Method for characterization of inert organic carbon in urbic anthrosols

Organic matter in Urbic Anthrosols often contains chemically and biologically inert organic carbon. This material, called black carbon (BC), originates from municipal wastes, coal-mine deposits and/or fly ash. This black carbon needs to be differentiated from the other soil organic substances because of its very different physical and chemical nature. In this paper, we propose a new method for determining BC, integrated into the humic fractionation procedure. The remaining organic carbon in the soil residue left after lipid extraction, alkaline extraction [0.5 M sodium hydroxide (NaOH)], and further oxidation with 30% hydrogen peroxide (H2O2) is defined as inert organic carbon or BC. The common fractions of soil organic matter, such as lipids, fulvic and humic acids, and humins are thus supplemented with a new fraction, BC. According to our results by C-13-NMR spectroscopy, this fraction consists mainly of polyaromatic hydrocarbons with few functional groups.