Variability of dust mass concentrations and deposition rates under different weather conditions in Cele Oasis, southern Tarim Basin

摘要

Sand and dust invasions are a serious issue for oases; therefore, understanding the characteristics of dust concentrations, deposition rates, and influencing factors, under a variety of differing dust weather intensities, is important for the prevention of dust disasters. Field observations made in the Cele Oasis, in the southern Tarim Basin, indicated that the atmospheric levels of suspended mineral dust were far above those of other regions in China, and very close to Sahelian belt. The mass concentrations of TSP (total suspended particulates) and PM10 (particles with aerodynamical diameter <10 mu m) span three orders of magnitude under different intensities of dust weathers. The TSP and PM10 concentrations exceeded the second grid of China's National Standard 66.0- and 20.8-fold during dust storms, 35.8- and 9.2-fold during blowing sand, and 17.8- and 3.8-fold during floating dust. The dust accumulation caused by dust storms, blowing sand, and floating dust accounted for 40.16, 31.57, and 28.27 % of the total accumulation, respectively, but the blowing sand and floating dust had almost the same average deposition rate, which was 37 % less than that of dust storms. Winds blowing from the WSW, W, WNW, and NW brought more dust into the oasis than other directions. The correlation analysis between the dust concentrations, deposition rates and meteorological factors revealed that the oasis microclimate effect plays an important role in enhancing dust deposition during blowing sand and floating dust days. The hygroscopic growth of particles, in particular, is most likely the main mechanism for enhancing deposition.