Municipal Environmental Research
Laboratory ,
Cincinnati OH 45268
EPA-600/2-80-119
August 1980
vvEPA
Land Disposal of
Hexachlorobenzene
Wastes
Controlling Vapor
Movement in Soil
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development. U S Environments1
Protection Agency, have been grouped into nine series These nine broad cate-
gores were established to facilitate further development and applica; on of en-
vironmental technology Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields
The n^e series are
1 Environmental Health Effects Research
2 Environmental Protection Technology
3. Ecological Research
4 Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-80-119
August 1980
LAND DISPOSAL OF HEXACHLOROBENZENE WASTES
Controlling Vapor Movement in Soil
by
Walter J. Farmer
Ming-Shyong Yang
John Letey
Department of Soil and Environmental Sciences
University of California
Riverside, California 92521
and
William F. Spencer
Science and Education Administration
Federal Research - USDA
Riverside, California 92521
Contract No. 68-03-2014
Project Officer
Mike H. Roulier
Solid and Hazardous Waste Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL EROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Municipal Environmental
Research Laboratory, U.S. Environmental Protection Agency, and
approved for publication. Approval does not signify that the contents
necessarily reflect the views and policies of the U.S. Environmental
Protection Agency, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use.
11
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FOREWORD
The Environmental Protection Agency was created because of increasing
public and government concern about the dangers of pollution to the health
and welfare of the American people. Noxious air, foul water, and spoiled
land are tragic testimony to the deterioration of our natural environment.
The complexity of that environment and the interplay between its com-
ponents require a concentrated and integrated attack on the problem.
Research and development is that necessary first step in problem
solution and it involves defining the problem, measuring its impact, and
searching for solutions. The Municipal Environmental Research Laboratory
develops new and improved technology and systems for prevention, treat-
ment, and management of wastewater and solid and hazardous waste pollutant
discharges from municipal and community sources, for the preservation and
treatment of public drinking water supplies, and to minimize the adverse
economic, social, health, and aesthetic effects of pollution. This
publication is one of the products of that research; a most vital
communications link between the researcher and the user community.
This report presents results of a study of the volatilization and
vapor phase movement of hexachlorobenzene (HCB) from industrial wastes
deposited on land. The work focused on understanding the factors that
control movement of HCB in soil. The principal application of the
results will be in designing adequate soil covers for land disposal
sites receiving HCB wastes.
Francis T. Mayo, Director
Municipal Environmental Research
Laboratory
111
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ABSTRACT
Hexachlorobenzene (HCB) is a persistent (chemically stable and
resistant to microbial degradation), water-insoluble, fat-soluble organic
compound present in some industrial wastes. Because of its low water-
solubility (6.2 ug/1), transport in water moving through soil will be
negligible_.r Its long term persistence and appreciable vapor pressure
(1.91 x 10 mm Hg at 25 C) allows significant volatilization to occur.
The potential for volatilization indicates a need for disposal site
coverings that will reduce the vapor phase transport of HCB into the
surrounding atmosphere. Research was initiated to determine the condi-
tions that would control the movement of HCB out of landfills and other
disposal/storage facilities into the surrounding atmosphere. The
volatilization fluxes of hexachlorobenzene from industrial wastes (hex
wastes) were determined using coverings of soil, water, and polyethylene
film in a simulated landfill under controlled laboratory conditions.
Coverings of water and soil were found to be highly efficient in reducing
volatilization. Polyethylene film was less efficient when compared on a
cost basis. Volatilization flux through a soil cover was directly
related to soil air-filled porosity and was therefore greatly reduced by
increased soil compaction and increased soil water content. An organic
liquid phase associated with the hex waste was heavier than water and
contained 1.4% HCB by weight. The presence of HCB in this liquid phase
creates the potential for the rapid transport of HCB in porous media.
A procedure is proposed for using the results of this study to design
a landfill cover that will limit the volatilization flux of HCB and
other compounds.
This report was submitted in fulfillment of Contract No. 68-03-2014
by the University of California, Riverside, under the sponsorship of the
U. S. Environmental Protection Agency. The report covers the period
from June 14, 1974, to September 13, 1976, and work was completed as
of September 13, 1976.
iv
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CONTENTS
Foreword iii
Abstract iv
Figures vi
Tables ix
Acknowledgement x
1. Introduction 1
2. Conclusions 6
3. Recommendations 8
4. Materials and Methods 9
Collection and preparation of hex waste and soil samples . 9
Recrystallized practical grade HCB 12
Measurement of HCB solubility and vapor pressure 12
Simulated landfill volatilization cell 14
HCB volatilization experiment 15
Extraction, clean-up, and analysis of HCB 17
5. Results and Discussion 19
Solubility and vapor pressure of HCB 19
Volatilization of HCB from simulated landfill 24
Uncovered hex waste 24
Hex waste covered with polyethylene film 25
Hex waste covered with water 28
Hex waste covered with soil layer 29
Hex waste covered with a composite layer
of soil and polyethylene film 36
Effect of soil parameters on HCB volatilization 37
Calculation of HCB vapor phase diffusion coefficient ... 43
6. Significance of Findings for Some Disposal Practices 49
Equivalent thickness of polyethylene film 49
Liquid component of the hex waste 50
7. Application of the Findings in Designing Landfill Covers. ... 52
Design application 54
Assessment application 58
Discussion 59
References 64
Appendix 67
Column cleanup procedure for volatilization products from
hex waste 67
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FIGURES
Number Page
1 Soil water release curve for soil taken from municipal
sanitary landfill used for the disposal of industrial
wastes containing hexachlorobenzene 10
2 Schematic drawing of vapor saturation cell 13
3 Details of volatilization cell used in simulated landfill. . . 14
A Schematic drawing of closed air flow system for collecting
volatilized HCB from a simulated landfill operation 15
5 Effect of temperature on the vapor pressure of hexachloro-
benzene. Extrapolated data are from Sears and Hopke (1949). 23
6 Volatilization vapor flux of hexachlorobenzene from hex
waste A covered with 0.015 cm (0.006 in) polyethylene
film in contact with waste which had been filtered only
(Experiment I) 26
7 Volatilization flux of hexachlorobenzene from hex waste A
covered with 0.025 on (0.01 in) polyethylene film in
contact with waste which had been filtered only
(Experiment II) 27
8 Effect of liquid phase in hex waste on volatilization of
hexachlorobenzene from polyethylene film covered hex
waste which had been filtered only (Experiment I) and
film covered waste which had been air-dried (Experiment
XII). The thickness of the films were each 0.015 cm
(0.006 in). Volatilization from uncovered hex waste is
shown for comparison 28
9 Volatilization vapor flux of hexachlorobenzene from un-
treated soil at bulk density of 1.19 g/cm3 and 17%
(w/w) soil water content. The soil was initially col-
lected from a landfill used for the disposal of HCB con-
taining wastes 30
10 Volatilization vapor flux of hexachlorobenzene from hex
waste A covered with 2.5 cm (1.0 in) soil at bulk
density of 1.19 g/cm3 (Experiment III). The hex waste
vi
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Number Pagt
used in this experiment had been filtered only and
contained considerable quantities of the liquid waste
component 32
11 Volatilization vapor flux of hexachlorobenzene from hex waste
A covered with 1.8 on (0.75 in) soil at bulk density of
1.19 g/cm3 (Experiment V). The hex waste used in this ex-
periment had contacted several layers of soil and therefore
did not contain significant amounts of the liquid waste. . . 34
12 Volatilization of hexachlorobenzene from two hex wastes
collected from separate industrial sources and covered
with 1.8 cm soil (Experiments V and VII) 35
13 Volatilization vapor flux of hexachlorobenzene from hex waste
A covered with a composite layer of 1.8 cm soil and 0.01 on
polyethylene film (Experiment IV). The hex waste used in
this experiment had been filtered only and contained con-
siderable quantities of the liquid waste component 36
14 Volatilization vapor flux from hex waste A covered with a
composite layer of 1.8 cm soil and 0.01 on polyethylene
film (Experiment VI). Results of duplicate experiments.
The hex waste used in this experiment had contacted several
layers of soil and therefore did not contain significant
amounts of the liquid waste 38
15 Effect of soil water content on the volatilization of hexachlor-
obenzene from recrystallized HCB covered with 1.8 cm soil at
bulk density of 1.15 g/cm3 (Experiments VIII and XI) .... 39
16 Effect of soil water content on the specific HCB volatili-
zation flux through a soil cover 40
17 Effect of soil bulk density on the volatilization of hexa-
chlorobenzene from recrystallized BOB covered with 1.8 on
soil cover (Experiments VIII, IX, and X) 41
18 Effect of soil bulk density on the specific HCB volatiliza-
tion flux through a soil cover 42
19 Effect of air-filled porosity on the specific HCB volatili-
zation flux through a soil cover 44
20 Linear regression line for the relationship between the
specific HCB volatilization flux and the ratio P^0/3/P^. . . 46
21 Predicted HCB volatilization flux through a soil cover as
a function of soil water content and soil bulk density
at 25 C. Soil thickness is 100 cm 48
vii
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Number Page
22 The equivalent thickness of polyethylene film to soil assum-
ing a soil bulk density of 1.19 g/cm3 and a soil water
content of 20% (w/w) 51
23 Flow diagram for predicting depth of soil cover required to
limit vapor flux through soil cover to an acceptable value . 57
24 Predicted HCB volatilization fluxes through a soil cover of
various soil bulk densities and soil thicknesses at 25 C.
The soil was assumed to be dry (zero soil water content) in
order to yield a maximum flux 60
25 Predicted HCB volatilization fluxes through a soil cover of
various soil water contents and soil thicknesses at 25 C.
Soil bulk density is 1.2 g/cm3 61
26 Predicted HCB volatilization fluxes through a soil cover as a
function of soil thickness and temperature. A bulk density
of 1.2 g/cm3 and a water content of 17% (w/w) is assumed . . 62
vili
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TABLES
Number Page
1 Summary of Variables Used in the Volatilization Studies. ... 16
2 HCB Saturation Vapor Densities from Practical Grade HCB and
Hex Waste at 15, 25, 35, and 45 C 21
3 Vapor Pressure of HCB at 15, 25, 35, and 45 C 22
4 HCB Vapor Density and Vapor Flux from Uncovered Hex Waste A.
The Data are for Consecutive Time Periods After Start of
the Experiment 24
5 HCB Vapor Density and Vapor Flux from Hex Waste A Covered
With Water. The Data are for Consecutive Time Periods
After Start of the Experiment 29
6 Conversion Factors 53
ix
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ACKNOWLEDGMENTS
The cooperation of the management and technical staff at the Indus-
trial facilities who arranged for site visitations and sample collection
is gratefully acknowledged. The Louisiana State Health Department, Air
Control Section, especially Mr. Von Bodungen provided invaluable Informa-
tion on the occurrence of hexachlorobenzene in Southern Louisiana and
assistance in sample collection. Thanks are due to TRW, especially Mrs.
Sandra Quinlivan, for discussions on current disposal practices for
hexachlorobenzene-containing wastes. The authors wish to acknowledge
Yukiko Aochi and Annamarie West lake for their invaluable contribution in
the development of the analytical clean-up procedure for HCB in the
presence of other volatile components of hexachlorobenzene wastes and to
Gus Parker for the construction of the plastic volatilization cells.
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SECTION 1
INTRODUCTION
Large quantities of synthetic compounds are being continuously
added to the land either intentionally or accidentally. The inten-
tional additions may be for beneficial purposes as in the case of
fertilizers and pesticides or more or less casually as in the case of
land as a disposal medium. Regardless of the reason for their presence,
when the properties of these compounds are ill-defined, their potential
distribution in the environment becomes of considerable concern. Prop-
perties which must be considered include toxicity, persistence, solu-
bility, concentration, volatility or combinations of them.
Hexachlorobenzene (HCB) is a compound whose presence in the environ-
ment has caused much concern due to the large quantities being released
into the environment, its extreme persistence, and potential toxicity.
The toxicity of hexachlorobenzene first became widely apparent after
approximately 5,000 people developed a condition called porphyria cutanea
tarda in Turkey in the 1950"s due to the accidental consumption of wheat
treated with HCB as a protective fungicide. The wheat contained 20 parts
per million HCB (Cam and Nygogosyan, 1963; Ochner & Schmid, 1961).
However, the present environmental concern is not over the use of
HCB as a fungicidal seed treatment, which is minimal, but over the
disposal of large quantities of HCB produced annually as a by-product
of several manufacturing processes. Hexachlorobenzene is present in
industrial waste as a by-product in the commercial production of var-
ious chlorinated solvents such as perchloroethylene and carbon tetra-
chloride. In addition significant quantities of HCB have been present
as impurities or by-products in the production of certain pesticides
such as PCNP, dacthal, mirex, simazine, atrazine, and propazine. By
far the largest quantities of HCB appear to be produced as the waste
product of the chlorinated solvent industry (Quinlivan, Ghassemi and
Santy. 1976).
Hexachlorobenzene is a stable persistent compound of low water sol-
ubility and moderate vapor pressure. It exists as a white powder at
room temperature. Its empirical formula is CgClg and its structural
formula is:
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Cl Cl
Hexachlorobenzene (HCB)
HCB has a melting point of 230 C and sublimes at 322 C (Handbook of
Chemistry & Physics, 1973). Little information is available in the
literature on HCB solubility, but it is essentially insoluble in water.
We have measured its solubility in water to be 6.2 ug/1. Sears and
Hopke (1949) reported a vapor pressure for HCB of 2.10 x 10~^ mm Hg at
25 C. We have measured its vapor pressure to be 1.91 x 10 mm Hg at
25 C. HCB is soluble in several organic solvents such as benzene and
hexane and is soluble in fats and oils. Hence it tends to accumulate
in the fatty tissues of animals. HCB should not be confused with the
organochlorine insecticide lindane which is hexachlorocyclohexane
(C/-H/-C1/-) - Lindane has the common name BHC (benzene hexachloride) .
This study was initiated because of a specific instance of HCB
contamination of beef cattle in December, 1972 in southern Louisiana.
Beef cattle to be slaughtered for consumption were quarantined from
sale in a 200-square mile area because of high levels of HCB in their
fat tissue. Following extensive investigations by local, state and
federal agencies and the cooperation of HCB-producing industries in
the area, the source of the HCB was traced to the disposal of waste
containing HCB (hex waste) in a municipal landfill. Uncovered trucks
had been used to haul hex waste from the industrial source to the land-
fill. This led to spillage and contamination along the pathways
followed by the trucks. Additionally, waste material deposited at the
landfill sites was left uncovered and was, in some cases, being used
as a covering over municipal waste to repel flies. Disposal of hex waste
in municipal landfills has ceased in affected areas in southern Louisiana.
The uncovered waste at these landfills has been collected into a small
area of the landfill and covered with 4 to 6 feet of soil, with a 10-mil
thick sheet of polyethyelene film buried approximately midway in the
soil cover.
The disposal of hex waste in landfill sites in southern Louisiana
as described above has resulted in HCB contamination of residents in
the area, operators of the municipal landfills, beef cattle, and soil,
plant and air samples (Burns and Miller, 1975; Louisiana Air Control
Commission, 1973; U.S.D.A., 1973; U.S.-E.P.A., 1973). Soil and plant
samples taken from near landfill areas used for disposal of hex waste
showed decreasing HCB contents as distance from the landfill increased
(Louisiana Air Control Commission, 1973).
