Effect of microplastics on the transport of extracellular DNA in an agricultural soil

The transport of eDNA is one of the key environmental behaviors for its spreading and dispersal. Microplastics (MPs) are widely present in the soil environment and directly affect the environmental behavior of co-coexisting soil pollutants. However, the effect of MPs on eDNA transport and its mechanism remain unclear. In this study, we systematically investigated the effect of MPs types and functional groups on eDNA transport. The results showed that different kinds of MPs promoted eDNA transport, but there was no significant difference between these two MPs types. MPs with two different functional groups inhibited eDNA transport, and the transport rate of eDNA decreased by 8.9% and 7.0%, respectively. PSNH2 inhibited eDNA transport by reducing electrostatic repulsion, enhancing electrostatic adsorption, and reducing porosity of porous media, enhancing the interaction between eDNA and MPs. In the presence of kaolin, the inhibition effect of MPs on eDNA transport increased with the proportion of kaolin increased. The positive charge of kaolin enhanced the electrostatic adsorption between MPs and eDNA, and inhibited the transport of eDNA. This study revealed the transport rule of eDNA in the presence of MPs, and provided a theoretical basis for a comprehensive assessment of the environmental and ecological risks of coexistence of MPs and eDNA.