2 Fate of Pollutants in Environment 2

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Fate of pollutants in the environmentFate of pollutants in the environment

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IV. Fate of IV. Fate of pollutantspollutants

1.1. The phases of a pollution The phases of a pollution Pollution are characterized by 3 phases that determine the fate Pollution are characterized by 3 phases that determine the fate of pollutants: Emission, of pollutants: Emission, dispersion and transformationdispersion and transformation..

Emission phaseEmission phaseThe emission is characterized by its location and its intensity,The emission is characterized by its location and its intensity, two factors that modulate two factors that modulate the capacity of the ecosystem to recover (high or low intensity,the capacity of the ecosystem to recover (high or low intensity, air, water, soilair, water, soil……))

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IV. Fate of pollutantsIV. Fate of pollutants 1. The phases of a pollution1. The phases of a pollution

Dispersion phaseDispersion phaseThe dispersion of the pollutants corresponds to a movement of thThe dispersion of the pollutants corresponds to a movement of the pollutants due e pollutants due transfer processes (diffusion, wind, water flow, transporttransfer processes (diffusion, wind, water flow, transport……).).A rapid dispersion may prevent local accumulation by decreasing A rapid dispersion may prevent local accumulation by decreasing the apparent levels of the apparent levels of pollutants in the environment. However, a rapid spreading of thepollutants in the environment. However, a rapid spreading of the pollution allows the pollution allows the contamination of other sites.contamination of other sites.

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Transformation phaseTransformation phaseThe transformation phase could occur at any step of the pollutioThe transformation phase could occur at any step of the pollution. Thus, a substance n. Thus, a substance emitted at low intensity and rapidly transformed may have a weakemitted at low intensity and rapidly transformed may have a weak impact on the living impact on the living organisms. Conversely a pollutant intensively and rapidly emitteorganisms. Conversely a pollutant intensively and rapidly emitted, slowly dispersed and d, slowly dispersed and transformed has the potential to have great impacts on living ortransformed has the potential to have great impacts on living organismganism

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Dispersal of a pollutionDispersal of a pollution

Case of slow dispersionCase of slow dispersion______ Analysis of the pollutant concentration Analysis of the pollutant concentration at the emission point.at the emission point.- - - - - Analysis of the pollutant concentration Analysis of the pollutant concentration at a point away from the emission point. The at a point away from the emission point. The delay in the appearance of the pollutant is delay in the appearance of the pollutant is due to the dispersion time. Note that the due to the dispersion time. Note that the concentration is always lower than that of the concentration is always lower than that of the origin because of spreading and origin because of spreading and transformation of the pollutant.transformation of the pollutant.

Case of rapid dispersionCase of rapid dispersion______ Analysis of the pollutant concentration Analysis of the pollutant concentration at the emission point.at the emission point.-- -- -- -- -- Analysis of the pollutant at a point Analysis of the pollutant at a point away from the emission point.away from the emission point.

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Contamination pointContamination pointTime tTime too

DistanceDistance ↑↑DelayDelay ↑↑AreaArea ↑↑TimeTime ↑↑ConcConc..↓↓

ttnn


Contaminated areaContaminated area Evolution of pollutionEvolution of pollutionDispersion only due to diffusion (above), and due to diffusion and external factors (wind, air stream, water flow…) (below)

Contamination pointContamination pointTime tTime too

DistanceDistance ↑↑DelayDelay ↑↑AreaArea ↑↑

TimeTime ↑↑ConcConc..↓↓

ttnn


Contaminated areaContaminated area

StreamStream

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IV. Fate of pollutantsIV. Fate of pollutants 2. Transfer of pollutants in the environment2. Transfer of pollutants in the environment

2.2. Transfer of pollutants in the environment Transfer of pollutants in the environment

Transfer of pollutants emitted in the atmosphere Transfer of pollutants emitted in the atmosphere The pollutants emitted in the atmosphere are gas, vapors, solidsThe pollutants emitted in the atmosphere are gas, vapors, solids matters and sprays. matters and sprays. After emission, pollutants undergo a dispersion in the atmospherAfter emission, pollutants undergo a dispersion in the atmosphere that depend both on e that depend both on the importance of air streams, the density of the pollutants andthe importance of air streams, the density of the pollutants and their diffusion velocity.their diffusion velocity.Gas and VaporsGas and VaporsGas and vapors of volatile substances (Solvents, metal vapors, sGas and vapors of volatile substances (Solvents, metal vapors, solid substances with olid substances with high vapor pressure) can diffuse relatively easily, especially ihigh vapor pressure) can diffuse relatively easily, especially in there are lighter than air.n there are lighter than air.Gas and vapors undergo a rather rapid diffusion in the atmospherGas and vapors undergo a rather rapid diffusion in the atmosphere. They can be e. They can be dissolved in the water in suspension in air and reach the earth dissolved in the water in suspension in air and reach the earth surface in rains.surface in rains.Examples of gas: Chlorofluorocarbons (CFC, ozone destroyer), COExamples of gas: Chlorofluorocarbons (CFC, ozone destroyer), CO22 SOSO22, Nitrogen , Nitrogen oxides (oxides (NOxNOx), H), H22S, S, HClHCl, NH, NH33, benzene vapors, Mercury vapors, benzene vapors, Mercury vapors……

