南京市几种行道树年轮重金属元素含量的变化

通过对南京市区干道行道树3个树种树木年轮中重金属元素Cd、Cr、Cu、Fe、Mn、Ni、Pb、Ti、Zn等9种元素的含量分析，发现自20世纪60年代以来，南京市行道树树木年轮中重金属元素含量总体上均表现出随时间逐渐上升的趋势，特别从1990年开始，南京市行道树树木年轮重金属元素含量的增长规律与南京市机动车的拥有量的变化规律表现出极显著的正相关关系，说明南京市机动车拥有量的增加应该是城市环境污染的主要因素之一。对比分析还发现，元素Cd、Ni、Pb、Zn增长幅度最为显著，可用于环境重金属监测。

The historical dynamics of concentrations of heavy metal in street tree rings in Nanjing, China

The concentration and historical changes of heavy metal element of Cd, Cr, Cu, Fe, Mn, Ni, Pb, Ti and Zn in street tree rings in Nanjing city were examined and analysed. It's found that the concentrations of heavy metals in tree rings at different tree species increased significantly from the 1960's to 2007,especially from 1990. It showed that the pollution of heavy metals accumulated during last decades of years. Correlation analysis revealed that significant positive correlation existed be-tween the the concentration of heavy metals in the tree rings and total amount of vehicles in Nanjing. Our findings suggested that the total amount of vehicles increasing might be the main factor leading to the city heavy metal pollution. It's also found that Cd, Ni, Pb, Zn have very significant increase and could be used as ideal indicator of environmental pollution.