MODELING EXPOSURE OF ROADSIDE ENVIRONMENT TO AIRBORNE SALT: CASE STUDY

A field study was performed in order to investigate the relationships between the salt use, the mechanisms affecting the salt emission and dispersion, and the salt exposure in a modeling approach. The salt was collected on gauze filter salt vanes at distances of 2.5 to 100 m from the road, allowing a time resolution of 30-min to 24-h exposure time. The results will be implemented in a winter maintenance management model under development by the Swedish National Road and Transport Research Institute. The results showed that the roadside exposure to airborne salt was related strongly to the wind direction. The road conditions of packed snow and thin ice seemed to abate the roadside exposure temporarily by capturing the salt on the road surface. Even at a distance of 100 m from the road, a positive relation of the wind sum and chloride deposition showed on days with strong winds. The modeling approach indicates the importance of residual salt, traffic, road surface characteristics, and wind for roadside exposure but also indicates that there are several aspects of these variables that need further investigation.