Sven Frei

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Verified

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• Dr. habil.
• Associate Professor at Wageningen University & Research

Aluminosilicates are commonly present in natural soils, contributing to their texture and composition. The fate and transport of nanoplastics within natural sediments containing aluminosilicates have not been comprehensively studied yet. To investigate the interactions between nanoplastics and sediments, polystyrene nanoplastics (PS-NPs) were injec...

Zusammenfassung Neben den Auswirkungen des Klimawandels gestaltet sich die Beurteilung der Effekte der Post-Bergbau-Ära auf Wasserhaushalt und Qualität der Spree in der Zukunft als anspruchsvoll. Ziel dieser Studie ist es, das komplexe Zusammenspiel zwischen Oberflächen- und Grundwasser im Kontext der Verockerungs-Problematik der Spree besser zu ve...

Groundwater-surface water interactions (GSI) connect rivers and streams with ripar-ian areas and the adjacent aquifer. Although these interactions exert a substantial control of quantity and quality of both groundwater and surface water, knowledge on GSI along rivers at the regional scale, particularly for inland waterways, is still limited. We inv...

The interface between groundwater and surface water is a critical zone influencing ecohydrological and biogeochemical cycles within surface water ecosystems. It is characterized by complex redox gradients, with groundwater-mediated inflow of reduced substances affecting the oxygen budget of stream water. In this study, we have experimentally simula...

Microplastics (MPs) have been detected ubiquitously in fluvial systems and advective transfer has been proposed as a potential mechanism for the transport of (sub‐) pore‐scale MPs from surface waters into streambed sediments. However, the influence of particle and sediment properties, as well as the hydrodynamic flow regime, on the infiltration beh...

Headwaters play a crucial role in maintaining forest biodiversity by providing unique habitats and are important for the regulation of water temperature and oxygen levels for downstream river networks. Approximately 90% of the total length of streams globally originate from headwaters and these systems are discussed to be especially vulnerable to i...

Study region: Our study region extends over 450 stream km of the German part of the Elbe River, an ecologically and economically important first order river, between Schöna and Wittenberge. Study focus: Diffuse groundwater born nutrients are major contributors to increased algae growth in rivers, leading to eutrophication with serious consequences...

Groundwater-surface water interactions (GSI) connect rivers and streams with riparian areas and the adjacent aquifer. Although these interactions represent a substantial control of quantity and quality of both groundwater and surface water, knowledge on GSI along rivers at the regional scale, particularly inland waterways, is still limited. We inve...

Despite the significance of rivers and streams as pathways for microplastics (MP) entering the marine environment, limited research has been conducted on the behavior of MP within fluvial systems. Specifically, there is a lack of understanding regarding the infiltration and transport dynamics of MP across the streambed interface and within the hypo...

Microplastic (MP) is potentially harmful to lake ecosystems, with its uptake into the food web largely controlled by its residence time in the lake water column. Here we combine laboratory and virtual experiments to quantify residence times of small MP (<15 μm) in two contrasting model lakes; Lake Constance (large lake) and Esthwaite Water (a small...

Quantifying the water flux between surface water (SW) and groundwater (GW) bodies is important for determining water balances and understanding controls on surface water quality and sustainable allocation of water resources. Methods that quantify water exchange at point scales are highly desirable due to the heterogeneous nature of SW-GW connectivi...

The microplastic residence time in lakes is a key factor controlling its uptake by lake organisms. In this work, we have, for the first time, conducted a series of microplastic addition experiments to a 12 × 3 m lake mesocosm and traced its transport through the water column. This was combined with a 1D physically based random walk model of micropl...

In aquatic ecosystems, filter feeders like mussels are particularly vulnerable to microplastics (MP). However, little is known about how the polymer type and the associated properties (like additives or remaining monomers) of MP impact organisms, as the predominant type of MP used for effect studies on the organismic level are micron grade polystyr...

Headwaters represent a significant fraction of the global stream length and are important for streamflow quality and quantity. Since climate change is predicted to affect runoff generation processes fundamentally, it is essential to understand potential consequences for the water availability in headwater catchments. The Lehstenbach catchment, loca...

Microplastic (MP) particles are commonly found in freshwater environments such as rivers and lakes, negatively affecting aquatic organisms and potentially causing water quality issues. Understanding the transport and fate of MP particles in these environments is a key prerequisite to mitigate the problem. For standing water bodies (lakes, ponds) th...

