Estimation of plutonium budget in August-one glacier of the Qilian Mountains, northeastern Tibetan Plateau
摘要
Under ongoing global warming, plutonium (Pu) stored in glaciers may be remobilized and released into downstream environments. However, the distribution patterns and mass balance of Pu in arid alpine glaciers of northwestern China remain poorly constrained. We present the first quantitative assessment of Pu budgets at the August-one ice cap located in the northeastern Qilian Mountains. Wet deposition was reconstructed using continuous Pu records from Tokyo in combination with regional precipitation data. The cumulative wet deposition of 239+240Pu at the August-one ice cap was estimated at (13 ± 1) Bq/m2, The inventory corresponds to a total atmospheric input of approximately (3.1 ± 0.2) × 107 Bq when scaled to the glacier area. Using three empirical area–volume scaling formulas, glacier volume loss between 1980 and 2023 was further reconstructed, and combined with measured Pu isotope concentrations in summer meltwater, the cumulative outflow was estimated at (1.3 ± 0.2) × 106 Bq, nearly an order of magnitude lower than the inferred atmospheric input. These results demonstrate that, despite pronounced glacier shrinkage over the past four decades, the August-one ice cap has acted as a persistent sink for Pu isotopes rather than a secondary source to downstream ecosystems. This study provides new insights into the environmental fate of Pu in cryospheric systems under ongoing climate change.