Xin Yuan, Zhang Xuehui, Zheng Dongmei, Zhang Zhongsheng, Jiang Ming
Institute of Northeast Geography and Agroecology, Chinese Academy of Science, No.4888, Shengbei Street, Kuancheng District, Changchun, 130102, China.
Environmental College, Shenyang University, Shenyang, 110044, China.
Environ Geochem Health. 2023 Mar;45(3):913-923. doi: 10.1007/s10653-022-01257-1. Epub 2022 Apr 3.
Dissolved organic matter (DOM) plays an important role in promoting or suppressing methylmercury (MeHg) production in wetlands. However, the effects of DOM spectral characteristics on MeHg levels remain poorly understood in boreal peatlands in Northeast China, where is undergoing remarkable climate warming. In the present work, soil samples were collected from 22 peatlands in the Greater Khingan Mountains (GKM) to test the hypothesis that DOM spectral properties control MeHg levels. DOM was characterized by UV-Vis absorption and fluorescence spectroscopy; the three-dimensional fluorescence excitation-emission matrix (EEM) was used to unveil the origin of DOM. The average total mercury (THg) and MeHg contents were 112.76 µg/kg and 12.43 µg/kg across all peatlands, respectively. There was a significantly positive correlation between MeHg and the longitude spanning the range from 120 to 123°E (p < 0.05). Proportions of MeHg to THg (%MeHg), 12.3% on average, were positively correlated with DOM humification degree at p < 0.05 level. Protein-like components of DOM (P-like) were negatively related to %MeHg. DOM had positive effects on THg, and P-like components, HIX and BIX can negatively affect THg as well as MeHg. Our findings demonstrate that the spectral characteristics of DOM in soil are crucial to the content of methyl mercury in the GKM soil.
溶解有机物（DOM）在促进或抑制湿地中甲基汞（MeHg）的产生方面发挥着重要作用。然而，在中国东北正在经历显著气候变暖的北方泥炭地，DOM光谱特征对甲基汞水平的影响仍知之甚少。在本研究中，从大兴安岭（GKM）的22个泥炭地采集了土壤样本，以检验DOM光谱特性控制甲基汞水平这一假设。通过紫外-可见吸收光谱和荧光光谱对DOM进行表征；利用三维荧光激发-发射矩阵（EEM）揭示DOM的来源。所有泥炭地的平均总汞（THg）和甲基汞含量分别为112.76µg/kg和12.43µg/kg。甲基汞与东经120至123°范围内的经度呈显著正相关（p < 0.05）。甲基汞占总汞的比例（%MeHg）平均为12.3%，在p < 0.05水平下与DOM腐殖化程度呈正相关。DOM中的类蛋白成分（P-like）与%MeHg呈负相关。DOM对总汞有正向影响，而P-like成分、腐殖化指数（HIX）和生物指数（BIX）对总汞和甲基汞均有负面影响。我们的研究结果表明，土壤中DOM的光谱特征对大兴安岭土壤中甲基汞的含量至关重要。
