Enhanced biodegradation of creosote-contaminated soil

Bioremediation, a viable option for treatment of cresote-contaminated soil, can be enhanced by the use of surfactant. A study was conducted to investigate the effect of a non-ionic surfactant, Triton X-100, on biodegradation of creosote-contaminated soil. Abiotic soil desorption experiments were performed to determine the kinetics of release of selected polynuclear aromatic hydrocarbon (PAH) compounds. Respirometric experiments were also conducted to evaluate the effect of nonionic surfactant on biodegradation. The N-Con system respirometer was used to monitor the oxygen uptake by the microorganisms. The abiotic experiments results indicated that the addition of surfactant to soil/water systems increased the desorption of PAH compounds. It was also observed that the desorption rate of PAH compounds depended on their molecular weight. The 3- and 4-ring PAH compounds showed higher and faster desorption rates than the 5- and 6-ring PAHs. The respirometric experiments indicated that an increase in soil contamination level from 112.5 to 771.8 mg/kg showed an increase in oxygen uptake. But for a soil contamination level of 1102.5 mg/kg, the oxygen uptake was similar to the contamination level of 771.8 mg/kg. This might be due to toxicity by the surfactant or the solubilized PAHs at high concentration or interference with contaminant transport into the cell or to reversible physical-chemical interferences with the activity of enzymes involved in the PAH degradation. The increase in PAH availability to the microorganisms in the aqueous phase produced an increase in oxygen consumption that is proportional to the biodegradation of organic compounds.     

Biodegradation of Crude Oil Contaminating Marine Shorelines and Freshwater Wetlands

This paper is a summary of the various factors influencing weathering of oil after it has been released into the environment from a spill incident. Special emphasis has been placed on biodegradation processes. Results from two field studies conducted in 1994 and 1999 involving bioremediation of an experimental oil spill on a marine sandy shoreline in Delaware and a freshwater wetland on the St. Lawrence River in Quebec, Canada have been presented in the paper.     

Oil uptake and depuration in oysters after use of dispersants in shallow water in El Salvador

Dispersants were used in shallow water (4–6 m) and in the surf zone at a small spill (400 bbls) of Venezuelan Recon at the port of Acajutla, El Salvador in June 1994. Subtidal oysters were collected 1 and 4 weeks post-spill to determine the degree of exposure of benthic resources to the dispersed oil. Two samples of oysters from the area of dispersed oil contained total PAHs of 147 and 164 ppm, dry weight, compared with background levels less than 1.0 ppm. Four weeks post-spill, PAH levels decreased by 94–98%. Half-lives for individual PAH compounds were estimated and were generally consistent with results from laboratory experiments. Monitoring of bivalves during dispersant applications can document the areal and vertical extent of dispersed oil in the water column.     

Oil Spill Contingency and Response (OSCAR) Analysis in Support of Environmental Impact Assessment Offshore Namibia

The work reported here encompasses analyses of specific potential spill scenarios for oil exploration activity planned offshore of Namibia. The analyses are carried out with the SINTEF Oil Spill Contingency and Response (OSCAR) 3-dimensional model system. A spill scenario using 150 m³ of marine diesel demonstrates the rapidity with which such a spill will dissipate naturally, even in light winds. Vertical and horizontal mixing bring subsurface hydrocarbon concentrations to background levels within a few days. A hypothetical 10 day blowout scenario releasing 11,000 bbl per day of light crude oil is investigated in terms of the potential for delivering oil to selected bird and marine mammal areas along the Namibian coast. Worst case scenarios are selected to investigate the potential mitigating effects of planned oil spill response actions. Mechanical recovery significantly reduces, and in some cases eliminates, potential environmental consequences of these worst case scenarios. Dispersant application from fixed wing aircraft further reduces the potential surface effects. The analysis supplies an objective basis for net environmental analysis of the planned response strategies.     

Literature overview: Microbial metabolism of high molecular weight polycyclic aromatic hydrocarbons

High molecular weight polycyclic aromatic hydrocarbons (HMW PAHs) increase in hydrophobicity with increases in their molecular weight and ring angularity. Microbial strategies to deal with PAH hydrophobicity include biofilm formation, enzyme induction, and biosurfactants, the effect of which is variable on PAH metabolism depending on the surfactant type and concentration, substrate, and microbial strain(s). Aerobic HMW PAH metabolism proceeds via mineralization, partial degradation, and cometabolic transformations. Generally, bacteria and nonlignolytic fungi metabolize PAHs via initial PAH ring oxidation by dioxygenases to form cis‐dihydrodiols, which are transformed to catechol compounds by dehydrogenases and other mono‐ and dioxygenases to substituted catechol and noncatechol compounds, all ortho‐ or metacleaved and further oxidized to simpler compounds. However, lignolytic fungi form quinones and acids to CO₂. This review discusses the pathways for HMW PAH microbial metabolism. © 2008 Wiley Periodicals, Inc.     

