Publications - Publications

Wed, 01 Oct 2025 20:23:21 +0200

Context: Nitrogen is an essential macronutrient in agriculture, affecting both crop yields and soil health. In Denmark, one of the most densely farmed regions in the world, excess reactive nitrogen (Nr) compounds are lost to the environment along gaseous and hydrological pathways in forms such as nitrate, ammonia, nitrogen oxides and dinitrogen. Objectives: Here, we aim to assess the effect of different field management practices (fertilisation, crop residue management or cultivation of catch crops) on environmental Nr losses and the field scale soil net GHG balance (i.e., sum of soil C stock changes and direct and indirect N₂O emissions). Methods: For this purpose, highly detailed data from the Danish Agricultural Watershed Monitoring Program (LOOP-program; 2013–2019) were used in combination with the process-based model LandscapeDNDC. Results and conclusions: The results indicate that a mixture of organic and synthetic fertilisers turns soils to a stronger net sink of GHGs (∼70 – ∼514 kgCO₂₋eq ha⁻¹ yr⁻¹) compared to exclusive use of only one type of fertiliser. In addition, incorporating crop residue and cultivation of catch crops increases the nitrogen use efficiency (NUE) by 3–11 % on average and decreases environmental Nr losses. Significance: These findings emphasize the potential of targeted fertiliser, residue and catch crop management to increase the sustainability of crop production systems in Denmark.

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Rolighed, J., Thers, H., Ugilt Larsen, S., Blicher-Mathiesen, G., Eriksen, J. — Mon, 07 Jul 2025 20:23:21 +0200

Nilsson, J. E., Audet, J., Ehde, P. M., Weisner, S. E.B., Liess, A. — Fri, 01 Aug 2025 20:23:21 +0200

Eutrophication and flood risk are pressing issues of ecological and societal relevance. A key driver of eutrophication is the use of nitrogen (N) fertiliser in agriculture, resulting in N exports from land to water. Climate change increases the risk of flood events which can increase N exports and further worsen eutrophication. Created wetlands in agricultural areas are recognised as effective nutrient sinks, and the flood attenuating capabilities of wetlands are well established. However, the combination of these two ecosystem services in agricultural landscapes is understudied. This study examines how water flow buffering in created wetlands affects N removal and greenhouse gas (GHG) emissions. The study was performed in experimental wetlands of different designs (depth and size) subjected to intermittent or permanent flooding (gradual emptying between inflow events or a constant water level). Intermittently flooded wetlands removed less N than permanently flooded wetlands, especially during no-flow periods. The largest difference was found among deep wetlands, where the average N removal across the study was 0.19 g m⁻² d⁻¹ (25 %) in intermittently flooded wetlands and 0.27 g m⁻² d⁻¹ (38 %) in permanently flooded wetlands. No differences in the aqueous concentrations of N₂O or CH₄ were observed between wetlands with high or low water storage capacity, thus indicating similar emissions. This study highlights a risk of lowered N removal in created wetlands designed for flood attenuation. Further studies are needed on synergies and trade-offs when aiming to combine flood attenuation and N removal in created wetlands.

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Wed, 01 Jan 2025 20:23:21 +0100

In Danish restoration projects, this risk is typically evaluated using a model that considers the soil molar ratio of P to Fe (extracted by bicarbonate-dithionite) alongside hydraulic loading rates (HLR). However, current assessments do not consider P release from drained soils prior to rewetting, which may lead to an overestimation of P release in the overall risk assessment.
This study monitored water, nitrogen (N), phosphorus (P), and carbon (C) balances in a pump-drained fen in northwestern Jutland, Denmark, comparing nutrient retention and export before and after rewetting. Preliminary findings indicate that significant amounts of N (>100 kg ha-1 yr-1), P (>5 kg ha-1 yr-1), and C (>1000 kg ha-1 yr-1) were released before rewetting, with N primarily in organic forms and P roughly split between particulate P (PP) and SRP.
After rewetting, which included hydrological reconnection to a nearby stream and a substantial increase in HLR, the fen shifted from a nutrient source to a significant nutrient sink, removing over 400 kg N ha-1 yr-1 and more than 15 kg P ha-1 yr.-1 Aqueous C export also decreased to about 200 kg ha-1 yr-1. Notably, SRP was the main form of retained P, while small amounts of PP were still released.
These results have important implications for the rewetting of pump-drained soils. Given the risk of SRP release, some restoration projects may be delayed to allow for P depletion through plant harvesting, or face additional costs for removal of degraded top soils. In some cases, restoration efforts may be abandoned entirely due to SRP risks. However, accounting for P release before rewetting could reduce the perceived risk and enable more projects to proceed, benefiting greenhouse gas reduction, nutrient management, and biodiversity.]]>

Frederiksen, R. R., Larsen, S. E., Tornbjerg, H., Thodsen, H., Kronvang, B. — Sun, 01 Jun 2025 20:23:21 +0200

