Abstract Acid sulphate soils from central Alberta were analyzed for mineralogical composition, pore water chemistry, and content of arsenic in order to determine the stability and weathering of minerals and the form, distribution, and mechanisms involved in the accumulation of native arsenic within the soil solum and acid shale parent materials. Weathering of pyrite in the soil solum resulted in strong acidity (pH values near 3) and formation of natrojarosite, selenite, and iron oxyhydroxides. Analyses for total As in soil and segregated mineral samples indicated the element partitioned into iron rich phases. Content of As in some samples of iron enriched soil were as high as 500 mg/kg. Use of selective extradants for estimation of Ca‐, Al‐, and Fe‐arsenate forms provide limited information in this study. Results of thermodynamic modeling of pore water chemistry using the MINTEQ computer code were compared to the empirical data on mineral association of As and mineral alteration during the genesis of the acid sulfate soil. The thermodynamic analyses indicated arsenate precipitates would not be stable under present soil solution conditions. Key words: Trace elementthermodynamic modelingformmineralogy
We discovered an error by a factor of 10 in our calculations for carbon stock in this published paper.This error does not affect any findings or conclusions.In the abstract, the unit was kg C•ha -1 , but should instead be t C•ha -1 :Considering the entire Ap horizon depth, we show that soil carbon stocks (t C•ha -1 ) may be constant or increasing. In the French translation:Prenant en compte l'horizon dans son entièreté, les auteurs montrent que les réserves de carbone dans le sol (t de C par hectare) pourraient bien être constantes, voire augmenter.
A new, rapid, and inexpensive method is described for digestion and dissolution of mineral soil and clay samples for determination of total elemental abundance. Standard soil samples were dissolved using HF and HNO 3 in 60 mL Teflon bombs. Dissolution was complete after 7 min using a household microwave oven operating at 350 W. Addition of H 3 BO 3 stabilized the digests against loss of silicon. Precise and accurate results were obtained for digests analyzed by inductively coupled plasma atomic emission spectrometry for total content of Si, Al, Fe, Mg, Ca, Na, K, and Mn. Key words: Elemental composition, standard soils, soil analysis
Drainage refers to the frequency and duration of periods of saturation, and how quickly excess water is removed from the soil profile. It is one of the central concepts used to differentiate soil series within the Canadian System of Soil Classification (CSSC). Currently, seven drainage classes are recognized in the CSSC: very rapid, rapid, well, moderately well, imperfect, poor, and very poor. In redoximorphic soils (imperfect, poor, and very poor drainage classes), drainage is typically differentiated based on morphological features (i.e., the presence of gleying and mottles). Non-redoximorphic soils (very rapid, rapid, and well-drained classes) do not display such morphological features but are differentiated based on available water holding capacity (AWHC) as inferred from soil texture and particle size. Moderately well-drained soils are intermediate, in some cases defined by the presence of redoximorphic characteristics, but in other cases inferred based on texture. In effect, drainage in materials without redoximorphic features is estimated based on AWHC as related to texture class, which should include sand subfractions. Values for AWHC were calculated using a published pedotransfer function for combinations of sand, silt, and clay-sized particles, including various combinations of very fine to very coarse sand separates as input. Calculated values were compared with currently assigned drainage classes and several inconsistencies were identified. Revisions are proposed to textural assessment of soil drainage for non-redoximorphic soils.
A series of artifically weathered fly ash samples were analyzed to examine the leaching behavior of trace constituents. The weathered samples represented a sequence of ash residues ranging from strongly weathered materials in which the exterior reactive glass of the particles had been removed, to moderately and minimally weathered ash in which limited dissolution had occurred and secondary precipitation products were formed. Contents of trace elements were measured by instrumental neutron activation analysis (INAA). Analysis of the solid weathered residues rather than leachates provided information on the behavior of many trace elements whose concentrations in aqueous leachates are far too low to measure by most analytical methods. Release of trace elements from the highly leached ash was primarily determined by their distribution among phases within fly ash particles. Most trace elements were associated with the internal glassy matracies of the fly ash particles. The elements Rb, Cs, Pb, Ti, Hf, Ta, W and, by inference, Fr, Ge, Sn, Zr and Nb were not dissolved by acid leaching solutions and accumulated within highly weathered ash particles. Approximately 75% of the Mn, Sb, Th, Cr, Zn, Co, Br, Sc, the rare earth elements and by inference, Bi, Cd, and Y, originally containedmore » in the ash remained in the weathered residues. Approximately 50% of the total Sr, Ba, V, Mo, U and, by inference, Li, in the fresh ash was mobilized and leached. The elements B, As, and Se were associated with the highly soluble ash fractions and were nearly completely leached from ash.« less
To address concerns among members of the Canadian Society of Soil Science (CSSS) regarding the discipline’s capacity to train new soil professionals, specifically in pedology and field skills, members of the CSSS’s soil education and pedology committees have proposed to develop a pedology field school. To aid in the selection of learning outcomes that are relevant to professional practice, an online survey was sent to Canadian soil professionals within private industry and governmental organizations. Professional feedback was also requested regarding the creation of a web-based national soil education resource and the certification of soil pedological skills. According to the survey results, the quality of new graduates’ pedology and field skills was perceived as poor. Certain soil field skills and knowledge were thought to be either completely absent from the current Canadian curriculum (e.g., spatial variability of soil processes), or not well mastered by graduates (e.g., interpreting soil survey reports). Important learning outcomes were identified, such as interpreting soil survey information, soil mapping, and soil-landscape classification with soil description–classification and soil genesis content needed as a refresher. Taking into consideration existing regional field schools, we recommend that the CSSS co-create, where needed, and coordinate, where they already exist, regional pedology field schools throughout Canada. We also propose that the CSSS develop a national pedology certification and a web-based soil education resource. Also, further study is necessary to shed light on the contribution of non-disciplinary graduates to the professional practice and the impact this has on the perception of soil education in Canada.
