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Understanding the sources, structure and fate of dissolved organic matter (DOM) in groundwater is paramount for the protection and sustainable use of this vital resource. On its passage through the Critical Zone, DOM is subject to biogeochemical conversions. Therefore, it carries valuable cross-habitat information for monitoring and predicting the stability of groundwater ecosystem services and assessing these ecosystems' response to fluctuations caused by external impacts such as climatic extremes. Challenges arise from insufficient knowledge on groundwater metabolite composition and dynamics due to a lack of consistent analytical approaches for long-term monitoring. Our study establishes groundwater metabolomics to decipher the complex biogeochemical transport and conversion of DOM. We explore fractured sedimentary bedrock along a hillslope recharge area by a 5-year untargeted metabolomics monitoring of oxic perched and anoxic phreatic groundwater. A summer with extremely high temperatures and low precipitation was included in the monitoring. Water was accessed by a monitoring well-transect and regularly collected for liquid chromatography-mass spectrometry (LC-MS) investigation. Dimension reduction of the resulting complex data set by principal component analysis revealed that metabolome dissimilarities between distant wells coincide with transient cross-stratal flow indicated by groundwater levels. Time series of the groundwater metabolome data provides detailed insights into subsurface responses to recharge dynamics. We demonstrate that dissimilarity variability between groundwater bodies with contrasting aquifer properties coincides with recharge dynamics. This includes groundwater high- and lowstands as well as recharge and recession phases. Our monitoring approach allows to survey groundwater ecosystems even under extreme conditions. Notably, the metabolome was highly variable lacking seasonal patterns and did not segregate by geographical location of sampli

Across a landscape, aquatic-terrestrial interfaces within and between ecosystems are hotspots of organic matter (OM) mineralization. These interfaces are characterized by sharp spatio-temporal changes in environmental conditions, which affect OM properties and thus control OM mineralization and other transformation processes. Consequently, the extent of OM movement at and across aquatic-terrestrial interfaces is crucial in determining OM turnover and carbon (C) cycling at the landscape scale. Here, we propose expanding current concepts in aquatic and terrestrial ecosystem sciences to comprehensively evaluate OM turnover at the landscape scale. We focus on three main concepts toward explaining OM turnover at the landscape scale: the landscape spatio-temporal context, OM turnover described by priming and ecological stoichiometry, and anthropogenic effects as a disruptor of natural OM transfer magnitudes and pathways. A conceptual framework is introduced that allows for discussing the disparities in spatial and temporal scales of OM transfer, changes in environmental conditions, ecosystem connectivity, and microbial–substrate interactions. The potential relevance of priming effects in both terrestrial and aquatic systems is addressed. For terrestrial systems, we hypothesize that the interplay between the influx of OM and its corresponding elemental composition and the elemental demand of the microbial communities – stoichiometric question – may alleviate spatial and metabolic thresholds. In comparison, substrate level OM dynamics may be substantially different in aquatic systems due to matrix effects that accentuate the role of abiotic conditions, substrate quality, and microbial community dynamics. We highlight the disproportionate impact anthropogenic activities can have on OM cycling across the landscape including reversing natural OM flows through the landscape, disrupting ecosystem connectivity, and nutrient additions that cascade across the landscape. This knowle

Across a landscape, aquatic-terrestrial interfaces within and between ecosystems are hotspots of organic matter (OM) mineralization. These interfaces are characterized by sharp spatio-temporal changes in environmental conditions, which affect OM properties and thus control OM mineralization and other transformation processes. Consequently, the extent of OM movement at and across aquatic-terrestrial interfaces is crucial in determining OM turnover and carbon (C) cycling at the landscape scale. Here, we propose expanding current concepts in aquatic and terrestrial ecosystem sciences to comprehensively evaluate OM turnover at the landscape scale. We focus on three main concepts toward explaining OM turnover at the landscape scale: the landscape spatio-temporal context, OM turnover described by priming and ecological stoichiometry, and anthropogenic effects as a disruptor of natural OM transfer magnitudes and pathways. A conceptual framework is introduced that allows for discussing the disparities in spatial and temporal scales of OM transfer, changes in environmental conditions, ecosystem connectivity, and microbial–substrate interactions. The potential relevance of priming effects in both terrestrial and aquatic systems is addressed. For terrestrial systems, we hypothesize that the interplay between the influx of OM and its corresponding elemental composition and the elemental demand of the microbial communities – stoichiometric question – may alleviate spatial and metabolic thresholds. In comparison, substrate level OM dynamics may be substantially different in aquatic systems due to matrix effects that accentuate the role of abiotic conditions, substrate quality, and microbial community dynamics. We highlight the disproportionate impact anthropogenic activities can have on OM cycling across the landscape including reversing natural OM flows through the landscape, disrupting ecosystem connectivity, and nutrient additions that cascade across the landscape. This knowle

