The North China and the neighbouring Mongolia in Asian Interior is characterized by extremely dry climate, resulted in one of the world's major dust emission centres. Deciphering the source region of Asian dust is critical for revealing the mechanism of the dust production, interpreting the paleo-environmental records of eolian deposits, predicting the overall environmental effects of dust, and setting the strategies for the control of contemporary dust storms. This paper summarizes the geochemical methods applied to the source tracing of Asian dust. Nd-Sr isotopes were the most extensively studied source tracer of Asian dust and have been successfully applied in many cases. Geochemistry of detrital monomineral shows great theoretical advantages in source tracing and deserves further studies. The short-range transportation of Chinese loess with direction similar to that of the prevailing near surface wind is revealed. Source tracing also shows that the Asian dust has two ultimate material sources from the northern margin of the Tibetan Plateau and the Central Asian Orogen, which confirms the importance of mountain processes in the production of silt eolian particles. Based on the recent progresses on the source tracing of Asian dust, discussions are expanded on the natural background of Asian dust storms and potential anthropogenic influence, the materials evolution of the source regions of Asian dust and its relationships with climate changes and Tibetan uplift, and the role of Tibetan uplift in the Asian dust system.
Suspended particulate matter samples were collected monthly for more than 2 years in Nanjing,China to examine seasonal changes in the Sr-Nd isotopic compositions of the lower Changjiang River(CR).The results indicate that the 87Sr/86Sr ratios of the samples ranges from 0.725352 to 0.738128,and the values ofεNd(0)ranges from-10.55 to-12.29.The Sr-Nd isotopic compositions show distinct seasonal variations.The samples had lower 87Sr/86Sr ratios and higherε Nd(0)values during the flood season than the dry seasons.The seasonal variations primarily reflect the controls of provenance rocks and erosion in different sub-catchments.The relative decrease in 87Sr/86Sr ratios and the increase inε Nd(0)values during the flood season may reflect an increasing in the mechanical erosion rate in the upper basin and the contribution of more sediment from the upper reaches.The end member values of 87Sr/86Sr andε Nd(0)of the samples were 0.728254 and?11.26,respectively.
MAO ChangPingCHEN JunYUAN XuYinYANG ZhongFangJI JunFeng
