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Following the 1989 Exxon Valdez oil spill (EVOS), the Prince William Sound Regional Citizens' Advisory Council began the Long-Term Environmental Monitoring Program (LTEMP) in 1993 to track oil hydrocarbon chemistry of recovering sediments and mussel tissues along the path of the spill in Prince William Sound (PWS) and across the Northern Gulf of Alaska (NGOA) region. The program also samples sites near the Alyeska Marine Terminal (AMT) within Port Valdez, primarily to monitor tanker operations and the resulting treatment and discharge of oil-contaminated tanker ballast water. Over the last 28 years, the program has documented EVOS oil's disappearance at the spill-impacted sites (albeit buried oil still exists at a few unique sheltered locations in PWS). Within the Port, a few tanker- and diesel-spill incidents have been documented over the years, but all were minor and with recovery times of < 1 yr. Of highest concern has been the permitted chronic release of weathered oil from tankers' ballast-water that is treated and discharged at the Alyeska Marine Terminal (AMT). In earlier years (1980s–90s), with discharge volumes reaching 17–18 MGD, up to a barrel of finely dispersed weathered oil would be released into the fjord daily. Over the last two decades, total petrogenic inputs (TPAH43) into the Port have declined as measured in the monitored mussels and sediments. This trend reflects a combination of decreased Alaska North Slope (ANS) oil production and thus, less tanker traffic, plus less ballast from the transition to double-hulled tankers with segregated ballast tanks, and improved treatment-facility efficiency in removing PAH. From the 2018 collections, mussel-tissue hydrocarbon concentrations from all eleven LTEMP stations (within Port Valdez as well as PWS and NGOA regions) were below method detection limits and similar to laboratory blanks (TPAH43 < 44 ng/g dry wt.). At these low background levels, elevated TPAH values from a minor 2020 spill incident at the Terminal were easily detected at all three Port Valdez stations.

NO. 2017-167 As part of the Natural Resource Damage Assessment (NRDA) effort following the Deepwater Horizon (MC252) blowout and oil spill in 2010, over 5,300 water samples were forensically evaluated both as evidence of exposure and to validate oil fate and transport modelling. In addition to whole water-sample grabs, particulate-oil and dissolved-phase samples from the subsurface release were separated (filtered) in the field to provide detailed information on the partitioning behavior of oil droplets in a deepwater plume (1,000–1,400m) extending to the southwest (SW) of the wellhead. Offshore, the subsurface plume was visually observed and photographed using remotely operated vehicles (ROVs), and tracked in conductivity, temperature, and depth (CTD), dissolved oxygen (DO), and fluorometry profiles. The farthest reach of the plume was 412 km (250 mi) SW of the wellhead as confirmed by multiple lines of evidence (i.e., depth, fluorometry spikes, DO sags, and dispersant indicators) and out to 267 km as weathered, phase-discriminated, confirmed hydrocarbon profiles. With increasing time and distance from the wellhead, the plume’s polycyclic aromatic hydrocarbon (PAH) signal became diluted and eventually no longer detectible using selected-ion-monitoring (SIM) gas chromatography/mass spectrometry (GC/MS), although the plume was still discernible in the corroborating data. We hypothesize that microbial degradation at depth converted the PAH and aliphatics into oxygenated and polar products not detectible using SIM GC/MS methods. Near-surface oil samples showed evidence of substantial dissolution weathering as the oil droplets rose through the water column, and further evaporative losses of lower-molecular-weight n-alkanes and aromatic hydrocarbons occurred after the oil reached the surface. Surface oil also showed evidence of photo-oxidation of alkylated chrysenes and triaromatic steranes. Typical of surface oil dynamics, increases in dissolved and particulate-oil fractions were observed in the shallow sub-surface as a result of both dispersant effects and wave reentrainment of surface films. Dispersant treatment effects, both as surface applications and injected at the wellhead, showed uniquely enhanced-dissolution weathering patterns in PAH profiles with limited or delayed microbial degradation of saturated hydrocarbons (SHC) close to the wellhead. From an oil-fate-and-transport standpoint, these data document that the dispersant applications at depth were functionally effective in breaking up the oil droplets and thereby preventing some portion of the oil from reaching the surface.

