# Presentation: 122327

## Organic Chemical Model

- Summary of Process Equations and Model Input Data

## Aquatic Transport, Speciation and Transformation Processes

## TOXI Organic Chemical Processes

- Equilibrium Processes
- Sorption
- Ionization
- Kinetic Processes
- Volatilization
- Photolysis
- Hydrolysis
- Bacterial Degradation
- Oxidation
- Reduction

## Sorption - Desorption

- Reaction
- 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 Equation
- Data
- Partition coefficient (Kp, Koc, or Kow), Lw/kgS
- Solids concentration, mg/L
- Solids organic fraction

## Ionization

- Reaction
- Dissociation of neutral parent molecule into ionic species
- Weak acid                            −  Weak base
- Equilibrium Equations
- Data
- pKai, negative log of Kai
- pKbi, negative log of Kbi
- pH,   negative log of [H+]

## Volatilization

- Data
- 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

- Reaction
- Movement of dissolved chemical between water and air

- Kinetic Equation

## Photolysis

- Data
- 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

- Reaction
- Degradation of dissolved chemical by sunlight

- Kinetic
-     Equation

## Hydrolysis

- Reaction
- Kinetic           Equation
- Data
- pH
- kH or kHn, day-1
- kHa, molar-1day-1
- kHb, molar-1day-1

## Bacterial Degradation

- Reaction
- Kinetic
-     Equation
- Data
- kBW or kBS, day-1
- kB, (cells/mL)-1day-1
- bacterial population density, bac, (cells/mL)

## Oxidation

- Reaction
- Kinetic
-     Equation
- Data
- kOX, day-1
- kO, (moles/L)-1day-1
- oxidant concentration, oxrad, (moles/L)

## Reduction

- Reaction
- Kinetic
-     Equation
- Data
- kEX, day-1
- kE, (moles/L)-1day-1
- reductant concentration, exrad, (moles/L)

## Organic Toxicant Time Functions

- Water temperature (4) (degrees C)
- Water velocity (4) (m/sec)
- pH of water column & benthic segments
- Normalized light intensity (photolysis option 2)
- Wind speed at 10 meters (m/sec)
- Bacteria population (Water & Benthos)
- Air temperature (degrees C)
- Reaeration rate constant (day-1)
- Chlorophyll-a (mg/L)

## Organic Toxicant Segment Parameters

- Water velocity time function pointer
- Water temperature (time function pointer and multiplier)
- Wind speed multiplier
- Reaeration rate multiplier
- Dissolved organic carbon, DOC (mg/L)
- Fraction organic carbon for solids 1, 2, 3 (fraction)
- Chlorophyll a concentration (mg/L)
- pH
- Light extinction coefficient (meter-1)
- Bacteria Population (cells/100 mL)
- Oxidative radical concentration (moles/L)
- Extra environmental property (e.g., reductant, moles/L)
- Overall decay rate constant for chemicals 1, 2, 3 (day-1)

## Organic Toxicant Constants

- Constants Groups
- Solids
- Ionization
- Sorption
- Volatilization
- Hydrolysis
- Photolysis
- Biodegradation
- Oxidation
- Reduction

- Notes 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

## Sorption Constants

## Volatilization Constants

## Hydrolysis Constants

## Hydrolysis Constants, cont’d

## Photolysis Constants

## Biodegradation Constants

## Oxidation Constants

## Reduction Constants

## Ionization Constants

## Additional Oxidation Constants for Ionic Chemical