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Burns and Miller (1975) reported high levels of RGB in the plasma
of individuals exposed through the transportation and disposal of hex
waste in southern Louisiana. In a sampling of 29 households situated
along the route of trucks transporting hex waste, the average plasma
level of HCB was 3.6 ppb with a high of 23 ppb. The range for landfill
workers was 2 to 345 ppb plasma HCB. The average plasma HCB level
in a control group was 0.5 ppb with a high of 1.8 ppb.
Presently there is no information to indicate that significant
degradation of HCB occurs in the environment. This means that HCB
persists long enough that even with its moderate vapor pressure,
significant quantities can escape into the atmosphere and can be
redistributed by moving air currents. Based on the pattern of HCB
contamination of soils and plants in the Louisiana incident, and the
moderate vapor pressure, low water solubility, and long-term persis-
tence of HCB, it was concluded that volatilization and subsequent
transport by moving air currents is the principal mechanism by which
HCB moves in the environment.
Since storage or disposal of hex wastes on land is currently a
common practice, information on movement of HCB in soil is needed as
a basis for improving the safety of future disposal practices and for
remedying problems with existing landfills. This study was initiated
to determine the optimum soil conditions for limiting movement of HCB
and to show how this information could be used in designing covers for
hex wastes disposed of on land. Although this study was conducted with
wastes containing HCB, the results will apply, in general, to any waste
material containing organic compounds of moderate vapor pressure and
persistence. In conducting this study, it was assumed that vapor phase
movement to the soil surface and subsequent volatilization from the soil
surface would be the only significant pathway for movement of HCB out of
wastes deposited on land. Consequently, the effectiveness of various
coverings — soil, water, and polyethylene film — in reducing vapor move-
ment of HCB was investigated. The study, and this report also, was
divided into several phases: theory, design and construction of a
simulated landfill, sample collection, measurement of essential chemical
and physical properties of samples, laboratory evaluation of covers
for controlling volatilization, calculation of vapor phase diffusion co-
efficients, and application of the findings in designing landfill covers.
The theoretical treatment of volatilization losses from a landfill
is based on our knowledge of vapor phase diffusion. The volatilization of
HCB from a landfill will be a diffusion controlled process. The rate at
which HCB is lost to the atmosphere from the surface of a soil cover will
be determined by how fast the HCB molecules diffuse through the soil cover
over the waste. Volatilization through a soil cover can thus be predicted
by use of the flux equation for steady state diffusion and expressed as:
J - -D (C -C )/L (1)
8 ^ B
-------
fy
where J is the volatilization vapor flux through the soil cover (ng/cm /
day),
2
Dg is the apparent steady state diffusion coefficient (cm /day),
62 is the concentration in the air at the surface of the soil
layer (ng/cm ).
Cg is the concentration in the air at the bottom of the soil
layer (ng/cm^), and
L is the depth of the soil layer (cm).
Experiments were designed in this project to evaluate the utility of
Equation (1) in predicting the volatilization flux of HCB and other com-
pounds through a soil layer. As will be shown in this report, the perti-
nent parameter in Equation (1) to be evaluated is the effect of soil
factors on Ds, the apparent steady state diffusion coefficient. The other
parameters can be readily measured or ascertained as will be discussed.
A simulated landfill was designed to evaluate Equation (1) and was
constructed for use in the laboratory. The simulated landfill had to
meet several constraints. It had to represent what would happen in the
field as closely as possible. At the same time it had to be subject to
close temperature and wind speed control as required when working with
gaseous compounds. Such control could only be readily attained in the
laboratory. In addition, the simulated landfill needed to be versatile
in order to accommodate several types of covers and the thickness of any
soil covers used had to remain small to allow completion of the project
in a reasonable time period.
An important phase of the project was the collection and character-
ization of soil and hex waste samples from actual land disposal oper-
ations. The collection of the samples accomplished two things. We were
able to observe actual methods being used and hopefully make our labor-
atory methods representative. Secondly, the samples collected at the
disposal sites were used in the laboratory experiments. The samples were
collected from locations in the southern and midwestern United States.
These samples were taken to our laboratories for determination of chemical
and physical properties as needed for predicting volatilization. These
properties included soil water content, soil bulk density, HCB vapor
pressure, and HCB aqueous solubility.
The major portion of the report was the evaluation of the various
covers for their potential for controlling HCB volatilization. The covers
evaluated were water, polyethylene film, soil, and a composite of soil and
polyethylene film. These covers were evaluated because each are being
used in land disposal procedures for HCB-containing wastes.
In a final section the results of this project were used to develop
a proposed procedure to design a landfill cover to limit the vapor phase
transport of HCB into the environment.
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There is another aspect to this report peripheral to the central
theme of controlling vapor movement in soil. Although originally
described as a solid, the hex waste samples were found to contain an
organic liquid component. One sample, referred to in the report as fresh
hex waste, was found to be approximately 75% organic liquid. Even the
wastes which appeared solid contained some amount of this liquid. This
organic liquid would not affect the volatilization of HCB from hex waste
when covered by several feet of soil but it did exhibit some interesting
properties. HCB was highly soluble in the organic liquid and the per-
formance of polyethylene film was affected by the presence of the
organic liquid when the film was used as a barrier for hex waste.
Therefore, our experiences with the organic liquid are presented in
detail throughout the report and some discussions presented on its
possible consequences for hex waste disposal.
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SECTION 2
CONCLUSIONS
The volatilization flux of hexachlorobenzene (HCB) through a soil
cover over wastes containing HCB can be predicted assuming that diffusion
in the vapor phase is the only transport process operating. Transport
of HCB by mass flow or by nonvapor phase diffusion will be insignificant.
Covering waste with soil was found to be highly effective in reducing
HCB volatilization. Air-filled porosity is the significant soil param-
eter affecting the final steady state HCB flux through a soil cover.
The bulk density and volumetric water content of a soil determine its
air-filled porosity. Consequently, highly compacted wet soil covers
are most effective in reducing volatilization. Other soil parameters
such as soil organic matter content and soil texture, which may affect
the extent to which HCB is adsorbed by soil, will influence the time
for the flux to arrive at a steady state but will not affect the magni-
tude of the final flux except as they influence soil bulk density.
Polyethylene film when used at a reasonable thickness (e.g., 10 mil)
is relatively inefficient as a barrier against the movement of HCB in
the vapor phase. Polyethylene film is more effective than an equal thick-
ness of soil and about as effective as as equal thickness of water in
reducing HCB flux. However, the cost of polyethylene film precludes
its use in layers thick enough to significantly retard HCB flux.
The use of a water cover in a temporary storage lagoon for waste
containing hexachlorobenzene (hex waste) is a highly effective means
of reducing HCB volatilization. The solubility of HCB in water is
extremely low (6.2 ug/l) and there is no hazard of HCB movement by leach-
ing with water. However some hex wastes contain a dense (1.67 g/cm )
organic liquid in which HCB is highly soluble (about 23,400 ug/ml).
If this liquid fraction drains from or is washed out of the waste, the
potential would be created for transmission of substantial amounts of HCB
through soil. Fresh hex waste from a typical perchloroethylene produc-
tion site contained significant quantities (about 75% by volume) of
organic liquids which wetted polyethylene film and caused partial dis-
solution and swelling of the film. The liquid fraction of the waste
thus increased the HCB transmission properties of the film.
The volatilization of HCB is independent of the origin of hex waste
as long as the HCB concentration in the hex waste is sufficiently high
(about 0.3% by weight) to yield an HCB vapor pressure equal to that of
pure HCB. Hexachlorobenzene volatilization from soils will increase
-------
exponentially with increases in soil temperature due to the effect of
increasing temperature on HCB vapor pressure. Each 10 C rise in soil
temperature will increase HCB flux about 3.5 times.
The chemical stability and resistance to microbial degradation of
HCB dictates that when deposited on land it will remain and continue to
volatilize at a maximum rate for long periods of time. Calculations of
vapor flux through a soil cover over hex waste assuming no degradation,
a soil bulk density of 1.2 g/cm^ (74.9 Ib/cu ft), a soil depth of 122 cm
(4 ft) covering hex wastes 91 cm (3 ft) in depth with a HCB concentration
of 54.9% (by weight) indicate that HCB would continue to volatilize at
its maximum rate from that soil for several million years. Although
no one would attempt to predict over such a time frame, it is obvious
that extremely long periods are involved. Secure storage for such a
period will require institutional arrangements that are beyond the scope
of this study.
This study has developed sufficient information to allow the design
of soil covers that will limit HCB vapor flux to a specified value.
However, because small cracks or other openings will appreciably increase
the flux of HCB through a soil cover, placement of hex waste with any
materials, such as municipal solid waste, that are subject to gradual
settling will likely impair the integrity of a soil cover.
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SECTION 3
RECOMMENDATIONS
If hex wastes are placed on land, the air-filled porosity of soil
covers should be minimized and placement with materials (such as municipal
solid waste) that are subject to settlement should be avoided.
If hex wastes are placed on land, consideration should be given to
the need for long-term arrangements for insuring the integrity of soil
covers.
Lagoons for storage of hex wastes should be covered, at all times,
with as great a depth of water as possible and should be constructed of
low permeability materials.
The organic liquid fraction of hex wastes should be removed or
reduced as much as possible before storage or disposal of the waste.
Further research is needed on movement of HCB in soil in the
organic liquid fraction of hex waste.
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SECTION 4
MATERIALS AND METHODS
COLLECTION AND PREPARATION OF HEX WASTE AND SOIL SAMPLES
Samples of waste containing hexachlorobenzene (hex wastes) were
collected from two chlorinated solvent industries. Hex wastes A and B
were collected from the southeastern and midwestern United States res-
pectively. A third sample of waste containing hexachlorobenzene was
collected from the same location as hex waste A and is described below
as fresh hex waste. Soil samples for use in the laboratory were
obtained from the actual landfill site used for the disposal of waste A.
In order to more fully understand the nature of the wastes discussed
in this study, a brief discussion of procedures used in handling these
wastes by industry is given. A typical operation where land disposal of
hex waste is used is as follows:
1
Woter Admixture
(Cooling and
Precipitation)
The solid phase remaining after the water admixture step may be either
hauled directly to the final land disposal site or temporarily remain
in a lagoon storage site. In cases where lagoon storage is used, the
cooling and crystallization step (water admixture) and lagooning are one
and the same. That is, the waste stream from the production process is
fed directly below the water surface of a water lagoon. Cooling and
precipitation take place and the solid phase is stored under water in the
lagoon. Periodically, the lagoon is emptied and the hex waste carried
by truck to the land disposal site. Hex wastes A and B were obtained
after the cooling and precipitation step. The sample referred to above
as fresh hex waste was collected prior to the cooling and precipitation
step. Detailed descriptions of the materials and procedures used in
the laboratory are given below.
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Soil Characteristics and Preparation
Soils from the 12.7-22.9 cm (5-9 in) depth were collected from a
municipal sanitary landfill which had previously been used for the dis-
posal of industrial wastes containing hexachlorobenzene (waste A). The
landfill was located in the southeastern United States. The soil
samples were collected directly over the portion of the landfill where
HCB-containing wastes had been previously covered with soil. Samples
were also taken for field bulk density measurements. The field bulk
density was found to be 1.2 g/cm3 (74.9 lb/ft3).
All soil was pulverized to pass a 2 mm sieve and thoroughly mixed
prior to use. The soil was a silty clay loam containing 1.4% organic
matter, 1.7% sand, 17.4% coarse silt, 42.1% fine silt, and 38.8% clay.
A soil water release curve is shown in Fig. 1.
=r
50 -
10
5
E
H 1-0
o
ID
^ 0.5
o
CO
O.I
0.05
.0
\
\
do
\
-
J_
10 20 30 40 50 60
SOIL WPXER CONTENT (g H20/lOOg O.D. SOIL)
Figure 1. Soil water release curve for soil taken from municipal sanitary
landfill used for the disposal of industrial wastes containing
hexachlorobenzene.
10
-------
For the volatilization experiments, initial soil water contents up
to 17.3% (w/w) were adjusted by atomizing water onto several kilograms
of soil in a 5-liter glass carboy. The soil in the carboy was turned
frequently during the atomizing step to obtain uniform water content.
The soil was then equilibrated in the carboy for 72 hours at 25 C in
a constant temperature chamber before placing in the volatilization cell.
The final soil water contents, as reported in a later section, varied
from the initial values due to water uptake from or loss to humidified
air which passed continuously over the soil surface during the vola-
tilization period. An attempt was made in one of the experiments
(Experiment VIII) to obtain higher soil water contents by placing the
center section of the plastic volatilization cell containing a given
amount of soil on a 3 atm (44.1 Ib/rn^) pressure plate with excess water
added to the plate. The system was equilibrated at 3 atm pressure for
one week. The plastic cell with soil in place was then used in the
volatilization experiment. Using this method an initial soil water con-
tent of 23.5% was attained. However, this soil lost water during the
experimental period even though humidified air was used for the
volatilization studies. Apparently the air was not completely saturated
with water. In all cases the final soil water content which existed at
the end of the volatilization period was assumed to be characteristic
of the steady state HCB volatilization flux.
Hexachlorobenzene-containing Industrial Wastes
As mentioned in the Introduction, the hex waste samples were found
to contain an organic liquid. This part of the Materials and Methods
Section describes how the organic liquid was removed from the hex waste
prior to the use of the hex waste in the volatilization experiments.
In addition, some of the samples containing the organic liquid are
described as some of their properties are explored in the Results and
Discussion Section.
Hexachlorobenzene-containing industrial wastes (hex waste) from
two different sources were used. Hex waste A from the storage lagoon
of manufacturer A was mixed and a subsample filtered with suction to
remove excess liquid. Most of the liquid filtered from the waste was
water with a small amount of reddish-brown liquid. The reddish-brown
liquid appeared to be similar to the liquid phase of the fresh hex
waste which will be discussed in the later part of this section. The
filtered hex waste A was spread on absorbent paper towel to remove
additional liquid. The waste was considered ready for experimental
use when a Kimwipe pressed against the waste with a spatula was not
wetted. Hex waste B from manufacturer B was air-dried over absorbent
paper towel at room temperature for 24 hours and the partially dried
waste thoroughly mixed for subsampling. Both hex wastes were analyzed
for their HCB content and stored in glass bottles with teflon lined
screw caps for future use in the volatilization experiments. Filtered
hex wastes A and B contained 54.9 and 56.9% (by weight) HCB respectively.
Portions of samples of hex waste A and B were allowed to air-dry
completely and were then analyzed for HCB content. These were collected
to determine the effect of extended drying on HCB content. The air-
11
-------
dried hex wastes A and B contained 65.7 and 90.5% (by weight) HCB
respectively. These completely air-dried hex wastes were not used in
the volatilization experiments as they may not have been characteristic
of hex waste deposited in a landfill site.
The fresh hex waste was the waste collected at manufacturer A from
the process line before it entered the storage lagoon. A uniform sub-
sample of fresh hex waste was filtered and the solid and liquid (reddish-
brown liquid waste) phases analyzed for HCB content. The solid and liquid
portions of fresh hex waste contained 74.5 and 1.4% (by weight) HCB
respectively. This fresh hex waste was not used in the volatilization
experiment; it was collected to assess the significance of the liquid
phase to HCB movement in soils via transport processes other than
volatilization.
RECRYSTALLIZED PRACTICAL GRADE HCB
Practical grade HCB was recrystallized three times from hexane and
the recrystallized material used as pure HCB in the experiments as noted.
