281 research outputs found
Detecting groundwater discharge dynamics from point-to-catchment scale in a lowland stream : Combining hydraulic and tracer methods
Acknowledgements. We would like to thank members of the Northern Rivers Institute, Aberdeen University, for helpful discussions of data. We also thank Lars Rasmussen, Jolanta Kazmierczak and Charlotte Ditlevsen for help in the field. This study is part of the Hydrology Observatory, HOBE (http://www.hobe.dk), funded by the Villum Foundation and was as well funded by the Aarhus University Research Foundation.Peer reviewedPublisher PD
Groundwater–surface water interaction in Denmark
The study of groundwater–surface water interaction has attracted growing interest
among researchers in recent years due to its wide range of implications from
the perspectives of water management, ecology and contamination. Many of the
studies shed light on conditions on a local scale only, without exploring a regional
angle. To provide a broad and historical overview of groundwater–surface water
interaction, a review of research carried out in Denmark was undertaken due to
the high density of studies conducted in the country. The extent to which this
topic has been investigated is related to Denmark's physiography and climate, the
presence of numerous streams and lakes combined with shallow groundwater,
and historical, funding, and administrative decisions. Study topics comprise
groundwater detection techniques, numerical modeling, and contaminant issues
including nutrients, ranging from point studies all the way to studies at national
scale. The increase in studies in recent decades corresponds with the need to
maintain the good status of groundwater-dependent ecosystems and protect
groundwater resources. This review of three decades of research revealed that
problems such as the difference in scales between numerical models and field
observations, interdisciplinary research integrating hydrological and biological
methods, and the effect of local processes in regional systems remain persistent
challenges. Technical progress in the use of unmanned aerial vehicles, distributed
temperature sensing, and new cost-effective methods for detecting groundwater
discharge as well as the increasing computing capacity of numerical models
emerge as opportunities for dealing with complex natural systems that are subject
to modifications in future triggered by climate change.Next-Generation EU fundingPrograma
Maria Zambrano Sénior (REF: MZSA03
Origin and Dynamics ofSaltwater Intrusion in a Regional Aquifer:Combining 3-D Saltwater Modeling With Geophysical and Geochemical Data
Investigating the molecular mechanism of positive and negative allosteric modulators in the calcium-sensing receptor dimer
Evaluation of Temperature Profiling and Seepage Meter Methods for Quantifying Submarine Groundwater Discharge to Coastal Lagoons:Impacts of Saltwater Intrusion and the Associated Thermal Regime
Application of Stable Isotopes of Water to Study Coupled Submarine Groundwater Discharge and Nutrient Delivery
Tracing the Spatial Distribution of Whole-Lake Exchange of Groundwater and Lake Water in Low-Hydraulic Gradient Systems Using delta O-18 and Electrical Conductivity and Uncertain End-Member Mixing Analysis
δ18O and electrical conductivity (EC) were used successfully to trace the spatial distribution of whole-lake groundwater-lake exchange for a small (four ha) groundwater-fed lake situated in a low relief and low hydraulic gradient area. The method relies on quick sampling of shallow groundwater, direct analysis of EC in the field, and relatively in-expensive analysis of δ18O in the laboratory. Ternary uncertain end-member mixing analysis (precipitation, groundwater, and lake water) quantified the composition of water discharging to and recharging from the lake. The tracer distribution and mixing analysis were in agreement with the interpreted groundwater flow near the lake. The use of only one tracer (either δ18O or EC) gave the same results for the recharge segments, but the discharge segments changed the origin of the water from being groundwater to precipitation controlled. The two tracers complemented each other, especially with different signals in precipitation and groundwater. The uncertain end-members were assessed based on local (groundwater and lake water) and off-site (precipitation) data. The off-site data were found to be useful if it contained representative information on local-site seasonality (uncertainty, variance). Final end-member concentrations could explain the transience of the hydrology at the site (i.e., flooding of the area adjacent to the lake during periods with high precipitation, and variability of the δ18O signal in precipitation). This methodology potentially represents a new option to study groundwater-lake systems. The tracer information collected over only two days is useful by itself for developing the next steps like the quantification of fluxes based on other standard methods (Darcy approach, seepage meters, or temperature). The tracer information can provide quantitative estimation of inputs and outputs by using the mixing analysis
Languages' impact on emotional classification methods
There is currently a lack of research concerning whether Emotional Classification (EC) research on a language is applicable to other languages. If this is the case then we can greatly reduce the amount of research needed for different languages. Therefore, we propose a framework to answer the following null hypothesis: The change in classification accuracy for Emotional Classification caused by changing a single preprocessor or classifier is independent of the target language within a significance level of p = 0.05. We test this hypothesis using an English and a Danish data set, and the classification algorithms: Support-Vector Machine, Naive Bayes, and Random Forest. From our statistical test, we got a p-value of 0.12852 and could therefore not reject our hypothesis. Thus, our hypothesis could still be true. More research is therefore needed within the field of cross-language EC in order to benefit EC for different languages
Subsurface nitrate reduction under wetlands takes place in narrow superficial zones
This study aims to investigate the depth distribution of the Nitrate Reduction Potential (NRP) on a natural and a re-established wetland. The obtained NRP provides a valuable data of the driving factors affecting denitrification, the Dissimilatory Nitrate Reduction to Ammonium (DNRA) process and the performance of a re-established wetland. Intact soil cores were collected and divided in slices for the determination of Organic Matter (OM) through Loss of Ignition (LOI) as well as Dissolved Organic Carbon (DOC) and NRP spiking nitrate in batch tests. The Nitrate Reduction (NR) was fitted as a pseudo-first order rate constant (k) from where NRPs were obtained. NR took place in a narrow superficial zone showing a dropping natural logarithmic trend along depth. The main driving factor of denitrification, besides depth, was OM. Although, DOC and LOI could not express by themselves and absolute correlation with NRP, high amounts of DOC ensured enough quantity and quality of labile OM for NR. Besides, high concentration of LOI but a scarce abundance of DOC failed to drive NR. DNRA was only important in superficial samples with high contents of OM. Lastly, the high NRP of the re-established wetland confirms that wetlands can be restored satisfactorily.Preprin
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