High cadmium pollution from sediments in a eutrophic lake caused by dissolved organic matter complexation and reduction of manganese oxide.
High cadmium pollution from sediments in a eutrophic lake caused by dissolved organic matter complexation and reduction of manganese oxide.
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DOI：
10.1016/j.watres.2020.116711
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发表时间：
2020-11
期刊：
影响因子：
12.8
通讯作者：
Musong Chen;S. Ding;Cai Li;Yazhou Tang;Xianfang Fan;Huacheng Xu;Daniel C W Tsang;Chaosheng Zhang-Chaosheng-Zh
中科院分区：
文献类型：
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作者：
Musong Chen;S. Ding;Cai Li;Yazhou Tang;Xianfang Fan;Huacheng Xu;Daniel C W Tsang;Chaosheng Zhang-Chaosheng-Zh
富营养化和金属污染是全球性的环境问题。由于沉积物中金属的高流动性，富营养化湖泊的金属污染风险很高。然而，镉(Cd)在沉积物中的迁移机制仍不清楚。本文采用薄膜扩散梯度法(DGT)和高分辨率透析法(HR-Peeper)对富营养化太湖沉积物中Cd的活化进行了研究。研究发现，2、3月份沉积物中Cd的活动性较高，这是由于微生物活性较高的氧化锰还原溶解所致，DGT不稳定的Cd和Mn的分布模式具有相似性。在5月和6月，溶解态Cd浓度出现了两个数量级的增加(约28μg和L−1)，上覆水中溶解态Cd浓度比环保局设定的连续浓度标准高出约110倍。在模拟厌氧条件下，溶解态Cd和溶解有机质(DOM)的小时变化一致且相关，这有力地表明了野外观测到的Cd污染的突然爆发是DOM与沉积物中Cd的络合作用的结果。这进一步得到了Nica-Donnan模型的支持，即5月和6月孔隙水中71%以上的溶解Cd以Cd-Dom络合物的形式存在。通过荧光激发发射矩阵-平行因子分析，确定了6月份沉积物中DOM的三个组分，包括腐植酸、色氨酸和酪氨酸。我们发现CD与酪氨酸类组分形成稳定的络合物。傅立叶变换红外光谱和二维相关光谱进一步表明，Cd与酚类单键H、烯类C双键C、醇类单键C、芳香族单键H和烯类双键CH键合在一起。我们的研究有效地促进了人们对沉积物中Cd迁移的了解，并强调了富营养化湖泊发生突发性Cd污染事件的风险。
Eutrophication and metal pollution are global environmental problems. The risk of metal pollution is high in the eutrophic lakes because of high mobility of metal in sediments. However, the mechanism of cadmium (Cd) mobility in sediments is still unclear. Here we study the mobilization of Cd in sediments from the eutrophic Lake Taihu via monthly field monitoring of mobile Cd using diffusive gradient in thin films (DGT) and high resolution dialysis (HR-Peeper) techniques. We found a high mobility of Cd in sediments in February and March, resulting from reductive dissolution of Mn oxide mediation by high microbial activities, as shown by the similarities in distribution patterns of DGT-labile Cd and Mn. A two orders of magnitude increase in dissolved Cd concentrations (about 28 μg L−1) was observed in May and June, with dissolved Cd concentrations in overlying water about 110 times higher than the criteria continuous concentration set by Environmental Protection Agency. Hourly changes were found to coincide and correlate between dissolved Cd and dissolved organic matter (DOM) under simulated anaerobic conditions, strongly suggesting that the sudden outbreak of Cd pollution observed in the field resulted from the complexation of DOM with Cd in sediments. This was further supported by the NICA-Donnan model that more than 71% of dissolved Cd in the pore water in May and June was present as Cd-DOM complexes. Three components of DOM including humic-, tryptophan-, and tyrosine-like components in the sediments in June was identified using the fluorescence excitation emission matrix-parallel factor analysis. We found that Cd was stable complexed with tyrosine-like component. The Fourier transform infrared and two-dimensional correlation spectroscopy further revealed that Cd was bound to phenolic Osingle bondH, alkene Cdouble bondC, alcoholic Csingle bondO, aromatic Csingle bondH, and alkene double bondCH groups. Our study effectively promotes the understanding of Cd mobilization in sediments and highlights the risk of sudden Cd pollution events in the eutrophic lakes.