Caracterização da matéria orgânica sedimentar antrópica em mangue tropical na costa do Nordeste: uma abordagem baseada em marcadores orgânicos geoquímicos e razões de diagnósticos

Abstract

The distribution, composition, sources and factors controlling the accumulation and distribution of alkanes, isoprenoids (pristane and phytane), petroleum biomarkers (hopans and steranes) and HPAs were investigated in the surface sediments of the Timonha-Ubatuba estuarine system, which Represents the second largest mangrove conservation area in Ceará and the first in Piauí. In surface sediments, the sum of the concentration of the C10-C38 n-alkane series ranged from approximately 754.38 ng.g-1 to 6026.95 ng.g-1; The sum of PAHs ranged from 23.41 (TIM 1) to 228.25 ng.g-1 (TIM 3). In turn, the sum of the biomarkers ranged from 28433.1 ng.g-1 to 392304.0 ng.g-1 with a prominence for C31-homohopane / 22S. For the characterization of the primary sources in the Timonha-Ubatuba estuarine system, several diagnostic reasons were used, such as LMW / HMW, ant / (ant + fen), BaA / (BaA + Cri), IP / (IP + BghiP) Fltr / Pir, % Per / 5 rings, IPC, nC17 / Pr, nC18 / Fit and Pr / Fit, TAR and Σn-alkanes / n-C16. According to the preferential carbon indices, the majority of the stations presented IPC> 1, which characterizes possible mixed or biogenic source, which was confirmed by the presence of Hopanos and Steranes in most stations. On the other hand, the analysis of PAHs returned primary pyrolytic sources that can be related to the burnings in the region, the use of firewood as a source of energy and vehicular emissions. The deposition of hydrocarbons had no correlation with grain size nor with organic carbon content or humic and fulvic acids.