Gradients controlling natural attenuation of ammonium

Maier, Uli; Hermann, R.; Grathwohl, Peter

doi:10.1016/j.apgeochem.2007.06.009

Cited by 19 publications

(13 citation statements)

References 21 publications

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“…In Fig. 3a, this is indicated by a sharp decrease of the oxygen concentration, which corresponded to earlier findings in similar settings (e.g., Barber et al, 1990; McCarthy and Johnson, 1993; Affek et al, 1998; Caron et al, 1998; Maier et al, 2007; Liu et al, 2010; Haberer et al, 2011). Based on numerical simulations, Liu (2008) estimated that within the CF a water saturation of 80 to 90% was required for an oxygen gradient to develop.…”

Section: Resultssupporting

confidence: 91%

“…In abiotic flow‐through experiments at steady state, earlier studies have shown that transverse vertical dispersion is essential for mass transfer of oxygen from the atmosphere to oxygen‐depleted groundwater (Klenk and Grathwohl, 2002; Haberer et al, 2011). The observed concentration gradients are steepest in the transition region between the unsaturated and the fully water‐saturated zone due to the limited mass transfer of oxygen in the water phase (e.g., Affek et al, 1998; Maier et al, 2007; Liu et al, 2010). Oxygen consumption by aerobic microorganisms results in partially increased mass fluxes across the CF and, thus, in oxygen gradients that are steeper than under abiotic conditions.…”

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confidence: 99%

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Oxygen Transfer in a Fluctuating Capillary Fringe: Impact of Microbial Respiratory Activity

Jost

Haberer

Grathwohl

et al. 2015

Vadose Zone Journal

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Laboratory‐scale flow‐through experiments in a sand‐filled chamber were performed to investigate the impact of aerobically growing Escherichia coli HB101‐K12 on oxygen transfer across the capillary fringe (CF) to oxygen‐depleted groundwater. In the experiments, both the effects of different nutrient concentrations and transient flow conditions were tested. The results of biotic experiments under oligotrophic and eutrophic conditions (6.8 g organic C L−1) were compared with those of an abiotic experiment. Moreover, in each experiment steady‐state and transient conditions were considered, the latter induced by changing the water‐table height. Growth of E. coli was quantified by cell counting in effluent samples and could be monitored due to intracellular production of the green fluorescent protein (GFP). Under eutrophic conditions, highest cell densities and strongest cell attachment were observed in the transition region of the CF. In this region, intensive bacterial respiration decreased oxygen concentrations relatively quickly, causing a steep oxygen gradient that resulted in a higher oxygen flux across the unsaturated–saturated interface. Under oligotrophic conditions, this effect was considerably reduced, but was still detectable. Due to oxygen supply from entrapped air, bacterial growth was slightly enhanced within the upper, newly formed CF region, directly after raising the water table. After lowering the water table to the initial height only a minor microbial impact on oxygen transfer was noticed, even under eutrophic conditions, because of the fast diffusion of oxygen in the (partially) air‐filled pore spaces. Bacteria that remained in the transition region of the CF grew to higher densities due to better oxygen supply.

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Section: Resultssupporting

confidence: 91%

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confidence: 99%

Oxygen Transfer in a Fluctuating Capillary Fringe: Impact of Microbial Respiratory Activity

Jost

Haberer

Grathwohl

et al. 2015

Vadose Zone Journal

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“…A similar conceptual model could be proposed for contamination situations other than phenoxy acids in landfill leachate plumes, where a micropollutant travels within a macropollutant plume that controls the redox conditions. Proposed examples are benzene in a landfill leachate plume (Baun et al 2003) or within an ethanol plume (Molson et al 2002), specific phenols in a creosote plume (Thornton 2001a, 2001b), and ammonium in landfill plumes (Maier et al 2007). For some of these compounds, however, degradation in the core may be substantial as well.…”

Section: Resultsmentioning

confidence: 99%

Natural Attenuation Processes in Landfill Leachate Plumes at Three Danish Sites

Bjerg¹,

Tuxen

Reitzel

et al. 2009

Ground Water

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This article provides an overview of comprehensive core and fringe field studies at three Danish landfill sites. The goal of the research activities is to provide a holistic description of core and fringe attenuation processes for xenobiotic organic compounds in landfill leachate plumes. The approach used is cross-disciplinary, encompassing integration of field-scale observations at different scales, field injection experiments, laboratory experiments, and reactive solute transport modeling. This is illustrated in examples from the most recently investigated site-the Sjoelund Landfill. The research performed serves as good case studies to conceptualize natural attenuation processes in landfill leachate plumes and also supports the notion that monitored natural attenuation (MNA) may be a possible remediation strategy at landfills. However, landfill leachate plumes challenge traditional approaches and tools used in the application of MNA. In particular, the use of in situ indicators to document mass removal in landfill leachate plumes is emphasized. In this article, we advocate the application of conceptual and numerical models as tools for the integration of data and testing of hypotheses.

