Nikos Pasadakis

Evaluation of autochthonous bioaugmentation and biostimulation during microcosm-simulated oil spills.

Oil spills are treated as a widespread problem that poses a great threat to any ecosystem. Following first response actions, bioremediation has emerged as the best strategy for combating oil spills and can be enhanced by the following two complementary approaches: bioaugmentation and biostimulation. Bioaugmentation is one of the most controversial issues of bioremediation. Studies that compare the relative performance of bioaugmentation and biostimulation suggest that nutrient addition alone has a greater effect on oil biodegradation than the addition of microbial products because the survival and degradation ability of microbes introduced to a contaminated site are highly dependent on environmental conditions. Microbial populations grown in rich media under laboratory conditions become stressed when exposed to field conditions in which nutrient concentrations are substantially lower. There is increasing evidence that the best approach to overcoming these barriers is the use of microorganisms from the polluted area, an approach proposed as autochthonous bioaugmentation (ABA) and defined as a bioaugmentation technology that exclusively uses microorganisms indigenous to the sites (soil, sand, and water) slated for decontamination. In this work, we examined the effectiveness of strategies combining autochthonous bioaugmentation with biostimulation for successful remediation of polluted marine environments. Seawater was collected from a pristine area (Agios Onoufrios Beach, Chania) and was placed in a bioreactor with 1% v/v crude oil to facilitate the adaptation of the indigenous microorganism population. The pre-adapted consortium and the indigenous population were tested in combination with inorganic or lipophilic nutrients in the presence (or absence) of biosurfactants (rhamnolipids) during 90-day long experiments. Chemical analysis (gas chromatography-mass spectrometry) of petroleum hydrocarbons confirmed the results of previous work demonstrating that the biodegradation processes were enhanced by the addition of lipophilic fertilizers (uric acid and lecithin) in combination with biosurfactants (rhamnolipids), resulting in increased removal of petroleum hydrocarbons as well as reduction of the lag phase within 15 days of treatment. Considering this outcome and examining the results, the use of biostimulation additives in combination with naturally pre-adapted hydrocarbon-degrading consortia (bioaugmentation) has proved to be an effective treatment and is a promising strategy that could be applied specifically when an oil spill approaches near a shore line and an immediate hydrocarbon degradation effort is needed.

Enhanced ex situ bioremediation of crude oil contaminated beach sand by supplementation with nutrients and rhamnolipids

Mediterranean coastal regions are particularly exposed to oil pollution due to extensive industrialization, urbanization and transport of crude and refined oil to and from refineries. Bioremediation of contaminated beach sand through landfarming is both simple and cost-effective to implement compared to other treatment technologies. The purpose of the present study was to investigate the effect of alternative nutrients on biodegradation of crude oil contaminated beach sand in an effort to reduce the time required for bioremediation employing only indigenous hydrocarbon degraders. A natural sandy soil was collected from Agios Onoufrios beach (Chania, Greece) and was contaminated with weathered crude oil. The indigenous microbial population in the contaminated sand was tested alone (control treatment) or in combination with inorganic nutrients (KNO3 and K2HPO4) to investigate their effects on oil biodegradation rates. In addition, the ability of biosurfactants (rhamnolipids), in the presence of organic nutrients (uric acid and lecithin), to further stimulate biodegradation was investigated in laboratory microcosms over a 45-day period. Biodegradation was tracked by GC/MS analysis of aliphatic and polycyclic aromatic hydrocarbons components and the measured concentrations were corrected for abiotic removal by hopane normalizations. It was found that the saturated fraction of the residual oil is degraded more extensively than the aromatic fraction and the bacterial growth after an incubation period of approximately 3 weeks was much greater from the bacterial growth in the control. The results show that the treatments with inorganic or organic nutrients are equally effective over almost 30 days where C12-C35n-alkanes were degraded more than 97% and polyaromatic hydrocarbons with two or three rings were degraded more than 95% within 45 days. The results clearly show that the addition of nutrients to contaminated beach sand significantly enhanced the activity of indigenous microorganisms, as well as the removal of total recoverable petroleum hydrocarbons (TRPH) over a 45-day study period.

