摘要:

SUMMARYBecause conventional Boolean retrieval of soil survey data and logical models for assessing land suitability treat both spatial units and attribute value ranges as exactly specifiable quantities, they ignore the continuous nature of soil and landscape variation and uncertainties in measurement which can result in the misclassification of sites that just fail to match strictly defined requirements. This paper uses fuzzy classification to determine land suitability from (i) multivariate point observations of soil attributes, (ii) topographically controlled site drainage conditions, and (iii) minimum contiguous areas, and compares the results obtained with conventional Boolean methods. The methods are illustrated using data from the Alberta Agricultural Department experimental farm at Lacombe in Alberta, Canada. Data on site elevation and soil chemical and physical properties measured at 154 soil profiles were interpolated by ordinary block kriging to 15 m × 15 m cells on a 50 × 50 grid. The soil property data for each cell were classified by Boolean and fuzzy methods. The digital elevation model created by interpolating the elevation data was used to determine the surface drainage network and map it in terms of the numbers of cells draining through each cell on the grid. This map was reclassified to yield Boolean and fuzzy maps of surface wetness which were then intersected with the soil profile classes. The resulting classification maps were examined for contiguity to locate areas where a block of minimum size (45m × 45m) could be located successfully. In this study Boolean methods reject larger numbers of cells than fuzzy classification, and select cells that are insufficiently contiguous to meet the aims of the land classification. Fuzzy methods produce contiguous areas and reject less information at all stages of the analyses than Boolean methods. They are much better than Boolean methods for classification of continuous variation, such as the results of the drainage analys

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1992.tb00129.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYTwo acoustic techniques for determining the air‐filled porosity and air permeability of soil surfaces, and the near‐surface variation of these properties with depth, have been applied to several soilsin situ.The techniques depend upon an inversion process using data on sound propagation near to the soil surface and through the soil surface. The measured difference in acoustic spectra received by two vertically separated microphones above the ground surface and by probe microphones beneath the surface were matched theoretically to deduce the porosity of air‐filled connected pores and an effective air permeability which depends on pore shape and size distribution. This modified permeability parameter and the acoustically deduced porosity varied realistically with surface sealing and compaction. The acoustically deduced porosities were within 10% of those obtained conventionally. Changes in acoustically deduced parameters occurred with changes in moisture content both in soil bin and field experiments. The acoustic techniques were successful in monitoring surface sealing and near‐surface layering on a fin

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1992.tb00130.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYA physically based model describing the mechanism of surface seal formation of soil from a suspension of soil in flowing water was formulated on the basis of the principle of conservation of mass and Darcy's equation for the flow of water through a layered soil column. The model shows that, for sufficiently large times, the flux density of the filtrate is proportional to the inverse square root of time. The proportionality constant is a function of the saturated hydraulic conductivity and bulk density of the seal, and the concentration of the suspension. The components of the proportionality constant suggest that the constant could be used as an index of structural stability of soil. For the three suspensions used in testing the validity of the model, log‐log plots of the flux densities of the filtrates and time showed linear relationships with slopes approximately equal to –0.5, as predicted by theory. However, using calculated components of the model to predict flux densities of the filtrates failed to show agreement for two out of the three suspensions used. This was attributed to some over‐simplified assumptions used in the model, such as constant concentration and no sedimentation effects during the filtering process. It is suggested that incorporation of a time‐dependent concentration and sedimentation factors could perhaps improve the efficacy of th

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1992.tb00131.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYTwo simple methods for estimating the soil water characteristic curve from saturated soil water content, or even just the soil bulk density, plus one other measured point on the curve (such as the water content at a matric potential of –33 kPa) were evaluated. A similar‐media scaling approach and the one‐parameter model of Gregsonet al.were compared for eight diverse soils from within the USA. The scaling method also requires knowledge of one complete curve to serve as a reference. The one‐parameter model was extended to include the residual water content, and the soils were divided into three textural groups for the analysis. Visual comparison of the calculated vs. measured soil water content for both methods showed less scatter in the relationship to the 1:1 line, concomitant with smaller calculated error terms, for the one‐parameter model. These results demonstrate that the one‐parameter model is better than similar‐media scaling in estimating soil

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1992.tb00132.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYGypsum application was highly efficient as a treatment for reducing amounts of exchangeable sodium and inhibiting clay dispersion in highly structured saline‐sodic clay topsoils.Phosphogypsum, applied to the surfaces of aggregates in soil columns treated with simulated rainfall, was dissolved efficiently by frequent intermittent ‘rainfall’. The calcium released by dissolution displaced sodium on the exchange complex within soil aggregates ranging from 7.5 mm to 45 mm in diameter. Of the applied calcium, 64–74% was transferred to ion exchange sites; however, almost one‐third of this adsorbed calcium displaced exchangeable magnesium.Comparison of three gypsum treatments, phosphogypsum, rock gypsum, and a saturated gypsum solution (representing a top dressing of highly soluble gypsum), showed that the effectiveness of calcium uptake on the exchange complex followed the order: rock gypsum

