Buried and surface oil degradation - Evaluating bioremediation to increase PAHs removal through linear mathematical models.

A bioremediation approach with tide simulation for buried and surface oil degradation was tested for removal of two, three and four rings polycyclic aromatic hydrocarbons (PAHs). Linear models depicted degradation constants of individual PAH as simple additive function of their initial concentrations (C) in contaminated sand, hydrophobicity, sampling layer and treatment conditions. For all PAHs and treatment conditions, the degradation of oil in buried layers was faster than at the surface.

Assessing and predicting the changes for inorganic mercury and methylmercury concentrations in surface waters of a tidal estuary (Adour Estuary, SW France).

Total and dissolved concentrations of inorganic mercury (IHg) and methylmercury (MeHg) in water (Adour Estuary) were determined during three sampling campaigns and related to biogeochemical variables (nutrients, organic matter). Factors (sampling time, sample type) were included in analysis of covariance with effect separation. The urban estuary suffered historically from anthropogenic sources, however, decreased emissions have reduced Hg concentrations.

Modeling the relationship between emerging and persistent organic contaminants in water, sediment and oysters from a temperate lagoon.

The concentrations of emerging and persistent organic contaminants (EPOC) in oysters (C) from Aveiro Lagoon are represented as a function of their concentrations in water (C) and sediment (C) using linear and generalized additive models (LM, GAM). Additionally, four sampling seasons, octanol/water partition coefficients (K) and type of EPOC (pyrethroids, flame-retardants, musks, UV filters, polycyclic aromatic hydrocarbons, others) are included in the models. The probabilities of detection of EPOC in water, sediment and oysters are analyzed by GAM.

Multiple regression analysis to assess the contamination with metals and metalloids in surface sediments (Aveiro Lagoon, Portugal).

An innovative multiple regression analysis was used to evaluate metal/metalloid contamination in the surface sediments of a coastal lagoon. The concentrations of metals/metalloids were represented as a function of geochemical characteristics of the sediments (fine fraction, concentrations of organic carbon, Ca, Al, Mn) and distances between sampling points. The effect of distances on the concentrations were negligible for Li, Co, Ni, Ba, V, Cr, and only geochemical variables specific for each element explained its spatial variation.

Modeling phaeopigment concentrations in water from a shallow mesotrophic lagoon.

Concentrations of phaeopigments (Pha) and chlorophyll a (Chl) were determined in surface waters from a temperate lagoon during six sampling campaigns at high and at low tide. In order to develop models for phaeopigment concentration in water, it was necessary to replace Chl with photosynthetic pigment concentration (P  = Pha+Chl) as one of the explanatory variables. Under first approximation, food availability and water temperature (T) could be considered as independent variables.

Multiple regression analysis to assess the spatial distribution and speciation of mercury in surface sediments of a contaminated lagoon.

The concentrations of inorganic mercury (IHg) and methylmercury (MeHg) in surface sediments from the contaminated Aveiro Lagoon (Portugal) were determined by species-specific isotope dilution analysis. Different behaviour of IHg and MeHg was observed based upon multiple regression analysis, including geochemical characteristics of the surface sediments (fine fraction, concentrations of organic matter and metals) and non-Euclidean distances between sampling points. This data treatment method was valid over the entire concentration range of IHg and MeHg, allowing robust quantitative evaluation with respect to extrapolation.

Methylation and dealkykation of tin compounds by sulfate- and nitrate-reducing bacteria.

In this study, axenic cultures of sulfate-reducing (SRB) and nitrate-reducing (NRB) bacteria were examined for their ability to methylate inorganic tin and to methylate or dealkylate butyltin compounds. Environmentally relevant concentrations of natural abundance tributyltin (TBT) and Sn-enriched inorganic tin were added to bacterial cultures to identify bacterial-mediated methylation and dealkylation reactions. The results show that none of the Desulfovibrio strains tested was able to induce any transformation process.

Flux model to estimate the transport of mercury species in a contaminated lagoon (Ria de Aveiro, Portugal).

