Bierl, R

Buis, K

De Sutter, Renaat

Eisold, B

Gallé, E

Kurtenbach, A

Symader, W

Troch, Peter

English

Ghent University Academic Bibliography

1Department of Hydrology, University of Trier, Behringstr. 21, Campus II, 54286 Trier, Germany, email: kurt6101@uni-trier.de2Resource Centre for Environmental Technologies, CRP - Henri Tudor, 66, rue de Luxembourg, 4002 Esch-sur-Alzette, Luxembourg3Ecosystem management research group (ECOBE) - Department of Biology, University of Antwerp, Universiteitsplein 1C, 2610 Wilrijk, Belgium4Hydraulics Laboratory, Department of Civil Engineering - Ghent University, Sint-Pietersnieuwstraat 41, 9000 Gent, BelgiumQuantifying the in-channel retention of cohesive sediments during controlled reservoir releases using FTIR-DRIFT spectrometryKurtenbach, A.1, Gallé, T.2, Bierl, R.1, Buis, K.3, De Sutter, R.4, Troch, P.4, Eisold, B.1,  Symader, W.1KaolinadditionNThe Laboratory experiments 1. Kaolinite features a unique infrared fingerprint around wave number 3695 cm-1 (Fig. 1). 2. The measurements show a good sensitivity at 3695 cm-1 down to only 2 % kaolinite content and a linear signal with increasing amount of kaolinite (Fig. 2).3. FTIR-DRIFT spectroscopy offers additional advantages such as the ability to assess organic fine-grained particles (Fig. 3), a high sample throughput and a very low amount of material needed for the analysis (only 10 mg). The Field experiments & Future perspectives 1. During the selected artificial flood experiment (Fig. 4) two transport phases can be differentiated:A: the bulk of the tracer passes the measuring site featuring a substantial longitudinal dispersion,B: delayed transport of kaolinite with tracer concentrations still significantly higher than the background. The corresponding mass balance (Fig. 4) show that 42 % of the kaolinite passes the station in phase A, 2 percent in phase B. Thus, in spite of the very fine material and the non-stationary boundary conditions over 50 % of the tracer was retained over a flow length of only 570 m. This is equivalent to a loss rate of 14,7 g kaolinite per meter (Fig. 5). 2. Phase B is associated with an additional  increase in dissolved organic carbon (DOC, not shown). The simultaneous rise of this tracer for interstitial water points at the role of the hyporheic zone in intermediate storage of kaolinite. 3. Within our multidisciplinary research group we will model the identified kaolinite retention using the new modular Stream - RIVer - Ecosystem package developed in the modelling platform “FEMME" (Flexible Environment for Mathematically Modelling the Environment, Fig. 6) Fig. 3: FTIR-DRIFT as a means for organic fine particle characterisation. Fig. 4: Cohesive sediment dynamics during an artificial flood, station Wiese,570 m downstream the injection point, 26.07.2006. Fig. 5: Transported absolute kaolinite amounts per station (blue) and loss rates per meter (green) along the brook axis of the Olewiger Bach. 1. DRIFT - technique efficient measuring device for the quantification of kaolinite mass transfer as well as the characterisation of organic fines2. High in-channel retention of cohesive fines even during floods owing to storage processes in channel periphery and dead zones and the hyporheic zoneFig. 2: Sensitivity and linearity of FTIR-DRIFT spectrometry for detecting the kaolinite tracer. Fig. 1: Exemplary DRIFT spectra for kaolinite and an Olewiger Bach - suspended sediment. The investigated Olewiger Bach basin. Introduction & ObjectivesSpecific results--- “ Take home messages ” ---Cohesive sediments play an important role in river ecosystem quality both as pollutant carriers and as clogging material in river channels. However, experimental studies with cohesive sediments in natural river systems are rather scarce owing to the lack of convenient tracers and detection methods. As a result, current modelling approaches only insufficiently describe the fluvial transport dynamics and depositional behaviour of fine sediments. The aims of our research are therefore  1. to investigate transport and retention dynamics of cohesive particles in a natural river system, 2. to evaluate the potential of FTIR-DRIFT spectrometry for quantifying mass transfer of fine particles. We adopted two strategies to specifically study cohesive sediment dynamics in natural systems under defined boundary conditions. First, artificial floods were generated by a waterworks in the Olewiger Bach basin (24 km²), a mid-mountain gravel bed river, in order to characterise the in-channel fine sediment dynamics on their own. The advantage of these artificial flood waves lies in the selective control on some governing processes by experimental design. Second, fine sediment transport and deposition during these controlled reservoir releases were analysed by introducing the clay mineral kaolinite as a fine particle tracer, whose concentration was measured by Fourier transform infrared spectroscopy (FTIR) in diffuse reflectance mode (DRIFT).Research approach Fig. 6: Coupling of field experiment results with a new modelling approach based on a flexible sub module structure using the STRIVE package in FEMME.Lab experiments Field experimentsFine-grained particle transport during an  artificial and a natural flood event. KaoliniteSuspended matterFingerprint region, wavenumber 3695 cm-1 0 2 4 60.00.20.40.60.8y=0.11176x+0.00471R=0.999Absolute Kaolinite [mg]Signal at 3695 cm-1 Kaolinite signal at 3695 cm Linear Fit of Data1_COlewiger Bach suspended sedimentGermany 15 kg6,6 kg3,1 kg570 m14,7 g/m1070 m3,3 g/mKaolin additionN1D – role of dynamics 2D – role of heterogeneityHydraulic module describing discharge and  water level, which forms the basis for:Hyporheic module for sediment-water exchanges and transformation processes within sediments3D-Groundwater model (Modflow) as boundary model to describe the advective water flow through the hyporheic zoneSurface water reaction modulefor transformation processes (algae, organic matter)Output modules to calculate and structure concentrations, fluxes, mass balances, residence times, etc.Transport ofwatersolutessolidsMacrophyte module formula-ting seasonal growth based on light and temperature, to be extended with uptake and release processes of nutrients  and internal  C, N and P dynamics of the plantsA solute transport moduleA solid transport module, with sedimentation and erosion processesSystem moduleformulating the morphology of the system

Quantifying the in-channel retention of cohesive sediments during controlled reservoir releases using FTIR-DRIFT spectometry

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Quantifying the in-channel retention of cohesive sediments during controlled reservoir releases using FTIR-DRIFT spectometry

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