Showing papers by "Yutaka Matsumi published in 2016"
TL;DR: In this article, the average enhancement factor of BC light absorption due to coating was estimated by comparing absorption coefficients at 781 nm for particles that with and without passing through a thermodenuder (TD) maintained at 300 or 400°C or a bypass line maintained at room temperature (25 °C).
Abstract: . The coating of black carbon (BC) with inorganic salts and organic compounds can enhance the magnitude of light absorption by BC. To elucidate the enhancement of light absorption of aged BC particles and its relation to the mixing state and morphology of individual particles, we conducted observations of particles at an Asian outflow site in Noto Peninsula, Japan, in the spring of 2013. Absorption and scattering coefficients at 405, 532, and 781 nm and mass concentrations/mixing states of refractory BC in PM2.5 were measured using a three-wavelength photoacoustic soot spectrometer and a single-particle soot photometer (SP2), respectively, after passage through a thermodenuder (TD) maintained at 300 or 400 °C or a bypass line maintained at room temperature (25 °C). The average enhancement factor of BC light absorption due to coating was estimated by comparing absorption coefficients at 781 nm for particles that with and without passing through the TD at 300 °C and was found to be 1.22. The largest enhancements (> 1.30) were observed under high absorption coefficient periods when the air mass was long-range transported from urban areas in China. Aerosol samples were also analyzed using a transmission electron microscope (TEM) equipped with an energy dispersive X-ray analyzer. The morphological features and mixing states of soot-containing particles of four samples collected during the high absorption events were analyzed by comparing microphotographs before and after the evaporation of beam-sensitive materials by irradiation with a high-density electron beam. The majority of the soot in all samples was found as mixed particles with sulfate-containing spherules or as clusters of such spherules. For samples showing high enhancement (> 1.30) of BC light absorption, the TEM showed that the internally mixed soot-containing particles tended to have a more spherical shape and to be thickly coated. The SP2 measurements also suggested that the proportion of thickly coated soot was greater. Thus, the observed enhancement of BC light absorption was found to differ according to the mixing states and morphology of soot-containing particles. The enhancement of BC light absorption in our in situ measurements and its relation with individual features of soot-containing particles will be useful to evaluate direct radiative forcing in the downwind areas of large emission sources of BC.
48 citations
TL;DR: In this article, the average total OH reactivity, measured using a laser-induced pump and probe technique was 7.1 s−1 with high missing sinks of 37.3% was determined.
26 citations
TL;DR: In this paper, a polar nephelometer was developed to measure the scattering angular distributions from 11.7° to 168.3° for individual particles in planes parallel and perpendicular to the polarization of the incident laser beam.
Abstract: A new polar nephelometer (PN) has been developed to measure simultaneously the scattering angular distributions from 11.7° to 168.3° for individual particles in planes parallel and perpendicular to the polarization of the incident laser beam. Each detection plane had 21 silicon photodiode detectors to detect scattered light at a rate of 100 Hz. Laboratory experiments to validate the performance of the instrument were conducted using nearly mono-disperse spherical particles (polystyrene latex [PSL] and nigrosine) and nonspherical particles (sodium chloride [NaCl] and soot). The observed scattering angular distributions for individual PSL particles were in good agreement with the results of simulations based on Mie theory. Complex refractive index values for nigrosine particles were determined by comparing the observed scattering angular distributions with the results of simulations. Clear differences between the measured scattering angular distributions and the results of simulations based on Mie t...
15 citations
15 citations
TL;DR: Continuous, high time-resolution measurements of CO2 and water vapour isotopologues in a red pine forest at the foot of Mt. Fuji found that the air masses with different water vapours isotopic ratios moved into the forest, and changed the atmosphere of the forest.
