State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China; University of Chinese Academy of Sciences, Beijing, 100039, China.
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China.
Environ Pollut. 2021 Mar 1;272:116002. doi: 10.1016/j.envpol.2020.116002. Epub 2020 Nov 7.
Black bloom has become an increasingly severe environmental and ecological problem in lots of lakes. Ferrous monosulfide (FeS), which is closely related to chemical iron reduction (CIR), is considered the major cause for black water in shallow lakes, but few studies focus on the effect of organic matters (OM) content on iron and sulfate reduction and its contribution to the black bloom in deep lakes. Here, in Lake Fuxian, a Chinese deep lake which has also suffered from black bloom, FeS was identified responsible for the surface water blackness by using multiple microscopy and element analyses. Dissolved oxygen (DO) penetrated 1.6-4.2 mm in all sediment sites, further indicating FeS formed in the sediments instead of the permanently oxic water column. Geochemical characteristics revealed by diffusive gradients in thin films (DGT) showed that DGT-Fe concentration was 57.6-1919.4 times higher than the DGT-S concentration and both were positively correlated with DGT-PO. Combining DGT profiles and anaerobic OM remineralization rate according to bag incubation, iron reduction is more effective than sulfate reduction although the two processes coexisted. Moreover, correlation of DGT-Fe and DGT-PO was better than that of DGT-PO and DGT-S at OM-depleted sites but opposite at OM-rich sites. In addition, total organic carbon (TOC) was significantly positively related to acid volatile sulfide (AVS). We therefore conclude that abundant OM potentially exacerbate chemical iron reduction and further lead to surface water blackness. Our study revealed the mechanisms behind the black bloom and gives credence to the management strategy of reducing OM loading to protect water quality in deep lakes.
黑臭现象已成为许多湖泊日益严重的环境和生态问题。亚铁单硫化物（FeS）与化学铁还原（CIR）密切相关，被认为是浅水湖黑水的主要原因，但很少有研究关注有机物（OM）含量对铁和硫酸盐还原的影响及其对深湖黑臭的贡献。本研究以中国富营养化深水湖泊抚仙湖为例，通过多种显微镜和元素分析方法，确定 FeS 是导致表层水变黑的主要原因。溶解氧（DO）在所有沉积物中渗透深度为 1.6-4.2 毫米，进一步表明 FeS 是在沉积物中形成的，而不是在永久氧化的水柱中形成的。薄膜扩散梯度（DGT）法揭示的地球化学特征表明，DGT-Fe 浓度比 DGT-S 浓度高 57.6-1919.4 倍，且两者均与 DGT-PO 呈正相关。结合 DGT 剖面和厌氧 OM 再矿化率的袋培养实验结果表明，尽管这两个过程同时存在，但铁还原比硫酸盐还原更为有效。此外，在 OM 耗尽的地点，DGT-Fe 和 DGT-PO 的相关性优于 DGT-PO 和 DGT-S 的相关性，而在 OM 丰富的地点则相反。此外，总有机碳（TOC）与酸可挥发性硫化物（AVS）呈显著正相关。因此，我们得出结论，丰富的 OM 可能会加剧化学铁还原，进一步导致地表水变黑。本研究揭示了黑臭现象的机制，并为减少 OM 负荷以保护深水湖泊水质的管理策略提供了依据。
