Elevated levels of lead and other metals in roadside soil and grass and their use to monitor aerial metal depositions in Hong Kong

The Pb, Cu, Zn, Fe, Mn and Cd contents in roadside soils and grass from 36 sites on the Island of Hong Kong were determined by atomic absorption spectrometry. Results showed that both soil and grass contained elevated levels of the metals studied. Linear regression analysis between the logarithmic concentration of the metals in the samples and the logarithmic traffic volume of the sites revealed that, apart from Cd in soil, the two were strongly related (variance ratios' P values <0.001), thus indicating that the motor vehicle forms a major source of these metals in the roadside. The regional distribution of Pb and Cu in roadside soil and grass (presented in maps herein) shows high levels of contamination occurring mainly in the highly urbanised northern part of the Island where most of the traffic is concentrated. Apparently, both soil and grass could be utilised to reflect the extent of aerial deposition of metals in the roadside.