Diagnostic properties,horizons, soils and landscapes

For the classification of soil individuals such properties or horizons are used as diagnostic ones, which – as indicators for the weakest or strongest consequent transformation of the parent material and for the complementary translocation of transformation products – are assumed to reflect best the soil genesis. It is discussed how far the FAO-Unesco system satisfies this pretension. Like soil individuals as metamorphic figures of rock or sediment material soil landscapes can be considered as such of rock or sediment bodies (geomorphic units). Since both are coined by principally the same processes, the soils reflecting best the extent of consequent transformations and complementary translocations of/in the geomorphic units can be used as diagnostic ones in the classification of soil landscapes. Principles of such a taxonomy and its relation to that of soil individuals are discussed, especially in view of the ?intrazonal”? soils.     

Mercury in humus horizons of soils in the Transbaikal region

The total mercury content has been determined in gray forest soils, chernozems, chestnut soils, and in different parent materials in the Transbaikal region. The mercury content is below the clarke value in the intrusive, effusive, and alluvial soil-forming rocks (0.004–0.024 mg/kg). In the humus horizons of the soils, it reaches 0.011–0.026 mg/kg, which is higher than the clarke value for the pedosphere. The mean background content of mercury in the soils of the Transbaikal region is 0.018 mg/kg. No significant positive correlation between the mercury content and the humus content of the soils has been revealed.     

Psychrotolerant actinomycetes of plants and organic horizons in tundra and taiga soils

It has been revealed that in organic horizons and plants of the tundra and taiga ecosystems under low temperatures, actinomycetal complexes form. The population density of psychrotolerant actinomycetes in organic horizons and plants reaches tens and hundreds of thousands CFU/g of substrate or soil, and decreases in the sequence litters > plants > soils > undecomposed plant remains > moss growths. The mycelium length of psychrotolerant actinomycetes reaches 220 m/g of substrate. Application of the FISH method has demonstrated that metabolically active psychrotolerant bacteria of the phylum Actinobacteria constitute 30% of all metabolically active psychrotolerant representatives of the Bacterià domain of the prokaryotic microbial community of soils and plants. Psychrotolerant actinomycetes in tundra and taiga ecosystems possess antimicrobial properties.     

Temporal denitrification patterns in different horizons of two riparian soils

The dynamics of biological denitrification in riparian soil is still poorly understood. We studied the spring‐time pattern of denitrifying enzyme activity (DEA) and the rate of denitrification (DNT) in two hydromorphic riparian soils, one a mollic Gleysol and the other a terric Histosol. The average DEA ranged from 73 to 1232 ng N g^?1 hour^?1, and DNT ranged from 4 to 36 ng N g^?1 hour^?1. Both DEA and DNT diminished with increasing depth in both soil types. This decrease corresponded to a decrease in total and K₂SO₄‐extractable organic carbon and K₂SO₄‐extractable mineral nitrogen. The DEA and DNT differed in their dynamics. The former had no evident pattern in subsurface horizons but increased with temperature at the end of spring in surface and structural horizons. The DNT diminished as the soil dried in the mollic Gleysol when the water table fell. In the terric Histosol, the water table was still too high at the end of spring to affect the DNT. The results suggest that the vertical pattern of denitrification is related to that of organic carbon content. This organic carbon content determines biological activity and the supply of carbon and nitrous oxides. In biologically active horizons temperature drives the dynamics of DEA, whereas soil moisture drives the dynamics of DNT. Our results show the importance of the dynamic soil–water relationship in controlling denitrification within the riparian zone.     

Modeling of the development of humus horizons in soils of Crimea

Current approaches to the simulation of pedogenesis processes in time are considered. Models for the formation of humus horizon on parent rocks of different genesis in Crimea are presented. Formation rates of humus horizons have been determined, which allows developing the remediation strategies for mining dumps of mineral deposits in Crimea.     

