Elevated methylmercury production in seasonally inundated sediments: Insights from DOM molecular composition

IF 12.2 1区环境科学与生态学 Q1 ENGINEERING, ENVIRONMENTAL

Journal of Hazardous Materials Pub Date : 2025-01-02 DOI:10.1016/j.jhazmat.2025.137095

Xian Zhou , Tianrong He , Yongguang Yin , Tao Jiang , Pan Wu , Jiang Liu , Yongmin Wang , Deliang Yin , Enxin Liu , Siyi Ma , Qing Xie

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Abstract

Seasonally inundated areas (SIA) within aquatic systems are characterized by elevated methylmercury (MeHg) production. Nevertheless, the response characteristics of dissolved organic matter (DOM) quality in SIA sediments, including its molecular compositions and structure, and their impacts on the MeHg production are not yet fully understood. This research gap has been addressed through field investigations and microcosm experiments conducted in a metal-polluted plateau wetland. The results revealed that DOM_SIA had lower levels of chromophoric DOM concentrations, protein-like fractions, molecular complexity, and debris size while exhibiting higher humic-like fractions, molecular weight, COO- groups, and bioavailability than DOM in permanently inundated areas (PIA). Compared with DOM_PIA, DOM_SIA was more easily biodegraded, and exhibited a higher adsorption capacity while lower binding affinity for Hg(Ⅱ). Moreover, MeHg synthesis by Desulfomicrobium escambiense was 29.6-fold higher in DOM_SIA than that in DOM_PIA, and DOM_SIA amendment also resulted in a higher MeHg production in the sediment. The PLS-PM model demonstrated that DOM compositions positively showed high contributions to MeHg levels in sediment porewater (0.51), while binding affinity had a negative pattern (-0.83), but adsorption capacity had a lower contribution (0.09). These findings provide an updated explanation for the elevated MeHg level in the SIA of aquatic systems, which are closely related to the adaptive response of DOM molecular composition and structure in the sediment.

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季节性淹没沉积物中甲基汞产量升高：来自DOM分子组成的见解

水生系统中的季节性淹没区（SIA）的特点是甲基汞（MeHg）产量升高。然而，SIA沉积物中溶解有机质（DOM）质量的响应特征，包括其分子组成和结构，以及它们对MeHg产生的影响尚未完全了解。通过对金属污染的高原湿地进行实地调查和微观实验，弥补了这一研究空白。结果表明，与永久淹没区（PIA）的DOM相比，DOMSIA具有较低的显色性DOM浓度、蛋白质样组分、分子复杂性和碎片大小，而具有较高的腐殖质样组分、分子量、COO-基团和生物利用度。与DOMPIA相比，DOMSIA更容易被生物降解，对汞的吸附能力更高，而结合亲和力较低（Ⅱ）。此外，DOMSIA中escambiense desulfomicroium escambiense的MeHg合成量是DOMPIA的29.6倍，DOMSIA的修正也导致了沉积物中MeHg产量的增加。PLS-PM模型表明，DOM组成对沉积物孔隙水中MeHg含量的贡献为正（0.51），而结合亲和力为负（-0.83），而吸附容量的贡献较低（0.09）。这些发现为水生系统SIA中MeHg水平升高提供了新的解释，这与沉积物中DOM分子组成和结构的适应性响应密切相关。

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来源期刊

Journal of Hazardous Materials 工程技术-工程：环境

CiteScore

25.40

自引率

5.90%

发文量

3059

审稿时长

58 days

期刊介绍： The Journal of Hazardous Materials serves as a global platform for promoting cutting-edge research in the field of Environmental Science and Engineering. Our publication features a wide range of articles, including full-length research papers, review articles, and perspectives, with the aim of enhancing our understanding of the dangers and risks associated with various materials concerning public health and the environment. It is important to note that the term "environmental contaminants" refers specifically to substances that pose hazardous effects through contamination, while excluding those that do not have such impacts on the environment or human health. Moreover, we emphasize the distinction between wastes and hazardous materials in order to provide further clarity on the scope of the journal. We have a keen interest in exploring specific compounds and microbial agents that have adverse effects on the environment.