Soluble Trace Metals and Major Ionic Species in the Bulk Deposition and Atmosphere of Hong Kong

Diurnal bulk deposition samples werecollected in an urban residential area in Hong Kongfrom 1996 to 1997, and were analyzed for major anionicand cationic species. The rapid Kuderna-Danish vacuumconcentration technique was adapted to preconcentratethe soluble components of rainwater samples prior tothe analysis of 7 trace metal species by GFAAS.Percentage recoveries in the range 80–115% wereobtained for the trace metals, without the addition ofany modifier. The results showed the importance ofbelow-cloud washout since the removal of the tracemetals from the atmosphere by precipitation dependedupon the rainfall pH and amount. Bulk depositionfluxes of the soluble trace metals are generallycomparable with literature values for (total) Al, Cu,Mn, V and Fe, but are much smaller for Cd and Pb. Acomparison of bulk deposition concentrations withsoluble and insoluble ambient particulate matterconcentrations in Hong Kong has also been made.Several occasions of low rainfall amount, smallrainfall intensity, and low windspeed, produced highconcentrations of trace metals in bulk deposition in1996, coinciding with pH values down to 3.6.