Understanding and quantifying total organic nitrogen (TON) concentrations in streams and their spatial variation is essential for accurately assessing their importance for total nitrogen (TN) loadings to coastal waters and the possible sources of TON in the landscape. Total organic nitrogen constitutes almost 20% of the TN riverine loadings to Danish coastal waters. We used environmental monitoring data from 390 stations across Denmark to calculate indirectly measured annual average TON concentrations using a wide range of predictor variables. We then trained a machine learning model to predict spatially distributed average annual TON concentrations in Danish streams, achieving a mean error of 0 mg L⁻¹ and a root-mean-squared error of 0.20 mg L⁻¹. The mean annual predicted (measured) TON concentrations in Danish streams were 0.84 (0.70) mg L⁻¹, with a standard deviation of 0.36 (0.31) mg L⁻¹. The model is primarily driven by mean elevation and the percentages of agricultural land, tile-drained areas, lakes and carbon-enriched soils in the catchment. The developed model contributes to our understanding of the spatial variation in annual TON concentrations in streams at a national scale, supporting our understanding of processes driving nitrogen cycling.

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Carstensen, M. V. — Wed, 30 Sep 2020 20:23:21 +0200

Rolighed, J. — Sun, 01 Jan 2023 20:23:21 +0100

Badawi, N., Karan, S., Haarder, E. B., et al. — Mon, 07 Apr 2025 20:23:21 +0200

Wiberg-Larsen, P., Kronvang, B., Kristensen, E. A., Baattrup-Pedersen, A. — Fri, 01 Aug 2025 20:23:21 +0200

Historically, the lower River Skjern (Denmark) was a biodiversity hotspot of national and European importance, but in the 1960s this part of the river was channelized and the wetlands drained to improve conditions for agriculture. However, to regain former biodiversity, a major restoration project was conducted in 2000–2002, which transformed a 19 km straight channel into a 26 km meandering river. In this study, we use historical data to evaluate how the channelization of the river and its restoration 40 years later affected the aquatic biodiversity. Generally, and as expected, we observed a significant reduction in the taxon richness of aquatic plants and EPT taxa (Ephemeroptera, Plecoptera, and Trichoptera) in response to the channelization, especially taxa associated with backwaters. As hoped, the restoration mediated an increase in taxon richness for both aquatic plants and EPT taxa. This positive response took place immediately after the restoration (1 year) and persisted throughout the study period (10 years). However, taxon richness did not reach the pre-channelization levels. Especially, we observed that the recovery of backwater-associated taxa was limited. The main reason for this is likely that only 5.8 % of the original backwater area was recreated and, additionally, that natural regeneration of these areas relies on natural hydromorphological processes that might take several decades. Furthermore, the possibility of several taxa to recolonize from other and distant areas is poor, reflecting today's rarity of backwater habitats in Danish rivers. Full recovery of the river's former biodiversity might therefore take decades or more without implementing active measures.

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Badawi, N., Karan, S., Haarder, E. B., et al. — Mon, 07 Apr 2025 20:23:21 +0200

The current report covers a period of two years from July 1, 2022 to June 30, 2024 and presents the results of tests performed on four different agricultural fields, of which one is sandy (Jyndevad) and the other three consist mainly of clay till (Silstrup, Estrup, Faardrup). It is noted that several active ingredients were applied to the fields before July 1, 2022, for which either the pesticides, degradation product/s, or both were included in the monitoring. In the evaluation of the individual test of specific compounds, we have therefore included the results of chemical analyses carried out before July 2022 in cases where this was needed. A summary of the results is given in Table 0.1 for all samples included in the monitoring in the present reporting period (July 2022 to June 2024). The report presents either preliminary or final results of the testing of nine pesticides, of which three pesticides and a total of 18 degradation products were included in the monitoring (21 analytes in total). The pesticides were applied to the PLAP fields by spraying nine different commercial products. In some cases, the commercial products contained one or more pesticides, and in other cases, the same pesticide was applied to the fields using different commercial products (Appendix 3). ]]>

