Nabais C, Freitas H, Hagemeyer J
Departamento de Botânica, Faculdade de Ciências e Tecnologia, Universidade de Coimbra, Portugal.
Sci Total Environ. 1999 Jul 15;232(1-2):33-7. doi: 10.1016/s0048-9697(99)00107-2.
Trees of temperate regions usually form visible annual growth rings, which can be dated accurately. It is therefore possible to collect wood samples of different age and analyse their heavy metals content in order to get a chronological record of trace elements pollution in the tree's environment. This method of retrospective biomonitoring was called dendroanalysis. A basic assumption of dendroanalysis is the stability of the mineral distribution patterns, i.e. once the elements are stored, no significant mobility should occur. Additionally, neighbouring trees growing in the same environment should show similar radial element patterns. While some studies presented good correlations between radial distributions of heavy metals in tree rings and temporal records of pollution from industry or traffic, others failed in using dendroanalysis as a chronological record of pollution. Probably some elements can move at a certain rate in radial direction through the ray parenchyma cells. In this way the radial element distributions are subsequently changed. Growth rates of tree rings can also influence the concentrations of elements in wood. During periods of slow growth higher concentrations of elements can be found in the wood. Therefore, radial distribution patterns of heavy metals in tree rings should be used with caution as a tool for retrospective biomonitoring of environmental pollution.
温带地区的树木通常会形成可见的年轮，这些年轮可以被准确测定年代。因此，收集不同树龄的木材样本并分析其重金属含量，以获得树木生长环境中微量元素污染的时间序列记录是可行的。这种追溯性生物监测方法被称为树木年轮分析。树木年轮分析的一个基本假设是矿物质分布模式的稳定性，即一旦元素被储存，就不应发生显著的迁移。此外，生长在同一环境中的相邻树木应显示出相似的径向元素模式。虽然一些研究表明树木年轮中重金属的径向分布与工业或交通污染的时间记录之间存在良好的相关性，但其他研究未能将树木年轮分析用作污染的时间序列记录。可能一些元素可以以一定速率通过射线薄壁细胞在径向移动。这样，径向元素分布随后就会发生变化。树木年轮的生长速率也会影响木材中元素的浓度。在生长缓慢的时期，木材中可以发现较高浓度的元素。因此，在将树木年轮中重金属的径向分布模式用作环境污染追溯性生物监测工具时应谨慎使用。
