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.

Comparisons of watershed sulfur budgets in southeast Canada and northeast US: new approaches and implications

“…The contribution of organic S dynamics to watershed budgets has been the focus of considerable attention due to its large pool size of which small changes could have dramatic effects on S export in drainage waters. Evidence using natural SO 4 2-isotope abundances (both d 34 S and d 18 O) from studies of forest ecosystems both in North America (Gélineau et al 1989;Zhang et al 1998;Eimers et al 2004c;Eimers and Houle 2005;Schiff et al 2005) and Europe (Alewell and Gehre 1999;Mayer et al 1995;Novák et al 2005Novák et al , 2007 has indicated the importance of the immobilization of SO 4 2-and organic S mineralization in affecting ecosystem S dynamics.…”

Immission-load-related dynamics of S-SO4 2− in precipitation and in lysimetric solutions penetrating through beech ecosystems

“…Kantor and Lochman (1985) found higher sulphur concentrations in throughfall and stemflow than in open area in the Orlické vrchy Mts. The total annual amount of sulphur reaching the soil surface in spruce stands can be 49-80 kg S ha -1 yr -1 (Novák et al, 2007 Dubová and Bublinec (2006), the maximum amounts of sulphate sulphur in autumn and winter precipitation are similar. On the other hand, Pichler et al (2006) found in mixed forests maximum values of S-SO 4 2-in winter precipitation.…”

The SO42- concentration and sulphur content in lysimetric water and throughfall in beech forest stands in the Štiavnické vrchy Mts. Ekológia

“…Tesař et al (2004) . yr -1 (Novák et al, 2007). Meanwhile, the soil at the research plots in the Štiavnické vrchy Mts received 23 kg S. ha -1 via throughfall in a 180-190 years old oak stand at 680 m a. s. l. altitude (Kunca, 2007).…”