Produced Water Discharges Research Articles

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

Concern has been raised over whether environmental release of alkylphenols (AP) in produced water (PW) discharges from the offshore oil industry could impose a risk to the reproduction of fish stocks in the North Sea. An environmental risk assessment (ERA) was performed to determine if environmental exposure to PW APs in North Sea fish populations is likely to be high enough to give effects on reproduction endpoints. The DREAM (Dose related Risk and Effect Assessment Model) software was used in the study and the inputs to the ERA model included PW discharge data, fate information of PW plumes, fish distribution information, as well as uptake and elimination information of PW APs. Toxicodynamic data from effect studies with Atlantic cod (Gadus morhua) exposed to APs were used to establish a conservative environmental risk threshold value for AP concentration in seawater. By using the DREAM software to 1) identify the areas of highest potential risk and 2) integrate fish movement and uptake/elimination rates of APs for the chosen areas we found that the environmental exposure of fish to APs from PW is most likely too low to affect reproduction in wild populations of fish in the North Sea. The implications related to risk management of offshore PW and uncertainties in the risk assessment performed are discussed.

Technology Focus: Health, Safety, Environment, and Social Responsibility (August 2011)

Technology Focus Offshore-drilling safety and oil-spill prevention and response have taken the lead in discussions, worldwide, as a consequence of the Macondo accident last year. Cap and containment became new key issues. Many initiatives have risen around the world; everybody fears that such an accident may happen in their backyard, if not in the center of their home. Many reports have already been published, and many more are expected to be issued in the coming weeks or months. There has been extensive discussion on this topic at all SPE major conferences this year. But a major accident does not write the whole story, nor does it stop the need for oil and gas. We should not forget that there are many more issues to be addressed by the upstream oil and gas industry. The industry is committed to improve its health, safety, and environment performances. A list of all health, safety, environment, and social responsibility topics that should be considered these days would be too long and may not be useful. To mention a just a few: safety culture, occupational health, security, asset integrity, naturally occurring radioactive material, aging installations, produced-water discharges, chemicals used and discharged, remote sensing (satellite imaging), emission of greenhouse gases, energy efficiency, shale gas, social impact, local content, and sustainable development. I stated last year that the industry—at least petroleum-industry professionals—needs to focus more on technology. We need more-efficient tools, pieces of equipment, and models. I reiterate the same view this year. It is the core for improvement. It is our license to operate that is at stake. Health, Safety, Environment, and Social Responsibility additional reading available at OnePetro: www.onepetro.org SPE 135004 • “Achieving Sustainable Incident-Free Operations Through Managing the Human Factor: A Success Story of Applying E-Colors” by Eli R. Barakat, SPE, Chevron, et al. OTC 21695 • “No-Solvent Oil-in-Water Analysis—A Robust Alternative to Conventional Solvent-Extraction Methods” by Dale F. Brost, Turner Designs Hydrocarbon Instruments, et al. OTC 22009 • “Satellite-Based Ice and Iceberg Monitoring for Offshore-Engineering Design and Tactical Operations” by C. Randell, C-CORE, et al. OTC 21515 • “Deepwater Archaeological AUV Surveys and Photo Capabilities” by Robert A. Church, C & C Technologies, et al. SPE 136576 • “Optimizing Stakeholder Communication Through Institutional and Community Focal Points To Foster a Stable Operating Environment” by Robert Hirst, Yemen LNG Company, et al. SPE 142803 • “Good Practice in Controlling Employees’ Exposure to Noise and Vibration in the Oil and Gas Industry” by Bruce Appleton, Health & Safety Executive, UK.

Achievements of risk-based produced water management on the Norwegian continental shelf (2002-2008)

In 1996, the Norwegian government issued a White Paper requiring the Norwegian oil industry to reach the goal of "zero discharge" for the marine environment by 2005. To achieve this goal, the Norwegian oil and gas industry initiated the Zero Discharge Programme for discharges of produced formation water from the hydrocarbon-containing reservoir, in close communication with regulators. The environmental impact factor (EIF), a risk-based management tool, was developed by the industry to quantify and document the environmental risks from produced water discharges. The EIF represents a volume of recipient water containing concentrations of one or more substances to a level exceeding a generic threshold for ecotoxicological effects. In addition, this tool facilitates the identification and selection of cost-effective risk mitigation measures. The EIF tool has been used by all operators on the Norwegian continental shelf since 2002 to report progress toward the goal of "zero discharge," interpreted as "zero harmful discharges," to the regulators. Even though produced water volumes have increased by approximately 30% between 2002 and 2008 on the Norwegian continental shelf, the total environmental risk from produced water discharges expressed by the summed EIF for all installations has been reduced by approximately 55%. The total amount of oil discharged to the sea has been reduced by 18% over the period 2000 to 2006. The experience from the Zero Discharge Programme shows that a risk-based approach is an excellent working tool to reduce discharges of potential harmful substances from offshore oil and gas installations.

