SEDIMENTOLOGICAL AND GEOCHEMICAL VARIABILITY IN A TROPICAL ESTUARINE SYSTEM WITH STRONG ANTHROPIC INFLUENCE (CAPIBARIBE RIVER, PE).

Abstract

The study aims to analyses the sedimentological and geochemistry seasonal variability in the Capibaribe estuary, Pernambuco. The samples were collected in dry and rainy periods on 2010 and 2011, and submitted the grain size analyses, total organic matter and calcium carbonate quantifications, and carbon and nitrogen percentages and isotopic compositions. The sedimentological results varied for estuary from very fine silt to coarse silt with coarse silt predominance and for inner continental shelf from coarse silt to coarse sand with medium sand predominance. The organic matter and carbonate contents varied from 1.5 to 21.7% and 1.7 to 87.3%, respectively. The organic carbon, total nitrogen, C/N ratios and its isotopic ratios varied from 0.11 to 8.87%, 0.01 to 1.02%, 6.01 to 18.81, -25.90 to -20.85‰PDB and -1.14 to 7.66‰Air, respectively. The high rainfall indexes incremented the river flux increasing the hydrodynamic energy, consequently, intensified the erosion processes of margins and the transport of fine sediments and TOM to the continental shelf. During the dry periods the estuary showed a retention behavior of fine sediments and organic matter occasioned by decrease of hydrodynamic energy in estuarine system. The isotopic results demonstrated that the Capibaribe estuary showed sources different of TOM. The estuary registered environmental impact, from domestic wastes released in system, characterizing evidence of anthropogenic pollution (δ15N <2‰Ar).