Carbon isotope behaviour in wood and cellulose during artificial aging

Modern wood was subjected to an artificial decay process to investigate its behaviour with respect to the stable carbon isotope composition of wood an d the corresponding cellulose. Four different woods were used, namely: oak (Quercus robur), beech (Fagus sylvatica), pine (Pinus sylvestris), sequoia (Sequoiadendron giganteum) and pure spruce cellulose. The process of decay was simulated by heating samples in water at 180 degrees C from minutes to months. During the decay period, the carbon content of wood increased to al most 70% while the cellulose content decreased gradually to zero. The degra dation proceeds according to a two stage process: an initial Very fast brea k down is followed by a rather slow degradation. After a strong discriminat ion against C-13 during the initial phase, the C-13/C-12 ratio increases ag ain, mostly up to its initial value. The carbon isotope trend for cellulose shows a similar pattern though it is less pronounced. Maximum discriminati on was 1 parts per thousand relative to the untreated wood. delta(13)C valu es of cellulose decreased by up to 0.3 parts per thousand. The C-13 depleti on is presumably a consequence of the preferential decomposition of cellulo se as compared to lignin. Data on fossil trees are compared with the result s obtained from this treatment of aging. The C-13 decrease is in line with observations from these fossil woods, but the ensuing C-13 enrichment is at most weakly to be seen. (C) 1999 Elsevier Science B.V. All rights reserved .