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Buenos Aires, Argentina

Nicolli H.B.,Institute Geoquimica INGEOQUI | Bundschuh J.,CONICET | Bundschuh J.,University of Southern Queensland | Blanco M.D.C.,KTH Royal Institute of Technology | And 6 more authors.
Science of the Total Environment | Year: 2012

The Chaco-Pampean plain, Argentina, is a vast geographical unit (1,000,000km 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: <10-5300μg As/L; 51-7,340μgF/L) exceeding the WHO guideline values (As: 10μg/L; F: 1,500μg/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 534-3340mg/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. © 2012. Source

Diaz S.L.,National University of the South | Esposito M.E.,National University of the South | Blanco M.D.C.,National University of the South | Amiotti N.M.,National University of the South | And 5 more authors.
Catena | Year: 2016

Surface and groundwaters of El Divisorio brook (Argentina) have excessive As (WHO, USEPA, CAA: >10 μg L-1). The rural population is at risk of arsenicism because groundwater is the only source of water for human consumption. We analyse geoavailability of As and other associated elements (Ba, Br, Co, Cr, Fe and Na) in the solid phase (INAA-Actlabs), determine the association between As and other elements in the mineral suite and in waters, quantify Fe oxides (Feox; Mehra and Jackson) and interpret their relationship with As, total Fe (Fetotal) and Na in the solid phase applying Principal Components (PC) to understand factors and processes that rule their incorporation into groundwaters and to identify areas at risk of elevated As in waters. Intrabasin variability of total As content (range 5.80-20.70 mg kg-1) with the highest amounts towards the discharge areas and a more irregular vertical distribution, particularly in the alluvial plain, reflects differences in As-bearer frequencies. Arsenic is slightly lower in the Bw horizons compared with the A and C horizons and it increases in the Bt horizon through clay illuviation. More than 90% of sodium-bicarbonated surface and groundwaters showed As >10 μg L-1 (range: 10 to 114 μg L-1) with the highest levels in the middle-lower basin. The highest contributions to PC1 were Br (0.673), Co (0.868) and Na (-0.769); As (0.814) and Cr (0.686) were relevant to PC2 and Ba (0.501) and Fe (0.783) were relevant to PC3. In the upper basin, a greater amount of Na withheld in the solids promotes a less aggressive geochemical environment and prevents As from entering waters, thus yielding lower As levels in the aquifer compared with the middle-lower basin. Here, alkalinity (pH: 7 up to >9) promotes weathering and liberation of As from volcanic glass and other carriers, formation of As oxyanion species together with As desorption from charged clays and Al-Fe-Mn sesquioxides and concentration up to unacceptable levels in solution. Landform configuration, climate and pedoclimate, the residence time of water and the local hydrogeochemical variables (pH, competition with other ions, adsorption-desorption) control mobility and concentration of As in a dynamic equilibrium with the local chemistry. Evaporation (subhumid to semiarid climate) and oxyion competition reinforce As accumulation in the shallow aquifers. © 2016 Elsevier B.V. Source

Bundschuh J.,University of Southern Queensland | Bundschuh J.,KTH Royal Institute of Technology | Bundschuh J.,National Cheng Kung University | Litter M.I.,Comision Nacional de la Energia Atomica | And 14 more authors.
Science of the Total Environment | Year: 2012

The global impact on public health of elevated arsenic (As) in water supplies is highlighted by an increasing number of countries worldwide reporting high As concentrations in drinking water. In Latin America, the problem of As contamination in water is known in 14 out of 20 countries: Argentina, Bolivia, Brazil, Chile, Colombia, Cuba, Ecuador, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Peru and Uruguay. Considering the 10 μg/L limit for As in drinking water established by international and several national agencies, the number of exposed people is estimated to be about 14. million. Health effects of As exposure were identified for the first time already in the 1910s in Bellville (Córdoba province, Argentina). Nevertheless, contamination of As in waters has been detected in 10 Latin American countries only within the last 10 to 15. years. Arsenic is mobilized predominantly from young volcanic rocks and their weathering products. In alluvial aquifers, which are water sources frequently used for water supply, desorption of As from metal oxyhydroxides at high pH (> 8) is the predominant mobility control; redox conditions are moderate reducing to oxidizing and As(V) is the predominant species. In the Andes, the Middle American cordillera and the Transmexican Volcanic Belt, oxidation of sulfide minerals is the primary As mobilization process. Rivers that originate in the Andean mountains, transport As to more densely populated areas in the lowlands (e.g. Rímac river in Peru, Pilcomayo river in Bolivia/Argentina/Paraguay). In many parts of Latin America, As often occurs together with F and B; in the Chaco-Pampean plain As is found additionally with V, Mo and U whereas in areas with sulfide ore deposits As often occurs together with heavy metals. These co-occurrences and the anthropogenic activities in mining areas that enhance the mobilization of As and other pollutants make more dramatic the environmental problem. © 2011 Elsevier B.V. Source

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