Decrease In Hydrocarbon Concentration Research Articles

Hydrocarbons in the Suspension and Sediments of the Baltic Sea

The article gives the results of studying the concentration and composition of aliphatic and polycyclic aromatic hydrocarbons in suspension in surface waters at sections from the English Channel and Skagerak Strait to various regions of the Baltic Sea (2010–2015) and in water and bottom sediments of the southeastern part of the sea in the water area of the Kravtsovskoe field (2008–2015). In recent years, the surface waters of open areas of the Baltic Sea showed a decrease in hydrocarbon concentrations down to background levels (12–33 μg/L). The maximal concentration of hydrocarbons (in excess of the MAC) was recorded in different seasons in navigation areas, including the English Channel and Pregola R. mouth. In the zone of the Kravtsovskoe field, the concentration and composition of hydrocarbons in water depends on their inflow from the bank, and the same characteristics in bottom sediments, on the rate of their leakage from sediment stratum. A decline in these processes have led to a decrease in hydrocarbon concentrations in the sediments of a local area near D-6 platform to background levels (5–7 μg/g) and to the predominance of terrigenous, rather than petroleum, alkanes in hydrocarbon compositions.

Respiratory quotients as a useful indicator of the enhancement of petroleum hydrocarbon biodegradation in field-aged contaminated soils in cold climates

The Respiration Quotient (RQ) is a substrate-dependent respiration indicator. The determination of RQ-values from soil gas data obtained during the bioremediation of contaminated soils provides useful information about whether or not microbial respiration activity is specific to the microbial degradation of contaminants. Less attention has been paid to the uses of RQ-values for petroleum hydrocarbon-contaminated cold-climate soils under a wide range of low temperature regimes including sub-zero temperatures. In this study, RQ-values were determined for biotreated petroleum hydrocarbon-contaminated soils shipped from two cold-region sites and were validated using pilot-scale aerobic bioremediation experiments with various soil treatments, low temperature regimes and soil types. The RQ-values (0.57 to 0.78), empirically determined from CO2 and O2 in soil gas, were consistently close to the theoretical RQ-values for target hydrocarbon fractions (0.65–0.8) only when the decrease in hydrocarbon concentration was statistically significant in the biotreated soils. In addition to the RQ-values, a strong linearity was observed in the RQ plots for CO2 production and O2 consumption, but only for the soils in which hydrocarbon biodegradation activity was significantly enhanced. Using confirmed hydrocarbon and microbial data for the occurrence of hydrocarbon biodegradation, the RQ plot characteristics (RQ-values and linearity) proved to be considerably relevant to hydrocarbon biodegradation. Due to the substrate-dependency of the RQ-values, conventional soil gas monitoring activities involved in the bioremediation and management of contaminated soils at remote cold sites can be more effective and meaningful by indicating enhanced microbial activity specific to petroleum hydrocarbon biodegradation.

Microbial Community Analysis of a Coastal Salt Marsh Affected by the Deepwater Horizon Oil Spill

Coastal salt marshes are highly sensitive wetland ecosystems that can sustain long-term impacts from anthropogenic events such as oil spills. In this study, we examined the microbial communities of a Gulf of Mexico coastal salt marsh during and after the influx of petroleum hydrocarbons following the Deepwater Horizon oil spill. Total hydrocarbon concentrations in salt marsh sediments were highest in June and July 2010 and decreased in September 2010. Coupled PhyloChip and GeoChip microarray analyses demonstrated that the microbial community structure and function of the extant salt marsh hydrocarbon-degrading microbial populations changed significantly during the study. The relative richness and abundance of phyla containing previously described hydrocarbon-degrading bacteria (Proteobacteria, Bacteroidetes, and Actinobacteria) increased in hydrocarbon-contaminated sediments and then decreased once hydrocarbons were below detection. Firmicutes, however, continued to increase in relative richness and abundance after hydrocarbon concentrations were below detection. Functional genes involved in hydrocarbon degradation were enriched in hydrocarbon-contaminated sediments then declined significantly (p<0.05) once hydrocarbon concentrations decreased. A greater decrease in hydrocarbon concentrations among marsh grass sediments compared to inlet sediments (lacking marsh grass) suggests that the marsh rhizosphere microbial communities could also be contributing to hydrocarbon degradation. The results of this study provide a comprehensive view of microbial community structural and functional dynamics within perturbed salt marsh ecosystems.

