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United States Department of Agriculture

Agricultural Research Service

Research Project: Reviewing the Use of the Adsorption Coefficient (KD) in the Dynamics of Pesticides

Location: Grassland, Soil and Water Research Laboratory

2012 Annual Report


1a.Objectives (from AD-416):
Evaluate various pesticides and other emerging contaminants, laboratory analytical methods, and soil-specific corrections for use in the current pesticide submodel of SWAT; (2) provide the basis for further development of transport and fate modeling of other emerging contaminants.


1b.Approach (from AD-416):
The pesticide submodel of the Soil and Water Assessment Tool currently does not adjust pesticide adsorption parameters to specific soil characteristics. To evaluate the effect of different soil characteristics and laboratory assessment methods, 10 different soils will be collected from a variety of environments and regions of the United States of America to represent a wide range of soil characteristics. Twelve different compounds will be tested on these soils using different laboratory techniques, including batch equilibrium and accelerated solvent extraction (ASE) methods. Targeted chemicals for evaluation are 5 herbicides (2,4-D, atrazine, clomazone, s-metolachlor, saflufenacil); 4 antimicrobials (chlortetracycline, tetracycline, carbodox, bacitracin); and 3 wastewater treatment indicator compounds (sucralose, caffeine, carbemazepine).


3.Progress Report:

Existing literature on the use of the adsorption coefficient (Kd) in modeling the fate and transport of pesticides was collected. Literature on existing Kd data, laboratory analysis, use of Kd in hydrologic models, and uncertainty in Kd measurements were collected and will be synthesized.


Last Modified: 8/30/2014
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