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

Summary

This methodological study evaluated differential scanning calorimetry (DSC) as a tool for identifying and quantifying black carbon (charcoal) in soil by characterising its distinct thermal signature relative to uncharred soil organic matter. Using soil samples from pre-industrial charcoal kiln sites in Belgium and Germany, the authors demonstrated that charcoal exhibits characteristic exothermic combustion peaks that vary with soil conditions and chemical bond strength, though decomposition temperatures overlap considerably with those of uncharred organic matter. Strong correlation (R² = 0.97) between DSC-derived charcoal-C estimates and BPCA marker abundance validates the thermal approach, whilst highlighting that operationally defined black carbon content requires careful control of recovery rates across different quantification methods.

UK applicability

The DSC methodology could be applied to UK soils to assess historical and contemporary black carbon stocks, particularly in agricultural soils benefiting from biochar amendment or in areas with archaeological charcoal deposits. UK soil scientists and land managers would benefit from improved quantification methods to evaluate black carbon's role in carbon storage and soil fertility improvement, though validation across diverse UK soil types and management histories would be necessary.

Key measures

Charcoal-C content (mg/g or % soil C); thermal exothermic peak height and position; BPCA abundance (μmol/g); decomposition temperature ranges; degree of aromatic condensation

Outcomes reported

The study developed and validated differential scanning calorimetry (DSC) as a method to identify and quantify charcoal in soil by analysing thermal signatures, comparing results against the established benzene polycarboxylic acid (BPCA) marker method. Analysis of 45 soil samples from pre-industrial charcoal kiln sites demonstrated strong correlation (R² = 0.97) between DSC-derived charcoal-C and BPCA abundance, though BPCA-C represented approximately one-fifth of DSC-derived charcoal-C.

Topic tags