Naoto Murao

Activation capability of water soluble organic substances as CCN

Abstract The activation capability of seven dicarboxylic acid compounds, ammonium oxalate, malonic acid, succinic acid, glutaric acid, adipic acid, malic acid and phthalic acid, was determined by laboratory experiments, and predictability by the Kohler theory was discussed. Experimental results showed that ammonium oxalate had the highest capability comparable to that of ammonium sulfate, and malic acid and phthalic acid followed, whereas adipic acid exhibited the lowest capability close to that of an insoluble particle. Malonic acid and glutaric acid were considered to evaporate under normal experimental operations at 8–9% RH but exhibited high and moderate capability, respectively, under supplementary humid operations. The activation capability of succinic acid tended to depend on the laboratory temperatures but was possibly high, comparable to that of malic acid. Particulate drying, associated solute vaporization, morphology and hydrophobicity of particles could be key factors in the theoretical prediction and the interpretation of the experimental results.

Seasonal variation in the chemical composition of atmospheric aerosols and gaseous species in Sapporo, Japan

Abstract Simultaneous samplings of atmospheric aerosols and gaseous precursors (SO2, HNO3,NH3) were conducted during an 18-month period in Sapporo, Japan. The monthly mean mass concentration of particles less than 10 μm in diameter (suspended particulate matter: SPM) and their chemical composition were measured for aerosols collected at two sites located in northern and southwestern regions of the urban area. In the central part of the city, two-week mean concentrations of SO2, HNO3 and NH3 were measured by using tandem filter packs. Seasonal variations of the SPM mass concentrations and composition are discussed along with the results of the gas measurements. In both northern and southwestern regions of the urban area, more than 85% of the mass concentration of SPM is characterized by considering eight major components (elemental carbon, particulate organics, SO42− NO3−, Cl−, NH4, Na+ and soil particles). The concentration of elemental carbon indicates a winter maximum and summer minimum at both sites. Excess SO42− concentrations at the two sites exhibit very similar values throughout the year. An analysis of the concentration of SO2 suggests that the existence of secondarily formed sulfate in the atmosphere may contribute to this feature. Values of NO3− and NH4+ exhibit marked seasonal variations: winter maxima and summer minima. By comparison with the concentration of total. inorganic nitrate ([NO3] in aerosols + [HNO3]) measured in the central part of the city, the variations of NO3− and NH4+ are attributed to the change in the gas-particle phase between HNO3, NH3 and NH4NO3 The measurements of total ammonia ([NH4+] in aerosols + [NH3]) suggest that, in urban area, significant ammonia sources exist other than the ground surface. From the molar equivalence of Na+ and Cl− it was found that the Cl− in SPM aerosols is mostly derived from sea salt; the contribution from NH4Cl is small, even in winter. Furthermore, the measured seasonal variation of Cl− was largely influenced by the chlorine loss from sea salt.

CO2 reduction to CH4 with H2 on photoirradiated TS-1

Abstract CO 2 reduction on reduced titanium silicalite (TS-1) with photoirradiation in the presence of H 2 was investigated in a closed circulation system. CO 2 was reduced to give CH 4 under u.v. irradiation, which TS-1 absorbs. The amount of the carbon species on TS-1 after photoirradiation indicated that all Ti atoms in the framework may act as a photocatalytic site. Infrared spectrum of TS-1 after the reaction showed that CH 2 and CH 3 were left on TS-1.

The causes of elevated concentrations of ozone in Sapporo

In order to investigate the causes of elevated concentrations of O3 in Sapporo which are observed under anticyclonic conditions in spring, we made measurements of O3 concentration at Teine mountain (43°04′N, 141°11′E, 1000m high) in the suburbs of Sapporo simultaneously with measurements of concentrations of HNO3, SO2, SO42−, NO3− and 7Be at ground level in the center of Sapporo in spring 1987. Ozone concentration at Teine mountain showed little diurnal variation. We found remarkably high positive correlation between O3 concentration and temperature at 850 mb, and positive correlation between concentrations of O3 and 7Be. No relationships were found between concentrations of O3 and PAN and between O3 concentration and ƒs (gas-particle distribution factor for S species). Backward trajectory on isentropic surface showed that the air parcel, which originally had existed in the western edge of the upper tropospheric cyclone, descended to the lower troposphere. The results indicate that elevated O3 concentrations in Sapporo in spring were mainly caused by downward transport of O3 from the middle troposphere rather than photochemical formation of O3 in the boundary layer (BL).

