Heavy metal pollution in Ancient Nara, Japan, during the eighth century

Takashi Okai,Gen Shimoda,Kyoko Yamaoka,Shusuke Yamashita,Hodaka Kawahata,Noboru Imai

doi:10.1186/2197-4284-1-15

Abstract

We quantitatively investigated the eighth century heavy metal pollution in Heijo-kyo (Ancient Nara), the first large, international city of Japan. In this metropolis, mercury, copper, and lead levels in soil were increased by urban activity and by the construction of the Great Buddha statue, Nara Daibutsu. Mercury and copper pollution associated with the construction of the statue was particularly high in the immediate vicinity of the statue, but markedly lower in the wider city environment. We therefore reject the hypothesis that extensive mercury pollution associated with the construction of the Nara Daibutsu made it necessary to abandon Ancient Nara, even though severe lead pollution was detected at several sites. The isotopic composition of the lead indicated that it originated mainly from the Naganobori mine in Yamaguchi, which was a major source of the copper for the Nara Daibutsu.

Highlights

Human civilizations are physical spheres of human activity on earth
We evaluate the effect of urban activity on ancient metal pollution and discuss the environmental effects associated with the construction of the Nara Daibutsu
Blue-gray silt Samples 1-A, 1-B Dark gray gravel (Middle 8th century) in order to evaluate the levels of pollution in the early stages of urban activity: the soil layers here corresponded to the foundation of Ancient Nara in the early eighth century, and iron blacksmiths are considered to have operated around the corner in the early eighth century (Nara National Research Institute for Cultural Properties 2012a, b; personal communication, Dr Jinno)

Summary

Background

Human civilizations are physical spheres of human activity on earth. This human activity is typically associated with pollution, which results in environments becoming dangerous to live in, or in which chemical substances or energy may become limited (Matsui 2007). Sample Hg ppb Cu ppm Pb ppm Fe ppm Mn ppm Co ppm Ni ppm Zn ppm 208Pb/206Pb 207Pb/206Pb. in order to evaluate the levels of pollution in the early stages of urban activity: the soil layers here corresponded to the foundation of Ancient Nara in the early eighth century, and iron blacksmiths are considered to have operated around the corner in the early eighth century (Nara National Research Institute for Cultural Properties 2012a, b; personal communication, Dr Jinno). Ten soil samples were collected from a ditch along Suzaku Boulevard, which was an extension of the central avenue, supervised by Dr Kinoshita and other archeologists working for the Archaeological Institute of Kashihara in Nara Prefecture Three of these samples were selected for the analysis of sewage and to determine the level of background pollution in the ancient city.

Findings

Discussion and evaluation

Conclusions