Water Resources in the Salado River Drainage Basin, Buenos Aires, Argentina: Chemical and Microbiological Characteristics

Abstract

Buenos Aires Province is located in the region of greatest agrarian importance in Argentina. Studies that have been carried out up to now are mainly hydrogeological, geological, and limnological and focused on localized specific problems. The aim of this article is to determine the chemical composition, including trace elements and the microbiological characteristics, of surface and shallow ground waters at a regional scale as a basis that may allow the relation of the dynamics of the natural systems with that of the economically productive systems. Groundwater and surface water were sampled in stations located with a global positioning system (GPS). Chemical and microbiological analyses were carried out using reference analytical methods. A representative group of samples was also analyzed with ICP-MS techniques for the determination of trace elements. Shallow groundwater is alkaline to strongly alkaline. The high sodium content is due to a cationic exchange process taking place in the clays of pampean loess. Surface waters, strongly alkaline and of sodium-chloride or sodium-sulfate type, come in part from the discharge of groundwater. The concentration of trace elements in shallow groundwater, does not respond strictly to the conditions of regional flow. Rather, their distribution is related to the morphology and distribution of several types of soils in the region. The microbiological analysis showed that in surface waters the number of total heterotrophic bacteria is within the usual ranges, fluctuating between 1 x 103 and 1 x 105 CFU/ml. The values of total coliforms and thermotolerant coliforms are in accordance with international established parameters for recreational waters.