1. General Model Information

Name: Interactive Model for Ranking the Potential of Organic Chemicals to Contaminte Groundwater

Acronym: CHEMRANK

Contact:

Author(s):

David L. Nofziger
Oklahoma State University;
Plant and Soil Sciences Department;
368 N. Agricultural Hall;
Stillwater, OK 74078-6028
phone: 405-744-6420
fax: 405-744-5269
email:dln@soilwater.agr.okstate.edu
homepage: http://clay.agr.okstate.edu/plantsoilsci/faculty/dln/nofziger.html

P.S.C. Rao
Soil & Water Science Department,
P.O. Box 110290
University of Florida,
Gainesville, FL 32611-0290
phone: 352-392-1951 (secretary) or 352-392-3021 (voice mail)
fax: 352-392-3902
email: pscr@GNV.IFAS.UFL.EDU
homepage: http://gnv.ifas.ufl.edu/~SOILWEB/rao.HTM

A.G. Hornsby
Soil and Water Science Department
2169 McCarty Hall
Gainesville, FL 32611
email:agh@gnv.ifas.ufl.edu
homepage: http://muck.soils.ufl.edu/people/agh/hornsby.html

Abstract:

Processes Simulated:
Partitioning to water-air-soil phases, advection and degradation.

CHEMRANK utilizes four schemes:
The schemes are based on rates of chemical movement or relative rates of mobility and degradation of the chemicals within the vadose (unsaturated) zone. Two schemes are based on the rates at which chemicals might leach through the unsaturated (vadose) zone (steady state groundwater recharge rates); the other two schemes require daily rainfall and evaporation data and use the relative rates of mobility and degradation of the chemicals within the vadose zone.

• Retardation Factor (RF) - based on relative rates of movement of chemicals. Model assumes steady water-flow.

• Attenuation Factor (AF) - based on fraction of applied amount that is likely to leach past a specified soil depth. Calculates rates of leaching and degradation. Model assumes steady water flow.

• Travel Time - based on relative rates of leaching using the CMLS model for soil-water balance.

• Mass emissions - similar to AF except that the fraction of applied chemical leaching past the specified soil depth is computed using the CMLS model.

Internal Diagnostics: Moderate

Critical Assessment:
Strengths of Model:
Simplicity and ease in use; fundamental processes accounted for; ability to use and maintain data bases.

Weaknesses of Model:
Recharge (effective rainfall or irrigation) must be calculated externally; water-balance and physicochemical processes are simplicit.

Current Version No.: 1988

Costs: MS- DOS. Nominal cost to cover distribution.

sources of abstract: American Crop Protection Association (ACPA) model database (04/1998); EPA/CSMoS database (see links at further information in the www)

II. Technical Information

II.1 Executables:

II.2 Source-code:

II.3 Manuals:

II.4 Data:

III. Mathematical Information

III.1 Mathematics

III.2 Quantities

III.2.1 Input

• Retardation Factor (RF): soils bulk density, soil-water contents at saturation and 0.1 bar tension, and sorption for each chemical for each soil horizon along with Henry's constant.
  
• Attenuation Factor (AF): same as for RF except degradation half-life is also required.
  
• Travel Time: water content at 0.1 and 15 bars, bulk density, and organic carbon for each horizon. Input requirements also include sorption for each chemical, crop rooting depth, daily water inputs (rainfall or irrigation) and daily evapotranspiration.
  
• Mass emissions: Input requirements are the same as for the Travel Time model except degradation half-life is also required.
  

III.2.2 Output

Output Flexibility:
User control over several output tables and graphs and whether output is directed to screen, printer, or output file.

IV. References