N. Takegawa

Current situation of atmospheric nanoparticles in Fukue Island, Japan

Abstract Emissions of polluted air in East Asia have gradually decreased over the last decade. Those air pollutants have been transported over long distances and influenced new particle formation (NPF) in the downstream region. We obtained 5-year data of the mobility size distribution and SO2 and particulate (PM2.5) emissions on Fukue Island (32.75°N, 128.68°E), Japan. Frequent NPF events in the 2013 campaign were observed around 60% under the transboundary transport of polluted air by northwesterly wind. In contrast to the data obtained in the last 2-year campaign (2016–2017), these NPF events (<25%) may reflect a relatively clean environment. The daily average SO2 and PM2.5 concentrations over the campaign periods are 2.3 ± 2.2 ppb and 17.6 ± 8.5 µg·m−3 (February 23 to March 7, 2013), 1.3 ± 0.9 ppb and 13.8 ± 4.7 µg·m−3 (February 27 to March 18, 2015), 0.8 ± 0.5 ppb and 14.7 ± 5.3 µg·m−3 (February 27 to March 25, 2016), and 0.5 ± 0.5 ppb and 12.1 ± 4.6 µg·m−3 (January 28 to April 19, 2017), respectively. These reductions of emissions may be due to the measures implemented by the local government in the source region to handle the adverse impacts of environmental pollution. The latest condition of atmospheric nanoparticles on Fukue Island can be used as an indicator to determine the concentration levels of regional air pollutants in East Asia.

Calibration of a particle mass spectrometer using polydispersed aerosol particles

Abstract Routine calibrations of online aerosol chemical composition analyzers are important for assessing data quality during field measurements. The combination of a differential mobility analyzer (DMA) and condensation particle counter (CPC) is a reliable, conventional method for calibrations. However, some logistical issues arise, including the use of radioactive material, quality control, and deployment costs. Herein, we propose a new, simple calibration method for a particle mass spectrometer using polydispersed aerosol particles combined with an optical particle sizer. We used a laser-induced incandescence–mass spectrometric analyzer (LII-MS) to test the new method. Polydispersed aerosol particles of selected chemical compounds (ammonium sulfate and potassium nitrate) were generated by an aerosol atomizer. The LII section was used as an optical particle sizer for measuring number/volume size distributions of polydispersed aerosol particles. The calibration of the MS section was performed based on the mass concentrations of polydispersed aerosol particles estimated from the integration of the volume size distributions. The accuracy of the particle sizing for each compound is a key issue and was evaluated by measuring optical pulse height distributions for monodispersed ammonium sulfate and potassium nitrate particles as well as polystyrene latex particles. A comparison of the proposed method with the conventional DMA-CPC method and its potential uncertainties are discussed. Copyright

Modification and laboratory evaluation of a TSI ultrafine condensation particle counter (Model 3776) for airborne measurements

ABSTRACT A butanol-type ultrafine condensation particle counter (UCPC, Model 3776, TSI, Inc., Shoreview, MN, USA), which can achieve a 50% detection efficiency diameter (d50) of 2.5 nm using a capillary-sheath structure, was modified and tested in the laboratory for airborne measurements. The aerosol flow rate through the capillary is a key factor affecting the quantification of aerosol particle number concentrations. A pressure-dependent correction factor for the aerosol flow rate was determined using a newly added mass flow meter for the sheath flow and the external calibration system. The effect of particle coincidence in the optical sensing volume was evaluated using an aerosol electrometer (AE, Model 3068B, TSI, Inc.) as a reference. An additional correction factor for the coincidence effect was derived to improve the quantification accuracy at higher concentrations. The particle detection efficiency relative to the AE was measured for mobility diameters of 3.1–50 nm and inlet absolute pressures of 101–40 kPa. The pressure dependence of the d50 value, asymptotic detection efficiency, and shape of the particle detection efficiency curve is discussed, along with simple theoretical calculations for the diffusion loss of particles and the butanol saturation ratio in the condenser.