United States
Environmental Protection
Agency
Robert S. Kerr Environmental
Research Laboratory
Ada OK 74820
Research and Development
EPA/600/S2-86/071 Nov. 1986
Project Summary
Evaluation of Volatilization of
Hazardous Constituents at
Hazardous Waste Land
Treatment Sites
R. Ryan Dupont and June A. Reineman
The volatilization of hazardous or-
ganics from hazardous waste land
treatment systems was evaluated in
laboratory and field studies using com-
plex petroleum refining hazardous
wastes. Laboratory experiments were
conducted using two soils and an inert
construction sand to investigate the
emission flux rates of seven volatile
constituents, i.e., benzene, toluene,
ethylbenzene, p-, m-, o-xylene, and
naphthalene, from API Separatory
Sludge and Slop Oil Emulsion Solids
wastes in column and flask laboratory
units. Emission flux rates were moni-
tored as a function of waste application
rate, application method (surface ver-
sus subsurface), soil type and soil phys-
ical characteristics. Field experiments
were conducted at an active petroleum
refinery hazardous waste land treat-
ment site to which a combined API Sep-
arator Sludge/DAF bottom sludge was
surface applied.
Pure constituent collection and quan-
tification in both laboratory and field
studies were carried out using an emis-
sion flux chamber and split stream
Tenax™ sorbent tube concentration
system. Suggested operating proce-
dures in terms of purge flow rates, split
stream sampling rates, sample collec-
tion volumes for minimal contaminant
sorbent tube breakthrough, etc., are
presented.
Measured laboratory and field data
were compared to the Thibodeaux-
Hwang Air Emission Release Rate
(AERR) model in an effort to validate
this state-of-the-art land treatment
emission model. Once specific data are
collected which describe the physical
environment of the land treatment sys-
tem, prediction of pure constituent air
emissions from surface application and
tilling can be provided by the model,
within a factor of two to ten, even for
complex hazardous wastes applied to
complex soil systems.
This Project Summary was devel-
oped by EPA's Robert S. Kerr Environ-
mental Research Laboratory, Ada, OK,
to announce key findings of the re-
search project that is fully documented
in a separate report of the same title
(see Project Report ordering informa-
tion at back).
Introduction
Land treatment may be defined as the
engineered usage of the upper soil zone
for the treatment and ultimate disposal
of waste materials at a rate and to an
extent that the land used for disposal
will not be irretrievably removed from
beneficial use sometime in the future.
The characteristics of waste con-
stituents and their interactions within
the land treatment system lead to a clas-
sification of loading limitations based
on: (1) the loss of waste components
due to volatility or teachability as af-
fected by soil and micrometerological
site conditions, (2) movement of com-
ponents from the land treatment area
due to their limited degradation, trans-
formation, and/or immobilization, or
(3) accumulation of non-assimilable
-------
V 4
components to levels that limit the fu-
ture beneficial use of the land treatment
area.
The primary emphasis in the monitor-
ing and evaluation of land treatment fa-
cilities has been related to rates of
degradation of biodegradable waste
constituents and to the impact of land
disposal activities on surface and
groundwater systems. However, the
1984 RCRA Amendments acknowledge
the potential for air emissions from haz-
ardous waste Treatment, Storage and
Disposal Facilities (TSDFs) in Sec-
tion 201 and specify that EPA promul-
gate regulations for the monitoring and
control of air emissions at hazardous
waste TSDFs within 30 months of the
enactment of these amendments.
The full report provides results of a
laboratory and field evaluation of a
sampling system used for the collection
of data describing the magnitude and
extent of the volatilization component
of hazardous constituent transport at
hazardous waste land treatment facili-
ties. Data from laboratory and field
scale validation of the Thibodeaux-
Hwang AERR model, which describes
the volatilization rates of hazardous or-
ganic waste constituents from land
treatment systems, are also presented.
Thibodeaux-Hwang AERR
Model
Use of a "dried-out" zone to model air
emissions from land treatment of
petroleum wastes has been carried out
by Thibodeaux and Hwang (1982) and
represents the state-of-the-art descrip-
tion for the volatilization of organics
from land treatment operations. Their
model assumes an isothermal soil
column, no capillary action through the
soil layer, no adsorption in the soil pore
space, and no biodegradation of ap-
plied organics within the soil column.
