David S. Page

Oil spill identification

Abstract To unambiguously identify spilled oils and petroleum products and to link them to the known sources are extremely important in settling questions of environmental impact and legal liability. This article briefly reviews the most recent development and advances of chemical fingerprinting and data interpretation techniques which are most frequently used in oil spill identification studies, including recognition of relative distribution patterns of petroleum hydrocarbons, analysis of ‘source-specific marker’ compounds, determination of diagnostic ratios of specific oil constituents, isotopic analysis, and several other emerging techniques. The issue of how biogenic and pyrogenic hydrocarbons are distinguished from petrogenic hydrocarbons is also addressed. Finally, the example of the Exxon Valdez spill is reviewed to illustrate how complex hydrocarbon mixtures were identified and allocated to multiple sources by using these advanced chemical fingerprinting techniques.

Pyrogenic polycyclic aromatic hydrocarbons in sediments record past human activity : A case study in Prince William Sound, Alaska

Polycyclic aromatic hydrocarbons (PAH) are sensitive recorders of past human activities in Prince William Sound, Alaska. In the nearshore subtidal sediments of bays, the fingerprints of the pyrogenic (combustion-derived) PAH record numerous sites of both present and historical human activities including active settlements, fish hatcheries, fish camps and recreational campsites, in addition to abandoned settlements, canneries, sawmills, and mining camps. In instances, there are high levels of PAH attributable to past human activities even though there is little remaining visual evidence of these activities on the shorelines. Forest fires are also an important source of pyrogenic PAH in subtidal sediments at certain time periods and locations and pyrogenic PAH from atmospheric fallout forms part of the regional PAH background. These pyrogenic PAH fingerprints are superimposed on a regional background of natural petroleum hydrocarbons derived from seeps in the eastern Gulf of Alaska. In isolated locations, weathered traces of the Exxon Valdez oil spill were detected as a minor part of the total PAH present from all sources.

Application of petroleum hydrocarbon chemical fingerprinting and allocation techniques after the Exxon Valdez oil spill

Advances in environmental chemistry laboratory and data interpretation techniques (i.e. chemical fingerprinting) contributed to a better understanding of the biological impact of the 1989 Exxon Valdez oil spill and the fate of the spilled oil. A review of the evolution of petroleum chemical fingerprinting techniques is presented followed by a summarization of how new approaches were used to characterize and differentiate among different petroleum sources in the Prince William Sound region after the spill. An assessment of the initial data suggested that multiple sources of polycyclic aromatic hydrocarbons (PAH) were present. These findings were further substantiated, even in samples of low part-per-billion PAH concentrations, by using refined and extended laboratory techniques including the analysis of saturate biomarkers. To interpret these mixtures of sources, fingerprint-analysis flow charts and source allocation techniques were developed and applied to the data, leading to the quantification of the spilled oil as a small increment on the natural hydrocarbon background in subtidal sediments.

Petroleum hydrocarbons and their effects in subtidal regions after major oil spills

Abstract The question often arises after large oil spills as to the extent and effect of oil entering the subtidal zones adjacent to heavily oiled shorelines. Estimates for a number of large spills suggest that 1 to 13% of the spilled oil can enter subtidal regions. Hydrocarbon concentrations in these subtidal zones are generally orders of magnitude lower than shoreline sediments. For example, in the Exxon Valdez oil spill, subtidal sediment hydrocarbon concentrations attributable to the spill were very low in the first year after the spill and barely detectable in the second year. The conditions necessary to produce high concentrations of hydrocarbons in the subtidal region include large amounts of oil in a semienclosed estuary or bay and high concentrations of fine particulate matter to associate with hydrocarbons to allow them to disperse and sink. Such conditions do not often occur after spills, with some exceptions, such as low energy tidal estuaries in the Amoco Cadiz spill in Brittany, France. More commonly sea floor sediment hydrocarbon concentrations, where sediment-associated hydrocarbons have settled, are generally near to background levels, due to dilution and weathering. A number of methods have been used to evaluate the biological effects of oil spills on subtidal fauna. These include toxicity to amphipods, increases in the concentrations of fluorescent aromatic metabolites in the bile of fish, histopathology of fish, increases in opportunistic species and infaunal succession. Sediments collected from the subtidal zone below heavily oiled shorelines of the Exxon Valdez spill showed low toxicity using standard amphipod bioassays. Well documented effects on the subtidal biota adjacent to heavily oiled shorelines are the increases in the number of hydrocarbon degrading microbes which are fed on by opportunistic species of meiofauna which in turn are food for macrofauna. The documented biological effects of oil in the subtidal region are generally of short duration and recovery back to an equilibrium or ‘normal’ condition is typically quite rapid.