The recrystallized HCB was analyzed for its HCB content using a standard
from Applied Science Laboratories, College Park, Maryland, and was found
to contain greater than 98% HCB.
MEASUREMENT OF HCB SOLUBILITY AND VAPOR PRESSURE
Vapor Pressure Measurement
Fig. 2 shows details of the vapor saturation cell. The saturation
vapor density (vapor pressure) of HCB was measured essentially by the
method previously described by Spencer and Cliath (1969). One kg of
acid-washed and distilled water-washed quartz sand was coated with
3 g of recrystallized practical grade HCB by mixing the quartz sand with
1 liter of benzene containing 3 g of recrystallized practical grade HCB
and evaporating the benzene. One kg of quartz sand was coated with 4 g
of air-dried hex waste in the same manner. The quartz sand was placed
into a vapor saturation cell. The vapor saturation cell contained a
6 cm ID x 43 cm glass column with a 10 mm OD inlet glass tube on the
bottom and a glass cap with a 10 mm OD outlet glass tube on the side.
The glass cap and the column were fitted together with a ground glass
joint. The cell was mounted in a constant temperature chamber.
Water-saturated air was passed through the vapor saturation cell from
the inlet tube and air coming out the outlet tube was passed through
an ethylene glycol trap. The air flow rate was varied between 2 and 7
ml/min by adjustment of a needle valve. HCB vapor densities were measured
at 15, 25, 35 and 45 C.
12
-------
OUTLET TUBE
QUARTZ SAND
INLET TUBE
NEEDLE VALVE
_PRESSURE
REGULATOR
Figure 2. Schematic drawing of vapor saturation cell.
Solubility Measurement
The solubility of HCB was measured in water and in municipal land-
fill leachate. The sample of municipal landfill leachate was collected
by the EPA project officer at the EPA Boone County Field Site near
Walton, Kentucky. For the measurements 0.2 g recrystallized practical
grade HCB was shaken with 2 liters of water or leachate for 24 hours
at 23.5 C. The HCB-liquid suspension was filtered through a Millipore
filter. The Millipore filter had a pore size of 0.22 u and was pre-
viously saturated with HCB by shaking with excess HCB in water for 24
hours. Five hundred ml increments of filtered aqueous sample were
extracted twice with 50 ml of hexane by shaking in a separatory funnel
13
-------
for 5 minutes. The hexane extract of the leachate formed a heavy emul-
sion and had to be cleaned up by washing with a 3% sodium carbonate
water solution. Fifty ml increments of hexane extract from the leachate
were shaken with 50 ml of a 3% sodium carbonate water solution in a
separatory funnel for about 1 minute and the aqueous phase discarded.
The washing was repeated (approximately 40 times) until most of the
organic matter was removed and the hexane then shaken with 50 ml of
saturated sodium sulfate aqueous solution to finally destroy the emulsion.
The hexane extract was separated from the aqueous phase and dried through
a 4" anhydrous sodium sulfate column. The hexane extract was evaporated
in a Kuderna-Danish evaporative concentrator tube fitted with a Snyder
distilling column and then adjusted to a suitable volume for HCB analysis.
SIMULATED LANDFILL VOLATILIZATION CELL
Figure 3 shows details of the volatilization cell which held the
waste and the various coverings. The cell has been designed to accom-
modate HCB waste with or without a covering of soil, water or poly-
ethylene film. The soil and polyethylene film can be used either alone
or in combination with each other. The cell is constructed of Plexiglas
(plastic) with a rectangular chamber 3 cm (1.2 in) wide and 10 cm (3.9
in) long. The depth of the cell is varied by stacking additional center
sections to accommodate the various layers of wastes and coverings.
HOLES FOR INSTALLATION OF
MOUNTING BOLTS
TOP VIEW
O
o
>5
T-
( 1
~~~/-J~
/ o
O O
-f r --^.
3cm 1 ~T
j V— -^"
o \ o
1
7
AIR FLOW
AIR
CHAMBER
\
SOIL AND WASTE
CHAMBER
^r
>*
DEMOUNTABLE/
SECTIONS r*
\
SIDE VIEW
<~--_\_
r- 10 cm — ^-»
i
i
/ ^^
ocrrri fc
^
2.54 cm
(Variable)
T
Figure 3. Details of volatilization cell used in simulated landfill.
14
-------
Each section is grooved for an 0-ring to provide a positive liquid and
vapor seal between sections. Provisions are made to allow each section
to be individually sealed in place and filled to a predetermined level
before the next section is added. The upper section contains an air
chamber 2 mm (0.08 in) deep and 3 cm (1.18 inch) wide matching the
width of the central soil and waste chamber. The air chamber extends
7.5 cm (3 in) on either side of the sample chamber to allow air to
spread out before reaching the soil surface, thus providing laminar air
flow across the central chamber.
HCB VOLATILIZATION EXPERIMENT
Fig. 4 shows the schematic drawing of the volatilization measure-
ment system for the simulated landfill. The rates of HCB volatilization
from industrial wastes were measured in a closed air-flow system by
collecting volatilized chemical in hexylene glycol traps in a manner
similar to that used by Farmer et al. (1972).
AIR
HEAT
EXCHANGER
R.H.
SENSOR
GLASS
FRIT
SOIL
WASTE
WATER
FLOW
METER
HEXYLENE
GLYCOL
Figure A. Schematic drawing of closed air flow system for collecting
volatilized HCB from a simulated landfill operation.
The entire apparatus with the exception of the first water-bubble
chamber and the flow meter were maintained inside a constant temperature
chamber. The temperature was slightly elevated in the first water-
bubble chamber to facilitate complete saturation of the air with water
vapor. Rates of volatilization were measured from uncovered wastes,
wastes covered with soil or polyethylene film alone, covered with soil
plus polyethylene film, and covered with water. Rates of volatilization
from recrystallized HCB covered with soil at various moisture contents
and bulk densities were also measured.
The treatments used in the various HCB volatilization experiments
are summarized in Table 1. Soil water contents changed slightly during
the long term of the volatilization experiments from that of the initial
15
-------
TABLE 1. SUMMARY OF VARIABLES USED IN
THE VOLATILIZATION STUDIES
Experiment
No.
Preliminary
I
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII
XIII
XIV
Types and Thicknesses
of Coverings
cm
Hex Waste Aj filtered
soil - 0.9
polyethylene film - 0.015
polyethylene film - 0.025
Hex Waste A
filtered and partially dried"^
soil - 2.5
composite soil - 1.8
and film - 0.01
Hex Waste A from above
after multiple soil contacts
soil - 1.8
composite soil - 1.8
and film - 0.01
Hex Waste B, partially air-dried
soil - 1.8
Recrystallized
practical grade HCB
soil - 1.8
soil - 1.8
soil - 1.8
soil - 1.8
Hex Waste A
powder, air-dried
polyethylene film - 0.015
Hex Waste A, uncovered
Hex Waste A
water - 1.43
Bulk
Density
g/cnr
1.19
—
—
1.19
1.19
1.19
1.19
1.19
1.15
1.05
0.96
1.15
— —
—
—
Final
Water
Content
% (w/w)
—
—
—
17-20
—
20.05
—
18.36
19.58
19.73
19.75
17.24
— —
—
— —
Collected from an industrial source in the southeastern United States.
** After filtering, sample was further dried by pressing with paper towel-
ing (III) or with soil (IV).
i
* Collected from an industrial source in the midwestern United States.
16
-------
soil water content. The final soil water contents are presented In Table
1 as that being most characteristic of steady state diffusion flux.
The lower 25.4 mn (one inch) section of the volatilization cell
was filled with hex waste or recrystallized HCB and coverings were added
above. In the experiment with recrystallized HCB, 19.05 mm (three-
quarter inch) of the lower portion of the bottom chamber was filled
with wetted, filtered, acid-washed quartz sand and the upper 6.35 mn
(one-quarter inch) was then filled with recrystallized HCB.
Sufficient soil, previously equilibrated to the appropriate water
content, was weighed to give the desired bulk density in the volatil-
ization cell. When the soil was packed into the soil chamber, a metal
plate was placed between layers of the cell to prevent compaction of the
layer below. The metal plate was removed during assembly of the cell.
When polyethylene film was used as a cover alone, or as part of a cover,
it was inserted at a Junction of two sections and the film allowed to
extend beyond the 0-ring seal in all horizontal directions to insure
a positive seal.
Packing and assembly of the cell were performed at room temperature.
The assembled cell was placed immediately in the constant temperature
chamber at 25 C. The cell was connected to the closed air-flow system
and air flow adjusted to 0.769 1/min (0.027 ft /min). The hexylene-
glycol trap was changed at suitable time intervals to obtain a measur-
able concentration and the HCB trapped in the hexylene glycol was ex-
tracted into hexane to be analyzed by gas liquid chromatography. All
volatilization experiments were conducted at 25 C.
EXTRACTION, CLEAN-UP, AND ANALYSIS OF HCB
HCB Extraction
The HCB trapped from air in hexylene glycol and ethylene glycol was
extracted into hexane by liquid-liquid partition. Fifty ml of glycol was
mixed with 100 ml of hexane-washed distilled water and the mixture shaken
with 50 ml of hexane for about 10 minutes in a glass bottle on a high
speed shaker. When hexylene glycol was utilized as the vapor trapping
medium, the mixture contained, in addition to hexane and water, 70 ml of
acetone used to wash the glycol from the trap. The hexane was separated
from the aqueous phase in a separatory funnel. The aqueous phase was
discarded and the hexane dried through a 4" anhydrous sodium sulfate
column.
Soil samples taken from the landfill were extracted with a 2:1 (v/v)
hexane-ethanol mixture. Twenty ml of distilled water was added to 100 g
of air-dried soil and shaken with 200 ml of 2:1 (v/v) hexane-ethanol mix-
ture for 1 hour. The slurry was filtered through Whatman GF/C grade
glass fiber filter paper. The filtrate was washed with 100 ml of hexane-
washed distilled water twice and the hexane extract dried through a 4"
17
-------
anhydrous sodium sulfate column. Soil samples, spiked with known concen-
trations of HCB, were extracted by the same method to verify the recovery
efficiency and accuracy of the analytical procedures.
S ample Clean-up
Considerable difficulty was encountered with the GC analysis of
several of the volatilized samples from the industrial waste. Tailing
solvent peaks, unstable base lines, overlapping peaks, and dirty
detectors were common occurrences. The difficulties were assumed to
be caused by the presence in the hex waste of interfering compounds
which volatilized into the air in the simulated landfill and were ex-
tracted into the hexane along with HCB. Certainly, one would suspect
the formation of compounds with similar chemical and physical prop-
erties to those of HCB during the industrial manufacturing process.
A column cleanup procedure was developed using activated neutral alumina
to remove the interferences. Anhydrous sodium sulfate was layered on
top of the alumina to remove any traces of water which may have been
present in the hexane extract containing the HCB. The hexane sample
was first placed on the cleanup column. The column was then eluted
with pure hexane followed by 10% benzene in hexane. Essentially all
of the HCB minus the interfering compounds eluted with the 10% benzene
in hexane fraction. This cleanup procedure was considered to be a sig-
nificant development. Essentially no information exists in the litera-
ture on procedures suitable for the cleanup of industrial waste samples
for analysis by GC. Details of the procedure are given in the appendix.
Gas Liquid Chromatographic Analysis of HCB
The HCB was analyzed by gas liquid chromatography (GC). A Varian
Aerograph model 1520 equipped with a tritium electron capture detector
and a 0.093" ID x 6 ft stainless steel column packed with 2.5% QF-1 and
2.5% DC-200 on 80/100 mesh Chromosorb W was used. The operating param-
eters were: injector 185 C, column 175 C, detector 220 C. Nitrogen
carrier gas was adjusted to obtain a retention time of 4 to 6 minutes.
All injections were made at 2 to 8 ul- The identity of HCB was confirmed
using a 5% OV-17 column. All HCB standard solutions were prepared from
recrystallized HCB or the HCB standard from Applied Science Laboratories,
College Park, Maryland.
18
-------
SECTION 5
RESULTS AND DISCUSSION
SOLUBILITY AND VAPOR PRESSURE OF HCB
HCB Solubility in Water and in Landfill Leachate
In the study of HCB solubility in distilled water and landfill
leachate, recrystallized practical grade HCB was used rather than the hex
waste. The recrystallized material, which contains more than 98% pure
HCB, was used in order to establish the maximum solubility level and
to exclude any compounds in the hex waste which may interfere with the
analysis. The solubility of HCB contained in the hex waste would not be
expected to be different from that of the pure material. Because HCB
is a non-polar, non-reactive compound, its solubility in aqueous solution
would not be influenced by the presence of other compounds.
The solubilities of HCB in distilled water and landfill leachate
at 23.5 C were found to be 6.2 and 5.1 ug/1, respectively. The solubility
is very low compared with many other chlorinated hydrocarbons. The
Millipore filter was saturated with HCB in advance and any chance for it
to adsorb HCB from the water is relatively small. However, the Millipore
filter has. a finite pore size of 0.22 u which may permit HCB particles
smaller than 0.22 u to pass through and result in an exaggerated solu-
bility. The actual solubilities might be smaller than the values obtained
here. Although little has been published on HCB solubilities, discussions
with other investigators have indicated solubilities as low as 0.4 ug/1.
At this low level, these differences in solubility values are of little
significance.
Any significant movement of chemicals into the deep soil strata and
groundwater will have to be by mass flow. Assuming other factors
being equal, the solubility of the chemical will determine the amount
transported by mass flow. Since the solubilities of HCB in water
and landfill leachate are extremely low, the transport of HCB by mass
flow would not be significant. Results using soil thin layer chroma-
tography have shown no movement of HCB on a silt loam soil when either
water or landfill leachate was used as the leaching medium (R. A. Griffin,
Illinois State Geological Survey). The lack of mobility of HCB in
aqueous systems would be expected based on its low water solubility.
Work by others with the chlorinated hydrocarbons has shown essen-
tially no leaching with compounds of comparable or even higher solubility
19
-------
than HCB. Helling, Kearney and Alexander (1971) in their review on
pesticide behavior in soils have ranked a number of pesticides according
to their relative mobilities in soils. The chlorinated hydrocarbons
were ranked as the least mobile of any group of pesticides. Many of
these compounds have solubilities considerably higher than that of HCB.
The chlorinated insecticide DDT [1,1,l-trichloro-2,2-bisCp-chlorophenyl)
ethane] was the least mobile of all pesticides tested and it has a
solubility comparable to that of HCB. In a more recent review of the
theory of pesticide movement, Letey and Farmer (1974) also concluded
that DDT and related compounds were among the least mobile of all pesti-
cides in soils. Based on our knowledge of the leaching characteristics
of the chlorinated hydrocarbons and on the measured solubilities of HCB
in water and landfill leachate, there is no leaching hazard expected
from HCB in soil.
The methods used in this study for measuring solubilities are
standard methods. However, the difficulties encountered in measuring the
solubility of HCB in landfill leachate suggest the need for additional
work to confirm our results with landfill leachate. Numerous washings
with 3% sodium sulfate in water as described in Section 4 under Materials
and Methods, were required to break a heavy emulsion which had formed
during the solubility measurement with landfill leachate. The action of
the sodium carbonate was to remove some of the organic matter originally
present in the landfill leachate and thereby reduce the emulsion in the
hexane layer. The high affinity of HCB for hexane compared to its
affinity for an aqueous layer would cause any HCB molecules to be retained
in the hexane phase during the washing with the sodium carbonate solution.
