• Asian Journal of Atmospheric Environment
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• 제11권4호
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• pp.300-312
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• 2017

To improve the understanding of secondary organic aerosol (SOA) formation from the photo-oxidation of anthropogenic and biogenic precursors at the regional background station on Baengnyeong Island, Korea, gas phase and aerosol chemistries were investigated using the Proton Transfer Reaction Time of Flight Mass Spectrometer (PTR-ToF-MS) and the Aerodyne High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS), respectively. HR-ToF-AMS measured fine particles ($PM_1$; diameter of particle matter less than $1{\mu}m$) at a 6-minute time resolution from February to November 2012, while PTR-ToF-MS was deployed during an intensive period from September 21 to 29, 2012. The one-minute time-resolution and high mass resolution (up to $4000m{\Delta}m^{-1}$) data from the PTR-ToF-MS provided the basis for calculations of the concentrations of anthropogenic and biogenic volatile organic compounds (BVOCs) including oxygenated VOCs (OVOCs). The dominant BVOCs from the site are isoprene (0.23 ppb), dimethyl sulphide (DMS, 0.20 ppb), and monoterpenes (0.38 ppb). Toluene (0.45 ppb) and benzene (0.32 ppb) accounted for the majority of anthropogenic VOCs (AVOCs). OVOCs including acetone (3.98 ppb), acetaldehyde (2.67 ppb), acetic acid (1.68 ppb), and formic acid (2.24 ppb) were measured. The OVOCs comprise approximately 75% of total measured VOCs, suggesting the occurrence of strong oxidation processes and/or long-range transported at the site. A strong photochemical aging and oxidation of the atmospheric pollutants were also observed in aerosol measured by HR-ToF-AMS, whereby a high $f_{44}:f_{43}$ value is shown for organic aerosols (OAs); however, relatively low $f_{44}:f_{43}$ values were observed when high concentrations of BVOCs and AVOCs were available, providing evidence of the formation of SOA from VOC precursors at the site. Overall, the results of this study revealed several different SOA formation mechanisms, and new particle formation and particle growth events were identified using the powerful tools scanning mobility particle sizer (SMPS), PTR-ToF-MS, and HR-ToF-AMS.

• 농촌계획
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• 제19권4호
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• pp.137-147
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• 2013

Most of livestock houses are concentrated in certain area with mass rearing system resulting in rapid spread of infectious diseases such as HPAI (highly pathogenic avian influenza). The livestock-related vehicles which frequently travel between farms could be a major factor for disease spread by means of transmission of airborne aerosol including pathogens. This study was focused on the quantitative measurement of aerosol concentration by field experiment while vehicles were passing through the road. The TSP (total suspended particle) and PM10 (particle matter) were measured using air sampler with teflon filter installed downward the road with consideration of weather forecast and the direction of road. And aerosol spectrometer and video recorders were also used to measure the real-time distribution of aerosol concentration by its size. The results showed that PM2.5 was not considerable for transmission of airborne aerosol from the livestock-related vehicle. The mass generated from the road during the vehicle movement was measured and calculated to 241.4 ${\mu}g/m^3$ by means of the difference between TSP and PM2.5. The dispersion distance was predicted by 79.6 m from the trend curve.

• 한국입자에어로졸학회지
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• 제14권4호
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• pp.145-151
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• 2018

Rod shaped Potassium hexatitanate ($K_2Ti_6O_{13}$) was synthesized from colloidal mixture of $TiO_2$, KOH and graphene oxide (GO) by aerosol spray drying and post heat treatment. Firstly, $TiO_2-KOH-GO$ composites were fabricated by aerosol spray drying in argon atmosphere. The composites were then calcined to form a rod shaped morphology of potassium titanate (KTO) in the presence of graphene at $900^{\circ}C$ for 3 h in argon atmosphere. Finally, the rod shaped KTO was obtained after removal of graphene (GR) at $800^{\circ}C$ and 3 h in air atmosphere. Characterization of the synthesized $K_2Ti_6O_{13}$ was carried out using the XRD, BET and FE-SEM. The length and diameter of the synthesized $K_2Ti_6O_{13}$ could be controlled by weight fraction of GO in the aerosol precursor. The length of $K_2Ti_6O_{13}$ rod increased with decreasing its diameter as GO concentration increased. The aspect ratio of the synthesized $K_2Ti_6O_{13}$ rod was controlled from 5 to 13.

• 한국입자에어로졸학회지
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• 제9권4호
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• pp.209-219
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• 2013

We have used the modified diffusion flame burner to synthesize silica coated iron oxide nanoparticles having enhanced superparamagnetic property. Silica-encapsulated iron oxide particles were directly observed using a high resolution transmission electron microscope. From the energy dispersive X-ray spectroscopy (EDS) and zeta potential measurements, the iron oxide particles were found to be completely covered by a silica coating layer. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) measurements revealed that the iron oxide core consists of ${\gamma}-Fe_2O_3$ rather than ${\alpha}-Fe_2O_3$. Our magnetization measurements support this conclusion. Biocompatibility test of the silica-coated iron oxide nanoparticles is also conducted using the protein adsorption onto the coated particle.

