Identification of thermal signature and quantification of charcoal in soil using differential scanning calorimetry and benzene polycarboxylic acid (BPCA) markers

Summary

This paper evaluates differential scanning calorimetry as a tool for identifying and quantifying black carbon in soil, using soil samples from pre-industrial charcoal kiln sites in Belgium and Germany. Charcoal exhibits distinct thermal signatures characterised by exothermic peaks that differ from uncharred soil organic matter, though thermal decomposition ranges overlap, complicating quantification. Strong correlation between DSC and BPCA methods (R² = 0.97) supports the validity of thermal approaches, whilst revealing that operationally defined black carbon measurements require controlled recovery rates for absolute quantitative accuracy.

UK applicability

The methodology may be applicable to UK soil archives and archaeological sites containing charcoal residues, particularly in assessing historical land use and carbon storage. UK regulatory frameworks for soil carbon monitoring and verification could benefit from standardised quantification methods, though further validation in UK soil conditions would be needed.

Key measures

Charcoal-C content by DSC (relative height of exothermic peaks); black carbon quantification by BPCA; thermal decomposition temperatures; degree of aromatic condensation

Outcomes reported

The study compared differential scanning calorimetry (DSC) and benzene polycarboxylic acid (BPCA) methods for quantifying charcoal-derived black carbon in soil samples from pre-industrial charcoal kiln sites. DSC and BPCA measurements showed strong correlation (R² = 0.97), though BPCA-derived carbon represented approximately one-fifth of DSC-derived charcoal carbon.

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