Development of an ombrotrophic peat bog (low ash) reference material for the determination of elemental concentrations

Abstract

Given the increasing interest in using peat bogs as archives of atmospheric metal deposition, the lack of validated sample preparation methods and suitable certified reference materials has hindered not only the quality assurance of the generated analytical data but also the interpretation and comparison of peat core metal profiles from different laboratories in the international community. Reference materials play an important role in the evaluation of the accuracy of analytical results and are essential parts of good laboratory practice. An ombrotrophic peat bog reference material has been developed by 14 laboratories from nine countries in an inter-laboratory comparison between February and October 2002. The material has been characterised for both acid-extractable and total concentrations of a range of elements, including Al,

Mobility of antimony, arsenic and lead at a former antimony mine, Glendinning, Scotland

“…Analytical precision (±RSD) for the independent reference solution, ICP Multielement Standard Solution VI (Pb: 10 mg L −1 ; As and Fe: 100 mg L −1 ), was <3.3% (n = 10). Analysis of ombrotrophic peat reference material NIMT/UOE/FM001 (Yafa et al, 2004) gave concentrations (Sb 2.00 ± 0.43, As 3.00 ± 0.56, Pb 159 ± 6 and Fe 803 ± 46, all in mg kg −1 ; n = 12) which were in good agreement with the certified (Pb 174 ±8 mg kg −1 ), and information only values (As 2.44 ± 0.55; Sb 2.37 ± 0.34; Fe 921 ± 84 mg kg −1 ) (Yafa et al, 2004;Cloy et al, 2009). …”

“…The ash residue was digested using a MARS 6 microwave digestion system (CEM) and the modified US EPA Method 3052 (HF-HNO 3 Aristar, VWR International Ltd., Leics., UK) published by Yafa and Farmer (2006). With every batch of ten samples, duplicate reagent blanks and duplicate samples of a peat certified reference material (NIMT/UOE/FM001 (Yafa et al, 2004)) were taken through the same procedure (see SI file).…”

Development and refinement of proxy-climate indicators from peats

“…The humification signal is a derived response to climate. The assumption that climate has been the major influence on variations in humification rests on the supposition that the botanical composition is relatively homogeneous throughout a peat profile; however, that is often not the case, making the use of humification data (on their own) as a climate proxy questionable (Yeloff and Mauquoy, 2006), because past changes in the botanical composition of the peat may have an influence on humification measurements, as acknowledged by Chambers et al (1997), who recognised the possibility of a 'species signal' in humification data. Caseldine et al (2000) questioned the assumption that the colorimetric technique, which uses weak alkali as a digestant, actually extracts 'humic acid'.…”

“…A cautionary note was sounded by Yeloff and Mauquoy (2006), who identified inconsistencies between peat humification and other proxy-records of mire surface wetness in a peat profile. The humification signal is a derived response to climate.…”

“…Other techniques have been used, such as inductively coupled plasma optical emission spectroscopy (ICP-OES, e.g. Yafa et al, 2004;Mighall et al, 2009), or scanning electron microscope equipped with an energy dispersive XRF analyser (SEM-EDX) for specific purposes (Rausch et al, 2005;De Vleeschouwer et al, 2008), such as mineral identification. Scanning XRF has also been used on peat cores (Lowe et al, 1981;Gehrels et al, 2008;De Vleeschouwer et al, 2008); it gives promising results but is limited by the problem of surface roughness and the pore spaces in peat cores, because these can generate high signal noise.…”