Abstract
Abstract. The development of a rapid and non-destructive method to assess purity levels in samples of biogenic silica prior to geochemical/isotope analysis remains a key objective in improving both the quality and use of such data in environmental and palaeoclimatic research. Here a Fourier Transform Infrared Spectroscopy (FTIR) mass-balance method is demonstrated for calculating levels of contamination in cleaned sediment core diatom samples from Lake Baikal, Russia. Following the selection of end-members representative of diatoms and contaminants in the analysed samples, a mass-balance model is generated to simulate the expected FTIR spectra for a given level of contamination. By fitting the sample FTIR spectra to the modelled FTIR spectra and calculating the residual spectra, the optimum best-fit model and level of contamination is obtained. When compared to X-ray Fluorescence (XRF) the FTIR method portrays the main changes in sample contamination through the core sequence, permitting its use in instances where other, destructive, techniques are not appropriate. The ability to analyse samples of <1 mg enables, for the first time, routine analyses of small sized samples. Discrepancies between FTIR and XRF measurements can be attributed to FTIR end-members not fully representing all contaminants and problems in using XRF to detect organic matter external to the diatom frustule. By analysing samples with both FTIR and XRF, these limitations can be eliminated to accurately identify contaminated samples. Future, routine use of these techniques in palaeoenvironmental research will therefore significantly reduce the number of erroneous measurements and so improve the accuracy of biogenic silica/diatom based climate reconstructions.
Highlights
IntroductionIncreased attention is focused on the potential for geochemical measurements of biogenic silica to be used in palaeoenvironmental research in both continental, riverine, lacustrine and marine settings (e.g., Filippelli et al, 2000; de la Rocha et al, 2000; de la Rocha, 2003, 2006; Derry et al, 2005; Hendry and Rickaby, 2008; Hodson et al, 2008; Opfergelt et al, 2008; Swann et al, 2010)
Whereas trace levels of contamination have been detected through X-ray Fluorescence (XRF) and light microscopy in BFCmod, no impurities have been found in PS1772-8 with additional Scanning Electron Microscope (SEM), light microscopy, X-ray Diffraction (XRD) and Nuclear Magnetic Resonance (NMR) analyses confirming the purity of both samples (Chapligin et al, 2011)
This variability in the Fourier Transform Infrared Spectroscopy (FTIR) spectra is apparent across all wavelengths, in cleaner samples being focused around the main spectral peak at ∼ 1100 cm−1 and centred over the main spectral “contaminant” peaks in more contaminated samples
Summary
Increased attention is focused on the potential for geochemical measurements of biogenic silica to be used in palaeoenvironmental research in both continental, riverine, lacustrine and marine settings (e.g., Filippelli et al, 2000; de la Rocha et al, 2000; de la Rocha, 2003, 2006; Derry et al, 2005; Hendry and Rickaby, 2008; Hodson et al, 2008; Opfergelt et al, 2008; Swann et al, 2010). Current methods for purifying/extracting biogenic silica samples involve a mixture of chemical and physical treatment stages including the use of heavy liquids and gravitational split-flow thin fractionation (SPLITT) (e.g., Giddings, 1985; Juillet-Leclerc, 1986; Shemesh et al, 1995; Ellwood and Hunter, 1999; Morley et al, 2004; Rings et al, 2004; Robinson et al, 2004; Hamilton et al, 2005; Tyler et al, 2007; Minoletti et al, 2009). While these techniques can result in the extraction of fully cleaned samples, in most instances a small
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
