Performance of a zerovalent iron reactive barrier for the treatment of arsenic in groundwater: Part 2. Geochemical modeling and solid phase studies

2009 ◽  
Vol 106 (1-2) ◽  
pp. 15-28 ◽  
Author(s):  
Douglas G. Beak ◽  
Richard T. Wilkin
Keyword(s):  
Solid Phase ◽  
Geochemical Modeling ◽  
Zerovalent Iron ◽  
Reactive Barrier ◽  
Arsenic In Groundwater

Performance of a zerovalent iron reactive barrier for the treatment of arsenic in groundwater: Part 1. Hydrogeochemical studies

2009 ◽  
Vol 106 (1-2) ◽  
pp. 1-14 ◽  
Author(s):  
Richard T. Wilkin ◽  
Steven D. Acree ◽  
Randall R. Ross ◽  
Douglas G. Beak ◽  
Tony R. Lee
Keyword(s):  
Zerovalent Iron ◽  
Reactive Barrier ◽  
Arsenic In Groundwater

The fate of arsenic in groundwater discharged to the Meghna River, Bangladesh

2018 ◽  
Vol 15 (2) ◽  
pp. 29 ◽  
Author(s):  
Michelle Berube ◽  
Katrina Jewell ◽  
Kimberly D. Myers ◽  
Peter S. K. Knappett ◽  
Pin Shuai ◽  
...  
Keyword(s):  
River Water ◽  
Solid Phase ◽  
Sediment Cores ◽  
Hydrologic Processes ◽  
Reactive Barrier ◽  
Arsenic In Groundwater ◽  
Phosphate Leaching ◽  
Induced Changes ◽  
The Ganges ◽  
The Impact

Environmental contextArsenic contamination of groundwater is a major environmental problem in many areas of the world. In south-east Asia, iron-rich reducing groundwater mixes with oxidising river water in hyporheic zones, precipitating iron oxides. These oxides can act as a natural reactive barrier capable of accumulating elevated solid-phase concentrations of arsenic. AbstractShallow, anoxic aquifers within the Ganges–Brahmaputra–Meghna Delta (GBMD) commonly contain elevated concentrations of arsenic (As), iron (Fe) and manganese (Mn). Highly enriched solid-phase concentrations of these elements have been observed within sediments lining the banks of the Meghna River. This zone has been described as a Natural Reactive Barrier (NRB). The impact of hydrological processes on NRB formation, such as transient river levels, which drive mixing between rivers and aquifers, is poorly understood. We evaluated the impact of groundwater flow dynamics on hydrobiogeochemical processes that led to the formation of an Fe- and Mn-rich NRB containing enriched As, within a riverbank aquifer along the Meghna River. The NRB dimensions were mapped using four complementary elemental analysis methods on sediment cores: X-ray fluorescence (XRF), aqua regia bulk extraction, and HCl and sodium phosphate leaching. It extended from 1.2 to 2.4 m in depth up to 15 m from the river’s edge. The accumulated As was advected to the NRB from offsite and released locally in response to mixing with aged river water. Nearly all of the As was subsequently deposited within the NRB before discharging to the Meghna. Significant FeII release to the aqueous phase was observed within the NRB. This indicates the NRB is a dynamic zone defined by the interplay between oxidative and reductive processes, causing the NRB to grow and recede in response to rapid and seasonal hydrologic processes. This implies that natural and artificially induced changes in river stages and groundwater-tables will impact where As accumulates and is released to aquifers.

scholarly journals Solid phase evolution in the Biosphere 2 hillslope experiment as predicted by modeling of hydrologic and geochemical fluxes

2009 ◽  
Vol 13 (12) ◽  
pp. 2273-2286 ◽  
Author(s):  
K. Dontsova ◽  
C. I. Steefel ◽  
S. Desilets ◽  
A. Thompson ◽  
J. Chorover
Keyword(s):  
Particle Size ◽  
Reactive Transport ◽  
Hydraulic Properties ◽  
Solid Phase ◽  
Geochemical Modeling ◽  
Flow Characteristics ◽  
Phase Evolution ◽  
Mineral Weathering ◽  
Biosphere 2 ◽  
Weathering Processes

