Occurrence and distribution of metals in mussels from the Cantabrian coast.

From February 2004 to April 2006, the concentrations of more than 10 metals in mussels (Mytilus galloprovincialis) were measured in 10 stations from Galicia to the Basque Country in 8 different times of sampling. The mean highest concentrations are found for Zn [226.8 microg/g, dry weight (d.w.)] followed by Mn, As, Cu, and Co (between 10 and 25 microg/g d.w.). Lower mean concentrations are found for Se, Cr, Pb, V, and Ni (between 2 and 8 microg/g d.w.) and the lowest are for Cd, Sn, Hg, and Sb (between 0.05 and 1 microg/g d.w.). Among the statistical treatments used, the factor analysis showed a clustering of the mussels according to the geographical location. In addition, the temporal trend of the metal concentrations was studied by means of the Mann-Kendall test. In this sense, some stations showed a decreasing trend in the accumulation of the metallic content. However, there were some local pollution events that could be explained as a consequence of anthropogenic activities. Finally, the effects of the oil spill from the Prestige are discussed based on the experimental Ni/V ratio values obtained from this work and those of the original oil.

Trace metals in oysters, Crassotrea sps., from UNESCO protected natural reserve of Urdaibai: space-time observations and source identification.

The seasonal and spatial variability of trace metal concentrations of oyster tissues (Crassostea sps.) was studied. The samples were collected between 2002 and 2004 along the Urdaibai estuary (Murueta, Kanala and Arteaga). The seasonal influence on some metal concentrations (higher values in spring-summer season than in autumn-winter season) is more pronounced than the local site-specific influence. Furthermore, within each location a significant time-specific dependence on the trace metal concentration variations can be detected. Substantially higher concentrations of Zn (445.5-2,403.3 mg kg(-1)) and Mn (29.4-169.6 mg kg(-1)) were recorded in oysters inhabiting estuarine locations, possibly indicating a markedly higher natural bioavailability at these locations. Principal component analysis demonstrated that oysters could be separated depending on the inhabiting areas: Sn for Murueta, essential metals for Kanala, and Co and Cd for Arteaga sampling points, respectively.

Distribution and bioaccumulation of PAHs in the UNESCO protected natural reserve of Urdaibai, Bay of Biscay.

Along 10 campaigns, from June 2002 to September 2004, the concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) were measured in sediments and oysters (Crassostrea sp.) taken from four sites in the Unesco protected natural reserve of Urdaibai (Basque Country, Bay of Biscay). Total PAH concentration ranged from 0.7 to 140 microg kg(-1) (dw) in the case of sediments, and from 300 to 1400 microg kg(-1) (dw) in the case of oysters. During this study, the coast of the Bay of Biscay was severely affected by the Prestige oil spill (November 2002). Presumably, as a consequence of this accident, both spatial and temporal variations of the PAHs, as well as the sources of the PAHs were affected by the oil spill, and this effect was observed in the total concentrations and, especially, in several diagnostic ratios and in multivariate data analysis. Finally, both BAF (bioaccumulation factor) and BSAF (biota-sediment accumulation factor) parameters were calculated to conclude that particulate matter seems to be the most favourable uptake pathway of PAHs in oysters from this estuary.

Mercury biomethylation assessment in the estuary of Bilbao (North of Spain).

The relationship between the microbial methylation of mercury and the microbial activities in sediments and water collected from the estuary of Bilbao (North of Spain) was studied in three different sampling points and in two different seasons. Three different cultures were prepared with a sediment slurry to distinguish between biotic and abiotic methylation pathways and the variations of the methylmercury concentration and the variations of the population of total number of bacteria (TDC), anaerobic heterotrophic bacteria (AHB), sulphate-reducing bacteria (SRB) and Desulfovibrio were measured. From this work, it can be concluded that the variation of MeHg concentrations is a result of the methylation/demethylation processes in the sediments, and that the abiotic processes have a negligible contribution to those processes. According to the statistical analysis of the results (partial least squares analysis) a significant statistical correlation was established between methylmercury and the SRB counts.

Comparison of solid phase extraction, saponification and gel permeation chromatography for the clean-up of microwave-assisted biological extracts in the analysis of polycyclic aromatic hydrocarbons.

