Discharge of nitrate-containing groundwater into a coastal marine environment

Andersen, Martin S.; Baron, Ludovic; Gudbjerg, Jacob; Gregersen, J.; Chapellier, D.; Jakobsen, Rasmus; Postma, Dieke

doi:10.1016/j.jhydrol.2006.12.023

Cited by 69 publications

(43 citation statements)

References 76 publications

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“…According to Carrera et al (2010), seawater intrusion is especially sensitive to the sea-aquifer connection, usually associated with the presence of preferential flow paths, a phenomenon which has been demonstrated also to affect fresh groundwater discharge to the sea Mulligan et al, 2007). A few studies have shown that structural anomalies like fractures, faults and paleo-channels control the saline-groundwater movement in some coastal aquifers (Calvache and Pulido-Bosch, 1997;Spechler, 2001;Yechieli et al, 2001;Mulligan et al, 2007;Nishikawa et al, 2009) or, reversely, fresh groundwater discharge to or below marine waters, as observed in two studies close to the area investigated in this study Andersen et al, 2007). In Mulligan et al (2007), the impact of a palaeo-channel breaching a clay layer separating a shallow surficial aquifer from an underlying confined aquifer was studied.…”

Section: Introductionsupporting

confidence: 67%

Transboundary geophysical mapping of geological elements and salinity distribution critical for the assessment of future sea water intrusion in response to sea level rise

Jørgensen

Scheer

Thomsen

et al. 2012

Hydrol. Earth Syst. Sci.

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Abstract. Geophysical techniques are increasingly being used as tools for characterising the subsurface, and they are generally required to develop subsurface models that properly delineate the distribution of aquifers and aquitards, salt/freshwater interfaces, and geological structures that affect groundwater flow. In a study area covering 730 km2 across the border between Germany and Denmark, a combination of an airborne electromagnetic survey (performed with the SkyTEM system), a high-resolution seismic survey and borehole logging has been used in an integrated mapping of important geological, physical and chemical features of the subsurface. The spacing between flight lines is 200–250 m which gives a total of about 3200 line km. About 38 km of seismic lines have been collected. Faults bordering a graben structure, buried tunnel valleys, glaciotectonic thrust complexes, marine clay units, and sand aquifers are all examples of geological structures mapped by the geophysical data that control groundwater flow and to some extent hydrochemistry. Additionally, the data provide an excellent picture of the salinity distribution in the area and thus provide important information on the salt/freshwater boundary and the chemical status of groundwater. Although the westernmost part of the study area along the North Sea coast is saturated with saline water and the TEM data therefore are strongly influenced by the increased electrical conductivity there, buried valleys and other geological elements are still revealed. The mapped salinity distribution indicates preferential flow paths through and along specific geological structures within the area. The effects of a future sea level rise on the groundwater system and groundwater chemistry are discussed with special emphasis on the importance of knowing the existence, distribution and geometry of the mapped geological elements, and their control on the groundwater salinity distribution is assessed.

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Section: Introductionsupporting

confidence: 67%

Transboundary geophysical mapping of geological elements and salinity distribution critical for the assessment of future sea water intrusion in response to sea level rise

Jørgensen

Scheer

Thomsen

et al. 2012

Hydrol. Earth Syst. Sci.

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“…The high NO x − concentrations up to 260 μM do not originate from fertilizers or sewage transported to the beach via groundwater flow because the study site is located in an environmentally protected area, where agriculture and fossil fuel traffic are absent. This is in contrast to several other subterranean estuaries where fertilizers and sewage represent an important nitrogen source (Andersen et al, 2007;Kroeger and Charette, 2008;Wong et al, 2014). Instead, the high NO x − concentrations may originate either from seawater or rainwater, or from biogeochemical reactions occurring on site.…”

Section: Pore Water Origin and Redox State Control Nutrient And Metalmentioning

confidence: 80%

The drivers of biogeochemistry in beach ecosystems: A cross-shore transect from the dunes to the low-water line

et al. 2017

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This study addresses key processes in high-energy beach systems using an interdisciplinary approach. We assess spatial variations in subsurface pore water residence times, salinity, organic matter (OM) availability, and redox conditions and their effects on nutrient cycles as well as on microbial community patterns and microphytobenthos growth. At the study site on Spiekeroog Island, southern North Sea, beach hydrology is characterized by the classical zonation with an upper saline plume (USP), a saltwater wedge, and a freshwater discharge tube in between. Sediment and pore water samples were taken along a cross-shore transect from the dunes to the low-water line reaching sediment depths down to 5 m below sediment surface. Spatial variations in pore water residence time, salinity, and organic matter availability lead to steep redox and nutrient gradients. Vertical and horizontal differences in the microbial community indicate the influence of these gradients and salinity on the community structure. shoreline. We propose that this nutrient efflux triggers growth of microphytobenthos on sediment surfaces of the discharge zone. A first comparison of nutrient discharge rates of the beach site with a nearby sandy backbarrier tidal flat margin indicates that the beach system might be of less importance in supplying recycled nutrients to nearshore waters than the backbarrier tidal flat area.

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“…Accurate prediction of the occurrence and morphological consequence of overtopping and overwash is of obvious importance for coastal flood risk assessment and management (Matias et al, 2008). Equally apparent is the relevance of being able to quantify and model cross-barrier groundwater fluxes, for example for assessing the dispersal of pollutants from coastal aquifers into the sea and saline intrusion as a result of sea-level rise (Andersen et al, 2007). A less obvious, but potentially significant and related process is the effect of interactions between the beach groundwater table and swash motion on sediment transport processes on the upper beach (Turner and Masselink, 1998) and, therefore, beach stability.…”

Section: Introductionmentioning

confidence: 99%

Large-scale Barrier Dynamics Experiment II (BARDEX II): Experimental design, instrumentation, test program, and data set

Masselink

Ruju

Conley

et al. 2016

Coastal Engineering

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Despite the increased sophistication of numerical models and field techniques for investigating wave-induced nearshore sediment transport and ensuing beach morphological response, there remains a significant demand for large-scale laboratory experiments to address this research topic. Here, we describe the Barrier Dynamics II experiment (BARDEX II), which involved placing a near prototype-scale sandy barrier in the middle of the Delta Flume in the Netherlands and subjecting the structure to a range of wave, tide and water level conditions. A unique aspect of the experiment was the presence of a lagoon behind the barrier, as often occurs in natural barrier settings, providing a convenient means to experimentally manipulate the groundwater hydrology within the barrier. The overall aim of the BARDEX II was to collect a large-scale data set of energetic waves acting on a sandy beach/barrier system to improve our quantitative understanding and modelling capability of shallow water sediment transport processes in the inner surf, swash and overwash zone. In this paper we introduce BARDEX II and provide a detailed description of the experiment, including the experimental design, instrumentation, test programme and data set, as well as presenting some examples of the morphological and hydrodynamic data set. We also reflect objectively on the strengths and weaknesses of the data set. This paper serves as an introduction to a special issue of Coastal Engineering, solely devoted to the results of BARDEX II.

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Discharge of nitrate-containing groundwater into a coastal marine environment

Cited by 69 publications

References 76 publications

Transboundary geophysical mapping of geological elements and salinity distribution critical for the assessment of future sea water intrusion in response to sea level rise

Transboundary geophysical mapping of geological elements and salinity distribution critical for the assessment of future sea water intrusion in response to sea level rise

The drivers of biogeochemistry in beach ecosystems: A cross-shore transect from the dunes to the low-water line

Large-scale Barrier Dynamics Experiment II (BARDEX II): Experimental design, instrumentation, test program, and data set

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