Nevertheless, there is the possibility for some HCB molecules to be carried
over into the sodium carbonate aqueous phase with the organic matter of
the landfill leachate. This would have the effect of causing our reported
value for HCB solubility in landfill leachate to be lower than the actual
value. This effect would be expected to be slight to non-existent. The
highly non polar nature of the HCB molecule would cause it to have a low
affinity for the organic matter of the landfill leachate. The HCB would
remain in the hexane phase and thereby be counted as present in the land-
fill leachate.
HCB Vapor Density and Vapor Pressure
The HCB saturation vapor densities from recrystallized practical
grade HCB and hex waste A at 15, 25, 35, and 45 C are shown in Table 2.
In the range of air flow rates used, the vapor density is not affected
by the flow rate and the air can be assumed to be saturated with HCB.
Spencer and Cliath (1969) were also able to obtain saturated vapor
densities with dieldrin at a similar range of air flow rates.
The vapor densities from recrystallized practical grade HCB and from
hex waste A are very close to each other at all four temperatures. The
differences between the vapor densities of recrystallized HCB and hex
waste A are less than 3% except at 15 C where the difference is 8%.
These small differences in vapor density are within experimental error
and it will be assumed that the recrystallized HCB and hex waste A have
20
-------
TABLE 2. HCB SATURATION VAPOR DENSITIES FROM PRACTICAL
GRADE HCB AND HEX WASTE AT 15, 25, 35, and 45 C
Flow
Rate
ml/min
7.53
5.74
4.06
3.57
3.93
3.84
15
HCB
Vapor
Density
ug/1
0.0612
0.0679
0.0666
0.0583
0.0615
0.0624
C
Hex
Flow
Rate
ml/min
10.81
6.02
5.05
7.76
4.96
3.31
Waste
Vapor
Density
ug/1
0.0746
0.0625
0.0594
0.0794
0.0678
0.0677
Flow
Rate
ml/min
5.68
6.02
6.76
7.14
6.93
6.74
Flow
Rate
ml/min
4.14
4.64
4.29
4.24
4.53
1.51
1.75
1.33
4.35
4.49
0.0630
35
HCB
Vapor
Density
ug/1
0.928
0.960
0.997
0.839
0.978
0.953
1.072
0.976
0.967
0.860
C
Hex
Flow
Rate
ml/min
4.35
4.35
5.13
5.13
5.25
2.18
1.55
2.07
2.11
Average
0.95
0.0686
Waste
Vapor
Density
ug/1
0.973
1.006
1.059
0.858
1.187
0.867
0.778
0.820
0.929
Flow
Rate
ml/min
3.51
3.82
25
HCB
Vapor
Density
ug/1
0.26
0.325
0.331
0.264
0.292
0.293
C
Hex
Flow
Rate
ml/min
6.75
5.86
5.97
2.86
2.90
7.95
7.16
Waste
Vapor
Density
ug/1
0.287
0.273
0.278
0.304
0.289
0.282
0.292
• — Average — -
0.294
45
HCB
Vapor
Density
ug/1
2.905
3.109
C
Hex
Flow
Rate
ml/min
3.29
3.45
3.31
2.49
3.36
3.68
0.286
Waste
Vapor
Density
ug/1
3.409
3.03
2.858
3.033
3.126
3.114
0.92
3.007
3.095
21
-------
the same vapor densities within the temperature range studied. For future
calculations the vapor density of the pure compound will be used and
assumed to be identical to that of HCB in hex waste. Comparison of the
vapor densities at different temperatures indicates that increasing the
temperature ten centigrade degrees increases the vapor density by more
than three times. Thus the temperature has an exponential effect on HCB
vapor density.
The vapor pressure of HCB can be calculated from the following
equation,
p = (W/V)(RT/M)
where p (mmHg) is vapor pressure, W/V (g/1) is vapor density, R (liter,
mmHg/deg/mole) is the universal gas constant, T ( K) is Kelvin temper-
ature and M (g/mole) is molecular weight.
The average vapor pressures of HCB calculated from the experimental
results are shown in Table 3. Sears and Hopke (1949) studied the vapor
pressure of HCB from 96 to 124 C, and HCB vapor pressures calculated
by extrapolating their empirical equation downward to our experimental
temperature range are also shown in Table 3. The vapor pressures cal-
culated from their equation are slightly greater than those obtained in
this experiment, and the differences increase with decreasing temperature
as also can be seen from Figure 5. However, the present data agree very
well with their extrapolated values except at 15 C where the difference
in vapor pressure between measured and extrapolated value amounts to 47%.
For this reason, the measured HCB vapor pressure probably is much closer
to the true value than the extrapolated value.
TABLE 3. VAPOR PRESSURE OF HCB AT 15, 25, 35, and 45 C
Temp. Vapor Pressure* Vapor Pressure**
(mm Hg) (mm Hg)
15 3
25 1
35 6
45 2
.96 x
.91 x
.36 x
.09 x
io-6
l(f5
io-5
io-4
5
2
6
2
.81
.10
.97
.15
x IO"6
x IO"5
x 10~5
x IO"4
* From experimental data.
** Extrapolated from Sears and Hopke, 1949,
22
-------
-3.5
-4.0 -
E
E
-4.5 -
en
O
-5.0 -
-5.5.
3.1
3.2
3.3 3.4
1000/T (I/°K)
Figure 5. Effect of temperature on the vapor pressure of hexachloroben-
zene. Extrapolated curve from data of Sears and Hopke, 1949.
The relation between the vapor pressure and the temperature within
the range of temperatures studied can be represented in the following
equation:
Iog10p = -(5217. 7/T) + 12.74
The heat of vaporization of HCB can be calculated from the Clausius-
Clapeyron equation
AH = -2.303 Rm
where AH is the heat of vaporization in calories per mole when R is in
calories per mole per degree and m is the slope of line when
plotted vs. 1/T. Thus the heat of vaporization of HCB is
s
AHy = (-5217.7X-4.58) = 23.9 kcal/mole
23
-------
As would be expected, this value for the heat of vaporization of HCB is
close to and greater than that of 21.9 kcal/mole obtained by Sears and
Hopke. This value also is close to that of 23.6 kcal/mole for dieldrin
(Spencer and Cliath, 1969) and 24.17 for lindane (Spencer and Cliath,
1970s).
VOLATILIZATION OF HCB FROM SIMULATED LANDFILL
HCB Volatilization from Uncovered Hex Waste
The HCB vapor density and flux from uncovered hex waste A (Experiment
XIII) are shown in Table 4. The vapor density is about 80.9% of that of
the saturated vapor density even though the air flow rate is about 100 to
200 times greater than that used in the saturation vapor density experiment,
This means that HCB from uncovered hex waste is highly volatile and that
the volatilization rate would be much higher at higher rates of air
exchange.
TABLE 4. HCB VAPOR DENSITY AND VAPOR FLUX FROM UNCOVERED
HEX WASTE AT 25 C. THE DATA ARE FOR CONSECUTIVE
TIME PERIODS AFTER START OF THE EXPERIMENT
Flow Vapor Flux
Rate Density „
1/min ug/1 ng/cm /day
.769 0.24 8861
,769 0.232 8566
Average
8713
The source of the hex waste would not have any significant effect on
HCB volatility from uncovered waste. This is based on the observation
that quartz sand containing a concentration as little as 3 mg of HCB per
gram of sand gives a saturated HCB vapor density and any solid-phase hex
waste containing more than 3 mg of HCB per gram of waste would also have
the potential to yield a saturated HCB vapor density at low air flow
rates unless HCB were to form complexes with other components of the
waste. Spencer et si. (1973) reviewed pesticide volatilization and
reported that in moist Gila silt loam, saturation vapor densities of
dieldrin, lindane, p,p'-DDT, and o.p'-DDT were reached at soil concen-
24
-------
trations of 25, 55, 12, and 39 ug/g, respectively. This relatively low
soil concentration needed for a saturated vapor in moist soil indicates
that weakly adsorbed pesticides such as lindane, dieldrin and DDT will be
subject to relatively high rates of loss by volatilization. HCB is a
weakly polar, relatively non-reactive compound and it is conceivable
that any waste containing as little as 10 to 100 ug HCB per gram waste
may have the potential to produce a saturated vapor density. This
would further indicate that the source of hex waste would not have any
great impact on HCB volatility. Measurements of HCB volatilization flux
from two different hex wastes covered with soil, which is discussed in
a later part of this report, support the conclusion that there is no
difference in HCB volatility from these two hex wastes.
HCB Volatilization from Hex Waste Covered with Polyethylene Film
Polyethylene film has been used in the past in conjunction with
soil as a covering material in landfill sites as an aid in reducing
volatilization of HCB from hex waste deposited in landfill. To eval-
uate the effectiveness of polyethylene film as a barrier to HCB vapor
movement, HCB volatilization fluxes from filtered hex waste A covered
with 0.015 cm (0.006 in) (Experiment I) and 0.025 cm (0.01 in)
(Experiment II) polyethylene film alone with the film in contact with
the hex waste were measured and results are shown in Figure 6 and Figure
7, respectively. In both cases the flux increases rapidly and reaches
steady state in about 8 days. The steady state fluxes are about 40%
and 80% of that from the uncovered hex waste A for 0.025 cm and 0.015
cm film, respectively. The flux at steady state from the 0.025 cm film
cover is about one-half that from the 0.015 cm cover. This can be expected
since the thickness of the film is approximately doubled. The polyethy-
lene film when used alone in direct contact with the hex waste appears
to be highly inefficient as a barrier for HCB movement.
At the end of the above studies, it was found that the reddish-
brown liquid component of the waste, which is part of the original hex
waste A, deposited on the film and caused the film to partially dissolve
and expand. It was suspected that partial dissolution and expansion of
the film might reduce its effectiveness as a vapor movement barrier.
HCB volatilization fluxes from air-dried hex waste A (Experiment XII)
covered with 0.015 cm polyethylene film were measured to determine the
effect of the absence of the liquid component of the waste on the effec-
tiveness of polyethylene film as a vapor movement barrier. The results
together with that from Experiment I are shown in Figure 8. The steady
state HCB volatilization flux from air-dried hex waste A is 5500 ng/cm
/day and is smaller than that of 7050 ng/cm /day from filtered hex
waste A. The fact that air-dried hex waste A yielded a volatilization
flux smaller than that from non-air-dried hex waste A clearly indicates
that the reddish-brown liquid waste component does reduce the effective-
ness of the polyethylene film as a vapor barrier.
25
-------
9000
8000
7000
o 6000
TD
cn
c
5000
x 4000
g 3000
2000
1000
0,
o or
I
68 10 12 14 16
TIME (days)
Figure 6. Volatilization vapor flux of hexachlorobenzene from hex waste
A covered with 0.015 cm (0.006 in) polyethylene film in contact
with waste which had been filtered only (Experiment I).
26
-------
5000
0
4 6
TIME (days)
10
Figure 7. Volatilization flux of hexachlorobenzene from hex waste A
covered with 0.025 cm (0.01 in) polyethylene film in contact
with waste which had been filtered only (Experiment II).
27
-------
9000
6000
7000
-g 6000
CJ
E
5000
c.
x 4000
o
I
3000
2000
1000
cP
1 A ' '
0 Uncovered
Solvated
0
Dried
0
8 10 12
TIME (days)
14
16
18
Figure 8. Effect of liquid phase in hex waste on volatilization of
hexachlorobenzene from polyethylene film covered hex
waste which had been filtered only (Experiment I) and
film covered waste which had been air-dried (Experiment
XII). The thickness of the films were each 0.015 cm
(0.006 in). Volatilization from uncovered hex waste is
shown for comparison.
HCB Volatilization from Hex Waste Covered With Water
Lagoon storage has been used as a temporary means for hex waste
retention prior to its disposal at a landfill site. Under these
circumstances, hex waste is temporarily stored under water. Therefore
it is necessary to evaluate the effectiveness of a water cover in
reducing volatilization. HCB volatilization fluxes from hex waste A
covered with 1.4 cm (0.56 in) of water (Experiment XIV) were measured
and the volatilization flux and vapor density are shown in Table 5.
28
-------
TABLE 5. HCB VAPOR DENSITY AND VAPOR FLUX FROM HEX WASTE A
COVERED WITH WATER AT 25 C. THE DATA ARE FOR
CONSECUTIVE TIME PERIODS AFTER START OF THE EXPERIMENT
Flow
Rate
1/min
0.769
0.769
0.769
0.769
Vapor
Density
ug/1
-4
2.82 x 10
-4
2.86 x 10
-4
2.60 x 10
2.97 x 10"
Flux
ng/cnr /day
10.4
10.4
9.6
11.0
10.4
Comparing HCB volatilization flux from water covered hex waste A with
that from uncovered hex waste A, the water cover reduces HCB volatiliza-
tion flux about 870 times and is the most effective cover yet tested to
reduce HCB volatilization. In the actual storage lagoon, the water cover
is likely to be much deeper and would therefore be even more effective
in reducing HCB volatilization.
HCB Volatilization from Hex Waste Covered With a Soil Layer
Volatilization from Untreated Soil - Vapor Phase Transport—
The soil used in the volatilization experiments as a cover for hex
waste was found to contain 0.25 ppm HCB; thus it was necessary to deter-
mine the background HCB volatilization flux from this untreated soil.
Since the soil was untreated, the source of the HCB had to be from
hex waste at the landfill location when the soil had been collected.
The HCB volatilization flux from the untreated soil is shown in Figure
9. The flux decreases rapidly with time and reaches steady state after
about 4 days as HCB diffusion to the soil surface controls the flux
rate. After 13 days the flux again decreases, slowly, presumably due
to soil depletion of HCB.
The HCB flux in Figure 9 represents desorption of HCB from the
soil. This gives an indication of how a soil which is lightly contami-
nated with HCB would "cleanse" itself. A heavily contaminated soil
would exhibit the same type of decay curve (decreasing volatilization
to the soil surface from below. This type of desorption curve from
soil has been well characterized for other chlorinated compounds such
as lindane, dieldrin, and DDT (Fanner et al., 1972; Spencer and Cliath,
29
-------
0
8 10
TIME (days)
12
14
16
Figure 9. Volatilization vapor flux of hexachlorobenzene from untreated
soil at bulk density of 1.19 g/cm and 17% (w/w) soil water
content. The soil was initially collected from a landfill
used for the disposal of HCB containing wastes.
1973; Guenzi and Beard, 1970; Mayer, Fanner and Letey, 1973). There
is a rapid initial decrease in the flux rate as surface concentrations
are depleted. The lower flux rate characteristic of the later portion
of the decay curve is determined by the rate at which pesticides move
to the soil surface. Thus the concentration in the soil below the sur-
face becomes the source term for surface volatilization. The rate of
diffusion of HCB to the soil surface will determine the actual vola-
tilization flux in Figure 9. Movement due to mass flow in moving
water would be negligible due to low water solubility of HCB and lack of
upward water movement in the soil during the experiment.
HCB may move by molecular diffusion in the vapor phase and in the
solution phase. The relative importance of vapor phase and solution
phase diffusion is determined by the relative magnitudes of the concen-
tration in air (vapor density) and the concentration in solution phase.
30
-------
Because the vapor phase diffusion coefficient is approximately
larger than the solution phase diffusion coefficient (Letey and
Farmer, 1974), vapor phase diffusion can be important even if the
chemicals have relatively low vapor densities. Hartley (1964)
suggested that the partition coefficient between soil solution and
soil air could be used to measure the relative importance of solution
phase and vapor phase diffusion. The ratio of the concentration in
saturated aqueous solution to that in saturated air may be used to
calculate the partition coefficient between the soil solution and the
soil air.
