The vertical distribution of the potential to mineralize [ring-U-14C]herbicides was investigated in samples from a sandy aquifer. Mecoprop, isoproturon, or atrazine were added to sediments from 0.06 to 7.68 m below the surface, and mineralization at 10°C was monitored as evolved 14CO2. The highest potential for mineralization was found in the plough layer, the upper 0.30 m. Here, approximately 43% of mecoprop, 14% of isoproturon, and 3% of atrazine were recovered as 14CO2 after 85, 267, and 119 days, respectively. The estimated doubling time, T(d), for 14CO2 evolution from the initially added herbicide was approximately 20 days for mecoprop in the plough layer increasing to more than 5 years below 4.73 m. For isoproturon incubated at 10 °C, T(d) was 700 days in the plough layer increasing to 6 years in the subsurface. At 20 °C the rate of mineralization of isoproturon doubled compared to the rate at 10 °C. Atrazine was mineralized slowly, T(d) was 5 years in the plough layer, and mineralization of atrazine below 0.70 m was not observed. None of the herbicides was mineralized anaerobically in the presence of nitrate.
- Programområde 2: Vandressourcer