Across a landscape, aquatic-terrestrial interfaces within and between ecosystems are hotspots of organic matter (OM) mineralization. These interfaces are characterized by sharp spatio-temporal changes in environmental conditions, which affect OM properties and thus control OM mineralization and other transformation processes. Consequently, the extent of OM movement at and across aquatic-terrestrial interfaces is crucial in determining OM turnover and carbon (C) cycling at the landscape scale. Here, we propose expanding current concepts in aquatic and terrestrial ecosystem sciences to comprehensively evaluate OM turnover at the landscape scale. We focus on three main concepts toward explaining OM turnover at the landscape scale: the landscape spatio-temporal context, OM turnover described by priming and ecological stoichiometry, and anthropogenic effects as a disruptor of natural OM transfer magnitudes and pathways. A conceptual framework is introduced that allows for discussing the disparities in spatial and temporal scales of OM transfer, changes in environmental conditions, ecosystem connectivity, and microbial–substrate interactions. The potential relevance of priming effects in both terrestrial and aquatic systems is addressed. For terrestrial systems, we hypothesize that the interplay between the influx of OM and its corresponding elemental composition and the elemental demand of the microbial communities – stoichiometric question – may alleviate spatial and metabolic thresholds. In comparison, substrate level OM dynamics may be substantially different in aquatic systems due to matrix effects that accentuate the role of abiotic conditions, substrate quality, and microbial community dynamics. We highlight the disproportionate impact anthropogenic activities can have on OM cycling across the landscape including reversing natural OM flows through the landscape, disrupting ecosystem connectivity, and nutrient additions that cascade across the landscape. This knowle

Across a landscape, aquatic-terrestrial interfaces within and between ecosystems are hotspots of organic matter (OM) mineralization. These interfaces are characterized by sharp spatio-temporal changes in environmental conditions, which affect OM properties and thus control OM mineralization and other transformation processes. Consequently, the extent of OM movement at and across aquatic-terrestrial interfaces is crucial in determining OM turnover and carbon (C) cycling at the landscape scale. Here, we propose expanding current concepts in aquatic and terrestrial ecosystem sciences to comprehensively evaluate OM turnover at the landscape scale. We focus on three main concepts toward explaining OM turnover at the landscape scale: the landscape spatio-temporal context, OM turnover described by priming and ecological stoichiometry, and anthropogenic effects as a disruptor of natural OM transfer magnitudes and pathways. A conceptual framework is introduced that allows for discussing the disparities in spatial and temporal scales of OM transfer, changes in environmental conditions, ecosystem connectivity, and microbial–substrate interactions. The potential relevance of priming effects in both terrestrial and aquatic systems is addressed. For terrestrial systems, we hypothesize that the interplay between the influx of OM and its corresponding elemental composition and the elemental demand of the microbial communities – stoichiometric question – may alleviate spatial and metabolic thresholds. In comparison, substrate level OM dynamics may be substantially different in aquatic systems due to matrix effects that accentuate the role of abiotic conditions, substrate quality, and microbial community dynamics. We highlight the disproportionate impact anthropogenic activities can have on OM cycling across the landscape including reversing natural OM flows through the landscape, disrupting ecosystem connectivity, and nutrient additions that cascade across the landscape. This knowle

