Photo-aged non-biodegradable and biodegradable mulching film microplastics alter the interfacial behaviors between agricultural soil and inorganic arsenic

The impacts of microplastics (MPs) prevalent in soil on the transport of pollutants were urged to be addressed, which has important implications for ecological risk assessment. Therefore, we investigated the influence of virgin/photo-aged biodegradable polylactic acid (PLA) and non-biodegradable black polyethylene (BPE) mulching films MPs on arsenic (As) transport behaviors in agricultural soil. Results showed that both virgin PLA (VPLA) and aged PLA (APLA) enhanced the adsorption of As(III) (9.5%, 13.3%) and As(V) (22.0%, 6.8%) due to the formation of abundant H-bonds. Conversely, virgin BPE (VBPE) reduced the adsorption of As(III) (11.0%) and As(V) (7.4%) in soil owing to the dilution effect, while aged BPE (ABPE) improved arsenic adsorption amount to the level of pure soil due to newly generated O-containing functional groups being feasible to form H-bonds with arsenic. Site energy distribution analysis indicated that the dominant adsorption mechanism of arsenic, chemisorption, was not impacted by MPs. The occurrence of biodegradable VPLA/APLA MPs rather than non -biodegradable VBPE/ABPE MPs resulted in an increased risk of soil accumulating As(III) (moderate) and As

Automated summary

The impacts of microplastics (MPs) in soil on pollutant transport were studied. It was found that biodegradable polylactic acid (PLA) enhanced arsenic (As) adsorption, while non-biodegradable black polyethylene (BPE) reduced As adsorption in soil. The dominant adsorption mechanism of As was not affected by MPs. Biodegradable MPs increased the risk of soil accumulating As.