Quantification methods of Black Carbon: Comparison of Rock-Eval analysis with traditional methods

Black Carbon (BC) quantification methods are reviewed, including new Rock-Eval 6 data on BC reference materials. BC has been reported to have major impacts on climate, human health and environmental quality. Especially for risk assessment of persistent organic pollutants (POPs) it is important to account for risk reduction caused by BC, as suggested for POP safety assessment in the framework of the new European Community Regulation on Registration, Evaluation, Authorization and Restriction of Chemicals (REACH). Four major classes of BC quantification methods are reviewed including application to BC reference materials. Methods include chemical oxidation, thermal oxidation, molecular marker, optical methods and Rock-Eval analyses. Residual carbon from Rock-Eval 6 analysis correlated well with BC data from ‘gentle’ methods like optical and molecular marker methods, which capture a major part of the BC continuum including labile fractions (e.g. char). In contrast, the temperature at which 50% of the organic matter was oxidized (T50%) in an oxidation-only Rock-Eval analysis, correlated well with data from chemothermal oxidation (CTO), which captures only refractory BC fractions (e.g. soot). Rock-Eval analysis can further be used for BC characterization through deconvolution of the dominant peaks of the thermogram and appears to be a powerful tool in BC analysis.