This description of vapor movement
through the soil/waste matrix is applica-
ble to surface or subsurface waste appli-
cation events through the use of surface
injection depth, hs, and depth of pene-
tration or plow slice depth, hp (Figure 1).
Under steady-state conditions, the time
for the initial mass applied to the soil to
completely volatilize into the soil pore
space, te, and the mass flux rate of each
component, FA, are determined through
a mass balance of each component as-
suming Fickian diffusion through the
soil column. With an air phase concen-
tration at the air/soil interface equal to
0, the following relationshipfor evapora-
tion time can be developed:
= Individual Contaminant Mass Application Rate
Uncontaminated Lower Soil Zone
= Contaminant Flux Rate
1T
h, = Injection Depth
hp = Penetration
Depth
Figure 1.
Theoretical contaminant behavior described by the Thibodeaux-Hwang AEEF,
model. Adapted from Thibodeaux and Hwang (1982).
,_MA-(hp+hs)
te~2A-DA-CA*
while mass flux rate is given as:
(1)
C4*=-
1+Hr
e-D.-zo
Do-as-(hp2+hp-hs-2hs2)
FA=-
2DA-t-A-(hp-hs)-CA*\i/2
MA /
(2)
where: t=time after component appli-
cation.
The component pore-space concen-
tration, CA*, is related to the component
concentration within the applied oil by
equating the rate of movement through
the oil phase to that through the dry soil
column. The concentration of the com-
ponent in the air and oil phases within
the soil pore space is related by a mod-
ified Henry's Law constant with units of
cm3 oil/cm3 air. The expression for the
concentration of the component in the
soil vapor phase in terms of its initial
concentration within the oil then be-
If the land treatment unit is tilled a
time t less than the volatilization life
time of the hazardous constituents o
interest, the equations above must bi
modified for the new geometry whicl
results. The mass of contaminant los
during the period prior to tilling, MA(, i;
determined from the integration o
Equation 2 from t=0 to t=time of tilling
resulting in Equation 5:
MA,=-
(5
comes:
CA*=-
Hc.
•Cio (3)
1+K
DA-Zo
C' '
Do-as-y(hp-y)
Estimating an average value for the
lengthening dry zone diffusion path,
V • (hp-y), by the integral of y • (hp-y)
from 0 to hp-hs divided by hp-hs
yields:
2DA-A-t-(hp-hs)-Cy
MA
The mass remaining after time t
MAr=MA-MAt, is then used in Equa
tions 1 and 2 above to determine thi
evaporation time and mass flux rate fo
the residual mass from the tilled soil
assuming uniform mass distributioi
within a soil column of dimension:
hp=tilling depth and hs=0.
With the use of Equations 1 through 5
the rate of organic emissions from lan<
treatment sites before and after tillin;
can be determined once the followim
three sets of parameters are measured
-------
1) soil parameters including bulk den-
sity, particle diameter and particle den-
sity; 2) compound parameters including
air and oil molecular diffusivity and
modified Henry's Law constant; and
3) operational parameters including
surface injection and penetration or
plow splice depth, tilling depth, surface
area of application, mass application
rate, and time. Further details of model
development and its application to lab-
oratory and field data are presented in
the full report, along with example cal-
culations for theoretical emission rates.
Laboratory Procedures
Sampling System Evaluation
Sampling is a key step in the meas-
urement and detection of contaminants
for evaluation and analysis of models
used for predicting their fate in the envi-
ronment. The flux chamber investigated
in this study (Figure 2) was a modifica-
tion of a design developed for the U.S.
EPA Environmental Monitoring Sys-
tems Laboratory, Las Vegas, Nevada, by
Radian Corporation (Schmidt and
Balfour 1983, Balfour et al. 1983). It con-
sisted of a 68.7 x 68.7 cm square exte-
rior dimension (effective emission sur-
face area=4560 cm2), clear acrylic
double-domed skylight modified for
isolation flux sampling as shown in
Figure 2. The acrylic double-dome in-
terior was lined with opaque, adhe-
sive Teflon™ tape to provide a non-
adsorbing, non-reactive interior
surface. Teflon™ was used for all bulk
head fittings and purge gas inflow and
outflow lines to provide an inert sur-
face in all areas of the chamber. Bulk
head openings were provided for in-
fluent and effluent lines as well as for
temperature and chamber interior
pressure measurements.
