Characterization of Atrazine in Source Water--A Case Study From Kansas

Abstract

Characterization of atrazine in source water can be achieved efficiently and economically using an approach developed by the U.S. Geological Survey for an artificial recharge demonstration project in south-central Kansas. The approach may be applied to many different areas, and the information obtained may be used to adjust treatment processes for atrazine in various source waters, making the processes even more economical.

The Little Arkansas River in south-central Kansas is being evaluated as a source for artificial recharge of water into the Equus Beds aquifer, which provides water for the city of Wichita. Atrazine, an herbicide commonly applied to row crops, is of particular concern because of potential effects on water quality. Stream discharge and atrazine concentrations, loads, and yields were examined at two U.S. Geological Survey gaging stations from January 1995 through December 1997. The use of automated equipment for sample collection and enzyme-linked immunosorbent assay (ELISA) for herbicide analysis allowed for the efficient collection of many samples at low cost. About 1,800 samples were analyzed by ELISA from 1995 to 1997, with a turnaround time of about 2 days per sample.

Average daily stream discharge at the two sites ranged from 112 to 697 cubic feet per second during the 2-year study period. Annual average atrazine concentrations at the Halstead and Sedgwick sites were 0.9 and 2.6 micrograms per liter, respectively. However, daily mean atrazine concentrations were as high as 33.5 micrograms per liter during spring and summer runoff. The U.S. Environmental Protection Agency's Maximum Contaminant Level (MCL) for atrazine is an annual average of 3 micrograms per liter. The annual atrazine loads ranged from 1,500 to 4,100 pounds. The annual yields ranged from 1.9 to 3.5 pounds per square mile. It was estimated that at least 260,000 pounds of atrazine were applied to crops in the Little Arkansas River Basin upstream from the Sedgwick site during the period of data collection. Of the 260,000 pounds applied, about 1 percent was transported in surface runoff to the Little Arkansas River. Ninety percent of the runoff load occurred during a very short period of time (about 15 to 40 days), generally following the application of herbicides in late spring and summer.

Additional information on the Equus Beds Project can be found at: http://ks.water.usgs.gov/studies/equus/

Christensen, V.G., and Ziegler, A.G., 1998, Characterization of atrazine in source water--A case study from Kansas, in Proceedings of Water Quality Technical Conference, San Diego, California, November 1-4, 1998, Proceedings: Denver, Colorado, American Water Works Association, CD-ROM catalog 20400, 1-9 p.

To request a paper copy of this proceedings article, email: vglenn@usgs.gov