Content and distribution of arsenic in soils, sediments and groundwater environments of the southern Pampa region, Argentina.
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.
Blanco
M del C
Mdel C
Depto. De Agronomía, Universidad Nacional del Sur, San Andrés 800, (8000) Bahía Blanca, Rca. Argentina. mcblanco@criba.edu.ar
Paoloni
J D
JD
Morrás
H J M
HJ
Fiorentino
C E
CE
Sequeira
M
M
D001118:Argentina; D001151:Arsenic / Q000032:analysis* / Q000633:toxicity; D004784:Environmental Monitoring / Q000379:methods*; D005618:Fresh Water / Q000737:chemistry*; D019015:Geologic Sediments / Q000737:chemistry*; D006801:Humans; D008903:Minerals / Q000032:analysis; D018570:Risk Assessment; D012987:Soil / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity; D014881:Water Supply
D008903:Minerals; D012987:Soil; D014874:Water Pollutants, Chemical; D001151:Arsenic