Solid Sorbent Collection/
Concentration System
Evaluation
Solid sorbent evaluation included the
analysis of collection and recovery effi-
ciency of pure compounds and their
mixtures identified as major volatile
components of petroleum refinery
wastes using Tenax™ and charcoal sor-
bent tubes. These compounds included
benzene, toluene, ethylbenzene, p-, m-,
o-xylene, and naphthalene. Spike recov-
ery analyses provided data for this eval-
uation. Tenax™ data were collected uti-
lizing U.S. EPA EMSL/RTP standard
operating procedures for the spiking of
effluent
Purge Gas
Tenax™
Sorbent Tubes
Purge Inflow.
Temperature
Measurement
Constant Flow
Sample Pump
Figure 2. Schematic of Isolation Flux Chamber/solid sorbent tube sampling system.
Tenax™ cartridges with a known mass
of an organic constituent via the flash
evaporation method. Data were col-
lected for compound mass injection lev-
els ranging from 0.09 to 250 ng/sorbent
tube. Charcoal sorbent tube recovery
data were obtained for the same pure
volatile compounds used in the Tenax™
studies according to standard NIOSH
methods. The effects of sampling
stream moisture content on the collec-
tion and recovery efficiency of the char-
coal tubes were also investigated.
Finally, the combined flux chamber/sor-
bent tube sampling train was evaluated
in terms of sampling train collection and
recovery efficiency using mixtures of
the pure compounds of interest.
Due to difficulties in consistently re-
covering naphthalene from the charcoal
tubes at efficiencies greater than 50 per-
cent, only Tenax™ traps were used for
breakthrough volume evaluation stud-
ies. Injected mass levels of 1.1 to 120 ^g
were used at collection temperatures of
20-22°C and 32-35°C. A purge flow rate
of 200 ml/min, comparable to that used
in laboratory and field emission meas-
urements, was used in these experi-
ments for time periods of 5 minutes to
2 hours.
Flux Chamber Pressure and
Mixing Studies
The flow regime within the flux cham-
ber is of critical importance as compo-
nent emission rate calculations are
based on the assumption that emission
measurements from the chamber efflu-
ent are representative of a completely-
mixed chamber volume. In addition, ad-
equate flow and turbulence must be
provided to assure no component mass
accumulation within the chamber that
may affect the component's flux from
the soil surface into the lower atmos-
phere. Counter to the desire for maxi-
mizing flow and turbulence within the
flux chamber is the need for minimizing
positive pressure development within
the chamber as it may cause emission
suppression and possibly flux reversal
during emission sampling.
The impact of purge flow rate on
chamber pressure build-up was evalu-
ated by monitoring chamber interior
pressure (with respect to ambient) as a
function of purge flow. Pressure meas-
urements were made over a range of
purge flows from 0.7 to 4 liters/min as
suggested in Radian protocol (Schmidt
and Balfour 1983, Balfour et al. 1983).
Mixing within the flux chamber as a
function of purge flow rate was evalu-
ated using standard tracer techniques.
The flash vaporization technique was
used to vaporize liquid acetone used as
a tracer. Flow curves were evaluated to
provide a quantitative description of
chamber mixing conditions in terms of
dimensionless indicator retention time
parameters and the Morril dispersion
index.
Flux Chamber/Sorbent Tube
Collection/Recovery Evaluation
Contaminant collection and recovery
efficiency for the combined flux cham-
ber/solid sorbent sampling train was
evaluated at 22°C ± 2°C to indicate the
effect if any the flux chamber had on
observed mass recovery efficiency re-
-------
suits for the Tenax1" sorbent collection/
concentration tubes. The flux chamber
was configured with a four position
Tenax™ sorbent split-stream sampling
system placed in the effluent purge gas
line. Compound recovery data using the
flux chamber/sorbent tube sampling
train were collected for compound
mass injection levels ranging from 0.5
to 90 fig/tube. Chamber purge flow was
maintained at 4 liters/minute and sam-
pling continued for three theoretical
chamber retention times to ensure rep-
resentative chamber volume sampling.
Laboratory Model Evaluation
Studies
Model evaluation was carried out
using modular, beaded glass process
pipe microcosm systems (Figure 3), and
ground-glass Erhlenmeyer flask screen-
ing apparatus (Figure 4) in conjunction
with Tenax™ sorbent sampling/concen-
tration systems. Measured versus pre-
dicted pure compound emission rates
using two listed hazardous wastes from
the petroleum refining industry, an API
Separator Sludge and Slop Oil Emul-
sion Solids, were compared under a
range of soil, waste loading, and waste
application conditions. Constituent
analyses were conducted on methanol
extracts of samples of the waste used in
each laboratory experiment. The extract
procedure used was a modification of
Method 5030 "Purge-and-Trap
Method," with analysis via purge and
trap/GC-FID detection. The pure com-
pounds of interest were quantified in
the complex wastes via standard spike
recovery analysis procedures.
