Estudo da presença de hidrocarbonetos alifáticos em sedimento de fundo do reservatório da Hidrelétrica de Balbina

Abstract

The reservoir of the Balbina hydroelectric, whose influential Uatumã river is, flooded about 240 thousand hectares of rain forest. In the flooded area were extensive areas of natural forest wetlands have provided organic matter to the water body contributing acidity of water and formation of the bottom sediment. The characterization of the sediment is important in the study of the changes that human activities have on the natural environment. Aliphatic hydrocarbons are among the compounds, which form sediment and are indicators of natural and anthropogenic environmental events. Therefore, the determination of the individual alkanes and are important diagnostic index in identifying sources of material deposited in the pellet. This study was conducted water sampling and sediment - Balbina hydroelectric reservoir in seven collection points properly distributed, the first collection was in September 2010 and the following months of January, April and July 2012. Measures dissolved oxygen (OD), suspended solids (SS) , dissolved organic carbon (DOC) , turbidity , color, transparency, pH, temperature and conductivity of the water reservoir were studied presenting own behavior environment rich in organic matter deposited . Particle size analysis shows the percentage of fine sediment fraction shows around 77 %. Aliphatic hydrocarbons are extracted from the pellet with organic solvents in ultrasonic bath fractionated micro glass column filled with silica gel, activated copper and eluted with 10 mL hexane, and subjected to gas chromatographic analysis. The resulting chromatograms show a predominance of odd carbon over the pairs with high carbon concentration of higher molecular weight, specifically C27, C29, C31 and C33 with no unresolved complex mixture (MCNR) alkanes, showing biogenic contribution to environmental records burning where C27 is abundant compound. The concentration of total n- alkanes shows up near the amounts recorded in environments where biogenic contribution is significant and well below the values recorded in petroleum -contaminated environment. The values of terrestrial and aquatic ratio (RTA) were greater than one, meaning predominance of terrigenous sources on aquatic sources and preferred carbon content (IPC) ranged from 1.2 to 30 contribution and records indicating biogenic burning