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Mercury contamination level and speciation inventory in Lakes Titicaca & Uru-Uru (Bolivia): Current status and future trends

TitreMercury contamination level and speciation inventory in Lakes Titicaca & Uru-Uru (Bolivia): Current status and future trends
Type de publicationJournal Article
Year of Publication2017
AuteursGuédron, S, Point, D, Acha, D, Bouchet, S, Baya, PA, Tessier, E, Monperrus, M, Molina, CI, Groleau, A, Chauvaud, L, Thebault, J, Amice, E, Alanoca, L, Duwig, C, Uzu, G, Lazzaro, X, Bertrand, A, Bertrand, S, Barbraud, C, Delord, K, Gibon, F-M, Ibanez, C, Flores, M, P. Saavedra, F, Ezpinoza, ME, Heredia, C, Rocha, F, Zepita, C, Amouroux, D
JournalEnvironmental Pollution
Volume231, Part 1
Pagination262 - 270

Abstract Aquatic ecosystems of the Bolivian Altiplano (∼3800 m a.s.l.) are characterized by extreme hydro-climatic constrains (e.g., high UV-radiations and low oxygen) and are under the pressure of increasing anthropogenic activities, unregulated mining, agricultural and urban development. We report here a complete inventory of mercury (Hg) levels and speciation in the water column, atmosphere, sediment and key sentinel organisms (i.e., plankton, fish and birds) of two endorheic Lakes of the same watershed differing with respect to their size, eutrophication and contamination levels. Total Hg (THg) and monomethylmercury (MMHg) concentrations in filtered water and sediment of Lake Titicaca are in the lowest range of reported levels in other large lakes worldwide. Downstream, Hg levels are 3–10 times higher in the shallow eutrophic Lake Uru-Uru than in Lake Titicaca due to high Hg inputs from the surrounding mining region. High percentages of \{MMHg\} were found in the filtered and unfiltered water rising up from <1 to ∼50% \{THg\} from the oligo/hetero-trophic Lake Titicaca to the eutrophic Lake Uru-Uru. Such high %MMHg is explained by a high in situ \{MMHg\} production in relation to the sulfate rich substrate, the low oxygen levels of the water column, and the stabilization of \{MMHg\} due to abundant ligands present in these alkaline waters. Differences in \{MMHg\} concentrations in water and sediments compartments between Lake Titicaca and Uru-Uru were found to mirror the offset in \{MMHg\} levels that also exist in their respective food webs. This suggests that in situ \{MMHg\} baseline production is likely the main factor controlling \{MMHg\} levels in fish species consumed by the local population. Finally, the increase of anthropogenic pressure in Lake Titicaca may probably enhance eutrophication processes which favor \{MMHg\} production and thus accumulation in water and biota.