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.     

R&D Users Guide to the Ohmsett Oil Spill Response Test Facility

Ohmsett – the National Oil Spill Response Test Facility, is the world's largest tow/wave tank designed to evaluate the performance of equipment that detects, monitors and clears up oil spills under environmentally safe conditions. Ohmsett is the only facility capable of testing and training with oil, using full-scale response equipment.     

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.     

Development of a National Marine Oil Transportation System Model

This paper presents the development of a model of the marine oil transportation in the United States. NMOTSM, the National Marine Oil Transportation System Model, is a high-level strategic decision-making tool that will be used to systematically identify causes of oil spills and prioritize oil pollution R and D needs for prevention and response. Three distinct phases in the analysis are identified, namely the formulation of the oil transport model, the risk and safety performance assessment and the evaluation of potential prevention, and response measures and approaches.     

Atmospheric Levels of Nitrogen Oxides at a Greek Oil Refinery Compared with the Urban Measurements in Athens

Oil refining is among the industrial activities that emit considerable amounts of air pollutants into the atmosphere. Nitrogen oxides are important air pollutants that are emitted by oil refineries as products of combustion processes. The ambient air concentrations of nitrogen oxide (NO) and nitrogen dioxide (NO₂) were monitored continuously at a site close to an oil refinery, near the city of Corinth in Greece, during autumn 1997 together with the main meteorological parameters. The contribution of the oil refinery to the measured atmospheric levels of nitrogen oxides was estimated. The ambient air concentration of nitrogen oxides in the area surrounding the oil refinery were generally lower than the ambient air concentrations in the urban area of Athens in Greece, and the NO₂ levels were always below the existing air quality standards. The influence of the refinery emitted NO_x in the photochemical production of ozone seems to be more important in terms of human and vegetation exposure given the high ozone backgrounds measured in the area.     

Laser fluorosensor overflights of the Santa Barbara oil seeps

The Emergencies Science Division of Environment Canada recently participated in a series of remote sensing flights over the naturally occurring oil seeps off Santa Barbara, California. During these flights the laser environmental airborne fluorosensor was operated to test its ability to detect oil in an actual marine environment. This joint project was sponsored by the United States Minerals Management Service and the Emergencies Science Division of Environment Canada. The Santa Barbara area of the California coastline contains numerous gas and petroleum deposits, which are slowly released from faults under the water and rise to the surface in the form of gas, oil and tar. In and around several of these seeps are kelp beds that release biogenic material, which can be mistaken for petroleum oil by certain remote sensors and human observers. This biogenic oil does not fluoresce when irradiated with ultraviolet light since it contains none of the aromatic compounds necessary to absorb the ultraviolet light and return fluorescence. The laser environmental airborne fluorosensor is, therefore, able to discriminate between this non-fluorescing oil and petroleum oils, which fluoresce with characteristic spectral signatures and intensities. High-resolution colour reconnaissance camera images and down-looking video images were collected concurrently with the fluorescence data for documentation purposes. Fluorescence data were collected at 100 Hz and correlated in real-time against reference spectra characteristic of light refined, crude and heavy oils. Maps of oil detection locations were produced in flight and printed in the aircraft. This paper will present details of the overflights and post-flight analysis of the fluorescence data using the Pearson correlation coefficient.     

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。     

Comparative occurrence rates for offshore oil spills

Estimates of occurrence rates for offshore oil spills are useful for analysis of potential oil spill impacts and for oil spill response contingency planning. As the Oil Pollution Act of 1990 (U.S. Public Law 101–380, 18 August 1990) becomes fully implemented, estimates of oil spill occurrence will become even more important to natural resource trustees and to responsible parties involved in oil and gas activities. Oil spill occurrence rate estimates have been revised based on U.S. Outer Continental Shelf platform and pipeline spill data (1964–1992) and worldwide tanker spill data (1974–1992). These spill rates are expressed and normalized in terms of number of spills per volume of crude oil handled. The revisions indicate that estimates for the platform spill occurrence rates declined, the pipeline spill occurrence rates increased, and the worldwide tanker spill occurrence rates remained unchanged. Calculated for the first time were estimates of tanker and barge spill rates for spills occuring in U.S. waters, and spill occurrence rates for spills of North Slope crude oil transported by tanker from Valdez, Alaska. All estimates of spill occurrence rates were restricted to spills greater than or equal to 159 m³ (1000 barrels).     

