The daily averaged PM_2.5 was measured using FRM samplers from April 2003 to March 2008 at an urban site in Nagoya City. The annual means of the PM_2.5 have decreased from 25.9μg/m³ to 21.9μg/m³. The chemical compositions of PM_2.5 were measured. Elemental carbon (EC), organic carbon (OC), sulfate (SO₄^2-), nitrate (NO₃^-) and ammonium (NH₄⁺) are the major contributors to the PM_2.5 mass. The EC concentrations tend to significantly decrease over these five years. The decrease in the EC was attributable to decrease in heavy-duty vehicle emissions and traffic volume. The EC accounted for 60% of the drop in the PM_2.5 from FY 2003 to FY 2007. The number of times that the daily PM_2.5 limit value of 35μg/m³ was exceeded had decreased. A cluster analysis grouped the high concentration samples into three clusters. One group was a high concentration by transboundary secondary aerosols, the second group was by local pollution, and the third group was by transboundary and local secondary aerosols. It is suggested that the number of high concentration groups decreased because the local emission decreased, and because of the decrease in the heavy-duty vehicle emissions and traffic volume.

View full abstract

The bio-briquette is a solid fuel which is produced from pulverized coal, biomass, and a sulfur fixation agent under high pressure without any binder. The ash generated from the bio-briquette combustion has been evaluated for use as an acid soil improvement agent. In this study, we tried to evaluate the effect of coaddition of the ash and manure compost on crop growth and element uptake by a laboratory-scale radish growth test. Radish plants cultivated during coaddition condition showed a sufficent growth without chemical fertilizer and no detrimental effect was recognized. The coaddition of the ash and manure compost contributed to fixation of potentially toxic elements derived from the ash or manure compost. The crop absorption of copper and zinc, which are considered as toxic heavy metals in the case of manure application, was decreased by the coaddition of the ash and manure compost, and the inhibition effect of Zn absorption by other than the soil pH reclamation was suggested. Our results suggested that the coaddition was a more effective method than the single application of the ash or manure compost for soil amelioration and crop production.

View full abstract

In order to understand the source apportionment of carbonaceous aerosols using a receptor model, we examined the source contribution of fine particles. The observation was done in the summer of 2007 at Maebashi and Kisai. Samples were collected every 6 hours (during the daytime) and 12 hours (during the nighttime), and the following chemical components were analyzed: carbonaceous compounds, ionic components, inorganic elements and radiocarbon content. The Chemical Mass Balance (CMB) method was applied to these data to estimate the source contribution into 10 sources. The carbonaceous compounds were apportioned into the 10 sources using these results, and elemental carbon (EC) was almost entirely diesel-exhaust derived. On the other hand, there was limited primary particle contribution in the organic carbon (OC), and it was estimated as either unknown or secondary particles. The EC and OC were divided into fossil-fuel-derived carbon and biogenic-derived carbon based on the value of the pMC (percent modern carbon) of individual sources derived from the literature. For the secondary organic carbon (SOC), it was found that although the ratio of the fossil-fuel-derived carbon to the biogenic-derived carbon was around 1:2 during the daytime, the fossil-fuel-derived carbon transported from metropolitan area decreased and the ratio dropped to 1:10 during the nighttime, and the observed pMC of total carbon (=EC+OC) increased. As the biogenic-derived-carbon accounted for 70 % of the SOC during the daytime, it was shown that biogenic-derived-carbon provided the major contributions to the SOC.

View full abstract

In order to shed light on the atmospheric fine particulate matter (PM_2.5) pollution of the roadside atmosphere in the Tokyo metropolitan area, we carried out high time-resolution sampling of PM_2.5 at the Ikegami-Shincho crossing in Kawasaki City, Kanagawa Prefecture, Japan at November 2003. The PM_2.5 sample (spot shaped sample) was collected every hour on an ultra-fine membrane PTFE tape-filter by a beta-ray attenuation PM_2.5 mass monitor Elemental composition (22 elements) of the PM_2.5 spot sample was analyzed by particle induced x-ray emission (PIXE) at the Nishina Memorial Cyclotron Center, Japan Radioisotope Association. Ionic species (seven ions) in the PM_2.5 spot sample was determined using ion chromatography. The analytical results are valuable for the physicochemical characterization of PM_2.5 in roadside atmosphere, enabling evaluation of various roadside emission sources and atmospheric processes. When information on organic and elemental carbons was added to these composition data and the component ratio was examined, for average composition of PM_2.5 in 2 day, organic carbon was 27%, elemental carbon was 43%, elements was 5%, ions was 25%. Results from the Positive Matrix Factorization (PMF) analysis suggested that sufficient part of the PM_2.5 on the roadside was derived from traffic related particles and atmospheric secondary formed particles.