As analytic instruments and methods have improved over the decades, so too, have insights into the fate and behavior of oil–water mixtures. Particularly relevant are understanding and documenting oil phase signatures that, while yielding forensic insights in our early studies, have led to the recent development of phase-specific methods appropriate for the forensic study of oiled water. The forensic applications of these methods include source matching, weathering, deconfounding background contaminants, distinguishing dissolved and particulate phases within whole water samples, and documenting chemical dispersant effects on polycyclic aromatic hydrocarbons (PAH) profiles. These methods, when collectively applied to deep-sea water of the Gulf of Mexico following the Deepwater Horizon (DWH) blowout, were used to ultimately track the subsurface plume of DWH-impacted water 412 km across the Gulf of Mexico to a final sample confirmed with only a trace dissolved-PAH pattern and supporting information.

During the Deepwater Horizon blowout, unprecedented volumes of dispersant were applied both on the surface and at depth. Application at depth was intended to disperse the oil into smaller microdroplets that would increase biodegradation and also reduce the volumes buoyantly rising to the surface, thereby reducing surface exposures, recovery efforts, and potential stranding. In forensically examining 5300 offshore water samples for the Natural Resource Damage Assessment (NRDA) effort, profiles of deep-plume oil droplets (from filtered water samples) were compared with those also containing dispersant indicators to reveal a previously hypothesized but undocumented, accelerated dissolution of the polycyclic aromatic hydrocarbons (PAH) in the plume samples. We interpret these data in a fate-and-transport context and conclude that dispersant applications were functionally effective at depth.

Forensic chemistry assessments documented the presence of Macondo (MC252) oil from the Deepwater Horizon (DWH) spill in offshore water samples collected under Natural Resource Damage Assessment (NRDA) protocols. In ocean depths, oiled water was sampled, observed, photographed, and tracked in dissolved oxygen (DO) and fluorometry profiles. Chemical analyses, sensor records, and observations confirmed the shifting, rising oil plume above the wellhead while smaller, less buoyant droplets were entrapped in a layer at ~1000–1400 m and advected up to 412 km southwest. Near-surface oil samples showed substantial dissolution weathering from oil droplets rising through the water column, as well as enhanced evaporative losses of lighter n-alkanes and aromatic hydrocarbons. Dispersant effects from surface applications and injected at the wellhead were seen in oil profiles as enhanced weathering patterns (increased dissolution), thus implying dispersants were a functionally effective mediation treatment. Forensic assessment methods are detailed in the Supplemental information (SI).

After a spill, oil is present in water as both dissolved and particulate (oil-droplet) phases due to entrainment and dissolution/weathering processes. The two phases, capable of physically separating and remixing in a body of water, complicate forensic evaluations but also contribute information on waterborne fate and transport. Identifying and tracking each phase in field samples has high forensic value in developing interpretive scenarios of weathering and exposure processes and for providing data germane to modeling and toxicology studies in damage assessments. Samples can be parsed into phase components either physically in the field using portable filtration equipment or later with data evaluation methods developed to parse out unfiltered samples using a weathered particulate-oil reference series generated from a few field-filtered samples. If done properly, sampling the water column for oil hydrocarbons during or after an oil spill can be highly insightful but the task is challenging and technically demanding with multiple opportunities to get it wrong, especially without feedback until weeks or months later when the data come back from the lab. This chapter presents water-sampling issues (and solutions), methods of forensically assessing quantified data, and adaptive sampling strategies that prove effective in tracking a deep submerged plume.

Oil stranded by the 1989 Exxon Valdez spill has persisted in subsurface sediments of exposed shores for 16 years. With annualized loss rates declining from approximately 68% yr(-1) prior to 1992 to approximately 4% yr(-1) after 2001, weathering processes are retarded in both sediments and residual emulsified oil ("oil mousse"), and retention of toxic polycyclic aromatic hydrocarbons is prolonged. The n-alkanes, typically very readily oxidized by microbes, instead remain abundant in many stranded emulsified oil samplesfrom the Gulf of Alaska. They are less abundant in Prince William Sound samples, where stranded oil was less viscous. Our results indicate that, at some locations, remaining subsurface oil may persist for decades with little change.

