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Title: The eco-physiology of outdoor airborne fungi in Hong Kong
Other Titles: Xianggang shi wai kong qi zhong zhen jun zhi sheng tai sheng li xue yan jiu
Authors: Chan, Wai Yee (陳慧儀)
Department: Dept. of Biology and Chemistry
Degree: Master of Philosophy
Issue Date: 2006
Publisher: City University of Hong Kong
Subjects: Fungi -- Ecophysiology -- China -- Hong Kong
Notes: CityU Call Number: QK604.2.E28 C45 2006
Includes bibliographical references (leaves 225-258)
Thesis (M.Phil.)--City University of Hong Kong, 2006
xxvi, 285 leaves : ill. ; 30 cm.
Type: Thesis
Abstract: It is well-proven that exposure to airborne fungi can induce adverse health effects. In Hong Kong, previous studies on airborne fungi have usually been confined to offices and public buildings. There are only few published on the study of outdoor airborne fungi. This study aims to generate a profile of outdoor airborne fungi in Hong Kong, so that a better understanding of their temporal and spatial occurrence in rural and urban areas; as well as their eco-physiology can be obtained. During each sampling, air samples were taken every 2.5 hours over 12.5 hours monthly from January 2003 to June 2005. Samples were collected from one rural area (Lantau Island) and two urban areas (Mong Kok and Kwun Tong) by using a sampler to collect culturable fungi – the Reuter Centrifugal Air Sampler (RCS) and a sampler which collects both cultuable and non-culturable fungi – the Air-O-CellTM (AOC) Sampler. The relationship between fungal abundances and the possible related environmental factors (i.e. temperature, relative humidity, rainfall and respirable suspended particles, and the physiological requirements (i.e. temperature and water activity) of the dominant fungi for growth, germination and sporulation were also investigated. In general, the AOC sampler yielded more abundant (3.5 to 12.5 times higher) but similar species diversity of airborne fungi compared with the RCS in the air samples. In the rural area, fungal count of samples collected by using culturable sampling ranged from 20 to 634 CFU/m3, with a much higher range (152 to 6660 count/m3) compared with that of the non-culturable sampling. Slightly lower fungal count and similar fungal compositions were recorded in the two urban areas. Significant variations in the fungal counts were observed during a day. Higher fungal counts were observed in the mornings and late afternoons; and the fungal counts were lowest at noon. The highest fungal counts were recorded in the autumn, while the lowest were recorded in the winter. The median values and ranges recorded in the rural area in spring, summer, autumn and winter were 228 (28 – 320 CFU/m3), 265 (40 – 360 CFU/m3), 270 (48 – 320 CFU/m3), and 145 (34 – 360 CFU/m3) respectively. Similar variations were observed throughout the study, except for the samples collected by using non-culturable sampling in the rural area (p = 0.025). The dominant fungal genera were Alternaria, Aspergillus, Cladosporium, and Penicillium. These results agree with the published information on outdoor fungal populations worldwide. Alternaria was the most dominant fungi throughout the year in the rural area, while Penicillium was the most dominant fungi in the two urban areas. In general, although Cladosporium was one of the most dominant genera, it was never the most abundant group. However, its abundances in the rural area (LI) and the urban area (KT) were greater in the cooler months (spring and winter) than in the warmer months (summer). In general, the percentage abundance of Penicillium was always higher than that of Aspergillus. With the exception of Cladosporium, significant positive correlations between temperature and the fungal abundances of Alternaria, Aspergillus and Penicillium were found. Positive correlations between fungal abundance and relative humidity was also found, but was less significance. With the exception of the samples collected in urban area (MK) by using non-culturable sampling, there was a negative but not significant correlation between rainfall and dominant fungal genera. A positive correlation was also observed between PM 10 and the fungal abundance collected by using non-culturable sampling in the two urban areas (MK and KT). Physiological studies showed that all of the fungi tested (Aspergillus cervinus, Alternaria alternata, Cladosporium oxysporum, Curvularia lunata, Penicillium brevicompactum and Pestalotiopsis sp.) were mesophilic exhibiting optimum growth, germination and sporulation between 25°C and 30°C at water activity levels of 0.897 and 0.963. The range of the optimum temperature and water activity for the growth, germination, and sporulation of these dominant groups of fungi fell within that of the climatic conditions in Hong Kong. Future studies should concentrate to collect samples at location with reference to the wind direction as to generate a seasonal profile of outdoor airborne fungi in Hong Kong territory.
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