Spill Site Research Articles

Emergency Oil Spill Response: Data Collection Automation, and Dissemination

ABSTRACT The California Department of Fish and Wildlife (CDFW), Office of Spill Prevention and Response (OSPR) has employed Geographic Information System (GIS) technology for oil spill planning and response since the early 1990's, adding remote sensing tools to the mix by the turn of the Century. Discussed herein are OSPR's current smartphone and tablet-based field data collection applications. We use an off-the-shelf tool for pre-response protection strategy planning and use customized tools developed in-house for California Sea Otter Surveys, Wildlife Search and Collection and the Shoreline Cleanup Assessment Technique (SCAT). The benefits of automated field data collection include the omission of transcription errors during manual data input and streamlined data processing. This results in accurate and timely information delivered to responders, thus enhancing their capability for informed decision making. OSPR uses the National Oceanic and Atmospheric Administration's (NOAA) Environmental Response Management Application® (ERMA), a web-based GIS data viewer as the Common Operational Picture (COP) for data dissemination throughout the incident response community during an oil spill event, and for the post emergency response cooperative Natural Resource Damage Assessment (NRDA). OSPR also uses ERMA a planning tool by uploading significant data layers from the U.S Coast Guard's (USCG) six Area Contingency Plans (ACP) for coastal California and OSPR's Geographic Response Plans for inland waters of the state with higher risk of an oil spill. These response planning data are freely downloadable from the ERMA platform. In the Summer/Fall of 2019 at the Cymric Oil Field in Kern County, California, over 1,000,000 gallons of oil, mud and steam seeped into a dry stream bed from several “surface expressions”. Direct access to the spill site was not permitted for Health and Safety concerns. OSPR used an off-the-shelf small Unmanned Aerial System (sUAS, aka drone) equipped with a standard high definition (HD) camera and a thermal infrared camera for SCAT reconnaissance, resources at risk evaluations, and regularly scheduled mapping missions for overall site situational awareness.

Decadal Assessment of Sperm Whale Site-Specific Abundance Trends in the Northern Gulf of Mexico Using Passive Acoustic Data

Passive acoustic monitoring has been successfully used to study deep-diving marine mammal populations. To assess regional population trends of sperm whales in the northern Gulf of Mexico (GoM), including impacts of the Deepwater Horizon platform oil spill in 2010, the Littoral Acoustic Demonstration Center-Gulf Ecological Monitoring and Modeling (LADC-GEMM) consortium collected broadband acoustic data in the Mississippi Valley/Canyon area between 2007 and 2017 using bottom-anchored moorings. These data allow the inference of short-term and long-term variations in site-specific abundances of sperm whales derived from their acoustic activity. A comparison is made between the abundances of sperm whales at specific sites in different years before and after the oil spill by estimating the regional abundance density. The results show that sperm whales were present in the region throughout the entire monitoring period. A habitat preference shift was observed for sperm whales after the 2010 oil spill with higher activities at sites farther away from the spill site. A comparison of the 2007 and 2015 results shows that the overall regional abundance of sperm whales did not recover to pre-spill levels. The results indicate that long-term spatially distributed acoustic monitoring is critical in characterizing sperm whale population changes and in understanding how environmental stressors impact regional abundances and the habitat use of sperm whales.

Age frequency, growth, mortality, and PAH levels of roughtongue bass (Pronotogrammus martinicensis) following the Deepwater Horizon oil spill

Age, growth, mortality, and polycyclic aromatic hydrocarbons (PAHs) in roughtongue bass (Pronotogrammus martinicensis) were examined in the northern Gulf of Mexico following the 2010 Deepwater Horizon oil spill. Fish (N = 1090) were collected from September 2014 to July 2015 from the Alabama Alps (54 km from the spill site) and Roughtongue Reef (111 km from the spill site). Sites were dominated by the 2010 year-class. Growth rates were significantly lower for fish from Alabama Alps compared to Roughtongue Reef (p < 0.001) and likely linked to proximity of the Mississippi River discharge. Mean total PAH ± SD was 50 ± 52.6 and ranged from 0 to 220 ppb. These PAH levels were below a 300-ppb minimum effect level and not significantly different between sites. The dominant 2010 year-class, low PAH levels, and similar growth rates to pre-spill measures indicated that the Deepwater Horizon oil spill had little effect on roughtongue bass.

