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Title: Detailed investigations on the inorganic chemical constituents of atmospheric aerosol and various depositions in Hong Kong
Other Titles: Xianggang da qi qi rong jiao ji ge zhong chen jiang wu ji hua xue cheng fen di xiang jin shen cha
Authors: Lai, Lotto Kim Hung (黎劍虹)
Department: Dept. of Biology and Chemistry
Degree: Master of Philosophy
Issue Date: 1997
Publisher: City University of Hong Kong
Subjects: Atmospheric deposition -- China -- Hong Kong
Notes: Bibliography: leaves 282-296.
CityU Call Number: QC882.42.L35 1997
Thesis (M.Phil.)--City University of Hong Kong, 1997
xix, 296 leaves : ill. ; 30 cm.
Type: Thesis
Abstract: Samples of the respirable suspended particulate (RSP) and bulk deposition at the semi-urban City University (CityU) site and the rural Kadoorie Agricultural Research Center (KARC) site were collected and analysed for their pH and remaining chemical composition. The data were studied in order to examine the influence of urban emissions on local precipitation chemistry in 1995. Canopy deposition, including stemflow, throughfall and fernfall, were also sampled and analysed between August and October 1995, in order to evaluate the impact of atmospheric pollutants on the deposition fluxes to vegetative surfaces in Hong Kong. Analyses were conducted to determine the concentrations of major cations (Na+, K+, Mg²+ and Ca¹+) and anions (C1-, NO3ˉ and SO4²ˉ) in the RSP samples, in various types of depositions, in which the pH and conductivity were also determined. In addition, aerosol samples were analyzed for 13 elements (Si, Ca, Al, Fe, Na, K, Ti, V, Mn, Co, Cu, Zn and Pb) by X-ray fluorescence (XRF) spectrometry. In general, the concentration levels of all chemical constituents in RSP samples were higher at the urban site, except for K and Cu. In bulk deposition, the ionic species at the urban site were higher than those at the rural site for Na+, Mg²+, Ca²+ and SO4²-; approximately equal for K+, C1ˉ and NO3ˉ; and lower for H+. Considering canopy deposition, throughfall has lower H+, higher Ca²+; and approximately equal NO3ˉ and SO4²ˉ compared with bulk deposition, implying that vegetation could effectively filter out the relatively massive dust particles. The methods of Principal Component Analysis (PCA) and hierarchical aggregate cluster analysis were employed for data analysis for discerning the possible sources. The PCA of the inorganic constituents in aerosol and various depositions reveal source types: 'anthropogenic/acidic', 'sea salt' and 'mineral' source-types through the factors isolated. The PCA of particulate elemental data revealed five particle source classes (soil, automobile/incineration, refuse burning, sea salt and oil combustion). Cluster analysis assisted in the interpretation of these factors. Finally, the deposition fluxes of various chemical constituents were estimated for Hong Kong. These suggest that the fluxes calculated from the EPD network data lead to underestimation, since such a network ignores dry deposition to vegetation, an effective process. The study shows that factor analysis is an effective method to isolate the various source types associated with urban and rural aerosol in general, and air pollutants in particular, and that vegetation is an effective sink for relatively large particles, e.g. salt, soil and flyash, but not of the smaller acidic particles which are largely due to urban sources.
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