Journal of Environmental Protection, 2011, 2, 873-881
doi:10.4236/jep.2011.27099 Published Online September 2011 (
Copyright © 2011 SciRes. JEP
Henry’s Equilibrium Partitioning between Ground
Water and Soil Air: Predictions versus
Jeroen Provoost1, Robbe Ottoy2, Lucas Reijnders3, Jan Bronders1, Ilse Van Keer1, Frank Swartjes4,
Daniel Wilczek1, David Poelmans1
1Flemish Institute for Technological Research (VITO), Antwerp, Belgium; 2Department PIH, Hogeschool West-Vlaanderen, West
Flanders, Belgium; 3Department of Science, Open University Netherlands (OUNL), Netherlands; 4National Institute for Public
Health and the Environment (RIVM), Netherlands.
Received July 3rd, 2011; revised August 5th, 2011; accepted September 6th, 2011.
Humans spend 64% - 94% of their time indoors; therefore, indoor air quality is very important for potential exposure to
volatile organ ic compound s (VOC). The source of VOC in the subsurface may come from accidental or intentional re-
leases, leaking land fills or leaking und erground and abo ve-ground storage tanks. Once these contaminan ts are present
near or beneath buildings, they may move as a vapour through soil gas and enter the building. A large number of va-
pour intrusion (VI) algorithms have been published in peer-reviewed publications that link indoor VOC concentrations
to the contamination of so ils. These models typically include phase partitio ning calculations of VOC based on Henry’s
law to estimate the con centration of a particular con taminant in soil gas. This paper presents the results from a series
of laboratory experiments concerning the use of the Henry’s Law constant for the calculation of toluene concentrations
in equilibrium between grou nd water and soil air. A series of column experiments were conducted with various toluene
concentrations in artificial (ground) water to contrast the predicted and observed (soil) air concentrations. The ex-
periments which exclude soil material show a toluene fugacity behaviour roughly in line with Henry’s law whereas the
experiments which include soil material result in equilibrium soil concentrations which were around one or-
der-of-magnitude lower than was expected from a Henry Law-based estimation. It is concluded that for toluene inclu-
sion of Henry’s Law in VI algorithms does not provide an adequate descriptio n of vola tilisa tion in so ils and may lead to
an overestimation of health risk. Instead, a model based on a simple description of the relevant intermolecular interac-
tions could be explored.
Keywords: Henry Law Coefficient, Equilibrium Partitioning, Ground Water, Soil Air, Toluene, Algorithm
1. Introduction
During the last two decades, soil and ground water
contaminated with volatile organic compounds (VOCs)
have received increased attention because of their po-
tential to migrate to indoor air and cause human health
problems [1-3]. Humans spend on average 80% of their
time indoors, ranging from 64% to 94%; therefore,
indoor air quality is very important for potential expo-
sure to VOCs [4-6]. Swartjes [7] demonstrated that the
variation in exposure through indoor air inhalation is
comparable to variations in the concentration in indoor
air. This suggests that the parameters controlling the
variation in the concentration in indoor air, resulting in
VOC migration into indoor air (i.e. ‘vapour intrusion’),
also control variations in exposure through indoor air
inhalation. ‘Vapour intrusion’ (VI) refers to the trans-
port of VOC vapours from ground water or soil into
buildings. The source of organic vapours in the sub-
surface can come from accidental or intentional re-
leases [8,9], leaking landfills [10], leaking underground
and above-ground storage tanks [11] or related to dry
cleaning facilities [12,13]. Once VOCs are introduced
into the subsurface, a complex series of fate and trans-
port mechanisms act, potentially moving them away
from the source area. The distribution of VOCs in soil
Henry’s Equilibrium Partitioning between Ground Water and Soil Air: Predictions versus Observations
depends on; the VOC concentration in the soil, soil
particle distribution (soil type), soil porosity, pore wa-
ter content, soil gas content, and organic carbon frac-
tion, and is also controlled by the physical-chemical
properties of the VOC [14]. Once VOC are present
near or beneath buildings, they may move as a vapour
through soil gas and enter into the building.
