Alkylnaphthalenes: priority pollutants or minor contributors to the poor health of marine mussels?

Anthropogenic petroleum signatures and biodegradation in subantarctic Macquarie Island soils

Special Antarctic Blend (SAB) diesel is the main fuel used on Macquarie Island and has been identified as the primary contaminant in several past spill events. This study evaluates the environmental impact of petroleum spills at high latitudes, in the soils of subantarctic Macquarie Island. Soil samples were collected from seven locations, including the "fuel farm" and main powerhouse that have been contaminated by petroleum in the past, and five reference locations, away from station infrastructure and from any obvious signs of contamination. Soils were solvent extracted and analysed using gas chromatography-mass spectrometry. The results show that both contaminated and uncontaminated sites contained a suite of different chain-length hydrocarbons. The more contaminated samples from the fuel farm and main powerhouse contained higher concentrations and a greater range of hydrocarbons that typically indicate numerous spills of varying ages. The hydrocarbon signature of samples collected near the fuel farm and at some of the main powerhouse sites was typical of SAB diesel. However, the hydrocarbon signature at other main powerhouse sites suggest contamination with a heavier fuel with different characteristics, including lower pristane/phytane ratios. Traces of C₂₁-C₃₅ cyclic biomarkers in the spill sites may be derived from additional heavier fuels, and include a signature characteristic of crude oil derived from marine carbonate source rocks. Reference samples had lower concentrations of hydrocarbons, and these were dominated by high molecular weight n-alkanes with an odd-carbon-number predominance, typical of higher-plant derived lipids. Some reference samples also contained geochemical signatures that suggest that they too were contaminated by fuel oil. Variable levels of biodegradation of fuels in soils are consistent with a heterogenous site and a relatively slow rate of biodegradation. The occurrence of fresh spilled fuel overprinting biodegraded fuel from earlier spills is compelling evidence of multiple spills and complex mixing in the environment.

Fish Fingerprinting: Identifying Crude Oil Pollutants using Bicyclic Sesquiterpanes (Bicyclanes) in the Tissues of Exposed Fish

In the present study, we investigated the possibility of identifying the source oils of exposed fish using ratios of bicyclic sesquiterpane (bicyclane) chemical biomarkers. In the event of an oil spill, identification of source oil(s) for assessment, or for litigation purposes, typically uses diagnostic ratios of chemical biomarkers to produce characteristic oil "fingerprints." Although this has been applied in identifying oil residues in sediments, water, and sessile filtering organisms, so far as we are aware this has never been successfully demonstrated for oil-exposed fish. In a 35-day laboratory trial, juvenile Lates calcarifer (barramundi or Asian seabass) were exposed, via the diet (1% w/w), to either a heavy fuel oil or to Montara, an Australian medium crude oil. Two-dimensional gas chromatography with high-resolution mass spectrometry and gas chromatography-mass spectrometry were then used to measure selected ratios of the bicyclanes to examine whether the ratios were statistically reproducibly conserved in the fish tissues. Six diagnostic bicyclane ratios showed high correlation (r²  > 0.98) with those of each of the two source oils. A linear discriminatory analysis model showed that nine different petroleum products could be reproducibly discriminated using these bicyclane ratios. The model was then used to correctly identify the bicyclane profiles of each of the two exposure oils in the adipose tissue extracts of each of the 18 fish fed oil-enriched diets. From our initial study, bicyclane biomarkers appear to show good potential for providing reliable forensic fingerprints of the sources of oil contamination of exposed fish. Further research is needed to investigate the minimum exposure times required for bicyclane bioaccumulation to achieve detectable concentrations in fish adipose tissues and to determine bicyclane depuration rates once exposure to oil has ceased. Environ Toxicol Chem 2023;42:7-18. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

MV Wakashio grounding incident in Mauritius 2020: The world's first major spillage of Very Low Sulfur Fuel Oil

