A new visible plume model is developed to predict visible plume, temperature, moisture and droplet from a mechanical-draft cooling tower. The developed model is a normal Gaussian plume model for moisture and temperature, considering fan configuration, wet-dry combined cooling tower system, vertical atmospheric temperature and atmospheric stability. The accuracy of previous models (FOG, SACTI) and the developed model is investigated to compare the model results with observation conducted in Japan. The results show that the previous models can not accurately predict the visible plume length and height because they have mainly developed for a natural-drift cooling tower, which is different type from a mechanical-draft cooling tower. On the other hand, the visible plume length and height predicted by the developed model are in good agreement with the observation, and statistical data analysis also shows that the model provides better performance than the previous models. Furthermore, the model predicts not only the visible plume region but also temperature, moisture and droplet from the cooling tower.

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We developed the new OH reactivity measurement method using neither laser nor chemical ionization mass spectrometry. The technique used here is comparative reactivity method (CRM) developed recently. We compared observed data obtained by this method with the already established laser pump and probe method. The advantage of the system developed here using CRM is smaller and less complicated. OH reactivity of standard gases (CO, ethane, propane, ethylene, isoprene, NO₂) was measured by CRM. All of the standard gases gave linear correlation between calculated and observed OH reactivity, but their absolute values were about 1/5 of expected OH reactivity. Correction by suitable factor is necessary for CRM. Comparison experiment of OH reactivity by laser method and CRM in ambient air was performed in October 2008, at suburban Tokyo. The results of both methods showed similar time variation, but the absolute value was about 30 % smaller for CRM method. The reason of the underestimate should be revealed and improved. However, as both methods showed similar variations for ambient air, thus the CRM can be used for ambient air measurements.

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Sample preparation and observation methods were examined to achieve rapid and reliable determination of the concentration of asbestos fibers collected at building dismantlement sites by analytical scanning electron microscope (A-SEM). Pretreatment of asbestos-bearing membrane filters by ashing with oxygen plasma (method A) was not suitable, because fiber migration due to coalescence of filter material during ashing was occurred, ashing efficiency was not reproducible, and was very time consuming. On the contrary, pretreatment of the filters by impregnation and fixing with water-based carbon paste (method B) was rapid and reproducible, while secondary-electron imaging at low magnifications (∼ x 1000) was hindered by filter background. However, the latter drawback was negligible by using backscattered-electron imaging, because inorganic fibers including asbestos on the filter could be clearly observed. According to the analytical results obtained here, measurement method for airborne asbestos was recommended as follows. Using the filter sample prepared by method B, inorganic fibers were searched by backscattered-electron imaging at the low magnification. When the inorganic fibers were found, secondary-electron imaging and energy dispersive X-ray spectrometer were performed at higher magnifications (∼ x 10000), in order to obtain their fine images and elemental compositions. The present method was applied to the analysis of airborne particles collected at the building dismantlement sites, and the asbestos concentrations including asbestos fibers of width less than 0.25 μm (less than the limit of detection by phase contrast microscopy) could be successfully determined.

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The present study aimed at elucidating the effects of time resolution of air concentration on the estimated exchange fluxes of ammonia (NH₃) and particulate ammonium (pNH₄) by a gradient method. Observation of their exchange fluxes was conducted at an upland filed in Hokkaido in spring in 2008 and 2009. The filter-pack method was applied to measure the air concentrations. Measurement frequencies were once to three times during daytime and once during nighttime. The errors in estimated fluxes by averaging the air concentrations during daytime were small both for NH₃ and pNH₄; however, the significant emission of NH₃ due to the manure application resulted in a relatively large error. By contrast, the error in estimated fluxes by averaging the air concentrations during a day was large for NH₃, which underestimated the exchange fluxes by 30% in average. It was concluded that day-night separation was indispensable for reducing the errors in estimated fluxes of NH₃. The day-night separation was also effective in estimating a weekly mean flux.

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Recently, power plant's cooling towers equipped with instruments for preventing plume to visualize, which is a mechanical-draft cooling tower, tend to be planned and be constructed in Japan. Traditional ways of environmental assessment for a cooling tower has adopted a visible plume prediction model based on a natural-draft cooling tower. The requirement of developing new visible plume model having capability of prediction of visible plume, temperature, moisture and droplet from a mechanical-draft cooling tower is rising up. A field campaign to obtain data from a power plant with a mechanical-draft cooling tower for evaluation and validation of a new visible plume model and some conventional models is conducted. Measurements of surface temperature and humidity distribution around the plant does not show a clear effect of visible plume. Over 100 pairs of visible plume height and length are obtained by using video cameras and thermographyies Furthermore, droplet from the cooling tower shows very few amounts at a ground because of adopting to it a eliminator for preventing droplet scattering.

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[in Japanese]

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