Environmental Exposure Assessment Environmental Fate Processes and Exposure

Modelling

Michael Matthies

Institute of Environmental Systems Research

University of Osnabrück, D-49069 Osnabrück

E-mail: matthies@uos.de

USF

Content

Introduction Basic Assumptions Environmental Fate Processes

- Partitioning- Transport- Transformation

Single Medium Modelling Intermedia Exchange Processes Multimedia Modelling Application and Applicability (Refined Approach)

Risk assessment

Effects assessmentExposure assessment

Risk characterisationRisk = f(Exposure,Effects,Probability)

Risk management

PEC

PEC / PNEC 1 ?

PNEC

Exposure ModellingAn exposure model converts a mass load [kg/a] into an

environmental concentration (PEC) [kg/m3].

Release estimation

Physico-chemical properties

Environmental fate processes

Exposure Model

Predicted Environmental Concentration (PEC)

Release, Distribution and Fate

Primary environmental

medium

Multimedia environment

Water

Air

Soil

Biota

Anthropo-sphere

Release Distribution

Local Scale Regional to global scale

Point or diffuse release

Environmental media can be defined in such a manner as to represent phases or mixtures of phases in a thermodynamic sense.

Rules and laws of chemical equilibrium and kinetics can be applied to environmental systems.

Feedback of toxic effects on organisms on the chemicals’ fate is neglected.

No mixtures, only single compounds are considered. Interaction between components of mixtures are therefore also not regarded.

Usually, only molecular-dispersively dissolved compounds and no separate phases of compounds are considered.

Environmental Fate Process ModellingBasic assumptions

Environmental Fate Processes

An environmental fate or chemodynamic process is the quantitative or qualitative change of a substance with time due to environmental factors. This can be a change of- mass,- concentration, - chemical structure, or- any substance property.

Chemodynamic points out the dynamic nature of processes involved.

Environmental Fate Processes

Partitioning- partitioning between two phases, e.g. air and water,- ad/desorption on particles,- uptake into lipid phases.

Transport- mixing and dilution,- ad/convection, - diffusion,- dispersion.

Transformation- photolysis and photochemical degradation,- hydrolysis,- microbial biotic degradation- metabolic transformation.

Partitioning

Environment is divided into non-mixable phases— Air, surface water, soil, sediment, ground water, plants, etc.

— Chemicals are partitioning into all or several phases in thermodynamic equilibrium.

Partition coefficients— partitioning of a substance between two phases.

— dependent on substance and phase properties.

— partition coefficient phase i and j:

j

iij C

CK

KOAKAW

KOW

Lipids (octanol)

Air

Water

Interdependence of physical-chemical properties

m olar m assM

m elting pointM P

air-waterpartition ing

K AW

octanol-waterpartition ing

K OW

watersolubility

W S

vapourpressure

VP

org. C -waterpartition ing

K OC

TRWS

MVP

TR

HenryKAW

1

KKmolJlmg

molgPa111

1 1

Transport and transformation processes

Diffusion— microscopic (molecular) isotropic random movement and mixing of

molecules (Brown’s molecular movement)

— based on 2nd law of thermodynamics (entropy)

— property of the molecule and the surrounding medium

Advection— directed flow of a medium, e.g. water or air flow

— based on 1nd law of thermodynamics (energy conservation)

— e.g. a substance is transported downstream by the flowing of a river

Dispersion— macroscopic flow dynamic process, occurs only in moving media

— orders of magnitudes faster than diffusion

— turbulent mixing (eddy diffusion)

Transport and Transformation Processes

diffusion/dispersion2

2

2

2

)(x

CDD

x

CD

t

CDispDiff

advectionx

Cu

t

C

degradation 1. orderCt

C

combinationof all processesC

x

Cu

x

CD

t

C

2

2

Fate processes in water

advection

volatilisationdischarge

deposition of particles (sedimentation)

degradation

Fate processes in water

Sorbed and dissolved fraction— deposition of particles (only sorbed fraction)

— volatilisation (only dissolved fraction)

— bioconcentration (only dissolved fraction)

Bioconcentration in fish— regression model:

— no biomagnification

fW = f (particle concentration, OC-content, KOC)

10log672,4log74,2log20,0

6log170,0log85,0log

2OWOWOW

OWOW

KKK

KKBCF

BCFCC WasserFisch

Example: Bioconcentration

Mass Distribution in the System Fish - Water

1,6

98,4

0

10

20

30

40

50

60

70

80

90

100

0 50 100 150 200 250 300 350 400

time (h)

