Bindler Richard, Renberg Ingemar, Klaminder Jonatan, Emteryd Ove
Department of Ecology and Environmental Science, Umeå University, Umea, Sweden.
Sci Total Environ. 2004 Feb 5;319(1-3):173-83. doi: 10.1016/S0048-9697(03)00397-8.
Tree rings, if validated as an environmental archive for pollution, would provide a convenient, geographically widespread archive for studying the temporal and spatial distribution of atmospheric pollutants. We collected tree-ring records from Scots pine (Pinus sylvestris L.), ranging in age from 100 to 300 years and from one spruce (Picea abies), from sites in southern and northern Sweden and analyzed their stable lead isotopic composition (206Pb/207Pb). These results are compared to the Pb isotopic composition in soil profiles from each of the sites and temporal changes in the 206Pb/207Pb ratio in peat and lake sediment deposits in Sweden. The mineral soils at each site are characterized by high 206Pb/207Pb ratios (> 1.35), while the ratios in the mor layer are low (1.14-1.16) and characterized by atmospheric lead pollution. The 206Pb/207Pb ratios of the tree rings, typically approximately 1.18-1.20, indicate a significant (10-30%) contribution of Pb derived from the underlying mineral soil. While peat and lake sediment records show that the 206Pb/207Pb ratio of atmospheric deposition has varied over time, with a pronounced trough between approximately 1930 and 1990, the tree rings show no similar trend. Further comparison of published Pb isotope data from other tree-ring records with time series from peat bogs and herbarium samples also shows poor agreement, and indicates that tree rings always contain a mixture of pollution Pb and Pb from the underlying mineral soil. The majority of Pb in the wood is derived from atmospheric pollution either directly, through aerial interception, or indirectly, through uptake from the large pool of accumulated pollution Pb in the soil. Since the Pb isotope ratios of the wood indicate that some natural Pb is taken up into the tree, then it must also be concluded that some fraction of the pollution Pb in the wood is likewise taken up from the forest soil. Based on the Pb isotope analyses, we can only conclude that dendrochemical records are not useful in temporal studies of metal pollution.
如果树木年轮被证实是一种用于污染研究的环境档案，那么它将为研究大气污染物的时空分布提供一种便捷且分布广泛的档案。我们收集了瑞典南部和北部地区树龄在100至300年的苏格兰松（Pinus sylvestris L.）以及一棵云杉（Picea abies）的年轮记录，并分析了它们的稳定铅同位素组成（206Pb/207Pb）。将这些结果与每个地点土壤剖面中的铅同位素组成以及瑞典泥炭和湖泊沉积物中206Pb/207Pb比值的时间变化进行了比较。每个地点的矿质土壤以高206Pb/207Pb比值（>1.35）为特征，而腐殖质层中的比值较低（1.14 - 1.16），且具有大气铅污染的特征。年轮的206Pb/207Pb比值通常约为1.18 - 1.20，表明来自下层矿质土壤的铅有显著（10 - 30%）的贡献。虽然泥炭和湖泊沉积物记录显示大气沉降的206Pb/207Pb比值随时间变化，在大约1930年至1990年之间有一个明显的低谷，但年轮并未显示出类似趋势。将其他树木年轮记录中已发表的铅同位素数据与泥炭沼泽和植物标本样本的时间序列进行进一步比较，也显示出较差的一致性，并表明树木年轮始终包含污染铅和来自下层矿质土壤的铅的混合物。木材中的大部分铅要么直接通过空中截留来自大气污染，要么间接通过从土壤中大量积累的污染铅库中吸收而来。由于木材的铅同位素比值表明一些天然铅被树木吸收，那么也必须得出结论，木材中部分污染铅同样是从森林土壤中吸收的。基于铅同位素分析，我们只能得出结论，树木化学记录在金属污染的时间研究中并无用处。
