Seasonal and annual deposition rates of sulphur, nitrogen and chloride species to an oak forest in north-eastern austria (wolkersdorf, 240 m a.s.l.)

Abstract

Dry deposition estimates of sulphur, nitrogen and chloride components to an oak forest in north-eastern Austria were performed using an “Inferential model.” The deposition calculations were performed with a modified Hicks et al. (1985) model based on chemical measurement data with 0.5 h (SO 2, NO, NO 2) and 24 h (HCl, HNO 3, NH 3, particulate chloride, nitrate, sulphate and ammonium) time resolution. Annual dry deposition rates of sulphur (SO 2+pSO 4) were estimated to amount around 13 kg ha -1, of oxidised nitrogen (NO+NO 2+HNO 3+pNO 3) 8.4 kg ha -1, of reduced nitrogen (NH 3+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, 55% for reduced nitrogen and 40% for chloride species. Total deposition of sulphur and reduced nitrogen species showed good agreement with data from throughfall measurements and a canopy exchange model. For oxidised nitrogen species the inferential modeling approach yielded a considerably higher deposition which could be explained by the inability of the canopy exchange model to account for stomatal uptake of NO 2. A comparison of dry and wet fluxes of sulphur and nitrogen species at European and U.S. sites indicates that in both environments large regional differences occur. Thus the hypothesis, that European forests receive substantially higher inputs of “major ions” than U.S. forests ( Lindberg et al., 1990) cannot be generalised. “Dry+wet” deposition of nitrogen species at two Austrian sites is well within the range of deposition 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 Chemistry Project and the Integrated Forest Study ( Lovett and Lindberg, 1993).