Effect Of Rice-Straw-Derived Char On Sorption/Desorption Behavior And Bioavailability Of Cabaryl In Soil

Crop residue burning is a historically common postharvest practiceadopted in most parts of our country for the purposes of clearing land andrecycling nutrients. This combustive carbonization results in char thatcontains a high-surface-area material like charcoal. It is the main sourceof black carbon in cultivated soils. The bioavailability of pesticides insoils is affected by the addition of biochar, which alters the sorption anddesorption characteristics of the soils. The sorption and desorptionbehavior of carbaryl in six typical soils and char-amended soils has beenstudied using batch sorption and successive desorption methods, and thebioavailability of cabaryl in char amended soils is also focused. Theobjective of this study is to learn the effect of biochar on sorption/desorption behavior and microbial degradation of carbaryl in soil. Theresults here would provide a theoretical basis for the evaluation ofenvironmental risks caused by the ash field farming practices.The results showed that Freundlich adsorption isotherm equationcould be well describe the sorption/desorption isotherm of carbaryl indifferent adsorbents with R2>0.96. The partition coefficient of carbaryl insoils is correlated positively with the contents of the soil organic mattersbut has little with cation exchange capacity. In addition, the partition coefficient may also have a positively correlated with soil clay content.The sorption capacity was closely correlated with the content of biocharadded in soils. The adsorption capacity of soils is significantly improvedwith the increase of char content added in soils, especially for low organicmatter content of soils. The increase in the amount of char in soils causesthe enhanced nonlinear sorption/desorption isotherm of carbaryl. Thesorption/desorption hysteresis was correlated with the biochar added insoil. The higher the char content in the soil, the more hysteresisphenomenon of carbaryl desorption in the soil is observed. Neither soilorganic mater nor cation exchange capacity has little effect to thesorption/desorption hysteresis. Chars added in soils can enhance theactivity of bacteria and ultimately stimulated the bioavailability ofcarbrayl dissolved in water. However, it also enhances desorptionhysteresis and then reduces the bioavailability of carbaryl, which result ina long-term threat to the environment.