Kooperativer Bibliotheksverbund

Berlin Brandenburg

and
and

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Language: English
    In: Chemosphere, 2010, Vol.81(11), pp.1469-1476
    Description: Soil metabolism of sulfonamides is largely unknown. Hence the sulfonamides sulfanilamide (SAA), sulfadimethoxine (SDT) and sulfapyridine (SPY) were reacted in model experiments with a fungal laccase from . Enzymatic transformation after a reaction time of 15 d ranged from 10.0% for SAA up to 95.6% for SPY and the difference was attributed to the different molecular substituents. Metabolites were first tentatively assigned after LC–ESI –MS full-scan analysis. Secondly, the proposed metabolites were further confirmed employing either multiple reaction monitoring in comparison with standard substances or precursor ion scan LC–ESI –MS/MS experiments striving for the precursor and two to three product ions. Aniline was confirmed as a breakdown product of SPY and further metabolites of SPY and of SDT were identified as rearranged SO extrusion products. Thirdly, some of the metabolites matched those that were previously reported for sulfonamide photodegradation and degradation in soil. It was concluded that enzymatic metabolism as investigated here also occurs in soil.
    Keywords: Sulfanilamide ; Sulfadimethoxine ; Sulfapyridine ; Enzymatic Metabolism ; LC–Esi +–MS/MS ; So 2 Extrusion ; Chemistry ; Ecology
    ISSN: 0045-6535
    E-ISSN: 1879-1298
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Language: English
    In: Journal of Thermal Analysis and Calorimetry, 2014, Vol.118(2), pp.1169-1182
    Description: Physicochemical aging of soil organic matter is assured by the dynamic character of weak interactions stabilizing its supramolecular structure. However, aging is difficult to monitor, due to low organic matter content in most soils and relatively large time constants. In order to overcome those problems, a model soil, sapric histosol, was exposed to the accelerated aging after a short heating event to 110 °C, and its thermal characteristics were monitored over several months. Classical and temperature modulated differential scanning calorimetry, microcalorimetry and solid-state NMR were used to elucidate the character of involved transitions. The heating event caused separation of an initially broad transition into two processes; a melting, which showed almost no response on the previous heating and a step transition, which is associated with the disruption of water molecule bridges (WaMB) between molecular segments of organic matter. Both processes are preceded by a preparatory phase, starting at subambient temperatures, in which aliphatic domains probably recrystallize and water molecules condensate forming WaMB stabilizing the physical structure of sapric histosol. The aliphatic moieties showed a particular behavior reflected in higher imperfection in crystallite structure upon slow cooling, which was attributed to their interaction with surrounding porous and heterogeneous structures. The results show that soil organic matter aging, considered as a natural process driven by thermodynamic principles, is caused by successive development of WaMB. This is potentially accompanied by recrystallization of aliphatic structures and both processes lead to higher physicochemical stability of soil organic matter.
    Keywords: Soil organic matter ; Aging ; Water molecule bridges (WaMB) ; Lipids ; Modulated DSC ; C CPMAS NMR
    ISSN: 1388-6150
    E-ISSN: 1588-2926
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Language: English
    In: Environmental Chemistry, 2015, Vol.13(1), p.50-57
    Description: The mobility of soil organic matter and water molecules has a strong influence on the availability of fertilisers as well as on the fate of pollutants in soil. Magnetic resonance techniques identified two regimes of mobility change on the molecular level occurring on a timescale of 1 year after initially heating the sample. The results can help to understand the effect of soil type and water content for agricultural use and soil protection.
    Keywords: Organic Matter ; Transition Temperatures ; Geochemistry ; Aging ; Soils ; Calorimetry ; Peat ; Bridges ; Organic Matter ; Heating ; Aging ; Networks ; Calorimetry ; Soil Organic Matter ; Dynamics ; Peat ; Structures ; Methods and Instruments;
    ISSN: 1448-2517
    E-ISSN: 1449-8979
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Language: English
    In: Environmental Chemistry, 2014, Vol.11(6), p.709-718
    Description:  The supramolecular structure and resulting physicochemical properties of soil organic matter (SOM) significantly control storage and buffer functions of soils, e.g. for nutrients, organic molecules and water. Multivalent cations, able to form complexes, are suggested to form inter- and intramolecular cross-links in SOM. At present, specific effects of the valence and type of cation on SOM properties are incompletely understood. We investigated changes in SOM interfacial properties, its ability to release mobile colloids in aqueous solutions and its sorption affinity towards organic chemicals in dependence on cation–SOM interactions, temperature and aging time.
    Keywords: colloids; contact angle; sorption; X-ray photoelectron spectroscopy.
    ISSN: 1448-2517
    E-ISSN: 1449-8979
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Language: English
    In: Journal of Thermal Analysis and Calorimetry, 2014, Vol.118(2), pp.1203-1213
    Description: Multivalent cations are suggested to influence the supramolecular structure of soil organic matter (SOM) via inter- and intra-molecular interactions with SOM functional groups. In this study, we tested the combined effect of cations, temperature treatment, and isothermal aging on SOM matrix properties. Samples from a peat and a mineral soil were either enriched with Na, Ca, and Al or desalinated in batch experiments. After treatment at 25, 40, 60, and 105 °C and after different periods of aging at 19 °C and 31 % relative humidity, we investigated the physicochemical matrix stability and the thermal stability against combustion. We hypothesized that multivalent cations stabilize the SOM matrix, that these structures disrupt at elevated temperatures, and that aging leads to an increase in matrix stability. The results show that cation-specific effects on matrix rigidity started to evolve in the peat only after 8 weeks of aging and were significantly lower than the temperature effects. Temperature treatment above 40 °C caused a non (or not immediately) reversible loss of water molecule bridges (WaMB) and above 60 °C a partly reversible melting process probably of semi-crystalline poly(methylene). Thermal stability increased with increasing cation valence and degree of protonation and was much less affected by temperature. Generally, Na-treated and control samples revealed lower thermal stability and lower increase in matrix rigidity with aging than those treated with Ca, Al, and H. We conclude that drying at elevated temperatures (〉40 °C) may irreversibly change SOM structure via disruption of labile cross-links and melting of semi-crystalline domains.
    Keywords: Cation ; Combustion enthalpy ; Differential scanning calorimetry (DSC) ; Soil organic matter (SOM) ; Step transition
    ISSN: 1388-6150
    E-ISSN: 1588-2926
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. Further information can be found on the KOBV privacy pages