Larsen, S. E. — Thu, 10 Apr 2025 20:23:21 +0200

Liu, J., Koch, J., Stisen, S., et al. — Mon, 14 Apr 2025 20:23:21 +0200

Large samples of hydrometeorological time series and catchment attributes are critical for improving the understanding of complex hydrological processes, hydrological model development, and performance benchmarking. CAMELS (Catchment Attributes and Meteorology for Large-sample Studies) datasets have been developed in several countries and regions around the world, providing valuable data sources and test beds for hydrological analysis and new frontiers in data-driven hydrological modeling. Regarding the lack of samples from lowland, groundwater-dominated, small-sized catchments, we develop an extensive repository of a CAMELS-style dataset for Denmark (CAMELS-DK). This CAMELS addition is the first containing both gauged and ungauged catchments as well as detailed groundwater information. The dataset provides dynamic and static variables for 3330 catchments covering all of Denmark from various hydrogeological datasets, meteorological observations, and a well-established national-scale hydrological model. For 304 of those catchments, streamflow observations are provided, whereas simulated streamflow is provided for all 3330 catchments. The dataset contains time series spanning 30 years (1989-2019) with a daily time step, and the data will be updated once new observations and model simulations become available. The dense and full spatial coverage for all 3330 catchments, instead of only gauged catchments, together with the addition of various simulation data from a distributed, process-based model, enhances the applicability of such CAMELS data, for example, for the development of data-driven and hybrid physically informed modeling frameworks or other cases where consistent full spatial coverage is required. We also provide quantities related to the human impact on the hydrological system in Denmark, such as groundwater abstraction and irrigation. The CAMELS-DK dataset is freely available at https://doi.org/10.22008/FK2/AZXSYP (Koch et al., 2024).

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2O Emissions]]>

Zhang, W., Nie, M., Yu, H., et al. — Tue, 01 Apr 2025 20:23:21 +0200

The response of nitrous oxide (N₂O) emissions to warming is critical for accurately projecting nitrogen-climate feedback. Compelling evidences have shown that N₂O emissions are temperature dependent, offering insights into their intrinsic temperature sensitivity. However, when extrapolating from laboratory-controlled to field-ambient conditions, it remains unclear how this temperature sensitivity varied across cropland fields subject to diverse environmental and anthropogenic constraints. We performed a comprehensive meta-analysis of 144 field-warming observations worldwide, aiming to address the magnitude, heterogeneity, and drivers of such apparent temperature sensitivity. The results showed that mean growing-season field-scale N₂O emissions were not strongly temperature dependent with low averaged activation energy (0.32 eV) compared with that of laboratory-scale observations (0.62 eV). At site levels, the spatial variation in such temperature sensitivity was primarily driven by the interactions of nitrogen fertilization, edaphic, and climatic variables. This analysis also identified a crucial yet frequently overlooked role of soil pH in nonlinearly modulating such temperature sensitivity. Our findings provide evidence for understanding nitrogen and climate feedback by capturing the soil-climate-management constrained warming response and highlight the importance of incorporating these constraints into models to improve prediction accuracy.

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Peters, K., Kiesel, J., Oswald, I., et al. — Tue, 01 Apr 2025 20:23:21 +0200

Stream temperature is among the main drivers affecting water quality by influencing chemical reaction rates and biological activity. Due to globally rising air temperatures, increased stream temperatures are equally rising and becoming more relevant for ecosystem health. Stream temperature is influenced by a complex interplay of climate, hydrological processes and catchment characteristics. However, these process interactions are often overlooked when being integrated with hydrological models. This study addresses the limitations of a simplified stream temperature model by using the ecohydrological model Soil and Water Assessment Tool (SWAT+). Our goal was to enhance the process representation in the current stream temperature model by refining the mass transfer processes. We included heat transfer processes improved by a channel shape parameter, and the influence of riparian shading with an improved equation to simplify the modified dew point temperature calculation. The enhanced SWAT+ model was tested at 23 stations in a medium-sized mountainous catchment with high-resolution observed stream temperature data. Our results show that the enhanced model significantly improved performance, achieving a mean Kling–Gupta Efficiency (KGE) of 0.8 across all calibration sites. We improved previous advances in stream temperature modelling within this work by focussing on the importance of accurate process representation. A key finding was the impact of runoff component contributions on the stream temperature model performance. The model performed particularly well during spring, autumn and very low to moderate flows. The improved stream temperature representation therefore not only serves as a valuable tool for management decisions and ecological applications but also benefits modelling other water quality variables.

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2 and N₂O Budgets]]>

Silverthorn, T., Audet, J., Evans, C. D., et al. — Sat, 01 Mar 2025 20:23:21 +0100

Ditches and canals are omitted from global budgets of inland water emissions, despite research showing them to be emitters of greenhouse gases (GHGs). Here, we synthesize data across climate zones and land use types to show, for the first time, that global ditches emit notable amounts of carbon dioxide (CO₂) and nitrous oxide (N₂O). Ditches had higher per-area emissions of CO₂ and N₂O than ponds, lakes, and reservoirs, likely due to high nutrient inputs. Preliminary upscaling showed that the inclusion of ditches would increase global inland water CO₂ emissions by 0.6%–1% and N₂O emissions by 3%–9%. Trophic state and climate influenced N₂O emissions, while CO₂ emissions had complex drivers difficult to disentangle at the global scale. This research highlights the importance of including ditches in global inland water GHG budgets and informs more accurate reporting of anthropogenic emissions in national inventories.

