Ion fluxes from fog and rain to an agricultural and a forest ecosystem in Europe

Thalmann E, Burkard R, Wrzesinsky T, Eugster W, Klemm O

Abstract

The deposition fluxes of inorganic compounds dissolved in fog and rain were quantified for two different ecosystems in Europe. The fogwater deposition fluxes were measured by employing the eddy covariance method. The site in Switzerland that lies within an agricultural area surrounded by the Jura mountains and the Alps is often exposed to radiation fog. At the German mountain forest ecosystem, on the other hand, advection fog occurs most frequently. At the Swiss site, fogwater deposition fluxes of the dominant components SO42- (0.027 mg S m(-2) day (-1)), NO3- (0.030 mg N m(-2) day(-1)) and 4 3 NH4+ (0.060 mg N m(-2) day (-1)) were estimated to be < 5% of the measured wet deposition (0.85, 0.70 and 1.34 mg m(-2) day(-1), respectively). The corresponding fluxes at the forest site (0.62, 0.82 and 1.16 mg m(-2) day(-1), respectively) were of the same order of magnitude as wet deposition (1.04, 1.01 and 1.36 mg m(-2) day(-1)), illustrating the importance of fog (or occult) deposition. Trajectory analyses at the forest site indicate significantly higher fogwater concentrations of all major ions if air originated from the cast (i.e. the Czech Republic), which is in close agreement with earlier studies. (C) 2002 Elsevier Science B.V. All rights reserved.