Degradation and adsorption of tralkoxydim in Chinese soils and water-sediment environments.

Tralkoxydim is a cyclohexanedione herbicide primarily used for gramineous weed control in China. In this paper, we present results of a tralkoxydim laboratory environmental fate study characterizing its degradation, adsorption, and mobility behavior in three different soils and two water-sediment systems (river and lake) in China. Degradation half-life of tralkoxydim in soil under aerobic conditions was 5.1, 7.7, and 7.9 days in Jiangxi red soil, Taihu paddy soil, and Northeast China black soil, respectively. Under anaerobic and flooding conditions, half-life values were 6.2, 15.1, and 19.8 days for the same three soils, respectively. Soil pH was the major factor effecting tralkoxydim degradation. In the aerobic water-sediment experiments, tralkoxydim degraded faster in the river system (total system half-life 43.3 days) than the lake system (total system half-life 99.0 days). Correspondingly, its anaerobic degradation half-life values were 46.2 and 53.3 days for the river and lake systems, respectively. Tralkoxydim adsorption in the three soils was found to follow the empirical Freundlich isotherm. The adsorption coefficient (K d ) was 8.60, 1.00, and 1.57 for Jiangxi red soil, Taihu paddy soil, and Northeast China black soil, respectively. Soil pH was the major factor effecting tralkoxydim adsorption. Adsorption free energy change was less than 40 kJ mol-1 in all three soils, indicating a physical mechanism in the process. Thin-layer chromatography (TLC) tests showed that relative to the solvent transport to 11.5 cm, the travel distance of tralkoxydim was 8-10 cm in the three soils, corresponding Rf values at 0.05, 0.35, and 0.75 for Jiangxi red soil, Taihu paddy soil, and Northeast China black soil, respectively. Results of this work suggest that under alkaline conditions, tralkoxydim adsorption becomes smaller; thus, assessments on its mobility and potential groundwater impact should focus on these soil types.

[Effects of multiple environmental factors on triflulsulfuron-methyl degradation in soils].

Triflulsulfuron-methyl, a widely used sulfonylurea herbicide, has done harm to the soil and crop. Its environment fate was affected by many factors such as physicochemical or biological factors. In order to understand the effects of different environmental factors on the degradation of triflulsulfuron-methyl in soil, simulated indoor incubation experiments were carried out to explore the effects of soil microbe, soil type, dissolved organic matter (DOM), temperature, and soil moisture on triflulsulfuron-methyl degradation in soils. The results showed that different environmental factors such as temperature, soil moisture, soil microorganisms and soil type influenced triflulsulfuron-methyl degradation in different degrees. The increased soil microbial biomass, soil organic matters and DOM were beneficial to the soil degradation of triflulsulfuron-methyl, meanwhile, the decrease in soil pH could accelerate its degradation in soils. The results showed that soil microorganisms were the main factor effecting the degradation of triflulsulfuron-methyl in soil. Our results provided initial data for the conclusion that a set of biological and physiochemical factors coordinately regulate the decay of triflulsulfuron-methyl in soils.