Psychrotolerant hydrocarbon-degrading Rhodococcus strains isolated from polluted Antarctic soils

Three hydrocarbon-degrading Rhodococcus strains isolated from polluted Antarctic soils proved to be closely related despite their different origins. Strains had a similar hydrocarbon degradation pattern and optimum growth temperature ranged between 25ºC and 30ºC, showing that strains are psychrotolerant but not psychrophiles. Specific growth rate on rich media ranged between 0.12 and 0.21 h−1, higher than those observed on hydrocarbons as carbon source. Results suggest that in Antarctic contaminated soils, closely related Rhodococcus strains are present and could play an important role in decontamination. Microcosm systems showed that, although the natural microflora respond significantly to the pollutants, bioaugmentation with Rhodococcus strain (ADH), improved biodegradation either alone or mixed with a hydrocarbon-degrading Acinetobacter strain. In comparison with microcosm where only ADH was inoculated, a non-significant decrease in hydrocarbon concentration was observed when ADH was inoculated as mixed culture with a previously tested strain. Pollutants dramatically reduced bacterial groups in soils resulting in a dominance of Pseudomonas. Microcosms showed that when natural microflora has no previous history of exposure to the pollutants, bioaugmentation with autochthonous strains improves degradation of the contaminants. The positive response of the native bacteria to the pollutants leaves the question open as to whether bioaugmentation is necessary when soils have a long previous exposure to hydrocarbons.

The biodegradation efficiency on diesel oil by two psychrotrophic Antarctic marine bacteria during a two-month-long experiment

Two psychrotrophic bacterial strains isolated from Antarctic seawaters were investigated for their capability to degrade commercial diesel oil. The efficiency of hydrocarbon utilization was studied at 4 and 20 °C over a period of two-months. Strains were cultured in a mineral liquid medium supplemented with diesel oil as the sole source of carbon and energy. The viable counts for the bacterial abundance estimation and the culture extractions for the subsequent gas-chromatographic analysis were carried out simultaneously. The biodegradation efficiency was higher at 20 °C than at 4 °C for both strains and the decrease in hydrocarbon concentrations reached more than 85% after 60 days of incubation at 20 °C. Our results suggest the possible exploitation of these two bacterial strains in future biotechnological processes, directly as field-released micro-organisms both in cold and temperate contaminated marine environments.

Origin and effect of impurity incorporation in plasma-enhanced ZrO2 deposition

The origin of impurity incorporation in the ZrO2 films deposition by plasma-enhanced chemical vapor deposition with Ar-carried zirconium t-butoxide (ZTB) and O2 was delineated by optical emission spectroscopy, quadrupole mass spectrometry, transmission Fourier transform infrared spectroscopy, and x-ray photoelectron spectroscopy. Hydrocarbons were the predominant contaminants in films obtained with only ZTB in the plasma, while their fractions decreased rapidly with the increasing O2 to ZTB-carrying Ar flow rate ratio (O2/Ar), and eventually became negligible in the oxygen-rich condition at O2/Ar⩾2. However, the increasing amount of oxygen led to the formation of hydrogen carbonate and formate from CO chemisorption at O2/Ar=0.5 to mostly bidentate carbonate from CO2 chemisorption at O2/Ar=2. The films from all conditions contained a significant amount of hydrogen-bonded hydroxyl groups. At higher O2/Ar ratios, the decrease in hydrocarbon concentration and the increase in carbonate fractions resulted in the increase in the dielectric constant and the negative oxide trapped charges.