A range of soil types were evaluated
in the study to identify soil characteris-
tics found to significantly affect con-
stituent volatilization. Soil parameters
evaluated included media texture,
media particle size distribution, particle
density, and bulk density. Soil chemical
parameters evaluated included soil or-
ganic carbon and specific organic con-
stituents by methanol extraction/purge
and trap analysis using a modified
Method 5030 procedure.
Microcosm Experiments
The application rates used in these
studies were based on a weight percent
of waste applied with respect to the top
15.24 cm (6 inches) of soil in the micro-
cosms. If subsurface injection was sim-
ulated, the appropriate amount of soil
was added to the unit immediately fol-
lowing waste application to provide the
desired soil depth above the point of
Influent
Purge Gas
Tenax™* Sorbent
Tubes
Magnehelic
Soil
Constant
Flow
Sample
Pump
Figure 3. Laboratory microcosm apparatus used in laboratory AERR model validation studies.
Influent
Purge
Gas
Effluent Purge •
Gas
Soil/Waste
Mixture
Tenax™ Sorbent
Tubes
Capillary
Flow Control
Effluent Purge Gas
Constant
Flow
Sample
Pump
Figure 4. Screening flask apparatus used in laboratory AERR model validation studies.
application. Purge gas was maintained
constant at 300 to 500 ml/min/micro-
cosm during the volatilization experi-
ments. The sorbent traps were sampled
at a rate of 50 to 200 ml/min/trap for a
period not exceeding five minutes to
minimize breakthrough of the benzene.
Breakthrough traps were used in the
first five sampling events to allow the
quantification of any breakthrough
which occurred. The sampling and anal-
ysis procedures were repeated at se-
lected time intervals following waste
addition corresponding to the predicted
log decay in emission rates of volatile
organics from the soil systems. Blank
and spike traps were used throughout
the sampling period to maintain QA/QC
standards during these studies.
Initial soil data collected for each mi-
crocosm included the soil depth above
the application point, hs, and total depth
and weight of soil in the microcosms.
Data relating to the physical conditions
of the microcosm systems were col-
lected at each sampling time and in-
-------
eluded air and soil temperature, height
of the capillary rise observed above the
injection point, and depth of the waste
wetting front below the soil surface, hp.
Measurements of hp and hs were deter-
mined in laboratory experiments by vis-
ual identification of the wetting fronts.
Screening Flask Experiments
The application rates used in these
studies were based on a weight percent
of waste applied with respect to 200 g of
the field soil placed within each test
unit. Sampling and analyses proce-
dures were repeated at selected time in-
tervals following waste addition in a
manner identical to those of the micro-
cosm units.
Field Procedures
The ultimate objective of this re-
search project was to provide field eval-
uation of the Thibodeaux-Hwang AERR
model for the prediction of volatile or-
ganic emissions from land treatment fa-
cilities. Field studies involved the use of
the emission isolation flux chamber for
the collection and concentration of
volatile organics emitted from a land
treatment facility during typical land
treatment activities.
Waste/Soil Characterization
Methods
Waste samples at flux chamber loca-
tions were collected in 15.24 cm (6
inch) x 68.6 cm (27 inch) x 10.2 cm (4
inch) sheet metal pans placed on either
side of the flux chamber sampling loca-
tions, perpendicular to the long axis of
the land treatment application area.
These sample collection pans were
used for mass application rate measure-
ments, and for sample collection for
physical/chemical property and specific
constituent concentration measure-
ments. The collection pans were imme-
diately analyzed on-site gravimetricalty
for application rate determinations
using a top loading balance. The two
pans at each sampling site were com-
posited and aliquot waste samples were
subsequently collected for density, vis-
cosity and specific constituent measure-
ments.
Composite soil samples for particle
size distribution, particle density, oil
and grease, and specific constituent
analyses were manually collected with
a trowel from the surface to a 15 cm
depth. The magnitude of hp prior to till-
ing was determined by visual identifica-
tion of the bottom of the wetting front
during collection of the composite soil
samples. The plow splice depth, hp, fol-
lowing tilling was estimated by visual
observation of subsurface soil condi-
tions at each sampler location following
each tilling event.
