Assimilation of radar measured surface current fields into a numerical model for oil spill modelling

In summer 1996, surface current fields were measured in the central Strait of Georgia using the SeaSonde, a portable shore-based HF radar system. The objective of the study was to assess the feasibility of blending SeaSonde currents with numerical model fields to fill gaps in the measured fields and reduce noise. Our eventual goal is to assimilate the blended SeaSonde fields into a three-dimensional numerical model to improve short-range current forecasts.The first part of the study involved using the blended current fields as input to a set of auto-regressive moving-average (ARMA) statistical models. The blended fields were found to give forecasts comparable in terms of RMS error with forecasts using raw SeaSonde measurements. Moreover, the blended fields were smoother and more spatially complete than the raw data. The second part of the study examined the suitability of using the SeaSonde current fields to update the surface layer of Seaconsult's C3 hydrodynamic model. A simple nudging method is presented as an economical way to drive the model surface layer using operationally gathered SeaSonde information.     

Real time oil spill forecasting during an experimental oil spill in the arctic ice

The oil spill trajectory and weathering model OILMAP was used to forecast spill trajectories for an experimental oil spill in the Barents Sea marginal ice zone. The model includes capabilities to enter graphically and display environmental data governing oil behavior: ice fields, tidal and background current fields, and wind time series, as well as geographical map information. Forecasts can also be updated from observations such as airplane overflights. The model performed well when wind was ‘off-ice’ and speeds were relatively low (3–7 m s⁻¹), with ice cover between 60 and 90%. Errors in forecasting the trajectory could be directly attributed to errors in the wind forecasts. Appropriate drift parameters for oil and ice were about 25% of the wind speed, with an Ekman veering angle of 35° to the right. Ice sheets were typically 1 m thick. When the wind became ‘on-ice’, wind speeds increased to about 10 m s⁻¹ and trajectory simulations began to diverge from the observations, with observed drift parameters being 1.5% of the wind speed, with a 60° veering angle. Although simple assumptions for the large scale movement of oil in dense ice fields appear appropriate, the importance of good wind forecasts as a basis for reliable trajectory prognoses cannot be overstated.     

Review of oil spill remote sensing

Airborne and space-borne sensors are reviewed and evaluated in terms of their usefulness in responding to oil spills. Recent developments and trends in sensor technology are illustrated with specific examples. The discussion of the sensors is divided into two main categories, namely active and passive. Active sensors are those that provide their own source of illumination or excitation, whereas passive sensors rely on illumination from a secondary source. A common passive sensor is an infrared camera or an IR/UV (infrared/ultraviolet) system. The inherent weaknesses include the inability to discriminate oil on beaches, among seaweeds or debris. Among active sensors, the laser fluorosensor is a most useful instrument because of its unique capability to identify oil on backgrounds that include water, soil, ice and snow. It is the only sensor that can positively discriminate oil on most backgrounds. Disadvantages include the large size, weight and high cost. Radar offers the only potential for large area searches and foul weather remote sensing. Radar is costly, requires a dedicated aircraft, and is prone to many interferences. Equipment that measures relative slick thickness is still under development. Passive microwave has been studied for several years, but many commercial instruments lack sufficient spatial resolution to be practical, operational instruments. A laser-acoustic instrument, which provides the only technology to measure absolute oil thickness, is under development. Equipment operating in the visible region of the spectrum, such as cameras and scanners, is useful for documentation or providing a basis for the overlay of other data. It is not useful beyond this because oil shows no spectral characteristics in the visible region which can be used to discriminate oil.     

Overview and future trends in oil spill remote sensing

Remote sensing has great potential to provide data to improve oil spill response efforts. There are a number of sensors available that have been proven capable of detecting oil on water and measuring some of its properties. There is no single sensor that provides all the data needed, and hence a combination of sensors must be used. Even if finances and aircraft load capacity were unlimited, there are still many parameters of an oil slick that cannot be measured by remote sensing. This paper describes the cyrrently available sensors and their method of operation and outlines some new developments that have the potential to increase the amount of data available from an airborne remote sensing operation.     

