title: Processes affecting oxygen isotope ratios of atmospheric and ecosystem sulfate in two contrasting forest catchments in Central Europe.
abstract: Sulfate aerosols are harmful as respirable particles. They also play a role as cloud condensation nuclei and have radiative effects on global climate. A combination of delta18O-SO4 data with catchment sulfur mass balances was used to constrain processes affecting S cycling in the atmosphere and spruce forests of the Czech Republic. Extremely high S fluxes via spruce throughfall and runoff were measured at Jezeri (49 and 80 kg S ha(-1) yr(-1), respectively). The second catchment, Na Lizu, was 10 times less polluted. In both catchments, delta18O-SO4 decreased in the following order: open-area precipitation > throughfall > runoff. The delta18O-SO4 values of throughfall exhibited a seasonal pattern at both sites, with maxima in summer and minima in winter. This seasonal pattern paralleled delta18O-H2O values, which were offset by -18 per thousand. Sulfate in throughfall was predominantly formed by heterogeneous (aqueous) oxidation of SO2. Wet-deposited sulfate in an open area did not show systematic delta18O-SO4 trends, suggesting formation by homogeneous (gaseous) oxidation and/or transport from large distances. The percentage of incoming S that is organically cycled in soil was similar under the high and the low pollution. High-temperature 18O-rich sulfate was not detected, which contrasts with North American industrial sites.
authors.affiliation: Department of Geochemistry, Czech Geological Survey, Geologicka 6, 152 00 Prague 5, Czech Republic. novak@cgu.cz
authors.forename: Martin
authors.initials: M
authors.lastname: Novák
authors.forename: Myron J
authors.initials: MJ
authors.lastname: Mitchell
authors.forename: Iva
authors.initials: I
authors.lastname: Jacková
authors.forename: Frantisek
authors.initials: F
authors.lastname: Buzek
authors.forename: Jana
authors.initials: J
authors.lastname: Schweigstillová
authors.forename: Lucie
authors.initials: L
authors.lastname: Erbanová
authors.forename: Richard
authors.initials: R
authors.lastname: Prikryl
authors.forename: Daniela
authors.initials: D
authors.lastname: Fottová
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D001272:Atmosphere; D002980:Climate; D017753:Ecosystem; D004784:Environmental Monitoring; D005060:Europe; D009656:North America; D010103:Oxygen Isotopes / Q000032:analysis*; D011891:Rain; D012621:Seasons; D013431:Sulfates / Q000032:analysis*; D014197:Trees
chemical_list: D000393:Air Pollutants; D010103:Oxygen Isotopes; D013431:Sulfates