摘要:

SUMMARYMost studies of relations between soil properties fail to take account of their regionalized nature because of the lack of appropriate methods. This paper describes a geostatistical technique, factorial kriging analysis, that bridges the gap between classical multivariate analysis and a univariate geostatistical approach. The basic feature of the method is the fitting of a linear model of coregionalization, i.e. all experimental simple and cross‐variograms are modelled with a linear combination of basic variogram functions. A particular variance‐covariance matrix, the coregionalization matrix, can then be associated with each spatial scale defined by the range of the basic variogram function. Each coregionalization matrix describes relationships between variables at a given spatial scale. A principal component analysis of these matrices produces a set of components, the regionalized factors, that reflect the main features of the multivariate information for each spatial scale and whose scores are estimated by cokriging.The technique is described and illustrated with three case studies based on a simulated data set and soil survey data. The results are compared with those of the principal component analysis of the variance‐covariance matrix and the variogram mat

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1992.tb00163.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYIn this first of three papers, the parent materials, morphology and field relationships of soils with fragipans, similar to those in north‐eastern United States, are described and analyses of their chemical and physical properties are presented to support a periglacial stage of development. The soil materials have been affected by periglacial processes, including ice‐wedge formation, the age of which has been established by reference to a buried paleosol. The fine earth bulk density of the fragipans is between 1.75 and 1.91 g cm−3whereas the density of overlying Eb horizons is<1.40 g cm−3. The formation of the compact lenticular structures and polygonal fissuring of fragipans is ascribed to the former presence of permafrost during the Loch Lomond Stadia1 11 000 to 10 000 years B.P. The polygonal fissures, after subsequent infilling with illuvial material, have determined the position of the greyish polygonal zones which have formed by the eluviation of Fe and Mn from fissure infill and fissure walls by redox processes. Clay migration from the Eb horizon into the fragipan is well marked. Clay and silt have also been locally removed from the upper parts of the greyish zones and redeposited towards their lower parts. Similar textural degradation has affected eluvial pockets in the upper fragipan. It is concluded that periglacial processes fully explain the genesis of macrostructural features but not the distinctive consistence of the f

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1992.tb00164.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYThe clay fraction of soils from south‐western Australia is dominated by kaolinite. These soil kaolinites give broad basal reflections (median value for WHH 001 =0.41° 2θ) and have poorly ordered structures. The median value of the Hughes&Brown crystallinity index for 35 soil kaolinites is 5.4 compared to 42.0 for mineral standard kaolinites. The median values for surface area and cation exchange capacity of soil kaolinites are 35 m2g−1and 56.7 mmolckg−1, respectively, compared to 10 m2g−1and 4.8 mmolckg‐lfor standard kaolinites. The dehydroxylation temperature of soil kaolinites is about 50 K lower than for standard kaolinites and decreases with increasing Fe content.Soil kaolinite crystals are much smaller (c. 0.10 pm) and are irregular subrounded to rounded plates in comparison to the larger (c. 0.28 pm), perfectly hexagonal euhedral plates of Georgia kaolinite. Analytical electron microscopy of single soil kaolinite crystals indicates that the Fe content varies with an average value ofc.2.5% Fe,2O3. X‐ray diffraction line broadening data indicate that crystal size decreases as the Fe content increases. Crystal order also decreases with increasing Fe content. The P sorption maximum of soil kaolinite ranges from 486–654 μg P g−land is thus about six times larger than for the clay fraction of

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1992.tb00165.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYThe use of a new method for characterizing humic acids based on the measurement of the cobaltihexammine cation exchange capacity (CEC) vs. pH is examined. The method was first verified on a macroporous weak‐acid cation exchange resin: charge vs. pH curves and pKvalues from cobaltihexammine adsorption identify with results from discontinuous acid‐base titrations at high ionic strength (5 M). Similar agreement was obtained for humic acids from a Podzol soil: the cobaltihexammine‐CEC identifies with the macromolecular charge (from continuous acid‐base titrations) at ionic strength of 3 and 5 M, but slightly underestimates (5%) the humic acid charge at 1 M ionic strength. The cobaltihexammine method is suitable for determining the potentially available charge in the pH range 2 to 12 and the intrinsic pKvalues of humi

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1992.tb00166.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYThe humate model, RANDOM, was investigated in combination with the general speciation program, PHREEQE. After an initial investigation of cobalt(II)–humic acid and copper(II)–fulvic acid interactions this coupled code approach was modified to include a sensitivity analysis which identified the ligands which were statistically significant in any one system. Subsequent speciation modelling with these significant ligands is shown to produce a reasonable agreement between experimental and modelled data. The systems chosen to demonstrate the advantages of this approach were uranyl–humate and nickel(II)–humate interactions. Although this technique is not fully developed, it shows great potential for improving the predictive qualities of the RANDO

