Microplastics Alter Dehydrogenase, Urease, and Cellulase Activities in Soil

Microplastic (MP) pollution poses a serious threat to soil ecosystems. Recent studies have observed that MPs may have adverse effects on soil flora and fauna. The studies conducted to observe the effect of MPs on microbial enzymes in soil were limited. Therefore, the present study was conducted to examine the impact of MPs, namely low-density polyethylene microplastics (LDPEMP), polystyrene microplastics (PSMP), and nylon microplastics (Nylon MP), on enzymes such as dehydrogenase, urease, and cellulose. The LDPEMPs increased the dehydrogenase enzyme activity at various concentrations, ranging from 0 to 5%. On the 60th day, the dehydrogenase activity was found to be 52.7 ± 0.8 g triphenyl formazon formed g soil⁻¹ day⁻¹ at 5% LDPEMP concentration. The urease activity on the 60th day was 0.59 ± 0.04, 0.15 ± 0.02, 0.13 ± 0.02, and 0.08 ± 0.01 mg NH₃–N g soil⁻¹ at 0%, 1%, and 5%, respectively. Further, cellulase activity was reduced at 3% and 5% LDPEMP concentrations. At 1% and 3% concentrations, PSMPs increased cellulase activity. However, at 1%, 3%, and 5% concentrations, nylonMPs reduced cellulase activity. This study found that MPs in soil affect the extracellular enzymes produced by microorganisms in the soil, which may influence mineralization.