Across a landscape, aquatic-terrestrial interfaces within and between ecosystems are hotspots of organic matter (OM) mineralization. These interfaces are characterized by sharp spatio-temporal changes in environmental conditions, which affect OM properties and thus control OM mineralization and other transformation processes. Consequently, the extent of OM movement at and across aquatic-terrestrial interfaces is crucial in determining OM turnover and carbon (C) cycling at the landscape scale. Here, we propose expanding current concepts in aquatic and terrestrial ecosystem sciences to comprehensively evaluate OM turnover at the landscape scale. We focus on three main concepts toward explaining OM turnover at the landscape scale: the landscape spatio-temporal context, OM turnover described by priming and ecological stoichiometry, and anthropogenic effects as a disruptor of natural OM transfer magnitudes and pathways. A conceptual framework is introduced that allows for discussing the disparities in spatial and temporal scales of OM transfer, changes in environmental conditions, ecosystem connectivity, and microbial–substrate interactions. The potential relevance of priming effects in both terrestrial and aquatic systems is addressed. For terrestrial systems, we hypothesize that the interplay between the influx of OM and its corresponding elemental composition and the elemental demand of the microbial communities – stoichiometric question – may alleviate spatial and metabolic thresholds. In comparison, substrate level OM dynamics may be substantially different in aquatic systems due to matrix effects that accentuate the role of abiotic conditions, substrate quality, and microbial community dynamics. We highlight the disproportionate impact anthropogenic activities can have on OM cycling across the landscape including reversing natural OM flows through the landscape, disrupting ecosystem connectivity, and nutrient additions that cascade across the landscape. This knowle

All soils harbor microaggregates, i.e., compound soil structures smaller than 250 µm. These microaggregates are composed of diverse mineral, organic and biotic materials that are bound together during pedogenesis by various physical, chemical and biological processes. Consequently, microaggregates can withstand strong mechanical and physicochemical stresses and survive slaking in water, allowing them to persist in soils for several decades. Together with the physiochemical heterogeneity of their surfaces, the three-dimensional structure of microaggregates provides a large variety of ecological niches that contribute to the vast biological diversity found in soils. As reported for larger aggregate units, microaggregates are composed of smaller building units that become more complex with increasing size. In this context, organo-mineral associations can be considered structural units of soil aggregates and as nanoparticulate fractions of the microaggregates themselves. The mineral phases considered to be the most important as microaggregate forming materials are the clay minerals and Fe- and Al-(hydr)oxides. Within microaggregates, minerals are bound together primarily by physicochemical and chemical interactions involving cementing and gluing agents. The former comprise, among others, carbonates and the short-range ordered phases of Fe, Mn, and Al. The latter comprise organic materials of diverse origin and probably involve macromolecules and macromolecular mixtures. Work on microaggregate structure and development has largely focused on organic matter stability and turnover. However, little is known concerning the role microaggregates play in the fate of elements like Si, Fe, Al, P, and S. More recently, the role of microaggregates in the formation of microhabitats and the biogeography and diversity of microbial communities has been investigated. Little is known regarding how microaggregates and their properties change in time, which strongly limits our understandin

This study investigates the release mechanisms and kinetics of PAH, DOC, and colloids/particles from a NAPL-contaminated gravelly soil with dialysis experiments, column outflow experiments in the laboratory and with free-drainage lysimeters under natural conditions. Results showed low release rates, long times of equilibration and a rate-limited release of PAH (<0.7 µm) and DOC. Under natural conditions, extended no-flow periods and freezing events induced the export of PAH. The high mechanical strain within the PAH source materials followed by high intensity rain or snowmelt events resulted in high amounts of particle-associated PAH (>0.7 µm) released from the lysimeters. PAH export is coupled to the formation and mobility of colloids and (NAPL-) particles. The release and transport process of particle-associated PAH should be more thoroughly considered in risk assessment at contaminated sites., Die vorliegende Arbeit befasst sich mit den Mechanismen und der Kinetik der Freisetzung von PAK, DOC und Kolloiden/Partikeln aus teerölkontaminiertem, kiesigem Substrat anhand von Dialyseexperimenten, gesättigten Säulenexperimenten im Labor und Lysimetern unter natürlichen Bedingungen. Die Ergebnisse zeigten niedrige Freisetzungsraten, hohe Equilibrierungszeiten für PAK und eine ratenlimitierte Freisetzung von PAK (<0,7 µm) und DOC. Im Feldversuch hatten lange Trockenperioden und Frostereignisse einen starken Einfluss auf den PAK-Austrag. Durch die mechanische Belastung des Quellmaterials und folgende Starkregenereignisse oder Schneeschmelzen wurden sehr hohe Mengen von partikelgebundenen PAK (>0,7 µm) ausgetragen. Der PAK-Austrag ist stark an die Bildung und Mobilität von Kolloiden und suspendierten (Teeröl-) Partikeln gebunden. Dieser Aspekt sollte daher bei der Bewertung des Stoffaustrages mit dem Sickerwasser innerhalb der Beurteilung kontaminierter Standorte in Betracht gezogen werden.