• 한국대기환경학회지
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• 제18권5호
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• pp.345-353
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• 2002

A study of polydispersed aerosol dynamics by Electrostatic Precipitator (ESP) was carried out. The log-normal particle size distribution was assumed and moment method was considered. In order to apply moment method in Deutsch-Anderson equation, Cunningham slip correction factor and Cochet's charge equation were simplified for certain range of particle size. The three parameters, which explain the particle size distribution, such as total number concentration, geometric mean diameter, and geometric standard deviation were considered to derive the analytic solution. The obtained solution was compared with available numerical results (Bai et al., 1995). The comparison of the numerical and analytic results showed a good agreement.

• 한국입자에어로졸학회지
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• 제10권3호
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• pp.93-97
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• 2014

Condensation particle counter (CPC) has been one of the most important basic instrument for measuring number concentration of submicron aerosols. The principle of the CPC is to expose aerosols to a supersaturated vapor and cool down which causes adiabatic expansion. The particles grow by heterogenous nucleation to a sufficient size for easy detection by optical method. However, for growth by condensation, CPC essentially needs both saturater and condensor causing a heavy system. Therefore, it is hard to install commercial CPC to tethered balloon package system. In this study, we developed customized CPC for tethered balloon package system called Hy-CPC which is lighter and smaller in structure than commercial CPCs, and evaluated activation efficiency and detection efficiency by Hy-CPC using electrostatic method (electrometer and Faraday cup).

• 한국입자에어로졸학회지
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• 제8권1호
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• pp.1-8
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• 2012

In this study, the collection efficiency of inertial impactors was numerically simulated by employing the statistical Lagrangian particle tracking(SLPT) model. The SLPT model was proven to be correct in predicting the impactor collection efficiency, when the numerically obtained collection efficiencies were compared with the experimental data of Marple et al.(1987) at normal pressure level and the experimental data of $Marjam{\ddot{a}}ki$ et al.(2000) at low pressure level. Based on the validation results, balloon-borne impactors with the cut-off sizes of $1{\mu}m$, $2.5{\mu}m$, and $10{\mu}m$ were designed. Then, the sampling flowrates of the inertial impactors, required to keep the cut-off sizes constant at different pressures and temperatures, were estimated according to the altitude.

• 한국입자에어로졸학회지
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• 제11권2호
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• pp.37-46
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• 2015

Dust particles, which inflow to the subway mechanical ventilation and air conditioning(MVAC) chamber, contain a fair amount of iron compounds, approximately 25.2w/w%. This work attempted to capture those iron containing dust using magnetic filters. Average magnetization value of the test MVAC dust was 0.012 emu on 5,000 Oe, which could correspond sufficiently with the magnetic interaction. External permanent magnets provided with magnetization of iron mesh screen showing high gradient magnetic field(HGM). It resulted in the capture efficiency with 84.0 ~ 99.7% and 81.2 ~ 99.8% for $PM_{10}$ and $PM_{2.5}$ respectively. Magnetic capture was found to be closely associated with the magnetic intensity, mesh opening size and flow velocity.

• 한국세라믹학회지
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• 제32권11호
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• pp.1246-1254
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• 1995

A numerical model for fabrication and deposition of ultrafine SiO2 particles were proposed in the simplified horizontal MCVD apparatus using tube furnace reactor. The model equations such as energy and mass balance equations and the 0th, 1st and 2nd moment balance equations of aerosols were considered in the reactor. The phenomena of SiCl4 chemical reaction, SiO2 particle formation and coagulation, diffusion and thermophoresis of SiO2 particles were included in the aerosol dynamic equation. The profiles of gas temperature, SiCl4 concentration and SiO2 particle volume were calculated for standard conditions. The concentrations, sizes and deposition efficiencies of SiO2 particles were calculated, changing the process conditions such as tube furnace setting temperature, total gas flow rate and inlet SiCl4 concentration.

• 한국입자에어로졸학회지
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• 제10권1호
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• pp.33-43
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• 2014

A differential mobility analyzer (DMA) has been widely used as a standard tool for classifying nanoparticles with a certain size. More recently, several new types of DMA have been tested in an attempt to produce size-monodisperse nanoparticles. It is a bit surprise to see how simple the working theory of the DMA is. Although the theory was demonstrated quite successful, no one can guarantee whether the theory still works in another geometry of the DMA. In this regard, we first investigated the validity of the theory under various working conditions and then moved to check the validity upon minor change in its design. For the valid test, we compared the results with those obtained from a computational fluid dynamics.