SEASONAL AND ANNUAL DEPOSITION RATES OF SULFUR, NITROGEN AND CHLORIDESPECIES TO AN OAK FOREST IN NORTH-EASTERN AUSTRIA (WOLKERSDORF, 240 MASL)

Dry deposition estimates of sulphur, nitrogen and chloride components to an oak forest in north-eastern Austria were performed using an ''In ferential model.'' The deposition calculations were performed with a m odified Hicks et nl. (1985) model based on chemical measurement data w ith 0.5 h (SO2, NO, NO2) and 24 h (HCl, HNO3, NH3, particulate chlorid e, nitrate, sulphate and ammonium) time resolution. Annual dry deposit ion rates of sulphur (SO2 + pSO(4)) were estimated to amount around 13 kg ha(-1), of oxidised nitrogen (NO + NO2 + HNO3 + pNO(3)) 8.4 kg ha( -1), of reduced nitrogen (NH3 + pNH(4)) 5.6 kg ha(-1) and of chloride (HCl + pCl) 2.1 kg ha(-1). The relative contribution of dry to total ( dry + wet) deposition is 68% for sulphur, 77% for oxidised nitrogen, 5 5% for reduced nitrogen and 40% for chloride species. Total deposition of sulphur and reduced nitrogen species showed good agreement with da ta from throughfall measurements and a canopy exchange model. For oxid ised nitrogen species the inferential modeling approach yielded a cons iderably higher deposition which could be explained by the inability o f the canopy exchange model to account for stomatal uptake of NO2. A c omparison of dry and wet fluxes of sulphur and nitrogen species at Eur opean and U.S. sites indicates that in both environments large regiona l differences occur. Thus the hypothesis, that European forests receiv e substantially higher inputs of ''major ions'' than U.S, forests (Lin dberg et al., 1990) cannot be generalised., ''Dry + wet'' deposition o f nitrogen species at two Austrian sites is well within the range of d eposition at 11 forested sites in the U.S., while at one Austrian site it is slightly higher than the highest N-deposition reported for U.S: sites. Compared sites From the U.S. are from the Mountain Cloud Chemi stry Project and the Integrated Forest Study (Lovett and Lindberg, 199 3). (C) 1998 Elsevier Science Ltd. All rights reserved.