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Title: Correlation between indoor and outdoor air pollutants for residential buildings in Hong Kong
Other Titles: Xianggang zhu zhai shi nei shi wai kong qi wu ran wu zhi xiang hu guan xi yan jiu
Authors: Ho, Pui Yi (何姵儀)
Department: Dept. of Physics and Materials Science
Degree: Master of Philosophy
Issue Date: 2004
Publisher: City University of Hong Kong
Subjects: Air -- Pollution -- China -- Hong Kong
Air quality -- China -- Hong Kong
Buildings -- Environmental aspects -- China -- Hong Kong
Dwellings -- Environmental aspects -- China -- Hong Kong
Indoor air pollution -- China -- Hong Kong
Indoor air pollution -- China -- Hong Kong
Notes: CityU Call Number: TD883.7.H6 H6 2004
Includes bibliographical references (leaves 68-71)
Thesis (M.Phil.)--City University of Hong Kong, 2004
xii, 71 leaves : ill. ; 30 cm.
Type: Thesis
Abstract: Hong Kong people have become more aware of the air quality in the last decade since the polluted air can cause harmful effects to human. In the present project, correlations among indoor air pollutants, outdoor air pollutants, indoor to outdoor ratios for elemental air pollutants, meteorological and non-meteorological conditions have been investigated. Eleven elements, namely, Na, Mg, Al, Si, K, Ca, Ti, Fe, Cu, Zn and Pb, are examined using Energy Dispersive X-ray Fluorescence (EDXRF) spectroscopy. In this project, the examined meteorological parameters include the relative humidity (%), wind speed (km/h) and atmospheric pressure (hPa). On the other hand, the non-meteorological parameters include the Air Pollution Index (API), the operation of the air conditioning system and the number of cars passing through the road next to the sampling sites. The correlations among the air pollutants and the various parameters are different for different elements. Regression analyses are first performed to identify the correlations. For different sites in different areas in Hong Kong, we have identified strong correlations between chemical elements for indoor to outdoor air pollutants. In particular, seven (Na, Al, Si, K, Ti, Fe and Cu) out of eleven studied elements show significant correlations (significance of F tests < 0.05). Moreover, outdoor air pollutants can effectively penetrate into indoor environment and the mean value of medians for indoor to outdoor air pollutant ratios is 0.96. For the particular selected site for the present study (Prince Edward), there are correlations among the meteorological parameters, the non-meteorological parameters and the examined chemical elements. The XRF intensities from the chemical elements (which reflect the abundance of the chemical elements) of indoor air pollutants, such as Al, Si, K and Fe, have been found to decrease with the relative humidity and increase with the Air Pollution Index (API). On the other hand, the abundance of the chemical elements Na, Cu and Zn are negatively correlated with the atmospheric pressure. For outdoor air pollutants, the amounts of Al, Si, K, Fe and Zn decrease while that of Na increases with the relative humidity. Most of them (Al, Si, K, Ca and Fe) are increase with API. Moreover, Ca and Fe intensities decrease with the wind speeds, and those for Na, Cu and Zn are negatively correlated with the atmospheric pressure. As regards the ratios between the chemical elements for indoor and outdoor air pollutants, the ratios for Si, Ca and Fe are positively correlated with the wind speed, while that for Si is negatively correlated with the atmospheric pressure. In general, the abundance of the chemical elements decreases with the relative humidity because of the enhancement of removal by precipitation. On the other hand, the abundances may increase or decrease with the atmospheric pressure, depending on the local generation of air pollutants or transportation over long distances. Wind speed had impacts on outdoor air pollutants as well as the penetration of outdoor air pollutants. Furthermore, API is a directly relevant parameter to reflect the amount of airborne pollutants. Besides, poor correlations for chemical elements have been found between indoor and outdoor air pollutants when the windows are closed and the air conditioner is turned on. Under such conditions, almost all chemical elements give significance of F tests larger than 0.05 for the regression analyses. The mean values of medians (for various chemical elements) for the indoor to outdoor ratios are 0.81 (when the windows are open and the air conditioner is turned off) and 0.66 (when the windows are closed and the air conditioner is turned on). This shows that operation of the air conditioner while closing the windows can significantly prevent the outdoor air pollutants from penetrating into the indoor environment. Factor Analysis (FA) and Principal Component Analysis (PCA) have been used to aid the identification of the sources of air pollutants. FA has been applied to indoor and outdoor air pollutants separately as well as together (the latter being referred to as the combined data). From such procedures, indoor air pollutants have been found to come from four sources, namely, soil aerosols, industrial emissions, marine aerosols and bonfire related source (from burning of incense and joss paper, etc.). In contrast, there are only three factors for outdoor air pollutants, namely, soil aerosols, emission from construction sites and vehicle exhausts. For combined data, three factors have been identified. These are soil aerosols, vehicular emissions and marine aerosols. It is also noted that soil or crustal elements are predominant in indoor and outdoor air.
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