Biotreatment of Flare Pit Waste

Abstract The upstream oil and gas industry has used flare pits (FPs) for decades to store and/or burn produced fluids generated at well sites, compressor stations, and batteries. Since produced fluids contain liquid hydrocarbons, process chemicals, crude bitumen, or salt water, FPs usually contain high levels of hydrocarbons, metals, and salts. At present, bioremediation by land application is the most common method practiced by the oil and gas industry to treat FP waste. High rate slurry-phase and solid-phase biotreatment methods are viable alternatives to the low cost, yet inefficient, land application option. The use of slurry-phase and solid-phase biotreatment in the overall strategy for FP waste remediation is reported in this paper. A laboratory solid-phase bioremediation study was conducted over a period of 270 days to investigate the effects of nitrogen, phosphorus, salinity levels, and incubation temperature on the biodegradation of hydrocarbons in FP pit waste employing a statistical partial factorial experimental design. A soil contaminated with flare pit hydrocarbons was treated with nitrogen (500, 1,250, or 2,000 mg/kg of soil), phosphorus (100, 250, or 400 mg/kg of soil), and salt (yielding electrical conductivities of 0, 20, or 40 dS/m), and incubated at three temperatures (20 °, 30 °, and 40 °C). The highest oil and grease (O&amp;G) reduction of 34% was observed in the soils incubated at 30 °C. Soil temperature had more influence on bioremediation rates than did N or P. The high P levels, up to 400 mg P/kg soil, had no detrimental effect on hydrocarbon biodegradation. High salinity levels reduced the rate of hydrocarbon biodegradation. The slurry-phase biotreatment of flare pit waste using 2 L slurry reactors showed an initial rapid decrease in hydrocarbon concentrations. However, biodegradation decreased with time and eventually ceased, leaving recalcitrant compounds. The nutrient concentrations (above 350 mg N/L, as ammonium nitrogen) did not exhibit statistically significant effects on hydrocarbon degradation. The primary effect of waste composition was highly significant, with higher soil clay content resulting in lower biodegradation. Introduction The produced fluids generated at oil and gas well sites, compressor stations, and batteries contain a variety of liquid hydrocarbons, process chemicals, crude bitumen, and salt water. Until recently, the industry practice was to store and intermittently burn these produced fluids in earthen pits called "flare pits." According to recent estimates, Alberta is home to about 30,000 flare pit (FP) sites(1). In 1996, the provincial government of Alberta banned the disposal of produced fluids in FPs, and requested the oil and gas industry to remediate former FP sites that are posing significant risks to human health and the surrounding environment. Because of the highly complex and variable nature of the waste, remediation of FP waste presents a serious challenge. At present, the most common technique used for remediation of FP sites is bioremediation by land application. Land application is relatively low-tech and less expensive (compared with competing techniques such as incineration). Furthermore, land application is popular in locations such as rural Alberta, because of the nature of the spatial distribution of FP sites.

Relations between Light Hydrocarbon, Carbon Monoxide, and Carbon Dioxide Concentrations in the Plume from the Combustion of Plant Material in a Furnace

To systematically explain relations between light hydrocarbons, CO, and CO2 concentrations/emissions of biomassburning, we measured concentrations/emissions of carbon gases – CO,CO2, light hydrocarbons (CH4, C2H6,C2H4, C2H2, C3H8, C3H6,n-C4H10, i-C4H10, n-C5H12,i-C5H12), and THC (total hydrocarbon) – in the burning of dead plant material, mainly Imperata grass, byclosed-chamber experiments and by time-series analyses of gas concentrations in combustion plumes in relatively efficient and inefficient combustion situations. Concentrations of hydrocarbons measured were well correlated to [CO] although [C2H2] was exceptionally well correlated to[CO2]. The phase diagrams (relation between [CO]/Δ [CO2] and [hydrocarbon]/Δ [CO2]) obtained by the time-seriesexperiments well illustrated the variation in the overall emission rates of the closed-chamber experiments. The higher rates of decrease in hydrocarbon concentration with increasing carbon number in the efficient case compared with the inefficient case probably reflected the rate of oxidation and the amount of radicals. The overall concentrations (or emissions) of C2H4 and C3H6 were higher thanthose of C2H6 and C3H8, suggesting a linkage to mechanisms in whichthe predominant path of hydrocarbon oxidation is through the degradation of alkyl radicals, which can be immediately converted into or formed from alkenes. For C3 and C4 species, normal-chain species hadhigher emissions than iso-chain species under lower combustion efficiency. This may be attributable to the presence of tertiary C–H bonds in iso-species,which show more reactivity in the abstraction of H than secondary C–H bonds unless the carbon number is large.