A large number of VI algorithms have been published
in peer-reviewed publications which link indoor VOC
concentrations, caused by VI, to the contamination of
soils with VOC [15,16]. These models are used by the
competent authorities and/or consultancies for con-
taminated land management (i.e. in deriving soil
screening values and/or for site-specific human health
risk assessment). These models typically include
transport and phase partitioning calculations of VOCs
to estimate the concentration of a particular contami-
nant in soil gas from its concentration in any other
phase (i.e. ground water, bulk soil or non-aqueous
phase liquid).
Most current VI models rely on a common set of
partitioning and transport relationships, including
Henry’s Law to estimate water to air partitioning, the
Millington [17] (or similar) approximation to estimate
effective diffusion coefficients, Darcy’s Law to de-
scribe vapour flow into the building, soil gas velocities
to estimate advective velocities using a foundation
crack area, and a steady-state mass balance.
Under most environmental conditions, molecular
diffusion in natural systems moves the compound away
from locations of higher concentration towards loca-
tions of lower concentrations [18]. In a typical scenario,
organic vapours above a contaminated water table
(high concentration) diffuse towards the surface (lower
concentration). The well-known relation describing the
diffusion of a compound is Fick’s First Law [2,19,20]:
JD z
 
is the mass flux [g/m²·s], is the ef-
fective diffusion coefficient of the compound in the gas
phase [m²/s], and
C is the contaminant vapour
concentration gradient in soil air [µg/L], is the
distance over which diffusion occurs. z
In porous media, the effective diffusion coefficient
depends on the total and water-filled porosities of the
medium [21], and can be estimated by formulations
such as that provided by Millington and Quirk [22].
10/3 10/3
eff a
 (2)
where a is the free-air diffusion coefficient [L2/T],
the aqueous diffusion coefficient [L2/T],
soil air filled porosity [volume vapour/total volume],
the soil total porosity [volume pores/total volume],
the soil water-filled porosity [volume water/total
volume], and
the dimensionless Henry’s Law
Constant [molar concentration in gas/molar concentra-
tion in water].
Finally, Henry’s Law relates the equilibrium con-
centrations in water and air as:
C is the contaminant vapour concentration in
soil air (µg/L),
is the Henry’s Law constant for the
contaminant (molar concentration in gas / molar con-
centration in water) and
C the concentration of the
contaminant in ground water (µg/L).
The environmental fate of volatile organic pollutants
strongly depends on their partitioning between the gas
phase and water phases as shown in (3).
Several authors have however questioned the use of
Henry’s Law for calculating soil gas concentrations of
volatile substances [23-35].
Results are presented from a series of laboratory in-
vestigation into the use of Henry’s Law coefficient for
the calcu lation of toluene co ncentra tions in eq uilibriu m
between (ground) water and (soil) air.
2. Materials and Methods
2.1. Observations and Predictions
A series of controlled column experiments were con-
ducted to compare observed and predicted soil air con-
centrations for different ground water concentrations.
The results contribute to the verification of model algo-
rithms that depend on the partitioning between the (soil)
gas phase and (ground) water phases by applying the
Henry Law constant. Therefore, the premise of the ex-
periment was to compare measured soil air concentra-
tions at equilibrium with the calculated soil air concen-
trations that apply for a gas in equilibriu m.
2.2. Physico-Chemical Properties of Toluene
The experiments were conducted by using the chemical
toluene with the following physico-chemical properties:
molecular mass 92 g/mol, solubility 515 mg/l (mol/m3), va-
pour pressure 2940 Pa, Henry Law constan t 531 Pa·m³/mo l ,
logKow 2.69 and diffusion in air 0.0265 m²/h [36]. Where
applicable, physico-chemical properties are reported at
20. Toluene was selected as it is considered to be a
volatile contaminant that is frequently found in the soil,
and in additional has a relative low toxicity.
