Ana Lúcia L. Dauner

Spatial and temporal distribution of aliphatic hydrocarbons and linear alkylbenzenes in the particulate phase from a subtropical estuary (Guaratuba Bay, SW Atlantic) under seasonal population fluctuation.

Guaratuba Bay, a subtropical estuary located in the SW Atlantic, is under variable anthropogenic pressure throughout the year. Samples of surficial suspended particulate matter (SPM) were collected at 22 sites during three different periods to evaluate the temporal and spatial variability of aliphatic hydrocarbons (AHs) and linear alkylbenzenes (LABs). These compounds were determined by gas chromatography with flame ionization detection (GC-FID) and mass spectrometry (GC/MS). The spatial distributions of both compound classes were similar and varied among the sampling campaigns. Generally, the highest concentrations were observed during the austral summer, highlighting the importance of the increased human influence during this season. The compound distributions were also affected by the natural geochemical processes of organic matter accumulation. AHs were associated with petroleum, derived from boat and vehicle traffic, and biogenic sources, related to mangrove forests and autochthonous production. The LAB composition evidenced preferential degradation processes during the austral summer.

Integrated assessment of contaminants and monitoring of an urbanized temperate harbor (Montevideo, Uruguay): a 12-year comparison

A cidade de Montevideu, com mais de 1,5 milhoes de habitantes, circunda a Baia de Montevideu, onde um dos portos mais ativos e poluidos da America do Sul esta localizado. No presente trabalho, foram avaliados esterois fecais, metais traco, compostos organoclorados e derivados de petroleo nos sedimentos superficiais do Porto de Montevideu, analisando sua distribuicao espacial no interior do porto, bem como em dois dos principais tributarios que chegam ao interior da baia. Especificamente para os sitios do porto, foi realizada uma comparacao temporal dos metais pesados e hidrocarbonetos, considerando dados preteritos de 12 anos. Foram observadas alteracoes significativas nos sitios estudados. Metais, tais como o Pb, Cr e Zn, apresentaram reducao nas suas concentracoes, enquanto os hidrocarbonetos alifaticos aumentaram seus valores em quase todas as estacoes. Foram observadas tambem diferencas entre o verao e o inverno, sugerindo mudancas no padrao de sedimentacao, nos ingressos de substâncias e/ou mudancas hidrodinâmicas na area. Os resultados podem vir auxiliar na compreensao do estado atual e para o desenvolvimento de medidas de gestao necessarias para melhorar a qualidade ambiental do porto e da baia.

Coupling spectroscopic and chromatographic techniques for evaluation of the depositional history of hydrocarbons in a subtropical estuary.

Spectroscopic and chromatographic techniques can be used together to evaluate hydrocarbon inputs to coastal environments such as the Paranaguá estuarine system (PES), located in the SW Atlantic, Brazil. Historical inputs of aliphatic hydrocarbons (AHs) and polycyclic aromatic hydrocarbons (PAHs) were analyzed using two sediment cores from the PES. The AHs were related to the presence of biogenic organic matter and degraded oil residues. The PAHs were associated with mixed sources. The highest hydrocarbon concentrations were related to oil spills, while relatively low levels could be attributed to the decrease in oil usage during the global oil crisis. The results of electron paramagnetic resonance were in agreement with the absolute AHs and PAHs concentrations measured by chromatographic techniques, while near-infrared spectroscopy results were consistent with unresolved complex mixture (UCM)/total n-alkanes ratios. These findings suggest that the use of a combination of techniques can increase the accuracy of assessment of contamination in sediments.

Sources and distribution of biomarkers in surficial sediments from a polar marine ecosystem (Potter Cove, King George Island, Antarctica)

Sedimentary organic matter (OM) represents the energy supply for the shelf benthos at the Antarctic Ocean, and has yet to be properly characterized in terms of sources and composition for the Potter Cove region, King George/25 de Mayo Island. This energy input occurs mainly during the brief summer and provides the majority of available energy for the year, in a region with high endemism and limited source variety of sedimentary OM. Thus, the aim of this study is to identify the OM origin and degradation degree based on the spatial distribution and type of organic biomarkers. Twelve surficial sediment samples were collected and analyzed for the presence of n-alkanols and sterols. The different spatial patterns between the analyzed compounds indicated distinct OM sources and degradation degrees. First, relatively fresh phytoplankton organic matter and an enhanced bacterial activity were associated with the occurrence of seaweeds detritus and represent the source of n-alkanols. Second, relatively fresh material mainly associated with seaweeds debris were identified as the source of macroalgae sterols. Our results shed some light into the base of the Potter Cove trophic benthic chain and increase our understanding on the region’s biogeochemical processes relating to OM recycling. It also provides a baseline for assessing future changes in the structure of the benthic food web in this environment, which is subject to noticeable glaciers retreat.

Depositional history of sedimentary sterols around Penguin Island, Antarctica

Abstract Lipid biomarkers are potential tools for identifying the sources, diagenesis and reactivity of organic matter (OM) in marine systems, including in Antarctica where the particular environmental characteristics have motivated several studies of organic markers. Sedimentary sterol distributions were determined in two sediment cores (PGI-1 and PGI-2) collected from the marine environment around Penguin Island, Antarctica, during the 2007–08 summer. The cores were sectioned at 1 cm intervals and the sterols were analysed using gas chromatography with flame ionization detection. The results indicate that the sterols were subjected to decades of degradation and transformation with depth in both cores. However, an expected progressive conversion of stenols to stanols (evaluated by 5α-stanols/Δ5-stenols ratio) within the deepest sediment layers was not clear, suggesting low degradation rates. In PGI-1, the deposition of large quantities of penguin guano affected the distribution of sterols and, consequently, primary production was favoured by the ornithogenic soil input. The results contribute to the understanding of the current processes associated with primary sources and transformation of OM in this important region of the Antarctic environment.