Lead isotope ratios of airborne particulate matter as tracers of long‐range transport of air pollutants around Japan

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Abstract
The use of airborne lead isotope ratios as tracers of long‐range transport of air pollutants in the Asian region was evaluated using air trajectory analysis. Airborne particulate matter was collected in various seasons from 1988 to 1991 at the Oki Islands located between the Asian continent and Japan. Air masses coming from Japan had lead isotope ratios nearly equal to those measured on mainland Japan. Air masses from the Asian continent had less radiogenic isotope ratios than those from Japan. Trajectory analysis showed that these less radiogenic values could be used to further subdivide Asian air masses as having come from one of three regions: the southern part of the Korean Peninsula, north China, and Russia. The isotope ratios of the samples classified into three regions were close to previously reported values measured in each region, except for those assigned to Korea, where it is believed that the ratios are currently changing. It was concluded that lead isotope ratios were reliable tracers of the long‐range transport of air pollutants, especially when used in conjunction with air trajectory analysis.