Heavy metal migration in sediment of ionic rare earth mining basin in China: Microbial-mediated processes and...

Heavy metals co-occurring in the ionic rare earth mining presents a significant threat to the environmental security of river basins. However, the complex interactions between key microbial communities and heavy metals in sediments remain poorly understood. Herein, we investigated the distribution of heavy metals in sediments from the headwater of Dongjiang river basin, focusing on the intricate relationships between microbial communities and heavy metals. Results indicated that the acid-extractable fraction of heavy metals in sediments represents a bioavailability risk to aquatic organisms, and abundant microbial communities have evolved robust adaptive strategies to cope with heavy metal contamination. Firmicutes, Actinobacteriota, and Chloroflexi were identified in the biogeochemical cycling of Mn and Pb, with the correlations of 83.3%, 54.8% and 52.5%, respectively. Phyla Myxococcota, Chloroflexi and Proteobacteria were identified as functional microbes associated with the metabolism of rare earth elements (La, Tb and Dy). Microbial adaptation mechanisms to heavy metal stress include oxidative stress response, metal efflux via transport pumps, as well as binding and sequestration of heavy metals. Notably, the genes cadA, zitB, gshA, and galA were identified as critical for detoxification of heavy metals in contaminated sediments. Overall, this study provides insights into microbial adaptation mechanisms in the sediments of ionic rare earth mining basins, and highlights the importance of microbial community in the rare earth mining basin ecological remediation.