| 1. |
- Fröberg, M, et al.
(författare)
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Contributions of Oi, Oe and Oa horizons to dissolved organic matter in forest floor leachates
- 2003
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Ingår i: Geoderma. - 0016-7061. ; 113:3-4, s. 311-322
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to identify the role of organic matter of the Oi, Oe and Oa layers for leaching of dissolved organic matter (DOM) from the O horizon in a podsolised forest soil in southern Sweden. Solid state C-13 cross polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectroscopy and C-14 measurements were used to analyse organic matter in solid material and water extracts from the Oi, Oe and Oa horizons, soil leachates collected below the Oe and Oa horizons and throughfall. The DOM in soil leachates from the Oe horizon had a C-14 content that was higher than the water extractable organic matter (WEOM) from the Oi horizon but equal to the C-14 content in the WEOM from the Oe horizon. The C-14 contents in WEOM and DOM from the Oe and Oa horizons were all equal. These results suggest that the DOM leaving the Oe horizon to a large extent had its origin within the Oe horizon itself. NMR spectroscopy showed that WEOM was higher in O-alkyl and lower in aromatic carbon than DOM in soil leachates.
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| 2. |
- Holmqvist, Johan, et al.
(författare)
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Vesicular-arbuscular mycorrizae for dating multiple paleosols and carbon loss rate determination
- 2000
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Ingår i: Geoderma. - 0016-7061. ; 97:1-2, s. 125-133
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Tidskriftsartikel (refereegranskat)abstract
- A promising technique for dating paleosols is reported based on radiocarbon (C-14) dating of asexual spores from vesicular-arbuscular mycorrizae (VAM). The soils are dispersed in water and some 6000-8000 spores separated by hand picking under a low power microscope. The dried spores are then dated by accelerator mass spectroscopy (AMS). A chronosequense of closely superimposed paleosols from an arctic/alpine meadow soil, northern Sweden, was dated and the long-term (i.e., over a millennium time-span) organic carbon loss rate determined. A very low carbon loss rate was obtained, 4.7 x 10(-4) +/- 9.2 x 10(-5) year(-1). It is argued that this approach is likely to give a better estimate for long-term loss than litter-bag studies covering a couple of decades. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 3. |
- Tyler, Germund
(författare)
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Effects of sample pretreatment and sequential fractionation by centrifuge drainage on concentrations of minerals in a calcareous soil solution
- 2000
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Ingår i: Geoderma. - 0016-7061. ; 94:1, s. 59-70
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Tidskriftsartikel (refereegranskat)abstract
- Soil solution is the direct source of mineral nutrients to vascular plants. Soil solutions of sieved samples at water-holding capacity of a seminatural calcareous soil, never cultivated or treated by fertilizers, were collected by sequential centrifugation at 24-18,900 X g relative centrifugal force (RCF), followed by ultrafiltration (0.2 mu m), and analysed for Al, Ca, Fe, K, Mg, Mn, Mo, Na, P, S, Si and pH. Soil solution held by weak forces (low RCF applied) had higher concentrations of base cations, Fe, and Si than soil solutions obtained at higher RCF. Opposite relationships were measured for P-TOT, molybdate-reactive P and Mo, whereas concentrations of Mn and S did not vary much according to RCF level. A comparison between centrifugation of soil cores at undisturbed stratification and mixed samples uncovered no great differences in soil solution pH or concentrations of major constituents, though concentrations of Ca, Si and S were 10-20% lower in solution from undisturbed cores. Possible mechanisms accounting for the observations are discussed. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 4. |
- Yasuda, H., et al.
(författare)
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Characterizing preferential transport during flood irrigation of a heavy clay soil using the dye vitasyn blau
- 2001
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Ingår i: Geoderma. - 0016-7061. ; 100:1-2, s. 49-66
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Tidskriftsartikel (refereegranskat)abstract
- Common irrigation procedures in many parts of the world involve flood irrigation. Observations during recent years have, however, indicated that preferential flow may be an important phenomenon that could affect the outcome of both irrigation and fertilizer application for this irrigation type. To analyze and visualize solute transport by preferential flow mechanisms, field experiments were carried out at the Cherfech Agricultural Research Station in northern Tunisia. Paths of solute transport were investigated by a 0.05-m ponded pulse of Vitasyn Blau dye allowed to infiltrate into the unsaturated heavy clay soil. Two experimental plots were prepared for the infiltration of dye by leveling the surface. Leveling was done to have similar surface conditions at the two plots. After infiltration, a trench was dug at the border of the dye-injected region to document the dye patterns vertically and horizontally. The patterns indicated strong dependence on the horizontal structure of the soil. In general, the dye was to a major extent transported along distinct cracks and ped faces in the prismatic silty clay. Only the upper 0-0.05 m depth of the tilled soil had almost a complete dye coverage. Below this depth, preferential dye patches start to develop and dye coverage is rapidly decreasing to below 50% at 0.15 m depth. Even though transport through the prismatic silty clay mainly followed cracks between the prisms, it is estimated that only 10-20% of these vertical cracks are active in conducting solutes. The results from the present study have implications for soil management in areas using flood and furrow irrigation with soils susceptible to preferential flow. Tillage depth is a factor that is likely to have a great impact on the amount of water that reaches the soil matrix. Increasing tillage depth and other management practices that break up the structure and make the soil more homogeneous will increase the efficiency of irrigation and reduce the susceptibility for preferential flow.
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| 5. |
- 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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| 6. |
- 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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| 7. |
- 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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| 8. |
- 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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| 9. |
- 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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| 10. |
- 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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