Behavior of cinosulfuron in paddy surface waters, sediments, and ground water

Cinosulfuron (3-(4,6-dimethoxy-1,3,5-triazin-2-yl)-1-[2-(2-methoxyethoxy)-p henylsulfonyl]-urea) is a sulfonylurea herbicide used to control a wide ran ge of broadleaf weeds in rice (Oryza sativa L.). A 2-yr field study was con ducted in northwest Italy to determine the effect of cinosulfuron on surfac e and subsoil waters in rice paddies. Cinosulfuron was applied at 70 g a.i. ha(-1) on 35 ha of flooded rice. After the treatment, the change in herbic ide concentration over time was studied by analyzing water and sediment sam ples in a test paddy field (2.16 ha, located in the treated area), water in a spring and a pond (both located near the test paddy), two wells (up- and downhill to the treated area), and two piezometers (along the test paddy l evee). To better understand some of the field study results, cinosulfuron d egradation was also evaluated in the laboratory in solutions buffered to di fferent pH values. Two weeks after the treatment, the cinosulfuron concentr ation in the paddy water decreased by about 60%. No cinosulfuron was detect ed at about 2.5 mo after the treatment. The concentration in the sediment g radually increased after the treatment, reaching the highest value (13.53 m ug kg(-1)) 3 wk later. The maximum cinosulfuron content in the spring and p ond were 0.91 and 029 mug L-1, respectively, and these were detected 60 to 90 days after treatment (DAT), The water collected in the piezometers reach ed the highest concentration (0.99 mug L-1) 29 DAT, Cinosulfuron was never detected in the wells. In the degradation study at different pH values, cin osulfuron degraded rapidly at low pH values.