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Abstract. We present the first systematic analysis for new particle formation (NPF), growth and shrinkage of new particles at four different sites in subtropical central Taiwan. A total of 14 NPF events were identified from 137 days of ambient measurements during a cold and warm season. The measured formation rates of 10 nm particles (J 10 ) and growth rates were in the range of 4.4-30 cm −3 s −1 and 7.4-24 nm h −1 , respectively. The onset of NPF events coincided with decreases of condensation sink (CS) and increases of SO 2 under enhanced atmospheric mixing and dilution. However, the lower or comparable SO 2 on event days than on non-event days suggests that SO 2 was not a limiting factor for NPF. On non-event days, the particle number concentrations were mostly driven by traffic emissions. We also observed shrinkage of new particles, the reversal of growth, during five out of the identified secondary formation. UFP particles events. In intense cases, the grown particles shrank back to the smallest measurable size of ∼ 10 nm, thereby creating a unique "arch-like" shape in the size distribution contour plot. The particle shrinkage rates ranged from −5.1 to −7.6 nm h −1 . The corresponding particle volume losses suggest that a notable fraction of the condensable species that contributed to growth was semi-volatile. The particle shrinkage was related to enhanced atmospheric dilution, high ambient temperature and low relative humidity, thus favoring the evaporation of semi-volatile species from the particulate phase to the gas phase. Our observations show that the new particle growth could be a reversible process, in which the evaporating semi-volatile species are important for the growth of new particles to sizes of environmental health concerns.

In this study, the aerosol optical properties and vertical distributions in major biomass-burning emission area of northern Indochina were investigated using ground-based remote sensing (i.e., four Sun-sky radiometers and one lidar) during the Seven South East Asian Studies/Biomass-burning Aerosols & Stratocumulus Environment: Lifecycles & Interactions Experiment conducted during spring 2014. Despite the high spatial variability of the aerosol optical depth (AOD; which at 500 nm ranged from 0.75 to 1.37 depending on the site), the temporal variation of the daily AOD demonstrated a consistent pattern among the observed sites, suggesting the presence of widespread smoke haze over the region. Smoke particles were characterized as small (Ångström exponent at 440-870 nm of 1.72 and fine mode fraction of 0.96), strongly absorbing (single-scattering albedo at 440 nm of 0.88), mixture of black and brown carbon particles (absorption Ångström exponent at 440-870 nm of 1.5) suspended within the planetary boundary layer (PBL). Smoke plumes driven by the PBL dynamics in the mountainous region reached as high as 5 km above sea level; these plumes subsequently spread out by westerly winds over northern Vietnam, southern China, and the neighboring South China Sea. Moreover, the analysis of diurnal variability of aerosol loading and optical properties as well as vertical profile in relation to PBL development, fire intensity, and aerosol mixing showed that various sites exhibited different variability based on meteorological conditions, fuel type, site elevation, and proximity to biomass-burning sources. These local factors influence the aerosol characteristics in the region and distinguish northern Indochina smoke from other biomass-burning regions in the world.

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Electrospray-differential mobility analysis coupled with aerosol particle mass analysis (ES-DMA/APM) was demonstrated for the development of a metal–organic framework (MOF) nanocarrier system. A successful quantification of ibuprofen loading in UiO-66-NH2 (i.e., the representative drug molecule and MOF, respectively) achieved based on the aerosol particle mass of MOF measured by ES-DMA/APM (≈55 mg of ibuprofen/g of UiO-66-NH2). The structural stability of UiO-66-NH2 versus ibuprofen release was successfully quantified over a 7-day period in an acidic phosphate buffer solution. The methodology provides a proof-of-concept scheme for controlled release studies of different types of active pharmaceutical ingredients from a variety of MOF-based nanocarrier systems.