干旱区生态环境知识资源中心

Dating lake sediments in arid and semi-arid zones by using Cs-137 and excessive Pb-210 (21 Pb-ex) methods is challenging because of the irregular climatic variations and anthropogenic effects. Here we try to establish the reliable geochronology of the lacustrine core drilled from Lake Ailike (northern Xinjiang of China) by using Cs-137 and Pb-210(ex) dating methods and improve our understanding of the principal factors that affect the dating results. The results indicate that it is important to normalize the Cs-137 activities by particle size and organic matter in order to diminish their enrichment effects on Cs-137 activities and thus help us to obtain the accurate Cs-137 ages. The performance of the sediment isotope tomography (SIT) model is better than the other Pb-210(ex)-derived models. The erosion process results in the failure of the commonly used constant rate of supply (CRS) model, as well as the low values of the sedimentation rate, the Cs-137 inventory and the post-1963 mean annual flux of Pb-210(ex) in Ailike core. Furthermore, based on the SIT model chronology, we further clarify the lake evolution history of the past century and assess the anthropogenic impacts on Lake Ailike. The hydrology of Lake Ailike was mainly controlled by natural climate before 1960 CE whereas it was completely controlled by intensive human activities after 1960 CE. This study supports that the Pb-210(ex)-based SIT model appears to be an adequate method for deriving ages in the lacustrine systems with strong hydrological variability.