques in
combination)
Fluorescence determination of N02 remotely
(Birnbaum et al., 1971)
(v)
Any airborne applications of such remote
probing techniques
Lidar or other optical devices for measuring
wind profiles.
Satellite Applications
Major advances in monitoring atmospheric behavior on the meso-
scale and synoptic scale are expected in the next five years from the use
of improved weather satellites. A careful study should be made to deter-
mine whether the benefits of satellites to RAPS will warrant the expense
of obtaining the data; our initial estimate is that this will be true.
111-72
-------
Perhaps the principal application of these data would be in providing an
overview of the clouds and weather systems in the area, with a resolution
(in the visible spectrum) of two miles or better. From the geosynchronous
satellites, such data may be obtained at approximately half-hour intervals
and therefore will be up-to-date. Infrared (11 micron) sensors will give
information with approximately four-mile resolution that can be used in
describing surface temperature when skies are clear, or the altitude of
cloud layers. Time lapse viewing of such pictures shows the cloud motions;
these may be used as data for objective wind analysis.
The first SMS/GOES satellite carrying the sensors mentioned above
will be launched in late 1972. Its subpoint will be over the equator at
100oW; therefore, it will have a good view of the central United States.
About a year or so later, the second satellite of this series will be
launched, and it will have additional sensors for measuring vertical tem-
perature and humidity profiles. However, it should be realized that these
profiles will give somewhat smoothed information in comparison to radio-
sondes and will not reveal the detailed structure of phenomena such as
temperature inversions.
Similar sensors carried by polar orbiting satellites are also
being improved. Scanning radiometers will obtain pictures in the visible
and infrared with 0.5 mile resolution. Such pictures will be obtained
twice a day in a given locality from the ITOS and Nimbus satellites.
Several of these polar-orbiters will be launched between 1972 and 1975.
The application of these satellite data for RAPS would include:
(1)
Monitoring weather systems in real time. Such systems
would include highs, lows, fronts, squall lines, fog,
and cyclone formation.
(2)
Making mesoscale analyses of winds and temperature for use
in diffusion models and air quality studies.
(3)
Controlling field experiments and data gathering activities.
(4)
Providing a live display for the public, illustrating the
relationships between air quality and weather patterns.
These satellite data may be obtained in two different ways. One
way is to obtain the data directly using a special ground receiving sta-
tion. This would require an installation worth at least several hundred
thousand dollars and would require a significant staff. The second al-
ternative would be to obtain the data by facsimile or by leased lines
111-73
-------
from a direct readout site that NOAA is planning for the severe storm
center at Kansas City. The associated costs would depend on the volume
of data needed. Further study of this question is required.
Upper Air Sampling Program
To understand and model the dispersion of contaminants on the re-
gional scale, routine measurements are required of the three-dimensional
(space) structure of the planetary boundary layer and its temporal varia-
tions; the specific application of these data was presented in the pre-
ceding discussions on dispersion modeling. The surface based monitoring
facility is designed to satisfy these requirements at the lower levels.
Two primary alternatives appear to be available for in situ measurements
at the upper levels: aircraft and balloon systems. The discussion on
remote probing techniques presents a possible alternate approach for up-
per air observations. However, in the near future, the latter may be
safely ruled out for routine, broad-scale usage.
The advantages and drawbacks of aircraft measurements are fairly
well known. To sum a few of the more important considerations, it should
be recognized that control of the measurement platform is a distinct ad-
vantage. Therefore, measurements can be made at the desired location
and can be repeated in short order. On the other hand, the accuracy of
the wind measurements in particular is open to question because of aero-
dynamic effects, and, equally important, the operating costs of the sys-
tem are quite high. As such, it seems that use of an aircraft would be
highly desirable for special, short-duration research studies but perhaps
not for daily operation. Specific recommendations for the use of aircraft
are given in Chapter XIV.
The collection of meteorological data by balloon techniques is re-
stricted to the more or less uncontrollable trajectory of the balloon.
This can be an advantage when studying Lagrangian or air parcel processes,
but it is a disadvantage when objective cross sections of Eulerian con-
ditions over the region are desired. Some flexibility is introduced in
the use of both rising and constant-level balloons, especially if it is
possible to simultaneously track several balloons of one or both types.
In this manner; one could observe the vertical structure of the atmo-
sphere at several locations (at the same time) while also observing the
nature of wind trajectories over the region at various altitudes and/or
geographical locales. Operating costs can differ widely among various
balloon systems and may thus be an advantage for one and a drawback of
another.
111-74
-------
The operational flexibility and expense of the proprietary CDC METRAC
system appear to be attractive features. The METRAC tracking system em-
ploys Doppler tracking techniques to determine a highly accurate three-
dimensional position of an inexpensive radio transmitter. This light-
weight transmitter, carried either on a rising or horizontally floating
small balloon, permits fine-scale measurements of the wind and as many
as four measurements from additional sensors on the balloon. After the
signal is received by a minimum of four portable ground stations, its
information is relayed by radio or landline communication to a central
data terminal. The data are then recorded for future use or processed
immediately by a small computer.
Primary METRAC advantages are low cost and high accuracy. Flight
packages are expendable, as in radiosondes, and the cost is comparable
or lower. Ground station costs are also much less than the usual in-
strumented towers, rawinsonde sounding system, or radar positioning
system. The master station is fully automated, and the only operator
requirement is starting the receivers before launch. Since data gen-
erated by the master station are formatted for direct computer process-
ing, no intermediate processing preparation is required. A small com-
puter can process an entire profile in less than five minutes. The high
accuracy in three-dimensional positioning permits detailed calculation
of resultant winds. This high resolution of data in time and space thus
enables the determination of small-scale features of vertical or hori-
zontal profiles.
Several other advantages are basic to the system. By using a net-
work of these systems, the inherent accuracy and range is limited only
by the boundary of the network. Thus, tracking over hundreds of kilo-
meters is possible as long as at least four receivers remain in radio
line-of-sight. Observations can be taken day or night in all weather
conditions. Simultaneous tracking of multiple balloons is possible with
special modification of the system. Finally, the flexibility provided
by the multisensor capability should not be underestimated. Simultaneous
point (single balloon) and gradient (multiple balloons) measurements of
wind, temperature, humidity, pressure, and net radiation can be obtained
at precisely determined locations.
The determination of space coordinates at any instant of time is
based on the system's ability to monitor differential Doppler shifts
between the received frequencies at the various ground-based receivers.
At each ground station, a receiver translates both the NBFM telemetry
information and its Doppler frequency shift from a radio frequency car-
rier to an audio frequency carrier signal that comes unmodulated from
the central data terminal, This data-carrying signal from each receiver
111-75
-------
is then transmitted to the central data terminal via a voice channel
communications link.
While a minimum of four ground stations is required, it is recom-
mended that seven stations, arranged in a hexagonal pattern with one
in the center, be used to provide some redundancy and thereby reduce the
vulnerability of the system to equipment failures or multipath and other
propagation effects. Use of seven stations allows the calculation of
35 coordinate positions for the mobile transmitter at any given instant.
Should propagation problems affect the signal at one ground station, a
total of 15 coordinate positions is available; while if the signals at
two of the ground stations are affected, a total of five coordinate
positions is still available.
At the data terminal, the signal from each ground station is sampled
a minimum of 50 times per second. This high rate is necessary to recover
the telemetry data even though the modulation deviation is low. Each
balloon-borne sensor is sampled once each second; however, 50 positions
per second may be computed if this fine a time scale is desired. Ordi-
narily, and especially in on-line computing, it is not desirable to ob-
tain position information at this rate, and digital filtering of the
data may be advantageous.
Indications are that the use of a six-balloon METRAC system could
provide six 15-second averages of vector winds every 15 seconds with a
resolution of better than 0.1 m/sec. Winds for a one-second average
(single balloon) can be resolved to 0.3 m/sec. Therefore, the system
is capable of resolving the vector velocity of the balloon to a degree
equal to or better than the representativeness of the balloon in de-
scribing the ambient wind field. Table 111-6 from the HMSO Handbook
of Meteorological Instruments (1961) is a comparison of alternate op-
tical and radio tracking techniques.
The ground-based receivers are housed in lightweight weatherproof
packages and can be mounted on a 10-foot pole that is used to support
the receiver antenna system. The pole itself is sectioned for easy
portability and is supported by a guy system that also functions as a
reflecting screen for the antenna. The antennas are simple and sta-
tionary, since the use of directional arrays is not required.
111-76
-------
Table I II-6
VECTOR ERROR OF WIND (m/sec) AT 5 km
AS A FUNCTION OF TRACKING SYSTEM AND
RATIO (Q) OF MEAN WIND TO ASCENT RATE
Q A B C D
-
1 0.5 0.5 0.5 1.0
2 0.5 1.0 1.0 2.0
3 0.5 2.0 1.5 3.6
4 1.0 3.6 2.5 5.1
5 1.0 5.6 3.6 7.1
A - Radar
B - Optical or radio-theodolite and
radiosonde height
C - Double theodolite or direction-
finder
D - Optical or radio-theodolite and
assumed ascent rate
Simultaneous tracking of more than one balloon requires equipment to
be added at both the receiver and data terminal sites in addition to the
use of separate transmitting frequencies for the mobile transmitters.
Each receiver will require an additional IF unit for each channel used
as well as a multiplex unit for the data link. A multiplex adapter will
also be needed at the data terminal unit in addition to either a high
speed incremental tape unit or a high speed data transmission link to a
computer.
Apart from the advantageous cost and high-resolution features of
METRAC, the flexibility of the system is particularly attractive. For
example, it would be extremely valuable to have the capability to collect
five or six vertical soundings simultaneously throughout the study region
at, for example, a one-hour periodicity during intensive model test pe-
riods or, say, four-to-six per day (perhaps at fewer locations) on a rou-
tine basis. The coincidental measurement of wind trajectories over the
111-77
-------
region would also provide necessary meteorological data. With a system
such as METRAC, both programs could be undertaken simultaneously, or per-
haps the vertical soundings could be interspersed in the horizontal track-
ing program.
Private communications with personnel at CDC have provided a tenta-
tive cost and time projection for implementation of an operational multi-
balloon, multisensor system. The basic system has been tested on a limited
basis, but an additional six-month preliminary design and test period is
required toward implementation as an operational system. This program
would evaluate and resolve design criteria for particular space and time
scales (resolution), available radio frequencies, and sensor requirements.
A projected estimate for the cost of this initial program is on the order
of $100,000 including hardware costs. At the end of the program, a final
decision could be made on the practical feasibility of incorporating the
system into RAPS. In the event the system did not satisfy its projections,
a more conventional system could be brought in with little or no tool-up
time required.
If METRAC does prove itself as a result of the test period, an addi-
tional outlay of about $250,000 would be necessary over the following year
to finalize software and station designs, fabricate the system, locate
and prepare the sites, and install the receivers. This cost is for a
multiple-balloon system; a single balloon system might save only 10%.
Hardware costs would be additional: central station, $50,000; slave
(remote) stations $1500 to $2000 each; small computer, $30,000 to $50,000.
For the St. Louis region, approximately 18 slave stations would be re-
quired to adequately track up to six packages simultaneously to a mini-
mum range of 150 km. Station hardware costs for a single-balloon system
would be approximately half of that.
In summary, the approximate total costs for the 18-month efforts for
single versus multiple-balloon systems are: (1) single-balloon tracking
capability for one central and six remote stations, including computer
and all design costs, is $395,000; and (2) six-balloon tracking capabil-
ity for one central and 18 remote stations, including computer and all
design costs, is $475,000.
As an example of the operating costs of an alternate system, the
NOAA radar-tracking tetroon system is estimated to cost in the neighbor-
hood of $100,000 for one month of intensive operation and subsequent data
processing. In fact, these data are not routinely available in real time
and require several to be fully processed. METRAC could be expected to
substantially reduce this operating cost to something on the order of
111-78
-------
$8000 (or less) per release location for the weighted manpower costs for
an intensive (round-the-clock) operation for one month; data processing
in real-time is included in the operation and costing schedule.
In summary. it is strongly recommended that the feasibility of a
system such as METRAC be explored for the routine collection of upper
level wind, temperature, humidity; and pressure data. Funding for upper
air measurements in the RAPS program has been based on the above listed
METRAC costs for the multiple-balloon tracking system.
Plume Dispersion Studies
The various aspects of the dispersion of a plume from a point source
should be studied within the framework of the regional program for a num-
ber of reasons. The most obvious reason is that the study of plume dis-
persion is an integral part of the small-scale or localized air quality
modeling and control program. Indeed, it is the large point source that
can have an overwhelming influence on the level of air quality of loca-
lized areas even though its effect on regional air quality may be mini-
mal. Careful treatment of the strength and location of the source, as
well as of the dispersion of the plume downwind, is required in the de-
velopment of regional emissions grids. Another important area for study
is the nature of long range plume dispersion, particularly from elevated
sources under stable atmospheric conditions or when a capping inversion
is present aloft. In these cases, the air quality of a given region may
be influenced severely by emissions from adjacent regions. As an example,
the characteristic reddish pall of Gary, Indiana, can sometimes be seen
at Madison, Wisconsin (about 250 km distant), under "favorable" atmo-
spheric conditions. Another ramification is the varied hue of the sun-
set on approaching the Northeast megalopolis from the sea.
Therefore, plume studies constitute a part of the Regional Study in
a number of ways: 0) through the evaluation of the impact of local
sources on both local and regional air quality observations and modeling,
(2) as basic or special studies directly concerned with the program of
detailed model evaluation, and (3) in determining the ramifications of
long range plume dispersion on regional air quality. Item (3) must not
of necessity be restricted to the St. Louis study region but would be
worthwhile in view of the wealth of additional data and special facili-
ties to be available there.
Plume-related studies may conveniently be classified into three
physically distinct areas, namely the physical processes related to the
initial behavior of the plume after it exits the stack, the transforma-
tion and removal processes affecting the pollutants, as well as their
1II-79
-------
transport and diffusion. Studies of the initial rise and dispersion of
the plume should seek to further verify the various available plume rise
formulations (Briggs, 1969) and to parameterize where necessary the
meteorological and engineering input requirements.
Three processes affecting initial plume behavior should be considered:
(1) rise of the plume relative to the ambient vector wind due to the initial
buoyancy and inertia of the efflux, as well as the effects of the release
of latent heat through plume condensation; (2) aerodynamic effects due to
nearby buildings and topographical features, in addition to effects of the
stack itself; and (3) diffusion by turbulence of the ambient air. Inten-
sive investigations on the nature of aerodynamic effects in general need
not be of concern to RAPS because of their extremely localized behavior
as in the case of structural effects; furthermore, these can be eliminated
with proper design before construction. Topographical (aerodynamic) ef-
fects may be of wider applicability, although the geography of the
St. Louis region may not permit or warrant research in this area. Briggs
(1969) suggests that additional effort be expended in defining the role
that atmospheric turbulence plays in the initial rise of the plume through
its effect on entrainment. Recent attention has been given to the role
that water vapor condensation plays in affecting plume buoyancy (e.g.,
Csanady, 1971, and Wigley, 1971); the effect may be significant in some
cases, since the latent heat released through condensation may on occa-
sion equal the sensible heat of the efflux. Additional research in the
way of special studies seems desirable in this area. Another area where
research may be warranted is defining the significance of radiative ef-
fects (both absorption of shortwave radiation and emission of longwave
radiation) on plume behavior. Transformation and removal process can
affect both the initial plume rise and subsequent concentrations down-
wind; their study within RAPS is discussed in Chapters IV and V.
Short and intermediate range studies of the dispersion of plumes
from elevated point sources fall partly within the scope of the tracer
programs discussed earlier in this chapter. An alternate program for
the study of plume behavior over the short to long range scales is
through the use of mobile, remote probing techniques. Two systems ap-
pear applicable, and they may be considered for both joint and in-
dependent usage; they are the correlation spectrometer and the lidar.
The former can provide data on the mass loading of a particular gas
in a vertical column, while the latter can give information on the
relative mass distribution of particles in one dimension with a single
" " .
shot and ln two or three dimensions by scanning and/or sweeping.
I II -80
-------
An experimental program should consider the use of more than one in-
strument of each type. One configuration would use a lidar and a correla-
tion spectrometer at each of two locations along the plume trajectory.
Cross-plume sections at the two ranges by the spectrometer would provide
data for the study of transformation and removal processes as a function
of time or distance. The data might also be useful for computing absolute
concentrations from the "relative" lidar returns. The lidar, in turn,
can provide information on the detailed structure of the plume cross
section, thereby permitting the evaluation of lateral and vertical dif-
fusive processes and also their dependence on height and lateral distance,
from the time-averaged returns. Maximum advantage can also be made from
the data available from the routine meteorological and air quality facil-
ity of the RAPS program. For example, a set of portable METRAC slave
stations should be used at the site to collect frequent vertical wind,
temperature, and humidity profiles at one or more points along the plume
trajectory. Additionally, a series of constant-level balloons should
be employed to document the mean wind trajectory and diffusion charac-
teristics at one or more heights (as dictated by the height of the plume
centerline). Furthermore, a helicopter-borne lidar system could be used
to study Lagrangian diffusion of the plume by following the tetroons.
Other possibilities for experimental design would incorporate, say, an
airborne lidar together with a surface-based system, and so forth; such
refinements would be a logical extension of the multiprobe experiment
outlined here.
Studies of Spatial Variabilities
In the analysis of the sensitivity of models, the objective is to
evaluate the response of the model output to variations in its input
parameters. For convenience, these variations have often been termed
errors and sometimes qualified as either random or systematic. In
practice, these "errors" may arise from a variety of sources: (1) in-
correct measurement or instrument error, (2) unrepresentative siting of
the sensors (such as too close to an obstruction for a wind measurement),
and (3) natural variability of the parameter over the region of interest.
Similar variations or errors can exist between an observed measure of air
quality and a value truly representative of conditions over a desired
area or volume. Therefore, a model with a I km2 spatial resolution re-
quires input data representative of conditions on this scale and, simi-
larly, representative air quality observations and/or the degree of
ambient variability with which its computations may effectively be veri-
fied. Some models, such as the SRI model described earlier, have at-
tempted to describe subgrid variations, but have only been successful
III-81
-------
because special representative measurements were made; in this case the
time-averaged subgrid spatial variations often exceeded the mean grid
value.
Therefore, it is recommended that a research task be delineated with
the objective of defining the spatial (on various scales according to the
simulation resolution that is required) variability of meteorological and
air quality conditions. Furthermore, the program should seek to explicitly
parameterize these variations on the basis of readily available physical
characteristics, such as the strength and distribution of emission sources,
atmospheric stability, wind speed, and the surface aerodynamic roughness
and zero-plane displacement height. Another objective of the program
should be to investigate simultaneously the analogous resolution required
for temporal considerations and the joint time-space criteria.
The hardware facility of the RAPS program has been designed to in-
vestigate these problems, among others, in addition to providing baseline
and routine model verification data. The basic grid of Class A meteoro-
logical and air quality (tower) stations, together with the objective
analysis techniques discussed earlier, will provide data for the eval-
uation of the significance of subregional scale features under various
weather types. Questions such as the parameter resolution that is re-
quired as a function of distance from a receptor can be answered, as
well as the applicability of the assumption of steady-state conditions
over particular averaging times. The upper air (balloon and aircraft)
programs will complement the surface facility for evaluation of the
significance of four-dimensional boundary layer structure toward making
predictions of ground level air quality or conditions, say, in the
"building height" zone.
Primary emphasis of the RAPS program, however, is on the simulation
and ultimate control of near-surface air quality. It is in this light
that the flexibility of the Class C, transportable station network will
be of extreme value in general and for the study of local variability
in particular. If it is assumed that, as an example, a one-kilometer
square represents the areal scale that is required for a particular ap-
plication, then a series of experiments should be designed as outlined
below. To summarize, the degree of variability of air quality over the
l-km square is controlled by three independent features: (1) the state
of the atmosphere, (2) the nature of the emissions field, and (3) geo-
graphical characteristics. In a controlled laboratory experiment, the
approach to solution of the problem would be to fix two of the three
features at any given time and to study the effects of variations of
the third, subsequently altering and repeating the scheme until the
I II-82
-------
effects of all combinations of features had been evaluated. Unfortunately,
the real world does not cooperate in providing these distinct combinations.
For a given region, geographical and emissions features are usually, and
for all practical purposes, fixed (not implying stationarity of emissions
sources). The third feature, the state of the atmosphere, does vary al-
though not always in a systematic or predictable fashion. Still, distinct
meteorological regimes (as described, for example, by the Pasquill-Gifford
stratifications) do exist and can be encountered throughout the year in
St. Louis. The general climatology for the region is discussed in Chap-
ter XV, while some specific data on the frequency of air pollution-potential
conditions are given in Chapter XI. Therefore, the emissions and geographi-
cal features of the St. Louis region must be examined on a l-km grid mesh,
and a number of squares selected that are representative of reasonably
distinct combinations of varied features. First, the geographical fea-
tures should be examined and stratified by their average values of aero-
dynamic roughness (zo) and, possibly, displacement height (d). For ex-
ample, combinations of Zo values for the ranges 0-10 cm, 10 cm-l m, and
> 1 m, and d values of 0-1 m, 1-5 m, and> 5 m might be chosen and would
result in nine geographical categories. Distribution of the emissions
may not be as straightforward and might follow in the first approxima-
tion simply by considerations of emission type (i.e., the type of pollu-
tant) and strength (say, moderate or strong). Thus for a given pollutant,
a possible total of 18 emission-geographic features may need to be studied
under the six stability categories. To evaluate all combinations would
be an endless and unnecessary task; priorities will be assigned by the
frequency and physical 'importance of the many types and only selected
combinations studied.
Having chosen the areas for study, the network of some 20 transpor-
table stations would be systematically deployed over the region to pro-
vide an objective analysis of spatial (subgrid) and temporal variations
of meteorological and air quality conditions. Each area would thus pro-
vide a statistical indication of the variabilities through stratification
by the atmospheric conditions. The length of time that a study might
require in each area will depend on the frequency of occurrence of the
weather types. The length of time will also depend on the time of the
year and to a lesser degree the local environment (i.e., rural or urban).
Data of this type can be obtained from the Environmental Data Service at
the National Climatic Center under the "Star Program," where the seasonal
and annual distribution of stability category (by wind direction) is tabu-
lated for five-year periods at various cities. These data should be ob-
tained for St. Louis (if available) and used to construct a reasonable
operational timetable for these (and other) experiments. However, a one-
to two-month minimum should be anticipated for each area.
1II-83
-------
REFERENCES
American Meteorological Society, Conference on Air Pollution Meteorology,
April 5-9, 1971, Raleigh, North Carolina
Belmont, A. D., Personal communication, Control Data Corporation, Research
Division, Minneapolis, Minnesota (1971)
Birnbaum M., et al., "Fluorescence Determination
N02'" paper presented at Joint Conference on
Alto, California, November 1971
of Atmospheric Pollutants,
Sensing Pollutants, Palo
Briggs, G. A., Plume Rise, U.S. Atomic Energy Commission, Division of Tech-
nical Information, 81 pp. and vi, 1969
Control Data Corporation, Minneapolis, Minnesota, private communication
(1971)
Corrsin, S., Outline of some topics in homogeneous turbulent flow,
J. Geophys. Res. 64(12), 1959, pp 2134-2150
Cramer, H. E., A practical method for estimating the dispersal of atmo-
spheric contaminants, Proceedings of 1st Nat'l. Conf. on Applied
Meteorology, pp. C33-C55, American Meteorological Society, Hartford,
Connecticut, 1957
Cressman, G. P., An operational objective analysis system, Monthly Weather
Review, 87 (10), 1959, pp. 367-374
Csanady, G. T., Bent-over vapour plumes, presented at conference on Air
Pollution Meteorology, April 5-9, 1971, Raleigh, North Carolina
Dabberdt, W. F., Wind and Turbulence Structure in the Boundary Layer
over the Antarctic Plateau, Ph.D. Dissertation, Met. Dept., U. Wis-
consin, Madison (1969)
Drummond, A. J. (ed), Precision Radiometry, Advances in Geophysics, Vol. 14,
Academic Press, New York and London, 1970
Edinger, J. G., Changes in the depth of the marine layer over the Los
Angeles Basin, J. of Meteorology, 16(3), 1959, pp. 219-226
111-84
-------
Edinger, J. G., and R. Helvey, The San Fernando convergence
Amer. Meteorological Society, 42(9), 1961, pp. 626-627
zone,
Bull.
Endlich, R. M., and R. L. Mancuso, 1968: Objective analysis of environ-
mental conditions associated with severe thunderstorms and tornadoes,
Monthly Weather Review, 96(6), pp. 342-350
Eschenroeder, A. Q. and J. R. Martinez, 1969: Mathematical Modeling of
Photochemical Smog, General Research Corp., Santa Barbara, California,
IMR 1210
Flowers, E., and J. Peterson, personal communication, Environmental Pro-
tection Agency, Research Triangle Park, North Carolj_na, 1971
Gifford, F. A., An outline of theories of diffusion in the lower
of the atmosphere, Meteorology and Atomic Energy: 1968, U.S.
Energy Commission, Division of Technical Information, 1968
layers
Atomic
, Use of routine observations for estimating atmospheric dis-
persion, Nuclear Safety, ~(4), 1961, pp. 47-51
Gifford, F. A., Jr., Atmospheric diffusion in an urban area. Paper pre-
sented at the 2nd IRPA Conference, Brighton, England, 1970
Gifford, F. A., Jr. and Steven R. Hanna,
Paper presented at'International Air
International Union of Air Pollution
Urban air pollution modeling.
Pollution Conference of the
Prevention Associations, 1970
Gerrity, J. P., A physical-numerical model for the prediction of synoptic-
scale low cloudiness, Monthly Weather Review, 95(5), 1967, pp. 261-
2~
Hadeen, Kenneth D., AFGWC boundary layer model. AFGWC Technical Memo-
randum 70-5. AFGWC Air Weather Service (MAC), Offutt AFB, Nebraska,
1970
Handbook of Meteorological Instruments, Instruments for upper air meas-
urements. London: Her Majesty's Stationery Office, M. O. 577, Air
Ministry, Meteorological Office, 1961
Hanna, Steven R.: Simple methods of calculating dispersion from urban
area sources. Presented at the Conference on Air Pollution Meteoro-
logy, Raleigh, North Carolina, sponsored by the American Meteorological
Society (April 1971)
111-85
-------
Hass, W. A., et al., Analysis of Low-Level Constant
(Tetroon) Flights over New York City, Quart. J.
93, 398, 483-493 (1967)
Volume Balloon
Roy Meteor. Soc.,
Hay, J. S., and F. Pasquill, 1959: Diffusion from a continuous source in
relation to the spectrum and scale of turbulence, Advances in Geo-
physics, Vol. 6, Academic Press, New York, 1959, pp. 345-365
Hilst, Glenn R., Sensitivities of Air Quality Prediction to Input Errors
and Uncertainties, Proceedings on Multiple-Source Urban Diffusion
Models, Editor: Arthur C. Stern, U.S. Environmental Protection
Agency, Air Pollution Control, Research Triangle Park, North Caro-
lina, 1970, pp. 8-1 to 8-40
Hilst, G. R., and N. E. Bowne, A Study of the Diffusion of Aerosols Re-
leased from Aerial Line Sources Upwind of an Urban Complex, Volumes I
and II, Final Report, IV 025001A 128, Travelers Research Center, Inc.
Hartford, Connecticut (1966)
Hilst, G., J. Yocum, and N. Bowne, The development of a simulation model
for air pollution over Connecticut, Vol. 1, Summary Report 7233-279a,
The Travelers Research Center, Inc., Hartford, Connecticut, 1967
Islitzer, N. F., and D. H. Slade, Diffusion and Transport Experiments,
Chapter 4, Meteorology and Atomic Energy 1968, U.S. Atomic Energy
Commission, Division of Technical Information, 1968
Johnson, W. B., et al., Field study for initial evaluation of an urban
diffusion model for carbon monoxide, Comprehensive Report, Coordi-
nating Research Council CAPA-3-68(1-69), Environmental Protection
Agency, Stanford Research Institute, Menlo Park, California,
215 pp and XXV, NTIS No. PB-203-469, 1971
Kerlin, James, AFGWC mesoscale
Memorandum 70-1, Air Force
Service (Mac), Offutt AFB,
prediction model. AFGWC Technical
Global Weather Central, Air Weather
Nebraska, 1970
Lamb, R., An Air Pollution Model of Los Angeles, Master's thesis, UCLA,
1968, 104 pp. and viii.
111-86
-------
Leighton, P. A., and R. B. Dittmar, Behavior of aerosol clouds within
cities, Joint Quarterly Report No.2, October-December 1952, Con-
tracts DA-18-064-cmc-1856 and DA-18-064-cml-2282, Stanford University
and Ralph M. Parsons Co., 100 pp., DDC No. AD 7261, 1952
, ibid., Joint Quarterly Report No.4, January-March 1953,
218 pp., DDC No. AD 31509, 1953
, ibid., Joint Quarterly Report No.4, April-June 1953,
196 pp., DDC No. AD 31508, 1953
, ibid., Joint Quarterly Report No.5, July-September,
238 pp., DDC No. AD 31507, 1953
, ibid., Joint Quarterly Report No.6, Vol. I, October-
December 1953, 246 pp., DDC No. AD 31510, 1953
, ibid., Joint Quarterly Report No.6, Vol. II, October-
December 1953, 187 pp., DDC No. AD 31511, 1953
Lettau, H. H., A new hypothesis for the relationship between eddy and
mean states, Physics of Fluids (Supplement 1967), S79-S83, 1967
, A new vorticity-transfer hypothesis of turbulence theory,
J. Atm. Sc., 21, 453-456, 1964
, Longitudinal Versus Lateral Eddy Length-Scale, J. Atm. Sc.,
23, 151-158, 1966
urban
Urban
, Physical and meteorological basis for mathematical models of
diffusion processes, presented at Symposium on Multiple-Source
Diffusion Models, Chapel Hill, North Carolina (October 1970)
, Shortwave Radiation Climatonomy, Tellus XXI, 1, pp. 1-14,
1969
, Synthetic Climatology, Berichte des Deutschen Wetterdienstes,
No. 38, Bad Kissingen, Germany, 1952
, Three-dimensional Turbulence in
Annual Reports 1966-1967, Contract No.
of Met., Univ. of Wis., 127-156, 1968
Unidirectional Mean Flow,
DA-AMC-28-043-66-G24, Dept.
111-87
-------
Ludwig, F. L., Urban air temperatures and their relation
meteorological measurements, January 1970 Meeting of
Heat., Refrig., and Vent. Eng., San Francisco, 1970
to extraurban
Amer. Soc.
, Urban Temperature Fields, presented at WMO Symposium on Urban
Climates and Building Climatology, Brussels, 15-25, October 1968
Ludwig, F. L., et al., A practical multipurpose urban diffusion model for
carbon monoxide, Final Report, Coordinating Research Council Contract
CAPA-3-68, National Air Pollution Control Administration Contract
CPA 22-69-64, Stanford Research Institute, Menlo Park, California,
184 pp., National Technical Information Service No. PB 196003, 1970
MacCracken, M.C., et al., Development of a multibox air pollution model
and initial verification for the San Francisco Bay area, presented
to 52nd Annual Meeting of American Meteorological Society, January 10-
13, New Orleans, Louisiana, 1970
Manabe, S., et al., Tropical circulation in a time-integration of a global
model of the atmosphere, J. Atm. Sc., 27(4), pp. 580-613
McElroy, James L. and Francis Pooler, Jr., St. Louis dispersion study
Volume II-analysis. Consumer Protection and Environmental Health
Service, National Air Pollution Control Administration, Arlington,
Virginia (1968)
ment
trol
, St. Louis Dispersion Study, Volumes I and II, U.S. Depart-
of Health, Education, and Welfare, National Air Pollution Con-
Administration, Arlington, Virginia, 1968
Meade, P. S., The effects of meteorological factors on the dispersion of
airborne material, Rassegna Internazionale Elettronica e Nucleare,
6 Rassegna, Rome, July 1959, Atti del Congresso SCientifico, Sezione,
Nucleare, 1959
Michael, A., The effects of wind and turbulence
dispersions, presented to Conference on Air
April 5-9, Raleigh, North Carolina, 1971
profiles upon atmospheric
Pollution Meteorology,
Moses, Harry, 1969: Mathematical urban air pollution models. ANL/ES-
RPY-001. Argonne National Laboratory, Argonne, Illinois, 1969
111-88
-------
Neiburger, M.,
pollution,
965
The role of meteorology in the study and control of air
Bull. Amer. Meteorol. Soc., Vol. 50, No. 12, 1969, pp. 957-
Pack, D. H., and J. K. Angell, A Preliminary Study of Air Trajectories in
the Los Angeles Basin as Derived from Tetroon Flights, Monthly Weather
Review, 91: 583-604, 1963
Pandolfo, J. P., et al., Prediction by numerical models of transport and
diffusion in an urban boundary layer, Final Report, Contract CPA 70-
62, Environmental Protection Agency; by The Center for the Environ-
ment and Man, Inc., Hartford, Connecticut, 1971
, The development of
planetary boundary layer.
Final Report, 1965
a numerical prediction model for the
U.S. Weather Bureau, Contract Cwb-l0960.
Pasquill, F., Atmospheric Diffusion, D. van Nostrand Co., London, 1962
Atmospheric dispersion of pollution, Quart. J. Roy.
Meteorol. Soc., Vol. 97, No. 414, 1971, pp. 369-395
, The estimation of the dispersion of windborne material,
Meteorological Magazine, 90 (1063), 1961, pp. 33-49
Pooler, F., 1966: A tracer study of dispersion over a city; J. Air
Poll. Contr. Assoc., 11 (1966), pp. 677-681
Roberts, John J., et al., An Urban Atmospheric Dispersion Model, Pro-
ceedings on Multiple-Source Urban Diffusion Models, Editor: Arthur C.
Stern, U.S. Environmental Protection Agency, Air Pollution Control,
Research Triangle Park, North Carolina, 1970, pp. 6-1 to 6-72
, An urban atmospheric dispersion model, presented at
Symposium on Multiple Source Urban Diffusion Models, Chapel
North Carolina (October 1969)
the
Hill,
Roth, P. M., et al., Development of a simulation model for estimating
ground level concentrations of photochemical pollutants, Final Report,
Contract CPA 70-148, Environmental Protection Agency, by Systems
Applications, Inc., Beverly Hills, California, 1971
111-89
-------
Sasaki, Y., A theoretical interpretation of anisotropically weighted
smoothing on the basis of numerical variational analysis, Monthly
Weather Review, 99(9), 1971, pp. 698-707
Seinfeld, J. H., Mathematical models of air quality control regions,
Development in Air Quality Standards, Charles E. Merrill, Columbus,
Ohio, 1970
Shieh, L. J., and P. K. Halpern, Numerical comparison of various model
representations for a continuous area source. G320-3293. IBM
Scientific Center, Palo Alto, California, 1971
Singer, Irving A. and Maynard E. Smith, Relation of gustiness to other
meteorological parameters. J. of Met., 10(2), 1953, pp. 121-126
Sklarew,
APCA
1970
R. C., A new approach: the grid model of urban air pollution,
Paper 70-79, Systems, Science and Software, La Jolla, California,
Slade, David (Editor), Meteorology and Atomic Energy 1968, U.S. Atomic
Energy Commission, Division of Technical Information, 445 pp, 1968
Smith, M. E., and I. A. Singer, An improved method of estimating
trations and related phenomena from a point source emission.
App. Met., 1966, ~~ pp. 631-639
conce-
J. of
Stephens, J. J., Variational initialization with the balance equation,
J. Applied Meteorology, 1970, ~(5), pp. 732-739
Stern, A. C. (ed.), Air Pollution, 2nd Edition, New York, Academic
Press, 1968
, Proceedings of the Symposium on Multiple-Source Urban
Diffusion Models, sponsored by National Air Pollution Control Ad-
ministration and the North Carolina Consortium on Air Pollution,
October 27-30, 1969, Chapel Hill, North Carolina, 1970
Summers, P. W., The seasonal; weekly, and
smoke content in central Montreal, J.