The technology windows-of-opportunity for marine oil spill response as related to oil weathering and operations

This paper identifies and estimates time periods as ‘windows-of-opportunity’ where specific response methods, technologies, equipment, or products are more effective in clean-up operations for several oils. These windows have been estimated utilizing oil weathering and technology performance data as tools to optimize effectiveness in marine oil spill response decision-making. The windows will also provide data for action or no-action alternatives. Crude oils and oil products differ greatly in physical and chemical properties, and these properties tend to change significantly during and after a spill with oil aging (weathering). Such properties have a direct bearing on oil recovery operations, influencing the selection of response methods and technologies applicable for clean up, including their effectiveness and capacity, which can influence the time and cost of operations and the effects on natural resources.The changes and variations in physical and chemical properties over time can be modeled using data from weathering studies of specific oils. When combined with performance data for various equipment and materials, tested over a range of weathering stages of oils, windows-of-opportunity can be estimated for spill response decision-making. Under experimental conditions discussed in this paper, windows-of-opportunity have been identified and estimated for four oils (for which data are available) under a given set of representative environmental conditions. These ‘generic’ windows have been delineated for the general categories of spill response namely: (1) dispersants, (2) in situ burning, (3) booms, (4) skimmers, (5) sorbents, and (6) oil-water separators. To estimate windows-of-opportunity for the above technologies (except booms), the IKU Oil Weathering Model was utilized to predict relationships—with 5 m s⁻¹ wind speed and seawater temperatures of 15°C.The window-of-opportunity for the dispersant (Corexit 9527^®) with Alaska North Slope (ANS) oil was estimated from laboratory data to be the first 26 h. A period of ‘reduced’ dispersibility, was estimated to last from 26–120 h. The oil was considered to be no longer dispersible if treated for the first time after 120 h. The most effective time window for dispersing Bonnic Light was 0–2 h, the time period of reduced dispersibility was 2–4 h, and after 4 h the oil was estimated to be no longer dispersible. These windows-of-opportunity are based on the most effective use of a dispersant estimated from laboratory dispersant effectiveness studies using fresh and weathered oils. Laboratory dispersant effectiveness data cannot be directly utilized to predict dispersant performance during spill response, however, laboratory results are of value for estimating viscosity and pour point limitations and for guiding the selection of an appropriate product during contingency planning and response. In addition, the window of opportunity for a dispersant may be lengthened if the dispersant contains an emulsion breaking agent or multiple applications of dispersant are utilized. Therefore, a long-term emulsion breaking effect may increase the effectiveness of a dispersant and lengthen the window-of-opportunity.The window-of-opportunity of in situ burning (based upon time required for an oil to form an emulsion with 50% water content) was estimated to be approximately 0–36 h for ANS oil and 0–1 h for Bonnie Light oil after being spilled. The estimation of windows-of-opportunity for offshore booms is constrained by the fact that many booms available on the market undergo submergence at speeds of less than 2 knots. The data suggest that booms with buoyancy to weight ratios less than 8:1 may submerge at speeds within the envelope in which they could be expected to operate. This submergence is an indication of poor wave conformance, caused by reduction of freeboard and reserve net buoyancy within the range of operation. The windows-of-opportunity for two selected skimming principles (disk and brush), were estimated using modeled oil viscosity data for BCF 17 and BCF 24 in combination with experimental performance data developed as a function of viscosity. These windows were estimated to be within 3–10 h (disk skimmer) and after 10 h (brush skimmer) for BCF 17. Whereas for BCF 24, it is within 2–3 d (disk skimmer) and after 3 d (brush skimmer).For sorbents, an upper viscosity limit for an effective and practical use has in studies been found to be approximately 15,000 cP, which is the viscosity range of some Bunker C oils. Using viscosity data for the relative heavy oils, BCF 17 and BCF 24 (API gravity 17 and 24), the time windows for a sorbent (polyamine flakes) was estimated to be 0–4 and 0–10 d, respectively. With BCF 24, the effectiveness of polyamine flakes, was reduced to 50% after 36 h, although it continued to adsorb for up to 10 d. For BCF 17, the effectiveness of polyamine flakes was reduced to 50% after 12 h, although it continued to adsorb for up to 4 d. The windows-of-opportunity for several centrifuged separators based upon the time period to close the density gap between weathered oils and seawater to less than 0.025 g ml⁻¹ (which is expected to be an end-point for effective use of centrifugal separation technology), were estimated to be 0–18 (ANS) and 0–24 h (Bonnie Light) after the spill. Utilizing the windows-of-opportunity concept, the combined information from a dynamic oil weathering model and a performance technology data base can become a decision-making tool; identifying and defining the windows of effectiveness of different response methods and equipment under given environmental conditions. Specific research and development needs are identified as related to further delineation of windows-of-opportunity.     

