Degradation of Carbendazim in Soil: Effect of Sewage Sludge-Derived Biochars

Application of biochar in soils can affect the soil properties and, in turn, the fate of pesticides. Batch experiments were conducted to investigate the effect of sewage sludge-derived biochars on the dissipation of a fungicide carbendazim in soil, and the transformation of carbendazim in soil was also studied. Results showed that the dissipation of carbendazim was fastest in a loamy soil SD with a half-life of 11.0 d among the three kinds of soils tested in this study. A dual effect (both acceleration and inhibition) of sewage sludge-derived biochars on carbendazim degradation in soil was reported. The addition of 10% biochars produced at 700 °C (BC 700) in soil could accelerate the carbendazim degradation, but an inhibitory effect was observed for 10% BC 300 or BC 500. Degradation of carbendazim was significantly inhibited when 0.5 or 5% BC 700 was added in soil but accelerated when the amendment ratio of BC 700 was increased to 10%. Such complex effects of the sewage sludge biochar should be taken into consideration in risk assessment of pesticides and the biochar effects on soil remediation. Eight metabolites of carbendazim were characterized, seven of which were reported in unamended soil for the first time. The metabolic pathways of carbendazim in soil are proposed.