Trace level pesticide detections in Arkansas surface waters

A pesticide survey of surface water was conducted in 1989, 1990, and 1991 in Lawrence, Mississippi, Phillips, and Jefferson counties in Arkansas to assess nonpoint source water pollution. During these 3 years, 59-62 lake and river/stream sites were sampled eight times and screened for 17 pesticides commonly used in Arkansas. Pesticides were extracted by solid-phase extraction (SPE) disks. Extracts were analyzed by gas chromatography-electron capture detection (ECD) and high-performance liquid chromatography-UV detection (LCUV). Detections were confirmed by gas chromatography-mass spectroscopy (MS) or ca-chromatography. The 256 detections during the survey represented 14 pesticides. Metolachlor (25% of total detections), atrazine (22%), norflurazon (16%), and cyanazine (14%) were the most commonly detected compounds. A total of 5% of the total detections was above health advisories. Spring and summer samples provided 73% of the total pesticide detections. Rivers and streams were responsible for 62% of the detections. The highest number of repeated detections of the same pesticide at a site was for cyanazine (six of eight sampling periods).