Salt Measurement in the Coastal Region

Concrete bridges and structures near the ocean have been severely deteriorated due to sea salt in the atmosphere. Design guides of highway bridges near the ocean are prescribed by Japan Road Association. According to the design guide, bridges within 200 meters from the coast shall be taken a measure to meet the rules preventing corrosion of steel in concrete. This distance of 200 meters has been determined basad on the bridge survey near the ocean. That is, deterioration is very rare for bridges located in the region more than 200 meters away from the coast. The present study aims to obtain the relationship between salt quantity in the air and distance from the coast. Measurement of salt in the air was conducted on the coast of the Japan Sea in winter seasons. Salt was measured with gauze of 100(cm)^2 in size. As the result, salt in the air is inversely proportional to the distance from the coast, and is very little at distances more than 100 meters from the coast. Furthermore, salt is little at the height of 30 meters. A simple model was proposed for phenomenon of blowing salt particles in the atmosphere.