Kansas Water Science Center
Formation and Transport of Deethylatrazine in the Soil and Vadose Zone
By C.D. Adams and E.M. Thurman
Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) and two degradation products were monitored at seven depths in the soil and vadose zone throughout the growing season in two experimental plots in which corn (Zea mays L.) was grown. The soils in these plots were a Kimo silty clay loam (clayey over loamy, montmorillonitic, mesic, Fluvaquentic Hapiudoll) and a Eudora silt loam (coarse, silty, mixed, mesic, Fluvaquentic Hapiudoll). The purpose of this field study was to identify and quantify the mobile and persistent degradation products of atrazine that comprise the input, or "source term," to groundwater resulting from the application of atrazine to the soils. The formation of deethylatrazine (2-amino-4-chloro-6-isopropylamino-s-triazine) and deisopropylatrazine (2-amino-4-chloro-6-ethylamino-s-triazine) was monitored at various depths using suction lysimeters to determine the relative proportions at which these compounds enter the aquifer. Deethylatrazine was the major degradation product of atrazine identified in the soil water and appeared to enter the underlying aquifer at a concentration of 5.0 Īg/L, which was greater than the concentration of atrazine entering the aquifer. Deisopropylatrazine also was detected in the soil water, but only in minor concentrations relative to atrazine and deethylatrazine. Because deethylatrazine was the major degradation product in the unsaturated zone, the deethylatrazine-to-atrazine ratio (DAR) may be a good indicator of transport of atrazine through the soil. The hypothesis is proposed that the DAR may be used to distinguish point-source from nonpoint-source contamination of an aquifer.
Additional information about the Organic Geochemistry Research Laboratory can be found at: http://ks.water.usgs.gov/pages/research-lab
Adams, C.D., and Thurman, E.M., 1991, Formation and Transport of Deethylatrazine in the Soil and Vadose Zone [abst.]: Journal of Environmental Quality, v. 20, no. 3, p. 540-547.
To request a paper copy of this journal article, email: scribner@.usgs.gov