*3.2.1.3 ALS*

The analysis conducted in a sediment core into ALS did not show a tendency to increase over time, possibly due to the source types of those compounds. The average sum of the 16 PAHs analyzed in the four strata was 1.84 ± 0.54 μg g<sup>−</sup><sup>1</sup> , which indicates a downtrend from the year 1929 to 1971 (with values from 1.5 to 1.3 μg g<sup>−</sup><sup>1</sup> ), and a slight increase near the superficial stratum corresponding to the year 1998 (about 2.0 μg g<sup>−</sup><sup>1</sup> ). These values are far below the ERL index of 4.02 μg g<sup>−</sup><sup>1</sup> . The compound with the highest value in all core strata was chrysene, except for the stratum from 26 to 36 cm, where it was below the detection limit; the highest concentration in this stratum corresponded to benzo[α]anthracene with 0.591 μg g<sup>−</sup><sup>1</sup> , benzo[κ]fluoranthene and indeno[1,2,3,c,d]pyrene compounds were not detected by the analytical method employed for their determination [41]; only the latter showed a concentration of 0.0427 μg g<sup>−</sup><sup>1</sup> in the deepest stratum corresponding to the year 1929. This study showed that compounds with four aromatic rings were predominant in all core strata (**Figure 2**), which suggests that they were byproducts of pyrolytic processes near the study zone, such as high-temperature combustion of organic matter and fossil fuels. The sum of the four-ring PAHs presented practically the same collective tendency as the sum of the 16 quantified PAHs. This indicates that the contribution to the entire historical profile of both

**Figure 2.** *ALS core concentrations of PAHs (μg g<sup>−</sup><sup>1</sup> ) based on number of aromatic rings.*

**Figure 3.** *Individual PAHs and ERL sedimentary quality criteria in the sedimentary core of TLS.*

five and six-ring PAHs, as well as two and three-ring ones (which originate from petrogenic sources associated to drilling activities, such as oil extraction and oil spills), was minor (**Figure 2**).

Most of the PAHs in the sediments proceed from pyrolytic sources, while the sources of compounds consisting of two and three rings are of petrogenic origin. The total PAHs sum was mostly contributed to by compounds consisting of four benzene rings, namely chrysene. Despite slightly higher than ERL index concentrations for anthracene, acenaphthylene, fluorene and dibenzo[α,h]anthracene, the total PAH sum did not exceed that limit. It has to be pointed that human activities are very intense in the lagoon as fisheries, shipping port, storage of petroleum and agriculture.
