CHARACTERIZATION OF ATMOSPHERIC TOTAL SUSPENDED PARTICULATE (TSP) IN A MIDSIZE CITY IN NORTHERN JAPAN: NON-SNOW-CLAD PERIOD TO SNOW-CLAD PERIOD COMPARISON

Abstract

Total suspended particulate (TSP) samples were collected from three areas (commercial, residential and agricultural) in and near Akita City in northern Japan, from May – June 1996 (non-snow-clad period) and January – February 1997 (snow-clad period), over three days with a one-hour sampling interval for each area. The elemental composition and particle shape of TSP samples were determined and/or observed by Particle Induced X-ray Emission (PIXE) and a Scanning Electron Microscope (SEM) combined with Energy Dispersive X-ray (EDX) analysis. In the hourly TSP samples collected during the non-snow-clad period, 23 elements were determined for each area, and Na , Mg , Al , Si , S , Cl , K , Ca and Fe were the major components. On the other hand, 25 elements, excluding As and Rb , were found in the snow-clad period samples, and P , Ga , Nb and Mo were only found in the snow-clad-period samples. Dominant elements, i.e., major components, of the snow-clad period were the same as the non-snow-clad period. Comparing the arithmetic means of elemental concentrations in TSP for the non-snow-clad and snow-clad periods, in the commercial area the elemental concentrations in the snow-clad period were the same or lower than those in the non-snow-clad period, with the concentrations of Na , Mg , Al , Si , S , K , Ca , Ti and Fe in particular being markedly lower. In the residential area the concentrations of Na , Mg and Cl were markedly higher in the snow-clad period than in the non-snow-clad period, while the concentrations of the other elements were the same or only slightly lower. In the agricultural area, the concentrations of Na and Cl were markedly higher in the snow-clad period relative to the non-snow-clad period, and the concentrations of the other elements, except for P , were low. The concentrations of the major elements and Pb were particularly low. Thus, in the residential and agricultural areas the effect of northwesterly winter wind on TSP can be observed by Cl , and it is conjectured that soil particles rising up into the air is inhibited by snow accumulation. Soil particles rising up into the air seems to be inhibited by snow accumulation in the commercial area as well. With the aid of SEM and EDX analysis, aggregates of diesel exhaust particles (DEP), soil particles and small silicon-rich spherical particles were observed in the non-snow-clad and snow-clad period samples for each area. In addition, small aluminum-rich and iron-rich spheres were observed during the non-snow-clad period in the commercial area. Zinc-rich fiber was observed during the non-snow-clad period in the residential area.