Atmospheric Deposition of V, Cr, and Ni since the Late Glacial:  Effects of Climatic Cycles, Human Impacts, and Comparison with Crustal Abundances

Abstract

Vanadium, Cr, and Ni accumulating in a Swiss peat bog since 12 370 14C yr B.P. have been measured using inductively coupled plasma-mass spectrometry (ICP-MS) after acid dissolution in a microwave autoclave. Strict quality control schemes were applied to guarantee the accuracy of the applied analytical methodology. The concentration gradients in the peat column and comparison with Pb indicate that V, Cr, and Ni are effectively immobile in the ombrotrophic section of the peat profile but that Ni is added to the minerotrophic peat layers by chemical weathering of the underlying sediments. The lowest metal concentrations were found during the Holocene climate optimum (5320-8230 14C yr B.P.) when "natural background" values averaged 0.55 +/- 0.13 microg g(-1) V, 0.76 +/- 0.17 microg g(-1) Cr, and 0.46 +/- 0.09 microg g(-1) Ni (n = 18); given the average bulk density (0.05 g/cm3) and accumulation rate (0.05 cm/ yr) of peat in this zone, the corresponding atmospheric fluxes are approximately 14, 19, and 12 microg m(-2) yr(-1) for V, Cr, and Ni, respectively. The highest concentrations of V, Cr, and Ni were found during the Younger Dryas cold climate event (centered at 10 590 14C yr B.P.) when background values were exceeded by about 40 times. Elevated concentrations and accumulation rates were also found at 8230 and 5320 14C yr B.P., which are consistent with the elevated dust fluxes recorded by Greenland ice cores. By far the greatest contribution of the three elements to the peat inventory is atmospheric soil dust, and the metal fluxes vary not only with climate change but also land-use history (especially the beginning of forest clearing for agriculture ca. 6 millennia ago). The V/Sc, Cr/Sc, and Ni/ Sc ratios were remarkably similar to their corresponding ratios in the earth's crust until the onset of the Industrial Revolution (240 14C yr B.P.), which largely validates the use of crustal concentrations for calculating enrichment factors (EF) for these elements. In modern samples, the EFs of V, Cr, and Ni reach maximum values between 2.4 and 4.1, relative to background; anthropogenic emissions are a more likely explanation of the elevated EFs than either plant uptake or chemical diagenesis. This study demonstrates the usefulness of peat bogs as archives of atmospheric metal deposition and underpins the potential of peat cores to help distinguish between lithogenic and anthropogenic metal sources.

Biogeochemistry of Nickel and Its Release into the Environment

“…In a peat core taken at a low-background area in Finland, post-depositional processes could not be excluded [132]. In contrast, the deposition of dust-related Ni phases appeared to be well preserved in an age-dated Swiss peat core (Figure 3) [129]. The highest concentrations of Ni were found during the Younger Dryas cold climate event (centered at 10 590 yr B.P.…”

“…In contrast, there are only a few systematic studies on the distribution and fate of Ni in ombrotrophic bogs [129][130][131][132][133][134]. The results indicate that the fate of Ni is strongly dependent upon the mineralogical form in which it is originally deposited, but also on the geochemical and hydrological conditions in the peat layers, and the peat accumulation rate [133].…”

“…The crucial factor might be the early oxidation of particles in the aerated surface layers of the bog [133]. The retention of anthropogenic Ni from long-range atmospheric transport shows some (apparent) inconsistencies [129,130,132]. In a peat core taken at a low-background area in Finland, post-depositional processes could not be excluded [132].…”

Anthropogenic impacts in North Poland over the last 1300years — A record of Pb, Zn, Cu, Ni and S in an ombrotrophic peat bog

“…Krachler et al (2003) concluded that Ni is mainly immobile in ombrotrophic peat, although it may be affected by weathering in minerotrophic peat. In contrast, Nieminen et al (2002) showed that Ni is mobile in ombrotrophic peat.…”

Atmospheric lead and heavy metal pollution records from a Belgian peat bog spanning the last two millenia: Human impact on a regional to global scale

“…Most importantly, peat is particularly effective at preserving atmospheric metal deposition in the form of lead (e.g. Shotyk, 2002;Shotyk et al, 1998Shotyk et al, , 2003Vile et al, 1999;Weiss et al, 1999), copper (Rausch et al, 2005;Mighall et al, 2002), nickel (Krachler et al, 2003) and zinc (Rausch et al, 2005;Twardowska et al, 1999). Recent research has shown that ancient Pb contamination in peat can be traced by Pb isotopes and fingerprinted to a local or regional origin (e.g.…”