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• 基金项目：

• 张甬元
• 中国科学院水生生物研究所

• 孙美娟
• 中国科学院水生生物研究所

• 谭渝云
• 中国科学院水生生物研究所

• 摘要：本文研究了氧化塘系统中六六六的转移和归趋。实验表明,由于氧化塘中藻类光合作用大量消耗游离二氧化碳而引起pH的上升;浮游动植物积累及通过它们转移和带入底泥;以及在底泥中的厌氧降解是六六六在氧化塘中被净化的主要原因。六六六在鱼体中积累和释放的动力学研究,证明六六六在鱼体的残留水平为水和体脂间的分配平衡所决定,水中六六六可以在鳃的气体交换过程中迅速进入体内。当水中六六六浓度低时,体内的残留又可释放到水中,其释放速率与温度有密切关系。

• Abstract：BHC removal effeciency of the oxidation pond system at YL region averages 80% over a period of three years. Factors responsible for purification of BHC in oxidation ponds are discussed. Removal of BHC from water takes place by several routes: first, BHC degrades in alkaline medium but is relatively stable in acid environment. pH of the oxidation pond is found raised because of the fact that the consumption of free C₂ by photosynthesis of algae is faster than its liberation through respiratory process of the heterotrophs. pH in oxidation ponds at YL region varies from 7.0 to 10.3. Thus, higher pH values due to ecological factor provide a favorable condition for efficient removal of BHC. Secondly, BHC accumulates in phytoplankton and zooplankton in the oxidation ponds. Studies show that accumulation factor of Scenedismus oblq. and Moina was 213 and 32, respectively. The concentration of BHC adsorbed from water depends upon both the concentration of BHC in water and the biomass of algae and zooplankton. Hence, algae and zooplankton as "carriers" play an important role in transporting BHC from water to bottom sediments. Thirdly, BHCWas degraded under anaerobic condition. Bottom mud of oxidation ponds is good in adsorbing BHC. The distribution coefficient of BHC is 80. Rapid degradation of BHC has been observed in sediments of oxidation ponds. Under laboratory conditions BHC degradation rate can be accelerated by repeated additions of BHC into the bottom mud. The maximum rate attained is 3.8mg/hr/kg mud. Owing to anaerobic degradation, BHC content in the sediment of oxidation ponds has not increased over a period of three years.Dynamics of BHC accumulation in fishes is also studied both in field and in laboratory. Our observation supports the speculation that the residue level in fishes is largely controlled through a solubility equilibrium with that in water. Experiments show that fish may acquire BHC directly from water via gills. When fish reared in BHC-contaminated water and then removed to a clean pond, BHC residues begin to decrease through discharging into the surrounding water. The percentage of discharging may be expressed by R= b(1 -6^{-Ct Kt}). The rate is closely related to water temperature. At 30°and 20 ℃, K value is found as 0.0072 and 0.0034, respectively. When water temperature is lower than 10℃the rate of BHC discharging is very slow.

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