KFW = 60____ k1 = 0.0001 1/h___ k2 = 0.006 1/h

--- k1 = 0.001 1/h--- k2 = 0.06 1/h

Water

Fish

Fate processes in water

Volatilisation— diffusive mass transfer between air and water

— two-films theory

— two serial resistances

Sedimentation— (effective) sedimentation velocity of particles

— diffusive mass transfer into sediment pore water

— sediment burial

Degradation— hydroloysis

— aquatic photolysis

— microbial degradation

Fate processes in air

atmospheric discharges— area sources (e.g. urban area or pesticide spraying)

— multi-point sources (e.g. stack or vent)

gas-particle distribution— sorption of gaseous compounds to particles

— dry and wet deposition of gaseous and particle-bound fraction

— Pankow-Junge equation:

— calculated particle-bound fraction:

Benzene: 0%, DEHP: 5%, TCDD: 32%, OCDD: 99%

VPL vapour pressure of sub-cooled liquidc Junge-‘constant‘ (ca. 17 [Pacm])s particle surface (ca. 1,5E-6 [cm²/cm³])scVP

scf

LPa

Fate processes in air

xyzxyvyzu

IC

dep

concentration = input / (advection + deposition + degradation)

Degradation

Deposition

Advection

Input (Area Emission)

x

z

y

stea

dy st

ate!

Fate processes in soil

Three input scenarios— puls input

— continuous substance input

— contaminated upper soil layer

Analytical solution— homogeneous vertical soil profile

— average continuous water input and output (generic scenario)

— water flow u and hydrodynmanic D are constant

— u.v.a.

Mathematical model

Cz

CD

z

Cu

t

C

2

2

z

Precipitation and evaporation

degradation

diffusion unddispersion

advectionu

D

Leaching

Plant model

Above ground plant parts

roots

degradation and growth

diffusion soil/roots

Wet and dry particle deposition

gaseous exchange

stem leaves

fruit

roots

Plant uptake model in EUSES

Cl8

Cl7

Cl4

Cl6 Cl5

Cl6

Cl6

28

180

52

153

101

1,E-10

1,E-09

1,E-08

1,E-07

1,E-06

1,E-05

1,E-04

1,E-03

1,E-10 1,E-09 1,E-08 1,E-07 1,E-06 1,E-05 1,E-04 1,E-03

Predicted conc. [mg/kg]

Me

asur

ed

conc

. [m

g/k

g]

TC D D -H xC D D

PC B 28-52PC B 101-180

H pC D DO C D D

med

ian

max

min

Transport for Multimedia Pollutants

Water

Sediment

Surface soil

Air

Root-zone soil

Roots

Leaves

Deep soil

Gases

Particles

— A compartment (or box) is a well-mixed component of a system.

— Differential mass balance: change of mass = dm/dt = Input - Output;

— linear differential equations e.g. dm1/dt = - k1m1 + k2m2 + I

— A multi-compartment model consisting of various different environmental media is a multimedia model.

Multimedia Exposure ModellingMass Balance Approach

m1 m2I

fat(octanol)

KOAKAW

KOW

air

water

Equilibrium and steady state

equilibrium— thermodynamic equilibrium in closed system

— immediate equilibration in open system

steady state in open systems— no mass change with time: dm/dt = 0

— Input = Output

I O

Unit World— generic global environment

— 1 km² area, 6 km height, 70% water, 30% soil

Fugacity concept— introduced for real gases to account for molecular interactíons; applied to all

other environmental media

— escaping tendency of a chemical

— dependency of partition coefficients on fugacity

(in equilibrium)j

i

jj

ii

j

iij Z

Z

Zf

Zf

C

CK

concentration = fugacity • fugacity capacitymol / m³ = Pa • mol / (m³ Pa)ZfC

Multi media models (Mackay,1991)

I

II

III & IV

Multi media models Level I - IV

Closed system:phase equilibrium (partition coefficients)

Open system:same as Level I but with advective input and output and degradation in steady-state

Open system:same as Level II but with interphasemass transfer non equilibriumLevel III: steady-stateLevel IV: non steady-state

fish

air

water

soil

sediment

plants

Multi-media models Form the environment to compartments

Background— ubiquitous occurrence of chemicals

— virtually all chemicals are distributed over various media due to advection and dispersion with wind and water partitioning between phases

Multi media modelwith 4 compartments (Unit World)

