210Pbex in lacustrine sediments: A half-century global synthesis (1977-2024)

Unsupported 210 Pb ( 210 Pb ex ) is a naturally occurring radionuclide widely used to establish sediment chronologies spanning the past ∼150 years, thereby providing high-resolution temporal frameworks for palaeolimnological reconstructions. Since the late 1970s, numerous hypotheses have been advanced to explain the environmental and climatic controls on 210 Pb ex deposition in lakes, yet no comprehensive synthesis of the accumulated empirical evidence is available. Here, we compile a global database of 210 Pb measurements from 670 lacustrine sediment cores from studies published between 1977 and 2024 CE, encompassing 530 lakes across 61 countries and all continents except Antarctica. Before 2000 CE, approximately 85% of the sediment cores studied were located in the Northern Hemisphere. This proportion declined to 45% after 2000, reflecting a geographic expansion of 210 Pb-based chronologies use toward the Southern Hemisphere. Using this dataset, we first assess the bivariate relationships between the 210 Pb ex surface activities, depositional fluxes, inventories, and individual environmental covariates, such as mean annual precipitation, land/ocean ratio, latitude and elevation. We then apply ordinary least squares multiple linear regression (OLS) and random forest (RF) models to rank the drivers of spatial variability in 210 Pb ex deposition at the global scale. The RF models outperform the OLS; the surface activity, flux and inventory models have low to high explanatory power for interpretation (R 2 = 0.21, 0.35 and 0.66, respectively). SHapley Additive exPlanations (SHAP) indicate that elevation is the dominant predictor of both fluxes and inventories, followed by latitude and mean annual precipitation. These findings demonstrate that large-scale atmospheric processes primarily govern global patterns of lacustrine 210 Pb ex deposition. This study provides the first quantitative, data-driven global assessment of the environmental controls on lacustrine 210 Pb deposition, enhancing the robustness and comparability of 210 Pb-based chronologies worldwide.