Since the vapor phase diffusion coefficient is approximately
larger than the solution phase diffusion coefficient, a partition co-
efficient of 10^ may be considered as a transition point for determining
when vapor diffusion or solution diffusion becomes dominant. Chemicals
with partition coefficients much smaller than 10^ will diffuse mainly
in the vapor phase and those with partition coefficients much greater
than 10^ will diffuse primarily in the solution phase. This kind of
classification principle to determine the major mode of diffusion of
a chemical in a soil-water-air system has been suggested by Goring
(1962). The HCB solubility in water at 23.5 C is 6.2 ug/1 and the
vapor density at 23.5 C can be calculated from the empirical relation
log10P = 12.94 -(5279 /t) to be 0.224 ug/1. This gives a partition
coefficient of 27 for HCB at 23.5 C and HCB would be expected to diffuse
primarily in the vapor phase.
Chemicals with partition coefficients around 10^ will have about an
equal magnitude of diffusion in vapor phase and solution phase. Lindane
(Y-BHC isomer) has a partition coefficient of 5.5 x ICH at 30 C and thus
should have about equal magnitudes of diffusion in vapor phase and solu-
tion phase. Shearer et al. (1973) reported that the diffusion of
lindane in the vapor and non-vapor phases was approximately equal at 30 C
over a wide range of soil water contents. A similar distribution of
vapor and solution diffusion was observed by Graham-Bryce (1969) for
the diffusion of disulfoton in soil- Disulfoton has a partition coeffi-
cient of 5.5 x 103.
It is important to note that this method of classification using the
partition coefficient between vapor and solution phases can be used for
assessing the vapor transport potential of materials other than HCB.
Those compounds with a partition coefficient less than 10^ would diffuse
primarily in the vapor phase and the procedures developed in this study for
HCB would apply similarly to those compounds.
Volatilization from Hex Waste Covered with Soil —
It was during our investigations with soil-covered hex waste that the
significance of the organic liquid phase as a transport medium for HCB
became evident. The first few experiments described below are included
because they are illustrative of how HCB can be carried in soil by liquid
flow. The experiments which are useful for predicting HCB vapor transport
are those performed after the organic liquid had been removed. These
begin with Experiments V and VI after the hex waste had been filtered,
31
-------
partially dried, and then used in several consecutive experiments so that
it contacted several layers of soil.
The HCB flux from hex waste A covered with 2.5 cm (1 in) soil
(Experiment III) is shown in Figure 10. The flux decreases initially
but begins to increase rapidly at about 2 days and reaches steady state
after 20 days. The initial HCB flux is from the HCB originally present
in the soil and the upswing at 2 days represents the emergence of HCB
800
24 68 10 12 14 16 18 20 22 24 26 28
TIME (doys)
Figure 10. Volatilization vapor flux of hexachlorobenzene from hex
waste A covered with 2.5 cm (1.0 in) soil at bulk
density of 1.19 g/cm (Experiment III). The hex waste
used in this experiment had been filtered only and
contained considerable quantities of the liquid waste
component.
32
-------
moving up from the hex waste in the chamber below the soil. The slow
emergence of HCB at the soil surface indicates, that adsorption of HCB by
the soil matrix is very significant in determining the initial movement
of HCB in soil and therefore will determine the length of time required
to reach steady state. The fact that the flux reaches a steady state
value of 680 ng/cm /day after 20 days indicates that there is no
additional adsorption taking place by the soil after this time. The
flux at steady state with a 2.5 cm soil cover is about 7.8% of that
of uncovered hex waste. Thus soil is an effective covering material
for reducing HCB volatilization. However, as shown below not all
of this flux can be attributed to diffusion. With this particular
hex waste sample, mass flow of HCB was taking place.
In the preliminary experiment with 0.9 cm (0.37 in) soil cover over
filtered hex waste A, it was noted that part of the soil surface became
wetted with the reddish-brown liquid waste shortly after placing the soil
layer over hex waste A and the initial HCB volatilization flux reached
as high as 200 ng/cm /day which is six times greater than that from
Experiment III. Diffusion of HCB alone could not produce such an
instantaneously high volatilization flux since diffusion is a relatively
slow molecular process. Analysis of the reddish-brown liquid waste
showed that the liquid waste contained 1.4% HCB. Movement of this
liquid waste by capillary action into the soil cover from hex waste A
would be expected to carry a large amount of HCB into the soil cover and
thus result in a higher HCB volatilization flux. It was suspected that
even in Experiment III a great portion of the HCB volatilization flux
from the hex waste might be contributed by the mass flow of HCB carried
by the reddish-brown liquid waste. The suspicion was reinforced by the
fact that at the end of the experiment there was an increase of 3% in
the soil "water" content, as measured by drying at 105 C, in the lower
portion of the soil cover thus indicating the soil was adsorbing a
significant mass from the waste that was lost on drying the soil.
To reduce the possibility of HCB mass flow caused by the liquid
component of the waste, a subsaraple of hex waste A which had been used
in earlier experiments and therefore had contacted a soil cover several
times was used to measure the HCB volatilization flux from hex waste
covered with 1.8 cm (0.75 in) soil (Experiment V). It was assumed that
any significant amount of liquid waste contained in hex waste A had been
adsorbed by soil covers in the previous experiments and the mass flow
effect of liquid waste could be eliminated or reduced to a minimum.
The HCB volatilization flux from Experiment V is shown in Figure 11.
The steady state HCB volatilization flux reached 123 ng/cm /day 30 days
after the start of this experiment. Comparing the steady state HCB
flux from Experiments III (Figure 10) and V (Figure 11), it can be seen
that the flux from the 2.5 cm soil-covered hex waste is 5 times greater
than that from the 1.8 cm soil-covered hex waste. It is obvious that the
capillary movement of the reddish-brown liquid waste into the soil cover
does cause mass flow of HCB from hex waste into the soil cover. Volatili-
zation experiments with recrystallized HCB to avoid any mass flow effect
from liquid waste at comparable experimental conditions which are dis-
cussed in a later'section of this report also yielded a steady state HCB
33
-------
160
140
en
5100
X
=>
80
cr
060
m
o
i
20
0
O O
o o
o
o
0 10 20 30 40 50 60
TIME (days)
70 80
Figure 11. Volatilization vapor flux of hexachlorobenzene from hex waste
A covered with 1.8 cm (0.75 in) soil at bulk density of
1.19 g/cm^ (Experiment V). The hex waste used in this experi-
ment had contacted several layers of soil and therefore did
not contain significant amounts of the liquid waste component.
flux of 126.3 ng/cm^/day (Experiment VIII) which is very close to that of
Experiment V. This would further substantiate the mass flow effect due to
the reddish-brown liquid waste. In the absence of a mass flow effect, a
soil cover of 1.8 cm reduced the HCB flux from approximately 8700 ng/cm^/
day for the uncovered waste to approximately 120 ng/cm^/day or a reduction
of 98.6 percent.
Volatilization from Hex Wastes from Different
Sources Covered With Soil—
Hex wastes from different industrial sources may contain different
components which may affect the volatility of HCB. Hex waste B from
manufacturer B was used to study HCB volatilization through a 1.8 cm
soil cover (Experiment VII); the HCB volatilization flux together with
that from hex waste A with a 1.8 cm soil cover (Experiment V) are shown in
Figure 12. The steady state HCB volatilization flux from hex waste B is
34
-------
O Waste A
Waste B
10
20
30 40 50
TIME (days)
60
70 80
Figure 12. Volatilization of hexachlorobenzene from two hex wastes
collected from separate industrial sources and covered
with 1.8 on soil (Experiments V and VII).
137 ng/cm^/day and is slightly greater than that of 123 ng/cm^/day from
hex waste A. The slightly higher HCB volatilization flux from hex
waste B can be explained by the fact that its soil cover has a slightly
lower soil water content and thus has more air-filled pores through
which HCB can diffuse. When the HCB flux is expressed as the flux per
unit air-filled porosity, by dividing the HCB flux by air-filled porosity,
the adjusted flux values are 424 ng/cm^/day and 406 ng/cm^/day for hex
waste B and A, respectively, and the difference between these adjusted
values is less than 5%. Thus the source of hex waste does not seem to
have any significant effect on HCB volatilization. Previous analysis
based on the concentration of HCB needed to produce a saturated vapor
provided a similar conclusion.
35
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Volatilization from Hex Waste Covered with a Composite Layer of Soil
and Polyethylene Film
Soil and polyethylene film are being used together as a covering
over hexachlorobenzene-containing industrial wastes in actual landfills;
thus information is needed on the effectiveness of a composite layer of
soil and polyethylene film in reducing HCB volatilization.
The HCB flux from hex waste A covered with a composite layer of
0.9 cm (0.35 in) soil, 0.01 cm (0.004 in) polyethylene film and 0.9 cm
soil (Experiment IV) are shown in Figure 13. The flux decreases initially
and begins to increase at about 2 days. After about 20 days the flux
reaches a steady state value of 355 ng/cnr/day, a flux about one-half
of that from the 2.5 cm soil cover (Experiment III). The slow increase
in flux and smaller steady state flux indicate that the polyethylene
film does act as a barrier to reduce HCB movement toward the soil sur-
face. Since Experiments III and IV use the same kind of hex waste A,
500
0
0 2
6 8
10 12 14 16 18
TIME (days)
20 22
26 28
Figure 13. Volatilization vapor flux of hexachlorobenzene from hex waste
A covered with a composite layer of 1.8 cm soil and 0.01 cm
polyethylene film (Experiment IV). The hex waste used in
this experiment had been filtered only and contained con-
siderable quantities of the liquid waste component.
36
-------
the reddish-brown liquid waste must also cause mass flow of HCB into
the soil cover in Experiment IV as it did in Experiment III. At the
end of Experiment IV, liquid waste was found to deposit on the poly-
ethylene film and to cause the film to partially dissolve and expand
similar to the phenomena observed in Experiments I and II using film
alone. The results obtained clearly show an exaggerated HCB flux due
to mass flow and cannot be used to quantitatively evaluate the effective-
ness of the composite layer in reducing HCB volatilization. Additional
experiments were required to evaluate the composite layer.
The hex waste A used in Experiment V does not exhibit any effect
due to liquid waste, thus it was used with the composite layer in a re-
peat of the previous experiment. Duplicate runs (Experiment VI) were
conducted and the HCB volatilization flux is shown in Figure 14. The
HCB volatilization flux increases gradually with time and reaches a
steady state flux of 70 ng/cm /day after 57 days. The composite layer
of 1.8 cm soil and 0.01 cm polyethylene film can reduce HCB volatiliza-
tion flux approximately 125 times compared to uncovered waste and is
quite effective in reducing HCB volatilization.
Comparing steady state HCB volatilization fluxes between Experiments
V (Fig. 11) and VI (Figure 14), the addition of 0.01 cm polyethylene
film to the 1.8 cm soil cover reduces HCB volatilization flux by 43%.
Data from Experiment XII (Figure 8) showed that covering with a thicker
polyethylene film (0.015 cm) over air-dried hex waste A reduces HCB vola-
tilization flux by 37%. These results indicate that polyethylene film
may tend to be more effective as an HCB vapor barrier when it is used
in conjunction with the soil as a covering. The explanation for this is
unknown. Perhaps the closer proximity of the film to the hex waste
in the case of film alone covering the waste causes partial swelling
and expansion of the film thus increasing its permeability.
EFFECT OF SOIL PARAMETERS ON HCB VOLATILIZATION FROM SIMULATED LANDFILL
In this section the effect of soil water content, soil bulk density,
and air-filled porosity on the vapor phase diffusion of HCB in soil are
investigated. This discussion will be limited for the most part to
results obtained using recrystallized practical grade HCB. Comparisons
of vapor pressures and volatilization fluxes have shown the various
industrial wastes to be similar in their HCB vapor activity to the
recrystallized material.
Soil Water Content
It is a common practice to spray water over soil as a dust control
measure when wastes are being covered with soil and also as an aid to
obtain maximum compaction of the soil. Natural rainfall also adds water
to the soil. The amount of water in a soil affects the pore space
available for HCB vapor diffusion, and thus affects the HCB volatiliza-
tion flux through the soil cover. Two HCB volatilization experiments
37
-------
140
120
100
80
cr.
o
CL
60
40
CD
£ 20
0
o
o
0 10 20 30 40 50 60 70 80 90
TIME (days)
Figure 14. Volatilization vapor flux of hexachlorobenzene from hex
waste A covered with a composite layer of 1.8 cm soil and
0.01 cm polyethylene film (Experiment VI). Results of
duplicate experiments. The hex waste used in this experiment
had contacted several layers of soil and therefore did
not contain significant amounts of the liquid waste component.
were conducted with the soil cover at the same bulk density of 1.15 g/cnT
but at different soil water contents (Experiments VIII and XI) using
recrystallized HCB. The HCB fluxes are shown in Fig. 15. It is clear
that steady state HCB volatilization flux through a 1.8 cm soil cover
with a water content of 17.24% is higher than that through a soil cover
of 19.58% water content. Since both soil covers have the same bulk
density and thickness, the difference in HCB flux must be caused by the
difference in water contents.
The effect of soil water content on HCB volatilization flux through
a soil cover can best be seen by plotting the steady state HCB specific
fluxes against the soil water contents. The specific flux is defined as
the flux per unit concentration gradient. The steady state HCB specific
fluxes from Experiments VIII and XI and those from Experiments V and VII
38
-------
160
140
I TA 1—
£
17.24%W/W A-^A'
A A^ A A
I"
O -
10 20 30 40 50 60 70 80 90 100
Figure 15. Effect of soil water content on the volatilization of hexa-
chlorobenzene from recrystallized HCB covered with 1.8 cm
soil at bulk density of 1.15 g/cm3 (Experiments VIII and XI)
at a slightly higher bulk density of 1.19 g/cm3 (74.29 lb/ft3) are
plotted against the soil water contents and are shown in Fig. 16. The
steep slope of the line passing through these points indicates a marked
effect of soil water content on HCB flux. Comparing the steady state
HCB specific fluxes between Experiments VIII and XI shows that decreasing
soil water content 2.3% increases HCB specific flux by 21.2%. Thus, the
effect of soil water content on HCB volatilization flux through soil
cover is exponential. Shearer et al- (1973) studied lindane diffusion
in soil and observed a similar exponential effect of soil water content
on vapor phase diffusion. Increasing soil water content decreases the
pore space available for HCB vapor diffusion and will decrease HCB
volatilization flux. When soil is saturated with water it will have
the same effect as a covering of water.
In contrast, increasing soil water content has been shown to increase
the volatility of pesticide in soils under certain circumstances. Gray
et al. (1965) pointed out that there appeared to be a critical soil water
level for each soil above which losses of EPTC were larger. Spencer
39
-------
'e 1100
§
1—
CT>
1000
o
•o
900
o
en
a
800
C 700
o
UJ
CL
cn
S 600
I I I
I I T
Experiment ZT
Experiment
Experiment
Experiment Y
\ L
i i i i
0.1
0.2
WATER CONTENT (g/g)
0.3
Figure 16. Effect of soil water content on the specific HCB volatilization
flux through a soil cover.
and Cliath (1969, 1970) found that vapor densities of dieldrin and lin-
dane in soil dropped to very low values when the soil water content was
decreased below that equivalent to one mono-molecular layer, but vapor
densities were not affected by soil water contents above one mono-
molecular layer of water. Yang (1974) reported that parathion volatili-
zation dropped rapidly when soil water content decreased below 8% and
this critical soil water content was much higher than that of one mono-
molecular layer of water. Spencer et al. (1973) reviewed pesticide
volatilization and pointed out that the soil water content at which
pesticide vapor density sharply decreased depends on the soil and the
ability of the pesticide to compete with water for adsorption sites.
