Hydrochemical evolution of a freshwater lens below a barrier island (Spiekeroog, Germany): The role of carbonate mineral reactions, cation exchange and redox processes

Seibert, Stephan L.; Holt, Tobias; Reckhardt, Anja; Ahrens, Janis; Beck, Mélanie; Pollmann, Thomas; Giani, Luise; Waska, Hannelore; Böttcher, Michael E.; Greskowiak, Janek; Massmann, Gudrun

doi:10.1016/j.apgeochem.2018.03.001

Cited by 38 publications

(22 citation statements)

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“…In addition, Fe(II) concentrations were very low in low-salinity patches compared to high-salinity areas at the low water line, probably because the fresh groundwater component was more depleted in Fe(II) compared to the exfiltrating seawater from the ridge. These results are in line with Seibert et al (2018), who attributed the absence of Fe(II) in the older groundwater of the island's freshwater lens to the formation of iron sulfides in succession to sulfate reduction.…”

Section: Biogeochemical Patternssupporting

confidence: 91%

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Spatial and Temporal Patterns of Pore Water Chemistry in the Inter-Tidal Zone of a High Energy Beach

et al. 2019

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Section: Biogeochemical Patternssupporting

confidence: 91%

“…The island is composed of fine-to medium grained Holocene sands above Pleistocene deposits. A clay layer at 40 m below surface confines the precipitation-fed freshwater lens toward its base, which has water ages of up to 51 years (Seibert et al, 2018).…”

Section: Study Sitementioning

confidence: 99%

Spatial and Temporal Patterns of Pore Water Chemistry in the Inter-Tidal Zone of a High Energy Beach

et al. 2019

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“…Additional NH 4 + was delivered to brackish mixing zones by fresh groundwater from the inland's freshwater lens, which carries up to 78 μM NH 4 + (Seibert et al, ), but highest NH 4 + concentrations were found in saline anoxic pore waters and most likely produced in situ during anaerobic respiration (Figure S4). Due to the cooccurrence with reduced substances like dissolved Fe and Mn (Figures and ), it is likely that NH 4 + was released during organic matter degradation via Mn or Fe oxide reduction and is not subject to rapid (re‐)oxidation in these environments.…”

Section: Discussionmentioning

confidence: 99%

“…The beach sediments of the upper meters are composed of fine to medium sand (mean grain size: 170–320 μm; Beck et al, ). The western part of the island is underlain by a freshwater lens (Figure b), which is confined by clay layer at about 40 m below NHN (standard elevation zero) and exhibits water ages up to 51 years (Röper et al, ; Seibert et al, ). Due to varying flow paths, fresh groundwater of various ages is delivered to the intertidal subsurface (Beck et al, ).…”

Section: Methodsmentioning

confidence: 99%

Seasonality of Organic Matter Degradation Regulates Nutrient and Metal Net Fluxes in a High Energy Sandy Beach

et al. 2020

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During seawater circulation in permeable intertidal sands, organic matter degradation alters the composition of percolating fluids and remineralization products discharge into surficial waters. Concurrently, coastal seawater nutrient and organic matter composition change seasonally due to variations in pelagic productivity. To assess seasonal changes in organic matter degradation in the intertidal zone of a high energy beach (Spiekeroog Island, southern North Sea, Germany), we analyzed shallow pore waters for major redox constituents (oxygen [O2], manganese [Mn], and iron [Fe]) and inorganic nitrogen species (nitrite [NO2−], nitrate [NO3−], and ammonium [NH4+]) in March, August, and October. Surface water samples from a local time series station were used to monitor seasonal changes in pelagic productivity. O2 and NO3− were the dominating pore water constituents in March and October. Dissolved Mn, Fe, and NH4+ were more widely distributed in August. Seasonal changes in seawater temperature as well as organic matter and nitrate supply by seawater were assumed to affect microbial rates and degradation pathways. Pore water and seawater variability led to seasonally changing constituent effluxes to surface waters. Mn, Fe, and NH4+ effluxes are minimal in March and reached their maximum in August. Furthermore, the intertidal sands switched from a net dissolved inorganic nitrogen sink in March to a net source in August. In conclusion, seasonal effects on intertidal pore water biogeochemistry affect constituent fluxes across the sediment‐water interface. The seasonality of the beach bioreactor must be considered when fluxes are extrapolated to annual timescales.

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“…There is a large body of literature dedicated to the water chemistry mechanisms associated with saline water leakage. Various methods have been used to examine the system in more detail, including factor analysis [ 22 ], the ion ratio method [ 23 ], isotope tests [ 24 ], trace element tests [ 25 ], and so on. Factor analysis is the principal approach used for the comprehensive evaluation of multi-factor systems.…”

Section: Introductionmentioning

confidence: 99%

The Blocking Effect of Clay in Groundwater Systems: A Case Study in an Inland Plain Area

Xing

Huang

Yang³

et al. 2018

IJERPH

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In order to increase understanding of the hydrogeochemical effects that influence changes in the quality of salt water, we investigated the distribution of saline and fresh water in an inland plain area and, in particular, the scarcity of fresh water resources. Taking the inland plain in Jiyang County as a specific case study, samples of undisturbed clay and underground saline water from different depths were collected to examine hydrogeological changes. A wide variety of methods was used to analyze the blocking effect of clay on the chemical characteristics of the groundwater. These include real-time monitoring for field water quality, tests for isothermal adsorption, a factor analysis model, physiochemical analysis, and correlation analysis. Our results show that the optimal adsorption isotherm of clay for Na+, Ca2+ and Mg2+ in groundwater conform to the established Henry and Langmuir equations for adsorption isotherms. The influence of clay mineral types and content on the blockage of Na+, Ca2+ and Mg2+ in groundwater samples were evident at different depths, with the clay adsorption capacity increasing in line with increases in the clay mineral content. Clay at different depths was found to have the strongest blocking effect on Na+ in groundwater, being systematically greater than its effect on Ca2+ and Mg2+. It is believed that the blocking effect of clay has an important influence on the hydrochemical zoning of groundwater in inland plains and the formation of saline water in groundwater systems. This study therefore provides concrete evidence in support of this supposed effect.

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Hydrochemical evolution of a freshwater lens below a barrier island (Spiekeroog, Germany): The role of carbonate mineral reactions, cation exchange and redox processes

Cited by 38 publications

References 41 publications

Spatial and Temporal Patterns of Pore Water Chemistry in the Inter-Tidal Zone of a High Energy Beach

Spatial and Temporal Patterns of Pore Water Chemistry in the Inter-Tidal Zone of a High Energy Beach

Seasonality of Organic Matter Degradation Regulates Nutrient and Metal Net Fluxes in a High Energy Sandy Beach

The Blocking Effect of Clay in Groundwater Systems: A Case Study in an Inland Plain Area

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