16, 1966, pp. 432-438
daily cycles of atmospheric
Air Poll. Control Assoc.,
111-90
-------
Sutton, O. G., Micrometeorology, McGraw-Hill Book Co., New York, 1953
Taylor, G. I., Diffusion by continuous movements, Proc. London Math. Soc.,
2(20), 1921, pp. 196-202
Wigley, T.M.L., Characteristics of Wet Plumes, presented at Conference on
Air Pollution Meteorology, April 5-9, Raleigh, North Carolina, 1971
World Meteorological Organization, Urban Climates, Technical Note No. 108,
WMO-No. 254. T.P. 141, Secretariat of the World Meteorological Orga.ni-
zation, Geneva, Switzerland (1970)
111-91
-------
Chapter IV
RESEARCH PLAN--ATMOSPHERIC CHEMISTRY
AND TRANSFORMATION PROCESSES
Introduction
The Regional Air Pollution Study (RAPS) provides an unparalleled
opportunity to study and improve the understanding of the chemical, phys-
ical, and biological processes that modify the concentrations of pollu-
tants in the atmosphere. Data on meteorological parameters and pollutant
concentrations will be provided not only by surface monitoring stations
but throughout the mixing layer through the use of airborne laboratories.
The long-term data acquisition within the RAPS will provide information
on the variations of pollutant concentrations and meteorological phenomena
as a function of hourly, diurnal, and seasonal changes. These data, in
conjunction with an emission inventory to identify and quantify the emitted
pollutants, will provide the requisite information on which to base studies
of atmospheric pollutant cycles.
These studies of atmospheric pollutant cycles will cover the trans-
port, transformation, and scavenging processes that modify the pollutant
burden of the atmosphere. The characterization of these processes can
provide the information necessary to verify and evaluate the capability
of mathematical simulation models to predict the transport, diffusion,
and concentrations of reactive pollutants over a region of interest.
Atmospheric cycles of most, if not all, pollutants are poorly understood,
and thus sufficient information should be generated within the RAPS to
develop more satisfactory simulation models.
A more complete understanding of pollutants, reaction products, re-
action intermediates, and scavenging mechanisms could define significant
factors basic to the design of control strategies, abatement procedures.
urban planning, and land use.
The Atmospheric Chemistry program will study the atmospheric cycles
of pollutants for which air quality criteria have been issued as well as
of those whose role is less well understood. Six major categories of pol-
lutants will be considered in detail in this program: sulfur oxides,
nitrogen oxides, hydrocarbons, particulate matter, photochemical oxidants,
and carbon monoxide. Many of these pollutant categories are so interrelated
IV-I
-------
and interreactive that a clearcut separation between them in either dis-
cussion or study is not possible or desirable. The study of particulate
material--composition, size distribution, and concentration--is of par-
ticular importance as the formation of particulate material is an im-
portant scavenging mechanism for many pollutants. The studies of inter-
reactions of hydrocarbons, nitrogen oxides, and photochemical oxidants
must be integrated to characterize photochemical activity in the atmo-
sphere. The role that precipitation plays in the removal of both gaseous
and particulate material will be studied within the Atmospheric Chemistry
program. The information on air quality and meteorological parameters
acquired from the RAPS monitoring network will be integrated with a large
number of research projects specifically directed toward acquiring infor-
mation on pollutant modification within the atmosphere.
The Atmospheric Chemistry program will be initiated in late 1972
and will continue through 1978. In the latter years of the RAPS, the
program will be expanded to include specific projects directed toward
the concentration and cycles of the more toxic trace constituents of at-
mosphere, such as mercury, cadmium, beryllium, vanadium, asbestos, and
polynuclear aromatic hydrocarbons. Also scheduled for the latter years
would be studies concerned with atmospheric odors and stable isotope
analyses of carbon monoxide and sulfates to indicate origin. Several
instrument developments including sulfate, nitrate, and hydrocarbon
analyzers would greatly aid the development of this chemical program.
The S02 Cycle
The sulfur compounds found in polluted urban atmospheres--H2S, S02,
and H2S04' or sulfate aerosols--constitute a noxious series of compounds.
Both H2S and S02 have an unpleasant odor; H2S is detectable at levels in
the ppb range; S02 is detectable at ppm levels; both are toxic at higher
concentrations. Sulfur compound aerosol particles can contribute to a
reduction in visibility--a primary manifestation of smog in urban atmo-
spheres--and have also been linked to adverse health effects.
Recognizing the adverse effects of gaseous and particulate sulfur
compounds in community atmospheres, the EPA has recommended a number of
air quality standards, including a limit of 0.14 ppm S02 over a 24-hour
period to be reached no more than once a year as the maximum permissible
S02 ambient atmospheric concentration level. Other standards deal with
atmospheric particles, and some local areas have adopted H2S regulations.
Since the EPA S02 recommendation has been issued, increasing criticism
of the regulation has been raised based on the large capital investment
required to meet the emission standards. One response could be more
IV-2
-------
flexible control strategy to ease the burden on emission sources and yet
meet the necessity of the populace for cleaner air.
Sulfur dioxide is one of the major urban pollutant emissions. Coal
and fuel oil contain significant amounts of sulfur, which is oxidized to
S02 during combustion. Since the concentrations within the effluent
streams are fairly low, it is difficult to remove the S02 either effi-
ciently or economically. Another source of the S02 found in the atmo-
sphere is the reaction of H2S (from either pollutant or natural sources)
and 03.
Existing models of the transport of S02 account for its loss or
scavenging by the application of a simple half-life factor. However,
this factor cannot be accurately determined from existing data, and it
appears to be strongly dependent on ambient atmospheric variables such
as relative humidity (RH). Improvement in models to predict the disper-
sion of S02 will depend on determining which reaction processes actually
contribute to changes in atmospheric S02 concentrations and the effects
of atmospheric parameters. These reactions are summarized in Table IV-1.
Therefore, to better define the S02 transformation processes, H2S, S02'
03' N02' NH3' hydrocarbons (HC), relative humidity, and solar radiation
should be measured regularly. Prior to the measurement program, the
point sources of S02 emissions (such as power plants) should be located
and estimates of the vegetation characteristics should be made. A pro-
gram to measure the average distribution of sulfate in the aerosols as
a function of particle ,size must be established. At the same time, an
empirical correlation between the nephelometer and particulate mass load-
ing data from the monitoring network and the aerosol particle size-
distribution and total mass should be made. Several laboratory programs
to establish clearly some of the reactions and inaction rates still in
question are also necessary. Development of a field instrument for rapid
determination of sulfate concentrations in aerosols should be encouraged.
Emission Sources of Sulfur Compounds
The largest source of H2S is the background emissions due to the
natural anerobic decay processes of organic materials. Robinson and
Robbins (1968) have estimated that the worldwide background emissions
will be 100 X 106 tons with an average concentration of about 0.2 ppb
over land regions. However, the estimates of the total emissions of
H2S have been calculated by difference based on the additional sulfur-
containing sources necessary to balance the overall sulfur cycle. The
major sources of industrial H2S emissions are primarily kraft paper mills
and oil refineries. Community sources include sewage treatment plants.
IV-3
-------
Table IV-l
CHEMICAL REACTION8 OF IMPORTANCE TO THE 802-CYCLE
Reaction
Required Validation Data
H 8 + ° '80 + H °
2 3 surface 2 2
80 , H 8, ° , aerosol
223
particle surface area
80 ~80
2 ° 3
2
= *
802' 804 light intensity
hv
N02 + HC + 802 - products + 803
N02' reactive HC,t 804
=
=
8°2 + °2 catalyst' 8°3
RH, catalyst con en. , 804
NH , rain
3
80 + ° , 80
2 2 or fog 3
=
NH3' weather, 804
*
In each case, where 803 is a product it rapidly and irreversibly
reacts with water to form H2804' which in turn forms a sulfate-
containing aerosol.
Determination of the relative importance of this reaction awaits
further laboratory experimentation.
t
IV-4
-------
There are no paper mills in St. Louis, and the refineries in Wood River,
Illinois, will probably be the only significant sources of H2S in the
area. Information from the Emissions Inventory will clarify this point.
In areas not directly downwind from identified sources, the levels of
H2S should be at or below the background levels measured upwind of st.
Louis.
The source of the background concentration of S02 (about 0.2 ppb)
may be attributed entirely to the oxidation of H2S by 03 (Robinson and
Robbins, 1968). The overwhelming majority of S02 emissions is related
to human activities, predominantly the combustion of coal and fuel oil
in power plants and heating units, smelting operations, and petroleum
refining.
The S02 air monitoring data, collected at the CAMP station in st.
Louis, showed that the annual 24-hour maximum concentration of S02 ranged
from 0.18 to 0.24 ppm between 1962-67 (USDHEW, 1969 b). The S02 sources
in st. Louis can be divided into two general categories: emissions from
combustion of coal and fuel oil for heating purposes, in relatively small
installations but spread over a large area, and point sources such as
manufacturing and power plants that are superimposed on the relatively
homogeneous smaller sources.
Sulfate-containing aerosols are found in stack plumes in the presence
of S02 emissions. While there may be some low concentrations of sulfate
minerals in the fuel, the majority of this sulfate is a secondary emis-
sion, formed by catalytic oxidation of S02 in the stack plume. While
sulfate-containing aerosols from evaporated sea spray are substantial
contributors to the global sulfur cycle, they should be relatively unim-
portant in the st. Louis area because it is so far inland.
Chemical Reactions of Importance to the S02-Cycle Model
The chemical reactions of importance to the development of a S02-
cycle model can be divided into two categories: the oxidation of H2S by
03 and the oxidation of S02 to S03 which is then rapidly converted to
H2S04 by water. The latter oxidation reaction can occur via several
pathways, including direct photooxidation of S02' oxidation of S02 in
the presence of the N02-HC photooxidation system, and catalytic oxida-
tion in stack plumes, aerosol particles, and rain or mist droplets.
Robbins (1961) found that in the presence of 03' H2S was oxidized
to S02' It was later shown by Cadle and Ledford (1966) that the reaction
was at least partially heterogeneous. with a rate proportional to the
IV-5
-------
square root of the surface area in the
so sensitive to surface catalysis that
not be measured.
reaction vessel. The reaction is
the homogeneous reaction rate could
The complex mechanisms of the oxidation of S02 to S03 have recently
been critically reviewed by Bufalini (1971). The problem may be divided
into three general categories: photooxidation of S02; oxidation of S02
in the presence of light, N02' and HC; and catalytic oxidation by metal
ions.
Numerous authors have studied the photooxidation of S02 in the pres-
ence of 02' The major product was S03, which is rapidly hydrolyzed to
H2S04 (Bufalini, 1971). Experimental values of the quantum yield for
S02 disappearance range from 0.02 to 0.22 depending on the RH and the
02 concentration. Several authors have predicted that 03 may be a photo-
product but this is not supported by more recent results (Sethi, 1971).
When N02 is added to the reaction mixture, reactions of NO and N02
with S02, S03' and the proposed intermediates--SO and S04--must all be
considered (Bufalini, 1971). When reactive HC are added to the mixture
and the effect of changing RH is considered, the reaction sequence be-
comes hopelessly complex.
Gerhard and Johnstone (1955) found no effect of added N02(1-2 ppm)
on the photooxidation of S02 (10-20 ppm). In contrast, Renzetti and
Doyle (1960) found increased aerosol production in a reaction mixture
of 0.14 ppm S02 when 1 ppm N02 was added. Several other equally conflict-
ing results are reviewed by Bufalini (1971). In general, enhanced con-
version of S02 to S03 in the presence of N02 was predicted.
In the presence of reactive HC to form an S02-N02-HC system photo-
chemical aerosols containing organic materials, H2S04, and water are
formed. Renzetti and Doyle's data indicate a definite increase in the
loss rate of S02 over the S02-02 system in absence of HC and N02' In
laboratory experiments where the aerosol formed was subjected to chemical
analysis, sulfate was found in the collected aerosol when S02 was present
at the start of the run (Endow et al., 1963).
Prager et al. (1960) and Harkins and Nicksic (1965) observed that
in static smog chamber experiments with mixtures of propylene, NO, and
S02' aerosol formation began after the conversion of NO to N02 was com-
plete. Subsequent data by Wilson and Levy (1968) and from SRI labora-
tories confirmed these results. Therefore, NO can be ruled out as a
participant in the aerosol formation mechanism. Extension of these re-
sults to the S02 simulation model may be difficult for two reasons.
IV-6
-------
First, in these laboratory experiments S02 is lost slowly before the N02
maximum is reached; the rate increases after the N02 maximum (Wilson and
Levy, 1968). We suspect that reactions of S02 on the walls of the cham-
bers may be of considerable importance in smog chamber experiments, es-
pecially at high RH. It is difficult to separate such losses from losses
due to photochemical reactions. Second, since the environment is a dy-
namic system where NO, N02, and 03 all coexist in substantial quantities,
extension of qualitative observations from static runs, except where
specific rate constants have been obtained, will be difficult.
There are indications that intermediates in the 03-HC reactions
(the 03 is formed during the N02-NO-HC photooxidation sequence) also
oxidize 802' While the S02-03 reaction is very slow (Cadle, 1956; Dun-
ham, 1960), Harkins and Nicksic (1965) observed that oxidation of S02
occurred in the dark in the presence of 03 and HC. The reactive inter-
mediates may be alkoxyl, peroxyalkyl, or peroxyacyl radicals formed dur-
ing the 03-HC reactions. Although such reactions may be important during
the day when relatively high concentrations of 03 and free radicals are
present, it should slow down after sunset and under other conditions when
the 03 concentration also decreases.
The catalytic oxidation of 802 by 02 has been studied under a vari-
ety of conditions. Drone et al. (1968) found that the oxidation was very
rapid in the presence of dry powdered metal oxides (aluminum, calcium,
chromium, iron, lead, and vanadium). Similar results were obtained with
metallic submicron particles of aluminum, iron, lead, and platinum, formed
from exploding wires (Smith et al., 1969), and from particles supported
on Teflon beads (Cheng, et al., 1971).
Junge and Ryan (1958) and Johnstone and Coughanowr (1958) found that
manganese salts were most active in catalyzing the oxidation of 802 to
sulfates in aqueous solution, although other salts, such as FeC13' were
tested. It was found that the reaction was even faster in the presence
of NH3 (McKay, 1971). When NH3 dissolves in the droplet, it raises the
pH and neutralizes the acid formed in the droplet by the H803 and S04
salts. The solubility of 802 is thereby raised, and as the concentra-
tion of 802 increases in the droplet, so does its rate of oxidation. It
was estimated that a cloud of droplets (fog, clouds, and the like) of
10-~m radius produce 10-11 g (NH4)2804 per hour per drop, resulting in
an S02 lifetime of about one hour under realistic urban conditions (Robin-
son and Robbins, 1968).
One may observe that most 802 emissions do not occur under foggy
conditions. However, much of the S02 is emitted in power plant stack
plumes, where the water vapor produced during the combustion of the fuel
condenses as the stack gases cool and may persist as droplets for a
IV-7
-------
considerable time. Gartrell and coworkers (1963) have studied the 802:
sulfate ratio in TVA power plant plumes using heliocopter transects at
successive distances downwind of the stack. Conversion rates of 802 to
sulfate as high as 2% per min were observed.
We have hinted at a number of interesting questions that remain un-
answered about the numerous possible reaction pathways for conversion of
S02 to sulfate. For the purposes of this Prospectus, the overriding
problem is to devise experiments that will distinguish between the dif-
ferent processes and then to compare their relative rates. Robinson and
Robbins concluded that in the daytime and at low RH (below 70%), the
photochemical reactions of S02 and N02 with 02 and HC will be of primary
importance. In this case the 802 will be converted into essentially an
H2S04 aerosol. In the daytime when the RH is between 70 and 100%, the
aerosols will absorb substantial quantities of water and the aerosol size
distribution should shift to larger sizes. Although the photochemical
mechanisms will still obtain, the rate of 802 conversion should be in-
creased via the solution oxidation mechanism, catalyzed by metal salts
present as nuclei or in stack plumes and aided by ammonia absorption, as
discussed above. In the presence of fog or rain, the volume of condensed
water greatly increases. The solution oxidation mechanism of 802 in the
droplets should then prevail.
Removal Mechanisms for Sulfur Compounds
,
To complete the formulation of any simulation model for sulfur com-
pound emissions, the mechanisms for the removal of sulfur compounds from
the atmosphere must be included. These mechanisms may be divided into
two general classes: (1) absorption of 802 by vegetation and (2) coagu-
lation, sedimentation, impaction, and precipitation scavenging of sulfate-
containing aerosol particles.
Vegetation absorbs 802' and damage to the plants can occur at higher
802 concentrations. The rate of absorption is a complex function of plant
growth factors including the weather and time of day. Katz and Ledingham
(1939) exposed field-grown alfalfa to S02 concentrations between 0.8 and
1.0 ppm. In full sun, S02 was rapidly absorbed; the absorption rate
dropped to 20% of the full sun value when the plants were fully shaded
and to below 5% at night. Chamberlain (1960) used the concept of a de-
position velocity, Vg' in an attempt to quantify the loss rate. He ob-
tained values for Vg between 0.3-0.7 cm/sec for grass. Robinson and
Robbins (1968) calculated a value of 1.3 cm/sec for alfalfa using Katz's
data. We suggest that a value of 1.0 cm/sec is reasonable for full sun-
light, 0.2 cm/sec for full shade, and 0.05 cm/sec for the nighttime rate.
IV-8
-------
Hill (1971) has studied the absorption
controlled envi.ronmental chamber. The
17 ~£ min-1 m-2 pphm-1.
of S02 by alfalfa in a carefully
absorption rate was expressed as
The nature and concentration of the inorganic ions in the droplets
and the RH determine the size of an individual aerosol particle. The
smaller particles remain suspended due to the molecular motions of the
air molecules. As S03 or H2S04 is absorbed by the aerosol droplets, the
droplet grows in size because its equilibrium vapor pressure is reduced.
Aerosol particles also grow by coagulation if two particles collide and
stick together. Aerosols will grow by a combination of these two mecha-
nisms, depending on atmospheric conditions, until they become so large
that gravitational forces cause them to settle out. Particles also are
removed by impaction onto fog and rain droplets. Under these conditions,
analysis of precipitation samples as well as hi-vol samples would be
necessary to account for all of the particulate matter.
The Research Program
The Emissions Inventory will locate and describe the important pri-
mary sources of H2S and S02 emissions. Additional data should not be
required.
Data from the ground level air quality monitoring stations will be
used along with the Emissions Inventory data to calculate the incoming
and outgoing flux of S02 in the st. Louis area. It would be useful to
supplement these calculations with airborne S02 measurements. Barringer
(Moffat, Robbins, and Barringer, 1971) has developed a technique of "cor-
relation spectrometry" which could conveniently provide the required data
If the natural sunlight and skylight are used as the light source, the
total amount of S02 between an aircraft-mounted monitor and the ground
or above a given surface point could be determined. By flying or driving
a series of transects upwind and downwind of st. Louis, the crosswind
profiles of S02 could be obtained. From these data plus the wind veloc-
ity, the S02 fluxes as a function of travel time could be calculated.
Such information would be of great value in the verification of the
S02-cycle simulation model.
A field program to assess the importance of the reaction between
H2S and 03' which yields S02, should be part of the Research Program.
The change in the concentration of H2S and 03 as an air mass passes
through st. Louis will be monitored by the monitoring network stations.
However, a surface is required to catalyze the reaction. Atmospheric
aerosols provide the largest surface in a polluted atmosphere (rather
IV-9
-------
than the buildings or ground). Therefore, the total area of the surfaces
present in the air mass due to the aerosols therein must be calculated.
The area will depend both on the particle size distribution and the total
numbers of particles at various times during the day. We recommend that
a preliminary program, utilizing various types of particle counters
(electric-mobility; nuclei counters, and photometric counters), be estab-
lished to develop an algorithm for calculating the total surface area
using the nephelometer data from the air quality network. If one assumes
the size distribution determined by Junge (1963) for an "average aged con-
tinental aerosol," the problem is greatly simplified. However, it will
still be necessary to relate the nephelometer readings to the total number
of particles and to the aerosol size distribution. As is discussed later
in this section, knowledge of the aerosol size distribution is also essen-
tial for model verification.
Currently there is no chemical model for the S02 cycle. One reason
for this is that there is insufficient laboratory data currently avail-
able to permit one to write a reasonable reaction scheme. Although there
is no doubt that appreciable quantities of S03 can be produced by the
photooxidation of S02 in the presence of 02' numerous questions remain
unanswered, such as quantum yields, the effect of RH, the possible for-
mation of 03 in the reaction, and the effect of wavelength and light in-
tensity on the course of the oxidation. The importance of S02 photooxi-
dation in the presence of N02 and HC has not been adequately studied.
We concur with Bufalini's recommendation (Bufalini, 1971) that the effect
of the S02:N02 ratio over a wide range of concentrations should be evalu-
ated. Better laboratory determinations of the rate constants in the oxi-
dation mechanisms are needed, as is better data on aerosol formation and
the effect of water vapor.
The effect of water vapor on the yield of photochemical aerosol is
well documented. However, this effect arises in part because the aerosol
size-distribution shifts towards larger sizes as RH increases. Since par-
ticles in the 0.3 to 1.0 ~ range scatter light more effectively than
smaller particles, and since in most experiments the yield of aerosol
particles is determined by light scattering devices, the apparent yield
of aerosol particles increases dramatically as RH increases. Laboratory
experiments designed to separate the effect of RH on aerosol size and
S02 conversion rates should be carried out.
Judging by the current literature and the research grants issued to
laboratories at Ohio State University, the Pennsylvania State University
and University of California at Riverside, these answers may be available
before the start of this program. If not, programs designed to obtain
them should be established as soon as possible, because they must be
answered before a chemically correct simulation model can be written.
IV-IO
-------
To the best of our knowledge, no one has attempted to measure the
catalytic oxidation rate of 802 on particles produced photochemically
in a mixture of N02' HC, and 802' or in the presence of trace metal salt
nuclei and (or) ammonia. There is evidence that above 70% RH, most aero-
sols absorb water, which is accompanied by a shift in the aerosol size
distribution toward larger sizes. Under these conditions, the effect of
NH3 in increasing the solubility of 802 in the aqueous droplet may be
very important in determining the overall reaction rate. Research into
this question should be encouraged.
Before the absorption of 802 by vegetation can be included in a
simulation model, information on the type and distribution of vegetation
in the 8t. Louis area will be needed. We recommend that the 8t. Louis
region be divided into subregions of similar vegetation types. The sur-
face area of vegetation within each subregion should be estimated so that
this concept can be considered for inclusion in the simulation model.
The appropriate data can probably be collected rather simply but the
final solution of the scavenging process may require a major research
effort. The goal would be to use the value for the plant surface area
within the region, plus the concentration of 802 from the monitoring
stations, to estimate the ratio of loss of 802 by vegetation absorption
per unit area within the subregion. However, lack of precision in the
various measurements may prevent conclusive results.
A complete simula~ion model for 802 will predict both the aerosol
size distribution and the 804= concentration in the aerosol. As was
discussed above, the aerosol size-distribution can be determined from
data obtained by a combination of an electric-mobility and photometric
counters and an Andersen cascade impactor. The distribution of 804= as
a function of aerosol particle size can be determined by chemical analy-
sis of the Andersen impactor samples. 8ince the contribution of the sub-
micron particle « 0.1 ~m) to the total aerosol mass is small, determina-
tion of 804= in these particles is of less importance.
We recommend that five sites for the aerosol research program be
selected, one upwind, two near the center of 8t. Louis, and two about
75-100 km downwind. It is recommended that periodic measurements for
1-2 weeks at regular intervals be made, starting January 1974. Chemical
analyses should be performed as soon after collection as possible. These
samples should also be analyzed for nitrate and perhaps HC to provide
data for other research programs. Continuous measurement would mean that
the number of samples for wet chemical analysis would quickly reach tre-
mendous proportions (six samples per site per measurement) and would be
accompanied by a large volume of numerical data from the particle coun-
ters. Therefore the selected time periods are suggested.
IV-II
-------
An instrument which would report automatically concentrations of
either total sulfur or S04= content of aerosol particles for storage in
the main data bank would be extremely useful for model verificati~n.
Furthermore, it would save considerable amounts of time since S04 de-
terminations on hi-vol samples would not be required. Development of
such an instrument should be encouraged early in the RAPS. Installation
in selected monitoring stations would be highly desirable.
Studies of the stable isotope ratio (S32/S34) within the latter years
of the RAPS could give information about the origin of atmospheric sulfur
compounds. In general, the tendency is for enrichment of S34 in inorganic
processes with enrichment of S32 in biological processes. The isotope
ratio and changes in ratio are more or less analogous to the behavior of
the stable carbon isotopes and could provide information to differentiate
natural atmospheric sulfur constituents from urban emission sources.
Measurement of the deposition velocity
particles will be discussed below under the
Cycle.
of sulfate-containing aerosol
heading, The Particulate
The Photochemical Cycle--Hydrocarbons:Nitrogen Oxides:Oxidant
The most important photochemical reactions in polluted atmospheres
are initiated by photodissociation of N02 to give NO and an oxygen atom.
The ensuing chain reaction with oxygen and hydrocarbons (HC) forms prod-
ucts that cause many of the harmful effects related to smog, including
formation of 03' PAN, formaldehyde, and aerosols. To help regional con-
trol districts meet the Air Quality Criteria for HC and nitrogen oxides
(NOx) , urban simulation models that include formation, dispersal, and
losses of HC and NOx will be written.
The major deficiency in existing meteorological models is that they
do not include terms that adequately represent environmental chemistry.
Before these terms can be included, the relative rates of competing re-
actions must be considered. One can conceive of separate simulation
models for HC and NOx' based solely on formation and loss processes.
However, inclusion of the chemical reactions would make this virtually
impossible since the reactions of NO and HC are intimately related.
Therefore, we have chosen to discuss them in the same chapter.
The major natural source of nonmethane or generally reactive HC is
vegetation, such as coniferous forests and farmland. Nitric oxide is
produced by anerobic reduction of nitrates by soil bacteria. However,
combustion sources such as power plants, automobiles, and space heaters
IV-12
-------
emit most of the HC and NOx found in the urban environment.
will be identified during the Emissions Inventory.
These sources
In the absence of HC but in the presence of sunlight, an equilibrium
between NO, NOZ' and 03 is established which can be summarized as
NOZ + 0z
hV "-
NO + 03
'"
When reactive HC are added, the O-atom (produced by photodissociation of
NOZ) and 03 attack on the HC is fast enough to perturb that equilibrium.
During the reactions, NO is converted to NOZ' HC are consumed, and 03'
PAN, formaldehyde, and other products are formed.
The most important loss mechanism for both HC and NOx is aerosol
formation in the following sequences:
HC
+ NO
Z
h\)
.. polymer
NH
3
~ NH4N03 in aerosols
NOZ +
°
3
The aerosol is ultimately removed by sedimentation or precipitation.
importance of absorption of NOZ and certain HC by plants must also be
evaluated.
The
Validation of simulation models for HC:NOx reactions will require a
variety of data. Real time measurement of NO, NOZ' 03' RH, and light in-
tensity will be carried out in monitoring stations throughout the RAPS
system. Additional data required by existing models include a simple
breakdown of the HC distribution into two or three reactivity classes
and the concentration of products such as formaldehyde, total aldehydes,
and PAN. The program for determining the HC distribution should be di-
vided into three phases. The first would involve construction of a HC
classification instrument for installation in a number of monitoring
stations. These instruments could be based on selective absorption of
olefins and aromatics prior to detection by a total HC analyzer. The
second phase would be the determination of the detailed HC distribution
by gas chromatography at five sites, and use of a coupled gas chromatograph-
mass spectrometer to determine organic materials including the oxygenated
compounds at selected intervals during the RAPS. Formaldehyde and total
aldehydes will be measured during the HC gas chromatography program. The
IV -13
-------
determination of PAN by either long-path infrared or electron capture gas
chromatography would not be considered a routine analysis at the concen-
trations anticipated in the st. Louis area. The infrared instrumentation
is expensive and of limited sensitivity. The gas chromatographic method
is difficult and requires very skilled technicians to perform satisfac-
tory analysis. In either case, analysis of PAN using current state-of-
the-art instrumentation would be expensive. Unless a need for PAN con-
centration data exists within a particular research project or program,
the cost-to-benefit ratio would probably preclude routine determination
of PAN in the RAPS program. Improvements in the state of the art for
PAN analysis may occur during the span of the RAPS program; however, it
probably would remain a research task rather than a technique suitable
for routine analysis.
Sources of Nitrogen Oxides
The most plentiful nitrogen oxide, N20 (the average background level
is about 0.25 ppm) is produced by biological action of soil bacteria on
nitrogen compounds. Other processes taking place in the soil are apparent
sinks for N20.
The major natural source of nitric oxide, NO, is anerobic reduction
of nitrates by soil bacteria. Robinson and Robbins (1968) estimated mean
NO values of 2 ppb over land areas and 0.2 ppb over polar and ocean re-
gions. In urban areas 'the pollution sources, mainly from combustion
processes, give concentrations far above the background levels. For in-
stance between 1964 and 1968 the maximum average NO concentration in st.
Louis over a 5-min interval was 0.44-0.84 ppm (USDHEW, 1970a). The lo-
cation and emission level of NO sources in the st. Louis area will be
determined as part of the Emissions Survey. Major point sources will be
power plants and industries. Area sources will include domestic heating
and cooking units and automobiles. Urban area NOx sources are typically
more-or-less evenly divided between stationary and mobile sources.
Natural emissions of N02 appear to be unimportant. Major pollution
sources will be the same as NO, but the maximum average N02 concentration
in st. Louis over a 5-min interval ranged from 0.17 to 0.31 ppm between
1964 and 1968 (USDHEW, 1970a). The majority of the N02 is not from pri-
mary sources, but from oxidation of NO by either 02 in stack plumes or
by photochemical or natural 03'
Significant concentrations of nitrate are found by chemical analysis
of particulate matter collected in polluted atmospheres. However, primary
sources of nitrate-containing particles have not been identified, although
IV-14
-------
nitric acid is emitted in small quantities by sulfuric acid plants. The
probable sources of nitrate particles will be located during the Emissions
Survey. The nitrate is most likely found in secondary particles, formed
by oxidation of N02 by 03 to give nitric acid which is subsequently neu-
tralized by ammonia.
Ammonia is not a nitrogen oxide, but it plays a special role in aero-
sol formation reactions. The major natural source is bacterial breakdown
of amino acids in the soil. Since NH3 is also a weak base, the emission
level is pH dependent. Average background concentrations of NH: in aero-
sols are 3-10 ~g/m3, and vary considerably by locality. Combustion proc-
esses may be minor sources of ammonia in urban areas.
Reactions of Nitrogen Oxides in the Absence of Hydrocarbons
In this section we shall consider the reactions of NOx in the absence
of HC. We shall consider reactions with 03 here, even though the 03 is
formed in significant concentrations by photolysis of N02 in the presence
of HC.
In the troposphere, N20 is essentially an inert compound. In the
stratosphere, photodissociation can occur, but radiation of wavelengths
below 2500 A, which never penetrates the troposphere, is required (Bates
and Hays, 1967). These reactions need not be considered further.
The oxidation of NO by 02 is possible but very slow at representa-
tive NO concentrations in urban atmospheres. Reactions of NO and N02
with 03 have been studied in great detail (Johnston and Crosby, 1954;
Ford, et al., 1957). The reaction
NO + °
3
~
N02 + 02
is the primary conversion mechanism of NO to N02 in both remote and urban
atmospheres. The rate constant is high and in static smog chamber experi-
ments, measurable yields of 03 do not appear until all of the NO has been
consumed.
The photolysis of N02 to give NO and an O-atom, which occurs during
the daylight hours, is the single most important reaction occurring in
polluted atmospheres. The O-atom reacts with 02 to give 03' which in
turn oxidizes the NO to N02'
IV-l5
-------
NO
2
hv
~ NO + °
° + °
2
°
3
° + NO
3
~
N02
In the absence of HC, an equilibrium is rapidly set up and
N02 + 02
hV
~
~
NO + °
3
as long as HC are absent, little else would happen. The chain reaction
which occurs in the presence of HC is discussed in a later section.
The reaction of N02 with 03 is about 500 times slower than the oxi-
dation of NO. However, this is sufficient to provide an important loss
mechanism for N02. The equilibrium reaction of N03 with N02 is estab-
lished very rapidly. but has not been studied quantitatively. Since
N205 reacts rapidly with water to give nitric acid, the equilibrium is
displaced to the left
NO + NO
2 3
~
~
N °
2 5
N ° + H °
252
~
2HNO
3
Leighton, using representative values of N02' 03' NO, and water in pol-
luted atmospheres, estimated that the equilibrium concentration of HN03
should be 300 ppm, far higher than has been observed. The maximum rate
of formation should be 9.2 ppm hr-1, Obviously, equilibrium is never
reached, probably because the rates are slow. However, these arguments
suggest that this could be an important loss mechanism for N02 in pol-
luted atmosphere (Leighton, 1961). Recent results obtained in these
laboratories suggested that when these reactions take place in the pres-
ence of NH3' a nitrate-containing aerosol was formed, provided the RH
was above about 70%. Presumably the NH3 neutralized the HN03' forming
a soluble salt which is hydroscopic if the RH is above 70%. Such a
process could be the major source of nitrate-containing aerosol in an
urban environment (Robbins et al., 1959).
IV-16
-------
other possible loss mechanisms have been considered:
NO + N02 + H20
~
~
2 HNO
2
3NO + H °
2 2
~
~
2HNO
3
+ NO
While the equilibrium constants suggest pphm concentrations of HN03 in
urban atmospheres, the rates of both reactions are slow and their con-
tribution to the NO and N02 loss is probably small. Robbins et al. (1959)
have suggested that in the presence of a NaCl-containing aerosol, these
equilibria may be established more readily.
On a worldwide basis, the absorption by plants and the soil of N02
is significant. Robinson and Robbins (1968) assumed an average deposi-
tion velocity of 1 cm/sec, based on results by Tingey (1968) for alfalfa
and oats.
In conclusion, there are two sink mechanisms for loss of nitrogen
oxides in urban areas: sedimentation or rainout of nitrate-containing
aerosols and absorption of N02 by vegetation. Obviously, competition
between these pathways depends on the daily weather variations and the
surface area of vegetation in the st. Louis area. Land use data should
be gathered early as part of the RAPS program. It is recommended that
the st. Louis area be divided into subdivisions to simplify the deter-
mination of the vegetation surface area.
Hydrocarbon Sources and Removal Processes
The major HC in the atmosphere is methane, which can be found in
concentrations above 1.5 ppm. The major methane source is decomposition
of vegetation. However, it is relatively unreactive when compared to
other HC. The reaction with 03 is extremely slow; reactions with O-atoms
or hydroxyl radicals are at least an order of magnitude slower than re-
actions with other HC. Therefore, since in ppm concentrations methane
is harmless to humans, we need not consider it further.
Vegetation, especially coniferous forests, sagebrush, hay fields,
and so forth, emits large quantities of volatile HC, such as terpenes.
Many of these compounds are strained, substituted olefins, and are rela-
tively reactive in forming photochemical smog (in the presence of N02)
(Went, 1960, 1966). The bluish haze often observed over such forested
areas (the classical example being the Great Smoky Mountains) is attrib-
uted to photolysis of N02 in the presence of terpenes, which produces
IV-17
-------
sizable quantities of aerosol (West, 1960, 1966; Ripperton, 1970). These
emissions will be the majority of the background HC level in the R~S.
