A statistical estimation of automobile hydrocarbon emissions by factor analysis was obtained from the results which were reported in our automobile road tunnel survey. As a result, seven common factors were obtained from 27 variable data. These were; vehicle traveling conditions, speed, LPG-powered automobiles, gasolinepowered automobiles, 2-cycle engine automobiles and two background factors. Further, in order to estimate the relative contributions of various types of hydrocarbon pollution sources, regression lines and emission factors were obtained from the statistical estimation.

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Suspended particles released from refuse incinerators were subjected to multielement analysis by means of instrumental neutron activation method and energy dispersive X-ray fluorescence spectrometry. The analytical results were compared with the elemental concentrations observed in the urban atmosphere, and the contribution of the refuse incineration to the urban atmosphere was roughly estimated. Greenberg et al. pointed out on the basis of their study on Washington, D.C. incinerators that the refuse incineration can account for major portions of the Zn, Cd and Sb observed on urban aerosols. According to our results, the contribution of the refuse incineration to the urban atmosphere for Zn, Cd and Sb is not negligible, but not so serious as in U.S.A. big cities. In big cities in Japan there must be other more important sources of these elements.

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A improved gas chromatographic determination of trace organic vapors such as esters, ketones, alchols and aromatic hydrocarbons in ambient air has been reported. The analytical system consists of a stainless steel sampling tubing (10 cm×3 mm i.d.) packed with 60-80 mesh Tenax GC (7 cm×3 mm i.d.), a sample concentration unit with a 120 ml sampling loop and a gas chromatograph with a flame ionization detector (FID). The sampling tubing is silver-welded on a modified stem assembly of Swagelok Quick-Connects so that the tubing can be instantly installed on or off the concentration unit or the injection port of the gas chromatograph.
Ambient air is sampled by a diaphram pump into a polyester bag (Flek Sampler) at 200-500 ml/min for 5-30 min. Using the concentration unit, 120 ml of the sample are taken into the sampling loop, and the trace organics contained in the sample are then trapped into the sampling tubing by passing helium gas at 120 ml/min for 4 min. After the tubing is transfered to the injection port of the gas chromatograph, the concentrated organics are thermally desorbed for 30 seconds, and introduced into the analytical column by backflushing the carrier gas through the tubing for 30 seconds. The operation conditions of the gas chromatograph are as follows: column-3 m×2 mm i.d. stainless steel tube packed with 20 % PEG 20M on 80-100 mesh Celite 545, injection port temperature-140°C, column temperature-90-120°C, FID temperature-140°C, carrier gas-40 ml/min nitrogen. Advantages of the technique
Advantages of the technique are low ppb sensitivity, excellent quantitative accuracy and rapid analysis time. Relative standard deviations of measured values for a number of organic vapors are 1.8-14.2 % in the range of 2-200 ppb, and analysis time can be 7-12 min per a sample.

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An attempt was made to study the applicability of simple method of nitrogen dioxide measurement as a personal monitor usable in some field study. The device which we tested was a modification of so called simplified measurement method for NO₂ using filter paper adsorbed triethanolamine.
We did two experiments, the one was preliminary exposure experiment and the other was the experiment exposing the device under the circumstances like an ordinary kitchen.
The coefficient of variation of the results of measurement of 24 hour exposure was less than 10 % and the range of the results was from 20 ppb to 200 ppb. They showed a good linearity within the range above noted.
By simple regression analysis between the measurement results by chemiluminescent method and that of the simple method, the error of estimation of the latter was±21 ppb (confidence coefficient was 90%).
According to these results, we believe that this simple measurement apparatus for NO₂ can be used for the evaluation of personal exposure dose for NO₂.

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The characterization of the trace odorants (ppt-ppb level) in air by gas chromatography using the preconcentration methods, such as the cold trapping with liquid oxygen and the trapping at room temperature with porous polymer beads were investigated. The trace odorants (147 odorants) were characterized as to the following eight groups (Table 1, 2) i.e., Group (I): Sulfur compounds; Group (II): Lower aliphatic amines; Group (III): Carbonyl compounds; Group (IV): Hydrocarbons; Group (V): Lower aliphatic mono alcohols; Group (VI): Phenols; Group (VII): Lower fatty acids; Group (VIII): Indoles. The conditions for the systematic gas chromatography of each groups are listed in Table 2 to 10. Theconcentration volume, detection limits, analytical times (including sampling times) and accuracy were as follows: concentration volume, (1-50) liter; detection limits, (0.05-2) ppb; analytical times, less than 40 min;accuracy, less than about 10%.

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