Fate and movement of endosulfan under field conditions

The impact, of soil mulches on movement of endosulfan (Thiodan 3 EC) was measured under field conditions. Three soil treatments on a Lowell silty loam soil (5% organic matter) were used to reduce soil erasion and surface water runoff. Living turf mulch (tall fescue) between every cropping row (turf-1), turf every other raw (turf-2), and no mulch (NIM) treatments were compared. Thiodan was used as foliar single spray on tomato and pepper at the rate of 0.61 kg Al/ha. Following field spraying, runoff water, sediment, and soil samples were collected and analyzed for endosulfan concentration, Endosulfan infiltration through the vadose zone was monitored using pressure-vacuum lysimeters. Studies were also undertaken to determine the magnitude and dissipation of endosulfan stereoisomers (alpha- and beta-endosulfan) and endosulfan sulfate. Analysis of samples was accomplished using gas chromatography (GC) and GC-coupled mass spectrometry (GC-MS). The results confirm the formation of endosulfan sulfate and its significance as a residue component in soil and also the relative persistence of the beta-isomer as compared to the alpha-isomer. Cultivation of turf between cropping rows and pepper intercropped with tomato reduced runoff water and sediment loss and endosulfan movement from application site to surface water runoff. Treatments planted with pepper intercropped with tomato have a tremendous impact on reducing runoff water discharge (67.3% reduction) and sediment loss (85.9% reduction) compared to that planted with pepper plants only. Results indicated the vertical movement of endosulfan through the vadose zone at a concentration of 0.63 mu g/L. Soil core data also indicated that endosulfan leached 23 to 46 cm in the soil.