Recently, the risk of the use of thiacloprid (THI) has attracted widespread attention due to its adverse effects on non-target organisms. Effective approaches to mitigate its ecological risk in agricultural fields are clearly needed. Biochar amendment not only affects the sorption of pesticides but also influences their transformation via different pathways.<br/>In this study, the sorption and degradation of THI in a black soil amended by various biochars were systematically investigated, and the mechanisms therein were explored by analyzing the changes in soil physicochemical properties, environmentally persistent free radicals in biochars and the microorganism community. The pH, electrical conductivity, available P, organic carbon (OC) contents and surface area (SA) of the soil were improved by the addition of biochar, while the H/C ratio decreased. With the increasing pyrolyzing temperature (PT) of biochars, the enhancement on THI sorption in the amended soil increased, which was associated with the increase in OC and SA and decrease in H/C. Sorption occurred via hydrogen bond, pore-filling and n-p and p-p electron donor-acceptor electron interactions besides hydrophobic partition.<br/>Amendments of 300-PT biochar promoted the biodegradation of THI by increasing nutrient availability for microbes but inhibited THI chemical degradation. In contrast, the amendments of 500- and 700-PT biochar inhibited biodegradation by reducing THI availability and instead promoted chemical degradation mainly through elevation of pH, active groups on mineral surface and generation of hydroxyl radical and other free radicals. The results of CCA and Pearson correlation analysis indicated that THI and biochar all shifted the soil microbial community. Eight THI-degradative genera belonging to the phylum Proteobacteria were found and the degradation of THI also changed the nitrifying-denitrifying bacteria. Biochar amendments changed soil bacterial community by modulating soil pH, OC and nitrogen cycling processes, further influencing THI biodegradation. These insights into mechanism help accurate application of biochar technology.

Biochars change the sorption and degradation of thiacloprid (THI) in soil: Insights into chemical and biological mechanisms

255th National Meeting (2018)

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