Chemical Distribution, Fate and 

Transport in the Environment

September 10, 2014

Jaeshin Kim and Gary E. Kozerski

Dow Corning Corporation
Acknowledgement

• Dr. David E. Powell (Dow Corning Co.)

• Dr. Don Mackay and Lauren Hughes (Trent University, Canada)

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Outline

• Background: Why do we need multimedia models?

• Introduction to the EQC model and recent update

• Applications of New EQC model

• Summary
What Do We Want to Know?

Distribution and 

important fate processes 

for different chemicals

Overall persistence (P)

Environmental 

concentrations and 

exposures

Potential for long range 

transport (LRT)

Bioaccumulation in 

organisms and food webs

Evaluation of likely 

recovery times of 

contaminated 

environments

Checking the consistency 

of monitoring data

Screening and prioritizing 

chemicals

Documenting the sources 

and nature of 

contamination and 

feasible remedial 

strategies

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Without 

Modeling

Why Do We Need Multimedia Modeling?

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Chemical 

Fate, 

Transport & 

Distribution

Chemical

Properties

Environment

Properties Emissions 

Scenarios

Environmental 

Exposure

Difficult to survey the set of properties 

and predict environmental behaviors of 

chemicals

Difficult to conceive how environmental 

assessments can be done consistently 

and openly without modeling
The EQC (Equilibrium Criterion) Model (Mackay et al. 1996)

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Mackay D., S. Paterson , A. Di Guardo, and C.E. Cowan. 1996. Evaluating the environmental fate of types of chemicals using the EQC model. Environ. Toxicol. 

Chem. 15:1627-1637.

McKone T.E. 1993. CalTox, a multi-media total-exposure model for hazardous waste sites part II the dynamic multi-media transport and transformation model. 

A report prepared for the State of California, Department Toxic Substances Control by the Lawrence Livermore National Laboratory No. UCRL-CR-111456PtII. 

Livermore, CA.

EC (1996). EUSES, the European Union System for the Evaluation of Substances. National Institute of Public Health and the Environment (RIVM), the 

Netherlands. Available from the European Chemicals Bureau (EC/JRC), Ispra, Italy.

• Based on fugacity-based mass balance

• Prediction of mass distribution, persistence and rates of transport 

and transformation

• Not site-specific but an evaluative standard environment

• Internationally used for regulation purposes

• Imbedded in EPI SuiteTM (US EPA)

– “Fugacity” Tab

• Similar models

– CalTox (McKone et al. 1993)

– SimpleBox (EUSES, EC 1996)
Level 1: Equilibrium

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Soil

Air

Water

Sediment

No degrading reactions

No advective processes

No intermedia transport processes

The equilibrium distribution of a fixed 

quantity of conserved chemical, in a closed 

environment at equilibrium
Level 2: Steady-state and Equilibrium

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Soil

Air

Water

Sediment

A

A

A

R

R

R

R

E

A chemical is continuously 

discharged at a constant rate 

and achieves a steady-state 

and equilibrium condition at 

which the input and output 

rates are equal. 

Degrading reactions and advective processes are the 

loss or output processes treated. 

Intermedia transport processes (e.g. wet deposition, 

or sedimentation) are not quantified.
Level 3: Steady-state and Non-Equilibrium

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Soil

Air

Water

Sediment

A

A

A

R

R

R

R

E

E

E

A chemical is continuously 

discharged at a constant rate 

and achieves a steady state 

condition in which input and 

output rates are equal. 

The loss processes are degrading reactions and 

advection. 

A mass balance applies to the system as a whole, as 

well as to each compartment. 

Rates of intermedia transport are calculated using D 

values which contain information on mass transfer 

coefficients, areas, deposition and resuspension 

rates, diffusion rates, and soil runoff rates. 
EQC Model Update

• More flexible input entries

– Chemical properties

– Emission scenarios

– Sensitivity/uncertainty analysis

• Spreadsheet platform

• Publically available at CEMC website

– http://www.trentu.ca/academic/aminss/envmodel/models/NewEQCv101.html

• Publications

– Hughes, Lauren, Don Mackay, David E. Powell, and Jaeshin Kim. 2012. An updated state of the science 

EQC model for evaluating chemical fate in the environment: Application to D5 

(decamethylcyclopentasiloxane). Chemosphere 87 (2):118-124.

