Effects of acid sulphate on DOC release in mineral soils: the influence of SO42− retention and Al release |
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| Authors: | S M Palmer J M Clark P J Chapman G M F van der Heijden S H Bottrell |
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| Institution: | 1. School of Geography, University of Leeds, , Leeds, LS2 9JT UK;2. Soil Research Centre, Department of Geography and Environmental Science, University of Reading, , Reading, RG6 6DW UK;3. University of Wisconsin‐Milwaukee, PO Box 413, , Milwaukee, WI, 53201 USA;4. Smithsonian Tropical Research Institute, , Apartado Postal, 0843‐03092 Panamá;5. School of Earth and Environment, University of Leeds, , Leeds, LS2 9JT UK |
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| Abstract: | Dissolved organic carbon (DOC) in acid‐sensitive upland waters is dominated by allochthonous inputs from organic‐rich soils, yet inter‐site variability in soil DOC release to changes in acidity has received scant attention in spite of the reported differences between locations in surface water DOC trends over the last few decades. In a previous paper, we demonstrated that pH‐related retention of DOC in O horizon soils was influenced by acid‐base status, particularly the exchangeable Al content. In the present paper, we investigate the effect of sulphate additions (0–437 µeq l?1) on DOC release in the mineral B horizon soils from the same locations. Dissolved organic carbon release decreased with declining pH in all soils, although the shape of the pH‐DOC relationships differed between locations, reflecting the multiple factors controlling DOC mobility. The release of DOC decreased by 32–91% in the treatment with the largest acid input (437 µeq l?1), with the greatest decreases occurring in soils with very small % base saturation (BS, < 3%) and/or large capacity for sulphate (SO42?) retention (up to 35% of added SO42?). The greatest DOC release occurred in the soil with the largest initial base status (12% BS). These results support our earlier conclusions that differences in acid‐base status between soils alter the sensitivity of DOC release to similar sulphur deposition declines. However, superimposed on this is the capacity of mineral soils to sorb DOC and SO42?, and more work is needed to determine the fate of sorbed DOC under conditions of increasing pH and decreasing SO42?. |
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