Perchlorate Ion in Aerosols Collected at Cape Hedo, Okinawa, Japan

Abstract

Perchlorate ion (ClO₄^-) has been recognized as a new environmental pollutant. The concern about ClO₄^- stems from the fact that it displaces iodide in the thyroid gland. Iodine-containing thyroid hormones are essential for proper neural development from the fetal stage through the first years of life. In this study, we determined the concentrations of ClO₄^- in aerosols collected at Cape Hedo Atmosphere Aerosol Monitoring Station of National Institute of Environmental Studies (NIES-CHAAMS) Okinawa Island, Japan. Aerosols were collected on quartz filters by using a high-volume air sampler. The ClO₄^- concentrations were determined by ion chromatography (ICS-2000, DIONEX). About 60% of the weekly-collected aerosols contained detectable level of ClO₄^-, and the highest ClO₄^- concentration for the samples collected at NIES-CHAAMS was 1.8ng m^-3. Back trajectory analysis showed that ClO₄^- concentrations were higher when air mass came from Asian continent, suggesting that ClO₄^- found at NIES-CHAAMS was probably due to long-range transport from Asian continent.