加速器质谱中心知识库

Paleoenvironmental and paleogeomagnetic tracing studies from Chinese loess Be-10 have progressed in recent years (Zhou et al. 2007a,b, 2010). In this approach, Be-10 flux determined from sediment concentration and accumulation rate may be used to recover information about paleomonsoon rainfall rates as well as past variations in the geomagnetic field strength. However, these methods require that a correction be made for residual undecayed Be-10 in remobilized dust. To better understand the feature of the Be-10 signals related to the remobilized dust, we report the first observational study on Be-10 concentration of modern falling dust using the 3MV multi-element accelerator mass spectrometer (AMS) in the Xi'an AMS Center. Ten samples collected at Ansai observation station (109 degrees 19'E, 36 degrees 51'N) in northern China from May 2008 to June 2009 are measured along with 3 chemical blanks. The results clearly show that the Be-10 content of modern falling dust is relatively uniform, with a mean value of 1.21 x 10(8) atoms/g, a measurement similar to that of Chinese loess (Zhou et al. 2007a) and to the value found in the study by Shen et al. (2009) on dust Be-10 falling near Dingbian, China (1.25 +/- 0.06 x 10(8) atoms/g). Despite the fact that modern dust flux is much higher in spring relative to summer in northern China, Be-10 concentration in falling dust remains fairly constant. In addition, we find that dust Be-10 concentration is roughly independent of the local precipitation changes. This feature might be considered as an analogue to improve our understanding on the fundamental information of the source component contained in loess Be-10 records and its spatial/temporal distribution features.