title: Natural contamination with arsenic and other trace elements in groundwater of the Central-West region of Chaco, Argentina.
abstract: This study covered the central agricultural region of the Chaco province, which lacks a permanent river networks. However, during the rainy period there is localized groundwater recharge. About 84 groundwater samples were taken during the period April-December 2007. These groundwater samples were collected from two different depths: 62 samples from shallow wells (4 to 20 m) and 24 samples from deep wells (20 to 100 m). Chemical variables were determined: pH, specific conductance, total dissolved solid, hardness, alkalinity, HCO(3)-, CO(3)(2-), SO(4)(2-), Cl-, NO(3)-, NO(2) -, NH(4)+, F-, As((tot)), Na+, K+, Ca2+, Mg2+, Fe, Cu, Ni, Pb and Zn. The chemical composition of groundwater in the study area is dominantly sodium bicarbonate and sodium chloride bicarbonate, comprising more than 60% (52/86) of shallow and deep groundwater samples. Of the 86 analyzed groundwater samples, 88% exceeded the WHO (World Health Organization) and CAA (Código Alimentario Argentino) standards (10 μg/L) for As (arsenic) and 9% exceeded the WHO standard (1.5 mg/L) for F(-).Groundwater highly contaminated with As (max. 1,073 μg/L) and F- (max. 4.2 mg/L) was found in shallow aquifer. The contaminated groundwater is characterized by high pH (max. 8.9), alkalinity (max. HCO(3)- 1,932 mg/L), SO(4)(2-) (max. 11,862 mg/L), Na(+) (max. 3,158 mg/L), Cl(-) (max. 10,493 mg/L) and electric conductivity greater than 33.3 μS/cm. Other associated elements (Ni, Pb, Cu and Zn) are present in low concentrations, except for Fe that in 32% of samples exceeded the guideline value of 0.3 mg/L suggested by the CAA.
authors: Academia Nacional de Ciencias Exactas, Físicas y Naturales, Buenos Aires, Argentina.
authors: Patricia S
authors: PS
authors: Blanes
authors: Edgar E
authors: EE
authors: Buchhamer
authors: María C
authors: MC
authors: Giménez
mesh_terms: D001118:Argentina; D001151:Arsenic / Q000032:analysis* / Q000737:chemistry / Q000592:standards; D060766:Drinking Water / Q000737:chemistry* / Q000592:standards; D004784:Environmental Monitoring / Q000379:methods; D005459:Fluorides / Q000032:analysis / Q000737:chemistry / Q000592:standards; D060587:Groundwater / Q000737:chemistry* / Q000592:standards; D013053:Spectrophotometry / Q000379:methods; D014131:Trace Elements / Q000032:analysis* / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry; D060986:Water Wells / Q000032:analysis / Q000737:chemistry
chemical_list: D060766:Drinking Water; D014131:Trace Elements; D014874:Water Pollutants, Chemical; D001151:Arsenic; D005459:Fluorides