Anaerobic degradation of chlorothalonil in four paddy soils

Degradation of Chlorothalonil (CTN) was investigated in four different paddy soils under anaerobic conditions. The CTN biodegradation is strongly affected by the properties of the paddy soils. Soils associating with rich total carbon (TC), repeated CTN application, and neutral pH have shown the high capacity to biodegrade CTN. Additionally, anaerobic CTN biodegradation was accompanied by the methane generation and a drop of oxidation–reduction potential (ORP). The initial CTN concentration had a significant effect on CTN removal efficiency, and increase in the initial CTN concentration resulted in the decreasing of CTN removal percentage. However, it is believed that the inhibitory effect on anaerobic biodegradation of CTN is negligible in natural environment due to the much lower concentration of CTN in natural environment (at ng g−1 or pg g−1 level) than the one (10 μg g−1) investigated in this study. The 4-hydroxy-2,5,6- trichloroisophthalonitrile (HTI), one of the major metabolites of CTN degradation, has shown the significant inhibitation to the anaerobic CTN biodegradation when its residual level is over 0.1 μg g−1.