According to (3), the Henry Law constant determines
the equilibrium concentration between (ground) water
and (soil) air. Different Henry Law constants for toluene
Copyright © 2011 SciRes. JEP
Henry’s Equilibrium Partitioning between Ground Water and Soil Air: Predictions versus Observations
Copyright © 2011 SciRes. JEP
were collected from previously published material at 20
[37]. All obtained Henry Law constants were used as
input for the calculation of a range of (soil) air concen-
trations. Mackay [37] reported 23 different Henry Law
constants for toluene that rang from 518 Pa·m³/mol to
825 Pa·m³/mol with a mean of 656 Pa·m³/mol. Henry
Law constants were only included in Mackay after the
measuring method of the Henry Law constant was veri-
fied and appropriate.
2.3. Column Experiments
2.3.1. Setup
Figure 1 provides a schematic diagram of the experi-
mental set-up. The column was made out of inert glass
and the top and bottom plate out of stainless steel. The
high-density polyethylene sealing rings prevented leak-
age of water or soil air and were non-permeable for VOC.
A septum was inserted to allow samples to be taken from
the soil air, and air just above the soil surface, without
disturbing the equilibrium air concentration in the col-
2.3.2 Procedure
For a series of ground water concentrations, duplicate
experiments were conducted and all used the same level
(volume) of soil and ground water in both columns (Fig-
ure 1(a)). The duplicate experiments were used to esti-
mate variability as a result of the co lumn setup and sam-
pling and to verify that the results are consistent.
As the Henry Law constant (3) applies to the equilib-
rium partitioning between (ground) water and (soil) air,
another series of experiments was conducted without soil
material in both columns (Figure 1(b)) to determine the
effect of the soil matrix on the vapour equilibrium con-
centration. It is assumed that the experiments with and
without soil result in similar (soil) air concentrations, as
this assumption forms the basis for the implementation of
the Henry Law constant in most current VI models.
The room temperature where the column experiments
were conducted was kept constant at 20 (± 1) and
measured during the full length of the exp eriments.
The characteristics of the soil were determined by ap-
plying several techniques. The soil bulk density and po-
rosity were derived from gravitational measurement of
Kopecký’s ring (100 cm3) [38] filled with the soil. This
resulted in a soil bulk density of 1758 kg/m³, total poros-
ity 0.34, water filled porosity 0.06 and air filled porosity
of 0.28. The sieve analysis procedure, or gradation test, is
used to assess the particle size distribution, also called
gradation, of a granular material, and allows the deter-
mination of the soil type. The procedure is described in
[39]. Figure 2 reveals that most of the soil particles had a
diameter between 300µm and 850 µm which results ac-
cording to the soil classification scheme [40] in a very
coarse sand.
The organic matter content was obtained by first dry-
ing 30 gram of soil at 110 for 8 hours after which 10
gram of dried soil was put in a container and heated up
till 500 [41]. The weight before and after glowing
represents the organic matter content. This procedure
resulted in an organic matter content of 0.21% which was
considered to be very low as a natural soil contains
Figure 1. Schematic diagram of the experimental column set-up with soil A and without soil B.
Henry’s Equilibrium Partitioning between Ground Water and Soil Air: Predictions versus Observations
Figure 2. Granular measurements.
around 1% - 2% organic matter. It is therefore not ex-
pected that adsorption of toluene to organic matter will
influence significantly the experiments.
The mineral composition of the water used to create the
toluene contaminated ground water was measured according
to ATM standards and resulted in a pH 6, calciu m 4.5 mg/l,
chloride 5 mg/l, potassium 0.5 mg/l, magnesium 1.3 mg/l,
sodium 3 mg/l, nitrate 1.9 mg/l, silicate 7 mg/l, sulphate 7
mg/l, and hydrogen carbonate 15 mg/l.
Each experiment started with packing two identical
columns with homogeneous mixed soil material up to a
predefined level. A kno wn volume of standard water was
then spiked with a concentration of toluene, mixed until
it was homogeneously distributed, and flushed into both
soil columns until it reached the preset level at the ce-
ramic filter (Figure 1(a)). The volume of water was the
same for all experiments conducted. A water sample was
taken, by using a needle and syringe, while the contami-
nated (ground) water was flushed into the column and
analysed for the toluene concentration. After reaching
equilibrium between ground water and soil air, an air
sample was taken. Following the experiments, the water
flowed into a collector, the columns were cleaned to re-
move any remaining residue, and the so il material in bo th
columns was replaced with clean soil.