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1992.tb00133.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYThe value of soil water samples used in ecological studies is highly dependent on the quality of the samplers. Tension soil‐water samplers are widely used to extract soil solutions, and the samplers are often tested in the laboratory under conditions that differ significantly from field conditions. This study describes a field procedure useful for comparison of two different tension soil‐water samplers. Ceramic and PTFE cups are compared. There were no differences in the concentrations sampled by the two different types of sampler for Na+, K+, Ca2+, Al3+, NH4+, H+and NPOC (non‐purgeable organic carbon). Change in the applied vacuum in the range 0 to –0.4 × 105Pa did not change the concentrations of chemical species in the collected soil water. The ceramic cups collected significantly larger amounts of water due to differences in the hydrostatic characteristics of the two samplers. It was found that the ceramic samplers collected the highest concentrations of Mg2+in some situations. The results are evaluated and discussed in relation to the possible sources of errors and the temporal and spatial varia

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1992.tb00134.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYPure calcite (AR grade CaCO3) was treated with ferrous perchlorate solution to give a surface coating of iron (Fe) oxide. Maximum sorption (xm) of phosphate (P) by the calcite increased from 18.2 to 160 mg P kg−1as the amount of coating increased from 0.00 to 16.0 g Fe2O3, kg−1CaCO3. Evidence for Fe oxide coatings on carbonate minerals in two Sudanese soils was obtained by optical microscopy and electron‐probe microanalysis. The relative contributions of carbonate and Fe oxide minerals, and Fe oxide coatings to P sorption in these soils were calculated, based on an assumed model of oxide distribution. Separate‐phase Fe oxide was the major contributor (30–40%) to P sorption in the soils; the Fe oxide coatings on carbonate minerals were only minor contributors (<6%), and the contribution of uncoated carbonate minerals was found to be negligible (<1 %). These results suggest a very minor role for carbonate minerals, even when coated with Fe oxide, in the sorption of P by these calcareous, Sudan

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1992.tb00135.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYLabile Al in the soil solution measured by 8‐hydroxyquinoline (AlHQ) was a better predictor of plant growth than trivalent Al (AlIC3+) measured by ion chromatography (IC). HQ reacted with some organic Al complexes which did not separate during chromatography. In the presence of oxalic acid, AlHQwas greater than AlIC3+, which was the same as the greater than Al3+(Al3+Calc), whereas in the presence of citric acid, AlHQwas greater than AlIC3+, and both were greater than Al+3Calc, In extracts of soils that had been acidified, Al3+ICwas less than AlHQ, which was similar to Al3+Calc, when it was assumed that the only complexing ligands were OH−and F−. The proportion of Al3+ICin the soil solutions decreased more than AlHQas the pH increased. Organic ligands appeared to form complexes with Al at the expense of AIF complexes. Forms of Al detected by IC differed in CaCl2extracts and soil solutions. AlHQin the CaCl2extracts and soil solution were closely correlated, although the proportion of AlHQwas higher in the CaCl2extracts. And soil solutions. AlHQin the CaCl2extracts and soil solution were closely correlated, although the proportion of AlHQwas higher in the CaCl2ext

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1992.tb00136.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYThe effects of mercury concentration, pH, and chloride concentration on mercury adsorption by goethite were measured. With increasing pH, mercury adsorption increased rapidly at first, until a maximum was reached, and then decreased slowly. In the absence of chloride, the maximum was just below pH 4. With increasing chloride concentration, the maximum moved to higher pH values. This behaviour contrasts with that of the other heavy metals for which, beyond a certain pH, adsorption increases rapidly with further increase in pH.The results were described by a model in which HgOH+and HgCl+ions were adsorbed and the electric potential of the reacting surfaces decreased with increasing pH. The maxima in the adsorption corresponded to maxima in the concentration of HgOH+. Although a good description of the results was obtained, there were consistent discrepancies. These suggested that the charge component of the model was unable to produce the correct relationship between electric potential and pH.The results indicated that mercury adsorption was controlled by the same principles as adsorption of the other heavy metals. However, mercury's lowerpKfor dissociation and its higher affinity for chloride mean that the effects of pH on the ions present in solution are different, and this is the cause of the different behaviour.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1992.tb00137.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYThe pH of a soil was altered by incubation with either acid or lime, and the sorption of mercury was measured in the absence of chloride and at three chloride concentrations. In the absence of chloride there were only small effects of pH on sorption between pH 4 and 6; sorption decreased at higher pH. Addition of chloride decreased sorption at low pH but had little effect on sorption at high pH. Consequently, in the presence of chloride, sorption increased with increasing pH between pH 4 and 6 and then decreased. Many of the mercury sorption curves were sigmoid. This was explained by assuming that a small amount of complexing material was present in the solution after mixing with the soil. Calculation of the mercury species present in solution was made difficult by uncertainties about the postulated complexing material. Nevertheless, between pH 4 and pH 5.8, it was possible to explain the effects of pH and of chloride concentration on sorption as entirely due to changes in the HgOH+concentration.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1992.tb00138.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY