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

Summary

This study evaluated differential scanning calorimetry as a method to identify and quantify black carbon in soil by exploiting distinct thermal signatures of charcoal versus uncharred soil organic matter. Although charcoal demonstrated greater thermal stability and characteristic exothermic peaks, the wide temperature range of charcoal decomposition overlaps substantially with uncharred organic matter, complicating accurate quantification using temperature cut-offs alone. Strong correlation between DSC-derived and BPCA-derived charcoal measurements (R² = 0.97) suggests DSC is a viable complementary approach, though the discrepancy in absolute values underscores the importance of controlling for method-specific recovery rates in black carbon quantification.

UK applicability

The methodological advances in black carbon quantification are applicable to UK soils where historical charcoal-making sites exist or where biochar amendments are being considered for carbon sequestration and soil improvement. However, the study focused on pre-industrial charcoal and temperate European conditions; validation in diverse UK soil types and under different management contexts would strengthen applicability to UK farming and land restoration practice.

Key measures

Charcoal-C content (DSC-derived and BPCA-derived); thermal signatures and exothermic peaks; soil sample composition from 45 sites in Belgium and Germany

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 historical charcoal kiln sites. DSC and BPCA measurements showed strong correlation (R² = 0.97), though BPCA-derived carbon represented approximately one-fifth of DSC-estimated charcoal carbon.

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