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Abstract: Due to enforcing vehicle emission reduction requirements in Japan, particulate matter (PM) concentration, especially elemental carbon (EC) concentration in roadside atmosphere, obviously decreased in the last decade. In spite of the previous vehicle emission reduction, EC concentration was not shown a clear decrease, recently. To achieve the PM2.5 environmental standard, measurements based on emission source contribution are desirable. However, source apportionment of carbonaceous aerosol was ambiguous because chemical components are complicated, and the components change through photochemical reaction. The goal of this study is to determine source apportionment for carbonaceous aerosols. Examination of PM2.5 was performed in south Kanto including Tokyo in the summer of 2008 and the winter of 2009. Emissions from the industrial area around Tokyo Bay and the agricultural northern area showed transportation and accumulation due to the seasonal prevailing wind. The emissions formed a geographical distribution due to photochemical reactions. The characteristics of carbonaceous aerosol were obtained using carbon profile analysis and carbon isotope analysis, including the source information such as fossil fuel emission origin, vegetation origin, and combustion product, photochemical reaction product, etc. Soot-EC was found as a substance with fossil fuel origin which did not contain biomass combustion matter, and since it is stable, there was no observed difference by site and a uniform concentration was observed in winter. It became apparent from the carbon isotope analysis using 14C that the carbon from the biomass origin involved 29% in total carbon in the summer, and 48% in winter even at Kudan of central Tokyo. [Copyright &y& Elsevier]

Abstract: The Japanese Ministry of the Environment established a new PM2.5 air quality standard in September 2009, which has lead to increased public interest in air quality improvement. Concentrations of primary particles such as elemental carbon have decreased during the last decade, but secondary particles have become a major concern. When ground-based observations are carried out, the influence of neighboring emissions must be considered. At the same time, as much as possible, particles must be collected in places that will allow the average behavior of secondary particles to be understood. Making observations using aircraft in city skies is advantageous in that samples taken there are not influenced by local exhaust, such observations can cover a wide range at one time, and they are useful in understanding the spatial character of secondary particles. Using a helicopter for sampling, we measured the spatial variation of particle size distribution (0.5–10 μm) on the coastline and over inland areas in the South Kanto region, including the Tokyo metropolitan area, nine times in three days starting on July 30, 2008. The vertical profile of pollutant concentrations was approximately constant between the altitudes of 300 m and 600 m, but concentrations varied both temporally and spatially. Data gathered in level flights at an altitude of 600 m showed that the particle number concentration increased while the mean particle diameter decreased as we flew north (inland). The particle number concentration and its relationship with the mean particle diameter showed a well-organized distribution. A volumetric change of more than 3-fold was seen in the distribution of particles sampled in the inland area, whereas no clear volumetric change was seen in the distribution of particles sampled along the coast. The particle number concentration, mean particle diameter, and particle volume changed at rates of 0.74 cm−3 km−1, −0.48 nm km−1, and 0.057 μm3 cm−3 km−1, respectively, with increasing distance from the coastline. The incremental volumetric growth rates were seen to relate positively in proportion to the NO2 concentration in particular. [Copyright &y& Elsevier]

Continuous monitoring of the concentration of atmospheric particulate matter was carried out for 7 years by both gravimetric method and β-ray attenuation method (BAM) from a building rooftop in the Tokyo metropolitan area. The two methods showed a different tendency in each season: the data observed by BAM were higher than those by the gravimetric method in summer, and this difference was reversed in winter. The volatilization of ammonium salts accounted for only 30% of the difference between the monitoring methods in summer. Thus, we considered the differences in the water content measured by each method. The concentration difference between methods increased when relative humidity exceeded the deliquescence point of ammonium sulfate in summer, and the water content was estimated to be 30%. However, differences in relative humidity did not explain why the data obtained by the gravimetric method exceeded BAM data by 20–30% in winter. We found that the gravimetric measurements generally exceeded BAM measurements in winter if the ambient absolute humidity during particle collection was higher than the absolute humidity during sample weighing. The water content of atmospheric aerosols greatly influences their mass concentrations. Care must be taken when using mass concentration data for purposes such as evaluating health effects. [Copyright &y& Elsevier]

