Round Robin Study—Oil Spill Identification

As part of the ongoing work to develop new guidelines for oil spill identification for the European Committee for Standardization (CEN), a Round Robin test was arranged by SINTEF in co-operation with the Norwegian General Standardizing Body (NAS). Twelve laboratories from ten countries participated in the Round Robin study. They include: Denmark, Finland, France, Germany, the Netherlands, Norway, Scotland, Sweden, Wales, and the U.S.A. The analytical methodology used for the Round Robin testing is a result of the ongoing project “Revision of the Nordtest Methodology for Oil Spill Identification”. The analytical methodology is described in the AMOP proceedings 2002. Seven oil samples (two artificially weathered “spill” samples and five possible sources) were analyzed following the recommended analytical protocols. The Round Robin study was a “difficult case”, because the two spill samples and three of the suspected sources were highly correlated to one another. These samples were from the same oil field in the North Sea, but from different production wells. The present paper summarizes the Round Robin study, and demonstrates the potential of this methodology as a strong technically defensible tool in oil spill identification due to its ability to distinguish qualitatively similar oils from a spill and any available candidate source.     

Improved and Standardized Methodology for Oil Spill Fingerprinting

The existing Nordtest methodology for oil spill Identification has over the past 10 years formed an important "platform" for solving oil spill identification cases both in the Scandinavian countries as well as other countries in Europe, the USA and Canada. " Revision of the Nordtest Methodology for Oil Spill Identification " is a cooperative project between the National Oil Spill Identification laboratories in Norway, Sweden, Finland, Denmark and the Battelle Memorial Institute (Duxbury) in the USA. The goals of the project are: (1) to refine the existing Nordtest methodology into a technically more robust and defensible oil spill identification methodology with focus on determination of quantitative diagnostic indices (ratios) and (2) to adjust the revised Nordtest methodology into guidelines for the European Committee for Standardization (CEN). This paper presents the recommended methodology for the analytical oil spill identification part. The sampling techniques and handling of oil samples and background (reference) samples prior to their arrival at the environmental forensic laboratory is not covered in this paper. The recommended methodology approach is a result of documented analytical improvements and a more quantitative treatment of analytical data from gas chromatographic-flame ionization detector (GC/FID) and gas chromatographic-mass spectrometer methods (GC/MS-SIM) and the operational experiences over past few years among the participating forensic laboratories. The experience and literature in the field of oil exploration and production geochemistry have also played an important role for the recommended methodology. The results from a recent Round Robin test carried out among 12 laboratories using this new methodology are presented in a separate paper in this issue (Faksness et at ., 2002d).     

Improved and Standardized Methodology for Oil Spill Fingerprinting

The existing Nordtest methodology for oil spill Identification has over the past 10 years formed an important “platform” for solving oil spill identification cases both in the Scandinavian countries as well as other countries in Europe, the USA and Canada. “Revision of the Nordtest Methodology for Oil Spill Identification” is a cooperative project between the National Oil Spill Identification laboratories in Norway, Sweden, Finland, Denmark and the Battelle Memorial Institute (Duxbury) in the USA. The goals of the project are: (1) to refine the existing Nordtest methodology into a technically more robust and defensible oil spill identification methodology with focus on determination of quantitative diagnostic indices (ratios) and (2) to adjust the revised Nordtest methodology into guidelines for the European Committee for Standardization (CEN). This paper presents the recommended methodology for the analytical oil spill identification part. The sampling techniques and handling of oil samples and background (reference) samples prior to their arrival at the environmental forensic laboratory is not covered in this paper. The recommended methodology approach is a result of documented analytical improvements and a more quantitative treatment of analytical data from gas chromatographic-flame ionization detector (GC/FID) and gas chromatographic-mass spectrometer methods (GC/MS-SIM) and the operational experiences over past few years among the participating forensic laboratories. The experience and literature in the field of oil exploration and production geochemistry have also played an important role for the recommended methodology. The results from a recent Round Robin test carried out among 12 laboratories using this new methodology are presented in a separate paper in this issue (8).     

