Geogenic arsenic and other trace elements in the shallow hydrogeologic system of Southern Poopó Basin, Bolivian Altiplano

Mauricio Ormachea Muñoz, Hannes Wern, Fredrick Johnsson, Prosun Bhattacharya, Ondra Sracek, Roger Thunvik, Jorge Quintanilla, Jochen Bundschuh

Research output: Contribution to journalArticlepeer-review

42 Scopus citations

Abstract

Environmental settings in the southern area of Lake Poopó in the Bolivian highlands, the Altiplano, have generated elevated amounts of arsenic (As) in the water. The area is characterised by a semiarid climate, slow hydrological flow and geologic formations of predominantly volcanic origin. The present study aimed at mapping the extent of the water contamination in the area and to investigate the geogenic sources and processes involved in the release of As to the groundwater.Ground- and surface-water samples were collected from 24 different sites, including drinking water wells and rivers, in the southern Poopó basin in two different field campaigns during the dry and rainy seasons. The results revealed variable levels of As in shallow drinking water wells and average concentration exceeding the WHO guidelines value. Arsenic concentrations range from below 5.2μg/L (the detection level) to 207μg/L and averages 72μg/L. Additionally, high boron (B) concentrations (average 1902μg/L), and high salinity are further serious concerns for deteriorating the groundwater quality and rendering it unsuitable for drinking. Groundwater is predominantly of the Na-Cl-HCO3 type or the Ca-Na-HCO3 type with neutral or slightly alkaline pH and oxidising character. While farmers are seriously concerned about the water scarcity, and on a few occasions about salinity, there are no concerns about As and B present at levels exceeding the WHO guidelines, and causing negative long term effects on human health.Sediment samples from two soil profiles and a river bed along with fourteen rock samples were also collected and analysed. Sequential extractions of the sediments together with the calculation of the mineral saturation indices indicate that iron oxides and hydroxides are the important secondary minerals phases which are important adsorbents for As. High pH values, and the competition of As with HCO3 and dissolved silica for the adsorption sites probably seems to be an important process for the mobilisation of As in the shallow groundwaters of the region. Continuous monitoring and expansion of monitoring systems are necessary prerequisites for better understanding of the pattern of As mobilisation in the Southern Poopó Basin.

Original languageEnglish
Pages (from-to)924-940
Number of pages17
JournalJournal of Hazardous Materials
Volume262
DOIs
StatePublished - 15 Nov 2013

Bibliographical note

Funding Information:
The present research forms part of the Asdi (Sida)-Bolivia Research Cooperation programme (Sida Contribution 7500707606 ). We would like to thank Ronald Zapata, UMSA students MacGuiver Pilco, Lizangela Huallpara and Efrain Blanco for field and laboratory assistance and Victor Sotil for driving us around the Altiplano – even where no roads were accessible. Geological data over the Altiplano region provided by the National Geological and Technical Mining Survey (Sergeotecmin), Bolivia is also gratefully acknowledged. We would like to thank Ann Fylkner and Monica Löwén for laboratory analyses at the Department of Land and Water Resources Engineering, KTH, and professor emeritus Gunnar Jacks for helping us with the rock sample preparations at the University of Turku, Finland. FJ and HW gratefully acknowledge the financial support provided by the Sida – Minor Field Study (MFS) programme and the Ångpanneföreningen Foundation for Research and Development (ÅForsk) for the field work, Sigrun Santesson and Åsa Andersson at KTH International Office, for the administrative support. Carin Alderman helped us with the determination of soil colours.

Keywords

  • Adsorption
  • Alluvial sediments
  • Arsenic
  • Bolivian Altiplano
  • Groundwater
  • Volcanic rocks

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