Abstract
In order to discuss the behavior of accumulating ions on inside-ward surface of a girder of the bridge, composition of accumulating ions on the girder are examined. Abundance of accumulating ions are high in winter and spring, and low in summer and autumn. The fluctuation of the abundance is associated with the quantities of air born salt in each season. The abundances of Na+ and Cl– on the inside-ward surface of girder decrease during days with a hard rain and high humidity. While the inside-ward surface of the girder can not be washed by rain, many traces of dew can be found on the girder. Therefore, the decrease of Na+ and Cl– on the girder is considered to result from that accumulating NaCl with high solubility are partly wash out by dew. Hence, chemical composition of salts on girders is influenced not only by the quantities of air born salts, but also by the quantities washed out by dew. As a result, the abundances of ions on girders are not proportional to length of period that ions have accumulated.