Buried oil residues in selected beaches that were heavily contaminated by the 1989 Exxon Valdez Oil Spill (EVOS) continue to leach oil-contaminated suspended particulate material (SPM) and dissolved-phase polycyclic aromatic hydrocarbons (PAH) into interstitial- and near-shore waters. Both are bioavailable forms of hydrocarbons that can be absorbed or consumed. On selected intertidal beaches in Prince William Sound (PWS) during June 2002, nearshore- and interstitial-water samples were collected during outgoing tides, first from a water depth of 10–15 cm above undisturbed sediments at water's edge and then from pits dug just above the waterline. At the time of collection, all samples were vacuum-filtered through 0.7-µm pore-size, glass-fiber filters using a Portable Large Volume Water Sampling System (PLVWSS) to separate dissolved- and oil-contaminated SPM fractions for detailed hydrocarbon analyses and fingerprinting. From intertidal pits at oil-impacted sites, interstitial water and SPM displayed strong oil signatures and elevated (albeit variable) PAH and n-alkane levels compared to the trivial non-petrogenic signatures seen at the reference sites. The dissolved-phase samples at the oil-impacted sites were typically characterized by water-soluble, lower-molecular-weight PAH, while the SPM/oil-phase contained the relatively-insoluble, higher-molecular-weight PAH and n-alkanes. Water's-edge samples (collected before any pits were excavated) typically showed a diluted- and degraded-compositional signature traceable to the interstitial water from higher tide levels. Interstitial-water dissolved-phase concentrations (average 1,200 ng/L.; 76–4,600 ng/L vs. 18–27 ng/L for reference sites) were above those reported to cause impacts to herring and salmon eggs (

For years, it has been known that oil released in seawater partitions into dissolved and oil-droplet phases; however, there has been little effort to discriminate between the phases in oil spill Natural Resource Damage Assessment (NRDA) programs. In 1999, portable field equipment was built for this task. By filtering 3.5 L volumes of seawater at the time of collection, method detection limits are improved and it is possible to discriminate between the phases, thereby improving understanding of oil fate and transport processes and providing more accurate toxicological assessments. First utilized in response to the M/V New Carissa oil spill at Coos Bay, Oregon, this approach proved highly successful in discriminating the phase signatures. The resulting data demonstrated that while the dissolved-phase signal appeared in places such as crab tissue and interstitial water on an otherwise clean beach, the oil-droplet phase appeared in tissues of filter-feeding Coos Bay mussels and oysters. In Port Valdez, Alaska, the portable sampler was used to assess the phase signatures in effluent from the Ballast Water Treatment Facility (BWTF) at the Alyeska Marine Terminal. The signatures were then used to reveal differential seasonal uptake in mussels at several sites within the port. During the winter, when the water column is unstratified, both dissolved- and oil-droplet phase contaminants from the BWTF diffuser can reach the upper water column, where they are transported as a surface microlayer by winds and surface currents throughout much the fjord. In the late spring, summer, and fall, when the water column is highly stratified, only the dissolved-phase components are observed in the mussels along the shoreline, as the oil droplets are preferentially trapped below the thermocline. These findings have compelled a reassessment of monitoring methods for oil spill NRDA efforts, National Pollutant Discharge Elimination System (NPDES) permitting, and general environmental monitoring.

We followed long-term dynamics of a conspicuous intertidal brown alga, Fucus gardneri, for seven years after the 1989 Exxon Valdez oil spill (EVOS) in Prince William Sound, Alaska, USA. We compared percent cover of Fucus over time at sites that had been oiled, some of which were washed with high-pressure hot water, relative to sites that had experienced neither oil nor cleanup activities (reference sites). Fucus cover at spill-disturbed sites was initially reduced due to toxic effects of oil and cleanup but rapidly increased to above normal levels and then subsequently dropped in 1994–1995. The changes in cover at spill-disturbed sites were dramatic (≥50% decline year-to-year) and synchronous across all quadrats at a site. In contrast, reference sites demonstrated little synchrony. We examined two possible mechanisms that could generate synchronous fluctuations at spill-disturbed sites, i.e., (1) plant–herbivore coupling, in which limpet or snail grazing would reduce Fucus populations (hypothesis tested b...