Waste Application/Tilling
Methods
The test plot used in field experiments
was approximately 6 m by 182 m in area
and was divided lengthwise in half.
Waste application was carried out via
gravity feed from a tank truck equipped
with a slotted application pipe approxi-
mately 3 m in length and 8 cm in diame-
ter. Each side of the application area re-
ceived a full truck load of waste
corresponding to approximately 880
gallons. Tilling of one half of the appli-
cation plot at a time was carried out
using a rototiller. Initial tilling was con-
ducted approximately 24 hours after
waste application. The test plot was
retilled approximately 155 hours after
waste application due to rainfall that
had occurred following the first tilling
event. Tiller depth was variable, ranging
from approximately 17 to 23 cm.
Flux Chamber Field Sampling
Procedures
Sampling was conducted at the field
plot using six sampling flux chambers.
Four distinct sampling phases were
conducted: 1) background sampling of
the test site prior to tillage (BBT),
2) background sampling of the test site
following tillage and prior to waste ap-
plication (BAT), 3) specific constituent
emission sampling following waste ad-
dition (WBT), and 4) specific constituent
emission sampling following two tilling
operations (WAT, WST).
Sampling chambers were systemati-
cally placed to provide a representative
estimate of emissions from the entire
application site both during background
and specific constituent emission sam-
pling. A systematic random sampling of
the application area, entailing a plot grid
and a random numbers table, was used
to select sampling locations. Once
placed at a sampling location, sampling
was conducted at that same location
during background and specific con-
stituent sampling to preserve spatial
continuity of the collected data. Sample
collection frequency was based on a
logarithmic time scale in anticipation of
results following the trends predicted
by the Thibodeaux-Hwang AERR
model.
Thermocouple temperature probes
were used for 0.6 cm (1/4 inch) and 5 cm
(2 inch) soil depth and chamber air tem-
perature measurements. Temperature
readings were also collected for soil and
ambient temperatures prior to chamber
placement in the land application area.
The chambers were forced into the soil
such that the bottom of the Teflon1"
lined acrylic dome rested on, and the
aluminum dome rim made a tight seal
with the soil surface. A pressurized
high-purity breathing air purge gas was
passed through the flux chambers via a
constant volume sampling pump oper-
ated at rates of 2 to 6 liters/minute for
three retention volumes (=15 minutes)
prior to sample collection with the sor-
bent traps. Purge gas flow adjustment
was made via a micro-valve flow con-
troller.
Large temperature differentials were
observed between the flux chamber in-
terior air space and ambient air temper-
ature that reached a maximum of 49.5°C
during initial background sampling and
33.7°C during sampling following waste
application. Flux chamber shading was
utilized in all WAT and WST sampling
events in order to evaluate the effect
shading had on chamber air and soil
temperatures and compound emission
flux rates. Flux chamber shading was
accomplished utilizing wooden 2 x 2's
supporting a sheet of plywood angled
to shade the entire flux chamber.
Field blank and spike traps were used
in conjunction with breakthrough traps
to provide quality control information
for the field sampling. The blanks were
collected by exposing them to ambient
conditions for approximately 15 sec-
onds, the approximate time required for
sorbent tube placement in the sampling
manifolds. Additionally, soil and waste
samples were split with the U.S. EPA
Robert S. Kerr Environmental Research
Laboratory (RSKERL), Ada, Oklahoma,
for oil and grease, and specific con-
stituent quantification using identical
sample processing and analytical pro-
cedures for comparison purposes to en-
sure quality control for these measure-
ment methods. All other measurements
were conducted in at least duplicate to
provide statistical information regard-
ing measurement precision for com-
parison with original QA/QC goals es-
tablished for the study.
Parameter Calculation/
Estimation Methods
A limited theoretical base exists for
the determination of many of the soil/
-------
waste/compound parameters critical to
emission estimation using the
Thibodeaux-Hwang AERR model. Con-
sequently, correlation equations were
used, when appropriate, for the estima-
tion of parameters that could not be
easily or accurately determined experi-
mentally.
Compound effective soil air diffusion
coefficients, DA, were estimated utiliz-
ing the method presented by Farmer et
al. (1973). The effective Henry's Law
constant, Hc', was determined from sol-
ubility, solvent:octanol, solvent:water,
and solubility characteristics of the indi-
vidual compounds of interest using cor-
relation equations from Lyman et al.