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Cao, Y., Scharfenberger, U., Shatwell, T., et al. — Wed, 01 Jan 2025 20:23:21 +0100

Net ecosystem production (NEP) is an important indicator of lake ecosystem function and integrity. An earlier study, restricted to one geographical region, indicated that oxygen saturation levels (DO%) might be used to predict daily NEP in shallow lakes. To test the generality of the method, we used DO% data collected in a standardised pan-European mesocosm experiment with contrasting trophic states and water levels covering a large climate gradient (from Sweden to Turkey). We corroborated these data with process-based DO simulations. The NEP ~ DO% relation depended on factors influencing gas transfer: water depth and wind. The NEP ~ DO% relation per volume became weaker with increasing depth (1–2 m) but was independent of depth when area based. Simulations indicated that the marginalisation of the depth was sensitive to wind conditions. Trophic status, temperature and light showed no or only marginal (climate zone) effects (experimental data), while the simulations indicated influence of those factors under particular wind–depth conditions. We confirmed that when considering also wind and depth effects, midday DO% potentially provides reliable estimates of daily NEP. Therefore, historical monitoring data of DO% might be used to estimate NEP, and process-based oxygen models may be valuable tool therein. We encourage further tests.

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Tue, 01 Apr 2025 20:23:21 +0200

Conventional catchment-scale models are often calibrated using a single set of parameters and considering only statistical performance, overlooking hydrological aspects of great relevance for a realistic modeling outcome. The main objectives of this study were to set up a hydrological model in the Tagus River headwaters (Spain) with the new version of the soil and water assessment tool and to develop a novel calibration and evaluation procedure to simulate the hydrological processes realistically, particularly focusing on groundwater contribution. The model was parameterized at three geological regions, and its performance was evaluated in representative sub-catchments, addressing both soft and hard calibration to focus not only on daily streamflow but also on two hydrological indices: the runoff coefficient and the groundwater contribution. Results were then evaluated at the reservoir catchment level (two large reservoirs constitute the catchment outlet) and further validated on reservoir inflows. After this innovative procedure that incorporates a zonal calibration and a comprehensive model evaluation, a very good statistical performance was obtained, with NSE, R², and PBIAS values (monthly) of 0.86%, 0.88%, and 2.5% for the Entrepeñas Reservoir inflows, and of 0.89%, 0.91%, and −8.5% for Buendía Reservoir. This performance was achieved while maintaining realistic values for the hydrological indices, providing a robust representation of the hydrological processes.

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Rozemeijer, J., Jordan, P., Hooijboer, A., et al. — Tue, 01 Apr 2025 20:23:21 +0200

The use of high-frequency water quality monitoring has increased over several decades. This has mostly been motivated by curiosity-driven research and has significantly improved our understanding of hydrochemical processes. Despite these scientific successes and the growth in sensor technology, the large-scale uptake of high-frequency water quality monitoring by water managers is hampered by a lack of comprehensive practical guidelines. Low-frequency hydrochemical data are still routinely used to review environmental policies but are prone to missing important event-driven processes. With a changing climate where such event-driven processes are more likely to occur and have a greater impact, the adoption of high-frequency water quality monitoring is becoming more pressing. To prepare regulators and environmental and hydrological agencies for these new challenges, this paper reviews international best practice in high-frequency data provision. As a result, we summarise the added value of high-frequency water quality monitoring, describe international best practices for sensors and analysers in the field, and evaluate the experience with high-frequency data cleaning. We propose a decision workflow that includes considerations of monitoring data needs, sensor choice, maintenance and calibration, and structured data processing. The workflow fills an important knowledge-exchange gap between research and statutory surveillance for future high-frequency water quality sensor uptake by practitioners and agencies.

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Rasmussen, J. J., Bundschuh, M., Jensen, T. M., et al. — Wed, 01 Jan 2025 20:23:21 +0100

At the global level, stream ecosystems are influenced by multiple anthropogenic stressors such as eutrophication, habitat deterioration, and water scarcity. Multiple stressor effects on stream biodiversity are well documented, but multiple stressor effects on stream ecosystem processes have received only limited attention. We conducted one mesocosm (stream channel) and one microcosm (feeding trial) experiment to study how combinations of reduced flow, increased nutrient concentrations, and increased fine sediment coverage would influence fungal and macroinvertebrate decomposer assemblages and their active contribution to leaf decomposition. In the stream channels, increased fine sediment coverage significantly reduced fungal biomass, occurrence frequencies of most aquatic hyphomycete species, and microbial leaf decomposition rates compared to untreated controls. Macroinvertebrate-induced leaf decomposition rates were mainly correlated to total fungal biomass and community composition. Neither increased nutrient concentrations, nor reduced flow conditions significantly influenced leaf decomposer communities or decomposition rates. The feeding trials revealed significantly reduced leaf consumption in the freshwater amphipod Gammarus pulex when feeding on leaf material from treatments with increased fine sediment coverage in the mesocosm experiment. When offered a food choice between sterile, unconditioned leaf material and leaf material from treatments with increased fine sediment coverage, G. pulex foraged mainly on sterile material. This study showed that increased fine sediment coverage can alter the flux of energy and material in the detrital food chain through bottom-up regulation of leaf conditioning by fungal decomposers. Our results suggest that increasing attention should be given to mitigating fine sediment transport and deposition in stream systems to preserve ecosystem functioning within the detrital food chain.