Petroleum contamination significantly changes soil microbial communities in three oilfield locations in Delta State, Nigeria.

Soil microbial community structure is altered by petroleum contamination in response to compound toxicity and degradation. Understanding the relation between petroleum contamination and soil microbial community structure is crucial to determine the amenability of contaminated soils to bacterial- and fungal-aided remediation. To understand how petroleum contamination and soil physicochemical properties jointly shaped the microbial structure of soils from different oilfields, high-throughput sequencing of 16S and ITS amplicons were used to evaluate the shifts of microbial communities in the petroleum-contaminated soils in Ughelli East (UE), Utorogu (UT), and Ughelli West (UW) oilfields located in Delta State, Nigeria. The results showed 1515 bacteria and 919 fungal average OTU number, and community richness and diversity, trending as AL > UT > UW > UE and AL > UW > UT > UE for bacteria, and AL > UW > UT > UE and UW > UT > AL > UE for fungi, respectively. The bacterial taxa KCM-B-112, unclassified Saccharibacteria, unclassified Rhizobiales, Desulfurellaceae, and Acidobacteriaceae and fungal Trichocomaceae, unclassified Ascomycota, unclassified Sporidiobolales, and unclassified Fungi were found to be the dominant families in petroleum-contaminated soils. Redundancy analysis (RDA) and Spearman's correlation analysis revealed that total carbon (TC), electric conductivity (EC), pH, and moisture content (MO) were the major drivers of bacterial and fungal communities, respectively. Gas chromatography-mass spectrophotometer (GC-MS) analysis exhibited that the differences in C7-C10, C11-C16, and C12-C29 compounds in the crude oil composition and soil MO content jointly constituted the microbial community variance among the contaminated soils. This study revealed the bacterial and fungal communities responsible for the biodegradation of petroleum contamination from these oilfields, which could serve as biomarkers to monitor oil spill site restoration within these areas. Further studies on these contaminated sites could offer useful insights into other contributing factors such as heavy metals.

Using an expert judgment response matrix to assess the risk of groundwater discharges from remediated fuel spill sites to the marine environment at sub-Antarctic Macquarie Island, Australia.

ABSTRACTThis study assesses toxicity of groundwater from remediated fuel spill sites, as the final phase of an environmental risk assessment of contaminated sites at sub‐Antarctic Macquarie Island, Tasmania, Australia. To complement previous terrestrial ecotoxicological research, we determine risk to marine environments from residual biodegraded hydrocarbon contaminants in groundwater discharges. Direct toxicity assessments were conducted on 7 composite groundwater test solutions, adjusted to ambient seawater salinity. Eleven native marine invertebrates (from varied taxa: gastropods, bivalves, flatworms, amphipods, copepods, isopods) were exposed and observed for up to 21 d. Lethal time estimates (LT10, LT50) showed sensitivity was time dependent (LT10s = 4–15 d) and variable between species. Three species showed no response to any test solution, and most species did not respond for up to 5 d. Data were interpreted using an expert judgment response matrix with multiple lines of evidence to predict risk. No consistent patterns in the relative toxicity of test solutions, based on polar or nonpolar hydrocarbon concentrations, were identified. Although toxicity was observed in some species, this was only under worst‐case conditions of undiluted, continuous, extended exposure. Natural dynamics of the site, including low groundwater discharge rates, high rainfall, and a highly energetic receiving environment, ensure groundwater is rapidly diluted and dispersed. In this context, and based on site conditions at the time of testing, these toxicity assessments provide robust evidence that residual contamination in groundwater at remediated sites at Macquarie Island is unlikely to represent a risk to the adjacent marine communities tested. Integr Environ Assess Manag 2021;17:785–801. © 2020 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC)

Factorial design study of total petroleum contaminated soil treatment using land farming technique

