Carrier effect of S-metolachlor by microplastics and environmental risk assessment

Organic pesticide pollutants have obvious negative effects on organisms in the environment. As an emerging organic contaminant, the ubiquitous microplastics (MPs) are undoubtedly regarded as the focus of global attention. MPs originate from the fragmentation of large plastic waste or direct environmental emissions. This research explored the adsorption characteristics of S-metolachlor (S-MET) by three types of MPs, namely polyvinyl chloride (PVC), polypropylene (PP) and polyethylene (PE). The effects of factors such as initial pH, contact time, dosage and ionic strength on the reaction were explored. SEM, XRD, FT-IR and other analytical methods were used to study its physical and chemical properties. Adsorption kinetics, isotherm and mechanism of S-MET on MPs were carried out. The environmental and risk assessment between MPs and S-MET were analyzed. The results showed that the saturated adsorption capacities of S-MET on PVC, PP and PE are 17.67 μg/g, 14.71 μg/g and 14.41 μg/g, respectively. In addition, adsorption has both physical and chemical adsorption processes, and physical adsorption is the main process. The main adsorption mechanism may be the process of hydrogen bonding and ligand complexation. The experimental results can provide a theoretical basis for the transfer and conversion of S-MET in areas with plastic pollution. The environmental benefits and risk assessment provide a reference for controlling the pollution of MPs and S-MET in the environment.