. Key Laboratory of the Three Gorges Reservoir Region’s Eco-Environment (Ministry of Education), Chongqing University, Chongqing 400045, China . College of Environment and Ecology, Chongqing University, Chongqing 400045, China
Microplastics have received increasing attention in soil ecosystems, and their potential impacts on soil properties have raised concerns. Pesticides are the most prevalent pollutants in soil, but their combined effects with microplastics on the soil environment have not been elucidated. In this study, polystyrene microplastics (PS MPs) and imidacloprid (IMI) were added to the soil to investigate their combined effects on soil physicochemical characteristics, nitrogen and phosphorus contents, related transformation activities, and the composition of nitrogen- and phosphorus-transforming microorganisms. The results revealed that the coexistence of PS MPs and IMI led to a significantly higher soil pH level and lower water-stable aggregate (WSA) content. Additionally, it increased the relative abundance of nitrogen- and phosphorus-transforming microorganisms, including ammonia-oxidizing archaea and bacteria, nitrite-oxidizing bacteria, heterotrophic denitrifying bacteria, phosphate-solubilizing bacteria. PS MPs increased the soil potential denitrification rate by 14.53% owing to a significantly higher pH level. However, this promotion disappeared when they combined with IMI. The coexistence of PS MPs and IMI caused a significant decrease in WSA content, thereby improving soil aeration and increasing the relative abundance of phosphate-solubilizing bacteria, which led to a 14.54% and 44.79% increase in soil phosphatase activity and Olsen-P content, respectively. Variance partitioning analysis revealed that the coexistence of PS MPs and IMI mainly influenced nitrogen and phosphorus transformations by altering soil pH and WSA content. These results reveal the combined effects of PS MPs and IMI on soil nitrogen and phosphorus transformations and elucidate soil environmental risks associated with microplastics and pesticides.
Shirong Zhang,Zichao Tang,Xiaowei Xu, et al. Effects of the coexistence of polystyrene microplastics and imidacloprid on nitrogen and phosphorus transformation in soil[J]. Front. Environ. Sci. Eng.,
2025, 19(2): 15.
Fig.1 Changes in soil physicochemical characteristics over the incubation period. (a) pH; (b) OM; (c) WSA. *p < 0.05, **p < 0.01, and ***p < 0.001 (compared with the C group).
Fig.2 Changes in the content of (a) NH4+–N; (b) NO3−–N; (c) PNRT; (d) PNRAOA; (e) PNRAOB; (f) PDR during the incubation period. *p < 0.05, **p < 0.01, and ***p < 0.001 (compared with the C group).
Fig.3 Changes in (a) the Olsen-P content and (b) phosphatase activity during the incubation period. *p < 0.05, **p < 0.01, and ***p < 0.001 (compared with the C group).
Fig.4 (a) Alpha diversity and (b) Beta diversity of microbial communities (displayed by principal coordinate analysis).
Fig.5 (a) Relative abundance of microorganisms at the genus level. (b) Relative abundance of genera related to nitrogen and phosphorus transformation. (c) Correlation network analysis of environmental factors and bacteria. Only genera with a relative abundance greater than 1% and strong correlations (Pearson’s r > 0.6 or r < −0.6) are shown. The size of a node is proportional to the strength of the correlation. Red lines indicate a positive correlation, while gray lines indicate a negative correlation.
Fig.6 (a) Heat map of correlation between nitrogen and phosphorus transformation, environmental factors and microorganisms. (*p < 0.05, **p < 0.01, and ***p < 0.001). (b) VPA for the contributions of pH, OM, WSA, and microbes to nitrogen and phosphorus transformation.
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