2.3.3 Verification
Several trail experiments were performed to derive a
standard procedure on how to pack the column, take air
samples, flush the water into the column and clean the
column to below detectable concentrations. Hereto, a
series of verification experiments were conducted for
various ground water concentrations to derive the time
needed to reach equilibrium in the columns and to deter-
mine the stability of the concentration in the co lumn ov er
a longer period of time. Figure 3 shows the result from
one of the verification experiments (in duplicate) for a
ground water concentration of 1000 µg/l. Air samples
were taken in two hours intervals to derive the minimum
time needed for toluene to reach equilibrium in the col-
From experiments with various concentrations, it was
concluded that a minimum of eight hours was needed
before ground water and soil air were in equilibrium and
samples could be taken. The results, as shown in Figure
3, indicate that between 8 and 26 hours after flushing
contaminated ground water in the columns the average
toluene air concentration in the first column was 121 µg/l
with a standard variation of 5.4 µg/l and for the second
column 124 µg/l with a standard deviation of 10.6 µg/l.
The concentration in the columns at equilibrium was
considered to be sufficien tly stable and air samples in th e
experiments were taken after 10 hours.
Further verification was performed to determine
whether the concentration in the soil air at equilibrium
differs from the concentration in the air just above the
soil (Figure 1(a)). Therefore, an experiment, also in du-
plicate, was conducted during which the concen tration in
the soil air and column air just above the soil were si-
multaneously sampled for around 14 hours and concen-
trations compared. The results, as shown in Figure 4,
revealed that after equilibrium is reached the difference
for all measurements varied on average 2.8 µg/l with a
standard deviation of 2.2 µg/l, which was considered to
be low in view of the analytical variability of 10%, which
is also indicated in Figure 4.
The findings in Figure 4 show that both sampling
points result in similar air concentrations and that the
Copyright © 2011 SciRes. JEP
Henry’s Equilibrium Partitioning between Ground Water and Soil Air: Predictions versus Observations 877
Figure 3. Difference between the concentration of toluene in the soil air and the air just above the soil. Whiskers indicate an
analytical variability of 10%.
Figure 4. Time needed for toluene to reach equilibrium for a ground water concentration of 1000 µg/l. The grey area indi-
cates where equilibrium occurs.
concentration from both sampling points could be con-
sidered to be within each other’s analytical variability.
The air just above the soil is expected to be less influ-
enced by heterogeneity in the soil air and is therefore
selected for sampling.
In addition a two-tailed t-test was applied to determine
if the air concentrations differ. Th e t-test resulted in a F (t
stat) 1.14, p-value 0.29 and t critical of 2.44 and an
of 0.05 (95% confidential level). The conclusion was that
the null hypothesis (H0 = the means do not differ) was
accepted. Therefore we can say, with a 95% confidential
level, that the average air concentration in the soil is the
same as the air concentration just above the soil.
2.4. Analytical Procedure
2.4.1 Setup
To sample both columns a syringe’s needle was inserted
in the septum and 10 ml of air from the column air was
extracted. For the analysis, a three module pre-concen-
trator was connected with a GCMS. Samples taken were
directly injected into the pre-concentra tor.
The column has a capillary of 60 meters by 320 µm by
1 µm nominal. The oven had an initial temperature of 35°C
with a ramp of 5°C/minute until 150°C is reached, fol-
lowed by a quick cryo-cooling to 55°C. The analytical
procedure applied to collect and analyse the samples is
described in detail in [42].
The detection limit for toluene was 0.06 µg/m³. The
variation in measured concentrations is around 10% and
this variation is indicated where relevant in the measured
air concentrations. During the analysis the ambient air
vapours pressure and temperature were kept constant,
regularly measured and recorded (20°C ± 1°C).
Copyright © 2011 SciRes. JEP
Henry’s Equilibrium Partitioning between Ground Water and Soil Air: Predictions versus Observations
2.4.2 Calibration
Different reference air concentrations for toluene were
injected into the GCMS pre-concentrator and further
analysed to verify the analytical equipment and to create
a calibration line. The calibration line (Figure 5) was
then used to derive concentrations of toluene for the in-
jected air samples.
