| 1. |
- Bergelin, A., et al.
(författare)
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The acid-base properties of high and low molecular weight organic acids in soil solutions of podzolic soils
- 2000
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Ingår i: Geoderma. - 0016-7061 .- 1872-6259. ; 94:2-4, s. 223-235
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Tidskriftsartikel (refereegranskat)abstract
- The acid properties of the organic acids and identified low molecular weight (LMW) organic acids in soil solutions of podzolic soils were determined using proton affinity spectra, based on EMF titration data, and Gran titrations. The proton affinity spectra showed apparent pKa values of 2.6, 4.1, 5.4 and 6.7 for the dissolved organic material. The LMW organic acids had similar pKa values. The average specific buffer capacity as determined by Gran titrations was 8.8±0.5 μmol H+/mg DOC. The specific buffer capacity for the identified low molecular acids was 40±2 μmol H+/mg DOC.
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| 2. |
- Giesler, R., et al.
(författare)
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Distribution and mobilization of Al, Fe and Si in three podzolic soil profiles in relation to the humus layer.
- 2000
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Ingår i: Geoderma. - 0016-7061 .- 1872-6259. ; 94:2-4, s. 249-263
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Tidskriftsartikel (refereegranskat)abstract
- The mobilization of Al, Fe and Si in podzols is often associated with the weathering of silicate minerals in the E horizon, downward migration, and their accumulation lower in the soil profile. This study investigated Al, Fe, and Si concentrations in soil water (centrifugation samples) and estimated leaching losses from the humus layer in comparison with those in the mineral E and B horizon. Concentrations of total soluble Al and Fe in soil water were higher in the O and E horizons than in B horizon samples, but not significantly different between the two uppermost horizons. Si concentrations were higher in the E than in the O horizon. The amount of Al and Fe leaching from the E horizon (i.e. input to the B horizon) compared to amount leaching from the O horizon (i.e. the input to the E horizon) ranged from 92% to 163%. Calculated leaching losses from the lower B horizon were less than 3% of the input to the B horizon. The results suggest that a large part of the illuviated Al and Fe in the Bs horizon is derived from the O horizon. Similar values for the Si ranged from 56% to 61% (comparing E horizon output with E horizon input). Budget estimates available for one of the investigated podzols indicated that biocycling via above-ground litter explained < 12% of the estimated annual input of Al and Fe to the forest floor. Inputs of Al and Fe due to upward flow of capillary water accounted for about 26% of the Al and Fe in the O layer. The results show that there is a considerable pool of Si Al, Fe in the humus layer. This pool plays an important part in the present day biogeochemical cycling of these elements in podzolic soils. Several mechanisms possibly involved in the transfer of Al, Fe and Si from the mineral soil to the humus layer are discussed.
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| 3. |
- Gustafsson, Jon Petter, et al.
(författare)
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Partitioning of base cations and sulphate between solid and dissolved phases in three podzolised forest soils
- 2000
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Ingår i: Geoderma. - 0016-7061 .- 1872-6259. ; 94:04-feb, s. 311-333
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Tidskriftsartikel (refereegranskat)abstract
- The cation and SO, adsorption properties of O and B horizons of three podzolised soils in Sweden and Finland were studied through analysing the soil solution at six different sampling occasions and through a set of batch experiments. High concentrations of dissolved organic carbon and cations were found in centrifuged soil solutions from the O horizon, especially during autumn. An analysis using the WHAM-S model suggested that most of the dissolved Ca, Mg, K and Mn were counter-ions, residing in the diffuse layers of dissolved fulvic acids. Hence, the solubility of these cations depended on the solubility of organic matter. Model exercises suggested that the solubility of humics in turn was influenced by seasonal differences in hydrophobicity and by the water content. Furthermore, the model results showed that only a low proportion of the B horizon organic matter was involved in calcium binding. This is probably due to the interaction between organic matter and oxide surfaces in this horizon. In the case of sulphate adsorption in the B horizons, a surface complexation model was tested for its ability to describe batch experiment data and temporal differences in soil water chemistry. This model was based on the diffuse-layer model and it was optimised by adjusting the surface site concentration and the point of zero charge. However. the interaction between Ca2+ and SO42- could not be modelled. Comparisons between the model and the field observations proved to be difficult due to a considerable soil heterogeneity.