(1982). The complex waste was mod-
eled as a hexane solvent system as hex-
ane was shown to be a prominent com-
ponent of the waste from GC/MS
analyses. Compound oil diffusion coef-
ficients were estimated using a modifi-
cation of the Wilke-Chang equation, and
temperature corrections for waste vis-
cosity, compound vapor pressure and
oil and air diffusion coefficients were
made using standard procedures (Ly-
man et al. 1982).
Results and Discussion
Waste Analyses
Pure constituent waste concentra-
tions are indicated in Table 1 for complex
hazardous wastes used in both labora-
tory and field studies. Data indicate that
the laboratory wastes were significantly
higher in pure volatile constituents than
the waste collected in the field study.
This result emphasizes the necessity for
accurate waste characterization due to
the significant effect waste generation
and handling practices have on final
waste composition. Results from analy-
sis of the field waste indicate that two
independent laboratories can duplicate
volatile constituent waste analyses if
strict QA/QC procedures are used.
Tenax™ Evaluation
Laboratory Tenax™ and Tenax™/
chamber recovery efficiency values
ranged from 61 to 94 percent, while field
spike results indicated recovery values
from 57 to 137 percent for the seven
pure compounds of interest. Due to the
wide variation in field results, no statis-
tically significant difference existed be-
tween these results.
Tenax™ breakthrough results are pre-
sented in Table 2. These results indicate
the major effect collected mass and
temperature have on compound break-
Table 1. Specific Organic Constituents of Hazardous Wastes Used in the Study
Mass (|xg/g Waste)
Compound
Mean
St. Dev.
C.V. (%)
SLOP OIL
Benzene
Toluene
Ethylbenzene
p-Xylene
m-Xylene
o-Xylene
Naphthalene
5421
7696
1639
3399
8500
3365
1621
2403
1953
657
928
1910
1108
687
44
25
40
27
22
33
42
16
18
18
18
18
18
16
SEPARATOR SLUDGE
Benzene
Toluene
Ethylbenzene
p-Xylene
m-Xylene
o-Xylene
Naphthalene
2350
2487
605
1686
3641
2194
2306
648
899
212
467
607
654
692
28
36
35
28
17
30
30
FIELD WASTE
UTAH WATER RESEARCH LABORATORY
(UWRL) Analyses (GO
Benzene 249.2
Toluene 631.7
Ethylbenzene 22.0
p-Xylene 33.2
m-Xylene 181.2
o-Xylene 56.0
Naphthalene 124.6
RSKERL Analyses (GC/MS)
Benzene 278
Toluene 687
Ethylbenzene 36
p-Xylene & m-Xylene 238
o-Xylene 81
Naphthalene 108
29.7
50.0
1.2
4.6
14.9
3.0
8.8
12.0
8.0
6.0
14.0
8.0
5.0
7.0
6
8
9
8
8
9
9
10
10
10
10
10
10
10
through and suggest that breakthrough
data provided by EPA protocol for use of
Tenax™ sorbent tubes for ambient
monitoring are not appropriate for the
high mass levels expected from land
treatment emissions.
Flux Chamber Evaluation
Interior chamber pressure develop-
ment was found to be greater than 0.25
cm (0.1 inch) of water at a purge flow of
1 liter/min for the chamber design used
in this study. Mixing results suggested,
however, that even at purge flow rates
below 1 liter/min, the chamber air ap-
proached theoretical complete-mixed
conditions. Operation of the isolation
chamber sampling system is possible at
low purge flow rates without a down-
stream purge pump or at high purge
flow rates with a downstream purge
pump to overcome pressure increase:
inside the chamber.
Laboratory Model Evaluation
Both upper and lower contaminatec
zone boundary movement was ob
served in laboratory studies, and was
shown to follow a linear relationship o
depth versus log(time). An effort was
made to accommodate these variabk
boundary conditions by using mear
values of hp and hs over discrete time
increments of 0 to 1, 1 to 10 and 10 tc
100 hours.
