干旱区生态环境知识资源中心

[1] Asian dust particles usually refer to mineral particles which originate from arid and semiarid areas in the Asian continent and disperse eastward in a wide range in the atmosphere. Their appearances in the downstream marine areas are always accompanied by high concentrations of sulfate and nitrate, suggesting their significance as a medium for pollutant conversion and transportation. However, analysis of particles collected at a coastal site in east China before and after the cold front arrival of a heavy dust - loading low-pressure system in this study revealed that air masses polluted by anthropogenic emissions from local or regional areas and the natural Asian dust plume from northwest China were in different air parcels. Anthropogenic pollutants were in the prefrontal air while the so-called Asian dust particles were in the postfrontal air. There was a large amount of anthropogenic mineral particles in the polluted air masses, and the particles were abundant in sulfur, sodium, and calcium, while the so-called Asian dust particles were very "clean’’ ( meaning lack of anthropogenic pollution). Continuous records of PM10, SO2, and O-3 concentrations indicated that the cold front was the boundary layer between the polluted air masses and the clean dust plume. Hence, at the coastal areas the Asian dust plume and polluted air masses did not mix with each other and were separated in two consecutive air parcels by the cold front although they were in the same low-pressure system. In addition, the analysis also revealed that calcium was not a good indicator for Asian dust from natural sources because the anthropogenic mineral particles contained significant calcium.