Microplastics Change Soil Nutrient Availability, Microbial Properties, and Ecosystem Multifunctionality of a Red Soil

Microplastics (MPs) contamination in soil has gained much attention due to their potential impairment to the soil ecosystem. However, limited information about their impacts on soil ecosystem multifunctionality (EMF) has been obtained. A two-month incubation experiment was conducted in a red soil using MPs of polyethylene (PE) and polyvinyl chloride (PVC), with varying addition doses (1% and 5%, w/w) and particle sizes (150 and 500 mesh). These treatments are referred to as PE150, PE500, PVC150, and PVC500, respectively. Soil properties, including available nutrients (dissolved organic carbon, DOC; available nitrogen, NO3−-N and NH4+-N; and available phosphorus, AP), enzymes activities (urease, invertase, and acid phosphatase), and microbial community composition (based on phospholipid fatty acids analysis), were measured. Soil EMF was evaluated using these parameters. Both MPs did not affect soil DOC, but significantly reduced the content of soil available nitrogen (AN) and AP. PE showed a stronger effect than PVC, particularly at higher dose and larger particle size. PE generally decreased microbial biomass while PVC increased it. However, the influence of both MPs on soil enzymes activity varied depending on their type, dose, particle size, and the duration of incubation. 1%‒5% of PE150 significantly decreased the soil EMF while 1% of PVC150 and 5% of PE500 improved it. The impact of MPs on soil properties was highly related to their characteristics, including type, dose, particle size, and their interactive effects. However, the type of MPs emerged as the primary factor influencing soil EMF, followed by particle size and addition dose. This study demonstrated the complex impact of MPs’ pollution on soil ecological processes and soil ecosystem functionality, highlighting the necessity for more studies on the impacts on soil ecosystems induced by MPs.