Very Low Sulfur Fuel Oils (VSLFO, <0.5% S) are a new class of marine fuel oils, introduced to meet recent International Maritime Organization regulations. The MV Wakashio was reported to have released 1000 t of VLSFO when it grounded on a reef in Mauritius on 25th July 2020. A field sample of oily residue contaminating the Mauritian coast was collected on 16th August 2020 and compared with the Wakashio fuel oil. Both oils were analyzed for organic and elemental content, and stable isotope ratios δ¹³C and δ²H measured. Comprehensive two-dimensional gas chromatography with high-resolution mass spectrometry was used to identify and compare biomarkers resistant to weathering. The aromatic content in the VLSFO was relatively low suggesting that the potential for ecosystem harm arising from exposure to toxic components may be less than with traditional fuel oil spills. The Wakashio oil spill is, to our knowledge, the first documented spill involving VLSFO.

Sublethal effects of contaminants on marine habitat-forming species: a review and meta-analysis

Contaminants may affect ecosystem functioning by reducing the fitness of organisms and these impacts may cascade through ecosystems, particularly if the sensitive organisms are also habitat‐forming species. Understanding how sub‐lethal effects of toxicants can affect the quality and functions of biogenic habitats is critical if we are to establish effective guidelines for protecting ecosystems. We carried out a global systematic review and meta‐analysis critically evaluating contaminant effects on properties of habitat‐formers linked to ecosystem functioning. We reviewed a total of 95 publications. However, 40% of publications initially captured by the literature search were identified as having flaws in experimental design and ~11% did not present results in an appropriate way and thus were excluded from the quantitative meta‐analysis. We quantitatively reviewed 410 studies from 46 publications, of which 313 (~76%) were on plants and seaweeds, that is macro‐algae, saltmarsh plants and seagrasses, 58 (~14%) studied corals and 39 (~10%) looked at toxicant impacts on bivalves, with 70% of those on mussels and the remaining studies on oysters. Response variables analysed were photosynthetic efficiency, amount of chlorophyll a (as a proxy for primary production) and growth of plants, seaweeds and corals as well as leaf area of plants. We also analysed filtration, growth and respiration rates of bivalves. Our meta‐analysis found that chemical contaminants have a significant negative impact on most of the analysed functional variables, with the exception of the amount of chlorophyll a. Metals were the most widely harmful type of contaminant, significantly decreasing photosynthetic efficiency of kelps, leaf area of saltmarsh plants, growth of fucoids, corals and saltmarsh plants and the filtration rates of bivalves. Organic contaminants decreased the photosynthetic efficiency of seagrass, but had no significant effects on bivalve filtration. We did not find significant effects of polycyclic aromatic hydrocarbons on any of the analysed functional variables or habitat‐forming taxa, but this could be due to the low number of studies available. A meta‐regression revealed that relationships between concentrations of metal contaminants and the magnitude of functional responses varied with the type of metal and habitat‐former. Increasing concentrations of contaminants significantly increased the negative effects on the photosynthetic efficiency of habitat‐formers. There was, however, no apparent relationship between ecologically relevant concentrations of metals and effect sizes of photosynthetic efficiency of corals and seaweeds. A qualitative analysis of all relevant studies found slightly different patterns when compared to our quantitative analysis, emphasising the need for studies to meet critical inclusion criteria for meta‐analyses. Our study highlights links between effects of contaminants at lower levels of organisation (i.e. at the biochemical and/or physiological level of individuals) and ecological, large‐scale impacts, through effects on habitat‐forming species. Contaminants can clearly reduce the functioning of many habitat‐forming marine species. We therefore recommend the adoption of routine measures of functional endpoints in monitoring and conservation programs to complement structural measures.

