Pollution in a Lowland River System. A Case Study: the Reconquista River (Buenos Aires,Argentina)

The Reconquista river is a lowland watercourse; about three million people and several thousands of industries are settled in its flood plain. It can be considered as one of the most polluted rivers of Argentina. The present work is an attempt to describe the quality of the surface water through 16 physicochemical variables measured monthly in five sites (S₁to S₅) during 1994. Univariate and multivariate analyses of data showed a clear difference of S₁and S₂respect to S₄and S₅for ammonium, ortophosphate, pH, hardness, chloride, phenols, BOD, COD, and DO values. S₃appears to be a transition site. DO content showed a significant negative regression respect to the distance from the mouth. In the multivariate analyses between seasons the concentration of phenols appeared as an important feature. However it can be considered that seasonal variations were difficult to explain because of the river is the receptor of both regular and intermitent pollution pulses. It was concluded that the deterioration of this water body was progressive downriver, the contribution of the Moron creek in S₄determined a sharp adverse change in the physicochemical conditions. In the two downstream sampling stations (S₄and S₅) the values were far from natural conditions.