Trace metals and Mo isotopic fractionation in Skagerrak sediments–effects of different oxygen conditions

IF 3.9 3区环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Biogeochemistry Pub Date : 2025-01-30 DOI:10.1007/s10533-024-01206-3

Anna Siems, Tristan Zimmermann, Tina Sanders, Michael E. Wieser, Daniel Pröfrock

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Abstract

The Skagerrak is the main depot center for organic matter and anthropogenic pollutants from the entire North Sea. Changes in ocean circulation or suspended matter supply might impact the sediment redox conditions. Indeed, little is known about the response of Skagerrak sediment and associated pollutants to different oxygen levels. We investigated sediments from three stations within the Skagerrak and incubated them for up to twelve months under aerobic and anaerobic conditions. Furthermore, we present the first δ^98/95Mo data for Skagerrak sediment profiles and the incubations to be utilized as a redox tracer. The sediment profiles of metals reflected anthropogenic pollution (Cu, Ni, Pb) but differed regionally with redox conditions. We differentiated redox conditions mainly by sediment and porewater Fe, Mn, Mo and δ^98/95Mo. In aerobic incubations, no Mn or Fe reduction was detected, while under anaerobic conditions, initial Mn and Fe reduction decreased after approximately three months. Under anaerobic conditions, a strong isotopic fractionation of Mo in the dissolved phase was found, reaching up to 5.03 ± 0.10‰, probably caused by incomplete thiolation of molybdate under low hydrogen sulfide levels. During the incubations, Cd, Cu, Ni, Pb were mobilized. While Cu and Cd were mobilized under aerobic conditions, Ni and Pb mobilization depended mainly on remineralization and redox conditions. Our results show that changes in oxygen conditions in the Skagerrak can have significant effects on the (legacy) metals stored in the sediment over the past decades.

Graphical Abstract

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来源期刊

Biogeochemistry 环境科学-地球科学综合

CiteScore

7.10

自引率

5.00%

发文量

112

审稿时长

3.2 months

期刊介绍： Biogeochemistry publishes original and synthetic papers dealing with biotic controls on the chemistry of the environment, or with the geochemical control of the structure and function of ecosystems. Cycles are considered, either of individual elements or of specific classes of natural or anthropogenic compounds in ecosystems. Particular emphasis is given to coupled interactions of element cycles. The journal spans from the molecular to global scales to elucidate the mechanisms driving patterns in biogeochemical cycles through space and time. Studies on both natural and artificial ecosystems are published when they contribute to a general understanding of biogeochemistry.