Compositional heterogeneity may limit the usefulness of some commercial naphthenic acids for toxicity assays

Naphthenic acids are considered variously as monocarboxylic acids fitting the formula C nH 2n + z O 2 (where z is a zero or negative even integer), as only alicyclic ( i.e. non-aromatic) monocarboxylic acids fitting this formula (z ≤ 0), or simply as those carboxylic acids occurring in petroleum products or crude oils that have been formed through biodegradation of hydrocarbons. Such acids are known constituents of the process-affected water associated with some expanding oil sands industries, of some immature and biodegraded crude oils, of produced water discharges from oil production platforms and are used as biocides and as components in the manufacture of steel radial tyres. As a result of these potential vectors of the acids into the environment, various naphthenic acid mixtures which are available commercially have been used for a range of toxicity studies. However, as some manufacturers make clear, but which is not often emphasised in the toxicity studies, a range of different quality naphthenic acids is produced commercially. It has been suggested previously, and we showed recently and elucidate further herein, that such commercial mixtures therefore sometimes contain toxic components other than carboxylic acids. For example, we identify herein by two-dimensional comprehensive gas chromatography–mass spectrometry, a range of C 0–6 alkylphenols in a batch of commercial naphthenic acids. Since these compounds are known toxicants, the contribution of such non-carboxylic acids, if any, to the toxicity attributed previously to the acids, should also be considered. This will be reflected in the concentrations and effective toxicities of such components. In order to establish the toxicity of the acids per se, assays of pure synthetic carboxylic acids of the type now known to be present in naphthenic acids from petroleum or oil sands may be more appropriate than tests of the toxicity of largely unknown, heterogeneous, mixtures.

PAH body burden and biomarker responses in mussels (Mytilus edulis) exposed to produced water from a North Sea oil field: Laboratory and field assessments

In order to study the impact of produced water (PW) from a North Sea oil field on blue mussels (Mytilus edulis), chemical and biological markers were selected. A laboratory exposure (0.125%, 0.25% and 0.5% of PW) and a field study (6 stations 0.2–2km from a PW discharge point) were conducted. In the laboratory study, PAH bioaccumulation increased in mussel soft tissue even at the lowest exposure dose. Micronuclei frequency demonstrated a dose–response pattern, whereas lysosomal membrane stability showed tendency towards a dose–response pattern. The same markers were assessed in the field study, biomarker analyses were consistent with the contamination level, as evaluated by mussel polycyclic aromatic hydrocarbons body burden. Overall, obtained results confirmed the value of an ecotoxicological approach for a scientifically sound characterisation of biological effects induced by offshore oilfield operational discharges.

Synthesis and toxicity of some metabolites of the microbial degradation of synthetic naphthenic acids

Some ill-defined carboxylic acids, termed ‘naphthenic acids’ (NA), are best known as important constituents of the > 720 billion litres of process-affected water associated with the expanding oil sands industries. Other NA are components of some immature and biodegraded crude oils and these may enter the environment via produced water discharges from oil production platforms. Yet others are used as biocides and in the manufacture of steel radial tyres and these may also enter the environment through disposal and/or weathering. The environmental fate of NA, including the mechanisms of biodegradation, therefore needs to be better understood. In order to better elucidate such mechanisms, previously we studied the biodegradation in the laboratory of some alkylcyclohexylbutanoic synthetic NA. However, we could only tentatively identify the metabolites produced. In the present study we report the synthesis and characterisation of six alkylcyclohexylethanoic NA. Each was characterised by gas chromatography–mass spectrometry (GC–MS; trimethylsilyl esters) and we show by co-chromatography that these were indeed the metabolites. Also, a preferential degradation of the trans- isomers was revealed. Assessment of the toxicity of the synthetic NA (Microtox assay), revealed that the relative toxicity of the alkylcyclohexylbutanoic acids was reduced by biotransformation to the alkylcyclohexylethanoic acids, as observed recently for the corresponding aromatic acids. Very recent studies have shown that at least one commercial NA mixture contains cyclohexylbutanoic and alkylcyclohexylethanoic acids, suggesting that the biotransformation of the acids studied herein may be quite relevant to the environmental fate of such acids. A similar study of the acid extractables of one oil sands process-affected water sample suggests that the synthetic acids may be less good ‘models’ for oil sands NA. The consortia of microbes present in oil sands process-affected water may also be different to those used herein. However, the heterogeneity of oil sands process water is well-known and further detailed studies will need to be made in order to establish whether degradation of oil sands NA proceeds by beta oxidation as observed for the acids herein, or whether the oil sands acids are more resistant to bioremediation.