A Strategy and Methodology for Defensibly Correlating Spilled Oil to Source Candidates

The source of crude oils and petroleum products released into navigable waterways and shipping lanes is not always known. Thus, the defensible identification of spilled crude oils and petroleum products and their correlation to suspected sources is a critical part of many oil spill assessments. Quantitative "fingerprinting" analysis, when evaluated using straightforward statistical and numerical analyses, provides a defensible means to differentiate among qualitatively similar oils and provides the best assessment of the source(s) for spilled oils. Polycyclic aromatic hydrocarbon (PAH) and petroleum biomarker concentration data are a particularly useful quantitative measure that can benefit most oil spill investigations. In this paper the strategy and methodology for correlation analysis that relies upon quantitative gas chromatography/mass spectrometry operated in the selected ion monitoring mode (GC/MS-SIM) is demonstrated in a case study involving 66 candidate sources for a heavy fuel oil spill of unknown origin. The strategy includes identification of 19 chemical indices (out of 45 evaluated) based upon PAH's and biomarkers that were (1) independent of weathering; and (2) precisely measured, both of which are determined by statistical analysis of the data. The 19 chemical indices meeting these criteria are subsequently analysed using principal component analysis (PCA), which helps to determine defensibly the "prime suspects" for the oil spill under investigation. The strategy and methodology described, which combines statistical and numerical analysis of quantitative chemical data, can be adapted and applied to other environmental forensic investigations with the objective of correlating any form of contamination to its suspected sources.     

A Strategy and Methodology for Defensibly Correlating Spilled Oil to Source Candidates

The source of crude oils and petroleum products released into navigable waterways and shipping lanes is not always known. Thus, the defensible identification of spilled crude oils and petroleum products and their correlation to suspected sources is a critical part of many oil spill assessments. Quantitative “fingerprinting” analysis, when evaluated using straightforward statistical and numerical analyses, provides a defensible means to differentiate among qualitatively similar oils and provides the best assessment of the source(s) for spilled oils. Polycyclic aromatic hydrocarbon (PAH) and petroleum biomarker concentration data are a particularly useful quantitative measure that can benefit most oil spill investigations. In this paper the strategy and methodology for correlation analysis that relies upon quantitative gas chromatography/mass spectrometry operated in the selected ion monitoring mode (GC/MS-SIM) is demonstrated in a case study involving 66 candidate sources for a heavy fuel oil spill of unknown origin. The strategy includes identification of 19 chemical indices (out of 45 evaluated) based upon PAH's and biomarkers that were (1) independent of weathering; and (2) precisely measured, both of which are determined by statistical analysis of the data. The 19 chemical indices meeting these criteria are subsequently analysed using principal component analysis (PCA), which helps to determine defensibly the “prime suspects” for the oil spill under investigation. The strategy and methodology described, which combines statistical and numerical analysis of quantitative chemical data, can be adapted and applied to other environmental forensic investigations with the objective of correlating any form of contamination to its suspected sources.     

Effects of an oil spill in a harbor assessed using biomarkers of exposure in eelpout

Oil spills occur commonly, and chemical compounds originating from oil spills are widespread in the aquatic environment. In order to monitor effects of a bunker oil spill on the aquatic environment, biomarker responses were measured in eelpout (Zoarces viviparus) sampled along a gradient in Göteborg harbor where the oil spill occurred and at a reference site, 2 weeks after the oil spill. Eelpout were also exposed to the bunker oil in a laboratory study to validate field data. The results show that eelpout from the Göteborg harbor are influenced by contaminants, especially polycyclic aromatic hydrocarbons (PAHs), also during “normal” conditions. The bunker oil spill strongly enhanced the biomarker responses. Results show elevated ethoxyresorufin-O-deethylase (EROD) activities in all exposed sites, but, closest to the oil spill, the EROD activity was partly inhibited, possibly by PAHs. Elevated DNA adduct levels were also observed after the bunker oil spill. Chemical analyses of bile revealed high concentrations of PAH metabolites in the eelpout exposed to the oil, and the same PAH metabolite profile was evident both in eelpout sampled in the harbor and in the eelpout exposed to the bunker oil in the laboratory study.     