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| 4. |
- Ilvesniemi, H., et al.
(författare)
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General description of the sampling techniques and the sites investigated in the Fennoscandinavian podzolization project
- 2000
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Ingår i: Geoderma. - 0016-7061 .- 1872-6259. ; 94:2-4, s. 109-123
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Tidskriftsartikel (refereegranskat)abstract
- A 3-year project focusing on the fundamental processes of podzolization was carried out on three sampling sites in northern Fennoscandinavia. The soils were selected based on the previous information of the soil properties to represent typical soils in the area. In this article, the post-glacial history of the sites, site vegetation and general properties of the soils, as well as the methods used are presented. Two of the sites were classified as Typic HapLocryods and one as an Entic Haplocryod. The post-glacial age of the sites was between 9000 and 9500 years BP and the parent material was glacial till in one of the sites and glaciofluvial material in two of them. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 5. |
- Johansson, Emma, et al.
(författare)
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Organic and chlorine in Swedish spruce forest soil : Influence of nitrogen
- 2001
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Ingår i: Geoderma. - 0016-7061 .- 1872-6259. ; 101:3-4, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- Concentrations of organic and inorganic chlorine were estimated in samples collected in forest soils in the southern part of Sweden, and changes were observed after the addition of nitrogen in incubated samples. All of the investigated samples contained both inorganic and organic chlorine, and the concentration of organic chlorine was 2-4 times larger than that of inorganic chlorine. The results suggest that the amount of organic chlorine in mature spruce forest soils with a moderate chloride deposition in the temperate region is larger than the amount of inorganic chlorine. The results of the nitrogen incubation indicate that addition of ammonium nitrate causes a net decrease in the concentration of organic chlorine and a net increase in chloride concentration. The observed change appears to mainly be a result of a dechlorination of the organic matter present in the water leachable fraction. © 2001 Elsevier Science B.V.
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| 6. |
- Karltun, E., et al.
(författare)
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Surface reactivity of poorly-ordered minerals in podzol B horizons
- 2000
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Ingår i: Geoderma. - 0016-7061 .- 1872-6259. ; 94:04-feb, s. 265-288
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Tidskriftsartikel (refereegranskat)abstract
- The surface reactivity of mineral soil horizons from three podzolised forest soils in Scandinavia was examined. The amount of accumulated C was low, between 1.8 and 2.3% in the top of the B horizons. Selective extractions in combination with infrared (IR) spectroscopy and transmission electron microscopy (TEM) indicated a predominance of poorly-ordered imogolite-type materials (ITM) in the oxalate extractable fraction in an examined B horizons. The presence of well-ordered imogolite was only indicated in the Nyanget B3 horizon. A large proportion of free Fe was removed by ammonium oxalate. Comparisons of Mossbauer spectra (both at room temperature and at 4.2 K) before and after treatment with ammonium oxalate showed that the oxalate treatment resulted in a removal of a (super)paramagnetic Fe3+ phase? probably ferrihydrite. A comparison of the Mossbauer Fe3+ parameters at room temperature and 4.2 K indicated a close intergrowth of a ferrihydrite-like oxide with a magnetically neutral matrix, e.g., allophane. The specific surface area (SSA) was determined by N-2 adsorption before and after treatment of the samples with acid ammonium oxalate. The loss of SSA after oxalate treatment was considerable in the B horizon where only between 3.8 to 13.38 of the original SSA remained after treatment. The point of zero charge salt effect (PZSE) increased with depth in the B horizon from between 4.4 and 5.1 in the upper horizons to between 5.7 and 7.7 in the lower part of the B horizon. The increased PZSE with depth paralleled a decrease in the ratio of pyrophosphate soluble C to oxalate soluble Fe + Al. The affinity for SO42-. a goad indicator of the presence of active surface hydroxyls, was measured by comparing the H+ buffering capacity of a sample titrated in 2.5 mM Na2SO4 with a sample titrated in 5 mh I NaNO3,. The buffering capacity of the soil in the Na2SO4, electrolyte was well correlated with the amount of oxalate minus pyrophosphate soluble Fe + Al (r(2) = 0.88). The sulphate exchange capacity was considerably higher than CEC, especially in lower parts of the B horizon. The calculated surface area of the oxalate soluble material (OSM) ranged between 74 and 289 m(2) g(-1) and the calculated surface site density of the same material ranged between 0.6 to 3.3 site nm(-2). It was concluded that the surface reactivity in the B horizons is dominated by the poorly-ordered variable-charge oxides resulting in a low capacity to retain cations but a high capacity for adsorption of weak acid anions like SO42- and organic acids.