Data observed in laboratory surface
application experiments followed th<
linear relationship of flux versus 1
time1'2 as indicated in the Thibodeaux
Hwang AERR model (Figure 5), howeve
subsurface application results generally
-------
Table 2. Tenax Sorbent Tube Breakthrough Volumes as a Function of Temperature and Mass
Injection Level
Mass Level Benzene Toluene Ethylbenzene p-Xylene m-Xylene o-Xylene Naphthalene
19-23°C Tenax Breakthrough Volumes (I) for a Given Percent Recovery
on First Trap of Two Trap Series
120.0 tig
30% Recovery
50% Recovery
50.0 jig
}0% Recovery
50% Recovery
0.20
3.15
1.87
4.90
5.08
14.68
25.01
110.6
32.55
150.0
25.84
115.1
21.03
91.78
Mass Range: 8.5-15.0 tig 10-15.3 tig 9.7
13.4 tig 29.8 tig 11.2 tig 18.0 tig
)0% Recovery
50% Recovery
3.02
7.79
25.41
49.52
t/lass Range: 1.8-2.0 tig 2.2 p-9
1.1 tig 1.8 (ig 4.2 tig 1.91
2.4 tig
J0% Recovery
50% Recovery
5.27
28.10
28-32°C Tenax Breakthrough Volumes (I) for a Given Percent Recovery
on First Trap of Two Trap Series
20.0 tig
J0% Recovery
50% Recovery
30.0 tig
)0% Recovery
50% Recovery
15.0 tig
)0% Recovery
50% Recovery
1.1-4.2 ,ig
M)% Recovery
50% Recovery
0.28
0.60
0.71
1.79
1.21
3.54
4.50
13.67
0.20
2.50
0.22
5.96
17.35
33.20
19.22
40.35
11.31
22.22
14.28
24.88
*
*
*
*
12.08
22.48
14.87
25.43
*
*
#
*
10.97
24.09
15.24
27.05
*
#
*
*
12.77
25.44
14.90
28.54
*
*
*
#
*
*
#
*
*
*
*
*
*=»24 liters
p-Xylene
Flux
(fig/cm2/sec)
Slope
r2
= 0.0124
= 0.9728
/jg/cm'/sec
0.030
0.025
0.020
0.0/5
0.070
0.005 •
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
1 /Time"2 (J /hour"2)
Figure 5. Slop oil surface application to Durant clay loam. Run #8, Position #5.
did not (Figure 6). The increase then de-
crease in emission rates in the subsur-
face experiments, as indicated in Fig-
ure 6, could be attributed to the variable
upper boundary condition with time,
along with unsteady-state diffusion dur-
ing the development of an upper uncon-
taminated soil zone compound concen-
tration gradient following waste
application. Subsurface application re-
sulted in from one to four orders of
magnitude reduction in compound flux
rates as compared to surface applica-
tion experiments, and soil versus sand
data suggested some reduction in com-
pound emissions due to adsorption to
soil organic matter.
Compound flux data for the emission
flasks and the surface application mi-
crocosm experiments correlated well
for most waste/soil mixtures evaluated.
The screening ftask method appears to
hold promise as a simple method for
the determination of waste/soil
volatilization potential.
Field Model Evaluation
Results of field blank, spike and repli-
cate data suggest the need for strict QA/
QC procedures to ensure adequately
prepared, stored and analyzed sorbent
tubes. Oil and grease data for field sam-
ples analyzed by both the Utah Water
Research Laboratory (UWRL) and the
RSKERL showed a variability of less
than 20 percent between samples, indi-
cating the validity of these analyses
methods.
Field emission rate data were found
to support the validity of the diffusion
assumption for describing soil
volatilization from land treatment sys-
tems, as most measured data followed
the linear flux versus 1/time1/2 relation-
ship with r2 values greater than 0.7.
Measured versus theoretical compound
emission flux rates compared quite well
for WBT sampling events once spatial
and temporal corrections for waste ap-
plication rate, soil characteristics (bulk
density, porosity, moisture content,
plow splice depth), and soil tempera-
ture conditions at the 5 cm (2 inch) soil
depth were made. Measured flux values
were within a factor of two to ten of
Thibodeaux-Hwang model predictions
for most data during WBT sampling,
while measured data diverged to one to
two orders of magnitude from predicted
rates some 70 to 170 hours following
waste application in the WAT and WST
sampling events. This increased diver-
gence from predicted values with time
indicates the possibility of compound
-------
Toluene
Flux
(ug/cm2/sec)
0.0030 ,
0.0025
0.0020
0.0015
0.0010
0.0005 •
Slope = 0.001 fjg/cm"/sec
r* = 0.4764
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
1/Time"* (1/houry2)
1.8 2.0
Figure 6. Separator sludge subsurface application to 30 mesh sand. Run #4, Position #5.
biodegradation/adsorption within the
soil column that is not accounted for in
the Thibodeaux-Hwang AERR model.