The more strongly adsorbed the pesticide, the higher the water content
at which an appreciable decrease in vapor density would occur.
In the very dry soil water content range, fewer water molecules are
available to compete with the pesticide molecules for adsorption sites on
the soil and more pesticide molecules are adsorbed by soil, thus having
fewer available for volatilization. In essence, the soil water content
affects the pesticide adsorption capacity of soil. The reduced pesticide
40
-------
volatilization at a very dry soil water content can be viewed as an
increased pesticide adsorption capacity of soil. The increased pesticide
adsorption capacity of the soil will increase the time required to reach
steady state HCB volatilization flux through the soil cover. However,
the magnitude of the steady state HCB volatilization flux through soil
cover at the very dry soil water content range will be much greater than
that through a wet soil at the same bulk density. Such a relationship
is indicated in Fig. 16.
Soil Bulk Density
When hex waste is covered with soil, the type of soil used and the
amount of pressure applied to compact the soil will affect the degree of
compaction of the cover soil. Soil compaction or bulk density determines
the porosity of a soil and thus affects HCB vapor diffusion through the
soil. HCB volatilization fluxes through a 1.8 cm soil cover (Experiments
VIII, IX and X) are shown in Fig. 17. Comparing the HCB fluxes shows
that HCB volatilization fluxes through a soil cover of lower bulk density
are greater than those through a soil cover of higher bulk density.
Since the final soil water contents are very close to one another and
all of the soil covers have the same thickness, the difference in HCB
volatilization must be caused by the difference in soil bulk density.
320
i 1 1 r
OQ O
t?
o A o o o
O'o'0 o'"
.0--6 o° o oo
/3= 1. 15 g /cm 3 —
0 10 20 30 40 50 60 70 80
TIME (days)
Figure 17- Effect of soil bulk density on the volatilization of hexa-
chlorobenzene from recrystallized HCB covered with 1.8 cm soil
cover (Experiments VIII, IX and X).
41
-------
The quantitative effect of soil bulk densities on HCB volatilization
fluxes through soil covers can be seen by plotting the steady state HCB
specific flux against the soil bulk density. The results from Experiments
VIII, IX and X, together with that from Experiment V are shown in Fig.
18. Comparing the steady state HCB specific fluxes from Experiments IX
and X shows that decreasing the bulk density by 0.09 g/cm increases the
steady state HCB specific flux by 45%. Thus the soil bulk density also
has an exponential effect on HCB volatilization flux through the soil
cover. Similar exponential effects of soil bulk density on vapor phase
diffusion flux has been shown for lindane (Ehlers et al., 1969).
E
o
D
T3
1800
1600
1400
CP
c
1200
x
ID
1000
o
UJ
Q-
CO
800
CD
CJ
x 600
Experiment X
Experiment JX
Experiment
~Experiment Y
1.0 1-
BULK DENSITY (g/cm3)
Figure 18. Effect of soil bulk density on the specific HCB volatilization
flux through a soil cover.
42
-------
From previous considerations of the effect of soil water content,
it is obvious that a higher soil bulk density will have effects similar
to that of an increased soil water content. The higher the soil bulk
density, the smaller the steady state HCB flux will be. However, for
any given soil there is a limit on the maximum bulk density that can be
reached and there will always be a finite amount of open pore space for
vapor diffusion to take place.
Air-filled Porosity
Previous theoretical analysis of HCB water-air partition coeffi-
cients and experimental results show that vapor phase diffusion is the
major mode of HCB movement through soil. HCB molecules will have to
diffuse through the air-filled pore space of the soil. Thus the effects
of soil water content and soil bulk density on HCB volatilization flux
through a soil cover can be attributed to their effect on the air-filled
porosity, which in turn is the major soil factor controlling HCB volatili-
zation through soil.
Figure 19 shows the effect of air-filled porosity on steady state
HCB volatilization flux through a soil cover (Experiments V, VII, VIII,
IX, X, and XI). Comparison of Experiments IX and X shows that increasing
the relative air-filled porosity 13.4% increases specific HCB volatiliza-
tion flux 45%, indicating that air-filled porosity has an exponential
effect on the HCB volatilization flux through soil.
CALCULATIONS OF DIFFUSION COEFFICIENT
As stated in the Introduction the steady state HCB volatilization flux
through a soil cover can be expressed as
J = -DS(C2-CS)/L (1)
2
where J is the vapor flux (ng/cm /day),
2
D is the apparent steady state diffusion coefficient (cm /day),
s
C2 is the concentration in the air at the surface of the
3
soil (ng/cm ),
C is the concentration in the air at the bottom of the
S
3
soil layer (ng/cm ), and
L is the depth of the soil layer (cm).
Since the HCB concentration measured is the average concentration
in the air above the soil surface, C? has to be estimated from the
relationship:
43
-------
2200
= 1.09 x I04x F=2-3
OExperiment X
Experiment XL
Experiment
QpExperiment VJIT
Experiment
0.0 O.I Q2 0.3 Q4 0.5
AIR-FILLED POROSITY P (cm3/cm3)
Figure 19. Effect of air-filled porosity on the specific HCB volatiliza-
tion flux through a soil cover.
Caw/Cs ' Ca/C2
(2)
where C is the average concentration in the air above the soil
a (ng/cm3),
C is the average concentration in the air above the uncovered
aw hex waste (ng/cm ), and
K/. is the ratio.
44
-------
Since Cg is the saturation vapor density and C is known from the un-
covered hex waste experiment, C2 can be estimated.
Although air-filled porosity is found to be the major factor con-
trolling HCB volatilization flux through the soil-water-air system, the
apparent vapor diffusion coefficient does not depend only on the amount
of air-filled pore space. Shearer et al. (1966) pointed out that in
adding liquid to a porous system, there was a much greater reduction
in the apparent gas diffusion coefficient than that found accompanying
reduction in gas-filled pore volume by the addition and closer packing
of the solid. The presence of liquid films on the solid surface not
only reduces the porosity, but also modifies the pore geometry and the
length of the gas passage. Thus the apparent gas diffusion coefficient
through a porous medium is clearly a function of both internal geometry
and porosity.
Millington and Quirk (1961) suggested an apparent vapor diffusion
coefficient which includes the porosity term to account for the
geometric effects of the soil system. Based on a theoretical derivation,
they presented a formula for the apparent vapor diffusion coefficient
including air-filled porosity and the total porosity of the soil
system. Shearer et al. (1973) successfully used the apparent vapor
diffusion coefficient formula suggested by Millington and Quirk (1961)
to compute the apparent vapor phase diffusion coefficient of lindane
in soil. The apparent vapor diffusion coefficient can be expressed as
2
where DO is the vapor diffusion coefficient in air (cm /day),
3 3
P is the air-filled porosity (cm /cm ), and
a
3 3
P is the total porosity (cm /cm ).
Substituting DS into equation (1) and rearranging the equation to
obtain the specific HCB volatilization flux -J/(C2-Cg)/L through soil
cover, the equation becomes
-J/(C2-Cg)/L = Do (P /p ) (4)
The diffusion coefficient D0 can be determined by plotting -J/(C2~CS)/L
against (pr°/3 /p| ) and the slope of the linear regression line is the
value of D* Figure 20 shows the experimentally determined linear re-
gression line -J/(C2-CS)/L = 20.2 + 10056.3 (Pa_ /PT ), and the
corresponding HCB vapor diffusion coefficient in air is found to be
1 x NT cm2/day.
45
-------
2OOO
Figure 20. Linear regression line for the relationship between the
specific HCB volatilization flux and the ratio P^ ' /?
The linear regression line shown as the solid line in Figure 20
does not pass through "zero" as Equation (3) predicted. However, the
deviation from passing through the origin is very small as can be seen
by comparing it with the linear regression line that results when the
constriction is added that it pass through the origin and shown as the
dashed line in Figure 20.
The vapor diffusion coefficient also can be estimated from the known
vapor diffusion coefficient in air of other compounds. The self-diffusion
coefficient of a gaseous compound has been shown as (Moore, 1962)
D = 1/3 XC
where X is the mean free path, and
C is the average speed.
C is shown as
_ 1
C = (SRT/nM)'
46
-------
where R is the gas constant,
T is the absolute temperature, and
M is the molecular weight.
The diffusion coefficient is then expressed as
D = 1/3 \(BRT/ nM)^
or
(5)
The vapor diffusion coefficient of compound A can be estimated
from the known vapor diffusion coefficient of compound B by using the
relation in Equation (5) and is expressed as
DA = °B (VV%
where the subscripts A and B denote compounds A and B, respectively.
When the temperature changes from T-^ to T2 , the diffusion coeffi-
cient at temperature T2 can be estimated by using Equation (5) and is
shown as
°2 = °1 (T2/T1} (7)
where the subscripts 1 and 2 denote the value at the temperatures T..
and T-, respectively.
The diffusion coefficient of oxygen in air at 0 C has been reported
to be 0.178 cm2/sec (Handbook of Chemistry and Physics, 1973). The
diffusion coefficient of oxygen in air can be used to estimate the vapor
diffusion coefficient of HCB in air at 25 C by using Equations (6) and (7).
The HCB vapor diffusion coefficient in air is estimated to be 0,54 x 10
cm /day which is about half of the measured value of 1 x 10 cm /day.
Thus the measured HCB vapor diffusion coefficient in air seems to be quite
reasonable. It is important to note here that diffusion coefficients of
other compounds which move mainly in the vapor phase can also be estimated
by using Equations (6) and (7) and the estimated diffusion coefficient
can then be used to predict vapor flux through soil.
Equation (4) can be used to show the effect of air-filled porosity
on vapor phase diffusion. This is illustrated in Fig. 21 where the HCB
vapor flux through a soil layer 100 cm in depth is plotted, using
Equation (4), as a function of soil water content and soil bulk density.
The temperature is 25 C.
47
-------
O O.IO O.20 O.3O O.4O '
SOIL WATER CONTENT (g/g)
Figure 21. Predicted HCB volatilization flux through a soil cover as a
function of soil water content and soil bulk density. Soil
thickness is 100 cm.
-------
SECTION 6
SIGNIFICANCE OF THE FINDINGS FOR SOME LANDFILL DISPOSAL PRACTICES
EQUIVALENT THICKNESS OF POLYETHYLENE FILM TO SOIL
Polyethylene film can be used alone or in conjunction with other
covering materials to reduce the volatilization of HCB from hex wastes.
The effects of polyethylene film are two-fold: the direct effect is
to act as a barrier to HCB vapor, and the Indirect effect is to maintain
a high water content in the soil underlying the film so that the soil
cover can be more effective in reducing HCB volatilization flux through
the soil cover. In order to aid in the design of the thickness of the
total covering and to achieve the maximum effectiveness of the covering,
it is necessary to know the quantitative effectiveness of the film or
the equivalent thickness of the film to soil.
When polyethylene film is used with soil, the equivalent thickness
of polyethylene film to soil in reducing HCB vapor flux at steady state
can be calculated when the diffusion coefficient of the polyethylene film
is known. The diffusion coefficient of the polyethylene film is deter-
mined using the flux data in Experiment VI (Figure 14) using the follow-
ing equation:
£ L±/DA = z (Li/V (8)
where L is the depth of an individual layer in a multilayered system
D is the average apparent diffusion coefficient over the whole
system, and
D is the apparent diffusion coefficient for each layer in a
multilayered system.
Experiment VI is a two- Layered system consisting of a 1.8 on deep
soil layer and a 0.01 cm deep polyethylene layer. The apparent diffu-
sion coefficient of the soil layer will be the same as the soil layer in
Experiment V since soil water contents and soil bulk densities were the
same in both experiments. Using Equation (8) the sum is:
49
-------
where LBO£^ is the depth of the soil layer in a multilayered system,
Lf is the depth of the polyethylene layer,
Dsoil is the apparent diffusion coefficient for the soil layer,
and
Df is the apparent diffusion coefficient of the polyethylene film.
The apparent diffusion coefficient of the polyethylene film was
calculated to be 5.6 cm^/day using the flux data from dry hex waste A
covered with a composite layer of soil and 0.01 on polyethylene film
(Experiment VI, Fig. 14).
The effectiveness of a 0.01 cm polyethylene film for reducing HCB
volatilization flux is equivalent to that of a 1.36 cm layer of soil at
1.19 (g/cm-*) bulk density and 20% dry weight soil water content. This
equivalent layer was extrapolated linearly to other film thicknesses and
plotted in Fig. 22. The film is not very effective in reducing HCB
volatilization flux, especially when considering the cost of the material
and the thickness of soil cover used.
It is valid to use Fig. 22 to estimate the equivalent film thick-
ness of other soils that have the same bulk density and soil water
content as that used in the figure. Comparisons with soils of other bulk
densities and soil water contents can be made by using Equation (3) to
calculate a Ds for the soil and comparing to the value of 5.6 cm^/day
diffusion coefficient of the polyethylene film.
PROBLEMS ASSOCIATED WITH LIQUID COMPONENT OF THE HCB WASTE
The sample referred to earlier as fresh hex waste was collected
from the process line before being discharged into the storage lagoon
and contained 76.6% liquid by volume. This liquid component has a very
strong odor and a reddish brown color. It has a density of about 1.67
g/ml and contains 1.4% HCB. Because it is heavier than water, it may
move downward when placed in a landfill or a storage lagoon and have a
potential to leach HCB into ground water.
The liquid component of the HCB waste A was found to deposit on
the polyethylene film in Experiments IV, I, and II and to cause the
film to partially dissolve and expand. The HCB volatilization flux
through the partially dissolved and expanded polyethylene film was
found to be 28% greater than that through an unaffected film . Obviously
the liquid component of HCB waste caused the polyethylene film to dis-
solve and expand and thus affected the HCB transmission properties of
the film. It is conceivable that this liquid component may also have
deleterious effects on other synthetic membranes and thereby reduce
their effectiveness as barriers to liquid and gas movement when used in a
landfill or storage Lagoon.
50
-------
Q
0.01 0.02 0.03
POLYETHYLENE FILM
0.04 0.05
THICKNESS (cm)
0.06
Figure 22. The equivalent thickness of polyethylene film to soil assuming
a soil bulk density of 1.19 g/cm^ and a soil water content of
20% (w/w).
51
-------
SECTION 7
APPLICATION OF THE FINDINGS IN DESIGNING LANDFILL COVERS
The findings of this study may be used to assist a planner in design-
ing a landfill cover that minimizes the escape of HCB or other vapors.
Alternatively, an existing landfill may be assessed, using the results of
this study, for its potential for allowing HCB vapor fluxes through the
surface of the landfill.
