Mt. Everest Ice Core Record of Atmospheric Cu, Zn, Cd, Pb, and Pb Isotopes Variations in Central Asia during the Past 800 Years

Abstract

Recent century scale time records for As, Mo, Sn, Sb, Bi, U, and Cs from Mt. Everest ice cores documented that a significant perturbation in the natural cycles of these elements took place during the second half of the 20th century due to increasing emissions of anthropogenic pollutants largely from fossil fuel combustion and non-ferrous metals production in central Asia. To evaluate to what extent human activities in central Asia have affected the natural atmospheric cycles of other heavy metals over time, Cu, Zn, Cd, and Pb concentrations and Pb isotopes were determined at 143 depth intervals from high-altitude Mt. Everest ice cores, covering an 800-year time period from 1205 to 2002 AD. This is the first reliable long-term time series of changes in the occurrence of Cu, Zn, Cd, and Pb and Pb isotopes in the remote Himalayan atmosphere. Our data show that these metals were primarily of natural origin up until the 1960s and significant increases in concentrations and crustal enrichment factors are observed from the 1970s onward. Such changes are attributed to massive emissions of anthropogenic Cu, Zn, Cd, and Pb from various anthropogenic sources in India. The Pb isotopic compositions provide clear evidence that anthropogenic Pb emitted from the use of leaded gasoline and coal combustion in India has affected the remote Himalayan atmosphere.