RESUMEN
Due to the sudden nature of oil spills, few controlled studies have documented how oil weathers immediately following accidental release into a natural lake environment. Here, we evaluated the weathering patterns of Cold Lake Winter Blend, a diluted bitumen (dilbit) product, by performing a series of controlled spills into limnocorrals installed in a freshwater lake in Northern Ontario, Canada. Using a regression-based design, we added seven different dilbit volumes, ranging from 1.5 to 180 L, resulting in oil-to-water ratios between 1:71,000 (v/v) and 1:500 (v/v). We monitored changes in the composition of various petroleum hydrocarbons (PHCs), including n-alkanes, polycyclic aromatic hydrocarbons (PAHs), and oil biomarkers in dilbit over time, as it naturally weathered for 70 days. Depletion rate constants (kD) of n-alkanes and PAHs ranged from 0.0009 to 0.41 d-1 and 0.0008 to 0.38 d-1, respectively. There was no significant relationship between kD and spill volume, suggesting that spill size did not influence the depletion of petroleum hydrocarbons from the slick. Diagnostic ratios calculated from concentrations of n-alkanes, isoprenoids, and PAHs indicated that evaporation and photooxidation were major processes contributing to dilbit weathering, whereas dissolution and biodegradation were less important. These results demonstrate the usefulness of large scale field studies carried out under realistic environmental conditions to elucidate the role of different weathering processes following a dilbit spill.
Asunto(s)
Contaminación por Petróleo , Petróleo , Hidrocarburos Policíclicos Aromáticos , Contaminantes Químicos del Agua , Hidrocarburos/química , Lagos/química , Alcanos , Ontario , Contaminantes Químicos del Agua/análisisRESUMEN
Following an oil spill into water, bacteria can biodegrade petroleum hydrocarbons which could lead to petrogenic carbon assimilation by aquatic biota. We used changes in the isotope ratios of radio- (Δ14C) and stable (δ13C) carbon to examine the potential for assimilation of petrogenic carbon into a freshwater food web following experimental spills of diluted bitumen (dilbit) into a boreal lake in northwestern Ontario, Canada. Different volumes (1.5, 2.9, 5.5, 18, 42, 82, and 180 L) of Cold Lake Winter Blend (a heavy crude blend of bitumen and condensate) dilbit were applied to seven 10-m diameter littoral limnocorrals (approximate volume of 100 m3), and two additional limnocorrals had no added dilbit to serve as controls. Particulate organic matter (POM) and periphyton from oil-treated limnocorrals had lower δ13C (up to 3.2 and 2.1 for POM and periphyton, respectively) than the control at every sampled interval (3, 6 and 10 weeks for POM and 6, 8 and 10 weeks for periphyton). Dissolved organic and inorganic carbon (DOC and DIC, respectively) had lower Δ14C in the oil-treated limnocorrals relative to the control (up to 122 and 440 lower, respectively). Giant floater mussel (Pyganodon grandis) housed for 25 days in aquaria containing oil-contaminated water from the limnocorrals did not show significant changes in δ13C values of muscle tissue compared to mussels housed in control water. Overall, the changes in δ13C and Δ14C observed indicated small amounts (up to 11% in DIC) of oil carbon incorporation into the food web. The combined δ13C and Δ14C data provide evidence for minimal incorporation of dilbit into the food web of this oligotrophic lake, suggesting that microbial degradation and subsequent incorporation of oil C into the food web may play a relatively small role in the ultimate fate of oil in this type of ecosystem.
Asunto(s)
Carbono , Cadena Alimentaria , Hidrocarburos , Contaminantes Químicos del Agua , Isótopos de Carbono/análisis , Ecosistema , Lagos , Ontario , Agua , Contaminantes Químicos del Agua/análisisRESUMEN
Diluted bitumen (dilbit) is an unconventional oil produced by the oil sands industry in Canada. Despite the knowledge available on hydrocarbon toxicity, the effects of diluted bitumen on benthic organisms are still largely unknown. Moreover, in Quebec there are only provisional threshold values of 164 mg/kg C10-C50 for chronic effects and 832 mg/kg for acute effects. The protectiveness of these values for benthic invertebrates has not been tested for heavy unconventional oils such as dilbit. Two benthic organisms, the larvae of Chironomus riparius and Hyalella azteca, were exposed to these two concentrations and to an intermediate concentration (416 mg/kg) of two dilbits (DB1 and DB2) and a heavy conventional oil (CO). The aim of the study was to assess the sublethal and lethal effects of spiked sediment by dilbit. The oil was rapidly degraded in the sediment, especially in the presence of C. riparius. Amphipods were much more sensitive to oil than chironomids. LC50-14d values for H. azteca were 199 mg/kg C10-C50 for DB1, 299 mg/kg for DB2 and 8.42 mg/kg for CO compared to LC50-7d values for C. riparius of 492 mg/kg for DB1, 563 mg/kg for DB2 and 514 mg/kg for CO. The size of the organisms was reduced compared to controls for both species. The defense enzymes (GST, GPx, SOD and CAT) were not good biomarkers in these two organisms for this type of contamination. The current provisional sediment quality criteria seem too permissive for heavy oils and should be lowered.