Microplastics residence times in lakes are currently poorly understood. In this work settling experiments with pristine and biofilm-colonized microplastic particles were combined with model calculations to evaluate settling velocities, particle distributions, and residence times in the epi- meta and hypolimnion of a hypothetical stratified lake bro...

Endocrine-disrupting compounds (EDCs), as well as microplastics, have drawn global attention due to their presence in the aquatic ecosystem and persistence in wastewater treatment plants (WWTPs). In the present study, for simultaneous bio-removal of two EDCs, 17α-ethinylestradiol (EE2), bisphenol A (BPA), and a microplastic, polypropylene (PP) four...

Headwaters represent a significant fraction of the global stream length and are important for streamflow quality and quantity. Since climate change is predicted to affect runoff generation processes fundamentally, it is essential to understand potential consequences for the water availability in headwater catchments. The Lehstenbach catchment, loca...

Rivers and streams are a primary transport vector for microplastics (MPs), connecting terrestrial sources to marine environments. While previous studies indicated that pore‐scale MPs can accumulate in streambed sediments, the specific MPs transport and retention mechanisms in fluvial systems remain poorly understood. As part of this technical note,...

Biogeochemical hotspots are defined as areas where biogeochemical processes occur with anomalously high reaction rates relative to their surroundings. Due to their importance in carbon and nutrient cycling, the characterization of hotspots is critical for predicting carbon budgets accurately in the context of climate change. However, biogeochemical...

Clay minerals are important constituents of porous media. To date, only little is known about the transport and retention behavior of nanoplastics in clay-containing soil. To investigate the effects of clay minerals on the mobility of nanoplastics in saturated porous media, polystyrene nanoplastics (PS-NPs) were pumped through columns packed with s...

Statement on the comment by Wilfried Uhlmann and Carolin Pezenka on the publication "Mapping and quantifying groundwater inflow to the Spree River (Lusatia) and its role in Fe precipitation and coating of the river bed" in Groundwater 25 (3), 231-241 (2020). Wir bedanken uns für das entgegengebrachte Interesse an unserer Arbeit sowie für die sachli...

Bank filtration is a cost-effective and sustainable method of improving surface water quality for drinking water production. During aquifer transit, natural biodegradation and physiochemical filtration improve the quality of the raw water by removing sediments, pollutants, and pathogens. Strict regulations prohibit the use of substances that can be...

The increasing use of plastic products and its inevitable decomposition after improper disposal has led to large numbers of nano- and microplastic in aqueous environments. There is currently a critical need to investigate the transport and retention mechanisms of nanoplastic particles in water-saturated porous media (e.g., aquifers or sediments) to...

Coastal ecosystem health and sustainability is tightly coupled to submarine groundwater discharge (SGD) and associated nutrient, carbon and pollutant fluxes. However, there are few studies that systematically analyse the interaction between the terrestrial aquifer system, catchment morphology and coastal SGD. The objective of this study was to eval...

The flux of water, nutrients, carbon and salt through the subsurface at the land-sea interface is an important control on coastal nutrient processes, salinization of coastal aquifers and carbon balances of the coastal zone. However, these fluxes are often spatially and temporally complex and difficult to quantify, especially in high-energy mesotida...

Biogeochemical hot spots are defined as areas where biogeochemical processes occur with anomalously high reaction rates relative to their surroundings. Due to their importance in carbon and nutrient cycling, characterization of hot spots is critical to accurately predict carbon budgets in the context of climate change. However, biogeochemical hot s...

Rivers and streams are a primary transport vector for microplastics (MPs), connecting terrestrial sources to marine environments. While previous studies indicated that pore-scale MPs can accumulate in streambed sediments, the specific MPs transport and retention mechanisms in fluvial systems remain poorly understood. As part of this technical note,...

Understanding of groundwater‐surface water (GW‐SW) interactions is vital for water management in karstic catchments due to its impact on water quality. The objective of this study was to evaluate and compare the applicability of seven environmental tracers to quantify and localize groundwater exfiltration into a small, human impacted karstic river...

Zusammenfassung Eine unbekannte, schwer zu bestimmende aber zentrale Komponente in der Verockerungs-Problematik der Spree ist der lokale Grundwasserzufluss. Als Teil dieser Studie wurden mithilfe des natürlichen Tracers Radon ( ²²² Rn) die lokalen Grundwasserzuflüsse in die Spree und Kleine Spree im Lausitzer Braunkohlerevier bestimmt. Der gesamte...

Two problems currently facing agriculture are drought and the availability of mineable phosphorus minerals used for fertilization. More frequent and longer drought periods are predicted to threaten agricultural yields in the future. The capacity of soils to hold water is a highly important factor controlling drought stress of plants during the grow...