Water Column Monitoring of the Biological Effects of Produced Water from the Ekofisk Offshore Oil Installation from 2006 to 2009

The Norwegian water column monitoring program investigates the biological effects of offshore oil and gas activities in Norwegian waters. In three separate surveys in 2006, 2008, and 2009, bioaccumulation and biomarker responses were measured in mussels (Mytilus edulis) and Atlantic cod (Gadus morhua) held in cages at known distances from the produced water (PW) discharge at the Ekofisk oil field. Identical monitoring studies performed in all three years have allowed the biological effects and bioaccumulation data to be compared, and in addition, enabled the potential environmental benefits of a PW treatment system (CTour), implemented in 2008, to be evaluated. The results of the 2009 survey showed that caged animals were exposed to low levels of PW components, with highest tissue concentrations in mussels located closest to the PW discharge. Mussels located approximately 1–2 km away demonstrated only background concentrations of target compounds. Concentrations of polycyclic aromatic hydrocarbons (PAH) and alkyl phenol (AP) metabolites in the bile of caged cod were elevated at stations 200–250 m from the discharge. There was also a signal of exposure relative to discharge for the biomarkers CYP1A in fish and micronuclei in mussels. All other fish and mussel biomarkers showed no significant exposure effects in 2009. The mussel bioaccumulation data in 2009 indicated a lower exposure to the PW effluent than seen previously in 2008 and 2006, resulting in an associated general improvement in the health of the caged mussels. This was due to the reduction in overall discharge of PW components (measured as oil in water) into the area in 2009 compared to previous years as a result of the improved PW treatment system.

Establishing Appropriate Water Quality Numeric Standards under the Clean Water Act: Lessons from a Case Study of Coalbed Methane Produced Water Discharge to the Powder River, Wyoming and Montana

Establishing Appropriate Water Quality Numeric Standards under the Clean Water Act: Lessons from a Case Study of Coalbed Methane Produced Water Discharge to the Powder River, Wyoming and Montana

Field comparison of passive sampling and biological approaches for measuring exposure to PAH and alkylphenols from offshore produced water discharges

Polycyclic aromatic hydrocarbons (PAH) and alkylphenols (AP) that are present in routine discharges of produced water (PW) from the offshore industry continue to cause concern. The suitability of biological methods and chemical based passive samplers to determine exposure to these compounds was tested by deploying them around an oil installation and at reference locations in the North Sea. PAH and AP were analysed either as parent compounds in passive samplers and mussel tissue or as metabolites in fish bile. Generally the pattern of exposure relative to proximity to the discharge was represented by mussels, SPMDs and fish for PAH. Fish and SPMDs showed good correlation for PAH accumulations, whereas some differences were apparent between mussels and SPMDs. POCIS was the only technique tested that could accurately measure the most abundant AP in PW. The advantages of biologically independent measures of exposure for inclusion in discharge monitoring studies are outlined.

Microbiological impacts of produce water discharges in nearshore shallow marine waters near Chevrons Escravos tank farm, Nigeria

Microbiological and Physicochemical survey was undertaken in produced water and its receiving environment with the aim of verifying the likely impacts of produced water constituents on the immediate receiving marine near shore shallow environment. The sampling was carried out in two seasons, late wet season and late dry season. The results obtained indicate that the chemical constituents of the discharged produce water are capable of sustaining microbial growth and proliferation. Produce water from Escravos tank farm had relatively moderate concentrations of hydrocarbon utilizing microorganisms and sulphate reducing bacteria and the concentration of these organisms were much higher at the point of discharge of the produced water. Physicochemical analysis showed that Produce water had lower salinity and sulphate levels than the receiving marine water but the reverse was the case with the BOD, COD and Hydrocarbon constituents. The two seasons under investigation showed similar results. From the analytical data, it can be advanced that the impacts of produced water microbial flora on the receiving environment is limited to the vicinity of the discharge point of about 100 m in diameter and also to some extent up to a distance of 500 m upstream along the direction of flow of produced water discharges. It is expected that while the hydrocarbon degrading microorganisms plays a beneficial role of degrading and detoxifying abundant produced water hydrocarbons in the sediment and the surface water, Sulphate reducing bacteria might at the same time be playing a detrimental role of oxidizing certain organic compounds or hydrogen and reducing sulphate and other reduced sulphur compounds in the marine water and sediment to hydrogen sulphide which can be very toxic to bacteria, aquatic animals and man. Key words: Produced water, sulphate reducing bacteria, hydrocarbon utilizing bacteria.

