Abstract

DIAZ, SILVANA LETISIA et al. GEODISPONIBILIDAD DE ARSÉNICO, HIERRO Y SODIO EN SUELOS DE LA CUENCA "EL DIVISORIO'' (BUENOS AIRES, ARGENTINA). Cienc. suelo [online]. 2015, vol.33, n.2. ISSN 1850-2067.

Arsenic concentration > 10 mg L-1 in drinking water harms human health and limits agriculture and livestock production since As can be integrated laterally into food chains. The objective of this work is to quantify As, Fet l, Feox and Na in soil-sediments through which rainfall water circulates, feeding the phreatic aquifer in El Divisorio brook basin. The hypothesis postulates that total geoavailable As and its spatial distribution respond to sedimentary dynamics. The Feox controls As transference to waters and Na determines alkaline pHs that also favours mobility and accumulation of elevated As (> 10 u,g L-1) into the aquifer. Three soils in the upper basin (high, terrace and alluvial plain) and four soils in the middle-lower basin (interfluve plain, valley slope, terrace, and alluvial plain) were described. Total contents of As, Fe and Na and iron oxides were determined in the whole horizon sequence of all the selected profiles. As (u,g L-1) and other elements were measured in the phreatic water through HG-ICP. A Principal Components analysis was performed in the solid phase. As geoavailability was normal (5.10-20.7 mg kg-1) with maximun levels in the middle-lower basin coinciding with excesive As (>10 u,g L-1) in phreatic waters. CP1 and CP2 explain 60% of total variability. Na (-0.70) and As (0.72) contribute to CP1; Fetotal (0.81) was more relevant to CP2 and Feox (0.71) contributed to CP3. Fe a and Feox do not correlate significantly (p>0.73). Feox behaves as a sink or as a source of As. A decrese in geoavailable Na resulted in higher Na concentrations and pHs in the aquifer of the middle-lower basin. 97.3% of the phreatic waters had elevated As (10-110 |ig L-1), B (120-1420 |ig L-1), F (200-4880 ug L-1) and V (40-800 |ig L-1). Arsenic increased in the direction of the flow towards the S and SE up to > 10 u,g L-1 in the aquifer's discharge and at the mouth of the brook into Paso de la Piedras Dam.

Keywords : Solid phase, As, Fe, and Na geoavailability, phreatic waters, hydrochemistry and As distribution..

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