碩士 / 國立交通大學 / 環境工程所 / 87 / Our previous studies, based on the alga Selenastrum capricornutum, indicate that the present algal toxicity test protocols (US EPA, ISO, ASTM, and OECD) are less sensitive and, incorrect in the relative toxicity relationships. The primary reasons for the above phenomena are due to the over-enriched growth medium for these test methods. In addition, we have developed a continuous algal toxicity test whereas algae are tested under a nutrient-limited conditions This new method has been proven to be more sensitive and precise. From the history of toxicity assessment, Chlorella pyrenoidosa has been frequently used as an indicator organism to evaluate the impact of various toxicants and waste discharges to phytoplankton communities. The purpose of this research is therefore to study the responses of this alga to various metal toxicants. Comparison well be made with respect to test sensitivity, and accuracy between the continuous test and the traditional batch test.
Based on the test results, these parameters at N/P=30, 15 μg/l Na2EDTA‧2H2O and dilution rate D=0.5/d are optimum which achieve a better growth condition and sensitivity. The performance of the modified testing technique is evaluated, employing five different metal toxicants(Cd、Zn、Co、Ni、Pb). Compared with batch test results reported by other researchers and our own experiment, the continuous test achieved superior sensitivities and reproducibility.The sensitivities of NOEC values based on cell density and mean cell volume were equal, while that on total cell volume was less than the formers. The EC50 values by total cell volume which relative to actual biomass were larger than those by cell density. These were due to the differences in biomass of treatments and controls were smaller when the mean cell volume increased under the exposure of toxicity. In standard toxicity tests the cell density is a frequently used surrogate measure of biomass without considering the mean cell volume changed. It would lead to serious discrepancies in toxicity assessment.
| Identifer | oai:union.ndltd.org:TW/087NCTU0515008 |
| Date | January 1999 |
| Creators | Lee , Yu-Lung, 李玉龍 |
| Contributors | Chen , Chung-Yung, 陳重元 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 112 |
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