Biogeochemical hot spots are spatially confined areas where biogeochemical processes take place with anomalously high reaction rates. On the landscape scale, biogeochemical hot spots are of major interest due to the possible emission of greenhouse gases (carbon dioxide) and high nutrient turnover. Such hot spots are sensitive environments and given...

Two problems currently facing agriculture are drought and the availability of mineable phosphorus minerals used for fertilization. More frequent and longer drought periods are predicted to threaten agricultural yields in the future. The capacity of soils to hold water is a highly important factor controlling drought stress of plants during the grow...

The rate of biogeochemical processing associated with natural degradation and transformation processes in the hyporheic zone (HZ) is one of the largest uncertainties in predicting nutrient fluxes. We present a lumped parameter (LPM) model that can be used to quantify the mass loss for nitrate in the HZ operating at the scale of river reaches to ent...

The rate of biogeochemical processing associated with natural degradation and transformation processes in the hyporheic zone (HZ) is one of the largest uncertainties in predicting nutrient fluxes. We present a lumped parameter model that can be used to quantify the mass loss for nitrate in the HZ operating at the scale of river reaches to the entire...

Although recent studies indicate that fluvial systems can be accumulation areas for microplastics (MPs), the common perception still treats rivers and streams primarily as pure transport vectors for Mps. In this study we investigate the occurrence of MPs in a yet unnoticed but essential compartment of fluvial ecosystems-the hyporheic zone (HZ). Lar...

222 86 as a hydrological tracer offers a method for studying short to medium term groundwater-surface water interactions. These high frequency processes play an important role in wetland hydrology and bio-geochemistry and may influence their contribution to the global carbon cycle. Therefore, there is a definite need for robust methods to measure h...

Wetlands are considered as regions where biogeochemical active areas are common. Biogeochemical hot spots are spatially limited areas where processes such as nitrate or sulfate reduction take place in high reaction rates compared to the surrounding area. Biogeochemical hot spots are also of major interest on larger scales due to their possible emis...

Transient storage zones (TSZs) are located at the interface of rivers and their abutting aquifers and play an important role in hydrological and biogeochemical functioning of rivers. The natural radioactive tracer 222 Rn is a particularly well-suited tracer for studying TSZ water exchange and age. Although 222 Rn measurement techniques have develop...

Hyporheic flow and nutrient turnover in hyporheic systems are strongly influenced by in-stream bedforms. An accurate representation of topographical variations of the stream-streambed interface is therefore essential in analytical models in order to represent the couplings between hydrological and biogeochemical processes correctly. The classical T...

The distribution of groundwater residence time in a catchment provides synoptic information about catchment functioning (e.g. nutrient retention and removal, hydrograph flashiness). In contrast with interpreted model results, which are often not directly comparable between studies, residence time distribution is a general output that could be used...

The interplay between precipitation and evapotranspiration determines the input into the hydrological system of a catchment. Annual values of precipitation, evapotranspiration, and runoff measured at the catchment outlet for the 2002–2009 period were available. Annual precipitation clearly surmounted the sum of evapotranspiration and runoff. Part o...

Quantifying and upscaling chemical turnover in the hyporheic zone (HZ) is difficult due to limited reaction rate data, unknown carbon quality, and few methods for upscaling local measurements to river networks. Here we develop a method for quantifying reaction kinetics in-situ in the HZ and upscaling biogeochemical turnover to catchment scales. Rad...

The highly dynamic processes within a hillslope-riparian-stream (HRS) continuum are known to affect streamflow generation, but are yet not fully understood. Within this study, we simulated a headwater HRS continuum in western Luxembourg with an integrated hydrologic surface subsurface model (HydroGeoSphere). The model was set up with thorough consi...

Predicting hydrological catchment behaviour based on measurable (and preferably widely available) catchment characteristics has been one of the main goals of hydrological modelling. Residence time distributions provide synoptic information about catchment functioning and can be useful metrics to predict their behaviours. Moreover, residence time di...

The concept of Damköhler numbers have been extensively used in the discipline of chemical engineering and lately increasingly found its application into environmental science in order to describe the integrated behavior of hydrological systems with respect to their physical transport and biogeochemical transformation capabilities. Defining characte...

The dynamic response of groundwater discharge to external influences such as rainfall is an often neglected part of water and solute balances in wetlands. Here we develop a new field platform for long-term continuous 222Rn and electrical conductivity (EC) measurements at Sale Wetland, Australia to study the response of groundwater discharge to stor...