Microbial Fe oxide reduction is essential in soil and groundwater ecosystems and plays an important role in microbial degradation of organic contaminants. This work showed that citrate, abundant in soils, leads to colloid stabilization out of macroaggregate ferrihydrite and enhances microbial Fe reduction. Results indicated that reactivity of ferrihydrite decreases with decreasing aggregation state below a critical size. Therefore, reactivity of Fe oxides and therefore microbial turnover rates are strongly influenced by their aggregate size and presence of organic acids., Die mikrobielle Fe-Oxidreduktion ist essentiell in Boden- und Grundwasserökosystemen und spielt eine wichtige Rolle im mikrobiellen Abbau organischer Schadstoffe. Diese Arbeit zeigte, dass Citrat zur Kolloidstabilisierung aus Ferrihydrit-Makroaggregaten und deswegen zur erhöhten mikrobiellen Reduktion führt. Weitere Ergebnisse deuten darauf hin, dass die Reaktivität von Ferrihydrit mit abnehmender Aggregierung, unterhalb einer kritischen Größe, abnimmt. Somit wird die Reaktivität von Fe-Oxiden stark von Aggregatgröße und organischen Säuren beeinflusst.

Microbial Fe oxide reduction is essential in soil and groundwater ecosystems and plays an important role in microbial degradation of organic contaminants. This work showed that citrate, abundant in soils, leads to colloid stabilization out of macroaggregate ferrihydrite and enhances microbial Fe reduction. Results indicated that reactivity of ferrihydrite decreases with decreasing aggregation state below a critical size. Therefore, reactivity of Fe oxides and therefore microbial turnover rates are strongly influenced by their aggregate size and presence of organic acids., Die mikrobielle Fe-Oxidreduktion ist essentiell in Boden- und Grundwasserökosystemen und spielt eine wichtige Rolle im mikrobiellen Abbau organischer Schadstoffe. Diese Arbeit zeigte, dass Citrat zur Kolloidstabilisierung aus Ferrihydrit-Makroaggregaten und deswegen zur erhöhten mikrobiellen Reduktion führt. Weitere Ergebnisse deuten darauf hin, dass die Reaktivität von Ferrihydrit mit abnehmender Aggregierung, unterhalb einer kritischen Größe, abnimmt. Somit wird die Reaktivität von Fe-Oxiden stark von Aggregatgröße und organischen Säuren beeinflusst.

The effect of different components on the properties of biogeochemical interfaces in soil was examined in natural arable soils and artificial soils composed of different mixtures of clean model materials, manure as organic carbon source and a microbial inoculum. In the natural soils, iron oxides were found to be important providers of interfaces, and phenanthrene sorption showed that both the surface area available in soil and the organic matter content determined the sorption interface for hydrophobic organic chemicals. The incubated artificial soils developed quickly from mixtures of clean model materials into soil-like systems where minerals, organic matter and microorganisms were closely associated. Overall, the results presented in this dissertation demonstrate that biogeochemical interfaces in soil are not only determined by the different components present, but foremost by the interaction between these components., Die Wirkung verschiedener Komponenten auf die Eigenschaften biogeochemischer Grenzflächen im Boden wurde in natürlichen Ackerböden und künstlichen Böden bestehend aus verschiedenen Mischungen von sauberen Modelmaterialien, Stallmist als organischer Kohlenstoffquelle und ein mikrobielles Inokulum untersucht. In den natürlichen Böden wurde die Relevanz von Eisenoxiden für die verfügbare Oberfläche bestimmt, und der Effekt von spezifischer Oberfläche und Kohlenstoffgehalt auf die Phenanthrensorption untersucht. Die inkubierten künstlichen Böden entwickelten sich von Mischungen aus sauberen Modelmaterialien zu Boden-ähnlichen Systemen, in denen Minerale, organische Substanz und Mikroorganismen stark assoziiert waren. Insgesamt zeigen die Ergebnisse, dass biogeochemische Grenzflächen im Boden nicht nur durch die verschiedenen Komponenten bestimmt werden, sondern vor allem auch durch die Interaktionen zwischen diesen Komponenten.

