Water management in semiarid and arid catchments such as the Poopó Lake Basin requires improved understanding of the complex behavior of the various contaminants, which affect the drinking water quality and considered as crucial for sustainable development of the region. Mechanisms of arsenic (As) release in the surface and groundwater were studied. Hydrochemical data for surface water (4 samples) and groundwater (28 samples) were collected in a small watershed in the Poopó catchment at the highland of the Bolivian Andes (Altiplano). All of them show high electrical conductivity values and moderately oxidizing conditions. The surface water contains high concentration of sulfate and the trace elements As, Zn and Pb in the zone affected by acid mine drainage. There is a large variability of the concentration of As and of the trace elements in the groundwater in the five different regions within the Poopó catchment. The metal concentrations sensitive to changes of redox state and results of speciation modeling suggest that As (V) is a predominant aqueous species, which conforms to the prevailing oxidizing conditions in the shallow groundwater environment. Two generalized trends for As distribution were identified in groundwater: (a) high concentrations are found in the arid zone (100-250 μg/L) in the southern (region III) and in the northwestern (region V) regions, and (b) low concentrations (< 50 μg/L) are found in the remaining part of the basin (region I, II and IV). However, the spatial distribution within these regions needs to be investigated further. A conclusion from the present study is that there are multiple sources of As as well as other trace elements (such as Cd, Mn and Zn) in the Poopó Lake Basin. Among the sources and the processes which led to the mobility of As and other trace metals in the region are: (a) weathering of sulfide minerals, (b) oxidation of pyrite and/or arsenopyrite in mineralized areas and (c) desorption from hydrous ferric oxide (HFO) surfaces. In non-mining areas, volcanic ash is suggested to be a significant source of As.
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Acknowledgments This research was funded through Swedish International Development Cooperation Agency in Bolivia (Sida Contribution: 7500707606). We extend our sincere appreciation to Eduardo Palenque for the review of the earlier version of this manuscript and to Moises Calliconde for clarifying the electrochemical concepts. We gratefully acknowledge the analytical support from Elvira Guisbert and Liliana Flores at the Instituto de Investigaciones Quimicas, UMSA, La Paz and Ann Fylkner, Monica Löwen and Bertil Nilsson at the Department of Land and Water Resources Engineering, KTH Stockholm for the major ion analyses. Magnus Mörth at the Department of Geological Sciences, Stockholm University is acknowledged for the trace element analyses. The authors also acknowledge the support of the CAMINAR project (INCO-CT-2006-032539) funded by the International Cooperation section of the European Commission under the 6th Framework Programme. JB thanks the CYTED Proyect Red Temática 406RT0282 Iberoarsen and the National Science Council of Taiwan for the financial support. We deeply acknowledge Mr S. Jayagopal and Srikanth Reddy of the Springer Correction team for their editorial support.
- Drinking water quality
- Trace elements