Comparative toxicity of Corexit® 9500, oil, and a Corexit®/oil mixture on the eastern oyster, Crassostrea virginica (Gmelin)

Given their particle feeding behavior, sessile nature, and abundance in coastal zones, bivalves are at significant risk for exposure to oil and oil dispersant following environmental disasters like the Deepwater Horizon oil spill. However, the effects of oil combined with oil dispersants on the health of oysters are not well studied. Therefore, eastern oysters (Crassostrea virginica) were exposed in vivo to Corexit^® 9500, crude oil (high-energy water accommodated fraction; HEWAF), and a Corexit^®/oil mixture (chemically-enhanced water accommodated fraction; CEWAF) to evaluate potential toxic effects on immunological (phagocytosis and respiratory burst), physiological (feeding rate), and histological endpoints. Phagocytosis was significantly increased following CEWAF exposure only. Respiratory burst was significantly decreased following Corexit^® exposure, but significantly increased following exposure to the highest concentration of CEWAF. Oyster feeding rates were significantly decreased following exposure to Corexit^®, HEWAF, and CEWAF, and were most sensitive to CEWAF exposure. These modulations of important immunological and physiological functions could result in serious health outcomes for oysters, such as increased parasitism and decreased growth. Our experiments showed that subtle, sub-lethal effects occurred following acute in vivo exposure to Corexit^®, HEWAF, and CEWAF, though oysters were not equally sensitive to the three components. Data from this study can be used for more accurate risk assessment concerning the impact of oil and Corexit^® on the health of oysters.

Fate and abundance of classical and heteroatomic naphthenic acid species after advanced oxidation processes: Insights and indicators of transformation and degradation

The toxicological effects from all components in oil sands process-affected water (OSPW) are not known. Alternatively, monitoring the variations and abundance of different classes and compounds after treatments might be a useful approach in OSPW remediation. In this study, the variations in the compositions of classical and heteroatomic naphthenic acids (NAs) after treatment using advanced oxidation processes (AOPs), mainly ozone and peroxone, and two different mass spectrometry methods; ultra-performance liquid chromatography time-of-flight (UPLC-TOFMS) and Fourier transform ion cyclotron resonance (FTICR-MS), were examined. Two markers (O₂S:O₃S:O₄S and O₂:O₄ ratios) were used to reveal changes and similarities of the treated water characteristics with those in natural waters. Both ratios decreased after all treatments, from 2.7:4.8:2.1 and 3.59 in raw OSPW to 0:1.4:0.5 and 0.7, respectively, in peroxone (1:2), becoming close to the reported ratios in natural waters. Toxicity toward Vibrio fischeri showed residual toxic effects after AOPs, suggesting that part of OSPW toxicity may be caused by specific compounds of NAs (i.e., similar reduction (50%) was achieved in both toxicity and abundance in O₂ species with carbon 15-26) and/or generated by-products (e.g., O₃S classes at double bond equivalent (DBE) = 4 and C₉H₁₂O₂ at DBE = 4). Although by-products were generated, the best biodegradability enhancement and chemical oxygen demand reduction were achieved in peroxone (1:2) compared to ozone, suggesting the possibility of using combined OSPW remediation approaches (i.e., peroxone coupled with biological process). The recommended indicators can assist in evaluating the treatments' performance and in examining the best removal levels to accomplish significant toxicity reduction.

Toxicity of organic compounds from unresolved complex mixtures (UCMs) to primary fish hepatocytes

