| Summary: | 碩士 === 國立高雄師範大學 === 生物科技系 === 106 === Sediments have a major role in ecosystem functioning but can also act as physical or chemical stressors. The importance of sediments as stressors will depend on site ecosystem attributes and the magnitude and preponderance of co-occurring stressors. Risk assessments and restoration strategies should better consider the role of chemical contamination in the context of multiple stressors. Methods for assessing site-specific ecological impairments resulting from the physical stress of excessive sediments are not highly developed. In contrast to aquatic toxicity testing where test protocols have been standardized, testing protocols for soils still lack harmonization. Biological assays have been developed by the Organization for Economic Co-operation and Development(OECD), the United States Environmental Protection Agency(U.S. EPA), and individual researchers for use in assessing soil toxicity related to earthworms(Perionyx excavatus), plants, and bacteria.
The objective of this study was to propose ecotoxicological studies to provide systematic assessment to evaluate ecological response when assessing contaminated sediment and soils. Bioassays used for sediment quality assessment typically rely on static continuous exposure of a test organism to a contaminant or contaminated sediment. Ecotoxicity testing has been used in combination with contaminant and remediated soils and sediments in site assessments. Earthworm and benthic species including Japanese swamp shrimp(Neocaridina denticulata), sludge worm(Tubifex hattai), and amphipod(Hyalella azteca) were adopted for toxicity test. Acute toxicity tests were used to assess the toxicity of contaminated sediments and soils to organisms. copper, cadmium, lead, and trichloroethylene were selected as target contaminants.
Results of acute toxicity indicated that copper posed highest toxicological effects onto earthworms in soil prepared in the laboratory. However, trichloroethylene posed highest toxicity onto earthworm in contaminated soil. Also it was found that trichloroethylene posed highest toxicity onto earthworm in subchronic toxicity tests(i.e., LC10=61.19 mg/kg). Cadmium posed highest toxic effects onto larvae.
Lead posed highest toxic effect onto Japanese swamp shrimp in sediment test. Sludge worm(Tubifex hattai) and amphipod(Hyalella azteca) was sensitive to copper with LC50 of 15.47 mg/kg and 1.14mg/kg, respectively. Japanese swamp shrimp was most sensitive by cadmium in sediment with mixture of target contaminants. However, sludge worm(Tubifex hattai) was most sensitive to lead. Cadmium posed highest toxicological effects onto amphiod(Hyalella azteca).
This study provided base-line toxicity information of aquatic species in contaminated sediments and toxicity information of terrestrial species in contaminated soils for ecological risk assessment, including the NOEC, LOEC, LC50 and EC50. Moreover to establish ecotoxicological test protocols of contaminated sediment and soils.
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