Asunto(s)
Anfípodos , Contaminantes Químicos del Agua , Animales , Yacimiento de Petróleo y Gas , Invertebrados , Agua Dulce , Hidrocarburos/toxicidad , Gestión de Riesgos , Aceites , Contaminantes Químicos del Agua/toxicidad , Sedimentos GeológicosRESUMEN
Given that the physicochemical properties of diluted bitumen (dilbit) can differ from those of conventional crude oil, understanding the fate and behavior of this petroleum product in the environment becomes vital. This study involves the analysis of the photolytic behavior of some representative petroleum biomarkers, bicyclic sesquiterpanes (BSs), admantanes (ADs), diamantanes (DAs), and mono- and triaromatic steranes (MASs and TASs), by exposing Cold Lake Blend (CLB) and Alberta Sweet Mixed Blend (MSW) to winter and summer insolation after being spilled onto artificial brines. Aromatic steranes in all control samples remained relatively stable, whereas the biomarkers of BSs, ADs, and DAs were less stable. Similar to the exhaustive loss of the C10-C17 alkanes, 91%-99% of BSs, ADs, and DAs were lost after five days of insolation, especially in summer. Both MASs and TASs were lost gradually in most scenarios, although both of them were lost faster in MSW than observed for CLB. The removal of MASs and TASs did not differ significantly from each other, although their loss was less than observed for PAHs having similar number of rings and greater than for the C21-C33n-alkanes. Therefore, photooxidation, not evaporation or biodegradation, was the main factor responsible for oxidizing these aromatic steranes. However, biomarkers of BSs, ADs and DAs were mostly lost through evaporation. Therefore, aromatic steranes have the potential to be utilized to evaluate the photolytic behavior of petroleum hydrocarbons, while BSs, ADs, and DAs should not be used for this purpose.
Asunto(s)
Contaminación por Petróleo , Petróleo , Hidrocarburos Policíclicos Aromáticos , Contaminantes Químicos del Agua , Petróleo/análisis , Luz Solar , Hidrocarburos/química , Agua de Mar , Hidrocarburos Policíclicos Aromáticos/análisis , Alcanos , Contaminantes Químicos del Agua/análisis , Contaminación por Petróleo/análisisRESUMEN
Increased oil production in Canada has resulted in proposals to extend or develop new oil pipelines. Many of these proposals have been met by concerns from the public over potential environmental impacts related to construction and the potential for oil spills to negatively affect groundwater quality. Crude oil sourced from the Alberta oil sands represents a significant proportion of this increase in production. This crude oil is produced as bitumen, which is subsequently diluted with light hydrocarbons to lower viscosity to allow for pipeline transport producing diluted bitumen. In this study, we pumped water through tanks filled with sand to simulate groundwater flow. Tanks were injected with either conventional crude or diluted bitumen to simulate a crude oil spill from a pipeline rupture occurring below the water table representing a pipeline river crossing scenario. Water samples were collected from the downstream end of the tanks throughout the experiment period (â¼two months). Compared to water quality guidelines, effluent waters from both conventional crude and diluted bitumen tanks contained elevated concentrations of dissolved organic compounds, particularly benzene, ethylbenzene, toluene and xylenes (BTEX). The effluent from each tank had similar concentrations of benzene, whereas discharge water from conventional crude tanks contained higher concentrations of ethylbenzene, toluene and xylenes. In both tanks, and as expected, the BTEX concentrations appeared to be proportional to those determined in their injected crude oils. The measured dissolved concentrations of benzene, ethylbenzene and toluene are lower than predicted which is attributed largely due to dilution along the flow path. In addition to organic constituents, effluent sampled from the diluted bitumen tank contained some metals (Co, Cr, Fe and V) which measured constituents of the oil.
