Endogenous and exogenous lead in soils of Yangtze River Delta region, China: identified by lead isotopic compositions and multi-elemental approaches

Thirty typical soil profiles were sampled in Yangtze River Delta (YRD) region and analyzed for stable lead (Pb) isotopes and total concentrations of Pb and scandium (Sc). Pb isotopic compositions of A-horizon and C-horizon and Pb/Sc ratio were combined to estimate the amounts of endogenous and exogenous Pb accumulated in topsoil and identify possible sources. The results indicated that Pb exhibits a trend of accumulation in topsoil at regional scale. The isotopic composition of endogenous Pb is characterized by a narrow range of isotope ratios, varying with parent material, while that of exogenous Pb is characterized by a comparatively wide range of isotope ratios, varying with anthropogenic source. Coal combustion is probably the most important anthropogenic source of exogenous Pb in the soils of YRD region, as identified by isotopic ratio cross-plot combined with multi-elemental approaches.