Reflectance of street dusts: Are darker dusts more polluted?

摘要

The reflectance of 39 street dust samples collected from playgrounds around Hong Kong have been measured to determine if there is a direct connection between the colour of street dust and extent of contamination. Digital imagings of the samples were undertaken using the GEOTEK imaging system. The spectral components-red (R), green (G), and blue (B) -of the samples were determined along with the absolute intensity. The results were compared to heavy metal abundances and magnetic properties already described by Ng et al. (2003). The reported data include concentrations of Cd, Cu, Mn, Pb, Zn, Fe and Cr, organic carbon content, and magnetic parameters Klf, Khf, SIRM, ARM, and the derived ratios SIRM/Klf and SIRM/ARM. Statistical analyses including Pearson correlation and factor analyses of the data reveal the lack of any association between the colour of street dusts and their magnetic properties or heavy metal abundances. Only the spectral components of the sample, in particular, the green and blue spectral intensities, show a weak correlation with organic carbon content, as well as Zn and Cu concentrations. In general, dust samples with a greater Zn and Cu concentration are darker. This study concludes that the colour of road dust cannot be regarded as an accurate indication of how polluted is the sample.