THE PHYSICAL AND CHEMICAL CHARACTERISTICS OF DESERT AEROSOLS IN THE HEIFE REGION

Measurements of the physical and chemical characteristics of desert ae rosols in the Heihe region (Northwestern China) were conducted during the periods of April 13-30 and October 3-14, 1991. It was found that b oth the number and elemental concentrations of desert aerosols showed seasonal differences: higher in April and lower in October. While fine particles remained dominant in desert aerosols, blowing dust remarkab ly enhanced the proportion of coarse particles. The desert aerosol siz e spectra were characterized by 2-modes and they could be fitted very well to log-normal distributions. Besides an abundance of crustal elem ents, the desert aerosols also contained abundant Mg and Cl, which may originate from the saline-alkali soil, and S was probably contributed comparably from the soil and secondary particles.