Geochemistry of naturally occurring arsenic in groundwater and surface-water in the southern part of the Poopó Lake basin, Bolivian Altiplano

Mauricio Ormachea Muñoz, José L. Garcia Aróstegui, Prosun Bhattacharya, Ondra Sracek, Maria E. Garcia Moreno, Claus Kohfahl, Jorge Quintanilla Aguirre, Jorge Hornero Diaz, Jochen Bundschuh

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27 Scopus citations

Abstract

Groundwaters from shallow aquifers and surface water from rivers of the southern part of Poopó Lake basin within the Bolivian Altiplano have significant quality problems such as high salinity and high concentrations of arsenic (As). The extent of As contamination is observed in the studied groundwater over large parts of the study area. Surface-waters are generally alkaline (pH 8.2–8.7) and oxidizing with dissolved oxygen (DO) concentrations in a range of 2.5–6.6 mg/L The water chemistry is predominantly of Na–Cl–HCO3–type, with concentrations of dissolved As in the range of 8.6–117 µg/L with As(V) as the main aqueous species. The concentration of Li varies in the range of 1.1–4.4 mg/L, while other trace elements occur in low concentrations. Groundwaters have a very large range of chemical compositions and the spatial variability of As concentrations is considerable over distances of a few km; dissolved As in groundwater spans over 4 orders of magnitude (3–3497 µg/L), while concentrations of Li have a range of 0.05–31.6 mg/L. Among the investigated drinking-water wells, 90% exceed the WHO guideline value of 10 µg As/L. Electrical conductivity ranges between 295 and 20,900 µS/cm; high salinity is resulting from evaporation under ambient semi-arid climatic conditions. The pH values of the groundwaters are generally slightly alkaline (5.5–8.7) and universally oxidizing, under these conditions As(V) is the prevalent specie. Groundwater As correlates positively with pH, electrical conductivity, Cl, Na+, HCO3, Ca2+ and SO42−. Weathering/dissolution of carbonates, evaporites, halite and plagioclase minerals incorporate Na+ and HCO3 in solution with consequent pH and alkalinity increase; these are favorable conditions for high mobility of As species. Stable isotopic signatures indicate recharge at the Altiplano with seasonal effects. All surface water and some groundwater samples are enriched due to evaporation, which probably increased concentration of dissolved As.

Original languageEnglish
Pages (from-to)104-116
Number of pages13
JournalGroundwater for Sustainable Development
Volume2-3
DOIs
StatePublished - 1 Aug 2016

Bibliographical note

Funding Information:
The authors acknowledge the financial support from Agencia Española de Cooperación Internacional para el Desarrollo, Spain (No. ref. 11-CAP2_1282 ) and from the Swedish International Development Cooperation Agency (Sida Contribution: 7500707606 ). We are thankful to Lizangela Huallpara, Beatriz Canaviri and Efraín Blanco at the Chemical Research Institute, Universidad Mayor de San Andres for field work and laboratory analyses and M.C. Hidalgo at the laboratories of the Scientific Instrumentation Centre of the University of Jaen in Spain for laboratory analyses. We acknowledge the thoughtful and constructive comments of the two anonymous reviewers which has helped to improve the earlier version of this manuscript.

Publisher Copyright:
© 2016

Keywords

  • Altiplano
  • Arsenic
  • Bolivia
  • Drinking water quality
  • Geochemistry

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