clase 3-distribucion fases

7/31/2019 Clase 3-Distribucion Fases

1/41

Clase 3 Distribucin de

contaminantes entre fases

1

Destino y Transporte de Contaminantes II-2012

Prof. Jorge E. Pachon, Ph.D.


2/41

Properties of Chemicals: Aqueous

Solubility When a chemical is contacted with water for an extended

period of time, the chemical will enter the aqueous phase untilthe water is fully saturated with that chemical.

= Maximum saturation concentration of A in water (mol/Lor g/L)

For solid chemicals:

For gaseous chemicals:

Larger nonpolar organic contaminants have lower aqueoussolubility.

Inclusion of polar groups (OH-, NH2-)on the benzene ring resultsin higher solubility in water.

A

sat,wC

CT Asat,wenv

CT Asat,wenv

Prof. Jorge E. Pachon, Ph.D. 2



3/41

Properties of Chemicals: Vapor Pressure

Vapor pressure is the analog of aqueous solubility for the airsystem

Smaller nonpolar compounds are lighter and more readilyescape to the vapor phase

env

AA

satairRT

MWC

A

v,

P(g/L)airin theAofconc.saturation

PT Avenv

Antoine Equation

aT

b

env

303..2

PlogA

v




4/41

Henrys Law

4

Lmol

atmsHenry

A

/CPConstantLaw'KA

eqw,

eqair,A

H

Para gases inorgnicos

(O2, CO2)




5/41

Impacts of Environmental Factors on Cw,sat, Pv

and KH

Environmental Factors Impacts on Cw, sat Impacts on Pvand KH

Tenv increaseCw, satof solid increase

Pvand KH increaseCwof gas decrease

Aqueous salt conc.

increaseCw, satdecrease Pvand KH increase

Presence of co-dissolvedchemicals in water

Solubility increase Varies, depending onvolatility of the co-solvent

pH increaseWhen pH> pKa, aqueous

solubility increase

When pH> pKa, Pv and KHdecrease




6/41

Intermedia Equalibrium

5 L Air

5 L Water

5 L Benzene

Container:

5L air

5L water

5L benzene

Calculate

benzene

air

benzene

eq,air

benzene

water

benzene

eq,w

M,C

M,C




7/41

Partition Coefficient

At equilibrium, the balance in contaminantconcentration Cbetween two media iandjis

described by a partition coefficient:

Air-water exchange

Soil-water exchange

Octanol-water exchange

j

iij

C

CK Medium 1

Medium 2

iC

jC




8/41

Environmental Partitioning

water)A/Lof(masswaterinAofionconcentratmEquilibriu

soil)A/kgof(masssoilinAofionconcentratmEquilibriu

C

CK


octonal)A/Lof(massoctonalinAofionconcentratmEquilibriu

C

CK


air)A/Lof(massairinAofionconcentratmEquilibriu

C

CK

A

eqw,

A

eqsoil,A

d

Aeqw,

A

eqo,A

ow

A

eqw,

A

eqair,A

aw

The concept of environmental partitioning wasdeveloped to describe the distribution of a

contaminant between pairs of media.

We define three equilibrium partition coefficients:




9/41

Air-Water Partitioning

Contaminant concentrations in air are represented interms of partial pressure (atmospheres)

Aqueous concentrations of contaminants are inmass/volume (M L-3) units.

L/molC

atmPConstantLaws'HenryKwhere

RT

KK

A

eqw,

A

eqair,A

H

env

A

HA

aw




10/41

Henry's law constants ( KH)

In general, lighter (smaller)and more nonpolar organic molecules will

prefer air to water.

Figure 3.3 Prof. Jorge E. Pachon, Ph.D. 10



11/41

11


12/41

12


13/41

Water Equilibrium

10L Water 0.1 g

benzene

Container: 10L water

0.1g benzene

Calculate

Solution: saturated or insaturated?

benzene

satw

benzene

eqw CC ,,




14/41

Air-Water Partitioning Example

10 L Air

10L Water 0.1 g

benzene

Container: 10L air

10L water

0.1g benzene

Calculate

Solution: using 1. Mass balance

2. air-water partitioning coefficient

benzene

eq,w

benzene

eq,air CandC




15/41

Container:

5L air

5mL water

5L benzene

Calculate

Intermedia Equalibrium

5 L Air

5 L Water

5 mL Benzene

benzene

air

benzene

eq,air

benzene

water

benzene

eq,w

M,CM,C




16/41

Air-Water Partitioning Excercise

Un tanque de 0.21 m3 de capacidad contiene

100 L de una mezcla de solventes

desengrasantes en agua. La presin parcial del

tricloroetileno (TCE) en la fase gaseosa arribadel agua es de 0.00301 atm. Cul es la

concentracin del TCE en el agua? Cul es la

masa de TCE en las dos fases (aire y agua)?R/ Cw,TCE=0.037 g/L; Mw,TCE=3.70g.; Ma,TCE=1.76g.

