地球科学进展

地球科学进展 ›› 2026, Vol. 41 ›› Issue (7): 692 -699. doi: 10.11867/j.issn.1001-8166.2026.047   cstr: 32269.14.adearth.CN62-1091/P.2026.047.

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DGT-汞同位素视角下稻田生态系统甲基汞来源与转化机制研究
尹宏倩1(), 姚珩1(), 冯新斌1,2   
  1. 1.中国科学院地球化学研究所 喀斯特环境演变与生态安全实验室，贵州 贵阳 550081
    2.中国科学院大学，北京 100049
  • 收稿日期:2026-05-16 修回日期:2026-06-24 出版日期:2026-07-10
  • 通讯作者: 姚珩 E-mail:yinhongqian@mail.gyig.ac.cn;yaoheng@mail.gyig.ac.cn
  • 基金资助:
    国家自然科学基金青年科学基金项目（C类）(42507356);贵州省农业社发领域科技支撑项目（编号：黔科合支撑［2026］一般326）资助

Sources and Transformation of Methylmercury in Paddy Ecosystems: Insights from DGT and Mercury Isotopes

Hongqian Yin1(), Heng Yao1(), Xinbin Feng1,2   

  1. 1.Laboratory of Karst Environmental Evolution and Ecological Security, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
    2.University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2026-05-16 Revised:2026-06-24 Online:2026-07-10 Published:2026-09-23
  • Contact: Heng Yao E-mail:yinhongqian@mail.gyig.ac.cn;yaoheng@mail.gyig.ac.cn
  • About author:Yin Hongqian, research area includes mercury biogeochemical cycle. E-mail: yinhongqian@mail.gyig.ac.cn
  • Supported by:
    the National Natural Science Foundation of China(42507356);Science and Technology Support Project in the Field of Agriculture and Social Development of Guizhou Province (Grant No. QKHZC[2026]YIBAN326)
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稻田生态系统特有的淹水厌氧环境，为甲基汞的生成提供了有利条件，且该物质易于在水稻中富集，并经由食物链传递，最终对人体健康构成威胁。然而，目前关于水稻植株体内甲基汞的来源归属、稻田水体中汞形态转化的主导机制等关键科学问题的认识仍有待深化。近年来，汞稳定同位素技术，特别是奇数汞同位素非质量分馏（odd-MIF），为解决上述问题提供了独特的研究视角。整合了目前报道的稻田土壤、水稻各组织以及梯度扩散薄膜技术所表征的水体甲基汞同位素端元数据，基于混合模型定量解析了水稻植株中甲基汞的来源贡献。结果表明，水稻组织中的甲基汞主要来源于土壤—孔隙水系统，其贡献比例为72%~97%，而上覆水的贡献仅为3%~28%。进一步地，基于梯度扩散薄膜技术获取稻田水体甲基汞的Δ199Hg/Δ201Hg斜率，并结合汞的光化学转化理论参数［甲基汞光降解过程中Δ199Hg/Δ201Hg斜率约为1.36，Hg（II）光还原过程中约为1.00］，定量计算得出：光还原对光化学反应的贡献约为75%，光降解的贡献约为25%。这表明光还原是稻田水体汞转化的主导机制。梯度扩散薄膜技术与汞同位素技术联用为理解稻田生态系统中甲基汞的生成、迁移与转化提供了新视角。在未来的工作中，需要进一步探索水体中超痕量甲基汞的预富集方法与同位素测试技术，以便更直接地研究水生生态系统中甲基汞的来源与迁移转化机制。

