Heavy dust fall in Beijing, on April 16-17, 2006: Geochemical properties and indications of the dust provenance

Abstract

A heavy dust fell in Beijing on April 16-17, 2006. The dust storm formed in middle and western Inner Mongolia, China, under a strong Mongolian Cyclone. During the dust fall, the near-surface wind speed was insignificant in Beijing. The minimal wind speed at ground level indicates that the dust must have been transported by upper northwestern winds, and the local dust of Beijing contributed little to dust fall. The lack of a contribution from local dust differed from previous dust fall events in Beijing. Therefore, this dust fall provides good information on the dust source. Dust samples colleted during this event and Pleistocene loess samples from the Beijing area were analyzed for magnetic susceptibility, bulk particle and quartz grain size distributions, bulk particle and quartz micro-textures, mineralogy, carbonate content, major element concentrations, trace element and rare earth element (REE) concentrations, and the oxygen isotope composition of quartz. The results indicate the following. (1) The dust of the April 2006 storm derives mainly from surface sediments in middle and western Inner Mongolia, with some minor contributions from anthropogenic emissions from coal combustion and mining. (2) The characteristics of the dust fall in China appear to vary with time and location, which has significance for palcoclimate reconstructions. (3) Many characteristics differ between the dust from 2006 event and Pleistocene loess in Beijing, and implying that the two have different sources. (4) The loess deposits found in Beijing and on the Loess Plateau also appear to differ in provenance.