运用生物法对褐土和潮土不同土层供钾能力的研究

运用玉米苗对褐土、潮土不同层次土壤进行了钾素生物耗竭试验 ,发现 :当土壤有效钾素趋向匮乏时 ,首先受到影响的是玉米苗的干生物产量 ,其次是植株总吸钾量 ,再其次才是植株含钾量 ;矿物钾对植株吸钾是有贡献的 ,但其贡献率因土壤不同而有很大的差异 ,褐土矿物钾的贡献率比潮土的要大 ;交换性钾、非交换性钾的生物有效性因土类的不同而存在明显差异 ,总的说来 ,潮土较褐土能提供较多的钾素 ;土壤供钾性能随深度增大而减弱     

Microstructure of genetic horizons in automorphic soils of the Timan Ridge

Data are presented on the physicochemical composition and specific macro-, meso- and micro-morphological features of automorphic soils formed on silty loams in the northern and middle taiga subzones of the Timan Ridge. These soils have a texture-differentiated profile and are well aggregated, which is manifested at all levels of structural organization of the soil mass. The morphological structure of the middle soil horizons is characterized by the presence of specific nongleyed cryometamorphic horizon CRM. Its formation is due to the development of long-term seasonal cryogenic processes in relatively deep (up to 40 cm) light and medium loam deposits under conditions of the northern and middle taiga subzones. The processes of cryometamorphism, combined with Al-Fe-humus and textural differentiation, result in the formation of podzolic, iron-illuvial, cryometamorphic, and textural horizons (O-E-BF-CRM-BT). The textural horizons have a set of micromorphological features indicating that recent clay illuviation is a weak process.     

Polycyclic aromatic hydrocarbons in different forest soils: Mineral horizons

The objective of this study was to assess the behavior of PAH in mineral soil horizons of different forest soils (Allersdorf, All: Inceptisol, mull humus type; Geisberg, Geis: Entisol, mull; Hohe Matzen, HoM: Spodosol, mor). At the mor site, the highest PAH loading was observed in the forest floor (HoM L to Oh, ΣX 20 PAH: 829 g ha^?1), whereas at the mull sites the humified mineral soil horizons were the main sink for PAH (All aAxh, Σ 20 PAH: 522 g ha^?1). In all soils, there was a significant PAH translocation into subsoil horizons (Σ 20 PAH in the subsoil: 76–195 g ha^?1). In order to delineate possible transport mechanisms, double-logarithmic relationships were established between the translocation of the distinct PAH from the surface soil to the subsoil and the PAH's K_ow values. The data suggested that transport of low-molecular PAH into the subsoil was primarily a function of the water solubility of each compound. In the biologically active All and Geis soils, high-molecular PAH were translocated independently from their K_ow value, and particle-bound transport probably by soil burrowing animals was assumed to control translocation of the penta- and hexacyclic PAH. In contrast, at HoM transfer of high-molecular PAH increased with increasing hydrophobicity, suggesting dissolved organic matter (DOM)-mediated transport of PAH. Fractionation of soil into a floatable fraction and into sand- (20–2000 μm), silt- (2–20 μm), coarse clay- (0.2–2 μm), and fine claysized (< 0.2 μm) separates revealed that more than 80% of the PAH loading could be assigned to silt- and coarse clay-sized separates, irrespective of the soil's texture (loamy sand to silty clay loam). Silt generally showed the highest C_org?related PAH concentrations. PAH profiles (relative proportion of each PAH on the sum of 20 PAH) revealed increasing proportions of high-molecular, more refractory PAH from the floatables and the sand-sized separates to the finer particles, corresponding with an increasing degree of SOM alteration in the same direction. At HoM, depth gradients of high-molecular PAH suggested co-transport of penta- and hexacyclic PAH with DOM and subsequent co-sorption selectively to the silt- and coarse-clay sized separates of the Bsh horizon.     

Copper and zinc sorption on some B horizons of Quebec soils

Abstract

The sorption of Cu and Zn on soils, as a function of pH, is important to an understanding of their mobility in the soil solution and their availability for plant nutrition. Copper and Zn sorption as a function of the pH were measured for six B horizons of two Orthic Humic Gleysols, two Orthic Humo‐Ferric Podzols, one Orthic Dystric Brunisol and one Orthic Sombric Brunisol. The results show that: 1) for the same amount of metal in solution and the same pH, more Cu is sorbed than Zn and 2) there is a maximum of sorption at or just above pH 5.00 and a large decrease as pH decreases.

During the pH‐dependent sorption of Cu and Zn on six B horizons of Quebec soils, it was found that ions were released into solution thus altering the charge generated by the soil at low pH and the sorption behavior of Cu and Zn. The solid phase most likely to control the level of ions in solution is believed to be the amorphous and oxide forms of Al and Fe. The dissolution of these metal oxide or hydrous oxide materials also releases cations adsorbed on, or occluded in, the amorphous material.     

