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: Geoderma, 01 September 2018, Vol.325, pp.37-48
    Description: Organic particles including microorganisms are a significant fraction of the mobile organic matter (MOM) pool that contributes to initial pedogenesis. Still, the dynamics and the interplay of the multitude of processes that control the mobilization, transport, and retention of MOM are vastly unclear. We studied this interplay using an ‘artificial soil’ as model for a young, unstructured soil with defined initial composition employing a novel two-layer column experiment. The upstream layer was composed of a mixture of well-defined mineral phases, a sterile organic matter source and a diverse, natural microbial inoculant mimicking an organic-rich topsoil. The downstream layer, mimicking the subsoil, was composed of the mineral phases, only. Columns were run under water-unsaturated flow conditions with multiple flow interruptions to reflect natural flow regimes and to detect possible non-equilibrium processes. Pore system changes caused by flow were inspected by scanning electron microscopy and computed micro-tomography. MOM-related physicochemical effluent parameters and bacterial community diversity and abundance were assessed by molecular analysis of the effluent and the solid phase obtained after the long-term irrigation experiment (75 d). Tomographic data showed homogeneous packing of the fine-grained media (sandy loam). During flow, the initially single-grain structured artificial soil showed no connected macropores. In total, 6% of the initial top layer organic matter was mobile. The release and transport of particulate (1.2%) and dissolved organic matter (4.8%) including bacteria were controlled by non-equilibrium conditions. Bacterial cells were released and selectively transported to downstream layer resulting in a depth-dependent and selective establishment of bacterial communities in the previously sterile artificial soil. This study underlines the importance of bacterial transport from the surface or topsoil for colonization and maturation of downstream compartments. This initial colonization of pristine surfaces is the major step in forming biogeochemical interfaces - the prominent locations of intensive biological activity and element turnover that seem to play a major role for the functioning of soil.
    Keywords: Mobile Organic Matter ; Unsaturated Two-Layer Column Experiment ; Experimental Pedogenesis ; Artificial Soil ; Computed Micro-Tomography ; Molecular Analysis ; Agriculture
    ISSN: 0016-7061
    E-ISSN: 1872-6259
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Language: English
    In: Journal of Contaminant Hydrology, December 2016, Vol.195, pp.31-39
    Description: Engineered nanoparticles released into soils may be coated with humic substances, potentially modifying their surface properties. Due to their amphiphilic nature, humic coating is expected to affect interaction of nanoparticle at the air-water interface. In this study, we explored the roles of the air-water interface and solid-water interface as potential sites for nanoparticle attachment and the importance of hydrophobic interactions for nanoparticle attachment at the air-water interface. By exposing Ag nanoparticles to soil solution extracted from the upper soil horizon of a floodplain soil, the mobility of the resulting “soil-aged” Ag nanoparticles was investigated and compared with the mobility of citrate-coated Ag nanoparticles as investigated in an earlier study. The mobility was determined as a function of hydrologic conditions and solution chemistry using column breakthrough curves and numerical modeling. Specifically, we compared the mobility of both types of nanoparticles for different unsaturated flow conditions and for pH = 5 and pH = 9. The soil-aged Ag NP were less mobile at pH = 5 than at pH = 9 due to lower electrostatic repulsion at pH = 5 for both types of interfaces. Moreover, the physical flow field at different water contents modified the impact of chemical forces at the solid-water interface. An extended Derjaguin-Landau-Verwey-Overbeek (eDLVO) model did not provide satisfactory explanation of the observed transport phenomena unlike for the citrate-coated case. For instance, the eDLVO model assuming sphere-plate geometry predicts a high energy barrier (〉 90 ) for the solid-water interface, indicating that nanoparticle attachment is less likely. Furthermore, retardation through reversible sorption at the air-water interface was probably less relevant for soil-aged nanoparticles than for citrate-coated nanoparticles. An additional cation bridging mechanism and straining within the flow field may have enhanced nanoparticle retention at the solid-water interface. The results indicate that the mobility of engineered Ag nanoparticles is sensitive to solution chemistry, especially pH and the concentration of multivalent cations, and to the unsaturated flow conditions influencing particle interaction at biogeochemical interfaces.
    Keywords: Unsaturated Transport ; Water Dynamics ; Cation Bridging ; Amphiphilic ; Edlvo ; Engineering ; Environmental Sciences ; Geography
    ISSN: 0169-7722
    E-ISSN: 1873-6009
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Language: English
    In: Geoderma, 15 July 2019, Vol.346, pp.52-62
    Description: Some soil physical properties can easily be measured using classical laboratory methods. However, explicit valuable information on the real morphology of the pore structure as well as soil physical properties cannot be obtained at the same time with classical methods. This requires non-destructive measurements such as X-ray computed tomography (CT). However, explicit valuable information on the real morphology of the pore structure as well as soil physical properties cannot be obtained at the same time with classical methods. This paper combines parameters obtained from CT analysis (mean macropore diameter, macroporosity, pore connectivity, anisotropy) and classical laboratory methods (dry bulk and aggregate density, saturated hydraulic conductivity, mechanical precompression stress) to analyse soil compaction, exemplified on samples from two tillage treatments (cultivator and plough) and at two moisture states (6 and 1000 kPa matric potential) on a Chernozem collected at a soil depth of 16–22 cm (texture 0–30 cm: silty clay loam). The study shows that the matric potential can have a decisive impact on the mechanical stability of soil. In the loose but less stable plough treatment a more negative matric potential was clearly beneficial to the mechanical stability. In already dense soil structures, as in the cultivator treatment, a reduction of water content was less effective in increasing soil stability. The CT parameters were all closely and uniquely related to each other. The shown CT parameters can be used for a standardized characterization of the soil. Ploughing has a positive effect on soil structure which persists only as long as macroporosity and mean macropore diameter remain high. Plough maintains higher pore connectivity when compacted under dry conditions.
    Keywords: X-Ray CT ; Mechanical Soil Analysis ; Conservation Tillage ; Conventional Tillage ; Soil Compaction ; Precompression Stress ; Agriculture
    ISSN: 0016-7061
    E-ISSN: 1872-6259
    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