Avaliação das condições da qualidade da água em tempo seco e durante eventos de chuvas em uma microbacia urbanizada no município de Belo Horizonte

Abstract

This research aims to characterize water quality and pollution loads in a micro-urban basin (Brejo do Quaresma stream), located in the city of Belo Horizonte and tributary of of the das Velhas river basin, one of the most important tributaries of the São Francisco river, and associate this water quality with soil uses and occupations. The monitoring of the quality and quantity of water was conducted between May 2007 and May 2008 with samples in dry weather (collections taken during the day 24 hours) and rainy events (collections taken in periods of 2 to 4 hours). The terms of water quality expressed by physic-chemical, chemical and microbiological parameters adopted for the dry period presented a behavior dictated by the domestic sewage that the stream has been receiving. During the rainy events, the concentrations were diluted, except for the suspended solids, turbidity and nitrate. The statistical tests used for the analysis of variance between the results of dry and rainy eventshad a significant variability for most of the parameters tracked, except for heavy metals and coliform. The phenomenon of the wash load during the rainy events was observed for the parameters of DBO5, COD, SS, Cu, Ni and Zn quality. Annual high loads of macronutrients were also observed (C, N, P) in dry weather, due to the sewage that the stream receives, andto high loads of SS carried by the stream during the rainy events, related to erosive processes in the channel and also to the municipal solid waste dumped into it. Therefore, the conditions of quality of the water body are highly impacted, and thus unable to comply with thepreponderant uses, due to contamination by non-point-source and point-source pollution