A SPACIAL ANALYSIS OF ORGANIC MATTER, OXIDES AND GRANULOMETRIC DISTRIBUTION ON SEDIMENTS AS A SUPPORT FOR GEOCHEMICAL ANALYSIS ON TRÊS MARIAS RESERVOIR – MINAS GERAIS

This research evaluates the granulometric, organic matter and oxides distribution on sediments of the Tres Marias lake. Thus, a sampling network was established based on the main input of sediment in the lake and on the morphology of the lake, totaling 40 samples. After collection, the material was dried at 40 ° C for 36 hours and then treated by dry sieving. The Fe and Al oxides content was determined by ICP-OES. The measurements using loss-on-ignition methods gave the organic matter content. The organic concentration was compared to the environmental guidelines established by CONAMA No. 354/2012. The concentrations was exceeded by seven samples. The sediment supply comming from Sao Francisco, Sao Vicente, Paraopeba, Extrema, Ribeirao do Boi, Borrachudo and Indaia rivers pointed to an overall predominance of the sand fraction along the margin sediments and high disparities between their granulometry. The higher aluminum concentrations are disposed at central-east zone of the Lake, concordantly with the higher organic matter ratios. The higher iron concentrations are mainly on Indaia River.