Abstract

ESPOSITO, Martín; BLANCO, María del Carmen; PAOLONI, Juan Darío  and  AMIOTTI, Nilda. Space-time variability of the pair As-Cd in the hydric resource and risk zones at the southwestern section of the pampean plain, Argentine. Geoacta [online]. 2017, vol.42, n.1, pp.24-37. ISSN 1852-7744.

Arsenic is among the most relevant natural contaminants and it coexists with other oligoelements in the hydric resource of the pampean plain of Argentine. Antecedent studies have postulated that the potential risk of As would be strengthened by the hydrogeochemical association with Cd, when their concentrations exceed the guide values settled by the World Health Organization (WHO). Depending on the degree of severity of water quality affection, cardiovascular diseases, hypertension, reproductive problems and bone abnormalities may develop. On this basis the following objectives were proposed in our research: 1- to study the space-time variability of the As-Cd concentrations, 2- to delimit the areas of the higher risk for the community, 3- to analyze their degree of correlation and 4- to evaluate the probable provision sources. The study was developed in the Aº. El Divisorio catchment (Buenos Aires province), whose principal course discharges into Paso de las Piedras dam, which is used to source tapped water to a population of >400,000 inhabitants. Three sampling campaings were developed during different seasonal periods: winter 2008, autumm 2009 and spring-season 2009. For water quality evaluation samples were collected at water wells (n: 38) and surface waters (n: 9). Quali-Quantitative analysis were performed at the Laboratorio de Análisis Químicos (LANAQUI) of CERZOS-CONICET (UNS). Maps of isoconcentrations were produced with the concentrations values using the Surfer V.8 software. The statistical analysis for correlation analysis, linear regressions and frequency analysis was performed applying the InfoStat software with a design of repeated measures. The space and time Cd concentrations do not show differences and in 36% of the groundwater samples exceeded the guide value, showing a patch of a high risk for human consumption as drinking water at southwestern areas. High arsenic levels surpassed the guide values in 86% of the sampled groundwaters with the highest levels in the low landforms of the studied basin. Towards the river mouth, the surface waters yielded increased Cd levels exceeding the reference level in 37.5% of samples. At this position and during the same period, As had the highest concentrations. Unacceptable Cd concentrations had a significant correlation with high As levels, increasing the risk for human consumption as drinking water. The presence of As-Cd is related to natural sources and appears linked to the aeolian loess lithologies contacting surface and groundwaters in the sedimentary sequences.

Keywords : Hydric resources; Cadmiun; Arsenic; Human consumption.

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