Polycyclic aromatic hydrocarbons in leaves of Cinnamomum camphora along the urban-rural gradient of a megacity: Distribution varies in concentration and potential toxicity

Abstract

Rapid urbanization and industrialization have precipitated the significant urban-rural gradient involving various aspects of human-related activities especially in megacities. Anthropogenic activities are the main source of polycyclic aromatic hydrocarbon (PAH) contamination, and the rising awareness concerning PAH potential toxicity to human health promotes a further understanding of its spatial distribution pattern in cities. Whether the distribution of PAH concentration and potential toxicity respond to the urban-rural gradient still requires investigation. This study applied a grid sampling method to investigate PAH concentration using Cinnamomum camphora leaves as bioindicators which were obtained from 84 sampling sites in a megacity, Shanghai. The potential toxicity of PAHs in leaves was calculated by toxicity factor equivalent method. Results revealed the patterns of PAH distribution in the city varied in concentration and potential toxicity: the total concentration of PAHs in leaves decreased along the urban-rural gradient, while the potential toxicity peaked at junction areas. The trend of PAH concentration along the distance from urban center corresponded to that of population density. The spatial distribution of potential toxicity did not correspond with the gradient but was influenced by high benzo(a)pyrene concentration originated from the industry districts nearby. Higher potential toxicity of PAHs was observed at the urban-suburban-rural junction areas of megacities, advocating health-risk attention and appropriate plan for land use of these transition areas in cities.

Keywords: Bioindicator; Industrial district; Junction area; Polycyclic aromatic hydrocarbons; Population density; Potential toxicity.