Effect-directed analysis of toxicants in unresolved complex mixtures (UCMs) of hydrocarbons from biodegraded crude oils

Merged with duplicate record 10026.1/686 on 14.03.2017 by CS (TIS)Contamination of the environment by petrogenic hydrocarbons continues to pose a threat to marine biota. Studies into the effects of hydrocarbon contamination have mainly been directed at a small number of polycyclic aromatic hydrocarbons (PAHs) that are known to be highly toxic to a wide range of biota. The majority of the hydrocarbons present in sediments and tissues are unresolved by conventional gas chromatography and have received little attention. Studies directed at these unresolved complex mixtures (UCMs) of hydrocarbons have previously identified the monoaromatic fraction as containing toxic UCM compounds. The studies reported herein have explored the toxicity of UCM compounds to marine biota using an effect-directed analysis approach: (i) population-level effects on the amphipod Corophium vo/utator arising from chronic exposure to UCM hydrocarbon contaminated sediments; (ii) bioaccumulation and depuration of UCM hydrocarbons by the blue mussel, Mytilus edulis using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GCxGC-ToF-MS); and, (iii) the possible trophic transfer of UCM hydrocarbons from contaminated mussels to the predatory shore crab Carcinus maenas. Chronic sediment exposure tests showed that oils dominated by UCM hydrocarbons reduced the growth rate and reproductive success of C. volutator. All fractions of the oils contributed towards the toxicity but the aromatic fraction produced effects at lower nominal sediment concentrations. The aromatic fraction was also responsible for the reduction of mussel filter-feeding clearance rates. Analyses of mussel tissue extracts by GCxGC-ToF-MS revealed that a range of aromatic compounds was rapidly accumulated, but most were readily depurated. Compounds that were more resistant to depuration, including branched alkylbenzenes (BABs), were also found in wild mussel populations previously reported to have poor health status. Tests using a commercially available complex mixture of C12.14 BABs confirmed that these compounds were toxic to mussels and were not readily depurated. Crabs that consumed mussels contaminated with BABs were found to behave abnormally, but cellular and physiological effects were not significantly different to control organisms. Crab midgut gland tissues were found to contain low concentrations of BABs and fluorescence from urine suggested that the BABs were metabolised and/or excreted. The results did not support the hypothesis that BABs were likely to biomagnify within the marine food web. The research reported herein supports the hypothesis that environmental UCMs are largely comprised of branched alkylated homologues of known petrogenic hydrocarbons. Of these, the BABs have been shown to bioaccumulate and cause adverse effects via a non-specific narcosis mode of action. Marine environment monitoring and regulatory bodies may benefit from taking into account the concentrations of UCM hydrocarbons, in particular the aromatic UCM, including the BABs

Remember they were emotional - effects of emotional qualifiers during sentence processing

We investigated whether emotional information facilitates retrieval and whether it makes representations more salient during sentence processing. Participants were presented with sentences including entities (nouns) that were either bare, with no additional information or that were emotionally or neutrally qualified by means of adjectives. Reading times in different word regions, specifically at the region following the verb where retrieval processes are measurable, were analysed. Qualified representations needed longer time to be build up than bare representations. Also, it was found that the amount of information and the type of information affect sentences processing and more specifically retrieval. In particular, retrieval for emotionally specified representations was faster than that for bare representations

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

Tracking your emotions – an eye-tracking study on reader's engagement with perspective during text comprehension

An eye-tracking study explored perspective effects on eye-movements during reading. We presented texts that included either a personal perspective (you) or an onlooker perspective (he/she). We measured whether fixations on the pronouns themselves differed as a function of perspective, and whether fixations on pronouns were affected by the emotional valence of the text which was either positive or negative. It was found that early in the text, processing of you is easier than he or she. However, as the character referred to by he/she becomes more familiar, fixations on he/she decrease, specifically in negative contexts

Anticipating causes and consequences

Two visual world eye-tracking experiments investigated anticipatory looks to implicit causes and implicit consequences in two clause sentences with mental state verbs (Stimulus-Experiencer and Experiencer-Stimulus) in the first main clause, and an explicit cause or consequence in the second. The first experiment showed that, just as when all continuations are causes, people look early at the implicit cause, when all continuations are consequences they look early at the implicit consequence, for the same verbs. When causes and consequences are intermixed, people direct their looks at the cause or consequence on a trial-by-trial basis depending on the connective (“because” or “and so”). Numerically, causes were favored overall, even when all the endings were consequences, but the effect was only significant at the end of the sentences in Experiment 2. The results are discussed in terms of rapid deployment of causal and consequential information implicit in mental state verbs, and in relation to conflicting accounts of why causes or consequences might generally be favored

