Development and application of a multimedia environmental model for assessing the behavior of chemical warfare agents

Chemical warfare agents (CWAs) are highly toxic and environmentally persistent, posing human health risks. For example, Venomous Agent X (VX) exhibits low volatility and water solubility, allowing persistence as liquid-phase droplets. To quantify liquid-phase CWA behavior, DREAM-CWA (Dynamic fugacity-based Regional Environmental model for Air-surface exchange and Multimedia fate of Chemical Warfare Agents) was developed as a GIS-based Level IV fugacity model incorporating a droplet compartment. The model estimates phase partitioning and intermedia transport of droplets. Soil, asphalt, coated concrete (non-porous), and water are represented as distinct surface compartments to reflect urban environmental characteristics. Validation against the fugacity model CoZMo-POP 2 confirmed the reliability of DREAM-CWA. A case study of a hypothetical VX chemical attack was conducted as a preliminary evaluation to optimize the multimedia framework, focusing on liquid-phase persistence and multimedia interactions. Initially, VX was retained in droplets and surfaces, with volatilization driving increases in air concentrations. Soil and sediment acted as a dominant short-term reservoir and long-term sink, respectively. Secondary emissions from droplets and surfaces sustained atmospheric exposure. By providing volatilization fluxes resolved in time and space, DREAM-CWA outputs can be coupled with computational fluid dynamics simulations to estimate near-surface dispersion and exposure. This integrated framework offers a robust tool for assessing the environmental risks of CWAs and supporting decision-making during chemical attack responses.