Estudo da qualidade da água na represa Dr. João Penido: metais, agrotóxicos, índices de qualidade da água e de estado trófico (Juiz de Fora, MG)

Abstract

Dr. João Penido Reservoir is the main human supply source of Juiz de Fora (MG). The aquatic ecosystem has suffered from the bad use and occupation of the lands of their watershed. The abundance of macrophytes at various points of the water surface and in the tributaries regions indicates eutrophication processes. The objectives of this study were to calculate the Water Quality Index (WQI) and Trophic State Index (TSI), to investigate the presence of metals and agrotoxics in five sampling points in the dam. 4 samples were collected to characterize the dry period and 4 for rainy, between 2011 and 2013. The physical-chemical and microbiological parameters analyzed were: temperature, pH, dissolved oxygen (DO), total phosphorus (TP), nitrate ( NO3-), nitrite (NO2-), ammonium (NH4 +), total nitrogen (TN), total solids (TS), biochemical oxygen demand (BOD), color, turbidity, conductivity, chlorophyll a, total coliforms and thermotolerant coliforms; the metals investigated in the total and dissolved forms were: Cu, Cr, Cd, Pb, Ni, Zn, Mn, Fe, Na, K and Ca; agrotoxics were those defined in Ordinances MS / GM 518/2004 and MS / GM 2914/2011 of the Ministry of Health. There was a predominance of the TSI "Mesotrophic" throughout the observed period and WQI "Good" in the dry season and "Medium" in rainy. The presence of metals in water is low, with the exception of dissolved Fe that had disagreement with CONAMA Resolution 357/2005 (BRAZIL, 2005) in 27.5% of a total of 40 of the samples. The total Zn has extrapolated the legal limits in just a sample of the P2 point. There was no presence of agrotoxics in the reservoir, despite the existing growing areas in the region. It is expected that the studies presented here may contribute to the implementation of the National Water Resources, enabling integrated management of the reservoir basin, to ensure the quantity and quality water offered to the population.