Abstract. A reactive transport geochemical modeling study was conducted to help predict the mineral transformations occurring over a ten year time-scale that are expected to impact soil hydraulic properties in the Biosphere 2 (B2) synthetic hillslope experiment. The modeling sought to predict the rate and extent of weathering of a granular basalt (selected for hillslope construction) as a function of climatic drivers, and to assess the feedback effects of such weathering processes on the hydraulic properties of the hillslope. Flow vectors were imported from HYDRUS into a reactive transport code, CrunchFlow2007, which was then used to model mineral weathering coupled to reactive solute transport. Associated particle size evolution was translated into changes in saturated hydraulic conductivity using Rosetta software. We found that flow characteristics, including velocity and saturation, strongly influenced the predicted extent of incongruent mineral weathering and neo-phase precipitation on the hillslope. Results were also highly sensitive to specific surface areas of the soil media, consistent with surface reaction controls on dissolution. Effects of fluid flow on weathering resulted in significant differences in the prediction of soil particle size distributions, which should feedback to alter hillslope hydraulic conductivities.

Microbial Sulfate Reduction Enhances Arsenic Mobility Downstream of Zerovalent-Iron-Based Permeable Reactive Barrier

2016 ◽  
Vol 50 (14) ◽  
pp. 7610-7617 ◽  
Author(s):  
Naresh Kumar ◽  
Raoul-Marie Couture ◽  
Romain Millot ◽  
Fabienne Battaglia-Brunet ◽  
Jérôme Rose
Keyword(s):  
Sulfate Reduction ◽  
Permeable Reactive Barrier ◽  
Zerovalent Iron ◽  
Arsenic Mobility ◽  
Reactive Barrier ◽  
Microbial Sulfate Reduction ◽  
Iron Based

scholarly journals Geochemical Controls on Uranium Release from Neutral-pH Rock Drainage Produced by Weathering of Granite, Gneiss, and Schist

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1104
Author(s):  
Elliott K. Skierszkan ◽  
John W. Dockrey ◽  
K. Ulrich Mayer ◽  
Viorica F. Bondici ◽  
Joyce M. McBeth ◽  
...  
Keyword(s):  
Calcium Release ◽  
Solid Phase ◽  
Mine Waste ◽  
Geochemical Modeling ◽  
Uranium Content ◽  
Sulfide Mineral ◽  
Waste Rock ◽  
Neutral Ph ◽  
Sequencing Experiment ◽  
Aqueous Complexes

We investigated geochemical processes controlling uranium release in neutral-pH (pH ≥ 6) rock drainage (NRD) at a prospective gold deposit hosted in granite, schist, and gneiss. Although uranium is not an economic target at this deposit, it is present in the host rock at a median abundance of 3.7 µg/g, i.e., above the average uranium content of the Earth’s crust. Field bin and column waste-rock weathering experiments using gneiss and schist mine waste rock produced circumneutral-pH (7.6 to 8.4) and high-alkalinity (41 to 499 mg/L as CaCO3) drainage, while granite produced drainage with lower pH (pH 4.7 to >8) and lower alkalinity (<10 to 210 mg/L as CaCO3). In all instances, U release was associated with calcium release and formation of weakly sorbing calcium-carbonato-uranyl aqueous complexes. This process accounted for the higher release of uranium from carbonate-bearing gneiss and schist than from granite despite the latter’s higher solid-phase uranium content. In addition, unweathered carbonate-bearing rocks having a higher sulfide-mineral content released more uranium than their oxidized counterparts because sulfuric acid produced during sulfide-mineral oxidation promoted dissolution of carbonate minerals, release of calcium, and formation of calcium-carbonato-uranyl aqueous complexes. Substantial uranium attenuation occurred during a sequencing experiment involving application of uranium-rich gneiss drainage into columns containing Fe-oxide rich schist. Geochemical modeling indicated that uranium attenuation in the sequencing experiment could be explained through surface complexation and that this process is highly sensitive to dissolved calcium concentrations and pCO2 under NRD conditions.

