Sedimentary and Geochemical Aspects of a Refinery Impacted Coastal Area: A Case Study of the Todos os Santos Bay (Bahia, Brazil)

Abstract

The present study was performed in the northeast portion of the Todosos Santos Bay, Bahia State, Brazil, an area under influence of the Landulpho Alves-Mataripe (RLAM) refinery effluents. The aim of this work is to evaluate the modern sedimentary processes based on grain-size analysis, calcium carbonate and sedimentary organic matter concentration and behavior considering the possible effects of the petroleum industry’s refining on these sediments. The concentrations and variations of the three main constituents of organic matter (total organic C, total N and organic P), and the resulting elemental ratios (C/N, C/P and N/P), were studied on a seasonal spatial and temporal scale (winter 2004 and summer 2005), therefore subsidizing the environmental analysis, especially in regards to the benthic ecosystem. Fifty samples from twenty-five sampling stations were collected with a grab sampler. Well sorted sandy sediments are observed in coastal sampling stations and in the Caboto channel. The recent deposition of fine sediments was observed especially in the west and central portions of study area. However, these spots contain the highest percentages of organic material, which do not present significant seasonal and spatial variations, revealed by the values of total organic C which reach values of up to 3.1%, total N (0.01% to 0.15%) and the organic P contents that reach a maximum of 15.9 μmol·g -1 . In general, the elemental ratios indicated continental organic matter inputs, probably derived from human activities.