Two thousand years of atmospheric rare earth element (REE) deposition as revealed by an ombrotrophic peat bog profile, Jura Mountains, Switzerland

Abstract

A peat core from a Swiss bog represents 2110 14C years of peat accumulation and provides a continuous record of atmospheric rare earth element (REE) deposition. This is the first study providing a time-series of all REE originating from the atmosphere. Concentrations of the 14 REE (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) were determined using inductively coupled plasma-mass spectrometry (ICP-MS) after dissolution of 200 mg aliquots of age-dated peat samples with 3 ml HNO3 and 0.1 ml HBF4 at 240 degrees C in a microwave autoclave. Strict quality control schemes were applied to ensure the accuracy of the applied analytical methodology. Previous analyses of selected REE by instrumental neutron activation analysis (INAA) in the same set of peat samples revealed that INAA frequently under- or overestimated REE concentrations in a systematic manner. Concentration profiles obtained for all REE were almost identical, except for Ce and Eu. Calculation of enrichment factors (EF) revealed a distinct depletion of heavy REE relative to light REE in peat samples since the beginning of the 19th century which marks the onset of the Industrial Revolution in Europe, suggesting a pronounced influence by anthropogenic activities. Enrichments of REE calculated using Sc as a reference element exceeded unity, relative to the Upper Continental Crust. Overall, EF in all peat samples ranged from 1.96 for Sm to 2.34 for Gd, with considerably lower EF for Ce (1.82) and Eu (1.44), respectively. A significant enrichment of all REE which may have been caused by military activities, was observed in the peat sample dating from World War II (1944); this exceptional sample, however, is not enriched in Ce. The concentration profiles of REE were similar but not identical to those of other lithogenic, conservative reference elements such as Sc, Y, Al, Zr and Ti. While it has been suggested that individual REE concentrations or the sum of REE can be used as a reference parameter to calculate crustal EF in environmental samples the data presented here indicates that anthropogenic emissions of REE cannot simply be ignored.

Deciphering human–climate interactions in an ombrotrophic peat record: REE, Nd and Pb isotope signatures of dust supplies over the last 2500years (Misten bog, Belgium)

“…The REE vary in parallel with the lithogenic elements such as Sc or Ti (e.g., coefficient correlation R 2 = 0.83 for Nd-Ti, 0.84 for La-Ti, 0.86 for Ce-Ti and 0.87 for Yb-Ti). Such trends demonstrate the conservative behavior of the REE in the peat sedimentary record, as previously demonstrated by Yliruokanen and Lehto (1995) and later by Krachler et al (2003). For instance, the La content ranges between 0.19 and 3.7 lg g À1 .…”

“…It is notable that data from the Black Forest in Germany (BFAubert et al, 2006) display the largest range of variation. The range of variation is narrow in the Swiss samples from Etang de la Gruère (ETG, Krachler et al, 2003) but its REE-richest sample is consistent with the two other European records. Grousset et al, 1988a,b;Goldstein et al, 1984;Colin, 1993;Henry et al, 1994).…”

“…The preanthropogenic REE AR measured at the base of the Misten peat accumulation (753 cm, 7500 BP) is reported for reference. La AR for Germany (BF, Aubert et al, 2006) and Switzerland (EGR, Krachler et al, 2003) are reported in comparison with Misten data EGR in the upper panel.…”

Mid- and late Holocene dust deposition in western Europe: the Misten peat bog (Hautes Fagnes – Belgium)

“…Consequently, the chemistry of atmospheric dust particles trapped in the peat bogs can be used to distinguish between local, regional and hemispheric dust input (e.g. Krachler et al, 2003;Kamanov et al, 2009;Müller et al, 2007;Sapkota et al, 2006;Shotyk et al, 2002).…”

Impact of the physico-chemical properties of fen peat on the metal accumulation patterns in mires of Latvia

“…The metal content was determined in acid-digested samples of fen peat, using atomic absorption spectroscopy (AAS), and in peat ashes, using the total reflection X-ray fluorescence (TXRF) method (Potts 1987;Bish et al 1989;Krachler et al 2003). Acid digestion was carried out using 25 ml 50% HNO 3 and 5 ml 30% H 2 O 2 per 1 g of oven-dried peat samples.…”