The toxic factor of copper should be adjusted during the ecological risk assessment for soil bacterial community
Jianwen Chen, Hong Zhang, Junjian Li, Yong Liu, Wei Shi, Hang‐Wei Hu
Abstract
The toxic factor (TF) is a key parameter commonly used to evaluate the potential ecological risk index (RI) of heavy metals. However, it remains largely unknown whether this traditional TF is applicable to the ecological risk assessment of heavy metal to soil microorganisms, which are essential to ecological functions and ecosystem sustainability. Here, based on the TF values of 5 and 30 for copper (Cu) and cadmium (Cd), respectively, we constructed soil microcosms to establish a gradient of ecological risk levels, and different combinations of Cu and Cd concentrations were used at each ecological risk level. We found that bacterial abundance and functional diversity significantly decreased and the metal resistance gene (MRG) abundances increased with the increasing RI level. At the same RI level, the bacterial abundance and functional diversity decreased while MRG abundances increased with increasing Cu concentrations, suggesting that the ecological risk to soil bacterial community was more relevant to Cu, rather than Cd. The traditional TF of Cu used to calculate the RI might be underestimated if it is used for evaluation of the risk to soil bacteria. Our calibration analysis revealed that the TF of Cu should be adjusted to 6 during the assessment of the RI for soil bacterial community in heavy-metal contaminated area.