Accurate determination of aromatic groups in heavy petroleum fractions using HPLC-UV-DAD

The purpose of this work is to identify specific aromatic component groups in heavy petroleum fractions based on their elution times and UV spectrum patterns using high performance liquid chromatography with ultraviolet diode array detection (HPLC-UV-DAD). Multivariate statistical methods such as evolving factor analysis and k-means clustering were used to interpret the signal obtained from the analysis of gas oil samples, in which strong overlapping of the eluting aromatic component groups occurs. The presented method allows the precise determination of the elution profiles of a series of aromatic component groups and therefore can be applied for their accurate quantitative determination.

Microcosm evaluation of autochthonous bioaugmentation to combat marine oil spills

Oil spills can be disastrous to any ecosystem. Bioremediation through bioaugmentation (addition of oil-degrading bacteria) and biostimulation (addition of nutrients N&P) options can be a promising strategy for combating oil spills following first response actions. However, bioaugmentation is one of the most controversial issues of bioremediation since nutrient addition alone has a greater effect on oil biodegradation than the addition of microbial products that are highly dependent on environmental conditions. There is increasing evidence that the best way to overcome the above barriers is to use microorganisms from the polluted area, an approach proposed as autochthonous bioaugmentation (ABA) and defined as the bioaugmentation technology that uses exclusively microorganisms indigenous to the sites (soil, sand, and water) to be decontaminated. In this study, we examined the effectiveness of an ABA strategy for the successful remediation of polluted marine environments. A consortium was enriched from seawater samples taken from Elefsina Gulf near the Hellenic Petroleum Refinery, a site exposed to chronic crude oil pollution. Pre-adapted consortium was tested alone or in combination with inorganic nutrients in the presence (or not) of biosurfactants (rhamnolipids) in 30-day experiments. Treatment with fertilizers in the presence of biosurfactants exhibited the highest alkane and PAH degradation and showed highest growth over a period of almost 15 days. Considering the above, the use of biostimulation additives in combination with naturally pre-adapted hydrocarbon degrading consortia has proved to be a very effective treatment and it is a promising strategy in the future especially when combined with lipophilic fertilizers instead of inorganic nutrients. Such an approach becomes more pertinent when the oil spill approaches near the shoreline and immediate hydrocarbon degradation is needed.

Stratigraphic evolution and source rock potential of a Lower Oligocene to Lower–Middle Miocene continental slope system, Hellenic Fold and Thrust Belt, Ionian Sea, northwest Greece

The Western flanks of the Hellenic Fold and Thrust Belt are similar to the nearby prolific Albanian oil and gas provinces, where commercial volumes of oil have been produced. The Lower Oligocene to Lower–Middle Miocene slope series at this part of the Hellenic Fold and Thrust Belt provides a unique opportunity to evaluate the anatomy and source rock potential of such a system from an outcrop perspective. Slope progradation is manifested as a vertical pattern exhibiting an increasing amount of sediment bypass upwards, which is interpreted as reflecting increasing gradient conditions. The palaeoflow trend exhibits a western direction during the Late Oligocene but since the Early Miocene has shifted to the East. The occurrence of reliable index species allowed us to recognize several nannoplankton biozones (NP23 to NN5). Organic geochemical data indicate that the containing organic matter is present in sufficient abundance and with good enough quality to be regarded as potential source rocks. The present Rock-Eval II pyrolytic yields and calculated values of hydrogen and oxygen indexes imply that the recent organic matter type is of type III kerogen. A terrestrial origin is suggested and is attributed to short transportation distance and accumulation at rather low water depth. The succession is immature with respect to oil generation and has not experienced high temperature during burial. However, its eastern down-slope equivalent deep-sea mudstone facies should be considered as good gas-prone source rocks onshore since they may have experienced higher thermal evolution. In addition, they may have improved organic geochemical parameters because there is no oxidization of the organic matter.

A novel approach for the characterization of aromatics in petroleum fractions using HPLC-UV-DAD and evolving factor analysis

The scope of this work is to investigate the applicability of the evolving factor analysis (EFA) in the characterization of the non-saturated fraction of petroleum mixtures by high performance liquid chromatography coupled with UV diode array detection (HPLC-UV-DAD). The EFA was used to interpret the signal obtained from the analysis of fluids, the aromatic peaks of which overlap to a great extent. It is shown that the method can precisely define the elution profile of each one of the constituents and determine the start and the end elution times of the main aromatic hydrocarbon groups based on their differences in the spectrum pattern. In addition, the method gives the UV spectra of the eluting constituents which can be further employed for the compositional characterization of the aromatic part of oil fractions.

