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Combined use of high-resolution dialysis, diffusive gradient in thin films (DGT) technique, and conventional methods to assess trace metals in reservoir sediments

Authors
  • Norgbey, Eyram1
  • Li, Yiping1
  • Zhu, Ya1
  • Nwankwegu, Amechi S.1
  • Bofah-Buah, Robert1
  • Nuamah, Linda1
  • Pu, Yashuai1
  • 1 Hohai University, Nanjing, 210098, China , Nanjing (China)
Type
Published Article
Journal
Environmental Monitoring and Assessment
Publisher
Springer-Verlag
Publication Date
Jul 05, 2021
Volume
193
Issue
8
Identifiers
DOI: 10.1007/s10661-021-09247-z
Source
Springer Nature
Keywords
Disciplines
  • Article
License
Yellow

Abstract

Recently, reservoirs in southern China are witnessing incidents involving black water, which are harmful to the aquatic ecosystem. This study unravels the cause of the black water events by studying the occurrence and the ecological risks of contaminants (Pb, Cu, Cd, Zn, Ni, TFe, Mn, S, P, and DOC) in sediments of Tianbao reservoir. Due to the significantly high concentration of TFe, Mn, and P in the sediments, the study further used the thin film diffusion gradient (DGT) technology and high-resolution dialysis method to investigate the movement of Fe2+, Mn2+, S2−, and reactive P within the sediments. The ecological risk assessment (threshold effect level and probable effect level) showed that the sediments had a low concentration of Pb, Cu, Cd, Zn, and Ni. High organic matter from the Eucalyptus plantation surrounding the reservoir, as well as the intense thermal stratification of the reservoir, caused the hypolimnion to be hypoxic (DO < 2 mg/L). The diffusion fluxes at the water–sediment boundary (WSB) demonstrated a significant movement of Fe2+, Mn2+, and PO43− from the sediments into the overlying water, while the movement of S2− was in both directions due to hypoxia. A high correlation Fe–DOC (r = 0.9), Fe–S (r = 0.8), and Mn–S (r = 0.7) and the redox interaction of Fe2+, Mn2+, S2−, P, and DOC at the hypoxic WSB caused the production of black substances in the hypolimnion contributing to the so-called black water reservoir.Graphical abstract

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