bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural optimization of pep7, a small peptide extracted from epimorphin, for effective induction of hair follicle anagen
Authors: Hirai Yohei , Takebe Kyoko , Nakajima Kiichiro
Published: August 2005

Abstract:  Epimorphin is representative of a unique class of stromal membrane‐anchored proteins that plays distinct functions depending on its membrane topology. When exposed extracellularly, this molecule acts as a morphoregulator for various tissues including hair follicle epithelia. Previous study identified its functional domain (the pep7 domain: SIEQSCDQDE) for hair follicular morphogenesis followed by the successful generation of a chemically modified active peptide. Here, we report optimization of this peptide by the introduction of sequential mutations and subsequent structural determination. We found that three residues from the C‐terminus are dispensable, and alternation of the seventh amino acid to an Alanine residue enhanced activity. To favour the biologically active conformation, ε‐Acp (NH(CH2)5CO) linked to a Cysteine residue was connected at the N‐terminus followed by the introduction of an intramolecular disulphide bridge, the modification process of which could be included in the peptide synthesis. The obtained modified peptide, termed ‘EPM (epimorphin‐derived) peptide’, has a Mw of 950 Da and exerts an inductive effect on hair follicle regeneration at a concentration of approximately 0.00001% or even lower. The action of this EPM peptide was more apparent in mice treated with 1% minoxidil, suggesting its potential clinical benefit as a new type of hair‐regenerating agent.
Experimental approaches to lymphocyte migration in dermatology in vitro and in vivo
Authors: Radeke Heinfried H. , Ludwig Ralf J. , Boehncke Wolf‐Henning
Published: August 2005

Abstract:  Lymphocyte trafficking through the dermal compartment is part of the physiological surveillance process of the adaptive immune system. On the other hand, persistent or recurrent lymphocyte infiltrates are hallmarks of both types of chronic inflammatory skin diseases, Th1‐type such as psoriasis or Th2/allergic‐type like atopic dermatitis. A better understanding of the mechanisms underlying lymphocyte movements is one of the key prerequisites for developing more effective therapies. In this review, we introduce a range of simple‐to‐sophisticated experimental in vitro and in vivo approaches to analyze lymphocyte migration. These methods start from static in vitro adhesion and chemotaxis assays, include dynamic endothelial flow chamber, intravital dual photon, and transcutaneous live‐video microscopy, and finally encompass specific genetically deficient or engineered animal models. Discussing pros and cons of these assay systems hopefully generates both state‐of‐the‐art knowledge about the factors involved in most common chronic skin diseases as well as an improved understanding of the limitations and chances of new biologic pharmaceuticals that are currently introduced into clinical practice.
Non‐uniform volume and water content changes in swelling clay soil: I. Theoretical analysis
Authors: VOLTZ M. , CABIDOCHE Y.‐M.
Published: August 2005

In many clay soils, drying and wetting cause non‐uniform changes in water content and in the volume of soil and peds. Theoretical relations between total volume of soil, soil thickness and water content are sought for non‐uniformly swelling and shrinking soil. Such soil is assumed to be composed of small elemental volumes, each of which does swell or shrink uniformly. It is also assumed that the non‐uniformity of swelling or shrinking in such soils arises solely from spatial variation brought about by variations in evapotranspiration and infiltration. A constant ratio between movement of the soil in the vertical and horizontal dimensions is assumed for all elements of soil. By averaging over the soil volume the equations describing the volume change of individual elemental volumes, the averaged equations for non‐uniform volume changes may be obtained. They show that the average and the spatial distribution of the changes in soil thickness determine the average changes in water content of the soil. It is concluded that the equations for uniform and non‐uniform volume changing soils, though formally different, should in practice produce nearly identical results for clay soils.
Non‐uniform volume and water content changes in swelling clay soil: II. A field study on a Vertisol
Authors: CABIDOCHE Y.‐M. , VOLTZ M.
Published: August 2005

A theoretical model of volume change in swelling clay soil is applied in a field study to determine the swelling‐shrinking behaviour of a Vertisol in Guadeloupe (French West Indies). The field experiment estimated the spatial averages of vertical soil movements and soil water content changes by measurements at the intersections of a sampling grid. The geometry of volume change was found to be anisotropic with vertical soil movements slightly larger than horizontal ones. The observed anisotropy seems to arise because the peds slide along oblique slickensides whereas individual peds shrink and expand isotropically. The discrepancy with earlier field results which indicated strictly isotropic volume changes is thought to arise in part from a difference in the nature of the clay soils investigated. An uncertainty analysis of the experiment shows that the main source of error is due to the estimation of the spatial averages of soil elevation.
Variation of textural porosity of a clay‐loam soil during compaction
Authors: BRUAND A. , COUSIN I.
Published: August 2005

The effect of compaction on the porosity of aggregates was studied in the laboratory using mercury porosimetry and backscattered electron scanning images (BESI) of polished thin sections. Porosity was divided into structural and textural porosity, and then textural porosity into lacunar and clayey porosity.

