The important role of heterogeneous chemical reactions and processes between gaseous pollutants and atmospheric aqueous droplets (clouds, fogs and rain) or particulate matter in tropospheric chemistry is reviewed. The main features of this article are sulfur dioxide oxidation (Chapter 3), transformation of nitrogen oxides (Chapter 4) and transformation/decomposition of organic matter (Chapter 5).

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Setting up a simple oxidant monitor using KI, the authors found that triethanolamine (TEA) buffer solution depressed the amount of iodine (I₂) liberated from KI. The reaction of TEA with I₂ was thus examined.
The reaction between TEA and I₂ was investigated by product analysis. A fine colorless crystal was obtained upon concentrating the solution of reaction products. The crystal was analyzed by elemental analysis, paper electrophoresis, gas chromatography, infrared spectrometry, and mass spectrometry. The crystalline product was found to be an adduct TEA·HI This colorless crystal is easily soluble in water, and its melting point is 167.5°C. Another product of TEA-I₂ reaction was determined to be HCHO by gas chromatography.
According to the experimental results, TEA and I₂ react irreversibly. The authors propose the following equations for TEA-I₂ reaction.
TEA+ 3I₂+3H₂O=NH₄I+5HI+6HCHO
TEA+HI=TEA·HI
(excess)

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1-nitropyrene (1-NP), which has recently been considered to be one of the important environmental mutagens among air pollutants, and benzo (a) pyrene (B (a) P), a well known environmental carcinogen, were intratracheally instilled into male Syrian golden hamsters once a week for 15 weeks. The total dosage was 30 mg. At the same time, a further control group received only phosphate buffer solution. During the total life span, tumor incidence rates in the 1-NP and B (a) P groups were 10% and 86%, respectively, but no tumor developed in the control group. The incidence rates of lung tumors in the 1-NP and B (a) P groups were significantly different, but not in the 1-NP and control groups. These results show that the carcinogenicity of B (a) P to the lung of Syrian golden hamsters should be considered more seriously than that of 1-NP.

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It was found from the observation of 0_x/0₃ during past seven years at Shiogama Station that the decrease of sensitivity of an oxidant meter was caused by “fouling” on the countercurrent absorption tube, especially in summer. The authors found that bacteria existed in all the piping of oxidant meter, and taht the number of them was remarkably large in the countercurrent absorption tube. The authors examined the reactivity of iodine toward bacteria in the absorbing solution and found that bacteria removes iodine in the absorbing solution. And it was found that the concentration of iodine in the absorption solution was decreased in inverse proportion to the quantity of bacteria. A considerably large quantity of iodine is decreased even by the reaction of iodine with bacteria at 0°C within ten minutes. These results indicated that the decrease of measured value of oxidants is caused by bacteria.

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Specimens of carbon steel were exposed to the atmosphere and air pollutants weremeasured at 7 sites in Tokyo. The relationship between corrosion rate of the steel and air polltion data was studied from the comparison of those taken at the sites and those temporal trends. Corrosion ratewas extremely high in the early 1970, s andthereafter but it gradually decreased and showed about 70% decrease for subsequent 10 years period. It seemed most likely that the decrease was due to the decreaseof air polluants, especially SO₂ concentration and the amount of fall dust.
The single correlation coefficient showed strong relationship between corrosion rate and air pollutants such as SO₂, fall dust soluble, meteorological factors such as temperature and relative humidity. Multiple linear regression was used to analyse the relatinship between corrosion behavior of this steel and the collected environmental data. From this analysis and the R value of observed and predicted values showed good correlation and both SO₂, humidity were especially significant to the rate of corrosion.

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Air pollutants from the fluidized bed municipal incinerator were investigated. The incinerator was able to incinerate 150 t refuse in a day. That discharged NO_x, dust and odor in much the same with the step-grate stoker type municipal incinerator. But, that discharged CO and THC in higher, SO₂ in lower concentration than the step-grate stoker type municipal incinerator. High HCl removal efficiency was gained by excess CaCO₃injection into the furnace.
O₂ and air pollutants' concentration were changing widely corresponding with the amount of refuse into the furnace.
Especially, when the amount of refuse into the furnace increased suddenly, O₂ concentration often decreased quickly under some percent. Then CO and THC, which was rich in aromatic or non-saturated hydrocarbons, were discharged in high concentration. Black smoke was discharged, too.

