The impact of oscillating redox conditions: Arsenic immobilisation in contaminated calcareous floodplain soils

Parsons, Christopher T.; Couture, Raoul-Marie; Omoregie, Enoma; Bardelli, Fabrizio; Grenèche, Jean‐Marc; Román-Ross, Gabriela; Charlet, Laurent

doi:10.1016/j.envpol.2013.02.028

Cited by 72 publications

(77 citation statements)

References 62 publications

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“…Note that NO 3 − is exclusively reduced via respiration in the presence of microorganisms. apparent stability of the reduced species observed here contrasts with previous studies of contaminant dynamics in topsoil suspensions under similar redox-oscillating conditions (e.g., Couture et al, 2015;Hockmann et al, 2014;Parsons et al, 2013), where re-oxidation is observed to various degrees. We hypothesize that the lack of re-oxidation reflects kinetic limitation in argillaceous materials lacking reactive Fe-and Mn-oxyhydroxides (Table A.2) (Leuz and Johnson, 2005;Rai et al, 1989).…”

Section: Stability Of Reduced Contaminantscontrasting

confidence: 55%

“…The inoculum was extracted from a natural floodplain soil located in a zone experiencing frequent redox fluctuations. Previous characterization of the microbial ecology at this field site demonstrated the presence of a broad diversity of aerobic and anaerobic bacteria (Parsons et al, 2013). Details on the preparation and injection of soil inoculum are given in Annex C.…”

Section: Methodsmentioning

confidence: 99%

“…Batch experiments were performed using a bioreactor system based on the design of Thompson et al (2006) and modified by Parsons et al (2013). Briefly, each reactor contained a suspension volume of 1 L with a headspace of about 300 ml and incubated in the dark.…”

Section: Methodsmentioning

confidence: 99%

“…Dynamic changes in redox conditions have significant effects on aqueous contaminant concentrations in saturated near-surface environments (Couture et al, 2015;Hindersmann and Mansfeldt, 2014;Parsons et al, 2013;Stewart et al, 2009;Thompson et al, 2006), suggesting that they also play a role in controlling contaminant mobility in subsurface argillaceous formations. Research on how redox phenomena control the long-term mobility of radionuclides in waste repositories has been performed by 32 European research institutes and universities within the ReCosy collaborative project (Duro et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

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Speciation dynamics of oxyanion contaminants (As, Sb, Cr) in argillaceous suspensions during oxic-anoxic cycles

Markelova

Couture

Parsons

et al. 2018

Applied Geochemistry

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A B S T R A C TArgillaceous geological formations are considered promising repositories for waste containing inorganic contaminants. However, the sequestration capacity of an argillaceous natural barrier may change as a result of dynamic environmental conditions, in particular changes in redox state. Here, we imposed redox cycles to argillaceous suspensions amended with a mixture of the inorganic contaminants As(V), Sb(V), Cr(VI), by alternating 7-day cycles of sparging with either oxic or anoxic gas mixtures. During the redox cycles, we assessed the relative importance of different contaminant sequestration mechanisms under sterile and non-sterile conditions. The non-sterile experiments were carried out 1) with the argillaceous material as is, that is, containing the native microbial population, 2) with the addition of ethanol as a source of labile organic carbon, and 3) with the addition of both ethanol and a soil microbial inoculum. In order to capture the observed solid-solution partitioning trends, a series of mixed thermodynamic-kinetic models representing the dynamic conditions in the experiments were developed using PHREEQC. Parameter values for processes such as adsorption, which occurred in all experiments, were kept constant across all the simulations. Additional formulations were introduced as needed to account for the microbial detoxification and respiration of the contaminants in the increasing complexity experiments. Abiotic adsorption of As and abiotic reductive precipitation of Cr dominated sequestration of these two contaminants under all experimental conditions, whereas the presence of microorganisms was essential to decrease the aqueous Sb concentration. Once reduced, As(III), Sb(III), and Cr(III) were not reoxidized upon exposure to dissolved O 2 in any of the experiments. Neither the mineralogy nor the native microbiota catalysed contaminant oxidation processes. Thus, kinetically, the reduction of As(V), Sb(V), and Cr(VI) was irreversible over the experimental duration (49 days). The capacity of the argillaceous matrix to reduce and sequester the aqueous contaminants, without subsequent remobilization to the aqueous phase during the oxic periods, supports the use of argillaceous barriers for geologic waste storage.

