潮土潜在硝化速率对重金属锌镉的响应研究

通过室内模拟和流动注射技术研究了不同月份潮土中氨氧化菌群对重金属锌镉的响应,即对潮土氨氧化菌群潜在硝化速率（Potential Nitrification Rate,PNR）的影响。结果表明,重金属对8月份土壤样品中氨氧化菌群的PNR的抑制作用大于5月份（P〈0.01）。低浓度重金属（即Zn2＋浓度为50～200mg·kg-1;Cd2＋浓度为0.5～10mg·kg-1）对潮土中PNR无影响或轻微促进作用,而在高浓度（即Zn2＋浓度大于200mg·kg-1;Cd2＋浓度大于10mg·kg-1）条件下有显著抑制作用。由于Zn2＋对PNR的抑制程度小于Cd2（＋Zn2＋：EC50〉Cd2＋：EC50）,并且PNR对Cd2＋的响应较Zn2＋易变,PNR的测定结果表明该指标应用于重金属Zn2＋的污染毒性评价时优于重金属Cd2＋的污染毒性评价。

The Response of Potential Nitrification Rate in Fluvo-aquic Soil to Heavy Metals Zn~（2＋） and Cd~（2＋）

To assess the effects of heavy metals Zn2＋ and Cd2＋ on the ammonium-oxidizing community in fluvo-aquic soil,the potential nitrification rates（PNR）with flow injection technology in May and August were studied.The results showed a significantly stronger inhibitory effect of heavy metals on PNR in soil in August than that in May（P0.01）.The low concentration of heavy metals（Zn2＋：50～ 200 mg·kg-1;Cd2＋：0.5～ 10 mg·kg-1）had no effects or a slightly positive effect on PNR,while high concentrations of Cd2＋ or Zn2（＋Zn2＋200 mg·kg-1;Cd2＋10 mg·kg-1） were a significant inhibitor of the potential nitrification process.Furthermore,the EC50 of Zn2＋ was higher than that of Cd2＋,which indicated the degree of inhibition of Zn2＋ on PNR was less than that of Cd2＋.The response of PNR to Zn2＋ was earlier to change than that of Cd2＋.PNR has been widely used as an indicator in assessing heavy metal toxicity,but it was more suitable for Zn2＋ than Cd2＋.