Monitoring network of atmospheric Radon-222 concentration in East Asia and backward trajectory analysis of Radon-222 concentration trend at a small solitary island on Pacific Ocean

Okura, Takehisa ; Yamazawa, Hiromi*; Moriizumi, Jun*; Hirao, Shigekazu*; Guo, Q.*; Tojima, Yasunori*; Iida, Takao*

Monitoring network of Rn concentration in air which was measured in Beijing, Nagoya, Hegura-jima, Hachijo-jima and Hateruma-jima, as a tracer for long-range transport in East Asia was established. At inland sites, Beijing and Nagoya, high concentrations Rn were measured, at marine sites, Hachijo-jima and Hateruma-jima, Rn concentrations level was very low. Seasonal variations of the Rn concentration show that Rn concentration was the lowest in the summer and the highest in the winter. Diurnal variations were measured at inland sites. At marine sites several-day-cycle variations were measured. It was pointed out by this study that the several-day-cycle variations at Hachijo-jima were dependent on synoptic-scale atmospheric disturbance. Backward trajectory analysis of the relationship between atmospheric Rn concentrations at Hachijo-jima and transport pathway of air mass indicates that atmospheric Rn at Hachijo-jima has much to do with transport pathway of air.