Pattern Recognition Based Software for Oil Spills Identification by Gas-Chromatography and IR Spectrophotometry

For environmental control purposes, floating oil spills in harbours, off shore areas and their sources must often be identified. Pattern recognition, applied to JR spectrophotometric data (600-2000 cm m 1 range), and to chromatographic data ( n -alkanes) for the spill and various suspected sources such as oil and fuels from ships bunkers and harbour installations, can lead to definite conclusions; particularly after artificial weathering formula are used. The software application provides quick and accurate identification of the pollution source. The identification algorithm has a learning stage in which the user creates a minimal database. This database has a tree structure with classes (fuels, crude, etc.) and members representing samples from already known sources. A sample contains JR and chromatographic data and information of the originating source. A larger database means more knowledge, which conveys a better identification. When the origin of an unknown sample is searched for, the software looks for the best match through the database and displays the results in two lists; sorted by calculated similarity. One list displays the classes in which the unknown sample could be included and the other displays the possible sources. An extra check can be done by visual inspection of the overlapped graphics (unknown sample and each of the identified sources).     

Pattern Recognition Based Software for Oil Spills Identification by Gas-Chromatography and IR Spectrophotometry

For environmental control purposes, floating oil spills in harbours, off shore areas and their sources must often be identified. Pattern recognition, applied to IR spectrophotometric data (600–2000 cm⁻¹ range), and to chromatographic data (n -alkanes) for the spill and various suspected sources such as oil and fuels from ships bunkers and harbour installations, can lead to definite conclusions; particularly after artificial weathering formula are used. The software application provides quick and accurate identification of the pollution source. The identification algorithm has a learning stage in which the user creates a minimal database. This database has a tree structure with classes (fuels, crude, etc.) and members representing samples from already known sources. A sample contains IR and chromatographic data and information of the originating source. A larger database means more knowledge, which conveys a better identification. When the origin of an unknown sample is searched for, the software looks for the best match through the database and displays the results in two lists; sorted by calculated similarity. One list displays the classes in which the unknown sample could be included and the other displays the possible sources. An extra check can be done by visual inspection of the overlapped graphics (unknown sample and each of the identified sources).     

Brazilian Oil Spills Chemical Characterization--Case Studies

In the last decade, PETROBRAS has experienced some significant oil spills cases and the PETROBRAS Research Center has played an important role in the company emergency response program by characterizing the spilled oil, monitoring the affected ecosystem, determining the fate of the oil in the environment, and, subsequently, helping the company in assessing the environmental damage. This paper presents the use of advanced chemical analytical techniques (GC/FID, P&T/GC/PID and GC/MS) in some Brazilian oil spill studies in order to determine fractions and individual petroleum hydrocarbons in different matrices such as water, groundwater, sediment, sand, fish and the spilled oil itself. The spill studies encompassed crude and fuel oil releases on land and coastal ecosystems, related to the incidents in Guanabara Bay (Rio de Janeiro), Barigui and Iguassu Rivers (Parana) and Sao Sebastiao Channel (Sao Paulo). Total petroleum hydrocarbons (TPH), n -alkanes, isoprenoids, unresolved complex mixtures (UCM), volatile monoaromatic compounds--benzene, toluene, ethylbenzene and xylenes (BTEX), parent and alkylated homologues polycyclic aromatic hydrocarbons (PAH), and terpanes and steranes were characterized for determining correlation to the spilled oil and other known oil sources and environmental assessment. Some of the acute ecotoxicity data for water and sediment samples is also presented.     

Ambient air concentrations exceeded health-based standards for fine particulate matter and benzene during the Deepwater Horizon oil spill

The Deepwater Horizon oil spill is considered one of the largest marine oil spills in the history of the United States. Air emissions associated with the oil spill caused concern among residents of Southeast Louisiana. The purpose of this study was to assess ambient concentrations of benzene (n=3,887) and fine particulate matter (n=102,682) during the oil spill and to evaluate potential exposure disparities in the region. Benzene and fine particulate matter (PM2.5) concentrations in the targeted parishes were generally higher following the oil spill, as expected. Benzene concentrations reached 2 to 19 times higher than background, and daily exceedances of PM2.5 were 10 to 45 times higher than background. Both benzene and PM2.5 concentrations were considered high enough to exceed public health criteria, with measurable exposure disparities in the coastal areas closer to the spill and clean-up activities. These findings raise questions about public disclosure of environmental health risks associated with the oil spill. The findings also provide a science-based rationale for establishing health-based action levels in future disasters.