There are many sources of HC in an urban area. Combustion of HC
fuels, including coal, fuel oil, and gasoline, results in emissions of
a wide variety of carbon-containing materials. The majority of the HC
are in the C1-C10 range, although low concentrations of polycyclic aro-
matics and other high molecular weight HC are present. Oxygenated spe-
cies--acids, aldehydes, and alcohols--are also fOl~ed in small amounts
during combustion. Major point sources will be power plants and coal-
burning heavy industries. The urban area will itself be a diffuse area-
source, due to heating, automobiles, and the like. Evaporative losses
from gas mains (mainly CH4)' solvent evaporation, petroleum products
from sources, such as gas tanks, carburator bowls, and fueling operations
at service stations, will also provide significant HC and oxygenated and
halogenated carbon-containing materials.
The most important removal process of HC occurs in the presence of
NOx and light by photochemical reactions. In view of the complexity of
these reactions, they are considered in the next section. Ultimately,
these materials are absorbed by aerosol particles, which are removed by
either sedimentation or by rain or fog. Absorption losses by vegetation
are also a possible sink for certain HC. For instance, ethylene in low
concentrations causes extensive damage to plants (USDHE\\', 1970a). The
damage by other carbonaceous materials is less well understood, and the
relati ve importance of this process compared to photochemical reactions
is not known.
The Hydrocarbon-Nitrogen Oxides Reactions
The HC:NOx photochemical reactions are important because they result
in many of the manifestations of urban smog. For detailed discussion, we
suggest the reviews by Leighton (1961) and Altshuller (1971).
The equilibrium between NO, N02' and 03' which is established in the
presence of light and 02' is upset by HC. They react with the O-atoms
and 03 to form oxygenated photoproducts and free radicals. The products
include fonnaldehyde, other aldehydes, PAN, and its homologues such as
PBzN. For instance, olefins react more rapidly with 03 than other IIC to
give aldehydes and ketones. O-atom attack on most HC is 103_10~ times
faster than the 03 reaction and is less selective. In general, n chain
reaction is started, which includes the following reactions
IV-18
-------
a + RH -> Ro + OH
Ro (or Ho) + a -> RO 0 (or HO 0)
2 2 2
RO 0 (or HO ) + NO -> ROo (or HO 0) + NO
2 2 2
RO 0 + NO -> PAN or its homologues
2 2
ROo (or I I
oOH) + R H -> R 0 + ROH (or H 0)
2
ROo (or oOH) + CO -> Ro (or H 0) + CO
2
When one considers a specific compound in place of RH above and considers
rearrangement of the radical fragments Ro, many more steps are possible.
For instance, Altshuller (1965) lists 39 steps for a general olefin re-
action sequence.
The kinetic equations for such a complicated reaction sequence can-
not be solved without the aid of a computer. These attempts have been
called simulation models. A variety of these models have been written
and the published information is listed below (Seinfeld, et al., 1971).
Highly simplified mechanism (fewer than ten reaction steps)
Friedlander and Seinfeld (1969)
Eschenroeder (1969)
Behar (1970)
*
general
general
general
Simplified mechanisms (10-25 reaction steps)
Wayne and Earnest (1969)
Behar (1970)
Seinfeld, et al. (1971)
propylene
propylene
general
Complex mechanisms (more than 25 reactions steps)
Westberg and Cohen (1969)
Wayne, et al. (1971)
isobutylene
general
*
Refers to HC species for which the mechanism was developed.
IV-19
-------
In the interest of computation time, it is necessary to write the
simplest mechanism possible which will include the major reactions. The
Systems Applications, Inc. (SAI) 14-step model (Seinfeld, et al., 1971)
is given in Table IV-2, along with the monitoring data required for veri-
fication (excluding meteorology and source data). These data include
solar light intensity, NO, N02' 03' RH, nitrate either as gaseous HN03
or nitrate in the aerosol, CO, HC, aldehydes, and PAN.
Several problems are immediately obvious. PAN is formed only if
R = CH3C=0. The aldehydes include formaldehyde plus aliphatic and aro-
matic aldehydes, depending on the structure of R. At the minimum, for-
maldehyde and total aldehydes should be measured during the RAPS.
The HC in the urban atmosphere include about 125 identified com-
pounds, excluding polycyclic aromatics such as benzanthracene. The
problem is that the reactivity of these HC can vary by about a factor of
100. depending on how one defines reactivity. Table IV-3 lists one such
reactivity scale. proposed by Glasson and Tuesday (1970). The values of
kg, k10' k1l, a, ~, and C (Table IV-2) will depend on the nature and re-
activity of the HC mixture. The general problem of how to incorporate
the relative reactivity of different HC mixtures into a simulation model
is currently being studied in several laboratories. Loss mechanisms
such as aerosol formation are not included in current simulation models,
nor are the effects of RH or S02' but will be a necessary part of future
models.
The Research Program
The most important variables, except for HC reactivity, that are
listed in Table IV-2 will be determined automatically at monitoring sta-
tions throughout the RAPS. These include NO, N02, 03' light intensity,
RH, and CO. While total HC and CH4 will also be automatically measured,
these data will not be sufficient for future more sophisticated models.
Furthermore, no provision has been made for determination of formalde-
hyde, total aldehydes, or PAN. These data must be collected as part of
the Research Program.
The ideal simulation model would require as inputs the concentra-
tions of the 25 to 50 more reactive HC, as determined by an analytical
gas chromatograph (gc). In that case, the value of the rate constants
and product yields for each HC can be determined quite accurately. Al-
though present models are not able to handle such a mass of data we
,
recommend that some information about the HC distribution should be ac-
quired early in the RAPS. The major difficulty in the gc technique is
IV-20
-------
Table IV-2
TIlE 14-STEP SAI MODEL
Reaction
Required
Validation Data
1
N02 + hv ~ NO + 0-
N02' light intensity
2
° + 02 + M ~ 03 + M
°
3
3
03 + NO ~ N02 + 02
NO
4 *
03 + 2 NO ~ 2 HN03
2 H20
RH, nitrate in aerosol
5
NO + NO ~ 2 HNO
2 H20 2
HNO
2
6
HN02 + hv ~ OH- + NO
7
CO + OH- 0 C02 + H02-
2
CO
8
HO - + NO ~ HNO + °
2 2 2 2
9
HC + 0- ~ 0: JW2.
Hydrocarbons
HC + 0
C!
ICJ
--; S R02- + y RCHO
Aldehydes
f.i:: -t Uti.
11
~ C R02 - + € RCHO
12
r.(:2- + NO -; N02 + 80H-
13
R02 - + N02 ~ PAN
PAN
14
NO - + NO ~ NO + OH-
2 2
*
Reaction 4 is a composite of these reactions:
4a
03 + N02 -; N03 + 02
4b
N03 + N02 -; N205
N °
2 5
+ H ° ~ 2 HNO
2 3
Therefore it is not necessary to
mechanism. The HN03 most likely
found in photochemical aerosols,
neutralization by NH3'
IV-21
retain N03 in the
forms the nitrate
probably after
-------
Table IV-3
*
HYDROCARBON REACTIVITY IN NO PHOTOOXIDATION
Internal olefins with two double bond
substitutions
Cyclopentenes, internal olefins with
one or no double bond substitutions
100
40
Cyclohexenes, tri- and tetra-
alkylbenzenes, diolefins
Terminal olefins, dialkylbenzenes
15
5
Mono alkylbenzenes, C4 and higher
paraffins
2,2-Dimethylpropane, C1-C3 paraffins,
benzene
2
o
*
Glasson and Tuesday, 1970.
that the equipment is expensive, a highly trained person is required to
operate it, and one analysis takes 1-2 hours. Furthermore, future simu-
lation models will probably be designed for day-to-day operation and
rapid predictions will,be needed for daily air pollution control strat-
egies.
At least one simulation model (Wayne, 1971) requires the division
of HC into reactive and unreactive classes. Several laboratory HC clas-
sifiers have been reported. A promising instrument designed for the
analysis of auto exhaust was described by Klosterman and Sigsby (1967).
A substractive scrubbing unit was coupled to a standard FID total
HC analyzer. The HC were separated into three groups: olefins and
acetylenes, aromatics excluding benzene, and other HC including benzene.
Olefins and acetylene were selectively removed by a scrubber column con-
taining mercuric sulfate. Alcohols, ketones, and organic acids also
were removed by this column. Aromatics, excluding benzene, plus alde-
hydes, ethers, and esters were all removed by a palladium sulfate column
The analysis was performed by determining total HC (that is, with no
scrubbing columns), then successively adding each scrubber. Automation
of the device should be relatively easy. Therefore, we recommend that
a fully automatic HC classifier should be developed, whose output is
compatible with the central data facility.
".u
-------
Gc analysis of the HC would provide a complete breakdown of the HC
distribution. In view of the high instrument cost and the fact that
automatic instrumentation is currently not available, we recommend in-
stallation of this equipment in three research sites. One should be
well upwind of st. Louis, one immediately downwind of the Wood River
area, and the third about 30 km farther downwind.
Specific wet chemical techniques for formaldehyde, by the chromo-
tropic acid method (Altshuller, et al., 1961), and total aldehydes, by
the MBTH or other methods (USDHEW, 1970), are available. The chromo-
tropic acid method is convenient and specific for formaldehyde. Methods
for total aldehydes are imprecise because organic and higher molecular
weight aliphatic aldehydes are not detected. We recommend that hourly
average formaldehyde and total aldehyde measurements be made by the gc
operator while the HC distribution program is being carried out.
It is extremely difficult to measure PAN routinely. The two avail-
able methods--long-path infrared or electron capture gc--require continu-
ous monitoring by a highly trained technician. A small research program
using one gc should be set up for occasional use during the aldehydes
and HC distribution program. If the need for more extensive PAN meas-
urements becomes more apparent, then construction of an automatic or
semiautomatic electron capture gc should be considered.
A principal loss mechanism for HC is the incorporation of HC photo-
oxidation products into the aerosol particles. Little is known about
the chemical nature of these materials, but data obtained by the Bay
Area Air Pollution Control District suggest that up to 50% of the aero-
sol mass collected on hi-vol samples is carbonaceous.* To study the na-
ture of the carbonaceous materials, an aerosol sample, collected on a
glass fiber filter, could be gradually heated in a vacuum line. The
volatilized material could either be separated into its components on a
gc column followed by detection by mass spectrometry, or placed directly
in the inlet system of the mass spectrometer. Scheutzle (1971) has re-
ported the development of the latter type of instrument, using a high
resolution mass spectrometer and a dedicated computer. Data from such
an instrument would be invaluable to the RAPS Research Program. Further-
more, the same instrument, equipped with a gc input, could be used to
provide even more detailed information about the HC distribution as well
as the oxygenated components in the atmosphere.
*
This is mostly the nonvolatile portion of the aerosol.
IV-23
-------
The Particulate Cycle
To help urban areas meet the Air Quality Criteria for particulate
matter, more data must be accumulated about the factors that determine
the amount of particulate matter in the atmosphere at a given time. The
ultimate objective of this research program will be to obtain the data
necessary to develop and validate a simulation model for particulate
matter. This model would, ideally, predict the particulate distribution
and concentrations at some later time, given a series of inputs including
the current meteorological conditions and emission levels. Both develop-
ment and validation are part of this program because there are no avail-
able particulate models at this time.
Particulate matter constitutes the most visible manifestation of a
polluted atmosphere. Primary stack emissions are often visible from dis-
tances of several miles away, and even quite dilute aerosols can signifi-
cantly reduce the visual range. The brown color often associated with
urban haze and smog may be due to preferential light scattering of cer-
tain wavelengths of light by the aerosol particles, although some authors
believe it is due to absorption of light by N02' In addition to the
visible effects of particulate matter, sedimentation of particles causes
soiling of buildings, textiles, painted surfaces, and so forth. Inhala-
tion of aerosol particles can cause a variety of respiratory diseases,
partially depending on chemical composition and particle size.
In view of these detrimental health and environmental effects of
particulate matter, Air Quality Criteria have been established. To
achieve these Criteria, many steps must be taken. Adequate control of
primary particulate emissions awaits engineering developments beyond the
scope of the RAPS; however, development of simulation models covering
formation and dispersal of both primary and secondary emissions will
greatly aid the control strategy for air pollution. Present models,
based on meteorological factors are inadequate, because secondary emis-
sions have not been included. Validation of present and future models
will depend on data accumulated in programs such as the RAPS.
The formation mechanism of particulate matter will be divided, some-
what artificially, in several categories, which include:
Natural background aerosols--pollen, dust, and sea spray
.
Primary particulate emissions--power plants, industrial emissions,
and automobiles
Secondary particles--sulfates, nitrates, photochemical products,
and carbonaceous aerosols formed in the atmosphere from gaseous
emissions.
IV-24
-------
Natural background aerosols contain chloride from evaporated sea spray,
sulfate from oxidized natural emissions of H2S, silicates from dust, am-
monium from natural ammonia emissions, photopolymerized organic materials
from natural HC emissions, such as forests, and nitrate from oxidized N02
Primary particulate emissions are found in many sizes and composi-
tions. Most obvious are the stack plumes of power plants and other in-
dustries, but emissions from domestic heating units, refuse disposal,
and automobiles are also significant. The location and strength of these
sources will be established during the Emissions Inventory.
Secondary particle formation can be divided into several processes
which are listed in Table IV-4. Oxidation of S02 in the presence of
either light or a catalyst, such as NH3 or a metal ion, are fairly well
understood. However, the relative importance of catalytic oxidation in
stack plumes should be investigated further. The last reaction involving
N02' 03' and HC is extremely complex, and aerosol formation can proceed
in the absence of either S02 or HC. Further laboratory studies of these
reactions are needed to evaluate the relative rates of competing steps.
Measurements of NO, N02, S02' H2S, 03' and HC at the regularly re-
porting monitoring stations should be adequate for the model validations
involving gaseous pollutants. Although the mass concentration and some
information of the aerosol size-distribution can be obtained in the
regular monitoring net~ork from the particle mass monitor and the inte-
grating nephelometer, these data will not be sufficient for model vali-
dations dealing directly with particulate concentrations. More complete
knowledge of the aerosol size distribution and the concentration of sul-
fate, nitrate, and HC in the aerosols will be required. Currently these
data observations require considerable manual sampling and analysis. As
part of RAPS, the development of field instruments for rapid determina-
tion of sulfate and nitrate in atmospheric particles should be encouraged
Otherwise, collection and analysis of hi-vol samples will be necessary.
A study of the average particle size distribution and the distribution of
sulfate and nitrate as a function of particle size is recommended. It
will probably not be necessary to monitor these variables throughout the
RAPS, but representative values for the st. Louis area should be obtained
Background Haze
The general problem of atmospheric haze formation has been recently
reviewed by Germogenova, Friend, and Sacco (1970). We shall assume that
the reader is familiar with this reference since we cannot hope to dup-
licate it here.
IV-25
-------
Table IV-4
CHEMICAL REACTIONS OF IMPORTANCE
TO THE PARTICULATE CYCLE
Reactions of Known Importance
Validation Data
Required
SO
2
+ h\)
+ catalyst I
- H SO (aerosol)
H ° 2 4
2
SO , NO , HC, light
2 2
intensity*
SO + °
2 2
2N02 + 03 - N20S + 02
t
N02' 03' RH, NH3
N ° + H ° - HNO (vapor)
2 S 2 3
HN03 + NH3 - NH4N03 (aerosol)
NO + air + HC - polymer in aerosol
2
N02' HC, RH, 03' light
intensity*
Reactions Whose Importance Must Be
Assessed During RAPS
3N02 + H20 - NO + 2HN03
N02' RH
NaCl (aerosol) + 2N02 - NaN03 (aerosol)
+ NOCI
NaCl in background
aerosol, N02
*
Also determined as part of S02-Cycle Research Program.
Also determined as part of HC:NOx-Cycle Research Program.
t
!V-26
-------
Natural Background Aerosols
There is a background level of particulate matter, even in the most
isolated areas. This material is largely evaporated sea spray (NaCl),
sulfate (s04=) from oxidation of H2S, usually as (NH4)2S04 or (NH4)HS04,
nitrate (N03-) from oxidation of N02' and organic material. Chemical
analyses of particulate matter from nonurban atmospheres are summarized
in Table IV-5.
Table IV-5
AVERAGE PARTICULATE CHEMICAL ANALYSES (~g/m3)
Source Area
Component Remote * Urban* St. Louis
Total mass 21.0 102 168
Benzene soluble 1.1 6.7 12.8
Sulfate 2.5 10.1
Nitrate 0.5 2.4
Iron 0.15 1.4
Lead 0.02 1.1
*
Averages for United States; Ludwig, J. H.,
G. B. Morgan, and T. B. McMullen, Trans. Amer.
Geophys. Union, 51, 468 (1970).
These data show that benzene-soluble materials, presumed to be organic
in nature, and sulfate constitute significant fractions of these aero-
sols. Other data show that chloride from sea spray is also an ubiquitous
aerosol constituent, but its mass concentration decreases over inland
areas.
The organic materials are emitted by forests, particularly conifer-
ous forests, hay fields, and so forth. Terpenes, which constitute a large
portion of the emissions, and other reactive HC are rapidly photooxidized
and photopolymerized in the presence of air, light, and N02' Anerobic
decay of vegetation produces H2S, which is oxidized first to S02 by back-
ground ozone and then to sulfate. Some sulfate is traceable to evaporated
IV-27
-------
sea spray. The source of nitrate is not well understood; explanations
include reaction of hydroxyl radicals with N02 to give nitric acid, and
oxidation of N02 to N03 by ozone.
The most numerous particles in the atmosphere are the Aitken par-
ticles. They are so small (0.005-0.1 ~) that they contribute little to
the aerosol mass-loading and nothing to the visibility reduction, even
though the background levels are as high as 104 particles/cm3. They are
produced during combustion and photooxidation of organic materials as
well as other natural processes. The chemical composition of these par-
ticles has not been established, partly because of the difficulties in
collecting them. They apparently are not important nuclei for cloud,
rain, or fog condensation, but, in view of their comparatively large
surface area, could serve as sites for further reactions of other chem-
ical constituents of polluted atmospheres, such as catalytic oxidation
of S02 and polymerization of HC derivatives.
Particles whose radius is greater than 10 ~ are so large that their
rate of gravitational settling is high. Consequently, they accumulate in
appreciable levels only under turbulent conditions such as dust storms.
These particles have significant concentrations of chloride, sulfate,
and complex silicates from wind erosion of rocks and dust. Their im-
portance on a number basis is negligible, but it can be significant on
a mass basis.
Particulate Emissions Inventory
Particulate emission inventories for st. Louis have been made fre-
qu~ntly. The data for 1963 are summarized in Table IV-6 (USDHEW, 1969).
Although the emission survey recommended in this Prospectus will undoubt-
edly show significant changes in amounts and types of emissions, the im-
portance of coal combustion as the major source of primary particulate
matter is probably unchanged.
Since coal contains 3 to 5% sulfur by weight, SO will be emitted
in significant levels. HC, NO, and N02 are also rele;sed during combus-
tion processes. The distribution of HC and oxygenated organic materials
is determined both by the fuel and the combustion process. An estimated
330,000 tons/yr of HC were emitted in the st. Louis area in 1967-68
(USDHEW, 1971), but the average distribution of these HC according to
compounds or types of compounds apparently has not been determined. All
of these emissions can playa significant role in the formation of secon-
dary particulate matter.
IV-28
-------
Table IV-6
PARTICULATE EMISSIONS INVENTORY OF ST. LOUIS
1963
Emissions
Source Class
Tons
Percent
Fuel combustion
86.8
58.9%
Power generation
Coal
Natural gas
22.4
22.4
0.068
15.2
15.2
Industrial
Coal
39.0
38.0
26.5
25.8
Domestic
Coal
19.9
18.9
13.5
12.8
Commercial and government
Coal
5.5
5.4
3.7
3.7
Refuse disposal
15.8
10.7
Motor vehicles
4.7
3.2
Industrial processes
37.5
25.4
Cement plants
3.6
2.4
Grain industry
6.7
4.5
Ferrous metals
12.4
8.3
Other
14.0
9.5
Totals
147.4
100.0%
IV-29
-------
The Chemistry of Particulate Formation in the Atmosphere
In addition to the background levels of aerosols and the industrial
emissions * there will be a large contribution from aerosols produced by
,
oxidation of 802, N02' and HC. We shall call these secondary aerosols.
to be distinguished from primary particles emitted directly from pollu-
tant sources and background aerosols. The mechanism of the formation of
these secondary aerosols is very complex and poorly understood. To sim-
plify the problem we shall include the formation of secondary aerosols
in the discussion of the 802 cycle (sulfate-containing aerosols) and the
HC:NOx cycle (nitrate- and carbon-containing aerosols). These cycles
are considered in separate sections in this Prospectus. The major de-
ficiency in the artificial separation of mechanisms is that it is more
difficult for allowance to be made for the possibility of synergistic
effects between the two cycles.
The size distribution of atmospheric aerosol particles is largely
controlled by the rates of coagulation and sedimentation. Coagulation
of Aitken particles effectively limits their numbers. Brownian movement
of the particles below about 1 ~m is high enough to prevent gravitational
settling. For the very large particles, gravitational forces are large
enough to cause significant sedimentation.
The theory of coagulation and sedimentation of aerosol particles
has been reviewed in detail by Junge (1963). We refer the reader to
this work for detailed 'references and the mathematical treatment of the
problem. Although various authors seem to argue about details and varia-
tions, it has been found typically that 'Well-aged continental aerosols"
achieve a uniform size distribution, regardless of their origin. The
size distribution is apparently maintained because the competitive phys-
ical processes of nucleation, growth by absorption and coagulation, and
loss of sedimentation, reach a steady state. A mathematical treatment
of these processes has been developed by Junge (1963, 1965) and others.
*
Background aerosols constitute about one-third of the total average
particulate loading in urban atmospheres; a crude calculation based
on a loading of 160 ~g/m3 particulate matter, spread over a 50 X 100
mi region, 1 km high, and with a residence time of one day, suggested
that about 10-20% of the total particulate loading was due to primary
industrial emission. Thus about half the atmospheric particle load
is due to secondary particle formation processes.
IV-30
-------
In addition to coagulation and sedimentation and because the smaller par-
ticles are in continuous motion, there is a finite probability that they
will collide with a surface such as the ground or a building, and stick
to it. This removal process is called impaction. The sum of sedimenta-
tion plus impaction gives a net downward particle flux.
Finally, aerosols are removed by precipitation--either raindrops or
fog or mist droplets. Particles become involved with droplets either by
coagulation or capture. For example, the droplets fall with a terminal
velocity given by the Stokes equation and as the falling droplet sweeps
out a volume of air, particles in the pathway are impacted on the droplet.
The higher the mass and cross-sectional area of the particles, the greater
the chances of impaction. The aerosol particles are trapped in the drop-
let. Collection of the precipitation followed by chemical analysis shows
significant concentrations of S04=, N03-' NH4+ and other cations.
To determine the relative importance of these processes, the concept
of deposition velocity Vg has been suggested (Junge, 1963) where
v
g
=
deposition rate
particulate concentration
=
mass/area.time
mass/volume
=
length
time
In fact, Vg is the sum of three terms
v
g
= v
p
+ v
s
+ v
i
where p, s, and i refer to precipitation, sedimentation, and impaction,
respectively. The value of vp can be calculated from
v
p
-3 kh
= 3.16 X 10 --
c
where k is the concentration of a rainwater constituent in mg/£, h is
the mm of precipitation per year, and the concentration c of an aerosol
3
constituent is in ~g/m .
The dry deposition rates, Vs and vi' can be determined by measuring
the weight of either a constituent or total mass of aerosol in a known
volume and the same measurements of aerosol deposited on a surface such
as a filter paper or microscope slide. Esmen and Corn (1971) used a
manual optical counting technique and a microscope to determine the par-
ticle flux in Pittsburgh. The deposition velocity in the absence of
IV-31
-------
precipitation was measured and used to
particulate matter, which was 102_103h
hr for particles in the 1-10 ~m range.
estimate the residence time of the
for submicron particles and 10-100
The Research Program
The research program will be designed to obtain data that will be
useful for validation of both a meteorological dispersion and a chemical
formation model--ultimately a combined model--using state-of-the-art in-
struments and current knowledge of the mechanisms of aerosol formation.
The necessary inputs will include
.
Meteorological data
Background aerosol levels and chemical composition
.
Primary particulate source location and emission levels from
both point and area sources
Concentrations of gaseous materials important in the formation
of secondary aerosols
Chemical composition, concentrations, and size distributions
of the aerosol particles.
Meteorological data will be routinely measured at all regular moni-
toring stations. Additional measurements should not be necessary.
Background aerosol concentrations will be available from those moni-
toring stations that are upwind of the source areas from the nephelometer
and mass-loading data. Methods of determining the chemical composition
of these aerosols are given below.
Knowledge of the location and types of emissions, including primary
particles, S02, N02' and HC from point sources, such as power plants,
steel mills, and refineries will be essential to any simulation model.
This information will become available at the completion of the Emissions
Inventory scheduled for the initial phases of the RAPS. Ideally, data
giving both the particulate mass emissions and chemical composition from
the point sources on a day-to-day basis would be made available while
the remainder of the particulate measurement program was in progress.
Alternatively, a specific sampling station could be located immediately
downwind of a particular stack to obtain specific information.
IV-32
-------
As part of the Emissions Inventory, data about area sources of par-
ticles S02, NOx' and HC should be obtained. Since the daily levels may
vary somewhat, the information supplied by the monitoring network stations
located in areas of light industry, dense housing, and major freeways will
permit some assessments of changes on a day-to-day basis to be made.
For the determination of gaseous pollutants, data from the monitor-
ing stations will be sufficient for NO, N02' S02' H2S, 03' and total HC.
Additional determinations of ammonia and nitric acid are necessary. After
completion of the short ammonia monitoring program recommended above, a
limited on-going measurement program mainly in upwind rural areas should
provide adequate data for ammonia. If an instrument for detection of
gaseous nitric acid can be developed for the RAPS program, the data gen-
erated would be useful in the validation of a particulate simulation
model which predicts the nitrate concentration in the aerosol.
Data for the particle size distribution and chemical composition of
the particulate matter found throughout the st. Louis area should be ob-
tained. These data should be measured at selected upwind locations, near
primary particulate sources, and downwind where secondary particulate
formation and dispersion of the stack plumes are important. As a bare
minimum, particle concentrations and chemical composition including sul-
fate, nitrate, and HC are required. Particle concentration data can be
obtained from nephelometer data, provided one assumes a refractive index
and particle size distribution for the aerosol.
Determination of the chemical composition of either the entire aero-
sol mass or of a size-fractionated portion of it will be time-consuming
and thus the sampling and analysis program must be designed for optimum
utility. There are dependable methods for analysis of hi-vol samples,
but since there will be at least 10 sites collecting these samples on a
regular basis throughout the program, the number of samples can reach
enormous proportions. If automatic instruments for sampling particulate
matter and determining the nitrate and sulfate concentrations are avail-
able and dependable, they would reduce the workload considerably. More
effort could then be placed on characterizing the organic constituents
in the aerosol particles. Such data would be invaluable in validating
models which predict the growth of aerosols in urban atmospheres.
To determine the relative importance of aerosol loss processes, the
deposition velocity of total aerosol, S04-, and N03- should be measured.
Millipore filters would be preweighed and used to collect aerosols. A
predetermined volume of air should be pulled through one filter mounted
perpendicular to the earth's surface. A second filter, parallel to the
earth's surface, should be exposed to the atmosphere but no air should
IV-33
-------
be pulled through it or blown over it. The total mass of material de-
posited on each filter can be measured and used to calculate the deposi-
tion velocity. Analysis of rain water samples for S04=' N03-' and total
nonvolatiles plus simultaneous measurement of the aerosol particle con-
centration will provide data for calculation of the deposition velocity
by precipitation.
Development of Continuous Rainfall pH Measurement and Sequential
Precipitation Collection
Precipitation is considered to be an important scavenging mechanism
for many of the pollutants emitted to the atmosphere by urban sources.
The role that precipitation plays in removal of both gaseous pollutants
and particulate material produced as reaction intermediates and products
can be defined within the RAPS program. The changes in pollutant con-
centrations observed by the monitoring network during periods of pre-
cipitation in conjunction with a study of the density of collected pre-
cipitation at selected sites will provide the requisite data to evaluate
the effectiveness of precipitation wash-out and rain-out as scavenging
mechanisms.
The instrumentation for obtaining measurements concerning the chem-
ical properties of precipitation is not available, apparentl~ as an off-
the-shelf item. Most components to perform the measurements are avail-
able, however, and the design of appropriate instrumentation for automated
pH measurements using commercially available components should be the
first priority of this research project. A tipping bucket rain gage
could be the basic component in which the discarded precipitation is
passed through a flow-through pH measurement cell. The measurement cell
must retain enough precipitation to keep the pH electrode moist during
the extended periods without precipitation (one week to ten days in St.
Louis). If the volume of the measurement cell is minimal, the volume of
precipitation in each bucket increment is adequate to rinse the cell
free of the retained volume of the preceding increment.
A separate tipping bucket rain gage should be used to collect se-
quential samples for further chemical analysis. A close fitting cover
activated by a precipitation sensor would protect the gage from dust fall
during dry intervals. The cover must be activated to cover the gage in-
let after precipitation has ceased. A rotary table containing sample
vessels could be used to collect samples for further analysis on a pe-
riodic basis. Ion concentrations of the precipitation could be deter-
mined through the use of specific ion electrodes. This is a rapid,
simple method of analysis that can yield valuable information about the
IV-34
-------
chemical constituents present in the precipitation. Specific ion elec-
trodes in conjunction with standard laboratory pH instrumentation can
determine the ion concentration of sodium, potassium, calcium, magnesium,
ammonium, nitrate, and chloride. Many other ion concentrations can be
measured using this technique, but the above would be of particular in-
terest in the RAPS program. Specific ion electrodes for the determina-
tion of sulfate ion are not currently available, but may be developed
during the span of RAPS. The ratios of sodium, potassium, calcium and
magnesium ion concentration can be used to determine if sea salt is
present as droplet nuclei. The volume of collected precipitation should
be sufficient to permit other techniques of analysis, such as for sulfate
concentration, to be employed as required by the individual research pro-
grams. The measurement of pH should be made at the collection site to
obviate errors due to absorption of atmospheric C02' The collected sam-
ples for subsequent analysis should be covered after collection to pre-
vent contamination by dust. The collected precipitation for chemical
analysis cannot be the discard from pH measurements as the sample will
be contaminated by leaching of the electrolyte through the glass elec-
trode of the pH measurement.
Precipitation measurements would not be required at all monitoring
stations, but instrumentation should be installed at selected stations
within the network. Currently, the Illinois State Water Survey is op-
erating and maintaining an extensive precipitation measurement network
in the area of st. Louis. Liaison between RAPS and the Illinois State
Water Survey should be'established to obtain and integrate the precipi-
tation collection data into the control data archive of RAPS.
Carbon Monoxide Cycle
Carbon monoxide (CO) is found in the highest concentration of any
pollutant gas in the urban environment. It is colorless, odorless, and
toxic to man at higher concentrations. At low concentrations, both
visual and cardiovascular effects have been noted on test subjects.
Comparison of background concentrations of CO (up to 0.6 ppm) and urban
concentrations (60 ppm and higher) show that the greater amount of CO
in the urban environment can be associated with human activity. In view
of the adverse health effects of long time exposure to 50 to 100 ppm con-
centrations of CO, Air Quality Criteria for CO have been issued.* To
*
An average of 9 ppm over an 8-hr period or 35 ppm over a 1-hr period
should not be exceeded more than once a year.
IV-35
-------
help meet these Air Quality Criteria, meteorological models has been de-
veloped that successfully model the transport of CO throughout the urban
area. It is the purpose of this research program to collect more com-
plete information than has been heretofore available for validation of
these models. Furthermore, existing diffusion models assume that CO is
unreactive in the environment. Recent chemical models for the HC:NOx
reactions and smog chamber experiments indicate that CO is not completely
unreactive. Refinements in current CO models may require an understand-
ing of the chemistry of CO in a polluted atmosphere. The chemical reac-
tions of importance will be discussed. In addition, active biospheric
scavenging processes and possible sources in the biosphere have been
noted for CO.
The background sources of CO include marine plants and invertebrates
found only in ocean regions. Biological sources on land areas have been
few but they cannot be entirely ruled out on the basis of current inci-
dence. The oxidation of background levels of methane by hydroxyl radi-
cals has been suggested as another important atmospheric CO source.
However, these sources will be of negligible importance when compared
to emission sources, primarily automobiles, in an urban area.
In 1968, the automobile accounted for 77% and
contributed about 20% of the total CO emissions in
1970B). All are due to incomplete combustion of HC
industrial operations
st. Louis (USDHEW,
fuels.
In a polluted atmosphere where N02 photolysis results in a signifi-
cant concentration of hydroxyl radicals, a chain reaction is established:
OH + CO ..... H + CO
2
H + 0 ..... HO
2 2
HO + NO ..... OH + NO
2 2
One molecule of NO is oxidized to N02 and one
to C02' While this reaction is slow compared
spheric reactions, it is of importance to the
sequence.
molecule of CO is oxidized
to other potential atmo-
overall HC:NOx reaction
Recent data have shown that the soil is an important sink for CO.
Of 200 fungi, yeasts, and bacteria tested, 16 species of fungi absorbed
CO at concentrations of less than 100 ppm. The rate of absorption will
be competitive with the losses by reaction with hydroxyl radicals.
IV-36
-------
Simulation models for CO have been developed that predict accurately
the distribution of CO in localized regions, such as city streets. There
are probably adequate data available now to validate these models. How-
ever, data for predicting the mass flux of CO at longer distances down-
wind of the sources are lacking. Such data will become available during
the RAPS from the regular monitoring system and airborne measurements
proposed in this Prospectus. In treating these data, the important ques-
tion will be: Are loss mechanisms--chemical reactions and soil absorp-
tion--fast enough so that they must be considered as a part of CO simula-
tion modeling?
A program designed to identify the sources of atmospheric CO upwind
and downwind of the st. Louis area, using the stable isotope ratio tech-
nique, is also recommended.
Source of CO
The sources of CO can be divided
sions associated with human activity.
most important in the RAPS.
into natural emissions and emis-
The latter sources are by far the
Major natural sources of CO have been found which include marine
plants and invertebrates (USDHEW, 1970b; Jaffe, 1968). The majority of
these sources occur only in ocean areas. McConnell, McElroy, and Wofsy
(1971) have suggested that a major source of atmospheric CO is oxidation
of methane (CH4) by hydroxyl radicals (OH). Swamps, rice paddies, and
other areas where biological materials decompose are major sources of
methane on a global basis. The following reaction sequence has been
suggested (McConnell, et al., 1971; Levy, 1971):
NO + hv -> NO + 0
2
0 + 0 + M -> 0 + M
2 3
H 0
hv 1 2
0 -> O( D) -> 2 OH
3
CH4 + OH -> CH + OH
3
CH + 0 -> CH 0
3 2 3 2
CH 0
3 2
+ NO -> CH 0 + NO
3
CH 0 + 0
3 2
-> CH 0 + HO
2 2
IV-37
-------
H02 + NO - HO + N02
CO + OH -+ CO
2
+ H
H + 0 + M -> HO + M
2 2
CH
2
~(CH=O + H
o + hv ~)
!CO + H2
Background concentrations of NO and methane were used to calculate a
lifetime for CO of 0.3 yr.
The background levels of CO from these sources range from 0.02 to
0.6 ppm; the sources apparently depend heavily on the local meteorology
and the proximity to urban sources. An average of 0.2 to 0.2 ppm is a
reasonable concentration to be expected upwind of the st. Louis area.