Source oil characterization and its subsequent identification and quantification in different receiving environments are integral components of a natural resource damage assessment (NRDA) following a spill. When the M/V New Carissa broke up on the Oregon coast in February 1999, it released an estimated 70,000 gallons of two bunker fuels and two diesel fuels. Numerous oil, water, sediment, and tissue samples were subsequently analyzed for the standard suite of aliphatic and polynuclear aromatic hydrocarbon (PAH) fractions, as well as steranes and triterpanes to use in chemical fingerprinting in support of the NRDA process. The fingerprinting task was uniquely complex with this spill because of the four major source oils of highly disparate compositions and additional compositional changes occurring as a result of partial in situ burning and release of residual fuels onboard the vessel during the response effort. Also unique to NRDA process was the segregated sampling of dissolved-phase and dispersed-oil droplet fractions from the water column, information that proved invaluable in the fingerprinting process. To assist with the complex data analysis in identifying New Carissa oil in environmental samples, a combination of multivariate principal-component analyses and hierarchical agglomerative-cluster analyses, conventional double-ratio analyses of selected PAH, and custom computer displays to allow comparison of multiple graphs on a single page was developed. Results show two different mechanisms of hydrocarbon uptake into affected organisms: direct uptake of dissolved-phase PAH from the water column into crab tissues, and accumulation of aliphatic and aromatic constituents from dispersed oil droplets and oiled suspended particulate material (SPM) by filter-feeding organisms. From the combined statistical and fingerprinting process, it was possible to differentiate New Carissa oil from background combustion-derived (and sediment-associated) PAH in selected clam and oyster tissue samples from inside Coos Bay. Also documented was interstitial water contamination of otherwise clean and unoiled sandy beach substrates by offshore dissolved-phase PAH, and the accumulation of hydrocarbons from the surface microlayer by diatoms.

Infaunal bivalves monitored in Prince William Sound intertidal sediments between 1990 through 1996 appear to have been affected more by shoreline treatment than by exposure to oil. Lower numbers were observed at oiled but treated (Category 3) sites whereas highest numbers were observed at reference (Category 1) sites. Species richness, very similar at reference and oiled but untreated (Category 2) sites after 1990, declined slightly during the study. Abundance, also quite similar at reference and Category 2 sites, peaked in 1992 or 1993 and then gradually declined through the remaining years. In contrast, averages for Category 3 sites exhibited no apparent trends representing recovery. Differences in both variables were highly significant between reference and Category 2 sites, on one hand, and Category 3 sites, on the other hand. Dominance patterns and behavior provide important insights into the effects of the spill, shoreline treatment, and the recovery process. Mysella tumida, Macoma spp., and Protothaca staminea dominated at reference and Category 2 sites but were far less common at Category 3 sites. These dominant species generally are relatively long-lived, slowly reproducing species that bury up to several centimeters below the surface of stable sediments. Mysella is typically commensal with larger burrowing species that are mostly absent or uncommon at Category 3 sites. In contrast, Hiatella arctica, the dominant at Category 3 sites, is an opportunist that nestles on the surface of disturbed sediments.

Eight years of quantitative biological and chemical data have been analyzed for trends in recovery of biota inhabiting beaches in Prince William Sound following the 1989 Exxon Valdez oil spill and subsequent shoreline treatments. Sampling has focused on biota at sheltered rocky and mixed-soft sites subjected to three degrees of disturbance (unoiled, oiled but not hot-water washed, and oiled/hot-water washed). Only epibiota on sheltered rocky habitats are covered in this paper. The majority of community dominants survived 1989 on oiled rocky shores that were not high-pressure, hot-water washed. These areas appeared to be nearly completely recovered by 1991, although subsequent monitoring has revealed oscillations in species abundances that exceed those on unoiled beaches. Hot-water treatments used in 1989 had severe short-term impacts on intertidal epibenthos. Some high-pressure, hot-water-treated rocky shores stripped of biota in 1989 showed very slow colonization through 1995; other areas that appeared to be nearly recovered in 1992 suffered severe declines in dominant taxa in 1995. The dominant age class of rockweed, which began life following hot-water treatment, matured in 1993 and died off in 1994 and 1995, resulting in declines of associated fauna. A new cycle of rockweed colonization has begun, and some recovery of rockweed and associated fauna was observed in 1996.