The immune response of juvenile Atlantic cod ( Gadus morhua L.) to chronic exposure to produced water

Produced water (PW) is the main discharge from the offshore oil industry and contains oil-derived compounds such as poly-aromatic hydrocarbons, phenols, alkylphenols, and heavy metals. Studies suggest that PW discharges may affect the biota over larger areas from the oil drilling sites at sea than originally predicted. We investigated the effects of chronic exposure to PW on some aspects of juvenile Atlantic cod immunity, stress response and growth by intermittently exposing fish to 0, 100 or 200 ppm of PW for 22 weeks. No significant effects of PW were observed on growth, hepatosomatic index, condition factor or plasma cortisol. The respiratory burst (RB) of circulating leukocytes was significantly elevated in the 100 ppm group only, while the RB of head–kidney leukocytes was significantly decreased in both the 100 and 200 ppm groups. Significant up-regulation of the mRNA expression of β-2-microglobulin, immunoglobulin-M light chain and interleukins-1β and −8 was observed in the 200 ppm group, while the down-regulation of interferon stimulated gene 15 was obvious for both the 100 and 200 ppm groups. The results suggest that chronic exposure to environmentally relevant concentrations of PW causes modulations of the immune system of juvenile Atlantic cod with most immune parameters being stimulated, potentially resulting in an energetic cost that may be detrimental to the fish.

Environmental risk assessment of offshore produced water discharges using a hybrid fuzzy-stochastic modeling approach

In recent years, regulators and environmental groups have identified the large volumes of wastewater discharged through offshore petroleum production activities as an issue of concern. In this paper, fuzzy set theory coupled with Monte Carlo analysis have provided a stochastic simulation of pollutant dispersion for the prediction of the environmental risks associated with produced water discharges. With the application of the fuzzy set to data drawn from previous risk-assessment studies, the model allowed the evaluation of various existing pollution standards for marine environments. The present modeling method was validated against data for lead (Pb) levels in the area adjacent to an offshore petroleum facility located on the Grand Banks of Newfoundland, Canada through a multi-year field expedition. The proposed risk-assessment approach contributes to the implementation of effective assessment and management of produced water discharges in the offshore water environment.

Effect-Directed Identification of Naphthenic Acids As Important in Vitro Xeno-Estrogens and Anti-Androgens in North Sea Offshore Produced Water Discharges

Produced water from offshore oil production platforms represents the largest direct discharge of effluent into the offshore environment. Produced water effluents contain a complex mixture of substances which are known to bind to the estrogen receptor (ER) and antagonize the androgen receptor (AR). Short-chain petrogenic alkylphenols have been identified as responsible for around 35% of the ER agonist activity measured in vitro while the compounds responsible for antagonizing the androgen receptor are unknown. For the first time we report that petrogenic naphthenic acids are weak ER agonists that account for much of the 65% of the "unknown" ER agonist potency in North Sea produced waters while also disrupting the binding of AR agonists to the AR ligand receptor. We also report other known petrogenic components such as polycyclic aromatic hydrocarbons (PAHs) and alkylphenols as environmental AR antagonists. Our investigation shows that these petrogenic components are responsible for the majority of the ER and AR receptor mediated activity in produced waters. This hypothesis is supported by data from an effects-directed analysis of produced water using normal-phase high-performance liquid chromatography (HPLC) fractionation in combination with the yeast estrogen and androgen assays as well as androgen receptor binding assays of commercially available mixtures of naphthenic acids.