16




17/41

Octonal-Water Partitioning

Large organic and highlynonpolar compounds(hydrophobic) prefer topartition to octanol relative to

water and hence have acorrespondingly large value ofKow.

The less soluble a chemical isin water, the more likely is to

sorb to the surfaces ofsediments (organic material).

Figure 3.4




18/41

Octonal-Water Partitioning

Laboratory procedure for measuring Kow:

1. Chemical is added to a mixture of pura octanol(non-polar solvent) and pure water (polarsolvent).

2. Mixture is agitated until equilibrium is reached.

3. Mixture is centrifugated to separate the twophases.

4. Kow is the ratio of the chemical concentration inthe octanol phase to chemical concentration inthe water phase.

18Prof. Jorge E. Pachon, Ph.D.



19/41

Soil Organic Matter/Carbon -Water Partitioning

Soil = mineral + organics from plants and animals

The mass fraction of organic material in soil

- fOM : mass fraction of organic matter (OM) in soil- fOC: mass fraction of organic carbon (OC) in soil

water)A/Lof(massin waterAofionconcentratmEquilibriu

OC)A/kgof(massOCsoilinAofionconcentratmEquilibriu

C

CK

water)A/Lof(massin waterAofionconcentratmEquilibriu

OM)A/kgof(massOMsoilinAofionconcentratmEquilibriu

C

CK

A

eqw,

A

eqOC,A

OC

Aeqw,

A

eqOM,A

OM




20/41

Emipirial determination of KOM and KOC

Karickhoff log KOC=1.00 log KOW 0.21 Schwarzenbach log KOC=0.72 log KOW + 0.49

20

Compounds with larger KOW have larger values of KOM and KOC.




21/41

Soil OM-Water Partitioning Example

5 L Air

5 L Water

5 L Benzene

100g

OM

Container:

5L air

5L water

5L benzene

Add 100 g OM

Calculate

Solution:eqwOM

benzeneeqOM xCKC ,,




22/41

soilkg

OCof

waterLperAofmass

OCkgperAofK

waterLperAofmass

soilkgperAofK

soilkg

OMof

waterLperAofmass

OMkgperAofK

waterLperAofmass

soilkgperAofK

A

OC

A

d

A

OM

A

d

massf

massmass

massf

massmass

OC

OM

Soil -Water Partitioning




23/41

Soil -Water Partitioning Example

Container:

10L air

10L water

0.1g benzene Add 10 kg soil (with 1% OM)

Calculate

Solution: 1. Mass balance for benzene

2. using

10 L Air

10 L Water

benzene

eq,soil

benzene

eq,air

benzene

eq,w CandC,C

benzene

d

benzene

aw KandK

10 kg soil




24/41

NAPL -Water Partitioning

A

sat,w

A

eq,w CC

NAPLs can serve as long-term sources ofcontamination to the surrounding environment.

Hence, equilibrium transfers of contaminants fromNAPL to water and from NAPL to air are of interest.

Pure NAPL




25/41

Multi-component NAPL for Ideal NAPL Mixture

A

v

A

NAPL

A

eq,air

A

sat,w

A

NAPL

A

eq,w

PXP

CXC

Raoults Law (for ideal NAPL mixture)

NAPLinAcompoundoffractionmoleXANAPL

Raoults Law: Discovered by Franois-Marie Raoult in 1880s.




26/41

NAPL-Water and NAPL-Air Partitioning

5 L Air

5 L Water

5 L NAPL

Container:

5L air

5L water

5L NAPL with 10% Naphthalene

Calculate

enaphthalen

eq,w

enaphthalen

v CandP




27/41

Environmental Intermedia Problems

- great abundance of pure chemicals

A

eq,w

A

d

A

eqsoil,

A

w

A

eqair,A

eqw,

A

v

A

eqair,

A

sa tw,

A

eqw,

CKC

RT

MPC

PP

CC

weightmolecularW

pressurevaporPysolubilitaqueousC

:propertiescompoundPure

A

w

A

v

A

satw,

tcoefficienngpartitioniwater-soilK

:tcoefficienngPartitioni

d



d


28/41


- great abundance of chemicals with a

multicomponent NAPL mixture

A

eq,w

A

d

A

eqsoil,

A

w

A

eqair,A

eqw,

A

v

A

NAPL

A

NAPL

A

eqair,

A

satw,

A

NAPL

A

NAPL

A

eqw,

CKC

RT

MPC

PXP

CXC

NAPLinAoffractionMole

1NAPLinAofActivity

:propertiesNAPL

A

NAPL

A

NAPL

X



d



D i T d C i II 2012


29/41


- limited mass of chemicals

A

eq,w

A

d

A

eqsoil,

A

eqw,

A

aw

A

eqair,

A

eqw,

A

H

A

eqair,

soil

A

dairaww

A

totalA

eqw,

CKC

CKC

CKP

MKVKV

MC

pressurevaporV

airofVolumeV

:sizetcompartmenMedia

air


tcoefficienngpartitioniwater-iraK

ConstantlawsHenry'K


d

aw

H



D i T d C i II 2012


30/41

Pregunta del primer examen I-2012

Se disuelven 0.5 gramos de naftaleno en un

recipiente hermtico que contiene 40L de

agua, 60L de aire y 500g de sedimentos (con

1.5% de carbono orgnico). Estimar lasconcentraciones de naftaleno en los tres

medios (agua, aire, suelo) en equilibrio.

Asumir KOC=0.41*KOW. Qu porcentaje de lamasa total se distribuye en cada medio?

30



D ti T t d C t i t II 2012


31/41

Bioconcentration and Bioaccumulation

Bioconcentration: the uptake of toxic organicsthrough the gill membrane and epithelial tissuefrom the dissolved phase.

Bioaccumulation: the total biouptake of toxicorganics by the organism from food items (fishprey, sediment ingestion, etc.)

Biomagnification: circumstance where

bioaccumulation causes an increase in total bodyburden as one proceeds up the trophic ladderfrom primary producers to top carnivore.

31Prof. Jorge E. Pachon, Ph.D.


D ti T t d C t i t II 2012


32/41

Pollutant Interactions with Fish

Bioconcentration Factor (BCF)

Physical exchange between the fish tissue and water.

Bioaccumulation factor (BAF)

ingestion, respiration, and physical exchange.

water)ofA/kgof(gwaterinAofionconcentratstateSteady

tissue)fishA/kgof(gfishinAofionconcentratstateSteady

C

CBCF

A

ssw,

A

ssf,A

Physical

exchange

ingestion,

respiration



Destino y Transporte de Contaminantes II 2012


33/41

Relationships between BCF in Fish and

Chemical Kow

Table 3.3Prof. Jorge E. Pachon, Ph.D. 33




34/41

BCF Example

Ideal NAPL with 10% molefraction benzene

Estimate the equilibrium benzene

concentration in the fish:





35/41

Pollutant Interactions with Plants

Plants can serve as important living links between air,

water, and soil, and transfer pollutants between the

different media.

Interaction between air pollutants and vegetation occurson a regional scale, with pollutant concentrations in leaves

often being monitored to determine the level of air

pollution.

Plant uptake of pollutants from soil and water occurs on a

more local scale and has been studied for application in

phytoremediation, that is, plant-assisted remediation at

contaminated land sites.





36/41

Interaction between Atmospheric PAHs

and Plants Polycyclic aromatic hydrocarbons (PAHs) reach pine

needles via atmospheric transport and depositionprocesses.

Atmospheric PAH concentrations are calculated throughBCF based on octanol-air partition coefficients (Koa).

Tremolada, ES&T, 1996





37/41

Phytoremediation of Organic

and Nutrient Contaminants

Schnoor, ES&T, 1995Prof. Jorge E. Pachon, Ph.D. 37




38/41


Root Concentration Factor (RCF)

rootBCF

C

CRCF

water)ofA/kgof(gwater-soilinAofononcentrati

tissue)A/kgof(grootsplantin wetAofononcentrati

The RCF addresses sorption of organic pollutants

from soil to plant root tissues, as well as pollutant

uptake by the root xylem-water that flows through

the plant during transpiration.





39/41


Transfer of pollutant from soil-water to the transpiration

Stream within the plant (TSCF)

(mg/L)water-soilinAofononcentratiC

(g/L)streamiontranspiratplantinAofononcentratiCTSCF

RUBIN & RAMASWAMI, Water Research, 2001

100

V

dV

%dMTSCF initial

transp

Slope





40/41

RCF

TSCF

Kleaf-air

BCFplant-soil

BCFplant-waterTable3.4





41/41

Impacts of Kow on TSCF

Kow =100Kow =10

Largest

TSCF

How to find the Kow for the

largest TSCF if only theequation is known?

f h h


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