Characterizations and comparison of low sulfur fuel oils compliant with 2020 global sulfur cap regulation for international shipping

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nelson, R. K., Scarlett, A. G., Gagnon, M. M., Holman, A. I., Reddy, C. M., Sutton, P. A., & Grice, K. Characterizations and comparison of low sulfur fuel oils compliant with 2020 global sulfur cap regulation for international shipping. Marine Pollution Bulletin, 180, (2022): 113791, https://doi.org/10.1016/j.marpolbul.2022.113791.The International Marine Organization 2020 Global Sulfur Cap requires ships to burn fuels with <0.50% S and some countries require <0.10% S in certain Sulfur Emission Control Areas but little is known about these new types of fuels. Using both traditional GC–MS and more advanced chromatographic and mass spectrometry techniques, plus stable isotopic, δ13C and δ2H, analyses of pristane, phytane and n-alkanes, the organic components of a suite of three 0.50% S and three 0.10% S compliant fuels were characterized. Two oils were found to be near identical but all of the remaining oils could be forensically distinguished by comparison of their molecular biomarkers and by the profiles of the heterocyclic parent and alkylated homologues. Oils could also be differentiated by their δ13C and δ2H of n-alkanes and isoprenoids. This study provides important forensic data that may prove invaluable in the event of future oil spills.This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. CMR and RKN were supported by the National Science Foundation (OCE-1634478 and OCE-1756242). GC × GC analysis support provided by WHOI's Investment in Science Fund

Multi-spectroscopic and elemental characterization of southern Australian asphaltites

Strandings of various types of bitumen along the coast of southern Australia are long known. Among these, brittle, angular lumps termed ‘asphaltites’ are possibly sourced from Cretaceous source rocks linked to an oceanic anoxic event (OAE), but the exact source remains unclear. The unusual chemical composition of these asphaltites and their survival during transport and shoreline stranding suggest that they formed by nearby submarine seepage of asphaltene-rich crude oils. Here, we provide a detailed organic and inorganic geochemical characterization of asphaltites to constrain their origin and age. High-pressure hydropyrolysis (HyPy) of asphaltene fractions from ten asphaltites released similar assemblages of macromolecularly bound compounds, suggesting a common source for all asphaltites. Comprehensive gas chromatography–time-of-flight mass spectrometry (GC×GC-TOFMS) was used to compare these asphaltene-derived compounds with the maltene fractions, while compound specific isotope analysis (CSIA) was used to compare δ13C and δ2H of n-alkanes and isoprenoids. A large offset between the δ2H of the n-alkanes and isoprenoids suggests oil generation and expulsion at low thermal maturity. The mean concentrations of isorenieratane and chlorobactane, carotenoid derivatives indicative of photic zone euxinia (PZE), in the asphaltites were 8.8 ± 0.8 SEM µg g−1 and 1.4 ± 0.1 SEM µg g−1, respectively. A mean Aryl Isoprenoid Ratio of 0.75 (SD = 0.17) is accompanied by Pr/Ph of ∼1.2. These features strongly support persistent PZE conditions at the level expected for an OAE. Trace metal contents of the asphaltites, including low selenium and high vanadium concentrations, also support anoxic conditions. Rhenium-osmium (Re-Os) analyses constrain the age of asphaltite generation to 103 ± 22 Ma, with a relatively low initial 187Os/188Os ratio of 0.44 ± 0.18. Integrating local geologic knowledge with organic and inorganic geochemistry and Re-Os isotopic results, we identify a Cretaceous unit associated with OAE1a (∼125 Ma) as the most likely source of the asphaltites. Alternative scenarios involving source rocks deposited during OAE1b (∼112 Ma) are possible, but require rapid burial of organic-rich sediments to reach required maturation levels in a shorter time

Aromatic hydrocarbons provide new insight into carbonate concretion formation and the impact of eogenesis on organic matter