Data taken at CAMP sites showed that the CO levels in st. Louis will be
more than an order of magnitude higher. Between 1962 and 1967, the geo-
metrical mean concentration was 5.3 ppm and the maximum 5-min average
concentration ranged from 45 to 68 ppm. These data show that on most
days the background CO is unimportant compared with CO from pollution
sources in st. Louis.
stevens, Krout, and Walling (1971) have attempted to determine the
source of atmospheric CO by measuring the c13:c12 ratio of CO from vari-
ous automotive, urban, and nonurban sources. The C13:C12 ratio from
automobile exhaust is quite different from that measured in rural areas,
suggesting that anthropogenic sources are not of primary importance on
a global basis. However, natural CO sources such as ocean water, kelp
floats, and marine invertebrates also did not produce CO having the same
isotope ratio of either automobile exhaust or rural area samples. They
concluded that there is another, as yet unidentified, source of atmo-
spheric CO. It is possible that reaction sequences such as CH4 plus OH,
which ultimately produce CO as an oxidation product, are the additional
CO sources (Levy, 1971).
In st. Louis (in 1968), an estimated 77% of the CO was from transpor-
tation sources--automobile, trucks, buses--and 20% was from industrial
sources. In other cities, the contribution from transportation sources
is much higher, with an average of 94% in Los Angeles. Therefore, the
major CO sources will be city streets, freeways, and the like, which are
represented as line sources in simulation models. Some industrial point
sources will be found during the RAPS Emissions Inventory. Petroleum
refinery catalytic cracking units can be significant industrial sources.
IV-38
-------
The emissions of CO result from incomplete combustion of HC fuels.
Recent CO emission limits of 39.0 g/mi for cars produced between 1972-74
should cause a gradual reduction of CO emission as older uncontrolled
cars are replaced. The effects of these changes should be measurable as
the RAPS progresses.
Important Chemical Reactions of CO
Oxidation of CO by various gaseous species in the atmosphere can
occur. Such reactions include the following:
Reaction
Activation
Energy (kcal)
CO + 02 - C02 + °
51
CO + H20 - C02 + H2
56
CO + °
3
- CO + °
2 2
20
CO + NO - CO + NO
2 2
28
In view of the high activation energies and the low concentrations of
03 and N02 in the environment. none of these reactions can be of impor-
tance to the chemistry of polluted atmospheres. Kummler et al. have
suggested that O(lD), 02(lIg), and 02(lLg) at realistic atmospheric
levels cannot oxidize CO directly (Kummler, et al., 1971).
In many simulation models CO has been assumed to be unreactive,
especially when only short time periods are considered. Many labora-
tories used CO as a tracer in smog chamber experiments to follow the
dilution of the chamber contents. Recent results of Westberg, Cohen,
and Wilson have shown that 100 ppm of CO accelerated the formation of
both N02 and 03 when isobutylene and NO were photolyzed in a smog cham-
ber (Westberg, et al., 1971). It was suggested that a chain reaction
involving CO, NO, N02, and OH-radicals was established which increased
the rate of oxidation of NO to N02 (McConnell et al., 1971).
IV-39
-------
OH + CO .... CO + H
2
H + 02 + M .... H02 + M
NO + H02 .... OH + N02
The result of the above mechanism is a gradual conversion of CO to C02
in the urban atmosphere. Hydroxyl radicals are thought to be an impor-
tant chain-carrying intermediate in the HC:NOx photochemical reactions.
The concentration of OH and therefore the rate of conversion of CO will
also depend on the HC, NO, and N02 concentration in the atmosphere. The
HC:NOx simulation models could generate an estimated steady-state concen-
tration of OH and H02 radicals. These numbers could be used to estimate
the rate of oxidation of CO to C02'
CO Sinks
A major CO sink in the biosphere appears to be the soil. Inman,
Ingersoll, and Levy (1971) found that soils can rapidly absorb CO at
concentrations of 100 ppm or less. Hill (1971) and Inman and Ingersoll
(1971) showed that plants did not absorb measurable quantities of CO.
About 200 species and strains of bacteria, fungi, and yeasts from sev-
eral soil samples were isolated and cultured. Of these, 16 cultures,
all fungi, were active'in CO uptake. Rates of CO uptake for various
soil samples ranged between 2.2 and 17 mg/hr per m2. The major defi-
ciency with these studies is that absorption rates at less than 5 to
10 ppm CO were not determined. Further studies are currently in progress
at SRI. As far as we know, there are no other biological sinks of sig-
nificance in the biosphere.
The major question is which of the two possible CO sinks--chemical
reaction or biological absorption--is of greater importance in the urban
environment. Using Levy's (1971) estimate of the background concentra-
tions of OH (4 X 108 mOlecules/cm3), an average CO concentration of 5 ppm,
and a rate of 1.5 X 10-13 cm3 molecules-1 sec-1 for the reaction of OH
and CO, we calculate a consumption rate of 7.5 X 109 molecules cm-3 mole-
1 -1 -1*. I
cu es sec. US1ng Inman s data (1971) for soil absorption, we chose
a representative absorption rate of 10 mg m-2 hr-1 or 6 X 1012 molecules
*
Note that the OH concentration will be higher in polluted environ-
ments. Therefore, the rate of conversion of CO is a minimum value.
IV-40
-------
-2 1
cm sec- The height of the inversion layer ranges from 0.5 to 5 km.
At the same time, the boundary layer above the soil is about 1 cm, and
about 6 X 1012 molecules sec-1 will be absorbed. Choosing 2 km as a
representative value, for every square centimeter of soil available for
the chemical reaction, about 2 X 1014 molecules sec-1 will be removed
by the chemical mechanism. In view of the assumptions that have been
made, we conclude that both chemical and biological sinks are of com-
parable importance.
The CO Research Program
Johnson et al. (1971) have developed an urban diffusion model for
CO that predicts fairly accurately the concentrations of CO in a down-
town urban area. Required inputs are the traffic patterns, wind speed
and direction, the mixing depth, and the vertical diffusion rate. Vali-
dation data were collected in downtown st. Louis and San Jose, California.
It was found that the CO concentratiop varied as much as 10 ppm from one
side of the street to the other. A street-canyon submodel was developed
to predict the effect of wind on concentrations at different locations
in the street.
The model was reasonably successful in predicting the CO concentra-
tions, and the program could be used either in a synoptic mode, in which
CO concentrations at downwind receptor stations could be calculated from
traffic and meteorological data, or in a climatological mode, in which
concentration frequency distributions could be calculated based on long-
term traffic and meteorological data sequences.
The overriding question which remains unanswered is whether or not
the model will correctly predict the mass flux across a vertical plane
downwind of the urban area. Given inputs such as the emission levels at
the sources plus the wind direction and velocity, the downwind pollutant
concentrations as a function of height can be predicted by the program.
The mass flux can be calculated from these data. To determine the effect
of chemical and biological CO sinks on the overall dispersal of pollutants
the mass flux should also be determined from actual measurements made in
st. Louis during the RAPS. For these calculations, wind trajectory and
CO concentration data from the regular monitoring stations should be sup-
plemented with airborne measurements. The mixing height should be lo-
cated and the CO concentrations at several altitudes at and below the
inversion layer should be measured. From these data, the actual mass
flux through a selected vertical downwind surface can be calculated.
If the measured flux is much less than the values predicted by the model,
then one must conclude that either the chemical or biological sink (or
both) is removing significant amounts of CO.
IV-41
-------
This program should also include supplementary CO isotope ratio
studies of samples collected upwind of st. Louis. in the downtown area,
and at sites as far as 200 km downwind. Samples should be collected
while the mass flux experiments are in progress. These data should show
a dramatic change in the isotope ratio between upwind and downwind sites
in the city. It is more difficult to predict the ratio 100 to 200 km
downwind, where possible CO sinks and biological sources may affect the
ratio.
The Chemical Research Program Schedule
Several research programs have been recommended in the preceding
discussion, which are designed to provide supplementary but vital infor-
mation for verification of simulation models. The Class A and B stations
will provide complete data for meteorological models and most of the
chemical data, including the visibility reduction and the concentrations
of NO, N02' H2S, S02' 03' CH4' and nonmethane hydrocarbons. Additional
information will be required for each model that cannot be obtained with
completely automated instruments because such instruments are not avail-
able. These programs are summarized in Table IV-7. In the discussion
that follows, we shall consider the nature and justifications for each
program relative to model development prospects. It is also likely that
there will be other applications for data resulting from the chemical
research program which cannot be anticipated.
A total of up to 15 of the Class A and B stations will be designated
as research stations. An upwind station should be selected far enough
upwind to permit reliable measurements of background pollutant concentra-
tions. Several stations will be located near St. Louis. At least one
should be just downwind of the Wood River area to measure refinery and
other industrial pollutants close to their sources. Others will be per-
haps 10 miles west and would be in the path of emissions from the city
itself (that is, from automobiles, space heaters, and the like), while
additional stations would be located at least 20 and 40 miles downwind.
These stations would measure the components of the st. Louis atmosphere
after several hours of transport--sufficient time for photochemical re-
actions to take place. The sites selected must be reasonably near good
roads to minimize travel time but must not be near major pollutant sources.
Atmospheric components to be measured at the sites are discussed below.
It will be necessary to perform some analyses at the central laboratory
facility. Complicated analyses will be sent to Durham to avoid duplica-
tion of expensive facilities.
IV-42
-------
Program Title
Particulate cycle
Total N03
and S04-
Determine aerosol size
distribution
Determine distribution of
N03
and S04- in aerosol
Importance of N02-Cl
reactions in aerosol
t-4
1
..,.
w
Characterization of organic
matter in aerosols
Hydrocarbon programs
Gc-HC analysis
Gc-mass spectrometer HC
analysis
Formaldehyde-total
aldehydes monitoring
PAN (optional)
NH3 Monitoring Program
Phase I - determine need
Phase II - routine program
CO Monitoring (supplementary)
Mass flux
Isotope ratio experiments
Table IV-7
TIIE CHEMICAL RESEARCH PROGRAM
Justification
Aerosol is principal sink for NOx
and S02
Aerosol models will predict size
distribution under various meteor-
ological conditions
Concentration of NH4N03 and NH4HS04
determines aerosol particle size
Evaluate importance of this N02
scavenging mechanism
Aerosol important
nature of organic
known
hydrocarbon sink;
material is not
Provides supplementary HC-distribution
data for total HC measurements
Supplements Gc program; provides best
available peak identification
These are products predicted in
current HC:NOx simulation models
Another predicted product
NH3 neutralizes HN03 and H2S04'
accelerating aerosol formation
Technique
Wet chemistry
Automatic instruments
Electric
particle
impactor
mobility, aerosol
counter, Andersen
Start Time
Number
of Sites
Andersen impactor
Wet chemistry
Gc-mass spectrometer
Gc
Automatic HC classifier
Gc-mass spectrometer
Wet chemistry
Electron-capture Gc
(1) Wet chemistry
(2) Modified NO detectors
January 1974
July 1975
15
15 or more
January 1G74
5
January 1974 5
January 1975 5
July 1975 1
January 1974
July 1975
July 1975
5
15
1
January 1974
5
January 1975
5
July 1973
July 1974
5
?
Verify existing models by providing Airborne CO monitor 1974 1
height profiles of CO
Provides experimental evidence for Mass s P'-~ troscopy 1974 1
CO sources
-------
Aerosol Research Program
Current evidence suggests that aerosol formation is the primary
loss mechanism for S02' HC, and NOx' Automatic instrumentation for moni-
toring these aerosol components is currently not available. However,
these data will be essential for model verification so that hourly con-
centrations of N03-' S04=' and the mass balance can be determined and
compared to values calculated in the model.
Sulfate and Nitrate Compounds--It is recommended that the EPA should
push for the development and testing of an instrument (or instruments)
that would automatically monitor N03- and S04= in aerosols. The output
of the instrument should be compatible with the RAPS central data collec-
tion facility. Such a device should result in more data with consider-
able long-term savings. An outside contract would probably be the most
efficient way to procure these devices. This instrument need has long
been recognized and there is real doubt that current technology can con-
ceive and produce instruments of these capabilities.
Since automatic instruments are currently not available, wet chem-
ical analyses of hi-vol samples will be necessary. Hi-vol samples will
be collected at all Class A and B stations on a semiweekly schedule.
= +
Although chemical analyses for N03 and S04 ' as well as NH4 ' Pb, and
other metals and HC would be desirable, the cost of routinely measuring
these components is high relative to the knowledge gained. It is our
recommendation that routine analyses for N03- and S04= in samples from
10 to 15 carefully selected sites would provide adequate data and could
be performed by one analyst in st. Louis. As part of the Ammonia Moni-
toring Program, some NH4+ analyses will be required. This program should
begin in January 1974 or whenever the monitoring stations are put into
operation. It may be possible to analyze samples collected less fre-
quently with no significant loss in data. Such decisions can be made
early in the program on the basis of the observed variability. Analyses
for trace metals should be done only after a need for such data has been
developed.
Organic Compound Aerosols--It would be desirable to study the carbon-
containing fraction of the collected aerosol. Several laboratories have
measured the infrared spectra of collected aerosols, but the technique
was laborious and not very successful. We recommend that a gas chromatograph-
mass spectrometer (gc-mass spec) instrument with a slave computer would
provide much useful information. For aerosol analysis, a temperature-
programmed pyrolysis input to the gc is recommended. The gases driven
IV-44
-------
off by either evaporation or pyrolysis would be detected in the mass
spectrometer and identified by the computer. It will be necessary to
hire a professional to operate the instrument and to develop techniques
for analyzing the samples. The cost of the instrument will be high
(about $80,000), but the instrument also will be used for the analysis
of gaseous hydrocarbons and oxygenated photoproducts discussed in the
HC:NOx cycle section. The program should start in July 1975.
Particle Size Distributions--Future aerosol simulation models should
predict both the :erosol s~ze distribution and the distribution of chem-
ical species (N03 and S04 ) as a function of particle size. Knowledge
of the size distribution is necessary to predict the total aerosol mass,
the visibility reduction, and the aerosol surface area. The last datum
will be a necessary input to the H2S + 03 reaction sequence, which is a
heterogeneous reaction requiring a surface as a catalyst. The aerosol
size distribution research program should be operational by January 1974.
To cover the particle size range of 0.005 to 5 ~, a number of de-
vices are necessary. Electric mobility counters are expensive but pro-
vide some idea of the size distribution between 0.005 to 0.1 ~m. The
condensation nuclei counter, available in both manual and automatic ver-
sions, will give the total number of particles in that size region but
no information as to their size distribution. However, the cost is a
fraction of the electric mobility counter and it is simpler to operate.
Particles in the 0.3 to 2-~m range cause the greatest light scat-
tering or visibility reduction. Larger particles are also effective but
the number of such particles is much lower so in effect they make little
contribution. Commercial photometric particle counters are available,
which are well suited to automatic operation and digital data output.
Simply stated, when a particle passes through the sensing region, a pulse
of light scattered by the particle is detected by a photomultiplier tube.
The electronic logic system within the counter registers the pulse in a
channel whose boundaries represent a size range. Counts are averaged
over a preselected time interval, then read out to a digital printer
such as a teletype. The system could easily be adapted to the RAPS cen-
tral data storage facility. The averaging time should be between 10 and
30 min.
Andersen impactors have been used for many years to fractionate and
collect the larger aerosol particles. Chemical analysis of each fraction
provides information on the distribution of important solutes in the aero-
sols. Serious drawbacks to these devices are the time required to col-
lect a sample large enough for analysis (6-24 hrs) and the number of
IV-45
-------
samples collected per run (six). Since automatic collection and handling
are impossible and the number of samples from five sites will be 30, the
number of runs must be limited. We recommend that the five sites should
be operated simultaneously every other day for two weeks. On these days,
the other particle counters should be operated simultaneously to maximize
the information collected. On alternate days, the samples will be col-
lected and weighed and the sampler cleaned and prepared for the next day's
operation. At the end of the period, the samples should be carefully
labeled, packed, and shipped to EPA, Durham, for analysis.
During these studies the integrating nephelometer, located at all
Class A and B stations, will be operating. After particle size distribu-
tion data and the N03- and S04~ composition have been collected for about
6 to 9 months, attempts to correlate nephelometer readings with HC, NOx'
and S02 concentrations, relative humidity, and meteorology should be made.
Future particulate models will predict aerosol size distributions based
on these inputs. If correlations between nephelometer readings and the
measured aerosol size distributions could be established, they would
greatly aid future model verification studies.
Chloride in Aerosols--As part of the RAPS, the importance of the
reaction between CI- in aerosol particles and N02 should be evaluated,
although we suspect that, since st. Louis is very far inland, there will
be little CI- from sea spray in the background aerosols.* However, CI-
could be provided by other sources and this mechanism could be an impor-
tant N02 scavenging process. Therefore, a limited number of CI- deter-
minations in aerosols collected on hi-vol samplers should be made. If
the CI- concentrations are high, more detailed studies will be required
and an expanded program could be planned. Initial studies could be made
at convenient times after January 1975.
The S02 Flux Measurement
Since the S02 flux through the st. Louis area could be calculated
by simulation models, it would be useful to measure the flux independently
to verify the model. The correlation spectrometer designed by Barringer
*
Junge (1963) indicates that the CI- content of precipitation in the
central midwestern area is about 0.2 mg/1. This figure is about 10%
of the S04= content, 20% of the N03- concentration, and greater than
the NH4+ concentration.
IV-46
-------
(Moffat, Robbins, and Barringer, 1971) should be used to measure the S02
altitude profiles throughout the st. Louis area. Airborne instruments
are currently available. The S02 profiles and the wind velocity measure-
ments from Class A and B stations will be inputs to a computer program
which calculates the S02 flux. These measurements should be made several
times a year, beginning in 1976.
It may be possible to gather similar data for N02' since it also
can be detected by correlation spectroscopy. By 1976, instruments for
CO. NH3' and other gases that have distinctive infrared absorption spec-
tra may be available. If so, then programs for measuring their fluxes
should be considered at that time.
The HC:NOx Research Program
The HC:NOx research program can be divided into two distinct cate-
gories: the distribution of HC in the urban atmosphere and the concen-
tration of the principal photoproducts of the HC photooxidation reaction.
The latter compounds include formaldehyde. total aldehydes. and peroxy-
acetyl nitrate (PAN), whose concentrations are specifically predicted
in current HC:NOx simulation models.
HC Distribution--The reactivity range of the various hydrocarbons
found in an urban atmosphere is about two orders of magnitude. For satis-
factory modeling, some estimate of the reactivity of the HC mixture will
be necessary- We recommend that determination of the HC distribution
should be broken down by the use of three types of instruments: (1) the
HC classifier, (2) an HC gas chromatograph (gc) and (3) a gc-mass spec-
trometer.
The HC classifier would be a new instrument design based on a total
HC analyzer. By using a series of programmed switching valves, several
absorption tubes can be selectively switched into the sample line for the
analyzer. Klosterman and Sigbsy (1967) used scrubbers containing mercuric
sulfate to remove olefins, acetylene, alcohols, ketones, and organic acids
and scrubbers containing palladium sulfate to remove aromatics (excluding
benzene) and aldehydes. The analysis was performed by determining total
HC, then successively adding each subtractive column to the inlet stream.
An automatic instrument could be built whose switching system would be
triggered by the interrogation signal from the RAPS data system and whose
output would be compatible with the RAPS data system. Five minute inter-
rogation intervals would allow time for the instrument to equilibrate
before readout to the data-handling system. Since it would be relatively
IV-47
-------
simple, inexpensive, and entirely automatic, we recommend that at least
15 instruments be procured. It might be more efficient to award an out-
side contract to develop, test, and deliver the instruments. They would
be located at selected upwind, downtown, and downwind sites. Since op-
eration should commence by January 1975, construction should begin before
January 1974.
Although the prospective HC hydrocarbon classifier should be sim-
ple and automatic, it would not provide a complete breakdown of the HC
composition. Satisfactory gc techniques using freeze-out loops and
temperature-programmed capillary columns have been developed and used
for similar experiments. However, the instruments are expensive and re-
quire an experienced operator. Therefore, a maximum of five research
sites should be established. It will be necessary to have a technician
present while the gc is being operated, but he will be available for
other tasks at the same time.
The gc output should be fed directly into a digital integrator,
which would record the retention time and area for each peak. If suit-
able instrumentation could be purchased, it would be best to have a sin-
gle integrator located at the central laboratory in st. Louis which would
monitor all five instruments simultaneously. Instead of requiring five
integrators at $6,000 each, one $30,000 computer could be purchased which
would be much more flexible and save time in later data workup. The big-
gest problem will be the identification of the gc peaks. The mixtures
that can be anticipated immediately downwind of the city are so complex
that completely automatic peak identification may be impossible. Data
workup procedures must be developed during the test and break-in periods
of the study. Therefore, acquisition of the required instrumentation
should begin in early 1974. The system should be operational in January
1975.
The technicians who will carry out the aerosol
experiments would also operate the gc apparatus. A
program would minimize the work load.
particle collection
staggered monitoring
The most satisfactory way to determine the HC distribution is also
the most complicated: gc-mass spectroscopy. In theory, complete iden-
tification of all compounds, including oxygenates, is possible. In many
cases, compounds that elute under the same peak can be identified sepa-
rately.
Due to equipment, personnel, and operating costs, only one gc-mass
spectrometer should be purchased and installed at the central laboratory
facility. Samples would be collected in evacuated glass or stainless
IV-48
-------
steel bottles at the five research sites and brought to the
cility for analysis. Coordination with the gc operation at
sites is desirable. In this way, scheduling conflicts with
identification program can be avoided.
central fa-
the research
the aerosol
Formaldehyde, Total Aldehydes, and PAN--Formaldehyde, other alde-
hydes, and PAN are all photoproducts whose concentrations as a function
of time are predicted in current simulation models. Therefore, a program
to monitor these materials is recommended for the RAPS to begin January
1974 at the five research sites. The major difficulty is that automatic
monitoring instruments are not available.
The chromotropic acid method for formaldehyde is specific, simple,
and thoroughly tested (USDHEW, 1970a). It is, however, a wet chemical
method. The sample is bubbled through a solution of chromotropic acid
in concentrated sulfuric acid. The collected sample solution is stable
for several days. Therefore, hourly samples from all sites could be col-
lected, brought to the central laboratory, and analyzed the next day.
A colorimeter, such as a Bausch and Lomb Spectronic 20, is required for
the analysis.
There are several methods available for determining total aldehydes
(USDHEW, 1970a). The 3-methyl-2-benzothiazole hydrazone (MBTH) method
(Altshuller et al., 1961) has been recommended by EPA as most suitable
for routine analysis (USDHEW, 1970a), even though aromatic aldehydes are
not quantitatively determined. Alternative methods, such as trapping in
bisulfite, are known. Two analytical methods have been used. The un-
complexed bisulfite can be titrated with iodine. Alternatively, the bi-
sulfite complex can be decomposed by acid and the released aldehydes
reacted with 2,4-dinitrophenyl hydrazine. However, the resulting phenyl
hydrazone derivatives have different absorption curves, complicating the
colorimetric analysis. Detection of higher aldehydes is apparently lim-
ited by their solubility in water. On the other hand, it was recently
shown in these laboratories that benzaldehyde was quantitatively trapped,
suggesting that the method may be more suitable than the MBTH method if
it could be shown that higher aromatic aldehydes can also be quantitatively
trapped. Therefore, we suggest that whereas the MBTH method is commonly
accepted, it should not be used without careful consideration early in
the RAPS program.
The well-known eye irritant peroxyacetyl nitrate (PAN) is also a
commonly predicted photoproduct in HC:NOx simulation models. Its con-
centration in Los Angeles rarely exceeds 0.05 ppm (USDHEW, 1970a). We
expect that the PAN concentrations in st. Louis should be even lower
IV-49
-------
since that atmosphere contains a higher concentration of chemically re-
ducing species.
Two methods of analysis are used for PAN detection: long path in-
frared and electron capture gas chromatography. Both are difficult meth-
ods. The long path infrared method can be ruled out immediately because
the equipment costs are high, it requires a skilled operator, and, most
important, it is of limited sensitivity (0.05 ppm). Electron capture
gas chromatography has a sensitivity to PAN in the ppb range and also a
low sensitivity to interfering compounds, such as hydrocarbons. Current
manual techniques are satisfactory, provided daily calibrations with
ethyl nitrate are performed. An experimental automatic detector has
been developed (stevens, 1969).
In view of the very low concentrations expected in the st. Louis
area and the difficulties in using the gc method on a routine basis, we
believe that the anticipated usefulness of the data does not warrant a
PAN measurement program for the RAPS research program at this time. If
later considerations suggest that PAN measurements would be useful, then
an automatic instrument should be developed with an output that is com-
patible with the central data storage system.
NH3 Monitoring Program--This program is designed to assess the im-
portance of NH3 in the formation of particulate matter. Initial experi-
ments should determine' the background concentration of NH3 upwind of the
st. Louis region. The change in concentration of gaseous NH3 as an air
parcel passes through the urban area should be measured. If there are
no NH3 sources in the st. Louis area, then the total mass of NH3 should
not change. However, as aerosol is formed, the NH3 will be absorbed and
partially neutralize the acidic materials (H2S04 and HN03) in the aerosol.
By measuring both gaseous NH3 and NH4+ contained in the aerosol, it should
be possible to account for all of the NH3' A simple model based entirely
on meteorological factors should account for changes in total NH3 + NH4+'
To the best of our knowledge, there have been no extensive NH3 moni-
toring programs. There are several analytical methods for NH3' The clas-
sical wet chemical method involves absorption in dilute H2S04 followed
by analysis with Nessler's reagent. However, large volumes of air must
be pulled through the dilute H2S04 solution and some methods require dis-
tillation of the NH3 from the neutralized absorption solution. An alter-
native instrumental method has been reported by Hodgeson et al. (1971).
The NH3 is catalytically oxidized to NO in a heated tube and detected by
a chemiluminescence NO detector.
IV-50
-------
Beginning in July 1973 the research staff should select and test
one of the possible NH3 wet chemical analytical methods. A preliminary
program should start as soon as facilities at the five research sites
are installed. At the same time, NH4+ should be measured in the hi-vol
samples collected at the five research sites. This brief program should
delineate the general NH3 concentration changes as an air parcel passes
through st. Louis. Examination of the direction and magnitude of the
changes should enable the research team to determine the course the NH3
monitoring program should take.
Final recommendations for the remainder of the RAPS should be com-
pleted by January 1974. The NH3 monitoring network should be operational
by July 1974. Investigation of the factors which determine the rate of
absorption of NH3 by aerosols will be much more difficult. !mportant
variables will include relative humidity (RH), S02' NOx' S04-, and N03
in the aerosol, which are already required for other research programs
during the RAPS. However, since the absorption of NH3 will be a_neces-
sary step for formation of aerosols containing both N03- and S04-' we
do not recommend an extensive NH3 monitoring and modeling program at
this time. However, the recommendations of the research team could in-
clude such a program.
The CO Research Program
There are two possible CO sinks in the biosphere. Inman et al.
(1971) have found that fungi in the soil rapidly absorb low concentra-
tions of CO. It is also well known that CO is oxidized to C02 by OH
radicals. Using estimated average values for the rate of CO uptake and
OH concentrations, we estimated that the rates could be comparable.
While better estimates of the OH concentration in urban atmospheres
would be desirable, it is virtually impossible to obtain such data with
present techniques. However, improvements could be made to the CO ab-
sorption rate measurements by using more sensitive CO detection techniques
Such measurements may be available by 1974. The research team should
evaluate these data as part of the CO monitoring program.
Current transport models simulate fairly well the dispersal of CO
from urban sources. However, verification has been by measuring CO con-
centrations downwind of the sources. Similar data will be collected
throughout the RAPS by the Class A and B stations. As a further verifi-
cation of the CO models, the mass flux of CO passing through a vertical
plane downwind from the urban area should be measured. Ground level
measurements can be made at the downwind Class A stations. Aircraft
transects will be necessary to obtain vertical CO profiles. From these
IV-51
-------
data it should be possible, by including meteorological data, to calcu-
late the mass flux through the vertical plane. The simulation model can
also calculate a value for the mass flux, based on input data, such as
traffic patterns, stationary CO sources, and meteorological conditions.
The model can then be validated by comparing the measured value with that
calculated using the model. This experiment would be invaluable in eval-
uating the importance of CO sinks. The measurements should be made three
times in 1974, once each in spring, summer, and fall. Three days of mea-
surements each time should provide sufficient validation data.
At the same time, atmospheric samples should be taken at the research
sites for later submission for C12/C13 isotope ratio measurements. These
data provide supplementary information as to the origin of atmospheric CO.
IV-52
-------
REFERENCES
Altshuller, A. P. and J. J. Bufalini, Photochem. Photobiol. 4, 97 (1965).
Altshuller, A. P. and J. J. Bufalini, Environ. Sci. and Tech. 5, 39 (1971)
Altshuller, A. P., D. L. Miller, and S. F. Sleva, Anal. Chern. 33, 621
(1961) .
Bates, D. R. and P. B. Hays, Planetary Space Sci. 15, 189 (1967).
Bufalini, M., Environ. Sci. Tech. 5, 685 (1971).
Cadle, R. D. and M. Ledford, Air and Water Poll. Int. J. 10. 25 (1966).
Chamberlain, A. C., Int. J. Air Poll. 3, 63 (1960).
Cheng, R. T., J. O. Frohliger,
Assoc. 21, 138 (1971).
and M. Corn, J. Air Pollut. Control
Dunham, S. B.,
Nature, 188, 51 (1960).
Endow, N., G. J. Doyle, and J. L. Jones, Air Poll. Control Assoc. J.
13, 141 (1963).
Esmen, N. A. and M. Corn, Atmos. Environ. 5, 571 (1971).
Ford, H. W., G. J. Doyle, and N. Endow, ibid. 26, 1336, 1337 (1957).
Gartrell, F. E., F. W. Thomas, and S. B. Carpenter, Am. Ind. Hyg. Assoc.
J. 24, 113 (1963).
Gerhard, E. R. and H. F. Johnstone, Ind. Eng. Chern. 47, 972 (1955).
Germogenova, O. A., J. P. Friend, and A. M. Sacco, Bolt Beranek and
Newman, Inc., Cambridge, Mass., Final Report, Contract Nos.
CAPA-6-68(1-68) and CPA 22-69-29 for Coordinating Research Council,
New York, March 31, 1970. PB 192102.
Glasson, W. A. and C. S. Tuesday, Environ. Sci. Tech. 4, 916 (1970).
IV-53
-------
Harkins, J. and S. W. Nicksic, presented at
Meeting, Division of Petroleum Chemistry
1965 (reviewed in Bufalini, 1971).
American Chemical Society
Detroit, Mich., April 4-9,
Hill, A. C., J. Air Poll. Control Assoc. 21, 6 (1971).
Hodgeson, J. et al., "Application of a Chemiluminescent Detector for the
Measurement of Total Oxided of Nitrogen and Basic Nitrogen in the
Atmosphere," presented at the Joint Conference on Sensing of Environ-
mental Pollutants, Palo Alto, Calif., 1971.
Inman, R. E., R. B. Ingersoll, and E. A. Levy, Science 172,1229 (1971).
Inman, R. E. and R. B. Ingersoll, ibid. 21, 646 (1971).
Jaffe, L. S., Air Pollut. Control Assoc. J. 18, 534 (1968).
Johnson, W. B., F. L. Ludwig, W. F. Dabberdt, and R. J. Allen, "Develop-
ment and Initial Evaluation of an Urban Diffusion Model for Carbon
Monoxide," Paper No. 25 B, presented at the 64th Annual Meeting,
American Institute of Chemical Engineers, San Francisco, California,
November 28-December 2, 1971.
Johnston, H. S. and H. J. Crosby, J. Chern. Phys. 22, 689 (1954).
Johnstone, H. F. and D'. R. Coughanowr, Ind. Eng. Chern. 50, 1169 (1958).
Junge, C. E.
and T. Ryan, Quart. J. Roy. Meteorol. Soc. 84, 46 (1958).
Junge, C. E., Air Chemistry and Radioactivity, Academic Press, New York,
New York, 1963, 123.
Katz, M. and G. A. Ledingham, National Research Council of Canada, in
Effect of Sulfur Dioxide on Vegetation, NCR No. 815, ottawa, 1939.
Klosterman, D. L. and J. E. Sigsley, Environ. Sci. Tech. 1, 309 (1967).
Kummler, R. H., M. H. Bortner, and L. S. Jaffe, Environmental Sci. Tech.
5, 1140 (1971).
Leighton, P. A., Photochemistry of Air Pollution, Academic Press, New
York, 1961.
Levy II, H., Science 173,141 (1971).
IV-54
-------
McConnell, J. C., M. B. McElroy, and S. C. Wofsy, Science 1 (1971).
McKay. H.A.C., Atmos. Environ. 5, 7 (1971) and references therein.
Moffat, A. J., J. R. Robbins, and A. R. Barringer, Atmos. Environ. 5,
511 (1971) and references therein.
Prager, M. J., E. R. Stephens, and W. E. Scott, Ind. Eng. Chern. 52,
521 (1960).
Renzetti, N. A. and G. J. Doyle, Int. J. Air Pollut. 2, 327 (1960).
Ripperton, L. A. and D. Lillian, Paper 70-122 presented at 63rd Annual
Meeting, Air Pollution Control Association, June 14-19, 1970,
Accession No. N71-11216.
Robbins, R. C., "Developments of methods for selective removal of
oxidants from smog," Final Report, Project S-3200, Stanford Research
Institute, for Agricultural Air Research Association, University of
California at Riverside, January 17, 1961.
Robbins, R. C., R. D. Cadle, and D. L. Eckhardt, J. Meteor. 16, 53 (1959)
Robinson, E. and R. C. Robbins, "Sources,
Atmospheric Pollutants," Final Report
ican Petroleum Institute, Washington,
Abundance, and Fate of Gaseous
SRI Project PR-6755 for Amer-
D.C., February 1968.
Schvetzle, D., private communication, 1971.
Seinfeld, J. H., P. M. Roth, and T. A. Hecht, "A Kinetic Mechanism for
Atmospheric Photochemical Reactions," Appendix B of Report 71SAI-9,
Systems Applications, Inc., Beverly Hills, Calif., for EPA Contract
NO CPA 70-148, May 1971.
Sethi, D. S., J. Air Pollut. Control Assoc. 21, 418 (1971).
Smith, B. M., J. Wagman, and B. R. Fish, ibid. 3, 5581 (1969).
Stevens, C. M., L. Krout, and D. Walling, "Carbon Monoxide of the Atmo-
sphere for the Northern Hemisphere and from Natural Sources of the
Biosphere," Annual Report to Coordinating Research Council, Contract
CAPA 4-68(1-69) and U.S. Atomic Energy Commission, May 1,1971.
IV-55
-------
stevens, E. R., in Advances in Environmental Sciences, Vol. 1, ed.
J. N. Pitts, Jr. and R. L. Metcalf, Wiley-Interscience, 1969, p. 119.
Tingey, D. T., "Foliar absorption of N02'" M.S. Thesis, Dept. of Botany,
Univ. of Utah, Salt Lake City, Utah, June 1968.
Urone; P., H. Lutsep, C. M. Noyes, and J. F. Parcher, Environ. Sci.
Tech. 2, 611 (1968).
u.S. Department of Health, Education, and Welfare, Public Health Service,
National Air Pollution Control Administration, Washington, D.C.,
"Air Quality Criteria for Carbon Monoxide," March 1970b.
u.S. Department of Health, Education, and Welfare, Public Health Service,
National Air Pollution Control Administration, "Air Quality Criteria
for Hydrocarbons," Publication No. AP-64, March 1970a.
u.S. Department of Health, Education, and Welfare, Public Health Service,
National Air Pollution Control Administration, "Air Quality Criteria
for Nitrogen Oxides," Publication No. AP-84, January 1971a.
u.S. Department of Health, Education, and Welfare, Public Health Service,
National Air Pollution Control Administration, "Air Quality Criteria
for Particulate Matter," Publication No. AP-49 , January 1969.
u.S. Department of Health, Education, and Welfare, Public Health Service,
National Air Pollution Control Administration, Washington, D.C.,
"Air Quality Criteria for Sulfur Oxides," January 1969b.
