Organic Chemical ModelOrganic Chemical Model
Summary of Process Equations Summary of Process Equations and Model Input Dataand Model Input Data
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Aquatic Transport, Speciation and Aquatic Transport, Speciation and Transformation ProcessesTransformation Processes
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TOXI Organic Chemical ProcessesTOXI Organic Chemical Processes• Equilibrium ProcessesEquilibrium Processes
– Sorption– Ionization
• Kinetic ProcessesKinetic Processes– Volatilization– Photolysis– Hydrolysis– Bacterial Degradation– Oxidation– Reduction
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Sorption - DesorptionSorption - Desorption• ReactionReaction
– Movement of chemical between the dissolved phase and particulate or solid phase. The chemical may be physically associated or chemically bound to functional groups on the solid.
• Linear Partitioning EquationLinear Partitioning Equation• DataData
– Partition coefficient (Kp, Koc, or Kow), Lw/kgS
– Solids concentration, mg/L– Solids organic fraction
psw KSCSC ,
kgLLmgkgmg
pws KCC
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IonizationIonization• ReactionReaction
– Dissociation of neutral parent molecule into ionic species– Weak acid − Weak base
• Equilibrium EquationsEquilibrium Equations
• Data Data – pKai, negative log of Kai
– pKbi, negative log of Kbi
– pH, negative log of [H+]
aiKHRCOORCOOH , biKOHRROH ,
HKCC ai0 OHKCC bi
0
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VolatilizationVolatilization
• DataData– Atmospheric concentration, g/m3
– Depth (surface area/volume), m– Henry’s Law constant, atm/molar– Water temperature, kelvin– Conductivity, kv, m/day
• Function of depth, current velocity and wind speed, m/sec
K
aw
vw
TRH
CC
D
k
t
C
• ReactionReaction– Movement of dissolved
chemical between water and air
• Kinetic EquationKinetic Equation
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PhotolysisPhotolysis
• DataData– Surface photolytic rate constant, kps, day-1
– Latitude and reference latitude, degrees– Light intensity at surface– Depth (surface area/volume), m– Light extinction coefficient, m-1
• Measured, or function of chl a, DOC, S
wPw Ckt
C
• ReactionReaction– Degradation of dissolved
chemical by sunlight
• KineticKinetic
EquationEquation
PlightCw
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HydrolysisHydrolysis• ReactionReaction
• Kinetic Kinetic EquationEquation
• DataData– pH– kH or kHn, day-1
– kHa, molar-1day-1
– kHb, molar-1day-1
OHKKHKk HbHnHaH
'
'3
'2
PPOHCCatalysisBase
PPOHCCatalysisAcid
PPOHCNeutral
Ckt
CH
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Bacterial DegradationBacterial Degradation
• ReactionReaction
• Kinetic Kinetic
EquationEquation
• DataData– kBW or kBS, day-1
– kB, (cells/mL)-1day-1
– bacterial population density, bac, (cells/mL)
isegBBSBWB backorkkk ,,
'' PbacteriaCmentSediBenthic
PbacteriaCColumnWater
sed
wc
Ckt
CB
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OxidationOxidation
• ReactionReaction
• KineticKinetic
EquationEquation
• DataData– kOX, day-1
– kO, (moles/L)-1day-1
– oxidant concentration, oxrad, (moles/L)
isegOOX oxradkk
PoxidantC
Ckt
COX
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ReductionReduction
• ReactionReaction
• KineticKinetic
EquationEquation
• DataData– kEX, day-1
– kE, (moles/L)-1day-1
– reductant concentration, exrad, (moles/L)
isegEEX exradkk
PreductantC
Ckt
CEX
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Organic Toxicant Time FunctionsOrganic Toxicant Time Functions
• Water temperature (4) (degrees C)Water temperature (4) (degrees C)• Water velocity (4) (m/sec)Water velocity (4) (m/sec)• pH of water column & benthic segmentspH of water column & benthic segments• Normalized light intensity (photolysis option 2)Normalized light intensity (photolysis option 2)• Wind speed at 10 meters (m/sec)Wind speed at 10 meters (m/sec)• Bacteria population (Water & Benthos)Bacteria population (Water & Benthos)• Air temperature (degrees C)Air temperature (degrees C)• Reaeration rate constant (dayReaeration rate constant (day-1-1))• Chlorophyll-a (mg/L)Chlorophyll-a (mg/L)
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Organic Toxicant Segment ParametersOrganic Toxicant Segment Parameters• Water velocity time function pointerWater velocity time function pointer• Water temperature (time function pointer and multiplier)Water temperature (time function pointer and multiplier)• Wind speed multiplierWind speed multiplier• Reaeration rate multiplierReaeration rate multiplier• Dissolved organic carbon, DOC (mg/L)Dissolved organic carbon, DOC (mg/L)• Fraction organic carbon for solids 1, 2, 3 (fraction)Fraction organic carbon for solids 1, 2, 3 (fraction)• Chlorophyll a concentration (mg/L)Chlorophyll a concentration (mg/L)• pHpH• Light extinction coefficient (meterLight extinction coefficient (meter-1-1))• Bacteria Population (cells/100 mL)Bacteria Population (cells/100 mL)• Oxidative radical concentration (moles/L)Oxidative radical concentration (moles/L)• Extra environmental property (e.g., reductant, moles/L)Extra environmental property (e.g., reductant, moles/L)• Overall decay rate constant for chemicals 1, 2, 3 (dayOverall decay rate constant for chemicals 1, 2, 3 (day -1-1))
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Organic Toxicant ConstantsOrganic Toxicant Constants
• Constants GroupsConstants Groups– Solids– Ionization– Sorption– Volatilization– Hydrolysis– Photolysis– Biodegradation– Oxidation– Reduction
• Notes on ListingNotes on Listing– Constants are listed by
group for Non-Ionic Toxicant module
– In the general Organic Toxicant Module, these constants are repeated for each of 5 ionic species
– Chemical 1 constants are shown; these are repeated for chemicals 2 and 3
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Sorption ConstantsSorption Constants
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Volatilization ConstantsVolatilization Constants
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Hydrolysis ConstantsHydrolysis Constants
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Hydrolysis Constants, cont’dHydrolysis Constants, cont’d
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Photolysis ConstantsPhotolysis Constants
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Biodegradation ConstantsBiodegradation Constants
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Oxidation ConstantsOxidation Constants
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Reduction ConstantsReduction Constants
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Ionization ConstantsIonization Constants