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Sat, 01 Feb 2025 20:23:21 +0100

Robust hydrological models require an accurate representation of hydrological processes, but modellers often rely solely on the streamflow simulation performance. This work presents an innovative zonal calibration workflow developed for a geologically heterogeneous basin, the Upper Tagus River Basin (Spain), towards achieving a realistic simulation of hydrological processes. A detailed SWAT+ model was built, and four geological regions were defined. The sensitivity of 10 parameters for two hydrological indices, runoff coefficient and groundwater contribution to the streamflow, was explored. Then, parameters were optimized for each region through a soft calibration to achieve an accurate simulation of these variables. Some parameters were identified as the most sensitive (cn2 and awc for runoff coefficient and perco for groundwater contribution). Sensitivity rankings and parameter adjustment varied among regions, revealing differences in the hydrological processes. The target values of the hydrological variables, previously estimated, were reached in every region, subsequently improving streamflow simulation performance.

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Zak, D. H., Christiansen, N. G., Winding, A., et al. — Wed, 01 Jan 2025 20:23:21 +0100

Hoffmann, C. C., Iversen, B. V., Børgesen, C. D. — Wed, 05 Mar 2025 20:23:21 +0100

Wed, 01 Jan 2014 20:23:21 +0100

Premise of the study: The species-rich Neotropical genera Centropogon, Burmeistera, and Siphocampylus represent more than half of the ∼1200 species in the subfamily Lobelioideae (Campanulaceae). They exhibit remarkable morphological variation in floral morphology and habit. Limited taxon sampling and phylogenetic resolution, however, obscures our understanding of relationships between and within these genera and underscores our uncertainty of the systematic value of fruit type as a major diagnostic character.

Methods: We inferred a phylogeny from five plastid DNA regions (rpl32-trnL, ndhF-rpl32, rps16-trnK, trnG-trnG-trns, rbcL) using maximum-likelihood and Bayesian inference. Ancestral character reconstructions were applied to infer patterns of fruit evolution.

Key results: Our results demonstrate that the majority of species in the genera Centropogon, Burmeistera, and Siphocampylus together form a primarily mainland Neotropical clade, collectively termed the "centropogonids." Caribbean Siphocampylus, however, group with other Caribbean lobelioid species. We find high support for the monophyly of Burmeistera and the poly-phyly of Centropogon and mainland Siphocampylus. The ancestral fruit type of the centropogonids is a capsule; berries have evolved independently multiple times.

Conclusions: Our plastid phylogeny greatly improves the phylogenetic resolution within Neotropical Lobelioideae and highlights the need for taxonomic revisions in the subfamily. Inference of ancestral character states identifies a dynamic pattern of fruit evolution within the centropogonids, emphasizing the difficulty of diagnosing broad taxonomic groups on the basis of fruit type. Finally, we identify that the centropogonids, Lysipomia, and Lobelia section Tupa form a Pan-Andean radiation with broad habitat diversity. This clade is a prime candidate for investigations of Neotropical biogeography and morphological evolution.

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Fri, 01 Jan 2021 20:23:21 +0100

Detailed 3D structural information of the subsurface is fundamental for development of both the hydrological and the geochemical models that can be used for analysis of nitrate reduction processes in the subsurface and targeted nitrate regulation. In some areas data, coverage might be sparse or suffering from bad data quality, which results in information gaps. We suggest therefore a workflow that merges tTEM resistivity data and borehole lithologies, and uses these datasets to generate an ensemble of equally plausible 3D models of hydrogeological units and redox conditions. In an initial step the input datasets are merged via accumulated clay thickness modeling. This dataset is in a second step transformed into a training image, that is to be used in multipoint statistical simulations. The application of Direct Sampling within this workflow allows for simultaneous simulation of these variables. This approach allows for retaining the complex geostatistical spatial relationships that can exist between the different datasets in the resulting generated 3D models.

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Shu, W., Zhang, Q., Audet, J., et al. — Tue, 14 Jan 2025 20:23:21 +0100

Mining activities cause severe nitrogen pollution in watersheds, yet our understanding of the transport pathways, transformation processes, and control mechanisms of nitrate (NO₃^-) in these areas is limited. Based on nearly 4-year observations of groundwater and river in China’s largest ion-adsorption rare earth mining watershed, we revealed the dynamics of NO₃^- and its drivers using stoichiometry-based load model, molecular biological, and multi-isotope approaches. Results indicated that the NO₃^- dynamics were jointly controlled by sources (precipitation, terrestrial inputs, and sediment supply) and processes (hydrological and biological). The monthly NO₃^- export load from the 444.4 km² watershed was 3.72 × 10⁵ kg. Groundwater (36 ± 26%) and soil nitrogen (25 ± 17%) were the primary exogenous sources of NO₃^-. Baseflow was the main hydrological pathway for legacy nitrogen into the river, contributing 66.8% of the NO₃^- load. Coupled nitrification-denitrification were key biological processes affecting the NO₃^- transformation, with denitrification contributing 58%. Burkholderia were most associated with NO₃^- transformation. Dissolved organic carbon and oxygen were major drivers affecting the NO₃^- production and consumption. This study highlights effective control and management strategies for nitrogen pollution in mining-affected watersheds, considering not only reducing nitrogen inputs but also integrating hydrological pathways and nitrogen transformation mechanisms.