Asunto(s)
Petróleo , Contaminantes Químicos del Agua , Xilenos , Benceno , Yacimiento de Petróleo y Gas , Contaminantes Químicos del Agua/análisis , Hidrocarburos , Tolueno , AlbertaRESUMEN
Oil spills constitute a major risk to the environment and the bioaccumulation potential of the derived oil constituents will influence their impact on aquatic biota. Here we determined the bioaccumulation potential and toxicokinetic parameters of polycyclic aromatic compounds (PACs) and various selected metals in the giant floater mussels (Pyganodon grandis) following experimental oil spills in a freshwater lake. Specifically, these mussels were exposed ex situ for 25 days to water contaminated with naturally weathered diluted bitumen (dilbit), a form of oil commonly transported through pipelines. We detected greater concentrations of total PAC in mussels (∑PAC44) exposed to dilbit-contaminated water (25.92-27.79 µg g-1 lipid, n = 9, at day 25 of the uptake phase) compared to mussels from a control with no exposure to dilbit (average of 2.62 ± 1.95 µg g-1 lipid; ±SD, n = 17). This study demonstrates the importance of including alkylated PACs when assessing the impacts of an oil spill as the concentration of alkylated PACs in mussel tissue were an order of magnitude higher than their parent counterparts. However, metal accumulation in dilbit-exposed mussels did not exceed the unexposed controls, suggesting no excess metal accumulation by mussels from a 25-day dilbit exposure. From first-order one-compartment models, mean uptake rate constants (0.78-18.11 L g-1 day-1, n = 29) and bioconcentration factors (log values from 4.02 to 5.92 L kg-1, n = 87) for the 29 individual PACs that accumulated in mussels demonstrated that some alkylated PACs had greater bioaccumulation potential compared to their parent PAC counterpart but for the most part, alkylated and parent PACs had comparable BCF values. Results from this study also demonstrated that giant floater mussels could be used to biomonitor PAC contamination following oil spills as PACs accumulated in mussel tissue and some were still detectable following the 16-day depuration phase. This study provides the largest, most comprehensive set of toxicokinetic and bioaccumulation parameters for PACs and their alkylated counterparts (44 analytes) in freshwater mussels obtained to date.
Asunto(s)
Bivalvos , Hidrocarburos Policíclicos Aromáticos , Compuestos Policíclicos , Unionidae , Contaminantes Químicos del Agua , Animales , Bioacumulación , Toxicocinética , Contaminantes Químicos del Agua/toxicidad , Hidrocarburos , Lagos , Metales , Agua , Lípidos , Hidrocarburos Policíclicos Aromáticos/toxicidadRESUMEN
With the increasing use of unconventional, heavy crude oils there is growing interest in potential impacts of a diluted bitumen (DB) spill in marine and freshwater environments. DB has the potential to release several toxic, trace organic contaminants to the water column. Here, the aqueous concentrations and compositions of two classes of organic contaminants, naphthenic acids (NAs) and polycyclic aromatic hydrocarbons (PAHs), are followed over 8 weeks after a simulated spill of DB (10 L) into a freshwater mesocosm (1200 L) with river sediment (2.4 kg). These complex samples contain biogenic dissolved organic matter, inorganic ions, petroleum contaminants, suspended sediments, and oil droplets. We report the first use of condensed phase membrane introduction mass spectrometry (CP-MIMS) as a direct sampling platform in a complex multi-phase mesocosm spill tank study to measure trace aqueous phase contaminants with little to no sample preparation (dilution and/or pH adjustment). CP-MIMS provides complementary strengths to conventional analytical approaches (e.g., gas- or liquid chromatography mass spectrometry) by allowing the entire sample series to be screened quickly. Trace NAs are measured as carboxylates ([M-H]-) using electrospray ionization and PAHs are detected as radical cations (M+â¢) using liquid electron ionization coupled to a triple quadrupole mass spectrometer. The DB-affected mesocosm exhibits NA concentrations from 0.3 to 1.2 mg/L, which rise quickly over the first 2 - 5 days , then decrease slowly over the remainder of the study period. The NA profile (measured as the full scan in negative-electrospray ionization at nominal mass resolution) shifts to lower m/z with weathering, a process followed by principal component analysis of the normalized mass spectra. We couple CP-MIMS with high-resolution mass spectrometry to follow changes in molecular speciation over time, which reveals a concomitant shift from classical 'O2' naphthenic acids to more oxidized analogues. Concentrations of PAHs and alkylated analogues (C1 - C4) in the DB-affected water range from 0 to 5 µg/L. Changes in PAH concentrations depend on ring number and degree of alkylation, with small and/or lightly alkylated (C0 - C2) PAH concentrations rising to a maximum in the first 4 - 8 days (100 - 200 h) before slowly decaying over the remainder of the study period. Larger and heavily alkylated (C3 - C4) PAH concentrations generally rise slower, with some species remaining below the detection limit throughout the study period (e.g., C20H12 class including benzo[a]pyrene). In contrast, a control mesocosm (without oil) exhibited NA concentrations below 0.05 mg/L and PAHs were below detection limit. Capitalizing on the rapid analytical workflow of CP-MIMS, we also investigate the impacts of sample filtration at the time of sampling (on NA and PAH data) and sample storage time (on NA data only).
