| Summary: | 碩士 === 國立嘉義大學 === 水生生物科學系研究所 === 96 === In order to investigates the bioaccumulate of lead and cadmium in tilapia (Oreochomis sp.) cluring the growth period, tilapia fry from the same source were released into two ponds located in Syuejia Township, Tainan County and Kouhu Township, Yunlin County. During the period between July 2007 and May 2008, surveys were carried out every two months. The concentration of lead and cadmium in pond water, bottom sediments and liver, gill and muscle of tilapia were measured.
The concentration ranges of lead and cadmium measured in pond water were 0.216 - 0.467 &;micro;g/L and 0.007 - 0.024 &;micro;g/L, respectively. Both of these concentrations completely follow the regulations of the Environmental Protection Adiministration of Taiwan. The concentration of lead and cadmium in sediment were determined to be ranging from 13.1 to 21.08 mg/kg and from 0.2 to 0.85 mg/kg, respectively. These concentrations were categorized as unpolluted according to the sediment quality guideline of the U.S. Environmental Protection Agency. The concentration ranges of lead in tilapia liver, gill and muscle were 134.73 - 268 &;micro;g/kg, 284.46 - 415.8 &;micro;g/kg and 19.98 - 40.2 &;micro;g/kg, respectively. While those of cadmium in tilapia liver, gill and muscle were 35.25 - 47.07 &;micro;g/kg, 0.69 - 2.02 &;micro;g/kg and 0.5 - 1.08 &;micro;g/kg, respectively. These concentrations in tilapia muscle completely follow the regulations of the European Union. These results conclusively show that the two aquaculture ponds were unpolluted by lead and cadmium, and the flesh of fish were safely to be esculent.
The concentration of lead and cadmium in pond water were easily affected by rainfall, and a significantly positive correlation of lead and cadmium level (r = 0.883 , r = 0.933, respectively) were found between pond water and tilapia gill. Consequently, tilapia gill can be a bioindicator of lead and cadmium pollution in pond water. The concentration of lead and cadmium in tilapia muscle were descended with increase of fork length (Pb = 46.103 – 1.101 SL , Cd = 1.579 – 0.0398 SL). But the content of lead and cadmium in tilapia muscle were the increasement with fork length (Pb = -2.755 + 0.438 SL , Cd = -0.128 + 0.017 SL). This results display that the concentration of lead and cadmium will descend and the content of lead and cadmium will increase in tilapia at growth period.
The BCF and BSAF of lead in aquaculture pond at Syuejia were measured to be 110.66, 0.0017, respectively; and those measured for cadmium were 56.19 and 0.0025, respectively. In the case of Kouhu, the BCF and BSAF were determined for lead to be 110.18 and 0.0019, respectively, and those for cadmium to be 47.78 and 0.00109, respectively. These results clearly demonstrate that accumulation in tilapia is easier in the case of lead rather than that of cadmium. The HQ of lead in pond water of Syuejia and Kouhu were 0.13 and 0.57, respectively, and that in sediment of the same place were 0.1 and 0.38, respectively. While that of cadmium at Syuejia and Kouhu were 0.04, 0.23 in pond water and 0.07, 0.81 in sediment. The HQ values evaluated in this study were all below 1.0, indicating no or light hazard risks for lead and cadmium in these two aquaculture ponds.
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