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Sánchez-Gómez, A., Arnold, J. G., Bieger, K., et al. — Sat, 01 Mar 2025 20:23:21 +0100

Incorporating the simulation of water management actions in hydrological models is paramount to enhance their reliability and usefulness. SWAT + (Soil and Water Assessment Tool) includes novelties in this aspect compared to its previous versions: the decision tables and the water allocation module provide enhanced capabilities for configuring management actions. Despite their potential, these features have not yet been applied due to their novelty. This study pioneers the use of SWAT + ’s new features applied in the Upper Tagus River Basin, a densely populated and highly regulated catchment. Irrigation, reservoir management, and various kinds of water transfers were incorporated in a SWAT + model of this basin. The implementation of management actions and their impact on the model performance were evaluated. The model accurately reproduced water demand for irrigation and water transfers, capturing both the demand volume and timing. The water sources were configured to meet most of the demand, with 73% of irrigation and 90% of water transfer requirements being satisfied. Release decision tables were configured for 31 reservoirs, resulting in an accurate simulation of outflow and storage in many of them. Incorporating management actions improved the streamflow simulation at the basin outlet, both considering the hydrograph and performance metrics (e.g., PBIAS was reduced by more than 50%). Some potential improvements in the model configuration and in the code were identified and will be addressed in future studies. This work provides a comprehensive guide to SWAT + ’s new features and the methodology employed, making it valuable for anyone working with the model.

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Larsen, S. E. — Wed, 05 Feb 2025 20:23:21 +0100

Blicher-Mathiesen, G., Thorsen, M. — Fri, 10 Jan 2025 20:23:21 +0100

van't Veen, S. G. M., Kronvang, B., Audet, J., et al. — Thu, 07 Nov 2024 20:23:21 +0100

The growing use of sensors in fresh waters for water quality measurements generates an increasingly large amount of data that requires quality assurance (QA)/quality control (QC) before the results can be exploited. Such a process is often resource-intensive and may not be consistent across users and sensors. SentemQC (QA-QC of high temporal resolution sensor data) is a cost-efficient, and open-source Python approach developed to ensure the quality of sensor data by performing data QA and QC on large volumes of high-frequency (HF) sensor data. The SentemQC method is computationally efficient and features a six-step user-friendly setup for anomaly detection. The method marks anomalies in data using five moving windows. These windows connect each data point to neighboring points, including those further away in the moving window. As a result, the method can mark not only individual outliers but also clusters of anomalies. Our analysis shows that the method is robust for detecting anomalies in HF sensor data from multiple water quality sensors measuring nitrate, turbidity, oxygen, and pH. The sensors were installed in three different freshwater ecosystems (two streams and one lake) and experimental lake mesocosms. Sensor data from the stream stations yielded anomaly percentages of 0.1%, 0.1%, and 0.2%, which were lower than the anomaly percentages of 0.5%, 0.6%, and 0.8% for the sensors in Lake and mesocosms, respectively. While the sensors in this study contained relatively few anomalies (<2%), they may represent a best-case scenario in terms of use and maintenance. SentemQC allows the user to include the individual sensor uncertainty/accuracy when performing QA-QC. However, SentemQC cannot function independently. Additional QA-QC steps are crucial, including calibration of the sensor data to correct for zero offsets and implementation of gap-filling methods prior to the use of the sensor data for determination of final real-time concentrations and load calculations.

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Pacheco, J. P., Larsen, S. E. — Fri, 01 Nov 2024 20:23:21 +0100

Larsen, S. E. — Tue, 17 Dec 2024 20:23:21 +0100

Mon, 09 Dec 2024 20:23:21 +0100

stoftransport af kvælstof og fosfor til kystvandene for perioden før og under NOVANA – og frem til og med 2023]]>

Thodsen, H., Erfurt, J., Tornbjerg, H., Larsen, S. E., Conradsen, A. R. — Fri, 20 Dec 2024 20:23:21 +0100

(OverfladevandsDAtabasen) og som anvendes i NOVANA med henblik på at
inkludere stoftransportberegninger i VanDa (VandDatabasen).
Miljøstyrelsen har desuden ønsket en beskrivelse af de metoder, der anvendes
til beregning af stoftransporter i regi af fx HELCOM og OSPAR. Der tages
udgangspunkt i metoder til beregning af stoftransporter for de stoffer, der
indgår i NOVANA under FDC for hydrometri og stoftransport dvs. næringsstoffer, suspenderet stof, jern mm.
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Hansen, A. S., Fredshavn, J. R., Uldal, C., et al. — Fri, 01 Dec 2023 20:23:21 +0100

