Spectroscopic techniques are powerful tools for molecular organic matter assessment in sediments, which analysis request low sample mass and are cheap, fast and easy to obtain. The aim of this work was to evaluate the elemental (C, N) and molecular composition of the organic matter in relation to the grain-size distribution over surface sediments from Sepetiba Bay. Spatial distribution of grain-size was remarkable heterogeneous, with the internal area presenting the highest levels of fine sediments, organic carbon (0.20-3.45%) and total nitrogen (<LQ-0.36%). Concentrations of organic carbon from surface sediments at the study area seem to be lower when compared to other degraded coastal systems. C/N ratio vary between 10 and 20, suggesting a mix of allochthonous and autochthonous sources of organic matter to the sediments. DRIFT spectra presented prominent and marked bands assigned to organic and mineral functional groups bonding and the spectra identified chemical bonds of molecular composition such as aliphatic and aromatic functional groups.
Keywords:
DRIFT; molecular composition; coastal zone