For aggregates equilibrated at a water potential of −1 kPa and pressures of 50 and 200 kPa, compaction of structural porosity resulted in an increase of textural porosity. For aggregates equilibrated at a water potential of −1 kPa and an applied pressure of 600 kPa, the structural porosity strongly decreased but did not result in a variation of textural porosity. For aggregates equilibrated at water potentials of −63 and −103 kPa and the three values of pressure studied, textural porosity was unaffected by compaction whatever the evolution of structural porosity. The BESI indicated that the increase in textural porosity which was recorded by mercury porosimetry for aggregates equilibrated at a water potential of −1 kPa and applied pressures of 50 and 200 kPa was due to the formation of relict structural pores during compaction. The relict structural pores resulted from partial distortion of the structural pores within the original aggregates. These relict structural pores still had the morphology of structural pores on BESI, but they were accessible to mercury through the necks of textural pores identified as lacunar pores.

Results also indicate that massive structure frequently seen in the field for these soils and interpreted as resulting either from structural collapse during rewetting or from compaction actually resulted mainly from wheel compaction.
The influence of increased NH4+ deposition rates on aluminium chemistry in the percolate of acid soils
Authors: EGLI M. , FITZE P.
Published: August 2005

The influence of different NH4+ loads on aluminium speciation in percolating water was studied on acid luvisols with similar soil‐pH values but with different soil adsorption surface characteristics. All of the applied NH4+ was nitrified and therefore led to proton production. Thus, Al displacement in the percolate was increased. The extent of this enhanced translocation was found to be chiefly a function of the amount of exchangeable base cations which buffered the protons produced by nitrification.

The proportion of the different Al species in the percolate was altered at large NH4+ loads. Very large A13+ concentrations eliminated Al species bound to dissolved organic matter and particles, presumably because of flocculation and precipitation of organic ligands. Furthermore, increased NO3− and A13+ concentrations enhanced the desorption of F− giving rise to an additional increase in Al displacement by the formation of Al fluoro complexes in the aqueous phase.
Radio‐caesium fixation dynamics: measurement in six Cumbrian soils
Authors: ABSALOM J.P. , YOUNG S.D. , CROUT N.M.J.
Published: August 2005

Five peat soils and a mineral soil were artificially contaminated with 137Cs. Soil solution activity and radio–lability of 137Cs were monitored over 709 days to quantify progressive 137Cs fixation. The peat soils fixed large amounts of 137Cs, but less than the mineral soil did. Distribution coefficients (Kd, cm3 g−1) ranged from 30 to 5000 at the end of equilibration. A labile 137Cs distribution coefficient, Kdt, was estimated by a method involving solid ⇌ solution equilibration in dilute solution.

In a separate study several concentrations of KCl were added to soils in increasing concentration both before and after the addition of 137Cs. Differences in apparent adsorption strength of radiocaesium indicated that K+ induced the collapse of expanded mineral interlayers, thereby trapping ions. It seemed that I37Cs adsorbs at sites in the small micaceous clay fraction of the peat soils.

The different rates of 137Cs adsorption and fixation in the peat and mineral soils, in which the rate of access of 137Cs to fixation sites in peat soils is less, seems to have been caused partly by lack of K, and partly by the scarcity of fixation sites.
Simplified models of anoxia and denitrification in aggregated and simple‐structured soils
Authors: ARAH J.R.M. , VINTEN A.J.A.
Published: August 2005

Two complementary approaches to modelling soil anoxia and denitrification are compared. The first postulates a structurally and biologically heterogeneous soil matrix (physical aggregates) and Michaelis—Menten kinetics; the second a random distribution of cylindrical air‐filled pores, a uniform metabolic activity and zero‐order reaction kinetics. Simple functional approximations to both models are developed, allowing their differences to be explored. At water contents corresponding to aggregate saturation the anoxic fractions and denitrification rates predicted by the aggregate model exceed those predicted by the simple‐structure model. In drier soils the predictions of the latter model typically exceed those of the former by between one and three orders of magnitude, the discrepancy lessening as the oxygen reaction potential and the mean radius of the aggregates increase. The aggregate model is much more sensitive to air‐filled porosity, and shows a decreased denitrification efficiency when nitrate concentrations are low. It is likely to predict sharper rainfall‐induced denitrification events, and a smaller background activity, than the distri‐buted‐pore treatment. Whichever of these or other process‐based treatments of denitrification is adopted, simple approximations like those presented here greatly facilitate inclusion in larger‐volume systems models.
Anaerobiosis in saturated soil aggregates: modelling and experiment
Authors: SIERRA J. , RENAULT P. , VALLES V.
Published: August 2005

A model of anaerobiosis based on gas diffusion and microbial respiration is proposed for soil aggregates. Unlike previous models, it accounts for the dependency of O2 consumption on O2 and CO2 concentrations and, consequently, on chemical reactions of CO2 in soil solution. The model is tested with experimental data of respiration and O2 distribution within spherical remoulded aggregates of different sizes saturated with water. Most of the model parameters were estimated experimentally.

