Temporal characteristics of mineral dust particles in precipitation of Urumqi River Valley in Tian Shan, China: A comparison of alpine site and rural site

Physico-chemical characteristics of mineral dust particles in the precipitation at both an alpine site and a rural site were determined in the Urumqi River Valley, Tian Shan, China. Results showed that the concentration, size distribution and chemical constitutes of dust particles in the precipitation varied seasonally at both two sites, though there existed obvious differences between them. Dust particle concentration in the precipitation increased during winter and springtime, but it decreased during summer and autumn, which had a positive correlation with strengthened wind speed and Asian dust activity, but a negative correlation with the seasonal variation of the precipitation amount, implying that aerosol dust in the precipitation of Urumqi River Valley in Tian Shan was very sensitive to the seasonal change of regional atmospheric environment in central Asia. Volume-size distribution of mineral dust particles showed larger modal size in Asian dust period of winter–spring, but relatively smaller modal size in non-dust period of summer–autumn. Moreover, the average modal size and mass concentration of dust particles at the rural site are larger than that of the alpine site. Chemical constitutes of dust indicated that the precipitation chemistry was mainly controlled by regional dust storms, local dust and anthropogenic activities in central Asia. HYSPLIT Model was also employed to examine the transport process of air mass and mineral dust particles in this region.