Heavy Metal Accumulation in the Street Dust, Roadside Soil and Roadside Tree Leaves Near by Main Streets in Tokyo, Japan.

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Concentrations of Mn, Fe, Cu, Zn, Cd, Pt and Pb were determined in the street dust, roadside soil and roadside tree leaves collected from main streets in Tokyo in 1997. Heavy metal concentrations in street dust increased depending on traffic density. These results suggested that automobile traffic is one of the major sources of heavy metals around streets. High concentrations of Cu, Zn and Pb were found in roadside soil. Lead concentrations in our results were lower than those in some data measured about 20 years ago. This decrease trend might be attributable to regulation of tetraalkyllead use as antiknocking in gasoline. Heavy metal concentrations in the 5 species of roadside tree leaves collected from streets of Tokyo were 1 to 4 times higher than those from reference site, and varied with each species. The highest level of heavy metals was detected in Rhododendron oomurasaki. The lowest concentration was observed in Ginkgo biroba. Concentrations of Mn, Fe, Cd and Pb increased from June to September generally. It was expected that these metals were binding to leaves tissue tightly. Leaf texture and plant height of roadside trees should be responsible for the different dynamics of heavy metal levels among tree species.
日本環境化学会の論文