Calculation of hydraulic conductivities and steady state capillary rise in peat soils from bulk density and solid matter volume

Values of the three constants in a convenient formula for the calculation of capillary conductivities of peat soils can be evaluated from bulk density and solid matter volume. Though some of the relative equations have a low significancy, they provide a means to calculate in a simple way a mean hydraulic conductivity function for peat soils with given values of the soil properties mentioned above. Examples of such functions are shown. The height of steady state capillary rise in homogeneous fen peats and high bog peats of increasing bulk density are comprised in some diagrams.     

A study of argillic horizons in some soils in Morocco

Whether some soils observed in Morocco prior to the 1966 conference on Mediterranean soils held in Madrid had argillic horizons was the subject of active discussions. Textural differences between A- and B-horizons were obvious. Consequently, individual horizons of a number of profiles were sampled for micromorphological study. No clay films were observed in thin sections representing the B-horizons free in carbonate. Peds had pressure faces and internal striations in the matrix. Microchurning and swelling and shrinking are believed to have obliterated evidence of clay illuviation in the B-horizons, but clay coatings were observed at greater depth in well-developed B_ca-horizons.     

Effect of an anionic surfactant on hydraulic conductivities of sodium- and calcium-saturated soils

The effect of sodium dodecylbenzenesulfonate （SDBS）, an anionic surfactant used widely in household products and industrial processes, on saturated hydraulic conductivities （Ksat） of an Anthrosol saturated with sodium （Na-soil） or calcium （Ca-soil） was analyzed in a laboratory experiment using the constant head method, and adsorption and dispersion experiments were also conducted to infer the possible mechanisms of Ksat fluctuations. The results showed that SDBS was more intensely adsorbed in the Ca-soil than in the Na-soil. With an increase in the SDBS concentration, the stability of the Na-soil suspensions decreased when the SDBS concentration was less than 1.2 mmol L^-1 and then above this concentration, increased markedly, while the stability of the Ca-soil suspensions increased gradually at all SDBS concentrations studied. With an increase in the SDBS concentration, the Ksat of the Na-soil increased, which resulted mainly from the increase of water channels in the soil because of the coagulation of the soil particles, while the Ksat of Ca-soil decreased mainly on account of the clogging of partial water channels by precipitated Ca（DBS）2 and the fine soil particles generated.     

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.     

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.     

美国土壤Salic层研究

The taxonomic hierarchy and nationwide distribution of soils with a salic horizon were studied using the USA Natural Resources Conservation Service Soil Survey Geographic (SSURGO) Database to provide a more holistic view of the role of soil-forming factors in pedogenesis than from isolated case studies.Soils with a salic horizon occupied an area of 11 000 km2,i.e.,0.1% of land area in the contiguous USA.These soils occur narrowly in three great groups(Aquisalids,Haplosalids and Halaquepts),11 subgroups,and 97 soil series.Soils with a salic horizon commonly had a mesic (50% of soil series) or thermic (19%) soil-temperature class,an aquic (89%) soil-moisture class,a mixed mineral class (79%),a calcareous (52%)reaction class,a superactive (59%) cation exchange activity class,and a fine (24% of soil series),fine-loamy (24% of soil series),or fine-silty (19% of soil series) particle-size class.Soils with a salic horizon were concentrated in the Basin and Range Province of western USA.The key pedogenic processes leading to the development of salic horizons were salinization,gleization,and calcification,with some evidence for argilluviation and silicification.     

中国下蜀黄土发育的土壤表层及典型剖面的硫状况

Studies were conducted to examine factors which might influence the status and distribution of S in some surface horizons and typical profiles of soils derived from Xiashu loess on the upper slope (US), middle slope (MS) and lower slope (LS) of Nanjing-Zhenjiang-Yangzhou hilly zone. The total S contents varied from 70.30 to 350.21 mg/kg, and the average for all surface soils was 218.3 mg/kg. The average S contents in the profiles followed the sequence: USo) and the ratio of amorphous iron oxide to free iron oxide (Fe_o/Fe_a), but no significant relationship was found between total S and the ratio of free iron oxide to total iron (Fe_d/Fe_t). Inorganic sulphate in paddy soils (MS and LS) was nearly higher in surface soil than in subsurface soil and subsoil, it, however, remained relatively unchanged with increasing depth for the original soil profile (US). The average organic S accounted for 94% of the total S in the surface soils, but the percentage decreased with depth in the profiles. Like the total S, the organic and inorganic S contents were highly significantly correlated with organic matter, total N, Fe_o and Fe_o/Fe_d ratio, but they were insignificantly related to Fe_d/Fe_t ratio. The C/S and N/S ratios in this study were somewhat lower than the results reported by others. The C/N/S ratios varied considerably within the same profile and among different soils but they fell within the range of values reported worldwide.     