The volatilization or vapor loss of HCB and other compounds from
landfill can be treated as a diffusion controlled process. The rate at
which compounds will volatilize from the soil surface and be lost to the
atmosphere will be controlled by the rate at which they diffuse through
the soil cover over the waste. Assuming no degradation of the compound
and no transport in moving water, the volatilization can be predicted
using Equation (l) of this report which is Pick's First Law for steady
state diffusion:
J = -D (C -C )/L (1)
s 2 s
2
where J is the vapor flux from the soil surface (ng/cm /day),
2
D is the apparent steady state diffusion coefficient (cm /day),
S
C? is the concentration of the volatilizing material in air or
vapor density at the surface of the soil (ug/1),
C is the concentration of the volatilizing material in air or
S vapor density at the bottom of the soil layer (ug/1), and
L is the soil depth (cm).
The negative sign is present to indicate that the vapor flux is in the
opposite direction from the vapor concentration gradient in the soil.
Table 6 gives several conversion factors which may be useful depending
on whether regulatory agencies specify flux in metric or English units.
52
-------
Table 6. Conversion Factors
To convert
into
multiply by
atmospheres
centimeters
f\
cm /day
feet
g/cm
kg/ha
mm Hg
ng/cm
mm Hg
ft
mnr /week
cm
lbs/ft3
Ibs/acre
atm
kg/ha
Ibs/acre
760
3.28 x
700
30.48
62.4
0.89
1.32 x
10
8.9 x
lO'2
10
io-5
In order to use Equation (1) for predicting volatilization, the
apparent diffusion coefficient, Dg, must be evaluated. The investiga-
tors, Millington and Quirk (1961) have suggested an apparent diffusion
coefficient which included a porosity term to account for the geometric
effects of soil on diffusion. This was Equation (3) of this report and
was expressed as
D - D (p10/3/P2T )
s o a T
(3)
where D is the vapor diffusion coefficient in air (cm /day),
3 3
P is the soil air-filled porosity (cm /cm ), and
a
/ 3. 3,
P is the total soil porosity (cm /cm ;.
Combining Equations (1) and (3) yields the following expression:
(4)
This equation will be used in this paper as the basis for a suggested
step-wise procedure intended to assist a planner in designing a landfill
cover that minimizes the escape of HCB or other vapors. Alternatively,
an existing landfill cover may be assessed, using Equation (4), for
its potential for allowing HCB vapor flux through the surface of the
landfill. The validity of Equation (4) has been experimentally verified
for hexachlorobenzene in this project.n The diffusion coefficient in air,
D
o>
s projec
for HCB was found to be 1 x 10 cm /day.
53
-------
This procedure for assisting in the design of a landfill cover
is only a suggested procedure and is not an accepted official EPA proce-
dure. This will be an example of how research findings can be used
to arrive at a suggested set of procedures that will assist planners
in designing landfill covers taking advantage of the best current know-
ledge available for reducing vapor flux from a landfill.
DESIGN APPLICATION
In order to use the results of this study in designing a proposed
landfill, the planner will normally begin with an acceptable value for
HCB flux through a cover and determine the most efficient combination
of soil porosity and soil depth to produce the acceptable value. The
establishment of the actual values for an acceptable flux through the
landfill cover is beyond the scope of this research or that of the
landfill designer. Flux from the soil will be established through regu-
lations by state or federal agencies. Alternatively the regulating
agencies may establish acceptable air concentration values at some
specified distance from the landfill site. In the latter case the
landfill designer may have to calculate the acceptable flux at the soil
surface using the specified air concentration and existing wind disper-
sion models (Fitter and Baum, 1975).
Once an acceptable flux value has been established either directly
by a regulatory agency or indirectly by use of an air dispersion model,
the following steps can be followed to determine what soil conditions
would limit flux to this value. The following steps are based on
Equation (4) relating vapor flux through soil to soil depth and soil
porosity. Initially the soil depth necessary to produce the desired
flux will be calculated assuming a dry soil and a minimum reasonable
compaction of the soil at the landfill site. If this calculated soil
depth is unrealistically high, then increased compaction and/or an
appropriate water content will be considered. Finally a modified soil
will be considered when necessary and a new flux value calculated.
Equation (4) is rearranged below to allow calculation of L, the soil
depth (cm).
L = -Do(P*°/3 /?£ )(C2-Cg)/J
or
L = -DoP10/3 (C2-Cs)/JP* (9)
By assuming that Co is zero, Equation (9) simplifies as follows:
1 (10)
54
-------
This Is a reasonable assumption since under actual landfill conditions
the amount of vapor reaching the soil surface from below hopefully
will be small and will be rapidly dispersed by wind currents and by
diffusion in air. Additionally the assumption of G£ equaling zero
introduces a safety factor into the calculation. Any increase in G£
will reduce the vapor flux from the soil surface.
The diffusion coefficient in air for HCB has been measured to
be 1.0 x lO^cm^/day. If soil cover is being designed for some material
other than HCB, values for diffusion coefficients in air are available
for a limited number of compounds. (Handbook of Chemistry and Physics,
1973.) For those compounds of interest for which no published values
are available, reasonable estimates can be made using the Equations (6)
and (7) which are reproduced below. The vapor diffusion coefficient
of compound A can be estimated from the known vapor diffusion coefficient
of compound B by using the previously given Equation (6)
DA = DB (MB/MA)% (6)
where the subscripts A and B denote the values of the diffusion coeffi-
cients for compounds with molecular weights MA and Mg, respectively.
When the temperature changes from T^ to T£, where T is the absolute
temperature (°K), the diffusion coefficient at temperature T2 can be
estimated using the previously given Equation (7)
D2 - D! (T2/T!)% (7)
where the subscripts 1 and 2 denote the values of the diffusion coeffi-
cients at the temperatures T^ and T£, respectively.
The value for the vapor concentration at the bottom of the soil
layer, C8, can be taken as that equivalent to the saturation vapor
pressure of the pure compound. This is true because a waste need contain
only a relatively small amount of a volatile material to give a saturated
vapor. In the case of HCB, a saturated vapor density was obtained
with only 0.3% HCB coated on sand. It is conservative to assume Cs equal
to the saturation vapor density. If the actual vapor density is
less than saturation, the actual vapor flux through the surface of
the soil layer will be less than calculated. Saturation vapor densities
are calculated from the following using vapor pressure data which are
available for a number of compounds
C8 - pM/RT
where p is the vapor pressure (mm Hg),
55
-------
M is the molecular weight of the compound (ug/mole) ,
R is the molar gas constant (1 mm Hg/deg mole), and
T is the absolute temperature ( °K) -
The value of Cg for HCB is 0.294 ug/1 at 25 C calculated from a vapor
pressure of 1.91 x 10 mm Hg.
Based on the above considerations the following steps are to be
followed in calculating the optimum combination of soil depth and soil
porosity to achieve the desired vapor flux. A suggested method or
sequence for working through these steps is shown in Figure 23.
1. Base all flux calculations on total soil porosity assuming
a dry soil. Thus P = P and Equation (10) is further simplified to
3. X
L = DCP/3 /J (11)
This not only simplifies the calculations but introduces another safety
margin. The addition of any water to the soil by irrigation or by
natural rainfall will reduce the air-filled porosity and thereby reduce
the vapor flux from the soil surface. The total porosity of the soil
can be calculated from the soil bulk density, P , using the following
equation:
PT= 1-P/P (12)
where p = soil bulk density (g/cm ) and
3
p = particle density (g/cm ).
The particle density can be measured. However, the part icle ^density
for most soil mineral material is usually taken as 2.65 g/cm (165
Ibs/cu ft).
2. Establish a minimum and maximum soil porosity that is likely
to be achieved through maximum and minimum compaction of the soil type
available at the proposed landfill site. Standardized procedures such
as the Procter (ASTM D-698) and modified Procter (ASTM D-1557) (American
Society for Testing Materials, 1976) tests are available for estimating
the densities that can be achieved for a given soil with various degrees
of effort. The degree of compaction need not be limited to either minimum
or maximum as intermediate values may be calculated if necessary to deter-
mine the precise limiting density.
3. Using the porosity value established in Step 2 above, Equation
(11) is used to determine the depth of soil necessary to attain the
acceptable vapor flux value through the soil surface.
56
-------
;BEGINJ
Estimote MINIMUM reosonoble density for
soil cover ond calculate corresponding porosity
(Eqn.12) assuming all porosity is air filled.
Estimate MAXIMUM density for soil cover and
calculate the corresponding porosity assuming
that all porosity is air-filled ( Eqn. 12 )
*- NO
Using the porosity corresponding
fo Maximum density, use Eqn. 13
ond the minimum water content
to calculate air-filled porosity.
Are soils or soil
materials (e.g.
Bentonite] available
for modifying or
substitutinq for
on-site soils ?
<-NO
I
I
I
"YES"
Using the oir-filled
porosity ond Eqn. 10
is the required soil
depth technicolly and
economically feasible?
YES-
Using the porosity corresponding
to Minimum density, use Eqn. 13
and the minimum water content
to calculate air-filled porosity
I NO
Using the air-filled
porosity and Eqn. 10
is the required soil
depth technicolly ond
economically feasible?
YES-
YES-
Repeot process for
modified cover material
Soil cover will not limit flux
to acceptable value.
Seek other method of dealing
with waste.
Develop landfill
design plans
*At this stage, could consider irrigation or
other treatment to maintain higher water
content (if a/lotted by regulatory agency)
Figure 23. Flow diagram for predicting depth of soil cover required to
limit vapor flux through soil cover to an acceptable value.
57
-------
A. If circumstances allow an estimate of long-term soil water
contents in the landfill cover, the planner can refine the flux calcu-
lations to give a reduced flux due to reduced air-filled porosity.
This refinement requires the use of Equation (10), taking into account
the air-filled porosity as affected by soil water content. The air-filled
porosity, Pa, is calculated from the total porosity, Pj, and the volu-
metric soil water content, 6 , by the following:
PQ = PT - e (is)
o. 1
n *J
The volumetric water content (cm /cm ) is determined from the gravimetric
soil water content as follows:
e = ^/PW
where W is the gravimetric soil water content (g/g), and p is the
density of water (g/cm ). For practical purposes the density of water
can be taken as one and the volumetric water content is simply the
gravimetric water content multiplied by the soil bulk density, p.
5. If the soil depths calculated in the previous steps prove
to be too great to be technically or economically feasible then the
planner will need to decide if it is possible to replace or modify
the on-site soil with other soil materials (e.g., bentonite) to increase
soil bulk density. If soil modification is feasible then it will be
necessary to go back and calculate a new soil porosity term, and thus
a new flux value, using the higher bulk density.
6. If none of the above procedures will produce a soil cover
that will limit the vapor flux to an acceptable value, other disposal
methods may have to be considered for dealing with the waste.
ASSESSMENT APPLICATION
In the case where an existing landfill site has a history of accept-
ing and disposing of HCB-containing materials or other waste of similar
concern, it may be desirable to evaluate the cover and to estimate
the HCB vapor flux through the surface of the soil to determine if
the landfill cover should be redesigned.
Equation (11) is rearranged as follows to calculate vapor flux
through a dry soil cover of depth, L, and total porosity, P^.
J - D.C.F*'3 il (15)
The same considerations apply to the use of this equation for calculating
flux as applied to Equation (11) for calculating soil depth:
58
-------
1. The diffusion coefficient in air for HCB is 1.0 x 104cm2/day.
For other compounds, a value for D can be estimated if the actual
value has not been determined °
2. The concentration in air at the soil surface, C^ , is assumed
to be zero. As discussed before, this is a reasonable assumption and
introduces a safety factor into the calculation of a maximum value
for the vapor flux through the soil surface.
3. The concentration in air at the bottom of the soil layer,
Cg , is the saturation vapor concentration of the compound calculated
trom its vapor pressure data.
4. In making these calculations a dry soil is assumed so that
Pa «
5. If data is available on soil water content, Equation (4) can
be used to estimate vapor flux assuming C2equal to zero.
DISCUSSION
Figures 24 and 25 illustrate the use of Equations (4) and (15) for
predicting vapor flux at different depths of soil cover. Figure 24
shows the HCB volatilization fluxes through soil cover with dry soil
at various bulk densities and thicknesses calculated with Equation
(15). Soil temperature was taken as 25 C. The vapor fluxes shown
in Figure 24 are the maximum to be expected through the soil cover because
the addition of water would reduce the air-filled porosity and thus
reduce the vapor flux through the soil. Figure 25 shows the predicted
HCB vapor flux through a soil cover at various soil water contents
and soil depths with the soil bulk density held constant at 1.2 g/cm
(74.9 Ibs/cu ft) calculated with Equation (4) assuming C_ equal to zero.
Figure 26 illustrates how changes in soil temperature would be
expected to influence HCB volatilization flux through a soil cover. HCB
flux is predicted as a function of soil thickness at three temperatures.
A bulk density of 1.2 g/cm and a water content of 17% (w/w) is assumed
in Figure 26. The increase in flux with increase in temperature is due
primarily to the effect of temperature upon the vapor pressure of the
compound causing an increase in the vapor concentration gradient across
the soil layer. The diffusion coefficient is also affected by temperature
and Equation (7) was used to calculate the diffusion coefficient at the
different temperatures in Figure 26. The location of a waste disposal
site and seasonal changes in climate will affect the temperature of a soil
cover over wastes containing HCB. In addition, heat generated inside
the landfill due to the aerobic decomposition of organic wastes will have
a short term effect on the temperature of the soil cover. From Figure 26
we can see that increasing temperature 10 degrees centigrade increases
the HCB volatilization flux approximately three times. Thus a disposal
site located in an area where the soil temperature was 10 degrees centi-
grade warmer than another site would have to use a soil cover at least
59
-------
1.0
5 0.
CQ
O
0.01
1
I I 1
I i
2.3
SO
2.2 2.1
L BULK
2.0 1.9 1.8 1.7 1.6
DENSITY (g/cm3)
1.4 1.2
Figure 24. Predicted HCB volatilization fluxes through a soil cover of
various soil bulk densities and soil thicknesses at 25 C.
The soil was assumed to be dry (zero soil water content) in
order to yield a maximum flux.
three times thicker to achieve the same degree of reduction in HCB
volatilization flux assuming the temperature is uniform throughout the
depth of soil cover and throughout the HCB waste deposit at both sites.
Heat generation within the landfill due to decomposing organic wastes
will eventually cease and soil temperatures along with volatilization
fluxes will, in the long run, be determined by local climates. In this
dicussion of temperature effects, we have been assuming a uniform soil
temperature throughout the soil profile. In actual fact temperature
gradients will exist across the soil cover due primarily to seasonal vari-
ations in temperature. Vapor diffusion, of course, is influenced by
temperature gradients. The vapor will condense in cooler zones of the
soil profile only to be vaporized later when the soil heats up. This
will take place, for example, at the soil surface as day and night time
temperatures fluctuate. These effects of fluctuating soil temperature
gradients will tend to cancel one another and the overall effect of
temperature on volatilization flux can be approximated by using an average
soil temperature value.
60
-------
X,
x^
o
CD
O
I
0.001
0.01 —
0.40
0.30
SOIL WATER
0.20 0.10
CONTENT (g/g)
0
Figure 25. Predicted HCB volatilization fluxes through a soil cover of
various soil water contents and soil thicknesses at 25 C.
Soil bulk density is 1.2 g/cm3.
The presence of decomposable organic wastes, such as municipal waste,
in a landfill often results in gas production, particularly methane gas.
This gas production may be accompanied by a positive flow of gases through
the soil cover which would carry HCB vapor by mass flow from any hex wastes
located near the decomposing wastes. The HCB flux from this type of mass
flow would be analogous to volatilization from uncovered hex waste as
depicted in Figure 8 of Section 5 of this report. This flux can be quite
high compared to diffusion controlled flux through a soil cover. Again,
this flux due to mass flow would be short-term in nature and the long-term
volatilization flux will be determined by diffusion.
