Photodegradation depth profile and penetration of light in Japanese cedar earlywood (Cryptomeria japonica D. Don) exposed to artificial solar radiation

Fourier transform-infrared (FT-IR) micro-spectroscopic depth profile analysis was used to monitor the penetration of photo-induced chemical changes in Japanese cedar earlywood, exposed for up to 1500 hours of artificial sunlight emitted by a xenon lamp producing 375W/m(2) of radiation (within the 300 to 700nm spectral range). Parallel experiments assessed the transmission of ultraviolet (UV)-near UV and UV-visible light through Japanese cedar earlywood (both unexposed and pre-exposed to 1000 hours of artificial sunlight), Infrared (IR) spectra showed that photo-induced chemical changes penetrated into the earlywood to a depth of up to 700mum and there was a logarithmic increase in the depth of degradation as a function of irradiation time. The penetration of light into wood showed an exponential decrease with wood depth. Nevertheless, sufficient photochemically active light may be present at depths, which could account for photodegradation depth profiles that were observed.