Børgesen, C. D., Bach, E. O., Iversen, B. V., Hoffmann, C. C. — Fri, 20 Dec 2024 20:23:21 +0100

Kaden, U. S., Scholz, M. ., Buijse, A. D., et al. — Sun, 01 Jan 2023 20:23:21 +0100

Florea, A. F., Heckrath, G. J., Zak, D. H., Mäenpää, M., Hansen, H. C. B. — Mon, 01 Jan 2024 20:23:21 +0100

Rewetting of drained agricultural lowland peat soils is followed by the risk of increased phosphorus (P) release to downstream systems, thereby challenging their restoration as nutrient sinks for years to decades. While extensive knowledge is available on P mobilization under anaerobic conditions caused by reductive (Fe(III))-oxide dissolution, the net P release to the aqueous phase (P_Sol) is only poorly understood due to unknown significance of P re-sorption to aluminum (Al) oxides and non-reduced Fe(III)-oxides. We therefore hypothesize that P_Sol is a function of the sorption capacity and P saturation of Al-oxides and non-reduced Fe(III)-oxides. A comprehensive set of 47 Danish topsoil and subsoil samples from agricultural lowlands were incubated for up to 148 days in the laboratory under anoxic and water-saturated conditions at room temperature. Oxalate-extractable Fe, Al and P (Fe_ox, Al_ox and P_ox) varied by three orders of magnitude, with Fe_ox ranging between 1.8 and 1590 mmol kg⁻¹; Al_ox and P_ox also showed high variation with maximum contents of 883 and 153 mmol kg⁻¹, respectively. Bicarbonate-dithionite generally extracted 2 times less Fe, Al and P (Fe_BD, Al_BD, P_BD) than oxalate. Oxalate extraction data were used to calculate the degree of P saturation (DPS) and P sorption capacity (PSC). The extent of Fe(III)-oxide reduction measured as 0.1 M HCl extractable Fe(II)_HCl was well described by first-order kinetics with rate constants ranging between 0.01 and 0.3 d^-1. The estimated maximum Fe(II)_HCl produced (Fe(II)_max) ranged between 3 and 1490 mmol Fe(II) kg⁻¹, with Fe_ox corresponding to Fe(II)_max values very closely. For most soils almost full dissolution of the entire Fe_ox pool was achieved within 21 days of incubation. P_Sol concentrations, measured in the soil solution extract, ranged between 0.05 and 5.05 mg L^-1, increasing with incubation time for most of the soils. While P_Sol was not correlated with Fe_BD:P_BD and Fe_ox:P_ox, DPS, total P (P_T) or total Fe (Fe_T):P_T ratio, the investigations revealed a strong reciprocal relationship between the residual sorption capacity (RSC) of the soils, i.e., PSC subtracted the Fe(III)-oxides reduced, and the P_Sol/P_ox ratio. Moreover, the results showed low or lack of P release to the aqueous phase, even for the soil samples where all Fe_ox pools were reduced, if the RSC of the soil was above 100 mmol kg⁻¹. This highlights the importance of redox-stable Al-oxides to capture mobilized P from rewetted lowland peat soils.

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Thodsen, H., Tornbjerg, H., Muff, E. — Wed, 06 Nov 2024 20:23:21 +0100

sammenlignet på tværs af de to opgørelser ”Vandløb 2018” (anvendt til VP3) og
”Vandløb 2021” (anvendt til VP3-G) for perioden 2016-2018 samt 2019-2021 for
”Vandløb 2021”. Der er anført en række grunde til at de opgjorte tilførsler ændrer sig
mellem opgørelser og perioder. Den seneste opgørelse ”Vandløb 2021” anses for den mest opdaterede og bedste opgørelse.]]>

Fri, 25 Oct 2024 20:23:21 +0200

The SentemQC method is computationally efficient and features a six-step user-friendly setup for anomaly detection. The method marks anomalies in data using five moving windows. These windows connect each data point to neighboring points, including those further away in the moving window. SentemQC is tested on HF data from multiple water quality sensors measuring pH, oxygen, nitrate-N, and turbidity installed in the following three Danish freshwater ecosystems: two smaller streams, one lake, and one experimental lake mesocosms.]]>

Kronvang, B., Thodsen, H., Tornbjerg, H., et al. — Thu, 10 Oct 2024 20:23:21 +0200

Audet, J., Levi, E. E., Jeppesen, E., Davidson, T. A. — Mon, 01 Jan 2024 20:23:21 +0100