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Between 1973 nad 1985 the Osaka Medical Society conducted surveys by means of questionnaires every other year for public school children in the Osaka Prefecture concerning the subjective symptoms of “usually coughing”(a total of 5, 480, 443 children in 6, 449 schools).
The results of these surveys were analysed and the following results obtianed:
(1) Between 1973 and 1981 the concentration of sulfur dioxide was found to decrease significantly throughout the Osaka Prefecture, while the concentration of nitrogen dioxide remained unchanged. Regional differences related to the prevalnce of cough complaint between polluted and control areas also decreased in parallel to the fall in sulfur doixide concentration. After 1981, however, the regional differences in the rate of cough complaint remained constant, despite a continued fall in sulfur dioxide concentration which is in contrast to the previously observed trend. The lower limit of the yearly mean sulfur dioxide concentration which appeared to influence the prevalence of cough complaint was 0.013-0.015 ppm.
(2) The correlation coefficient between the rate for complaint of cough and for the nitrogen dioxide concentration was+0.708 (p<0. 001) in those schools located within 1 km of the 27 air pollution monitoring stations (the number of children surveyed, 89, 866). The lower limit for the yearly mean nitrogen dioxide concentration which influenced the complaint of cough was 0.020-0.025 ppm.
(3) Based on these results, a formula for a model was proposed which shows the relationship between the rate for cough complaint and the degree of air pollution.

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It was considered that the leaf damage observed on pear leaves was caused by iodine emitted from a iodine refinery. Therefore, we have confirmed this by exposing pear plants to artificially emitted iodine gas in a chamber. The characteristics of iodine gas sorption by pear leaves were also clarified. Experimental results are obtained as follows:
(1) The main observable damage was brown spots on leaves. Furthermore, the injured leaves became yellow or orange-color, and finally fell down at early growth stage.
(2) The extent of leaf damage differed depending on pear cultivars: Kosui and Hakko were sensitive, while Chojuro was resistant.
(3) Gas sorption rate of iodine by pear leaves was constant at the constant concentration of iodine gas, and that rate was increased along-with the increase of iodine gas concentration.

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Stack dust sampling is often carried out using a sampling nozzle and a certain length of sampling line which is connected with a dust sensor or a dust collector.
Dust deposition was experimented using CaCO₃ powder (mmd=4μm) as test dust and 2m of sampling tube (dia.=φ6-14 mm). The test dust was deposited about 45-53% upstream of the dust collector, and especially 20-26% in the 90° bend of the sampling nozzle.
In order to prevent dust deposition the mechanical vibration was added to the sampling line using a magnetic vibrator. As a result of the experiment the prevention effect or dust re-bounce was confirmed significantly with the stronger vibration effect, which was defined as the ratio of vibration acceleration to vibration frequency. About 86% of dust deposition was reduced in the range above 1.5 G/Hz for flyash and CaCO₃ dust respectively, though vibration effect was applied up to 1.7 G/Hz in this experiment.
Vibration Reynolds number was adopted by non-dimensionizing the strength of vibration effect. It was found that the relation between vibration Re and reduction of dust deposition was expressed in a curve line for both the test dusts, and from the relation high reduction rate over 90% can be predicted to be obtained for above 700 of vibration Re.

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The statistical properties concerning the frequency distribution in nitrogen dioxide concentration measured by the triethanolamine filter paper method for the intermittent long time was examined.
The investigation areas and times were (1) Nishinomiya-Kohshien area (1977. Oct.-1985. Oct., nine times) and (2) Nishiharima area (1981. Jan.-1985. Mar., twelve times.)
(1) Analyzing the data, the peak-concentration of NO₂ concentration distribution in recent years was found to be increased compared with that of the precious distribution in either (1) or (2) areas.
(2) The form of NO₂ concentration distribution was shown to be similar in the neighboring towns.
(3) The measured data in each of 160 investigation points in (2) area could be expressed as normal distribution, log-normal forms, or two log-normal forms.

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