Atrazine Contamination in a Rural Source-Water Supply: Spa Lake, Lewisburg, Kentucky

摘要

In 1998, Western Kentucky University (WKU) worked in collaboration with the Environmental Protection Agency (EPA), Drinking Water Protection Division, to investigate methods to improve source-water quality for rural-water supply systems (RWSS). Through partial funding from the EPA, WKU developed a Technical Assistance Center for Water Quality (TACWQ), which focused resources and expertise toward assisting RWSS in achieving and maintaining capacity development goals and protecting public health. The TACWQ established the Source Water Protection Initiative (SWPI) to assist RWSS in acquiring and monitoring the technical, financial and managerial capacity needed to provide safe drinking water and achieve the public health protection goals of the EPA Safe Drinking Water Act (Technical Assistance Center, July 1998). The SWPI also provided technical assistance toward identifying and reducing source water impacts throughout Kentucky. Monthly sampling during 2000 from seven watersheds in western and south central Kentucky showed that levels of several pesticides and herbicides were elevated above Maximum Contaminant Levels (MCLs) in their source waters. Of the MCL exceedences, three commonly used pesticides (atrazine, alachlor, and simazine) were repeatedly being detected at several sites. Of the three compounds, atrazine, a triazineclass herbicide widely used in Kentucky to control broad leaf and grassy weeds in row crops such as corn, drew the most interest. Atrazine has been classified as a spring use only, u22Restricted Use Pesticide due to its potential for groundwater contamination.u22 (EXTOXNET, 1996) It is regulated as a compound with class III (slight) toxicity. In 1994, EPA took atrazine under special review to evaluate the ecological and biological effects it may cause. EPA later deemed atrazine not to significantly increase the risk of cancer in humans and went as far as lifting its use restrictions. Independent researchers still dispute EPA claims. The exceedences of the MCLs by many compounds in source water do not immediately result in violations. The source water must go through treatment processes. Water-supply operators must strive to meet National Primary Drinking Water Standards (EPA, 1999) prior to going to the consumer. However, the fundamental concept driving the SWPI is that the technical and financial challenges faced by RWSS are proportional to the quality of their source water. At several sites, even treated water that was distributed to customers exceeded federally mandated MCLs. Levels of atrazine in finished water reached 17 parts per billion (ppb) in Lewisburg, Kentucky. The MCL for atrazine is currently 3.0 ppb.