Pesticide Adsorption and Leaching in Soil: An ELISA Laboratory Experiment

Inexpensive pesticide measurement by Enzyme-Linked lmmunoSorbent Assay (ELISA) technology, widely used for environmental monitoring, may be a useful tool for providing instruction on the environmental f te of pesticides in the classroom. A laboratory experiment hat provides instruction in state-of-the-art ELISA pesticide testing methods and demonstrates the effect of soil organic matter content on atrazine (6-chloro-N-ethyI-N’-(1-methylethyl)ol,3,5-triazine-2,4-diamine) transport is described. Atrazine transport through several soils was determined by a column leaching study. Atrazine adsorption by soils was also determined in a distribution coefficient (Ko) study. Results from both studies were used to predict the relative mobility of atrazine in a soil with an unknown organic carbon (OC) content. Results from a classroom experiment showed atrazine from soil column leachate was directly related to soil OC content. Column leachates from Clarion (fine-loamy mixed mesic Typic Hapludoll) (3.1070 OC) and Dougherty (loamy, mixed, thermic Arenic Haplustalf) (0.7070 OC) soils tained 0.8 and 27.6 tzg L -1 atrazine, respectively. Results from the column study were consistent with results from the K a study. Atrazine in column leachate was inversely related to calculated Kd values of 8.2 and 2.2 L kg -1 for the Clarion and Dougherty soils, respectively. Atrazine in the column leachate of an unknown soil with an intermediate Kd value of 4.1 L kg-~ was 9.2 #g L-~. The ELISA experiment requires minimal supplies and can easily be incorporated into soil science classes or other courses concerned with water quality. THE ENVIRONMENTAL FATE of soil-incorporated many pesticides depends on soil and pesticide properties. Soil chemical properties that increase pesticide adsorption reduce pesticide transport and protect groundwater. The effect of soil properties on pesticide adsorption can be easily shown, but classroom demonstration requires sophisticated and expensive (>$20 000) analytical instrumentation. Recently, rapid and inexpensive (< $500) methods for measuring pesticides have become available. These methods feature pesticide measurement by Enzyme-Linked ImmunoSorbent Assay (ELISA) technology and do not require sophisticated laboratory instrumentation. Pesticide ELISA kits are commercially available and are rapidly gaining acceptance. Use of ELISA methods for analysis of pesticides in water (Buser, 1990; Thurman et al., 1990) and in soil (Bushaway et al., 1988; Kaufman and Clower, 1991; Leavitt et al., 1991) have been reported. Because ELISA kits are portable and allow on-site pesticide analysis, use of ELISA technology is expected to continue to increase in the future (SandDepartment of Agronomy, Oklahoma State Univ., Stillwater, OK 74078. Contribution from the Oklahoma Agric. Exp. Stn. Received 19 May 1994. *Corresponding author ([email protected]). Published in J. Nat. Resour. Life Sci. Educ. 24:23-26 (1995). berg et al., 1992; Schrynemeeckers, 1993). The objectives of this ELISA laboratory experiment were (i) to evaluate hands-on instruction in state-of-the-art ELISA pesticide testing methods, and (ii) to demonstrate the effect of soil organic matter content on adsorption and leaching of atrazine in soil.