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.     

Looking to the Future––Setting the Agenda for Oil Spill Prevention,Preparedness and Response in the 21st Century

The Oil Pollution Act of 1990 (OPA 90) was largely driven by the catastrophic EXXON VALDEZ tanker spill and several other major tanker spills that followed in 1989. Under the OPA 90 mandate, the US Coast Guard, in partnership with other Federal agencies and industry have implemented a number of initiatives that have significantly enhanced the national oil spill prevention, preparedness and response capability. Declining trends in the volume of oil spilled into US waters indicates that these initiatives are at least in some measure successful.The Coast Guard is now concerned about what the future may hold in terms of oil pollution threats, and prevention, preparedness and response program shortcomings and opportunities in the future. To address this issue, the Coast Guard, in partnership with other National Response Team agencies and industry, is conducting a Broad-Based Programmatic Risk Assessment to develop a comprehensive vision and strategy for the Oil Spill Prevention, Preparedness and Response (OSPPR) Program in the 21st Century. This study will characterize the current and emerging oil spill threats by source category, assess the potential impacts of these threats to define overall risk, and examine the current and projected effectiveness of OSPPR initiatives in minimizing these risks. Key issues, problems and focus areas will be identified and targeted for follow-on risk analysis and management activities by the Coast Guard and agency and industry stakeholders.     

Oil Spill Modeling towards the Close of the 20th Century: Overview of the State of the Art

The state-of-the-art in oil spill modeling is summarized, focusing primarily on the years from 1990 to the present. All models seek to describe the key physical and chemical processes that transport and weather the oil on and in the sea. Current insights into the mechanisms of these processes and the availability of algorithms for describing and predicting process rates are discussed. Advances are noted in the areas of advection, spreading, evaporation, dispersion, emulsification, and interactions with ice and shorelines. Knowledge of the relationship between oil properties, and oil weathering and fate, and the development of models for the evaluation of oil spill response strategies are summarized. Specific models are used as examples where appropriate. Future directions in these and other areas are indicated     

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.     

Oil Erosion in an Annular Flume by Seawater of Varying Turbidities: A Critical Bed Shear Stress Approach

Laboratory experiments were conducted in an annular flume using Hibernia crude oil to determine: (1) the critical shear stress (τ_c) necessary to remove stranded oil from a surface by resuspension and (2) the effect of suspended sediment concentrations (SSCs) on the oil erosion processes. Two types of erosion were evident: Type I––solution and erosion of soluble aromatics; and Type II––mass erosion of visible droplets. In particulate free seawater at 13 °C, the Type II erosion threshold τ_cII is 5.0 Pa. This is equivalent to a mean current velocity (U_y) of 0.55 m s⁻¹. At U_y values <0.55 m s⁻¹, Type I erosion occurred as shown by the increase of oil concentrations without visible erosion of the oil surface. Temperature has a strong control on the threshold and rate of oil erosion: the threshold for Type I erosion at 4 °C was higher and erosion rate lower than at 13 °C. No Type II erosion was observed at 4 °C. SSCs also affects the entrainment of oil. Oil erosion was most efficient at moderate SSCs. At very high SSCs, turbulence suppression and drag reduction became effective and oil erosion rate decreased. SSC at 200–250 mg l⁻¹ were observed to give maximum erosion efficiency and is therefore suggested as the optimal concentration for erosion and elimination of heavy crude oil at a water temperature of 13 °C.     

