2018 Volume 49 Pages 125-142
We have conducted the analysis of chemical species of water-insoluble sulfur compounds in rime ice and snow and used the analysis to propose a long-range transport mechanism for coal-burning emissions in East Asia under winter monsoon conditions. Thin films of insoluble substances included in rime ice and snow on a 0.45 μm pore size membrane filter were analyzed by wavelength-dispersive X-ray fluorescence spectrometry with single dispersive crystal. Using this approach, we could analyze the sulfur-containing chemical species by examining the chemical shift of the S-Kα line. The chemical species containing sulfur were analyzed exclusively from the Ca and S concentrations in the residues of rime ice and snow. Single-particle analysis of the thin film on the membrane filter was performed for particles with size below 3 μm using a tabletop low-vacuum scanning electron microscopy with energy dispersive X-ray spectroscopy instrument. Particles were classified into six categories according to their compositions. Five major categories of spider chart distribution patterns were identified, and we proposed that they depended on the 24-hour back trajectory, such as Huabei, China, Northeast China, Korea Peninsula, Heilongjiang-Russia, and Japan types. We could assign the generating area of the air pollutants using the mole ratios of water-soluble Cd, Pb, and nss-SO42-species. These categories corresponded with the areas in China based on the isotope ratio of sulfur in Chinese coal and the isotope ratio of Pb collected in Japan.