Many environmental matrices contaminated with organic pollutants derived from crude oil or degraded petroleum contain mixtures so complex that they are typically unresolved by conventional analytical techniques such as gas chromatography. The resulting chromatographic features have become known as 'humps' or unresolved complex mixtures (UCMs). These UCMs often dominate the organic contaminants of polluted environmental samples: for example, in oil sands produced water up to 150mgL^-1 of 'naphthenic acids' appear as UCMs when examined by gas chromatography as the esters. In oil-contaminated mussels, aromatic hydrocarbon UCMs may comprise almost all of the total toxic hydrocarbons, with over 7000μgg^-1 dry weight reported in some samples. Over the last 25 years, efforts to resolve and thus identify, or at least to produce average structures, for some UCM components, have proved fruitful. Numerous non-polar UCM hydrocarbons and more polar UCM acids have been identified, then synthesised or purchased from commercial suppliers. As UCMs have been proposed to represent a risk to aquatic organisms, the need for assessment of the ecotoxicological effects and characterisation of the mode of action (MoA) of these environmental pollutants has arisen. In the present study, several chemicals with structures typical of those found in some UCMs, were assessed for their potential to disrupt membrane integrity, inhibit metabolic activity, activate the aryl hydrocarbon receptor (AhR), and activate the estrogen receptor (ER) in primary rainbow trout hepatocytes (Oncorhynchus mykiss). These endpoints were determined in order to screen for common toxic modes of action (MoA) in this diverse group of chemicals. The results from the in vitro screening indicated that of the endpoints tested, the predominant toxic MoA was cytotoxicity. EC₅₀ values for cytotoxicity were obtained for 16 compounds and ranged from 77μM-24mM, whereof aliphatic monocyclic acids, monoaromatic acids, polycyclic monoaromatic acids and alkylnaphthalenes were the most toxic. The observed cytotoxicity of the chemicals correlated well with the hydrophobicity (LogK_OW) suggesting that the toxicity was predominantly due to a non-specific MoA. Interestingly, two compounds induced the ER-mediated production of vitellogenin (Vtg) and six compounds induced the AhR-mediated Ethoxyresorufin-O-deethylase (EROD) enzymatic activity to >20% of the positive control; by doing so suggesting that they may act as ER or AhR agonists in fish. The heterogeneous group of 'UCM compounds' tested exhibited multiple MoA that may potentially cause adverse effects in fish. Additional studies to determine if these compounds may cause adverse effects in vivo at environmentally relevant concentrations, are warranted to identify if such compounds are indeed of potential environmental concern.

Diamondoid naphthenic acids cause in vivo genetic damage in gills and haemocytes of marine mussels

Diamondoids are polycyclic saturated hydrocarbons that possess a cage-like carbon skeleton approaching that of diamond. These 'nano-diamonds' are used in a range of industries including nanotechnologies and biomedicine. Diamondoids were thought to be highly resistant to degradation, but their presumed degradation acid products have now been found in oil sands process-affected waters (OSPW) and numerous crude oils. Recently, a diamondoid-related structure, 3-noradamantane carboxylic acid, was reported to cause genetic damage in trout hepatocytes under in vitro conditions. This particular compound has never been reported in the environment but led us to hypothesise that other more environmentally relevant diamondoid acids could also be genotoxic. We carried out in vivo exposures (3 days, semi-static) of marine mussels to two environmentally relevant diamondoid acids, 1-adamantane carboxylic acid and 3,5-dimethyladamantane carboxylic acid plus 3-noradamantane carboxylic acid with genotoxic damage assessed using the Comet assay. An initial screening test confirmed that these acids displayed varying degrees of genotoxicity to haemocytes (increased DNA damage above that of controls) when exposed in vivo to a concentration of 30 μmol L(-1). In a further test focused on 1-adamantane carboxylic acid with varying concentrations (0.6, 6 and 30 μmol L(-1)), significant (P < 0.05%) DNA damage was observed in different target cells (viz. gills and haemocytes) at 0.6 μmol L(-1). Such a level of induced genetic damage was similar to that observed following exposure to a known genotoxin, benzo(a)pyrene (exposure concentration, 0.8 μmol L(-1)). These findings may have implications for a range of worldwide industries including oil extraction, nanotechnology and biomedicine.

Vapor pressures, thermodynamic stability, and fluorescence properties of three 2,6-alkyl naphthalenes

