Elevated tropospheric CO 2 and O 3 concentrations impair organic pollutant removal from grassland soil.

The concentrations of tropospheric CO ₂ and O ₃ have been rising due to human activities. These rising concentrations may have strong impacts on soil functions as changes in plant physiology may lead to altered plant-soil interactions. Here, the effects of eCO ₂ and eO ₃ on the removal of polycyclic aromatic hydrocarbon (PAH) pollutants in grassland soil were studied. Both elevated CO ₂ and O ₃ concentrations decreased PAH removal with lowest removal rates at elevated CO ₂ and elevated O ₃ concentrations. This effect was linked to a shift in soil microbial community structure by structural equation modeling. Elevated CO ₂ and O ₃ concentrations reduced the abundance of gram-positive bacteria, which were tightly linked to soil enzyme production and PAH degradation. Although plant diversity did not buffer CO ₂ and O ₃ effects, certain soil microbial communities and functions were affected by plant communities, indicating the potential for longer-term phytoremediation approaches. Results of this study show that elevated CO ₂ and O ₃ concentrations may compromise the ability of soils to degrade organic pollutants. On the other hand, the present study also indicates that the targeted assembly of plant communities may be a promising tool to shape soil microbial communities for the degradation of organic pollutants in a changing world.