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| 7. |
- Lundström, Ulla, et al.
(författare)
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Advances in understanding the podzolization process resulting from a multidisciplinary study of three coniferous forest soils in the Nordic Countries
- 2000
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Ingår i: Geoderma. - 0016-7061 .- 1872-6259. ; 94:04-feb, s. 335-353
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Tidskriftsartikel (refereegranskat)abstract
- Geochemical, mineralogical, micromorphological, microbiological, hydrochemical and hpdrological joint investigations were performed at two coniferous podzolic sites in the north of Sweden and at one in the south of Finland. Mycorrhizal fungi were found to create numerous pens (3-10-mu m diameter) in many weatherable mineral grains in the eluvial (E) horizon. During the growing season, identified low molecular weight (LMW) organic acids such as citric, shikimic, oxalic and fumaric acids comprised 0.5-5% of the DOC and 0.5-15% of the total acidity in soil solutions. Between 20% and 40% of the dissolved Al was bound to the identified LMW organic acids. Mineral dissolution via complexing LMW acids, probably exuded in part by the mycorrhiza hyphae, is likely to be a major weathering process in podzols. We found no evidence for a decreasing C/metal ratio of the migrating organo-metal complexes that could explain the precipitation of secondary Fe and AL in the illuvial (B) horizon. Instead, microbial degradation of organic ligands resulting in the release of ionic,Al and Fe to the soil solution may he an important process facilitating the formation of solid Al-SI-OH and Fe-OH phases in the podzol B horizon. However, within the B horizon transport as proto-imogilite (PI) sols might be possible. In the B horizon, the extractable,Al and Fe was predominantly inorganic. The large specific surface area (SSA) removable by oxalate extraction, the high point of zero charge salt effect (PZSE), the low cation exchange capacity (CEC) and the high sulphate exchange capacity (SEC), painted to the presence of short-range ordered variable charge phases. Imogolite type material (ITM) was indeed identified in all B horizons by IR spectroscopy and crystalline imogolite was found in the deep B horizon of one profile. Mossbauer spectroscopy indicated that Fe in the form of ferrihydrite was formed by intergrowth with an Al-Si-OH phase. The high amounts of Fe and Al transported from the O to the E horizon indicate that there could be an upward transport of these elements before they are leached to the B horizon. We hypothesize that the LMW Al complexes an transported by hyphae to the mor (O) layer, partly released and subsequently complexed by high molecular weight (HMW) acids.
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| 8. |
- van Breemen, Nico, et al.
(författare)
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Do plants drive podzolization via rock-eating mycorrizhal fungi?