Water0.7 km² • 10 m= 7 • 106 m³

Sediment0.7 km² • 3 cm= 2.1 • 104 m³

Soil0,3 km² • 15 cm= 4.5 • 104 m³

Air1 km² • 6 km= 6 • 109 m³

Illustration of Level I and II model

f = fugacityZ = fugacity capacityV = volume

C = f·ZM = C·V = f·Z·V

Input

air water soil

Z

Output

Level I: no input and outputLevel II: with input and output

Multi-media modelsLevel I example calculation (Unit World)

2,3,7,8 - TCDD LAS BENZENE

MW [g/mol] 322 348 78

logK OW [-] 6,8 2,0 2,1

VP [Pa] (25°C) 2,0E-07 0 12.700

WS [mg/l] (25°C) 1,9E-05 1.100 1.760

results [%]

Sediment Soil Water Air

run off

diffusionemission degradation

Natural soil

Air

Agricultural soil Industrial soil

Sediment

Water

Regional scale

Continental scale

indirect emissions (STP sludge)

dry and wet deposition

leaching

adsorption/volatilisation

air flow

water flow

advection

adsorption/desorption

burial

sedimentation/resuspensation

Regional emission and distribution model

Illustration of Level III

f = fugacityZ = fugacity capacityV = volume

= valve (== resistance)

Input

air

water

sediment

Z

Output

Output

Input

f

V

Input

European Union System for the Evaluation of Substances (EUSES)

Model structure

STP m odel

Level IIIM ulti-m edia

m odel

locald istribution

hum ans

worm /fish

R eleaseestim ation

Environm ental distribution Indirect exposure

Local emission and distribution pathways

All stagesoflife-cycle

Model optimizationModel and parameter uncertainties

level of detail / com plexity

error due touncerta inty

structura lerror

tota l error

Restricted Applicability

Polar substances Super lipophilic compounds Surfactants Heavy metals Polymers Complexes Metabolites Mixtures

Exposure and Risk Assessment Software

CemoS— „Chemical Exposure Model System“

— Compilation of nine exposure models; substance data base; estimation routines

— mainly for educational purposes

EUSES— „European Union System for the Evaluation of Substances“

— Official software for the risk assessment of chemicals in the EU

— Based on Technical Guidance Document

CalTOX— 8-compartment multi-media programme; hazard and risk assessment

— recommended for the risk assessment of contaminated soil in California

— Excel-spreadsheet

Questions?

Decision support system EUSESParameters and Connectivity

D T 50b io water

C loca lairC std air

D ILU T IO N

k Plant

D E P T H i

Food chain I: Secondary poisoning

C inh

Q Prod

F c prod

V room

I inh

n

T contact

Ioral

C der

C oral

C prod

U to t

V prod

D

A der

V appl

T H der

A R E A der

U der,pot

W der

A m igr,der

F c m igr

F oral

T H art

A R E A art

C artC der,ann

C inh,ann

C oral,ann

a rt2

a rt2

a rt2

m ed .

a rt1

m ed .

a rt1

a rt2

a rt1

a rt2

m ed .

m ed.: substance con ta ined in a m ed iumart1 : non-vo la tile substance m igra ting from an a rtic leart2 : substance m igra ting from an a rtic le in to food o r d rink

