不同氮形态对重金属Cu Zn Cd生物毒性效应的影响

运用水溢趋光行为的抑制试验研究了水体中不同氮形态和重金属（Cu、Zn、Cd）共存时的联合生物毒性效应。结果表明，不同形态N对重金属（Me）Cu^2＋、Zn^2＋、Cd^2＋生物毒性的影响存在显著差异，溶液中N对重金属生物毒性的复合作用既与重金属的种类有关。也取决于N在溶液中存在形态。在中等营养水平下，除No2^--N以外，其他3种形态的N尤其是NH4^＋和NO3^-,对重金属的毒性起拮抗作用：NH4^＋-N及NO3^--N能明显的降低水体中重金属Cu^2＋、Zn^2＋、Cd^2＋的生物毒性，可一定程度地减轻重金属污染的危害；而NO2^--N及较高浓度水平的NH3-N却对重金属的生物毒性效应起协同作用，混合溶液生物毒性的大小顺序为NO2^--N＋Me〉NH3-N＋Me〉NH4^＋-N＋Me〉NO36--N＋Me。表明在水环境调查及污染评价等工作中，仅考虑单一污染是远远不够的，必须考虑共有污染物的相互作用及其综合影响。研究结果可为进一步了解富营养化和重金属污染的相互关系及生态毒性效应提供理论依据。

The Joint-biotoxicity Effect of Different Forms of Nitrogen on Heavy Metals in Water by the Phototacti Behavior of Daphnia

The effects of different forms of nitrogen on heavy metal(Cu2 ,Zn2 and Cd2 ) joint-biotoxicity by the phototactic behaviour of Daphnia carinata were researched.The results showed that the toxicity of heavy metals was mainly related to their concentrations and also influenced significantly by the forms of nitrogen coexisted.The same heavy metal had different inhibition on Daphnia phototaxis when the different forms of nitrogen coexisted in waters.NH 4-N and NO-3-N were the main pollutants in eutrophic waters but they could decrease the toxicities of heavy metals.The toxicity of Cu2 ,Zn2 or Cd2 to D.carinata was reduced in the presence of moderate level of NH3-N,NH 4-N,NO-3-N or NO-2-N,except that the combined toxicity of Cu2 and NO-2 was stronger than that of the single Cu2 .The synergism and antagonism among nitrogen and heavy metal would decrease or increase the toxicity produced by each of them,and thus somewhat reduced or increased the toxicity of heavy metals to aquatic organisms,indicating that heavy metal biotoxicity was correlated not only with themselves but also with the forms of nitrogen in eutrophication waters.The correlation between bio-toxicity and concentration of heavy metals in solutions was not linear.These results implied that the biological harm caused by eutrophication varied with nitrogen forms.