The concentrations of dissolved and particulate inorganic mercury (IHg(II)) and methylmercury (MeHg) from the contaminated Laranjo Bay (main freshwater discharge from the Antuã River) were measured by species-specific isotope dilution during six sampling campaigns at high and at low tide. Different effective riverine concentrations were calculated, based on salinity profiles, for specific hydrological conditions. The export fluxes of total Hg and MeHg (324 and 1.

Multiple regression analysis to assess the role of plankton on the distribution and speciation of mercury in water of a contaminated lagoon.

Spatial and seasonal variation of mercury species aqueous concentrations and distributions was carried out during six sampling campaigns at four locations within Laranjo Bay, the most mercury-contaminated area of the Aveiro Lagoon (Portugal). Inorganic mercury (IHg(II)) and methylmercury (MeHg) were determined in filter-retained (IHgPART, MeHgPART) and filtered (<0.45μm) fractions (IHg(II)DISS, MeHgDISS).

Spatial distribution of some trace and major elements in sediments of the Cávado estuary (Esposende, Portugal).

For the first time, the occurrence and spatial distribution of several elements, including some toxic metals, have been investigated in sediments of the estuary of the Cávado River (Esposende, Portugal). The pseudo total concentrations of Al, As, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sn, V and Zn in sediments collected at 24 sites covering the tidal part of the estuary were determined. According to the concentrations measured, the Cávado estuary can be considered as non-contaminated.

A chemical status predictor. A methodology based on World-Wide sediment samples.

As a consequence of the limited resources of underdeveloped countries and the limited interest of the developed ones, the assessment of the chemical quality of entire water bodies around the world is a utopia in the near future. The methodology described here may serve as a first approach for the fast identification of water bodies that do not meet the good chemical status demanded by the European Water Framework Directive (WFD). It also allows estimating the natural background (or reference values of concentration) of the areas under study using a simple criterion.

Interferences of surfactants during determination of chlorophenols by acetylation coupled to headspace-solid phase microextraction-gas chromatography with an electron capture detector.

The micellar extraction (ME) of chlorophenols (CPs) from solid samples is rapid and avoids the use of organic solvents. The cationic surfactant cetyltrimethylammonium bromide (CTAB) is a powerful agent for ME of CPs. However, CTAB will be an important interference when the extracts are subsequently analyzed by direct solid phase microextraction (SPME) without a previous derivatization step.

Pentachlorophenol toxicity to a mixture of Microcystis aeruginosa and Chlorella vulgaris cultures.

Pentachlorophenol (PCP) is a priority pollutant due to its persistence and high toxicity. For the first time, PCP effects were investigated at laboratory scale on co-cultures of two ubiquitous freshwater phytoplankton species: the cyanobacterium Microcystis aeruginosa and the microalgae Chlorella vulgaris. The cells were exposed to environmental levels of PCP for 10 days in Fraquil culture medium, at nominal concentrations from 0.

Stability of chlorophenols and their acetylated derivatives in water: sample storage procedures.

The determination of chlorophenols (CPs) in water samples is a subject of increasing interest. Reduction of sample storage space and the stability of CPs when present at very low levels are still problems that deserve research. The stability of CPs at ng/L levels at different temperatures and in the presence or absence of sodium carbonate and acetic anhydride was studied for up to 39 days.

Cyanobacterium Microcystis aeruginosa response to pentachlorophenol and comparison with that of the microalga Chlorella vulgaris.

Pentachlorophenol (PCP) effects on a strain of the cyanobacterium Microcystis aeruginosa were investigated at laboratory scale. This is the first systematic ecotoxicity study of the effects of PCP on an aquatic cyanobacterium. The microalga Chlorella vulgaris was studied in the same conditions as the cyanobacterium, in order to compare the PCP toxicity and its removal by the species.

Extraction and preconcentration techniques for chromatographic determination of chlorophenols in environmental and food samples.

Methods for chlorophenols (CPs) determination (with low limits of detection) that can be applied to real environmental samples (waters, sediments, soils, biological tissues) and food are reviewed. Special emphasis is given to sampling, storage conditions and the application of preconcentration techniques for the determination of CPs using chromatographic methods. Solid phase extraction, solid phase microextraction, stir bar sorptive extraction, liquid phase microextraction, dispersive liquid-liquid microextraction, liquid-liquid-liquid microextraction and purge and trap methods are considered.

