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  • 1
    Electronic Resource
    Electronic Resource
    Adsorption of Triclopyr on Soil and Some of Its Components (1994)
    s.l. : American Chemical Society
    Journal of agricultural and food chemistry 42 (1994), S. 1026-1029 
    Details
    ISSN: 1520-5118
    Source: ACS Legacy Archives
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jf00040a036
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of metal-binding ability on the adsorption of acifluorfen on soil (1993)
    s.l. : American Chemical Society
    Journal of agricultural and food chemistry 41 (1993), S. 502-505 
    Details
    ISSN: 1520-5118
    Source: ACS Legacy Archives
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jf00027a029
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  • 3
    Electronic Resource
    Electronic Resource
    Binding ability of pesticides. X-ray, spectroscopic, and polarographic studies of the copper(II) interaction with acifluorfen (1990)
    s.l. : American Chemical Society
    Journal of agricultural and food chemistry 38 (1990), S. 1989-1992 
    Details
    ISSN: 1520-5118
    Source: ACS Legacy Archives
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jf00100a023
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  • 4
    Electronic Resource
    Electronic Resource
    Activity and stability of jack bean urease in the presence of peat humic acids obtained using different extractants (2000)
    Springer
    Biology and fertility of soils 32 (2000), S. 415-420 
    Details
    ISSN: 1432-0789
    Keywords: Keywords Urease ; Activity stability ; Humic acids ; Extractants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The effects of two humic acid extractants, 0.1 M Na4P2O7 plus 0.1 M NaOH (NaPP) and 0.1 M NaOH (NaOH), on the activity and stability of a humic-urease complex were studied. The two humic acids isolated (HANaPP and HANaOH) exhibited different elemental compositions, metal concentrations and structural modifications in the FT-IR spectra. Depending on the pH, HANaPP and HANaOH influenced both the urease activity and urease kinetic parameters (V max and K m) in the same way. They inhibited urease activity between pH 6 and 7 and reduced the V max of the reaction at pH 6 and 7. The presence of humic acids improved the affinity of the enzyme for the substrate (K m). The stability of the urease with time, and in the presence of pronase, was improved by HANaPP and HANaOH with respect to free enzyme. These results confirm the importance of the interaction of urease with humic acids as a fundamental gateway for extracellular urease stabilisation. Since no difference in the extent of urease inhibition and urease stabilisation was observed for the two humic acids, it may be concluded that neither urease activity nor stability are influenced by the humic acid extractant used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740000272
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  • 5
    Electronic Resource
    Electronic Resource
    Phosphate adsorption and precipitation in calcareous soils: the role of calcium ions in solution and carbonate minerals (1999)
    Springer
    Nutrient cycling in agroecosystems 53 (1999), S. 219-227 
    Details
    ISSN: 1573-0867
    Keywords: calcium ions ; carbonates ; P adsorption ; P precipitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract P-removal from soil solution is mainly due to adsorption and precipitation reactions. For calcareous soils two pathways have been proposed as being relevant: partitioning on soil surfaces and precipitation induced by Ca2+ ions in solution. To define P-speciation in soil and reduce P-immobilisation following fertilisation, the relative importance of these two reactions needs to be quantitatively established. This investigation, conducted on two calcareous soils, suggests that Ca-ion activity in the liquid phase is mainly responsible for the formation of insoluble Ca-P phases. Our study was carried out by determining: a) batch sorption isotherms at different slurry concentrations, times of contact, pH and indifferent electrolyte concentrations; b) supernatant isotherms on soil suspensions; c) insolubilisation kinetics of P added to soil columns. The shape of the sorption isotherms indicated that adsorption predominated at low concentrations (below approximately 0.5 mM); above this level precipitation became predominant. Precipitation from solution was demonstrated by adding increasing amounts of phosphate to soil suspension supernatants and precipitation levels comparable to those observed in sorption isotherms were obtained. Thus, carbonate mineral surfaces were not necessary for the induction of P precipitation. The formation of Ca-P mineral phases was increased with reaction time and was governed by the concentration of Ca-ions, pH and indifferent electrolyte concentration. P added at the top of soil columns was rapidly insolubilised: after 5 weeks the P-Olsen value was reduced to about 60% and P was not transported to the deepest layers but remained in the surface ones. These results suggest that, for soils with a high reservoir of exchangeable cations able to form insoluble P phases, precipitation is the predominant mechanism which reduces P availability for plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009709005147
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  • 6
    Electronic Resource
    Electronic Resource
    Extraction of humic acids from a natural matrix by alkaline pyrophosphate. Evaluation of the molecular weight of fractions obtained by ultrafiltration (1997)
    Springer
    Fresenius' journal of analytical chemistry 359 (1997), S. 555-560 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract  Fractions of humic acids, resolved by ultrafiltration of extracts from a sample of peat treated with alkaline pyrophosphate solution, have been submitted to high-performance size-exclusion chromatography, with the aim of determining the molecular weight distributions. Anomalous peaks, located at retention volumes higher than those corresponding to the main signal, are present in the elution profiles relative to the lightest fractions. These peaks are more intense when using a refractive index detector rather than a UV detector. Elemental analysis data for the lightest fractions suggested that the spurious peaks are due to the presence of inorganic material. The hypothesis that pyrophosphate interacts with humic acids in the course of the extraction has been confirmed by colorimetric determination of the phosphorus content in the different fractions. As a consequence, the extraction procedure has been modified by using 0.1 mol/L NaOH as extractant. The average molecular weights of the various fractions, following NaOH extraction, result in substantial agreement with those obtained following pyrophosphate solution extraction (if the ‘pyrophosphate peaks’ present in the chromatographic profile are discarded in the calculations).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050631
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  • 7
    Electronic Resource
    Electronic Resource
    Adsorption and desorption of dimepiperate by soils (1994)
    Springer
    Water, air & soil pollution 73 (1994), S. 325-331 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The adsorption and desorption of dimepiperate, S-(α,α-dimethylbenzyl)-1-piperidinecarbothioate, on three soils of various physical and chemical properties was studied. Adsorption isotherms conformed to Freundlich equation. The k f values increased with increasing organic carbon content of the soils. To confirm the effect of organic matter, the adsorption of the herbicide was studied after removal of organic matter by peroxidation. This soil treatment caused a sequential loss of adsorptive capacity. Desorption isotherms also conformed to Freundlich equation, but K des values were higher than those for adsorption and increased with increase in concentration of initially adsorbed dimepiperate. Hysteresis was indicated by the decrease in slope of desorption compared to adsorption isotherms. Hysteresis decreased with increasing methanol content in the extracting solution. The factors involved are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00477996
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  • 8
    Electronic Resource
    Electronic Resource
    Investigation of fulvic acids from peat using capillary electrophoresis (CE) (1997)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 20 (1997), S. 67-71 
    Details
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; Fulvic acids ; Humic Substances ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The aim of this work was to characterize the fulvic acids (FA) extracted from peat by use of capillary electrophoresis (CE). Two FA extracts have been obtained using two different extractants (0.1 M NaOH and 0.1 M NaOH plus 0.1 M Na4P2O7, Na+PP). The CE runs wre performed using a coated silica capillary, and several buffer solutions at different PH values. The results obtained show that the Fa extracts may be well characterized by CE even if the isolelectric point of the fulvic compounds is very low. The best fractionation has been obtained using a buffer borate at PH 8.9 as funning buffer. The charcterization of the two extracts also showed some important differences between the NaOH extract and the Na+PP extract.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240200204
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