Heavy metal contents and magnetic properties of playground dust in Hong Kong.

This study examined the levels of seven heavy metals (namely zinc, copper, cadmium, chromium, lead, manganese and iron) and their associations with magnetic properties in playground dust of Hong Kong. Results showed that the playground dust contained high concentrations of Zn (mean = 1883 microg g(-1)), Cu (mean = 143 microg g(-1)) and Cr (mean = 263 microg g(-1)). Qualitative examination of dust samples under microscope indicated local traffic as one of the important pollutant sources. Magnetic measurements indicated that these anthropogenic pollutants mainly consisted of coarse-grained multidomain (MD) ferrimagnetic minerals. Superparamagnetic (SP), stable single domain (SSD) ferrimagnetic grains and non-ferrimagnetic minerals were present in relatively small amounts. Significant correlations between heavy metals and various magnetic parameters indicated a strong affinity of heavy metals to magnetic minerals hence pointed out the potential of magnetic properties for simple and rapid proxy indications of heavy metal pollution in playground dust.