Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou 310014, China.
Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou 310014, China.
Sci Total Environ. 2022 Jun 25;827:154356. doi: 10.1016/j.scitotenv.2022.154356. Epub 2022 Mar 6.
Methylmercury (MeHg) is a neurotoxin that bioaccumulates in organisms and it forms strong complexes with reduced sulfur-containing ligands in dissolved organic matter (DOM). In the present study, the influences of solar radiation and sulfide addition reaction of humic acids (HA) on MeHg binding to HA were investigated using synchronous fluorescence and FT-IR two-dimensional correlation spectroscopic (2DCOS) analysis. Results showed that the complexation of fluorescent fractions of HA and sulfur-reacted HA (S-HA) with MeHg was not significantly affected by photoreaction treatments and the affinity of fluorescent fractions followed the order of protein-like fractions > humic-like fractions > fulvic-like fractions for both HA and S-HA. FT-IR 2DCOS analysis showed that the affinity of various binding sites in DOM for MeHg changed under different photoreaction treatments. Under dark treatment, small molecular compounds with low humification degree such as aromatic amino acids may be the site with the strongest binding ability to MeHg in HA, whereas aliphatic amino acids and sulfur-containing groups from sulfide addition reactions play a role in complexing of S-HA and MeHg. Under BS treatment (irradiation of DOM before MeHg binding), aliphatic compounds in HA preferentially bind to MeHg and aliphatic amino acids are the components with the strongest complexing ability; but for S-HA binding to MeHg, unsaturated functional groups and aromatic groups are more sensitive (alkenes > alkanes, phenols > alcohols). Under AS treatment (irradiation of DOM after MeHg binding), unsaturated bonds and aromatic compounds in HA preferentially bind to MeHg and aromatic amino acids show the strongest complexing ability; but for S-HA binding to MeHg, aliphatic groups show the strongest complexing ability (alkanes, alkenes > aromatics). These findings help us to better understand the complexation mechanisms between MeHg and DOM.
甲基汞（MeHg）是一种生物累积的神经毒素，它与溶解有机质（DOM）中含还原态硫的配体形成强复合物。本研究采用同步荧光和二维相关光谱（2DCOS）分析方法，考察了太阳辐射和腐殖酸（HA）硫化添加反应对 MeHg 与 HA 结合的影响。结果表明，光化学反应处理对 HA 和硫反应 HA（S-HA）荧光分与 MeHg 的络合作用没有显著影响，且荧光分与 HA 和 S-HA 的络合亲和力顺序为类蛋白质分＞类腐殖质分＞类富里酸分。FT-IR 2DCOS 分析表明，DOM 中各种结合位点与 MeHg 的亲和力在不同光化学反应处理下发生了变化。在暗处理下，芳香族氨基酸等低腐殖化程度的小分子化合物可能是 HA 中与 MeHg 结合能力最强的位点，而来自硫化添加反应的脂肪族氨基酸和含硫基团则在 S-HA 与 MeHg 的络合中起作用。在 BS 处理下（在 MeHg 结合之前对 DOM 进行辐照），HA 中的脂肪族化合物优先与 MeHg 结合，且脂肪族氨基酸具有最强的络合能力；但对于 S-HA 与 MeHg 的结合，不饱和官能团和芳香族基团更为敏感（烯烃＞烷烃，酚类＞醇类）。在 AS 处理下（在 MeHg 结合之后对 DOM 进行辐照），HA 中的不饱和键和芳香族化合物优先与 MeHg 结合，且芳香族氨基酸显示出最强的络合能力；但对于 S-HA 与 MeHg 的结合，脂肪族基团表现出最强的络合能力（烷烃、烯烃＞芳烃）。这些发现有助于我们更好地理解 MeHg 与 DOM 之间的络合机制。