Stochastic Modeling Concepts in Groundwater and Risk Assessment: Potential Application to Marine Problems

Parameter uncertainty is ubiquitous in marine environmental processes. Failure to account for this uncertainty may lead to erroneous results, and may have significant environmental and economic ramifications. Stochastic modeling of oil spill transport and fate is, therefore, central in the development of an oil spill contingency plan for new oil and gas projects. Over the past twenty years, several stochastic modeling tools have been developed for modeling parameter uncertainty, including the spectral, perturbation, and simulation methods. In this work we explore the application of a new stochastic methodology, the first-order reliability method (FORM), in oil spill modeling. FORM was originally developed in the structural reliability field and has been recently applied to various environmental problems. The method has many appealing features that makes it a powerful tool for modeling complex environmental systems. The theory of FORM is presented, identifying the features that distinguish the method from other stochastic tools. Different formulations to the reliability-based stochastic oil spill modeling are presented in a decision-analytic context.     

Factors affecting polycyclic aromatic hydrocarbon biodegradation by Aspergillus flavus

This study investigated the ability of fungi isolated from highly contaminated soil to biodegrade polycyclic aromatic hydrocarbon (PAH) compounds, as well as the effect of several parameters on the biodegradation ability of these fungi. The isolated fungi were identified using ITS rDNA sequencing and tested using 2,6‐dichlorophinolendophenol to determine their preliminary ability to degrade crude oil. The top‐performing fungi, Aspergillus flavus and Aspergillus fumigatus, were selected to test their ability to biodegrade PAH compounds as single isolates. After 15 days of incubation, A. flavus degraded 82.7% of the total PAH compounds, with the complete degradation of six compounds, whereas A. fumigatus degraded 68.9% of the total PAHs, with four aromatic compounds completely degraded. We also tested whether different temperatures, pH, and nitrogen sources influenced the growth of A. flavus and the degradation rate. The degradation process was optimal at a temperature of 30°C, pH of 5.5, and with nitrogen in the form of yeast extract. Finally, the ability of the fungal candidate, A. flavus, to degrade PAH compounds under these optimum conditions was studied. The results showed that 95.87% of the total PAHs, including 11 aromatic compounds, were completely degraded after 15 days of incubation. This suggests that A. flavus is a potential microorganism for the degradation of PAH compounds in aqueous cultures.     

Oil/Suspended Particulate Material Interactions and Sedimentation

The interactions of physically dispersed oil droplets with suspended particulate material (SPM) can be important for the transport of bulk quantities of spilled crude oil and polycyclic aromatic hydrocarbons (PAH) to subtidal sediments. The literature regarding oil/SPM interactions is reviewed, and results from whole-oil droplet/SPM interaction kinetics and pure-component (Prudhoe Bay crude oil distillate cut) equilibrium partitioning experiments are presented. The effects of oil type, SPM characteristics, and salinity on the interaction rates are examined, and the importance of whole-oil droplet/SPM interactions on particle agglomeration and settling behavior are discussed. Whole-oil droplet/SPM interactions are retarded as oil droplet dispersion into the water column is inhibited by oil viscosity increases due to evaporation weathering and water-in-oil emulsification. Compared to whole oil droplet/SPM interactions, dissolved-component/SPM adsorption is not as significant for transport of individual components to sediments. The information presented in this paper can be used to augment computer-based models designed to predict oil-spill trajectories, oil-weathering behavior, and spilled oil impacts to the marine environment.     

Current status and challenges of remediating petroleum‐derived PAHs in soils: Nigeria as a case study for developing countries

Polycyclic aromatic hydrocarbons (PAHs) are among the world's most significant environmental organic contaminants because of their carcinogenic properties. PAHs are widely distributed globally as a result of releases from numerous natural and anthropogenic activities. Consequently, several PAH monitoring studies have been conducted and remediation approaches explored. This article aims to provide the current status of PAH distribution in Nigeria's oil and gas industrial region in relation to the technologies adopted for PAH remediation. Ideally, the findings will provide insight into the challenges in managing organic contaminants derived from petroleum exploration activities in developing countries with Nigeria as a case study.     

