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Content and distribution of arsenic in soils, sediments and groundwater environments of the southern Pampa region, Argentina
Author(s) -
Blanco M. del C.,
Paoloni J. D.,
Morrás H. J. M.,
Fiorentino C. E.,
Sequeira M.
Publication year - 2006
Publication title -
environmental toxicology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.813
H-Index - 77
eISSN - 1522-7278
pISSN - 1520-4081
DOI - 10.1002/tox.20219
Subject(s) - groundwater , geology , aquifer , loess , sedimentary rock , soil water , population , geochemistry , provenance , holocene , soil science , geomorphology , oceanography , demography , geotechnical engineering , sociology
The health of a large rural population in the southern Pampa (Argentina) is at risk owing to newly detected areas where As‐groundwater exceeds 0.01 mg/L standard (WHO (1995) Guidelines for drinking water quality, 2nd edition. pp 43–45). Currently, devitrification of volcanic glass is invoked to interpret the origin of arsenic in the aquifers hosted in a sequence of pampean loess (Plio‐Pleistocene) juxtaposed with postpampean loess (Holocene). Our data suggest that arsenic is not specifically associated with volcanic glass and that other minerals contribute to As‐release into groundwater. The goals were (1) to understand As‐groundwater spatial variability, (2) to explore soils/sediments/water relationships and to identify the probable As‐provenance. Comparable As concentrations of the light and the heavy sand fractions suggest that though detrital glass is a major light constituent, other existing primary minerals are As‐bearers that contribute to As‐release into groundwater. Grouping of materials according to their As‐content indicated spatial variability in the sedimentary distribution pattern leading to differences in the frequencies of occurrence of As‐bearing minerals. Phreatic waters were Ca + Mg bicarbonate and devoid of As in the intake areas (Ventania System) and Na‐carbonate but As‐rich towards the discharge (Atlantic coast and local depressions). As‐groundwater reflects a patchy distribution within the pampean landscape. A correspondence between As‐high groundwater, EC >1 dSm, CO 3 H − , alkaline pH and a longer water residence time do exist triggering As extraction from the loess sand fraction and desorption from charged fine particles which lead to As‐toxicity towards groundwater discharge. © 2006 Wiley Periodicals, Inc. Environ Toxicol 21: 561–574, 2006.