Land farming technique was used to treat hydrocarbon contaminated soil collected from a crude oil spill sites in Edo State, Nigeria. Calibrated standard auger was used to collect soil samples from the site at depth below 30 cm. The samples were characterized and classified. Cow dung and NPK fertilizer were added as additives to complement the nutriments of the soil samples before total petroleum hydrocarbon (TPH) quantification and remediation procedures. Factorial design was applied to vary the input parameters such as pH, mass of substrate, moisture content and turning times of land farming so to ascertain the optimal conditions for the procedure. The result revealed that the in-situ TPH value was 5000 mg kg− 1 on the average and after 90 d of treatment, TPH reduced to 646 mg kg− 1. The turning rate, pH, moisture content and mass of substrate hade 83, 4.36, 0.48 and 0.046% contribution, respectively, for the degradation process using land farming treatment. Numerical optimization techniques applied in the optimum point for land farming input parameters to achieve predicted maximum removal of 99% were evaluated as pH, mass of substrate, moisture content and turning rate to be 6.01, 1 kg, 10% and 5 times in a week, respectively. TPH removed at this optimum point was 98% reducing from 5000 to 636 mg kg− 1. The high coefficient of determination (r2 = 0.9865) as observed in the closeness of predicted and experimental values reflects the reliability of the model and hence, land farming practice with close attention on turning rate as revealed by this study, is recommended for TPH contaminated soil remediation.

A perspective on oil spills: What we should have learned about global warming

Scientific knowledge of marine pollution and oil spill response (OSR) innovation has diffused over half a century. Local community resilience to spills and the equitable application of knowledge worldwide are constrained by several barriers. These range from access, governance, cost minimisation, through austerity and poverty in affected areas, to realpolitik (e.g. vested interests, nationalism, corruption, security breakdown and war). Ongoing incidents show inequalities in spill risk and OSR capability. Advances in knowledge have belatedly brought us to the conclusion that the logical way to reduce adverse impacts of oil in an era of global warming is to accelerate decarbonisation. This would rapidly and simultaneously reduce the frequency, magnitude and consequences of oil spills. Meanwhile, mitigating spills, managing OSR, and restoring local communities and ecosystems at spill sites are fundamental obligations for the oil industry. These obligations should be routinely enforced by all responsible governments, and backed by inter-governmental agencies and conventions. However, we must no longer assume that even the best practices in exploration, production, refining, transport and consumption of hydrocarbons can adequately reduce their leading role in the ongoing destruction of the global environment.

Post Oil Spill Petroleum Hydrocarbon Components Transport and Evaluation in Parts of the Niger Delta Mangrove Swamp of Nigeria: A Case of Hydrocarbon Component Transport through Non-Turbulent Water

Parts of the Nigerian Niger Delta which also accommodates huge number of oil facilities has swamps in some parts with non – turbulent water bodies. These water bodies are negatively impacted from oil pollution but lack the capacities to self-clean like high flowing waters. The calm nature of these swamps result in higher than normal retention, partitioning and diffusion of hydrocarbon components. This study investigated aliphatic and aromatic hydrocarbon concentrations at different depths for a period of ten months by simulating an oil spill site (8m by 5m and 1.5m deep) typical of a non-turbulent mangrove swamp with suspended sediments and vegetation polluted with 60 litres of crude oil. Impacted water samples were collected at depths of 0.25m, 0.5m, 0.75m and 1.0m. They were filtered and the petroleum aliphatic and aromatic contents analyzed using a GC-FID. The results obtained showed that petroleum hydrocarbons can dissolve and diffuse to different depths at concentrations above safe limits, thus posing great danger to aquatic life and its entire value chain.