– Kim, Jaeshin, David E. Powell, Lauren Hughes, and Don Mackay. 2013. Uncertainty analysis using a 

fugacity-based multimedia mass-balance model: Application of the updated EQC model to 

decamethylcyclopentasiloxane (D5). Chemosphere 93 (5):819-829.

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Applications of New EQC to Hypothetical Chemicals

1. An Easy-to-Test Compound

1. Non-volatile

2. High water solubility

2. A Difficult-to-Test Compound, DTC1

1. Non-volatile

2. Low water solubility

3. High Log Kow and Log Koc

3. A Difficult-to-Test Compound, DTC2

1. Volatile

2. Low water solubility

3. Mid-high Log Koc

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Example 1: An Easy-to-Test Compound

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Physico-chemical properties Half-lives (hr)

• Henry's Law constant: 9.38E-04 Pa·m3/mol

• Log Kow: 2

• Log Koc: 2

• Log BCF: 2

• Air: 15.8

• Water: 360

• Soil: 720

• Sediment: 3,240

Total

Emission

Initial

Release

WWTP

AIR

(0%)

Sludge SOIL

(4%)

Effluent WATER

(96%)

Emission Scenario

100%

100%

0%

0%

100%

100%

4%

96%
Example 1: An Easy-to-Test Compound

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Soil

Air

Water

Sediment

0.005

329 kg/h

0.04

R

R

R

R

960 kg/h

40 kg/h

3.51 kg/h

Fugacity: 4.34E-11 Pa

Mass fraction: 0%

Concentration: 4.56E-12 g/m3

Fugacity: 5.31E-9 Pa

Mass fraction: 0.5%

Concentration: 3.85E-3 g/m3

Fugacity: 2.92E-9 Pa

Mass fraction: 10.3%

Concentration: 2.11E-13 g/m3

Fugacity: 6.17E-9 Pa

Mass fraction: 89.2%

Concentration: 1.65E-3 g/m3

0.11 kg/h

0.11 kg/h

0.03 kg/h

0.01 kg/h

1.89 kg/h 1.44 kg/h 36.5 kg/h

634 kg/h

0.41 kg/h

0.02 kg/h

Advection time: 1,121 h

Reaction time: 550 h

Overall persistence: 369 h

Total emission: 1,000 kg/h

Total mass: 3.69E5 kg
Example 2: A Difficult-to-Test Compound DTC1

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Physico-chemical properties Half-lives (hr)

• Henry's Law constant: 2.35 Pa·m3/mol

• Log Kow: 7.2

• Log Koc: 6.8

• Log BCF: 10,000

• Air: 2,450

• Water: 4,320

• Soil: 8,640

• Sediment: 38,900

Total

Emission

Initial

Release

WWTP

AIR

(0%)

Sludge SOIL

(90%)

Effluent WATER

(10%)

Emission Scenario

100%

100%

0%

0%

100%

100%

90%

10%
Example 2: A Difficult-to-Test Compound DTC1

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Soil

Air

Water

Sediment

0.22

24.7 kg/h

38.1

R

R

R

R

100 kg/h

900 kg/h

1.14 kg/h

Fugacity: 6.18E-10 Pa

Mass fraction: 0%

Concentration: 2.19E-10 g/m3

Fugacity: 2.12E-7 Pa

Mass fraction: 14.5%

Concentration: 3.81E0 g/m3

Fugacity: 2.78E-8 Pa

Mass fraction: 85.3%

Concentration: 6.23E-1 g/m3

Fugacity: 7.85E-8 Pa

Mass fraction: 0.19%

Concentration: 1.23E-4 g/m3

0.01 kg/h

0.32 kg/h

0.58 kg/h

0.04 kg/h

110 kg/h 38.1 kg/h 899 kg/h

4.0 kg/h

33.9 kg/h

0.01 kg/h

Advection time: 208,657 h

Reaction time: 14,021 h

Overall persistence: 13,138 h

Total emission: 1,000 kg/h

Total mass: 1.31E7 kg
Example 3: A Difficult-to-Test Compound DTC2

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Physico-chemical properties Half-lives (hr)