Implications: Benzene and particulate matter monitoring during the Deepwater Horizon oil spill revealed that ambient air quality was a likely threat to public health and that residents in coastal Louisiana experienced significantly greater exposures than urban residents. Threshold air pollution levels established for the oil spill apparently were not used as a basis for informing the public about these potential health impacts. Also, despite carrying out the most comprehensive air monitoring ever conducted in the region, none of the agencies involved provided integrated analysis of the data or conclusive statements about public health risk. Better information about real-time risk is needed in future environmental disasters.     

Brazilian Oil Spills Chemical Characterization—Case Studies

In the last decade, PETROBRAS has experienced some significant oil spills cases and the PETROBRAS Research Center has played an important role in the company emergency response program by characterizing the spilled oil, monitoring the affected ecosystem, determining the fate of the oil in the environment, and, subsequently, helping the company in assessing the environmental damage. This paper presents the use of advanced chemical analytical techniques (GC/FID, P&T/GC/PID and GC/MS) in some Brazilian oil spill studies in order to determine fractions and individual petroleum hydrocarbons in different matrices such as water, groundwater, sediment, sand, fish and the spilled oil itself. The spill studies encompassed crude and fuel oil releases on land and coastal ecosystems, related to the incidents in Guanabara Bay (Rio de Janeiro), Barigui and Iguassu Rivers (Parana) and Sao Sebastiao Channel (Sao Paulo). Total petroleum hydrocarbons (TPH), n -alkanes, isoprenoids, unresolved complex mixtures (UCM), volatile monoaromatic compounds—benzene, toluene, ethylbenzene and xylenes (BTEX), parent and alkylated homologues polycyclic aromatic hydrocarbons (PAH), and terpanes and steranes were characterized for determining correlation to the spilled oil and other known oil sources and environmental assessment. Some of the acute ecotoxicity data for water and sediment samples is also presented.     

Comparing sediment quality in Spanish littoral areas affected by acute (Prestige, 2002) and chronic (Bay of Algeciras) oil spills

The quality of sediments collected from two areas of the Spanish coast affected by different sources of contaminants has been compared in this study. The areas studied are the coast of Galicia affected by the oil spill from the tanker Prestige (November 2002) and the Gulf of Cádiz which suffers continuous inputs of contaminants from industries located in the area and from oil spills. Contamination by several chemicals (metals, PCBs and PAHs) that bind to sediments was analyzed, and two toxicity tests (Microtox) and amphipod 10-day bioassay) were conducted. PAHs were identified as the compounds responsible for the toxic effects. Results show differences between an acute impact related to the sinking of the tanker Prestige and the chronic impact associated with continuous oil spills associated with the maritime and industrial activities in the Bay of Algeciras, this being the most polluted part of the two coastal areas studied in this work.     

Survey of Airborne 2,4-D in South-Central Washington

The extensive application of 2,4-D herbicides to wheat and other agricultural crops in the states of Washington and Oregon can produce "off-target" damage when the 2,4-D formulations are transported by the atmosphere to sensitive crops, such as grapes. During May-June of 1973 and April-June of 1974, a 2,4-D monitoring network in south-central Washington collected samples for subsequent herbicide analysis. The daily, 24 hr field samples were collected with differential Impactor-impinger air samplers and were routinely analyzed in the analytical laboratory by electron-capture gas chromatography. In addition, gas chromatography/mass spec-trometry was employed for positive identification of the 2,4-D esters and for comparative quantitative analysis. The complete sampling and analytical methodology, the 2,4-D concentration data for 1973 and 1974, the agricultural 2,4-D application records and crop Injury reports, and the concomitant meteorological data are described in this paper.     

