FLUCTUATION OF ION COMPONENTS, TRACE METALS, AND Pb/Zn RATIO IN PRECIPITATION AT TSU CITY

Abstract

 To elucidate the air pollution, its features, its sources, and the influence of yellow sand (kosa) in Tsu City, the ion components and trace metals in precipitation at Mie University were measured along with their temporal changes. From the obtained correlation coefficients and the results of the principal component analysis, the ions and the trace metals in the precipitation were classified into three groups: the SSI group (the ions of Cl^-, Na⁺, K⁺, Mg²⁺, ss-SO₄^2- and ss-Ca²⁺, of which the main sources were sea salt); the ASI group (the ions of F^-, NO₃^-, NH₄⁺, nss-SO₄^2- and nss-Ca²⁺, of which the main sources were anthropogenic pollution and soil); and the ASM group (trace metals of Al, Fe, Mn, Pb, and Zn, of which the main sources were anthropogenic pollution and soil). The concentrations of the SSI group tended to be higher with increased wind velocity. Results suggest that seawater was raised into the atmosphere in proportion to the wind velocity, and that the sea salt ions were transported and increased in the precipitation. The effects of long-range transport and local pollution on the pollutants and the soil elements in the precipitation were discussed from measurements of the concentration ratios of Pb and Zn (Pb/Zn) and backward trajectory analysis. The concentrations of ion components and trace metals during the rain events in Tsu City, Mie generally decreased over time. The condensed pollutants in the air are regarded as removed in the initial period of the rain events. We can confirm that the concentration ratios (Pb/Zn ratios) are almost identical to reported values for rain clouds through Japan. Only one day showed high rates of pollutants, but it is presumed to be not the effect of kosa but of the industrial zone to the north east of Tsu City.