This work reports the experimental determination of relevant thermodynamic properties and the characterization of luminescence properties of the following polycyclic aromatic hydrocarbons (PAHs): 2,6-diethylnaphthalene, 2,6-diisopropylnaphthalene and 2,6-di-tert-butylnaphthalene. The standard (p(o) = 0.1 MPa) molar enthalpies of combustion, ΔcHm(o), of the three compounds were determined using static bomb combustion calorimetry. The vapor pressures of the crystalline phase of 2,6-diisopropylnaphthalene and 2,6-di-tert-butylnaphthalene were measured at different temperatures using the Knudsen effusion method and the vapor pressures of both liquid and crystalline phases of 2,6-diethylnaphthalene were measured by means of a static method. The temperatures and the molar enthalpies of fusion of the three compounds were determined using differential scanning calorimetry. The gas-phase molar heat capacities and absolute entropies of the three 2,6-dialkylnaphthalenes studied were determined computationally. The thermodynamic stability of the compounds in both the crystalline and gaseous phases was evaluated by the determination of the Gibbs energies of formation and compared with the ones reported in the literature for 2,6-dimethylnaphthalene. From fluorescence spectroscopy measurements, the optical properties of the compounds studied and of naphthalene were evaluated in solution and in the solid state.

Synergistic androgenic effect of a petroleum product caused by the joint action of at least three different types of compounds

In a previous study, we found a dose-dependent synergistic effect in recombinant yeast stably transfected with the human androgen receptor (AR), in response to co-exposure to testosterone and a commercially-available lubricant (engine) oil for cars. As there is relatively little knowledge on synergistic toxic effects and causative compounds, particularly for the androgenic system, the objective of the present study was to investigate this oil in more detail. The oil was fractionated into SARA fractions (so-called 'saturates', 'aromatics', 'resins', and 'asphaltenes') by open column chromatography. Surprisingly, when exposing the recombinant AR yeast to testosterone in combination with the separate SARA fractions, the synergistic effect could not be reproduced fully. After pooling the fractions again however, the full synergism returned. From subsequent exposures to combinations of two or three SARA fractions, it appeared that both the 'saturates' and the 'resins' fraction were required for obtaining the synergistic response with testosterone. This clearly demonstrates a synergistic effect related to the androgenic system caused by the joint action of at least three chemically-distinct compounds, or groups of compounds (i.e. testosterone, 'resins' and 'saturates'). Although detailed chemical analyses could not reveal the identity of the causative compounds and the in vivo relevance of the present results remains unclear, the results do add to the growing body of evidence on the potentially extremely complex character of mixture effects.

Structural identification of petroleum acids by conversion to hydrocarbons and multidimensional gas chromatography-mass spectrometry

Identification of individual petroleum acids ("naphthenic" acids, NA) has proved challenging for decades, due to the extreme complexity of many petroleum acid mixtures. This has hindered detailed understanding of the role of NA in petroleum generation and oil production processes, refinery corrosion, as wood preservatives, and as environmental toxicants. Some recent advances have been made due to improved chromatographic separation of esters of the acids by multidimensional gas chromatography-mass spectrometry (GC × GC-MS), but relatively few reference spectra of esters are available for comparison. Here we report a complementary method based on a combination of a modified historical approach of converting NA to the corresponding hydrocarbons, followed by analysis by GC × GC-MS. Many published spectra exist for reference hydrocarbons making comparisons of reference spectra with those of the unknowns, much more feasible. As an example, we report identification of over 30 individual bicyclic naphthenic acids as the bicyclane hydrocarbons. These include both fused and bridged acids possessing methyl, dimethyl, and ethyl alkyl substituents as well as some terpenoid-derived acids. The study provides the most comprehensive analysis of one of the major classes of NA (the bicyclic acids) to date. There is now clear potential for this method to be used for the structural elucidation of other unknown acids (e.g., oil sands acids) and functionalized biomarkers in complex mixtures.

Identification of unresolved complex mixtures (UCMs) of hydrocarbons in commercial fish oil supplements

BACKGROUND

Heightened awareness of the health benefits of fish oil consumption has led to a great increase in the number of fish oil supplements available to the consumer. Therefore manufacturers are continually looking for ways to distinguish their products from those of competitors. Minimally refined or virgin fish oils provide a unique feature; however, petroleum hydrocarbon contamination from oil spills is a reality in the world's oceans. The question arises whether oil produced from fish species caught in these polluted areas is free of petroleum hydrocarbons, with particular interest in unresolved complex mixtures (UCMs). This study investigates the presence of UCMs in commercially available fish oil supplements advertised as being virgin, as well as refined.

