A literature retrieval was performed for whole rock geochemical analyses of sedimentary, magmatic and metamorphic rocks in the catchment of River Thuringian Saale for the past 600 Ma. Considering availability and coincidence with paleontological an facies data the following indicators seem suitable to detect environmental and climatic changes: biogenic P for Paleoproductivity, STI Index for weathering intensity, Ni/Co-ratio for redox conditions, relative enrichments of Co, Ba and Rb versus crustal values for volcanic activity at varying differentiation. The Mg/Ca-ratio as proxy for salinity is applicable in evaporites. The binary plot Nb/Y versus Zr/TiO2 indicates a presently eroded volcanic level of the Bohemian Massif as catchment area for the Middle Bunter, whereas higly differentiated volcanics provided source material for Neoproterozoic greywackes. A positive Eu-anomaly is limited to the Lower Bunter and implies mafic source rocks perhaps formerly located in the Bohemian Massif.
Sediment cores were recovered using a hand-held Cobra Pro (Atlas Copco) core drilling system with a 60 mm diameter open corer. One-meter segments were retrieved and assessed in the field for sedimentological features, including estimations of grain size, carbonate content, humus content, and redox features (AG Boden 2005, 2024). Colour descriptions were carried out using the Munsell Soil Color Chart. The exact positions of the drilling points were recorded using a differential GPS device (TOPCON HiPer II). The cores were photographed, documented and sampled at 5–10 cm intervals for subsequent laboratory analyses.
Bulk samples from five selected cores (RK1, RK3, RK13, RK15, RK17) were freeze-dried, sieved (2 mm), and weighed. Total carbon (TC), total nitrogen (TN), and total sulfur (TS) contents were measured using a CNS analyzer (Vario EL cube, Elementar). Inorganic carbon (TIC) was determined using calcimeter measurements (Scheibler method, Eijkelkamp). Organic carbon (TOC) was calculated as TOC = TC − TIC.
For the grain size analyses, sediment samples were first sieved to <2 mm and subsamples of 10 g were treated with 50 ml of 35% hydrogen peroxide (H₂O₂) and gently heated to remove organic matter. Following this, 10 ml of 0.4 N sodium pyrophosphate solution (Na₄P₂O₇) was added to disperse the particles, and the suspension was subjected to ultrasonic treatment for 45 minutes. The sand fraction was analysed by dry sieving and classified into four size classes: coarse sand (2000–630 µm), medium sand (630–200 µm), fine sand (200–125 µm), and very fine sand (125–63 µm). Finer fractions were determined using X-ray granulometry (XRG) with a SediGraph III 5120 (Micromeritics). These included coarse silt (63–20 µm), medium silt (20–6.3 µm), fine silt (6.3–2.0 µm), coarse clay (2.0–0.6 µm), medium clay (0.6–0.2 µm), and fine clay (<0.2 µm).
Veranlassung
Der gelöste und der partikuläre organische Kohlenstoff (dissolved organic carbon, DOC und particulate organic carbon, POC) sind zentrale Komponenten im Naturhaushalt von Gewässern. Die Akkumulation von organischem Kohlenstoff - beziehungsweise die damit verbundene hohe Sauerstoffzehrung - ist insbesondere in den Ästuaren ein wichtiger Belastungsfaktor für den Sauerstoffhaushalt und trägt damit zu deren schlechtem ökologischem Zustand bei. Die Bewertung der zu erwartenden Sauerstoffzehrung kann aber nur mit umfassender Kenntnis der Qualität der organischen Kohlenstoffgehalte in gelöster Form oder als Bestandteil der Schwebstoffe erreicht werden. Des Weiteren spielt die Zusammensetzung des organischen Materials eine wichtige Rolle bei der Sorption und dem Transport von Schadstoffen, sodass eine umfassende Beschreibung des organischen Kohlenstoffs auch die Vorhersage der Ausbreitung von Schadstoffen ermöglicht. Im Projekt OrgCarbon soll eine umfassende Charakterisierung des organischen Kohlenstoffs jenseits der traditionell erfassten Parameter (TOC, DOC und POC) stattfinden, da bekannt ist, dass sowohl POC als auch DOC eine komplexe, bisher wenig erforschte Vielzahl unterschiedlicher Stoffklassen beinhaltet. In einem ersten Schritt erfolgt eine Fraktionierung von partikulärem und gelöstem organischem Material, basierend auf der chemischen Zusammensetzung und mikrobiellen Abbaubarkeit. Wichtige Parameter wie Sauerstoffverbrauch, mikrobielle Atmung, chemische Zusammensetzung und die Herkunft des organischen Materials werden für jede Kohlenstofffraktion bestimmt. Durch die daraus resultierende Verbesserung des Verständnisses bezüglich organischem Kohlenstoff in Ästuaren und Flüssen zielt das OrgCarbon-Projekt darauf ab, zu besseren Umweltmanagement- und Naturschutzstrategien für die Bundeswasserstraßen beizutragen.
