Cláudia Hamacher

Hydrocarbons in sediments of a chronically contaminated bay: the challenge of source assignment.

Aliphatic hydrocarbons and 39 PAH (parental and alkylated homologs) determined in ca. 100 sediment samples from the Guanabara Bay, Rio de Janeiro, were evaluated for source discrimination using new approaches. Concentrations of total PAH were in the range of 96-135,000 μg kg(-1) similar to other coastal urbanized embayment. Traditional diagnostic ratios were not as efficient PAH source indicators, e.g. biomass combustion was assigned as the major source of the pyrolytic PAH although the hydrographic basin is highly industrialized and urbanized. It is proved petrogenic imprint cannot be detected if only the 16 USEPA PAH are determined. The high production in the eutrophic system is not apparent in the aliphatic fraction dominated by land derived n-alkanes due to the effectiveness of microbial degradation. The present work demonstrates the complexity of hydrocarbon forensics when applied to chronically contaminated environments.

Trace metal contamination in mangrove sediments, Guanabara Bay, Rio de Janeiro, Brazil

The Guanabara Bay in Rio de Janeiro has undergone profound alterations of its natural environmental conditions. Metal concentration increase in sediments has been reported to be among these alterations. Trace-metal contamination and availability were studied in sediments of 3 mangrove areas of the bay. Cd, Zn, Pb, Ni, Cu and Al concentrations were determined in segments of sediment cores, after treatment with 1 mol L-1 HCl and with concentrated HNO3. Fe and Mn were determined in the leach with HNO3. Concentrations were low in comparison to those reported for Guanabara Bay and Cd showed up to 90% recovery in the HCl extract. Sediments found to be oxic to suboxic showed AVS concentrations in range of 0.07 (bottom) to 18.79 mmol g-1(sub-surface) indicating heterogeneity and apparent disequilibrium. Fe and Mn oxides, carbonates and organic matter may be the most important phases controlling metal availability and distribution.

Is Copper an Inhibiting Factor for Primary Production in the Upwelling Waters of Cabo Frio

The goal of the present work was to test the hypothesis that inorganic species of copper may inhibit primary production in upwelling waters from the Cabo Frio region. Water samples were collected from four different depths up to 50 m at three stations of Cabo Frio and nutrient concentration, pH, dissolved oxygen, alkalinity, seston, chlorophyll a, primary production, NPP, copper speciation, Cu(II) and Cu(I) and complexing capacity were determined. The results indicate that the rate of photosynthesis in nutrient rich waters with higher copper content and lower complexing capacity is significantly reduced. Cu(I) made up 2-15% of the total copper, however, there was no evidence to suggest that the photochemical production of Cu(I) affects NPP.

Hydrocarbon composition and distribution in a coastal region under influence of oil production in northeast Brazil

Waters and sediments from the Potiguar Basin (NE Brazilian coast) were investigated for the presence and nature of polycyclic aromatic hydrocarbons (PAH) and aliphatic hydrocarbons. The region receives treated produced waters through a submarine outfall system serving the industrial district. The total dispersed/dissolved concentrations in the water column ranged from 10-50 ng L(-1) for ∑16PAH and 5-10 μg L(-1) for total aliphatic hydrocarbons. In the sediments, hydrocarbon concentrations were low (0.5-10 ng g(-1)for ∑16PAH and 0.01-5.0 μg g(-1) for total aliphatic hydrocarbons) and were consistent with the low organic carbon content of the local sandy sediments. These data indicate little and/or absence of anthropogenic influence on hydrocarbon distribution in water and sediment. Therefore, the measured values may be taken as background values for the region and can be used as future reference following new developments of the petroleum industry in the Potiguar Basin.

Evaluation of a commercially available ELISA kit as a tool to determine BTEX in groundwater

Abstract The reliability of enzyme‐linked immunosorbent assay (ELISA) tests as a screening technique to address groundwater contamination was tested in an area following leakage of gasoline from a petrol station. Immunoassay data of benzene, toluene, ethylbenzene, and o‐, m‐ and p‐xylene (BTEX) were compared with results obtained using capillary gas chromatographic analysis. Detection limits were of 20 μg l−1 for ELISA and 0.3 (μg l−1 for gas chromatography with flame ionization and photoionization detectors (GC‐FID/PID) determination. Despite an observed overestimation of BTEX concentrations as given by ELISA, the tests responded reliably to different levels of contamination.

Historical evolution of organic matter accumulation in a coastal bay in the SW Atlantic, Brazil: use of sterols and n-alcohols as molecular markers

The deposition processes and preservation of organic matter (OM) in the sediments of Ilha Grande Bay, SW Atlantic, were evaluated based on elemental composition (C and N) and molecular markers (sterols and n-alcohols). Samples from four dated sediment cores, representing distinct levels and type of human influence, were analyzed. The concentration of total sterols ranged from 71 to 9,320 ng g-1, with 24-ethyl-cholesta-5,22-dien-3β-ol, 24-ethyl-cholesta-5-en-3β-ol and 24-ethyl-5a-cholesta-3β-ol as the most abundant compounds. The n-alcohols, with a total concentration between 130 and 15,407 ng g-1, were dominated by long-chain compounds (> C22). Assignments of the selected markers to terrestrial or marine sources were evaluated using principal component analysis (PCA). The trends and events that influenced the OM accumulation in the last decades were also revealed by the PCA, as the increasing human settlement in the region and the removal of a mangrove forest occurred between 1940 and 1960. The absence or low level of sewage contamination was indicated by the sterol coprostanol and associated indexes.