Fick's law could describe O2 diffusion inside the saturated aggregates. The model agreed well with O2 profiles measured soon after saturation. Later, the model underestimated anaerobiosis, probably because of changes in radial distribution of microbial activity inside the aggregates. Respiration as a function of O2 concentration was satisfactorily described by the model. Nevertheless, each size of aggregate was analysed separately because of an apparent relation between size and maximal aerobic respiration. This seems to be associated with a non‐homogeneous distribution of aerobic respiration. The model represents an improvement on those currently used to estimate anaerobiosis inside aggregates.
Pyrolysis methylation—mass spectrometry of whole soils
Authors: SCHULTEN H.‐R. , SORGE C.
Published: August 2005

In‐source pyrolysis field ionization mass spectrometry (Py‐FIMS) and Curie–point pyrolysis gas chromatography/mass spectrometry (Py‐GC/MS) have been applied to the characterization of whole soils methylated off–line and on–line by two methylation reagents. Samples of a gleysolic Ap–horizon and a podzolic Bh horizon (Corg concentrations 2–3%) were investigated by conventional on–line and developed off–line methylation with tetramethylammonium hydroxide (TMAH) and by off–line methylation with diazomethane. For the first method, the soils were dried, milled and pretreated with TMAH for 10 min at 250°C at ambient pressure outside the pyrolyzers. For the second method, the dried and milled soils were methylated with an ether solution of diazomethane for 12 h at room temperature (∼20°C). Pyrolysis methylation with TMAH enabled aliphatic C2–C39 monocarboxylic acid methyl esters, C4–C30 dicarboxylic acid dimethyl esters and benzenecarboxylic acid methyl esters to be detected. Methoxybenzenes from phenols, benzenediols and benzenetriols, methoxybenzenecarboxylic acid methyl esters from phenolic acids and furancarboxylic acid methyl esters from carbohydrates were also identified. Nitrogen–containing compounds in soil organic matter were obtained as N,N–dimethylamides. Using diazomethane as methylation reagent, distinct Py‐FIMS signals were observed for aliphatic C2–C32 monocarboxylic acid methyl esters and C3–C24 dicarboxylic acid dimethyl esters. Additionally, methoxybenzenes originating from lignins, methoxybenzenecarboxylic acid methyl esters from phenolic acids and N,N–dimethylamides from amides were detected. The more acid podzolic Bh horizon showed higher relative intensities for dicarboxylic acid dimethyl esters and methylated phenolic acids compared to the gleysolic Ap horizon. Similarly, benzenecarboxylic acids are connected mainly by ester linkages to the macromolecular network of soil organic matter. Both methylation procedures support conventional Py‐FIMS and Py‐GC/MS and give valuable additional information on the occurrence of aliphatic and aromatic carboxylic acids, substituted phenols, benzenediols, benzenetriols, phenolic acids and amides in soil organic matter.
Characterizing trace metal adsorption on kaolinite
Authors: SPARK K.M. , WELLS J.D. , JOHNSON B.B.
Published: August 2005

Adsorption of Cu(II), Zn(II), Co(II) and Cd(II) on kaolinite has been investigated at 25°C as a function of pH, concentration of the substrate, and the nature and concentration of the supporting electrolyte. The adsorption edges for three metals (Zn(II), Co(II) and Cd(II)) showed clear evidence of two distinct adsorption processes. As the pH was increased adsorption began at pH 4.5 for all metals, but the fraction of metal adsorbed at the completion of the first stage differed, the order being Zn(II)>Co(II)∼Cd(II). The second stage of adsorption had characteristics similar to those for adsorption of the metals on alumina and silica. Type 1 adsorption (the first stage) probably occurs on the permanent negatively charged kaolinite faces, while Type 2 (the second stage) is associated with the variable‐charge surfaces.

Increasing the concentration of supporting electrolyte (KNO3 or NaCl) dramatically reduced the extent of Type 1 adsorption: at 0.1 m no evidence of this process existed. At intermediate concentrations electrolytes containing K+ suppressed Type 1 adsorption more than those containing Na+.
Speciation and calcium competition effects on cadmium sorption by sandy soil at various pHs
Authors: TEMMINGHOFF E.J.M. , VAN DER ZEE S.E.A.T.M. , DE HAAN F.A.M.
Published: August 2005

The effects of Ca competition, ionic strength, inorganic complexation and pH on cadmium adsorption by a sandy soil were studied. Sorption of Cd was measured using four different electrolytes CaCl2, Ca(NO3)2, NaNO3 and NaCl at a constant ionic strength (I) of 0.003 M at three different pHs, at variable Ca/Na ratio with a constant ionic strength of 0.03 and at variable ionic strengths between 0.003 and 0.3 M for two different pHs for Ca(NO3)2 and NaNO3. The measured Cd sorption isotherms were non‐linear. In the case of Cl as electrolyte anion, 13% of the Cd in solution is complexed at I= 0.003 (0.002 M Cl) and 91% of Cd is complexed at I= 0.3 (0.2 M Cl). If NO3 is the anion, none of Cd is complexed at I= 0.003 and 11% at I= 0.3. The Cd complexes do not adsorb significantly. Calcium competition, at an ionic strength of 0.03, reduced the Cd adsorption by 60–80% compared with the case that Na is the cation. Increasing the ionic strength from 0.003 to 0.3 decreased Cd sorption by 60% for Ca(NO3)2 and 25% for NaNO3 due to a decrease of the activity coefficient, increase of inorganic complexation and increase of Ca competition. A decrease of one pH unit reduces Cd sorption of about 75%. Sorption of Cd by soil could be described adequately with the three‐species Freundlich (3SF) equation in which pH, complexation, Ca competition and ionic strength effects were taken into account.
The application of some image‐analysis techniques to recognition of soil micromorphological features
Authors: TERRIBILE F. , FITZPATRICK E.A.
Published: August 2005

A number of image analysis techniques, largely drawn from remote sensing, have been applied to soil thin sections in an attempt (i) to overcome some of the limitations of previous approaches and (ii) to identify some complex soil features.

