title: Toxic gas clouds: effects and implications of dry deposition on concentration.
abstract: The influence of the dry deposition process on concentration pertaining to toxic gas clouds was investigated by model calculations. Three main release scenarios were simulated, with nine micrometeorological cases considered for each. To compare and confirm the results, two model types, a stochastic particle model and a box-type model, were independently used to simulate many of the different cases. The results showed that the effects of dry deposition may be strong for releases at, or confined close to the ground, e.g. neutral or unstable stratification can cause higher concentrations than stable stratification after 10-15 km. Risk distances are in turn affected and may be substantially shortened, e.g. for a zero-height release like that from an evaporating pool, a 50% reduction in total airborne substance may occur within 500 m at a low wind velocity and neutral or stable stratification.
authors.affiliation: FOI, Swedish Defence Research Agency, Division of NBC Defence, SE-901 82 Umeå, Sweden. lage.jonsson@foi.se
authors.forename: Lage
authors.initials: L
authors.lastname: Jonsson
authors.forename: Edvard
authors.initials: E
authors.lastname: Karlsson
authors.forename: Lennart
authors.initials: L
authors.lastname: Thaning
mesh_terms: D000531:Altitude; D005740:Gases / Q000737:chemistry*; D015386:Hazardous Substances; D008685:Meteorological Concepts; D008956:Models, Chemical; D009994:Osmolar Concentration
chemical_list: D005740:Gases; D015386:Hazardous Substances