Stephen de Mora

Aliphatic and aromatic hydrocarbons in coastal Caspian Sea sediments

This investigation represents the first extensive study of the spatial distribution and sources of aliphatic (n-alkanes and unresolved complex mixture of fossil hydrocarbons) and polycyclic aromatic hydrocarbons (PAHs) in coastal sediments from the Caspian Sea. PAH concentrations, n-alkanes and biomarker profiles all suggested that there was limited petrogenic contamination in the shallow North Caspian Sea sediments, which are coarse with a low total organic carbon content. In contrast, moderate to high petrogenic contamination was found in the South Caspian Sea, in particular in the offshore oil fields near Baku, Azerbaijan. Contaminant patterns indicated that the PAHs were mainly from fossil sources, with higher contributions of pyrolytic only near industrialized and urban areas. A high contribution of perylene, a geochemically derived PAH, to the total PAHs was found in the west and south at sites influenced by the Kura, Safid Rud, Terek, Sulak and Samur Rivers.

An assessment of metal contamination in coastal sediments of the Caspian Sea

An assessment of marine pollution due to metals was made in the Caspian Sea based on coastal sediment collected in Azerbaijan, Iran, Kazakhstan, Russia and Turkmenistan. Despite the high carbonate content, the distribution of most metals was largely controlled by terrigenous inputs. Several metals (As, Cr, Ni) exhibited concentrations that exceed sediment quality guidelines. Such metals have a high natural background but anthropogenic activities, notably mining, may further enhance concentrations. This would explain hot spots for Cu and Zn in Azerbaijan and Iran, and Cr at the mouth of the Ural River in Kazakhstan. Contamination by Hg was observed to the south of Baku Bay, Azerbaijan. Some anomalously high concentrations of Ba in the central Caspian are probably from offshore drilling operations, but the elevated U concentrations (up to 11.1 microg g(-1)) may be natural in origin. Several metals (Ag, Cd, Pb) have relatively low levels that pose no environmental concerns.

Distribution of petroleum hydrocarbons and organochlorinated contaminants in marine biota and coastal sediments from the ROPME Sea Area during 2005.

The composition and spatial distribution of various petroleum hydrocarbons (PHs), comprising both aliphatic and polycyclic aromatic hydrocarbons (PAHs), and selected chlorinated pesticides and PCBs were measured in biota and coastal sediments from seven countries in the Persian Gulf and the Gulf of Oman (Bahrain, Iran, Kuwait, Oman, Qatar, Saudi Arabia and the United Arab Emirates). Evidence of extensive marine contamination with respect to organochlorinated compounds and PHs was not observed. Only one site, namely the BAPCO oil refinery in Bahrain, was considered to be chronically contaminated. Comparison of the results from this survey for Σ DDTs and Σ PCBs in rock oysters from the Gulf of Oman with similar measurements made at the same locations over the past two decades indicates a temporal trend of overall decreasing Σ PCB concentrations in oysters, whereas Σ DDTs levels have little changed during that period.

Assessment of organotin contamination in marine sediments and biota from the Gulf and adjacent region

Butyltin species were measured in sediments from coastal locations in the Gulf and Gulf of Oman. Both butyltin and phenyltin species were measured in biota samples from four countries in this region. With tributyltin (TBT) concentrations up to 60 ngSng(-1), some sediments could be classified as contaminated (i.e. TBT>1.3 ngSng(-1)), namely Dukhan (Qatar), the BAPCO industrial complex and Askar (Bahrain), and Hilf and the Raysut Port Area (Oman). Higher concentrations of total butyltins were found in oysters relative to fish, but ranging from 6.5 to 488 ngSng(-1) dry weight they are nonetheless relatively low. Diphenyltin and triphenyltin were found in some fish and bivalves from the Gulf, but not in biota from the Gulf of Oman. The environmental levels of organotin species are comparatively low by global standards and pose no immediate public health problems.

Thermodynamic Constraints on Microbially Mediated Processes in Lakes of the McMurdo Dry Valleys, Antarctica

Recent research has shown that the distribution of biogenic nitrogen and sulfur compounds (in particular, N 2 O, DMS and dissolved DMSO) observed in five perennially ice-covered lakes of the McMurdo Dry Valleys, Antarctica, appear to lack obvious biogeochemical explanations. This study examined the hypothesis that the distribution of these compounds resulted from thermodynamic constraints on microbially mediated processes. The thermodynamic favorableness of a number of ecologically important redox reactions in these lakes was assessed using a simplified Nernst equation and mathematically modified E h measurements. Our qualitative analysis revealed that the relative dominance of denitrification and nitrification as formation and loss processes for N 2 O was a complex pattern that was related to the redox conditions present. The results indicate that nitrification was initially the sole pathway for the formation of N 2 O with denitrification being thermodynamically unfavorable. As the redox conditions became less oxic, both denitrification and nitrification were possible. Once complete anoxia occurred, the importance of nitrification decreased considerably and the loss of N 2 O via denitrification became increasingly important. With respect to DMSO, the results indicated that DMSO was thermodynamically unfavorable as an electron acceptor for the respiration of organic material by bacteria in well-oxygenated environments, giving a partial explanation for the relatively elevated levels of DMSO found in many aquatic environments. Overall, the results of this study showed that subtle variations in the redox conditions present provided a plausible explanation for the unusual distributions of biogenic sulfur and nitrogen compounds observed in the lakes of the McMurdo Dry Valleys.

Hepatic Butyltin Concentrations in Beluga Whales (Delphinapterus leucas) from the St Lawrence Estuary and Northern Quebec, Canada

Butyltin (tributyltin TBT; dibutyltin DBT and monobutyltin MBT) speciation was measured in the liver of beluga whales from the St Lawrence Estuary and Hudson Strait (northern Quebec). Using GC–MS, liver samples were analysed from 21 beluga whales found dead, stranded along the shores of the St Lawrence during the period 1995–1998. In all cases, including a neonate specimen, the liver was contaminated with butyltin compounds with concentrations in the range 0.04–2.1 mg Sn kg−1 on a dry weight basis. Liver samples of five beluga whales from Hudson Strait obtained in the summer of 1998 were also analysed. For these animals, hepatic butyltin concentrations were consistently below the detection limit (<0.5 ng Sn g−1 for MBT and <0.2 ng Sn g−1 for DBT and TBT). Compared with published data on the contamination by TBT of the marine mammals of the St Lawrence in 1988, these contemporary results clearly indicate that the level of contamination of the beluga whales in this coastal marine ecosystem has not decreased ten years after regulating the use of TBT-based antifoulants on small craft. Copyright

Determination of organochlorinated compoundsand petroleum hydrocarbons in sediment sample IAEA-408. Results from aworld-wide intercalibration exercise

A sediment sample from the intertidal mudflats of the Tagus estuary was prepared, homogenised and distributed globally to laboratories as the IAEA-408 intercomparison material for the analyses of organochlorinated pesticides, PCBs and petroleum hydrocarbons (PHs). A total of 48 laboratories from 36 countries reported their results. The data from participants show that there still remain some difficulties with the accurate determination of organic contaminants such as pesticides and polycyclic aromatic hydrocarbons (PAHs). More consistent interlaboratory results were obtained for PCBs congeners. The final results of this intercomparison exercise enable individual participants to assess their performance and, where necessary, to introduce appropriate modifications in their analytical procedures. Furthermore, as a series of statistical criteria was fulfilled for a number of compounds, the sample IAEA-408 can now be used as a reference material for quality control in the determination of some persistant organic pollutants (POPs) in marine sediment samples.

Determination of organochlorinated compounds and petroleum hydrocarbons in fish-homogenate sample IAEA-406: results from a worldwide interlaboratory study

Fish-homogenate IAEA-406 was used as an intercomparison sample for the analyses of organochlorinated pesticides, polychlorinated biphenyls (PCBs) and petroleum hydrocarbons. The sample material was analysed by 59 laboratories from 36 countries. The results reported by the laboratories shows that there are still some difficulties with the accurate determination of organic contaminants, notably pesticides and polycyclic aromatic hydrocarbons (PAHs). More consistent interlaboratory results were obtained for PCB congeners. Many laboratories reported results in close agreement and, after statistical screening of the data, consensus values were obtained for the concentration of several analytes in this sample. These results allowed several values for the concentrations of the analytes to be assigned, and the sample IAEA-406 can be used as a reference material (RM) for quality control of data in the determination of chlorinated compounds and petroleum hydrocarbons in biological samples. Furthermore, considering the matrix type and the number of contaminants certified, this sample is unique in the collection of RMs available at present.

Characterisation of trace elements and methylmercury in an estuarine sediment reference material, IAEA-405

An estuarine sediment sample, IAEA-405, was recently characterised for trace elements and methylmercury (MeHg) for ultimate use as a marine reference material. The reference values were calculated using data sets from 120 laboratories that participated in a world-wide intercomparison exercise. The data evaluation is highlighted, and includes comparisons of different analytical methods, as well as the distribution of data. Overall laboratory performance for this exercise was encouraging: 86 laboratories (72%) reported data with <25% outliers. There was sufficient acceptable data to establish recommended values for 17 elements and information values for a further 15 elements. In addition, a recommended value was established for methylmercury. The estuarine sediment sample, IAEA-405, can be used as a reference material for quality control in the determination of trace elements and methylmercury in moderately polluted sediments.

Occurrence and seasonal variation of butyltin species along the mediterranean coast of Turkey

Organotin compounds are extensively used in industrial andagricultural applications, as disinfectants and antifouling additives.The use of TBT as an antifoulant additive in paints increases its le-vel in seawater, especially near marinas and harbours. In general,progressive substitution of organic groups to the tin atom in anyR