61
-------
180 120 90
SOIL
60 50 40
DEPTH (cm)
35
Figure 26. Predicted HCB volatilization fluxes through a soil cover as a
function of soil thickness and temperature. A bulk density
of 1.2 g/cm-' and a water content of 17% (w/w) is assumed.
These procedures detailed in Section 7 are written for application
to disposal of HCB-containing wastes. However, these same methods can
be used to aid in designing landfill covers for other compounds as well,
subject to the following qualifications. Hexachlorobenzene degrades
very slowly, if at all. Since HCB is very slightly soluble (6.2 ug/1)
its transport by moving water is negligible. For compounds which degrade
more readily or are more mobile in moving water than HCB, these procedures
will tend to overestimate the actual flux through the soil cover. These
procedures assume no movement of the compound in water which may be per-
colating through the soil profile. If a compound is more soluble in
water than HCB, it may eventually move with the water; its actual
mobility being dependent upon the extent to which it is adsorbed by the
soil materials. Assuming that net water flow will be downward in soil,
62
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mobility in water will move the compound away from the surface of the
soil cover. These procedures assume no decomposition of the material.
Any decomposition which may occur will serve as a sink for the compound
and will decrease the amount escaping as a vapor. The procedures presented
here, therefore, will not account for any reduction in vapor flux due
to decomposition of the compound or due to transport of the compound in
water.
If hex wastes are to be placed on land, our work has shown the
importance of minimizing the air-filled porosity of soil covers. How-
ever, our contribution to the design of a landfill assumes an intact
soil cover is maintained. If any cracks or other small openings
develop in the soil cover, they will result in an appreciable increase
in HCB flux through the soil cover. The placement of hex waste with
any material, such as municipal solid waste, that is subject to settle-
ment could cause such cracking and flux increase.
If hex wastes are placed on land, consideration should be given
to the need for long-term arrangements for ensuring the integrity of
soil covers. Calculations assuming no degradation indicate that HCB
placed on land could continue to volatilize at a maximum rate for
several centuries. The integrity of the soil cover must be maintained
for this period by preventing such things as erosion or digging.
63
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REFERENCES
American Society for Testing and Materials. 1976. Tests for moisture-
density relations in soils. ASTM-D-698-70 and ASTM-D-1557-70, vol.
19, Philadelphia, PA.
Burns, J. E., and F. E. Miller. 1975. Hexachlorobenzene contamination:
Its effects in a Louisiana population. Arch. Environ. Health
30:44-48.
Cam, C., and G. Nygogosyan. 1963. Acquired prophyria cutanea tarda due
to hexachlorobenzene. J. Am. Med. Assoc. 183:88-91.
Ehlers, W., W. J. Farmer, W. F. Spencer, and J. Letey. 1969. Lindane
diffusion in soils. II. Water content, bulk density, and temperature
effects. Soil Sci. Soc. Amer. Proc. 33:505-508.
Farmer, W. J., K. Igue, W. F. Spencer, and J. P. Martin. 1972.
Volatility of organochlorine insecticides from soil: I. Effect
of concentration, temperature, air flow rate, and vapor pressure.
Soil Sci. Soc. Amer. Proc. 36:443-447.
Graham-Bryce, I. J. 1969. Diffusion of organophosphorus insecticides
in soils. J. Sci. Food Agr. 20:489-494.
Goring, C. A. I. 1962. Theory and principles of soil fumigation. In
R. I. Metcalf (ed.) Advan. Pest Control Res. 5:47-84. Interscience
Publishers, N.Y.
Gray, R. A., and A. J- Weierich. 1965. Factors affecting the vapor loss
of EPTC from soils. Weeds 13:141-147.
Guenzi, W. D., and W. E. Beard. 1970. Volatilization of lindane and DDT
from soil. Soil Sci. Soc. Amer. Proc . 34:443-447.
Handbook of Chemistry and Physics. 1973. R. C. Weast, editor. 53rd Ed.
CRC Press, Inc., Cleveland, Ohio.
Harris, C. R., and E. P. Lichtenstein. 1961. Factors affecting the
volatilization of insecticidal residues from soils. J. Econ.
Entomol. 54:1038-1045.
Hartley: G. S. 1964. Herbicide behavior in the soil. I. Physical
factors and action through the soil. P. 111-161. In L. J. Audus
64
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(ed.) The Physiology and Biochemistry of Herbicides. Academic
Press, London and New York.
Helling, C. S., P. c. Kearney, and M. Alexander. 1971. Behavior of
pesticides in soils. Advan. Agron. 23:147-240.
Isensee, A. R., and G. E. Jones. 1974. Distribution of hexachlorobenzene
in an aquatic model ecosystem. Agronomy Abstracts, p. 185.
Lai, S. H., J. M. Tiedie, and A. E. Erickson. 1976. In situ measurement
of gas diffusion coefficient in soils. Soil Sci. Soc. Amer. Proc.
40:3-6.
Letey, J. and W. J. Farmer. 1974. Movement of pesticides in soils.
P. 67-97 rn Pesticides in Soil and Water. W. D. Guenzi (ed.) Soil
Sci. Soc. Amer. Inc. Madison, Wisconsin.
Louisiana Air Control Commission and Louisiana Division of Health,
Maintenance and Ambulatory Patient Services: Summary of sampling
results for hexachlorobenzene in Geismar, Louisiana, vicinity.
New Orleans, loose-leaf publication, Aug. 5, 1973.
Mayer, R., W. J. Farmer, and J. Letey. 1973. Models for predicting
pesticide volatilization of soil applied pesticides. Soil. Sci.
Soc. Amer. Proc. 37: 563-567.
Millington, R. J. and J. P. Quirk. 1961. Permeability of porous solids.
Trans. Faraday Soc. 57:1200-1207.
Moore, W. J. 1962. Physical Chemistry. 3rd Edition. Prentice-Hall,
Inc., Englewood Cliffs, N. J.
Ockner, R. K., and R. Schmid. 1961. Acquired porphyria in man and rat
due to hexachlorobenzene intoxication. Nature No. 4763.
Fitter, R. L., and E. J. Baum. 1975. Chemicals in the air: The atmos-
pheric system and dispersal of chemicals. In Environmental Dynamics
of Pesticides, R. Haque and V- H. Freed, editors, Plenum Press, New
York and London, pp. 5-16.
Quinlivan, S., M. Ghassemi, and M. Santy. 1976. Survey of methods used
to control wastes containing hexachlorobenzene. U. S. Environmental
Protection Agency, Office of Solid Waste Management Programs,
Washington, D. C. EPA/530/SW-120c.
Sears, G. W., and E. R. Hopke. 1949. Vapor pressures of naphthalene,
anthracene, and hexachlorobenzene in a low pressure range. J. Amer.
Chem. Soc. 71:1632-1634.
Shearer, R. C., J. Letey, W. J. Farmer, and A. Klute. 1973. Lindane
diffusion in soil. Soil Sci. Soc. Amer- Proc. 37:189-193.
65
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Shearer, R. C., R. J. Millington, and J. P. Quirk. 1966. Oxygen
diffusion through sands in relation to capillary hysteresis: 2.
Quasi-steady state diffusion of oxygen through partially saturated
sand. Soil Sci. 101:432-436.
Spencer, W. F., and M. M. Cliath. 1969. Vapor density of dieldrin.
Environ. Sci. Technol. 3:670-674.
Spencer, W. F., and M. M. Cliath. 1970a. Vapor density and apparent
vapor pressure of lindane. J. Agr. Food Chem. 18:529-530.
Spencer, W. F., and M. M. Cliath. 1970b. Desorption of lindane
from soil as related to vapor density. SSSAP 34:574-578.
Spencer, W. F., W. J. Farmer, and M. M. Cliath. 1973b. Pesticide
volatilization. In: F. A. Gunther (ed.). Residue Reviews 49:1-47.
Spencer, W. F., and M. M. Cliath. 1973. Pesticide volatilization
as related to water loss from soil. J. Env. Qual. 2:284-289.
U. S. Department of Agriculture News Release No. 1105-73, Washington,
D. C. 1973.
U. S. Environmental Protection Agency, Open Public Hearing of the
Environmental Hazardous Materials Advisory Committee Meeting,
chaired by E. Mrak. August 6-7, 1973, Washington, D. C.
Yang, Ming-shyong. 1974. Processes of adsorption, desorption,
degradation, volatilization, and movement of 0,0,-diethyl 0-p
nitrophenol phosphorothioate (parathion) in soils. Ph.D. thesis.
University of California, Davis.
66
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APPENDIX
COLUMN CLEANUP PROCEDURE FOR VOLATILIZATION PRODUCTS FROM HEX WASTE
The following procedure was developed because of a serious analytical
problem which existed while attempting to analyze for HCB in samples
collected from the volatilization cell when it contained hex waste. As
discussed in Section 4, Materials and Methods, when hex waste volatili-
zation products were injected into the GC following extraction from
hexylene glycol or ethylene glycol, the GC trace was often impossible to
quantify. The problem was corrected with the clean-up procedure described
below using activated alumina. Although activated alumina has proved
invaluable in this study for sample cleanup, the material must be used
with caution to insure it remains dry and activated. Frequent checks
using standards should be run to ensure that a given method is operating
as intended. Reproducibility of results from the same bottle of alumina
was improved by shaking the alumina bottle thoroughly each time before
opening. A common practice with florisil to ensure constant activity
is to keep it in a 200 C oven until it is used. This method does not
work with alumina since its activation temperature is 500-600 C and heat-
ing at a lower temperature only serves to deactivate it.
The samples to be cleaned-up are contained in 100 ml volumetrics
in hexane after extraction from the hexylene glycol or ethylene glycol
traps. If any acetone had been used during the extraction of the
samples from the traps, three water washes are added to the extraction
procedure. This greatly improved sample uniformity and reproducibility.
Acetone can serve to deactivate the alumina in a manner similar to water.
The columns were 1.5 cm ID with 2.54 cm (1 in) Na2S04 on top of 10 cm
(4 in) Al 0 . Prepare cleanup columns as follows:
1. Put glass columns in oven (110-120 C) for 5-10 minutes. They
must be completely dry so that they do not deactivate the aluminum oxide.
2. When the columns are cool enough to handle, clamp them in a
verticle position on stand or rack. Plug them with a little glass wool.
(Push glass wool down with 5 ml pipette or something else suitable.)
wool.
3. Mark columns on the outside at 4 and 5 inches above the glass
»
4. Through powder funnel, carefully pour A1203 W 200 neutral (Woelm)
into column up to the 4 inch mark; tap it a little at the end. (If you
overfill, don* t just pour out excess; this distorts the even layering of
the alumina and later causes streaking of the sample. Start completely
67
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over with a new column.) Close A^C^ bottle immediately \Aien you are
finished; never let moist air get Into it. (It is important that the
A1203 is in its most active state. Any deactivation will cause the HCB
to partially elute with the first hexane fraction.)
5. Add one inch of anhydrous Na2S04 on top (up to the 5 inch mark).
6. Open stopcocks and wet the columns with nanograde hexane, 15-20
ml. Let hexane drain into columns until 3 mm above the Na2S04, then close
stopcocks .
7. Measure 40 ml of hexane for each column into graduated cylinders.
8. Make sample volumetrics up to volume - be sure to note subtracted
aliquots! Add exactly 10 ml of sample onto each column. Label columns
and /or receiving Erlenmeyer flasks.
9. Open stopcocks and adjust to a flow of approximately 2 drops per
second .
10. Let samples completely drain into column, but don't let surface
dry.
11. Immediately wash with 3 ml of hexane; rinse the inner walls of
the ml iimn - Let hexane drain In and repeat washing twice more with 3 ml
hexane each.
12. Add remaining hexane onto column and readjust flow (2 drops per
second) .
13. Prepare 10% analytical grade benzene in nanograde hexane. (Each
time a new bottle of benzene is opened, inject some of it into GC to make
sure that it does not contain interferences.) Measure 100 ml of the
mixture for each column into graduated cylinders.
14. When all hexane has drained into the column, immediately add
100 ml of 10% benzene in hexane and readjust flow if necessary.
15. Change receiving containers. Discard eluted hexane (it contains
the GC -interfering substances) and collect the 10% benzene- in-hexane
fraction in a clean 125 ml Erlenmeyer flask. Wrap some aluminum foil
around end of column and neck of flask and place flask so that the drops
will not splash. (Now you can go for a coffee break. Never stop the
column flow once the sample Is on!)
16. When column has run dry, take benzene-hexane eluate, transfer
quantitatively into Kuderna-Danish with hexane and evaporate to less
than 10 ml.
17. Transfer cooled concentrate quantitatively into a 10 ml volu-
metric flask with hexane and make up to volume with hexane.
18. Sample is ready for injection into GC.
68
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
^REPORT NO.
'EPA-eoo/z-so-ng
3. RECIPIENT'S ACCESSION NO.
U.TITLE ANDSUBTITLE
5. REPORT DATE
LAND DISPOSAL OF HEXACHLOROBENZENE WASTES
Controlling Vapor Movement in Soil
August 1980 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Walter J. Farmer
Ming-Shyong Yang
John Letey
William F. Spencer
8. PERFORMING ORGANIZATION REPORT NO.
ERFORMING ORGANIZATION NAME AND ADDRESS
I PERFOR - -----
Dept. of Soil & Envir. Sciences Science & Educ. Admin
10. PROGRAM ELEMENT NO.
University of California
Riverside, CA 92521
Federal Research-USDA
Riverside, CA 92521
1DC618
11. CONTRACT/GRANT NO.
68-03-2014
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory--Cin.,OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
6/14/74 to 9/13/76
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
Project Officer: Mike H. Roulier (513) 684-7871
16. ABSTRACT
Hexachlorobenzene (HCB) is a persistent, fat-soluble organic compound of low
aqueous solubility (6.2 yg/1) present in some industrial wastes. Transport in
water moving through soil will be negligible but its long term persistence and
^ appreciable vapor pressure (1.91 x 10 mm Hg at 25 C) allows significant
volatilization to occur. Conditions for soil covers that would control the
movement of HCB out of landfills and other disposal/storage facilities into the
surrounding atmosphere were studied. The volatilization fluxes of HCB from
industrial wastes (hex wastes) were determined in a simulated landfill under
controlled laboratory conditions. Coverings of water and soil were found to be
highly efficient in reducing volatilization. Polyethylene film was less efficient
when compared on a cost basis. Volatilization flux through a soil cover was
directly related to soil air-filled porosity and was greatly reduced by increased
soil compaction and water content. An organic liquid phase associated with the
hex waste was heavier than water and contained 1.4% HCB by weight. The presence
of HCB in this liquid phase creates the potential for rapid transport of HCB in
porous media. A procedure is proposed for using the results of this study to
design a landfill cover that will limit the volatilization flux of HCB and other
compounds.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
COSATI Field/Group
Volatilization
Diffusion
Polyethelene
Vapor Pressure
Soil Chemistry
Extraction
Hexachlorobenzene
HCB Volatilization
Pollutant Migration
13B
IB. DISTRIBUTION STATEMENT
Release to Public
19. SE.CURITY CLASS (This Report)
SECURITY CLASS (Tl
Unclassified
!1. NO. OF PA
79
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
69
o u S SOVEMIHEin reimiHG Offld 1MJ-6S7-16S/0035
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