Environmental fate of the triazole fungicide propiconazole in a rice-paddy-soil lysimeter

Environmental fate of the triazole fungicide propiconazole, 1-[[2(2,4-dichlorophenyl)-4-propyl-1,3-diox olane-2-yl]methyl]1H-1,2,4-triazole, in soil was investigated using lysimeters simulating a rice-paddy-soil conditions. Two lysimeters composed of different soil types, a sandy loam (lysimeter A) and silty clay (lysimeter B), were used. Propiconazole (Tilt 250R EC) plus [U-14C]-propiconazole was applied over a two-year period to the soil surface of the lysimeters. Propiconazole fate in the lysimeters was assessed by measuring total radioactivity in the leachate, evolved 14CO2, and 14C-residues in the soil and rice plants. The amounts of applied 14C in the leachate from lysimeter A were 4.4 and 5.2% in the first and second year, respectively. A background level of (0.00005% of applied) 14C in the leachate from lysimeter B was detected, suggesting negligible movement of the fungicide to groundwater in the silty clay soil. The amount of 14CO2 evolved from lysimeter A accounted for 7.8 and 12.2% of applied 14C in the first and second year, respectively, whereas those from lysimeter B were 5.7 and 7.1%. Total 14C detected in the rice plants grown in lysimeter A were 7.3 and 9.8% of applied 14C in the first and second year, respectively, which compared to 3.0 and 7.6% in lysimeter B. Most of the applied 14C was detected in the top 10 cm soil layer, suggesting that propiconazole remains close to the soil surface after application in soil. Degradation products of propiconazole identified in the lysimeter soils were 1-[[2(2,4-dichlorophenyl)-2-(1,2,4-triazole-1-yl) ketone (DP-1), 1-(2,4-dichlorophenyl)-2-(1,2,4-triazole-1-yl) ethanol (DP-2) and 1-[[2(2,4-dichlorophenyl)-4-hydroxypropyl-1,3-dioxolane-2-yl]methyl]1H-1,2,4-triazole (DP-3 and DP-4).