Role of Surface Vegetation in 210Pb-Dating of Peat Cores

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• 作者：Carolina Olid ; Jordi Garcia-Orellana ; Antonio Martí ; nez-Cortizas ; Pere Masqué ; Eva Peiteado ; Joan-Albert Sanchez-Cabeza
• 刊名：Environmental Science & Technology
• 出版年：2008
• 出版时间：December 1, 2008
• 年：2008
• 卷：42
• 期：23
• 页码：8858-8864
• 全文大小：208K
• 年卷期：v.42,no.23(December 1, 2008)
• ISSN：1520-5851

文摘

²¹⁰Pb-dated ombrotrophic peat cores have been widely used to reconstruct the atmospheric fluxes of heavy metals for the past century. Many of these studies rarely include the overlying vegetation compartment (i.e., the aerial part of vegetation and decayed plant remains) in the analysis although it represents the first layer capturing atmospheric deposition. The aim of this study was to evaluate the radionuclide and Pb content of this biologically active layer in bogs and to assess its implications on the total inventories and the ²¹⁰Pb-derived chronology. We analyzed two short ombrotrophic peat cores from the same bog (Chao de Lamoso, Galicia, Spain) for ²¹⁰Pb, artificial radionuclides (¹³⁷Cs and ²⁴¹Am), and Pb. The total Pb inventory was underestimated by about 12% when the plant material was not included in the record. The atmospheric origin of ²¹⁰Pb and the uptake of ¹³⁷Cs by roots led to significant activities of these radionuclides in the upper layers. Therefore, removing them from the peat record would imply even larger underestimations of the total inventories, ranging from 25% to 36% for ¹³⁷Cs and from 39% to 49% for ²¹⁰Pb. In contrast to the chronologies inferred from the constant rate of supply (CRS) model when only peat layers are considered, the ²¹⁰Pb chronology agreed well with artificial radionuclide dating when surface vegetation was included. These results suggest that an accurate peat chronology requires an initial evaluation of the relevance of plant inventories and emphasizes the need of considering the biologically active layer when atmospheric fluxes of heavy metals and other pollutants are reconstructed.