Quantitative spatiotemporal evolution of deposited lead sources in Tibetan Plateau glaciers: Insights from lead...

Lead (Pb), owing to its high toxicity and low-level environmental exposure, is internationally regulated. Nevertheless, anthropogenic Pb signals have been detected in remote glaciers of the Tibetan Plateau (TP). In this review, we compile available Pb isotope data (n = 439) from multiple glacial archives (ice cores, snowpits, cryoconite, and precipitation) and employ the concentration-dependent MixSIAR isotope mixing model to quantitatively reconstruct the spatiotemporal evolution of Pb sources in TP glaciers. First, the multiple media distribution and spatiotemporal patterns of Pb isotopes are qualitatively summarized. Lead isotopic compositions in ice cores and snowpits show relatively clustered distributions, whereas precipitation yields a more dispersed isotopic pattern. Glacier records reveal systematic spatiotemporal isotopic variability, characterized by a temporal shift toward less radiogenic signatures and a spatial increase along a north-south transect. Second, to better contextualize Pb isotopic signatures in TP glaciers from a global perspective, we compare them with records from polar regions and lowland emission hotspots worldwide, revealing more radiogenic signatures in TP glaciers. Finally, using concentration-dependent MixSIAR model, we quantitatively reconstruct the evolution of Pb sources across spatiotemporal dimensions. Quantitative analysis from the East Rongbuk ice core reveals that the contribution of anthropogenic sources to ice core Pb increased from 10.7% to 46.8%. Snowpit source apportionment likewise reveals a stronger anthropogenic Pb influence (estimate of 59.6%-81.4%) across the plateau, with Indian coal combustion contributing most prominently and showing a distinct south to north attenuation. Through data integration, this review provides a quantitative understanding of anthropogenic Pb intrusion into the plateau.