Arsenic and associated trace-elements in groundwater from the Chaco-Pampean plain, Argentina: Results from 100years of research

• DOI: 10.1016/j.scitotenv.2012.04.048
• Publication Date: 2012-05-29T04:18:54Z
• Authors: Hugo B. Nicolli; Jochen Bundschuh; María del C. Blanco; Ofelia C. Tujchne...; Héctor O. Panarello; Cristina Dapeña; Jorge E. Rusansky
• Keywords: Trace Element Sources And Mobility; hydrogeochemistry; Argentina; Endemic Hydroarsenicism And Fluorosis; 910; 01 natural sciences; trace-element sources and mobility; Arsenic; https://purl.org/becyt/ford/1.5; Hydrogeochemistry; Fluoride; https://purl.org/becyt/ford/1; Groundwater; 0105 earth and related environmental sciences; endemic hydroarsenicism and fluorosis; 2. Zero hunger; fluoride; Chaco-Pampean aquifers; arsenic; 15. Life on land; 6. Clean water; Trace Elements; 13. Climate action; Chaco-Pampean Aquifers; Water Pollutants, Chemical

The Chaco-Pampean plain, Argentina, is a vast geographical unit (1,000,000 km²) 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 μg As/L; 51-7,340 μg F/L) exceeding the WHO guideline values (As: 10 μg/L; F: 1,500 μg/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-Salteña 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 Salí 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.