Particle deposition to forests - Summary of results and application

Particle deposition to forest was studied at Speulder forest using experimental and modelling results. In this paper a short overview of the main results is given and they are applied in generalisation of deposition in The Netherlands. The results of the Aerosol project show that the deposition of particles to forests has been underestimated until now. Particle deposition makes a reasonable contribution to the total deposition of acidifying components and base cations to forests. Parametrisations of the deposition processes were derived from the experiments and model developed for particle deposition to Speulder forest. The parametrisations were used together with concentrations, meteorological observations and land-use data to determine the deposition on a 5 x 5 km basis in The Netherlands. Results of the canopy exchange experiments at Speulder forest and of the comparison of atmospheric deposition estimates and throughfall estimates at Speuld and other locations in The Netherlands show that throughfall fluxes and atmospheric deposition estimates are reasonably in agreement for all components, except nitrate. There is still large uncertainty in canopy exchange processes of oxidised nitrogen and in deposition estimates of the different gases contributing to the total oxidised nitrogen flux. The contribution of aerosol deposition to the total deposition in The Netherlands is 7% for SO42-, 11% for NH4+ and 9% for NO3-; for deciduous forests these numbers are 14, 15 and 17%, and for coniferous forests 10, 17 and 20% respectively. Dry deposition is estimated to amount to about 21% of total deposition for Na+, 20% for K+, 27% for Mg2+ and 25% for Ca2+.