- 2000
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Ingår i: Geoderma. - 0016-7061 .- 1872-6259. ; 94:2-4, s. 163-171
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Tidskriftsartikel (refereegranskat)abstract
- Weathering and supply of nutrients derived from minerals to plants is known to be stimulated by plant symbiotic mycorrhizal fungi. Nutrients are generally thought to pass the bulk soil solution before plant uptake. Jongmans et al. [Jongmans, A.G., van Breemen, N., Lundstrom, U.S., van Hees, P.A.W., Finlay, R.D., Srinivasan M., Unestam, T., Giesler, R., Melkerud, P.-A., Olsson, M., 1997. Rock-eating fungi. Nature, 389, 682-683] showed that (ectomycorrhizal) fungi drill innumerable narrow cylindrical pores (diameter 3-10 μm) into weatherable minerals in podzol E horizons. The fungi probably form micropores by exuding strongly complexing low-molecular weight organic acids at their hyphal tips, causing highly local dissolution of Al silicates. Micropores occurred in all thin sections of podzols under Pinus sylvestris and Picea abies available from Sweden (3), Finland (2), Switzerland (2), Denmark (2) and the Netherlands (3), but not in the few available thin sections of non-podzolic soils under broadleaves. Many weatherable minerals in the podzol E horizon appeared to be perforated, as opposed to few if any in the abruptly underlying B horizon, suggesting a link to podzolization. High concentrations of Al and Si in organic surface horizons under boreal and temperate conifers can be explained by transfer by hypha of weathering products from the minerals to mycorrhizal roots in the O horizon, followed by release of weathering products that are not taken up by the plants. Rock-eating ectomycorrhizal fungi suggest a more direct role for plants in podzolization than hitherto realized, providing tight coupling between podzolization and mineral weathering. Preliminary observations, however, indicate that mycorrhizal fungi do not play a role in podzolization under Kauri (Agathis australis) in New Zealand. (C) 2000 Elsevier Science B.V.
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| 9. |
- van Hees, P. A. W., et al.
(författare)
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Equilibrium models of aluminium and iron complexation with different organic acids in soil solution
- 2000
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Ingår i: Geoderma. - 0016-7061 .- 1872-6259. ; 94:2-4, s. 201-221
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Tidskriftsartikel (refereegranskat)abstract
- The percentage of Al and Fe bound to identified low molecular weight (LMW) organic acids and phosphate in soil solution was calculated using a chemical equilibrium model. The highest fractions were obtained for the O1 horizon solutions with median values between 38-49% for Al and 18-29% for Fe. Generally the percentage declined in the deeper horizons. Acceptable agreement with experimental values using ultrafiltration (< 1000 D) was found especially for the spring and summer samplings. In the autumn samples, larger deviations between the modelled and ultrafiltered fractions were found. The major part of the remaining Al and Fe in solution was calculated to be bound to undefined organic acids most likely of higher molecular weight. Speciation studies of some individual organic acids are presented. Citric acid proved to be the most important complex former of the LMW acids in the O and E horizons while oxalic acid was dominant in the B horizon solutions. The total level of organic complexation of Al, Fe, Ca and Mg was also studied. It was found that > 85% of the Al and > 95% of the Fe were organically bound. The opposite was seen for Ca and Mg for which > 85% was modelled to occur as inorganic ions. The modelling results support the theory that LMW organic acids contribute to the translocation of Al and Fe in the podzolization process.
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| 10. |
- van Hees, P. A. W., et al.
(författare)
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Factors influencing aluminium concentrations in soil solution of podzols
- 2000
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Ingår i: Geoderma. - 0016-7061 .- 1872-6259. ; 94:2-4, s. 289-310
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Tidskriftsartikel (refereegranskat)abstract
- Mechanisms controlling the concentrations of free Al3+ and total Al in the soil solution from three podzolic soils were evaluated. Saturation indices (SI) were calculated for five mineral phases, but no single phase determined the Al3+ activity. E horizon samples were found to be undersaturated with respect to all phases. A more detailed equilibrium study indicated that formation of proto-imogolite sols was commonly possible in B horizon solutions with pH > 5. The poor relationship between pH and pAl3+ in the E and B1 horizons did not support control by exchange reactions with solid organic matter, although partial least square (PLS) regressions indicated importance of soil-exchangeable Al in the B and C horizons. It was concluded that in the E and most of the B1 horizon solutions, Al3+ activity is controlled by equilibrium with soluble organic acids which was supported by the PLS regressions. (C) 2000 Elsevier Science B.V.
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