Evaluation of absorption properties of atmospheric aerosols at solar wavelengths based on chemical characterization

Abstract The imaginary part of the complex index of refraction of atmospheric aerosols was determined by calculation based on chemical characterization. Atmospheric aerosols in Sapporo were chemically characterized, and were estimated to be mainly composed of elemental C, organics, (NH4)2SO4, NH4NO3, sea salt and soil particles. Using the complex index of refraction of each chemical species, the volume extinction and scattering coefficients of the particles composed of the chemical species were calculated, using Mie scattering theory. The single scattering albedo of the aerosols was obtained as the ratio of the total volume scattering coefficient to the total volume extinction coefficient. The imaginary part of the complex index of refraction of the aerosols was determined by matching the calculated sigle scattering albedo for the aggregate aerosol to that calculated from the sum of the individual aerosol components. The monthly mean imaginary part of the complex index of refraction of aerosols in Sapporo ranged from 0.024 in August to 0.047 in February in 1982. The atmospheric solar heating rate was calculated by solving the equation of radiative transfer in turbid atmospheres. It was estimated that the atmospheric boundary layer in Sapporo was heated at the rate of 2.0–2.5°C day−1 in February as a result of absorption of visible solar radiation by aerosols.

Extreme air pollution events in Hokkaido, Japan, traced back to early snowmelt and large-scale wildfires over East Eurasia: Case studies

To identify the unusual climate conditions and their connections to air pollutions in a remote area due to wildfires, we examine three anomalous large-scale wildfires in May 2003, April 2008, and July 2014 over East Eurasia, as well as how products of those wildfires reached an urban city, Sapporo, in the northern part of Japan (Hokkaido), significantly affecting the air quality. NASA’s MERRA-2 (the Modern-Era Retrospective analysis for Research and Applications, Version 2) aerosol re-analysis data closely reproduced the PM2.5 variations in Sapporo for the case of smoke arrival in July 2014. Results show that all three cases featured unusually early snowmelt in East Eurasia, accompanied by warmer and drier surface conditions in the months leading to the fires, inducing long-lasting soil dryness and producing climate and environmental conditions conducive to active wildfires. Due to prevailing anomalous synoptic-scale atmospheric motions, smoke from those fires eventually reached a remote area, Hokkaido, and worsened the air quality in Sapporo. In future studies, continuous monitoring of the timing of Eurasian snowmelt and the air quality from the source regions to remote regions, coupled with the analysis of atmospheric and surface conditions, may be essential in more accurately predicting the effects of wildfires on air quality.

A PMF-based trajectory methodology applied to daily precipitation and wet deposition data in Japan

Positive matrix factorization (PMF) was applied to daily wet deposition data from three stations in Japan to find the source profiles from which the precipitation samples are constituted. For most ions more than 90% of the weighted variation was explained with 4 factors. The factors are characterized by the following compounds: strong acids (H2SO4 and HNO3), (NH4)2SO4, NaCl, and CaSO4. The anion-cation balance was fairly good in the factors. Based on the chemical compositions of the factors, a time series of the factor contributions, and the results from trajectory analysis, the factors are considered to represent sea salt, soil, (NH4) 2SO4 and acidity. Although the total nss-SO4 wet deposition amount decreased in the last 7 years at Wajima station, the contributions of the (NH4) 2SO4 factor to nss-SO4 wet deposition were fairly constant (ca.50%). The acidity seemed to be controlled by the neutralization by soil particles.