2.4. Calculation of the Soil Air Concentration
Observed column (soil) air concentrations were com-
pared to predicted concentrations. Air concentrations
were calculated by using (1) to (3). For each measured
ground water concentration a range of predicted air con-
centrations were calculated by using the minimum, av-
erage and maximum reported Henry Law constant (see
Figure 6).
3. Results
Figure 6 below displays the data obtained from a series
of duplicate experiments for which soil material was in-
cluded or excluded from the experiment. For each ex-
periment (in the two columns), the toluene ground water
concentration was measured in addition to the air con-
centrations at equilibrium (10 hours after flushing in the
ground water).
Comparison of results indicates that a linear increase
in air concentration is observed as a result of increasing
ground water concentrations. The experiments which
exclude soil show a fugacity which is roughly in line
with Henry’s Law whereas the experiments which in-
clude soil result in around one order-of-magnitude lower
air toluene concentration s after reaching equilibriu m than
was expected on the b asis of He nry’s law.
4. Discussion
This study adds to the argument that partitioning VOCs
on the basis of Henry’s Law, as included in current VI
algorithms, does not always provide an adequate descrip-
tion of experimental data. This is in line with findings
from [34] and [43]. A main contribution to divergence
form Henry’s law might come from a rate-limiting mass
transfer from ground water to soil gas [44,45]. As the
present study only regards toluene, additional research
into the partitioning of other VOCs is needed to test the
more general adequacy of current VI algorithms for vola-
tile organic compounds. Equally important is the as-
sumption that the soil and groundwater properties were
considered to be constant. Under slightly different condi-
tions, for example different volumes of soil and ground-
water, the results may have varied.
For toluene the present study indicates that current use
of Henry’s law in VI algorithms may lead to an overes-
timation of toluene concentrations in soil gas, which in
turn might give rise to an overestimate of potential health
Figure 5. Calibration line deriving the peak surface area for various known toluene concentrations.
Copyright © 2011 SciRes. JEP
Henry’s Equilibrium Partitioning between Ground Water and Soil Air: Predictions versus Observations879
Figure 6. Observed and pre dicted conce ntrations in the column air for different ground w ater concentrations measured after
10 hours. Data is provided for air concentrations with and without soil material present in the columns. The dotted line indi-
cates the average (mean) predicted air concentrations based on the Henry Law constants with the grey area representing the
variation. Whiskers indicate the 10% variation in the measured air concentration.
risk of toluene intrusion into buildings. While this might
be acceptable for screening level assessments, which
should be conservative [16,44-46], this is not acceptable
for estimates of real life risks. The latter should rather be
estimated on the basis of direct measurements of toluene
concentrations in indoor air and actual soil, water and
soil gaseous phase contamination. The findings presented
also indicate the need to improve current VI algorithms.
Such improvement might be based on a simple descrip-
tion of the relevant intermolecular interactions could as
described by [34].
5. Conclusions
This paper shows that column experiments which ex-
clude soil show a toluene fugacity behaviour roughly in
line with Henry’s law whereas column experiments
which include soil material result in around one or-
der-of-magnitude lower air concentrations after reaching
equilibrium than was expected on the basis of Henry’s
It is concluded that for toluene inclusion of Henry’s
Law in VI algorithms does not provide an adequate de-
scription of experimental data and may lead to an overes-
timation of health risk. Instead, a model based on a sim-
ple description of the relevant intermolecular interactions
could be explored.
[1] J. Kliest, T. Fast, J. S. M. Boley, H. van de Wiel and H.
Bloemen, “The Relationship between Soil Contaminated
with Volatile Organic Compounds and Indoor Air Pollu-
tion,” Environment International, Vol. 15, No. 1-6, 1989,
pp. 419-425.
[2] J. C. Little, J. M. Daisey and W. W. Nazaroff, “Transport
of Subsurface Contaminants into Buildings. An Exposure
Pathway for Volatile Organics,” Environmental Scientific
Technology, Vol. 26, No. 11, 1992, pp. 2058-2066.
