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Abstract Title: Downstream Reactivity of Mercury in Contrasting Catchment Environments in the Swedish Sub-Arctic
Presenter Name: Sonja Gindorf
Company/Institution: Department of Environmental Science, Stockholm University
Session: Special Session - Climate-Driven Perturbations of Arctic Mercury Cycling
Co-Authors: Sonja Gindorf,Carluvy Baptista-Salazar,Van Liem-Nguyen,Reiner Giesler,Carl-Magnus M”rth,Sofi Jonsson

Abstract Information :

Dissolved organic matter (DOM) is an important vector for the transport and reactivity of mercury (Hg) in aquatic systems. The composition and concentration of DOM have been shown to control Hg bioavailability and bacterial Hg methylation rates and may vary depending on catchment properties. To understand the coupling between catchment properties and levels of Hg in freshwater systems, we sampled different streams (n=18) and lakes (n=8) along a climate and vegetation gradient in the Swedish sub-arctic, encompassing tundra-, birch-, and coniferous catchments. We quantified total Hg (THg), methylated Hg (MeHg) and ancillary parameters in the water as well as THg and MeHg in plankton. Moreover, we used fluorescence spectroscopy to characterize the DOM. Concentrations of THg and MeHg ranged from 0.19 to 2.8, and from undetectable to 0.12 pg L 1, respectively, in the water. In the collected seston, THg and MeHg ranged from 42 to 190, and 4 to 99 ng g-1, respectively. Across all systems, we observed a strong correlation between dissolved organic carbon (DOC) and THg and MeHg, respectively. Even though, the highest THg and MeHg were observed in the water collected from the coniferous lakes, no significant difference in THg or MeHg concentrations in lake biota was found. We observe a significant correlation in certain DOM fluorescence characteristics and biota MeHg concentrations indicating lower MeHg concentration in biota in the lakes with more labile fluorescence. Overall, our study suggests catchment properties could play a critical role for the fate of remobilized terrestrial Hg and the availability of Hg for bioaccumulation.

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