Asunto(s)
Petróleo , Hidrocarburos Policíclicos Aromáticos , Benzo(a)pireno , Ácidos Carboxílicos , Hidrocarburos , Espectrometría de Masas/métodos , Petróleo/análisis , Hidrocarburos Policíclicos Aromáticos/análisis , Agua/químicaRESUMEN
Oil and gas development and transportation in many areas of the world, such as the oil sands region of Alberta, Canada, are heavily monitored to minimize the environmental impacts of development and the risk of oil spills. However, oil spills to aquatic environments still occur. Although the science of oil spills has received considerable attention of late, uncertainty still remains in evaluating the fate and transport of oil spills as well as the effects of those spills on aquatic biota. Experiments using meso-scale spill tanks were used to examine the physical and chemical behavior of two types of oil, conventional crude (CC) and diluted bitumen (DB), under similar environmentally relevant scenarios (i.e., volume of spill, temperature, duration, wave action, and presence of river sediment). In addition, biological impact assessments via sediment toxicity testing collected from the oil spill tests were conducted. Sediments were evaluated for acute toxicity using three standard sediment test species: Hyalella azteca, Lumbriculus variegatus, and Chironomus dilutus. Sediments collected from the CC simulated spill showed a higher level of acute toxicity than sediments collected from spills with DB. Higher toxicity in the CC-contaminated sediment was supported by higher concentrations of low molecular weight polycyclic aromatic hydrocarbons (PAHs) when compared with the DB-contaminated sediment, while the remaining PAH profile was similar between the contaminated sediments. The use of a meso-scale spill tank in combination with sediment bioassays allowed for the evaluation of oil spills under controlled and environmentally relevant conditions (e.g., nearshore high sediment loading river), and in turn provides assessors with additional information to identify the appropriate mitigation and remediation efforts needed in the event of future spills. Environ Toxicol Chem 2022;41:2797-2807. © 2022 SETAC.
Asunto(s)
Hidrocarburos Policíclicos Aromáticos , Contaminantes Químicos del Agua , Animales , Yacimiento de Petróleo y Gas , Contaminantes Químicos del Agua/análisis , Hidrocarburos Policíclicos Aromáticos/toxicidad , Hidrocarburos Policíclicos Aromáticos/análisis , Agua Dulce , AlbertaRESUMEN
An understanding of the risks associated with diluted bitumen (dilbit) transport through Pacific salmon habitat necessitates the identification and quantification of hazards posed to early life stages. Sockeye from the embryo to juvenile stage (8 months old) were exposed to four concentrations of the water-soluble fraction of Cold Lake dilbit (summer blend; concentrations of 0, 13.7, 34.7, and 124.5 µg/L total polycyclic aromatic compounds). Significant mortality (up to 18% over controls) only occurred in the embryo to swim-up fry stage. Impaired growth was seen in the alevin, swim-up, and juvenile stages (maximum reduction 15% in mass but not fork length). Reductions in both critical (maximum 24% reductions) and burst (maximum 47% reductions) swimming speed in swim-up fry and juveniles were seen. Alterations in energy substrate reserves (reductions in soluble protein and glycogen content, elevations in whole-body lipid and triglyceride levels) at all stages may underlie the effects seen in swimming and growth. Dilbit exposure induced a preexercise physiological stress response that affected the recovery of postexercise biochemistry (cortisol, glycogen, lactate, triglyceride concentrations). The transcript abundance of the cytochrome P450 1A gene (cyp1a) was quantified in alevin head regions (containing the heart) and in the hearts of swim-up fry and juveniles and showed a concentration-dependent increase in the expression of cyp1a at all life stages. Environ Toxicol Chem 2022;41:1937-1949. © 2022 SETAC.
