Assessing bioaccumulation with biomagnification factors from dietary bioaccumulation tests.

Despite the fact that the UN Stockholm Convention on persistent organic pollutants specifically acknowledges that Arctic ecosystems and Indigenous communities are particularly at risk due to biomagnification of contaminants in traditional foods, the bioconcentration factor (BCF) of substances in fish remains the preferred metric for identifying the biomagnification potential of organic substances. The BCF measures uptake of substances from water in water-breathing organisms, but not biomagnification of contaminants from food sources. The purpose of this study is to investigate how the biomagnification factor (BMF) can be used in bioaccumulation assessments.

Environmental hazard and preliminary risk assessment of herding agents used in next generation oil spill response.

Herding agents offer a significant advance in oil spill response by overcoming past barriers limiting effectiveness of in-situ burning. This paper reviews the use, environmental fate and effects of two commercial herders, Siltech OP-40 and ThickSlick 6535. A conceptual model is proposed to describe herder fate followed by a screening exposure analysis.

Direct and indirect photodegradation in aquatic systems mitigates photosensitized toxicity in screening-level substance risk assessments of selected petrochemical structures.

Photochemical processes are typically not incorporated in screening-level substance risk assessments due to the complexity of modeling sunlight co-exposures and resulting interactions on environmental fate and effects. However, for many substances, sunlight exerts a profound influence on environmental degradation rates and ecotoxicities. Recent modeling advances provide an improved technical basis for estimating the effect of sunlight in modulating both substance exposure and toxicity in the aquatic environment.

Parsing the toxicity paradox: Composition and duration of exposure alter predicted oil spill effects by orders of magnitude.

Oil spilled into an aquatic environment produces oil droplet and dissolved component concentrations and compositions that are highly variable in space and time. Toxic effects on aquatic biota vary with sensitivity of the organism, concentration, composition, environmental conditions, and frequency and duration of exposure to the mixture of oil-derived dissolved compounds. For a range of spill (surface, subsea, blowout) and oil types under different environmental conditions, modeling of oil transport, fate, and organism behavior was used to quantify expected exposures over time for planktonic, motile, and stationary organisms.

In Silico Acute Aquatic Hazard Assessment and Prioritization Using a Grouped Target Site Model: A Case Study of Organic Substances Reported in Permian Basin Hydraulic Fracturing Operations.

Hydraulic fracturing (HF) is commonly used to enhance onshore recovery of oil and gas during production. This process involves the use of a variety of chemicals to support the physical extraction of oil and gas, maintain appropriate conditions downhole (e.g.

Effects of aromatic hydrocarbons and evaluation of oil toxicity modelling for larvae of a tropical coral.

Application of oil toxicity modelling for assessing the risk of spills to coral reefs remains uncertain due to a lack of data for key tropical species and environmental conditions. In this study, larvae of the coral Acropora millepora were exposed to six aromatic hydrocarbons individually to generate critical target lipid body burdens (CTLBBs). Larval metamorphosis was inhibited by all six aromatic hydrocarbons, while larval survival was only affected at concentrations >2000 μg L.

Improving the design and conduct of aquatic toxicity studies with oils based on 20 years of CROSERF experience.

Laboratory toxicity testing is a key tool used in oil spill science, spill effects assessment, and mitigation strategy decisions to minimize environmental impacts. A major consideration in oil toxicity testing is how to replicate real-world spill conditions, oil types, weathering states, receptor organisms, and modifying environmental factors under laboratory conditions. Oils and petroleum-derived products are comprised of thousands of compounds with different physicochemical and toxicological properties, and this leads to challenges in conducting and interpreting oil toxicity studies.

Sensitivity of the Indo-Pacific coral Acropora millepora to aromatic hydrocarbons.

The risks posed by petroleum spills to coral reefs are poorly understood and quantifying acute toxicity thresholds for aromatic hydrocarbons to reef-building corals is required to assess their sensitivity relative to other taxa. In this study, we exposed Acropora millepora to toluene, naphthalene and 1-methylnaphthalene (1-MN) in a flow-through system and assessed survivorship and sublethal responses including growth, colour and the photosynthetic performance of symbionts. Median 50% lethal concentrations (LC50s) decreased over the 7-d exposure period, reaching asymptotic values of 22,921, 5,268, 1167 μg L for toluene, naphthalene and 1-MN, respectively.

Recommendations for advancing media preparation methods used to assess aquatic hazards of oils and spill response agents.

Laboratory preparation of aqueous test media is a critical step in developing toxicity information needed for oil spill response decision-making. Multiple methods have been used to prepare physically and chemically dispersed oils which influence test outcome, interpretation, and utility for hazard assessment and modeling. This paper aims to review media preparation strategies, highlight advantages and limitations, provide recommendations for improvement, and promote the standardization of methods to better inform assessment and modeling.