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Section: Stability Of Reduced Contaminantscontrasting

confidence: 55%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Speciation dynamics of oxyanion contaminants (As, Sb, Cr) in argillaceous suspensions during oxic-anoxic cycles

Markelova

Couture

Parsons

et al. 2018

Applied Geochemistry

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“…The dry weight was then re-determined, and the sieved solution was diluted with filtered surface water to a final concentration of 247 ± 2 g L −1 . The resulting suspension was transferred to a bioreactor system (Applikon Biotechnology) after Thompson et al (2006) and Parsons et al (2013). In addition to affording precise temperature control and continuous logging of temperature, redox potential (E h ) and pH, the system offers significant advancements over previous designs (Thompson 2006;Guo, 2007;Parsons, 2013).…”

Section: Bioreactor Experiments and Redox Oscillation Proceduresmentioning

confidence: 99%

Sediment phosphorus speciation and mobility under dynamic redox conditions

Parsons¹,

Rezanezhad²,

O’Connell³

et al. 2017

Biogeosciences

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Abstract. Anthropogenic nutrient enrichment has caused phosphorus (P) accumulation in many freshwater sediments, raising concerns that internal loading from legacy P may delay the recovery of aquatic ecosystems suffering from eutrophication. Benthic recycling of P strongly depends on the redox regime within surficial sediment. In many shallow environments, redox conditions tend to be highly dynamic as a result of, among others, bioturbation by macrofauna, root activity, sediment resuspension and seasonal variations in bottom-water oxygen (O 2 ) concentrations. To gain insight into the mobility and biogeochemistry of P under fluctuating redox conditions, a suspension of sediment from a hypereutrophic freshwater marsh was exposed to alternating 7-day periods of purging with air and nitrogen gas (N 2 ), for a total duration of 74 days, in a bioreactor system. We present comprehensive data time series of bulk aqueous-and solidphase chemistry, solid-phase phosphorus speciation and hydrolytic enzyme activities demonstrating the mass balanced redistribution of P in sediment during redox cycling. Aqueous phosphate concentrations remained low (∼ 2.5 µM) under oxic conditions due to sorption to iron(III) oxyhydroxides. During anoxic periods, once nitrate was depleted, the reductive dissolution of iron(III) oxyhydroxides released P. However, only 4.5 % of the released P accumulated in solution while the rest was redistributed between the MgCl 2 and NaHCO 3 extractable fractions of the solid phase. Thus, under the short redox fluctuations imposed in the experiments, P remobilization to the aqueous phase remained relatively limited. Orthophosphate predominated at all times during the experiment in both the solid and aqueous phase. Combined P monoesters and diesters accounted for between 9 and 16 % of sediment particulate P. Phosphatase activities up to 2.4 mmol h −1 kg −1 indicated the potential for rapid mineralization of organic P (P o ), in particular during periods of aeration when the activity of phosphomonoesterases was 37 % higher than under N 2 sparging. The results emphasize that the magnitude and timing of internal P loading during periods of anoxia are dependent on both P redistribution within sediments and bottom-water nitrate concentrations.

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Bacterial Fe(II) oxidation distinguished by long‐range correlation in redox potential

Enright

Ferris

2016

JGR Biogeosciences

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The impact of oscillating redox conditions: Arsenic immobilisation in contaminated calcareous floodplain soils

Cited by 72 publications

References 62 publications

Speciation dynamics of oxyanion contaminants (As, Sb, Cr) in argillaceous suspensions during oxic-anoxic cycles

Speciation dynamics of oxyanion contaminants (As, Sb, Cr) in argillaceous suspensions during oxic-anoxic cycles

Sediment phosphorus speciation and mobility under dynamic redox conditions

Bacterial Fe(II) oxidation distinguished by long‐range correlation in redox potential

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