China National Institute of Standardization, Beijing, 100191, PR China.
Department of Materials Chemistry, Huzhou University, 313009, Zhejiang, PR China.
Chemosphere. 2022 Sep;303(Pt 2):135058. doi: 10.1016/j.chemosphere.2022.135058. Epub 2022 May 25.
Straw will degrade into segment, powder and crystalline cellulose, while the agricultural film will degrade into microplastics (MPs) in farmland soils. The specific surface area of these micro-particles increases and many new functional groups are formed in the degradation process, which can be a good vector of pesticides. To more accurately and truly analyze the risk of main imported substances and their degradation products against pollutants in soil, the adsorption behavior and mechanism of four commonly used pesticides on aged polyethylene microplastics (APE), wheat straw segment (WSS), wheat straw powder (WSP), and straw crystalline cellulose (SCC) were analyzed and compared through batch adsorption experiments and infrared spectrum. The adsorption kinetics of four pesticides on MPs and straw degradation products tended to be pseudo-second-order kinetics; the adsorption isotherms of pesticides on APE and SCC tended to fit the Freundlich model, while on WSP and WSS tended to fit the Langmuir model. The adsorption was a spontaneous endothermic increase process, suggesting that the main adsorption force of pesticides on MPs and straw degradation products was hydrophobic diffusion. The adsorption of pesticides against WSP and WSS still had a certain π-π conjugation and electrostatic interaction. And the adsorption amount on the straw degradation products followed the order of WSP > WSS > APE > SCC, presumably related to the specific surface area and pore volume of the adsorbent. As WSP, WSS could adsorb more pesticides, the straw returning to the field can be used for slow-release of pesticides to reduce the dosage of pesticides.
秸秆将降解为段、粉和结晶纤维素，而农用薄膜将在农田土壤中降解为微塑料（MPs）。这些微颗粒的比表面积增加，在降解过程中形成许多新的功能基团，它们可以成为农药的良好载体。为了更准确、真实地分析主要进口物质及其降解产物对土壤污染物的风险，通过批量吸附实验和红外光谱，分析和比较了四种常用农药在老化聚乙烯微塑料（APE）、麦秸秆段（WSS）、麦秸秆粉（WSP）和秸秆结晶纤维素（SCC）上的吸附行为和机制。四种农药在 MPs 和秸秆降解产物上的吸附动力学均趋于准二级动力学；农药在 APE 和 SCC 上的吸附等温线趋于符合 Freundlich 模型，而在 WSP 和 WSS 上则趋于符合 Langmuir 模型。吸附是一个自发的吸热增加过程，表明农药对 MPs 和秸秆降解产物的主要吸附力是疏水性扩散。农药对 WSP 和 WSS 的吸附仍然存在一定的π-π共轭和静电相互作用。而且，对秸秆降解产物的吸附量顺序为 WSP＞WSS＞APE＞SCC，这可能与吸附剂的比表面积和孔体积有关。由于 WSP、WSS 可以吸附更多的农药，因此可以将秸秆还田作为农药的缓释，以减少农药的用量。
