Ice core dust particulate by XPS-SEM/EDAX -: Impact of dust particulate on SO2-4 record in ice cores

The ice core dust particulate sampled from Mt. Xixabangma has been analyzed by means of X-ray photoelectron spectrometer (XPS) and scanning electron microscope with energy dispersion X-ray analysis (SEM/EDAX). The results show that the contents of SO42- and SO32- in the surface layer of the dust are significantly higher than those in the subsurface layer (with the exception of organic sulfide). This difference indicates that the surface SOx has been captured and then chemically converted by the atmospheric dust particulate before its deposition with snow, which is obviously different from those inner layer sulfates and sulfites contained by dust itself. In addition, it has been determined by SEM/EDAX that the dust contains relatively high concentrations of transition metal elements such as Fe and Ti oxides which could function as photocatalysts to the conversion of SOx adhered on the surface of the dust, and consequently accelerate the deposition of SOx to snow. Our research also demonstrates that the adsorptive carrying and the catalytic performance of the dust to the atmospheric SOx are most important causes of the positive correlation between SO42- and dust concentration records in ice cores.