Measurements of ozone and nonmethane hydrocarbons at Chichi-jima island, a remote island in the western Pacific: long-range transport of polluted air from the Pacific rim region

Chichi-jima island is located in the Pacific about 1000 km from the Japanese main island and is an ideal remote observatory from which to assess the long-range transport of polluted air from East Asia. The ozone concentration was measured from August 1997 to August 1998. Owing to the air mass change, the seasonal variation of ozone shows a distinct character: low concentration (about 13 ppbv) for the maritime air mass during the summer, and high concentration (about 40 ppbv) for the continental air mass during the winter. To assess the contribution of the long-range transport of polluted air during winter, nonmethane hydrocarbons were also measured in December 1999. Using backward trajectory analysis, the transport time of the air mass from the source area in the Pacific rim region was calculated for each sample. The concentration of hydrocarbons shows a clear negative correlation against the transport time. This analysis clearly shows the transport of polluted air, emitted in East Asia, to the Pacific during the winter. The plots of suitable hydrocarbon pairs showed that the decrease of hydrocarbon concentrations during winter is mainly caused by the mixing with clean background air.

Artificial Wetland Performances in the Purification Efficiency of Hydrocarbon Wastewater

An artificial wetland planted with Typha latifolia was fed during a 360-day experiment with a reconstituted hydrocarbon wastewater (60 ppm, 850 L day−1). Concentrations and chemical composition were periodically monitored. The epuration efficiency was studied together with the accumulation in sediment and the bacterial development. The apparent effluent concentration was below 8 mg L−1 and the decrease in hydrocarbon concentration raised 90%. pH ranged between 6.9 and 8 and Total Suspended Solids (TSS) were below 10 mg L−1. Hydrocarbon amount accumulated in sediment was estimated to be less than 10% of the input amount. We observed a high development of aerobic heterotrophic bacteria (106 bac mL−1) and hydrocarbon-utilizing bacteria (105 bac mL−1), which probably interacted with the plants for the biodegradation of hydrocarbon (in the saturated effluent fraction, normal alkane biodegradation amounted to approximatively 80%). A comparative system with floating plants (Lemma minor), named ‘control bed’, was studied in parellel and showed lower performances.

Microbial degradation in soil microcosms of fuel oil hydrocarbons from drilling cuttings: C. H. Chaineau, J.-L. Morel & J. Oudot, Environmental Science & Technology, 29(6), 1995, pp 1615–1621

The biodegradation of the fuel oil hydrocarbons contained in drilling cuttings was studied in soil microcosms during a 270-day experiment. Concentration and chemical composition of residual hydrocarbons were periodically monitored by quantitative capillary gas chromatography. The decrease in hydrocarbon concentration was logarithmic with time. At the end of the experiment, the fuel oil was 75% degraded. In the saturated fraction, normal and branched alkanes were almost totally eliminated in 16 days ; 22% of the cycloalkanes were not assimilated. The aromatic fraction was 71% degraded ; some polycyclic aromatics were persistent. The resin fraction (10% of the initial weight) was completely refractory to biodegradation. The inorganic part of drilling cuttings had no influence on the biodegradation rates of hydrocarbons. Biogenic hydrocarbons and traces of degradable fuel oil hydrocarbons were protected from microbial activity by the soil and cuttings matrix. Enumerations of total heterotrophic bacteria and hydrocarbon-utilizing bacteria showed a strong stimulation in both populations. Hydrocarbon-degrading strains of bacteria and fungi were isolated and identified at the generic or specific level.

Microbial Degradation in Soil Microcosms of Fuel Oil Hydrocarbons from Drilling Cuttings

The biodegradation of the fuel oil hydrocarbons contained in drilling cuttings was studied in soil microcosms during a 270-day experiment. Concentration and chemical composition of residual hydrocarbons were periodically monitored by quantitative capillary gas chromatography. The decrease in hydrocarbon concentration was logarithmic with time. At the end of the experiment, the fuel oil was 75% degraded. In the saturated fraction, normal and branched alkanes were almost totally eliminated in 16 days ; 22% of the cycloalkanes were not assimilated. The aromatic fraction was 71% degraded ; some polycyclic aromatics were persistent. The resin fraction (10% of the initial weight) was completely refractory to biodegradation. The inorganic part of drilling cuttings had no influence on the biodegradation rates of hydrocarbons. Biogenic hydrocarbons and traces of degradable fuel oil hydrocarbons were protected from microbial activity by the soil and cuttings matrix. Enumerations of total heterotrophic bacteria and hydrocarbon-utilizing bacteria showed a strong stimulation in both populations. Hydrocarbon-degrading strains of bacteria and fungi were isolated and identified at the generic or specific level.

