Impact of the Morón stream on water quality of the Reconquista River (Buenos Aires, Argentina).

DE CABO L,; ARREGHINI S,; IORIO A,; RENDINA A,; BARGIELA M,; VELLA R,; BONETTO, C.

Revista Del Museo Argentino de Ciencias Naturales

Lugar: Buenos Aires; Año: 2000 vol. 2 p. 123 - 130

1514-5158

   The Reconquista River basin is located in an urban area where 2.5 106 inhabitants and 4,242 industries are settled. The confluence with the Morón stream shows  the largest anthropogenic impact. The effect of the Morón stream on the water quality of the Reconquista River was evaluated in relation to its organic, mineral and metal contribution. Bimonthly samplings were carried out  in the Reconquista river up (GOR), and downstream (SMT) the confluence with the Morón stream and in the later (MOR). Dissolved oxygen, pH, conductivity, temperature, transparency, nutrients, major ions, suspended solids, particulate and total organic carbon, nitrogen Kjeldahl, total phosphorus and heavy metals were determined in water samples. Discharge ratios between the Reconquista and Moron streams were estimated based on chloride concentrations. The samplings were ordered from the Principal Components Analysis in: GOR, SMT and MOR according to a growing gradient of organic and mineral contamination. This gradient has a spatial component (related to the discharge point of the Morón stream) and one related with the Reconquista river’s flow. Mean levels of metals were higher than the thresholds for the aquatic life protection. The most important were: lead, zinc, copper and mainly chromium, being all of them related to the industrial activity. Their concentrations responded to an irregular and intermittent discharge. Sometimes, metals levels in SMT and GOR were higher than in MOR, indicating other sources of contamination besides the Morón stream.