Geophysical Characterization of Oil Spill Sites in Parts of Niger Delta Using Electrical Resistivity Tomography, Southern Nigeria

Geophysical survey using 2D resistivity tomography was acquired to characterize two hydrocarbon impacted sites of Ikarama and Kalaba. In the impacted sites six (6) 2D resistivity imaging profiles were carried out to understand the resistivity distribution as basis for interpreting the depth and lateral extent of contamination. Additionally, two (2) 2D resistivity imaging profiles were also carried out in the un-impacted sites to serve as control. Surface geophysical survey was acquired using ABEM SAS 1000 terammeter set with electrode constant separation of 6 step array system with a maximum electrode separation of five metres in a traverse of 100 meters. The 2D resistivity imaging data was interpreted using Res2Div. The results indicated the distribution of electrical resistivity within the subsurface. The resistivity sections were displayed in shades of rainbow colours. The values for the models range from 1.05 the resistivity models show a general increase of resistivity with depth relative to the control points. The 2D resistivity models correlate well with the borehole logs as top soil, clay, sandy clay and sand. Also, some of the 2D models indicate increases in resistivity with depth. They also show interaction of water interplaying with the contaminant plume. The resistivity range of 0.005 to 11.3 which occurred from the surface is interpreted as top soil. Immediately underlying this layer is a region of high resistivity with range of 9.4 to 78.1 which indicate petroleum contamination that may have seeped through the clay horizon to the sandy layer. This may be due to the fact that the invading crude oil may have exceeded the retention capacity of the porous medium hence allowing crude oil to spread to other zones of high hydraulic conductivity materials. In addition, it is also possible that the clay bodies were not localized. Superimposition of the main profile generated to monitor petroleum contaminant and the control profiles established a remarkably difference showing the main profiles increases of resistivity with depth, while the resistivity of the control profiles decreases with depth and possibly with materials highly resistive at the top. The study established that biodegradation increases as the depth decreases. The characterization of high resistivity with decrease in depth of the impacted sites were due to oil spill contamination whereas, decrease in resistivity with respect to depth is agreeable to non-petroleum site having materials that were restive at the top. The study pointed out hydrocarbon contamination of the both sites between shallow depths of 3m to 7m which may infiltrate to change the composition of near surface aquifers in the locality. Therefore, more geophysical studies is recommended in this area. Keywords: Electrical Resistivity Tomography, Oil spill, Geophysical Characterization DOI: 10.7176/JEES/11-2-08 Publication date: February 28 th 2021

IMPACT OF OIL EXPLORATION ON THE NIGER DELTA: THE DRIVERS AND DYNAMICS OF CONFLICT OVER ENVIRONMENTAL DEGRADATION

The study examines the drivers of conflict over environmental degradation in the Niger Delta. The study also investigates the mechanism used to manage conflict relating to oil spills and gas flares in the area. The study was carried out in B-Dere and Bomu communities in Gokana Local Government Area of Rivers State. Primary data was obtained through oral interview and questionnaires that were used to elicit responses from the target population. Taro Yamane formular was used to determine the sample size. The data was analyzed using quantitative method of analysis. The study found that the inability of oil companies especially Shell Petroleum to respond immediately after there is a report of oil pollution and clean-up the environment was the major driver of conflict in the area. The study also found the mechanism used by Shell to manage conflict relating to oil spills was that of divide-and rule tactics, whereby the chiefs and elders are used against the youth. The study concluded that until Shell responds swiftly to cases of oil spills and remediates the polluted environment and compensates victims of oil spills and gas flares, as a way of assuaging their grievances, conflict between Shell and the oil bearing communities will continue to be a recurrent phenomenon. The study recommends that Shell should promptly respond to cases of oil spills, cleaning of spill sites, and compensation and rehabilitation of affected victims in order to reduce conflict in the area.

In situ bioremediation of Fenton\u2019s reaction\u2013treated oil spill site, with a soil inoculum, slow release additives, and methyl-\u03b2-cyclodextrin

A residential lot impacted by spills from a leaking light heating oil tank was treated with a combination of chemical oxidation and bioremediation to avoid technically challenging excavation. The tank left emptied in the ground was used for slow infiltration of the remediation additives to the low permeability, clayey soil. First, hydrogen peroxide and citrate chelate was added for Fenton’s reaction–based chemical oxidation, resulting in a ca. 50% reduction from the initial 25,000 mg/kg average oil concentration in the soil below the tank. Part of this was likely achieved through mobilization of oily soil into the tank, which was beneficial in regards to the following biological treatment. By first adding live bacteria in a soil inoculum, and then oxygen and nutrients in different forms, an approximately 90% average reduction was achieved. To further enhance the effect, methyl-β-cyclodextrin surfactant (CD) was added, resulting finally in a 98% reduction from the initial average level. The applicability of the surfactant was based on laboratory-scale tests demonstrating that CD promoted oil degradation and, unlike pine soap, was not utilized by the bacteria as a carbon source, and thus inhibiting degradation of oils regardless of the positive effect on biological activity. The effect of CD on water solubility for different hydrocarbon fractions was tested to serve as the basis for risk assessment requirements for authorizing the use of the surfactant at the site.