Field surveys were conducted throughout Prince William Sound in the summers of 1990 through 1992 to evaluate recovery of infauna from the effects of oiling and shoreline cleaning treatments following the Exxon Valdez oil spill. Infauna were quantitatively sampled at mixed sand/gravel/cobble beaches categorized into treatment groups according to their general degree of disturbance.Category 1: unoiled reference sitesCategory 2: oiled sites, not hot-water-washedCategory 3: oiled sites, “cleaned” with hot-water flushes Shoreline treatments applied in 1989 and 1990 had varied effects on intertidal infauna including organism displacement and burial, thermal stress, oil dispersion, and transformed beach morphology. These treatments resulted in significant reductions in infauna (total abundance and diversity, as well as densities of polychaetes, bivalves, and some crustaceans) at Category 3 beaches. In contrast, Category 2 beaches had a richer and more varied infauna than Category 3 beaches. Multivariate analyses indicate some trends in recovery: namely, a convergence by certain Category 2 sites toward the Outside Bay, Category 1 control site. PAH concentrations in 1990 also suggest that treatments acted to move some hydrocarbons downslope from the upper beach into the shallow subtidal. By 1991, PAH concentrations in the shallow subtidal were no longer at the high levels seen in 1990, but PAH levels at other elevations of Category 3 sites remained at about the same levels as in 1990.

Following the Exxon Valdez spill, several approaches were used to remove crude oil from the beaches of Prince William Sound. Pre- and post-treatment monitoring in 1989 documented the severe short-term impacts to intertidal epibenthos of hot water wash treatments widely used to remove stranded oil. Quantitative field surveys were conducted in 1990 and 1991 to evaluate recovery of littoral habitats from the effects of oiling and hot water washing. Stratified random sampling was used to assess epibiota at sites representing several habitats and degrees of disturbance. Effects of hot water treatments applied in 1989 remained visible in intertidal assemblages through 1991. Some hot water-treated rocky beaches that had been stripped of biota at middle and upper intertidal elevations showed little colonization by 1990. In 1990, statistically significant differences were noted between variables measured on unoiled beaches and those same variables on hot water-treated beaches. On other oiled rocky beaches that received less severe or no treatment, the majority of the community dominants, including rockweed, mussels, barnacles, limpets, drills, and littorines, survived the oiling. While these populations were still depressed below abundance levels on unoiled beaches in May 1991, by July recovery of most species had raised abundances to levels seen on unoiled beaches. In the summer of 1991, few statistically significant differences remained between the biota of unoiled rocky shores and those of hot water-washed shores, but full recovery is still several years away in many areas.

A substantial amount of the crude oil which spilled from the tanker Exxon Valdez on March 24, 1989, was deposited on beaches in Prince William Sound. Major beach cleanup activities began in May and continued throughout the summer of 1989. Additional cleanup activities occurred during the summer of 1990. A study was conducted in 1989 to document the short-term impact to biota of hot water wash treatments. Additional field surveys were conducted in the summer of 1990 to evaluate recovery of littoral habitats from the effects of oiling and shoreline treatment. Stratified-random sampling was used to assess epibiota and infauna at 27 sites, representing several habitats and degrees of disturbance. Preliminary data evaluations indicate that treatment methodologies applied in 1989 had varied effects on intertidal assemblages. Some treated rocky beaches were stripped of flora and fauna at mid- and upper intertidal elevations and showed relatively little colonization by mid summer 1990. On other oiled rocky beaches that received less severe or no treatment, the majority of the community dominants remained in place and significant recolonization was underway. Protected sand and gravel beaches subjected to hydraulic treatments displayed greatly altered beach morphology. Finer sands and gravels were flushed from upper intertidal elevations, often burying the lower beach in several centimeters of sediment, resulting in major reductions in infauna in 1990. Oiled but untreated sand and gravel beaches had a rich and varied infauna. The effects of 1989 shoreline treatment activities on intertidal flora and fauna were significant and widespread and will greatly complicate assessment of the long-term impacts of the oil itself.

In the aftermath of the 1989 Exxon Valdez oil spill, a Long Term Environmental Monitoring Program (LTEMP) has been regularly sampling mussels (and some sediments) for polycyclic aromatic and saturated hydrocarbons (PAH and SHC) at sites in Port Valdez, Prince William Sound, and the nearby Gulf of Alaska region. After 1999, a decreasing trend appears in total PAH (TPAH) in tissues at all sites with current values below 100 ng/g dry weight (many below 50 ng/g). Currently, most samples reflect a predominantly dissolved-phase signal. This new low in TPAH likely represents ambient background levels. Synchrony in TPAH time-series and similarities in the hydrocarbon signatures portray regional-scale dynamics. The five inner Prince William Sound sites show similar composition and fluctuations that are different from the three Gulf of Alaska sites. The two Port Valdez sites represent a unique third region primarily influenced by the treated ballast water discharge from the Alyeska Marine Terminal. Prince William Sound has reverted to a stable environment of extremely low level contamination in which local perturbations are easily detected.