P. Artaxo et al in ref 3, p139. J.-P. Lacaux in ref 3, p159. Sulphur is an essential nutrient present in living matter, and it is oxidised to SO 2 during combustion. Nitrogen present in amino acids and proteins is oxidised to NO 2 . The detailed mechanism of combustion is considerably more complex involving many high-temperature free radical reactions.
Most emissions take place during flaming and smouldering.
These two processes are quite different both in appearance and the types of chemical reactions involved. Water and volatile extractables are volatilised from the fuel material in an initial pyrolytic step, and the high temperatures cause cracking of the fuel molecules. In general, reactions tend to go more to completion during the flaming stage and some of the more oxidised forms are observed. A number of factors can influence forest fires and the emissions produced. The type of vegetation has an important influence, ie its water content, density and structure.