Paleofire indicated by polycyclic aromatic hydrocarbons in soil of Jinluojia archaeological site, Hubei, China

Abstract

Combustion-derived and land-plant-derived polycyclic aromatic hydrocarbons (PAHs) have been investigated by using the GC-MS analysis in an ancient soil profile from Jinluojia (金罗家) archaeological site at Macheng (麻城), Hubei (湖北) Province, Central China. Retene, cadalene and si- monellite were proposed to be derived from contemporary land plants. The pyrolytic PAHs identified include fluoranthene, pyrene, benzofluoranthenes, benzo(e)pyrene and benzo(a)pyrene. The distribu- tion of these pyrolytic PAHs varies with depth, displaying a pattern different from the land-plant-derived compounds. On the basis of the parameter diagnostic of sources and the distribution patterns, these pyrolytic PAHs were demonstrated to be of combustion origin, rather than petrogenic origins, combustion of petroleum products and coal, or a post-depositional process such as pedogenesis or leaching. These combustion-induced PAHs were believed to result from both natural processes and anthropogenic activities. Two episodes of the elevated content of pyrolytic PAHs and charcoal frag- ments were identified in Ming-Qing (明清) Dynasty and late Xizhou (西周) to early Dongzhou (东周) Dynasty, inferring the occurrence of two enhanced paleofires. The two enhanced paleofire episodes were found in association with the two cold and dry paleoclimate and two episodes of enhanced abun- dance of charcoal fragments, inferring a dominance of the natural processes triggering the enhanced