Mercury patterns in lakes within a natural hotspot in the Southern Volcanic Zone of the Andes (Nahuel Huapi National Park, Patagonia, South America)

Carolina Soto Cárdenas; Zaida Fernandez; Marina Arcagni; Andrea Rizzo; María Diéguez

Just Accepted

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Mercury patterns in lakes within a natural hotspot in the Southern Volcanic Zone of the Andes (Nahuel Huapi National Park, Patagonia, South America)

Carolina Soto Cárdenas , Zaida Fernandez, Marina Arcagni, Andrea Rizzo, María Diéguez

Abstract

Rationale Mercury hotspots have been identified in pristine volcanic areas of the northern Patagonian Andes (South America). In this study, we investigated spatial and seasonal patterns of total mercury (THg) in two oligotrophic lakes in Nahuel Huapi National Park (Argentina), adjacent to the Puyehue Cordón Caulle volcanic complex (Chile). We hypothesize that THg levels in the lakes are linked to seasonal terrestrial inputs and that in-lake processes influence its distribution and availability. Methodology Water samples were collected seasonally in the connected lakes Pire (shallow) and Brazo Rincón branch of L. Nahuel Huapi (BR, deep). The concentration of THg was studied together with physicochemical variables, including the concentration and quality of dissolved organic matter (DOM). THg was measured by cold vapor atomic fluorescence spectrometry (CVAF) and DOM was characterized through absorbance and fluorescence spectroscopy . Results Lakes showed moderate to high THg concentrations and remarkable availability. THg increased downwards in the landscape and was associated with DOM terrestrial prints, indicating its co-transport from the catchment during high connectivity periods (from winter to early summer). In summer, THg levels were associated with higher mineralisation (>DIC) and diffusion from sediments, especially in the shallow lake. THg availability and distribution were related to the quality of the DOM pool and the total suspended solids (TSS) year round. The high biotic contribution to TSS (>chlorophylla:TSS) in BR indicated Hg binding to phytoplankton and incorporation into lake food webs. Discussion Pristine oligotrophic lakes influenced by natural Hg sources have a high potential for Hg accumulation in food webs because their high Hg and low DOC concentrations allow for Hg availability to be taken up by food webs.

EN24088 Accepted 30 December 2024