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ARS Home » Southeast Area » Tifton, Georgia » Southeast Watershed Research » Research » Publications at this Location » Publication #133071
Title: PESTICIDE SOIL SORPTION PARAMETERS: THEORY, MEASUREMENT, USES, LIMITATIONS AND RELIABILITY

Author
item Wauchope, Robert - Don
item LINDERS, J - ZENECA DUTCH EPA
item YEH, S - ZENECA DUTCH EPA
item KLOSKOWSKI, R - GERMAN EPA, SANKYO
item TANAKA, K - GERMAN EPA, SANKYO
item RUBIN, B - HEBREW UNIV.NAGOYA
item KATAYAMA, A - HEBREW UNIV.NAGOYA
item KORDEL, W - FRANHOFER INST.
item GRSTL, Z - FRANHOFER INST.
item LANE, M - ZENECA,AVENTIS

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/11/2002
Publication Date: 3/1/2002
Citation: WAUCHOPE, R.D., LINDERS, J.B., YEH, S., KLOSKOWSKI, R., TANAKA, K., RUBIN, B., KATAYAMA, A., KORDEL, W., GRSTL, Z., LANE, M. PESTICIDE SOIL SORPTION PARAMETERS: THEORY, MEASUREMENT, USES, LIMITATIONS AND RELIABILITY. PEST MANAGEMENT SCIENCE 58:419-445. 2002.

Interpretive Summary: Regulatory agencies and environmental scientists universally rely on a simple laboratory test, the "soil absorption coefficient" test, to predict a pesticide's mobility in the environment. In this test a small amount of pesticide is added to a wet soil and mixed and the degree to which the pesticide concentrates in the soil from the water is measured. A chemical with low absorption has a high likelihood of becoming a water and air pollutant. The "Commission on Agrochemicals in the Environment" of IUPAC, an international scientific standards-setting organization, convened a task force to critically examine the assumptions of this universally-used test after 40 years of experience. A team of 11 experts from 7 countries contributed to this report. The conclusion: "soil sorption parameters are adequate for discriminating between broad leaching classes of pesticides, and early-tier risk assessment. Attempts to develop a more precise and/or accurate descriptor appears to be problematic at this time, given (a) the large spatial and temporal variability of soil properties, (b) the precision with which we are able to model these systems, and (c) the complexities of integration from point scale to real hydrologic systems. However, these difficulties may be expected to yield to the continuing increases in simulation power available to us, and to continued innovations in experimental approaches".

Technical Abstract: The soil sorption coefficient Kd and the soil organic carbon sorption coefficient Koc of pesticides are basic parameters used worldwide in describing the environmental behavior of pesticides. They are a measure of the strength of sorption of pesticides to soils and other geosorbent surfaces at the water/solid interface, and thus related to both environmental mobility and persistence. Koc is regarded as a universal parameter which applies to a given pesticide in all soils. This assumption is known to be inexact but it is used in this way in modeling and estimating risk for pesticide leaching and runoff. In this report we examine the theory, uses, measurement or estimation, limitations and reliability of these parameters and provide some "rules of thumb" for the use of these parameters in describing the behavior and fate of pesticides in the environment, especially in analysis by modeling. We conclude that these soil sorption parameters are adequate for discriminating between broad leaching classes of pesticides, and early-tier risk assessment. Attempts to develop a more precise and/or accurate descriptor appears to be problematic at this time, given (a) the large spatial and temporal variability of soil properties, (b) the precision with which we are able to model these systems, and (c) the complexities of integration from point scale to real hydrologic systems. However, these difficulties may be expected to yield to the continuing increases in simulation power available to us, and to continued innovations in experimental approaches.