Formation and weathering assessment of oil-suspended sediment aggregates through a laboratory investigation.

Formation of oil-suspended sediment aggregates (OSAs) is believed to be one of the natural cleaning processes in the marine environment. In this study, we have investigated the formation processes of OSAs under different mixing periods (continuous mixing and with the addition of sediments in between), oil-sediment ratios (1:1, 1:2 and 2:1) and crude oils (Arabian Light (AL), Kuwait (KW) and Murban (MB)). The results revealed that size of OSAs significantly increased (up to ≈ 1.41mm) with the addition of sediments. Aggregates (total 36) were extracted for n-alkanes and polycyclic aromatic hydrocarbons to quantify and assess their weathering and toxic levels. The maximum n-alkane depletion was 84% (111-02), 94% (212-02) and 84% (321-02) and PAH depletion was ≈ 72% (111-02), 79% (212-02) and 81% (311-03) for the OSAs of AL, KW and MB crude oils, respectively, for the different samples considered, indicating that n-alkanes were depleted relatively higher than the PAHs. The highest depletion of both n-alkane and PAHs has occurred in OSAs of 10-h continuous mixing. The depletion of both n-alkane and PAHs reduced after the addition of sediments, however, escalated the growth of OSAs, resulting in bigger size OSAs. The concentration of PAHs of all 36 OSAs is greater than 5000ng/g, indicating very high PAH pollution. Though the formation of OSAs helps in cleaning the spill sites, the carcinogenic threat to the marine ecosystem caused by these OSAs cannot be ignored.

Blood biochemical status of deep-sea sharks following longline capture in the Gulf of Mexico.

Prior to the Deepwater Horizon (DWH) oil spill, little research effort was focused on studying deep-sea sharks in the Gulf of Mexico (GoM). While the biology of these fishes remains virtually unknown, they are routinely captured in commercial fisheries as bycatch. In the absence of basic biological data, and with the probability of post-release survival unknown for most species, effective management plans cannot be formulated, making populations highly susceptible to overfishing. Any potential detrimental effects of the DWH oil spill, which occurred at 1500m deep, are also unknown. Following longline capture, we characterized the physiological blood biochemical parameters related to secondary stress and compared them among seven shark species occurring on the continental shelf edge and slope in the GoM at depths ranging from 200 to 2000m. We also investigated the relationship between blood parameters and depth as well as proximity to the oil spill site. The deep-sea sharks examined here exhibited variability in blood chemistry associated with the secondary stress response, with values falling within published records for previously studied elasmobranchs. Results suggested that there is greater relative physiological stress in shallower-dwelling sharks as well as smaller-bodied sharks. Further, the rate of core temperature warming was fastest in smaller bodied sharks, which likely contributes to greater physiological stress. The core temperatures of the larger-bodied, deeper-dwelling species were not altered as drastically as the smaller-bodied sharks after being hauled to the surface. Any chronic physiological effects of the oil spill were not detectable as there were no relevant correlations between blood chemistry metrics and proximity to the DWH oil spill site.

MONITORING OF EMERGENCY SITUATIONS AT OIL AND GAS FACILITIES

The paper briefly presents a methodological approach to processing multi-zone satellite images of moderate spatial resolution. This approach allows detecting oil spill sites with sufficient reliability during rapid response and subsequent liquidation of the consequences of man-made emergencies at oil and gas facilities. The properties of modern, often used for monitoring territories, space remote sensing tools are analyzed in relation to the monitoring of man-made emergencies. The object of the study is the vicinity of the CHPP 3 of the Norilsk-Taimyr Energy Company, where a major accident occurred on May 29, 2020 – a tank with diesel fuel was depressurized at the facility – and as a result of the spill, more than 20 tons of fuel fell into the waters of the Daldykan and Ambarnaya rivers. This is one of the largest leaks of petroleum products in the Arctic zone in history, posing a threat to the ecosystem of the Arctic Ocean. Processing and subsequent analysis of satellite images of the territory of interest and surrounding objects were made during the research. According to satellite images, it became possible to assess the scale of the environmental disaster.

