IVL Throughfall network

Deposition measurements are mainly made in forest injury observation plots laid out by the Swedish Forestry Agency (SST). The observations made are: Air Chemistry: SO2, NO2, NH3, O3 Soil Water Chemistry: pH, Alk, SO4-S, Cl, NO3-N, NH4-N, Ca, Mg, Na, K, Mn, Fe, ooAl, oAl, Al-tot, TOC Deposition open field precipitation: H+, SO4-S, Cl, NO3-N, NH4-N, Ca, Mg, Na, K, Mn Deposition in forest throughfall: H+, SO4-S, Cl, NO3-N, NH4-N, Ca, Mg, Na, K, Mn A notorious problem in deposition assessments is dry deposition on forest canopies. If throughfall is sampled below the canopy it will consist not only of dry and wet deposition, but also of canopy leakage, i.e. exudates and diffusion of substances from within the leaves. However, it has been argued that throughfall sampling, even if not free from problems, may add information to the normal wet deposition sampling. IVL operates a throughfall sampling network comprised of 10 forest sites for sampling, from which monthly samples are analyzed for pH, SO4, NO3, NH4, Kjeldahl-N, Cl, K, Ca, Na, Mg, TOC, conductivity, alkalinity, and amount of throughfall.