Effects of single and combined contamination of microplastics and cadmium on soil organic carbon and microbial community structural: A comparison with different types of soil

Microplastics (MPs) are an emerging contaminant that have attracted a growing concern about their behavior in soil environment in recent years. However, the research on the interaction between MPs and heavy metal pollution in the soil environment is still scarce. This study investigated the effects of high-density polyethylene (HDPE) and Cd on two soil types (phaeozem and fluvo-aquic soil), and explored their interaction mechanisms. The addition of HDPE significantly increased the content of available Cd in the phaeozem and enhanced the soil organic carbon (SOC) content and the abundance of microbial available carbon source. The presence of Cd reduced the content of SOC and dissolved organic carbon (DOC) in phaeozem and changed the soil bacteria community structure. The combined pollution of HDPE and Cd had a superimposed effect on the increment of DOC content in fluvo-aquic, and in phaeozem, the combined pollution had an antagonistic effect on SOC and DOC. In conclusion, the coexistence of MPs and Cd would affect soil carbon cycling and microbial community structure, especially in phaeozem. These results contribute to understanding the effects of MPs and/or Cd on soil biological properties.