As an exogenous pollutant, microplastics (MPs) have several effects on the soil enzyme activity and microbial community. However, the clear relationship between MPs and microorganisms has not been explored in vegetable farms with long-term continuous cropping. This study investigated the abundance and particle size of MPs, the concentration of phthalate esters (PAEs), and effects of MP pollution on soil microbial and enzyme activities in greenhouse vegetable soil with different numbers of years of continuous cropping (5, 10, 15, 20, 25 and 30 years) in Hebei Province, China. The results showed that MPs abundance increased with planting years. Moreover, both the proportion of MPs with particle sizes of 0-2 mm and the total concentration of PAEs increased over time. These results suggest that MPs in the soil gradually undergo cleavage over time. The abundance of MPs was significantly negatively correlated with dehydrogenase activity (P<0.05), which implies that the accumulation and degradation of MPs inhibits microbial cell activity. In addition, MP accumulation caused by continuous cropping and the release of PAEs from the degradation of MPs led to an increase in the relative abundance of microorganisms associated with the degradation of soil organic matter (Actinobacteria, Bacteroidetes). Overall, this study provides a theoretical basis for a better understanding of the environmental effects arising from the accumulation of MPs in greenhouse vegetable fields and is useful for assessing the ecological risks of MPs.

 

Microplastics (MPs); Enzyme activity; Microorganisms; Greenhouse vegetable fields