Clay mineralogy and some chemical properties of Ap horizons of Ando soils used for paddy rice in Japan

The clay mineralogy of the Ap horizons of Ando soils in Japanese paddies was determined by a combination of methods and compared with that of Ando soils of uplands. Six of 13 paddy soil samples contained allophane and imogolite and none contained gibbsite, whereas parallel figures were 15 and 7 for 22 upland soil samples. Substantial numbers of diatoms were found in 5 paddy and 1 paddy-converted upland soil samples. The lack of gibbsite was related to the stage of soil formation rather than the paddy condition, whereas the presence of diatoms was related to both. Regarding layer silicates, there was no particular difference between the paddy and upland soil samples but one unidentified mineral with unique morphology and infrared spectrum was found in two paddy soil samples. There was no particular difference in phosphate adsorption between the paddy and upland soil samples.     

The determination of field-saturated hydraulic conductivity in some Scottish soils using the Guelph permeameter

Abstract. Soil hydraulic conductivities are frequently required for process-based modelling of the soil water regime. Field-saturated hydraulic conductivity was measured with the Guelph permeameter in 10 soil series with a range of structures and textures. The permeameter offers a range of options for calculating conductivities depending on soil conditions, particularly homogeneity of pore distribution within each horizon. However, even horizons described as massive or apedal were not sufficiently homogeneous to satisfy the boundary conditions entirely.
Hydraulic conductivities were calculated by the one head, fixed α* procedure; α* is an index of capillarity. No direct correlations were found between hydraulic conductivity and land use. However, the average hydraulic conductivity of coarse textured topsoils which were mainly under arable agriculture was less than that of the finer textured topsoils largely under grassland. Even limited structural development increased the hydraulic conductivities of fine textured, compact subsurface horizons. It is important to match the adopted procedure to the soil conditions both during the determination of flow rates in the field and in the subsequent analyses.     

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.     

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.     

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.     

美国路易斯安那州铁矿石土壤薄层磐层的表征特性

Placic horizons, defined as thin, wavy, hardened layers of iron and organic matter, are rare within the United States, occurring only in Washington, Alaska, and Hawaii. While ironstone is common in many soils of the southeastern United States, it is not known to contain appreciable organic matter. As a pilot study evaluating the justification for a larger study on ironstone in Louisiana, a 40 m lateral exposure with suspected placic horizons was evaluated in Vernon Parish, Louisiana. Results of laboratory analysis show elevated levels of iron and organic matter in the suspect horizons that meet the criteria of placic horizons as defined by the Soil Survey Staff. Based on the results of this study, additional evaluation of multiple pedons with similar features is warranted. Should additional pedons demonstrate similar properties, a new great group of ‘Petrudepts’ would be needed to describe both the placic horizons in the pedon and the udic moisture regime in which they occur.     

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.     

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.     

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.     

Buried organic horizons represent amino acid reservoirs in boreal forest soils

We examined the composition and concentration of amino acids by soil horizon and depth on the Tanana River floodplain in interior Alaska. Soils from mid-successional stages of balsam poplar and white spruce were separated into successive forest floor (Oe/Oa), buried organic horizons (BOHs), and mineral horizons; and water-extractable amino acid composition and concentration were determined by HPLC. The number, depth, and thickness of BOHs were highly variable across the landscape and among replicates of the same stand type, reflecting differences in terrace age, flood frequency, flood intensity, river channel position, vegetation inputs, and decomposition. BOHs generally had lower pH and bulk density, higher moisture content, and greater concentrations of carbon, nitrogen, and roots than the surrounding mineral horizons. In each horizon of both successional stages, the soil amino acid pool was dominated by glutamic acid, glutamine, alanine, asparagine, aspartic acid, and histidine, which together accounted for approximately 80% of the total amino acids found. Despite the similar overall amino acid composition among the horizons, proportions of glutamine generally increased with depth and were generally greater in the mineral horizons than in the BOHs, suggesting root exudation or fine root turnover as an amino acid source. In both successional stages, amino acid concentrations were nearly always highest in the Oe/Oa horizon and rapidly decreased with depth. BOHs generally had greater amino acid concentrations than the surrounding mineral horizons in both successional stages, but amino acid concentrations in successive BOHs declined with depth in the soil profile, suggesting that although BOHs do remain as biological hot spots and potential nutrient reservoirs as far down as 60 cm depth, their importance declines over time.