Ten Year Historical Perspective of the NOAA Damage Assessment and Restoration Program

The United States Oil Pollution Act of 1990 (OPA) was enacted to reduce the probability of oil spills in U.S. waters. A key provision of the legislation enables recovery of damages for restoration of injured natural resources and lost services due to oil spills. The National Oceanic and Atmospheric Administration (NOAA) developed regulations that set out a process for determining the appropriate type and scale of restoration actions to accomplish this goal. The restoration plan developed through this process is the basis for an economic claim for natural resource damages. The regulations recognize that various methods, including environmental models, may be used in identifying and quantifying injuries to natural resources and losses of their services and in developing a restoration approach for these injuries. Rather than designating particular assessment measures, NOAA requires each trustee to decide which methodologies are appropriate for each incident, given its particular facts and circumstances. Any procedure chosen must meet the standards in the rule: it must provide information useful for determining restoration needed for an incident, the cost of the method must be commensurate with the quality and quantity of information it is expected to generate, and, of particular significance here, the method must be reliable and valid for the particular incident. This paper describes how methods are selected, how they might be used, and what legal standards would be applied should these methods be used as evidence in litigation.     

Weathering of Oils at Sea: Model/Field Data Comparisons

The SINTEF Oil Weathering Model (OWM) has been extensively tested with results from full-scale field trials with experimental oil slicks in the Norwegian NOFO Sea trials in 1994 and 1995 and the AEA 1997 trials in UK. The comparisons between oil weathering values predicted by the model and ground-truth obtained from the field trials are presented and discussed. Good laboratory weathering data of the specific oil as input to the model is essential for obtaining reliable weathering predictions. Predictions provided by the SINTEF-OWM enable oil spill personnel to estimate the most appropriate “window of opportunity” for use of chemical dispersants under various spill situations. Pre-spill scenario analysis with the SINTEF Oil Spill Contingency and Response (OSCAR) model system, in which the SINTEF-OWM is one of several components, has become an important part of contingency plans as well as contingency training of oil spill personnel at refineries, oil terminals and offshore installations in Norway.     

Australia's National Plan to Combat Pollution of the Sea by Oil and Other Noxious and Hazardous Substances – Overview and Current Issues

Australia's National Plan to Combat Pollution of the Sea by Oil and Other Noxious and Hazardous Substances (the National Plan) has operated since 1973. The objectives of the National Plan are based on Australia's obligations as a signatory to the International Convention on Oil Pollution Preparedness, Response and Co-operation 1990 and a responsibility to protect natural and artificial (man made) environments from the adverse effects of oil pollution and minimise those effects where protection is not possible.The Australian Maritime Safety Authority (AMSA) is the managing agency of the National Plan, working together with the States and Northern Territory governments, other Commonwealth agencies, ports, and the shipping, oil and exploration industries, to maximise Australia's marine pollution response capability.The 1990s have been a period of significant change for oil spill response arrangements in Australia. The National Plan was extended in 1998 to cover chemical spills and is currently in the process of implementing the oil spill response incident control system (OSRICS). A fixed wing aerial dispersant spraying capability was implemented in 1996 and a research and development program has been put in place. The development of a computer-based National Oil Spill Response Atlas was a major project completed during 1999.     

The Oil Pollution Act of 1990: A Decade Later

Analysis of oil spills data confirms that accidental oil spills are natural phenomenon and that there is a relationship between accidental oil spills and variables like vessel size, vessel type, time and region of spill. The volume of oil spilled bears relationship with the volume of petroleum imports and domestic movement of petroleum and proportion of large oil spills. Finally, navigational risk increases with increase in marine traffic and is also determined by variables like hydrographic and meteorological conditions, water configuration, maneuvering space, obstructions and nuisance vessels. The Oil Pollution Act, 1990 (OPA 90) was passed by the US Congress in the aftermath of 11 million gallon spill of crude oil in Prince William Sound, Alaska. The objective of OPA 90 was to minimize marine casualties and oil spills by addressing preventive, protective, deterrent and performance aspects of accidental oil spills. The arm of various regulations like double-hull tankers and vessel response plans extended to both US flagged and foreign-flagged tank vessels. The cost–benefit analysis of major regulations shows that the estimated costs exceed estimated benefits. We observe from USCG data on oil spills by size, by vessel type, Coast guard district and type of petroleum product that there have been significant reductions in the number and the quantity of oil spills. Our regression results show that the quantity of oil spilled increases with increase in oil imports but increases at a decreasing rate. The quantity of oil spilled decreases with increases in the domestic oil movements. Furthermore, percent of oil spills larger than 10,000 gallons also increases the potential quantity of oil spilled. OPA 90 has been a deterrent to accidental oil spills but the finding is not conclusive.     

