Using carbon-dated core sediments taken from Liangzhi Lake in Hubei province, Xiang-Dong Li and colleagues were able to track metal deposit trends at the lake dating back to 5,000 B. C. Liangzhi Lake, located in an important region in the development of Chinese civilization, is relatively undistributed by local wastewater discharges and is therefore an ideal site to study ecological changes and the effects of past human activity, the scientists say.
Beginning in about 3,000 B.C. concentrations of copper, nickel, lead and zinc in the sediments began to rise, indicating the onset of Bronze Age in ancient China, the researchers found. In the late Bronze Age (475 B.C. to 220 A.D.), an era corresponding with numerous wars, sediment concentrations of copper increased 36 percent and lead by 82 percent. Copper and lead were used extensively to make bronze tools and weapons. The sediments suggest mining and metal usage in the region continued to wax and wane into the modern era, reflecting the environmental changes influenced by past human activity. -American Chemical Society