Research on Environmental Impact of De-Icing Salts

In snowy cold regions of Japan, road administrators spread de-icing salts on roads to ensure safe driving in the winter. The quantity of de-icing salts has increased every year since the use of spiked tires was prohibited. Some people have expressed their fear that scattering de-icing salts that have been spread damages roadside environments. It is necessary to spread de-icing salts in order to ensure safe driving with minimum harming the natural environment. This is a report on surveys of (1) the relationship of the quantity of de-icing salts spread with the quantity of scattered and run off from roads, (2) salinity of roadside soil, and (3) salinity tolerance of vegetation that were conducted to study its impact on soil and vegetation. These surveys revealed the following. 20% of the quantity spread was scattered outside the roadway, and 72.5% of this scattered salt remained within 3 meters from the edge of the road. Approximately 70% of the quantity of de-icing salt that was spread flowed into drainage ditches and 2% adhered to motor vehicles. The material balance of 94% of the quantity spread was clarified. The salinity of soil along roadsides in snowy regions was measured. The concentration of chloride was found out to be much lower than damage threshold of weak salinity vegetation in most cases. The standard internal salt content and allowed salt penetration etc. were used to clarify the salinity tolerance of vegetation. For the covering abstract see ITRD E143097.