Investigations of aromatic biomarkers extracted from carbonate concretions can contribute to characterization of the enhanced microbial activity that mediates carbonate concretion formation. This microbial footprint can be further inferred from the stable isotopic values of carbonate (δ13C) and pyrite (δ34S). Here, we used a combination of GC–MS and GC × GC-ToF-MS to compare the aromatic fractions of two Toarcian carbonate concretions from the H. falciferum ammonite zone of the Posidonia Shale (SW-Germany) and their host sediment. The results revealed that n-alkylated and phytanyl arenes were enhanced in the concretions, relative to the host sediment. These findings support a very early diagenetic (eogenetic) microbial source for alkylated and phytanyl arenes derived from the microbial ecosystem mediating concretion formation. In contrast, aromatic compounds formed by thermal maturation (e.g. polycyclic aromatic hydrocarbons, aromatic steroids, organic sulphur compounds) remained invariant in host rock and concretion samples. When combined with bulk sediment and concretion properties, the distribution of aromatic compounds indicates that eogenetic microbial activity upon concretion growth does not diminish organic matter quality

Comprehensive two-dimensional gas chromatography-mass spectrometry of complex mixtures of anaerobic bacterial metabolites of petroleum hydrocarbons

Anaerobic biotransformation of petroleum hydrocarbons is an important alteration mechanism, both subsurface in geological reservoirs, in aquifers and in anoxic deep sea environments. Here we report the resolution and identification, by comprehensive two-dimensional gas chromatography-mass spectrometry (GC×GC-MS), of complex mixtures of aromatic acid and diacid metabolites of the anaerobic biodegradation of many crude oil hydrocarbons. An extended range of metabolites, including alkylbenzyl, alkylindanyl, alkyltetralinyl, alkylnaphthyl succinic acids and alkyltetralin, alkylnaphthoic and phenanthrene carboxylic acids, is reported in samples from experiments conducted under sulfate-reducing conditions in a microcosm over two years. The range of metabolites identified shows that the fumarate addition mechanism applies to the alteration of hydrocarbons with up to C 8 alkylation in monoaromatics and that functionalisation of up to three ring aromatic hydrocarbons with at least C 1 alkylation occurs. The GC×GC-MS method might now be applied to the identification of complex mixtures of metabolites in samples from real environmental oil spills

Around the plastic world in 455 days - a citizen science global transect quantifying microplastics in the oceans

Public perception of plastics in the oceans has increased over the last few decades, but only more recently has the potential harm to organisms due to ingestion of microplastics started to be recognized. The monitoring of larger plastics lends itself to Citizen Science projects but sample collection and analysis of microplastics (0.05 – 5 mm) is more challenging. In this Citizen Science project, world-renowned, single-handed yachtsman Jon Sanders (AO, OBE) teamed up with Western Australian Isotope and Geochemistry Centre (WA-OIGC) researchers at Curtin University, to raise awareness of microplastics in the oceans, and to quantify the numbers of microplastic particles present along a global transect using daily water filtration. In particular, the study aimed to provide data for remote areas of the southern hemisphere for which very little data existed previously. The voyage was carried out by Jon Sanders on board Yacht Perie Banou II, departing Fremantle port, Western Australia, on 3rd November 2019 and returning on 31st January 2021, a total of 455 days (somewhat longer than anticipated due to the Covid-19 Pandemic) and spanning 46,100 km. Approximately 115 L of seawater was pumped per day from an inlet in the hull, close to the bow of Perie Banou II, and filtered onto stainless steel woven filters with 43 µm aperture (equivalent imperial: mesh 325). No plastic was present in the filtration system. During stopovers in ports, the filters were couriered to the WA-OIGC laboratories for processing and analyzes by Attenuated Total Reflectance (ATR) Fourier-transform infrared spectroscopy (FTIR). A total of 177 filters were analyzed resulting in a mean count of 33 microplastics m-3 seawater across the entire global transect. The Pacific Ocean was found to contain the least numbers of microplastic particles with 23 and 15 microplastics m-3 seawater for the eastern and western sides of the Pacific transect respectively. The highest recorded numbers were 291 and 246 microplastics m-3 seawater for two contiguous stations south of the equator in the Atlantic Ocean, both of which were over 600 km from the Brazilian coastline. Microplastic particles found were typically close to the lower size limit defined as microplastic i.e. 50 µm and were mostly grey/black in color. The collaboration between Jon Sanders’ Citizen Science team and WA-OIGC researchers was highly successful. The study was the first global transect of microplastics in the oceans that utilized consistent sampling methods throughout. The data was consistent with other scientific surveys of remote areas of ocean and could act as a benchmark for future studies into microplastics in the oceans