Asunto(s)
Salmón , Contaminantes Químicos del Agua , Animales , Glucógeno/metabolismo , Hidrocarburos , Salmón/metabolismo , Triglicéridos/metabolismo , Contaminantes Químicos del Agua/químicaRESUMEN
The oil sands industry in Canada, produces heavy unconventional oils, diluted for transport and called diluted bitumen. However, despite advances in our knowledge of the ecotoxicological risk that these products represent, their effects on benthic organisms following a spill are still largely unknown. In order to fill these gaps, this study aims to determine the lethal and sublethal effects of two diluted bitumens (Bluesky and Cold Lake) and one conventional oil (Lloydminster) for two freshwater benthic invertebrates: Chironomus riparius and Hyalella azteca. The objective of this study is to assess the toxicity of dissolved hydrocarbons, resulting from the physical dispersion of oil, immediately after a spill on the benthic invertebrates. To this end, organisms were exposed for 7 days for chironomids and 14 days for amphipods to a fraction containing soluble hydrocarbons (WAF: water accommodated fraction; 10 g/L, 18 h of agitation, followed by 6 h of sedimentation) with natural or artificial sediment. After exposure, the effects of hydrocarbons were determined using size, mortality, and antioxidant capacities. Dissolved hydrocarbons induced mortality for both species, but these hydrocarbons disappeared very quickly from the water column, regardless of the oil type. The amphipods were sensitive to both types of oil while the chironomids were only sensitive to diluted bitumens. The presence of a natural sediment seems to provide a protective role against dissolved hydrocarbons. The antioxidant enzymes measured (CAT, SOD and GPx) do not appear to be relevant biomarkers for the exposure of these organisms to diluted bitumen.
Asunto(s)
Anfípodos , Chironomidae , Contaminación por Petróleo , Petróleo , Hidrocarburos Policíclicos Aromáticos , Contaminantes Químicos del Agua , Animales , Antioxidantes , Hidrocarburos/toxicidad , Invertebrados , Lagos , Yacimiento de Petróleo y Gas , Petróleo/análisis , Petróleo/toxicidad , Contaminación por Petróleo/efectos adversos , Hidrocarburos Policíclicos Aromáticos/toxicidad , Agua , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/toxicidadRESUMEN
The transportation of heavy crudes such as diluted bitumen (dilbit) sourced from Canadian oil sands through freshwater habitat requires the generation of information that will contribute to risk assessments, spill modelling, management, and remediation for the protection of aquatic organisms. Juvenile sockeye salmon (Oncorhynchus nerka) were exposed acutely (96 h) or subchronically (28 d) to the water-soluble fraction (WSFd) of Cold Lake Blend dilbit at initial total polycyclic aromatic compound (TPAC) concentrations of 0, 13.7, 34.7, and 124.5 µg/L. A significant induction (>3-fold) of hepatic liver ethoxyresorufin-O-deethylase (EROD) activity was induced by 96 h in fish exposed to [TPAC] ≥ 34.7 µg/L and at ≥13.7 µg/L for a 28 d exposure. Exposure resulted in a typical physiological stress response and disturbance of ion homeostasis; this included elevations in plasma [cortisol], [lactate], [Na+], and [Cl-], and significant reductions in muscle [glycogen]. Critical swimming speed (Ucrit) was significantly reduced (28.4%) in the acute exposure at [TPAC] 124.5 µg/L; reductions of 14.2% and 35.4% were seen in fish subchronically exposed at the two highest concentrations. Reductions in Ucrit were related to significant reductions in aerobic scope (24.3-46.6%) at [TPAC]s of 34.7 and 124.5 µg/L, respectively. Exposure did not impair the ability to mount a secondary stress response following burst exercise, however, the time required for biochemical parameters to return to baseline values was prolonged. Alterations in critical systems supporting swimming, exercise recovery and the physiological stress response could result in decreased salmonid fitness and contribute to population declines if a dilbit spill occurs.
Asunto(s)
Salmón , Contaminantes Químicos del Agua , Animales , Canadá , Peces , Hidrocarburos , Lagos , Yacimiento de Petróleo y Gas , Salmón/fisiología , Natación , Contaminantes Químicos del Agua/toxicidadRESUMEN
Oil spills in coastal waters can have devastating impacts on local ecosystems, from the microscopic base through to mammals and seabirds. Increasing transport of diluted bitumen has led to concerns about how this novel product might impact coastal ecosystems. A mesocosm study determined that the type of diluent and the season can affect the concentrations of hydrocarbons entering the water column from a surface spill. Those same mesocosms were sampled to determine whether diluent type and season also affected the microbial response to a surface spill. Overall, there were no differences in impacts among the three types of diluted bitumen, but there were consistent responses to all products within each season. Although microbial abundances with diluted bitumen rarely differed from unoiled controls, community structure in these organisms shifted in response to hydrocarbons, with hydrocarbon-degrading bacteria becoming more abundant. The relative abundance of heterotrophic eukaryotes also increased with diluted bitumen, with few photosynthetic organisms responding positively to oil. Overall shifts in the microbial communities were minimal relative to spills of conventional oil products, with low concentrations of hydrocarbons in the water column. Oil spill response should focus on addressing the surface slick to prevent sinking or stranding to minimize ecosystem impacts.