Exposure, geochemical, and spatial distribution patterns of an oil spill in parts of the Niger Delta Region of Nigeria

Large-scale and small-scale spilt oil is as old as exploration activities in the Niger Delta region of Nigeria. There is a need to provide the exposure, geochemical and spatial characteristics in the Niger Delta Region of Nigeria because of the effects of the spilt oil on the communities and the environment. Some of the spilt oil-disaster impacts for exposed communities include psychological effects and socio-demographic characteristics. In this study, the characteristics, sources, spatial and socio-demographic risk predictions of the spilt oil discovered by Kolo Creek coastal residents are examined. A random sample of 900 residents of Kolo Creek coastal communities included exposure characteristics linked to health, the social and economic lifestyle of the communities. The demographic characteristics included age, gender, literacy, and occupation as covariates in the analyses. Respondents provided varied information on the amount of health, the social, and economic impacts. The highest and lowest direct exposure impact accounts 94.65±2.0% and 5.95±1.52% for smoggy weather and obstruction to watercourses respectively. The geochemical distribution pattern was examined using standard laboratory procedures. This investigation included the determination of the physical and chemical characteristics of water samples at the oil spill sites. Also, the biochemical oxygen demand (BOD), chemical oxygen demand (COD), total hydrocarbon content (THC), and total petroleum hydrocarbon (TPH) of both water and sediment samples were carried out. A strong correlation exists between these parameters (i.e. at p &lt; 0.01) and indicate communalities greater than 0.5. The pollution distribution maps support the spatial distribution pattern and correlate significantly (p &lt; 0.01) with the exposure distribution, and the geochemical distribution patterns.

Application of Combined Chemical Oxidation and Microwave Treatment for Hydrocarbon-Contaminated Soil from an Urban Oil Spill Site

Abstract This study will evaluate the feasibility of treating diesel contaminated soil excavated from a metro rail construction site in Chennai, Tamil Nadu, India. Total petroleum hydrocarbon (TPH)...

An insight into the current oil spills and on-site bioremediation approaches to contaminated sites in Nigeria.

Land oil spills in Nigeria have a long history of contaminating the soil, groundwater, vegetation, and streams with spill extension being the primary of numerous ordeals. These have left the host communities of oil fields and pipelines in crucial need of soil rehabilitation. Thus, this review provides insights into the current state of land oil spills and the effectiveness of on-site remediation approaches across communities. A total of 44 incidents of land oil spills of ≥ 500 bbl, amounting to 53,631 bbl between 2011 and 2019, was recorded by the Shell Petroleum Development Company, which primarily attributed to 83% of the total sabotage. Over 73% of the 53,631 bbl spills were unrecovered from the spill areas, which had deleterious impacts on farmlands, fishponds, rivers, and residential areas. Remediation by enhanced natural attenuation (RENA) is a feasible technique for restoring petroleum hydrocarbon-contaminated sites, but it might be ineffective when limited to tiling, windrows, and fertilizer applications due to the presence of non-biodegradable residues and contaminants beyond the aeration depth. However, bioremediation techniques ranging from non-supplemented in-situ and fertilizer supplemented in-situ to mixed in-situ and ex-situ bio-cells supplemented RENA are feasible approaches for spill sites. However, challenging limitations with regard to RENA application failures in the region include delayed responses to spill emergency, large amounts of un-recovered spilled oil, and un-implemented legislative guidelines for spill cleanup. Nevertheless, the temperature, moisture, nutrient, oxygen, and pH of the soil are essential parameters to be considered when implementing a landfarming remediation approach.

