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Title: Organochlorine bioaccumulation from coastal sediments in representative Hong Kong benthic invertebrates = 香港底棲無椎脊椎動物對沿岸沉積物中有機氧化合物的生物富集作用研究
Other Titles: Organochlorine bioaccumulation from coastal sediments in representative Hong Kong benthic invertebrates = Xianggang di qi wu zhui ji zhui dong wu dui yan an chen ji wu zhong you ji yang hua he wu de sheng wu fu ji zuo yong yan jiu
Xianggang di qi wu zhui ji zhui dong wu dui yan an chen ji wu zhong you ji yang hua he wu de sheng wu fu ji zuo yong yan jiu
Authors: Moganti, Shanti
Department: Dept. of Biology and Chemistry
Degree: Doctor of Philosophy
Issue Date: 2007
Publisher: City University of Hong Kong
Subjects: Benthic animals -- Effect of sediments on -- China -- Hong Kong
Coastal sediments -- Microbiology -- China -- Hong Kong
Organochlorine compounds -- Bioaccumulation -- China -- Hong Kong
Notes: CityU Call Number: QH545.O72 M63 2007
Includes bibliographical references.
Thesis (Ph.D.)--City University of Hong Kong, 2007
xx, 255 leaves : ill. (some col.) ; 30 cm.
Type: Thesis
Abstract: Bioaccumulation is a process by which potentially toxic chemicals can gain access to and cause effects upon living organisms. Bioaccumulation leads to an increase in the concentration of a chemical in an organism over time compared to the chemical's concentration in the environment. The extent to which a chemical can bioaccumulate depends on several factors including the concentration of a chemical in the environment and its availability to an organism. Chemicals accumulate through a variety of pathways, including uptake through water and across respiratory surfaces of an organism and ingestion through food. The nature of the chemical itself is a very important factor affecting tissue uptake. Subsequent sequestering of the chemical into the body of an organism depends on the ability of the organism to metabolize and eliminate the particular chemical from its body. Bioaccumulation is a normal process that can ultimately have adverse effect on an organism only when this equilibrium between exposure and bioaccumulation is disturbed. The objective of this study was to undertake research on native indicator species and the methodologies that could be used to assess and monitor the phenomenon of sediment-based bioaccumulation, taking into account local parameters including sea water salinity, sediment grain size, total organic carbon, etc. Biological effects are usually a function of bioaccumulation. Thus, whole body concentration may serve as a better predictor of effects than concentrations in sediment or water. Studies on metal accumulation by animal and plant species in Hong Kong have been performed in the past, but there is little documented evidence regarding the phenomenon of bioaccumulation from sediments of the more persistent classes of contaminants, such as trace organics. Thus, the main focus of this study was to expose sediment inhabiting, deposit feeding organisms to organochlorine contaminants (polychlorinated biphenyls, PCBs) to test their bioaccumulation potential. The approach used was an estimation of the uptake of contaminants based on the critical body burden concept. The selection of the test species played a very important role in the project. It was decided to work with deposit feeding test species, as only these animals could reflect the true contaminant concentrations in the sediment by feeding on related organic matter. The second key aspect in selecting the test species was based on the condition index values of these animals, which could potentially reveal the “health status” of the test species during the 28 d exposure period. Various invertebrate species were held in the laboratory and examined. Finally, a bivalve clam species (Asaphis deflorata) was chosen as the test species. Field-collected animals were first depurated in the laboratory for a period of 10 days and then exposed in the laboratory for 28 days to sediments spiked with polychlorinated biphenyl congener 153. During the exposure, various physicochemical factors, including temperature, salinity, dissolved oxygen, pH and ammonia were measured daily to check the tank conditions. The animals were supplied with clean, filtered seawater every day. The potential of these animals to bioaccumulate the toxicants from the sediments was tested and the uptake concentrations on various sampling days (0, 10 and 28) were measured by chemical analysis. Following this successful exposure, the test species was exposed to field-collected sediments of varying contaminant concentrations and grain size to test their real-time uptake scenarios. Sediments from various locations close to Hong Kong shorelines were collected based on the suspected gradient of contamination and data from previous studies (e.g., Richardson and Zheng, 1999) which categorized sites based on varying degrees of pollution. Four sites, namely Shek O in the southeast of Hong Kong Island, Ap Lei Chau in Aberdeen district, Tai Kok Tsui in the Mong Kok waterfront, and To Kwa Wan near Kowloon City pier were chosen. Shek O was the cleanest and To Kwa Wan was the most polluted site. 30 L fiberglass tanks with equal number of test species were maintained in replicate tanks (for each concentration) for 28 days, with equal quantities of sediment and filtered seawater. Prior to this the animals were depurated for 10 days in clean sediment. During the 28 d holding period, sampling of both sediment and clams was performed on days 0, 10 and 28, along with condition index measurements. Concentrations of organochlorine pesticides and polychlorinated biphenyls in sediments indicated that Shek O was the cleanest of the sites, followed by Ap Lei Chau and Tai Kok Tsui. To Kwa Wan is an industrial site and the sediment concentrations of all the contaminants there were found to be very high. There were marked differences among the sites, especially in PAH concentrations, with To Kwa Wan showing extremely high sediment concentrations. The biota concentrations of various organochlorine pesticides and PCBs suggested that there was sediment concentration-dependent accumulation by A. deflorata on day 10 of the experiment. However, there was no significant increase on day 28 for any of the compounds tested. Contaminant concentrations in clams feeding on Shek O sediments were minimal and almost the same on all sampling days, indicating the presence of only baseline concentrations. Measurement of sediment and tissue concentrations from Shek O sediment showed that this site was undoubtedly the cleanest, and was ideal as a control site. Mortality was observed in all the test tanks including that in Shek O sediment tanks. However, clams appeared to bury faster in the control (Shek O) sediment and remained buried, unlike those in the sediment from the other locations, where some remained predominantly on the surface. Nevertheless, despite not completely burying, the clams in other test sediments still exhibited sediment concentration-dependent tissue accumulations. Results of the investigation indicate the possibility of developing a standard test protocol for bioaccumulation by sediment dwelling invertebrates, for practical use in Hong Kong, using A. deflorata.
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