Synthesis and characterisation of laboratory-charred grass straw (Oryza saliva) and chestnut wood (Castanea sativa) as reference materials for black carbon quantification

We synthesised large (similar to 2 kg) quantities of two chars for use as commercially available reference materials for the quantification of black carbon (BC). We pyrolysed chestnut wood (Castanea saliva) and grass straw (Oryza sativa) at 450 C under a N-2 atmosphere, which mimics the oxygen-free conditions on the inside of burning material at a moderate burning temperature. The charred materials were dominated by aromatic carbon (similar to 70%), had low H/C (similar to 0.7) and O/C (similar to 0.3) ratios and low surface areas (2-6 m(2) g(-1)). Isotopic changes on charring were small (<= 0.3 parts per thousand). In these respects, the synthesised chars were similar to chars produced at low temperature (< 500 degrees C) in natural fires and thus may prove to be appropriate materials for calibrating BC quantification methods. Both chars have been used in a comparative study of BC quantification. (c) 2006 Elsevier Ltd. All rights reserved.