Jean-Claude Marty

Aliphatic and aromatic hydrocarbons in different sized aerosols over the Mediterranean Sea: Occurrence and origin

Marine aerosols were collected using a five-stage cascade impactor during the PHYCEMED II cruise in the Western Mediterranean Sea (October 1983). Their composition in aliphatic and aromatic hydrocarbons (HCs) was analyzed, representing the first time that concentrations of polynuclear aromatic HCs (PAH) are reported in relation to particle size for aerosols of remote marine areas. The HC concentrations were found to be dependent on the origin of the air masses. They were higher for air coming from North European countries than for air originating in the Atlantic and the South of Spain. The concentrations range between 7 and 14 ng m−3for n-alkanes and between 0.2 and 0.4 ng m−3for total PAH. Based on molecular criteria, several sources for these HCs have been identified: continental higher plant waxes, petroleum and pyrolysis (namely coal combustion and vehicular exhausts). Mass medium equivalent diameters (MMED) for the naturally derived n-alkanes are in the 1.79-2.53 μm range, indicating an origin related with the emission of large particles from higher plant waxes or from soil dusts. In contrast, MMED for the anthropogenic HCs, both aliphatic and aromatic, are smaller than the micron, suggesting initial emission of PAH through pyrolytic processes in the vapor phase followed by condensation onto larger sub-μm particles.

The C37 alkenone record of seawater temperature during seasonal thermocline stratification

Abstract The concentrations of suspended particulate pigments, C37–C38 alkenones, total organic carbon and nitrogen in the Ligurian Sea (northwestern Mediterranean) have been studied at 5 and 30 m depth during well defined thermocline conditions. An accurate description of the short term changes of these compounds has been achieved by means of four 36-h sampling cycles each encompassing consecutive filtration periods of 4 h. During sampling the thermocline changes were followed closely by simultaneous measurements of water column temperature, salinity and other physical parameters. The analysis of the collected samples indicates that the Haptophyte pigments and alkenones are essentially synthesized at the levels of highest primary production and therefore the C37 alkenone record reflects the seawater temperature at this depth level. The study also shows that part of these alkenones are distributed throughout the water column in association to the suspended particles. This process results in C37 alkenone distributions that, due to their high resistance to chemical and microbial degradation, record the temperature of the highest primary productivity layers even at shallow (e.g., 5 m depth) or deep (e.g., 1100 m depth) waters.

Production pattern of alkenones in the Mediterranean Sea

Time-series of downward alkenone fluxes have been investigated at 200 m depth over a one year sediment trap experiment, in the Northwestern Mediterranean Sea. Alkenone flux maxima occurred in autumn and to a lesser extent in May, during the spring bloom. Temperature estimates calculated from the UK′37 index revealed that alkenone producers preferentially develop in subsurface waters (at about 50 m) in spring, whereas the autumn alkenone production occurred upper in the water column (around 30 m). Examination of the core-top UK′37 index values at various sites of the Northwestern Mediterranean basin, suggested that the spring bloom period do not significantly imprint the temperatures recorded in the sediments. The sedimentary temperature estimates would rather reflect annually integrated SST, with a major influence of the autumnal post-bloom development of the coccolithophores in the euphotic zone.

Characterization of seawater samples using chemometric methods applied to biomarker fatty acids

Abstract Dissolved and particulate fatty acids have been analyzed by gas chromatography and gas chromatography/mass spectrometry in microlayer and subsurface water samples from the open Mediterranean sea. Structural elucidation of these compounds was performed before and after derivatization with dimethyldisulfide (DMDS) by GC/MS analyses of the fatty acid methyl esters (FAMEs) and their methylthio derivatives to locate the double bond of the monounsaturated FAMEs. Several hundred data were analyzed using a statistical approach. A multivariate method, CFA (Correspondence Factorial Analysis), and a non-parametric procedure. HCC (Hierarchical Clustering Classification), were used together to investigate the planktonic and microbiological sources in order to further characterize our samples. These statistical treatments allowed us to distinguish different inputs in the dissolved and particulate material: esters in the particulate material showed a major phytoplanktonic input dominated by the presence of diatoms except in one sample where zooplankton prevailed. Higher amounts of C 15 and C 17 branched and monounsaturated FAMEs indicated a stronger bacterial fingerprint for the dissolved FAMEs. C 16:1 ω 10 , previously unreported in seawater displayed a similar statistical behavior as other bacterial FAMEs suggesting a microbial origin of this compound. Dissolved FAMEs extracted from acidified seawater and particulate esterified FAMEs showed similar composition.

Aliphatic and Aromatic Hydrocarbons in the Mediterranean Aerosol

The atmospheric transport of organic pollutants over long distances and their effect on the biological cycles of the sea are two major questions of concern in environmental chemistry. These processes are of particular importance in the Mediterranean Sea because of its semi-enclosed characteristics, which determine the accumulation of the pollutants entering into the system. In order to get some insight into these processes a project (PHYCEMED), was developed for the evaluation of the atmospheric budget of organic and inorganic substances in the Western Mediterranean and for the investigation of the exchange mechanisms of these materials across the air/sea interface. A high volume air sampling system including a cascade impactor was placed on board of the R/V le Suroit for collecting the aerosols along several transects parallel to the French, Spanish and North-African coasts, facing areas of different population densities and industrial activities. The cruise was realised on October 1983 and the particulate material was fractionated into the following sizes: 7.2, 3.0, 1.5, 0.96, and 0.03 micron. Quantitative and qualitative analyses of the aliphatic and the aromatic hydrocarbons present in these fractions were performed by high resolution gas chromatography and gas chromatography-mass spectrometry.

Alkenones in the northwestern Mediterranean Sea: Interannual variability and vertical transfer

C 37 alkenone fluxes were measured with sediment traps at 200 m depth over the years 1989/1990 and 1993/1994 to assess the interannual variability of the alkenone flux from the surface waters of the Mediterranean Sea. Fall and spring were identified as the high flux periods. SST estimates derived from the U 37 κ index indicated 50 m and 30 m as major production depths in spring and fall, respectively. Althought interannual variation of alkenone fluxes was notable, the seasonality and depth of production appeared to be recurrent features of the coccolithophorid cycle of production. Alkenone fluxes at 1000 m measured over the year 1993/1994 were about 5 times lower than at 200 m and show no evidence of preferential preservation relative to the organic carbon between these depths. SST predicted at 200 m and 1000 m indicated a remarkably good transfer of the surface temperature signal to deeper layers.

Gaseous and particulate polycyclic aromatic hydrocarbons (PAH) from the marine atmosphere

Despite their importance in environmental studies, there are very few data concerning the gaseous polycyclic aromatic hydrocarbons (PAH) in the marine atmosphere and their potential importance. We present here concentrations and distributions for gaseous and particulate PAH sampled in the atmosphere over the Tropical and Equatorial East Atlantic. After collection respecting ultra-clean conditions, PAH were isolated and analysed through capillary GC and GC/MS. Concentrations of gaseous PAH ranged from 7 to 18 ngm−3. They are an order of magnitude higher than those encountered for particulate PAH. This enhances the importance of gaseous PAH vs PAH associated with aerosols and strongly shows their mode in transport and ocean-atmosphere exchange processes. Gaseous PAH are composed almost entirely of extremely volatile compounds such as phenanthrene. On the other hand, aerosol PAH distributions exhibit a predominance of phenanthrene, but also contain substantial amounts of other PAH: fluoranthene, pyrene, chrysene, benzofluoranthenes and benzopyrenes. The comparison between the distributions of PAH and their alkylated homologues, both in the atmosphere and the sea surface mkrolayer collected in the same area, suggests a mixed origin for the gaseous PAH: non-combusted petroleum residues and pyrolytic-like compounds emitted from the ocean.

Aerosol transport of polynuclear aromatic hydrocarbons over the mediterranean sea

Fig. 5. SE image of the Tl-rich part of the Alshar ore at SEM. Lorandite is completely surrounded by the new mineral T13AsS 4. Both minerals are embedded in dolomite matrix. Operating conditions: 30keV, x 600 around lorandite, realgar, and orpiment. The chemical composition determined by the electron microprobe is displayed on Table 3. In contrast to loTI Fe randite, the new mineral contains deZn tectable amounts of Sb (as T13SbS4) and Cu Fe (0.16070 and 0.12%, respectively). Ni The calculated formula indicates a T1 As occupancy less than 3 with the formula Sb T13_xASS4; 0 .10<x<0 .170 . Phase relaS tions in the system T1-As-S by Sobott Totals [3], however, did not indicate or mention deviation from stoichiometry. It is unclear how the compositions of the T1 synthetic binary and ternary phases in Fe the system T1-As-S [3] were deZn termined. According to [3], the upper Ca stability limit of T13AsS 4 is 416 ~ at Ni which the phase melts congruently. The As Sb presence of this phase manifests the S fact that the last episode during the mineralization in Alshar was characTotals terized by a strong spike in T1 in the ore-bearing solutions. This spike must have taken place below 292~ (the upper stability temperature of lorandite) since neither lorandite nor orpiment show any indications of melting.

Characterization of particulate organic matter in Mediterranean sea-surface films and underlying water by flash pyrolysis and gas chromatographic analyses

Abstract Sea-surface films and the corresponding 20 cm subsurface waters were sampled during four cruises in the Western Mediterranean and in the Northern Adriatic Sea. The composition of the particulate material was determined by a combination of several methods: analysis of total organic carbon and proteins, gas chromatographic analysis of fatty acids and non-aromatic hydrocarbons, and by flash pyrolysis-mass spectrometry (Py-MS). Enrichment factors in the sea-surface films were: 1.4–6.1 for organic carbon; 1–17.7 for proteins; 2.1–47.5 for total carbohydrates; 4.4–45 for total lipids. The relative values of proteins and carbohydrates, for four pairs of microlayer and subsurface water samples, were discussed from their scores on two significant discriminant functions derived from pyrolysis mass spectral data. Details of the chemical structure of the surface film/underlying water pair were derived from complementary analyses of particulate organic matter by Py-MS and GC. It was shown that the fatty acids originating from autochtonous biological productivity were dominant in the sea-surface film. Unsaturated compounds were however depleted in the microlayer.

Hydrocarbons in the Western Mediterranean Sea, 1981

Hydrocarbons in the western Mediterranean Sea were analysed for surface microlayer and subsurface waters during April 1981. Three methods were used for determining both concentrations and markers distribution patterns: U.V. spectrofluorimetry, and original HPLC/U.V. spectrophotometry method and capillary gas liquid chromatography. No systematic relationship was found between concentrations determined by U.V. spectrofluorimetry and HPLC/U.V. spectrophotometry. Concentrations variation ranges are: 0.01-0.20 microgram 1(-1) for dissolved aromatic hydrocarbons; 0.02-0.13 microgram 1(-1) for particulate aromatic hydrocarbons; 0.02-20.57 micrograms 1(-1) for dissolved n-alkanes; 0.13-0.83 microgram 1(-1) for particulate n-alkanes. Surficial waters appear as very slightly polluted with an exception the Ligurian Sea for which highest concentrations were encountered. There is a slight enrichment of particulate hydrocarbons in the surface microlayer in the range 1-3. But, dissolved hydrocarbons can be either depleted or enriched up to 270 times in the surface microlayer, indicating the extreme efficiency of sea-air exchange processes. Aromatic fingerprints and n-alkane distribution patterns are discussed both for pollution and fractionation processes indicators at the sea-air interface.