Arsenic in groundwater in La Pampa Province, Argentina

Landscape shot of the Pampean plain showing a windmill used to pump groundwater from a well

Groundwater abstraction, Pampean style.

In a collaboration with Instituto de Geoquímica in Buenos Aires, the BGS has been involved with investigations of arsenic occurrence in groundwater in Argentina over the last decade.

Studies have focused on La Pampa Province, part of the vast Chaco-Pampean Plain, which covers a large part of the country.

The region is a semi-arid plain where shallow groundwater resources occur largely in Quaternary loess deposits.

Arsenic in Pampean groundwater

Distribution of total arsenic (As_T) in shallow groundwaters from the loess aquifer of La Pampa.

Cattle on the Pampean plain of central Argentina.

The shallow Pampean aquifer of La Pampa is typically oxic and analysed samples of groundwater show a very large range of arsenic concentrations (<4 – 5300 µg/L observed in our studies).

The arsenic is dominated by As(V) and correlates positively with a number of other anions and oxyanions (HCO₃, V, B, F and to a lesser extent, Mo and U). Concentrations of V, B, F, Mo and U range up to 5.4 mg/L, 14 mg/L, 29 mg/l, 990 µg/L and 250 µg/L respectively and many exceed WHO guideline values or national limits for drinking water. Concentrations of arsenic and the associated trace elements in the groundwaters are extremely variable on a local scale.

Release of arsenic(V) from the Pampean sediments under high-pH (alkaline) conditions is seen as a critical part of the mobilisation mechanism.

In urban areas, response to the groundwater-quality problems is to treat by reverse osmosis to remove solutes from drinking water. Such options are less viable in rural areas and poor drinking-water quality remains an important issue for the rural populations.

Publications

Nicolli, H B, García, J W, Falcón, C M, and Smedley, P L. 2012. Mobilization of arsenic and other trace elements of health concern in groundwater from the Salí River Basin, Tucumán Province, Argentina. Environmental Geochemistry & Health, 34, 251–262.

Smedley, P L, Nicolli, H B, Macdonald, D M J, and Kinniburgh, D G. 2008. Arsenic in groundwater and sediments from La Pampa Province, Argentina. In: Bundschuh, J Armienta, M A, Birkle, P, Bhattacharya, P, Matschullat, J, Mukherjee, A B. (editors). Natural Arsenic in Groundwaters of Latin America, Taylor & Francis, 35–45.

Smedley, P L, Kinniburgh, D G, Macdonald, D M J, Nicolli, H B, Barros, A J, Tullio, J O, Pearce, J M, and Alonso, M S. 2005. Arsenic associations in sediments from the loess aquifer of La Pampa, Argentina. Applied Geochemistry, 20, 989-1016.

Smedley, P L, Nicolli, H B, Macdonald, D M J, Barros A J, and Tullio, J O. 2002. Hydrogeochemistry of arsenic and other inorganic constituents in groundwaters from La Pampa, Argentina. Applied Geochemistry, 17, 259–284.