Characterization and Modeling of Polycyclic Aromatic Compound Uptake into Spruce Tree Wood

This study highlights the potential of uptake into tree inner wood via direct-transfer through bark, as one contributing mechanism to describe atmospheric uptake of polycyclic aromatic compounds (PACs) into trees. The uptake of PACs into blue spruce tree wood was measured, with wood-air partition coefficients (K_{WOOD_AIR}) determined for five PACs. A correlation between the octanol-air partition coefficient (K_OA) and K_{WOOD_AIR} for these five chemicals was determined and the K_{WOOD_AIR} for 43 PACs were derived. A ratio of solubility (activity) difference between tree wood and octanol was also determined for these chemicals from this correlation. Finally, the derived K_{WOOD_AIR} values were further applied to calculate an air volume sampled by the inner wood layer (cambium) of a tree during a one year growth (sampling) period. PACs with a log K_{WOOD_AIR} > 6 remained in the linear sampling phase over one year of sampling. The results further highlight the important sink that forests provide for atmospheric organic chemicals which should be considered for emissions monitoring and impact assessments from destructive events such as forest fires or clear felling of forests.