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The underlying mechanism of crop mercury hyperaccumulation in HgS-rich soils: microbially driven enlargement of the bioavailable mercury pool
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J
刘
J
冯
DOI：10.1016/j.gca.2026.07.033.png)
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Abstract
En 中文
In geological settings rich in mercury sulfide (HgS) minerals, the interaction between microbes and minerals, as a key mechanism driving Hg hyperaccumulation in crops, has long been largely neglected in environmental geochemistry and agricultural research. Microbial acquisition of sulfur from HgS minerals mobilizes Hg(II) and enhances its bioavailability. Under pure culture conditions in LB medium, microbially mediated HgS dissolution and subsequent Hg(II) reduction were correlated with oxidation–reduction potential (ORP). Hg accumulation and distribution in crops are jointly governed by the microbially mediated enlargement of the bioavailable Hg pool and by the plant's patterns of uptake, translocation, and partitioning. Mechanistically, microbes secrete cysteine, which converts bulk HgS minerals into bioavailable Hg(II)–cysteine complexes for subsequent crop uptake. Hg isotope analysis (δ202Hg and Δ199Hg) enabled clear source attribution of Hg in the model crop (shallot). The Δ199Hg binary mixing model demonstrated that Hg in roots mainly originated from the soil bioavailable Hg pool, whereas leaf Hg originated from both atmosphere and soil. In soil, the Hg extracted by 0.1 M cysteine (2853 ± 740 ng/g) was approximately three orders of magnitude higher than that extracted by 0.1 M HCl (5.53 ± 4.80 ng/g). However, the difference in Δ199Hg between the two extracts was small (only 0.04‰) and fell within the analytical uncertainty. These results indicate that cysteine can effectively mobilize the bioavailable Hg pool in soil, and the isotopic signature of this pool is likely regulated by cysteine‑mediated processes. Microbe–mineral interactions underscore the significant ecological risks posed by microbial activation of HgS in contaminated agricultural soils. Our findings reveal that conventional understanding may lead to substantial underestimation of ecological and health risks at HgS-rich contaminated sites, as well as uncertainties in the management and disposal of HgS-bearing waste.
Keywords:
Mercury sulfide mineral
Mercury activation
Microorganism
Crop
Soil
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