Effect of PVC microplastics on soil microbial community and nitrogen availability under laboratory-controlled and field-relevant temperatures

Microplastics have been reported to affect soil microbiota and nitrogen cycling under controlled temperature conditions, but their impact under field temperature regimes remains unclear. In this study, we compared the impacts of plasticized polyvinyl chloride (PVC) microplastics in an acidic agricultural soil at laboratory-controlled (25 °C) and field-relevant (outdoor ambient, 2–26 °C) temperature conditions. The results showed that changes in soil indicators were roughly the same under the two temperature conditions after 30 d, with increased NH4+-N content and urease activity, decreased NO3−-N content, potential nitrification rate and ammonia-oxidizing archaea abundance, unaltered bacterial abundance, and significant shifts in bacterial community composition. Probably because microbial activity differed at different temperatures, clear discrepancies were also observed: 1) the lowest observed effect concentration was 0.1 % w/w at 25 °C while it was 0.05 % w/w at ambient temperature; 2) a clear dose-effect relationship was observed at 25 °C but not at ambient temperature; and 3) in addition to a range of bacterial taxa that were commonly influenced by microplastics (e.g., Bradyrhizobium, Burkholderia-Caballeronia-Paraburkholderia, Sinomonas, and Sphingomonas), Amycolatopsis, Nocardia and unclassified Saccharimonadales were more responsive at 25 °C while Bacillus and Mycobacterium for ambient temperature. The findings provide insights into the interaction of microplastics with soil microbes under different temperatures and help to understand the threshold values of plasticized PVC microplastics in soil ecosystems.