scholarly journals Coupled modeling of hydrologic and geochemical fluxes for prediction of solid phase evolution in the Biosphere 2 hillslope experiment

2009 ◽  
Vol 6 (3) ◽  
pp. 4449-4483 ◽  
Author(s):  
K. Dontsova ◽  
C. I. Steefel ◽  
S. Desilets ◽  
A. Thompson ◽  
J. Chorover
Keyword(s):  
Particle Size ◽  
Reactive Transport ◽  
Hydraulic Properties ◽  
Solid Phase ◽  
Geochemical Modeling ◽  
Flow Characteristics ◽  
Phase Evolution ◽  
Mineral Weathering ◽  
Coupled Modeling ◽  
Biosphere 2

Abstract. A reactive transport geochemical modeling study was conducted to help predict the mineral transformations occurring over a ten year time-scale that are expected to impact soil hydraulic properties in the Biosphere 2 (B2) synthetic hillslope experiment. The modeling sought to predict the rate and extent of weathering of a granular basalt (selected for hillslope construction) as a function of climatic drivers, and to assess the feedback effects of such weathering processes on the hydraulic properties of the hillslope. Flow vectors were imported from HYDRUS into a reactive transport code, CrunchFlow2007, which was then used to model mineral weathering coupled to reactive solute transport. Associated particle size evolution was translated into changes in saturated hydraulic conductivity using Rosetta software. We found that flow characteristics, including velocity and saturation, strongly influenced the predicted extent of incongruent mineral weathering and neo-phase precipitation on the hillslope. Results were also highly sensitive to specific surface areas of the soil media, consistent with surface reaction controls on dissolution. Effects of fluid flow on weathering resulted in significant differences in the prediction of soil particle size distributions, which should feedback to alter hillslope hydraulic conductivities.

scholarly journals Denitrification of nitrate-contaminated groundwater in columns packed with PHBV and ceramsites for application as a permeable reactive barrier

2017 ◽  
Vol 17 (5) ◽  
pp. 1241-1248 ◽  
Author(s):  
Liangtao Ye ◽  
Ge Yu ◽  
Shoubiao Zhou ◽  
Shengpeng Zuo ◽  
Caixia Fang
Keyword(s):  
Organic Compound ◽  
Carbon Source ◽  
Groundwater Contamination ◽  
Nitrate Leaching ◽  
Solid Phase ◽  
Sharp Decrease ◽  
Permeable Reactive Barrier ◽  
Contaminated Groundwater ◽  
Mass Ratio ◽  
Reactive Barrier

Groundwater contamination via nitrate leaching has been observed in many countries. The denitrification performance of a poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV)–ceramsite-based reactive barrier system was evaluated in continuous upflow bioreactors. Artificial groundwater spiked with nitrate (44.75–57.25 mg NO3−-N/L) was tested under different hydraulic retention times (HRT; 5.2 h and 2.6 h). The continuous experiment for 35 days showed that more than 95% NO3−-N was removed. The maximum denitrification rate was determined to be 241 mg NO3−-N/(L· d), and NO2−-N concentration was below 0.1 mg/L in the effluent at the substrate:ceramsite mass ratio of 1:40. Rapid biodegradation of PHBV granules caused an initial excess release of dissolved organic compound (DOC), and shortening HRT from 5.2 h to 2.6 h can result in a sharp decrease of DOC. The minimum DOC concentrations were determined to be 20–33 mg/L in the effluent when the HRT was set at 2.6 h. So the PHBV granules may be a suitable solid-phase carbon source for enhancing denitrification in nitrate-contaminated groundwater.

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