Hydrogeological Investigation of Hydrocarbon Contamination of Ground Water in Albolote (Granada, Spain)

AbstractIn July 1988, hydrocarbons were detected in wells in the urban area of Albolote, near Granada, Spain, near the border of the “Vega de Granada” alluvial aquifer. According to available hydrogeological data, the contamination was attributed to leaks in the underground pipelines of a nearby (300m) industrial factory, where the loss of 40,000 to 50,000 liters of gasoline had been detected some weeks before. A complete hydrogeological investigation was then undertaken, involving, among other techniques: (a) an inventory of the existing wells in the area; (b) the preparation of piezometric maps; (c) the application of electrical geophysical methods; (d) the drilling of piezometers and new pumping wells between the urbanized area and the leak point; (e) the improvement of the pluviometric and piezometric control by the installation of a pluviograph and several limnigraphs; (f) the sampling, initially daily and finally weekly, in a 20‐well observation network, also used for piezometric control; and (g) the geostatistical study of the analytical data. The contamination plume, extended in the direction of the flow lines, has a length of 500m and a width of less than 50m, and appears to have occurred mainly in a paleochannel. Hydrocarbons (1600 liters) were recovered by pumping and by using absorbent blankets, as well as by a gas and liquid suction method. Hydrocarbon concentrations have continuously decreased. However, sporadic increases, associated with rainfall, have been observed suggesting the presence of retained hydrocarbons in the unsaturated zone. The rate of decrease in hydrocarbon concentrations has currently slowed, particularly in the less affected zone. As a means of activating the cleaning up of the unsaturated zone, an artificial recharging method has been designed.

COMPOSITIONAL CHANGES IN DISPERSED CRUDE OIL IN THE WATER COLUMN DURING A NEARSHORE TEST SPILL

ABSTRACT As part of the American Petroleum Institute sponsored tidal area dispersant project involving two test spills of Murban crude oil in Long Cove, Searsport, Maine in August, 1981, water samples were collected. This paper deals with the analytical results for the analyses of water samples collected for analysis of non-volatile hydrocarbons by: infrared spectrophotometric quantitation of total CCl4 extractables, and gravimetric analysis of aliphatic and aromatic hydrocarbon fractions followed by capillary gas chromatography. In the dispersant-treated oil discharge area, there were two primary water sampling locations during the discharge phase of the experiment: an upper intertidal area (maximum depth = 2 meters) and a lower intertidal area (maximum depth = 3.5 meters). The gas chromatographic data for the water samples were treated numerically to obtain parameters whose values reflect the extent of dispersed oil weathering. For the aliphatics, the peak area ratio for n C14/n C18 was calculated for each sample. For the aromatics, the ratio for the peak area sum of the mono, di, and trimethyl naphthalenes to that for the mono, di, tri, and tetramethyl dibenzothiophenes was determined for each sample. At both sampling locations, dispersed oil in water sampled 10 cm off the bottom consistently had a smaller fraction of lower boiling aliphatic and aromatic hydrocarbons than water sampled at the same place and the same time ½ meter below the surface. In addition, the data show that there is a 12–50 fold decrease in hydrocarbon concentration on going from near surface to near bottom at any given time, even in water as shallow as 2 meters. The data indicate that the primary mechanism for hydrocarbon loss involves volatilization of hydrocarbon fractions. Analyses of water samples taken from submerged plumes of dispersed oil outside the sampling areas demonstrated slower loss of low boiling components consistent with the importance of atmospheric exchange in the weathering process. In the chemical dispersal of an oil spill, it may be most advantageous to use mixing methods that minimize vertical mixing in order to maintain a high concentration of emulsified oil in the upper ½ meter water layer. This will maximize the extent of loss of lower boiling hydrocarbon components into the atmosphere and thus minimize the toxicity of any dispersed oil fractions that diffuse downward and interact with benthic communities.