Water pollution in an urban Argentine river

Abstract

Discharges derived from industries, crude sewage, municipal wastes and petroleum have been the most common and important source of pollution to the main rivers of the Province of Buenos Aires, Argentina. During the last decade, several investigations have been carried out to determine the effects of pollution upon the biotic communities of the rivers located in this region. The present paper describes the density variations of the main groups of phyto- and zooplankton in relation to several environmental variables, including heavy metals, throughout the main channel of the river. The effects of complex chemical mixtures present in the water were assessed through genotoxic activity and algal assays. Phytoplankton (mean: 25,000 ind. mL-1) and zooplankton (mean: 534 ind. L-1) densities were high, exceeding by approximately an order of magnitude the mean records from Reconquista River. Cyanophyceae (38%), Chlorophyceae (33%), Bacillariophyceae (23%) and Euglenophyceae (10%) were the dominant algal classes. Rotifers were widely dominant among zooplankton groups (99%). Algal bioassays showed that the inhibition of growth was correlated with nickel. This river has been and still undergoes recovery plans that focus the treatment mainly on the cleaning of its river bed. The results obtained suggest that a definitive recovery of the river should not only rely on river bed cleaning and a decrease in the input of crude effluents, but also on the care and recovery of the river banks and surrounding lands.