Kaoru KOIKE
Influence of Rainfall Characteristics on Road runoff Loads of Heavy Metals based on Long-term Monitoring Data
Toshiya KOMATSU, Syuji HIMENO
Non-point pollution is caused by pollutant loads outflowing from diffuse sources. Especially, road runoff has a significant role in non-point pollution. The purpose of this study is to measure heavy metals contained in road runoff for many rainfall events, and to clarify the heavy metal loads under various rainfall characteristics. Sampling of road runoff was conducted using a developed compact sampler which can accurately divide water volumes into a fixed ratio. The device has been improved for corresponding to high rainfall intensity. Twenty one composite road runoff samples were collected using this device in 2009 and 2010.
Concentrations of seven heavy metals (Cd, Cr, Pb, Zn, Cu, Fe and Mn) in the samples were measured and the load was calculated. Total rainfall amounts, no rainfall period before the event and the maximum rainfall intensity were considered as rainfall characteristics. Among the three parameters, only the total rainfall amounts showed some influence on the heavy metal loads. The correlation coefficient was in the range 0.19 to 0.41. Annual load of each heavy metal was calculated using the measured and the estimated value in this study.
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