Examining quartz OSL age underestimation for loess samples from Luochuan in the Chinese Loess Plateau

When using quartz OSL to date loess samples from the Chinese Loess Plateau, it has been reported that the agreement between OSL ages and the independent ages is limited to the samples younger than ～70 ka with a corresponding D_e of ～230 Gy, and a sample with an expected age of 780 ka was dated to 107 ka, corresponding to 403 Gy. The growth curves of these samples do not saturate at doses of 700 Gy, and a linear growth part was observed for doses higher than 200 Gy. However, the maximum measured age of ～100 ka imply that the D_e determined using this linear part of a growth curve could be problematic, or that the quartz OSL signal is not as stable as previously thought and has a barrier age of ～100 ka. In the current study, we examine the reasons for the age underestimation. We examined the shape of growth curves, anomalous fading, thermal stability, etc. The results show that, for the loess samples examined, quartz OSL does not fade anomalously, and the barrier age of ～100 ka is due to the fact that the OSL signals are less thermally stable, the lifetime of 0.311 Ma at 20°C obtained is much smaller than those for quartz samples from other regions such as Australia (～100 Ma).     

用示踪气体法检测文物展柜换气率技术研究

摘要文物展柜为文物的展示和保存提供了一个相对独立的空间,展柜密封度的高低影响着展柜内微环境调控的效果。为评价文物展柜的密封度,用示踪气体法检测展柜换气率,从检测便捷、安全和实验数据可靠角度分析比较了二氧化碳和乙烯的实验结果。结果显示,两种示踪气体均可用于检测展柜的密封度。其中,二氧化碳气体检测法比较方便,但其密度较大,易于沉降,检测结果偏低。环境湿度对二氧化碳示踪气体法检测的结果有一定影响。应用二氧化碳示踪气体法测试了多种展柜的换气率表明,各展柜的密封度有较大差别,每天换气率从0.1次到37次不等。检测结果提示,二氧化碳示踪气体法为评价展柜的密封度提供了一个简便易行的方法。