[3] F. D. Tillman and J. W. Weaver, “Temporal Moisture
Content Variability Beneath and External to a Building
and the Potential Effects on Vapour Intrusion Risk As-
sessment,” Science of the Total Environment, Vol. 379,
2007, pp. 1-15.
[4] M. B. Kaplan, P. Brandt-Rauf, J. W. Axley, T. T. Shen
and G. H. Sewell, “Residential Releases of Number 2
Fuel Oil: A Contributor to Indoor Air Pollution,” Ameri-
can Journal of Public Health, Vol. 83, No.1, 1993, pp.
[5] D. Fugler and M. Adomait, “Indoor Infiltration of Vola-
tile Organic Contaminants: Measured Soil Gas Entry
Rates and Other Research Results from Canadian
Copyright © 2011 SciRes. JEP
Henry’s Equilibrium Partitioning between Ground Water and Soil Air: Predictions versus Observations
Houses,” Journal of Soil Contamination, Vol. 6, No. 1,
1997, pp. 9-13. doi:10.1080/15320389709383542
[6] D. A. Olson and R. L. Corsi, “Fate and Transport of Con-
taminants in Indoor Air,” Journal of Soil and Sediment
Contamination, Vol. 11, No. 4, 2002, pp. 583-601.
[7] F. A. Swartjes, “Evaluation of the Variation in Calculated
Human Exposure to Soil Contaminants Using Seven Dif-
ferent European Models,” Human and Ecological Risk
Assessment, Vol. 15, No. 1, 2009, pp. 138-158.
[8] M. C. Underwood, “Assessing the Indoor Air Impact
from a Hazardous Waste Si te: A Case Study,” Toxicology
and Industrial Health, Vol. 12, No. 2, 1996, pp. 179-188.
[9] B. Eklund, D. Folkes, J. Kabel and R. Farnum, “An Over-
view of State Approaches to Vapor Intrusion,” Environ-
mental Manager, Air & Waste Management Association,
February 2007, pp. 10-13.
[10] J. F. Foster and B. D. Beck, “Basement Gas: Issues Re-
lated to the Migration of Potentially Toxic Chemicals into
House Basements from Distant Sources,” Advanced Mod-
elling Environmental Toxicology, Vol. 25, 1998, pp.
[11] S. Chowdhury and S. L. Brock, “Indoor Air Inhalation
Risk Assessment for Volatiles Emanating from Light
Nonaqueous Phase Liquids,” Soil and Sediment Con-
tamination, Vol. 10, No. 4, 2001, pp. 387-403.
[12] M. J. Moran, J. S. Zogorski and P. J. Squllace, “Chlorin-
ated Solvents in Groundwater of the United States,” E nvi-
ronmental Science and Technology, Vol. 41, No. 1, 2007,
pp. 74-81. doi:10.1021/es061553y
[13] J. Roy and G. Bickerton, “Proactive Screening Approach
for Detecting Groundwater Contaminants along Urban
Streams at the Reach-Scale,” Environmental Science and
Technology, Vol. 44, No. 16, 2010, pp. 6088-6094.
[14] D. R. Williams, J. C. Paslawski and G. M. Richardson,
“Development of a Screening Relationship to Describe
Migration of Contaminant Vapours into Buildings,” Jour-
nal of Soil Contamination, Vol. 5, No. 2, 1996, pp.
141-156. doi:10.1080/15320389609383519
[15] T. McAlary, J. Provoost and H. Dawson, “Chapter
10—Vapour Intrusion,” In: F. Swartjes, Ed., Dealing with
Contaminated SitesFrom Theory towards Practical
Application, Springer Publishers, Netherlands, January
2011, pp. 409-453.
[16] J. Provoost, F. Tillman, J. Weaver, L. Reijnders, J.
Bronders, I. Van Keer and F. Swartjes, “Chapter 2 Va-
pour Intrusion into Buildings—A Literature Review,” In:
J. A. Daniels, Ed., Advances in Environmental Research,
Nova Science Publishers Inc., New York, 2010, pp.
