Southeastern Tibetan Plateau Glaciers Severely Contaminated by Lead Emissions from Indian Coal Combustion

Anthropogenic lead (Pb) is pervasive in alpine environments of the Tibetan Plateau (TP). Nevertheless, the source apportionment of deposited Pb within glacierized regions of the Southeastern Tibetan Plateau (SETP)─where glacier shrinkage is most severe across the entire TP─remain poorly quantified. To address this gap, this study integrates newly obtained Pb isotopic data from cryoconite samples with published data sets to elucidate the spatial distribution of Pb isotopic compositions and quantitatively reveal the origins of anthropogenic Pb deposited in the extensively SETP glaciers. The results show that Pb isotopic ratios range from 1.166 to 1.204 for ²⁰⁶Pb/²⁰⁷Pb and from 2.446 to 2.525 for ²⁰⁸Pb/²⁰⁷Pb, with large variability. Moreover, distinct spatial heterogeneity in the isotopic compositions is observed, with a decreasing trend along the longitudinal gradient. Source apportionment demonstrate that Indian coal combustion represents the primary source of Pb in SETP glaciers, accounting for 75.5%, with the strongest influence occurring at glaciers situated at valleys. At the plateau scale, Pb derived from Indian coal combustion exerts the greatest impact on this region, with its contribution decreasing from 75.5% to 21.3% along the south-north transect.