Environmental risk assessment of alkylphenols from offshore produced water on fish reproduction

An impact-based environmental risk assessment model toolbox for offshore produced water discharges

We present a novel approach to environmental risk assessment of produced water discharges based on explicit impact and probability, using a combination of transport, fate and toxicokinetic-toxicodynamic models within a super-individual framework, with a probabilistic element obtained from ensemble simulations. Our approach is motivated by a need for location and species specific tools which also accounts for the dynamic nature of exposure and uptake of produced water components in the sea. Our approach is based on the well-established fate model DREAM, and accounts for time-variable exposure, considers body burden and effects for specific species and stressors, and assesses the probability of impact. Using a produced water discharge in the Barents Sea, with early life stages of spawning haddock, we demonstrate that it is possible to conduct a model-based risk assessment that highlights the effect of natural variations in environmental conditions. The benefits, limitations and potential for further improvements are discussed.

Hazard assessment of chemical constituents in biocide formulations used in offshore oil and gas operations

Biocides used in offshore oil and gas operations could be present in water discharges, and thus identifying such chemicals and their hazard could help address concerns regarding non-target organisms. Aquatic toxicity data, queried from different sources and augmented with predictive models, were used to develop species sensitivity distributions and their corresponding 5th percentile hazard concentrations (HC5s). Curated data, including over 1000 empirical records for 137 species, indicated no evidence of bias when comparing sensitivity between marine and freshwater species, even when predicted data were used. HC5s facilitated estimation of an acute-to-chronic ratio (ACR = 10), appropriate for most chemicals and useful in filling data gaps. Comparison of chronic-HC5s with the default approach for deriving predicted no effect concentrations showed that the latter systematically overstates aquatic hazard. The present approach shows promise of using acute-to-chronic HC5 ratios for defining assessment factors for different chemical classes, instead of the use of generic assessment factors.

North sea produced water PAH exposure and uptake in early life stages of Atlantic Cod

Produced water discharges from offshore oil and gas platforms represent a significant source of petroleum components such as polycyclic aromatic hydrocarbons (PAHs) released to the ocean. High molecular weight PAHs are persistent in the environment and have a potential for bioaccumulation, and the investigation of their fate and uptake pathways in marine life are relevant when assessing environmental risk of produced water discharges. To study the exposure and uptake of 2-5 ring PAHs in early life stages of Atlantic Cod in the North Sea, we run a coupled fate and individual-based numerical model that includes discharges from 26 platforms. We consider 26 different PAH components in produced water which biodegrade with primary degradation rates; intermediate degradation products are not included. Model simulations are run covering multiple years (2009-2012) to study annual exposure variability, while a one-day time slice of spawning products from the peak spawning season are followed. By covering multiple release points and large spatio-temporal scales, we show how individuals can be exposed to produced water from multiple regions in the North Sea. We find that a combination of oceanic fate processes and toxicokinetics lead to markedly different compositions in the predicted internal concentrations of PAHs compared to discharge concentrations; for instance, naphthalene makes up 30% of the total discharged PAHs, but contributes to at most 1% of internal concentrations. In all simulations we find the predicted total internal PAH concentration (26 components) to be below 1.2 nmol/g, a factor of 1000 less than concentrations commonly associated with acute narcotic effects.

Environmental effects of offshore produced water discharges: A review focused on the Norwegian continental shelf

Produced water (PW), a large byproduct of offshore oil and gas extraction, is reinjected to formations or discharged to the sea after treatment. The discharges contain dispersed crude oil, polycyclic aromatic hydrocarbons (PAHs), alkylphenols (APs), metals, and many other constituents of environmental relevance. Risk-based regulation, greener offshore chemicals and improved cleaning systems have reduced environmental risks of PW discharges, but PW is still the largest operational source of oil pollution to the sea from the offshore petroleum industry. Monitoring surveys find detectable exposures in caged mussel and fish several km downstream from PW outfalls, but biomarkers indicate only mild acute effects in these sentinels. On the other hand, increased concentrations of DNA adducts are found repeatedly in benthic fish populations, especially in haddock. It is uncertain whether increased adducts could be a long-term effect of sediment contamination due to ongoing PW discharges, or earlier discharges of oil-containing drilling waste. Another concern is uncertainty regarding the possible effect of PW discharges in the sub-Arctic Southern Barents Sea. So far, research suggests that sub-arctic species are largely comparable to temperate species in their sensitivity to PW exposure. Larval deformities and cardiac toxicity in fish early life stages are among the biomarkers and adverse outcome pathways that currently receive much attention in PW effect research. Herein, we summarize the accumulated ecotoxicological knowledge of offshore PW discharges and highlight some key remaining knowledge needs.

