Tackling the evaporation rates of volatile HNS: A lab- scale experiment to serve marine pollution response

Release of volatile Hazard Noxious Substances (HNS) at sea can lead to the formation of toxic, flammable or explosive gas plumes that can travel large distances and pose risks over a wide area in relatively short timescales. Yet, when an emergency is declared, key information regarding the short-term behavior of HNS is not available for responders. For volatile organic compounds (VOCs), one critical parameter that should be systematically predicted and/or assessed is the evaporation kinetics: this would warn first-responders against risks of gas clouds that might originate from the HNS slick. This paper presents new experimental data on the evaporation kinetics of several VOCs that were collected using the new Cedre’s wind tunnel in the framework of the MANIFESTS1 project. The air and liquid temperatures as well as the wind velocity profile were continuously monitored above the pool. The evaporation of each liquid was monitored following the weight loss fraction over time. The final objective was to assess mass fluxes at the sea-air interface and to compare it to analytical models. It appeared that, while pure chemicals showed a linear mass loss over time, the same chemicals spilled at the surface of seawater generally presented a non-linear mass loss over time, i.e., different and longer evaporation rates. The evaporation was also generally highlighted by a sharp decrease in temperature of the liquid. These new data were finally compared to the OSERIT – Evaporation module developed in MANIFESTS and will contribute to the improvement of the prediction accuracy of existing evaporation models. This will offer crisis management stakeholders more precise information regarding the formation of toxic gas clouds (Go/No Go decision).

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Models, Modelling