Abstract: We conducted continuous, high time-resolution measurements of CO2 and water vapour isotopologues ((16)O(12)C(16)O, (16)O(13)C(16)O and (18)O(12)C(16)O for CO2, and H2(18)O for water vapour) in a red pine forest at the foot of Mt. Fuji for 9 days from the end of July 2010 using in situ absorption laser spectroscopy. The δ(18)O values in water vapour were estimated using the δ(2)H-δ(18)O relationship. At a scale of several days, the temporal variations in δ(18)O-CO2 and δ(18)O-H2O are similar. The orders of the daily Keeling plots are almost identical. A possible reason for the similar behaviour of δ(18)O-CO2 and δ(18)O-H2O is considered to be that the air masses with different water vapour isotopic ratios moved into the forest, and changed the atmosphere of the forest. A significant correlation was observed between δ(18)O-CO2 and δ(13)C-CO2 values at nighttime (r(2)≈0.9) due to mixing between soil (and/or leaf) respiration and tropospheric CO2. The ratios of the discrimination coefficients (Δa/Δ) for oxygen (Δa) and carbon (Δ) isotopes during photosynthesis were estimated in the range of 0.7-1.2 from the daytime correlations between δ(18)O-CO2 and δ(13)C-CO2 values.
2 citations
Journal Article•
TL;DR: Nakagawa et al. as mentioned in this paper developed a new polar nephelometer which can measure angular distribution of the optical light scattered by an individual particle, which is one of the important optical properties contributing to the radiation balance in the Earth's atmosphere.
Abstract: Angular distribution of scattering is one of the important optical properties contributing to the radiation balance in the Earth’s atmosphere. Therefore, accurate description of the single-scattering properties of aerosol particles is required. The angular distribution of light scattering is an important optical property. In addition, because the angular distribution of scattering depend on size, shape, and refractive index of particles, the angular distribution for individual aerosol particles may provide useful information to estimate mixing state and type of particles. In the present study, applicability of the angular distribution for individual particles to the estimation of mixing state and type of particles was examined by comparing the temporal variations of the angular distributions with those of chemical compositions for ambient particles. We have developed a new polar nephelometer, which can measure angular distribution of the optical light scattered by an individual particle. Laser beam at 532 nm from a 300 mW YAG laser was used as light source. The laser beam intersects with a stream of aerosol particles introduced with a sheath flow using a double pipe. There are 21 photodiode detectors arrayed in each plane, totaling 42. Detector apertures were placed to limit sensing angles and minimize background light scattered from walls. In this system, the angular distributions for an incident light polarized parallel and perpendicular to the scattering plane can be measured simultaneously. Ambient particles were measured at the Higashiyama campus of Nagoya University (35°09¢N, 136°58¢E, 60 m above sea level) located in an urban area in Nagoya, Japan, from July 1 to 7, 2015. After being dried by a diffusion dryer with silica gel, ambient particles were introduced alternately to a heated line (maintained at 300°C) or the bypass line to measure, respectively, ambient particles directly and after the evaporation of volatile materials under high temperature conditions. The lines were switched every 15 min using two-way ball valves. Then, the particles were passed through a differential mobility analyzer (DMA) and introduced into the polar nephelometer. The DMA voltage was switched to select the nearly monodispersed particle with a mobility diameter 300 or 500 nm every 30 min. Most of organics, sulfate, nitrate, and ammonium are expected to be vaporized at temperatures below 300°C. Therefore, black carbon (BC) particles are expected to be mainly measured when particles were passed through the heated line. During the observation, mass concentrations of BC were measured using a particle soot absorption photometer (PSAP) combined with a heated inlet (maintained at 300°C). The mass concentrations organics, sulfate, nitrate, and ammonium were measured using a time-of-flight aerosol mass spectrometer (AMS). In the presentation, relationship between the temporal variations of scattering angular distributions of individual particles and those of chemical compositions will be discussed. Reference 1) Nakagawa, M., Nakayama. T., Sasago, H., Ueda, S., Venables. D. S., Matsumi, Y., Design and Characterization of a Novel Single-Particle Polar Nephelometer, Aerosol Sci. Technol. (in press). 2) Nakayama, T., Ikeda, Y., Sawada, Y., Setoguchi, Y., Ogawa, S., Kawana, K., Mochida, M., Ikemori, F., Matsumoto, K., Matsumi, Y., Properties of light-absorbing aerosols in the Nagoya urban area, Japan, in August 2011 and January 2012: Contributions of brown carbon and lensing effect, J. Geophys. Res. Atmos., 119, 12721-12739 (2014). AAS12-P16 Japan Geoscience Union Meeting 2016