Wayne, L. et al., J. Air Pollut. Control Assoc. 21, 334 (1971).
Went, F. W., Proc. Nat. Acad. Sci. 46, 212 (1960); Tellus, 18(203),
549 (1966).
Westberg, K., N. Cohen, and K. W. Wilson, Science 171, 1013 (1971).
Wilson, W. E. and A. Levy, "A Study of
Smog," Battelle Memorial Institute
Institute, August 1968.
Sulfur Dioxide in Photochemical
Report to the American Petroleum
IV-56
-------
Chapter V
RESEARCH PLAN--EMISSION ESTIMATES
Requirements of the Emission Inventory System
An emissions inventory system is an essential feature of any com-
prehensive air pollution abatement program for an area containing a sub-
stantial number of sources. At the very least, it serves to establish
the dimensions of the problem. It furnishes the basis for planning any
emissions reduction program, whether or not linked specifically or
quantitatively to air quality considerations, and thus is a necessary
component of an air quality implementation plan. Finally, an emissions
inventory must be employed in any attempt to predict air quality through
use of atmospheric diffusion models, simple or complex. It is this last
application that imposes the most stringent demands upon the emissions
inventory, since the time intervals of interest are generally relatively
short and the problem of producing an accurate inventory is thereby
accentuated. A number of emission inventories have been carried out for
various portions of the Greater St. Louis area, but they have been based
on long-term average emission rates.
The emission inventory system must satisfy two basic requirements:
The system must be applicable to the inventory of all
and all pollutants, including any not currently being
for immediate study or application of controls.
sources
considered
The system must be adaptable to the needs of atmospheric dif-
fusion modeling.
To satisfy the latter requirement, the inventory must be able to
predict with reasonable precision the emissions of any given pollutant
within any specified one-hour period. The inventory must therefore be
given in terms of baseline values of pollutant emissions together with
appropriate factors for adjusting the baseline emissions to the condi-
tions of the specified time interval. In this form, it is probably
better described as an "emission model." Determination of the base-
line emissions will necessarily require an extended period of time, but
the inventory system must permit ready correction of the baseline values
for long-term changes. The adjustment factors for short-term temporal
V-I
-------
variations should require use of the least possible number of independ-
ent measurements to describe the conditions of the specified time
interval.
Classification of Emission Sources
The broad classification of emission sources is presented in
Table V-I. This scheme is intended to accommodate all possible sources
and pollutants in a format that is structured according to the methodology
that must be used to gather the data and according to the way that the
information must be applied in diffusion modeling.
The primary division of sources into categories separates the
stationary from the mobile sources, since these present radically dif-
ferent problems with respect to both emission inventories and modeling.
In the secondary division, stationary sources are divided into area
sources and point sources, whereas mobile sources are composed of area
and line sources. Dividing the mobile sources into area or line sources
is a matter of expediency. Well-defined and heavily traveled traffic
arteries, such as freeways, can be treated as individual line sources.
The more diffuse traffic on city streets can best be handled on an area
basis.
The division of stationary sources into point and area sources is
necessarily arbitrary. The point sources, or source units, are those
large enough to warrant individual consideration. Area source units
are, by contrast, ones having relatively small emissions, and they can-
not for practical purposes be treated individually. The emissions from
those small units existing in a given area are therefore aggregated and
estimated from some factor, such as the consumption of fuel within the
specified area. In diffusion modeling, the aggregate emission may either
be considered as discharged from the center of the pertinent area, or as
distributed uniformly over it, depending on the requirements of the
model.
The criterion of size for the definition of point source units is
relative, and is related mainly to the precision desired for the inven-
tory and for the diffusion estimates derived from it. A unit emitting
a small absolute quantity of pollutant material may in fact be an impor-
tant point source if it nevertheless contributes an appreciable fraction
of the total emission of that specific pollutant into the region. A
given source unit may be relatively insignificant with respect to one
pollutant of interest, and at the same time be a very large emitter of
another pollutant.
V-2
-------
Table V-I
CLASSIFICATION OF SOURCES FOR EMISSION INVENTORY
<:
I
W
Source Stationary Sources Moblle Sources ]
Category
~----- -- --
Source Area Sources Point Sources I Area and Line Sources '
Subcategory i
- - .--- - -,------ -- -- 1
Source ,
Combustion Noncombustion Combustion Noncombustion Combustion I NoncombustioD
Process
Source Commercial Commercia 1 Uti 1i ties Industrial Surface Vehic les Surface Vehicles
Uni ts and Alrcraft
Iosti tutional Small Industrial Power plants Direct-fired Passenger cars
Residential Venting of process units VentJ.ng of fuel
org ani c Municipal Trucks and buses
vapors (dry incinerators All other industrial vapors t
Small Industrial CommercJ.al vehic les
cleaning, painting, processes, material Wear of tires
gasoline storage Industrial st orage and Railroads and brakes
Fuel Use
and handling, and handling
80i ler Vessels
Space heaters food preparation plant s
Water heaters power Off-highway vehicles
Boilers Indirect-fired and equipment
air and process
Waste Disposal heaters Aircraft
Incinerators Stationary internal Piston engines
combustion engi nes
Gas turbines
Stationary gas
turbi ne eog! nes
Incinerators
Gases and Vapors Gases and Vapors Gases and Vapors Gases and Vapors
Pollutants SO Organic vapors SO All pollutants SO Hydrocarbon
x (sol vent s. gasol i ne) x x
NO NO NO Vapors
x Odors x x
Part1culates
CO CO CO
Particulates Organic
Hydrocarbons Hydrocarbons Hydrocarbons Inorganlc
Organic aerosols deri vati ves and derivatives
and deri vati ves and
Smoke
HCI HCI Odors
HF HF Particulates
Odors Odors Smoke
Particulates Particulates Lead
Fly ash and its Fly as h and its Oi1 aerosols
specific chemi cal specific chemical Deri vat! ves of
components component 5 fuel addi ti yes
Smoke Smoke
-------
The decision as to whether a given emitter should be considered a
point source is also dependent on the location of the receptor. (The
receptor may in this case be considered as the point of measurement of
the pollutant atmospheric concentration.) If the receptor is located
nearby, even a relatively small emitter may have to be considered as a
point source. On the other hand, if the receptor is located at a
relatively great distance from the same emitter, the individual influence
of the latter on the pollutant concentration at the point of measure-
ment may be indistinguishable from the influence of a mass of other
small sources.
The potential accuracy of an emission inventory or model, and hence
of diffusion models employing its output, is largely related to the fine-
ness of resolution of the inventory; that is, to the degree to which
individual source units are specified. The actual accuracy required will
depend on the purposes for which the inventory is used and the partic-
ular circumstances under which it is applied. In general, the degree
of source resolution actually employed in diffusion modeling will prob-
ably be less than that attained in the emission inventory. However,
this cannot be assumed to be true in all cases, and it will be necessary
to be reasonably conservative in specifying source resolution in the
inventories. Workers engaged in diffusion modeling should undertake
to indicate the maximum resolution that they will require, although
compromises between the accuracy and the data-gathering effort will
often be required. Diffusion modelers will also have to exercise judg-
ment in deciding what part of the source resolution available to them
should actually be employed in any given study or set of circumstances.
Agricultural activities give rise to a number of atmospheric pol-
lutants, which generally come from emission sources in the categories
defined in Table V-I, or in directly analogous categories. For example,
engine exhausts from tractors and other powered agricultural equipment
fall directly into the category of mobile (or semimobile) combustion
sources. Dusts raised by operation of agricultural equipment are com-
parable with those produced by materials handling and storage in indus-
trial operations. Odors from cattle feed lots are likewise comparable
with those from various industrial processes. The wind-blown dust from
farm land is analogous to that from material storage piles at industrial
plants, and its amount is closely related to farming practice. Burning
of agricultural wastes parallels waste incineration in urban areas.
On the other hand, the application of agricultural chemicals such
as insecticides, fungicides, and herbicides, is in some degree a special
case. The agents are specific in their chemistry and effects. They
are also deliberately disseminated into the atmosphere, and become air
V-4
-------
pollutants to the extent that they drift beyond the area of intended
application.
Source Processes
The source processes are conveniently classified as either com-
bustion or noncombustion processes. Combustion processes are defined
as those in which the pollutants are produced exclusively by the burn-
ing of fuels or of solid or liquid wastes. They include all those
processes in which there is indirect transfer of the heat produced (e.g.,
boilers, indirect-fired air heaters) as well as incinerators, internal
combustion engines, and gas turbines. Noncombustion processes comprise
all other pollutant sources not falling under the specific definition
of combustion processes. They include operations in which combustion
takes place, but in which part or all of the pollutants emitted arise
from operations other than the burning of fuel or wastes. Examples are
those processes in which the products of fuel combustion come into direct
contact with materials being processed such as calcining of materials in
kilns.
By far the largest number of pollutant sources, stationary and
mobile, are combustion sources. In particular, combustion processes
comprise the most important area source units, and estimates of emissions
from these numerous contributors can be made from estimates of fuel con-
sumption. The most important noncombustion sources are industrial, and
are generally point sources.
Source Units
Stationary Sources
Area Sources--The stationary area sources are composed of residences,
commercial establishments and activities, institutional establishments
(e.g., schools, hospitals, and public buildings), and some small indus-
trial (manufacturing) establishments. Most of the pollutants arise from
the combustion of fuels used for space and water heating and steam
generation, and from combustion of wastes in small incinerators. How-
ever, the commercial category of sources includes some noncombustion
sources--primarily the venting of organic vapors from gasoline storage
and handling by distributors and service stations, dry cleaning, paint-
ing, degreasing, and application of asphalt to roofing and pavement.
Odors and smoke from large-scale food preparation, such as commercial
barbecue pits, sometimes constitute local nuisances, but are unlikely
to contribute significantly to total area emissions.
V-5
-------
Industrial establishments in this category are composed mostly of
small manufacturing operations that employ fuels primarily for space
heating, or that burn wastes.
Occasionally, individual source units in the residential, commercial,
or institutional classes may be large enough to constitute point sources.
Possible examples are the central heating plants of a large apartment
complex or of a university.
Point Sources--The stationary point sources comprise an extremely
wide variety of public utility and industrial (manufacturing) activities.
They may also include a few commercial and institutional sources, as
noted above.
When industrial plants are considered, it may be desirable to define
"sources" as entire plants rather than process units, at least from the
standpoint of data gathering. Some operations within an industrial
plant, such as space heating, might individually be of a scale to rank
only as contributors to area sources. Nevertheless, the data should be
accumulated initially as for other point sources, however it may be
treated thereafter.
Utility power plants include all forms of thermal power generation
systems: gas-, oil-, and coal-fired boilers, gas turbines, and diesel
engines. They may also include some noncombustion sources, such as coal
grinders and driers, and coal- and ash-handling systems. Gas turbines
and internal combustion engines are commonly employed as prime movers
for compressor stations on natural gas transmission lines. Municipal
incinerators and most industrial incinerators for solid and liquid wastes
will also fall in the category of point combustion sources.
Industrial point combustion sources will include steam boilers for
generation of either electrical power or process steam, indirect-fired
air and process heaters, and stationary internal combustion and gas
turbine engines. Industrial noncombustion processes will best be treated
exclusively as point sources. Even in cases where their emissions prove
to be small, this condition will not generally be obvious without exami-
nation of the particular instances. The industrial noncombustion source
category can be used to encompass virtually all stationary pollutant
sources not specifically defined elsewhere, including sources as diverse
as cement kilns, windblown dust from material storage piles, and vents
of organic chemical manufacturing processes.
V-6
-------
Mobile Sources
Mobile sources cannot, by their nature, be considered in a practical
way as individual units. However, they must be broken down by classes
to permit application of appropriate emission factors. The classes of
surface vehicles and aircraft are presented in Table I. The class of
off-highway vehicles and equipment includes tractors, earth-moving equip-
ment, and so on.
With respect to emissions inventory procedure, the distinction
between combustion and noncombustion sources is of far less importance
in the case of mobile sources than in that of stationary ones. Whereas
the stationary source units in the two categories are usually physically as
well as conceptually distinct from one another, the mobile source units
fall in both categories. The same inventory procedures and operations
that may be used to estimate combustion-related pollutants from vehicles
can also be used simultaneously to provide data on emissions of the non-
combustion pollutants, since volatilization of fuel and generation of
particulates by wear of brakes and tires can, like the emission of engine
exhaust, be related to the mileage that a vehicle is driven.
Pollutants
The pollutants f~om noncombustion sources may include anything (see
Table V-I). The major pollutants from combustion sources are relatively
few in number, although many other materials may be present in relatively
small quantities. Broadly, there are two groups of pollutants from com-
bustion of fuels. First, there are those arising from the oxidation of
the atmospheric nitrogen itself (nitrogen oxides) and from incomplete
combustion of the hydrocarbon or carbon fuels, such as unburned hydro-
carbons, aldehydes, carbon monoxide, and soot. Second, there are the
pollutants arising from the materials in the fuel other than hydrogen
and carbon--sulfur, chlorine, selenium, mercury, iron, alumina, silica,
and so on. These latter materials may either be chemically combined with
the hydrocarbon materials, or merely be mixed with the fuel (e.g., the
ash in coal).
The incineration of solid or liquid wastes can, of course, be respon-
sible for the emission of a very wide variety of pollutants, depending
on the composition of both the combustible and noncombustible portions
of the waste.
Mobile sources primarily emit pollutants associated with combustion
of fuels, including fuel additives such as tetraethyl lead. However,
V-7
-------
they are also responsible for
Hydrocarbon vapors are emitted
dumping of fuel from aircraft.
tires and brakes.
emission of noncombustion pollutants.
by the venting of fuel tanks and by the
Motor vehicles generate dust by wear of
Factors Affecting Emission Levels
Stationary Sources
Area Combustion Sources--The greater portion of the fuel consumed
by area combustion sources is used in space and water heating and in
cooking. The rate of fuel consumption therefore exhibits pronounced
diurnal and seasonal variations as well as variations related to ambient
temperatures. Fuel consumption peaks appear over periods of one to three
hours. Fuel consumption patterns at commercial, institutional, and small
industrial operations depend on whether operations are carried on only
during the day. or during nights and weekends as well. They therefore
vary from the consumption patterns of residential resources. Both the
nature and the amounts of pollutants generated vary with the type of
fuel used, which is in turn undergoing changes throughout many cities,
including St. Louis. Individual residences and small apartments increas-
ingly tend to use natural gas, whereas large apartment houses and com-
mercial, institutional, and industrial operations are relatively more
likely to use oil or coal. Emissions are also related to the size and
type of combustion equipment, with the effect of such factors on emis-
sions probably being most pronounced in coal-fired units.
Practices employed in waste incineration may vary widely. where
incineration is used at all.
Area Noncombustion Sources--The most important of the area noncom-
bustion sources are those emitting organic vapors. The emissions of
gasoline vapors from automobile service stations will vary with the day
of the week and the hour of the day, as the volume of business fluc-
tuates. The emission of cleaning fluid vapors from dry cleaning estab-
lishments should be relatively more constant during actual working hours.
Solvent vapor emissions from the painting of products in small manu-
facturing establishments will have a similar temporal pattern. On the
other hand, the solvent vapor emissions from the painting of buildings
will be irregular with respect to both the time and the location of the
operation.
V-8
-------
Point Combustion Sources--Utility power plants handle a fluctuating
generating load that usually follows a fairly well defined cycle.l The
typical load passes through a minimum in the early morning hours and
reaches its peak value in the afternoon. The absolute levels are func-
tions of the season of the year, as are the hours at which the minimum
and maximum values are reached. The daily peak load varies with the
average daily temperature,l and presumably could be even more closely
correlated with the hourly mean temperature. The daily peak load
increases with lowering of the average daily temperature during the fall,
winter, and spring, evidently reflecting increased space heating loads.
It increases sharply with increasing average daily temperature during
the summer, and more moderately in the fall, showing clearly the influence
of the air conditioning load.
The pattern of emissions from power plants will reflect the generat-
ing load cycle, but the absolute emission levels at any given plant will
be set largely by the fuel and the air pollution equipment used. Some
power plants, at least, may be able to shift from one fuel to another
during various periods, and a general trend toward use of low-sulfur
fuels is probable during the early phases of control implementation plans.
The performance of fly-ash control equipment will be the most important
factor determining emissions of particulate matter from coal-burning
plants.
Industrial power 'and steam plants will usually display load patterns
substantially different from those of the public utility plants serving
the general area. Where the manufacturing plants are operated on a
24-hour basis, both the electrical power and the steam required for
process use should in general represent fairly steady loads. The power
and steam required for air conditioning and space heating will, of course,
superimpose a fluctuating load on that resulting from process requirements.
Depending on the type of manufacturing, the process loads may
exhibit cyclic behavior, perhaps over short intervals (electrical power
loads in a steel rolling mill). However, the hourly average demand may
not vary much from hour to hour.
Point Noncombustion Sources--Point noncombustion sources comprise
such a diverse collection of manufacturing operations that little of a
1.
J. J. Roberts et al., A Multiple-Source Urban Atmospheric Dispersion
Model, Argonne National Laboratory Report No. ANL/ES-CC-007 (May
1970) .
V-9
-------
general nature can be said of the factors affecting their emissions.
Most of the large emitters operate fairly steadily on a 24-hour basis,
but there are a number of batch processes whose emissions show a cyclic
behavior over short intervals even though their longer term averages
are relatively constant. An example of the latter category is the
pushing and quenching of coke at coke oven plants.
part
that
When the point noncumbustion sources are
of the task will be determination of the
short term emissions can be estimated.
inventoried, an essential
pattern of operation so
Mobile Sources
The average emissions from automobiles, expressed as mass emitted
per mile of travel, are functions of the average vehicle speed. The
emissions of hydrocarbons and carbon monoxide per mile driven tend to
decrease as driving speed increases until about 70 mph is reached, then
increase again. At the lower driving speeds, the approach to the idling
mode results in a richer engine mixture, with accompanying higher emis-
sions. Also, in actual highway travel, acceleration and deceleration tend
to be more prevalent at the lower than at the higher speeds, and lead to
relatively higher emissions. At very high speeds, also, the engine mix-
ture tends to be richer.
In contrast to the emissions of carbon monoxide and hydrocarbons,
the emission of nitrogen oxides can be expected to increase generally
with increase in driving speed.
The volume of traffic of course exhibits a very marked diurnal
pattern, with the patterns for Saturday and Sunday differing from those
for weekdays.2 The pattern of use of various streets and other traffic
arteries also varies at different hours of the day. There is also some
seasonal variation in traffic volume. Since average vehicular speeds on
the different types of traffic arteries vary, so do the emission rates.
Obviously, the installation of emission control devices will in the
future be a major factor affecting emissions from motor vehicles. Esti-
mation of emissions must include allowances for the distribution of ages
among the automobile population.
2.
Ludwig, F. L., A. E. Moon, W. B. Johnson, and R. L. Mancuso, A
Practical, Multipurpose Diffusion Model for Carbon Monoxide,
Stanford Research Institute Final Report to CRC/NAPCA, Contract
No. CAPA-3-68/CPA 22-69-64 (September 1970).
V-IO
-------
Inventory Procedures and Accuracy
Accuracy of Estimates
Atmospheric diffusion models are based on the assumption that the
predicted atmospheric concentration of a pollutant is directly propor-
tional to the source strength (i.e., the estimated pollutant emitted per
unit time from the source). Therefore, for the case of a single emission
source, the error in the predicted concentration will also be directly
proportional to any error in the estimate of the emission. If there are
multiple pollutant sources, the error in the predicted concentration will
still be directly proportional to any systematic error in the total
estimated emission. However, random errors in the estimates of the com-
ponent emissions will tend to cancel each other, reducing their effect on
the predicted concentration. Obviously, the degree to which the random
errors actually do cancel depends on the weighting of the individual
component estimates (and their errors) in the total.
In the limit, of course, the accuracy of predictions made from dif-
fusion modeling cannot exceed the accuracy of the input data on pollutant
emissions, and may be less because of other and possibly larger errors
in other input data. In the testing of diffusion models, it is essential
that the accuracy of the emission estimate be such that it will not be
the ultimate limiting factor in the accuracy of the tests. An essential
part of the research program will be an examination of the magnitude of
the errors introduced into the emission inventory by the procedures and
assumptions used, and of the effects of these errors on the validation
of the diffusion models. Another essential research task will be to
devise inventory procedures that will minimize these errors without adding
unreasonably to the time and costs required for execution of the inventory.
Long term emission inventories (e.g., those yielding annual average
emission rates) can be made with a relatively high degree of accuracy,
limited primarily by the level of effort that can be devoted to data
gathering. However, several man-years of effort will generally be
required to obtain the data for a large metropolitan region, such as St.
Louis. Furthermore, when emissions are to be estimated for some specific
area and for a short interval of time, primary data leading directly to
emission estimates may simply not exist; indirect means of estimation
must be used. The other inputs to the diffusion model, primarily meteor-
ological data, will be obtained on a real-time basis, as will be the
measured atmospheric pollutant concentrations used to check the predicted
values. However, essentially no primary emission data can be gathered
on a real-time basis. A stated goal for the modeling program is to treat
time intervals as short as one hour. For intervals of one hour, or even
V-II
-------
of several days, it is possible only to measure certain variables that
may be used to adjust baseline values of emission rates to the conditions
of the particular period of concern. In the case of fuel combustion for
space heating, the pertinent variables may include the atmospheric
temperature, the hour of the day. and the season of the year, which will
all affect the consumption of fuel. In a power plant, the consumption
of fuel can be related to the amount of electrical power generated.
Once the amount of fuel consumed is known, the estimate of the emission
still depends on another predetermined or assumed quantity, the emission
factor. Emission factors can represent quite accurately the magnitudes
of long-term, average emissions. On the other hand, the use of average
emission factors can easily result in an error of twofold or more when
a short time interval is involved. This is particularly true of noncom-
bustion processes. Additional, subsidiary factors descriptive of the
emitting process may therefore have to be applied to the emission factor
for an important point source.
In the Chicago Air Pollution Systems Analysis Program conducted by
Argonne National Laboratory.l algorithms were developed to simulate the
hourly variation of utility power plant electricity generation and pol-
lutant output. Although ANL used actual hourly megawatt production as
input data in its validation tests of the diffusion model, the algorithms
are used in routine applications of the model. ANL also developed
algorithms to simulate the emissions from other point combustion sources.
Although similar algorithms can be derived for point sources in the
St. Louis area, it appears advisable to employ specific and directly
obtainable data to the maximum degree possible during model validation
tests. Each simulation necessarily involves certain potential errors
that should, if possible, be avoided in the validation tests even though
they may be acceptable in more routine applications of diffusion models.
It will also be necessary to develop more accurate emission factors
for large individual emission sources, probably including values specific
to some of the St. Louis operations. For small, numerous units, such as
gas-fired space heaters, average factors can be developed from tests of
typical units, either in the St. Louis area or elsewhere. However, for
at least part of the large sources, such as power plant boilers, it will
probably be necessary to develop data from sampling of the specific units
in the St. Louis area. Accurate information must also be obtained on the
efficiencies of air pollution control systems in use.
V-12
-------
Procedures
Execution of Emission Inventories--The emission inventory for the
St. Louis region, which contains a complex combination of many different
sources, will actually consist of a number of subsidiary inventories that
can, and in some cases probably should, be conducted separately, since
some of them call for different kinds of talents and experience on the
part of the personnel carrying out the work. In the case of point sources,
it will be necessary to make a source-by-source survey, employing direct
interviews. Mailed questionnaires cannot be expected to yield the
detailed information needed. Because of the extreme diversity of the
industrial noncombustion sources, in particular, it is not practical even
to produce an adequate, generalized questionnaire. Individuals conduct-
ing the interviews must make themselves reasonably familiar with the
process technology of the pollution sources.
It is essential that whatever agency conducts the emission inven-
tories have full legal authority to require submission of complete infor-
mation from all pollutant emitters. Otherwise, the required information
simply will not be obtained, as has been demonstrated by the experience
of agencies that have sought to obtain information on a voluntary basis.
However, it is obvious that the required data may include industrial
information that either is, or may be claimed to be, confidential or
proprietary. It is here assumed that the EPA will have authority under
the Clean Air Act of 1970 to collect the information needed, but it is
not clear whether the'task can be delegated to a contractor or even to
state or local government agencies. For the present it is assumed that
collection of the information will have to be carried out by EPA person-
nel. Furthermore, since analysis of the data and their incorporation
into emission models will also require contact with the same confidential
information, it must also be assumed that only EPA personnel will be able
to carry out that work.
In any case, it is essential that a single agency carry out (or,
at least, prescribe and supervise) the collection of inventory informa-
tion for the entire air quality region under study, without regard to
state or local governmental boundaries. Only in this way can uniform
procedure and treatment of information be assured.
Point Sources--Previous emission inventories of the St. Louis area
have identified about 100 to 150 point sources of one or more of the
following major pollutants: sulfur oxides, particulates, carbon monoxide,
hydrocarbons, and nitrogen oxides. A more refined inventory and inventory
V-13
-------
procedure necessary to support the diffusion modeling program may require
a finer solution of sources, with specification of a much greater number
of point sources. In particular; the number of point sources treated
must be increased once consideration is given to the noncombustion sources
of particular pollutants not specifically indicated in the listing given
above.
From data of the U.S. Census of Manufacturers and other sources, it
appears that there may be within the St. Louis Interstate AQCR as many
as 1000 or more manufacturing establishments, utility plants, and other
operations that might be considered point sources with respect to some
pollutant or other. Some of these establishments may have a number of
emission points differing with respect to pollutant emitted, stack height,
and stack gas temperature and exit velocity, as well as with respect to
physical location. A steel plant may easily have several dozen emission
points, but not all of these will necessarily qualify for classification
as point sources with respect to any given pollutant being considered.
Actual or potential point sources must be identified at a relatively
early date in the inventory program, but in a few cases information from
the survey itself may be necessary to establish definitely whether the
sources should actually be treated as point sources.
The data collected for the point sources must include not only the
emissions, but also the information necessary to permit calculation of
the diffusion of the pollutants emitted--stack height and diameter, stack
gas exit velocity and temperature, and information for adjusting the
latter two factors for variations in the source operating conditions.
For the individual point sources--or for groups of point sources,
if possible--it will be necessary to establish a baseline level of emis-
sions that can be adjusted to the circumstances of a particular hour.
The baseline condition can be chosen for convenience, and need not be
the same for all sources. However, the inventory system must provide
for review at frequent intervals to maintain current information on major
systematic changes in the sources, such as changes of fuel or installa-
tion or upgrading of control equipment.
The factors used to adjust the baseline inventory values to the
conditions of the desired one-hour period should be few in number, and
should as far as possible consist of (or be derived from) routinely
recorded operating data. In the case of power plants, this will be the
electrical energy generated. For industrial boilers, it may be the
quantity of steam produced. Provisions must be made to collect such
information rapidly and with a minimum of effort.
V-14
-------
Because industrial sources are extremely diverse and information
about them is relatively less accessible than for utilities, the deriva-
tion of adjustment factors for their emissions will be particularly
dependent on the survey interviews. One of the tasks of the inventory
will be to decide which industrial sources will have to be checked
specifically with respect to their operations during the given hour of
a model validation test, and which can safely be assumed to be operating
in their steady, "normal" condition. Adjusting the baseline emission
rates to the circumstances of a particular hour may be relatively easy
for some processes that operate steadily on a 24-hour basis, but very
difficult for certain other processes that operate irregularly, or on a
batch or cyclic basis.
Stationary Area Sources--Area combustion source units cannot be
surveyed individually, and their emissions can be estimated only through
estimation of their fuel consumption and consumption patterns. Emission
factors characteristic of the general type of combustion equipment and
of the type of fuel must be applied to the quantity of fuel burned to
obtain estimates of the amounts of pollutants emitted. The greatest
problem lies in determining the rates of consumption of each kind of fuel
in a given area during the specific, short (one-hour) time intervals of
interest.
In the case of natural gas, the overall consumption pattern for
large areas is well known by utility companies supplying the gas. How-
ever, the degree to which the consumption of gas can be broken down by
areas within a city or other region is uncertain. Practice in locating
metering stations is not uniform. Furthermore, the gross usage of gas
in the area supplied from a given metering station will in general repre-
sent the overall pattern of consumption for a variety of emission sources,
possibly including some point sources being accounted for separately.
Where oil and coal are used for space and water heating in area sources,
information on fuel consumption is necessarily limited to data on the
total quantities consumed, generally over periods ranging from weeks to
months.
Determination of the short-term patterns of consumption of the dif-
ferent types of fuels by area emission source units will call for
relatively extensive field sampling surveys, such as have been made in
Chicago by ANL and described by Roberts at al.l in the report cited above.
Models must then be developed to represent the emissions from each type
of source in terms of the amount and kind of fuel used, the time of year,
the time of the day and day of the week, and the ambient temperature.
Survey information must be used to derive the number of each type of
source unit in a given area.
V-15
-------
The emission models for the stationary area sources must be reviewed
at frequent intervals to take into account changes in the types of fuel
used, such as substitution of natural gas for oil or coal, or of oil for
coal.
The average emissions (primarily organic vapors) from area noncom-
bustion sources can be estimated by applying appropriate emission factors
to the quantity of gasoline handled, the amount of cleaning fluids con-
sumed, the amount of paint applied, and so on. However, it will be
necessary to determine the actual temporal pattern of operations to per-
mit estimation of the emissions during a given short time interval. To
do this will require surveying the operations at a representative sample
of establishments or activities of each type.
Mobile Line and Area Sources--A number of diffusion models have
been developed for estimating the spread of pollutants from vehicular
traffic, and Ludwig et al.2 have already applied one to the St. Louis
area. Corresponding emission inventories have been developed for use
these diffusion models, and an example is presented in the report by
Ludwig et al.2
with
The automotive emissions can be divided into two components:
(1) primary network link emissions from vehicles traveling on the net-
work of major arterial streets and freeways, and (2) secondary background
emissions from vehicles traveling over the less densely traveled local
and feeder streets. The primary network links comprise the sections of
major arterial streets and freeways between intersections with other
major arterials and freeways. The emissions from each link, which con-
stitute a line source, can be computed from the estimated traffic flow
and emission factors characteristic of the vehicles and their average
speed of travel. The vehicles traveling on streets not represented by
the primary network are treated as contributors to area sources. The
area under study is divided into squares according to the chosen grid
system, and the emissions from the local street travel in a given square
are assumed to emanate uniformly from that square.
The foregoing basic inventory system can be applied in the Regional
Air Pollution Study. The necessary refinements in the inventory will
deal with the methods for estimating the flow of traffic and the emis-
sions from the vehicles. One of the more critical and difficult problems
will probably be the determination of truly representative emission fac-
tors for vehicles operating under each set of circumstances.
V-16
-------
The data on total volume of traffic passing over the primary network
links can, for the most part, be obtained from the traffic departments
of the city or county governments. Data on the diurnal variations in
traffic flow can be obtained from the urban transportation studies made
under terms of the Federal Aid Highway Act. However, obtaining an ade-
quate definition of the diurnal variation in traffic will probably require
that some special measurements be made. Allowance must also be made for
the growth in the volume of traffic over the period of the Regional Study,
and this will probably call for special measurements. The accuracy of
forecast traffic data is uncertain.2
Special measurements and driver surveys will probably also be neces-
sary to determine the patterns of secondary automotive traffic and its
emissions.
The patterns of operation of public transportation facilities--
including buses, trains, and aircraft--are easily determined. In some
previous inventories, airports have been treated as point sources. How-
ever, for the purpose of short-term diffusion modeling, aircraft taking
off and landing are probably better treated as intermittent line sources.
The method of treatment of emissions from aircraft flying over the area
at relatively high altitudes remains to be decided.
The emissions from off-highway vehicles and mobile equipment, such
as tractors and earthmoving equipment, are probably a very minor part
of the total and of little influence in the immediate area where the
equipment is working.
Emission Model
The emission model will consist of algorithms developed from the
emission inventories for all the sources and pollutants in the St. Louis
area. Input to the algorithms of appropriate data descriptive of the
particular time interval of interest will yield the corresponding emis-
sions estimates. The model must supply not only the mass emission rate
for the pollutant in question, but also the information on stack exit
velocities and thermal emissions that are essential to estimating the
effective plume rises employed in the diffusion models.
When established in this form, the emission model will be readily
adaptable to a variety of purposes, the first in order of priority being,
of course, the validation testing of diffusion models. A second important
application will be in the testing of control strategies, although the
validity of such studies will hinge on prior validation of the diffusion
model employed.
V-17
-------
Control Strategy Studies
Except for preliminary training exercises, meaningful control
strategy studies using the diffusion and emission models must wait upon
experimental demonstration of the validity of the diffusion model or
models. The validity of the diffusion model must in this case be under-
stood to mean the ability of the model to predict atmospheric pollutant
concentrations within some specified degree of accuracy. The first
diffusion models tested may not meet the requirements for accuracy
necessary to make the results of control strategy studies significant,
even though they may be useful for other purposes.
Unless the alternative control strategies being considered in a
given case are widely different (e.g., overall emission reductions of
50% and 90%), an air quality model will have to be highly accurate to
predict whether the more lenient of the alternatives will actually meet
the specified air quality standard. For example, an error of I25% in
prediction of the actual atmospheric concentration may, in a simple case,
permit one to decide whether the overall control efficiency should be
95% rather than 90%, which is a substantial difference in required per-
formance. In more complex cases, and where proposed control efficiencies
are closer together, prediction errors will have to be reduced below I25%.
Inventory Schedule
In principle, it would obviously be desirable to inventory as many
of the pollutant emissions as possible at the same time, to avoid
repetitions of interviews and other duplications of effort. In practice,
it will probably be necessary to limit the number of pollutants covered
in anyone inventory. The development of basic information essential
to the inventory of certain pollutants may lag substantially behind the
need to inventory other pollutants. For example, emission factors for
nitrogen oxides are much less well established than those for sulfur
oxides, and are far more difficult to determine experimentally or to
predict. For numerous industrial noncombustion processes, emission fac-
tors for some pollutants will have to be determined experimentally before
statistical data on production operations can be used with confidence
to estimate emissions.
Since sulfur dioxide and carbon monoxide are the pollutants that
will be used in the first tests of air quality models, the initial emis-
sion inventories will be focused upon them. The tests with sulfur diox-
ide essentially treat the case of gaseous pollutant diffusion from
V-18
-------
stationary sources, since motor vehicles are only relatively minor
emitters of sulfur dioxide. On the other hand, motor vehicles contribute
by far the largest portion of the total emission of carbon monoxide.
Tests of diffusion models for photochemically reactive materials
(hydrocarbons and nitrogen oxides) will take longer to develop and
execute than those for relatively nonreactive compounds, such as sulfur
dioxide and carbon monoxide. Not only are the diffusion models themselves
more complex, but developing the inventory information is more difficult.
Emission factors for both hydrocarbons and nitrogen oxide are far less
well established than those for sulfur dioxides, for example, and con-
siderable experimental work will have to precede diffusion model tests.
As is discussed in Chapter III, the testing of diffusion models for
particulate matter; poses special problems and is probably better handled
in a different way. Modeling the diffusion of the particulate matter
actually being emitted from various sources will therefore be carried on
as a practical field demonstration of the technique rather than as a
primary test of the model. Completion of the particulate inventory,
including acquisition of the data on particle characteristics necessary
for successful modeling, will be scheduled for a later date in the study.
