Dissolved organic matter (DOM) influences the environmental fate and toxic effects of trace metals such as mercury (Hg). However, because of limits in DOM analytical techniques and lack of sample diversity in past studies, it remains unclear whether the binding strength of DOM complexed with Hg(II) is related to the DOM properties. In this study, different DOM isolates (n = 26) from various sources were used to determine the conditional stability constant (logK) of DOM-Hg complexes using the equilibrium dialysis ligand exchange (EDLE) method. UV–Vis and fluorescence spectrometry was used to evaluate the correlation between logK values and DOM properties, such as chromophoric moieties, aromaticity, and molecular weight. Results demonstrated that the DOM from different sources presented a large range of binding strengths to Hg(II), because of their heterogeneous properties. Moreover, DOM chromophores, including aromaticity and molecular weight, are critical indicators of the DOM-Hg affinity in ambient-relevant circumstances. Especially, higher terrestrial DOM led to greater DOM-Hg affinity. Additionally, this study supports that UV–Vis and fluorescence spectroscopy can be used to estimate DOM composition and its binding strength with Hg(II). Furthermore, the observed relationship between logK and DOM properties provided a possible pathway of explanation for the spatial co-variations between Hg(II) concentrations and DOM characters observed in previous field investigations.

溶解有机物 (DOM) 会影响汞 (Hg) 等痕量金属的环境归宿和毒性作用。然而，由于过去研究中 DOM 分析技术的限制和样本多样性的缺乏，目前尚不清楚与 Hg(II) 复合的 DOM 的结合强度是否与 DOM 特性有关。在本研究中，使用平衡透析配体交换 (EDLE) 方法 ，使用来自不同来源的不同 DOM 分离物 ( n = 26) 来确定DOM-Hg 复合物的条件稳定性常数 (log K )。UV-Vis 和荧光光谱法用于评估 log K之间的相关性值和 DOM 属性，例如发色部分、芳香性和分子量。结果表明，来自不同来源的 DOM 对 Hg(II) 呈现出大范围的结合强度，因为它们具有异质性。此外，DOM 发色团，包括芳香性和分子量，是环境相关环境中 DOM-Hg 亲和力的关键指标。特别是，较高的陆地 DOM 导致更大的 DOM-Hg 亲和力。此外，该研究支持紫外-可见光和荧光光谱可用于估计 DOM 组成及其与 Hg(II) 的结合强度。此外，观察到的 log K之间的关系 和 DOM 特性为先前实地调查中观察到的 Hg(II) 浓度和 DOM 特征之间的空间协变提供了可能的解释途径。