Uncovering geochemical fractionation of the newly deposited Hg in paddy soil using a stable isotope tracer.

Jiang Liu, Lei Zhao, Kun Kong, Mahmoud A Abdelhafiz, Shanyi Tian, Tao Jiang, Bo Meng, Xinbin Feng

Journal: Journal of hazardous materials 2022;433():128752

PMID: 35364530

Full Text on Elsevier Science View on PubMed

Abstract

The newly deposited mercury (Hg) is more readily methylated to methylmercury (MeHg) than native Hg in paddy soil. However, the biogeochemical processes of the newly deposited Hg in soil are still unknown. Here, a field experimental plot together with a stable Hg isotope tracing technique was used to demonstrate the geochemical fractionation (partitioning and redistribution) of the newly deposited Hg in paddy soils during the rice-growing period. We showed that the majority of Hg tracer (Hg, 115.09 ± 0.36 μg kg) was partitioned as organic matter bound Hg (84.6-89.4%), followed by residual Hg (7.6-8.1%), Fe/Mn oxides bound Hg (2.8-7.2%), soluble and exchangeable Hg (0.05-0.2%), and carbonates bound Hg (0.04-0.07%) in paddy soils. Correlation analysis and partial least squares path modeling revealed that the coupling of autochthonous dissolved organic matter and poorly crystalline Fe (oxyhydr)oxides played a predominant role in controlling the redistribution of the newly deposited Hg among geochemical fractions (i.e., fraction changes). The expected aging processes of the newly deposited Hg were absent, potentially explaining the high bioavailability of these Hg in paddy soil. This study implies that other Hg pools (e.g., organic matter bound Hg) should be considered instead of merely soluble Hg pools when evaluating the environmental risks of Hg from atmospheric depositions.

Address: State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China.; School of Management Science, Guizhou University of Finance and Economics, Guiyang 550025, China; Guizhou Key Laboratory of Big Data Statistical Analysis (No. [2019]5103), Guiyang 550025, China. Electronic address: [email protected].; State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China.; State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China; Geology Department, Faculty of Science, Al-Azhar University, Assiut 71524, Egypt.; Soil Ecology Lab, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China.; State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; Interdisciplinary Research Centre for Agriculture Green Development in Yangtze River Basin, Department of Environmental Sciences and Engineering, College of Resources and Environment, Southwest University, Chongqing 400716, China.; State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China. Electronic address: [email protected].

DOI: 10.1016/j.jhazmat.2022.128752

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MeSH Terms: Environmental Monitoring, Isotopes, Mercury, Methylmercury Compounds, Oryza, Oxides, Soil, Soil Pollutants