Consum er Exposure

T em iss ion

R E LE A S E reg production,am ount used

R E LE A S E contprivate use,rest

kdeg stp

C loca leff

Sim ple Treat

T O N N A G E k

T O N N A G E reg

P R O D V O Lreg

P R O D V O Lcont

F m ainsource ii: p roduction , fo rm u la tion , p rocess ing ,

p riva te use , recove ry

F connec tstp

K air-water

khydrwater

kpho to water

D T 50hydrwater

kdeg water

kb io water

kab io soil

D T 50b io -aersed

Sim pleBox

K p RS

K p PS

K p A

K p SLS

H E IG H T air

R A IN R A T E

R E LE A S E contproduction,j

j: a ir, water, ind, agric, surf,to ta l

F production, j

j: a ir,water,ind,agric,surf

F form ulation, j

j: a ir,water,ind,agric,surf

F processing, j

j: a ir,water,ind,agric,surf

F private use, j

j: a ir,water,ind,agric,surf

F recovery, j

j: a ir,water,ind,agric,surf

R E LE A S E cont form ulation,jj: a ir, water, ind, agric,

surf,to ta l,rest

R E LE A S E contprocessing,jj: a ir, water, ind, agric,

surf,to ta l,rest

R E LE A S E contprivate use,j

j: a ir, water, ind, agric, surf,to ta l

R E LE A S E cont recovery,j

j: a ir, water, ind, agric, surf,to ta l

R E LE A S E contproduction,am ount used

A -T ab les

B -T ab les

F LO W water*

P E C oral,wormi=agric

R E LE A S E reg private use,rest

B IO T A water

K oc

K plant-water

F a irplant

F lip id plant

F w ate rplant

b

F oc soil g plant

R H O plan t

A R E A plant

Q transp

V leafK leaf-a ir

T S C F

F ass aer

C leaf;C grass

i=grassland; agric

C root

B C F Fish

C fish

IC grass

IC soil

C O N V grass

IC dw tgrass

IC dw tsoil

C drwF pur

D O S E drw,fish,leaf

,

root,m eat,m ilk

B A F m eatB A F m ilk

H E N R Y

K ow

V P

S O L

T E M P bo il

T E M P m elt

kb io stp

kab io stp

E stp air

C sludge

P E C stp

E stp -reg air

E stp -reg water

E stp -reg agric

E stp -con tair

E stp -con twater

E stp -con tagric

H R T PS

D E P T H PS

R H O RS

S O LID S

B O D

C A S

D E P T H A

R H O PS

R H O A

C O X

G

D E P T H SLS

R H O SLS

H R T SLS

Q stp

N *

k SLR

T E M P stp air

T E M P stp water

M

W IN D S P E E D

P R O D V O L

T O N N A G EE X P O R T

IM P O R T

F tonnage k

F prodvo l reg

T O N N A G E cont

T O N N A G E reg form

F chem form

E loca l i,ji: p roduction , fo rm u la tion , p rocess ing , p riva te use ,

recove ryj: a ir, w a te r

T em iss ion ii: p roduction , fo rm u la tion , p rocess ing ,

p riva te use , recove ry

E cont jj: a ir, ind

R ho Soil

R ho water

R ho Air

R ho Solid

F so lid soil

F w ate rsoil

F a irsoil

R ho Sed

R ho Susp

F so lid susp

F so lid sed

F w ate rsusp

F w ate rsedC O N V sed

C O N V soil

C O N junge

S U R F aer

V P L

T E M P

R

K p susp

K p Sed

K p Soil

F oc susp

F oc sed

K soil-water

K susp-water

K sed-water

k O H kdeg air

D T 50photo water

O H C O N C air

D T 50b io soil kb io soil

kdeg soil

kb io -aersed

kdeg sed

F aerSed

kb io -anaersed

kab io sed

F Resp

IH air

IH drw

IH fish

IH leaf

IH root

IH m eat

IH m ilk

B W

B IO inh

B IO oral

P E C contwater,to t

P E C contwater

P E C contair

P E C contagric

P E C contagric,porew

P E C contnatura l

P E C cont ind

P E C contsed

P E C reg water, to t

P E C reg air

P E C reg agric

P E C reg agric, porew

P E C reg natura l

P E C reg ind

P E C reg sed

A R E A *

D E P R A T E aer

C O LLE F F aer

F water *

D E P T H water *

F flow out reg

S U S P water *

D E P T H sed

S E T T LR A Tsusp

S U S P P R O Dwater

S U S P eff

F ind *

F runo ffsoil

F agric *

E R O S IO N

F in fsoil

F natura l *

kas lsoila ir

kas lsoilwater

kw s water

kaw air

kaw water

kw s sed

C m eat;C m ilk

i=grassland

B IO der

D O S E air D O S E to t

C loca l in fE F F LU E N T loca lstpN loca l

F s tp air

F stp -reg air

F stp -reg water

F stp -reg agric

F stp -con tair

F stp -con twater

F stp -con tagric

H P V C

IN D C A T

U S E C A T

M A IN C A T

E contwater

E contdirect-water

j:surf,water

E reg water(j: water)