Water-in-oil emulsion formation: A review of physics and mathematical modelling

A literature review of the physics and modelling of water-in-oil emulsification is presented. The understanding of the physics of emulsion formation is still incomplete, but developing. The formation of emulsions is due to the surfactant-like action of polar compounds (resins) and asphaltenes in oil. These compounds act to maintain small (1–20 μm) droplets of water in oil. Volatile aromatic compounds in crude oils solubilize asphaltenes and resins. Crude oils containing lower quantities of these volatile compounds or BTEX (benzene, toluene, ethylbenzene, xylenes) will form emulsions given sufficient turbulent sea energy. Oils may lose the BTEX component by weathering before being capable of forming stable emulsions. The kinetics and energy of formation of emulsions is not well understood. Emulsions are often reported to form rapidly after the necessary chemical conditions are achieved and where there is significant wave action or other turbulent energy. Oil spill models generally employ a first-order rate law (exponential) to predict emulsion formation.     

The Significance of Oil Spill Dispersants

There is growing acceptance worldwide that use of dispersants to counter the effects of an oil spill offers many advantages and can often result in a net environmental benefit when considered in relation to other response options. A major reason for this growing support and increased reliance on dispersants is the advent of improved dispersant products that are low in toxicity to marine life and more effective at dispersing heavy and weathered oils – oils previously believed to be undispersible. This capability has been demonstrated through extensive laboratory testing, field trials, and dispersant application on actual spills. This paper summarizes recent advances in dispersant R&D and reviews the implications of technology advances.     

Contributions of common sources of polycyclic aromatic hydrocarbons to soil contamination

Asphalt products, particularly sealants, are prepared using petroleum products that contain a com‐plex mixture of aliphatic and aromatic hydrocarbons, including polycyclic aromatic hydrocarbons (PAHs). Clearly, these products are ubiquitous in urban environments, which raises an issue regard‐ing the potential for PAHs to be transported from parking lots to underlying or adjacent soil, surface‐water bodies, or groundwater. Based on a literature review, there are limited studies focus‐ing on this issue; however, the studies that have been published have fascinating conclusions. The literature shows, as expected, that asphalt‐based products contain PAHs. The highest PAH concen‐trations are present in asphalt sealants, particularly those manufactured using coal tar. Furthermore, due to the low solubility and high partition coefficients of PAHs, the potential for PAHs to leach from asphalt surfaces is negligible, which has been confirmed by leachability studies. Thus, there is little risk that PAHs will be present in stormwater runoff or leach into groundwater from asphalt‐paved areas in a dissolved form. However, asphalt pavement and sealants produce particulate matter that can contain concentrations of PAHs in the sub‐percent range (100s to 1,000s mg/kg total PAHs) that is transported in stormwater runoff. Some studies show that this can cause soil and sediment con‐tamination with total PAH concentrations in the range of 1 to 10 mg/kg. From a remediation per‐spective, many site cleanups are conducted to remediate the presence of PAHs to cleanup goals below 1 mg/kg or, in some cases, 0.1 mg/kg or lower. From a total risk perspective, remediating sites to low PAH cleanup goals may be unwarranted in light of the risk of transportable PAHs produced from paved parking surfaces. In other words, is it reasonable to conduct a cleanup to remediate low PAH concentrations and then redevelop the area with asphalt pavement and sealant, which may pose a greater PAH‐related risk? © 2006 Wiley Periodicals, Inc.     

溢油监测技术在石油石化企业环境风险防控中的应用

针对石油石化企业的溢油风险,提出企业在厂区雨水系统、外排口、涉水生产设施、环境敏感受体、溢油事故应急处置5类场景下的溢油监测需求,总结了溢油监测技术的类型和特点,介绍了可见光、红外、紫外、荧光、高光谱、微波辐射、雷达、电磁能量吸收等溢油监测技术的应用现状和优缺点。提出:企业溢油监测系统可分为企业内部溢油风险分级管控监测、企业边界的溢油风险报警监测、敏感环境监视的风险预警监测、溢油事故应急救援的溢油处置监测4个层次的运行模式。     

