Pyrolytic combustion analysis of carbon - a new approach for characterizing growing media

摘要

Traditionally carbon is analysed by combustion analysis under air or pure oxygen atmosphere at 450 or 550°C for total organic carbon (TOC) and at about 1000°C for total carbon (TC). But informative value of results is limited because none of these methods provide information about quality (e.g., degradability by saprophytic fungi) of analysed carbon. As new approach stepwise thermal carbon fractionation under pyrolytic conditions (Py-TA-EGA) was tested in the current research with a range of growing media. Therefor an elemental analyser RC 612 (LECO Corporation, Monchengladbach, Germany) was modified to run under N2 atmosphere. To reach a complete oxidation of released carbon to carbon dioxide, oxygen was injected behind the combustion zone. In total 43 growing media constituents and another 44 mixtures of two of these constituents were analysed using a temperature ramp with eight steps between 200 and 1000°C. Furthermore samples were analysed for TOC and TC by combustion under 02 and carbon wasfractionated by hydrolysis with hydrochloric acid (0.005 and 1 M respectively). Additionally samples were inoculated with mycelium of the saprophytic fungus Peziza ostracoderma and fungal biomass was measured after incubation for twelve days. Results show significant positive correlations between carbon cleavable under pyrolytic conditions (PC) at low temperature (<350°C) and hydrolysable carbon (r>0.55). Contrary PC released at high temperature (>500°C) was negatively correlated with hydrolysable carbon. The intensity of fungal growth could be estimated by combining PC fractions released at low and high temperatures.