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Combined dynamics of mercury and terrigenous organic matter following impoundment of Churchill Falls Hydroelectric Reservoir, Labrador

Teisserenc, Roman and Lucotte, Marc and Canuel, René and Moingt, Matthieu and Obrist, Daniel Combined dynamics of mercury and terrigenous organic matter following impoundment of Churchill Falls Hydroelectric Reservoir, Labrador. (2013) Biogeochemistry, 118 (1-3). 21-34. ISSN 0168-2563

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Official URL: http://dx.doi.org/10.1007/s10533-013-9902-9

Abstract

Sediments from two recently (40 years) flooded lakes (Gabbro lake and Sandgirt lake) and an unflooded lake (Atikonak lake) were sampled to investigate the effects of reservoir impoundment on mercury (Hg) and terrigenous organic matter (TOM) loading in the Churchill Falls Hydroelectric complex in Labrador, Canada. Lignin biomarkers in TOM, which exclusively derive from terrestrial vegetation, were used as biomarkers for the presence and source origin of TOM—and for Hg due to their close associations—in sediments. In the two flooded Gabbro and Sandgirt lakes, we observed drastic increases in total mercury concentrations, T-[Hg], in sediments, which temporally coincided with the time of reservoir impoundment as assessed by 210Pb age dating. In the natural Atikonak lake sediments, on the other hand, T-[Hg] showed no such step-increase but gradually and slowly increased until present. T-[Hg] increases in lake sediments after flooding were also associated with a change in the nature of TOM: biomarker signatures changed to typical signatures of TOM from vegetated terrestrial landscape surrounding the lakes, and indicate a change to TOM that was much less degraded and typical of forest soil organic horizons. We conclude that T-[Hg] increase in the sediments of the two flooded reservoirs was the result of flooding of surrounding forests, whereby mainly surface organic horizons and upper soil horizons were prone to erosion and subsequent re-sedimentation in the reservoirs. The fact that T-[Hg] was still enriched 40 years after reservoir impoundment indicates prolonged response time of lake Hg and sediment loadings after reservoir impoundments.

Item Type:Article
Additional Information:Thanks to Springer Science editor. The definitive version is available at http://link.springer.com/article/10.1007%2Fs10533-013-9902-9
HAL Id:hal-01068161
Audience (journal):International peer-reviewed journal
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Institution:Other partners > Desert Research Institute - DRI (USA)
Other partners > Université du Québec à Montréal - UQAM (CANADA)
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Deposited On:27 Nov 2013 08:36

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