Measurement of ¹⁰be concentration of modern falling dust in northern China

Paleoenvironmental and paleogeomagnetic tracing studies from Chinese loess ¹⁰Be have progressed in recent years (Zhou et al. 2007a,b, 2010). In this approach,¹⁰Be 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 ¹⁰Be in remobilized dust. To better understand the feature of the ¹⁰Be signals related to the remobilized dust, we report the first observational study on ¹⁰Be concentration of modern falling dust using the 3MV multi-element accelerator mass spectrometer (AMS) in Xi'an AMS Center. Ten samples collected at Ansai observation station (109°19'E, 36°51'N) in northern China from May 2008 to June 2009 are measured along with 3 chemical blanks. The results clearly show that the ¹⁰Be content of modern falling dust is relatively uniform, with a mean value of 1.21 × 10⁸ 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 ¹⁰Be falling near Dingbian, China (1.25 ± 0.06 × 10⁸ atoms/g). Despite the fact that modern dust flux is much higher in spring relative to summer in northern China, ¹⁰Be concentration in falling dust remains fairly constant. In addition, we find that dust ¹⁰Be 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 ¹⁰Be records and its spatial/temporal distribution features.