Elevated CO2 aggravated polystyrene microplastics effects on the rice-soil system under field conditions

Polystyrene microplastics (PS) are decomposed very slowly due to their recalcitrance and inevitably interact with the changing climate. How the interaction between PS and increasing CO2 concentration affects the plant-soil system is rarely investigated. Here, a free-air CO2 enrichment system in farm fields was used to study the impacts of PS added to soil at 10 mg kg-1 on rice and soil bacterial communities at different CO2 levels (ambient∼390 ppm and elevated∼590 ppm). Results showed that single PS interfered with Fe, Mn and Zn uptake of rice, and it increased the abundances of bacteria taxa assigned to N turnover and urease activities, leading to altered soil N transformation and availability. Elevated CO2 alone enhanced rice photosynthesis, decreased the abundances of nitrogen-fixation bacteria, and induced co-occurrence patterns between bacteria simplified and decentralized. Combined PS and elevated CO2 significantly decreased rice stomatal conductance and transpiration rate by 56.70% and 29.46%, respectively, and further inhibited elements uptake. Besides, combined exposure significantly disturbed bacterial amino acid metabolism, and stimulated the adaptative responses of resistant bacteria. Overall, this study revealed that increasing CO2 concentrations may exacerbate the impacts of PS on rice performance and soil bacterial communities, providing new insights into the interaction between microplastics and climate change.