V-19
-------
Chapter VI
RESEARCH PLAN--ECONOMIC AND SOCIAL IMPACT STUDIES
Introduction
Air pollution problems are concerned not only with engineering,
chemistry, physics, and meteorology, but also have large-scale impacts
on the economic and social life of a community and a nation. The Regional
Air Pollution Study provides an unparalleled opportunity to accumulate
information on these community air pollution impacts because, if the
necessary economic and social data are collected within the RAPS area,
they can be related to detailed air pollution concentrations and exposure
information. This correlation between detailed physical and social
information on air pollution within the community should lead to an in-
creased understanding and more accurate assessment of the actual impact
of air pollution on the life of a community. Once a factual assessment
of air pollution impact is available, air pollution control operations
can be directed toward the most critical problem areas through new and
revised control strat~gy programs. These programs can be judged not only
on the basis of their impact on pollutant concentrations within the area
but also upon their costs and expected benefits. Thus, this type of
analysis can lead to control strategies that are judged upon their least
cost maximum benefit performance as well as upon their performance
relative to established air quality criteria.
There are several obvious costs of air pollution to the community.
These include damage to health, damage to property through corrosion and
staining, and reduced property values due to the unwillingness of buyers
to accept obvious impacts of air pollution, such as increased dust fall,
odors, and the like. Within a community the obvious benefits of air
pollution control are reductions in the costs that are attributed to
adverse pollutant levels. However, air pollution control has certain
well-identified costs; these include the cost of operating a control
agency, the cost to industry and to the public of buying and operating
pollutant control equipment, and the increased cost of goods and services
produced by industries where air pollution control significantly increases
the operating overhead expenses of the operation. All of these factors--
the damage due to air pollution, the benefits resulting from air pollution
control, and the costs of air pollution control--are interwoven in a
VI-l
-------
detailed fashion in the economic structure of any complex community.
These factors are also related in a very detailed fashion to the
meteorological and atmospheric pollutant patterns within the urban area.
Figure VI-l illustrates the three model components that might be con-
sidered necessary to define completely the impact of air pollution and
its control on a community. As illustrated in this figure, the air
quality and meteorological situations within an urban area impact on
control strategies and in turn lead to community benefits and community
costs. On a regional basis, both benefits and costs of air pollution
control lead to industrial investments and economic gains for the com-
munity, which again are related to the total economic structure of the
regional area.
The RAPS research program provides an ideal situation within which
to collect specific costs and benefit data, such as source control costs,
pollutant receptor distributions, and information on various air pollutant
damage functions. The RAPS air sampling network and the RAPS research
program will provide a vehicle within which the assessment of pollutant
concentrations and pollutant exposures can be made for correlation with
the observed or calculated costs and benefits. Although most of the
needs of the economic cost and benefit program for detailed air quality
and exposure data can probably be met by the regular air sampling program
planned for the RAPS operation, it may be necessary in some cases to
design special experimental or data-gathering projects to meet the needs
of specific economic or pollutant damage programs.
Human and Social Factors
Within the area of human and social impact, factors dealing with
the epidemiology and other health effects of air pollution must be con-
sidered to be of great importance. These research studies on health
effects would involve not only the gathering of data on health factors
and epidemiology for various population groups within the community but
also the assessment of the exposure of these population groups to air
pollution on the basis of models of pollutant distribution that are
available or will be available from other aspects of the RAPS research
program. After an initial assessment of health effects and their relation-
ship to modeled air pollution exposures, it is likely that additional
exposure information over particular population groups will be desirable.
A network of transportable air pollutant monitoring stations can gather
specific information in the neighborhood of the population groups under
study. Through the use of adequately developed models and historical
data on emissions within the RAPS experimental area, long-term exposures
of subjects and population groups can be calculated with much greater
VI-2
-------
<:
H
I
c..J
- - ECONOMIC MODElSYSHM - - - - - -,
(CONSAD RESEARCH CORP) I
I
I
I
I
1
I
I
REGIONAL INDUSTRIAL REGIONAL CHANGES OF REGIONAL I
INVESTMENT RE- ECONOMETRIC INCOME, CONSUMP- I
QUIRED BY AIR MODEL TION, VALUE ADDED,
POLLUTION ABATEMENT INVESTMENT AND EM- I
I STRATEGY PLOYMENT BY INDUS-
TRY, REGIONAL UNEM- I
I PLOYMENT GENERATED
ECONOMIC GAINS BY DIRECT COSTS AND I
I OF AIR POLLUTION BENEFITS OF EACH
CONTROL ABATEMENT STRATEGY I
I I
- --- ---- --1--- - ------ -- - - ---------.1
SA-1365-33
r - - - - - -I MPLEMENTATIONPLANNiNG PROGRAM - -
I . AIR QUALITY ITRW SYSTEMS)
DATA
I
I
I
I
I
I
I
I
I
. METEOROLOG-
ICAL DATA
ATMOSPHERIC
DIFFUSION
MODEL
. EMISSION
INVENTORY
. CONTROL
TECHNIQUES
AND COSTS
CONTROL
COST FILE
AIR QUALITY
DISPLAY
1------------
. CONTROL
I SUPPLIER
FUNCTIONS
I
I
I
I
I
I
I COST/BENEFIT MODEL
L - (PARTlAL~UNDER~EVELOPMENT) - -
POINT
SOURCE
CONTROL
__COST- ---4
AREA I
SOURCE
CONTROL 1
COSTS
I
I
. RECEPTOR
DATA
. DAMAGE
FUNCTIONS
. DIRECT EFFECTS
. ADJUSTMENTS
. MARKET EFFECTS
SOURCE:
-.
I
I
I
1----
I
I
I
I
I
REGIONAL VARIABLES
AT PREVIOUS YEAR:
VALUE ADDED
CAPITAL STOCK
CONSUMPTION
REGIONAL INCOME
REGIONAL INCOME
AND CONSUMPTION
INDUSTRIAL
OUTPUT
INVESTMENT
EMPLOYMENT
CAPITAL STOCK
NATIONAl
INPUT/OUTPUT
MODEL
POPULATION AND
MIGRATION
REGIONAl
UN EMPlOY MENT
LABOR FORCE
GOVERNMENT
EXPENDITURE
Woodcock, Kenneth R. A Model for Regional Air Pollution Cost/Benefit Analysis, TRW Systems
Group, McLean, Virginia, May 1971
FIGURE VI-1
INTERRELATIONSHIP OF MODELS PERTAINING TO AIR QUALITY
-------
accuracy than has probably been possible in previous studies of this type.
In fact, the use of the RAPS modeling program and emission inventories to
synthesize prior air pollution exposure patterns for use in epidemiological
studies may be one of the more significant contributions of this RAPS
experimental program.
It has been postulated that air pollution is one of the factors that
causes a shift in population and the resulting changes in land use. Thus,
the RAPS experimental program will be able to model air pollution concen-
tration patterns and air pollution exposures for current periods and also
to synthesize prior conditions. The results could serve as a basis for
the analysis of population and land use patterns and the determination of
correlations between the two sets of data. To support this correlation
study, detailed survey data on population distribution, population move-
ment, the development of new population centers, and the changes that
have taken place in land use over the RAPS area will have to be obtained.
If these changes can be shown to be closely correlated with air pollution
exposures, then it should be possible to describe the impact of this
particular situation on the structure of the regional community.
A relationship has often been claimed between air pollution or air
pollution control activities and employment or unemployment within an
urban or industrial area. The RAPS, especially the emission inventory
and control engineering information gathering system, will provide detailed
information on current air pollution and air pollution control activities
within the RAPS area and probably on major changes that have occurred
within the area during recent times. Detailed employment statistics are
also readily available for the St. Louis area. These two sets of data
should be analyzed to determine the degree to which changes in air pollu-
tion control activities or the development of air pollution problems has
impacted on the labor force within the regional area. Several possible
situations could be hypothesized for this relationship; the most obvious,
but not necessarily the most correct, is that the imposition of air pollu-
tion control measures has caused industrial operations to close and thus
to reduce the number of jobs available in a particular sector of the
industry. Probably an equally likely situation is that the development
of air pollution control programs within an urban area has produced a
better environment for general industrial development and, through the
increased attractiveness of an area for nonpolluting or pollution-sensitive
industries, a regional job force has been able to expand. Both effects
could obviously be going on simultaneously. By using the detailed data
on community air pollution situations available through the RAPS program,
it should be possible to separate these various factors as they pertain
to the RAPS community.
VI-4
-------
Economic Factors
Although all air pollution impacts on a community can be interpreted
in terms of economic impact, a number of conditions are recognized more
clearly than others as economic factors. The RAPS program thus should
be used as an experimental program through which to collect and analyze
the wide range of economic impacts that can result from air pollution and
air pollution control activities within a complex urban and rural regional
community. An obvious task is the collection of data on the costs of
inferior air quality to the general population, the commercial business
sector, the industrial and manufacturing sector, and the agricultural
sector. To collect these cost data it will first be necessary to develop
a model of probable cost impact and then to design a practical survey
technique by which data can be gathered for use in the cost model. Other
segments of the RAPS program, including particularly the source emission
estimation program and the air quality measurement program, can provide
direct input into this cost assessment study.
As a corollary study to the assessment of the costs of inferior air
quality, an assessment should be made of the costs related to control
agency operations and to the application of control technology to air
pollution sources. Control costs should be considered not only as direct
costs, such as equipment, but indirect costs such as changes in labor
utilization resulting from the introduction of new processes or the move-
ment of industries to new locations within a community.
Because of the detailed data that will be gathered within the RAPS
program on such factors as emissions, air quality, and community exposure,
it seems highly likely that the RAPS program can serve as a basis for a
number of special intensive studies in the economics and social area.
While this utilization of the RAPS program can be expected, it is more
difficult to point to a long list of intensive studies that might fall
in this category. However, some of the types of studies that should be
considered for this operation would include the costs and benefits of
changing additives in motor fuels, the costs and benefits of detailed
fuel switch operations, and the impact of specific sources, such as
fluoride emissions, on neighboring community activities.
In summary, the RAPS program, although strongly oriented towards
the gathering of physical data describing air pollution and its distribu-
tion within the regional area, can serve in an unparalleled way as the
foundation for comprehensive analyses of the impact of air pollution and
its control on the regional area. It can be argued that the success or
failure of an air pollution control strategy or program must ultimately
be measured by the cost and benefits that accrue to the community as a
VI-5
-------
result of its application rather than simply by the observed changes in
air quality that result from the modifications of emissions. In this
context the projects dealing with economic and social impacts effectively
closed the cycle of the RAPS research program within the regional area
since the air pollution cycle begins with the source emissions, includes
an atmospheric transport phase in which the pollutants are distributed
across the regional area, and finally results in some economic or other
impact upon the regional community.
VI-6
-------
Chapter VII
RESEARCH PLAN--TECHNOLOGY TRANSFER
Introduction
One of the major ongoing benefits of the RAPS is the fact that sub-
stantial technology will be developed that can be directly applied to
air pollution control programs throughout the nation. Thus, the RAPS
operation will serve as a means of upgrading local air pollution control
programs and in this way will make a major contribution to the nationwide
effort toward improved air quality. The need for improved technology at
the local level can be seen when it is realized that most local air
pollution control programs have grown primarily on the basis of local
needs and with minimum reference to modern technological resources. Only
in very recent years and under pressure from the Federal Air Quality Acts
and increased public demands for improved air quality have local programs
had the financial support that would permit them to expand their use of
advanced technology in seeking solutions to air pollution problems. Thus,
the RAPS with its numerous projects that can be related to local control
problems comes at a very critical time in the nation's air pollution
control operations; it is a time when there are increasing demands for
new and improved technology and increasing resources to implement new
technological programs. It is expected that the transfer of RAPS tech-
nology into the local sector will go a long way toward meeting the tech-
nological needs of air pollution control programs for new and advanced
technology.
Technology Transfer Program
The RAPS staff organization has a specific office with the prescribed
responsibility of directing a program to transfer technology developed
for the regional area into a form whereby it can be applied to local prob-
lems. Programs within the RAPS operation that will have important impact
on local operations include emission inventory techniques, air quality
and meteorological measurements, data handling and analysis, the objective
assessment of control strategies, and application of simulation modeling
to a wide range of problems.
VII-l
-------
The RAPS program in source estimation and emission inventory should
provide a basis by which local control programs can increase their effec-
tiveness in estimating emissions within their control area and, from
increased knowledge of emissions, can develop more effective control
strategies and better air quality at a lower cost for the community.
Emission inventory technology will be especially directed toward the
development of procedures to estimate emissions over short time periods
and toward improved understanding of emission factors to apply to spe-
cific sources. Improved data handling and data retrieval techniques
should also result from the RAPS program and be directly translatable
into local program operations.
Atmospheric monitoring networks are being required in the expanded
federal program under the Clean Air Act, and the sophisticated RAPS net-
work for both air quality measurements and meteorological measurements
should contribute to increased design effectiveness and the development
of more nearly optimum monitoring systems applicable to local area prob-
lems. The RAPS program will also provide means by which new technology,
such as remote sensing and aircraft monitoring of local sources, can be
integrated into local air monitoring programs.
Data acquisition technology including the topics already mentioned,
a source inventory and air quality data, is a very important area in which
improved technology can measurably improve the effectiveness of local
air pollution control programs. Computer operations are becoming wide-
spread and thus the translation of RAPS experience with automatic data
acquisition, data storage, and data retrieval can provide an excellent
background for upgrading local control operations in this area.
The Clean Air Act implies that local areas should use modeling
technology to design implementation plans and to provide some assurance
that planned control operations and control strategies will produce
acceptable air quality. To date, however, suitable models that have
gone through a program of verification and detailed application to air
pollution control operations have pot been available for the use of local
agencies in their design of control strategies. The RAPS program with
its heavy emphasis on model verification and subsequent model development
and model revision, including air quality strategy models, can provide
a major input into local air pollution control district operations because
simulation modeling techniques should be available and would provide
predictable degrees of accuracy and precision. The RAPS technology trans-
fer program in the area of modeling will be able to publish descriptions
of models and their performance and to supply information on the uses of
these models in the formulation of implementation plans and environmental
impact statements.
VII-2
-------
The design and operation of various control strategies to achieve
a desired air quality within a local region is an obvious ongoing require-
ment for local agency operations. Within the RAPS technology transfer
area, the problems of control strategy formulation will be considered as
a separate topic and the various areas of the RAPS that impinge on control
strategy development and control strategy testing will be integrated into
one program so that this important aspect of local control operations can
be presented as a single program for the use of local agencies.
The RAPS will also provide an impetus for the development of new
technology through instrumentation developments and the identification of
special needs for new measurement techniques and instrumental observations.
Instrumentation needs that have already been identified include aerosol
chemistry instruments, aircraft surveillance data acquisition packages,
and meteorological sensor packages. All of these areas have obvious
applications in local program areas, and, once the RAPS program has pro-
vided well-tested instrumentation designs, these procedures can be adopted
by local control operations.
In summary. the RAPS technology transfer program will have the spe-
cific obligation of surveying the total RAPS operation and of translating
the program carried out by RAPS into individual programs and information
circulars and reports that can provide local agency programs with improved
technology that has been proven by its application in the RAPS program.
VII-3
-------
Chapter VIII
OTHER AGENCY RESEARCH PROGRAMS
In developing this Prospectus, objectives and plans were developed
on the basis that RAPS would be an autonomous, independent study. The
possibility of collaboration with other programs that might be going on
in the same area was, of course, noted, but the principle was followed
that inputs and results from other programs would be supplementary rather
than complementary. This principle was based upon the belief that the
scope and objectives of RAPS were sufficiently important to warrant an
independent, sustained, and comprehensive effort. Certainly this prin-
ciple was a necessary factor in the planning phase--although the possi-
bility could arise, when the actual instrumentation and data collection
phases were begun, that some modifications and savings could be possible
by taking advantage of the existing data-collection facilities. Again,
the results of independent experiments would obviously be welcome in the
scientific analyses and studies being conducted under RAPS. On the other
hand, it is fully expected that the data collected and the results of
particular experiments carried out in RAPS would be fully and readily
available to other researchers working in the area, or, for that matter,
to Control Agency personnel for use in their control operations.
Many reasons that prompted the selection of St. Louis for the EPA
study have resulted in the selection of the St. Louis area for a number
of other studies in the past, as well as currently and in prospect. The
data acquired under past studies will be used in the early stages of RAPS
in developing a comprehensive data bank. As to current and planned pro-
grams, it is considered most important that close cooperation and col-
laboration be established and main~ained from the very beginning of RAPS.
Specifically, the RAPS Director should maintain liaison with such pro-
grams and in particular, be at pains to ensure that any economies that
can be effected by arranging for common service or shared facilities
should be taken. Further, it is considered that a specific Research Task
be identified that has as its objective the fullest exchange of plans,
data, and results on a scientific basis. Under this Task, the Leader
would be responsible for maintaining a continuing liaison with all other
groups and programs carrying out research in the area, and for ensuring
that there is a timely exchange of ideas, facts, and data. Thus, not
only would the material aspects of cooperation be covered, but the possibly
more important scientific aspects.
VIII-I
-------
Of recent years it has been increasingly realized that certain prob-
lems, or groups of problems, can be usefully addressed only on an
appropriately large scale, with a complex effort mounted by a number
of teams of workers. RAPS itself is, of course, such an undertaking.
The other major programs in progress or planned to take place in the
St. Louis area are of the same type. These will be considered in turn,
and discussed in terms of their relationship to RAPS.
METROMEX
METROMEX is a joint program concerned with the relationship between
urban pollution and precipitation. Four major groups are involved:
Illinois State Water Survey, Argonne National Laboratory, University of
Chicago, and the University of Wyoming. The project completed its first
season in the summer of 1971. The leader of the project is Mr. Stanley
Changnon of Illinois State Water Survey, and funding is largely provided
by NSF, AEC, and the State of Illinois. The Illinois State Water Survey
element has the following goals: (1) to explore the magnitude and
distribution of urban precipitation, (2) to study the temporal and spa-
tial variation of artificial tracers, and (3) to study local severe
storms. The primary monitoring entails a network of 220 weighing bucket
rain gauges within a 25-mile radius of St. Louis, half of which are to
be in operation throughout the year. Two weather radars are operated
during the experimental period and data were also collected from six
recording wind stations located around the 25-mile circle. Analyses
were also made of drop size distributions, the rain collected at 70 sta-
tions was analyzed for trace indicators, and a number of other records
were made including temperature and humidity at seven stations.
The Argonne National Laboratory element was concerned with the
mechanical and thermal effects of the urban core upon the wind distri-
bution over the area. The primary tool was a network of nine PIBAL
(pilot balloon) stations from which wind profiles were measured simul-
taneously at 20-minute intervals QY theodolite observations. Work was
also carried out on the analysis of rain water to measure the presence
of some 10 trace elements. The University of Chicago element was con-
cerned with the cloud physics of the effect of the city on precipitation:
(1) as shown by variations in nuclei population, (2) size distribution
of cloud droplets, (3) precipitation mapping by radar, and (4) delineat-
ing the urban cloud plume. Observations were made by an additional
ground-based radar and from an aircraft, which also had a radar, but
whose main role was in situ sampling of the cloud and aerosol.
VIII-2
-------
The University of Wyoming element had four objectives: (1) a study
of the mesoscale circulation in conjunction with their modeling efforts,
(2) a study of the Aitken and ice nuclei in urban areas, and (3) study
of the effects of urban areas on cloud growth. Most of the observations
were carried out by in situ sampling from an aircraft in flight, but PIBAL
observations were made at four stations and a series of radiosonde
measurements was also made.
It will be seen that the objectives of METROMEX coincide to a large
extent with those of Task 204 in the RAPS program.
NCAR Fate of Pollutants Study (FAPS)
During the past season's work on METROMEX, NCAR participated by
carrying out what is intended to be the first year's work on a more
extensive, independent study entitled, "Fate of Pollutants Study." Its
objectives are to determine the extent to which various pollutants are
removed from the air by nonmeteorological processes, such as chemical
reaction, absorption by plants, adsorption on surfaces and bacterial
action in the soil, and are thus prevented from contributing to regional
and world-wide atmospheric pollution. The NCAR activities at the time
of the METROMEX work were designed to answer certain questions related
to the experimental plan of the major FAPS study. These were: (1) Can
the plume position downwind of the city be forecast with sufficient
accuracy to allow stations to be placed in the plume? (2) At a distance
of 120 km, is there sufficient contrast between concentration in the
plume and the background concentration? Both these questions were
answered in the affirmative. In addition, they explored whether addi-
tional sources were present downwind of the city to cause complications
in the interpretation of the data. Some sources of S02 were found to
exist but could be identified and allowed for. (Concentrations of N02'
however, appeared to fall to the background level within 50 km or so of
the city.)
Longer-term plans of NCAR include sampling along two arcs, both
subtending an angle of 800 from the center of the city and located 80 and
120 km respectively, downwind. A variety of pollutants will be measured
at ground stations and from the air along these areas. Interpretation
of the data will be undertaken on three bases:
(1)
Model concentration comparison--relating measurements with
model computations for reactive species, validated against
unreactive species such as CO
2
VIII-3
-------
(2)
Flux through two planes--in which a mass balance of various
pollutants can be established
(3)
Ratios of pollutants--in which the relative concentrations
of various species are compared to determine the change and
rate of change of concentration of various contaminants.
Thus it will be seen that the NCAR program, which is scheduled for
its major session in the late summer of 1973, has very similar objec-
tives and approaches as the RAPS Task 205, and it is to be hoped that
the results of both experiments can be mutually supporting and beneficial.
NOAA's MESOMEX
A third major study in prospect is that planned by NOAA. The
objectives of this study are a better understanding and prediction capa-
bility (preferably objective) of atmospheric conditions in the boundary
layer on the mesoscale (250 by 250 km or so). Some initial experiments
have in fact been carried out in the Oklahoma City area last summer (1971),
but it is understood that the St. Louis area is being considered for
this project.
It would seem that this program would relate very closely to RAPS
plans for modeling th~ meteorological conditions of the boundary layer,
which have been described in the Research Plan Task 101.
Additionally recognizing the value of carrying out individual
experiments in areas in which minor observational programs are being
carried out, a number of separate research projects are in progress or
have been planned in the St. Louis area.
Finally, relevant research programs outside the St. Louis area
should be noted by the Task Leader of Task 400, and every effort made
to ensure a free flow of information in and out of the RAPS project.
A particularly important series of major experiments is about to be
carried out by various research teams under the sponsorship of the State
of California and the Coordinating Research Council in various parts of
California. Since these experiments will be a major source of informa-
tion on photochemical effects, particularly those related to smog forma-
tion from automotive products, their results should be carefully con-
sidered in the RAPS study for, in the St. Louis area, such effects will
not be highly developed.
VIII-4
-------
In conclusion, it appears that there is a considerable potential for
deriving benefits for the RAPS program from other ongoing programs, and
vice versa. Certainly, care must be taken to ensure that there is no
wasteful duplication of effort, although some overlap is probable and not
wholly undesirable. Regardless of other efforts in the same and similar
areas, it would be important to maintain a well-focused RAPS effort in
its own right for two reasons: (1) only by so doing will it be possible
to ensure a closely meshed, well-integrated contribution to the overall
RAPS program. (Many of the other proposed studies are planned to operate
on the basis of short-term intensive experiments, rather than on an ex-
tended basis.) (2) It is emphasized that RAPS objectives are directed
specifically towards a different goal. In the other programs noted, the
emphasis is mainly on the scientific aspects of the problems attacked, or
upon operational problems quite different from those of RAPS. RAPS is
concerned with the development of improved air pollution control strategies,
and this concept must dominate all its research tasks.
VIII-5
-------
Appendix
SCHEDULES AND TASK SPECIFICATIONS
FOR THE RESEARCH PLAN
A-I
-------
SCHEDULES AND TASK SPECIFICATIONS FOR THE RESEARCH PLAN
Introduction
The following schedules and specifications show how the Research
Plan would be accomplished within the proposed 5-year period. They fol-
Iowa structure reflecting the principal objectives of the study. Thus,
each principal objective is approached within principal tasks numbered
100, 200, 300, and 400, respectively. Separate research tasks are
assigned numbers within the 100, 200, 300, and 400 series, and a further
division into sub tasks is provided by adding numbers after the decimal
point. For example, Task 101 Boundary Layer Meteorology is a task with-
in the 100 series which is concerned with Model Verification. (Task
No. 100). Task 101.1 Area Climatology is an element of Task 101. A
task specification is given for each task, which states the objective
and purposes and scope of the research element concerned. It is intended
that professional responsibility for each task be assigned to an indi-
vidual, who would be charged with accomplishing his task in terms of its
stated objective. The Principal Tasks 100, 200, 300, and 400 in fact
would be carried out by the senior personnel of the project as part of
their assigned responsibilities. However, the leaders of the subordi-
nate tasks and subtasks (e.g., 101 and 101.1) would be engaged in the
day-to-day accomplishment of the work specified, each task leader of a
separate task (e.g., 101) being responsible for the product of the sub-
task leaders (e.g., 101.1) and responsible to the principal task leader
( e. g., 100).
Specifications for these tasks follow. Also presented are schedules
showing the general timing of the activity within the five-year period.
In both cases, the amount of effort that has been used as a basis for
planning and costing is indicated in terms of man-years of professional
and subprofessional effort.
A-3
-------
100 MODEL VERIFICATION
1972 1973 1974 1975 1976 1977
101 Boundary Layer Meteorology xx xxxx xxxx xxx x xxxx xx
(2.5 p)
101.1 Area climatology xx xx..
(.5 p, .5 s)
101. 2 Prior diffusion data xx xx..
( .5 p, .5 s)
101. 3 Compilation and analysis .xxx xxx x xxxx xxx x xx
of upper air data
(2.1 p, 2.1 s)
101.4 Compilation and analysis .xxx xxxx xxxx xxxx xx
of near-surface data
(2.1 p, 2.1 s)
101.5 Balloon-tracking experi- .xx.
ment
( .5 p, 1.5 s)
101.6 Diffusion tracer experi- .xx.
ments
( .5 p, 1.5 s)
101.7 Weather satellite appli- xxxx xx..
cations
(1. 5 p, .75 s)
101. 8 Forecast models . .xx xxxx xx
(2 p, 2 s)
Total effort
12.25 man-years--professional (p)
11.00 man-years--subprofessional (s)
A-4
-------
100 MODEL VERIFICATION (Continued)
1972 1973 1974 1975 1976 1977
102 Emission Inventory xx xxxx xxxx xxxx xxxx xx
(5 p)
102.1 Emission inventory design .x x...
(1 P. 1 s)
102.2 Collection of emission data xxxx xxxx (xxxx xxx x xx)
for stationary sources
(5.25 P. 5.25 s)
102.3
102.4
102.5
102.6
102.7
102.8
Collection of emission data
for mobile sources
( .5 P. 5. 25 s)
.xx(x xxxx
xxxx
xx)
xxxx
Emission model for station-
ary sources
(1 p, 1 s)
.xxx
xxxx
x.. .
Emission model for mobile
sources
. .xx
xxxx
xx. .
(lp,ls)
Emission source test
(6 p, 6 s)
xx (xx xxxx
xx)
. .xx
xxxx
Analysis of status of
source controls
( 1. 25 p)
.xxx
Emissions inventory of
cultural data sources
( .25 p, .25 s)
agri,-
.xx.
Total effort
20.25 man-years--professional
19.75 man-years--subprofessional
A-5
-------
100 MODEL VERIFICATION (Continued)
1972 1973 1974 1975 1976 1977
-
103 Air Quality Measurement xx xxxx xxxx xxxx xxx x xx
(4.25 p)
103.1 Data base .x x...
( .25 p)
103.2 Air quality data from local .x xxxx xxxx xxxx xxxx xx
agencies
( 1. 18 p, 4.75 s)
103.3 Analysis of air quality and .x xxxx xxxx xxxx xxxx xx
meteorological data acquired
by RAPS
(4.5 p, 8.5 s)
103.4 Analysis of air quality . (xxx xxxx xxxx xxxx xx)
data acquired by aircraft
( 1. 06 p, 2.1 s)
103.5 Fine scale spatial variation xxxx xx..
of air quality
( .75 p)
Total effort
12 man-years--professional
15.35 man years--subprofessional
A-6
-------
100 MODEL VERIFICATION (Concluded)
1972 1973 1974 1975 1976 1977
104 Model Calculation and xx xxxx xxxx xxxx xxxx xx
Verification
(2.5 p)
104.1 Evaluation of selected xx xxxx xxxx xxxx xxxx xx
models
(30 p, 70 s)
104.2 Model modification and . .xx xxxx xxxx xxxx xx
improvement
(2 p, 2 s)
104.3 Methodology for determining ...x xxxx xxxx xxxx xx
model accuracy
( 1. 88 p)
104.4 On-site computation and data . .xx xxxx xxxx xxx x xx
display
(2 p)
Total effort
38.35 man-years--professional
72 man-years--subprofessional
A-7
-------
200 ATMOSPHERIC, CHEMICAL, AND BIOLOGICAL PROCESSES
1972 1973 1974 1975 1976 1977
201 Gaseous Chemical Processes xx xxxx xxxx xxxx xxx x xx
(5 p shared wi th 202)
201.1 Hydrocarbon analyses and xxxx xxxx xxxx
monitoring
(2.06 p, 5.63 s)
201.2 Development of hydrocarbon xx xxxx
classifier instrumentation
(1.38 p)
201. 3 Total aldehyde-formaldehyde xxx x xxxx xxx x
monitoring program
(.19 p, .31 s)
201. 4 Determination of peroxy- xxxx xxx x
acetyl nitrate
( .44 p, .75 s)
201.5 Ammonia monitoring program ...x xxxx xxxx xxxx xx
(1 p, 3.12 s) .
201. 6 CO, S02' and N02 mass flux . .xx xxxx xxxx xx
measurements
( . 81 p, .88 s)
201. 7 Origin of atmospheric CO . .xx xxxx xx
(106 p, .75 s)
201. 8 Atmospheric odor identifi- ...x xx
cation
( .75 p, 1 s)
Total effort
11.69 man-years--professional
12.45 man-years--subprofessional
A-8
-------
200 ATMOSPHERIC, CHEMICAL, AND BIOLOGICAL PROCESSES (Continued)
1972 1973 1974 1975 1976 1977
202 Atmospheric Aerosol Processes xx xxxx xxxx xxxx xxxx xx
(Shared with 201)
202.1 Determination of total xxxx
nitrate in aerosol samples
( .31 p, 1.5 s)
202.2 Determination of total sul- xxxx
fate in aerosol samples
( .31 p, 1. 38 s)
202.3 Determination of aerosol xxxx xx..
size-distribution
( .69 p, 2.75 s)
202.4 The N02NaCl reaction in .xxx xxx x xxxx xx
aerosol
( .25 p, .13 s)
202.5 Isotope ratios of sulfate . .xx xxx x
aerosols
( .56 p, .75 s)
202.6 Organic compounds in partic- xxx x xx..
ulate material
( .75 p, .88 s)
202.7 Experimental measurements xxxx xx
of deposition velocity
( .56 p, 2.5 s)
Total effort
3.44 man-years--professional
9.87 man-years--subprofessional
A-9
-------
200 ATMOSPHERIC, CHEMICAL, AND BIOLOGICAL PROCESSES (Continued)
1972 1973 1974 1975 1976 1977
203 Other Pollutant Related Processes xx xxx x xxxx xxxx xxxx xx
203.1 Radiation balance modifica- . .xx xxxx xxxx
tion
(.69 p, 1 s)
203.2 Visibility reduction in xxxx xxxx
urban and rural areas
( .69 p, 1 s)
203.3 Transport of atmospheric . .xx xx
odors
( .25 p, .25 s)
203.4 Trace metals and toxic trace xxxx xxxx
materials
( .69 p, 2.5 s)
203.5 Agricultural chemical dis- . .xx xxxx xx
tribution
( .25 p, .75 s)
203.6 Natural sources of air pol- xxxx xxxx xxxx
luted compounds
(1.13 p, .19 s)
Total effort
3.69 man-years--professional
5.69 man-years--subprofessional
A-lO
-------
200 ATMOSPHERIC, CHEMICAL, AND BIOLOGICAL PROCESSES (Continued)
1972 1973 1974 1975 1976 1977
204 Atmospheric Scavenging by Pre-
cipitation
204.1 Instrument development for xx xxxx
pH and chemical sampling
(.50 p, .5 s)
204.2 Rainfall pH measurement xxxx xxxx xxxx xx
( .53 p)
204.3 Measurements of rainfall .xxx xxxx xxx x xx
chemistry
(.88 p, 5.25 s)
Total effort
1.90 man-years--professional
5.75 man-years--subprofessional
205 Air Pollutant Scavenging by the
Biosphere
205.1
Chemical content of vege-
tation
.xx.
. .xx
xxxx
(.5 p, 2 s)
205.2
Atmospheric pollutant con-
centrations related to vege-
tation absorption
(.5 p, 1.5 s)
. .xx
xxxx
xx
Total effort
1 man-year--professional
3.5 man year--subprofessional
A-ll
-------
200 ATMOSPHERIC, CHEMICAL, AND BIOLOGICAL PROCESSES (Concluded)
1972 1973 1974 1975 1976 1977
206 Atmospheric Processes
(1.5 p, 3 s)
206.1 Source factors in pollutant . .xx xxxx xxxx xx..
dispersal
( .5 p)
206.2 Terrain and surface rough- . xxx
ness effects
( .38 pJ
206.3 Extraregional and synoptic ...x xxxx xx..
scale circulation
( .75 p)
Total effort
3.12 man-years--professional
3 man-years--subprofessional
A-12
-------
300 HUMAN, SOCIAL, AND ECONOMIC FACTORS
1972
1975
1976
1977
1973
1974
301 Human and Social Factors
301.1
301.2
301.3
Data on epidemiology and
health effects
(4.5 p, 4.5 s)
Data on population and land-
use characteristics
Continuing low scale effort
Data on labor force utili-
zation
Total effort
4.5 man-year--professional
4.5 man-year--subprofessional
302 Economic Factors
302.1
302.2
303.3
Costs of inferior air
quality to industrial and
general population
(4.5 p, 4.5 s)
Continuing low scale effort
Costs of control strategies
Data collection surveys of'
specific effects
Total effort
4.5 man-years--professional
4.5 man-years--subprofessional
A-13
-------
400 TRANSFER OF RAPS TECHNOLOGY FOR CONTROL AGENCY APPLICATIONS AND THE
FORMULATION OF CONTROL STRATEGIES
1972
1973
1974
1975
1976
1977
401 Source Inventory Procedures
(lp,ls)
401.1
Techniques for making
source inventory procedures
401. 2
Techniques for inventory
storage and retrieval
xx. .
xx
401. 3
Techniques for updating
the source inventory
401.4
Relating source inventory
to control strategy
Total effort
1 man-year--professional
1 man-year-subprofessional
A-14
-------
400 TRANSFER OF RAPS TECHNOLOGY FOR CONTROL AGENCY APPLICATIONS AND THE
FORMULAT ION OF CONTROL STRATEG IES (Continued)
1972 1973 1974 1975 1976 1977
402 Atmospheric Monitoring
402.1 Basic network principles "xx xx
(.5 p)
402.2 Criteria for organization xx.. xx
and maintenance of ob-
servational networks
(.5 p)
402.3 Station siting and instru- xxxx xxxx xx
ment exposure criteria
(.25 p)
402.4 Methodology for modern~ xx" xx
ization of monitoring
networks
( .25 p)
402.5 Evaluation of ,new aircraft . . xx (xxxx xxxx xxxx xx)
measurement techniques
( 1. 63 p)
402.6 Evaluation of remote measur- . .xx (xx xxxx xxxx xx)
ing techniques
(2.75 p, 3 s)
Total effort
5.89 man-years--professional
3 man-years-subprofessional
A-15
-------
400 TRANSFER OF RAPS TECHNOLOGY FOR CONTROL AGENCY APPLICATIONS AND THE
FORMULATION OF CONTROL STRATEGIES (Continued)
1972
1973
1975
1976
1977
1974
403 Data Handling
403.1
. .xx
Optimize techniques for
data acquisition, storage,
and retrieval
( .5 p)
xx
Total effort
.5 man-year--professional
404 Modeling Technology
404.1
404.2
404.3
404.4
Significance of modeling to
the formation of control
strategies and their
implementation
( 2 . 25 p)
xx
xxxx
xxx x
xxxx
xxxx
xx
Implementation Plan appli-
cations
( . 75 p, . 75 s)
xx. .
