Lake Sediment Archive Reveals a Distinct Response to Anthropogenic Pb and Zn Deposition with Historical Periods: Pb–Zn Isotope Evidence

Abstract

Anthropogenic activities release large quantities of heavy metals into the atmosphere. In China, the input of these heavy metals through local and trans-boundary atmospheric deposition is poorly understood. To assess this issue, herein, we use Pb and Zn isotopes to constrain the sources of Pb and Zn in a ²¹⁰Pb-dated sediment core collected from the enclosed lake in South China. We observed a progressive shift toward higher ²⁰⁸Pb/²⁰⁶Pb and Pb fluxes (0.79-4.02 μg·cm^-2·a^-1) from 1850 to 1950 and a consistent decrease in δ⁶⁶Zn_IRMM (as low as -0.097 ± 0.030‰) coupled with an increase in Pb (1.74-3.36 μg·cm^-2·a^-1) and Zn (8.07-10.44 μg·cm^-2·a^-1) fluxes after 1980. These distinguished isotopic signals and flux variations reveal the presence of trans-boundary Pb since 1900, with the addition of local industrial Pb and Zn pollution after 1980. Up to 72.3% of Pb deposited at our site can be attributed to long-distance transportation from previously industrialized countries, resulting in a noteworthy legacy of Pb in China since 1900. Despite the phasing out of leaded gasoline, Chinese gasoline still contributes an average of 20.9%. The contribution of China's mining and smelting activities to Pb has increased steadily since 1980 and remained stable at an average of 25.1% since 2000.