23 research outputs found
Mobilization of arsenic and other trace elements of health concern in groundwater from the Sali River Basin, Tucuman Province, Argentina
The SalĂ River Basin in north-west Argentina (7,000 km2) is composed of a sequence of Tertiary and Quaternary loess deposits, which have been substantially reworked by fluvial and aeolian processes. As with other areas of the Chaco-Pampean Plain, groundwater in the basin suffers a range of chemical quality problems, including arsenic (concentrations in the range of 12.2â1,660 ÎŒg Lâ1), fluoride (50â8,740 ÎŒg Lâ1), boron (34.0â9,550 ÎŒg Lâ1), vanadium (30.7â300 ÎŒg Lâ1) and uranium (0.03â125 ÎŒg Lâ1). Shallow groundwater (depths up to 15 m) has particularly high concentrations of these elements. Exceedances above WHO (2011) guideline values are 100% for As, 35% for B, 21% for U and 17% for F. Concentrations in deep (>200 m) and artesian groundwater in the basin are also often high, though less extreme than at shallow depths. The waters are oxidizing, with often high bicarbonate concentrations (50.0â1,260 mg Lâ1) and pH (6.28â9.24). The ultimate sources of these trace elements are the volcanic components of the loess deposits, although sorption reactions involving secondary Al and Fe oxides also regulate the distribution and mobility of trace elements in the aquifers. In addition, concentrations of chromium lie in range of 79.4â232 ÎŒg Lâ1 in shallow groundwater, 129â250 ÎŒg Lâ1 in deep groundwater and 110â218 ÎŒg Lâ1 in artesian groundwater. All exceed the WHO guideline value of 50 ÎŒg Lâ1. Their origin is likely to be predominantly geogenic, present as chromate in the ambient oxic and alkaline aquifer conditions
Groundwater geochemical evolution under the influence of polymetallic deposit in CzarnĂłw (Western Sudetes, SW Poland)
Arsenic contamination of natural waters in San Juan and La Pampa, Argentina
Arsenic (As) speciation in surface and groundwater from two provinces in Argentina (San Juan and La Pampa) was investigated using solid phase extraction (SPE) cartridge methodology with comparison to total arsenic concentrations. A third province, RĂo Negro, was used as a control to the study. Strong cation exchange (SCX) and strong anion exchange (SAX) cartridges were utilised in series for the separation and preservation of arsenite (AsIII), arsenate (AsV), monomethylarsonic acid (MAV) and dimethylarsinic acid (DMAV). Samples were collected from a range of water outlets (rivers/streams, wells, untreated domestic taps, well water treatment works) to assess the relationship between total arsenic and arsenic species, water type and water parameters (pH, conductivity and total dissolved solids, TDS). Analysis of the waters for arsenic (total and species) was performed by inductively coupled plasma mass spectrometry (ICP-MS) in collision cell mode. Total arsenic concentrations in the surface and groundwater from Encon and the San JosĂ© de JĂĄchal region of San Juan (north-west Argentina within the Cuyo region) ranged from 9 to 357 ÎŒg lâ1 As. Groundwater from Eduardo Castex (EC) and Ingeniero Luiggi (LU) in La Pampa (central Argentina within the Chaco-Pampean Plain) ranged from 3 to 1326 ÎŒg lâ1 As. The pH range for the provinces of San Juan (7.2â9.7) and La Pampa (7.0â9.9) are in agreement with other published literature. The highest total arsenic concentrations were found in La Pampa well waters (both rural farms and pre-treated urban sources), particularly where there was high pH (typically > 8.2), conductivity (>2,600 ÎŒS cmâ1) and TDS (>1,400 mg lâ1). Reverse osmosis (RO) treatment of well waters in La Pampa for domestic drinking water in EC and LU significantly reduced total arsenic concentrations from a range of 216â224 ÎŒg lâ1 As to 0.3â0.8 ÎŒg lâ1 As. Arsenic species for both provinces were predominantly AsIII and AsV. AsIII and AsV concentrations in San Juan ranged from 4â138 ÎŒg lâ1 to <0.02â22 ÎŒg lâ1 for surface waters (in the San JosĂ© de JĂĄchal region) and 23â346 ÎŒg lâ1 and 0.04â76 ÎŒg lâ1 for groundwater, respectively. This translates to a relative AsIII abundance of 69â100% of the total arsenic in surface waters and 32â100% in groundwater. This is unexpected because it is typically thought that in oxidising conditions (surface waters), the dominant arsenic species is AsV. However, data from the SPE methodology suggests that AsIII is the prevalent species in San Juan, indicating a greater influence from reductive processes. La Pampa groundwater had AsIII and AsV concentrations of 5â1,332 ÎŒg lâ1 and 0.09â592 ÎŒg lâ1 for EC and 32â242 ÎŒg lâ1 and 30â277 ÎŒg lâ1 As for LU, respectively. Detectable levels of MAV were reported in both provinces up to a concentration of 79 ÎŒg lâ1 (equating to up to 33% of the total arsenic). Previously published literature has focused primarily on the inorganic arsenic species, however this study highlights the potentially significant concentrations of organoarsenicals present in natural waters. The potential for separating and preserving individual arsenic species in the field to avoid transformation during transport to the laboratory, enabling an accurate assessment of in situ arsenic speciation in water supplies is discussed