Hindcast of a Japan Sea oil spill

An oil spill model was applied to the Nakhodka tanker spill accident that occurred in the Japan Sea in January 1997. The amount of oil spilled was estimated to be around 5000 kl, released over 1 day. Under a 2-m wave height condition, and a 3.5% of drift factor, the model simulated the oil slick to hit the shoreline after 6 days. This was in good agreement with the observed conditions. After drifting to the shoreline, the oil slick moved northeastward with the current. In the model, the simulation where the shoreline absorbs 100% of stranded oil failed to reproduce the actual oil slick trajectory. The simulation in which oil resuspended after stranding indicated a similar trend to the actual case. Therefore, it is likely that a considerable amount of oil that hit the shoreline may have returned to the sea and moved with the current. The effects of current pattern and wind drift angle on the oil slick trajectory were also examined. It is suggested that the wind parameters were of prime importance in reproducing a realistic distribution.     

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.     

Quantitative analysis of alternate oil spill response strategies using OSCAR

A three-dimensional numerical model of the physical and chemical behavior and fate of spilled oil has been coupled to a model of oil spill response actions. This coupled system of models for Oil Spill Contingency and Response (OSCAR), provides a tool for quantitative, objective assessment of alternative oil spill response strategies. Criteria for response effectiveness can be either physical (‘How much oil comes ashore?’ or ‘How much oil have we recovered?’) or biological (‘How many biologically sensitive areas were affected?’ or ‘What exposures will fish eggs and larvae experience in the water column?’). The oil spill combat module in the simulator represents individual sets of equipment, with capabilities and deployment strategies being specified explicitly by the user. The coupling to the oil spill model allows the mass balance of the spill to be affected appropriately in space and time by the cleanup operation as the simulation proceeds. An example application is described to demonstrate system capabilities, which include evaluation of the potential for both surface and subsurface environmental effects. This quantitative, objective approach to analysis of alternative response strategies provides a useful tool for designing more optimal, functional, rational, and cost-effective oil spill contingency solutions for offshore platforms, and coastal terminals and refineries.     

Remote sensing systems considerations and user requirements for oil spill surveillance

New communications technology coupled with using GIS and GPS technology gives an opportunity to bridge the gap from the sensor-equipped aircraft to the user of the information. Finally, remote sensing information can be delivered in a form that is tailored to the needs of the end user. The challenge today is to keep to simple systems that make sense operationally rather than try to integrate every new technology.     

COASTMAP: An integrated monitoring and modeling system to support oil spill response

One of the most difficult tasks in oil spill response modeling is to provide accurate estimates of the currents and winds during the spill event. This is typically done in an ad-hoc, subjective manner combining very limited field observations with simplified hydrodynamic and meteorological models. As an alternative an integrated environmental monitoring and modeling system, called COASTMAP, is presented. COASTMAP allows the user to collect, manipulate, display, and archive real-time environmental data through an embedded geographic information system and environmental data management tools; to perform simulations with a suite of environmental models (e.g. hydrodynamics, meteorological) in order to predict dynamics in the operational area and to assimilate real-time data into the models to allow hindcasting, nowcasting and forecasting. COASTMAP, operational on a personal computer, is controlled by mouse/keyboard through a series of menus and uses color graphics to present model predictions (plots, graphs, animations) and the results of data analyses. The software is designed using a shell based architecture making application to any geographic location simple and straightforward.In the present paper, COASTMAP is linked with OILMAP to provide a fully operational, real-time system that allows prediction of circulation, winds and oil spill trajectory and fate for estuarine and coastal sea areas. System performance is illustrated by the simulation of the trajectory of oil tracking buoys during two experiments performed in the lower west passage of Narragansett Bay. Simulation results using several forecast procedures, with/without real-time data, are presented.     

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。     

Maersk Navigator oil spill in the great channel (Andaman Sea) in January 1993 and its environmental impact

Observations on oil slicks, tar residues and dissolved petroleum hydrocarbons (DPH) shortly after the oil spill resulting from the tanker accident in January 1993 showed negligible impact on the Indian EEZ of the Great Channel (Andaman Sea). DPH were between 0.31 and 1.85 μg l⁻¹ in the area examined. Tar residues were absent throughout the study area. Prevailing NE wind with resultant SW surface current appears to have pushed the oil patches out towards the open Indian Ocean.A follow-up survey of the same area was carried out in September-October 1993 and observations similar to those made during the earlier survey were recorded. The zooplankton biomass had increased considerably during the interval between the two surveys, but this was probably due to seasonal changes and natural variability.The spill did not cause any perceptible impact on the environment.     

