Insights on the effects of ZnO nanoparticle exposure on soil heterotrophic respiration as revealed by soil microbial communities and activities

Abstract

The information on the effects of ZnONPs on soil biological processes and the resulting changes of ecosystem function is limited in wheat straw return agricultural soil. This study investigated the effects of ZnONPs on soil heterotrophic respiration and biochemical properties in wheat straw return farmland soil. An 84-day microcosm incubation experiment was implemented after the exposure of different doses of ZnONPs (0, 100, and 500 mg kg−1 dry soil) in a greenhouse under the temperature of 25 ± 3 °C. Soil heterotrophic respiration and soil enzyme activities were detected. Microbial community composition and diversity were analyzed by Illumina MiSeq platform. Heterotrophic respiration was significantly inhibited by ZnONPs at 500 mg kg−1. The activities of β-glucosidase, cellulose, and cellobiohydrolase decreased under high-level exposure of ZnONPs. The labile Zn2+ assimilated by soil microorganism was increased by 331% and 707%, respectively. Bacterial communities in the soil are more sensitive to ZnONPs than fungal ones. The changes of heterotrophic respiration were closely correlated with soil pH values and microbial compositions, especially fungal communities. Although ascomycetes were inhibited by ZnONPs, their abundance was the highest within soil fungal community. The inhibition of heterotrophic respiration was associated with the variation of soil fungal communities, although the bacterial communities are sensitive to ZnONPs. The microbiome modulation is necessary for the management of the decomposition of returned wheat straw in the field contaminated by ZnONPs. The effects of ZnONPs on soil ecological process should be considered when the application of fertilizers and pesticides which contain ZnONPs.