Extractives, acidity, buffering capacity, ash and inorganic elements of black locust wood and bark of different clones and origin

Chemical properties of black locust wood and bark from Greece, Bulgaria and Hungary (clones NY, U and J) were investigated. Disks at breast height were taken from 25 black locust trees (five trees per origin and clone) and were divided into separate biomass components (juvenile heartwood, mature heartwood, sapwood and bark). Hot water soluble (HWSE) and dichloromethane soluble extractives (DSE), acidity (pH), buffering capacity, ash content and inorganic elements were determined according to standard laboratory techniques. Bark had the highest extractive content for both HWSE ( 9.25-13.49%) and DSE (3.09-4.03%). Differences of extractive contents in wood were found to exist between trees of different origin and between the three clones and ranged in heartwood between 5.04-10.10% for HWSE and 0.53-1.83% for DSE and in sapwood between 3.33-6.76% for HWSE and 0.48-1.47% for DSE. The higher values of pH occurred in sapwood (4.92-5.35), while the differences between bark (4.44-5.12) and heartwood (4.35-4.92) were small. Acid (ABC) and base (BBC) buffering capacities from the initial to pH 10 for ABC and to pH 3 for BBC were greater in bark (ABC 0.0172-0.0219 ml/ml and BBC 0.0079-0.0141 ml/ml) than in the other wood components (for heartwood ABC 0.0069-0.0159 ml/ml and BBC 0.0022-0.0096 ml/ml and for sapwood ABC 0.00330.0066 ml/ml and BBC 0.00330.0049 ml/ml). The total ash content was greater in bark (7.24-8.56%) than in other biomass components (for heartwood 0.34-0.89% and for sapwood 0.72-1.24%). The content of the main inorganic elements (Ca, K, Mg, Na, P) were also found to be much higher in bark while sapwood values were greater than heartwood.