Influence of Motor Vehicle Exhausts on Chemical Components in Rainwater

In order to clarify the possibility of NO₃⁻ being one of concomitants for acid rain, we have measured pH, electric conductivity (EC) and cationic and anionic ion levels in rain water collected from three different locations in Kobe, Japan: The distances from the highway (Hanshin Highway) are 50 m at the A point, 1,500 m at the B point and 2,900 m at the C point, respectively. Significant correlations were observed between the respective NO₃⁻ and Ni²⁺ levels in the rain water obtained from the A and B points. Since these ions are usually included in motor vehicle exhausts, the results suggest that acidity in rain water is mainly derived from NO₃⁻ due to motor vehicles and that the levels of Ni²⁺ in rain water are evaluated as an indication of air pollution by motor vehicle exhausts.