| Summary: | 碩士 === 臺灣大學 === 生物環境系統工程學研究所 === 95 === The purpose of this thesis is to develop a biological response mechanistic model based on the gill-based physiological interactions among sodium (Na) transport, Na membrane potential and valve closure response in freshwater clam (Corbicula fluminea) in response to waterborne copper (Cu) for providing a tool to assess Cu-bioavailability. This study have integrated Cu bioavailability based on biotic ligand model (BLM), Na and Cu uptake flux based on Michaelis-Menten kinetics, and electrochemically-based gill potentials, to derive an electrophysiological response model of C. fluminea describing the action mechanisms of a gill-based membrane interface by which valve closure behavior and Cu toxicity can be predicted. To test the proposed model against published data regarding inhibition of Na uptake in rainbow trout in response to Cu and Na total/active transport in equilibrium/non-equilibrium conditions in C. fluminea. The predictions are reasonably agreed with published measured, confirming that the predictive model is robust. The results show the physiological toxic response including (i) inhibition of M-M maximum Na uptake rate is 12.9 to 0.4 μmol g-1 hr-1, (ii) decrease of internal Na concentration is 10.5 to 7.5 mM, and (iii) depolarization of total and active transport are -84.2-10 and -8-0 mV, respectively in response to external Cu activity from 0 to 0.2 μM. This proposed framework captures the general features observed in the model applications including: (i) 50% inhibitory Cu2+ activities for Na membrane potential and uptake rate are estimated to be 0.072 and 0.043 μM, respectively, with a stoichiometry of 3Cu2+: 1 and 1 , (ii) predicted M-M maximum Cu uptake flux in C. fluminea is 0.369 (95% CI: 0.26-0.51) μmol g-1 h-1 with a half-saturation affinity constant of 7.87×10-3 (95% CI: 5.72×10-3-11.20×10-3) μM, and (iii) the site-specific clam gill potentials can be predicted in aquaculture settings. Here this study successfully provide a general approach to harness the potential new biomonitoring techniques for assessing the environmental impact of waterborne Cu.
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