Atmospheric pollutants of low concentration are recently attracting much attention. Among those pollutants organic hydroperoxides are important because they may cause the forest damage as well as they are closely related to the formation of acid rain or acid fog on account of their ability to oxidize SO₂ in the aqueous phase. The formation mechanism and the measurement techniques for organic hydroperoxides are reviewed. Organic peroxides are mainly produced by the reactions of ozone with natural hydrocarbons emitted from forest trees. Measurement of each component of hydroperoxides became more popular, recently. Methylhydroperoxide and hydroxymethylhydroperoxide are the major organic hydroperoxides in the atmosphere.

View full abstract

The Monin-Obukhov length values (L) corresponding to dispersion coefficients on Pasquill/Gifford chart (P/G chart), which are widely used for esimating air pollution concentration, are derived in order to use the equations of atmospheric boundary layer for the research on the atomospheric diffusion.
The classified table for atmospheric stability categories corresponding to P/G chart were proposed by Nuclear Safety Research Association originaly in 1973, revised in 1981 and used by Environmental Agency, Nuclear Safety Commission and so on in Japan. The classified table constructed by the categories of surface wind speed and insolation in daytime or net radiation in nighttime is converted to the table of Lcorresponding to boundary of atmospheric stability categories assuming mean values of albedo (25%) and Bowen ratio (0.4 in daytime, latent heat flux is 0 in nighttime.) on the grass plane in the middle latitude. The roughness length (z₀) was assumed to be 3cm because the atmospheric diffusion experiments corresponding to P/G chart were done in the field of z₀ of about 3 cm. The values of L derived in this research are compared with one of Golder (1972)'s chart, which were made by the observations of atmospheric stability categories on Pasquill's or Turner's methods and Ls in the several field experiments in abroad. Both values of L coincide comparatively well.
Therefore, the atmospheric stability categories of the method of Nuclear Safety Research Association of Japan, which are corresponding to the dispersion coefficients on P/G chart, are practically corresponding to Golder's Ls in the case of z₀ of about 3 cm.

View full abstract

The present study was performed to clarify the role of active oxygen species produced by macrophages in acute lung injury induced by asbestos (chrysotile) inhalation. Using a sound-wave sifter, we separated chrysotile particles into two types, i.e., fibrous and granular ones, and measured the chemiluminescence (CL) velocity when each type was mixed in a macrophage suspension together with a chemiluminescent agent, lucigenin. The CL was inhibited by superoxide dismutase (SOD), indicating that superoxide is produced in this reaction. The CL intensity was enhanced in the case of fibrous chrysotile but not granular one. These chrysotile particles were instilled into mouse trachea. After 4 days, the lung weight had increased almost twice with the fibrous chrysotile bot not garanular chrysotile. The permeability of the lung capillary, which was examined by a modified Evans blue method, varied in proportion to the lung weight, proving that the increase in lung weight is due to augmented permeability of lung capillaries. Also these inflammatory reactions were suppressed by intravenous SOD injection to the mice. These results suggest that the lung edema induced by asbestos inhalation arises due to particle-geometry-dependent superoxide production by macrophages.

View full abstract

Airborne particulate matter (PM) emissions from motor vehicles were studied using a motor vehicle tunnel in Japan where leaded gasoline has been completely depleted. Size separated samples of airborne PM were collected in the tunnel, and analyzed for more than thirty chemical components using neutron activation analysis, ion chromatography and carbon analysis. Target-transformation factor analysis (TTFA) was applied to the obtained data set to identify the emission sources of the PM together with their chemical component profiles. The results of TTFA indicated the presence of three sources: automotive exhaust particles, road dirt and tire-and brake-dust. The automotive exhaust particles were characterized by the fine carbon particles (<2.1μm) accompanied by sulfate of 7.7% and many trace elements. The road dirt contribution was distributed more than 90% in coarse particles (> 2.1μm). Tire-and brake-dust mostly belonged to coarse particles, in which carbon was the main chemical component, and some elements such as Zn, Mo, Sb and Ba were remarkably enriched.

View full abstract

A numerial model developed for simulating dispersion of automotive exhaust gas near complex urban roadways and buildings was applied to simple velocity field on flat surface in order to make comparison with conventional analytical dispersion models. Under neutral and cross wind condition, results from the numerical model reproduced well the results from the two types of major analytical models, by calibrating parameter on surface roughness and by devising the allocation of emission source. Parameter of numerical model for taking initial dispersion effect into account was derived from the inter-comparison with the analytical model calibrated by field surveys. The inter-comparison revealed that conventional gaussian model which depends on a single parameter σ_z can appropriately represent only a part of whole concentration distribution under the existence of wind velocity gradient. Finite difference solution of concentration field may be feasibly applied for practical use, as a better model to describe whole concentration field under simple flow on flat boundary.

View full abstract

Due to the widespread concern about acidrain, monitoring of rain composition as well as deposition rates have been conducted widely. Automatic acid rain measuring equipment was installed in our country to continuosly monitor the pH and electrical conductivity of every rainfall more than O.5 mm. This equipment monitor all ion concentrations every 2 weeks. Effective continuous monitoring equipment is needed in order to clarify the mechanisms of both rain acidification and the scavenging of gaseous and particulate air pollutant by rain. We combined commercially available automatic acid rain measuring equipment with two channel ion chromatograph, to establish an automatic acid rain collection and analysis system, which can obtain real time concentration data for anions (Cl^-, NO₃^-, SO₄^2-) and cations (Na⁺, NH₄⁺, K⁺). We obtained reasonable performance with the system and demonstrated its use with a field survey.

View full abstract

Soluble and insoluble selenium (Se) in the atmospheric deposits were determined at Nagaoka in Niigata Prefecture, and their sources were evaluated taking into account the seasonal variation and the ratios of Se to non-seasalt sulfur (nss-S). The soluble Se concentrations ranged from 0.032 to 0.41 pgμ1^-1, and its annual deposition ranged from 0.22 to 0.43 mgμm^-2. The annual deposition of insoluble Se was approximately less than 10 percent of the total Se deposition.
The concentration and deposition of soluble Se indicated remarkable seasonal variation, which was higher in winter and lower in summer, along with nss-S. Similar variation was also obtained for the Se to nss-S ratios (Se/ nss-S).
The main sources of soluble Se in summer at Nagaoka were supposed to be relatively local anthropogenic sources such as oli combustion and natural biological activities, because of its higher concentrations than those at non-polluted mountainous area and the lower Se/nss-S ratios. On the other hand, the ratios approached to the reported values of Se/ sulfur ratios of coal in winter. So, it can be estimated that East Asian anthropogenic sources, namely coal combustion, affected the increasing concentration of deposition of Se in winter.

View full abstract

The influences by configurations of roadway and surrounding buildings upon the dispersion of automotive exhaust gas were assessed by numerical models based on finite difference solutions of wind velocity and concentration fields as well as by tracer gas dispersion experiments in a wind tunnel. Configurations of roadway including flat, raised bank, open cut, and elevated, and configurations of surrounding buildings, as well as the combination of those configurations were set up both in numerical and experimental simulations. Results from numerical and experimental simulations fairly coincided with each other, and well described the characteristics of dispersion pattern for various configurations.
A number of runs revealed that physical structures, which were involved in the initial stage of pollutants dispersion, gave major influence upon concentration distribution, which includes configuration of roadways, their attachments (e. g. noise barrier walls) and configurations of buildings directly facing to the roadway. The study also revealed that combination of complex configurations might lead to seriously high concentration as in the case, that double-decker road within street-canyon badly disturbs dispersion of pollutants.

View full abstract