Whole Effluent Toxicity Data and Discharge Volumes to Assess the Likelihood that Environmental Risks of Offshore Produced Water Discharges Are Adequately Controlled

In 2012, the Oslo-Paris (OSPAR) Commission adopted Recommendation 2012/5 for a risk-based approach (RBA) to the management of produced water discharges from offshore installations. As part of this recommendation, OSPAR requires that the environmental risk of the discharge of produced water is characterized based on whole effluent toxicity (WET) studies and/or on a substance-based assessment. In this paper we describe an assessment of the likelihood that the environmental risk of produced water discharges is adequately controlled based on WET data for 19 oil- and gas-producing platforms and their discharge volumes. Our analysis shows that, with the selected risk criterion of predicted exposure concentration (PEC)/predicted no-effect concentration (PNEC) should not exceed 1 at 500 m, there is a mean likelihood of 99.5% (or more) that the environmental risk from the produced water discharges is adequately controlled for installations that discharge 30 × 10³ m³ /y (or less). The method presented in this paper can be used for screening purposes to ensure that efforts are directed toward installations with a high likelihood that risk is not adequately controlled. Integr Environ Assess Manag 2019;15:584-595. © 2019 SETAC.

Monitoring wastewater discharge from the oil and gas industry using passive sampling and Danio rerio bioassay as complimentary tools

Produced water (PW) represents the largest volume waste stream in oil and gas production operations from most offshore platforms. PW is difficult to monitor as releases are rapidly diluted and concentrations can reach trace levels. The use of passive samplers can over come this. Here polyethylene (PE) was calibrated for a diverse range of PW pollutants. Zebrafish were exposed to dilutions of PW and passive sampler extracts in order to investigate the relationship between freely dissolved chemical concentrations and acute toxic effects. The raw PW had an LC50 of 13% (percentage of PW in the standardized zebrafish medium). Observed non-viable deformations to embryos (at 5 hpf) included heart and yolk edema, head, spine and tail deformations. The dose-response relationship of lethal effects showed that if 0.0041 g of PE is exposed to this PW, then extracted, 50% of exposed D. rerio will suffer lethal effects. The sum of tested freely dissolved concentrations that led to 50% lethal effects (mortality and non-viable deformations) was 2.32 × 10^-4 mg/L for PW and 7.92 × 10^-2 mg/L for PE. This implies that exposure to raw PW was more toxic than exposure to PE extracts. This toxicity was attributed both to the presence of contaminants as well as PW salinity. Passive samplers are able to detect very low freely dissolved pollutant concentrations which is important for assessing the spatial dilution of PW releases. Bioassays provide complimentary information as they account for all toxic compounds including those that are not taken up by passive samplers.

Biodegradation in seawater of PAH and alkylphenols from produced water of a North Sea platform

Operational planned discharges of produced water (PW) to the marine environment from offshore oil production installations, contain low concentrations of dispersed oil compounds, like polycyclic aromatic hydrocarbons (PAHs) and alkylated phenols (APs). Biotransformation in natural seawater (SW) of naphthalenes/PAHs and phenol/APs in field-collected PW from a North Sea platform was investigated in this biodegradation study. The PW was diluted in SW from a Norwegian fjord, and the biodegradation study was performed in slowly rotating carousels at 13 °C over a period of 62 days. Naphthalenes/PAHs and phenol/APs biotransformation was determined by first-order rate kinetics, after normalization against the recalcitrant biomarker 17α(H),21β(H)-Hopane. The results from this study showed total biotransformation half-lives ranging from 10 to 19 days for groups of naphthalenes and PAHs, while half-lives for APs (C0- to C9-alkylated) were 10-14 days. Biotransformation half-lives of single compounds ranged from 8 to >100 days for naphthalenes and PAHs (median 16 days), and from 5 to 70 days (median 15 days) for phenols and APs. Four of the tested PAHs (chrysene, benzo(b)fluoranthene, benzo(e)pyrene, benzo(g,h,i)perylene) and one AP (4-tert-butylphenol) showed biotransformation half-lives >50 days. This is one of a few studies that has investigated the potential for biodegradation of PW in natural SW. Methods and data from this study may be used as a part of Risk Based Approaches (RBA) for assessments of environmental fate of PW released to the marine environment and as part of the persistence related to risk.

An evaluation of cumulative risks from offshore produced water discharges in the Bass Strait

Chemical analyses and toxicity testing using six marine species were used to characterize the hazard of produced waters (PW) to marine life from twelve Australian offshore platforms. Hazard data were used in conjunction with platform-specific plume discharge dilution and species sensitivity distribution modeling to estimate cumulative risks by calculating the multiple substance potentially affected fraction of species in the local marine environment. Results provided two independent lines of evidence demonstrating that cumulative risks to marine life from these discharges meet intended 95% species protection goals at the edge of the mixing zone. A limited number of PW constituents (hydrocarbons, sulphide and ammonia) appeared to dictate risk thereby informing management and providing a rationale for more targeted analyses in future monitoring studies. Based on these findings a tiered framework is proposed to foster consistent screening and potential refinement of cumulative risk evaluations for PW discharges.

