Occurrence, sources, and risk assessment of unconventional polycyclic aromatic compounds in marine sediments from sandy beach intertidal zones

This study investigated the concentrations of polycyclic aromatic compounds (PACs), including parent polyaromatic hydrocarbons (PAHs) and their nitrated and oxygenated derivatives, in 48 sediment samples from the intertidal region of sandy beaches in Baía de Todos os Santos (BTS), Salvador, State of Bahia, Brazil. The total PAH (∑PAH) concentration, total nitro-PAH (∑nitro-PAH) concentration, and total oxy-PAH (∑oxy-PAH) concentration ranged from 2.11 μg g^-1 dry weight (dw) to 28.0 μg g^-1 dw, 2.58 μg g^-1 dw to 30.2 μg g^-1 dw, and 0.34 μg g^-1 dw to 3.65 μg g^-1 dw, respectively. Elevated concentrations of parent PAHs and nitro-PAHs were found in samples from two sites in BTS, which were also characterized by high percentages of fine-medium sand and low organic matter contents. Potent mutagenic 3-nitrobenzanthrone (3-NBA) was found in 86% of the samples at concentrations ranging from 0.200 μg g^-1 dw to 0.690 μg g^-1 dw. Furthermore, calculations of the benzo[a]pyrene toxicity equivalency (BaPTEQ) indicated that three carcinogenic high-molecular-weight PAHs accounted for 98.7% of the total maximum PAH concentration. Finally, we assessed the possible environmental risks posed to benthic species living in the sediments of BTS. The results showed that the risk quotient for PAHs (RQ_PAHs) was ≥1. In turn, the summed RQ for all PACs (∑RQ_mixture) ranged from 1 to 30, but did not exceed the maximum allowable threshold; thus, the risks posed to benthic species were moderate for all sediment samples.