High-Resolution AMS ¹⁴C Dating of Post-Bomb Peat Archives of Atmospheric Pollutants

Abstract

Peat deposits in Greenland and Denmark were investigated to show that high-resolution dating of these archives of atmospheric deposition can be provided for the last 50 years by radiocarbon dating using the atmospheric bomb pulse. 14C was determined in macrofossils from sequential one cm slices using accelerator mass spectrometry (AMS). Values were calibrated with a general-purpose curve derived from annually averaged atmospheric 14CO2 values in the northernmost northern hemisphere (NNH, 30°–90°N). We present a thorough review of 14C bomb-pulse data from the NNH including our own measurements made in tree rings and seeds from Arizona as well as other previously published data. We show that our general-purpose calibration curve is valid for the whole NNH producing accurate dates within 1–2 years. In consequence, 14C AMS can precisely date individual points in recent peat deposits within the range of the bomb-pulse (from the mid-1950s on). Comparing the 14C AMS results with the customary dating method for recent peat profiles by 210Pb, we show that the use of 137Cs to validate and correct 210Pb dates proves to be more problematic than previously supposed.As a unique example of our technique, we show how this chronometer can be applied to identify temporal changes in Hg concentrations from Danish and Greenland peat cores.

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

“…Moreover, using such isotopic fingerprints, Weiss et al (1999) demonstrated Pb immobility by comparing Pb isotopic composition in dated herbarium Sphagnum samples from Swiss and Southern Germany and in 210 Pb-dated peat samples from the same age and same location. The similarity of age dating made using the 210 Pb CRS model and 14 C Bomb Pulse Curve also supports the immobility of Pb (Goodsite et al, 2001). Over the last few years however, as some authors have continued to investigate the behaviour of lead in peat, the debate over Pb mobility reopened.…”

Dating Recent Peat Accumulation in European Ombrotrophic Bogs

“…The age estimates produced by one (or both) of these methods are prone to significant inaccuracy. Goodsite et al (2001) also found a discrepancy between 210 Pb and 14 C age estimates of peat profiles from Greenland and Denmark, where the 14 C dates were much younger than 210 Pb age estimates in the pre-1963 section of the core. In this study, the FI and SP cores also have a few 14 C dates before 1963 that are much younger than the 210 Pb age estimates.…”

“…Nevertheless, relatively few studies have used the 14 C bomb peak technique to date peats (e.g. Goodsite et al 2001;Donders et al 2004;Garnett and Stevenson 2004;Goslar et al 2005;Sjögren et al 2006;van der Linden and van Geel 2006;Hua 2009;Piotrowska et al 2010). Goslar et al (2005) observed that any depth increment will likely correspond to more than a single year of peat growth, with an incorporation of 14 C activities in the Sphagnum within that increment.…”

New Bomb Pulse Radiocarbon Records from Annual Tree Rings in the Northern Hemisphere Temperate Region

“…In order to check this, we compared our data with the "atmospheric" calibration curve averaged over the whole year (solid line in Figure 1) and that one averaged over the tree growing season (dashed line in Figure 1) as reported by Goodsite et al (2001). Table 1); b) tree-ring data from Acacia, Hungary (Hertelendi et al 1982); c) tree-ring and seeds (Douglas fir and cotton) data from Arizona (USA), 32°N (Goodsite et al 2001); d) annual averaged 14 CO 2 curve for the 30-90° latitude band (Goodsite et al 2001); e) atmospheric 14 CO 2 from Austria and Germany (48°N) (Levin et al 1997;Goodsite et al 2001) averaged only for the oak growing season (April to August). From Figure 1, it is clear that our data follow the annual averaged "atmospheric" curve very well, and no higher values are observed in the 14 C concentration in the tree rings.…”