Conclusions and
Recommendations
Experience utilizing the isolation flux
chamber/split stream sampling system
with Tenax™ solid sorbent collection/
concentration tubes in flask, microcosm
and field studies for the RCRA volatile
organic profile observed in three
petroleum refining wastes suggests the
system is simple and straightforward
and can provide continuity in sampling
protocol over a wide range of sampling
activities with little modification be-
tween source configurations. From
analysis of the chamber/Tenax™ sor-
bent collection system it can be con-
cluded that:
1. Mean recoveries from the cham-
ber/Tenax™ sorbent collection system
for the seven aromatic compounds of
interest in this study can be expected to
range from 61 to 94 percent.
2. Tenax™ breakthrough volumes are
a strong function of collected mass as
well as temperature. Ambient air proto-
col breakthrough volumes are not ap-
propriate for source emission sampling
from land treatment facilities.
3. Sampling systems must be oper-
ated at purge flow rates less than 1 liter/
min or in conjunction with a down-
stream purge pump to minimize
chamber internal pressures and poten-
tial soil emission suppression.
Both laboratory and field model vali-
dation studies indicated the general
validity of the Thibodeaux-Hwang AERR
model for describing volatile emissions
from land treatment facilities. The fol-
lowing conclusions can be made based
on model verification results:
1. Owing to the unsteady-state na-
ture of contaminant emissions in the
subsurface application experiments
caused by variable boundary conditions
and soil vapor phase concentration gra-
dient development following waste ap-
plication, the Thibodeaux-Hwang AERR
model cannot be used to accurately pre-
dict flux rates during this initial
unsteady-state period.
2. The temporal variation in both hp
and hs are of such a magnitude that this
variation should be included in future
Thibodeaux-Hwang AERR model refine-
ments.
3. Surface versus subsurface applica-
tion experiments indicated a one to four
order of magnitude decrease in flux
rates when wastes are subsurface ap-
plied. This reduction is more significant
for soils than sand indicating the impor-
tance of soil organic matter to soil vapor
emission attenuation.
4. Site specific information for waste
application rates, and site and time
specific data for soil physical and tem-
perature characteristics are required to
provide accurate correlation between
measured and predicted compound
emission flux rates.
5. The validity of the modeling ap-
proach in field studies, especially imme-
diately following waste application
events indicates that a simple diffusion
based modeling approach, as used in
the Thibodeaux-Hwang AERR model, is
valid for describing hazardous organic
air emission rates from complex haz
ardous waste land treatment systems
References
Balfour, W.D., R.M. Eklund, and S.J
Williamson. 1983. Measurement o
volatile organic emissions from sur
face contaminants. Proc. of the Na
tional Conference on Management o
Uncontrolled Waste Sites, Washing
ton, D.C. pp. 77-80.
Farmer, W.J., K. Igue, and W.F. Spencer
1973. Effects of bulk density on the
diffusion/volatilization of dieldrir
from soil. J. Env. Qua/. 2:107.
Lyman, W.J., W.F. Rechl, and D.H
Rosenblatt. 1982. Chemical property
estimation methods. McGraw-Hill
New York.
Schmidt, C.E., and W.D. Balfour. 1983
Direct gas measurement techniques
and the utilization of emissions data
from hazardous waste sites. Proceed
ings of the 1983 ASCE National Spe
cialty Conference on Environmenta
Engineering, Boulder, Colorado, Jul^
6-8. p. 690.
Thibodeaux, L.J., and S.T. Hwang. 1982
Landfarming of petroleum wastes
modeling the air emission problem
Env. Progress 1:42.
a
-------
R. Ryan Dupont and June A. Reineman are with Utah State University, Logan. UT
84322,
Fred M. Pfafter is the EPA Project Officer (see below).
The complete report, entitled "Evaluation of Volatilization of Hazardous Constit-
uents at Hazardous Waste Land Treatment Sites," (Order No. PB 86-233
939/AS; Cost: $16.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Robert S. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
-------
N>
g 2 »
_i »
V)
•
0>
O
O
03 C
O 3
01
I/I
VI
30
0)
3)
2
p •
9
u
01
------- |