Characterization of the composition of dust fallout and identification of dust sources in arid and semiarid North China

A source analysis to characterize the composition of dust fallout in arid and semiarid North China, an important source area of dust for East Asia, was performed. Monthly samples were obtained from April 2001 to March 2002 at 29 sites in sandy and gobi deserts, steppes, and loess areas, and the following elements were analyzed: Ce, Co, Cs, Eu, Fe, Hf, Lu, Nd, Rb, Sc, Ta, Tb, Th, As, La, Na, Sb, Sm, U, Yb, Al, Ca, Mg, Mn, Ti, and V. Although the dust compositions differed, it was difficult to determine the potential dust source areas based solely on the elemental fingerprints of the dust. Principal components analysis showed that at most sites Sm, Sc, La, Ce, Eu, and Th were most strongly correlated (r > 0.7) with other elements, whereas crustal elements such as Al, Fe, and Ti were only strongly correlated with the other elements at a few sites. Of the 26 elements that we analyzed, maybe only Sb was representative of anthropogenic pollution, but pollutant sources were unclear because at most sites, in different months, the crustal-derived elements and those derived from anthropogenic pollutants always appeared synchronously, creating difficulties and high uncertainties in source identification.