Journal
SCIENCE OF THE TOTAL ENVIRONMENT
Volume 429, Issue -, Pages 36-56Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.scitotenv.2012.04.048
Keywords
Hydrogeochemistry; Trace-element sources and mobility; Arsenic; Fluoride; Chaco-Pampean aquifers; Endemic hydroarsenicism and fluorosis
Categories
Funding
- CONICET (Argentine Scientific Research Council), PIP [5775]
- CYTED Thematic Network [IBEROARSEN 406RT0282]
- ANPCYT (Argentine Agency for Scientific and Technologic Development)
- SeCyT-UNS (Secretariat of Science and Technology, Universidad Nacional del Sur, Argentina)
- National Science Council of Taiwan
- University of Southern Queensland, Australia, and the Swedish International Development Cooperation Agency (Sida)
- Strategic Environmental Research Foundation (MISTRA) [Idea 428, dnr: 2005-035-137]
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The Chaco-Pampean plain, Argentina, is a vast geographical unit (1,000,000 km(2)) affected by high arsenic (As) concentrations in universal oxidizing groundwater. The socio-economic development of the region is restricted by water availability and its low quality caused by high salinity and hardness. In addition, high As and associated trace-elements (F, U, V. B, Se, Sb, Mo) concentrations of geogenic origin turn waters unsuitable for human consumption. Shallow groundwater with high As and F concentrations (ranges: <10-5300 mu g As/L; 51-7,340 mu g F/L) exceeding the WHO guideline values (As: 10 mu g/L; F: 1,500 mu g/L) introduces a potential risk of hydroarsenicism disease in the entire region and fluorosis in some areas. The rural population is affected (2-8 million inhabitants). Calcareous loess-type sediments and/or intercalated volcanic ash layers in pedosedimentary sequences hosting the aquifers are the sources of contaminant trace-elements. Large intra and interbasin variabilities of trace-element concentrations, especially between shallow and deep aquifers have been observed. All areas of the Chaco-Pampean plain were affected in different grades: the Chaco-Saltena plain (in the NNE of the region) and the northern La Pampa plain (in the center-south) have been shown the highest concentrations. The ranges of As and F contents in loess-sediments are 6-25 and 534-3340 mg/kg, respectively in the Sali River basin. Three key processes render high As concentrations in shallow aquifers: i) volcanic glass dissolution and/or hydrolysis and leaching of silicates minerals hosted in loess; ii) desorption processes from the surface of Al-, Fe- and Mn-oxi-hydroxides (coating lithic fragments) at high pH and mobilization as complex oxyanions (As and trace elements)in Na-bicarbonate type groundwaters; and iii) evaporative concentration in areas with semiarid and arid climates. Local factors play also an important role in the control of high As concentrations, highly influenced by lithology-mineralogy, soils-geomorphology, actual climate and paleoclimates, hydraulic parameters, and residence time of groundwaters. (C) 2012 Published by Elsevier B.V.
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