III: Use of biomarkers as Risk Indicators in Environmental Risk Assessment of oil based discharges offshore

Offshore oil and gas activities are required not to cause adverse environmental effects, and risk based management has been established to meet environmental standards. In some risk assessment schemes, Risk Indicators (RIs) are parameters to monitor the development of risk affecting factors. RIs have not yet been established in the Environmental Risk Assessment procedures for management of oil based discharges offshore. This paper evaluates the usefulness of biomarkers as RIs, based on their properties, existing laboratory biomarker data and assessment methods. Data shows several correlations between oil concentrations and biomarker responses, and assessment principles exist that qualify biomarkers for integration into risk procedures. Different ways that these existing biomarkers and methods can be applied as RIs in a probabilistic risk assessment system when linked with whole organism responses are discussed. This can be a useful approach to integrate biomarkers into probabilistic risk assessment related to oil based discharges, representing a potential supplement to information that biomarkers already provide about environmental impact and risk related to these kind of discharges.

I: Biomarker quantification in fish exposed to crude oil as input to species sensitivity distributions and threshold values for environmental monitoring

The aim of this study was to determine a suitable set of biomarker based methods for environmental monitoring in sub-arctic and temperate offshore areas using scientific knowledge on the sensitivity of fish species to dispersed crude oil. Threshold values for environmental monitoring and risk assessment were obtained based on a quantitative comparison of biomarker responses. Turbot, halibut, salmon and sprat were exposed for up to 8 weeks to five different sub-lethal concentrations of dispersed crude oil. Biomarkers assessing PAH metabolites, oxidative stress, detoxification system I activity, genotoxicity, immunotoxicity, endocrine disruption, general cellular stress and histological changes were measured. Results showed that PAH metabolites, CYP1A/EROD, DNA adducts and histopathology rendered the most robust results across the different fish species, both in terms of sensitivity and dose-responsiveness. The reported results contributed to forming links between biomonitoring and risk assessment procedures by using biomarker species sensitivity distributions.

The role of passive sampling in monitoring the environmental impacts of produced water discharges from the Norwegian oil and gas industry

Stringent and periodic iteration of regulations related to the monitoring of chemical releases from the offshore oil and gas industry requires the use of ever changing, rapidly developing and technologically advancing techniques. Passive samplers play an important role in water column monitoring of produced water (PW) discharge to seawater under Norwegian regulation, where they are used to; i) measure aqueous concentrations of pollutants, ii) quantify the exposure of caged organisms and investigate PW dispersal, and iii) validate dispersal models. This article summarises current Norwegian water column monitoring practice and identifies research and methodological gaps for the use of passive samplers in monitoring. The main gaps are; i) the range of passive samplers used should be extended, ii) differences observed in absolute concentrations accumulated by passive samplers and organisms should be understood, and iii) the link between PW discharge concentrations and observed acute and sub-lethal ecotoxicological end points in organisms should be investigated.

Identification of petrogenic produced water components as acetylcholine esterase inhibitors

Effect-directed analysis (EDA) was applied to identify acetylcholine esterase (AChE) inhibitors in produced water. Common produced water components from oil production activities, such as polycyclic aromatic hydrocarbons (PAHs), alkylphenols, and naphthenic acids were tested for AChE inhibition using a simple mixture of PAHs and naphthenic acids. Produced water samples collected from two offshore platforms in the Norwegian sector of the North Sea were extracted by solid phase extraction and fractionated by open-column liquid solid chromatography and high-performance liquid chromatography (HPLC) before being tested using a high-throughput and automated AChE assay. The HPLC fractions causing the strongest AChE inhibition were analysed by gas chromatography coupled to a high-resolution time-of-flight mass spectrometry (GC-HR-ToF-MS). Butylated hydroxytoluene and 4-phenyl-1,2-dihydronaphthalene were identified as two produced water components capable of inhibiting AChE at low concentrations. In order to assess the potential presence of such compounds discharged into aquatic ecosystems, AChE activity in fish tissues was measured. Saithe (Pollachius virens) caught near two offshore platforms showed lower enzymatic activity than those collected from a reference location. Target analysis of saithe did not detected the presence of these two putative AChE inhibitors and suggest that additional compounds such as PAHs, naphthenic acids and yet un-identified compounds may also contribute to the purported AChE inhibition observed in saithe.