Asunto(s)
Microbiota , Contaminación por Petróleo , Petróleo , Contaminantes Químicos del Agua , Animales , Hidrocarburos , Mamíferos , Contaminación por Petróleo/análisis , Agua de Mar/microbiología , Agua , Contaminantes Químicos del Agua/análisisRESUMEN
The risks to aquatic wildlife from spills of diluted bitumen (dilbit) into inland waters are poorly understood. In this paper, we describe the response of larval wood frogs (Rana sylvatica) to hydrocarbons and other compounds released from experimental spills of dilbit in a temperate boreal lake. To simulate a wide range of environmentally relevant oil spill scenarios, different volumes of Cold Lake Winter Blend dilbit (0, 1.5, 2.9, 5.5, 18, 42, 82, and 180 L) were added to 10 m diameter in-lake limnocorrals. Larvae (n = 360) were reared (from Gosner Stage (GS) 25 to â¼42) in land-based aquatic microcosms, where they were first exposed to clean water during a 2-week baseline phase, and then (at GS â¼30), to contaminated water withdrawn from the limnocorrals for 3 weeks. We observed no statistically significant trends in survival, growth, or development of larvae as a consequence of exposure to the chemical compounds released from naturally weathered dilbit. Likewise, neither cytochrome P450 1A biomarkers nor levels of thyroid hormones in wood frogs near metamorphic climax were significantly related to volume of the oil spills. However, there was a modest statistically significant decrease in larval activity (up to 8.7% relative to the control), but no change in other behavioral metrics (i.e., sociality or space use). Our work adds to the limited body of literature on the effects of unconventional oils on aquatic wildlife and helps to inform risk assessments regarding pipeline projects.
Asunto(s)
Lagos , Contaminantes Químicos del Agua , Animales , Hidrocarburos , Lagos/química , Larva , Ranidae , Contaminantes Químicos del Agua/toxicidadRESUMEN
To help better assist the management of Diluted bitumen (DilBit) spills in marine environment, a model named as DilBit Weathering Model (DBWM) was developed in this study to simulate DilBits weathering in marine environment. The DBWM was developed based on specific algorithms for evaporation, dispersion, biodegradation, as well as density and viscosity changes for DilBit weathering and other widely used algorithms for conventional oil weathering in marine environment. To validate the model, a series of DilBit weathering simulation were conducted and compared with the experimental data. Furthermore, the performance of DBWM was compared with a widely used oil weathering model (Automated Data Inquiry for Oil Spills, ADIOS2). The results demonstrated the feasibility and advantages of the developed DBWM in simulating the weathering of marine DilBit spills. Thus, the proposed DBWM can provide effective decision support to marine DilBit spill management.
Asunto(s)
Contaminación por Petróleo , Petróleo , Contaminantes Químicos del Agua , Hidrocarburos , Contaminación por Petróleo/análisis , Contaminantes Químicos del Agua/análisis , Tiempo (Meteorología)RESUMEN
Diluted bitumen (dilbit) is an unconventional crude petroleum increasingly being extracted and transported to market by pipeline and tanker. Despite the transport of dilbit through terrestrial, aquatic, and coastal habitat important to diverse bird fauna, toxicity data are currently only available for fish and invertebrates. We used the zebra finch (Taeniopygia guttata) as a tractable, avian model system to investigate exposure effects of lightly weathered Cold Lake blend dilbit on survival, tissue residue, and a range of physiological and behavioural endpoints. Birds were exposed via oral gavage over 14-days with dosages of 0, 2, 4, 6, 8, 10, or 12 mL dilbit/kg bw/day. We identified an LD50 of 9.4 mL/kg/d dilbit, with complete mortality at 12 mL/kg/d. Mortality was associated with mass loss, external oiling, decreased pectoral and heart mass, and increased liver mass. Hepatic ethoxyresorufin-O-deethylase activity (EROD) was elevated in all dilbit-dosed birds compared with controls but there was limited evidence of sublethal effects of dilbit on physiological endpoints at doses < 10 mL/kg/d (hematocrit, hemoglobin, total antioxidants, and reactive oxygen metabolites). Dilbit exposure affected behavior, with more dilbit-treated birds foraging away from the feeder, more birds sleeping or idle at low dilbit doses, and fewer birds huddling together at high dilbit doses. Naphthalene, dibenzothiophene, and their alkylated congeners in particular (e.g. C2-napthalene and C2-dibenzothiophene) accumulated in the liver at greater concentrations in dilbit-treated birds compared to controls. Although directly comparable studies in the zebra finch are limited, our mortality data suggest that dilbit is more toxic than the well-studied MC252 conventional light crude oil with this exposure regime. A lack of overt sublethal effects at lower doses, but effects on body mass and composition, behaviour, high mortality, and elevated PAC residue at doses ≥ 10 mL/kg/d suggest a threshold effect.
