Historical trends of anthropogenic metals in Eastern Tibetan Plateau as reconstructed from alpine lake sediments over the last century

• Alpine lake sediments in the Eastern Tibetan Plateau reflected regional anthropogenic metal emissions.
• Anthropogenic metals appeared around 1950, significantly increased in the 1980s, and peaked in the mid-1990s.
• Over 80% of Cd, Pb and Zn were quantified from anthropogenic emissions in atmospheric deposition since the mid-1990s.
• Regional anthropogenic emissions are expected to continue for Cd and Zn, but decrease for Pb.

Reconstructing trace metal historical trends are essential for better understanding anthropogenic impact on remote alpine ecosystems. We present results from an alpine lake sediment from the Eastern Tibetan Plateau to decipher the accumulation history of cadmium (Cd), lead (Pb) and zinc (Zn) over last century, from the preindustrial to the modern period. Cd, Pb and Zn in the sediment of Caohaizi Lake clearly suffered from atmospheric deposition, and the mining and smelting were regarded as the main anthropogenic sources. Since the mid-1990s, over 80% of trace metals were quantified from anthropogenic emissions. The temporal trends of anthropogenic metal fluxes showed that the contamination history of Pb was earlier than that of Cd and Zn, which was in agreement with the regional Pb emission history, but lagged behind the Pb decline in Europe and North America. The fluxes of anthropogenic Cd and Zn were relatively constant until the 1980s, increased sharply between the 1980s and the mid-1990s, and then kept the high values. The anthropogenic fluxes of Pb showed a marked rise around 1950, and increased sharply in the 1980s. In the mid-1990s, this flux reached the peak, and then decreased gradually. The Pb deposition flux at present in comparison with other lake records in the areas of Tibetan Plateau further demonstrated that trace metals in the Caohaizi Lake region were probably from Southwest China and South Asia. Economic development in these regions still puts pressure on the remote alpine ecosystems, and thus the impact of trace metals merits more attention.