THROUGHFALL MEASUREMENTS OF NITROGEN AND SULFUR-COMPOUNDS

The wet- and throughfall deposition of nitrogen and sulphur compounds to a spruce forest edge in Sweden was studied using preserved as well as unpreserved collectors. During the warmer part of the year inorgani c nitrogen was lost in unpreserved throughfall collectors, if they wer e not shielded from light. Several days of light exposure was needed t o transform most of the ammonium, most likely to an organic form. The rate was enhanced by the addition of glucose. High throughfall deposit ion of organic nitrogen has been found using preserved collectors. The origin of this organic nitrogen in throughfall is not clear, but it s eems likely that it comes from transformation of wet and dry deposited ammonium. Rough estimates of the dry deposition were made from air co ncentration measurements inside and outside the forest. The dry deposi tion of SO2, HNO3 and NH3 was more significant than their particulate forms.