Characteristics of Elemental Composition of PM_(2.5) in the Spring Period at Tongyu in the Semi-arid Region of Northeast China

Continuous observations of mass concentration and elemental composition of aerosol particles （PM2.5） were conducted at Tongyu, a semi-arid site in Northeast China in the spring of 2006. The average mass concentration of PM2.5 at Tongyu station was 260.9±274.4 μg m^-3 during the observation period. Nine dust events were monitored with a mean concentration of 528.0±302.7 μgm^-3. The PM2.5 level during non- dust storm （NDS） period was 111.65±63.37 μg m^-3. High mass concentration shows that fine-size particles pollution was very serious in the semi-arid area in Northeast China. The enrichment factor values for crust elements during the dust storm （DS） period are close to those in the NDS period, while the enrichment factor values for pollution elements during the NDS period are much higher than those in the DS period, showing these elements were from anthropogenic sources. The ratios of dust elements to Fe were relative constant during the DS period. The Ca/Fe ratio in dust aerosols at Tongyu is remarkably different from that observed in other source regions and downwind regions. Meteorological analysis shows that dust events at Tongyu are usually associated with dry, low pressure and high wind speed weather conditions. Air mass back-trajectory analysis identified three kinds of general pathways were associated with the aerosol particle transport to Tongyu, and the northwest direction pathway was the main transport route.

Chemical characteristics of aerosol particles (PM_(2.5)) at a site of Horqin Sand-land in northeast China

The objective of this study was to characterize the mass concentration and chemical composition of aerosol particles（PM2.5） collected at Tongliao（Inner Mongolia Autonomous Region, China）, a site in Horqin Sand-land in northeast China. During spring 2005, the mass concentration for PM2.5 was （126±71）μg/m^3 in average. Five dust storm events were monitored with higher concentration of （255 ± 77）μg/m^3 in average than the non dusty days of （106 ± 44）μg/m^3. Concentrations for 20 elements were obtained by the PIXE method. Mass concentrations of ALl, Mg, Si, K, Ca, Ti, Mn, and V, which increased with the PM2.5 concentration, were higher than the pollution elements （S, Cl, Zn, Ar, Se, Br, and Pb）. Enrichment factor relative to crust material was also calculated, which showed dust trace elements were mainly from earth upper crust and pollution elements were dominated the anthropogenic aerosols. The Si/Al, Ca/Al, and Fe/Al ratios in PM2.5 samples at Tongliao were 4.07, 0.94, and 0.82, respectively, which were remarkably different with those on other source regions, such as ＂Western desert source region＂, ＂North desert source region＂ and central Asia source. Air mass back-trajectory analysis identified three kinds of general pathways were associated with the aerosol particle transport to Tongliao, but have the similar elemental ratios, implying that elemental signatures for dust aerosol from Horqin Sand-land were different with other regions.