Oil and water separation in marine oil spill clean-up operations

This paper discusses the changes in spilled oil properties over time and how these changes affect differential density separation. It presents methods to improve differential density, and operational effectiveness when oil-water separation is incorporated in a recovery system. Separators function because of the difference in density between oil and seawater. As an oil weathers this difference decreases, because the oil density increases as the lighter components evaporate. The density also increases as the oil incorporates water droplets to form a water-in-oil emulsion. These changes occur simultaneously during weathering and reduce the effectiveness of separators. Today, the state-of-the-art technologies have limited capabilities for separating spilled marine oil that has weathered.For separation of emulsified water in an emulsion, the viscosity of the oil will have a significant impact on drag forces, reducing the effect of gravity or centrifugal separation. Since water content in an emulsion greatly increases the clean up volume (which can contain as much as two to five times as much water as the volume of recovered oil), it is equally important to remove water from an emulsion as to remove free water recovered owing to low skimmer effectiveness. Removal of both free water and water from an emulsion, has the potential to increase effective skimming time, recovery effectiveness and capacity, and facilitate waste handling and disposal. Therefore, effective oil and water separation in marine oil spill clean-up operations may be a more critical process than credited because it can mean that fewer resources are needed to clean up an oil spill with subsequent effects on capital investment and basic stand-by and operating costs for a spill response organization.A large increase in continuous skimming time and recovery has been demonstrated for total water (free and emulsified water) separation. Assuming a 200 m³ storage tank, 100 m³ h⁻¹ skimmer capacity, 25% skimmer effectiveness, and 80% water content in the emulsion, the time of continuous operation (before discharge of oil residue is needed), increases from 2 to 40 h and recovery of oil residue from 10 to 200 m³.Use of emulsion breakers to enhance and accelerate the separation process may, in some cases, be a rapid and cost effective method to separate crude oil emulsions. Decrease of water content in an emulsion, by heating or use of emulsion breakers and subsequent reduction in viscosity, may improve pumpability, reduce transfer and discharge time, and can reduce oily waste handling, and disposal costs by a factor of 10. However, effective use of emulsion breakers is dependant on the effectiveness of the product, oil properties, application methods and time of application after a spill.     

Effects of physicochemical factors on PAH degradation by Planomicrobium alkanoclasticum

Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants that are mutagenic, carcinogenic, and toxic to living organisms. Here, the ability and effectiveness of selected bacteria isolated from an oil‐contaminated area in biodegrading PAHs were evaluated, and the optimal conditions conducive to bacterial PAH biodegradation were determined. Of six bacterial isolates identified based on their 16S rRNA sequences, Planomicrobium alkanoclasticum could subsist on and consume nearly all hydrocarbons according to the 2,6‐dichlorophenolindophenol assay. The efficacy of this isolate at PAH biodegradation was then empirically confirmed. After 30 days of incubation, P. alkanoclasticum degraded 90.8% of the 16 PAH compounds analyzed and fully degraded eight of them. The optimum P. alkanoclasticum growth conditions were 35°C, pH 7.5, and NaNO₃ as the nitrogen source. Under these biostimulant conditions, P. alkanoclasticum degraded 91.4% of the total PAH concentration and completely decomposed seven PAHs after 15 days incubation. Hence, P. alkanoclasticum is an apt candidate for the biodegradation of PAHs and the bioremediation of sites contaminated by them.     

Toxicity and source assignment of polycyclic aromatic hydrocarbons in road dust from urban residential and industrial areas in a typical industrial city in Korea

This study analyzed the toxicity and sources of polycyclic aromatic hydrocarbons (PAHs) in road dust from six representative areas (three urban residential areas and three industrial areas) from a typical industrial city in Korea. The concentrations and the toxicity equivalent concentrations (TEQs) in road dust varied by area, depending on the type of traffic and industrial activities and the PAHs identified. High correlations between the total concentration and the TEQ of PAHs in road dust were found in road dust from both the urban and industrial areas. To identify the sources of PAHs, this study utilized a factor loading method in a principal component analysis, the ratio of PAHs from combustion sources to total PAHs (ΣCOMB to ΣPAH), and bivariate plots of phenanthrene/anthracene (PA/Ant) versus fluoranthene/pyrene (FL/Pyr), and ΣCOMB/ΣPAH versus FL/Pyr in road dust. The identified origin of the PAHs was fuel combustion, including gasoline, diesel, oil, and coal, used in urban and industrial areas.     

Long-term Environmental Impact of Oil Spills

Oil contamination may persist in the marine environment for many years after an oil spill and, in exceptional cases such as salt marshes and mangrove swamps, the effects may be measurable for decades after the event. However, in most cases, environmental recovery is relatively swift and is complete within 2–10 years. Where oil has been eliminated from the scene, the long-term environmental impacts are generally confined to community structure anomalies that persist because of the longevity of the component species.     