Concentration of butyltin species in sediments associated with shipyard activity.

Tributyltin (TBT) and dibutyltin (DBT) were analyzed in sediment samples collected from intertidal locations in Portland and Boothbay Harbor, Maine (USA) in 1990 and 1992. Surface sediment TBT concentrations ranged from 24 to 12 400 ng gm(-1) (dry wt basis). Sediments with the highest TBT concentrations were associated with shipyard hull washing/refinishing activities. Analysis of different layers in core samples found that butyltin concentrations decreased with depth at the Boothbay site and remained relatively constant with depth at the Portland site. Elutriate analysis showed that soluble TBT was released from a heavily contaminated sediment. The resulting TBT seawater concentration 1400 ng liter(-1) was < 0.03% of reported seawater solubilities of TBT and was only 0.14% of the total TBT in the sediment sample. This suggests that the TBT in the sediments analyzed is in a bound matrix form, such as paint particles, that releases the biocide slowly. The results indicate that there is a potential for future release of TBT from the resuspension of fine sediments at certain locations in Maine.

Effects of tributyltin and dibutyltin on the physiological energetics of the mussel, Mytilus edulis

Abstract Sublethal physiological responses (clearance rate, oxygen uptake, absorption efficiency and scope for growth) of mussels (Mytilus edulis) were measured following exposure to tributyltin (TBT) and dibutyltin (DBT). Effects were related to the concentration of TBT and DBT in the mussel tissues. Rate of oxygen uptake increased two-fold with increasing TBT concentration from 0·5 to 10 μg TBT g−1 (dry weight). Clearance (= feeding) rate was significantly reduced above a threshold concentration of 3 to 4 μg TBT g−1. Absorption efficiency was unaffected at concentrations below 10 μg TBT g−1. The overall effect, in terms of scope for growth, indicated a severe inhibition of growth above 4 μg TBT g−1. DBT was shown to be an order of magnitude less toxic than TBT, when expressed in terms of the tissue concentration inducing toxic effects. The threshold concentrations causing a reduction in the rates of feeding and oxygen uptake were 23 and 36 μg DBT g−1, respectively. These sublethal effects are discussed in relation to mechanisms of toxicity, previous alkyltin studies and environmental concentrations.

Temporal and spatial variation in levels of alkyltins in mussel tissues: A toxicological interpretation of field data

This study presents results of mussel tissue tributyltin (TBT) analyses from four study areas; the Lynher River, Cornwall, UK; Sullom Voe oil terminal, Shetlands, UK; Langesundfjord, Norway; Hamilton Harbour, Bermuda. To illustrate temporal variations in TBT concentrations, mussels Mytilus edulis were sampled and analysed for alkyltins at 1–3 month intervals between 1987 and 1989 from the Lynher River. The results show an inter-annual variation in [TBT] of lower winter values and higher late-spring-early-summer values, consistent with probable inputs from seasonal recreational boating superimposed on a background of dockyard-shipping TBT inputs and seasonal water exchange variations. An overall decrease in TBT inputs from 1987 to 1989 was observed. For the remaining three study areas, the spatial variation in tissue TBT concentration was related to scope for growth (SFG), a measure of net energy available for growth and reproduction. For both Sullom Voe oil terminal and Langesundfjord, Norway, the measured TBT concentration in M. edulis from the field were below the TBT concentration shown to have threshold of effect on SFG in laboratory studies. In both cases, observed variations in SFG could be related to other toxicants such as aromatic hydrocarbons. In Hamilton Harbor both petroleum-derived toxicants and TBT were identified as the major toxic contaminants causing a reduction in SFG in Arca zebra. Toxicological interpretation of the contaminants and their effects on the components of SFG indicated that TBT accounted for 35% of the observed decline in SFG from the innermost harbour site and petroleum-derived toxicants, the remaining 65%. The overall results show that it is possible to use toxicological relationships between tissue TBT concentrations and a physiological stress indicator such as SFG to interpret the likely toxic effects of TBT in field populations of mussels.

