南京市郊蔬菜地土壤中重金属含量的时空变化规律

Spatio-temporal distributions of soil heavy meals in vegetable plots in Nanjing

测定了28份蔬菜地土壤样品中的铜、锌、铅、镉、汞的含量,从城市化的角度研究了南京市郊蔬菜地土壤重金属在“城区、郊区和农区”的水平空间变化和在层次间的纵向空间变化,并结合历史数据分析了蔬菜地土壤重金属的时间累积作用。结果表明,城市化影响重金属的水平空间变化,蔬菜地土壤重金属含量随着蔬菜地与城市距离的增加,在城区到郊区这一距离段呈下降趋势,在郊区到农区则基本不变;城市化影响重金属的纵向空间变化,蔬菜地各重金属元素表层减底层差值的均值,城区均为正值且绝对值较高,郊区和农区各值都在0浓度附近摆动且绝对值较小。由于受城市化的时间累积作用的影响,1999年土壤中重金属Pb和Zn含量显著高于1985年。

The levels of Cu, Zn, Pb, Cd and Hg in 28 soil sample of vegetable plots were detected. The transverse, vertical spatial and temporal variability of soil heavy metals were analyzed on the base of field investigations and laboratory analysis in Nanjing. The conclusions showed in that: (1) In vegetable plots, the contents of heavy metals went down gradually from urban to suburban; the contents of main heavy metals in suburban and rural area had an significant difference; (2) The means of heavy metals contents, which were calculated by the surface layer and the bottom layer subtracting, are all up zero and large in absolute value in urban area, but in suburban and rural area, the means are all up or down zero and small in absolute value. (3) The contents of heavy metals Zn and Pb in 1999 were higher significantly than those in 1985 in vegetable plots.