[17] R. J. Millington, “Gas Diffusion in Porous Media,” Sci-
ence, Vol. 130, No. 3367, 1959, pp. 100-102.
[18] H. L. Penman, “Gas and Vapour Movements in Soil I, the
Diffusion of Vapours through Porous Solids,” Journal of
Agricultural Science, Vol. 30, 1940, pp. 463-462.
[19] W. W. Nazaroff, “Radon Transport from Soil to Air, Re-
view of Geophysics,” American Geophysical Union, Vol.
30, No. 2, 1992, pp. 137-160.
[20] W. A. Jury, W. F. Spencer and W. J. Farmer, “Behavior
Assessment Model for Trace Organics in Soil: I. Model
Description,” Journal of Environmental Quality, Vol. 12,
No. 4, 1983, pp. 558-563.
[21] J. A. Currie, “Movement of Gases in Soil Respiration,
Sorption and Transport Processes in Soils,” SCI Mono-
graph Series, Vol. 37, 1970, pp. 152-171.
[22] R. J. Millington and J. P. Quirk, “Permeability of Porous
Solids,” Transactions of the Faraday Society, Vol. 57,
1961, pp. 1200-1207. doi:10.1039/tf9615701200
[23] W. Malesinski, “Azeotropy and Other Theoretical Prob-
lems of Vapour-Liquid Equilibrium,” InterScience, 1965,
pp. 222.
[24] W. F. Spencer, M. M. Cliath, W. A. Jury and L. Z. Zhang,
“Volatilization of Organic Chemicals from Soil as Re-
lated to their Henry’s Law Constants,” Journal Environ-
mental Quality, Vol. 17, No. 3, 1988, pp. 504-509.
[25] J. E. Dunn and T. Chen, “Critical Evaluation of the Dif-
fusion Hypothesis in the Theory of Porous Media Volatile
Organic Compound (VOC) Sources and Sinks,” In: N. L.
Nagda, Ed., Modelling of Indoor Air Quality and Expo-
sure, American Society for Testing and Materials, Phila-
delphia, 1993, pp. 64-80.
[26] A. L. Robinson, R. G. Sexto and W. J. Fisk, “Soil-Gas
Entry into an Experimental Basement Driven by Atmos-
pheric Pressure Fluctuations—Measurements, Spectral
Analysis, and Model Comparison,” Atmospheric Envi-
ronment, Vol. 31, No. 10, 1997, pp. 1477-1485.
[27] A. L. Robinson, R. G. Sexto and W. J. Riley, “Soil-Gas
Entry into an Experimental Basement Driven by Atmos-
pheric Pressure Fluctuations—The Influence of Soil
Properties,” Atmospheric Environment, Vol. 31, No. 10,
1997, pp. 1487-1495.
[28] J. Grifoll and Y. Cohen, “Chemical Volatilization from
the Soil Matrix—Transport through the Air and Water
Phases,” Journal of Hazardous Materials, Vol. 37, No. 3,
1994, pp. 445-457. doi:10.1016/0304-3894(93)E0100-G
[29] R. L. Scott, “Azeotropy and Other Theoretical Problems
of Vapour-Liquid Equilibrium,” Journal of American
Chemistry Society, Vol. 88, No. 21, 1966, pp. 5053.
[30] K. U. Goss, “Adsorption of Organic Vapours on Polar
Mineral Surfaces and on a Bulk Water Surface: Devel-
opment of an Empirical Predictive Model,” Environ-
mental Science and Technology, Vol. 28, No. 4, 1994, pp.
640-645. doi:10.1021/es00053a017
[31] K. U. Goss, “Effects of Temperature and Relative Hu-
midity on the Sorption of Vapours on Quartz Sand,” En-
vironmental Science and Technology, Vol. 26, No. 11,
1992, pp. 2287-2294. doi:10.1021/es00035a030
[32] K. U. Goss and S. J. Eisenreich, “Adsorption of VOCs
Copyright © 2011 SciRes. JEP
Henry’s Equilibrium Partitioning between Ground Water and Soil Air: Predictions versus Observations
Copyright © 2011 SciRes. JEP
from the Gas Phase to Different Minerals and a Mineral
Mixture,” Environmental Science and Technology, Vol.
