UM ESTUDO DE IMPACTO AMBIENTAL UTILIZANDO ANÁLISES ESTATÍSTICAS ESPACIAL E MULTIVARIADA

Abstract

Evaluation of the impact caused by an effluent in a river is needed to understand the changes caused in the environmental factors that control the dynamics of the aquatic ecosystems. Pollutant agents control is punctual and made just in the entrances of the effluent, close to the receiving bodies, and the plume isn't considered. However, to monitoring this impact, is necessary to know its space distribution. The purpose of this study was to verify the impact of the emission of an effluent in Paraíba do Sul River, near Pindamonhangaba, São Paulo State/Brazil, applying trend surface analysis and principal component analysis. The focused variables were: plankton genera, pH, temperature, dissolved oxygen, water transparency, color and water turbidity. Trend surface analysis helped understand the origin of the movements of the effluent plume on the receiving river that could be used as base for a possible monitoring. Residual values from the first-degree polynomial surface showed local differences between the margins and the middle of the river and the control of the effluent in number of the plankton genera. The Principal Component Analysis indicated the most important variables like: DBO, OD, transparency of the water, color and number of plankton genera. The two main components are: the first, and more important, denominated abiotic, controlled by physical-chemical factors and a second, biological, controlled by plankton genera. The plotted scores in space surfaces showed the impact of the effluent with relationship to the studied variables and the reclamation in the river water at the end of the sampling grid.