Science Inventory

Recommendations for Advancing Media Preparation Methods Used to Assess Aquatic Hazards of Oils and Spill Response Agents

Citation:

Parkerton, T., M. Boufadel, T. Nordtug, C. Mitchelmore, K. Colvin, D. Wetzel, M. Barron, G. Bragin, B. de Jourdan, AND J. Loughery. Recommendations for Advancing Media Preparation Methods Used to Assess Aquatic Hazards of Oils and Spill Response Agents. AQUATIC TOXICOLOGY. Elsevier Science Ltd, New York, NY, 259:106518, (2023). https://doi.org/10.1016/j.aquatox.2023.106518

Impact/Purpose:

The purpose of this article is to communicate recommendations for advancing oil spill science related to the toxicity testing of petroleum. The paper will be published in a high impact journal and will present consensus recommendations on for mixing oil and water for laboratory testing of petroleum. The impact is that adoption of the recommended methods will faciliate greater standardization and utility of oil toxicity tests that ulimately may improve oil spill preparedness, response and impact assessment.

Description:

Laboratory preparation of aqueous test media for toxicity testing is critical in developing 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. A benefit of media preparation methods for oil that rely on low to moderate mixing energy coupled with a variable dilution design is that the dissolved oil composition of the water accommodation fraction (WAF) stock is consistent across diluted treatments. Further, analyses that supports exposure confirmation can be reduced and reflects dissolved oil exposures that are bioavailable and amenable to toxicity modeling. Variable loading tests require analytical verification at each treatment due to changes in dissolved oil composition at each oil loading. Regardless of test design, a preliminary study is recommended to optimize WAF mixing and settling times to achieve equilibrium between oil and test media. Variable dilution tests generated using chemical dispersants (CEWAF) or high energy mixing (HEWAF) can increase dissolved oil exposures in treatment dilutions due to droplet dissolution when compared to WAFs. In contrast, HEWAF/CEWAFs generated using variable oil loadings are expected to provide more comparable dissolved oil exposures to WAFs prepared at the same loadings. Preparation methods that provide droplet oil exposures should be environmentally relevant and informed by oil droplet concentrations, compositions, sizes, and exposure durations characteristic of field spill scenarios. Oil droplet generators and passive dosing techniques offer advantages for delivering controlled constant or dynamic dissolved exposures. Adoption of proposed guidance for improving media preparation methods will provide greater comparability and utility of toxicity testing in supporting oil spill response and assessment.