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Title: Composição e distribuição espacial da matéria orgânica sedimentar nos estuários do Rio Paraíba do Sul, Rio das Ostras e Rio São João, RJ
Other Titles: Composition and spatial distribution of sedimentary organic matter in the estuary of the Paraíba do Sul River, das Ostras River and São João River
Keywords: Estuários;  Marcadores;  Isótopos;  Biopolímeros;  Esteróis;  N-alcanos;  Estuaries;  Markers;  Isotopes;  Biopolymers;  Sterols;  N-alkanes
Issue Date: 18-Mar-2013
Abstract: Fluvial transport of OM to the sea consists of an important link between global cycles of bioactive elements. The main goal of this work is to understand the spatial dynamics of organic matter (OM) in estuaries of mesoscale - Paraíba do Sul River (RPS) and small scale São João River (RSJ) and Das Ostras River (RDO), through identification of sources, transport and biogeochemical processes that occur in organic materials located at the interface continent seas. The source`s composition of terrigenous OM was similar to reported in the literature, demonstrating that there is great variation between different local vegetation. The hydrogeochemical confirmed the RPS as exporter environment, featuring on outer estuary salinity values of 11.5. The material biogenic> 20μm presents predominance of plankton (δ13C -21 e δ15N 12) and terrestrial OM more processed (δ13C -27 e δ15N 10), while the> 64μm showed a predominance of recent terrestrial OM (δ13C -27, δ15N 6). The analysis revealed a large sedimentary deposit of terrigenous OM in the external estuary with contribution planktonic and bacterial activity, at the same time, indicated the presence of OM soil and C3 plants in all their extension evidenced by the C/N ratio (average 16), major sterol typically found in higher plants (-sitosterol, -sitostanol, stigmasterol and campesterol) and n-alkanes odd long chain (C29, C31). The biopolymer composition and concentrations/ratiosof coprostanol showed eutrophic stations and sewage contaminated in almost all portions of estuary. High concentrations of total aliphatic hydrocarbons (HTA) were found in the RPS, ranging from 6.46 to 392.39 μg.g-1, this values have high correlation with organic carbon (OC) and low values of compounds unresolved (UCM), suggesting biogenic origin. Only the sediment of a pier has been indicated oil contamination, due to the large concentration of HTA not correlated with OC. Analysis of the estuarine sediment smallscale (RSJ and RDO) demonstrated that the accumulation of OC is greater as smaller the size of the drainage basin and river flow, and OC concentrations of RDO (3.19%)> RSJ ( 1.7%)> RPS (1.4%). Similarlyhowoccurred in the RPS, RSJ and RDO, the OM was mainly composed of soil and plants C3 respectively, with planktonic contribution only in the portion nearest the estuary to the sea. However, the largest accumulation of organic matter, and bacterial activity stations eutrophic estuaries in small scale was present in the fluvial portion of estuary and not external as occurred with the RPS. At the das Ostras River all portions were contaminated by sewage and only one station was nominated with contamination by petroleum products, while in the São João River just the fluvial portion was contaminated by sewage.
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