Arsénico y Otros Oligoelementos en Los Recursos Hídricos de La Región Pampeana Sur (Argentina): Análisis de Los Acuíferos Freático y Termal Profundo en El Área de Bahía Blanca

BLANCO, MARÍA DEL CARMEN; ESPOSITO, MARTIN EDUARDO; PAOLONI, JUAN DARIO; SEQUEIRA, MARIO EDUARDO; NICOLLI, H. B.; AMIOTTI, NILDA MABEL

Mar del Plata

Congreso; Congreso Internacional de Ciencia y Tecnología Ambiental, y I Congreso Nacional de la Sociedad Argentina de Ciencia y Tecnología Ambiental - ARGENTINA AMBIENTAL 2012; 2012

The area of Bahía Blanca district, in the SW pampean region of Argentina, was recently affected by a hydric crisis owed to lower rainfall (2010: 581 mm, 2009: 213 mm, 2008: 544 mm, 2007: 697 mm, 2006: 575 mm) compared with the mean (664 mm) of 1971-2000 period. Water storage in Paso de Las Piedras dam was reduced to levels lower than usual (minimun: 154.1 m a. s. l, present: 156 m a.s.l). Emergency state is not finished, hence, population utilizes the phreatic and thermal aquiphers (700-800 m; 55.5 ºC-61.5 ºC) as alternative sources. This last is an artesian flowing level mostly utilized by population close to fluency points. Aiming to a comparison of water quality in both sources, As, F, B and V concentrations were determined. Maximun values of CAA (Código Alimentario Argentino) coinciding with guide values of WHO (World Health Organization) were considered: 10 µg L-1 for As and 1,500 µg L-1 for F.  For B 500 µg L-1 (CAA) was considered, which was recently modified to 2,400 µg L-1 (OMS, 2011). Actually, neither a guide value WHO (2011) nor maximun contaminant level (MCL, USEPA 2004) do exist. Phreatic waters have As, F, and B exceeding their respective guide values. As ranged 18-500 µg L-1 with the maximun levels detected in Gral. D. Cerri and Villa aeropuerto associated to F higher than guide values (range: 2,500-3,500 µg L-1). The most saline waters correspond to Los Chañares neighbourhood, which does not pose potable water. Solely a 3% of phreatic waters at the NE of Bahía Blanca district has B<300 µg L-1 increasing, even above the new WHO limit, towards the Atlantic coast (up to 5,300 µg L-1). Moreover, V concentrations between 50-500 µg L-1 (43% sampled waters), 500-1,000 µg L-1 (35%) and 1,000-2,450 µg L-1 (12%). The general trend showed increasing concentrations of the studied trace elements towards the atlantic litoral, although  with a patchy pattern having little coincidence betwen each on. The deep thermal waters had mostly aceptable concentrations of As, B and F for human consumption. Some wells at the WNW of Bahía Blanca city showed sodium chloride waters with high salinity and B concentrations between 300 and 600 µg L-1, moreover, V >50 µg L-1 was found in a 35% of  samples.