Abstract
A de-icing agent, containing NaCl as the main component, is often sprayed on expressways in winter months to prevent freezing of road surfaces. The de-icing agent becomes scattered along expressways and over the edges by passing vehicles. Depending on the concentration of the agent, this scattering induces risk of inhibiting growth of plants and contaminating water. In this study, we summarized the index values for the influence of NaCl on agricultural crops, farmland soil and agricultural water. In addition, we investigated the amount of NaCl infiltration into the farmland soil located along such expressways and the amount of its inflow into agricultural water. We then evaluated the influence of NaCl based on results of the investigation. As a result, Cl concentration was found to be 90 mg · kg -1 at the 1.5-m ridge of road edge, which is 23% of the threshold value 400 mg · kg-1. Exchangeable Na+ saturation was 16.3%, which is 81.5% of the threshold value 20%. Electrical conductivity of the agricultural water was 0.15 dS · m -1 in the busy farming season, which is 50% of the threshold value 0.3 dS · m-1. All three values were below the threshold values, and thus, it became clear that the influence of the de-icing agent on farmland soil and agricultural water was extremely small.