Using different wavelengths and light polarizations, microscopic images of thin sections obtained from different horizons were digitized. It was then possible to carry out a series of experiments including geometric corrections, creation of multilayer images, principal component transformation, classification procedures, morphological analysis and modelling of bi‐dimensional optical anisotropy of the soil matrix.

As a special procedure, principal component images were included in the multilayer images, thereby improving the classification on which a morphological analysis was conducted. The reliability of the procedure was tested against point counting and was found to be successful. The overall procedure allowed the combination of brightness and shape classifications. Bi‐dimensional matrix optical anisotropy was detected at 256 levels and plotted as a three‐dimensional perspective view, thus creating a new way of studying this feature.
Adsorption of selenite to goethite in a flow‐through reaction chamber
Authors: GLASAUER S. , DONER H.E. , GEHRING A.U.
Published: August 2005

Adsorption of selenite on goethites in NaCl and Na2SO4 solutions was performed in a newly designed flow‐through reaction chamber as well as in a traditional batch system. Six goethites with different morphologies were used as adsorbents. For the experiments the goethite was placed in the chamber prior to flushing with the salts. Introduction of the NaCl and Na2SO4 solutions only, and in combination with selenite, resulted in different responses with respect to the pH. The pH changes were explained by means of anion‐binding energies, with Cl− <SC42− <SeO32−. Neither the morphological characteristics of the adsorbents nor the electrolyte anion influenced the amount and the rate of selenite adsorption, The mixing mode in the reactor chamber affected the selenite adsorption density, as indicated by higher densities in the batch experiments.
Evaluation of two coal‐derived organic products in ameliorating surface and subsurface soil acidity
Authors: NOBLE A. D. , RANDALL P. J. , JAMES T. R.
Published: August 2005

Acidity in the soil surface and subsurface is of major concern in horticulture, cropping and pasture production systems in southern Australia. Broadcast applications of lime to the surface have proved to be ineffective in ameliorating subsurface acidity in the short term. Two calcium‐saturated coal‐derived organic products, an ‘oxi‐product’ (OXPR) and an ‘oxi‐fulvate’ (OXFU), were evaluated for use as liming materials with specific consideration given to amelioration of subsurface acidity. The effects of these two organic products and of lime on the chemical composition of the A1 and A2 horizons of an acid red podzol were investigated in leaching columns, 20 cm long. OXPR and OXFU supplying 80 or 160 g Ca m−2 were compared to 160 g Ca m−2 applied as CaCO3 and a control receiving no amendments. The effects of CaCO3 on exchangeable Al and pH were limited to the surface 2 cm. In contrast, the two organic amendments were effective in decreasing exchangeable Al and increasing pH and exchangeable Ca to depth, the extent being a function of amendment and rate applied. The formation of inorganic and organic complexes were assumed to be responsible for the movement of Al out of the column in the leachate, although significant quantities of Al were precipitated in the column. Significant linear regressions were observed between the ionic strength and Al in the leachate. Significant quantities of Mg and K were displaced by Ca and leached from the column; consequently, this loss must be considered against the benefits of decreased exchangeable Al when assessing fertility for plant production.
Proton and copper binding by humic acid: application of a discrete‐site/electrostatic ion‐binding model
Authors: TIPPING E. , FITCH A. , STEVENSON F. J.
Published: August 2005

A discrete‐site/electrostatic model of ion binding by humic substances has been applied to proton‐and copper‐binding data for a soil humic acid. The proton data cover the pH range 3–9 and the ionic strength range 0.001 m‐0.1 m, while those for copper refer to the pH range 4–5, ionic strengths between 0.005 m and 0.1 m, and p[Cu] values between 3 and 8. The model is able to explain the major observed trends, including the dependence of proton and copper binding on ionic strength and the binding of copper as a function of pH. However, the calculated ionic strength dependence of copper binding is slightly less than that observed. In addition, the model has been used to predict ratios of protons released to copper bound under different conditions, on the basis of the separately estimated parameters for proton and copper binding. The model correctly predicts the ratios to be between 1 and 2, and to decrease with increasing bound copper and with pH.
Iron(III) reduction by natural humic acids: a potentiometric and spectroscopic study
Authors: DEIANA S. , GESSA C. , MANUNZA B. , RAUSA R. , SOLINAS V.
Published: August 2005

The reduction of iron(III) by natural humic acid (NHA) was studied in aqueous solution as a function of pH, time and iron(III) concentration. The information gained from FTIR and ESR spectroscopies as well as potentiometric data suggests that redox reactions occur at a low pH due to the involvement of phenolic groups and radicals. At pH values higher than 3.5 the reaction is strongly inhibited by the formation of iron(III)–humate complexes.
Entropy and sustainability
Authors: ADDISCOTT T.M.
Published: August 2005

Soil–plant systems exchange both energy and matter with their surroundings and are consequently open systems thermodynamically. They should therefore tend towards a steady state described by non‐equilibrium thermodynamics and characterized by minimum production of entropy. The theory surrounding the principle of minimum entropy production provides a good analogue of the behaviour of natural and agricultural ecosystems subjected to perturbations. Entropy‐increasing processes are those that degrade complex, ordered structures of large molecular weight to small molecules such as CO2, NH3 and H2O. Processes such as photosynthesis that build small molecules into larger ones lessen entropy. These ordering processes are permitted by thermodynamic work performed when heat is transferred from the sun. They depend critically on the capacity of the system for self‐organization, which is identified with its biological potential. Several of the small molecules are environmentally undesirable in excess. This, together with the theoretical considerations above, suggests that minimum production of entropy should be a criterion of sustainability. It implies that agricultural systems should be allowed to become steady states where possible and that maintaining the biological potential is essential. An ‘audit of small molecules’ is suggested as a way of assessing sustainability.
Effects of addition of clay minerals on the fatty acid fraction of a podzol soil
Authors: JAMBU P. , AMBLÈS A. , MAGNOUX P. , PARLANTI E.
Published: August 2005

