Variations of atmospheric Radon-222 on Rishiri Island, Japan based on quantitative trajectory analysis

Abstract

In order to examine transport processes of air mass as well as source/sink term of atmospheric Radon-222 on the Eurasia continent, measurements of atmospheric Radon-222 were made on Rishiri Island (45°07'N, 141°12'E), northernmost Japan. Diurnal variation was observed with maximum Radon-222 concentration before the dawn, while the minimum appeared in the afternoon. Seasonal Radon-222 variation was characterized by high concentration from November to February and low from May to July. High Radon-222 was caused by air mass originated from 40° to 60°N of Eurasian continent and low Radon-222 caused by air mass originated from the western North Pacific. Based on air mass pathways calculated by trajectory model and radon-222 source/sink term, air mass origins were examined quantitatively.