Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IRD, IFSTTAR, ISTerre, 38000 Grenoble, France; Laboratorio de Hidroquímica, Instituto de Investigaciones Químicas, Universidad Mayor de San Andrés, Campus Universitario de Cota-Cota, Casilla 3161, La Paz, Bolivia.
Géosciences Environnement Toulouse, UMR5563 - IRD UR 234, Université Paul Sabatier, 14 Avenue Edouard Belin 31400 Toulouse, France; Unidad de Calidad Ambiental (UCA), Instituto de Ecología, Universidad Mayor de San Andrés, Campus Universitario de Cota Cota, Casilla 3161, La Paz, Bolivia.
Environ Pollut. 2017 Dec;231(Pt 1):262-270. doi: 10.1016/j.envpol.2017.08.009. Epub 2017 Aug 12.
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.
玻利维亚高原（约 3800 米海拔）的水生生态系统以极端的水文气候条件为特征（例如，高紫外线辐射和低氧气），并且受到人为活动、不受监管的采矿、农业和城市发展的压力。我们在此报告了同一流域两个内陆湖泊的水柱、大气、沉积物和关键指示生物（即浮游生物、鱼类和鸟类）中的汞（Hg）水平和形态的完整清单，这些湖泊在大小、富营养化和污染水平方面有所不同。的 Titicaca 湖中过滤水和沉积物中的总汞（THg）和甲基汞（MMHg）浓度处于全球其他大型湖泊报告水平的最低范围。下游，由于周围采矿区的 Hg 输入较高，浅水富营养化的 Uru-Uru 湖中 Hg 水平比 Titicaca 湖高 3-10 倍。在从贫/寡营养的 Titicaca 湖到富营养的 Uru-Uru 湖的上升过程中，过滤水和未过滤水中的 MMHg 百分比很高，THg 中约有 1-50%来自 MMHg。这种高的 %MMHg 可以用富硫酸盐基质中高的原位 MMHg 生成、水柱中的低氧气水平以及由于这些碱性水中存在丰富的配体而稳定 MMHg 来解释。Titicaca 湖和 Uru-Uru 湖之间在水和沉积物部分中 MMHg 浓度的差异反映了它们各自食物网中存在的 MMHg 水平的偏移。这表明，原位 MMHg 基线生成可能是控制当地居民食用的鱼类物种中 MMHg 水平的主要因素。最后，Titicaca 湖中人为压力的增加可能会加剧富营养化过程，从而有利于 MMHg 的生成，进而在水和生物群中积累。
