Department of Ecology and Environmental Science, Umeå University, 90187 Umeå, Sweden.
Sci Total Environ. 2011 Sep 15;409(20):4344-50. doi: 10.1016/j.scitotenv.2011.07.005. Epub 2011 Aug 4.
Knowledge of the anthropogenic contribution to lead (Pb) concentrations in surface soils in high latitude ecosystems is central to our understanding of the extent of atmospheric Pb contamination. In this study, we reconstructed fallout of Pb at a remote sub-arctic region by using two ombrotrophic peat cores and assessed the extent to which this airborne Pb is able to explain the isotopic composition ((206)Pb/(207)Pb ratio) in the O-horizon of tundra soils. In the peat cores, long-range atmospheric fallout appeared to be the main source of Pb as indicated by temporal trends that followed the known European pollution history, i.e. accelerated fallout at the onset of industrialization and peak fallout around the 1960s-70s. The Pb isotopic composition of the O-horizon of podzolic tundra soil ((206)Pb/(207)Pb=1.170 ± 0.002; mean ± SD) overlapped with that of the peat ((206)Pb/(207)Pb=1.16 ± 0.01) representing a proxy for atmospheric aerosols, but was clearly different from that of the parent soil material ((206)Pb/(207)Pb=1.22-1.30). This finding indicated that long-range fallout of atmospheric Pb is the main driver of Pb accumulation in podzolic tundra soil. In O-horizons of tundra soil weakly affected by cryoturbation (cryosols) however, the input of Pb from the underlying mineral soil increased as indicated by (206)Pb/(207)Pb ratios of up to 1.20, a value closer to that of local soil minerals. Nevertheless, atmospheric Pb appeared to be the dominant source in this soil compartment. We conclude that Pb concentrations in the O-horizon of studied tundra soils - despite being much lower than in boreal soils and representative for one of the least exposed sites to atmospheric Pb contaminants in Europe - are mainly controlled by atmospheric inputs from distant anthropogenic sources.
在高纬度生态系统中，对人为因素导致表层土壤中铅（Pb）浓度的了解，对于我们理解大气 Pb 污染的程度至关重要。在这项研究中，我们利用两个寡营养泥炭芯重建了偏远亚北极地区的 Pb 沉降，并评估了这种空气传播的 Pb 能够在多大程度上解释苔原土壤 O 层的同位素组成（（206）Pb/（207）Pb 比值）。在泥炭芯中，长距离大气沉降似乎是 Pb 的主要来源，这一点可以从时间趋势中看出，这些趋势与已知的欧洲污染历史相吻合，即在工业化开始时加速沉降，以及在 20 世纪 60 年代至 70 年代达到峰值。灰化土苔原土壤 O 层的 Pb 同位素组成（（206）Pb/（207）Pb=1.170±0.002；平均值±SD）与泥炭的 Pb 同位素组成（（206）Pb/（207）Pb=1.16±0.01）重叠，代表大气气溶胶的替代物，但明显不同于母质土壤材料的 Pb 同位素组成（（206）Pb/（207）Pb=1.22-1.30）。这一发现表明，长距离大气 Pb 沉降是灰化土苔原土壤 Pb 积累的主要驱动因素。然而，在受低温蠕动作用影响较弱的苔原土壤 O 层（冷冻土）中，来自下层矿物土壤的 Pb 输入增加，这一点可以从高达 1.20 的（206）Pb/（207）Pb 比值看出，这一比值更接近当地土壤矿物质的比值。尽管如此，大气 Pb 似乎仍是这一土壤层的主要来源。我们得出结论，尽管研究中苔原土壤 O 层的 Pb 浓度远低于北方土壤，且代表了欧洲受大气 Pb 污染物影响最小的地点之一，但仍主要受到来自遥远人为源的大气输入的控制。