Development of a laboratory exposure system using marine fish to carry out realistic effect studies with produced water discharged from offshore oil production

A biotest system for environmentally realistic exposure of fish to produced water (PW) was developed and tested. Authentic PW was collected at an oil production platform in the North Sea and preserved by freezing in multiple aliquots a 25L. After transport to the test laboratory onshore, daily PW aliquots were thawed, homogenised and administered to the test fish, Atlantic cod (Gadus morhua), in two diluted exposure concentrations, 0.1% and 0.5%, during a 15 d period, using a continuous flow-through exposure setup. Positive control groups were exposed to two crude oil treatments for comparison. Chemical analyses showed that alkylphenol (AP) and PAH concentrations in PW exposure waters were very low. Observations of significantly increased AP and PAH metabolite levels in PW exposed fish demonstrated the suitability of the biotest system for its use in biological exposure/effect studies of PW, and it also demonstrated the sensitivity of bile metabolites as PW exposure markers in fish. The relevance of the biotest system for PW effect studies and for validating modelled environmental risk estimates of PW dischargers from offshore oil production is discussed.

Applications of Autonomous Underwater Vehicles in Offshore Petroleum Industry Environmental Effects Monitoring

Abstract Environmental Effects Monitoring (EEM) is an important tool in assisting Environmental Risk Assessment (ERA). EEM in the offshore petroleum industry has been conducted worldwide, but traditional approaches have struggled to keep apace as exploration and production activities move to frontier regions, such as increasingly deeper waters and Arctic regions. This paper proposes the use of autonomous underwater vehicles (AUVs) for environmental monitoring of offshore facilities as a means of improving and expanding the overall monitoring program. The paper provides a review of technical and procedural issues involved in this application of AUV technology, including the current status of offshore oil and gas EEM, a review of available AUVs and a survey of developments in in situ sensors. Introduction Offshore petroleum industry operations affect the marine environment in a variety of ways: high sound levels from seismic surveys that affect marine animals; exposure of marine organisms to drilling mud, produced water discharges and accidentally spilled oils; and the physical alteration of habitat due to the construction of submarine structures. The potential risks to the environment posed by offshore oil and gas operations support the need for effective Environmental Effects Monitoring (EEM) around the project development areas. EEM is a central component of environmental protection and management strategies designed to minimize the consequences of anthropogenic activities(1). It is a very important tool in assisting Environmental Risk Assessment (ERA) which is seen from many studies that link EEM and ERA together(2, 3). EEM is required by regulations governing industry activities offshore, and by government agencies in relation to cumulative impact assessment studies(4). The United States started the use of environmental monitoring programs in 1973. The Mineral Management Services (MMS) is currently responsible for managing oil and gas activities on the outer continental shelf (OCS). In the early stages of EEM programs, MMS monitored the effects of petroleum exploration activities on the George's Bank, Middle Atlantic OCS and the Gulf of Mexico. Early monitoring programs mainly focused on the effects of drilling wastes on benthic communities through a variety of sampling methods, such as camera transects, crab traps, bottom trawls and box corers. The MMS has also monitored the effects of petroleum development and production activities in the Gulf of Mexico, Santa Maria and Western Santa Barbara Channels off California, and in the Alaska Beaufort Sea. Trace metals and hydrocarbons in the water column, sediments, pore waters and biological tissues are collected and analyzed. In Canada, both government agencies and operators have carried out EEM. For example, Petro-Canada collected sediment samples from 49 stations and water samples from 24 stations in an area located in the vicinity of the Terra Nova Oil Field during 2000 to 2001. Analyses of samples included hydrocarbon concentration, metal concentration, particle size and the presence of sulphur, sulphide and ammonia(5). Fisheries and Oceans Canada also conducts annual EEM missions at the Hibernia, Terra Nova and The baud fields off the east coast of Canada. Both sediment and water samples are collected and the biodiversity of benthic organisms are studied using underwater photography.

Relationship Between Polycyclic Aromatic Hydrocarbon (PAH) Accumulation in Semipermeable Membrane Devices and PAH Bile Metabolite Levels in Atlantic Cod (Gadus morhua)

The extent to which accumulations of polycyclic aromatic hydrocarbons (PAH) by semipermeable membrane devices (SPMD) may be correlated to the concentration of PAH metabolites in fish was examined. Atlantic cod (Gadus morhua) and SPMD were exposed over a 4-wk period to a mixture that was designed to simulate the composition of PAH in produced water discharges in the North Sea. Fish bile and whole SPMD were analyzed after exposure in a high, low, and a control treatment tank. PAH metabolites were detected and quantified by means of high-performance liquid chromatography (HPLC) or gas chromatography–time-of-flight mass spectroscopy (GC-ToF-MS) and PAH in SPMD by gas chromatography–mass spectroscopy (GC-MS). The level and duration of exposure were generally reflected in both matrices. Exposure water concentrations, calculated from SPMD accumulations, showed some considerable differences from nominal concentrations for volatile compounds. Concentration factors (CF) for fish based on SPMD-derived water concentrations ranged from 2.9 to 354.3 L/g. CF increased with hydrophobicity with more variation at higher log K ow. Regression analysis of accumulations of individual compounds in fish and SPMDs showed reasonable but compound-specific correlation, r 2 = .54−.85 (C1-phenanthrenes/anthracenes and pyrene, respectively). Comparison of the two exposures suggests that fish CF may not be entirely independent of water concentrations. Overall the results show that accumulation of up to four-ring PAH in SPMD may be related to internal exposure of fish to these substances when exposed through water, as evidenced by metabolite concentrations. The usefulness of using SPMD to measure exposure concentrations in a large-scale flow-through study is also examined.

