Provenance of Aeolian Dust Revealed by (²³⁴U/²³⁸U) Activity Ratios in Cryoconites From High‐Altitude Glaciers in Western China and Its Transport and Settlement Mechanisms

Abstract

Asian dust has significant impacts on atmospheric systems and global biogeochemical cycles. In this study, we applied the U isotopic method to trace sediments based on their comminuting age, analyzing the uranium isotopes of cryoconite samples from various glaciers in western China, including the Tibetan Plateau (TP) and Tianshan Mountains. We aimed to explore the spatial variability of (234U/238U) activity ratio and residence time, as well as the transport mechanism of dust cycle in the region. Additionally, we used Nd‐Sr isotopes data from our previous work to jointly determine the provenance. Our results indicate that the average (234U/238U) activity ratios in southern TP glaciers are higher, with mean range of 0.981‐0.993, while those in northeastern TP locations are lower, with mean of 0.974. This suggests a decreasing trend from south to north. In the Tianshan region, the (234U/238U) activity ratio is higher in central areas compared to eastern areas, with a mean range of 0.984‐0.996, indicating a decreasing trend from west to east. U‐Sr‐Nd isotopes analysis showed that dust provenance is from multiple sources, including long‐range transported and local dust inputs from the glacier basins, mainly originating from the TP surface and central Asian arid regions. Using the End‐member mixing model analysis and meteorological data, we confirmed that the cryoconite dust in eastern Tianshan and Qilian Mountains comes from a complex mixture of the southern Gobi, northern TP surface dust, and Taklimakan and Alxa arid deserts. In contrast, the glacial dust in southern TP locations originates mainly from the plateau surface dust. Our findings suggest that the uranium isotopes in high‐altitude glaciers are primarily influenced by the origins of dust, which are affected by related atmospheric circulation. We also developed a conceptual model to illustrate the complete process of U isotopic fragmentation and migration changes during dust production, transport, and deposition in the Tibetan Plateau region.

Uranium Isotope Constraints on the Pre‐Deposition Time of Asian Dust to the North Pacific Ocean: Implications for Provenance and Iron Supply

“…Yet, evidence based on electron spin resonance and quartz crystallinity, trace element and Sr‐Nd isotopes, have identified that other deserts such as the Mongolian Gobi Desert and Ordos Desert as significant dust sources (Nagashima et al., 2007; W. Wang et al., 2019; Xu et al., 2018). These disparities arise mainly because the potential source regions in the Asian interior often have overlapping geochemical characteristics (Che & Li, 2013; Chen et al., 2007; Dong et al., 2020; Jiao et al., 2023; Wei et al., 2021), resulting in the difficulty to differentiate using conventional geochemical tracers. Additionally, Pacific sediments contain volcanic ash, which introduces interference and obscures geochemical signatures.…”

“…Wang et al, 2019;Xu et al, 2018). These disparities arise mainly because the potential source regions in the Asian interior often have overlapping geochemical characteristics (Che & Li, 2013;Chen et al, 2007;Dong et al, 2020;Jiao et al, 2023;Wei et al, 2021), resulting in the difficulty to differentiate using conventional geochemical tracers. Additionally, Pacific sediments contain volcanic ash, which introduces interference and obscures geochemical signatures.…”