View full abstract

The variation pattern of potential ozone (PO) in four urban sites, Osaka, Kobe, Tokyo, and Kawasaki, were separated into the diurnal and seasonal components using Bayesian statistical analysis to evaluate the individual contributions from in situ photochemical production and the background concentration to total ozone (O₃) concentrations. The Bayesian model involved a diurnal component expressed as the product of the time-of-day dependent diurnal variation pattern (D_h), its month-dependent amplitude (B_m), and a month-dependent seasonal component (A_m). The estimated D_h for the four urban sites showed good agreement with each other, having the diurnal cycle resembling those of the hydroperoxy radicals observed at an urban site. B_m showed a seasonal pattern with a significant increase in the summer season. The sudden increase in B_m in August was characteristic of two sites in the Kanto area. The variation in A_m was similar among the four sites, however, a slight difference in the variation of A_m during the summer season was detected between the Kansai and the Kanto regions. When the diurnal and seasonal components were regarded as the local photochemical production and the background contributions, respectively, the local contribution was the highest in August. The extremely large photochemical production in the Kanto area seemed to cause the vague autumn maximum in the seasonal variations of PO in the area.

View full abstract

We are developing a system to reduce air pollutants including the major NO_X concentration over the roadside based on consideration of the purifying characteristics of the ACF. The air purification systems that we are proposing are the following two types: (1) “Forced air intake system” in which contaminated air is made to pass through the ACF using an electric fan, and (2) a “natural wind ventilation system” by application of the natural wind.
In this study “I”, we carried out the basic experiments on (1) the “Forced air intake system”. We investigated the NO purifying efficiency of the ACF unit and aimed to realize the effective purification of NO and NO₂ at the same time. In addition, we examined the regeneration technology of the used ACF unit. The ACF was packed into a cylindrical pipe and the contaminated air over the road was made to pass through the ACF by a pump in the field. The value obtained by dividing the ACF packing amount (g) by the flow rate of air (mL/min) was defined as the W / F value (g•min/mL). The NO_X concentration at both ends of the cylindrical pipe was measured continuously throughout the year while changing the W / F value was in the range of 5.7 × 10^-3 to 2.1 × 10^-2. As a result, the annual average NO and NO₂ purification rates were 80.5 % and 90.2 %, respectively. It was proven that most of the NO and NO₂ could be simultaneously purified by the ACF without using large-scale incidental facilities other than an electric fan for one year with the W / F value set to 1.0 × 10^-2 or more. This system was able to effectively purify the NO_X of approx. 100 ppb on the roadside. It was also considered that the system could be operated for 5 years or more with free maintenance even without regenerating the ACF.
We examined the simplified regeneration technology of the used ACF unit. Consequently, the simple water-flow treatment could remove 60 % to 70 % of the HNO₃ captured in the used ACF unit. It was also found that the water-flow treatment could regenerate 60 % to 80 % of the NO_X purifying performance in the ACF unit. The simple water-flow treatment was even able to repeatedly regenerate the NO_X purifying performance in the ACF unit.

View full abstract

This paper describes an evaluation of the organic carbon concentrations on fine particles (PM_2.5) using commercially available multi-channel denuder samplers. Three different sampling systems — filter sampling as the typical method (reference), a KI-denuder for removing ozone, and a XAD4-denuder for trapping gaseous semi-volatile organic compounds — were selected and demonstrated for the collection of PM_2.5 sample during the summer of 2004 in Saitama in Japan. The results of the comparison between reference samples and KI-denuded samples suggest that the organic carbon (OC) were not susceptible to ozone degradation although relatively high ozone atmospheric concentrations (O₃ for 12 h averages: 5-65 ppb) were observed during the sampling periods (< 12 h). The comparison between the reference samples and XAD4-denuder samples results indicated that semi-volatile organic carbon (SVOC) had a significant effect on the organic carbon concentration. Positive artifact, adsorptions on typical filtering samples were estimated to be 2.3 ± 0.7 μgC/m³ which was similar to the calculated capacity of the adsorbed organic vapor on a quartz filter.

View full abstract

The atmospheric nitrous oxide (N₂O) concentration has been measured at four sites, Urawa, Kumagaya, Mt. Dodaira, and the Center for Environmental Science in Saitama (CESS), in Saitama Prefecture for approximately 20 years since 1991. In this study, we examined the long-term trend and seasonal variation in the N₂O concentration, and a comparison with other prefectural areas such as Ryori (Iwate Pref.) and Hateruma (Okinawa Pref.) that are observation sites providing the background levels of our country was performed. As a result, there was not a significant difference in the N₂O concentration among the four sites in Saitama. In addition, No difference in the N₂O concentration was recognized between those in Saitama and those in Ryori and Hateruma. These results suggest that there is little regional variation in the N₂O concentration in our country. The concentration of N₂O continues to rise at all the observation sites. The increasing rate in the N₂O is approximately 0.66-0.68 ppbv per year and more steady than that in the 1990's. On the other hand, it was observed that the N₂O concentration was relatively higher in the winter and shows the tendency to be lower from the summer to autumn. However, the variation in the N₂O concentration was relatively small at all the observation sites. In particular, seasonal change of the N₂O concentration was low in the background area.

View full abstract

The 15th International Union of Air Pollution Prevention and Environmental Protection Associations'(IUAPPA) World Clean Air Congress was held from September 12th to 16th in Vancouver, Canada. The theme of the congress was 'Achieving Environmental Sustainability in a Resource Hungry World'. Over three hundred participants from 35 countries attended the congress. A total of 148 oral presentations and 27 poster presentations was held during this congress.

View full abstract