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Research article - Peer-reviewed, 2022

Sources of riverine mercury across the Mackenzie River Basin; inferences from a combined Hg\\C isotopes and optical properties approach

Campeau, Audrey; Eklof, Karin; Soerensen, Anne L.; Akerblom, Staffan; Yuan, Shengliu; Hintelmann, Holger; Bieroza, Magdalena; Kohler, Stephan; Zdanowicz, Christian


The Arctic environment harbors a complex mosaic of mercury (Hg) and carbon (C) reservoirs, some of which are rapidly destabilizing in response to climate warming. The sources of riverine Hg across the Mackenzie River basin (MRB) are uncertain, which leads to a poor understanding of potential future release. Measurements of dissolved and particulate mercury (DHg, PHg) and carbon (DOC, POC) concentration were performed, along with analyses of Hg stable isotope ratios (incl. Delta 199Hg, delta 202Hg), radiocarbon content (Delta 14C) and optical properties of DOC of river water. Isotopic ratios of Hg revealed a closer association to terrestrial Hg reservoirs for the particulate fraction, while the dissolved fraction was more closely associated with atmospheric deposition sources of shorter turnover time. There was a positive correlation between the Delta 14C-OC and riverine Hg concentration for both particulate and dissolved fractions, indicating that waters transporting older-OC (14C-depleted) also contained higher levels of Hg. In the dissolved fraction, older DOC was also associated with higher molecular weight, aromaticity and humic content, which are likely associated with higher Hg-binding potential. Riverine PHg concentration increased with turbidity and SO4 concentration. There were large contrasts in Hg concentration and OC age and quality among the mountain and lowland sectors of the MRB, which likely reflect the spatial distribution of various terrestrial Hg and OC reservoirs, including weathering of sulfate minerals, erosion and extraction of coal deposits, thawing permafrost, forest fires, peatlands, and forests. Results revealed major differences in the sources of particulate and dissolved riverine Hg, but nonetheless a common positive association with older


Mercury; Organic carbon; Stable; Radiocarbon; Fluorescence; Mackenzie River

Published in

Science of the Total Environment
2022, volume: 806, article number: 150808
Publisher: ELSEVIER

Authors' information

Swedish University of Agricultural Sciences, Department of Forest Ecology and Management
Uppsala University
Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment
Soerensen, Anne L.
Swedish Museum of Natural History
Akerblom, Staffan
Statistics Sweden
Yuan, Shengliu
Trent University
Hintelmann, Holger
Trent University
Swedish University of Agricultural Sciences, Department of Soil and Environment
Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment
Zdanowicz, Christian
Uppsala University

UKÄ Subject classification

Environmental Sciences

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