Microplastics (MPs) enter the soil through a variety of pathways, including plastic mulching, sludge, and organic manure application. In recent years, domestic and foreign experts and scholars have been concerned about the residues and contamination of MPs in the soil of greenhouse agriculture. In this investigation, five types of MPs including low-density polyethylene (LDPE), high-density polyethylene (HDPE), polystyrene (PS), polypropylene (PP), and polyethylene terephthalate (PET), and two concentrations (1% and 5%, w/w) were used in a 30-day external exposure test. Evidence of microbial enrichment was found on the surface of the MPs. The total amount of biofilm on the surface of MPs increased dramatically with increasing exposure time and MP concentrations. The polysaccharide content of extracellular polymers (EPS) in biofilms was significantly different, and the maximum PS1 (1% (w/w) PS) concentration was 50.17 mg/L. However, EPS protein content did not change significantly. The dominant bacteria on the surface of MPs with different types and concentrations were specific, and the relative abundance of Patescibacteria was significantly changed at the phylum level. At the genus level, Methylophaga, Saccharimonadales, and Sphingomonas dominated the flora of LDPE1 (1% (w/w) LDPE), PS1, and PET5 (5% (w/w) PET). The dominant bacteria decompose organic materials and biodegrade organic contaminants. According to the FAPROTAX functional prediction study, chemoheterotrophy and aerobic chemoheterotrophyplay a role in ecosystem processes such as carbon cycle and climate regulation. The application of LDPE1 has a greater impact on the carbon cycle. Plant development and soil nutrients in greenhouse agriculture may be influenced by the interaction between MPs and microorganisms in the growing area, while MP biofilms have an impact on the surrounding environment and pose an ecological hazard.

This work examined the adsorption mechanism of microplastics made of polypropylene (PP), polyethylene (PE), and polyvinyl chloride (PVC) on Cd2+ and its effects on the environment. The fi ndings demonstrated that microplastics’ crystallinity and unique functional groups also affected the adsorption of Cd2+, besides being a critical factor regulating the particle size of the MPs. The three MPs’ Cd2+ adsorption kinetics conformed to the quasi-secondary kinetic model, confi rming that the adsorption was nonlinear. Besides, the three MPs’ Cd2+ isothermal adsorption process can be adequately described by the Langmuir and Freundlich models, demonstrating that monolayer and multilayer adsorption coexist and are heterogeneous adsorption processes. As indicated by the fi ndings of the energy spectrum study, PVC (0.78%), PP (0.25%), and PE (0.18%) exhibited the maximum concentrations of Cd2+ adsorbed in MPs. As revealed by the fi ndings of the effect of environmental conditions on the adsorption of Cd2+ by the MPs, the three MPs exhibited the maximum adsorption capacity at 35ºC and a pH of 6.0. The equilibrium adsorption of Cd2+ by PP, PE, and PVC was reduced by 3.3, 8, and 13 times, respectively, compared with no salt at a salt concentration of 1 mg/L salt solution.