Suggested protocol for collecting, handling and preparing peat cores and peat samples for physical, chemical, mineralogical and isotopic analyses

Abstract

For detailed reconstructions of atmospheric metal deposition using peat cores from bogs, a comprehensive protocol for working with peat cores is proposed. The first step is to locate and determine suitable sampling sites in accordance with the principal goal of the study, the period of time of interest and the precision required. Using the state of the art procedures and field equipment, peat cores are collected in such a way as to provide high quality records for paleoenvironmental study. Pertinent field observations gathered during the fieldwork are recorded in a field report. Cores are kept frozen at -18 degree C until they can be prepared in the laboratory. Frozen peat cores are precisely cut into 1 cm slices using a stainless steel band saw with stainless steel blades. The outside edges of each slice are removed using a titanium knife to avoid any possible contamination which might have occurred during the sampling and handling stage. Each slice is split, with one-half kept frozen for future studies (archived), and the other half further subdivided for physical, chemical, and mineralogical analyses. Physical parameters such as ash and water contents, the bulk density and the degree of decomposition of the peat are determined using established methods. A subsample is dried overnight at 105 degree C in a drying oven and milled in a centrifugal mill with titanium sieve. Prior to any expensive and time consuming chemical procedures and analyses, the resulting powdered samples, after manual homogenisation, are measured for more than twenty-two major and trace elements using non-destructive X-Ray fluorescence (XRF) methods. This approach provides lots of valuable geochemical data which documents the natural geochemical processes which occur in the peat profiles and their possible effect on the trace metal profiles. The development, evaluation and use of peat cores from bogs as archives of high-resolution records of atmospheric deposition of mineral dust and trace elements have led to the development of many analytical procedures which now permit the measurement of a wide range of elements in peat samples such as lead and lead isotope ratios, mercury, arsenic, antimony, silver, molybdenum, thorium, uranium, rare earth elements. Radiometric methods (the carbon bomb pulse of (14)C, (210)Pb and conventional (14)C dating) are combined to allow reliable age-depth models to be reconstructed for each peat profile.

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)

“…For this study, cores were taken in February 2008: the upper meter was retrieved with a TiWardenaar corer (Wardenaar, 1987) (core MIS-08-01W), whilst the next few meters were extracted with a Bielorussian corer (Belokopytov and Veresnevich, 1955) (core MIS-08-01b). The cores were stored at À40°C, and frozen cores were cut at a 1.5 cm sampling interval by a stainless steel band saw at the University of Heidelberg (Givelet et al, 2004). The sample slices were sub-sampled into two.…”

Development and refinement of proxy-climate indicators from peats

“…Direct dust analyses can be performed after extraction on peat ashes using soft acids and bases and particle collection by filtration and/or centrifugation (Givelet et al, 2004). This is particularly relevant for large mineral particles like quartz grains and minerals that are resistant to peat acidic conditions, such as aluminosilicates or zircon (Le Roux and Shotyk, 2006).…”

Developing statistical models to estimate the carbon density of organic soils

“…Real differences in CD may reflect local differences in material decay and compaction (Tolonen and Saarenmaa 1979;Minkkinen and Laine 1998), and extreme values can be caused, for example, by the presence of segregation ice in permafrost peat (Vardy et al 2000). Differences between methods may result from the coring or sampling protocol used (Sheppard et al 1993;Givelet et al 2004), drying times and temperatures (e.g., Avramidis 1989), and the temperature and duration of ignition to measure ash Heiri et al 2001). Since the relative magnitude of these error sources cannot be determined from the data available, we recommend the development of taskspecific equations to suit a given research question and region.…”