%0 Thesis
%A Burkhardt, Michael
%T Feldversuche zur Erfassung des Transportverhaltens von gelösten und partikulären Tracern mittels Multitracing-Technik in einem schluffigen Boden
%V 4058
%N Juel-4058
%@ 0944-2952
%I Univ. Bonn
%V Dr. (Univ.)
%C Jülich
%M PreJuSER-30845
%M Juel-4058
%B Berichte des Forschungszentrums Jülich
%P XIII, 192 p.
%D 2003
%Z Record converted from VDB: 12.11.2012
%Z Bonn, Univ., Diss., 2003
%X The spatial variability of physical properties in structured soils and the precipitation rate are two important factors that determine the transport behaviour of dissolved and particulate substances through the vadose zone into ground and surface waters. A multitracing-technique was used to identify and characterize the transport phenomena using the herbicide isoproturon, the conservative tracer bromide (Br), the dye tracer Brilliant Blue (BB) and fluorescent microspheres (MS) with 1 and 10 μm diameter. Eight irrigation experiments on plots with an area of 2 m$^{2}$ were performed in a silty soil under different tillage and irrigation conditions. MS were used for the first time on field scale to mimic particulate transport. Four plots were excavated directly after irrigation whilst the other four were excavated after an exposure of 90 days to the weather conditions, which were constantly monitored. For each plot, horizontal cross-sections were photographed at intervals between 5 to 10 cm for digital imaging analysis. Disturbed soil samples were taken from all cross-sections to analyse the applied substances and the chemical soil properties. Br and isoproturon concentrations were determined on 15 samples, whereas MS were determined on 50 samples. Furthermore, undisturbed soil cores were used to determine the physical properties. The quantification of the MS was done by fluorescence microscopy and digital imaging. The BB concentrations were determined photometrically and then related to the colour spectra of the digitised photographs using two second-order, polynomial regression functions. These functions were successfully transferred to all plots to get spatially highly resolved concentration patterns of each horizontal cross-section. The representativeness of the sampling strategy based on 15 samples was confirmed by similar recoveries of the dye tracer on 1 m$^{2}$. The transport behaviour of the applied substances were compared by quantifying depth distributions and spatial moment analysis. The results showed that the depth of tillage directly influenced the mean transport distance and the occurrence of preferential flow: deeper tilled soils showed a larger mean transport distance of the tracers and preferential flow was reduced. The dye coverage and the depth distributions indicated that all substances were transported preferentially up to 120 cm depth if an irrigation rate of at least 6.7 mm h$^{-1}$ followed directly after application. All results for the dissolved and particulate tracers showed, that small quantities of these substances are transported preferentially irrespective of their physico-chemical properties. However, the mean transport distance through the soil matrix is influenced by these properties. The mean effective retardation of BB was about 2 and 4 on the plots excavated 1 day and 90 days, respectively, that of the MS between 1 and 7. A constant ratio of approximately 0.2 was found between the mean transport distance of Br and the maximum distance. The convection-dispersion-equation (CDE) was able to describe the bulk transport of Br with depth. The CDE could not account for the tailing part of the depth distribution probably caused by preferential flow. A possible explanation for the occurrence of preferential flow is that the higher irrigation and precipitation intensity destroy aggregates at the soil surface and water ponded at the surface. This results in a heterogeneous infiltration, although the infiltration capacity of the matrix is not exceeded. The highest concentrations of MS were always determined on these consolidated soil surfaces. The precipitation rates had no influence on the number of preferential flow pathways created, however it directly influenced the transport distance within the existing pathways and the mean transport distance. Dye distribution and zones with local saturation indicated that the plough layer is an important zone, which may induce preferential flow.
%F PUB:(DE-HGF)11 ; PUB:(DE-HGF)3
%9 Dissertation / PhD ThesisBook
%U https://juser.fz-juelich.de/record/30845