Solid matters and spraysSolid matters and spraysLight matters such as fumes, dusts (asbestos, coalLight matters such as fumes, dusts (asbestos, coal……), ), nanoparticlesnanoparticles or sprays (a spray or sprays (a spray is a suspension of small liquid droplets). Dusts and sprays willis a suspension of small liquid droplets). Dusts and sprays will undergoes a undergoes a sedimentation after an eventual dispersion by winds.sedimentation after an eventual dispersion by winds.

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Transfer of pollutants emitted in the atmosphere (Transfer of pollutants emitted in the atmosphere (ctdctd))The atmospheric pollutants may follow two ways that determine thThe atmospheric pollutants may follow two ways that determine they toxicity:ey toxicity:

A penetration in terrestrial and aerial organismsA penetration in terrestrial and aerial organismsThe penetration can occur through lungs or teguments and skin.The penetration can occur through lungs or teguments and skin.

They can reach the earth surfaceThey can reach the earth surfaceIn the aquatic environment, they can penetrate the organism or cIn the aquatic environment, they can penetrate the organism or can be linked to an be linked to organic and mineral matter.organic and mineral matter.In soil, they can deposit on soil surface, or can undergo transfIn soil, they can deposit on soil surface, or can undergo transfer processes: infiltration, er processes: infiltration, drainage (free form), lixiviation/leaching (adsorbed form) and drainage (free form), lixiviation/leaching (adsorbed form) and exfiltrationexfiltration..

Transfer of pollutants emitted on soils and in water Transfer of pollutants emitted on soils and in water Pollutants emitted on soils surface and in water environment arePollutants emitted on soils surface and in water environment are::Liquids, substances in solutions, solid substances that can dissLiquids, substances in solutions, solid substances that can dissolve or undergo a olve or undergo a degradation.degradation.The transfer of these pollutant are the same than those having rThe transfer of these pollutant are the same than those having reached the soil surface eached the soil surface or water environment.or water environment.

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General scheme of pollutant transfer in the environmentGeneral scheme of pollutant transfer in the environment

InfiltrationDrainageLixiviation

ExfiltrationStream

Groundwater

Trophic transfer

Sediments

Telluric biomass

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IV. Fate of pollutantsIV. Fate of pollutants 2. Availability of environmental pollutants2. Availability of environmental pollutants

3.3. AvailabiltyAvailabilty of environmental pollutants of environmental pollutants In all media, a substance undergoes exchange processes that deteIn all media, a substance undergoes exchange processes that determine it distribution rmine it distribution in the environment.in the environment.A substance may have different states:A substance may have different states:

In airIn air-- Free substance (dusts and particles, gas, vapor, microorganismsFree substance (dusts and particles, gas, vapor, microorganisms and virus)and virus)-- Substance adsorbed on particles and dustsSubstance adsorbed on particles and dusts-- Substance dissolved in or associated with atmospheric waterSubstance dissolved in or associated with atmospheric water

((HClHCl, SO, SO22, microorganisms and virus, microorganisms and virus……))

In water and soilsIn water and soils-- Dissolved substances and waterDissolved substances and water--miscible liquids (water soluble, water mixable )miscible liquids (water soluble, water mixable )-- Liquid in heterogeneous phase (non water miscible liquids)Liquid in heterogeneous phase (non water miscible liquids)-- Substances in suspension: particles, colloids (2Substances in suspension: particles, colloids (2--200 nm)200 nm)-- Substances adsorbed on mineral particulate fraction (soil matriSubstances adsorbed on mineral particulate fraction (soil matrix, colloids, sediments)x, colloids, sediments)

or organic particulate fraction (organic matter, microorganismor organic particulate fraction (organic matter, microorganisms)s)

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IV. Fate of pollutantsIV. Fate of pollutants 3. Availability of environmental pollutants (3. Availability of environmental pollutants (ctdctd))

