Interference by organic complexation of Fe and A1 on the SO2-4 adsorption in Spodic B horizons in Sweden |
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Authors: | E. KARLTUN J. P. GUSTAFSSON |
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Affiliation: | Department of Soil Sciences, Swedish University of Agricultural Sciences, P.O. Box 7014, 750 07 Uppsala;Department of Land and Wafer Resources, Royal Institute of Technology, 100 44 Stockholm, Sweden |
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Abstract: | The relations between pH, different fractions of Fe and A1 and Na4P2O7-soluble C and the amount of adsorbed SO2-4 were assessed by analysing 63 soil samples from 14 podsolized soils in Sweden. The amount of adsorbed SO2-4 was significantly better correlated with the calculated amount of the inorganic fraction of Fe and A1 oxides obtained by subtracting Na4P2O7-soluble Fe and A1 from oxalate-soluble Fe and Al than with the oxalate extraction alone. There was a close correlation between C and organically-bound S in the Na4P2O7 extract which shows that the C:S ratio of the extracted fulvic acids is about constant in the soils studied. It was found that, as the proportion of organically-complexed Fe and Al increases, the ability of the soil to adsorb SO2-4 decreases. The amount of adsorbed SO2-4 expressed on the basis of the amounts of oxalate-soluble Fe and Al was generally smaller in areas with low S deposition (< 60 mmol m-2 a-1). The ratio between pyrophosphate-soluble C and oxalate-extractable Fe and Al was negatively correlated with pH in water. It was concluded that Fe and Al associated with organic matter cannot adsorb SO2-4 and that the degree of this association is pH dependent. These observations have important implications regarding the effects of anthropogenic acidification. |
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