Abundant sediment organic matter potentially facilitates chemical iron reduction and surface water blackness in a Chinese deep lake. (1st March 2021)

• Record Type: Journal Article
• Authors: Li, Biao; Feng, Muhua; Chen, Xiangchao; Wang, Yarui; Shen, Yue; Wu, Qinglong L.
• Is Part Of: Environmental pollution. Volume 272(2021)
• Publication Date: 2021-03-01
• Subjects: Black bloom -- Ferrous monosulfide -- Organic detritus -- Diffusive gradients in thin films (DGT); Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2020.116002
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: 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 2+ concentration was 57.6–1919.4 times higher than the DGT-S 2− concentration and both were positively correlated with DGT-PO4 3− . 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 2+ and DGT-PO4 3- was better than that of DGT-PO4 3- and DGT-S 2- 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. Graphical abstract: Image 1 Highlights: Fe(II) and S 2− account for 38.8% and 46.9% of the total Fe and S contents. Dissolved oxygen penetrates 1.6–4.2 mm into the sediments. FeS is the major cause for the water blackness and formed in the sediments. Porewater Fe 2+ concentration are 57.6–1919.4 times higher than the S 2− contents. Organic matter accumulation facilitates chemical iron reduction and black bloom. Abstract : Abundant sediment organic matter potentially enhances chemical iron reduction and AVS production, which could further lead to surface water blackness even during stratification period.