Whatever the substance, it is distributed into 2 phases:Whatever the substance, it is distributed into 2 phases:

A particulate phaseA particulate phase : Adsorbed substance (S: Adsorbed substance (SAA)): Linked substance (S: Linked substance (SLL))

A free phaseA free phase : Dissolved substance (in water) or free substance (in air) (S: Dissolved substance (in water) or free substance (in air) (SFF))

The disposition (or availability) of a substance, corresponds toThe disposition (or availability) of a substance, corresponds to its state at a given time, its state at a given time, which is in equilibrium between 3 stateswhich is in equilibrium between 3 states

SSFF

SSAASSLL

Free/Dissolved

Adsorbed/Sorbed

Strongly adsorbed

Linked

Particles

Sorp

tion

Desor

ption

Sorption

Desorption

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IV. Fate of pollutantsIV. Fate of pollutants 3. Availability of environmental pollutants (3. Availability of environmental pollutants (ctdctd))

A substance bound to a particulate fraction can be releasedA substance bound to a particulate fraction can be released

Free/DissolvedAdsorbed

Strongly adsorbed

Linked

kk+1+1

kk--11

kk+1 +1 >>>> kk--11

kk+1 +1 <<<< kk--11

kk+1 +1 ≈≈ kk--11

Weakly adsorbed, easy releaseWeakly adsorbed, easy release

Strongly adsorbed, difficult releaseStrongly adsorbed, difficult release

Apparent equilibrium, easily displacedApparent equilibrium, easily displaced

Linked

Slow processSlow process

Linked

Linked

++

++

Original substanceOriginal substance

Modified substanceModified substance

Note :Note : kk are time constants, or velocity constants (timeare time constants, or velocity constants (time--11))

kk+1+1 Sorption constant (timeSorption constant (time--11))kk--11 DesorptionDesorption constant (timeconstant (time--11))

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IV. Fate of pollutantsIV. Fate of pollutants

4.4. Transformation of pollutants in the environment Transformation of pollutants in the environment Organic substancesOrganic substancesOrganic substances include a very large part of pesticides. OrgaOrganic substances include a very large part of pesticides. Organic substances may nic substances may undergo two degradation processes:undergo two degradation processes:

PhysicoPhysico--chemical processeschemical processes-- HydrolysisHydrolysis-- Photolysis (solar and cosmic radiations)Photolysis (solar and cosmic radiations)-- OxydoOxydo--reduction reactionsreduction reactions-- ThermolysisThermolysis (fire, high ambient temperature, volcanic activity)(fire, high ambient temperature, volcanic activity)-- Reaction with environmental molecules (including Reaction with environmental molecules (including xenobioticsxenobiotics))PhysicoPhysico--chemical transformation of a substance results in transformationchemical transformation of a substance results in transformations productss products

Biological processesBiological processes-- The biological degradation of pollutants is the biotransformatiThe biological degradation of pollutants is the biotransformation of the on of the metabolizationmetabolization. . -- The environmental degradation involves main microorganisms.The environmental degradation involves main microorganisms.-- The biotransformation involves The biotransformation involves oxidasesoxidases, , reductasesreductases, , hydrolaseshydrolases and conjugation and conjugation enzymes.enzymes.The biotransformation products are metabolites.The biotransformation products are metabolites.

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IV. Fate of pollutantsIV. Fate of pollutants 4. Transformation of pollutants in the environment4. Transformation of pollutants in the environment

MetabolitesMetabolites

Parent compoundParent compound

PT1PT1 PT2PT2 PT3PT3 PTnPTn M1M1 M2M2 M3M3 MnMn

PT1PT1’’ PT2PT2’’ M3M3’’ MnMn’’

TransformationTransformationproductsproducts

PhysicoPhysico--chemical chemical transformationtransformation MetabolizationMetabolization

Parent compoundParent compound

Transformation of pollutants in the environment Transformation of pollutants in the environment

Secondary Secondary metabolitesmetabolites

SecondarySecondaryproductsproducts

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Kinetic of environmental transformationKinetic of environmental transformation

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Global degradationGlobal degradation

PhysicoPhysico--chemical degradationchemical degradation

Biological degradationBiological degradation

DT50DT50

10

DT90DT90

Environmental degradation of a pollutantEnvironmental degradation of a pollutantDT50 and DT90 are the degradation times DT50 and DT90 are the degradation times 50% and 90%, times for which 50% and 90% 50% and 90%, times for which 50% and 90% of the product are degraded, respectively.of the product are degraded, respectively.DT50 and DT90 represent indicator of the DT50 and DT90 represent indicator of the degradation velocity.degradation velocity.In term of impacts on the ecosystem, DT90 In term of impacts on the ecosystem, DT90 is preferred to DT50.is preferred to DT50.DT50 is also called the halfDT50 is also called the half--life of the life of the compound.compound.