Geochemical and geophysical indicators of oil and gas wastewater can trace potential exposure pathways following releases to surface waters

Releases of oil and gas (OG) wastewaters can have complex effects on stream-water quality and downstream organisms, due to sediment-water interactions and groundwater/surface water exchange. Previously, elevated concentrations of sodium (Na), chloride (Cl), barium (Ba), strontium (Sr), and lithium (Li), and trace hydrocarbons were determined to be key markers of OG wastewater releases when combined with Sr and radium (Ra) isotopic compositions. Here, we assessed the persistence of an OG wastewater spill in a creek in North Dakota using a combination of geochemical measurements and modeling, hydrologic analysis, and geophysical investigations. OG wastewater comprised 0.1 to 0.3% of the stream-water compositions at downstream sites in February and June 2015 but could not be quantified in 2016 and 2017. However, OG-wastewater markers persisted in sediments and pore water for 2.5 years after the spill and up to 7.2-km downstream from the spill site. Concentrations of OG wastewater constituents were highly variable depending on the hydrologic conditions. Electromagnetic measurements indicated substantially higher electrical conductivity under the bank adjacent to a seep 7.2 km downstream from the spill site. Geomorphic investigations revealed mobilization of sediment is an important contaminant transport process. Labile Ba, Ra, Sr, and ammonium (NH4) concentrations extracted from sediments indicated sediments are a long-term reservoir of these constituents, both in the creek and on the floodplain. Using the drivers of ecological effects identified at this intensively studied site we identified 41 watersheds across the North Dakota landscape that may be subject to similar episodic inputs from OG wastewater spills. Effects of contaminants released to the environment during OG waste management activities remain poorly understood; however, analyses of Ra and Sr isotopic compositions, as well as trace inorganic and organic compound concentrations at these sites in pore-water provide insights into potentials for animal and human exposures well outside source-remediation zones.

Comparing Trace Element Bioaccumulation and Depuration in Snails and Mayfly Nymphs at a Coal Ash-Contaminated Site.

We examined the bioaccumulation of essential (Cu, Fe, Se, and Zn) and nonessential (As and Hg) trace elements in 2 aquatic invertebrate species (adult snails and mayfly nymphs) with different feeding habits at the site of a coal ash spill. Differences in food web pathway, exposure concentrations, and biological processing affected bioaccumulation patterns in these species. Mayflies had higher body burdens, but snails had higher retention of most elements studied. Environ Toxicol Chem 2020;39:2437-2449. © 2020 SETAC.

Beyond Thresholds: A Holistic Approach to Impact Assessment Is Needed to Enable Accurate Predictions of Environmental Risk from Oil Spills.

The risk assessment for the environmental impact of oil spills in Australia is often conducted in part using a combination of spill mapping and toxicological thresholds derived from laboratory studies. While this process is useful in planning operational responses, such as where to position equipment stockpiles and whether to disperse oil, and can be used to identify areas near the spill site where impacts are likely to occur, it cannot accurately predict the environmental consequences of an oil spill or the ecosystem recovery times. Evidence of this disconnect between model predictions and observed impacts is the lack of a profound effect of the Deepwater Horizon wellhead blowout on recruitment to fisheries in the northern Gulf of Mexico, contrary to the predictions made in the Natural Resources Damage Assessment and despite the occurrence of impacts of the spill on marine mammals, marshes, and deep water ecosystems. The incongruity between predictions made with the current approach using threshold monitoring and impacts measured in the field results from some of the assumptions included in the oil spill models. The incorrect assumptions include that toxicity is acute, results from dissolved phase exposure, and would be readily reversible. The toxicity tests from which threshold models are derived use members of the ecosystem that are easily studied in the lab but may not represent the ecosystem as a whole. The test species are typically highly abundant plankton or planktonic life stages, and they have life histories that account for rapid changes in environmental conditions. As a consequence, these organisms recover quickly from an oil spill. The interdependence of ecosystem components, including the reliance of organisms on their microbiomes, is often overlooked. Additional research to assess these data gaps conducted using economically and ecologically relevant species, especially in Australia and other understudied areas of the world, and the use of population dynamic models, will improve the accuracy of environmental risk assessment for oil spills. Integr Environ Assess Manag 2020;16:813-830. © 2020 SETAC.