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“…The supply of O 2 influences subsurface redox conditions and the rates of many biological and geochemical reactions (e.g., Stumm and Morgan, 1996; Chapelle, 2001; Mächler et al, 2013; Rezanezhad et al, 2014). The importance of O 2 transport across the capillary fringe has been shown in detailed experimental and modeling studies focusing on conservative transport (e.g., Williams and Oostrom, 2000; Haberer et al, 2011, 2014, 2015), microbially mediated reactions (e.g., Sobolev and Roden, 2001; Maier et al, 2007; Dobson et al, 2007; Jost et al, 2015), and abiotic reactions (Farnsworth et al, 2012). The objective of this work was the simultaneous investigation of diffusive–dispersive O 2 transport under conservative and reactive conditions.…”

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Diffusive–Dispersive and Reactive Fronts in Porous Media: Iron(II) Oxidation at the Unsaturated–Saturated Interface

Haberer

Muniruzzaman

Grathwohl

et al. 2015

Vadose Zone Journal

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Impact StatementUsing a combined experimental and modeling approach we investigate the coupling between diffusive/dispersive processes and kinetic iron(II) oxidation in batch, 1-D column, and 2-D flow-through systems. 2 Abstract 1Diffusive/dispersive mass transfer is important for many groundwater quality problems as it drives the 2 interaction between different reactants, thus influencing a wide variety of biogeochemical processes. In 3 this study we performed laboratory experiments to quantify oxygen transport in porous media, across the 4 unsaturated/saturated interface, under both conservative and reactive transport conditions. As reactive 5 system we considered the abiotic oxidation of ferrous iron in the presence of oxygen. We studied the 6 reaction kinetics in batch experiments and its coupling with diffusive and dispersive transport processes 7 by means of 1-D columns and 2-D flow-through experiments, respectively. A non-invasive optode 8 technique was used to track oxygen transport into the initially anoxic porous media at highly resolved 9 spatial and temporal scales. The results show significant differences in the propagation of the conservative 10 and reactive oxygen fronts. Under reactive conditions oxygen, continuously provided from the 11 atmosphere, was considerably retarded due to the interaction with dissolved iron(II), initially present in 12 the anoxic groundwater. The reaction between dissolved oxygen and ferrous iron led to the formation of 13 an iron(III) precipitation zone in the experiments. Reactive transport modeling based on a kinetic 14 PHREEQC module tested in controlled batch experiments allowed a quantitative interpretation of the 15 experimental results in both 1-D and 2-D setups. 16 Keywords: diffusion; transverse dispersion; unsaturated/saturated interface; iron(II) oxidation; porous media. 18In natural systems, the geochemical and biological activity at the interface between different 19 compartments, such as the unsaturated and the saturated zone in the subsurface, is determined by the 20 fluxes and exchange rates across the interface. Interface regions are highly active in terms of 21 physicochemical and microbiological processes (e.g., Sobolev and Roden, 2001; Bauer et al., 2009; Jost et 22 al., 2014). A number of experimental and modeling studies have identified diffusive and dispersive 23 processes as key mechanisms for mass transfer of volatile compounds to or from groundwater systems 24 (e.g., Barber and Davis, 1987; Barber et al., 1990; McCarthy and Johnson, 1993; Klenk and Grathwohl, 25 2002;Werner and Höhener, 2002;Prommer et al., 2009; Haberer et al., 2011 Haberer et al., , 2012 Freitas et al., 2011). 26 3Of particular importance is the mass transfer of oxygen to anoxic groundwater since dissolved oxygen 27 plays a key role for many biogeochemical processes. The supply of oxygen influences the subsurface 28 redox conditions and the rates of many biological and geochemical reactions (e.g., Stumm and Morgan, 29 1996; Chapelle, 2001; Mächler et al., 2013; Re...

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Gradients controlling natural attenuation of ammonium

Cited by 19 publications

References 21 publications

Oxygen Transfer in a Fluctuating Capillary Fringe: Impact of Microbial Respiratory Activity

Oxygen Transfer in a Fluctuating Capillary Fringe: Impact of Microbial Respiratory Activity

Natural Attenuation Processes in Landfill Leachate Plumes at Three Danish Sites

Diffusive–Dispersive and Reactive Fronts in Porous Media: Iron(II) Oxidation at the Unsaturated–Saturated Interface

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