Trading Water for Gas: Application of the Public Interest Review to Coalbed Methane Produced Water Discharge in Wyoming

Trading Water for Gas: Application of the Public Interest Review to Coalbed Methane Produced Water Discharge in Wyoming

Modeling the discharge of cuttings and drilling fluids in a deep-water environment

Abstract Discharge models allow the prediction of the potential impact associated with drilling activities based on estimates of the initial spatial extent and thickness of accumulations on the seabed. As such, they are a valuable tool for both the oil industry and regulatory agencies. In this study we present the use of the Offshore Operators Committee Mud and Produced Water Discharge Model (OOC Model) in modeling the discharge of drilling activities in a deep-water environment, from a well located in the Campos Basin, offshore Brazil, at a depth of around 900 m. Field and discharge data collected during the drilling and discharge activities allowed us to carry out a modeling based on real data, that is, hindcast modeling. The verification of the model was made by comparing the hindcast modeling results with field observations. Discharges from both riserless and riser drilling were modeled. The riserless drilling was performed with seawater and water-based fluid (WBF), and riser drilling with non-aqueous fluid (NAF). According to model estimates, the deposits with greater thickness (∼66.5 cm) were those from the riserless phase. Maximum estimated thickness for the discharge of NAF cuttings was 0.76 cm. The comparison of modeling results with field observations showed that the estimates of both the area affected by the deposits and maximum thickness are satisfactory. The configuration of the affected area is harder to predict because small uncertainties, mainly related to the discharge activity itself, introduce a significant error. Thicknesses predicted from real data by hindcast modeling agree with estimates provided by forecast modeling presented by other authors. This means that, in areas where there is certain knowledge of the hydrodynamics, the OOC Model can be a valuable tool to determine the degree of potential impact associated with drilling activities.

Uptake and tissue distribution of C 4–C 7 alkylphenols in Atlantic cod ( Gadus morhua): Relevance for biomonitoring of produced water discharges from oil production

The sensitivity of different tissues for assessment of chronic low-dose environmental exposure of fish to alkylphenols (APs) was investigated. We exposed Atlantic cod ( Gadus morhua) in the laboratory to tritium labelled 4-tert-butylphenol, 4 n-pentylphenol, 4 n-hexylphenol, and 4 n-heptylphenol via seawater (8 ng/l) and via contaminated feed (5 μg/kg fish per day). Measurements of different fish tissues during eight days of exposure and eight subsequent days of recovery revealed that APs administered via spiked seawater were readily taken up whereas the uptake was far less efficient when APs were administered in spiked feed. AP residues were mainly located in the bile fluid whereas the concentrations in liver were very low, indicating a rapid excretion and the liver–bile axis to be the major route of elimination. The biological half-life of APs in the exposed cod was short, between 10 and 20 h. Our study shows that in connection with biomonitoring of AP exposure in fish, assessment of AP metabolites in bile fluid is a more sensitive tool than detection of parent AP levels in liver or other internal tissues.

A risk assessment model for produced water discharge from offshore petroleum platforms-development and validation

Produced water discharge accounts for the greater portion of wastes arising from offshore oil and gas production operations. Development and expansion of Canada’s offshore oil and gas reserves has led to concerns over the potential long-term impacts of produced water discharges to the ocean. To examine this emerging environmental issue at a regional scale, an integrated risk assessment approach was developed in this study based on the princeton ocean model (POM), a random walk (RW) and Monte Carlo simulation. The use of water quality standards arrayed in a Monte Carlo design in the developed approach has served to reflect uncertainties and quantify environmental risks associated with produced water discharge. The model was validated against field data from a platform operating off Canada’s east coast, demonstrating its usefulness in supporting effective management of future produced water discharge.