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RadionuclidesRadionuclidesMost of the Most of the radionuclidesradionuclides generated by nuclear activity are heavy metals. They present generated by nuclear activity are heavy metals. They present both chemical and radiological toxicity.both chemical and radiological toxicity.They can ionize matter, especially biological molecules, and indThey can ionize matter, especially biological molecules, and induce irreversible uce irreversible damages to DNA.damages to DNA.

If N is the number of If N is the number of radionuclidesradionuclides able to disintegrate and Nable to disintegrate and Noo the initial number of the initial number of radionuclidesradionuclides able to disintegrate, the law of radioactive disintegration is:able to disintegrate, the law of radioactive disintegration is:

N = NN = Noo . . ee--k.tk.t

N = NN = Noo . . ee--Ln2.t/TLn2.t/T

Where N is the number of disintegration at the time tWhere N is the number of disintegration at the time tk, the radioactive constant (k = Ln2/T)k, the radioactive constant (k = Ln2/T)T, the period of the radionuclide, time for which half of the raT, the period of the radionuclide, time for which half of the radioactivity disintegratesdioactivity disintegratesNNoo, the initial number of disintegration, the initial number of disintegration

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T of some T of some radionuclidesradionuclides

6060C cobalt C cobalt 5.27 years5.27 years235235U uranium U uranium 704 M years704 M years3232P P phosphorephosphore 14.2 days14.2 days125125I iodineI iodine 60.1 days60.1 days33H hydrogen H hydrogen 12.3 years12.3 years1414C carbon C carbon 5730 years5730 years

0 1 2 3 4 5 6 70

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Time (number of T)

Disintegration kinetic of Disintegration kinetic of radionuclidesradionuclidesThe disintegration curve is asymptotic. For each time equivalentThe disintegration curve is asymptotic. For each time equivalent to T, the period or the to T, the period or the halfhalf--life of the radionuclide, half of the life of the radionuclide, half of the radionuclidesradionuclides disintegrates.disintegrates.

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RadionuclidesRadionuclides ((ctdctd))In living organism, In living organism, radionuclidesradionuclides have a fate that depends on their affinity for biological have a fate that depends on their affinity for biological tissues.tissues.For example, iodine has an affinity for thyroid, lead and strontFor example, iodine has an affinity for thyroid, lead and strontium are stored in bones, ium are stored in bones, cadmium is accumulated in liver and kidney.cadmium is accumulated in liver and kidney.The toxicity of the The toxicity of the radionuclidesradionuclides depends on the quantity of radioactivity, the type and depends on the quantity of radioactivity, the type and the energy of radiations emitted and the halfthe energy of radiations emitted and the half--life of the radionuclide in the organism life of the radionuclide in the organism (effective half(effective half--life).life).The effective halfThe effective half--life (Tlife (TEE) on the radionuclide is a function of the biological half) on the radionuclide is a function of the biological half--life (Tlife (TBB) ) and the radiological halfand the radiological half--life (Tlife (TRR).).

TTEE < T< TBB and Tand TEE< T< TRR

Tritium Tritium 33H:H: TTRR = 12.3 years = 12.3 years –– TTBB ≈≈ 10 days 10 days –– TTEE slightly less than 10 daysslightly less than 10 daysStrontium Strontium 9090Sr:Sr: TTRR = 29 years = 29 years -- TTBB ≈≈ 50 years 50 years –– TTEE = 18 years= 18 years

TTEE ==TTRR . T. TBB

TTRR + T+ TBB

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Elimination of radioactivity in living organismsElimination of radioactivity in living organisms

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Biological elimination

Global elimination0

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Biological elimination

Global elimination

TR < TB TR > TB

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Metal trace elementsMetal trace elementsFor metal trace elements (MTE) this is no For metal trace elements (MTE) this is no metabolizationmetabolization but a speciationbut a speciationThe speciation corresponds to the distribution of one element inThe speciation corresponds to the distribution of one element into different to different physicophysico--chemical species.chemical species.Speciation is a continuous sequence of processes in an environmeSpeciation is a continuous sequence of processes in an environmental continuum.ntal continuum.The speciation has an history. The speciation has an history.

