树木年轮元素含量与环境演变

THE CHEMICAL ELEMENT CONTENTS IN TREE RINGS AND THE DYNAMIC CHANGES OF THE SURROUNDINGS

用实测数据阐明了白桦１９９５年年轮中化学元素钾、锰、铜、锌、锶、镉、钡、铅含量Ｃ（Ｚ，ｔ）和根部暗棕壤中对应元素的Ｃ′（Ｚ，ｔ）具有相关性，并且满足对数线性相关模式：ｌｇＣ′（Ｚ，ｔ）＝ａ（Ｚ）＋ｂ（Ｚ）ｌｇＣ（Ｚ，ｔ），其中原子序数Ｚ用于表征不同元素，ｔ是年轮所属的年份，统计系数ａ、ｂ由线性回归确定。利用相关模式，可由实测的逐年年轮中化学元素含量的年份序列Ｃ（Ｚ，ｔ），得到环境（土壤）中化学元素含量的逐年演变Ｃ′（Ｚ，ｔ），由Ｃ′（Ｚ，ｔ）的最低值可以估算当地表层土壤元素背景值的上限。

Three white birch trees growing at shuangling Forei Farm in Heilongjiang province were selected to determine the contents of 8 chemical elements both in the 1995′s growth rings, C(Z、t) , and in the soils near the roots, C′(Z,t) , of the trees. The results showed that the relationship between C(Z,t) and C′(Z,t) followed the logarithmic linear correlation model, lg C′(Z,t) = a(Z)+b(Z) lg C(Z,t) .Where Z is the atomic number of element, and the year when the tree ring grows. Based on this model the chrono sequences of chemical element contents in the soils were reproduced from those in the tree rings; i. e., the dynamic variations in the chemical element contents of the soils at the sites were traced. In this study the chrono sequences of the chemical elements including k, Mn, Cu, Zn, Sr, Cd, Ba and Pb in the soils near the roots of white birch trees from 1954 to 1995 were established, and the background values of K, Mn, Cu, Zn, Sr, Cd, Ba and Pb in the soil were calculated by taking the lowest values of the chrono sequences of the element contents as upper limits of the background values.