Forest canopies represent an extensive organic surface available for partitioning of semivolatile organic pollutants with the atmosphere. To date, the ability of forests to sequester such compounds (the so-called "forest filter effect") has been investigated using indirect methods that yield time integrated deposition fluxes and scenario-dependent deposition velocities. In the present study, experimental data collected at three different alpine forest sites were used to assess the dynamics of PCB deposition fluxes (F, ng m(-2) d(-1)) during the growing season. Estimated values of Fwere consistent with previously reported data. Furthermore, this study showed that maximum levels of F in late spring can be a factor of 1.4-3.4 higher than their seasonal mean value. These data, in conjunction with a simple modelframeworkthatincludesthe main forcing parameters of air concentration, temperature, foliage structure, and biomass dynamics, are used to estimate the plant-air mass transfer coefficient (ku, m d(-1)) and its variation with time in one of the forests. ku did not appear to significantly vary during the season, and its mean seasonal value ranged between 43 and 95 m d(-1) for selected compounds. The proposed framework was successfully applied to predict the variation in canopy concentration with time in the other two forests.