Arsenic mobility in hydrogeologic system of Bolivian Altiplano: Status and comparison of the Lower Katari and Southern Poopó Basins

Abstract

Water resource in LKB (Lower Katari Basin) and SPB (Southern Poopó Basin) [TDPS (Lake Titicaca – Desaguadero River – Lake Poopó – Salt Flat of Coipasa) system] the southeastern part of Lake Titicaca and Lake Poopó in Bolivian Altiplano are contaminated with high concentrations of arsenic (As) (>10 μg/L) compared to the WHO and NB-512 guideline. Studied regions are characterized by a semiarid climate, slow hydrological flow, with geological formations of volcanic origin including brines and mineral deposits. The investigation focused on evaluating the present status and comparison of the geochemical processes of As in relation to the sources and mobilization in groundwater (GW) in LKB and SPB. Groundwater (GW), surface water (SW) and sediment samples were collected from both basins. The elevated concentration of As (LKB: 0.8–288 μg/L and SPB: 2.6–207 μg/L), boron (B) (LKB: 96–2473 μg/L and SPB: 507–4359 μg/L), manganese (Mn) (LKB: 0.6–7259 μg/L) and salinity (LKB: 125–11740 μS/cm) were observed in water compared to the WHO limit and is a serious concern about the GW quality for human consumption. The mineralization of GW is governing by the dissolution and exchange process of bases and anthropogenic generated solids and liquids effects the surface water quality in LKB as well as river bank communities. The spatial distribution of As was attributed to the geology of both the basins and the heterogeneously distributed evaporites in the sediments. The concentrations of As are found in alluvial sediments in northern region of LKB and “PACK belt” (an approximately 25 km long belt stretching along the southern shores of the Lake Poopó, between the villages of Pampa Aullagas and Condo K) in SPB, where iron (Fe) and aluminum (Al) oxides as well as hydroxides are the most predominant mineral phases as potential sorbents of As.