The summer of 2018 was the longest and hottest ever. The highest temperature in the history of domestic meteorological observation, 41.1°C, was observed at the Kumagaya Meteorological Station, Saitama Prefecture.
Generally, photochemical air pollution and secondary aerosol formation occur easily in summer. In order to characterize air pollutants, such as photochemical oxidant (mainly ozone, O3) and fine particles less than 2.5 micrometers in diameter (PM2.5), in the 2018 summer, trends of meteorological data and changes in air pollutant concentrations from 2009 to 2018 were obtained from the Automated Meteorological Data Acquisition System (AMeDAS) and the air pollution monitoring station, respectively; relationships between them were investigated with focus on Saitama Prefecture, where the levels of both temperature and O3 concentration were highest in the Kanto region.
The highest temperatures in the northern area were higher than those in the southern area of Saitama Prefecture, while O3 levels exhibited the opposite pattern. In addition, the obvious weekend effect was found in the recent three years.
Daily PM2.5 concentrations in July and August were lower than the air quality standard (i.e., 35 μg/m3). No regional differences were observed within Saitama Prefecture. On all the days when the highest O3 concentration was ≥100 ppb or the highest PM2.5 concentration was ≥25 μg/m3, the highest temperature was greater than 35°C. The lowest values among the maximum daily O3 and PM2.5 concentrations increased with increase in the highest temperature beyond 35°C.
The effect of terephthalic acid particle properties on particle fracture phenomena was investigated in this study. Furthermore, to evaluate the fracture characteristics in real process, the effect of the particle impact angle on particle fracture phenomena was also investigated. The results of this study indicated that: (i) the crystallite particle size correlated with the fracture stress of the particle; (ii) the crystallite particle size also showed a correlation with the critical fracture velocity and the kinetic energy of the particle; and (iii) the particle fractured more easily at impact angles under 45°.
A proton transfer reaction-quadrupole interface-time of flight mass spectrometer was combined with a hand-made thermal desorption instrument for real-time analysis of organic aerosol particles. Size-selected single component organic particles were generated using a nebulizer combined with a differential mobility analyzer. We tested Teflon and copper tubing for the thermal desorption instrument. Higher signal intensities were observed when we used Teflon tubing, suggesting that wall deposition loss of vaporized semivolatile organic compounds is suppressed when Teflon tubing is used. Protonated molecules, [M＋H]＋, had the highest intensity in the mass spectrum of carbonyl particles (i.e., terephthaldialdehyde particles), whereas ions formed by the dehydration from protonated molecules, [M＋H－H2O]＋, had the highest intensities in the mass spectra of carboxylic acid particles (i.e., adipic acid, phthalic acid and cis-pinonic acid particles) and alcohol particles (i.e., meso-erythritol particles). The mass spectra obtained for organic aerosol markers will be useful to interpret mass spectra measured for organic aerosol particles by thermal desorption-proton transfer reaction-mass spectrometry.