Major Factors Influencing Long-term Periodic Variation of the Radon Concentration in the Atmosphere: A Comparative Study between the Ocean and Land Conditions

Abstract

We compared the periodic characteristics of the atmospheric radon concentration on the land and ocean, using data simultaneously measured at Oki Island in the Sea of Japan and Matsue, which is located 70 km south of the island and on the Shimane peninsula. The radon concentration was the highest in the fall at Matsue and in the winter at Oki Island and the lowest during the summer at both locations. The frequency distributions and the annual periodic variations of the arriving pathways of the air masses and these radon concentrations at Matsue and Oki Island showed the same tendency. At Matsue, the monthly average of diurnal minimum of the radon concentration was highest in the winter that was three month late from the maximum season of the monthly average of all measurements. The monthly average of radon concentration at Matsue showed the positive correlation between the monthly occurrence times of temperature inversion. The annual periodic variation of the radon concentration at Oki Island depends on the long-term variation of the distribution of arriving pathways of the air masses. KEY WORDS: atmospheric radon concentration, diurnal variation, seasonal variation, maritime air mass, continental air mass, backward trajectory, long range transport, Sea of Japan, Shimane peninsula, Oki Island. 1‚Í ‚ ¶ ‚ß ‚É ƒ‰ ƒhƒ"•[222(ˆÈ ‰ºƒ‰ƒhƒ")‚Í ƒ‰ ƒW ƒEƒ€•[226‚Ì ‰ó •Ï • ¶ •¬ •¨ ‚ʼn» Šw"I ‚É•s Šˆ•Šˆ•« ‚È, "¼OE¸Šú3. 82"ú ‚Ì •ú ŽË•« ‹C'Ì OE³ 'f ‚Å‚ ‚é•B ƒ‰ƒhƒ"‚Í •~•…"™ ‚É‚ae‚Á‚Ä•oe‹Ž ‚³ ‚ê ‚È‚¢•« Ž¿‚â-A '-' † ‚ɉ» Šw"I ‚É•Ï Ž¿ ‚µ‚È‚¢ •« Ž¿‚ð-L ‚· ‚é ‚½‚ß, '· ‹-£-A '-‰ß 'ö ‚É‚¨‚¯‚É‚¨‚¯ ‚é-¤ •ã ‹C‰ò ‚Ì ƒgƒOE •[ ƒT•[ ‚AE‚µ‚Ä-p ‚¢ ‚ç ‚ê ‚é1•`7)•B-¤ 'n ‚Ì 'å ‹C‹« ŠE'w "à ‚Å‚Í, ƒ‰ƒhƒ""Z"x ‚â ƒ‰ƒh ƒ"‰ó •Ï • ¶ •¬•¨ "Z"x ‚Í •U•• ‚Ì ‹É ‚ß ‚Ä'å ‚« ‚È "úŽüŠú•Ï "®‚¨‚ae®‚¨‚ae ‚ÑOE°'˜ ‚ÈŽüŠú•« ‚Ì ‹G•ß •Ï "®‚ðOE» ‚· ‚± ‚AE‚Í-Ç ‚-'m ‚ç ‚ê ‚Ä‚¢ ‚é8•`12)•B "ž-ˆ‚· ‚é ‹C ‰ò ‚Ì ƒ‰ƒhƒ""Z"x ‚̈á‚Ìˆá ‚¢ ‚É ‚ae ‚Á‚Ä, 'å ‹C ' † ƒ‰ƒhƒ""Z"x ‚â •~•…' † ƒ‰ ƒhƒ"‰ó •Ï • ¶ •¬•¨ "Z"x ‚Í ‹} OEƒ ‚É•Ï "®‚· ‚é ‚± ‚AE‚à •ñ •• ‚³ ‚ê ‚Ä‚¢ ‚é13•`15)•B ŠC•…' † ‚Ì ƒ‰ ƒW ƒEƒ€"Z"x ‚Í 'å-¤ 'n Šk' † ‚ae ‚è4OE…ˆÈ‚è4OE…ˆÈ•ã ‚à 'á ‚¢ ‚½‚ß, ŠC-m 'å ‹C ' † ‚Ì ƒ‰ ƒhƒ""Z"x ‚Í-¤ 'n 'å ‹C ' † ‚ae ‚è‹É ‚ß ‚Ä'á ‚¢16•`19)•B ŠC-m 'å ‹C ' † ‚Ì ƒ‰ƒhƒ""Z"x ‚Ì '· ŠúŠÔ‚Ì 'ª 'è ƒf •[ ƒ^‚ð•ñ •• ‚µ‚½˜_ • ¶ ‚Í •-‚È ‚-, "úŽüŠú•Ï "®‚â ‹G•ß •Ï "® ‚Ì •ñ •• ‚à•-‚È‚¢20•`23)•B OEÇ " ‡‚Ì ƒ‰ƒhƒ""Z"x ‚Í ŠC-m 'å ‹C ‚AE ‚Ì •¬ • ‡ ‚É‚ae‚Á‚Ä-é ŠÔ‚Å ‚à'• ‰Á ‚µ‚È‚¢ ‚½‚ß, •¬ ‚³ ‚¢ •U•• ‚Ì 'Z ŽžŠÔ•Ï "®‚¨‚ae‚Ñ‹G®‚¨‚ae‚Ñ‹G•ß •Ï "®‚ðOE»‚µ‚Ä‚¢ ‚é12,14)•B ŠC-m ‚AE-¤ 'n ‚É‚¨‚¯‚É‚¨‚¯ ‚é 'å ‹C ' † ƒ‰ƒhƒ""Z"x‚Ì ŽžŠÔ •Ï "®‚Ìˆá®‚Ìˆá ‚¢ ‚ð˜_ ‚ ¶ ‚½•ñ •• ‚Í •-‚È‚¢•B ŠC-m ‚Ì OEÇ " ‡ ‚AE-¤ 'n ‚AE ‚Å‚Í, 'n *1" ‡ •ª OE § •ÛOE' ŠÂ ‹« ‰È Šw OE¤ ‹ †•Š; " ‡•ª OE § •¼•] Žs•¼•l •² 'É'¬582-1(T690-0122)