30, No. 7, 1996, pp. 2135-2142. doi:10.1021/es950508f
[33] K. U. Goss, J. Buschmann and R. P. Schwarzenbach,
“Linear Free Energy Relationships Used to Evaluate
Equilibrium Partitioning of Organic Compounds,” Envi-
ronmental Science and Technology, Vol. 35, No. 1, 2001,
pp. 1-9. doi:10.1021/es000996d
[34] K. U. Goss, “The Air/Surface Adsorption Equilibrium of
Organic Compounds under Ambient Conditions, Critical
Reviews,” Environmental Science and Technology, Vol.
34, No. 4, 2004, pp. 339-389.
[35] K. U. Goss, J. Buschmann and R. P. Schwarzenbach,
“Adsorption of Organic Vapours to Air-Dry Soils: Model
Predictions and Experimental Validation,” Environmental
Science and Technology, Vol. 38, 2004, pp. 3667-3673.
[36] J. Provoost, J. Nouwen, C. Cornelis, G. Van Gestel and R.
Engels, Technical Guidance Document, Part 4—Back-
ground Document for Chemical Properties and Specifica-
tions, Advise on Behalf of the Flemish Public Waste
Agency OVAM, Dutch, 2004.
[37] D. Mackay, W.-Y. Shiu, K. C. Ma and S. C. Lee, “Hand-
book of Physical-Chemical Properties and Environmental
Fate for Organic Chemicals,” Second Edition, Vol. 1-4,
CRC Press, 2006.
[38] S. Matula, M. Mojrova and K. Spongrova, “Estimation of
the Soil Water Retention Curve (SWRC) Using Pe-
dotransfer Functions (PTFs),” Soil and Water Research,
Vol. 2, No. 4, 2007, pp. 113-122.
[39] ASTM, “Astm Standard C136-06 Standard Test Method
for Sieve Analysis of Fine and Coarse Aggregates,”
ASTM International, West Conshohocken, PA, 2006.
[40] R. B. Brown, “Soil Texture,” Fact Sheet SL-29, Institute
of Food and Agricultural Sciences, University of Florida,
[41] ASTM, “ASTM Standard D2974-07a Standard Test
Methods for Moisture, Ash, and Organic Matter of Peat
and Other Organic Soils,” ASTM International, West
Conshohocken, PA, 2007. doi:10.1520/C0136-06
[42] US EPA, Compendium of Methods for the Determination
of Toxic Organic Compounds in Ambient Air, Second
Edition, Compendium Method TO-15, Determination of
Volatile Organic Compounds (VOCs) in Air Collected in
Specially-Prepared Canisters and Analyzed by Gas
Chromatography/Mass Spectrometry (GC/MS), Center
for Environmental Research Information, Office of Re-
search and Development, U.S. Environmental Protection
Agency, Cincinnati, 1999.
[43] S. W. Webb and K. Pruess, “The Use of Fick’s Law for
Modeling Trace Gas Diffusion in Porous Media,” Trans-
port in Porous Media, Vol. 51, 2003, pp. 327-341.
[44] J. Provoost, L. Reijnders, F. Swartjes, J. Bronders, P.
Seuntjens and J. Lijzen, J, “Functionality and Accuracy of
Seven Vapour Intrusion Screening Models for VOC in
Groundwater,” Journal of Soil s and Sedi ment sProtection,
Risk Assessment, and Remediation, Vol. 9, 2008.
[45] J. Provoost, A. Bosman, L. Reijnders, J. Bronders, K.
Touchant and F. Swartjes, “Vapour Intrusion from the
Vadose Zone—Seven Algorithms Compared,” Journal of
Soils and SedimentsProtection, Risk Assessment, and
Remediation, 2009. doi:10.1007/s11368-009-0127-4
[46] P. C. Johnson, M. W. Kemblowski and R. L. Johnson,
“Assessing the Significance of Subsurface Contaminant
Vapour Migration to Enclosed Spaces: Site-Specific Al-
ternatives to Generic Estimates,” Journal of Soil Con-
tamination, Vol. 8, 1999, pp. 389-421.