Identifying Sources of Oil Spills in a Refinery by Gas Chromatography and Chemometrics: A Case Study

The aim of this study was the characterization of samples of petroleum spills that were derived from the oily free-phase zone in the subsurface of a petroleum refinery and the identification of the leakage origin. Principal component analysis and k-means clustering were applied on a simplified and easily obtained gas chromatographic data set. It was established that these methods are capable of discriminating among samples that exhibit similar composition and of identifying the refinery fractions that exist in the spills. The proposed methodology can be employed as a rapid and reliable screening tool in environmental studies dealing with oil spills, where mixed sources of leakage are expected.

The Production of Activated Carbons Using Greek Lignites by Physical and Chemical Activation Methods: A Comparative Study

Abstract Twenty-six lignite samples, from eleven different basins of Greece, were examined as a precursor material to produce activated carbons. Two different experimental procedures were compared, a physical one, using CO2 as the activation agent after carbonization in N2, and a chemical one where lignites impregnated with KOH were thereafter activated. Raw materials and activated products were characterized using a variety of analytical techniques, including ultimate, proximate analysis, and X-ray diffraction. Specific surface areas and pore size distributions were also determined by means of liquid nitrogen isotherms. It was found that the obtained surface area and texture of the activated lignites depend mainly on the nature of the precursor material. The inorganic content had a negative effect on the developed surface area and the pore volume of the CO2 activated carbons. This effect was minor for the KOH activated samples, due to leaching reactions. Regardless of the activation procedure, the samples exhibited a quite similar pore texture consisting of narrow micropores and narrow mesopores. Especially for the KOH activated carbons, the mesopores occupied the higher portion of the total pore volume.

THE INFLUENCE OF PRESSURE ON THE ASPHALTENES CONTENT AND COMPOSITION IN OILS

The objective of this work was to investigate the effect of pressure on the concentration of the dissolved asphaltenes in a heavy oil. The asphaltenes content was determined in oil samples, produced at reservoir temperature and different pressures ranging from the initial reservoir pressure to the atmospheric one, using the standard IP143/90 method. Additionally, the content of nine trace metals in the asphaltenes, produced at each pressure step was studied by Total Reflection X-Ray Fluorescence (TXRF). It was found that the amount of the dissolved asphaltenes in oil decreases as pressure falls from the initial reservoir pressure down to bubble point pressure and subsequently increases as the pressure is reduced further. A positive correlation was observed between the concentration of several metals (Ni, V, Cr, Mn) and the dissolved asphaltenes content.

Hydrocarbon prospectivity in the Hellenic trench system: organic geochemistry and source rock potential of upper Miocene–lower Pliocene successions in the eastern Crete Island, Greece

Abstract Results of the current and already published studies suggest that the Tortonian in age deposits could serve a major source rocks (for both oil and gas) beneath the Messinian evaporites in the Hellenic trench system. Additionally, the strong terrestrial input in Pliocene deposits could lead to the production of biogenic gas, similar to the Po basin in Adriatic Sea (Italy). In the current study, fourteen samples from late Miocene Faneromeni section and twelve samples from the early Pliocene Makrilia section in eastern Crete were collected in order to evaluate their hydrocarbon generation potential. For this purpose, Rock-Eval analysis and characterization of the organic matter were performed. The results document a clear distinction between the two sections. Faneromeni section contains organic matter of kerogen type III, whereas the Makrilia section contains organic matter of kerogen type IV. The HI/TOC plot diagram, in both sections, indicates poor oil generating potential, with the exception of several samples showing fair to good gas and oil potential. Although thermal maturities of the samples from the two successions are similar, according to the Tmax values, samples from Faneromeni succession exhibit higher hydrogen index values, indicating a better quality of organic matter in terms of hydrocarbon generation. Very low obtained concentrations of bitumen (mg/g of rock), as well as the predominance of NSO compounds, compared to the saturates and aromatics, indicate low maturation level. The n-alkanes profiles exhibit a bimodal distribution, indicating a mixed origin (marine and terrestrial) of the organic matter in both areas. Terrestrial organic matter input is more pronounced in Makrilia section. The analysis of saturated biomarkers indicates that Faneromeni deposits were accumulated under constant organic matter input in an environment influenced by cyclic changes (from marine to lagoon origin and vice versa). Faneromeni section corresponds to a restricted basin during Tortonian, with quick and often sea-level fluctuations just before the Messinian crisis, while Makrilia section represents a very restricted intramontane basin with strong terrestrial influence.