An approach to evaluate the application of the vulnerability index for oil spills in tropical Red Sea environments

The Egyptian national marine oil pollution contingency plan was urgently initiated after the Nabila oil spill in 1982, to provide an estimate of its environmental effects on the Egyptian Red Sea coastal areas and to determine geomorphological features and cuastal processes, together with physical, chemical and biological baseline data for this tropical environment.The ‘Vulnerability Index’ (VI) was applied to evaluate and calibrate the effect of the Nabila oil spill on the Egyptian Red Sea Coastal area. A detailed in situ coastal survey was conducted during two visits in November 1982 and May 1983 to 80 shore sites from Suez to Ras Banas to monitor the oil pollution and to apply the ‘Vulnerability Index’. A comparative assessment of the index over time by comparing it with a quick ground inspection in November 1993 to some sites to evaluate the applicability of this index for oil spills in such environments. In addition, the physical effects of fresh and weathered crude oil and/with dispersant on water filtration by different beaches were preliminary studied.The geomorphological/Vulnerability Index results show that most of the Egyptian Red Sea coastal environments have medium to high vulnerability to immediate and medium term oil spill damage. The oil pollution spread estimated to be 250 km south of the oil spill and about 200 km north of it. The quantity of oil along the shoreline was reduced by about 60% due to natural and authorities clean up. The third survey after 11 years showed that the VI could be used as a predictive tool for assessment of oil spill effects on such tropical environments.     

Removal of Oil from the Sea Surface through Particulate Interactions: Review and Prospectus

The fate of oil spilled in coastal zones depends in large part on the interactions with environmental factors existing within a short time of the spill event. In addition to weathering which produces changes in the chemistry of the hydrocarbon stock, physical interactions between oil and suspended particulate matter (SPM), both organic and inorganic, play a role in determining the dispersal and sedimentation rates of the spill. This in turn affects the degradation rate of the oil. This paper provides a comprehensive literature review of the role of oil–particle interactions in removal of petroleum hydrocarbons from the sea surface and provides estimates of the degree to which SPM may augment the deposition of oil. Both field and laboratory observations have shown widely varying rates of oil removal due to particulate interactions. The discussion covers the interaction between oil weathering, injection, sinking, adsorption, microbial processes, flocculation and ingestion by zooplankton, which all contribute to packaging oil and SPM into settling aggregates.     

Biodegradation of Dispersed Forties Crude and Alaskan North Slope Oils in Microcosms Under Simulated Marine Conditions

For oil spills in the open sea, operational experience has found that conventional response techniques, such as mechanical recovery, tend to remove only a small fraction of oil during major spills, a recent exception being the Mississippi River spill in Louisiana [Spill Sci. Technol. Bull. 7 (2002) 155]. By contrast, the use of dispersants can enable significant fractions of oil to be removed from the sea surface by dispersing the oil into the water column. It is thought that once dispersed the oil can biodegrade in the water column, although there is little information on the mechanism and rate of biodegradation. Two studies were undertaken on dispersion, microbial colonisation and biodegradation of Forties crude and Alaskan North Slope (ANS) oils under simulated marine conditions. The study using the Forties crude lasted 27 days and was carried out in conditions simulating estuarine and coastal conditions in waters around the UK (15 °C and in the presence of nutrients, 1 mg N-NO₃/l), while the ANS study simulated low temperature conditions typical of Prince William Sound (8 °C) and took place over 35 days. The results of both studies demonstrated microbial colonisation of oil droplets after 4 days, and the formation of neutrally buoyant clusters consisting of oil, bacteria, protozoa and nematodes. By day 16, the size of the clusters increased and they sank to the bottom of the microcosms, presumably because of a decrease in buoyancy due to oil biodegradation, however biodegradation of n-alkanes was confirmed only in the Forties study. No colonisation or biodegradation of oil was noted in the controls in which biological action was inhibited. Oil degrading bacteria proliferated in all biologically active microcosms. Without dispersant, the onset of colonisation was delayed, although microbial growth rates and population size in ANS were greater than observed with the Forties. This difference reflected the greater droplet number seen with ANS at 8 °C than with Forties crude at 15 °C. Although these studies differed by more than one variable, complicating comparison, the findings suggest that dispersion (natural or chemical) changes the impact of the oil on the marine environment, potentially having important implications for management of oil spills in relation to the policy of dispersant use in an oil spill event.