A PM_1.0/2.5/10 trichotomous virtual impactor based sampler: Design and applied to arid southwest aerosols part II: Application to arid southwest aerosols

A PM_1.0/2.5/10 Trichotomous sampler has been developed to determine if the particles in the saddle point between the coarse and fine particle modes (specifically the 1.0 μm to 2.5 μm size range) are primarily coarse or fine mode particles. The sampler consists of a standard high volume sampler with two high volume virtual impactors (one with a cut size of 2.5 μm and the other with a cut size of 1.0 μm) inserted between the PM₁₀ inlet and the 8 × 10 inch after filter. Filters in this sampler were analyzed with ion chromatography (IC) to determine SO₄ ^-2 concentrations, representing a specie primarily found in the fine mode aerosol and proton-induced X-ray emission (PIXE) for determining concentrations of Si, S, Ca and Fe, representing species normally found in coarse mode aerosols. Application of this sampler to Phoenix, AZ, representing an arid region, showed that particles in the saddle point consisted of about 75% of particles from the coarse mode and about 25% from the fine mode.