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1992.tb00167.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYSoaking for 7 d with 0.05 M NaCl resulted in less caesium being sorbed by bentonite and kaolinite, but more by illite, compared to soaking for 2 d prior to addition of Cs. Overall the amount of Cs sorbed by the three clays was in the order bentonite>illite>kaolinite. Addition of humic acid to the clays depressed the sorption of Cs by all three clays, with illite showing the greatest effect. Desorption of added Cs was not totally reversible. The presence of humic acid resulted in an enhanced desorption of Cs from bentonite and to a lesser extent kaolinite. This enhanced desorption in the presence of humic acid was not seen for illite. The order of Cs retention following desorption for both clay and clay/ humic‐acid mixtures was illite>bentonite>kaolinite. A singleKdvalue could not describe the whole isotherm, but individual values were calculated at different Cs concentrations to cover the range of the isotherm.Kdvalues for desorption were higher than the correspondingKdfor sorption. For both sorption and desorption, the presence of humic acid resulted in lowerKdvalues than in its absenc

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1992.tb00168.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYA soil climosequence in tussock grasslands in South Island, New Zealand, encompassing climates ranging from cold to warm temperate provided a spatial analogue of climate change for investigating the effects of global warming on soil C contents and turnover. Mean annual temperature (T) and annual precipitation (P) ranged from 2 to 10°C, and 350 to 5000 mm, respectively. Soil C contents were curvilinearly related toT/Pacross the sequence (r=−0.95, significant atP<0.0l), indicating that east of the Southern Alps, increased decomposition of organic matter with global warming would provide a positive feedback to further increase atmospheric CO2. This decrease in New Zealand's soil C, estimated to be up to 10% of the current content for a global temperature rise of 0.03 K a−1to 2050, could contribute about 0.5 × 1015g C to the atmosphere over the next 60 years. These conclusions were generally supported by changes in soil C turnover estimated from ‘bomb’14C enrichment. The unexpectedly slow turnover found for two soils was explained by a ‘memory’ effect from the former southern beech forest that grew on these soils in prehistoric times. Accumulation of Al‐humus under the forest may be responsible for the slow C tu

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1992.tb00169.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYThe reaction of Cu, Zn and Cd with soils with carbonate contents ranging from 0 to 75 mg g−1was studied before and after removal of soil carbonates with acetate buffer at pH 5. Treatment with acetate buffer caused a strong decrease in metal retention by those soils containing carbonates, although if no carbonate was originally present, the treatment caused little effect or even an increase in the amounts sorbed. Before the treatment, adsorption of increasing amounts of Cu and Zn was accompanied by a continuous increase in Ca + Mg released, and those soils containing carbonate released Ca + Mg in excess of their exchangeable amounts, due to dissolution of carbonates and/or penetration of the heavy metal into the carbonate structure.It is suggested that Cu was preferentially retained by the treated soils through precipitation of Cu oxide, and by adsorption on the soil carbonates in the case of the original samples. Zn was removed from the solution by the original carbonate soils through formation of ZnCO3. Treated soils were likely to retain Zn by cation exchange and/or adsorption. Adsorption was probably the main process involved in retention of Cd.In all cases pH was the master variable in controlling the extent and probably the nature of the reactio

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1992.tb00170.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYA change in the pH of the rhizosphere may alter the effect that organic ligands have on the concentration of Zn in the soil solution. To assess this effect, Zn adsorption by a lateritic soil was measured in the presence of 0, 1 and 3 mM of citrate and oxalate at nine values of pH ranging from pH 2 to 8. The concentrations of Zn and the ligands remaining in the solution were determined after 17 h shaking with the soil at soil:liquid ratio of 1:5. Subsequently, Zn speciation was calculated. The effectiveness of an organic ligand (L) in changing Zn adsorption was influenced by the sign of the charge of the Zn‐L complex, the point of zero salt effect (PZSE) of the soil, the pH of the soil solution and the quantity of the complex formed. When the pH was above the PZSE of the soil, citrate decreased Zn adsorption by up to 38% whereas it increased Zn adsorption by as much as 51 % when the pH was below the PZSE. Oxalate had a similar but smaller effect than citrate under the conditions of the experiment. Zn adsorption was correlated with the concentration of zinc citrate in both pH regions (r2>0.98) and with oxalate above pH 2.7. The increase in Zn adsorption at low pH could have been caused by the adsorption of negatively charged Zn‐L comple

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1992.tb00171.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYPhosphate sorption on topsoil and subsoil samples from different soils located in the eastern part of Germany was studied. Two models were fitted to sorption data obtained after 4 and 40 d of gentle shaking. The models differ with respect to the fractions of iron and aluminium (hydr)oxides that are considered and whether the phosphate initially sorbed in the soil is taken into zccount. Oxalate‐extractable P,(Pox), appears to be a major part of the total soil P. The total P sorption measured,F, was predominantly related to the amounts of amorphous iron(Feox)and aluminium(Alox).A significant relation between crystalline iron(Fed– Feox)and total P sorption was not found. Reversibly adsorbed phosphate(Pi), measured after 40 d reaction time, was a function of clay content and content of amorphous iron and aluminium (hydr)oxi

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1992.tb00172.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY