Elevated CO2 levels alleviated toxicity of ZnO nanoparticles to rice and soil bacteria.

Abstract Rising CO2 levels will change the behavior and toxicity of soil contaminants. However, it remains unclear whether elevated CO2 levels will change the nanoparticle dissolution or their biological effects in soil. In this study, we used a free-air CO2 enrichment system to examine the effects of elevated CO2 on phytotoxicity and bacterial toxicity of zinc oxide nanoparticles (nZnO) in a paddy soil system. The elevated CO2 changed the nZnO diffraction in soil, slightly increasing its dissolution but remarkably improving its bioavailability. Elevated CO2 did not change Zn accumulation in rice, but still alleviated the adverse effects of nZnO on rice growth, although grain protein, K and P decreased. Moreover, nZnO alone significantly decreased the number of observed soil bacterial species and altered the community organization, while elevated CO2 moderated such changes. Overall, these results increase our understanding of plant response and microbial variation in nanoparticle-contaminated soil under elevated-CO2 conditions. It is necessary to pay attention to soil pollution while facing climate change.