Coupling surface and subsurface water flow in fully integrated hydrological codes is becoming common in hydrological research; however, the coupling of surface-subsurface solute transport has received much less attention. Previous studies on fully integrated solute transport focus on small scales, simple geometric domains, and have not utilised man...

A quantitative understanding of groundwater-surface water interactions is vital for sustainable management of water quantity and quality. The noble gas radon-222 (Rn) is becoming increasingly used as a sensitive tracer to quantify groundwater discharge to wetlands, lakes and rivers; a development driven by technical and methodological advances in R...

An adequate representation of micro-topography in spatially explicit, physically based models can be crucial in modeling runoff generation, surface/subsurface flow interactions or subsurface flow patterns in hydrological systems with pronounced micro-topography. However, representation of micro-topography in numerical models usually requires high g...

The understanding of streamflow generation processes is vitally important in the management of water resources. In the absence of the data required to achieve this, Integrated Surface-Subsurface Hydrological Models (ISSHM) can be used to assist with the development of this understanding. However, the standard outputs from these models only enable e...

Peatlands are important ecohydrological systems and contribute significantly to the global carbon cycle. They function as carbon sinks through CO2-sequestration but also emit methane depending i.a. on the prevailing hydrological structures. Knowledge of their hydrology including exchange between the groundwater and surface water domain is thus nece...

Groundwater pollution by fertilizer NO3 - is a major problem recognized in many parts of the world. The excessive use of mineral fertilizers to assure high yields in agricultural production intensifies the leaching problem especially in regions affected by a monsoon climate as in South Korea. The extent that leaching occurs depends on several facto...

Concentrations of dissolved organic carbon (DOC) in runoff from catchments are often subject to substantial short-term variations. The aim of this study was to identify the compartmental sources of DOC in a forested catchment and the causes for short-term variations in runoff. Furthermore, we investigated the implication of short-term variations fo...

[1] Wetlands provide important ecohydrological services by regulating fluxes of nutrients and pollutants to receiving waters, which can in turn mitigate adverse effects on water quality. Turnover of redox-sensitive solutes in wetlands has been shown to take place in distinct spatial and temporal patterns, commonly referred to as hot spots and hot m...

Concentrations of dissolved organic carbon (DOC) in runoff from catchments are often subject to substantial short-term variations. The aim of this study was to identify the compartmental sources of DOC in a forested catchment and the causes for short-term variations in runoff. Furthermore, we investigated the implication of short-term variations fo...

Wetlands provide important ecohydrological services by regulating fluxes of nutrients and pollutants to receiving waters, which can in turn mitigate adverse effects on water quality. Turnover of redox-sensitive solutes in wetlands has been shown to take place in distinct spatial and temporal patterns, commonly referred to as hot spots and hot momen...

Low order streams often show complex, nonlinear relationships between hydrologic conditions in the riparian zone, streamflow generation and the chemical signature of the stream water. Dynamic surface and subsurface flow paths create a mosaic of biogeochemical conditions that affect the transformation and export of solutes. These relationships are e...

In humid upland catchments wetlands are often a prominent feature in the vicinity of streams and have potential implications for runoff generation and nutrient export. Wetland surfaces are often characterized by distinct micro-topography (hollows and hummocks). The effects of such micro-topography on surface–subsurface exchange and runoff generatio...

Dissolved organic carbon (DOC) plays a crucial role in the global carbon cycle and directly influences water quality and mobility/toxicity of metals. Its concentration is rising in large areas throughout the northern hemisphere with unforeseeable implications for ecosystems. Recent studies have postulated temperature increase and reduction of atmos...

The interaction between streams and their riparian zone during rainstorms of variable intensity is still poorly understood. Field observations suggest the development of complex surface and subsurface drainage patterns, which are difficult to characterize and a challenge for simulation. Several studies based on hydro chemical and hydrometric data a...

The parallel physically-based surface–subsurface model PARFLOW was used to investigate the spatial patterns and temporal dynamics of river–aquifer exchange in a heterogeneous alluvial river–aquifer system with deep water table. Aquifer heterogeneity at two scales was incorporated into the model. The architecture of the alluvial hydrofacies was repr...

The interaction between streams and their surrounding near stream zone (riparian zone) during rainstorms of variable intensity is still poorly understood. Field observations suggest that distinct exchange flow paths develop, which are difficult to characterize and a challenge for simulation. Recent studies based on hydro chemical and hydrometric da...