Charcoal Analysis for Paleoenvironmental Interpretation: A Chemical Assay

A nitric acid digestion and ignition technique developed to measure relative frequencies of charcoal in lake and bog sediments measures the weight of charcoal relative to the dry weight of the sample (percentage charcoal) and gives results comparable to counting of microscopic charcoal. Differences in the two techniques caused by changes in sediment type were found especially in postsettlement and late-glacial parts of cores. Charcoal values from sediments less than 100-yr old cannot be compared to older charcoal values unless wood charcoal and charcoal from fossil fuel burning are separated microscopically. Tests of this chemical assay on mixtures of known weights of charcoal, leaves, and sand give correlations between observed and expected values of 0.99 to 1.00.