Aluminium solubility mechanisms in moderately acid Bs horizons of podzolized soils

The processes controlling the retention and release of aluminium in acid forest soils are still subject to controversy, and therefore a universal hypothesis as to what mechanisms are operating has not been firmly established. By studying the Bs horizons of Swedish and Swiss podzolized soils, and by analysing data in the literature, we have found that aluminium hydroxide, and in some cases also poorly ordered imogolite, may control Al solubility in moderately acid (pH > 4.2–4.3) Bs horizons. The strongest evidence in support of the presence of a quickly reacting Al(OH)₃ pool came from the temperature dependence of Al solubility in a Bs horizon, which was consistent with the reaction enthalpy of an Al(OH)₃ phase such as gibbsite, and from the observation that the ion activity product for Al(OH)₃ was the same regardless of whether equilibrium was reached from over‐ or undersaturation. The pool of Al(OH)₃ is commonly small and may be completely dissolved after large additions of acid. This may be explained by the continuing redissolution of reactive Al(OH)₃ to form less soluble imogolite‐type phases. By using the same methods it was found that soil suspensions did not reach equilibrium with poorly ordered imogolite even after 17 days. Thus, imogolite probably does not control Al solubility in the short term in many soils despite the common occurrence of this mineral. This is due to the relatively slow kinetics of imogolite formation and dissolution, especially at low temperatures and at small solution H₄SiO₄ concentrations.     

Soil horizons as the basis for classification of alluvial soils

The horizons of different types in alluvial soils of central Russia are compared with respect to their morphological characteristics using the method of dendrograms. It is argued that diagnostic soil horizons should clearly reflect in their properties the character of pedogenic processes and, thus, be the basis for classification of alluvial soils. Overall, seven types of soil horizons are suggested as diagnostic horizons for flood-plain soils of the Russian Plain.     

Micromorphometric features of pore space in the plow horizons of loamy soils

A computer-based analysis of thin sections has been applied to study pore space in the plow horizons of loamy soils in European Russia and Ukraine. Differences in the morphology of soil macro-and mesopores are shown. It is argued that agrogenic impacts result in the convergence of the shape and orientation of macropores in plowed loamy soils of the forest, forest-steppe, and steppe zones. At the same time, this convergence is not observed for the soil mesopores.     

Characterization of maghemite in B horizons of three soils from Southern Portugal

Maghemite with an unusual habit was identified in the sandy fraction of two Alfisols and one Ultisol by X-ray and electron diffraction. Hematite was also present. Morphological analyses by scanning and transmission electron microscopy showed needle-like particles of maghemite with average lengths of 200–500 nm depending on the degree of the crystallinity. Those particles are arranged in star-like patterns as shown by ultrathin sections. Experimental synthesis of maghemite was successfully attempted in the presence of quartz sand with the freshly-formed crystals displaying the same particular morphology. Formation of acicular maghemite catalysed by quartz surfaces is, therefore, postulated.     

Identification of podzols and podzolised soils in New Zealand by relative absorbance of oxalate extracts of A and B horizons

A method for separating podzols and podzolised soils from other New Zealand soils is proposed. The method is based on measurement of the optical density of acid oxalate extracts of soils. A number of soil leaching sequences and some individual soils are examined.It is assumed that the optical density of the oxalate extracts is due mainly to extracted fulvic acid and that detection of appreciable quantities of this material in the B horizon indicates that podzolisation is an active process in the soil.The technique separated the soils of the leaching sequences well, following the observable increase of podzolic characteristics with increased leaching.When the B horizon/A horizon ODOE (optical density of the oxalate extracts) ratios were compared with the criteria for the spodic horizon in “Soil Taxonomy” (Soil Survey Staff, 1975), it was found that all soils with a ratio of less than 1.0 did not satisfy spodic horizon criteria and were not classified as podzol/podzolised. All the soils examined with ratios > 1.0 satisfied spodic horizon criteria or were classified as podzol/podzolised, usually both.     

