Dry deposition velocity of PM2.5 ammonium sulfate particles to a Norway spruce forest on the basis of S- and N-balance estimations

In this paper we make an attempt to estimate the dry deposition velocity of ammonium sulfate particles using the results of sulfur and nitrogen balance determined between the atmosphere and a forest ecosystem for the years of 1996–1998. Results of these measurements and of a campaign conducted during summer of 2001 demonstrate that ammonium and sulfate ions exist in nearly equivalent ratio in particle phase. According to the size distribution measurements majority (92%) of ammonium sulfate can be found in the fraction of PM2.5. For the balance calculation, results of throughfall, stemflow and wet-only deposition measurements have been used, together with dry deposition measurements of gaseous sulfur dioxide and ammonia. Dry deposition velocity of ammonium sulfate particles determined from sulfur and nitrogen balance were v 0.82±0.25 and =0.84±0.25 cms−1, respectively. The two figures determined by different ways are in good agreement and they are in accordance with other experimental results found in the literature. The results suggest the necessity of the revision of the models applied during the theoretical calculation of dry deposition velocity of PM2.5 particles.