Atmospheric Deposition of V, Cr, and Ni since the Late Glacial: Effects of Climatic Cycles, Human Impacts, and Comparison with Crustal Abundances
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- 作者：Michael Krachler ; Carola Mohl ; Hendrik Emons ; and William Shotyk
- 刊名：Environmental Science & Technology
- 出版年：2003
- 出版时间：June 15, 2003
- 年：2003
- 卷：37
- 期：12
- 页码：2658 - 2667
- 全文大小：264K
- 年卷期：v.37,no.12(June 15, 2003)
- ISSN：1520-5851
文摘
Vanadium, Cr, and Ni accumulating in a Swiss peat bogsince 12 370 14C yr B.P. have been measured usinginductively coupled plasma-mass spectrometry (ICP-MS)after acid dissolution in a microwave autoclave. Strict qualitycontrol schemes were applied to guarantee the accuracyof the applied analytical methodology. The concentrationgradients in the peat column and comparison with Pb indicatethat V, Cr, and Ni are effectively immobile in theombrotrophic section of the peat profile but that Ni isadded to the minerotrophic peat layers by chemicalweathering of the underlying sediments. The lowest metalconcentrations were found during the Holocene climateoptimum (5320-8230 14C yr B.P.) when "natural background"values averaged 0.55 ± 0.13 
g g-1 V, 0.76 ± 0.17 gg-1 Cr, and 0.46 ± 0.09 g g-1 Ni (n = 18); given the averagebulk density (0.05 g/cm3) and accumulation rate (0.05 cm/yr) of peat in this zone, the corresponding atmosphericfluxes are approximately 14, 19, and 12 g m-2 yr-1 for V,Cr, and Ni, respectively. The highest concentrations ofV, Cr, and Ni were found during the Younger Dryas coldclimate event (centered at 10 590 14C yr B.P.) when backgroundvalues were exceeded by about 40 times. Elevatedconcentrations and accumulation rates were also foundat 8230 and 5320 14C yr B.P., which are consistent with theelevated dust fluxes recorded by Greenland ice cores.By far the greatest contribution of the three elements tothe peat inventory is atmospheric soil dust, and the metalfluxes vary not only with climate change but also land-use history (especially the beginning of forest clearing foragriculture ca. 6 millennia ago). The V/Sc, Cr/Sc, and Ni/Sc ratios were remarkably similar to their correspondingratios in the earth's crust until the onset of the IndustrialRevolution (240 14C yr B.P.), which largely validates the useof crustal concentrations for calculating enrichmentfactors (EF) for these elements. In modern samples, theEFs of V, Cr, and Ni reach maximum values between 2.4and 4.1, relative to background; anthropogenic emissions area more likely explanation of the elevated EFs than eitherplant uptake or chemical diagenesis. This study demonstratesthe usefulness of peat bogs as archives of atmosphericmetal deposition and underpins the potential of peat coresto help distinguish between lithogenic and anthropogenicmetal sources.
g g-1 V, 0.76 ± 0.17 gg-1 Cr, and 0.46 ± 0.09 g g-1 Ni (n = 18); given the averagebulk density (0.05 g/cm3) and accumulation rate (0.05 cm/yr) of peat in this zone, the corresponding atmosphericfluxes are approximately 14, 19, and 12 g m-2 yr-1 for V,Cr, and Ni, respectively. The highest concentrations ofV, Cr, and Ni were found during the Younger Dryas coldclimate event (centered at 10 590 14C yr B.P.) when backgroundvalues were exceeded by about 40 times. Elevatedconcentrations and accumulation rates were also foundat 8230 and 5320 14C yr B.P., which are consistent with theelevated dust fluxes recorded by Greenland ice cores.By far the greatest contribution of the three elements tothe peat inventory is atmospheric soil dust, and the metalfluxes vary not only with climate change but also land-use history (especially the beginning of forest clearing foragriculture ca. 6 millennia ago). The V/Sc, Cr/Sc, and Ni/Sc ratios were remarkably similar to their correspondingratios in the earth's crust until the onset of the IndustrialRevolution (240 14C yr B.P.), which largely validates the useof crustal concentrations for calculating enrichmentfactors (EF) for these elements. In modern samples, theEFs of V, Cr, and Ni reach maximum values between 2.4and 4.1, relative to background; anthropogenic emissions area more likely explanation of the elevated EFs than eitherplant uptake or chemical diagenesis. This study demonstratesthe usefulness of peat bogs as archives of atmosphericmetal deposition and underpins the potential of peat coresto help distinguish between lithogenic and anthropogenicmetal sources.