Abstract
For the evaluation of density distribution patterns of trace metallic compounds in the atmosphere, the fractions of atmospheric aerosols obtained by the heavy-liquid separation method with a series of dichloromethanemethylene iodide mixtures were subjected to elemental analysis for Zn, Fe, Mn, Cu and so forth using inductively coupled plasma-atomic emission spectrometry. The aerosol samples involve urban dust collected from air-inlet filters of air conditioning system, suspended particulate matter collected on polystyrene filters using a concentional high-volume sampler, a Japanese standard low-volume sampler and an Andersen size-fractionating sampler, and dustfall collected in a dust jar.
Concentration profiles as a function of density appreciably differ one another among these samples. Metallic compounds with the density lower than 2.3g/cm3 predominate in suspended particulate matter. On the other band, metallic compounds in dustfall are mainly associated with aerosols of high density (>3.3g/cm3). The density distribution curves also have the maxima at the density of 2.7g/cm3 which corresponds to the density of wind-blown silica. Differences in the density distributions of metallic compounds are also evident among the aerosols collected separatively in the size ranges 0.06-0.43, 0.43-1.1, 1.1-3.3, 3.3-11 and 11-33μm effective aerodynamic diameter at unit density. Aerosols with lower density tend to be collected on the higher stage of the Andersen sampler. For example, the concentration of Fe aerosols collected on stage 1 (11-30μm fraction) goes through a maximum at the density of 2.5g/cm3 and another small maximum at the density of >3.3g/cm3, while low-density Fe aerosols with the density of 1.7g/cm3 are predominant in the 0.06-0.43μm fraction.
