『Abstract
　Monitoring systems along roads are needed to facilitate decisions on improving protection of water resources and decreasing the impact of road-related pollutants on the roadside environment. This paper presents a monitoring system using permanently installed electrodes and monthly measurements of resistivity at a motorway in Sweden with heavy loads of de-icing salt. A significant increase in resistivity in the vadose zone with increasing distance from the road was shown in both sand and glacial till areas during the whole year. By measuring temporal variations in a less affected environment further from the road, a distinction could be made between more natural variations and variations due to de-icing salt and melting of roadside snowbanks. The highest resistivities occurred in October-November and the lowest in January-March, while the more natural resistivities showed an opposing temporal variation. The difference was up to 35％ on a log-scale in the sand area during the latter period. Hence, the time-lapse resistivity measurements clearly showed a strong influence of de-icing salt on roadside soils and groundwater during winter and spring. The measurement system and the analysis methods proved useful for monitoring both the spatial and seasonal variation in resistivity.

Keywords: De-icing salt; Road; Resistivity measurement; Monitoring; Seasonal variation』

Introduction
Materials and methods
　The study site
　Resistivity survey
　Data processing and interpretation
Results
　Spatial variation in resistivity
　Temporal variation in resistivity
Discussion and conclusions
Acknowledgments
References