关键词: 稻田生态系统, 汞同位素, 甲基汞来源, 汞形态转化机制, 梯度扩散薄膜（DGT）技术

Paddy ecosystems are recognized as critical hotspots for the generation of methylmercury (MeHg), a potent neurotoxin that poses substantial health risks to humans through dietary exposure via contaminated rice grains. Unlike aquatic food chains, where fish consumption is the primary route of MeHg intake, rice-based diets represent a major but often overlooked pathway in many regions, particularly in Hg-contaminated areas in China. Despite decades of research, several key scientific questions persist, notably the precise provenance of MeHg in rice plants and the prevailing mechanisms that govern Hg transformation within paddy water columns. In recent years, Hg stable isotope techniques, particularly odd-Mass Independent Fractionation (odd-MIF), have provided a unique research perspective for addressing the aforementioned issues. In this study, we compiled a comprehensive database of previously reported MeHg isotope end-member values derived from paddy soil, various rice tissues (roots, stems, leaves, and grains), and paddy water samples collected using the Diffusive Gradients in Thin films (DGT) technique, which provides time-integrated in situ pre-concentration of soluble MeHg. Using a mixing model, we then quantitatively constrained the source contributions of MeHg from different end-members to rice plants. Our modeling results unequivocally demonstrate that MeHg in rice plants originates predominantly from the soil-porewater system, contributing from 72% to 97% of the total MeHg burden, whereas the overlying water plays only a minor role, accounting for merely from 3% to 28%. This finding highlights the critical importance of managing soil biogeochemical conditions to mitigate MeHg transfer into rice plants. Furthermore, according to the Δ199Hg/Δ201Hg slope of MeHg in paddy water captured by DGT and the theoretical parameters of Hg photochemical transformation (the slope is approximately 1.36 for MeHg photodegradation and approximately 1.00 for Hg(II) photoreduction), we quantitatively estimated that photoreduction accounts for about 75% of the photochemical reactions, while photodegradation accounts for about 25%. This indicates that photoreduction is the dominant process driving Hg transformation in paddy water. Overall, this study couples the DGT technique with Hg stable isotopes, providing a novel methodological paradigm and offering new perspectives for a deeper understanding of the formation, transport, and fate of MeHg in aquatic ecosystems. Finally, we emphasize that future efforts should be directed toward developing robust pre-concentration methods and isotopic analytical techniques for ultra-trace MeHg in aquatic systems, thereby enabling a more direct elucidation of its sources, transport, and transformation dynamics within aquatic ecosystems.

Key words: Paddy ecosystem, Mercury isotope, Methylmercury sources, Transformation mechanisms of mercury species, Diffusive Gradients in Thin films (DGT) technique

中图分类号: 

表1 水稻植株各组织中甲基汞（MeHg）的同位素组成特征 (‰)
Table 1 Characteristics of methylmercury （MeHg） isotopic composition in rice plant tissues
植株组织nδ202HgMeHgΔ199HgMeHg
均值标准差（SD）均值标准差（SD）
根4-1.300.480.120.05
茎4-1.180.600.150.04
叶3-1.130.540.130.04
籽粒8-0.920.420.090.05
图1 稻田生态系统不同环境介质样品中甲基汞（MeHg）的汞同位素组成特征
水稻根、茎、叶及土壤中MeHg的同位素数据引自参考文献［18］；籽粒的相应数据引自参考文献［10，18］；孔隙水与上覆水中MeHg的同位素数据引自参考文献［26］。
Fig. 1 Mercury isotopic composition characteristics of methylmercury （MeHg） in different environmental media samples in paddy field ecosystems
MeHg isotope data for rice roots， stalks， leaves， and soil are cited from reference ［18］； for rice grains from references ［10， 18］； and for porewater and overlying water from reference ［26］.
图2 稻田水体中汞转化途径示意图
Fig. 2 Schematic diagram of Hg transformation pathways in paddy water
图3 梯度扩散薄膜（DGT）技术捕获的稻田水体中甲基汞（MeHg）的Δ199Hg/Δ201Hg斜率
孔隙水与上覆水中MeHg的同位素组成数据来自参考文献［26］，图例中DGT下标数字表示水稻的不同生长时期。
Fig. 3 The Δ199Hg/Δ201Hg slope of methylmercury （MeHg） in paddy water captured by Diffusive Gradients in Thin films （DGT）
MeHg isotope data for porewater and overlying water from reference ［26］. The subscript numbers of DGT in the legend denote the different growth stages of rice.
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