. .xx
xx
Environmental Impact
ment applications
( .75 p, . 75 s)
State-
xx. .
. .xx
xx
Methodology for assessing
model validity in control
agency operations
( .75 p, .75 s)
Total effort
4.5 man-years--professional
2.25 man-years--subprofessional
A-16
-------
400 TRANSFER OF RAPS TECHNOLOGY FOR CONTROL AGENCY APPLICATIONS AND THE
FORMULATION OF CONTROL STRATEGIES (Concluded)
1972
1976
1977
1973
1974
1975
405 Other Significant Factors in
Control Strategy Formulation
405.1
405.2
405.3
405.4
405.5
Liaison and interaction
with other environmental
research programs
Techniques
social and
factors
of assessing
economic
Methodology of assessing
operational costs of con-
trol strategies
Continuing low scale effort
Methodology of assessing
resultant costs of con-
trol strategies
Institutional aspects
Total effort
4.5 man-year--professional
4.5 man-year--subprofessional
A-l7
-------
100
Model Verification
Objective
The objective is to tes~ evaluate, and verify the capability of
mathematical simulation models to describe and predict the transport,
diffusion, and concentration of both inert and reactive pollutants over
a regional area.
Purpose and Scope
The purpose of this series is to investigate the performance of a
series of selected mathematical simulation models in circumstances such
that as many variables as possible are known. In this way the validity
of the model can be determined, or its deficiencies identified, and
methods of measuring input or verification data can be optimized for use
in subsequent operational applications. The program will investigate
emission source assessment, the modeling of atmospheric physical and
chemical factors, and the methods of verifying and evaluating the opera-
tion of the models.
The approach follows two major lines. The first approach is develop-
ment of the most complete description possible of the meteorological con-
ditions, emissions, and air quality. The second approach applies the
appropriate input data to a series of selected models and examines their
product against observed data.
The selection of models will follow an evolutionary program, start-
ing with the models ready for immediate testing. Where possible,
competing models will be applied to the same data sets. Subsequent
tests will be made of improvements of such models on an iterative basis,
or in combinations of the most successful features of such models. Major
emphasis will be on models relating to the regional scale, but subscale
models will be treated in time. First priority will be given to the
development of useful tools for reviewing and assessing Implementation
Plans. The similar need for Environmental Impact Statements will be
given concurrent but subordinate attention. Subsequently, the aim will
be to provide fully tested optimum models, the performance of which can
be objectively assessed, at each scale for each main class of pollutants.
Consideration will also be given to the role of modeling in connec-
tion with air pollution episode prediction.
A-IS
-------
101
Boundary Layer Meteorology Program
Objective
The objective is to collect meteorological data on the parameters
that affect the dispersion of atmospheric pollutants in the St. Louis
region.
Purpose and Scope
The purpose of this task is to:
.
Provide the meteorological data that are required as inputs
to air quality simulation models.
.
Obtain data with which to evaluate model computations of
meteorological parameters.
.
Provide supplemental measurements of meteorological param-
eters for study of fundamental meteorological processes
for subsequent use in the revision of various model components.
The program will commence with the collection of historical clima-
tological and experimental diffusion data for the St. Louis area. Later,
data from the various routine RAPS meteorological facilities will be
assembled and compiled in a meaningful format using standard metric
units; the routine facilities include the basic surface network and the
upper air (aircraft and balloon) systems. The program will also include
collection and compilation of data from special research programs.
101.1
Area Climatology
Objective
The objective
climatology of the
and transformation
of this subtask is to determine the nature of the
St. Louis region as it is related to the dispersion
of atmospheric pollutants.
Purpose and Scope
The purpose of this subtask is to
the St. Louis region to aid in station
tion and scope of atmospheric research
assemble climatological data from
siting, as well as in the direc-
programs that are aimed at the
A-19
-------
study of dynamic, kinematic, energetic, and chemical
the research will provide data for input to, and the
matological air quality simulation models.
processes. Also,
evaluation of, cli-
101.2
Prior Diffusion Data
Objective
The objective of this subtask is to determine the probable nature
of atmospheric diffusion properties in St. Louis on the basis of earlier
diffusion experiments in this and other similar regions.
Purpose and Scope
The purpose of the research is to collect results of prior diffusion
experiments to assist in the planning of special research studies within
RAPS, as well as in the number and spacing of surface-based monitoring
stations. These data will be summarized through stratification by the
relevant physical parameters and used for the planning of the scope and
direction of diffusion studies in St. Louis.
101.3
Compilation and Analysis of Upper Air Data
Objective
The objective of this sub task is to provide meteorological data on
the initial and boundary conditions of the three-dimensional structure
of the planetary boundary layer.
Purpose and Scope
The work in this sub task will provide these data for input to, and
the subsequent evaluation of, regional air quality simulation models.
These data will be obtained through the use of balloon-tracking, heli-
copter, and airplane systems and therefore will also provide flexibility
in the support of special research programs, e.g., radiation, tracer,
transformation, and long range dispersion studies. The data from the
routine upper-air network will also be used for the development of an
extensive climatology of regional boundary layer meteorology.
A-20
-------
101.4
Compilation and Analysis of Near-Surface Data
Objective
The objective of this subtask is to provide relatively detailed and
comprehensive micrometeorological data on the three-dimensional structure
of the atmospheric surface layer on the regional scale.
Purpose and Scope
Research will be conducted to obtain these micrometeorological data
for input to air quality simulation models and for their subsequent veri-
fication. The data will also be used to study the effects of topographic,
anthropogenic, and pollutant features together with mesoscale weather
types, on the dynamics of low-level atmospheric motions and the feedback
on the distribution of contaminants. As such, this program will support
many of the special research experiments as well.
101.5
Balloon-Tracking Experiment
Objective
The objective of this experiment is to provide information on
Lagrangian atmospheric, characteristics, as well as on their spatial
distribution.
Purpose and Scope
Purpose of the experiment is to provide these data for studies
seeking to evaluate the spatial resolution required in the specifica-
tion of upper-level meteorological fields (e.g., wind, temperature,
humidity) on the mesoscale in consideration of the distribution of sur-
face features (e.g., roughness, drainage, soil type). More specifically,
these data will be available for use in studies of long range disper-
sion, evaluation of topographic effects, city-induced changes in wind
structure, urban heat island, and urban-rural radiation difference. In
summary, the purpose is to provide input to the detailed study of upper-
level atmospheric processes and their incorporation in air quality sim-
ulation models.
A-2l
-------
101.6
Diffusion Tracer Experiments
Objective
The objective of these experiments is to provide information on
the diffusion of a known trace element under a variety of conditions of
meteorology, topography, and source characteristics.
Purpose and Scope
The experiments will be conducted to provide the necessary data
for studies of the effects of atmospheric, topographic, and source char-
acteristics on the diffusion of plumes from isolated point sources as
well as trace element(s) that can be released under controlled condi-
tions of source rate, duration, height, and type. These data also will
provide a selected base for the evaluation and subsequent verification
of certain types of air quality simulation models.
101.7
Weather Satellite Applications
Objective
The objective of this sub task is
logical data obtained by satellite to
air quality monitoring in general.
to assess the value of meteoro-
the RAPS program and for use in
Purpose and Scope
Meteorological satellites offer the potential of being able to pro-
vide meteorological data of the type required in air pollution programs
on a routine basis and at a minimal cost. This program should seek to
define objectively the specific advantages and limitations of these data
to the special and routine studies embodied in the RAPS program. If the
evaluation shows the desirability of obtaining these data in St. Louis,
then the next task will be the acquisition of the data and subsequent
cataloging as required by the specific purposes or experiments these
data will serve.
A-22
-------
101.8
Forecast Models
Objective
The objective
weather prediction
program.
of this subtask is the incorporation of routine,
models operated by other agencies into the RAPS
Purpose and Scope
Numerical weather prediction models are currently in operational
use by three agencies in the United States: NOAA (National Weather
Service), the Navy (Fleet Numerical Weather Facility), and the Air
Force (Global Weather Central). Of these groups, only the Air Force
routinely operates a mesoscale, boundary layer model. The purpose of
this program is to assess the advantages of incorporating the routinely
available boundary layer forecast into the RAPS program. These fore-
casts may provide the mesoscale boundary conditions required by some
prognostic air quality models or they may even provide the necessary
prognostic meteorological field. Additionally, the evaluation of the
applicability of these forecasts should consider their benefit in ex-
perimental planning. If these data can be efficiently used within RAPS,
the assessment program must also consider problems of data acquisition,
format and display.
102
Emission Inventory
Objective
The objective of this task is to develop and maintain a comprehen-
sive source inventory.
Purpose and Scope
Numerous components of the Research Plan will require a complete
inventory of all emission sources in the study area. This will include
both fixed and mobile sources of all major pollutants and perhaps se-
lected minor materials. Emission levels must be described for selected
times ranging from yearly to hourly intervals. The inventory should
serve in the validation of models, analysis of control strategies, and
the investigation of air quality impacts on the human, social, and
economic systems of the area.
A-23
-------
102.1
Emission Inventory Design
Objective
The objective of this sub task is to develop a detailed method for
taking an inventory of the emissions from both stationary and mobile
sources.
Purpose and Scope
Emission inventories must be designed to serve a variety of uses,
including input data for model verification programs, studies of control
strategies, and impact analyses. The development of emission inventories
can be an extremely costly enterprise requiring extended periods of time.
For these two reasons, a specific task is required to design procedures
for an emission inventory before full scale field surveys.
The task should first provide for the review of previous inventories
to identify the method used to classify sources by type, location, emis-
sion levels over time, and other characteristics. The desirability of
incorporating these data into the Regional Study emission inventory
should be assessed.
Procedures should then be developed for obtaining data describing
all classes of sources, such as point, area, and mobile. Questionnaires
should be designed to cover certain classes of sources, whereas proce-
dures may be designed for physical measurement of other sources. In the
case of vehicular emissions, procedures may be required to determine
traffic flows to be combined with the characteristics of the sources
themselves.
Finally, methods for computer storage and retrieval of the emission
inventory data will require development.
102.2
Collection of Emission Data for Stationary Sources
Objective
The objective of this subtask is to collect emission data from both
point and area sources and to maintain these data on a continuing basis.
A-24
-------
Purpose and Scope
The purpose of this effort is to identify pollution sources in terms
of the chemical and physical characteristics of their emissions, the
magnitude over time of the emissions, their location, and all other
descriptors as may be required for purposes of model evaluation, control
strategy development, impact studies, and the like.
The collection of emission data initially will emphasize the pre-
dominant pollutants, such as S02' CO, NOx' and particulates, originating
primarily from combustion sources but including the larger noncombustion
sources. The general sequence of collection will be derived from exist-
ing emission inventories reviewed in 102.1 to eliminate duplication of
valid current data. Data will be collected by questionnaire and on-site
visits. As this effort is concluded, the survey of sources of lower
emissions, such as industrial processes, will be initiated. Pollutants
in addition to those listed above will also be included.
This task will continue at a relatively
Regional Study for continual revision of the
tions change or are controlled.
low level through the
inventory as source opera-
102.3
Collection of Emission Data for Mobile Sources
Objective
The objective of this subtask is to collect emission data from
mobile sources, including motor vehicles and aircraft.
Purpose and Scope
The purpose of this effort is to determine the flow pattern of motor
vehicles, aircraft, and other mobile sources of interest as a function of
time and by their emission characteristics. The mobile units will be
characterized by selected characteristics, including size, fuel, engine
type, and similar features and emission factors assigned to each.
Flow patterns of mobile sources in the region will first
The definition will be developed by review of available motor
traffic studies in the region, airport schedules, and similar
Since the street and highwaypattern in the area is undergoing
changes, field surveys may be required for the more important
fares not included in existing data.
be defined.
vehicle
sources.
significant
thorough-
A-25
-------
This effort should continue throughout the study and be revised as
vehicle emission control techniques and movement patterns change.
Emission Model for Stationary Sources
102.4
Objective
The objective of this sub task is to develop a model for predicting
emissions from stationary sources over specified time intervals.
Purpose and Scope
The purpose of this task is to develop a set of models to predict
emissions from stationary sources under specified conditions for periods
ranging from one hour to one year. Baseline emission estimates for
specific conditions of the source first will be developed. These condi-
tions perhaps can be defined as the average or typical conditions of
the source. Preparation of adjustment factors for correcting the base-
line emissions for other conditions of the source will follow. These
adjustment factors will include numerous variables, including atmos-
pheric temperature, time of day, season of year, and shifts in the
type of fuel used. Additional factors, especially important for indus-
trial plants, will include variations in shift levels and resulting
production rates, together with changes in product mix. The emission
model undoubtedly will be sufficiently complex to require the use of
computer techniques in its development and operation.
102.5
Emission Model for Mobile Sources
Objective
The objective of this subtask is to develop a model for predicting
emissions from mobile sources over specified time intervals.
Purpose and Scope
The purpose of this task essentially parallels that of 102.4.
On the basis of the survey of 102.2, selected models will be developed
covering motor vehicle flows, aircraft movements, and perhaps railroad
and ship activities. These movement patterns will be combined with the
emission factors to develop estimates of emissions for specified periods
A-26
-------
ranging from one hour to one year. The complexity of the model undoubt-
edly will be such that a computer will be required.
102.6
Emission Source Test
Objective
The objective of this subtask is to conduct field measurements of
emissions from stationary sources and develop emission factors.
Purpose and Scope
Although emission factors for many sources can be adequately esti-
mated by comparison with similar sources or by other methods, the more
important combustion and noncombustion sources will require field mea-
surements to determine reliable emission factors. Measurements will be
made under a range of source conditions, such as level of production
and electric power output and correlated with emission characteristics.
These analyses should produce reliable baseline emissions and adjust-
ment factors for incorporation into the emission model developed in
102.4.
102.7
Analysis of Status of Source Controls
Objective
The objective of this analysis is to determine the degree of emis-
sion control in effect.
Purpose and Scope
The stationary source inventory should reveal the extent to which
emission control equipment and operational procedures are used in the
area along with measures of their effectiveness and perhaps cost. These
data will be used to determine efficiency of these control measures and
in conjunction with any implementation plans.
A-27
-------
102.8
Emissions Inventory of Agricultural Sources
Objective
The objective of this subtask is to estimate the emissions from
agricultural operations within the St. Louis region.
Purpose and Scope
A wide variety of materials are emitted to the atmosphere as a
result of agricultural operations. These include fungicides, insecti-
cides, and herbicides; emissions of contaminants from burning agricul-
tural waste products; and dust from plowing, harrowing, and the like.
Emission factors covering these and perhaps other materials will be re-
quired as part of the total emission inventory of the region in terms
of both baseline levels and adjustment factors.
Air Quality Measurement
103
Objective
The objective of this task is to provide as complete and detailed
a description as possible of the distribution (both in space and time)
and concentration of air pollutants in the St. Louis region.
Purpose and Scope
The purpose of this task is to provide the data on pollutant dis-
tribution necessary for the verification of simulation models of various
scales (in space and time) and for various types of pollutant (i.e.,
both reactive and nonreactive) and various types of source.
Data will be obtained from past records,
already being made in the St. Louis area, and
ment networks of the RAPS facility.
from routine measurements
from the special measure-
A-28
-------
103.1
Data Base
Objective
The objective of this subtask is to provide a data base of relevant
information concerning pollutant concentrations measured in past air
quality surveys of the St. Louis area that can be integrated into the
RAPS and used in developing methodologies for using such data in other
areas.
Purpose and Scope
The purpose of this subtask is to take advantage of the data han-
dling and analysis capabilities of the RAPS organization to correlate
historical pollution data with RAPS network data to delineate changes
and trends in pollutant concentrations and to indicate disparities due
to measurement techniques, site locations, source locations, and the
like. Also, this subtask will determine the effectiveness of control
and abatement procedures.
103.2
Air Quality Data from Local Agencies
Objective
The objective of this subtask is to collect and evaluate air
quality measurement data acquired by the local agencies, Air Pollution
Control, City of St. Louis, and Air Pollution Control, St. Louis County,
and to integrate agency measurements into RAPS program and initiate
agency access to RAPS data.
Purpose and Scope
Purposes of this subtask are to:
.
Assemble and correlate data from the existing local
monitoring networks with that obtained by RAPS with
respect to site location, measurement techniques, and
data handling so as to take advantage of the data han-
dling and analysis capability of RAPS.
A-29
-------
.
Evaluate the effectiveness of a modest network to obtain
measurements representative of the area of interest.
Analysis of Air Quality and Meteorological Data Acquired by RAPS
103.3
Objective
The objective of this subtask is to develop
compilation, retrieval, and analysis of the data
monitoring network.
computer software for
acquired by the RAPS
Purpose and Scope
This effort will be to take advantage of the data handling and
analysis capability of a RAPS organization to provide data tabulation,
measurement correlations, and continuously updated analysis techniques.
Analysis display techniques, such as isopleth maps and displays to sim-
plify data interpretation, also will be developed.
103.4
Analysis of Air Quality Data Acquired by Aircraft
Objective
The objective of this subtask is to develop computer software for
compilation, retrieval, and analysis of the air quality data acquired
by the airborne laboratory.
Purpose and Scope
This subtask will take advantage of the data handling and analysis
capability of a RAPS organization to provide data tabulation, aircraft
to network measurement correlation, horizontal and vertical profile
analysis and display, flight pattern mapping, concentration mapping,
and, where sufficient data are obtained, isopleth mapping.
A-3D
-------
103.5
Fine Scale Spatial Variation of Air Quality
Objective
The objective of this subtask is
spatial variability of air quality in
sions, meteorology, and topography.
to ascertain the subgrid scale
the region as a function of emis-
Purpose and Scope
This subtask will assess, through a series of field measurement
programs, the fine-scale variability of air quality throughout the region.
The variability should be assessed over areas corresponding to the model
resolution that is required so that the representativeness of measure-
ments and predictions of air quality can be evaluated.
These assessments will be vital to the intelligent evaluation and
verification of simulation models, as well as toward an understanding of
the influence of distributions of emission, meteorological, and topo-
graphical factors on the level and variance of air quality.
104
Model Calculation and Verification
Objective
The objective of
series of air quality
are most suitable for
this task is to operate, evaluate, and modify a
simulation models and identify the models that
use in formulating air pollution control strategies.
Purpose and Scope
Purposes of this task are to:
.
Provide evidence and information as to the effectiveness
of a series of selected candidate models so that optimum
models can be selected for each aspect of air pollution
control.
.
Develop techniques of categorizing models in terms of their
applicability in respect to both the temporal and spatial
resolution and the type or class of pollutants for which
they are appropriate.
A-31
-------
.
Develop techniques of comparing and assessing the relative
accuracy and precision of models.
.
Provide a local capability for carrying out computations
and investigating the way in which submodels may be devel-
oped or major models improved.
104.1
Evaluation of Selected Models
Objective
The objective of this subtask is to operate, test, and evaluate a
series of air quality simulation models.
Purpose and Scope
The purpose of this subtask is to carry out actual modeling proce-
dures using input data in various degrees of sophistication and complete-
ness with a series of candidate models. The products of these procedures
then will be confronted with air quality measurements and the validity of
the model assessed, using methodologies developed in parallel in Task 104.3
Models will be categorized in terms of their applicability for
various types of pollutants and for various spatial and temporal resolu-
tions. Their fitness for use for air pollution control operations and
the formulation of improved strategies (short term episodes and longer
term occurrences) will be assessed by evaluating their: (1) mathematical
integrity, (2) nature and extent of input data, and (3) utility of the
output data format of the model, in addition to their accuracy and
precision.
Model Modification and Imprqvement
104.2
Objective
The objective of this subtask is to develop the best available forms
of candidate models or of combinations of their subelements.
A-32
-------
Purpose and Scope
The purpose of the subtask is to provide an opportunity to experi-
ment with and investigate optimum combinations of elements of candidate
models in the light of their use in the test and evaluation phase of this
study, Le., in Task 101.4. (In practice, this task may well be incor-
porated with Task 104.1. It is treated separately here for planning and
costing purposes.)
104.3
Methodology for Determining Accuracy
Objective
The objective of this subtask is to provide a methodology by which
the accuracy of various models may be measured and assessed.
Purpose and Scope
The purposes of the subtask are to:
.
Develop objective techniques to facilitate the comparison
of models, where rival candidates exist.
.
Develop ways o'f evaluating and describing the accuracy
and precision of any proposed model in terms of its poten-
tial use in the formulation of control strategies (episode
and long term). In this way, the sensitivity of models
to the degree of completeness and sophistication of their
input data can be assessed. Additionally; the usefulness
of the models' output as determined from the user's point of
view can be assessed and the uncertainties considered
quantitatively in the event control strategies are to be
based on the models.
A-33
-------
104.4
On-Site Computation and Data Display
Objective
The objective of this sub task is to provide computational and
display capability at the RAPS central facility to evaluate selected
portions of network data for applicability to simplified models.
Purpose and Scope
Although the principal computations for data processing and analysis
will be performed in Durham, a need will exist for the preliminary evalua-
tion of measurements, experimental results, and computational models on
site in near real time. One aspect of this evaluation can be met simply
by providing for a convenient "quick look" at data. Beyond this, there
should be facilities for making computations on the basis of simplified
models for selected portions of observational records. In this manner,
the quality of results can be monitored and improved with minimal delay,
and flaws in sensors, techniques, or logic can be detected and remedied
early in the RAPS. The computational and display facility should be in-
corporated into the computational system required for the balloon-
tracking facility.
A-34
-------
200
Atmospheric, Chemical, and Biological Processes
Objective
The objective of this series of tasks is to develop an improved
understanding of the chemical, physical, and biological processes that
are entailed in determining the concentration (the dispersal) of pollu-
tants and the modification of air quality.
Purpose and Scope
Purposes of these tasks are to:
.
Investigate in a number of parallel programs the various
mechanisms entailed in the transport, transformation, and
removal of pollutants not now well understood.
Develop techniques of describing (or better describing) such
mechanisms so that they can be accounted for in existing
models or models to be developed to accommodate them.
.
Identify conditions or processes that are significant in
formulating control and abatement strategies to provide air
quality amelioration.
The approach follows three major lines. The first approach is the
acquisition of a better quantitative knowledge of processes already
recognized as significant but that have not been adequately described
for modeling purposes. The second approach is development of a better
understanding of the significance of various processes in terms of ade-
quately modeling complex air quality factors. The third approach is
investigation of pollutants and pollutant processes that are not yet
considered in control strategies, and assessment of their importance so
that appropriate strategies can be formulated.
201
Gaseous Chemical Processes
Objective
The objective of this task is to develop an improved understanding
of the gaseous chemical processes that are important in determining the
concentrations of air pollutants and in the design and specifications
of simulation models dealing with the transport of gaseous pollutants.
A-35
-------
Purpose and Scope
Purposes of these tasks are to:
Investigate through a number of discrete but interrelated
projects various mechanisms that are important in the trans-
formation and scavenging of gaseous air pollutants.
Carry out specific sampling programs designed to better
the concentration field of various important pollutants
are not covered by the regular monitoring system.
describe
that
Develop special measurement techniques and automatic instru-
mentation that can be used to describe in more detail the
atmospheric concentration fields of specific air pollutants.
Relate the processes and conditions observed in the field
program to existing or potential simulation models and to
abatement strategies.
Hydrocarbon Analyses and Monitoring
201.1
Objective
The objective of this subtask is to determine hydrocarbon reaction
products in the atmosphere over the regional study area.
Purpose and Scope
This project area will carry out research and monitoring studies
directed toward determining the nature of gaseous hydrocarbon materials
and reaction products in the atmosphere. The materials that will be
covered in these studies include both primary emissions of hydrocarbon
compounds and reaction products that are specifically considered in
modeling studies. The program will also be concerned with the primary
and reaction constituents and the various scavenging processes that
serve to transform them in the atmosphere or to remove them from the
atmospheric system. Variations in reaction rates from nonhomogeneous
mixing in the lower surface layer because of surface roughness and cer-
tain meteorological conditions (gustiness) should be assessed as well.
A-36
-------
201.2
Development of Hydrocarbon Classifier Instrumentation
Objective
The objective of this subtask is to develop instrumentation to
monitor classes of hydrocarbons in the atmosphere.
Purpose and Scope
Atmospheric reaction studies and modeling programs generally treat
hydrocarbon compounds as classes rather than specific compounds. Ana-
lytical procedures are available for monitoring hydrocarbons as classes
rather than specific compounds, and these techniques are amenable to
automatic instrumentation and, therefore, to the development of field
instrumentation. However, instruments are not now available to carry,
out these tasks. The regional study program should support the develop-
ment of instrumentation that will monitor hydrocarbon classes, because
these data are necessary for the development and verification of reac-
tive chemical models and appear to be well within the present state of
the art.
Note: At the conclusion of the development phase, a decision will
be made whether to procure instruments for routine use in the facility.
Provided satisfactory automatic instruments can be procured, it is an-
ticipated that they wtll be installed and operated at 17 Class A stations
and 10 selected Class B stations.
201.3
Total Aldehydes-Formaldehyde Monitoring Program
Objective
The objective of this subtask is to determine daily variation in
concentrations of total aldehyde and formaldehyde in the region study
area.
Purpose and Scope
Aldehydes and in particular formaldehyde are products of atmospheric
photochemical reactions and data on concentration patterns are necessary
for the development and verification of photochemical reactive simulation
models.
A-37
-------
201.4
Determination of Peroxyacetyl Nitrate
Objective
The objective of this subtask is to carry out a measurement program
of atmospheric concentrations of peroxyacetyl nitrate (PAN) in connection
with studies of photochemical reactions in the regional study area.
Purpose and Scope
PAN is an important end product of photochemical smog reactions and
as such is a major subject of photochemical modeling processes. Thus,
data on PAN should be obtained for use in the simulation modeling program,
201.5
Ammonia Monitoring Program
Objective
The objective of this program is to determine ammonia concentration
trends as air parcels passes through urban areas.
Purpose and Scope
Ammonia plays an important role in scavenging S02 and N02 from the
atmosphere through the formation of ammonium salts. Thus, it is also a
factor in aerosol formation processes. Both the gaseous scavenging and
aerosol formation processes will be included in comprehensive modeling
of pollutant chemical processes.
201.6
CO, S02' and N02 Mass Flux Measurements
Objective
The objectives of this subtask are to:
Provide, using aircraft and ground-level measurements,
sects through selected vertical planes downwind of St.
to permit calculation of CO, S02, and N02 mass flux.
tran-
Louis
A-38
-------
.
Provide a measure of integrated sunlight intensity from both
aircraft and ground level in the spectral region responsible
for photolysis of nitrogen dioxide.
Purpose and Scope
The long distance transport of pollutants can be considered on the
basis of the mass flux across vertical planes normal to the wind. Net
loss of total pollutant mass as a function of time and other conditions
will indicate the magnitude of removal processes and are needed as input
to modeling procedures. Processes that are important can be shown by
measurements that attempt to obtain a total mass balance regardless of
the atmospheric state, e.g., sulfur could be present either as S02 or as
sulfate particles. Unaccounted losses probably would be attributed to
absorption by soils and other surfaces.
The photolysis of nitrogen dioxide is closely related to the in-
tensity of light in the 2900 to 4000 A region. Because of selective
absorption, the proportion of light in the photochemically active region
may vary somewhat independently of the total sunlight intensity. There-
fore, light intensity measurements should be made in this spectral region.
Existing simulation models do not require these data; however, if such
data were available, they could result in improved model simulation.
201.7
Origin of Atmospheric CO
Objective
The objective of this subtask is to determine atmospheric CO by
C12/C13 isotope ratio measurements.
Purpose and Scope
The atmospheric and environmental cycle of CO is not well understood.
Current data indicate significant biological involvement in scavenging
processes and possibly as a source of natural CO. Studies that can lead
to the solution of the CO cycle will contribute to an understanding of
the long term global impact of air pollution.
A-39
-------
201.8
Atmospheric Odor Identification
Objective
The objective of this subtask is to carry out chemical identifica-
tion studies to characterize odors observed in urban and rural areas.
Purpose and Scope
The information obtained in the sampling studies and other identi-
fication procedures will be used in conjunction with source inventory
information to define the extent of specific odors and sources and their
impact on the local community. This information in time will be used to
provide basic data for the development of control strategies dealing with
urban odor problems.
202
Atmospheric Aerosol Processes
Objective
The objective of this area of the program is to develop improved
understanding of, and expanded data on, the nature of atmospheric urban
aerosols and the processes that are important in determining (1) the
chemistry and concentrations of these materials and (2) the application
of this information in the design and specifications of simulation models
dealing with the transport and transformation of atmospheric aerosols.
Purpose and Scope
The purposes of this task are to:
Investigate through a number of individual but interrelated
projects the various mechanisms that are important in the
formation, transformation, and scavenging of atmospheric
aerosol particles.
Carry out specific sampling programs designed to better de-
scribe both the chemistry and concentration fields of various
atmospheric aerosols and to relate these measurements to the
routine measurements obtained by the regular monitoring system.
A-40
-------
.
Conduct a coordinated program of gaseous and particulate
sampling experiments with the goal of describing the specific
mechanisms by which atmospheric aerosol particles are formed
from gaseous contaminants.
.
Develop special measurement and instrumentation techniques that
through automatic operation can be used to describe in more
detail the atmospheric concentration fields of specific par-
ticulate materials.
.
Relate the processes and conditions relative to the formation
and transport of atmospheric aerosols to existing and future
simulation models and to abatement strategies.
The individual projects within this program area fall into three
general categories: (1) special monitoring programs for specific aero-
sol materials, including size distribution studies, aerosol chemistry,
and studies of the interaction of aerosols and gaseous contaminants;
(2) development of instrumentation and analytical techniques to improve
the effectiveness of aerosol monitoring programs and to provide the data
necessary for simulation modeling applications; and (3) special trans-
port and scavenging research studies aimed specifically at delineating
atmospheric processes that serve to determine the characteristics of
atmospheric aerosols in urban and rural areas.
For the most par~, research in atmospheric aerosols is hampered by
the fact that relatively little automatic instrumentation can be used
to obtain detailed data on the chemical constituents that make up the
atmospheric mass. As a result, most of the programs are based on a
gathering of specific field samples followed by a period of laboratory
analysis to determine the nature of the collected samples. This means
that the samples generally have poor time resolution because of the
length of time necessary to collect enough material for adequate anal-
ysis, and because the number of samples that can be collectSd practically
is limited because of lack of available manpower and laboratory facilities.
If suggested instrumentation development is successful, some of these
problems may be ameliorated; however, since the suggested instrumentation
is not new but has been recognized for a number of years, a higher degree
of hope cannot be expressed for the successful resolution of this instru-
mentation design problem.
A-41
-------
202.1
Determination of Total Nitrate in Aerosol Samples
Objective
The objective of this subtask is to determine the concentration of
nitrate in aerosols collected on high-volume sampler samples.
Purpose and Scope
One of the scavenging processes for N02 is considered to be the
formation of N03- salts. If a satisfactory modeling program is to be
undertaken for the dispersion of N02' then this conversion to an aero-
sol must be considered. The process must be considered as being rela-
tive to other ambient conditions such as sunlight and humidity.
202.2
Determination of Total Sulfate in Aerosol Samples
Objective
The objective of this subtask is to determine the concentration
of sulfate in aerosols collected on high-volume sampler samples.
Purpose and Scope
One of the scavenging processes for S02 is considered to be the
formation of S04= salts. If a satisfactory modeling program is to be
undertaken for the dispersion of S02, then this conversion to an aerosol
must be considered. The process must be considered as being relative
to other ambient conditions such as sunlight and humidity.
202.3
Determination of Aerosol Size-Distribution
Objective
The objective of this subtask is to determine aerosol size dis-
tribution under a variety of atmospheric conditions.
A-42
-------
Purpose and Scope
The research will obtain detailed data on the size distributions
of the total atmospheric particulate material and on specific chemical
fractions. The data should apply to a variety of ambient conditions
and coordinated with other data gathering programs so that the mechanisms
governing the areawide distribution of urban and rural aerosols can be
obtained. These mechanisms will then lead to model development of aero-
sol formation and dispersion.
202.4
The N02 NaCl Reaction in Aerosol
Objective
The objective of this subtask is to make a preliminary estimate of
the importance of the N02 - NaCl reaction in aerosols and recommend the
need for more extensive programs.
Purpose and Scope
One process proposed as a scavenging process for N02 is its reaction
with NaCl in droplets. The result is the release of chlorine. This
program is exploratory to determine whether chloride is prevalent enough
in the RAPS area to make this mechanism worthy of further consideration.
202.5
Isotope Ratios of Sulfate Aerosols
Objective
The objective of this subtask is to develop
possible sources of atmospheric sulfate aerosols
isotope ratio analyses.
information on the
on the basis of sulfur
Purpose and Scope
Sulfate aerosols are an important component of urban and natural
atmospheric aerosol systems and can result from several different
sources, namely, the oxidation of pollutant generated S02' the oxida-
tion of H2S from natural sources, and from residual sulfate contained
in marine aerosols. These several sources have different ratios between
the two sulfur isotopes S34 and S32. On the basis of the isotope ratios
A-43
-------
found in atmospheric aerosols, inferences can be
sources of these aerosol materials. Thus, these
to provide increased information on the probable
aerosol particles.
drawn concerning the
studies will be directed
sources of atmospheric
Organic Compounds in Particulate Material
202.6
Objective
The objective of this subtask is to develop data on the specific
organic compounds that are present in urban and rural particulate samples.
Purpose and Scope
Organic compounds of a wide variety make up a major share of the
atmospheric particulate material; however, relatively little is known
about the specific compounds that constitute this total mass of organic
material.
To better understand the formation mechanisms and the importance
of various sources of urban and rural haze, it is important to know what
specific materials are present in the atmospheric aerosols. After the
nature of the various components are known, it should be possible to
assess the importance of various urban and rural sources as contributors
to pollutant haze concentrations and to include relevant mechanisms in
simulation models and control strategies.
202.7
Experimental Measurements of Deposition Velocity
Objective
The objective of this subtask is to determine through direct ex-
perimental measurements the apparent deposition velocity applicable to
atmospheric aerosol particles of different chemical constituents.
Purpose and Scope
Atmospheric particles, especially those in the small-size ranges,
and particularly less than one micron in diameter, deposit on surfaces
at a rate that is not always predictable on the basis of the physical
size of the particle and the accepted Stokes' settling velocity. Since
A-44
-------
ground deposition is an important mechanism by which particles are re-
moved from the atmosphere, it will be extremely useful to measure the
apparent deposition velocity that is applicable to various atmospheric
particles and to different types of ground surface. Once deposition
velocities are determined that are applicable to atmospheric aerosol
particles, this term can be introduced into simulation modeling for-
mulas and used to estimate the dispersion of aerosol materials and
subsequent concentration patterns.
203
Other Pollutant Related Atmospheric Processes
Objective
The objective of this task is to develop an improved understanding
of a wide range of atmospheric processes that are important in under-
standing the transport, transformation, and final removal processes of
atmospheric pollutants.
Purpose and Scope
The research effort will investigate through a number of individual
research projects various atmospheric processes and mechanisms that are
related to the understanding of pollutant distribution over an urban and
rural area. These atmospheric processes cover a range of applicable
conditions and have not been readily classifiable into other areas of
this research prospectus.
