The influence of sulfur deposition rates on sulfate retention patterns and mechanisms in aerated forest soils

摘要: Abstract Stable isotope ratios were used as a tracer for S flow and transformations in an irrigation experiment with 5 different German forest soils. Seventy-five lysimeters constructed from soil cores, 15 each site, irrigated over 20 months SO 4 -rich artificial canopy throughfall, simulating 3 input levels: 35 kg ha −1 treatment I, 63 II, 131 III. The δ 34 value of the was more than 22‰ higher those total untreated Mass balances compounds to assess patterns mechanisms retention individual horizons their dependence on deposition levels. Independent level, average 12±5 applied bound organically by microbial biomass all Immobilization occurred predominantly topsoil formation C-bonded being prevalent synthesis organic sulfates. Tracer via accounted up 50% 16 25% less 20% dominant process inorganic soils appeared be adsorption , but precipitation aluminum hydroxy sulfate minerals constituted second potential some Sulfate increased increasing sesquioxide content rates. In high contents, typically 70% retained inorganically, whereas lowest content, generally labeled detected form. latter soil, not enough fully adsorb elevated inputs treatments II Consequently, export seepage water observed experimental variants III form during thus observed. ability inorganically retain mineral identified major factor regulating extent at 60 cm depth. combined comparatively low recovery implies that mean transit time uppermost acid varies between several years many decades, much longer previously thought.