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Receptor modeling of respirable suspended particulate matters in Hong Kong

Authors Lee, Eddie
Issue Date 2000
Summary Results from the receptor modeling of atmospheric aerosols, in particular, Respirable Suspended Particulates (RSP) with aerodynamic diameter less than or equal to 10 μm, or known as PM10, in Hong Kong measured by the Environmental Protection Department between 1992 and 1994 are presented. The source apportionment techniques employed in this study include correlation matrix of logarithmic transformed chemical species concentrations and wind field data to derive source-wind direction relationships and an advanced algorithm called positive matrix factorization (PMF) in receptor modeling for identification of RSP sources subject to a rigorous approach to eliminate rotation ambiguity. The Pearson correlation coefficient was used in the wind sector analysis RSP in Hong Kong. The species analyzed in this study were Al, Ca, Mg, Pb, Naplus, V, Clminus, NH4+, NO3minus, SO42minus, Brminus, Mn, Fe, Ni, Zn, EC (elemental carbon), THC (total hydrocarbon), Cd, Kplus, Ba, Cu, As, and Be. The study aimed to develop a relationship between the sources and wind characteristics using a purely statistical analysis of the particulate database. The Kolmogorov-Smirnov goodness-of-fit test shows that the 24-hour cumulative wind speed from all directions and the mass concentrations of some chemical species follow lognormal distributions. Logarithmic transformed species concentrations and 'wind speeds were used as inputs to minimize the effect of fluctuation of wind direction due to local topography under low wind speed conditions. The four sources identified by filtered matrix were marine, crustal, "non-ferrous smelters" and fuel oil burning sources. Marine aerosols were found to be predominately associated with southeastern winds. Nevertheless, they were also -xi- correlated with some localized coastal northwesterly winds. Crustal particulates were mostly locally driven such as reclamation, large-scale construction activities or soil erosion. Although found in some residential/commercial areas, aerosols derived from non-ferrous smelters and fuel oil burning were mostly identified in a major industrial area in Hong Kong. EC, NH4plus, NO3minus and SO42minus are found to be independent of wind directions and are ubiquitously present in Hong Kong as "background species". PMF was used to identify the sources of RSP in Hong Kong. The compositional data obtained from the Hong Kong Environmental Protection Department from 1992 to 1994 were analyzed. The species analyzed in this study are Al, Ca, Mg, Pb, Naplus, V, Clminus, NH4plus, SO42minus, Brminus, Mn, Fe, Ni, Zn, Cd, Kplus, Ba, Cu, and As. Unlike the conventional receptor modeling algorithm, Factor Analysis (FA), PMF only generates non-negative source profiles. To eliminate sulfate from such factors where it is not physically plausible, special penalty terms were included in the model so that sulfate concentrations could be selectively decreased in specified factors. A 9-factor model containing non-zero sulfate concentrations in three factors gives the most satisfactory source profiles. Ammonium sulfate, chloride depleted marine aerosols and crustal aerosols are the three non-zero sulfate sources. Other factors are marine aerosols, non-ferrous smelters, particulate copper, fuel oil burning, vehicular emission and bromide/road dust. The last two sources can be combined as a single source of vehicle/road dust. The 'compositional profiles of these factors were also developed. The mass profiles obtained can be improved by further refinement of distribution of sulfate in the sources.
Note Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2000
Language English
Format Thesis
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