合肥市城区臭椿树木60年年轮铅含量动态分析

The dynamic pattern of Pb concentration in annual rings of 70-year tree of Ailanthus altissima in Hefei city

通过对生长在合肥老城区臭椿树木60年年轮序列中重金属元素Pb含量分析,研究年轮中Pb元素积累的动态分布特点;该树木年轮中Pb平均含量为0.668mg/kg,明显高于自然环境中黄山松的年轮的铅平均浓度,表明城市地区受重金属污染的程度高;年轮序列中Pb积累量出现明显的波动、差值达到14.5倍;47%的年轮Pb含量低于6mg/kg;出现峰值的年轮段分别为1951-1960,1973-1978及1985-1990年,恰好是城市经济增长、城市规模快速发展时期,显示工业及城市发展是导致年轮Pb含量增加的主要原因,但Pb在年轮中积累的总趋势则是呈下降的态势,显示合肥城市内部Pb污染问题得到一定程度的改善。年轮中Pb含量与树龄及年轮宽度无相关性,而与当地的年平均降水有较显著的相关性。

Based on chemical analysis of heavy metal Pb in a 60-year ring set of Ailanthus altissima growing in the center of Hefei city, the study was conducted to look at the dynamic characteristics of Pb concentration in the ring set. The results showed that the average concentration of Pb in the ring set reached 0.668 mg/kg, which was obviously higher than that in Huangshan pine growing in natural conditions. It also indicated that Hefei city has heavy metal pollution. Pb accumulation in ring fluctuated among years, ranging from 0.098 mg/kg to 1.42; Pb contents in 47% of total rings is less than 6 mg/kg; Pb contents in the rings of the periods of 1951-1960,1973-1978 and 1985-1990 were higher than the average, which just in the period of more rapid development of economy and city expansion; However Pb accumulation in the whole ring set had a downward trend, reflecting that Pb pollution has been improved somehow; it was found that there is no relationship between Pb concentration in rings and tree age or ring width; but there is significant relation between Pb concentration in rings and annual precipitation.