High-molecular weight sulfur-containing aromatics refractory to weathering as determined by Fourier transform ion cyclotron resonance mass spectrometry

Biomarkers and low-molecular weight polyaromatic compounds have been extensively studied for their fate in the environment. They are used for oil spill source identification and monitoring of weathering and degradation processes. However, in some cases, the absence or presence of very low concentration of such components restricts the access of information to spill source. Here we followed the resistance of high-molecular weight sulfur-containing aromatics to the simulated weathering condition of North Sea crude oil by ultra high-resolution Fourier transform ion cyclotron resonance mass spectrometry. The sulfur aromatics in North Sea crude having double bond equivalents (DBE) from 6 to 14 with a mass range 188-674 Da were less influenced even after 6 months artificial weathering. Moreover, the ratio of dibenzothiophenes (DBE 9)/naphthenodibenzothiophenes (DBE 10) was 1.30 and 1.36 in crude oil and 6 months weathered sample, respectively reflecting its weathering stability. It also showed some differences within other oils. Hence, this ratio can be used as a marker of the studied crude and accordingly may be applied for spilled oil source identification in such instances where the light components have already been lost due to environmental influences.     

3-Way pattern-recognition of PAHs from Galicia (NW Spain) seawater samples after the Prestige's wreck

In November 2002 the oil tanker ‘Prestige’ released 65 000 tons of a heavy fuel oil throughout the Galician coastline (NW Spain), causing extensive damage to marine life, natural resources and economic activities at Northern Portugal, Spain and SW France. To evaluate the impact of the oil spill on the aquatic system, 30 polycyclic aromatic hydrocarbons (PAHs), including alkylated derivatives, were analyzed in seawater on five different sampling campaigns from 2002 to 2004. Sampling was made along the Galician continental shelf. In each station three samples were collected at three different depths (surface, mid-depth and bottom). Four different approaches for 3-way analyses (Catenated-PCA, Matrix-Augmented Principal Components Analysis, Parallel Factor Analysis and Procrustes rotation) have been used to asses the major sources of PAHs into the seawater. They revealed two main pollution patterns: one related to oil spillages and discharge of petroleum products, and another more associated with a diffuse anthropogenic origin.     

A Holistic Approach to Hydrocarbon Source Allocation in the Subtidal Sediments of Prince William Sound,Alaska, Embayments

Prince William Sound (PWS), Alaska has an extensive history of human and industrial activity that has produced a complex organic geochemistry record in subtidal sediments of embayments throughout the sound. In addition to contributions from recent oil spills and a regional background of natural petroleum hydrocarbons originating from active hydrocarbon systems in the northern Gulf of Alaska (GOA), pyrogenic and petrogenic PAH were, and continue to be introduced to subtidal sediments at numerous sites of past and present human activities. These sites include villages, fish hatcheries, fish camps and recreational campsites in addition to abandoned settlements, canneries, sawmills, and mines. A holistic approach is used to fingerprint and quantify hydrocarbon contributions from multiple sources in a sediment sample. It involves acquiring a comprehensive understanding of the history of the area to identify potential sources, collection of representative samples, and accurate quantitative analyses of the source and sediment samples for a suite of diagnostic PAH analytes and chemical biomarker compounds. Unlike the deepwater sediments of the sound and GOA, the TOC tool, described elsewhere, does not work as well in some restricted embayments due to their high contents of recent organic matter (ROM). The current study employs a constrained least-squares algorithm to allocate hydrocarbon sources contributing to subtidal sediments collected from PWS embayments in 1991, 1999 and 2000. Results show that sources contributing to the natural petrogenic background are present in the embayments, pyrogenic hydrocarbons including combustion products of diesel are important where human activity was high, and petroleum produced from the Monterey Formation (CA) is present locally. Oil and asphalt shipped from California were widely used for fuel and construction prior to development of the Cook Inlet and North Slope fields. In certain locations that were oiled in 1989, low levels of highly degraded Alaska North Slope crude oil residues attributable to the Exxon Valdez spill remain.     