Ziele
Ein zentrales Ziel des OrgCarbon-Projekts ist es, eine Vielzahl interdisziplinärer Methoden zu testen, um die vielfältigen Eigenschaften des Kohlenstoffes zu erfassen. Es werden verschiedene chemisch-analytische Verfahren mit Messungen zur biologischen Aktivität und Abbaubarkeit des Kohlenstoffs sowie mit mineralogischen Untersuchungen kombiniert. Dadurch lässt sich ein Set an Methoden identifizieren, das zukünftig auch mit weniger Aufwand eine detaillierte Charakterisierung des Kohlenstoffs ermöglicht. Als Ergebnis von OrgCarbon angestrebt ist die Entwicklung eines standardisierten Protokolls, das den gesamten Prozess von der Probenahme über die Kohlenstofffraktionierung bis hin zur Analyse und Datenauswertung umfasst. Dieses ermöglicht es, die Qualität des organischen Kohlenstoffs sowie dessen Eigenschaften und Abbaubarkeit in Zukunft besser abzuschätzen und gemeinsam zu interpretieren. Dieses Protokoll soll in bestehende Messprogramme der BfG integriert werden, um regelmäßig die Herkunft, das Sorptionspotenzial für Schadstoffe sowie die Abbaubarkeit und die Sauerstoffzehrung von organischem Kohlenstoff zu bestimmen.
Organischer Kohlenstoff spielt eine entscheidende Rolle in Ästuaren und Flüssen. Seine Zusammensetzung beeinflusst Prozesse wie die (mikro)biologische Produktivität, den Sauerstoffverbrauch, den Schadstofftransport und die Agglomeration von Schwebstoffen. Die Bestimmung erfolgt routinemäßig nur als Summenparameter (total organic carbon, TOC) weshalb über die Zusammensetzung des organischen Materials, dessen Abbauverhalten und Quellen meist wenig bekannt ist. Darüber hinaus reicht die Betrachtung des Gesamtkohlenstoffgehalts in vielen Fällen nicht aus, um eine Vergleichbarkeit von Schwebstoffen aus unterschiedlichen Quellen zu gewährleisten. Das OrgCarbon-Projekt widmet sich darum einer umfassenden Analyse des organischen Kohlenstoffs in Feldproben aus Ästuaren und Flüssen mit unterschiedlichen Kohlenstoffgehalten und Zusammensetzungen, wie der Tide-Ems und der Tide-Elbe. (Text gekürzt)
To investigate subsurface features in the Lower Havel River floodplain, we conducted Electrical Resistivity Tomography (ERT) transects and Electromagnetic Induction (EMI) surveys at three different depths in 2023 and 2024. These near surface geophysical methods were complemented by 24 driving core drillings to relate the electrical properties with sedimentological characteristics. Additionally, five selected sediment cores were used for subsequent geochemical lab analyses (grain size, CNS, TOC, TIC).
