Natural arsenic groundwater contamination of the sedimentary aquifiers of southwestern Sebaco Valley, Nicaragua

Altamirano Espinoza, M. and Bundschuh, Jochen (2009) Natural arsenic groundwater contamination of the sedimentary aquifiers of southwestern Sebaco Valley, Nicaragua. In: Natural arsenic in groundwaters of Latin America. Arsenic in the Environment, 1. Taylor & Francis (CRC Press), London, United Kingdom, pp. 109-122. ISBN 9780415407717


In Nicaragua, arsenic (As) contamination of drinking water resources due to geogenic sources can be identified in the southwestern part of Sébaco valley. The As sources are weathering products of Tertiary volcanic rocks of the Coyol group that form the alluvial aquifer of Sébaco valley. This valley is located at the external eastern margin of the Nicaraguan depression (or Central American graben). The region is characterized by intensive tectonic stress and the
presence of different active and non-active fault systems, intensive fracturing and hydrothermal alteration along faults. The volcanic rocks outcrop at the margins and at several locations within the valley overlying the alluvial aquifer. This aquifer is used by several communities for drinking water supply. In 21 of 57 water samples collected from wells of this alluvial aquifer, As concentrations
ranged from 10 to 122 μg/l, exceeding the national and the WHO limit of 10 μg/l for As in drinking water. Several hot spots with high groundwater As were identified, e.g., El Zapote village with 122 μg/l. In comparison, the localities of Las Mangas and Tatazcame, were identified as areas with safe groundwater, most suitable for future drinking water supply projects. The high As concentration in El Zapote water is correlated with elevated As concentrations in rocks and soils (14.98 and 57.19 μg/kg, respectively). Arsenic sources are the volcanic hard rocks, the alluvial
sediments composing the alluvial aquifer and the unsaturated zone, and the hydrothermally altered
volcanic rocks. Chemical mineral weathering and changing redox conditions increase mobility of As and its transfer from solid to dissolved form. Similar Tertiary volcanic rocks cover wide parts of Nicaragua and other Central American countries. It can be expected that many other not yet identified sites with groundwater As problems exist in the region.

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Item Type: Book Chapter (Commonwealth Reporting Category B)
Refereed: Yes
Item Status: Live Archive
Additional Information: Permanent restricted access to published version due to publisher copyright policy. Print copy not held in the USQ Library.
Faculty/School / Institute/Centre: Historic - Faculty of Engineering and Surveying - Department of Agricultural, Civil and Environmental Engineering
Date Deposited: 05 Nov 2014 04:22
Last Modified: 05 Nov 2014 04:27
Uncontrolled Keywords: arsenic; groundwater; aquifiers; Sebaco Valley
Fields of Research : 05 Environmental Sciences > 0502 Environmental Science and Management > 050204 Environmental Impact Assessment
04 Earth Sciences > 0406 Physical Geography and Environmental Geoscience > 040603 Hydrogeology

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