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- Title
Mercury methylation in the soils and sediments of Three Gorges Reservoir Region.
- Authors
Ma, Ming; Du, Hongxia; Wang, Dingyong; Sun, Tao
- Abstract
Purpose: Previous studies demonstrated that microorganisms had an important role in the mercury (Hg) methylation process in the water and sediments of Three Gorges Reservoir (TGR). The purpose of this research was to analyze the microbial methylation of Hg in the soils and sediments of the water-level-fluctuating zone (WLFZ) of TGR.Materials and methods: Different types of soils, sediment (≤ 155 m), semi-inundated soil (≥ 155 m), and non-inundated soil (≥ 175 m) of the WLFZ of Shibao (S), Zhenxi (Z), and Tujing (T) were investigated. Real-time PCR, terminal restriction fragment length polymorphism (T-RFLP), cloning, sequencing, and phylogenetic analysis were used to analyze the abundance and diversity of <italic>dsrB</italic>, <italic>hgcA</italic>, and <italic>mcrA</italic> genes, and their relationship with the levels of total Hg (THg), MeHg, and several biogeochemical factors that probably affected microbial methylation reaction.Results and discussion: THg concentrations in different soil types of the WLFZ of TGR did not show significant differences (<italic>p</italic> > 0.05) in site S, while there were significant differences (<italic>p</italic> < 0.05) of MeHg levels in different soil types of the three sites. Phylogenetic analyses found that the dominant groups of microorganisms with <italic>dsrB</italic> in the sediment and non-inundated soil in site S differed remarkably. Microorganisms that probably related with Hg methylation mainly distributed in the sediment, with <italic>δ-proteobacteria</italic> as the dominant class. Real-time PCR found that soil MeHg levels correlated positively with the resident quantities of microorganisms with <italic>dsrB</italic>. The abundance of <italic>dsrB</italic> was much higher than that of <italic>hgcA</italic> which may indicate that only a small part of sulfate-reducing bacteria (SRB) related with Hg methylation.Conclusions: Soil MeHg levels correlated positively with the resident quantities of microorganisms with the <italic>dsrB</italic> gene. The phylogenetic analysis indicated that SRB that probably related with Hg methylation distributed mainly in the sediment, rather than in the non-inundated soil.
- Subjects
MICROORGANISMS; PHYSIOLOGICAL effects of mercury; METHYLATION kinetics; POLYMERASE chain reaction; SAN Xia Reservoir (China)
- Publication
Journal of Soils & Sediments: Protection, Risk Assessment, & Remediation, 2018, Vol 18, Issue 3, p1100
- ISSN
1439-0108
- Publication type
Article
- DOI
10.1007/s11368-017-1827-9