Rapid spectrophotometric determination of red and yellow isochromic carotenoid fractions in paprika and red pepper oleoresins

A rapid method has been developed for the determination of the red (R) and yellow (Y) isochromic carotenoid pigments fractions in paprika and oleoresins, based on UV-visible spectrophotometric measurement at two characteristic wavelengths and application of the Lambert-Beer law for multicomponent mixtures. The wavelengths 472 and 508 nm were selected as the most appropriate for simultaneous quantification of these fractions in the acetone extract of pigments. Experimental determination of the specific absorption coefficients (epsilon) for the two pigment fractions (R, Y) at 472 and 508 nm yielded equations to calculate the concentration of the two fractions, the total pigment content, and the ratio between the two fractions. The error in the determination of the isochromic fractions by the proposed spectrophotometric method was <5% when the results were compared with those obtained by HPLC analysis. The method can be applied to the direct extract of pigments, thereby avoiding saponification and minimizing errors from pigment degradation and sample manipulation as well as shortening the time of analysis (5 min in the case of oleoresins).     

Disintegration of the clay fraction in the eluvial horizons of some Danish podzolized soils

Abstract

Using sequential extractions, total elemental analysis, and X‐ray diffraction, we have investigated the impact of the podzolization process on component composition of the clay fraction in the eluvial horizons of eight more or less podzolized Danish soils. The results indicate that podzolization is highly aggressive towards all clay components in the eluvial horizons eventually leading to their disintegration. The 2:1 layer silicate clay minerals, illite and chlorite, are first transformed into other 2:1 layer silicate clay minerals. After passing through a microcrystalline phase high in Si but low in Al, Fe, Mg, and K, they finally disintegrate completely. Even gibbsite and kaolinite disintegrate under the aggressive conditions, caused among other things by the presence of dissolved complex forming organic molecules in these horizons. Application of lime and fertilizers seems to be able to reverse the process in case of the 2:1 layer silicate clay minerals.     

Interactions between anthropogenic sulphate and marine salts in the Bs horizons of acidic soils in Scotland

In laboratory adsorption experiments, the comparison of podzol Bs horizons from coastal and inland moderately-impacted catchments with those from a severely-acidified inland region has demonstrated the effect of marine inputs on SO₄ ^2– -retention. Moderate sea-salt inputs and low acid deposition leads to the retention of most of the SO₄ ^2– and the release of soluble Mg²⁺; increasing the marine salt loading causes the development of a selectivity towards retention of acidic SO₄ ^2– and the retention of Mg²⁺. In the highly-impacted soil, the marine input caused a decrease in SO₄ ^2– retention in open moorland soils. The opposite occurred under forest, due to the ion-exchange of marine Mg²⁺ for soil Al³⁺, increasing soil acidity towards the pH₀ (Gillman and Uehara, 1980), which is depressed below that of its moorland equivalent.     

Highly weathered soils in the east coast hinterland of Southern Africa with thick, humus-rich A1 horizons

Strongly weathered red and yellow soils with thick (490–900 mm) humic Al horizons (Haplohumox and Palchumults) derived from sandstones and basic igneous rocks, and occurring near the east coast of Southern Africa, are described and discussed in terms of their distribution, morphology, texture, mineralogy, chemistry, genesis and classification. The high organic matter content (2–5%C) of the Al contributes significantly to a high pH-dependent negative charge, probably to poorer crystallinity of goethite and kaolinite and to the transformation of haematite to goethite. Varying proportions of kaolinite and gibbsite reflect different soil ages within these old landscapes. The yellow colour of aluminous goethite, the main pedogenic iron oxide, is masked in the Al by organic matter and in red B2 horizons by haematite. Temperature may have influenced the broad pattern of occurrence of red and yellow B2 horizons. These soils need not, as previously suggested, have developed from the weathering products of an ancient laterite. Neither Soil Taxonomy nor the South African soil classification system accommodates the soils entirely satisfactorily and possible improvements to the latter are discussed.     

Redoximorphic Bt horizons of the Calhoun CZO soils exhibit depth-dependent iron-oxide crystallinity

Journal of Soils and Sediments - Iron (Fe) oxyhydroxides and their degree of ordering or crystallinity strongly impact the role that Fe plays in ecosystem function. Lower crystallinity phases are...     

Natural radioactivity of some red Mediterranean soils

Seventeen samples of B-horizon of Pleistocene Terra Rossa soils from carbonate rock were collected in different Countries of the Mediterranean regions (Spain, Italy and Southern Turkey).