Hidrocarbonetos alifáticos e policíclicos aromáticos totais em sedimentos da Baía de Sepetiba/RJ

Abstract

The Sepetiba Bay, region of intense social-economic and environmental importance, located in the main geo-economic pool of the country, has been considered a catalyst area of the national development and one of the industrial and turistic poles of the State of Rio de Janeiro. The hydrocarbons, organic compounds ubiquitous in modern marine sediment were studied in this dissertation with the objective of verifying the origin, the levels and their distribution in this important bay. Therefore, 26 samples of superficial sediment were collected in sites of intense maritime traffic, near marinas and ports, urban centers, mangrove areas and river mouths. The collected samples of sediment were divided in two aliquot, one for complimentary analysis (CHN and grain size) the other for analysis of both aliphatic hydrocarbons and total PAHs. Before the extraction in soxhlet, recuperation standards n-C16, n-C24 and n-C30 were added. The samples were fractionated in a glass column filled with silica and alumina, as well as sodium sulfate and copper. The samples were eluties with hexane for the fractioning of fraction f1 (aliphatic hydrocarbons) and with a solution of dichloromethane and hexane for the elution of the second fraction (f2 – PAHs). The samples were then concentrated in vacuum rotational evaporator and reduced under nitrogen flow. For the determination of the aliphatic hydrocarbons a GC-FID was used and for the Total PAHs a spectrofluorescence. The results obtained showed that the Sepetiba Bay receives input both from petroleum hydrocarbons and biogenic hydrocarbons, characterizing a mixture of sources. Through the of the PAHs and UCM, it becomes noticeable that the Sepetiba Bay is contaminated by petroleum compounds, displaying areas of greater and lesser impact. The areas near the Port of Sepetiba and the mouths of the rivers Guandu and São Francisco, mainly, are the regions more affected by these compounds, reflecting anthropic activities developed in its around . The region of the Canal de Itacuruça and of the Saco da Coroa Grande, in spite of their display of compounds indicative of petroleum pollution, were dominated by biogenic hydrocarbons from vascular terrestrial plants, observed mainly in the distribution of the individual n-alkanes and CPI values.