R E LE A S E reg production,j

j: a ir, water, ind, agric, surf,to ta l

R E LE A S E reg form ulation,jj: a ir, water, ind, agric,

surf,to ta l,rest

R E LE A S E reg processing,jj: a ir, water, ind, agric,

surf,to ta l,rest

R E LE A S E reg private use,j

j: a ir, water, ind, agric, surf,to ta l

R E LE A S E reg recovery,j

j: a ir, water, ind, surf,to ta l

E reg j

j: a ir,ind

E reg direct-water

j:surf,water

E loca lwater

F oc RS

F oc PS

F oc A

F oc SLS

W IN D S P E E D T A U air *

R A IN D IR E C T *

R U N O F F *

T A U water *

N E T sedra te *

E F F LU E N T stp *

P E C reg water

B C F biota

E loca lair

C loca lair,ann

P E C loca lair,ann

D E P to ta l D E P to ta lann

F A S S aer

D E P std aer

C loca lwater C loca lwater,ann

F LO W

P E C loca lwater,ann

P E C loca lwater

P E C loca lsed

k volat i

kas lair

k leach i

k i

D air i

C dep10 i

C sludge1 iA P P Ls ludge i

F acc i

C sludge10 i

C loca l10 i

C loca l i

T i

P E C loca l i P E C loca l i, porew

F st-s t i

C in f i

P E C loca lgrwi=agric

P E C oral,fish

K worm -porew B C F worm

T A B III-6

T A B III-7

T A B III-7

C inh, worker, vapourT E M P w ork

C 1 inh, worker, vapour

U der,pot,workerW der, workerA R E A der, worker

W orkplace Exposure

kgrow th plant

ke lim plant

km etab plant IC drw

IC air

Food Chain II: Indirect exposure of hum ans via the environm ent

i=so il; agric; grassland Local environm ental d istribution

Em ission part

M O LW

D T 50b io stp

n worker

EASE

D E P std gas

F LO W air*

D R Y D E P aerosol

W A S H O U T

S C A V ra tio

W A S T E W *

G A S A B S w ater

G A S A B S so il

V O LA T w ater *

F d iss lvd water *

V O LA T so il

A D S O R B sed *

D E S O R B sed *

G R O S S sedra te *

R E S U S P ra te *

S E D R A T E *

LE A C H so il

C reg natura l

C reg agric

C reg ind

C reg air

C reg water

C reg sed

Literature

Trapp,S., Matthies,M.: Chemodynamics and Environmental Modeling - An Introduction, Springer, Heidelberg, 1997

Trapp,S., Matthies,M.: Dynamik von Schadstoffen - Umweltmodellierung mit CemoS, Springer, Heidelberg, 1996

Thibodeaux,L.: Environmental Chemodynamics: movement of chemicals in air, water and soil (2. Aufl.), Wiley, New York, 1996

Klöpffer, W.: Verhalten und Abbau von Umweltchemikalien - Physikalisch chemische Grundlagen, ecomed, Landsberg, 1996

Mackay,D.: The Fugacity Approach - Multimedia Environmental Models, Lewis Pub., Michigan, 1991

van Leeuwen,C., Hermens,J.: Risk Assessment of Chemicals - An Introduction, Kluwer Acad. Publ., Dordrecht, 1995

Exposure Assessment

release estimation

physico-chemical properties

environmentalparameters

Exposure Model

Predicted Environmental Concentration (PEC)

Flow dynamic approach— Based on first physical principles of mass and energy conservation and

entropy changes.

— Flow dynamics in atmosphere, ground and surface water etc.

— Partial differential equations, which usually have to be solved numerically.

— Examples: global circulation model, groundwater transport.

Mass balance approach— Similar to the pharmaco-kinetic models for drugs.

— Same approach as in cost accounting or demographic models.

— Based on exchange of matter between compartments and reaction kinetics.

— Linear differential equations, which can be solved analytically or numerically.

— Examples: Multi-media models of Mackay; (bio-)reactor models.

Exposure ModellingTwo Approaches

Plant model

Model assumptions— roots: Gleichgewichtsverteilung mit dem Boden

— leaves: gewöhnliche Differentialgleichung

Benötigte Daten— 10 pflanzenspezifische Parameter: Blattoberfläche, Wachstumsrate, etc.

— 2 Konzentrationen: Bodenwasser und Luft (Gasphase)

— 1 substanzabhängiger Parameter (logKOW)

Transferpfade— Quelle - Luft - Blätter

— Quelle - Boden - Wurzel

— Quelle - Boden - Luft (Ausgasung, Resuspension) - Blätter

Alternative Modellierungsansätze— Biokonzentrationsfaktoren

— Mehr-Kompartimentmodelle

Aquatic Bioconcentration model in EUSES

1,E-04

1,E-03

1,E-02

1,E-01

1,E+00

1,E+01

1,E+02

1,E-04 1,E-03 1,E-02 1,E-01 1,E+00 1,E+01 1,E+02

Predicted conc. [mg/kg]

Me

asur

ed

conc

. [m

g/k

g]

m ax

m in

uncerta inty analysism edian

DEHP

PCB

101-180 (eel)28-52 (eel)101-18028-52

Illustration of Level I model

f = fugacityZ = fugacity capacityV = volume

C = f·Zm = C·V = f·Z·V

V

Air Water Soil

Z

f