重金属对土壤—植物系统中氮的转化与NO3-淋失影响的研究

本项研究采用“微宇宙”方法,在实验室植物生长箱可控条件下,进行动态模拟实验。实验选择了七种重金属,按照土壤阳离子代换量计算出三种不同等级的土壤重金属剂量,研究它们对京津渤地区典型土壤(碳酸盐草甸土)中氮的转化与NO_3~-淋失影响。实验结果表明:七种重金属对该类土壤中氮的转化与NO_3~-淋失量有明显影响,但其表现的程度和特征有很大差异。其作用强度的次序为:Hg~(2 )>>Cd~(2 )>>Ni~(2 )>>Zn~(2 )>Pb~(2 )>Cu~(2 )>Cr~(3 )。各重金属作用的持续时间不同:Hg~(2 )、Cd~(2 )达7—11周以上,而其余重金属在4—7周。实验结论:本地区碳酸盐土壤虽然对重金属有较大的容量,但从土壤—植物系统污染生态学角度,仍可选择NO_3~-作为一项反映重金属对土壤生态毒性的早期诊断指标。

STUDY ON EFFECT OF HEAVY METALS ONTRANSFORMATION OF NITROGEN AND LEACHING OF NO3- IN SOIL-PLANT SYSTEM

To estimate gross effects of seven heavy metals on soil in three doses on transformation of nitrogen according to cation exchange capacity and leaching of NO^3- in calcareous fluviogenic soil of Beijing-Tianjin region, a series of experiments was carried out by means of microcosms under simulated conditions in plant growth chamber.Results obtained show that the order of inhibitory nitrification intensity and magnitude of NO^3- leaching is as follows:Hg²⁺>>Cd²⁺>>Ni²⁺>-Zn²⁺>Pb²⁺>-Cr³⁺, and the durations of effects caused by various heavy metals appear to be different:Hg²⁺, Cd²⁺, 7^-10 weeks, whereas others last only about 4-7 weeks.Thus conclusion can be made through analysis of the comprehensive experimental data that NO^3- may be considered to be an early indicator for diagnosing ecological toxicity of heavy metals in soil-plant system despite great environmental capacity of the calcareous soil mentioned. And, this is of both theoretical and practical significance.