Avaliação da contaminação histórica por HPAs dos sedimentos da porção nordeste da baía de Guanabara

Abstract

The sediments of coastal regions encompass contributions from both natural and anthropogenic processes. Particularly in recent decades, these sediments have been receiving significant inputs of contaminants of anthropogenic origin. Guanabara bay is located on the coast of the state of Rio de Janeiro and is a well-known highly polluted environment, yet it possesses great biodiversity and provides many resources to the traditional communities that inhabit its shores. The bay has been subjected to various anthropogenic impacts for many years, and despite this, it remains essential for the maintenance of its associated ecosystems and for the daily lives of millions of residents. The study of contamination in the northeastern portion of Guanabara bay was conducted through geochemical analyses of sediment cores up to 1 meter in length. The core was dated using 210Pb determination by gamma spectrometry. The application of the CRS model resulted in an average sedimentation rate of 0.17 cm/year, indicating an increase between the 1960s and 70s. In the laboratory, determinations were made for fine content, total organic carbon (TOC), total nitrogen (TN), and polycyclic aromatic hydrocarbons (PAHs). The fine content showed a median value of 98.30%, TOC values ranged from 1.79 to 4.74%, and TN values ranged from 0.14 to 0.64%. The C/N ratio exhibited high variability throughout the core, oscillating between 6.12 and 19.45, indicating alternations in the composition of organic matter from both terrestrial and marine origins. The sum of the 16 priority PAHs by USEPA ranged from 12.40 to 3952.05 ng g-1. Total PAH concentrations, covering 38 compounds including 6 alkylated series, ranged from 23.36 to 5863.75 ng g -1, classified from low to very high contamination; however, when compared to other regions of the bay, the region in focus is considered the most preserved, being less contaminated. The highest PAH concentrations were found between the 26 to 28 cm depth layers, corresponding to the years 1933-1928. It is believed that the main influence for the observed peak is linked to wood burning activities in the old brickworks, which were highly concentrated in the northeastern region around the bay during the peak period. Analyzing the diagnostic ratios of PAHs, there is a predominance of contributions from pyrogenic sources and biomass combustion. Once a marine environment contamination study is conducted, it generates tools for the research line of Environmental Marine Biotechnology, since this field aims to prevent, deter, and reverse marine environmental degradation.