The feasibility of different clean-up procedures was studied for the determination of polycyclic aromatic hydrocarbons (PAHs) in biota samples such as oysters, mussels and fish liver. In this sense, once the samples were extracted--essentially with acetone and in a microwave system--and before they could be analysed by gas chromatography-mass spectrometry (GC-MS), three different approaches were studied for the clean-up step: solid phase extraction (SPE), microwave-assisted saponification (MAS) and gel permeation chromatography (GPC). The main aim of this work was to maximise the recoveries of PAHs and to minimise the presence of interfering compounds in the last extract. In the case of SPE, Florisil cartridges of 1, 2 and 5 g, and silica cartridges of 5 g were studied. In that case, and with oysters and mussels, microwave-assisted extraction and 5 g Florisil cartridges provided good results. In addition, the concentrations obtained for Standard Reference Material (SRM) NIST 2977 (mussel tissue) were in good agreement with the certified values. In the case of microwave-assisted saponification, the extracts were not as clean as those obtained with 5 g Florisil and this fact lead to overestimate the concentration of the heaviest PAHs. Finally, the cleanest extracts were obtained by GPC. The method was successfully applied to mussels, oysters and hake liver, and the results obtained for NIST 2977 (mussel tissue) were within the confidence interval of the certified reference material for most of the certified analytes.

Simultaneous microwave-assisted extraction of polycyclic aromatic hydrocarbons, polychlorinated biphenyls, phthalate esters and nonylphenols in sediments.

A new method was developed for the simultaneous extraction of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), phthalate esters (PEs), nonylphenols (NPs) and nonylphenol mono- and diethoxylates (NP1EOs and NP2EOs, respectively) in sediment samples by means of a closed microwave system. The extractions were carried out at 21 psi and 80% of microwave power and 15 ml of acetone were used as the common extraction solvent. The filtered extract was further fractionated in two groups using Florisil cartridges: PAHs and PCBs were eluted with n-hexane:toluene (4:1) and the PEs, NPs and ethoxylates were eluted with ethyl acetate. All the compounds were analysed by gas chromatography-mass spectrometry (GC-MS). In case of PAHs and PCBs, the developed method was validated by comparison of the results obtained for the certified reference material NIST 1944 with the certified values. In the absence of a reference material for phthalate esters and nonylphenols, one sediment sample was extracted twice under the optimal conditions in order to check than an exhaustive extraction of the analytes occurred. This method is currently used in the study of the distribution of those organic contaminants in the estuaries of the Bay of Biscay (Spain).

Optimisation of flow-injection-hydride generation inductively coupled plasma spectrometric determination of selenium in electrolytic manganese.

Flow-injection-hydride generation procedure for Se in electrolytic manganese was optimized by means of the experimental design approach. Instrumental variables like power supplied (P), sample (F) and argon (G) flow rates together with chemical variables like NaBH(4) and HCl concentrations were studied. In case of the chemical variables, it was concluded that sodium tetrahydridoborate concentrations higher than 1.0% extinguished the plasma while HCl concentration should always be higher than 0.6moldm(-3). The analysis of effects suggested that all the instrumental variables are significant factors, and the optimum conditions were P=1550W, F=4.75mLmin(-1) and G=0.6mLmin(-1). The influence of Mn was specially studied and it was concluded that the interferences were negligible if Mn is below 2.0gL(-1). In the same sense, the interferences of antimony(III), arsenic(V) and mercury(II) were also considered negligible. Finally, a detection limit of 0.0005% (w/w) was obtained (a repeatability R.S.D. <2.0% for all Se concentrations tried). Some manganese samples were also spiked with different concentrations of Se(IV) and the results demonstrated to be in good statistical agreement with expected values.

MultiSimplex optimisation of the solid-phase microextraction-gas chromatographic-mass spectrometric determination of polycyclic aromatic hydrocarbons, polychlorinated biphenyls and phthalates from water samples.

Solid-phase microextraction coupled to GC-MS was optimised for the determination of polycyclic aromatic hydrocarbons (PAHs), phthalate esters and polychlorinated biphenyls (PCBs) in water samples. A 30-microm polydimethylsiloxane fiber was immersed in a 30-ml water sample that contained the analytes of interest (PAHs, PCBs and phthalate esters) and the variables studied were extraction time (15-60 min), extraction temperature (30-90 degrees C), desorption time (1-5 min), desorption temperature (220-270 degrees C) and the addition of sodium chloride (0-9 g). The MultiSimplex programme based on the simplex algorithm was used to establish the optimal conditions. MultiSimplex allowed the simultaneous study of the variables mentioned above and considered the answers of all types of compounds studied in this work. Thus, the optimal conditions obtained allowed the simultaneous determination of PAHs, phthalate esters and PCBs. Furthermore, the accuracy and repeatability of the developed method were calculated from water samples spiked at known concentrations of the analytes. Finally, the optimised method was used to analyse water samples from different sampling points of the Urdaibai and Nerbioi-Ibaizabal estuaries (Biscay, Spain).