A Holistic Approach to Hydrocarbon Source Allocation in the Subtidal Sediments of Prince William Sound,Alaska, Embayments

Prince William Sound (PWS), Alaska has an extensive history of human and industrial activity that has produced a complex organic geochemistry record in subtidal sediments of embayments throughout the sound. In addition to contributions from recent oil spills and a regional background of natural petroleum hydrocarbons originating from active hydrocarbon systems in the northern Gulf of Alaska (GOA), pyrogenic and petrogenic PAH were, and continue to be introduced to subtidal sediments at numerous sites of past and present human activities. These sites include villages, fish hatcheries, fish camps and recreational campsites in addition to abandoned settlements, canneries, sawmills, and mines. A holistic approach is used to fingerprint and quantify hydrocarbon contributions from multiple sources in a sediment sample. It involves acquiring a comprehensive understanding of the history of the area to identify potential sources, collection of representative samples, and accurate quantitative analyses of the source and sediment samples for a suite of diagnostic PAH analytes and chemical biomarker compounds. Unlike the deepwater sediments of the sound and GOA, the TOC tool, described elsewhere, does not work as well in some restricted embayments due to their high contents of recent organic matter (ROM). The current study employs a constrained least-squares algorithm to allocate hydrocarbon sources contributing to subtidal sediments collected from PWS embayments in 1991, 1999 and 2000. Results show that sources contributing to the natural petrogenic background are present in the embayments, pyrogenic hydrocarbons including combustion products of diesel are important where human activity was high, and petroleum produced from the Monterey Formation (CA) is present locally. Oil and asphalt shipped from California were widely used for fuel and construction prior to development of the Cook Inlet and North Slope fields. In certain locations that were oiled in 1989, low levels of highly degraded Alaska North Slope crude oil residues attributable to the Exxon Valdez spill remain.     

EROD activity and stable isotopes in seabirds to disentangle marine food web contamination after the Prestige oil spill

In this study, we measured via surgical sampling hepatic EROD activity in yellow-legged gulls from oiled and unoiled colonies, 17 months after the Prestige oil spill. We also analyzed stable isotope composition in feathers of the biopsied gulls, in an attempt to monitor oil incorporation into marine food web. We found that yellow-legged gulls in oiled colonies were being exposed to remnant oil as shown by hepatic EROD activity levels. EROD activity was related to feeding habits of individual gulls with apparent consequences on delayed lethality. Capture-recapture analysis of biopsied gulls suggests that the surgery technique did not affect gull survival, giving support to this technique as a monitoring tool for oil exposure assessment. Our study highlights the combination of different veterinary, toxicological and ecological methodologies as a useful approach for the monitoring of exposure to remnant oil after a large oil spill.     

Oil spill response capabilities and technologies for ice-covered Arctic marine waters: A review of recent developments and established practices

Renewed political and commercial interest in the resources of the Arctic, the reduction in the extent and thickness of sea ice, and the recent failings that led to the Deepwater Horizon oil spill, have prompted industry and its regulatory agencies, governments, local communities and NGOs to look at all aspects of Arctic oil spill countermeasures with fresh eyes. This paper provides an overview of present oil spill response capabilities and technologies for ice-covered waters, as well as under potential future conditions driven by a changing climate. Though not an exhaustive review, we provide the key research results for oil spill response from knowledge accumulated over many decades, including significant review papers that have been prepared as well as results from recent laboratory tests, field programmes and modelling work. The three main areas covered by the review are as follows: oil weathering and modelling; oil detection and monitoring; and oil spill response techniques.     

Oil Identification Based on a Goodness-of-Fit Metric Applied to Hydrocarbon Analysis Results

Assessment of environmental damage following accidental oil spills requires reliable oil identification methods. Results from hydrocarbon analyses of environmental samples are often difficult to interpret, because of the changes in oil composition (or weathering) that follows release into the environment, and because of confounding by hydrocarbons from other sources. To a first-order approximation, weathering proceeds according to simple first-order loss-rate (FOLR) kinetics for polycyclic aromatic hydrocarbons (PAH) based on molecular size. This relationship between relative weathering rate and molecular size can be exploited to infer the initial PAH composition of spilled oils, and this information can be combined with results for weathering-invariant analytes to substantially increase the precision and accuracy of hydrocarbon source recognition methods. The approach presented here evaluates a goodness-of-fit metric between the measured hydrocarbon composition of an environmental sample and a suspected source, after correcting for PAR weathering losses based on FOLR kinetics. Variability from analytical and sampling error may thus be accounted for, and source identifications can be expressed as objective probability statements. This approach is illustrated by application to four independent case studies.