A headspace SPME-GC-ECD method suitable for determination of chlorophenols in water samples.

A headspace solid phase microextraction coupled to gas chromatography with electron capture detector (HS-SPME-GC-ECD) method was optimized for the determination of seven chlorophenols (CPs) with different levels of chlorination. This is the first time that HS-SPME-GC-ECD with acetylation of the analytes is used for the simultaneous determination of CPs in water samples. The influence of fibre type, derivatization conditions, salt addition, temperature and time of extraction and temperature of desorption was checked.

Effects of minocycline and its degradation products on the growth of Microcystis aeruginosa.

This work aimed to investigate the influence of Microcystis aeruginosa on the rate of minocycline (MNC) removal (abiotic degradation, physical binding or chemical transformation by cells) and the toxicity of MNC and its degradation products to the cyanobacterium. Most of the work was carried out in culture media in the presence or in the absence of M. aeruginosa.

Fate and effects of octylphenol in a Microcystis aeruginosa culture medium.

Octylphenol (OP) is a xenobiotic with endocrine disrupting properties found in freshwaters worldwide. Its effects have been studied in organisms with nuclear receptors but effects on phytoplankton communities are poorly characterized, despite the fact that these organisms are constantly exposed to this compound. For this reason fate and effects of OP in the cyanobacterium Microcystis aeruginosa were assessed from 10 nM to 5 microM OP concentration.

Improvement of analytical performances for mercury speciation by on-line derivatization, cryofocussing and atomic fluorescence spectrometry.

A modified automated on-line hyphenated system for simultaneous inorganic ionic mercury (Hg(2+)) and monomethylmercury (MeHg(+)) analysis by hydride generation (HG) or ethylation (Eth), cryofocussing, gas chromatography (GC) separation and atomic fluorescence spectrometry (AFS) detection has been improved. Both derivatization methods are investigated with respect to the chromatographic and analytical performances. They can be both affected by interferences when the AFS detection system is used.

Application of SPME to the determination of alkylphenols and bisphenol A in cyanobacteria culture media.

In order to survey the influence of estrogenic compounds on cyanobacteria, solid-phase microextraction (SPME) with a carbowax-divinylbenzene fibre was used for the determination of tert-octylphenol (tert-OP), n-nonylphenol (n-NP), technical nonylphenol (tech-NP) and bisphenol A (BPA) in cyanobacteria culture media by gas chromatography with flame ionization detection. Determinations were carried out without derivatization in deionized water and filtered culture media. A comparison between f2 and Fraquil culture media was performed, which showed that only f2 allowed quantitative recoveries.

Application of cryofocusing hydride generation and atomic fluorescence detection for dissolved mercury species determination in natural water samples.

The concentration levels of mercury (Hg) species in natural water samples are usually low. Consequently, accurate analysis with low detection limits is still a major problem. In this work, a method was applied for the simultaneous direct determination of dissolved mercury species in water samples by on-line hydride generation (HG), cryogenic trapping (CT), gas chromatography (GC) and detection by atomic fluorescence spectrometry (AFS).

[Induction of cytochrome P-450 forms by prolonged administration of nifedipine].

In experiments on male Wistar rats it has been found that nifedipine applied in a dose of 10 mg/kg body weight i.p. daily for 20 days did not significantly increase the total amount of cytochrome P-450 but markedly increased the 7 alpha-, 16 beta- and 6 beta-hydroxylation of androstenedione in liver microsomes, suggesting the induction of cytochromes P-450a, P-450b and P-450p respectively.

[Protective action of fat- and water-soluble antioxidants on the cytochrome P-450 system during lipid peroxidation in liver microsomes].

The protective effects of alpha-tocopherol, carnosine and their mixture on monooxygenase system during lipid peroxidation in liver microsome membranes were studied. It was shown that for optimal protection effect of cytochrome P-450 system the mixture of water and liposoluble antioxidants is required.