Dynamic modelling of oil boom failure using computational fluid dynamics

The common response to an oil spill on water is to contain the oil with booms and recover it with skimming devices. In some situations, however, the booms cannot hold the oil and the oil will escape underneath the boom due to hydrodynamic forces. Computational fluid dynamics (CFD) is a powerful modelling tool combining fluid dynamics and computer technology. We have utilized a commercial CFD program, Fluent, to simulate the oil-water flow around a boom. The studies accurately model channel experiments conducted in recent years. The studies show that the flow patterns around booms are modified by the presence of oil and, therefore, suggest that towing and wave-conformity tests of booms will not be meaningful unless they are undertaken with the presence of oil.     

The integration of trajectory models and analysis into spill response information systems

The spill response community is engaged in a technological rush towards computer-based, information-synthesis systems. Typically, they are modeled after many successful ‘incident command’ or ‘command and control’ systems that rely on micro- or mini-computer technology that is friendly and graphically oriented. Virtually all of these systems offer spill trajectory modeling components. What is typically lacking in this modeling output is any reliable way to estimate the uncertainty. This means that advice derived from the models is of questionable value, and when integrated into a complex response plan, the propagation of errors could seriously compromise the usefulness of results. It is shown that no single trajectory model run can provide the necessary information to respond in an optimal, ‘minimum regret’ strategy. However, a well-defined series of model runs used as the basis for trajectory analysis can provide the required information. A discussion of options suggests that the adoption of a minimum standard analysis procedure would significantly improve the ability of integrated response systems to use the predictions of oil distributions.     

In situ bioremediation of an aniline spill in an industrial setting

In situ remediation of aniline from soils and groundwater using biological and physical treatments was conducted at the BASF Corporation facility in Geismar, Louisiana. To mitigate the migration of aniline, remediate contaminated soil and groundwater, and determine concentrations, 24 immobilized microbe bioreactors were fixed in the subsoil, and a horizontal recovery well and 7 monitoring wells were installed. Soil and monitoring wells were sampled quarterly to assess bioplug impact on the aniline concentrations. The recovery well was sampled monthly to estimate the pounds of aniline removed from groundwater. Soil pH, composition, and microbial counts were used to estimate the fate and transport. Aniline levels were lowered significantly after remediation and total cancer risk was below levels for industrial sites, as established by State of Louisiana Risk Evaluation/Corrective Action Program guidelines. © 2010 Wiley Periodicals, Inc.     

Application of in-situ bioremediation to a gasoline spill in fractured bedrock

After achieving remediation goals during only thirty-two months of operation, the first full-scale in-situ bioremediation (ISB) system in the state of Missouri was shut down in 1990. In addition to ISB, the system included a combination of soil venting and air stripping to remediate subsurface gasoline contamination at a large manufacturing facility. More than 84,000 pounds of gasoline were degraded or removed from the fractured limestone bedrock aquifer and overburden materials. The successful application of ISB in this complex geologic environment and the fact that this was the first such system to complete remediation in Missouri make this system unique.     

The use of tyre pyrolysis oil in diesel engines

Tests have been carried out to evaluate the performance, emission, and combustion characteristics of a single cylinder direct injection diesel engine fueled with 10%, 30%, and 50% of tyre pyrolysis oil (TPO) blended with diesel fuel (DF). The TPO was derived from waste automobile tyres through vacuum pyrolysis. The combustion parameters such as heat release rate, cylinder peak pressure, and maximum rate of pressure rise also analysed. Results showed that the brake thermal efficiency of the engine fueled with TPO-DF blends increased with an increase in blend concentration and reduction of DF concentration. NO(x), HC, CO, and smoke emissions were found to be higher at higher loads due to the high aromatic content and longer ignition delay. The cylinder peak pressure increased from 71 bars to 74 bars. The ignition delays were longer than with DF. It is concluded that it is possible to use tyre pyrolysis oil in diesel engines as an alternate fuel in the future.     

The role of cost in remedy selection

Records of Decision from 16 environmental cleanup sites on 11 different Air Force bases were evaluated to determine if cost plays a role in remedy selection. Cost percentile (the cost of the selected remedy compared to the ranges of costs in the alternatives considered) was evaluated against the variables of risk (current and future, carcinogenic and noncarcinogenic), location, and contaminated media at the sites. Despite a statutory preference for permanent (and usually more expensive) remedies, the study found that cost is a significant factor in remedy selection. Eighty percent of the selected remedies fell in the bottom two thirds of alternatives by cost. Current carcinogenic risk and cost percentile were moderately correlated, but no significant correlation was found between the percentile of the selected remedy and future risk at the site or the location of the site. There was a moderate correlation between the contaminated medium and the percentile. Decision makers at sites with contaminated groundwater were more likely to select a high-cost alternative than sites with other contaminated media.