Spatiotemporal trends in lead pollution worldwide over the past millennium

Reconstructing spatiotemporal trends in Pb pollution history is important for understanding global Pb cycling, controlling Pb pollution, and allowing assessment of the extent and timing of human impacts on environments. In this study, the high-resolution heavy-metals (Pb, Zn, Cd, Cu, Co, and Ti) pollution history over the past millennium was reconstructed based on sedimentary records from Lake Chenghai in Southwestern China, and the possible origins of Pb and its relationship with global Pb records were revealed. The marked high Pb concentrations occurred during the Medieval period (1200s–1400s), and enrichment factor analysis suggested that the high pollution degrees during the Medieval period were derived primarily from the anthropogenic sources of mining activity. Furthermore, our compilation records worldwide showed that Pb pollution level in most areas of China during the Medieval period is the same as or even higher than present, while in the other regions such as America and Europe, modern-day Pb pollution level is significantly higher than that in the Medieval period. In the past two centuries, Pb concentration rapidly increased again since the 1980s in China, coinciding with China's reform and opening up that spawned social economic transformation and rapid industrial economic growth, while in America and Europe, it rapidly increased in the 1950s and then declined in the 1980s, coinciding with the impacts of industrial revolution on developed regions. Those records imply Pb could be regards as the regional human activity intensity index during the Anthropocene. This study could provide insight into the onset timing of anthropogenic impacts in different areas and also provide scientific supports for Pb pollution control.