Asunto(s)
Pinzones , Petróleo , Contaminantes Químicos del Agua , Animales , HidrocarburosRESUMEN
Breeding birds that become oiled may contaminate the shells of their eggs, and studies of conventional crude oil suggest that even small quantities can be absorbed through the eggshell and cause embryotoxicity. Unconventional crude oils remain untested, so we evaluated whether a major Canadian oil sands product, diluted bitumen (dilbit), would be absorbed and cause toxicity when applied to eggshells of two species, domestic chicken (Gallus gallus domesticus) and double-crested cormorant (Nannopterum auritum). We artificially incubated eggs and applied lightly weathered dilbit (Cold Lake blend) to the eggshells (0.015-0.15 mg g-1 egg in chicken; 0.1-0.4 mg g-1 egg in cormorant) at various points during incubation before sampling prehatch embryos. Polycyclic aromatic compound (PAC) residue in cormorant embryos was elevated only at the highest dilbit application (0.4 mg g-1 egg) closest (day 16) to sampling on day 22. In contrast, cormorant liver cytochrome P450 1a4 (Cyp1a4) mRNA expression (quantitative polymerase chain reaction assay) was elevated only in embryos treated with the earliest and lowest dilbit application (0.1 mg g-1 egg on day 4). These results confirm that dilbit can cross through the eggshell and be absorbed by embryos, and they imply rapid biotransformation of PACs and a nonmonotonic Cyp1a4 response. Despite evidence of exposure in cormorant, we found no detectable effects on the frequency of survival, deformity, and gross lesions, nor did we find effects on physiological endpoints indicative of growth and cardiovascular function in either chicken or cormorant. In ovo dilbit exposure may be less toxic than well-studied conventional crude oils. The effects of an oil spill scenario involving dilbit to bird embryos might be subtle, and PACs may be rapidly metabolized. Environ Toxicol Chem 2022;41:159-174. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.
Asunto(s)
Contaminación por Petróleo , Petróleo , Contaminantes Químicos del Agua , Animales , Aves , Canadá , Cáscara de Huevo/química , Hidrocarburos/toxicidad , Yacimiento de Petróleo y Gas , Petróleo/análisis , Petróleo/toxicidad , Contaminación por Petróleo/análisis , Contaminantes Químicos del Agua/toxicidadRESUMEN
Following spills into water, petroleum oils can spread widely and produce surface slicks. Resulting slicks may impede volatilization and possibly increase chemical persistence in water. While the influence of oil films on chemical air-water exchange has been examined through theoretical and laboratory studies, field studies have not been conducted to assess the relevance of these effects following actual oil spill events. Here we evaluated the effect of diluted bitumen (dilbit) experimentally spilled in limnocorrals installed in a boreal lake on the volatilization of sulfur hexafluoride (SF6), a non-reactive volatile tracer gas. Dilbit spills were monitored over 70 days and SF6 was introduced twice (after 7 and 48 days) to evaluate the influence of spilled dilbit on the loss of SF6 from water. Volatilization rate constants of SF6 (kVOL) significantly decreased by up to 80% with increasing total dilbit spill cover. Using a theoretical equation, decreases in kVOL were largely explained by a reduction in open water area where chemical exchange across the air-water interface occurs. Apparent effects of the slick on SF6 mass transfer were estimated to be smaller by comparison (20%).To account for this reduction in volatilization, oil spill fate models should include a correction to consider the impact of spill cover on the air-water exchange of organic chemicals.
