| Studies were conducted to (1) assess pesticide contamination in Arkansas surface and ground water and (2) to evaluate and develop the use of solid-phase extraction disks as a routine analysis tool for pesticide analysis in water.; A two-year monitoring study including five collections at 16 mixer/loader sites was conducted to assess pesticide and nitrate contamination. Fourteen detections of atrazine, cyanazine, methyl parathion, metolachlor, norflurazon, pendimethalin, propanil, or trifluralin at eight locations were confirmed by mass spectroscopy. Three detections were above the health advisory level (HAL).; A three-year pesticide survey of surface water in Lawrence, Mississippi, Phillips, and Jefferson counties of Arkansas was conducted to assess pesticide contamination from nonpoint sources. Fourteen pesticides were represented in 256 total detections. Metolachlor (25% of total detections), atrazine (22%), norflurazon (16%), and cyanazine (14%) were the most commonly detected compounds. Five percent (5%) of the total detections were above health advisories.; The stability of various pesticides in water at 4 C was compared with their stability when partitioned onto C{dollar}sb{lcub}18{rcub}{dollar} solid-phase extraction (SPE) disks that were stored at either 4 C, {dollar}-{dollar}20 C, Or 4 C for 1 d, then {dollar}-{dollar}20 C up to 180 d of storage. Pesticides showed equivalent or greater stability when stored on the SPE disk compared to storage in water.; Desiccation methods were applied to pesticide enriched SPE disks to determine if enhanced stability would result when residual water was removed before storage. Freeze-drying greater stability for hydrolysis-susceptible compounds compared to other desiccation treatments. Disk storage at frozen temperatures provided a more stable environment than disk storage at ambient temperatures for metribuzin, profenofos, and cyanazine, but had little effect on the other compounds.; A study was conducted to determine the effect of potential sediment components in water, Ca-montmorillinite clay and commercial humic acid, on the extraction efficiency of various pesticides. The effects of these additions were generally pH-dependent and acted independently. Lower recovery of most pesticides occurred at pH 8 when Ca-montmorillinite was {dollar}ge{dollar}0.1 g. Concentrations of humic acid had less effect on lowering extraction efficiency at pH 8 compared to water at pH 6. |