Responses of cytochromeP-450 systems in marine crab and polychaetes to organic pollutants

A number of field and laboratory studies were carried out to determine responses of the cytochromeP-450 dependent mixed-function oxygenase systems in crabs (Callinecles sapidus, Sesarma cinerum and Uca pugilaior) and polychactes (Nereis virens) to organic pollutants. Mixed function oxygenase (benzo[a]pyrene hydroxylase) activity and cytochromeP-450 content generally increased in polychaetes and crabs after exposure to oil, benzo[a]pyrene or polychlorinated biphenyls. No changes were observed in the cytochrome bs or the content of NADPH cylochrome c reductase activity after the animals were exposed to pollutants. A consistent response to foreign organic compounds were changes in the binding to cytochromeP-450 reflected in the apparent binding constant, Ks. In the present rcpon, we studied the binding properties of several type I (benzphetamine and SKF-525A) and type II (aniline. n-octylamine and n-hexylamine) substrates to the cytochromeP-450 of polychaetes and crabs. In all crabs exposed to oil, both in the field and laboratory, the Ks for aniline was approximately half that of unexposed animals. In polychactes large increases in Ks with SKF-525A wert observed after exposure to both enzo[a]pyrene and Aroclor 1254. Such changes in Ks may indicate the production of new forms of cylochromeP-450 after exposure to certain classes of organic pollutants.

Identification of petroleum sources in an area impacted by the Amoco Cadiz oil spill

Samples of oiled sediment and tar were taken at locations in the area of Brittany, France known as the ‘Pink Granite Coast’. Each sample was analysed for hydrocarbons by gas chromatography and gas chromatography/mass spectrometry to determine the probable source of any petroleum residues present. The results show numerous recent inputs of various petroleum products including crude oils and light fuel oils at various locations. By 1985, the data indicate that the contribution from remaining weathered residues of Amoco Cadiz oil to the hydrocarbon baseline is small compared to more recent inputs of petroleum.

Polycyclic aromatic hydrocarbon levels in mussels from prince william sound, ALASKA, USA, document the return to baseline conditions

Bioavailable hydrocarbons in the Exxon Valdez oil spill zone in Prince William Sound (PWS; AK, USA) shorelines were at or near background levels in 2002, as indicated by low concentrations of polycyclic aromatic hydrocarbons (PAHs) in mussels (Mytilus trossulus) collected from sites throughout PWS. Total PAH (TPAH) minus parent naphthalene concentrations in mussels collected in 1998 to 2002 from sites oiled in 1989 were at or near reference-site values. Both oiled and reference sites included locations associated with past human and industrial activity (HA). Inclusion of the unoiled HA sites in the range of reference sites that define prespill conditions is consistent with federal regulations. For the period from 1998 to 2002, the geometric mean of TPAH concentrations for 218 mussel samples collected from 72 sites, including four HA sites that had been heavily oiled in 1989, is 54 ng/g dry weight (range, 2-1,190 ng/g). The maximum mussel TPAH concentrations are equivalent to a weathered-oil exposure dose to intertidal foragers that is one to three orders of magnitude less than the doses shown to cause sublethal effects in surrogate species. The geometric mean of TPAH concentrations for mussel samples from 28 locations not oiled in 1989 and unaffected by human use (NHA sites) is 28 ng/g (range, 3-355 ng/g), whereas the geometric mean of TPAH concentrations for mussel samples from 14 locations not oiled in 1989 and affected by human use (HA sites) is 106 ng/g (range, 2-12,056 ng/g). The range of data for the unoiled HA and NHA sites defines the background of bioavailable PAHs to mussels on western PWS shorelines that would have prevailed if the oil spill had not occurred. The low PAH concentrations in mussels from sites known to have subsurface oil residues demonstrates the low bioavailability of these spill remnants and, thus, are a low additional risk to foraging wildlife. The present study shows continuous exposure from four- to six-ring PAHs originating at HA sites in western PWS. At low concentrations, these PAHs are known to cause adverse biological effects. However, in the context of PWS, oiled and HA sites represent a small percentage (approximately 0.1-0.2%) of the total PWS shoreline.