PAH baselines for riverine surficial sediments from Amazonian Coastal Zone

The distribution, sources and ecological risk assessment of 16 polycyclic aromatic hydrocarbons (PAH) in surface sediments from 3 aquatic bodies (Guajará Bay, Guamá River and Amazon River Estuary) from the Amazonian coastal zone (Northern Brazil) (Figure 1) were determined. The aim of this study was to suggest baselines for PAH in the presented area. Baseline levels are considered an important tool in environmental management. PAH were identified and quantified by GC/MS. The total PAH concentration ranged from 18.6 to 46.9 ng g−1 dw (mean value 29.3 ng g−1 dw), which were generally low compared to other coastal zones in Brazil and around the world. The upper 95% confidence interval on the mean was 2.9 ng g-1 for total PAH. Naphthalene was the most representative PAH in sediment samples (38% of the total PAH concentration). The presence of this PAH in natural forests can be associated to a biogenic origin as termite nests because they product Naphthalene as a part of their defensive system. Termites are common in the studied area. PAH diagnostic ratios showed that pyrogenic PAH (mainly caused by grass, wood and coal combustion) from local emissions were predominant in the surface sediments. The ecological risk assessment indicated that non-negative effects in this area are expected. Based on all the results obtained with a multiple tools and statistical analysis done, the presented data can be assumed as baselines for PAH in the Amazonian Coastal Zone.