Abstract

This study examined the influence of moisture content (MC) on NO₂ sorption ability of cedar (Cryptomeria japonica) wood using the specimens with different MCs. Four MC conditions were applied, namely 0%, 8.6%, 12.7% and 16.5%, based on the differences of bonding condition of water molecule in the wood substances. As a result, the NO₂ sorption volume increased drastically due to the presence of water, and as the MC increased, the NO₂ sorption volume increased slightly. The NO generation volume and nitric acid concentration in the specimens were evaluated after an aeration test, and it was strongly indicated that the NO₂ reacted with water in the specimen, and that the NO generation volume increased as the content of multilayer adsorbed water increased. The nitric acid seemed to be formed by the reaction between NO₂ and water, and it was then held in the specimen. Based on the NO₂ sorption volume calculated using the NO generation volume, it was shown that the NO₂ sorption after 12-h aeration was caused mainly by the reaction between NO₂ and water. Furthermore, the presence of both water and extractives contributed to the NO₂ sorption in the initial period, and the presence of water contributed greatly to the NO₂ sorption over the long term.