Asunto(s)
Contaminación por Petróleo , Petróleo , Contaminantes Químicos del Agua , Hidrocarburos , Lagos , Contaminación por Petróleo/análisis , Agua , Contaminantes Químicos del Agua/análisisRESUMEN
Canadian freshwater ecosystems are vulnerable to oil spills from pipelines, which contain mostly diluted bitumen. This study aimed to compare the toxicity of a dilbit and a conventional oil on developing rainbow trout. A total of five exposure scenarios were performed, from 10 to 43 days, using water-accommodated fraction (WAF) with an initial loading of 1:9 oil to water ratio (w/v) in a range of dilutions from 0.32 to 32% WAF, respectively, with TPAH and VOC concentrations from 2.41 to 17.5 µg/L and 7.94-660.99 µg/L, and with or without a recovery period. Following the five exposures, several endpoints were examined, including survivorship, morphometrics, gene expression, and enzymatic activity. Significant mortality rates were measured for the highest WAF concentration of the dilbit in all five exposures (60-100% mortality at 32% WAF). In comparison, the highest WAF concentration of the conventional oil induced significant mortality in three out of the five exposure (from 35 to 100% mortality at 32% WAF). Hatching delays were noted in embryos exposed to both oils. Developmental delays were observed in dilbit-exposed embryos and are suspected to be an indicator of reduced survivorship after hatching. The induced expression of cyp1a remained a reliable biomarker of exposure and of fish malformations, though it did not always predict mortality. Using CYP1A activity in combination with cyp1a may bring more insights in studies of oil risk assessment. This study demonstrates that dilbits are more toxic to early life stages compared to conventional oils and highlights the need to consider the most sensitive stage of development when performing risk assessment studies on oils.
Asunto(s)
Oncorhynchus mykiss , Animales , Canadá , Ecosistema , AceitesRESUMEN
Petroleum hydrocarbons are widely used and transported, increasing the risks of spills to the environment. Although conventional oils are the most commonly produced, the production of unconventional oils (i.e. diluted bitumen or dilbit) is increasing. In this study, we compared the effects of conventional oils (Arabian Light and Lloydminster) and dilbits (Bluesky and Clearwater) on early life stages of a salmonid. To this end, aqueous fractions (WAF: water accommodated fraction) of these oils were extracted using mountain spring water. Rainbow trout (Oncorhynchus mykiss) larvae were exposed to 10 and 50% dilutions of these WAFs from hatching (340 DD; degree days) until yolk sac resorption (541 DD). Exposure to WAFs increased skeletal malformations (both dilbits) and hemorrhage (both conventional oils and Bluesky) and decreased head growth (Arabian Light). In addition, increases in EROD activity and DNA damage were measured for all oils and an increase in cyp1a gene expression was measured for Arabian Light, Bluesky and Clearwater. The PAH and C10C50 concentrations were positively correlated to total larval EROD activity, whereas concentrations of total hydrocarbons, VOCs, PAHs, and C10C50 were positively correlated to cyp1a expression. Total hydrocarbon, VOC, and C10C50 concentrations were also negatively correlated to larval growth. This study supports that petroleum hydrocarbons are toxic to early developmental stages of rainbow trout and show that their degree and spectrum of toxicity depends on their chemical composition.
Asunto(s)
Oncorhynchus mykiss , Petróleo , Contaminantes Químicos del Agua , Animales , Hidrocarburos/toxicidad , Aceites , Petróleo/toxicidad , Contaminantes Químicos del Agua/toxicidadRESUMEN
The response of freshwater invertebrates following accidental releases of oil is not well understood. This knowledge gap is more substantial for unconventional oils such as diluted bitumen (dilbit). We evaluated the effects of dilbit on insect emergence and benthic invertebrates by conducting experimental spills in limnocorrals (10-m diameter; ~100-m3) deployed in a boreal lake at the IISD-Experimental Lakes Area, Canada. The study included seven dilbit treatments (spill volumes ranged from 1.5 L [1:66,000, oil:water, v/v] to 180 L [1:590, oil:water, v/v]), two controls, and additional lake reference sites, monitored for 11 weeks. Invertebrate emergence declined at the community level following oil addition in a significantly volume-dependent manner, and by 93-100 % over the 11 weeks following the spill in the highest treatment. Dilbit altered community structure of benthic invertebrates, but not abundance. One-year post-spill and following oil removal using traditional skimming and absorption techniques, benthic richness and abundance were greater among all treatments than the previous year. These results indicate that recovery in community composition is possible following oil removal from a lake ecosystem. Research is needed concerning the mechanisms by which surface oil directly affect adult invertebrates, whether through limiting oviposition, limiting emergence, or both. The response of benthic communities to sediment tar mats is also warranted.