Spatial And Temporal Distribution Of Fomesafen During Soil Erosion And Its Fate In Aquatic Ecosystem

Fomesafen, 5-[2-chloro-4-(trifluoromethyl)phenoxy]-N-(methylsulfonyl) -2-nitrobenzamide, is used widely for weed control in peanuts and soybeans, most of which are planted in slopy field, as pre- or post-emergent treatment. Soil erosion takes place severely during growth of peanuts and soybeans and would cause leaching and washing off of pesticide residues and pesticide-contaminated soils/sediments to waterways, floodplains and water bodies. Pesticides and their metabolites may be toxic to aquatic plants and animals and be harmful to human being finally through food chain.The spatial and temporal distribution during soil erosion and behavior of fomesafen in aquatic ecosystem was evaluated by using runoff plot, radiotracer, simulation and indoor culture technique.The loss of 14C-fomesafen through runoff decreased with time, and the total amount was 136.33 μg m-2, which accounted for 0.28% of applied. Occurring at day 2 after application, the first runoff of fomesafen by water was 4.8 times to that by sediment, the ratio gradually decreased. Temporal and spatial distribution of 14C-fomesafen residues in 0-2.5 cm soils appeared obviously different from the other deeper soil layer and 14C-fomesafen residues are less mobile vertically. At upper part of slope, 14C-fomesafen residues in upper 2.5 cm layer decreased about 9 times (from 0.65 to 0.07 μg g-1). Whereas, finally, soil at the lower part of slope contained most residues (0.22 μg g-1), comparing to 0.07, 0.12 μg g-1 at upper, middle part. Bound residue increased with elapsed time, at 75 day after application, about 63.16%, 67.31%, 59.66% of total residues still remained bound to soil particles along slope, respectively.