Regional characteristics of sulfur and lead isotope ratios in the atmosphere at several Chinese urban sites

Sulfur and lead isotope ratios in the atmosphere were measured at several s elected sites (Harbin, Changchun, Dalian, Waliguan, Shanghai, Nanjing, Guiy ang) in China and Tsukuba (Ja pan), to reveal regional sources characterist ics over Eastern Asia. Average S isotope ratios for SO2 and sulfate in the atmosphere in China were close to those of the coals used in each region, i ndicating a considerable contribution of coal combustion to the sulfur comp ounds in the atmosphere. Most northern cities had around 5 parts per thousa nd sulfur isotope ratio, while Guiyang, a southwestern city in China, showe d a considerably lower sulfur isotope ratio (about -3 parts per thousand) b ecause of the unusually light sulfur isotope ratio of coals in this region. These were considerably different from the value (-1.4 parts per thousand) for Tsukuba (Japan). Lead isotope ratios also suggested that coal combusti on considerably contributed to atmospheric lead in some cases in China. At the same time, influences by the emission of Chinese lead ores were also ob served in northern cities. Seasonal variations of both sulfur and lead isot ope ratios indicated the existence of a certain amount of industrial source s other than coal combustion. In addition, fractionation effect between SO2 and sulfate showed a seasonal tendency (high in winter (0-6 parts per thou sand) and low in summer (-1-3 parts per thousand)), suggesting the oxidatio n pathway of SO2 changed seasonally.