Behaviors of 7 principal halocarbons such as chlorofluorocarbons (CFCs) and chlorohydrocarbons and 6 aromatic hydrocarbonsuch as benzene and its substitutes were investigated during 15 months at 2 sites in urban areas in Yokohama, Japan.
The concentrations of CFC11 and carbon tetrachloride were low and their seasonal variations were small as shown in Fig. 1. The concentrations of p-dichlorobenzene were high in summer and low in winter, but these of the other compounds were low in summer and high in fall and winter as shown in Figs. 2-4. The concentrations of 1, 1, 1-trichloroethane, trichloroethylene and tterachloroethylene were much higher than those in rural areas in Hokkaido and Atlantic Ocean as shown in Table 1. They decreased from May 1990 as shown in Figs. 1 and 2 due to the effective regulations and guidances of treatment for them.
Intakes of benzene and several chlorohydrocarbons by man from the urban air were estimated and compared to their allowable intakes determined by WHO and US EPA for drinking water in Table 6. The results suggest that the concentrations of these compounds in urban air in Japan are in significant levels.

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Routine-basis air quality monitoring has been made for aerosol components at Beijing (Lishuiqiao), China since December 1988. Sampling and analytical methods of National Air Surveillance Network, Japan (NASN) were adopted in this study with some modifications and additions for target substances. Analytical results showed several characteristic aspects of air pollution at Beijing area. The possible influence of the coal combustion, which is a dominant energy source in Beijing area, was shown from the seasonal variations and mutual correlationships of tracer substances such as Te and B (a) P. The oil combustion was inferred to be not influential on the air quality of Beijing from the low levels of the enrichment factors of V and Ni. The soil dust, which was estimated to be long staying in spring, was the most influential air pollutant of ambient aerosols in Beijing, accounting for about 64% of TSP concentrations.

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Wintertime high concentration of NO₂ was analyzed by using data from air quality monitoring stations and a photochemical box model (PBM) application. The typical time variations of NO, NO₂ and O₃ during the high concentration days were clarified for sunny and cloudy day, respectively. Application of PBM was conducted by using NO_x's and NMHC's typical emission strength from Tokyo downtown area and a meteorological condition (such as temperature, humidity and mixing layer height). The relative contribution of NO2 time variation among the emission from various sources, the chemical reaction with background O₃ and the photochemical reactions were evaluated from the PBM calculation results. It was found that the oxidation of NO by the background O3 plays an important role for the concentration of NO₂ in the morning, while the contribution of the photochemical reactions becomes important in the afternoon. Also, it was concluded that the effect of photochemical reaction (oxidation of NO to NO₂) and the transformation from NO_x to PAN and HNO₃ play the significant role even in winter. These effects decrease the concentration of NO₂ in the daytime, however, these photochemically generated secondary pollutants in the daytime accelerate the increase of NO2 concentration in the evening hours.

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An improved sampling method was developed for determination of the average concentration levels of organic pollutants during field tests for two weeks. The column packed with 5 g of purified granular activated carbon was used for sampling. The twelve organic pollutants in air could be adsorbed by sampling of 1.7-2.3 m³ of air into the two columns connected in series under general conditions, though four columns were necessary under the hot and humid conditions such as in summer in Japan. All the pollutants collected could be eluted from a column with 50-100ml of hexane. The eluate was analyzed by GC and GC/MS. These compounds collected in the column were stable for two weeks.

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An application of ion chromatography (IC) using column switching method, in which one eluent and two kinds of columns were employed, and the two pathes of the eluent were switched for determination of cations concentration in rain water, was examined.
It was found that the IC using column switching method was suitable for the rapid analysis within 8 minutes and the simultaneous determination of five cations (Na⁺, K⁺, NH₄⁺, Ca²⁺ and Mg²⁺) with the eluent of 20mM HCl-0.2mM DL-2, 3-diaminopropionic acid monohydrochloride (DAP·HCl) at the flow rate of 2.0ml/min. Moreover, by the use of 500μl sample loop, this method showed good reproducibility and detection limits of ng/ml level concentration.

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