Peat records of human impacts on the atmosphere in Northwest China during the late Neolithic and Bronze Ages

Man has played a major role in shaping the landscape in inland China during the second half of the Holocene. However, little is known about the impact on atmospheric environments. Here we present a high-resolution peat record of atmospheric variations in Northwest China, which covers the late Neolithic and Bronze Ages. Ten heavy metallic elements (Pb, Zn, Fe, Mn, Cu, Co, Ni, Ti, V, and Al) were analyzed, and the abundances of Cu, Pb, and Zn were found to be significantly above their background levels during some periods while intensified human activities occurred in the adjacent Gansu–Qinghai area. Modern meteorological observations and sedimentological analyses indicate that the element-bearing aerosol was transported by the strengthened northeast wind. Four elements (Ti, V, Co, and Ni) exhibit coherent variations with Pb prior to 5500 cal a B.P., and thus they were used to reconstruct the background level of Pb. The human-induced Pb signal correlates well with the population inferred from archaeological excavations in the Liuwan Tombs in Qinghai Province, suggesting that human activities may have a great impact on the atmospheric environment in this area.