This study compared three dichromate-oxidation methods adapted for use with 100-mL digestion tubes and 40-tube block digester (for controlled heating), the Walkley-Black method, a loss-on-ignition procedure and an automated dry combustion method for the determination of organic carbon in soils of the northwestern Canadian prairie. The Walkley-Black method required a correction factor of 1.40. The modified Tinsley method and the Mebius procedure, adapted for use with 100-mL digestion tubes, recovered 95% and 98%, respectively, of soil carbon against the dry combustion procedure. The presence of elemental carbon in some soils probably caused, at least partially, the slightly incomplete recovery; thermal decomposition of dichromate may not have been accurately corrected for. A dichromate-oxidation procedure with controlled digestion at 135°C gave 100% recovery, but somewhat more variable results. The loss-on-ignition procedure, even when allowance was made for clay content of the soils, was the least satisfactory of the methods tested. All procedures produced correlation coefficients of 0.980 or better against the dry combustion method.

No abstract

Abstract--The objectives of the study were to determine the chemical composition and layer charge of smectite found in calcareous till of the Interior Plains region of western Canada and to examine the effects of acidification on alteration of the smectite. Samples of acidified and non-acidified (calcareous) lateWisconsin till were obtained from four soil pits located immediately adjacent to an elemental sulfur block located in southern Alberta. Samples of the surface material (0-10 cm depth) had been subjected to extreme acidity for 25 years due to the oxidation of elemental sulfur and displayed pH values of about 2.0. Samples of the till obtained at depth (65-75 cm) remained calcareous with pH values between 7.3 and 7.6. A combination of analytical methods was used to determine the chemical composition of the smectite found in the samples. The layer charge of the smectite was determined independently using X-ray diffraction data for n-alkylammonium saturated specimens. Smectite found in the non-acidified calcareous material was characteristic of montmorillonite with a low content of Fe and very little substitution of A1 for Si in the tetrahedral sheet. The smectite had a structural formula of M+o 40(Si3.96A10 04)(ml= 56Fe3+o.~oMgo.33)O~o(OH)2 , which compared well with a mean value for layer charge of 0.399 mol(-)/O~o(OH)2 determined using X-ray diffraction data for n-alkylammonium treated specimens. Smectite remaining in the till material subjected to extreme acidity underwent incongruent dissolution with a net loss of layer charge and preferential loss of octahedral Mg.

No abstract

. 2005. Trends in dissolved phosphorus in Gray Luvisol soil profiles after forest harvest . Can. J. Soil Sci. 85: 89-101. Forest disturbances that increase P export from hillslopes will have negative consequences for site productivity and regional water quality. We studied P behavior in Gray Luvisols to understand the soil profile's influence on P export from typical hillslopes of the Boreal Plain ecozone. We hypothesized that (1) P concentration is highest in upper horizons, (2) solution P is primarily in the dissolved and organic form, and (3) forest harvest will increase solution P concentration. We analyzed the soil solution, with emphasis on P, and determined P sorption properties of key soil horizons. Mean soluble reactive phosphorus concentration decreased with depth, ranging from 64 mg L -1 in the forest floor to 0.01 mg L -1 in the groundwater zone; solution P was mostly orthophosphate. Water soluble phosphorus decreased from 74 ± 9 to 41 ± 9 mg L -1 and extractable phosphorus was reduced in the forest floor only on two of four sampling occasions after harvest. Dissolved organic carbon may indirectly promote orthophosphate dominance in solution by complexing metal cations that would otherwise precipitate metal-P from solution. Gray Luvisols probably export P to soils lower on the hillslope catena, such as those of the Gleysolic and Organic Orders, both commonly associated with wetlands.Key words: Forest soil, phosphorus, orthophosphate, Gray Luvisol, biogeochemistry, sorption Whitson, I. R., Abboud, S., Prepas, E. E. et Chanasyk, D. S. 2005. Progression du phosphore dissous dans les luvisols gris : profil des sols forestiers après leur exploitation. Can. J. Soil Sci. 85: 89-101. Les aménagements forestiers qui accentuent l'exportation de phosphore (P) des pentes voisines auront des répercussions néfastes sur la productivité du site et sur la qualité des eaux locales. Les auteurs ont étudié le comportement du P dans les luvisols gris afin de mieux comprendre l'incidence du profil sur l'exportation de cet élément à partir des pentes typiques dans l'écozone des plaines boréales. Pour cela, ils ont formulé les hypothèses suivantes : (1) la concentration la plus élevée de P se retrouve dans les horizons supérieurs; (2) la solution phosphorée se compose surtout de P dissous et organique; (3) l'exploitation forestière concentre la solution P. Ils ont ensuite analysé la solution de sol en insistant sur le P et établi les propriétés de sorption du P pour les principaux horizons. La concentration moyenne de phosphore soluble réactif diminue avec la profondeur, pour passer de 64 mg par litre dans le sol forestier à 0,01 mg par litre dans la nappe phréatique. La solution P se compose principalement d'orthophosphates. La concentration de phosphore hydrosoluble baisse de 74 ± 9 à 41 ± 9 mg par litre, mais celle de phosphore extractible dans le sol forestier n'a diminué qu'à deux occasions sur quatre lors de l'échantillonnage après récolte du bois. Le carbone organique dissous pourrait entraîner indirectement la domin...

No abstract

No abstract

No abstract