• Henry's Law constant: 7.2×105 Pa·m3/mol

• Log Kow: 8.0

• Log Koc: 4.2

• Log BCF: 10,000

• Air: 250

• Water: 100

• Soil: 120

• Sediment: 9,000

Total

Emission

Initial

Release

WWTP

AIR

(94.8%)

Sludge SOIL

(4.7%)

Effluent WATER

(0.5%)

Emission Scenario

100%

10%

48%

90%

100%

100%

47%

5%
Example 3: A Difficult-to-Test Compound DTC2

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Soil

Air

Water

Sediment

776 kg/h

0.48 kg/h

0.01

R

R

R

R

5 kg/h

<0.001 kg/h

Fugacity: 4.18E-6 Pa

Mass fraction: 97.6%

Concentration: 7.76E-7 g/m3

Fugacity: 5.41E-3 Pa

Mass fraction: 0.70%

Concentration: 1.17E-3 g/m3

Fugacity: 1.51E-4 Pa

Mass fraction: 1.03%

Concentration: 4.55E-5 g/m3

Fugacity: 4.10E-3 Pa

Mass fraction: 0.60%

Concentration: 2.39E-6 g/m3

43.7 kg/h

1.39 kg/h

1.15 kg/h

0.002 kg/h

0.07kg/h 0.01 kg/h 4.73 kg/h

3.32 kg/h

0.05 kg/h

215 kg/h

Advection time: 102 h

Reaction time: 356 h

Overall persistence: 80 h

Total emission: 1,000 kg/h

Total mass: 7.95E4 kg

47 kg/h

948 kg/h
Comparison of Three Test Compounds

Compound Major 

compartment

Major loss 

mechanism

Major 

intermedia 

transport

Overall 

persistence

(h)

Easy-to-Test Water Degradation 

and advection 

in water

No significant 

transport

369

DTC1 Soil, 

Sediment

Degradation 

in soil

Water to 

sediment

13,138

DTC2 Air Degradation 

and advection 

in air

Soil to air 80

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Uncertainty Analysis

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Input uncertainty Output uncertainty Propagates

Probability density function

95% confidence interval

X1

X2

X3

Y = f(X1,X2,X3)

95% confidence interval

X1

X2 X3

Model

Contribution

Factors

to the variance
Example 3: A Difficult-to-Test Compound DTC2

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95% of log-normal distribution

Assumption Best Val. Disp. F Min Max Unit Distribution

Henry's Law Constant 7.14E+05 2 3.57E+05 1.43E+06 Pa.m3/mol 95% log-normal

Koc 2.00E+04 2 1.00E+04 4.00E+04 (L/kg) 95% log-normal

BCF 1.00E+04 2 5.00E+03 2.00E+04 95% log-normal

Half-life in air 250 3 83.3 750 hr 95% log-normal

Half-life in water 100 3 33.3 300 hr 95% log-normal

Half-life in soil 120 3 40.0 360 hr 95% log-normal

Half-life in sediment 9000 3 3000 27000 hr 95% log-normal

Uncertainty Analysis

Oracle Crystal Ball (v7.3.1)

Monte Carlo simulation

10,000 trials of random sets
95% Confidence Intervals and Contribution factors

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0%

20%

40%

60%

80%

100%

Air Water Soil Sediment

% of total mass

Mass distribution

0

200

400

600

Advection Reaction Overall

Persistence (hr)

Persistence

0.0%

2.0%

4.0%

6.0%

A→S A→W W→A W→Sed S→A S→W Sed→W % of total emission rate

Normalized emission rate Henry's Law Constant

Koc

BCF

Half-life in air

Half-life in water

Half-life in soil

Half-life in sediment

Normalized intermedia transport rates
Summary

• Multimedia environmental modeling like the EQC model is useful to 

predict chemical distributions, fate processes, exposure 

concentrations and overall persistence.

• The inputs of the EQC model (partition coefficients, half-lives and 

emission scenarios) are more easily entered with the recent 

update.

• Uncertainty analysis can provide confidence intervals of model 

outcomes and contributing factors.

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