The individual research projects carried out within this section,
while dealing with specific and identifiable objectives, will generally
relate in some detail to one or more of the other research projects
described in other parts of this Prospectus.
203.1
Radiation Balance Studies
Objective
The objective of this subtask is to assess the influence of urban
areas on the radiation balance of the lower atmosphere.
A-45
-------
Purpose and Scope
The purpose of the sub task is to:
Document differences in urban and rural radiation budgets for
the surface and boundary layer along with differences in pol-
lutant concentrations, temperature, water vapor, and cloudiness.
Provide radiation data required for the formulation of direct
input into applied mathematical models of the boundary layer.
Evaluate, modify and verify pertinent radiative components cur-
rently used in mathematical models.
203.2
Visibility Reduction in Urban and Rural Areas
Objective
The objective of this subtask is to develop quantitative data on
urban visibility restrictions and to determine from relationships with
aerosol particle studies the mechanisms and processes responsible for
observed reduced visibility conditions.
Purpose and Scope
Concentrations of urban haze that result in visible pollutant con-
centrations are an important aspect of urban air pollution problems.
Although these are directly relatable to atmospheric aerosol concentra-
tions and perhaps to the concentrations of visible gaseous pollutants
such as N02' it is important to analyze this concentration data in terms
of observed or expected visibility reduction. Only by relating the tech-
nical findings to the conditions reviewed by the general population of
an area can the technical program be put on a practical basis. After
pollutant concentration data and other factors are related to the urban
visibility restriction problem, simulation modeling techniques that
tackle specifically the problem of visibility restriction can be de-
veloped and sUbsequently verified.
A-46
-------
203.3
Transport of Atmospheric Odors
Objective
The objective of this subtask is to determine the specific transport
phenomena that may relate directly to the transport of atmospheric odors
and in particular to the long distance transport of identifiable odors.
Purpose and Scope
Odor identification apparently does not require that the odor con-
centration exists for a long period of time to be detected. Thus, at-
mospheric studies and transport mechanisms, whereby even relatively small
volumes of gas can remain at high concentrations even though an average
integrated concentration is extremely low. can result in the long distance
transport of identifiable odors. If it were possible to characterize the
conditions under which long distance odor transport was significant, spe-
cific modeling techniques could be developed for odor detection and odor-
ous sources. These subsequently could be used in the design of control
strategies and air quality criteria related directly to odor sources.
203.4
Trace Metals and Toxic Trace Materials
Objective
The objective of this subtask is to determine in detail
tribution and atmospheric concentrations of trace metals and
trace materials throughout the regional study area.
the dis-
other toxic
Purpose and Scope
The purposes of this research are to develop information on the
extent to which toxic trace materials such as beryllium, mercury. cad-
mium, and asbestos are distributed throughout the Regional Study area
and, in particular, to determine the relationship of identifiable sources
to atmospheric concentration patterns and to deposition rates onto sur-
faces, vegetation, and bodies of water. Lead aerosols from the combustion
of vehicular fuels should also be considered in this program, although
these materials are so widespread in both the urban and rural areas that
it is questionable whether lead aerosols can be considered as a trace
material in the same manner as cadmium or beryllium. Once the distribution
A-47
-------
of these materials is characterized, urban area exposures can be deter-
mined and control strategies designed.
203.5
Agricultural Chemical Distribution
Objective
The objective of this subtask is to determine the distribution and
concentration patterns of agricultural chemicals throughout the Regional
Study areas, including both agricultural and urban areas.
Purpose and Scope
A wide range of agricultural chemicals, including pesticides, her-
bicides, and fertilizers, are applied as sprays from aircraft over large
areas of agricultural land, and little is known about the transport and
the concentrations of these materials beyond their area of application.
However, considerable concern is shown about the adverse effect that may
result from widespread distribution of agricultural chemicals in both
rural and urban areas. Once data are obtained on the areawide distri-
bution of agricultural chemicals and related to the nature of their ap-
plication, control strategies can be devised to protect the community
from indiscriminate use of agricultural chemicals.
203.6
Natural Sources of Air Polluted Compounds
Objective
The
tudes of
that are
objective of this subtask is to determine
sources within the natural environment of
also emitted as air pollutants from urban
the types and magni-
chemical compounds
and industrial sources.
Purpose and Scope
Practically all the materials that are classed as air pollutants
because of their emission from urban and industrial pollutants sources
also have sources within the natural environment; although these are
almost always incapable of producing significant concentrations of mate-
rial, their total contribution on a global atmospheric basis to the at-
mospheres chemistry is usually calculated as being very significant.
Within an urban area, the existence of natural sources of contaminant
A-48
-------
materials results in a very low background level being observed. Thus,
to complete the description of the areawide distribution of urban pollu-
tants, it is highly desirable to be able to include recognition of the
presence of this natural low level background concentration. In addition,
careful analysis of background pollutant emissions may also provide clues
as to the most effective scavenging mechanisms that serve to remove these
materials from the atmosphere, including pollutant generated materials.
204
Atmospheric Scavenging by Precipitation
Objective
The objective of this task is to develop an improved understanding
of the nature of precipitation scavenging of atmospheric pollutants and
to relate these processes to other environmental factors such as water
quality.
Purpose and Scope
Purposes of this task are to:
Investigate through sampling and analytical projects the ex-
tent and processes of precipitation scavenging of atmospheric
pollutants.
.
Relate the observed precipitation scavenging processes to
pollutant emissions and downwind pollutant concentration pat-
terns and to develop models by which the impact of precipita-
tion scavenging can be included in simulation modeling of the
transport and dispersion of atmospheric pollutants.
.
Develop special instrumentation where necessary to sample and
analyze precipitation for scavenged air pollutants.
The individual projects within this program area include instrument
development and sampling programs directed toward the measurement of
precipitation chemistry. After analytical results are available, the
data will be related to air quality concentration patterns and to meteo-
rological conditions to develop a better understanding of the nature of
the precipitation scavenging process.
A-49
-------
204.1
Instrument Development for pH and Chemical Sampling
Objective
The objective of this subtask is to develop the instrumentation
necessary to include pH sampling and chemical sampling of rainfall in
the regular monitoring stations within the Regional Study network.
Purpose and Scope
It is desirable to obtain data on precipitation pH and chemical
content on a more or less routine basis at the regularly reporting Re-
gional Study network stations. Suitable standard equipment is not avail-
able for these measurements, and special designs suitable for the Regional
Study network will have to be developed.
204.2
Rainfall pH Measurements
Objective
The objective of these measurements is to determine the spatial
variation of the acidity of rainfall in the St. Louis regional area.
Purpose and Scope
The pH of rainfall is often used to indicate the effect of atmos-
pheric pollutants on rainfall chemistry. This conclusion is a result
of the fact that many atmospheric contaminants, especially S02 and N02'
lead to the formation of ascetic particulate material which is readily
incorporated in precipitation and thus can affect the pH of the precip-
itation. Thus, an areawide distribution pattern of rainfall pH can be
used to indicate the impact of urban area pollutant sources on precipi-
tation. These data will provide another indication of the magnitude of
the transport of pollutants from the urban area and their possible impact
on the surrounding environment.
A-50
-------
204.3
Measurement of Rainfall Chemistry
Objective
The objective of these measurements is to determine the chemical
constituents contained in precipitation samples in the Regional Study
area.
Purpose and Scope
Details on the precipitation scavenging process for atmospheric
pollutants can be obtained by making chemical analyses for various mate-
rials on samples of collected precipitation. With these data and
corresponding air quality and meteorological information, important
factors describing the precipitation scavenging process for specific
pollutants can be obtained. Once the precipitation scavenging process
has been described, it can be incorporated in simulation models and lead
to an improvement in the simulation modeling process for the distribution
and transport of atmospher~c pollutants.
2~
Air Pollutant Scavenging by the Biosphere
Objective
The objective of this task is to develop an improved understanding
of the relationship of the biosphere to air pollutant dispersion and
transport and in particular the effect that the biosphere has on the
scavenging of air pollutants from the atmosphere.
Purpose and Scope
Atmospheric transport and dispersion processes serve to bring air
pollutants in contact with large amounts of biological material, and it
is known that plants are effective absorbers of trace chemical materials
from the atmosphere. This program will conduct projects designed to
provide quantitative estimates of the scavenging mechanisms that are
effective within the biosphere in removing air pollutants from the
atmosphere.
The research effort also will relate the scavenging processes ob-
served in the field to existing or potential simulation models and to
an evaluation of the interaction between air pollution and the biosphere.
A-51
-------
The individual projects within this program area will include
chemical analyses of vegetation material to determine the extent to which
absorbed pollutants are reflected in changed chemical composition and
special monitoring studies to determine the extent to which vegetation
absorption can be observed to be reflected in actual changes or anomalous
concentration patterns in the atmosphere. Once quantitative values are
obtained for the scavenging of vegetation materials for air pollutants,
the relationships can be interpreted in terms of simulation model param-
eters and used as a basis for further research studies.
Chemical Content of Vegetation
205.1
Objective
The objective of this analysis is to determine the concentration
of various pollutant chemicals in plant materials growing in areas ex-
posed to a variety of pollutants and pollutant concentrations.
Purpose and Scope
When vegetation is exposed to contaminated atmospheres, it is common
for the pollutant material to be detected in the vegetation itself, and
the content of vegetation often is different for different species or
types of material even though the exposures are essentially the same.
Pollutants for which changes in vegetation concentration might be ex-
pected and that could provide additional measurements on the distribu-
tion of these contaminants include lead aerosols, fluorides, and perhaps
some of the heavy trace metals. The more soluble materials and materials
involved directly in plant metabolism such as sulfur and sulfate are un-
likely candidates for plant surveys because of the relatively high con-
centrations already present in the vegetation and the likelihood that
atmospheric concentrations would be completely masked by this background
concentration.
205.2
Atmospheric Pollutant Concentrations Related to Vegetation
Absorption
Objective
The objective
mospheric sampling
vegetated surfaces
air pollutants.
of this subtask is to determine on the basis of at-
the extent to which travel across various types of
causes anomalous reductions in the concentration of
A-52
-------
Purpose and Scope
During its life cycle, vegetation has a large intake of atmospheric
air and this forms a very large part of the plant life cycle. During
the intake of atmospheric air, pollutants are also brought into the
plant where they are retained; in addition, plant surfaces are exposed
to the flow of air, and as such they provide areas where pollutants may
be deposited or absorbed even though not being brought directly into
the plant tissues. These are loss mechanisms that in some cases have
been shown to be significant and to cause measurable changes in the
ground level concentrations of specific air pollutants. This research
project will attempt to quantify these absorption or removal mechanisms.
206
Atmospheric Processes
Objective
The objective
and description of
for in generalized
of this task is to provide an additional understanding
physical atmospheric processes not already accounted
boundary layer meteorological modeling.
Purpose and Scope
The research for 'this task will extend the capability of general
boundary layer theory to include anomalous physical factors of signif-
icance in the dispersal of pollutants. These factors include smaller
scale phenomena, such as the effects of special emission conditions
(i.e., at the stack) on the behavior of effluent plumes, or the local
variation of surface roughness (i.e., different terrain or land use
conditions) on air flow--or larger scale phenomena, such as the influence
of extraregional features or synoptic scale circulations on the air flow
characteristics within the Region.
Inputs will be obtained from other ongoing research programs or
from special studies conducted within the RAPS program. Consideration
will be given to conducting physical modeling studies in the laboratory
where appropriate.
A-53
-------
206.1
Source Factors in Pollutant Dispersal
Objective
The objective of this subtask is to attain a better understanding
of the nature and significance of source factors and processes and their
relationship to the dispersion of effluents.
Purpose and Scope
The purpose of this research area is to achieve an improved capa-
bility to describe through simulation modeling the interactions and
ramifications of various source-related factors, e.g., source height,
efflux velocity and buoyancy, aerodynamic characteristics of stack and
local environment, moisture, and plume opacity and composition. Addi-
tionally, the program should seek to examine the integrated effect of
anthropogenic processes on diffusion characteristics and the depth of
the atmospheric mixing layer.
206.2
Terrain and Surface Roughness Effects
Objective
The objective of this subtask is to attain an improved
ing of the effects of topographical surface characteristics
port and dispersion of effluvia.
understand-
on the trans-
Purpose and Scope
The purpose of this subtask is to achieve the capability to describe
and predict the effects of surface features on atmospheric dispersion
processes in general. In particular, the program will seek to under-
stand and model the effects on the eddy diffusivity, the near-surface
vertical veering of the wind, the effective horizontal transport wind
speed, the mean and fluctuating nature of the vertical component of the
wind, horizontal veering (curvature) of the wind field, the depth and
structure of the mixing layer, and the temporal and lateral variability
of these factors.
A-54
-------
206.3
Extra Regional and Synoptic Scale Circulations
Objective
The objective of this subtask is to develop techniques of account-
ing for extraregional factors and synoptic scale effects on the meteo-
rology and air flow patterns of the regional area.
Purpose and Scope
The research in this program will ascertain to what extent and in
what manner macroscale factors contribute to regional meteorology and
climatology in terms of the air flow patterns or the modification of
air masses as a function of the upstream terrain or orography.
Although this subtask is primarily concerned with physical factors
such as wind trajectories, stability, and moisture content, consideration
also will be given to the effects of the upwind history on the condition
of the air entering the regional area--in terms of both natural factors
such as dust loading and man-made pollution content.
A-55
-------
300
Human, Social, and Economic Factors
Objective
The objective of the tasks in this series is to develop a better
understanding of factors of significance to the design of improved con-
trol strategies in the urban/rural complex, including health and economic
effects and the role of land use and community planning.
Purpose and Scope
Purposes of this research program are to take advantage of the
unique facility the RAPS organization provides to collect data on human,
social, and economic factors in an economical and well focused manner to
complement the purely physical aspects of RAPS, for the subsequent for-
mulation of improved control strategies. The data will provide the addi-
tional basis that will be needed to apply the lessons learned in the RAPS
in improved control strategies that are effective and acceptable in terms
of priorities, costs of implementation, and value of results.
The resources of field teams, data analysts, and data processing
facilities will be made available to collect human, social, and economic
data identified as significant to the purpose noted. Data will be col-
lected either by adding elements to other data collection surveys or by
initiating special surveys. Steps will be taken to ensure that the data
are compatible with the physical data collected so that interpretation
and evaluation of the data on effects will be facilitated.
301
Human and Social Factors
Objective
The objective of this task is to provide a data base of relevant
information on human and social factors that can be used in RAPS and in
developing methodologies for using such data in other areas.
A-56
-------
Purpose and Scope
Purposes of the task are to:
.
Take advantage of the data handling and analysis capabilities of
a RAPS organization to gather data on epidemiology, mortality,
and the like.
.
Determine population concentrations and land use characteristics.
.
Provide information on the utilization of the labor force and
its skills and mobility.
301.1
Data on Epidemiology and Health Effects
Objective
The
scribing
terms of
believed
objective of the subtask is to develop quantitative data de-
the characteristics of the population in the St. Louis area in
epidemiology, health, and demographic factors that are known or
to be interrelated with air quality.
Purpose and Scope
The RAPS area will be defined in unprecedented detail in terms of
meteorology, air quality, and emission sources. These, and perhaps other
data, will be used intensively for the scientific purposes of model ver-
ification and related goals. Many of these data can be utilized in the
analysis of other air pollution problems, such as the probable effects
on the health of the population. Accordingly, this task is designed to
acquire detailed data covering the status of the health and related fac-
tors of the resident population and to couple these data with the appro-
priate aerometric data using the St. Louis data handling facilities.
These data generally would be designed to support ongoing research efforts
elsewhere in EPA not currently considered as part of RAPS.
A-57
-------
301.2
Data on Population and Land Use Characteristics
Objective
The objective of this subtask is to develop quantitative data de-
scribing the characteristics of the population distribution and land use
patterns in the St. Louis area.
Purpose and Scope
The RAPS area will be defined in unprecedented detail in terms of
meteorology, air quality, and emission sources. These, and perhaps other
data, will be used intensively for the scientific purposes of model ver-
ification and related goals. Many of these data can be used in the anal-
ysis of other air pollution problems, such as the correlation of land
use patterns and population distributions with air quality. This task
is designed to acquire detailed data covering these characteristics and
related factors and to combine these data with the appropriate aerometric
data using the St. Louis data handling facilities. These data generally
will be designed to support ongoing research efforts elsewhere in EPA
not currently considered as part of RAPS.
301.3
Data on Labor Force Utilization
Objective
The objective of this subtask is to develop quantitative data de-
scribing the characteristics of the labor force in the St. Louis area
in terms of skills, mobility, and patterns of utilization.
Purpose and Scope
The development of profiles of labor force utilization in the
St. Louis area will provide the basis of assessing the impact of alter-
native control and abatement strategies on employment. The mix of gained
and lost employment opportunities can be developed for selected strate-
gies, with the results formulated in both economic and social terms.
These data generally will be designed to support ongoing research efforts
elsewhere in EPA not currently considered as part of RAPS.
A-58
-------
302
Economic Factors
Objective
The objective of this economic research is to provide a data base
of relevant information on economic factors that can be used in RAPS and
in developing methodologies for using such data in other areas.
Purpose and Scope
The purpose of the task is to take advantage of the data handling
and analysis capabilities of the RAPS organization to gather data on the
various costs of air pollution to the industrial and general population
(e.g., depression of property values, damage to property, loss of produc-
tivity due to sickness) and also the cost of air pollution control strat-
egies, in terms of both plant modification and increased costs of
production.
302.1
Costs of Inferior Air Quality to Industrial and
General Population
Objective
The objective of this cost study is to develop quantitative data
to provide measures of the cost of inferior air quality.
Purpose and Scope
The costs of low quality air are revealed in a variety of forms,
including medical costs, job absenteeism, reduced property values, in-
creased maintenance, and more rapid deterioration of materials. The
RAPS data bank on regional air quality will provide a heretofore unavail-
able opportunity to carry out detailed analyses of the costs of inferior
air quality. This task is designed to acquire detailed data covering
these and other pertinent costs and related factors of the resident popu-
lation and industry and to combine these data with the appropriate aero-
metric data, using the St. Louis data handling facilities. These data
generally will be designed to support ongoing research efforts elsewhere
in EPA not currently considered as part of RAPS.
A-59
-------
302.2
Costs of Control Strategies
Objective
The objective of this subtask is to assemble information to support
analyses of the costs of alternative control strategies.
Purpose and Scope
An immense number and variety of alternative control strategies
have been identified, including installation of various types of control
equipment, changes in fuel usage, plant shutdown, traffic controls, and
land use restrictions on source densities. Each has a cost associated
with its implementation, and many of these costs are not known to a
satisfactory level of accuracy. Accordingly, this task covers the de-
velopment of the necessary data to support further studies of the cost
of control strategies. The collection of these data should be coordinated
with other collection tasks, especially with 102--Source Inventories.
These data generally will be designed to support ongoing research efforts
elsewhere in EPA that are not currently considered as part of RAPS.
302.3
Data Collection Surveys of Specific Effects
Objective
The objective of this subtask is to assemble information to support
analyses of specific effects of pollutants on selected receptors.
Purpose and Scope
The effects of pollutants on receptors naturally vary widely with
the nature of each. Typical effects may include corrosion of metals,
hardening and cracking of electrical insulation, and damage to growing
plants. The nature of the damage will be quantified and where possible
combined with the RAPS air quality data. These data generally will be
designed to support ongoing research efforts elsewhere in EPA not cur-
rently considered as part of RAPS.
A-60
-------
400
Transfer of RAPS Technology for Control Agency Applications
and the Formulation of Control Strategies
Objective
The objective of this series of tasks and supplies is to develop im-
proved technology that can be applied in local and regional control agency
operations, including techniques for emission inventories, air quality and
meteorological measurement, data handling and analysis, and the objective
assessment of control strategy effectiveness.
Purpose and Scope
The purpose of this research area is to ensure that the knowledge
and technology developed in the RAPS is transferred widely to the
air pollution control community at large as early and effectively as
possible. This requires passing on improvements and innovations in the
techniques of measurement, data handling, utilization in a direct form.
It also includes the conversion and distillation of the knowledge and
technology developed in RAPS in the specific test region to a generalized
form, so that it can be applied in other regions and for other problems
with minimum difficulty. Above all, however, this task provides the
basis for the development of improved control strategies, by national,
state and local agenci~s.
The approach follows four major lines. The first approach is de-
velopment and description of techniques and criteria by which the basic
air pollution factors can be assessed and monitored on an operational
(as distinct from research) basis. Particular attention will be given
to identifying and developing new techniques of monitoring atmospheric
and air quality conditions on extended scales appropriate to regional
and subregional control strategies so that the costs may be minimized.
The use of aircraft and remote probing techniques either from such air-
craft, or from the surface are especially suited to this purpose and
every attempt should be made to advance their applicability.
The second approach is the provision of tested, effective simula-
tion models, suitable for operational use on a generalized basis (that
can be readily modified and adapted) ,for other areas and conditions.
The third approach is development of a methodology for assessing the
validity (in terms of confidence, accuracy, and precision) of the pre-
ferred models, for varying degrees of input data quality. The fourth
approach is to provide methodologies for determining and assessing other
A-61
-------
factors such as health effects and economic costs and benefits relevant
to the formulation of improved control strategies.
First priority will be to provide data applicable to current data
resources, deficient though these may be, with emphasis on the optimum
methods of providing more complete data for input to models and for air
quality monitoring and model verification purposes. The needs of the
states and local authorities (and EPA) to improve and extend Implementa-
tion Plans will be treated first, with concurrent although subordinate
attention to Environmental Impact Statement requirements. First mile-
stone will be the achievement of interim capabilities for these purposes.
Thereafter, a more complete and detailed facility will be developed,
covering all aspects of control strategies formulation then current and
capable of extension to other pollutants and the like as the need arises.
401
Source Inventory Procedures
Objective
The objective of the task is to provide guidelines for the develop-
ment and maintenance of source inventories as derived from the experience
in the Regional Study.
Purpose and Scope
The source inventory for the Regional Study is likely to be the most
comprehensive such inventory yet developed. The methods by which the
source data are acquired and updated, and the manner in which the inven-
tory is organized, stored, and retrieved should prove to be of consider-
able value to others faced with the task of preparing sources inventories.
Accordingly, this component of the Research Plan includes efforts required
to prepare guidelines and reports for the benefit of others, covering the
techniques developed in the Regional Study for the management and use of
source inventories.
401.1
Techniques for Making Source Inventories
Objectives
The objective of this subtask is to provide guidelines for the prep-
aration of source inventories.
A-62
-------
Purpose and Scope
The development of the source inventory for the Regional Study is
likely to reveal many near optimal techniques by which all but the most
unique sources should be inventoried. For example, requirements for
field measurements of the various types of sources versus the more eco-
nomical on-site inspection and similar procedures should be readily de-
termined. The most appropriate classification scheme for the many types
of sources should also be apparent. These and other findings should be
provided to all organizations confronted with responsibilities for the
development of emission inventories whether for research control, strategy
design, or enforcement.
401.2
Techniques for Inventory Storage and Retrievel
Objective
The objective of this sub task is to provide gUidelines for the de-
velopment of techniques for source inventory storage and retrieval.
Purpose and Scope
The magnitude of the source inventory of the Regional Study undoubt-
edly will require the use of electronic data processing equipment. Be-
cause of the many anticipated uses of the inventory during the work, the
storage and retrieval techniques used to treat the inventory should be
highly flexible and have the capability to provide the required data to
each user in almost any form requested. These techniques should have
ready application to emission inventories maintained by other research
groups, control agencies, and the like. Therefore, these groups should
be provided with both the concepts and the computer programs developed
in the Regional Study for application elsewhere.
401.3
Techniques for Updating the Source Inventory
Objective
The objective of this subtask is to provide guidelines for updating
source inventories.
A-63
-------
Purpose and Scope
Tasks 102.2 and 102.3 provide for the development of inventories
for stationary and mobile sources for the Regional Study and the main-
tenance of these inventories throughout the study. This maintenance
program should provide measures of the rate of change of emission levels
over the five-year period for all important classes of sources. More-
over, the causes of the change should be available. While perhaps the
St. Louis area is not precisely typical of other urban areas, valuable
clues of inventory changes based on the St. Louis experience should be
provided to others as gUidance for updating their inventories.
401.4
Relating Source Inventory to Control Strategy
Objective
The objective of this subtask is to provide guidelines for the de-
velopment and maintenance of source inventories to support control strat-
egies.
Purpose and Scope
The design and implementation of control strategies require some
form of source inventory. A difficult fact to ascertain in this regard
is the required size and level of detail of the inventory. The source
inventory of the Regional Study perhaps will be the most complete and
detailed inventory yet developed. Appreciable costs are associated with
inventory development, but these costs are justified for the comprehen-
sive Regional Study. On the other hand, in view of the number of areas
in the nation for which control strategies may be designed, the cost and
time to develop an emission inventory equivalent to St. Louis may be un-
acceptable and possibly unnecessary.
To develop guidelines for inventory development to support control
strategies, the comprehensive Regional Study inventory should provide
the opportunity to develop alternative control strategies based on use
of the inventory at successive levels of detail. The level of detail
will vary as a function of the number of sources included and the time
interval over which emission levels can be characterized, such as annually,
daily, or hourly. Comparison of the potential success of each control
strategy should reveal the required level of detail required in a source
inventory.
A-64
-------
402
Atmospheric Monitoring
Objective
The objective of this task is to improve the technology and tech-
nique of monitoring atmospheric conditions, particularly on extended
scales, so that control strategies can be better implemented.
Purpose and Scope
The purpose of this task is to make available for use in all types
of air pollution control operations as early as possible, the lessons
learned and the techniques developed in the RAPS.
Basic principles for designing measurement networks for control agency
operation and criteria for the siting of monitoring stations and instru-
ment exposure, will be developed on the basis of experience with the RAPS
data collection network.
Criteria for the organization and maintenance of extended networks
of measuring instruments, with special reference to calibration and stan-
dardization, will be established. This research effort also will develop
a methodology by which newly acquired data, using new techniques, can be
related to older data s~ that the value of the latter is fully realized,
even if strict continuity is not maintained.
Remote probing systems will be tested and evaluated, in comparative
trials as candidate systems become available. Such tests will be conducted
in conjunction with both the standard RAPS data collection system and
special programs that provide especially detailed knowledge of meteoro-
logical conditions or the concentration of pollutants.
In particular, use will be made of helicopter soundings and other
aircraft acquired data. The application of remote probing techniques
from aircraft, as well as of aircraft in situ measuring techniques, is
an additional and important study subject.
402.1
Basic Network Principles
Objective
The objective of this subtask is to develop and define the basic
principles applicable to the design and implementation of a monitoring
A-65
-------
net\vork that will provide representative data concerning the meteorology
and air quality of a region. Data manipulation required to achieve the
information goals of a monitoring network also will be defined.
Purpose and Scope
The purpose of the research effort is to make available the expe-
rience gained in the RAPS in the design, implementation, and operation
of an extensive monitoring network and to develop principles and cri-
teria that can be applied to the establishment or modification of a
monitoring network by control agencies.
The desirability of
layer will be defined on
respect to cost.
three dimensional measurements in the surface
the basis of measurement significance with
Data acquisition techniques, data analysis, and the data format for
ease of archiving and retrieval will be characterized in terms of versa-
tility, cost, and applicability to the more limited networks of local
control agencies.
The principles and guidelines of monitoring network function will
be developed with the required flexibility to find application not only
with today's information goals but also with future goals.
402.2
Criteria for Organization and Maintenance
of Observational Networks
Objective
The object of this subtask is to develop criteria for the organiza-
tion and maintenance of observational networks applicable to control
agencies whose region of responsibility is extensive and complex in terms
of source emissions and location, topography, and land usage.
Purpose and Scope
Criteria for organization, function, support functions, and the
mechanics of implementing an extended network will be established on
the basis of experience with the RAPS data collection network.
A-66
-------
Maintenance, downtime, station calibration, inters tat ion calibra-
tion, station accessibility, and instrument shelter parameters will be
defined where appropriate in terms of frequency, accuracy, cost, diffi-
culty, and time.
402.3
Station Siting and Instrument Exposure Criteria
Objective
The objective of this subtask is to define criteria for the optimum
location of fixed and mobile stations and for the choice, exposure, and
operation of meteorological and air quality sensors.
Purpose and Scope
Purposes of this research effort are to:
.
Ensure that the measurements obtained at an atmospheric monitor-
ing station are representative of average conditions over a
reasonably extensive area and do not reflect the influences of
extremely local factors.
.
Determine the sampling frequency and period that is required for
the various sensors as dictated by the physics of the processes
being monitored and the models or studies that will use the data.
.
Define objective criteria for the station density that
for various parts of the region (e.g., urban or rural)
requirements of special research studies.
is required
and the
402.4
Methodology for Modernization of Monitoring Networks
Objective
The objective of this subtask is to use the RAPS monitoring network
with its sophisticated instrumentation as a reference standard against
which to compare older design pollutant monitors and their inaccuracies
resulting from interferer compounds. Included in the comparison will be
new and promising monitors based on new or different measurement techniques
and other aspects of network operation such as data acquisition, calibra-
tion stability, sample handling.
A-67
-------
Purpose and Scope
The purposes of this subtask are to identify older design monitors
still in use whose measurement characteristics are such that upgrading
with modern instrumentation would be recommended, to identify and define
the inaccuracy of monitors resulting from interferer compounds, and to
identify new and promising measurement techniques. The data obtained
precisely could define the older instrument measurement characteristics
and the contribution of interferers. This information can be used to
reevaluate data from previous aerometric surveys and to permit the survey
data to be upgraded without repeating the measurements.
402.5
New Aircraft Measurement Techniques
Objective
The objective of this subtask is to test and evaluate new
measurement techniques as a means of obtaining meteorology and
data over extended areas with three dimensional definition.
aircraft
air quality
Purpose and Scope
Purposes of the subtask are to:
.
Make available the experience gained in RAPS in using new and
promising airborne measurements.
.
Determine the types of
nificant data basic to
quality of a region.
airborne measurements that can add sig-
the understanding, meteorology, and air
.
Evaluate new instruments as to their applicability of airborne
operation and correlate their measurments to current instru-
mentation.
.
Define those aircraft measurement techniques most feasible for
augmentation of local control agency ground based monitoring
networks in terms of expense and adaptability to light aircraft.
A-68
-------
402.6
Evaluation of Remote Measuring Techniques
Objective
The objective of this subtask is to test and evaluate remote measur.
ing techniques and to correlate remote probing data with those obtained
by ground based and airborne monitors. It will also be determined if
the integrated remote measurements can provide measurements representa-
tive of the air quality within a region.
Purpose and Scope
Purposes of this research effort are to:
.
Make available the experience gained in RAPS in the operation,
accuracy, and interpretation of data acquired by remote measur-
ing techniques.
.
Evaluate the capability of remote measurement techniques to
integrate pollutant concentrations through both vertical and
horizontal planes within a region of interest.
.
Evaluate the use of remote measuring techniques as to its poten-
tial as a policing or reconnaissance tool for local control
agencies.
.
Evaluate and correlate pollutant concentration measurements
over a similar measurement path obtained with remote probing
techniques based on different measurement principles.
403
Data Handling
Objective
The objective of the data output task is to develop optimum tech-
niques for acquiring, storing, and retrieving data on an extended scale
for use in air pollution control agency operations.
A-69
-------
Purpose and Scope
The purposes of the task are to:
.
Make availabe the lessons learned and techniques developed in
RAPS regarding the handling of all types of data collected and
used in an extensive monitoring network and emission inventory.
.
Develop and publish Standard formats as used in RAPS that are
suitable for general use.
.
Develop and publish manuals and computer programs for all
types of data collection and initial processing, suitable
use in air pollution control agency use.
major
for
.
Provide guidelines on quality control procedures for use in
collecting data.
404
Modeling Technology
Objective
The objective of this task is to provide the best available model-
ing capability for use in operation in air quality management.
Purpose and Scope
The purpose of this task is to extract from the research and ex-
perience of RAPS a number of models that have been tried and demonstrated
and to show how these can be adapted and used for a range of specific
operational requirements in an optimum fashion.
A most important major task is to evaluate the significance of model.
ing techniques to the formulation of control strategies and their imple-
mentation. This entails an assessment of the accuracy and precision of
the models output as a function of the degree of completeness of the
input. Given that the resources for data collection and monitoring in
the general case will be far less complete than those for RAPS, it will
be necessary to analyze the way in which limitations of the input can
compromise the output of the models. Any shortcomings or uncertainties
of the predictions derived from the models must be fully assessed and
understood in terms of the control strategies based on them--especially
where such strategies have significant economic or social impacts.
A-70
-------
In addition to models suited to regional areas in general for the
range of significant pollutants, special attention must be paid to pro-
viding suitable models for use in formulating or checking Implementation
Plans, as well as for use in Environmental Impact Statements, and the
requirements of air pollution episode prediction.
For all these purposes it will be necessary to:
(1)
Select and publish a series of models relating to appropriate
scales or pollutants in a form in which they can be readily
applied in an operational role.
(2)
Develop and provide a methodology for assessing the sensitivity
of such models to practical limitations--such as the quantity
or quality of input data, and qualifying topographical features.
(3)
Develop and provide a methodology for measuring the accuracy
of predictions based on such models, using either existing or
specially provided (but limited) additional measurement fa-
cilities.
In general the detailed tasks, covered within the 404 series are sched.
uled well along in the Research Plan at a relatively low level of effort.
Accordingly, their ultimate detailed content tends to be somewhat more
speculative than tasks,presented elsewhere in the Research Plan, so that
presentation of their content in detail does not appear warranted at this
early time. Broadly, however, the tasks included in the 404 series are
as follows:
404.1
The significance of Modeling to the formulation of control
strategies and their implementation
404.2
Implementation Plan Applications
404.3
Environmental Impact Statement applications
404.4
Methodology for assessing model validity in Control Agency
operations.
A-71
-------
405
Other Significant Factors in Control Strategy Formulation
Objective
The objective of the other tasks concerned with strategy formulation
is to ensure that all knowledge and experience acquired under the RAPS
program is made available for use by the air pollution control community
in general and those concerned with formulating improved control strat-
egies in particular.
Purpose
The purpose of these other efforts is to take care that both during
the RAPS program and at its conclusion, fullest advantage is taken of
other research in progress (both by EPA and other agencies) and also that
the products of RAPS not directly connected with its principal objectives
nevertheless are made available in appropriate form to potential users.
Five principal components are involved.
( 1)
Liaison and interaction will be required with other research
programs, both inside EPA and in other agencies, particularly
those being carried out in the St. Louis area, such as METROMEX
( 2)
Techniques should be developed to assess and evaluate
and economic factors in control strategy formulation,
a base the data collected in 301 and 302.
social
using as
( 3)
A methodology for assessing operational costs of control strat-
egies should be developed for use in areas where available data
are less complete than in the RAPS area.
( 4)
Similarly, the development of a methodology for assessing the
resultant costs in terms of lost production and increased pro-
duction costs of proposed strategies will be appropriate.
( 5 )
Investigations on the basis of study and experience in the
St. Louis region should be carried forward to identify the
interaction of local government and other instutional aspects
that are relevant to the formulation of effective control
strategies and their enforcement.
A-72
-------
In general the detailed tasks, covered within the 405 series are
scheduled well along in the Research Plan at a relatively low level of
effort. Accordingly, their ultimate detailed content tends to be some-
what more speculative than tasks presented elsewhere in the Research Plan
so that presentation of their content in detail does not appear warranted.
Broadly, however, the tasks included in the 405 series are as follows:
405.1
Liaison and
Interaction
Programs
with other Environmental Control
405.2
Techniques of Assessing
Social and Economic Factors
405.3
Methodology of
Assessing Operational
Control Strategies
Costs of
405.4
Methodology of
Assessing Resultant Costs of Control Strategies
405.5
Institutional Aspects
A-73
------- |