Sorption of Lipophilic Organic Compounds to Wood and Implications for Their Environmental Fate

The sorption from water to wood (KWood) of 10 organic chemicals (log KOW, 1.48-6.20) was experimentally determined for oak (Quercus robur) and basket willow (Salix viminalis). Linear regression yielded log KWood = -0.27 (+/- 0.25) + 0.632 (+/- 0.063) log KOW for oak (r = 0.90, n = 27) and log KWood = -0.28 (+/- 0.40) + 0.668 (+/- 0.103) log KOW for willow (r = 0.79, n = 27). According to an equilibrium-partitioning model, wood should be an important storage compartment for lipophilic environmental chemicals, but this is contrary to analytical results. Diffusive uptake from air into wood was estimated to be a relevant transport process only for chemicals with a high KAW. Uptake of chemicals from soil via xylem into stem was simulated with a dynamic one-compartment model. This pathway seems to be important for chemicals with low and intermediate lipophilicity. In large trees, the chemicals are retained for a long time. If metabolism inside the stem occurs, wood can serve as a "safe sink" for environmental chemicals. This might be of use in phytoremediation.