The Al horizon of a sandy podzol soil, with a very small proportion of clay‐sized material, was sampled and homogenized. Samples, both with and without supplementation with 150 g clay minerals kg−1, natural heteroionic bentonite (saturated with Na, Ca, Mg, K), Mg‐bentonite or Fe‐kaolinite, were moistened to two‐thirds of water‐holding capacity and incubated at 28°C for 16 weeks.

After incubation, lipids were extracted with 3:1 light petroleum: ethylacetate mixture in a Soxhlet apparatus as unbound components (directly extractable by organic solvents) and bound components (only extractable after treatment with acids). Monoacids (free and esterified), diacids, ketoacids and hydroxyacids were isolated from the two lipidic fractions (unbound and bound) by column chromatography. The different components of each family were analyzed by gas chromatography (GC) or gas chromatography‐mass spectrometry (GC‐MS).

Incubation without supplementation generated a selective decrease in abundance of free mono‐acids in unbound and bound fractions. The decrease was in inverse proportion to the chain‐length of components. Soil supplementation with bentonite (homoionic or heteroionic) did not induce an overall quantitative change, but promoted a transfer of fatty acids from the unbound to the bound fraction, increased the exchange between free and esterified monoacids (transesterification) and stimulated hydrolysis of glycerides. In contrast, soil supplementation with Fe‐kaolinite caused much decomposition or biotransformation of monoacids but it did not induce change either in the intensity of transesterification in the wax ester fraction or in the intensity of hydrolysis in the glyceride fraction.
Use and accuracy of the filter‐paper technique for measurement of soil matric potential
Authors: DEKA R.N. , WAIRIU M. , MTAKWA P.W. , MULLINS C.E. , VEENENDAAL E.M. , TOWNEND J.
Published: August 2005

A filter–paper technique that can be used to measure the matric potential of field soil is described in detail. When a calibrated batch of filter papers is used, the precision is limited by the variability between individual papers and the limitation of weighing to the nearest mg. The absolute accuracy is also limited by the instruments used for calibration. There was reasonable agreement between batches of the same type of paper, suggesting that our generalized calibration curves can be used for Whatman No. 42 filter papers where accuracy is not paramount.

For potentials ≥−2.5 MPa, papers need to be equilibrated with the soil for 6 d. To achieve the same accuracy at lower potentials longer equilibration periods are required. Results suggest that the technique should be effective down to at least −100 MPa if soils are allowed to equilibrate fully with the papers. Coefficients of determination (r2) for the calibration lines were all ≥0.92. A regression of log(‐matric potential) measured by the filter paper technique against measurements made using tensiometers and a psychrometer over a range of potentials between −1 kPa and −10 MPa gave an r2 value of 0.995.
Field‐based partition coefficients for trace elements in soil solutions
Authors: GOODDY D.C. , SHAND P. , KINNIBURGH D.G. , VAN RIEMSDIJK W.H.
Published: August 2005

A total of 48 elements was detected in the soil solutions centrifuged from two acid sandy (humus‐iron podzol) profiles from southern England. Concentrations ranged from mm for the major ions to mm for trace metals such as U and the rare earth elements. Field‐based solid/solution partition coefficients, Kd, were determined by calculating the ratio of the amount of an element extracted by 0.43 m HNO3 or a neutral salt (0.01 m CaCl2 or 0.1 m Ba(NO3)2) to the concentration in the soil solution. These partition coefficients did not show the expected trend in selectivity. For example, Cd consistently had one of the highest Kd values, higher even than Cu. This was thought to be due in part to the nature of the Kd which reflects a balance between binding to the soil solids and to the dissolved organic carbon (DOC), which is present at relatively high concentrations (1–20 mm) in the soil solutions. Because of the underlying functional similarity between metal binding by the solid and dissolved organic matter, the partition coefficient (and hence element mobility) will be relatively insensitive to changes in pH and metal‐ion activity in the soil solution.
Sorptive interactions of pesticides in soils treated with modified humic acids
Authors: ALMENDROS G.
Published: August 2005

Different structural changes in peat humic acid (HA) were induced through treatments leading to chemical derivatization and/or the removal of functional groups. Eleven humic products were obtained after acetylation, amidation, ammonia fixation, methylation, nitration, oximation, sulphonation, selective degradations and ‘fixation’ of stearic acid. The sorption of 12 pesticides (alachlor, atrazine, carbofuran, 2,4‐D, 2,4‐DB, methyl parathion, metoxuron, monouron, prometryne, propanil, fenoprop and chloranil) on the above products was determined by ultraviolet derivatographic spectroscopy. In addition, pesticide sorption was evaluated on samples from neutral and calcic soils treated with the corresponding potassium humates. The most intense interactions occurred in samples from the neutral plot, whereas the greatest effect of the humic matter in enhancing pesticide sorption was found with the calcic soil. As expected, the sorption patterns in HA‐pesticide systems were poorly correlated with those in soil‐HA‐pesticide systems. In the former case, the sorption performance was influenced mainly by hydrophobic interactions, whereas in the latter it depended on the participation of multiple parameters suggesting that the molecular volume and the van der Waals energy of the pesticide molecule play a chief role. The HA characteristics most frequently correlated with pesticide sorption were those connected with the aromatic/aliphatic ratio and the particle size. In the calcic‐soil‐HA‐pesticide systems, the base saturation of the exchange complex correlated negatively with pesticide sorption.
Applications of the continuous‐flow stirred‐cell (CFSC) technique: II. The adsorption behaviour of Na, Cs, Sr, Cu, Ni and Pb on humic acids
Authors: RANDLE K. , HARTMANN E.H.
Published: August 2005

