Impact of oil on bacterial community structure in bioturbated sediments

Oil spills threaten coastlines where biological processes supply essential ecosystem services. Therefore, it is crucial to understand how oil influences the microbial communities in sediments that play key roles in ecosystem functioning. Ecosystems such as sediments are characterized by intensive bioturbation due to burrowing macrofauna that may modify the microbial metabolisms. It is thus essential to consider the bioturbation when determining the impact of oil on microbial communities. In this study, an experimental laboratory device maintaining pristine collected mudflat sediments in microcosms closer to true environmental conditions - with tidal cycles and natural seawater - was used to simulate an oil spill under bioturbation conditions. Different conditions were applied to the microcosms including an addition of: standardized oil (Blend Arabian Light crude oil, 25.6 mg.g21 wet sediment), the common burrowing organism Hediste (Nereis) diversicolor and both the oil and H. diversicolor. The addition of H. diversicolor and its associated bioturbation did not affect the removal of petroleum hydrocarbons. After 270 days, 60% of hydrocarbons had been removed in all microcosms irrespective of the H. diversicolor addition. However, 16S-rRNA gene and 16S-cDNA T-RFLP and RT-PCR-amplicon libraries analysis showed an effect of the condition on the bacterial community structure, composition, and dynamics, supported by PerMANOVA analysis. The 16S-cDNA libraries from microcosms where H. diversicolor was added (oiled and un-oiled) showed a marked dominance of sequences related to Gammaproteobacteria. However, in the oiled-library sequences associated to Deltaproteobacteria and Bacteroidetes were also highly represented. The 16S-cDNA libraries from oiled-microcosms (with and without H. diversicolor addition) revealed two distinct microbial communities characterized by different phylotypes associated to known hydrocarbonoclastic bacteria and dominated by Gammaproteobacteria and Deltaproteobacteria. In the oiled-microcosms, the addition of H. diversicolor reduced the phylotype-richness, sequences associated to Actinobacteria, Firmicutes and Plantomycetes were not detected. These observations highlight the influence of the bioturbation on the bacterial community structure without affecting the biodegradation capacities

Trace elements transfer from gas to water: Study of Ar-Hg°-H2O system in the pressure range 1-20 MPa for temperatures up to 473 K

ACTInternational audienc

An experimental investigation of metallic mercury solubility in Ar in the pressure range 1-200 bar for temperature up to 200°C

AFFInternational audienc

Analytical Methods for Speciation of Mercury in Gas Condensates: Critical Assessment and Recommendations

The wide range of mercury species present in gas condensates can cause major problems such as corrosion of installations and reduced catalyst life. The understanding of speciation of this element is required to predict and improve the efficiency of mercury removal technologies. This review paper presents the state-of-the-art of the analytical methods available for the analysis of mercury speciation in gas condensates, highlighting the advantages and drawbacks. Particular attention is given to gas chromatography with mercury specific detection as the most promising tool for mercury speciation analysis in hydrocarbon-rich samples. Questions regarding accuracy of the data available are raised in view of the limited stability of mercury species in organic solutions, possibility of artefacts formation and unavailability of reference materials

Multielement analysis of petroleum samples by laser ablation double focusing sector field inductively coupled plasma mass spectrometry (LA-ICP MS)

International audienceA method was developed for the direct analysis of petroleum samples. A silica gel plate, commonly used in thin layer chromatography, was impregnated for 30 min with a sample solution and analyzed by laser ablation-ICP MS. The use of a doubly focusing sector field mass analyzer allowed the demonstration of the absence of carbon-related polyatomic interferences. Matrix suppression effects, common in nebulization-based sample introduction, were absent which enabled quantitation by external calibration. The detection limits were in the low ng g -1 range. The method was validated by the analysis of NIST 1084a and 1085b certified reference materials (wear metals in lubricating oils) and applied to the analysis of crude oil and asphaltene samples

Study of metal trace element transfers in a natural gas aquifer storage

AFFInternational audienc

Assessment of trace metals in natural gas, biogas and biomethane

AFFInternational audienc

Redox activity of nickel and vanadium porphyrins: a possible mechanism behind petroleum genesis and maturation?

International audienceThe presence of metalloporphyrins in crude oil has been known for many years. In contrast, their role on the physical–chemical properties is only now beginning to be understood. In this study, we test using high-level ab initio calculations, the hypothesis of a possible redox catalytic activity of vanadium and nickel metalloporphyrins in crude oil, illustrated by the oxidation of methanol to formaldehyde and hydrogen dissociation, respectively. This process which may take place during petroleum genesis and maturation, explains some of its physical–chemical properties, such as polar chains, the absence of alcohols, the trapping of porphyrins within macromolecular aggregates