Avaliação dos efeitos de atividades antrópicas por meio da análise integrada de variáveis de uso da terra e limnológicas em Itaqui, RS

Abstract

This research aims to analyze the relationships between land use and limnological variables in urban and rural watersheds around the city of Itaqui, Rio Grande do Sul, Brazil, looking for the causes of water contamination. For this goal, it was built a database associated with a Geographic Information System (GIS) using satellite images and limnological data collected in the field from September to November of 2011. The study area was divided into 12 watersheds corresponding to the water collection points, using radar images from the SRTM mission and Spring 5.1.5 software. Subsequently, classes of land use were investigated by Landsat 5 and CBERS 2B images processing, and maps were produced. Limnological data was integrated as a geo-relational data bank, connecting the sample points with results data sheets. The statistical inference methods used were based in Pearson and Spearman correlations among the land use and limnological variables. The laboratory analysis and sampling procedures followed the recommendations of the Standard Methods for the Examination of Water and Wastewater. The results showed effects of pollution coming from urban areas and cattle fields, that showed significant positive correlations with mesophiles, total coliforms, chloride, sodium and electrical conductivity values. On the other hand, negative correlations occurred between limnological variables and areas of vegetation, forest and crops. This facts point to the city sewage and the livestock farming as the main sources of water contamination.