Abstract. Effective density is a crucial parameter used to predict
the transport behaviour and fate of particles in the atmosphere, and to
measure instruments used ultimately in the human respiratory tract
(Ristimäki et al., 2002). The aerosol particle mass analyser (APM) was
first proposed by Ehara et al. (1996) and is used to determine the effective
density of aerosol particles. A compact design (Kanomax APM-3601) was
subsequently developed by Tajima et al. (2013). Recently, a growing number
of field studies have reported application of the APM, and experimental
schemes using the differential mobility analyser alongside the APM have been
adopted extensively. However, environmental conditions such as ambient
pressure and temperature vary with the experimental location, and this could
affect the performance of the APM. Gas viscosity and Cunningham slip factors
are parameters associated with temperature and pressure and are included in
the APM's classification performance parameter: λ. In this study,
the effects of temperature and pressure were analysed through theoretical
calculation, and the influence of varying carrier gas was experimentally
evaluated. The transfer function and APM operational region were further
calculated and discussed to examine their applicability. Based on the
theoretical analysis of the APM's operational region, the mass detection
limits are changed with the properties of carrier gases under a chosen
λ value. Moreover, the detection limit can be lowered when the
pressure is reduced, which implies that performance may be affected during
field study. In experimental evaluation, air, oxygen, and carbon dioxide
were selected to atomize aerosols in the laboratory with the aim of
evaluating the effect of gas viscosity on the APM's performance. Using
monodisperse polystyrene latex (PSL) spheres with nominal diameters of 50
and 100 nm, the classification performance of the APM was slightly varied
with carrier gases, while the classification accuracy was consistently
within 10 %.
Determination of Particle Effective Density in Urban Environments with a Differential Mobility Analyzer and Aerosol Particle Mass Analyzer