Speciation involves different phenomenaSpeciation involves different phenomenaOxydoOxydo--reduction (reduction (redoxredox) reactions (electron transfers). They depends on ) reactions (electron transfers). They depends on redoxredoxpotential of chemical species in presencepotential of chemical species in presence

Chemical reactions with surrounding moleculesChemical reactions with surrounding molecules

Biological reactions. They lead to a change in the chemical statBiological reactions. They lead to a change in the chemical state of the MTE or to e of the MTE or to its its complexationcomplexation with other biological molecules. with other biological molecules.

The speciation state determines the toxicity MTE for biological The speciation state determines the toxicity MTE for biological organismsorganisms

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In aquatic medium, speciation depends on:In aquatic medium, speciation depends on:

Oxygen concentrationOxygen concentration

MTE in presenceMTE in presence

Microorganisms (production of ROS and action of Microorganisms (production of ROS and action of monooxygenasesmonooxygenases))

Nature of the particulate fraction: sediments, colloids, OrganicNature of the particulate fraction: sediments, colloids, Organic and mineral and mineral mattersmatters

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IIn soils, speciation depends on:n soils, speciation depends on:

Oxygen concentration (changing with the depth)Oxygen concentration (changing with the depth)

Nature of the soil matrixNature of the soil matrix

The soil solutionThe soil solution

MicroorganismsMicroorganisms

Organic matterOrganic matter

Oxic zone [O2] ≈ [O2]air

Suboxic zone [O2] < [O2]air

Anoxic zone [O2] << [O2]air

Aerobic microorganismsAerobic microorganisms

Aero-anaerobic microorganisms

Anaerobic microorganisms

Invertebrates +++

Invertebrates ++

Invertebrates +/0

[O2]Soil surface

Repartition of oxygen in soils

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FeFeMetal ironMetal iron

Example of iron (Fe)Example of iron (Fe)

FeFe33OO44FerrosoFerroso--ferric oxideferric oxide

FeFe2+2+

Ferrous ironFerrous ironFeFe3+3+

Ferric ironFerric ironFe(NOFe(NO33))33Ferric nitrateFerric nitrate

Fe(OH)Fe(OH)22Ferrous hydroxideFerrous hydroxide

Fe(OH)(CHFe(OH)(CH33--COOCOO--))Ferric acetateFerric acetate

FeOFeOFerrous oxideFerrous oxide

FeFe22OO33Ferric oxideFerric oxide

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Example of leadExample of lead

Lead can exist under two oxidized states in equilibriumLead can exist under two oxidized states in equilibrium

Lead can also exist as organic lead as shown in the following exLead can also exist as organic lead as shown in the following examples amples

PbO

O

O

O

Lead phtalate

CH3

O

O Pb OCH3

O

Lead acetate

O

O

Pb

Lead catechol

Pb

C2H5

C2H5

C2H5

C2H5

Tetraethyl lead

Pb

CH3

CH3

CH3CH3

Tetramethyl lead

PbPb PbPb2+2+ PbPb3+3+

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Example of mercuryExample of mercuryMercury can exist under two oxidized states in equilibriumMercury can exist under two oxidized states in equilibrium

Mercury can also exist as organic mercury as shown in the followMercury can also exist as organic mercury as shown in the following examplesing examplesMethyl mercuryMethyl mercury CHCH33--HgHg++

DimethylDimethyl mercurymercury CHCH33--HgHg--CHCH33

EhtylEhtyl mercurymercury CC22HH55--HgHg++

Diethyl mercuryDiethyl mercury CC22HH55--HgHg--CC22HH55

MethylmercuryMethylmercury is the most toxic derivative and inhibits fetal brain developmeis the most toxic derivative and inhibits fetal brain development.nt.DimethylDimethyl mercury can cross the BBB and is mercury can cross the BBB and is neurotoxicneurotoxic (lack of coordination, sensory (lack of coordination, sensory disturbance, change in mental state.disturbance, change in mental state.Organic mercury is produced by soil and water microorganisms andOrganic mercury is produced by soil and water microorganisms and can can bioaccumulatebioaccumulatein a in a trophictrophic chain and undergoes a chain and undergoes a biomagnificationbiomagnification..

HgHg HgHg++

MercurousMercurous saltsaltHg IHg I

HgHg2+2+

Mercuric saltMercuric saltHg IIHg II

Inorganic HgInorganic Hg Organic HgOrganic Hg ZooplanctonZooplanctonPhytoplanctonPhytoplancton FishFish ManManMicroorganismsMicroorganisms

2 Fate of Pollutants in Environment 2

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