Sample preparation methods and replicability in macroscopic charcoal analysis |
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Authors: | Kyle J Schlachter and Sally P Horn |
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Institution: | (1) Department of Geography, The University of Tennessee, Knoxville, TN 37966-0925, USA;(2) Present address: Department of Geography, University of Denver, Denver, CO 80208, USA |
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Abstract: | We explored the use of hydrogen peroxide (H2O2) of different strengths (1, 3, 6, and 9%) in the preparation of lake-sediment samples for macroscopic charcoal determination.
In previous work we found that soaking sediment samples in 3% H2O2 for 24 h disaggregates samples and removes or bleaches some non-charred organic material, making it easier to distinguish
macroscopic charcoal particles from dark, non-charred organic matter. To determine whether this procedure alters charcoal
particle abundances and size distributions, we tested the procedure on wood and grass samples containing a known number of
laboratory-produced charcoal particles from different size classes (250–500, 500–1,000, and 1,000–2,000 μm). For both sample
types, we found that post-treatment numbers were not statistically different from pre-treatment numbers. However, application
of hydrogen peroxide solutions of 3, 6, and 9% to fossil charcoal assemblages in a sediment core from northwestern Costa Rica
reduced charcoal concentrations markedly, by bleaching or removing particles that were not fully charred. We also tested the
replicability of charcoal counts by conducting enumerations on multiple samples from the same stratigraphic depths in a core.
Horizontally adjacent samples from the same core may vary in charcoal concentration. This finding has implications for establishing
sample volume in macroscopic charcoal analysis. |
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