Underwater HNS Release: Modeling Gas Behavior

The maritime transportation of Hazardous and Noxious Substances (HNS) continues to grow, posing significant risks to the marine environment and human health. In the event of an accidental release, these substances can create severe hazards, including toxic gas clouds, fires, and potential explosions. While existing models are effective for simulating conventional hydrocarbon spills, they lack the capability to accurately represent the complex behavior of volatile HNS released at sea. As part of the MANIFESTS-Genius European project, research has been conducted to advance knowledge in this area. A new module has been developed to simulate underwater gas releases, aiming to evaluate the quantity of gas dissolution as a gas plume rises through the water column from sources such as underwater pipelines or shipwrecks. By accurately modeling this process, it becomes possible to predict the characteristics of the gas cloud that may form at the surface. The module consists of a Python-based bubble rising and dissolution tracker. Its outputs can be used as standalone data or integrated into the OSERIT Lagrangian transport model, which is currently employed by the Belgian coastguard and member states of the Bonn Agreement. This integration enhances OSERIT's predictive capabilities for underwater gaseous releases by determining the initial distribution of HNS between the water column and the atmosphere. Consequently, this improvement strengthens decision-support tools used by responders to manage HNS-related incidents at sea. In this communication, we will present the processes implemented in the module, and how they have been validated using experimental data produced in the framework of the project.