Avaliação do uso da Baía de Camamu, Bahia, como área de referência para ambientes tropicais

Abstract

References sites are areas that have undergone little or no anthropogenic impact and therefore represent the natural state of an environment. These sites are generally used as controls to assess, in a comparative way, the extent of contamination and/or remediation of impacted areas. The objective of this study was to test if the Camamu Bay, Bahia, can be used as a reference area for tropical coastal environments. Sediment cores and surface sediment samples were collected in the bay. Trace and major elements, polycyclic aromatic hydrocarbons (PAH), grain size and organic matter were determined. The trace elements and the fine fraction of the sediment (silt + clay) showed similar distribution patterns. To compare the studied sites and identify the possible occurrence of anomalous concentrations, trace elements were normalized by Al and linear regressions were also performed. For all trace elements (except Cu), the regressions showed significant correlation (p < 0.005) and few outliers (<3% of cases), showing that the concentrations found represent natural values for this bay. In the case of Cu, the highest concentrations were found near urban centers, which may be associated with domestic sewage. Copper concentrations, nevertheless, were lower than TEL values, which represents the level of concentration that is rarely expected to cause adverse effects in biota. The concentrations of trace elements in sediments cores showed small variation, indicating no significant temporal changes. About 60% of the organic compounds measured occurred at levels below the limit of quantitation (<0.26 ng g-1 ). The sum of PAHs was low for all stations, ranging from 1.17 to 313 ng g-1 . All concentrations of PAHs were below the individual values recommended by TEL. The concentrations of trace elements, organic matter and PAHs showed that Camamu Bay can be used as a reference area for tropical environments.