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Title: A study of trace metal contamination in different urban terrestrial compartments in Hong Kong and Guangzhou
Authors: Liang, Siyuan
Degree: Ph.D.
Issue Date: 2019
Abstract: Trace metal contamination in urban terrestrial environments is a major environmental problem throughout the world, due to its harmful implications on human health. This research aims to conduct a multi-compartmental environmental investigation on trace metal distribution in urban environments of Hong Kong and Guangzhou, focusing on: (1) soil geochemical signature of urbanization and industrialization in the two cities; (2) quantitative source contributions of trace metals in soils, road dust, and foliar dust, and comparison of their suitability for monitoring urban contamination conditions in a typical megacity; and (3) chemical partitioning of trace metals in various particle size fractions of soil dust, associations of trace metals between soil dust and other types of dust, and potential health risks. Firstly, the vertical and horizontal distribution patterns of trace metals in urban soils were compared between Hong Kong and Guangzhou. Slightly lower trace metal concentrations and higher Pb isotopic compositions (206Pb/207Pb) of surface soils (0 to 3 cm) compared to top soils (0 to 15 cm) were found in Hong Kong, possibly due to the temporally decrease of anthropogenic deposition and a downward migration of trace metals in urban soils. Higher trace metal concentrations and lower Pb isotopic compositions (206Pb/207Pb) in surface soils than top soils were observed in Guangzhou, consistent with the temporally increase of trace metal inputs in soils. The remarkable hotspots of trace metals in urban soils were mainly attributed to industrial and traffic sources in these two cities. Secondly, a multi-compartmental investigation of trace metal contamination was conducted in the urban environment of Guangzhou. Lead isotopic data and modeling (Absolute Principal Component Scores-Multiple Linear Regression, APCS-MLR) results identified industrial and traffic emissions as the major sources of trace metals in urban soils, road dust, and foliar dust. Spatial distribution patterns implied that Cu in road dust was a good indicator for traffic contamination, particularly influenced by traffic volume and vehicle speed. Lead and Zn in foliar dust indicated the industrial contamination, which decreased from the emission source (e.g., power plant and steel factory) to the surrounding environment. Finally, the chemical partitioning of trace metals in soil dust was studied. Trace metal concentrations were inversely associated with particle sizes in soil dust of Guangzhou and Hong Kong. Source apportionment and chemical composition of trace metals illustrated the important influence of anthropogenic particles, as well as Mn/Fe oxides and organic complexes, on the metal accumulation in fine particles of soil dust. Results of Pb isotopes and the comparison of temporal trace metal variations indicated the similar metal sources and potential metal exchange between fine soil dust particles and other types of dust (e.g., fine road dust and respirable suspended particles (PM10)). Health risks posed by trace metals elevated with decreasing soil particle sizes. 53% and 100% of the soil dust <10 ┬Ám in Hong Kong showed a probability of noncarcinogenic hazard and a nonnegligible carcinogenic risk, respectively. Thus, the re-suspension of soil dust should be paid more attention to control health risks caused by trace metal contamination in urban environments.
Subjects: Hong Kong Polytechnic University -- Dissertations
Metals -- Environmental aspects -- China -- Hong Kong
Soil pollution -- China -- Hong Kong
Metals -- Environmental aspects -- China -- Guangzhou
Soil pollution -- China -- Guangzhou
Pages: 18, 188 pages : color illustrations
Appears in Collections:Thesis

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