Shallow lakes and ponds play a crucial role in the processing of carbon and other nutrients. However, many lakes and ponds worldwide are affected by climate change and nutrient pollution. How these pressures affect the emission of the greenhouse gas nitrous oxide (N₂O) is unclear. Warming and eutrophication are expected to increase the production and emission of N₂O in lakes and ponds, but changes in ecological structure and function may complicate these seemingly straightforward relationships. In this study, we used the world's longest running, mesocosm-based, freshwater climate change experiment to disentangle the effect of nutrient enrichment and warming on N₂O emissions. We gathered a large dataset on N₂O concentrations and ancillary variables, comprising three sampling campaigns between 2011 and 2020 and a total of 687 individual mesocosm measurements. Our results demonstrated that nutrient enrichment increased N₂O emissions, while warming (+2.5–4.0°C and +3.75–6.0°C) had no discernable effect. Our study indicates that curtailing nitrogen influxes into lakes and ponds is the most effective strategy to minimize N₂O emissions, and while warming may influence N₂O emissions, it does not appear to be a direct driver. These findings underscore the importance of prioritizing nitrogen mitigation efforts to curb N₂O emissions from shallow lakes and ponds.

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Hoffmann, C. C., Iversen, B. V., Børgesen, C. D. — Mon, 30 Sep 2024 20:23:21 +0200

Adetsu, D. V., Koganti, T., Petersen, R. J., et al. — Sun, 01 Dec 2024 20:23:21 +0100

Draining peatlands for agriculture transforms them into significant carbon (C) sources. Restoring drained peatlands is increasingly recognized as a climate action strategy to reduce terrestrial greenhouse gas emissions. Restoration efforts often require accurate inputs, like peat thickness (PT), for C-stock estimation and monitoring; however, these are often lacking or available at suboptimal accuracy levels. In this study, apparent electrical conductivity (EC_a) from proximal electromagnetic induction (EMI) surveys and topographic variables derived from a LiDAR-based digital elevation model were assessed as covariates for PT mapping of an agricultural bog, separately and combined, using the quantile random forest algorithm. Local models were trained separately for the large (308 ha) and small (42 ha) EMI surveyed areas, while global models combined data from both areas for a full site analysis. The subsurface was characterized based on resistivity variations in inverted towed transient electromagnetic (tTEM) data. The results indicated that combining topographic and EC_a covariates yielded the best PT prediction accuracy for the global model, with a coefficient of determination of 0.61 and a normalized root mean square error (NRMSE) of 0.10. The best large area local model was less accurate than the former (NRMSE of 0.18), while the best small area local model (NRMSE of 0.11) was superior to the best global model. Models trained with only topographic or EC_a covariates were the least accurate, especially for the EC_a-only model. The tTEM results revealed a heterogenous site characterized by a thin, resistive peat layer overlying stratified postglacial deposits of clay, sand, and saline chalk. Our findings show that covariates characterizing surface and subsurface properties are essential for accurate PT mapping and can inform tailored land use planning and restoration initiatives for degraded peatlands.

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Adetsu, D. V., Koganti, T., Petersen, R. J., et al. — Mon, 01 Jan 2024 20:23:21 +0100

Upon drainage, peatlands subside and release stored carbon (C) into the atmosphere. However, little is known about the magnitude of the total, physical and oxidative subsidence (TS, PS and OS) over long historical periods and the past contribution of humans to the degradation observed in contemporary times. Lack of historical subsidence data may hinder contemporary restoration efforts, highlighting the need for insights into past degradation to inform current management practices. Therefore, the present study aims to assess the effect of human activities on the degradation of a raised bog in Denmark in terms of the TS, PS, OS and the C lost between 1880 and 2010 using legacy datasets. The results indicate that 84 % of the bog had been drained by 1997. The TS was 1.6 m on average with a rate of 1.8 cm y^-1. A total of 117 million m³ of peat was lost in the 130-year period. The PS was most important shortly after the start of drainage while OS gained importance in the long term. Up to 540 t ha^-1 of C-stock was lost at a rate of 6 t ha^-1 y^-1, translating to 22 t ha^-1 y^-1 in carbon dioxide equivalents. Therefore, the bog represents a C source in contemporary times, which necessitates targeted and positive management interventions that favour peat growth and C accumulation.

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Trolle, D., Andersen, T. K., Nielsen, A., et al. — Thu, 26 Jan 2023 20:23:21 +0100

Transport Model (pyGETM) for Horsens fjord. ]]>

Thodsen, H., Tornbjerg, H., Rolighed, J., Nedergaard, D., Muff, E. — Thu, 11 Jul 2024 20:23:21 +0200

Hasler, B., Filippelli, R., Andersen, H. E., Levin, G. — Sun, 01 Sep 2024 20:23:21 +0200

Kronvang, B., Larsen, S. E., Thodsen, H., Petersen, R. J., Andersen, H. E. — Thu, 01 Aug 2024 20:23:22 +0200

Kronvang, B., Windolf, J., Rolighed, J., Tornbjerg, H., Larsen, S. E. — Thu, 01 Aug 2024 20:23:22 +0200

Kronvang, B., Bieger, K., Carstensen, M. V. — Mon, 01 Apr 2024 20:23:22 +0200

Publications - Publications

2O Emissions]]>

2 and N2O Budgets]]>

2 and N₂O Budgets]]>