Effects of microplastics on NO production and reduction potential in crop soils of northern China.

Microplastics (MPs) pollution are found to be increasing in vegetable soils and potentially affecting NO production and their associated pathways; however, its specific effects remain unclear. Here, we selected two common MPs, PE and PP at four different concentration levels of 0, 0.5, 1.5 and 3%, and conducted several incubation experiments aiming to explore soil bacterial and fungal NO production. Results showed that the bacteria were the main contributors for the production of NO, regardless of the absence or presence of MPs; and its contribution was decreased with increasing concentrations of PE and PP. The nosZ clade I and II genes were positively correlated with NO reduction rates, indicating a combined regulation on soil NO reduction. PE significantly inhibited the bacterial nitrification and denitrification, but did not affect the total NO production rates; while PP significantly reduced both the bacterial and fungal NO production rates. The resistance of fungal NO production to MPs pollution was stronger than that of the bacterial NO production. It highlights that the MPs pollution could reduce the potential of NO production and reduction, and thus disturb soil nitrogen cycling system; while the inhibition on NO production via bacteria and fungi varies with different types of MPs. This study is conducive to an improved and more comprehensive understanding of the ecological impacts of MPs within the agroecosystem.