Assessing the potential impact of water-based drill cuttings on deep-water calcareous red algae using species specific impact categories and measured oceanographic and discharge data

The potential impact of drill cuttings on the two deep water calcareous red algae Mesophyllum engelhartii and Lithothamnion sp. from the Peregrino oil field was assessed. Dispersion modelling of drill cuttings was performed for a two year period using measured oceanographic and discharge data with 24 h resolution. The model was also used to assess the impact on the two algae species using four species specific impact categories: No, minor, medium and severe impact. The corresponding intervals for photosynthetic efficiency (ΦPSIImax) and sediment coverage were obtained from exposure-response relationship for photosynthetic efficiency as function of sediment coverage for the two algae species. The temporal resolution enabled more accurate model predictions as short-term changes in discharges and environmental conditions could be detected. The assessment shows that there is a patchy risk for severe impact on the calcareous algae stretching across the transitional zone and into the calcareous algae bed at Peregrino.

Comparison of produced water toxicity to Arctic and temperate species

Produced water is the main discharge stream from oil and gas production. For offshore activities this water is usually discharged to the marine environment. Produced water contains traces of hydrocarbons such as polycyclic aromatic hydrocarbons as well as alkylphenols, which are relatively resistant to biodegradation and have been reported to cause adverse effects to marine organisms in laboratory studies. For management of produced water, risk-based tools have been developed using toxicity data for mainly non-Arctic species. Reliable risk assessment approaches for Arctic environments are requested to manage potential impacts of produced water associated with increased oil and gas activities in Arctic regions. In order to assess the applicability of existing risk tools for Arctic areas, basic knowledge on the sensitivity of Arctic species has to be developed. In the present study, acute and chronic toxicity of artificial produced water for 6 Arctic and 6 temperate species was experimentally tested and evaluated. The hazardous concentrations affecting 5% and 50% of the species were calculated from species sensitivity distribution curves. Hazardous concentrations were compared to elucidate whether temperate toxicity data used in risk assessment are sufficiently representative for Arctic species. From the study it can be concluded that hazardous concentration derived from individual species' toxicity data of temperate and Arctic species are comparable. However, the manner in which Arctic and non-Arctic populations and communities respond to exposure levels above established thresholds remains to be investigated. Hence, responses at higher levels of biological organization should be studied to reveal potential differences in sensitivities to produced water between Arctic and non-Arctic ecosystems.

In vivo effects of environmental concentrations of produced water on the reproductive function of polar cod (Boreogadus saida)

Offshore oil and gas drilling processes generate operational discharges such as produced water (PW), a complex mixture of seawater with polycyclic aromatic hydrocarbons (PAH) and alkylphenols (AP). Some of these compounds may interact with the endocrine system of marine organisms and alter reproductive functions. In this study, polar cod were exposed for up to 28 d to a mixture of PAH, alkylated PAH, and AP simulating the composition of North Sea PW, at low and high concentrations (1:2000 and 1:1000 dilution of the original concentrate, respectively). Potential adverse effects of PW on polar cod physiology were investigated through biomarkers of biotransformation (hepatic ethoxyresorufin O-deethylase [EROD] activity and bile PAH metabolites), endocrine disruption (plasma vitellogenin [VTG] levels and sex steroid concentrations), and gonad histology. Plasma sexual steroid levels in fish were not markedly affected by PW exposure, while higher plasma VTG concentrations were measured in females exposed to the high PW treatment for 7 and 28 d. In males exposed to the higher PW concentration, inhibition of spermatogenesis was observed after 28 d in addition to increase of melano-macrophage occurrence in testis. Females exposed to the high PW treatment for 21 d showed a significant increase of atresia incidence. Finally, a significant decrease in oocyte number was observed in high PW exposed female ovaries after 28 d of exposure.

Environmental impacts of produced water and drilling waste discharges from the Norwegian offshore petroleum industry

Operational discharges of produced water and drill cuttings from offshore oil and gas platforms are a continuous source of contaminants to continental shelf ecosystems. This paper reviews recent research on the biological effects of such discharges with focus on the Norwegian Continental Shelf. The greatest concern is linked to effects of produced water. Alkylphenols (AP) and polyaromatic hydrocarbons (PAH) from produced water accumulate in cod and blue mussel caged near outlets, but are rapidly metabolized in cod. APs, naphtenic acids, and PAHs may disturb reproductive functions, and affect several chemical, biochemical and genetic biomarkers. Toxic concentrations seem restricted to <2 km distance. At the peak of discharge of oil-contaminated cuttings fauna disturbance was found at more than 5 km from some platforms, but is now seldom detected beyond 500 m. Water-based cuttings may seriously affect biomarkers in filter feeding bivalves, and cause elevated sediment oxygen consumption and mortality in benthic fauna. Effects levels occur within 0.5-1 km distance. The stress is mainly physical. The risk of widespread, long term impact from the operational discharges on populations and the ecosystem is presently considered low, but this cannot be verified from the published literature.