Pinus Sylvestris and Picea Abies Canopy Effects on Deposition of Air Pollutants

Tree canopies influence atmospheric pollutant depositions depending on type, ecosystem characteristics, and local climatic conditions. This study investigated the impact of Pinus sylvestris L. and Picea abies (L.) H. Karst., and a mixture of both, on the chemical composition of precipitation. Three permanent plots within the ICP forest level II monitoring network in Lithuania were selected to illustrate typical hemiboreal coniferous forests. The study analysed (1) the concentrations of NO2, NH3 and SO2 in the ambient air; (2) the concentrations of SO42−, NO3−, NH4+, Na+, K+, Ca2+ and Cl– in throughfall beneath canopies and in precipitation collected in an adjacent field, and (3) S and total N, Na+, K+, Ca2+ and Cl− depositions in throughfall and precipitation over 2006–2022. Results show a significant decrease in SO2 emissions in the ambient air; NO2 and NH3 emissions also decreased. The canopies reduced the acidity of throughfall, although they led to notably higher concentrations of SO42−, NO3−, Na+, and particularly K+. During the study, low variability in NO3– deposition and a decrease in NH4+ deposition occurred. Deposition loads increased by 20–30