Fig. 3From: Artificial formation of benzene polycarboxylic acids during sample processing of black carbon analysis: the role of organic carbon amountIndividual and sum of BPCA with three (B3CA), four (B4CA), five (B5CA) and six (B6CA) carboxylic groups of plant samples, as function of amount of total organic carbon (TOC) and thus, sample weight, after conventional high-pressure digestion (a) and microwave-assisted digestion (b). Different lowercase letters indicate significant differences among BPCA in the same soil profile p < 0.05Back to article page