Mercury Enrichment Characteristics and Rhizosphere Bacterial Community of Ramie (Boehmeria Nivea L. Gaud.) in Mercury-Contaminated Soil

Abstract

Phytoremediation is a promising technique for reducing mercury (Hg) pollution. Little is known about the phytoremediation potential of ramie (Boehmeria nivea L. Gaud.) and the response of its rhizosphere soil microbiome to Hg contamination. In this study, we planted ramie in three plots contaminated with different levels of Hg pollution and evaluated ramie Hg accumulation and translocation. We also analyzed the abundance, composition, and predominant taxa of the rhizosphere soil bacterial community. Results showed that the average THg concentration decreased by 30.80%, 18.36%, and 16.31% in plots L, M, and H, respectively. Ramie displayed strong Hg tolerance and good Hg accumulation performance, especially in soil contaminated with a low level of Hg. After ramie planting, soil SOM and CEC increased while pH, Eh, and THg content decreased in rhizosphere soil. Proteobacteria, Actinobacteriota, Gemmatimonadota, Latescibacterota, and NB1-j were identified as potential Hg-tolerant taxa at the phylum level, and their abundance increased in highly Hg-contaminated soil. Redundancy and correlation analyses indicated that soil bacterial community structure was significantly correlated with soil pH, Eh, and Hg content. This study provides a better understanding of the phytoremediation capacity of ramie and its rhizosphere function and thus lays a theoretical foundation for the phytoremediation of Hg-contaminated soils.