The first part of this paper deals with the sorption of Na, Cs, Sr, Ni, Cu and Pb on two humic fractions derived from a soil. The sorption data for individual elements were obtained using the continuous‐flow stirred‐cell (CFSC) technique, in which the metal sorptive solution is pumped through a cell containing a known mass of the humic acid retained by a filter and the solution emerging from the cell was analysed by either atomic absorption spectrometry (Cu, Ni and Pb) or by the combined use of radioisotope dilution and gamma‐ray spectroscopy (Na, Cs and Sr). Sorption isotherms were determined at two flow rates. It was found that, in general, the sorption isotherms for all the metals studied could be described by the Langmuir equation and parameters derived from the fitted line provided information on the metal‐humate binding strengths and the maximum amount of metal sorbed per unit mass of humic acid. Caesium showed anomalous behaviour at certain flow rates in both its sorption and desorption behaviour.

In the second part of the paper we discuss the sequential sorption and desorption of one metal by another on the same humic fraction, using Na, Cs, Zn and Cd. The aim was to elucidate the nature of the binding process when several metals were competing simultaneously for the functional groups on the humic acids. In addition, at the end of the experiment, the humic material was isolated and analysed by gamma‐ray spectroscopy to determine the metals still bound in this fraction. Some tentative conclusions concerning the nature of the metal‐humate complexes are made on the basis of these data.
Zinc sorption by acid tropical soils as affected by cultivation
Authors: GUADALIX M.E. , PARDO M.T.
Published: August 2005

The sorption of zinc (Zn) by two acid tropical soils, Mazowe clay loam (kaolinitic, coarse, Rhodic Kandiustalf) and Bulawayo clay loam (coarse, kaolinitic, Lithic Rodustalf), was studied over a wide range of Zn solution concentrations. Samples of the two soils used in the experiments were collected at both uncleared, uncultivated (virgin) sites and cultivated sites. The two virgin soils showed similar abilities to bind Zn. Mazowe soil (40 g organic matter kg−1) presented the highest affinity for Zn. Yet, Bulawayo soil (23.5 g organic matter kg−1) sorbed almost the same amount. Bulawayo soil had higher pH and Fe and Mn‐oxide content than Mazowe soil. Once cultivated, the two soils behaved quite differently. After 50 years, Mazowe soil had lost 60% of its organic matter and effective cation exchange capacity (ECEC). In this soil, Zn sorption capacity had also been decreased by 60%. Clearing and 10 years under cultivation had affected neither the organic matter content nor the ECEC of Bulawayo soil. For this soil, Zn sorption was even higher in the cultivated soil, presumably due to an increase in the amount of Fe and Mn oxide from subsoiling. Zinc sorption was dependent upon pH, with retention dramatically increasing in the pH range 6–7. Sorption occurred at pH values below the point of zero charge (PZC), indicating that the sorption reaction can proceed even in the presence of electrostatic repulsion between the positively charged soil surface and the cation. In the two soils, the reversibility of the sorption reaction was very low. More than 90% of the sorbed Zn was apparently strongly bonded.
Water retention models for fractal soil structures
Authors: BIRD N.R.A. , BARTOLI F. , DEXTER A.R.
Published: August 2005

A review of water retention functions based upon fractal soil structures is presented. We consider the modelling approach for a fractal fabric, a fractal pore boundary and a fractal pore space, identifying the latter case as one of particular complexity. In each case, the water retention function is derived from the pore volume distribution arising from the structural model in question. We examine published models and highlight problems, namely lack of generality and inconsistency with the assumed fractal structure. The models considered in this paper do not account for the effects of pore connectivity, and as such their validity as a necessary condition for the existence of fractal structure is questionable.
Spectroscopic control of iron oxide dissolution in two ferralitic soils
Authors: MALENGREAU N. , BEDIDI A. , MULLER J.‐P. , HERBILLON A.J.
Published: August 2005

Second derivative diffuse reflectance spectroscopy (DRS) in the visible range has been used to characterize changes in colour and identify the nature of Fe oxides which withstand reduction during experimental yellowing of reddish materials. It is accepted that haematite dissolves preferentially and faster than goethite, and Al‐substitution controls the dissolution kinetics of Fe oxides. However, DRS has shown that haematite is more resistant than predicted and that some Fe‐oxides, probably trapped within kaolinite particles, are inaccessible to solvents. DRS allows the nature of dissolved phases at each deferration step to be determined and changes in Al‐content of residual phases throughout deferration to be followed. It also demonstrated that Helmholtz coordinates correlate very well with changes in Fe‐oxide mineralogy and are preferable to redness ratings when monitoring differential dissolution of Fe oxides through colour measurements. DRS is a powerful and sensitive technique for monitoring the dissolution of Fe oxides in soils.
Organic matter composition in sewage farm soils: Investigations by 13C‐NMR and pyrolysis‐field ionization mass spectrometry
Authors: LEINWEBER P. , BLUMENSTEIN O. , SCHULTEN H.‐R.
Published: August 2005