Mottling and gleying remain important characteristics for the classification of soils in Canada. The development of criteria for the morphological description of these redoximorphic soil features, for soil horizon nomenclature, for the taxonomy of gleysolic and gleyed soils, as well as for soil drainage classification, began in the mid-1940s and continued for the next four decades. Despite advancements elsewhere, notably with Soil Taxonomy and the World Reference Base, there have been minimal refinements made in Canada, during the past quarter century. Various issues are identified, including the need for more succinct and clearer definitions, a revision of standards for the field characterization of redoximorphic features, as well as more consistency in the application of concepts across existing taxa and systems. A taxonomic framework to more effectively reflect redoximorphic features, such as a new “Redoximorphic Phase” is also discussed. Ultimately, it is recommended that a special committee to be established to conduct a thorough study and present recommendations.
Shallow soils occur throughout the world and are recognized as Leptosols at the highest level in the World Reference Base. These soils are notionally characterized as having a lithic contact close to the soil surface. Within the Canadian System of Soil Classification (CSSC), shallow soils are currently handled at the family level according to the depth at which the lithic contact is encountered. At the series level, these soils are usually designated as a shallow phase of a non-shallow soil series, ignoring the hierarchical structure of the CSSC. Shallow soils occur almost anywhere in Canada where the glacial drift is thin. The presence of bedrock close to the surface impacts drainage, the amount of available moisture, depth for rooting, and has a major influence on soil formation. Consequently, it is proposed that the importance of shallow soils be elevated to the order level, to be consistent with the frequency of their occurrence in the Canadian landscape and for consistency with other soil classification systems of the world. This requires integration at the great group and subgroup levels within all orders of the CSSC, as well as changes to the current formal definition of soil. These proposed modifications include nullifying the minimum 10 cm depth requirement as part of the current definition of soil in the CSSC for closer consistency with ecological land classification and other soil classification systems of the world. Proposed modifications to the current key to the soil orders, great groups, and subgroups are presented and discussed.
The purpose of this study was to examine the relationship between the concentration of boron (B) and some other selected trace elements in soil solution as effected by hydrogen ion activity within the normal pH range for acidic soils commonly amended with agricultural limestone and, alternatively, alkaline fly ash. Sluiced alkaline fly ash was applied to an acidic, clay textured soil at rates equivalent to 0, 42, 84, 125 and 167 tonne ha -1 based on the soil lime requirement. After wheat was grown and harvested the soil-ash mixtures were maintained at field capacity moisture content for an additional 4 months before pore water samples were extracted by immiscible displacement. The total concentrations of Co, Cr, Fe, V and Zn in the ash treated soils increased by < 10% at the highest application rate of ash, the content of Cu was increased by 13% and B by 38%. Only the concentration of boron increased appreciably in the pore water extracts. Release of B from the ash was correlated with the solubility behaviour of Ca and Mg, and not with the dissolution of glass phases in the ash. Speciation and adsorption calculations for the extracts were carried out using the program MINTEQ. Common Ca, Mg and Na borate minerals were undersaturated with respect to the equilibrated solutions. Application of the constant capacitance model to the adsorption of B on mineral surfaces suggested that adsorption had little effect on total dissolved B at pH values below 6.0. Predicted concentrations of B in solutions, equilibrated with calcite in a subsurface horizon, were up to 10.6 mg dm -3 ; more than double the recommended maximum concentration for B (5 mg dm -3 ) in potable water in Ontario.
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