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PETROMAKS2-Stort program petroleum

Field-based oil depletion processes in temperate and Arctic seawater

Alternative title: Felt-basert degradering av olje i temperert og arktisk sjøvann

Awarded: NOK 6.8 mill.

Project Number:

294755

Application Type:

Project Period:

2019 - 2022

Partner countries:

Chemical dispersants are used to combat oil spills in the marine environment. The dispersant is applied to the oil surface, and small oil droplets will be formed with neutral buoyancies in the seawater column. Most of the oil will then be removed from the sea surface into the water column, and the oil will also be diluted in the water. These processes will also result in increased oil biodegradation by microbes naturally present in the seawater. To predict the spreading and fate of spilled oil, tree-dimensional model, like the fate and contingency model OSCAR, are used. Biodegradation is incorporated in the OSCAR model as one of several fate processes for the determination of the fate of the oil in the marine environment. Biodegradation is determined in the model for several oil compound groups, representing up to 70-80% of the oil. Several biodegradation studies have been performed in recent years to improve the biodegradation data in the OSCAR model. These studies have mainly been performed with natural local seawater from the Trondheimsfjord as source of oil-degrading bacteria. In addition, studies have also been performed with seawater from Arctic environments (Svalbard and Greenland), and indicate that the water source may be important for the degradation results. In this project, field trials have been performed to determine the importance of the seawater source for the biodegradation rates of oil compounds. We have also compared biodegradation to other processes, like photooxidation (degradation caused by sunlight) and dissolution of water-soluble oil compounds, to separate these processes. Field systems have been established with oil immobilized to hydrophobic surfaces (adsorbents) and deployed in different localities along the Norwegian coast and on Svalbard. We have collaborated with similar projects on Greenland and Canada, so relevant data have been collected from several localities in the North Atlantic Ocean and in the Arctic. Four field trials were performed in 2020, two in the Trondheimsfjord, and two in Northern-Norway (summer and winter experiments in Fiskebøl, Vesterålen). These trials were performed both as light- and dark-exposed experiments in order to investigate possible interactions between photooxidation and biodegradation. Two 2-months field trial were performed on Svalbard (Longyearbyen) in 2021 (June to August) and 2022 (February to April), in collaboration with the Polar Institute in Longyearbyen. The work in 2021 has further been focused on extractions, analyses and data treatments of samples from the field trials in 2020 and 2021/2022. This work has included both chemical analyses (oil analyses for characterization of oil compound degradation), and microbial analyses (extraction of DNA and characterization of microbial communities associated with biodegradation of defined oil compound groups). The studies have been linked to separate projects on field trials performed for Norwegian oil companies, and studies performed as part of the Canadian MPRI program. The work in 2022 has also been focused on publication, and the first of 3 planned manuscripts has been submitted for publication.

In this project we have achieved the following outcomes: 1) We have compared two biodegradation field systems and concluded that one of these proved better than the other for determination of oil biodegradation 2) By using the better of these two systems, we have collected oil biodegradation data from different field localities which will be used for strengthening the OSCAR model and make it more robust, mainly for cold seawater. This has been done by comparison of the field data gathered in this project with previously collected biodegradation data from laboratory studies 2) We are currently working in the aftermath of the project on what extent components like geography, season, light conditions, and microbial communities will have on oil degradation, ans we also trying to separate processes like biodegradation and photooxidation by comparison of results from light-exposed and 'dark' systems. 3) Based on the final data from the project, decisions will be made on what type of fate data should be included in the OSCAR model (generic or site-specific) 4) The project has improved the understanding of interactions between fate processes (biodegradation, photooxidation, dissolution), particularly with respect to which oil compound groups are subject to the different degradation processes. This is still work that will be continued in the aftermath of the project 5) We have strengthened international trans-Atlantic collaboration on oil spill fate research, which opens up for further collaboration in years to come. We believe the project outcome have and will contribute to a sustainable environment by improving data input for oil spill models. These models are used for predictions of the environmental impacts of oil spills and to decide on oil spill preparedness/response tools to reduce these impacts as much as possible in vulnerable environments. This will be of particular importance in cold seawater/the Arctic and can be relevant both to spills of crude oil and fuels.

Oil spill preparedness, e.g. the use of dispersants, includes the use of numerical models to predict the fate of the spilled oil, and for decisions on the use of oil spill response (OSRs) methods for environmental impact reductions. One such predictive model is the OSCAR model, which is used today as an industry standard for oil spill contingency planning on the Norwegian Continental Shelf (NCS). This model includes biodegradation rates of 25 oil compound groups, based on data from laboratory studies. However, comparison to real field data is highly needed to decide if factors like geography, season, water depth, and other local environmental conditions, will affect the depletion processes significantly, in particular biodegradation. In collaboration with the Canadian MPRI program, in situ microcosm field systems (systems already established), based on oil immobilization to solid matrices, will be deployed in seawater on locations along the coasts of the North Atlantic and Arctic Oceans. Microcosms will be deployed along the temperate and Arctic coasts of East Canada (National Research Council of Canada) and Greenland (Arctic Research Centre), financed by MPRI, while SINTEF will establish and deploy microcosms for the NCS in temperate and Arctic waters, including both winter and summer seasons, and in near-surface and subsurface seawater. Microcosms will be deployed in both pristine and previously oil-exposed seawater. Rates of oil compound dissolution, photooxidation, and biodegradation will be differentiated in the different localities, water depths and seasons, as parts of the fate processes. Biodegradation of oil compounds/oil compound groups will be related to successions of oil-degrading microbes and genes associated with the degradation in the different environments. The field data will be compared to existing data from laboratory studies, for possible model calibration, and to determine the potential effects of dispersants on oil biodegradation in these environments.

Funding scheme:

PETROMAKS2-Stort program petroleum