ESTUDO DE INDICADORES DA CONTAMINAÇÃO DO RIO MELCHIOR, DISTRITO FEDERAL, PELA OCUPAÇÃO DA BACIA POR USO URBANO

The Melchior River is the main tributary of the Descoberto River and has recurrent contamination and alteration problems with few studies aiming at geochemical indicators of contamination. It can be considered strongly affected by activities related to urbanization, since there are no industries, mining or other potentially polluting activities in this region. The general objective of this study is to identify the indicators of contamination by urban occupation in the basin. The adopted procedures include: sampling of water and sediment; measurements of electrical conductivity, temperature, pH and total dissolved solids in the water; determination of chemical elements (major and trace) using the analytical techniques Optical Emission Spectrometry with Plasma (ICP/OES), Atomic Absorption Spectrometry (AAS) and ion chromatography; statistical treatment of the data by means of Geoaccumulation Index and Enrichment Factors. The results indicate that the environmental quality of water and sediments of Melchior River is altered due to anthropic activities developed in the basin. Analysis of water samples highlighted the parameters electrical conductivity, calcium, sodium, phosphorus, ammonia, nitrate, chloride, sulfate and bicarbonate as indicators of water quality alterations. Analyses using geoaccumulation indices pointed to the parameters phosphorus, calcium, copper, zinc, titanium, strontium, sodium and vanadium as indicators of contamination in sediments. Analyses by enrichment factors demonstrated that the parameters phosphorus, copper, zinc, calcium, sodium, manganese, nickel, strontium and zinc can indicate altered environmental quality of sediments in the basin.