The composition of soil organic matter (SOM) on sewage farms south of Berlin was investigated by solid‐state CP/MAS 13C‐NMR and pyrolysis‐field ionization mass spectrometry (Py‐FIMS) of freeze‐dried sewage solids and soil samples of differing contamination. These were an untreated soil (USOIL), a former sewage farm used as arable land since 1990 (SF90A), and a recent sewage farm (SF1994). The CP/MAS 13C‐NMR spectra showed enrichments of the sewage‐treated soils with aliphatic C and C in OCH3‐groups and amino acids. In the Py‐FI mass spectra the major markers of sewage and SOM in sewage farm soils were (i) N‐containing compounds, in particular peptides, (ii) dimethylphthalate (m/z 194), (iii) sterols, and (iv) signals in the mass range m/z 502 to 554 of mono‐ and diaryl esters which were substituted by long aliphatic chains. The latter signals were intense in the sewage solids, increased in intensity from sample SF90A to SF1994; but they were not present in the USOIL, thus clearly indicating anthropogenic origin. Temperature‐resolved Py‐FIMS showed that the SOM compounds in the sewage farm soils were generally incorporated into bonds with widely different stabilities which could be relevant for SOM turnover and environmental effects. This is demonstrated for the trapping of dimethylphthalate in a modelled humic substance.
Total carbon and nitrogen in the soils of the world
Authors: BATJES N.H.
Published: August 2005

The soil is important in sequestering atmospheric CO2 and in emitting trace gases (e.g. CO2, CH4 and N2O) that are radiatively active and enhance the ‘greenhouse’ effect. Land use changes and predicted global warming, through their effects on net primary productivity, the plant community and soil conditions, may have important effects on the size of the organic matter pool in the soil and directly affect the atmospheric concentration of these trace gases.

A discrepancy of approximately 350 × 1015 g (or Pg) of C in two recent estimates of soil carbon reserves worldwide is evaluated using the geo‐referenced database developed for the World Inventory of Soil Emission Potentials (WISE) project. This database holds 4353 soil profiles distributed globally which are considered to represent the soil units shown on a 1/2° latitude by 1/2° longitude version of the corrected and digitized 1:5 M FAO–UNESCO Soil Map of the World.

Total soil carbon pools for the entire land area of the world, excluding carbon held in the litter layer and charcoal, amounts to 2157–2293 Pg of C in the upper 100 cm. Soil organic carbon is estimated to be 684–724 Pg of C in the upper 30 cm, 1462–1548 Pg of C in the upper 100 cm, and 2376–2456 Pg of C in the upper 200 cm. Although deforestation, changes in land use and predicted climate change can alter the amount of organic carbon held in the superficial soil layers rapidly, this is less so for the soil carbonate carbon. An estimated 695–748 Pg of carbonate‐C is held in the upper 100 cm of the world's soils. Mean C: N ratios of soil organic matter range from 9.9 for arid Yermosols to 25.8 for Histosols. Global amounts of soil nitrogen are estimated to be 133–140 Pg of N for the upper 100 cm. Possible changes in soil organic carbon and nitrogen dynamics caused by increased concentrations of atmospheric CO2 and the predicted associated rise in temperature are discussed.
Analysis of the green fraction of humic acids
Authors: WATANABE A. , FUJIMORI H. , NAGAI Y. , MIYAJIMA T. , KUWATSUKA S.
Published: August 2005

The green fraction of humic acids (HAs), Pg, was fractionated by gel chromatography on Sephadex G‐50. Repeated chromatography of the crude Pg obtained by the first chromatography of HA yielded a sharp peak (G1) and two broad bands (G2) of purified Pg. The recovery of Pg in G1 and G2 as percentages of the total Pg content of the HA were 16.2 and 14.5%, respectively. Distinct peaks were detected at 615, 570, 450 and 280 nm in the UV‐visible spectra of both G1 and G2 in alkali solutions. Estimates of weight‐average molecular weight were 9.7 * 103 for G1 and 1.23 * 104 for G2. In the 1H‐NMR spectra the percentage of hydroxyl groups of 4,9‐dihydroxy‐perylene‐3, 10‐quinone (DHPQ) nuclei, which are known to be the chromophore of Pg, was 4.1 and 4.5% of the total H, respectively. Based on these values and the H/C ratios, DHPQ‐C was estimated as 28% of total C. 13C‐NMR spectra obtained using inverse‐gated decoupling yielded 40–41% aromatic C, which suggested the presence of aromatic rings other than DHPQ. All of the IR, 13C‐ and 1H‐NMR spectra indicated that the two purified Pg samples largely differed from each other in their contents of alkyl and polysaccharide components.
Assessment of the effect of molecular size on the electrophoretic mobility of humic substances
Authors: DE NOBILI M. , FORNASIER F.
Published: August 2005