Bridging the lab to field divide: Advancing oil spill biological effects models requires revisiting aquatic toxicity testing.

Oil fate and exposure modeling addresses the complexities of oil composition, weathering, partitioning in the environment, and the distributions and behaviors of aquatic biota to estimate exposure histories, i.e., oil component concentrations and environmental conditions experienced over time.

Recommendations for improving the reporting and communication of aquatic toxicity studies for oil spill planning, response, and environmental assessment.

Standardized oil toxicity testing is important to ensure comparability of study results, and to generate information to support oil spill planning, response, and environmental assessments. Outcomes from toxicity tests are useful in the development, improvement and validation of effects models, and new or revised knowledge could be integrated into existing databases and related tools. To foster transparency, facilitate repeatability and maximize use and impact, outcomes from toxicity tests need to be clearly reported and communicated.

Adopting a toxic unit model paradigm in design, analysis and interpretation of oil toxicity testing.

The lack of a conceptual understanding and unifying quantitative framework to guide conduct and interpretation of laboratory oil toxicity tests, has led investigators to divergent conclusions that can confuse stakeholders and impede sound decision-making. While a plethora of oil toxicity studies are available and continue to be published, due to differences in experimental design, results between studies often cannot be compared. Furthermore, much resulting data fails to advance quantitative effect models that are critically needed for oil spill risk and impact assessments.

Calibration of an acute toxicity model for the marine crustacean, Artemia franciscana, nauplii to support oil spill effect assessments.

Oil spill risk and impact assessments rely on time-dependent toxicity models to predict the hazard of the constituents that comprise crude oils and petroleum substances. Dissolved aromatic compounds (ACs) are recognized as a primary driver of aquatic toxicity in surface spill exposure scenarios. However, limited time-dependent toxicity data are available for different classes of ACs to calibrate such models.

Temporal chemical composition changes in water below a crude oil slick irradiated with natural sunlight.

Photooxidation can alter the environmental fate and effects of spilled oil. To better understand this process, oil slicks were generated on seawater mesocosms and exposed to sunlight for 8 days. The molecular composition of seawater under irradiated and non-irradiated oil slicks was characterized using ion mobility spectrometry-mass spectrometry and polyaromatic hydrocarbons analyses.

Ferrocyanide enhanced evaporative flux to remediate soils contaminated with produced water brine.

Accidental releases of highly saline produced water (PW) to land can impact soil quality. The release of associated salts can clog soil pores, disperse soil clays, and inhibit plants and other soil biota. This study explores a novel remediation technique using ferrocyanide to enhance the evaporative flux of soil porewater to transport dissolved salts to the soil surface, where crystallization then occurs.

Modeling Time-Dependent Aquatic Toxicity of Hydrocarbons: Role of Organism Weight, Temperature, and Substance Hydrophobicity.

Oil spill exposures are highly dynamic and are not comparable to laboratory exposures used in standard toxicity tests. Toxicokinetic-toxicodynamic (TKTD) models allow translation of effects observed in the laboratory to the field. To improve TKTD model calibration, new and previously published data from 148 tests were analyzed to estimate rates characterizing the time course of toxicity for 10 fish and 42 invertebrate species across 37 hydrocarbons.

Oil Irradiation Experiments Document Changes in Oil Properties, Molecular Composition, and Dispersant Effectiveness Associated with Oil Photo-Oxidation.

While chemical dispersants are a powerful tool for treating spilled oil, their effectiveness can be limited by oil weathering processes such as evaporation and emulsification. It has been suggested that oil photo-oxidation could exacerbate these challenges. To address the role of oil photo-oxidation in dispersant effectiveness, outdoor mesocosm experiments with crude oil on seawater were performed.

Derivation of toxicity thresholds for gas condensate oils protective of tropical species using experimental and modelling approaches.

Toxicity thresholds for dissolved oil applied in tropical ocean risk assessments are largely based on the sensitivities of temperate and/or freshwater species. To explore the suitability of these thresholds for tropical habitats we experimentally determined toxicity thresholds for eight tropical species for a partially weathered gas condensate, applied the target lipid model (TLM) to predict toxicity of fresh and weathered condensates and compared sensitivities of the tropical species with model predictions. The experimental condensate-specific hazard concentration (HC5) was 167 μg L total aromatic hydrocarbons (TAH), with the TLM-modelled HC5 (78 μg L TAH) being more conservative, supporting TLM-modelled thresholds for tropical application.

Toxicity of two representative petroleum hydrocarbons, toluene and phenanthrene, to five Atlantic coral species.