The effect of different components on the properties of biogeochemical interfaces in soil was examined in natural arable soils and artificial soils composed of different mixtures of clean model materials, manure as organic carbon source and a microbial inoculum. In the natural soils, iron oxides were found to be important providers of interfaces, and phenanthrene sorption showed that both the surface area available in soil and the organic matter content determined the sorption interface for hydrophobic organic chemicals. The incubated artificial soils developed quickly from mixtures of clean model materials into soil-like systems where minerals, organic matter and microorganisms were closely associated. Overall, the results presented in this dissertation demonstrate that biogeochemical interfaces in soil are not only determined by the different components present, but foremost by the interaction between these components., Die Wirkung verschiedener Komponenten auf die Eigenschaften biogeochemischer Grenzflächen im Boden wurde in natürlichen Ackerböden und künstlichen Böden bestehend aus verschiedenen Mischungen von sauberen Modelmaterialien, Stallmist als organischer Kohlenstoffquelle und ein mikrobielles Inokulum untersucht. In den natürlichen Böden wurde die Relevanz von Eisenoxiden für die verfügbare Oberfläche bestimmt, und der Effekt von spezifischer Oberfläche und Kohlenstoffgehalt auf die Phenanthrensorption untersucht. Die inkubierten künstlichen Böden entwickelten sich von Mischungen aus sauberen Modelmaterialien zu Boden-ähnlichen Systemen, in denen Minerale, organische Substanz und Mikroorganismen stark assoziiert waren. Insgesamt zeigen die Ergebnisse, dass biogeochemische Grenzflächen im Boden nicht nur durch die verschiedenen Komponenten bestimmt werden, sondern vor allem auch durch die Interaktionen zwischen diesen Komponenten.

This study investigates the release mechanisms and kinetics of PAH, DOC, and colloids/particles from a NAPL-contaminated gravelly soil with dialysis experiments, column outflow experiments in the laboratory and with free-drainage lysimeters under natural conditions. Results showed low release rates, long times of equilibration and a rate-limited release of PAH (<0.7 µm) and DOC. Under natural conditions, extended no-flow periods and freezing events induced the export of PAH. The high mechanical strain within the PAH source materials followed by high intensity rain or snowmelt events resulted in high amounts of particle-associated PAH (>0.7 µm) released from the lysimeters. PAH export is coupled to the formation and mobility of colloids and (NAPL-) particles. The release and transport process of particle-associated PAH should be more thoroughly considered in risk assessment at contaminated sites., Die vorliegende Arbeit befasst sich mit den Mechanismen und der Kinetik der Freisetzung von PAK, DOC und Kolloiden/Partikeln aus teerölkontaminiertem, kiesigem Substrat anhand von Dialyseexperimenten, gesättigten Säulenexperimenten im Labor und Lysimetern unter natürlichen Bedingungen. Die Ergebnisse zeigten niedrige Freisetzungsraten, hohe Equilibrierungszeiten für PAK und eine ratenlimitierte Freisetzung von PAK (<0,7 µm) und DOC. Im Feldversuch hatten lange Trockenperioden und Frostereignisse einen starken Einfluss auf den PAK-Austrag. Durch die mechanische Belastung des Quellmaterials und folgende Starkregenereignisse oder Schneeschmelzen wurden sehr hohe Mengen von partikelgebundenen PAK (>0,7 µm) ausgetragen. Der PAK-Austrag ist stark an die Bildung und Mobilität von Kolloiden und suspendierten (Teeröl-) Partikeln gebunden. Dieser Aspekt sollte daher bei der Bewertung des Stoffaustrages mit dem Sickerwasser innerhalb der Beurteilung kontaminierter Standorte in Betracht gezogen werden.