The basic principles of the electrophoretic behaviour of humic substances (HS) still need to be systematically investigated. HS extracted from a Cryorthod (HS–1) and from an Haplumbrept (HS–2) were first fractionated by ultrafiltration to obtain two series of fractions of reduced polydispersity with a nominal mean relative molecular mass (M) of 7500, 20000, 40000, 75000 and 200 000 Da. Fractions extracted from the same soil behaved like an homologous series when tested by size exclusion chromatography, showing a linear relation of M with molecular size. When plotted against their mean M, the elution volumes of HS fractions extracted from the two different soils originated lines of different slope. Absolute electrophoretic mobilities of the fractions were determined in polyacrylamide gel slabs of increasing polyacrylamide concentration using a single buffer system; in all gels there was a close linear relation between the electrophoretic mobility and the logarithm of the mean M of HS fractions. Extrapolation of mobilities of HS–1 at zero gel concentration gave intercepts that did not differ significantly, showing that there was a constant mobility for all fractions in free solution. These results mean that charge differences have little effect on the electrophoretic mobilities of HS extracted from the same soil and imply the theoretical possibility of determining M distributions of HS by polyacrylamide gel electrophoresis in a single buffer system. Mobilities of HS–2 fractions were compared with those of HS–1: the latter fitted the regression equations of mobility against logarithm of the molecular weight obtained from HS–1 humic substances only in gels of small acrylamide concentration. Deviations were larger at small M, probably because of the increasing fulvic character of the fractions, and increased in gels of greater acrylamide concentration, indicating that charge differences may not be negligible when comparing humic substances extracted from different soils.
Sorption of phosphate and oxalate by a synthetic aluminium hydroxysulphate complex
Authors: VIOLANTE A. , RAO M.A. , DE CHIARA A. , GIANFREDA L.
Published: August 2005

We studied the sorption of phosphate and oxalate on a synthetic aluminium hydroxysulphate complex and the associated release of sulphate from this complex. In the pH range 4.0–9.0 the presence of phosphate or oxalate tended to increase the release of sulphate. Much more phosphate than oxalate was sorbed, but in most cases oxalate caused more removal of sulphate than did phosphate. Only in acid systems may these results be partly attributed to the greater solubilization of the complex in the presence of oxalate than in the presence of phosphate. At pH > 8.0 in the presence of phosphate, and at pH > 6.5 in the presence of oxalate, the quantities of sulphate replaced were greater than the quantities of phosphate or oxalate sorbed, suggesting that hydroxyl ions competed with phosphate and oxalate for sorption sites and sulphate removal. Sulphate was only partly removed from the complex even after repeated washings with phosphate or oxalate solutions or after 120 h in the presence of these ligands at pH 6.0. When phosphate and oxalate were added as a mixture much more phosphate than oxalate was retained. Phosphate strongly inhibited oxalate sorption, whereas oxalate partly prevented phosphate sorption only at pH < 7.0. More sulphate was removed in the presence of both the anions than in the presence of phosphate alone, but less than that desorbed in the presence of oxalate alone.
Atomic force microscopy (AFM) investigations of the surface topography of a multidomain porous goethite
Authors: FISCHER L. , MÜHLEN E. ZUR , BRÜMMER G.W. , NIEHUS H.
Published: August 2005

A multidomain goethite was analysed with atomic force microscopy (AFM) to obtain information about the size and shape of pores on the surface, which are important for sorption processes of cations and anions. Wedge‐shaped pores > 100 nm long at the surface occurred at the domain boundaries. They were 20‐30 nm wide, becoming narrower towards the interior of the crystals to 2 nm and less. The AFM showed these pores to be at least 4–6 nm deep. The shape of the pores suggests that smaller pores continue much further into the interior of the crystals. Besides the irregularities between domains, randomly distributed steps of < 1 nm occurred. Hydrothermal treatment did not change crystal size, but made the surfaces smoother and reduced both the size and number of the pores and also the BET surface area (from 75.3 to 35.1 m2 g−1). The existence of meso‐ (2–30 nm width) and micropores (< 2 nm width) in goethite crystals explains the slow diffusion of heavy metals, phosphate and other ions into goethite particles. Therefore, the external and internal surfaces of goethite crystals and their spatial heterogeneity have to be taken into account in models of ion adsorption by goethite.
Effects of associations between humic acids and iron or aluminium on the flocculation and aggregation of kaolin and quartz
Authors: ARIAS M. , BARRAL M.T. , DIAZ‐FIERROS F.
Published: August 2005

The aggregative effect of organic matter on soil particles is conditioned by its composition and concentration and the degree to which it is associated with metal ions and oxides in the soil. We treated suspensions of kaolin or quartz substrates at pH 5 with metal (Fe or Al; c. 3 to 23 mg g−1 of substrate) or humic acid (HA; 7 to 53 mg g−1 of substrate) or both. In the absence of added Fe or Al, the proportion of HA retained by the substrate decreased from 98.5 to 50.8% for kaolinitic samples, and from 35.8 to 23.4 for quartz‐based samples, as the HA dose increased. In the presence of Fe or Al, the proportion of HA removed from solution increased and was always >91%.

Untreated kaolin flocculated between pH 2.0 and 4.5. This flocculation interval narrowed as the dose of HA increased, widened as the dose of HA‐A1 increased, but was barely affected by HA‐Fe. Similarly, the aggregative effect of HA‐Fe associations on kaolin was smaller than that of HA‐A1 associations, which induced formation of aggregates >100 μm that were essentially absent in the untreated substrate. There was a similar but less marked difference between the aggregative effects of HA‐Fe and HA‐A1 on quartz.