Abstract: Long-term measurements of suspended particulate matter (SPM, <7μm), PMfine (<2.1μm), and PMcoarse (2.1–7μm) were obtained from a traffic-dominated site in Tokyo, Japan for the period 1994–2004 to evaluate the effects of emission reduction measures for motor-vehicle emissions. SPM decreased from 1996 forward, with all of the downward trend attributable to the PMfine fraction. Annual average PMcoarse was constant over the 10-yr period. From 1996 to 2004, PMfine decreased at a rate of 2.37μgm−3 yr−1 for PM2.1 mass. Most of this decrease was attributable to decreases in organic and elemental carbon. This decrease is consistent with fleet penetration of engines and fuels that complied with a stringent Japanese emission reduction limit which began to take effect in 1994. Sulfate and nitrate concentrations did not decrease over this period. Evidence of Asian dust storm contributions was found in elevated PMcoarse and water-soluble calcium levels during the spring. [Copyright &y& Elsevier]

We report the results of year-long PM2.5 (particulate matter less than 2.5 µm in diameter) simulations over Northeast Asia for the base year of 2013 under the framework of the Long-range Transboundary Air Pollutants in Northeast Asia (LTP) project. LTP is a tripartite project launched by China, Japan, and Korea for cooperative monitoring and modeling of the long-range transport (LRT) of air pollutants. In the modeling aspect in the LTP project, each country's modeling group employs its own original air quality model and options. The three regional air quality models employed by the modeling groups are WRF-CAMx, NHM-RAQM2, and WRF-CMAQ. PM2.5 concentrations were simulated in remote exit-and-entrance areas associated with the LRT process over China, Japan, and Korea. The results showed apparent bias that remains unexplored due to a series of uncertainties from emission estimates and inherent model limitations. The simulated PM10 levels at seven remote exit-and-entrance sites were underestimated with the normalized mean bias of 0.4 ± 0.2. Among the four chemical components of PM2.5 (SO42−, NO3−, organic carbon (OC), and elemental carbon (EC)), the largest inter-model variability was in OC, with the second largest discrepancy in NO3−. Our simulation results also indicated that under considerable SO42− levels, favorable environments for ammonium nitrate formation were found in exit-and-entrance areas between China and Korea, and gas-aerosol partitioning for semi-volatile species of ammonium nitrate could be fully achieved prior to arrival at the entrance areas. Other chemical characteristics, including NO3−/SO42− and OC/EC ratios, are discussed to diagnose the LRT characteristics of PM2.5 in exit-and-entrance areas associated with transboundary transport over China, Japan, and Korea. [ABSTRACT FROM AUTHOR]

Abstract: As the U.S. Environmental Protection Agency updates the National Emission Inventory (NEI), the source contributions (SC) of major source sectors to major pollutants based on source apportionment techniques should be periodically reassessed to reflect changes in SCs due to changes in emissions. This work assesses emission updates from the 1999 NEI version 2 (NEI99v2) and the 2005 NEI (NEI05) and the resulting differences in SCs using the two inventories. Large differences exist in the emissions of nitrogen oxide, formaldehyde, ammonia, terpene, and primary PM2.5 between NEI99v2 and NEI05. Differences in emissions lead to differences in model performance and source appointment. SCs of ten major source categories to fine particulate matter (PM2.5) are estimated using the Community Multiscale Air Quality modeling system with the Brute Force Method (CMAQ/BFM) andNEI05and compared with those obtained previously using CMAQ/BFM with NEI99v2. In January, compared to CMAQ/BFM (NEI99v2), CMAQ/BFM (NEI05) shows that miscellaneous areas, biomass burning, and coal combustion remain the top three contributors to PM2.5 but with different ranking and higher SCs (17.7%, 16.0%, and 14.1% for NEI05 vs. 11.8%, 13.7%, and 10.8% for NEI99v2, respectively). In July, coal combustion, miscellaneous areas, and industrial processes remain the top three with higher SCs (41.9%, 14.1%, and 8.8% for NEI05 vs.30.8%, 8.9%, and 6.9% for NEI99v2, respectively). Those changes in SCs are attributed to increased primary PM2.5 (PPM) emissions in NEI05 and increases in relative contributions of miscellaneous areas and coal combustion to the emissions of PPM, NH3, and SO2.SCs from diesel and gasoline vehicles decrease in both months, due to decreased contributions of gasoline vehicles to SO2 and NH3 emissions and those of diesel vehicles to NO x and PPM emissions. Compared with CMAQ/BFM (NEI99v2), SCs from other combustion and biomass burning are higher in Florida, due to substantial increases in formaldehyde and PPM emissions in NEI05, resulting from higher wildfire emissions and state emission updates. SCs from industrial processes increase and those from diesel and gasoline vehicles decrease in urban areas. SCs of O3 from most sources in both months increase due to a large increase in their contributions to NO x emissions, except for diesel vehicles in July, which decreases over domainwide due to a relative decrease in NO x emissions. These results provide valuable information for policy makers to formulate and adjust emission control strategies as the NEI is continuously updated. [Copyright &y& Elsevier]