干旱区生态环境知识资源中心

Cosmogenic Be-10 is produced in the atmosphere, and deposits onto the surface of the earth mainly through wet precipitation and dust. Based on the analysis of Be-10 in Chinese loess, we believe that Be-10 in loess is composed of two components: locally precipitated atmospheric Be-10, and windblown Be-10 adsorbed on the surface of silt grains. On the Loess Plateau, Be-10 concentrations in loess and paleosol range from (1.4 to 2.8) x 10(8) atoms/g and (2.7 to 4.5) x 10(8) atoms/g, respectively. To investigate the sources of Be-10 in loess, we measured Be-10 in sand grains from deserts in western China and falling dust from the deposition regions. The results show that the Be-10 concentrations in sand and dust are (1.1-5.1) x 10(7) atoms/g and (1.3-2.8) x 10(8) atoms/g, respectively. Loess and paleosol on the Loess Plateau both contain inherited Be-10 adsorbed on silt grains from dust; most of the windblown deposited loess materials do not directly come from the Gobi and other sand deserts, but mainly from the loess-desert transitional zones, which are characterized by silt and dust holding areas. (C) 2009 Elsevier B.V. All rights reserved.