Aspectos limnológicos do Córrego São Pedro Juiz de Fora – Minas Gerais

Abstract

The São Pedro stream, located at Juiz de Fora – MG, makes part of the micro basin of Middle Paraibuna river, which is a basin of Paraiba do Sul river. Although the impact of the anthropic activities on its physical environment is clear - generated mainly by the discharge of domestic sewage - the data related to the chemical, physical and biological changes resulting from these activities are not available. Variable data such as water and air temperature, pH, dissolved oxygen, conductivity, nutrients and chlorofile concentration and bacteria counting are needed for the appraisal of these changes. This work aimed to achieve the limnologic characterization of the São Pedro stream - by means of these parameters – seeking to identify the temporal and spatial changes on its waters quality, quantify the planctonic and phytoplanctonic bacteria, so as to enable the understanding of the trophic relations and influence of the abiotic factors on the organisms abundance and arrangement. Therefore, eleven sampling collections were accomplished in five sites throughout the stream, starting on May’2005 and ending on April’2006. Low contens of OD, high concentration of chlorofile-a and pHs inferior to 6 proved that the stream could not be classified as Class 1 for the sites 1 and 2, neither Class 2 for the remaining sites, provided goals or forecast for future use of the stream are settled. As shown by the analysis of the samples collected for the present survey, the site 1 should be classified as Class 2, the sites 2 and 3 as Class 4, and the sites 4 and 5 as Class 3. Parallely, it was proposed an alternative methodology of analysis for nitrite and nitrate using the Capillary Electrophoresis - a segregation technique which offers the following advantages: short time of analysis (less than 3 minutes), small volume of sample needed for injection (less than 1 mL), method easiness, high rate of analysis (5 samples pper hour, including the recovery percentage) and dispensable pretreatment.