Coral reefs are keystone coastal ecosystems that can be exposed to petroleum hydrocarbons from multiple sources, and when selecting spill response methods to limit environmental damages, corals represent one of the highest valued resources for protection. Because previous research to characterize the sensitivity of coral species to petroleum hydrocarbon exposures is limited, a continuous-flow passive dosing system and toxicity testing protocol was designed to evaluate the acute effects of two representative petroleum compounds, toluene and phenanthrene, on five coral species: Acropora cervicornis, Porites astreoides, Siderastera siderea, Stephanocoenia intersepta, and Solenastrea bournoni. Using analytically confirmed exposures, sublethal and lethal endpoints were calculated for each species, and used as model inputs to determine critical target lipid body burdens (CTLBBs) for characterizing species sensitivity.

Acritical review and weight of evidence approach for assessing the bioaccumulation of phenanthrene in aquatic environments.

Bioaccumulation (B) assessment is challenging because there are various B-metrics from laboratory and field studies, multiple criteria and thresholds for classifying bioaccumulative (B), very bioaccumulative (vB), and not bioaccumulative (nB) chemicals, as well as inherent variability and uncertainty in the data. These challenges can be met using a weight of evidence (WoE) approach. The Bioaccumulation Assessment Tool (BAT) provides a transparent WoE assessment framework that follows Organisation for Economic Co-operation and Development (OECD) principles for performing a WoE analysis.

Miniaturised marine tests as indicators of aromatic hydrocarbon toxicity: Potential applicability to oil spill assessment.

Assessing oil spill toxicity in real time is challenging due to dynamic field exposures and lack of simple, rapid, and sensitive tests. We investigated the relative sensitivity of two commercially available marine toxicity tests to aromatic hydrocarbons using the target lipid model (TLM). State of the art passive dosing in sealed vials was used to assess the sensitivity of brine shrimp (Artemia franciscana) and rotifer (Brachionus plicatilis).

Assessing the Toxicity of Individual Aromatic Compounds and Mixtures to American Lobster (Homarus americanus) Larvae Using a Passive Dosing System.

Aquatic exposures to aromatic compounds (ACs) may be important contributors to biological effects of oil spills. The present study examined the acute toxicity of 11 ACs and 3 binary AC mixtures on stage 1 American lobster larvae using a passive dosing test design. The ACs investigated covered a range of classes and log octanol-water partition coefficient values (K ; 2.

Assessing toxicity of hydrophobic aliphatic and monoaromatic hydrocarbons at the solubility limit using novel dosing methods.

Reliable delineation of aquatic toxicity cut-offs for poorly soluble hydrocarbons is lacking. In this study, vapor and passive dosing methods were applied in limit tests with algae and daphnids to evaluate the presence or absence of chronic effects at exposures corresponding to the water solubility for representative hydrocarbons from five structural classes: branched alkanes, mono, di, and polynaphthenic (cyclic) alkanes and monoaromatic naphthenic hydrocarbons (MANHs). Algal growth rate and daphnid immobilization, growth and reproduction served as the chronic endpoints investigated.

Comparison of In Situ and Ex Situ Equilibrium Passive Sampling for Measuring Freely Dissolved Concentrations of Parent and Alkylated Polycyclic Aromatic Hydrocarbons in Sediments.

Equilibrium passive sampling methods (EPSMs) allow quantification of freely dissolved contaminant concentrations (C ) in sediment porewater. Polydimethylsiloxane (PDMS) is a convenient sampling polymer that can be equilibrated in field (in situ) or laboratory (ex situ) sediments to determine C , providing reliable compound-specific PDMS-water partition coefficients (K ) are available. Polycyclic aromatic hydrocarbons (PAHs) are an important class of sediment contaminants comprised of parent and alkylated homologs.

The sensitivity of the deepsea species northern shrimp (Pandalus borealis) and the cold-water coral (Lophelia pertusa) to oil-associated aromatic compounds, dispersant, and Alaskan North Slope crude oil.

This study investigated the sensitivity of two deepsea species using mortality of northern shrimp (Pandalus borealis) and polyp activity of stony coral (Lophelia pertusa) to dispersant, Corexit 9500 and aromatic hydrocarbons (toluene, 2-methylnaphthalene, phenanthrene) in 96-h tests. Resulting hydrocarbon toxicity data were fit to the Target Lipid Model to generate predictive models and determine species sensitivity. Toxicity of chemically enhanced water accommodated fractions of Alaskan North Slope crude oil (ANS-oil) was also investigated with shrimp using nominal loading, total petroleum hydrocarbons and biomimetic extraction (BE) as oil exposure metrics.