Abstract Aerial observations over the seas between Asian continent and Japan were conducted for twenty years in order to analyze the transport and transformation of log-range transported atmospheric pollutants. Covered areas were the East China Sea, the Sea of Japan, and the Yellow Sea. Long term trend of atmospheric pollutants over the East China Sea was discussed on the basis of aerial observation data obtained since 1991. It was found clear upward trend of NO3-/SO42- ratio which was caused by an increase of NO3- or a decrease of SO42- or both. Ozone at a lower altitude showed a clear increase.Ground-based observations were done in April, October, December, 2012 and April, 2013 at Cape Hedo, Okinawa to analyze size-segregated chemical composition of aerosols. Eight kinds of ions (Cl-, NO3-, SO42-, Na+, NH4+, K+, Mg2+, Ca2+) were analyzed with ion chromatography. Species from anthropogenic sources such as NH4+ and SO42- were dominant in fine mode particles (0.5–1 μm, 0.1–0.5 μm). On the contrary, species from natural sources such as Cl-, Na+, and Ca2+ were dominant in coarse mode particles (＞10 μm, 2.5–10 μm).
Abstract Graphene (GR) is made of a flat single layer of sp2-bonded single carbon atoms densely packed into a honeycomb crystal lattice. Due to GR’s unique characteristics, GR based composites as well as GR are expected to contribute to new functions based on synergetic effects, providing a new opportunity for designing and developing next-generation bio, energy, and environmental applications. However, two-dimensional (2D) layered GR sheets have a tendency to form irreversible or even to restack easily due to π-π stacking and van der Waals attraction. In order to prevent critical stacking of GR sheets, we developed three-dimensional (3D) crumpled balls using an aerosol process because GR-based composites with a 3D morphology have a high free volume and good compressive strength. We introduce the aerosol process fabrication of 3D crumpled GR and GR based composites such as 3D crumpled GR-metal oxide, 3D crumpled GR-metal, and 3D hollow GR balls. We then discuss potential bio, energy, and environmental applications using 3D crumpled GR-based composites.
Abstract The diesel engine is preferred for its fuel efficiency, drivability, durability and high energy output. On the other hand the diesel engine is a major source of criteria pollutants as well as halogenated organic chemicals such as brominated persistent compounds, which are classified as toxic and carcinogenic emissions of brominated pollutant such as PBDEs, PBBs and PBDD/Fs and reduction techniques are discussed based on the studies available in open source literature. In Taiwan the PBDE emission concentration (29.1 ng/Nm3) from diesel vehicles is higher than those from sintering plants and electric arc furnaces. Additionally, in the diesel exhaust the mass concentrations of PBDD/Fs (417 ng/Nm3) and PBDEs (41.3 ng/Nm3) are relatively higher than those of chlorinated pollutants such as PCDD/Fs (156 pg/Nm3) and PCBs (267 pg/Nm3). These values point out the significance as well as the contribution of the less understood and investigated brominated pollutants in comparison to their chlorinated homologues. Reduction efficiencies of up to 95% can be obtained using diesel particulate filters (DPF) for PBDEs. When using biodiesel blends the reduction efficiencies ranged from 46–62% and 53–73% for PBDD/Fs and PBDEs, respectively. Another study reported reduction in PBDE emission by blends containing 10% water containing butanol (WBT10) and 20% water containing butanol (WBT20). The emission factors were 399, 309 and 245 ng/kWh, for B2, WBT10 and WBT20 respectively. Additionally, this review points out the existing research gap on the study of brominated pollutants in diesel engines as well as gasoline engines. These kinds of pollutants even though they are unregulated; more attention should be paid to them owing to their toxicity and carcinogenic potentials.
Abstract CaCO3 in mineral dusts can be converted to highly hygroscopic substances, which affect the formation of clouds, by reactions with gaseous oxidative species in the atmosphere. It is important to investigate CaCO3 reactions in the presence of various kinds of gaseous oxidative species in order to improve the understanding of climate change. In this study, heterogeneous chemical reaction of CaCO3 particles in the presence of HCl, NO2 and O3 was evaluated using the Raman microscope coupled with aerosol reaction chamber. The reaction of CaCO3 particles with HCl and NO2 resulted in the formation of internal mixtures of Ca(NO3)2 and CaCl2, both of which were very hygroscopic and undergoes deliquescence at low relative humidity. Ca(NO3)2 did not change into CaCl2 by the subsequent reactions with HCl, whereas the produced CaCl2 reacted partially with NO2 and O3 to form Ca(NO3)2. Mixed particles including large amounts of Ca(NO3)2 were most frequently seen in microscope observation and existed in the state of supersaturated droplets under a low humidity condition. On the other hand, the particles containing large amount of CaCl2 were observed as transparent particles with wrinkled surfaces, which included CaCl2･2H2O hydrate under low humidity condition.
Abstract Measurements of aerosol number concentration using a polarization optical particle counter (POPC) and filter sampling were simultaneously conducted in Kofu, Japan, from February 17 till July 1 in 2013 to develop an identification procedure of Asian dust (mineral dust) particles from the POPC measurements. The correlations of the particle volume concentrations in 40-size bins to the depolarization ratio calculated from the POPC measurement, the mass concentrations of ionic species, and the volume concentrations of water-insoluble particles were investigated. We proposed the classification criteria for mineral dust, anthropogenic, and sea-salt particles using the POPC. The mass concentrations of mineral dust particles estimated using the criteria from the POPC measurement correlated strongly with those calculated from the mass concentrations of non-sea-salt Ca2+ (R2=0.936).
Abstract In order to evaluate the effectiveness of the PM2.5 emisson control measures for domestic sources, emission sensitivity analysis for seasonal trends and the high concentrations of SO42- in PM2.5, observed in 2010 at Meisei University located in western Tokyo, was implemented based on WRF/CMAQ simulation. The sensitivity was estimated for the emission from volcano, ship, domestic land-based and foreign sources. The sensitivity of foreign emission sources was highest (50.7%) on annual average at the observation site where the local emission strength was relatively small. Especially, it was suggested that the foreign emission sources had a larger contribution to the variation of SO42- concentration during the period of January to April and November to December of 2010. On the other hand, the contribution of foreign emission sources to the high concentration of SO42- decreased during the summer season because of the southern wind from the Pacific High. Since the contribution of both domestic land-based and the ship emission sources was estimated as 41.5% in August 2010, it seemed that the countermeasures implemented for the domestic emissions in summer season was effective in achieving the environmental standard in western Tokyo.