RESULTS

Weathered petroleum hydrocarbons in the form of a UCM were found at 523 µg g(-1) in a virgin Alaskan salmon oil supplement. Supplements that were refined were free of this contamination.

CONCLUSION

Fish used in the production of fish oil supplements appear to have accumulated petrogenic hydrocarbons in their tissues which were not removed by minimal oil refining. Further study is required to determine if there are any health implications associated with long-term consumption of these contaminated supplements.

Polycyclic aromatic compounds (PAHs and oxygenated PAHs) and trace metals in fish species from Ghana (West Africa): bioaccumulation and health risk assessment

We report the concentrations of 28 PAHs, 15 oxygenated PAHs (OPAHs) and 11 trace metals/metalloids (As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Se, and Zn) in muscle and gut+gill tissues of demersal fishes (Drapane africana, Cynoglossus senegalensis and Pomadasys peroteti) from three locations along the coast of the Gulf of Guinea (Ghana). The concentrations of ∑28PAHs in muscle tissues averaged 192ngg(-1) dw (range: 71-481ngg(-1) dw) and were not statistically different between locations. The concentrations of ∑28 PAHs were higher in guts+gills than in muscles. The PAH composition pattern was dominated by low molecular weight compounds (naphthalene, alkyl-naphthalenes and phenanthrene). All fish tissues had benzo[a]pyrene concentrations lower than the EU limit for food safety. Excess cancer risk from consumption of some fish was higher than the guideline value of 1×10(-6). The concentrations of ∑15 OPAHs in fish muscles averaged 422ngg(-1) dw (range: 28-1715ngg(-1)dw). The ∑15 OPAHs/∑16 US-EPA PAHs concentration ratio was >1 in 68% of the fish muscles and 100% of guts+gills. The log-transformed concentrations of PAHs and OPAHs in muscles, guts+gills were significantly (p<0.05) correlated with their octanol-water partitioning coefficients, strongly suggesting that equilibrium partitioning from water/sediment into fish tissue was the main mechanism of bioaccumulation. The trace metal concentrations in the fish tissues were in the medium range when compared to fish from other parts of the world. The concentrations of some trace metals (Cd, Cu, Fe, Mn, Zn) were higher in guts+gills than in muscle tissues. The target hazard quotients for metals were<1 and did not indicate a danger to the local population. We conclude that the health risk arising from the consumption of the studied fish (due to their PAHs and trace metals content) is minimal.

Investigation of environmental contamination of mono-isopropylnaphthalene, di-isopropylnaphthalene and tri-isopropylnaphthalene in Hyogo in Japan

Di-isopropylnaphthalene (DIPN) has highly persistent and bioaccumulative properties, and a large amount of DIPN is used as a PCB substitute in Japan. However, DIPN in the environment has not been thoroughly investigated. In addition, mono-isopropylnaphthalene (MIPN) and tri-isopropylnaphthalene (TIPN), which are the homologues of DIPN, have similar properties to DIPN. In this study, simultaneous analytical methods for MIPN, DIPN, and TIPN for air, environmental water, sediment, and biological samples were developed, and the resultant contamination caused by each in the environment was investigated. DIPN was detected at 1.1 ± 0.38 ng/m(3) in air and between < 1.9 and 9.8 ng/L in river water, but MIPN and TIPN were not. In Lateolabrax japonicas (Japanese sea perch), TIPN was detected from only females at between 0.65 and 1.4 ng/g-wet. DIPN was detected from all perches at between 1.2 and 3.4 ng/g-wet. DIPN and TIPN isomer fingerprints in females were different from those in the reference standard stock solution ones. In sediments, MIPN, DIPN, and TIPN were detected at between < 0.16 and 8.6 ng/g-dry, between < 1.1 and 4400 ng/g-dry, and between < 0.83 and 500 ng/g-dry, respectively. The contamination trend of DIPN in the sediments was similar to that of PCBs.