Electromagnetic induction (EMI) was measured with a CMD-Mini Explorer (GF Instruments s.r.o., Brno, Czech Republic) in June 2023 and June 2024. We used the vertical dipole (VDP) at coil spacings of 0.32 m (VDP1), 0.71 m (VDP2) and 1.18 m (VDP3), archieving effective penetration depths of 0.5 m (VDP1), 1.0 m (VDP2) and 1.8 m (VDP3). According to the manufacturer, 70% of the signal originate from above these depths. The EMI sensors measure the apparent electrical conductivity (ECa, in mS/m). Measurements were taken by carrying the instrument about 0.2 m above ground while being directly connected to D-GPS (Leica GPS1200) for positioning. The acquisition rate was five measurements per second. Data quality was checked by measuring a reference line before and after each measurement. The area investigated by EMI in June 2023 is located to the north and northeast of the Gülpe research station. It has a total area of 12.3 ha. The reference line was located in the southern part of the study area. No drift correction had to be applied due to good data quality. Reference lines and single outliers were removed. The area investigated by EMI in June 2024 is located southeast of the research station. The survey area there is 8.1 ha in size. The reference line for the measurements there was located in the north-westernmost area of the site. No drift correction had to be applied due to good data quality. Reference lines and single outliers were removed.
The Electrical Resistivity Tomography (ERT) data were acquired by using a PC controlled DC resistivity meter system (RESECS, Geoserve, Kiel, Germany). In total, we measured four ERT transects. Two transects in June 2023, where transect 1 had a total length of 259 m with an electrode spacing of 0.5 m and transect 2 had a total length of 223 m with an electrode spacing of 1 m. The measurements in 2023 were carried out under extreme dry conditions. Two further transects were measured in June 2024 with an electrode spacing of 1m, transect 3 with a total length of 207 m and transect 4 with a total length of 239 m. We applied wenner alpha and dipol-dipol configuration. The coordinates and the height of the electrodes were measured with a D-GPS (2023: TOPCON HiPer II / 2024: Leica GPS1200).
Sediment cores were recovered using a hand-held Cobra Pro (Atlas Copco) core drilling system with a 60 mm diameter open corer. One-meter segments were retrieved and assessed in the field for sedimentological features, including estimations of grain size, carbonate content, humus content, and redox features (AG Boden 2005, 2024). Colour descriptions were carried out using the Munsell Soil Color Chart. The exact positions of the drilling points were recorded using a differential GPS device (TOPCON HiPer II). The cores were photographed, documented and sampled at 5–10 cm intervals for subsequent laboratory analyses.
Bulk samples from five selected cores (RK1, RK3, RK13, RK15, RK17) were freeze-dried, sieved (2 mm), and weighed. Total carbon (TC), total nitrogen (TN), and total sulfur (TS) contents were measured using a CNS analyzer (Vario EL cube, Elementar). Inorganic carbon (TIC) was determined using calcimeter measurements (Scheibler method, Eijkelkamp). Organic carbon (TOC) was calculated as TOC = TC − TIC.
For the grain size analyses, sediment samples were first sieved to <2 mm and subsamples of 10 g were treated with 50 ml of 35% hydrogen peroxide (H₂O₂) and gently heated to remove organic matter. Following this, 10 ml of 0.4 N sodium pyrophosphate solution (Na₄P₂O₇) was added to disperse the particles, and the suspension was subjected to ultrasonic treatment for 45 minutes. The sand fraction was analysed by dry sieving and classified into four size classes: coarse sand (2000–630 µm), medium sand (630–200 µm), fine sand (200–125 µm), and very fine sand (125–63 µm). Finer fractions were determined using X-ray granulometry (XRG) with a SediGraph III 5120 (Micromeritics). These included coarse silt (63–20 µm), medium silt (20–6.3 µm), fine silt (6.3–2.0 µm), coarse clay (2.0–0.6 µm), medium clay (0.6–0.2 µm), and fine clay (<0.2 µm).