SESOIL

Model for Long-Term Pollutant Fate and Migration

SESOIL is a seasonal compartment model which simulates long-term pollutant fate and migration in the unsaturated soil zone. The model describes the following components of a user-specified soil column which extends from the ground surface to the ground-water table.

Hydrologic cycle of the unsaturated soil zone.
Pollutant concentrations and masses in water, soil, and air phases.
Pollutant migration to ground water.
Pollutant volatilization at the ground surface.
Pollutant transport in washload due to surface runoff and erosion at the ground surface.

SESOIL estimates all of the above components on a monthly basis for up to 999 years of simulation time. It can be used to estimate the average concentrations in ground water. The soil column may be composed of up to four layers, each layer having different soil properties which affect the pollutant fate. In addition, each soil layer may be subdivided into a maximum of 10 sublayers in order to provide enhanced resolution of pollutant fate and migration in the soil column. The following pollutant fate processes are accounted for: Volatilization, Adsorption, Cation Exchange, Biodegradation, Hydrolysis and Complexation.

SESOIL can be used as a screening tool in performing exposure assessments. EPA uses the model to predict the behavior of pollutants in soil compartments for analyzing and prioritizing chemical exposures.

SESOIL accepts time-varying pollutant loading. For example, it is able to simulate chemical releases to soil from a variety of sources such as landfill disposal, accidental leaks, agricultural applications, leaking underground storage tanks, or deposition from the atmosphere. Other potential applications include long-term leaching studies from waste disposal sites, pesticide and sediment transport on watersheds, studies of hydrologic cycles and water balances of soil compartments. SESOIL can also be used to estimate the effects of various site management/ design strategies on pollutant distributions and concentrations in the environment.

INPUT DATA

Climate Data-consists of monthly rainfall and climatic statistics for a typical year for the rain gauge of interest.
Soil Data-consists of soil parameters averaged over the entire soil zone such as the bulk density of the soil, intrinsic permeability, etc.
Chemical Data-requires the solubility and the adsorption coefficient of the chemical.
Application Input-describes the compartment specifications, characteristics of the pollutant loadings, and some layer-dependent soil properties.
Washload Data-optional and contains data used by SESOIL to calculate washload transport, the migration of the pollutant adsorbed to eroding soil particles.

DATABASE SUPPORT

The Climate Database consists of 3,225 weather stations throughout the continental U.S. is available for purchase by state and the entire U.S. The data originally came from the National Climatic Data Center (NCDC) of the National Oceanographic and Atmospheric Administration (NOAA). It consists of all the monthly statistical parameters required by SESOIL (rainfall information from hourly precipitation stations and evaporation-related information from monthly state climatic division means) accessed by latitude/longitude coordinates of the U.S. An additional variable, ALBEDO, which represents the monthly shortwave albedo of the land surface is also incorporated into the data.
The Zip Code Database contains the zip codes and the corresponding latitude/longitude coordinates for all of the U.S.
The SOILS-5 Database provides soil information required by SESOIL for over 14,000 soil series across the U.S. and comes from the USDA Soil Conservation Service's (SCS) Soils-5 database. Single variables, i.e., bulk density of the soil, effective porosity, and layer-dependent variables, i.e., thickness, intrinsic permeability, are retrieved from the database. Included with SESOIL are eight measured property files for the most commonly-modeled chemicals - Benzene, 1,1,1-Trichloroethylene, Trichloroethylene, Naphthalene, Ethylbenzene Toluene, Hexachlorobenzene, and Tetrachloroethylene.
SESOIL creates an output file which contains monthly results for hydrologic cycle components, pollutant mass distribution, and pollutant concentration distribution for each layer or sublayer. SESOIL also generates a SESOIL-AT123D link file which contains pollutant mass-to-ground-water leachate quantities entering the aquifer from the unsaturated zone. This file can be used as input to the AT123D ground-water model in RISKPRO. Within RISKPRO, line graphs of "concentration vs time" at any specified depth within the unsaturated zone may be created from SESOIL results. " Pollutant-front-depth vs. time" may also be created.

TABLE 1 Input Parameters for SESOIL
DATA CATEGORY (Input File)	PARAMETER	SESOIL INTERFACE
CLIMATE	Evapotranspiration-Monthly Air temperature Cloud cover fraction Relative humidity Short wave albedo Rainfall Statistics-Monthly Mean storm duration Rainfall depth Number of storms per month Length of rainy season within month	All climatic parameters can be obtained from the RISKPRO Climate Database
SOIL	Bulk density of the soil Intrinsic permeability Soil disconnectedness index Effective porosity Organic carbon content Cation exchange coefficient Freundlich equation exponent	All soil parameters except Freundlich exponent can be obtained from the RISKPRO Soils Database
CHEMICAL	Compound Solubility in water Diffusion coefficient in air Henry's Law Constant Adsorption coefficient on organic carbon Adsorption coefficient in soil Molecular weight; Valence Hydrolysis rates (neutral, base, acid) Biodegradation rates (liquid and soil phases) Ligand (optional) Ligand stability constant Moles. ligand per mole. compound Molecular weight of ligand	Common Chemical Files are available for: Benzene 1,1,1,- Trichloroethylene Trichloroethylene Naphthalene Ethylbenzene Toluene Hexachlorobenzene Tetrachloroethylene
APPLICATION	Compartment Specifications Number of soil layers and number of sublayers for each layer Application area and latitude of site Layer-Dependent Soil Properties Thickness Permeability pH Biodegradation rate ratios for lower layers Organic carbon content ratios for lower layers Cation exchange coefficient ratios for lower layers Pollutant Loading Instantaneous or continuous Initial pollutant concentration for any sublayer Monthly loading rates and miscellaneous parameters Pollutant loading for the major layer Pollutant transformed/removed for the major layer Pollutant concentration in rain Ligand input mass Volatilization index Surface runoff participation index Groundwater Parameters Saturated hydraulic conductivity, horizontal gradient, thickness, and width.	Layer-dependent parameters can be obtained from the RISKPRO Soil Database Thickness Intrinsic permeability Organic carbon content pH
WASHLOAD (Optional)	Washload area Percent of silt, sand, and clay Slope length; Average land slope Soil erodibility factor and soil loss ratio Contouring factor and Manning's coefficient	Erodibility factor can be obtained from the RISKPRO Soils Database

Requirements

PC 486/Pentium running Microsoft Windows.

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Τελευταία Ενημέρωση 27 Ιουλίου 2004 - Last Revised on July 27, 2004