Introduction/Overview to In Situ Burning of Oil Spills

In situ burning is an oil spill response technique or tool that involves the controlled ignition and burning of the oil at or near the spill site on the surface of the water or in a marsh (see Lindau et al., this volume). Although controversial, burning has been shown on several recent occasions to be an appropriate oil spill countermeasure. When used early in a spill before the oil weathers and releases its volatile components, burning can remove oil from the waters surface very efficiently and at very high rates. Removal efficiencies for thick slicks can easily exceed 95% (Advanced In Situ Burn Course, Spiltec, Woodinville, WA, 1997). In situ burning offers a logistically simple, rapid, inexpensive and if controlled a relatively safe means for reducing the environmental impacts of an oil spill. Because burning rapidly changes large quantities of oil into its primary combustion products (water and carbon dioxide), the need for collection, storage, transport and disposal of recovered material is greatly reduced. The use of towed fire containment boom to capture, thicken and isolate a portion of a spill, followed by ignition, is far less complex than the operations involved in mechanical recovery, transfer, storage, treatment and disposal (The Science, Technology, and Effects of Controlled Burning of Oil Spills at Sea, Marine Spill Response Corporation, Washington, DC, 1994).However, there is a limited window-of-opportunity (or time period of effectiveness) to conduct successful burn operations. The type of oil spilled, prevailing meteorological and oceanographic (environmental) conditions and the time it takes for the oil to emulsify define the window (see Buist, this volume and Nordvik et al., this volume). Once spilled, oil begins to form a stable emulsion: when the water content exceeds 25% most slicks are unignitable. In situ burning is being viewed with renewed interest as a response tool in high latitude waters where other techniques may not be possible or advisable due to the physical environment (extreme low temperatures, ice-infested waters), or the remoteness of the impacted area. Additionally, the magnitude of the spill may quickly overwhelm the deployed equipment necessitating the consideration of other techniques in the overall response strategy (The Science, Technology, and Effects of Controlled Burning of Oil Spills at Sea, Marine Spill Response Corporation, Washington, DC, 1994; Proceedings of the In Situ Burning of Oil Spills Workshop. NIST. SP934. MMS. 1998, p. 31; Basics of Oil Spill Cleanup, Lewis Publishers, Washington, DC, 2001, p. 233). This paper brings together the current knowledge on in situ burning and is an effort to gain regulatory acceptance for this promising oil spill response tool.     

Oil adsorbent produced by the carbonization of rice husks

In this study, rice husks considered to be agricultural waste are converted into an adsorbent intended for use in the disposal of oil spills. The raw and refined (defiberized) husks of Japanese Akita Komachi rice were pyrolyzed in a vacuum (500 Pa) at 300-800 degrees C. The amount of A-heavy and B-heavy oils adsorbed on the carbonized rice husk were then evaluated. Oil adsorption is dependent on the type of oil. Rice husks refined and then pyrolyzed at 600-700 degrees C (1.0 g) adsorbed >6.0 g of B-heavy oil and <1.5 g of water, which indicates their usefulness as an adsorbent for oil spill cleanup in Japan. The refining process contributes to an improvement in the oil adsorption capacity, while the carbonization time (at 600 degrees C) has only a minor influence. The residual fluid components in the carbonized rice husks, rather than their porosity, are closely related to oil adsorption capacity.