Distribution of low-density microplastics in the mollisol farmlands of northeast China

Plastic pollution, especially microplastic (MP), which is small in size (<5 mm) is one of the main environmental problems in global ecosystems and can cause harm to organisms. Low-density plastic has been widely used in farmlands, but the factors that influence Low-density microplastic (LDMP) distribution are still not clear. In this study, both field investigations at small and large scales and laboratory simulations, and both geostatistics and classical statistics were used to examine LDMP distributions and the main driving factors in farmland soils. The results showed the following. (1) Only polyethylene (PE) of LDMP was found in farmland. (2) The means of LDMP weight content (LDMP-W), LDMP abundance (LDMP-AB) and LDMP area content (LDMP-A) were 0.27 mg kg, 107 N kg and 12.6 mm kg in mollisol farmlands, respectively. (3) LDMPs were positively correlated with macroplastics (MAP) at the large scale, while any correlations were not obvious at small scales. (4) LDMPs were not only transported by surface soil-water loss (>96%) but were also transported by infiltration through soil pores (<4%). (5). LDMP loss increased with soil bulk density (BD) increasing, and low BD tends to increase LDMP loss by interflow. (6) LDMP distribution was not only influenced by water movement but also maybe influenced by microorganisms and crops. For LDMP pollution control, the focus on both surface soil-water loss and the infiltration processes is necessary, and a combination of the functions of microorganisms and crops probably accelerate LDMP decomposition in soils.