Ferrihydrite, which is known to form in the presence of oxygen and be stabilized by adsorption Si, PO4 SO4, ubiquitous fine-grained fractions permeable reactive barrier (PRB) samples from U.S. Coast Guard Support Center (Elizabeth City, NC) Denver Federal (Lakewood, CO) studied high-resolution transmission electron microscopy selected area diffraction. The concurrent energy-dispersive X-ray data indicate a strong association between ferrihydrite metals such as Ca, Cr. Magnetite, green rust...

Formation constants for thioarsenite species have been determined in dilute solutions at 25°C, ΣH2S from 10-7.5 to 10-3.0 M, ΣAs 10-5.6 10-4.8 and pH 7 10. The principal inorganic arsenic anoxic aquatic systems are arsenite, As(OH)30, a mononuclear with an S/As ratio of 3:1. Thioarsenic ratios 1 : 1,2 1, 4 lesser components sulfidic that might be encountered natural environments. Thioarsenites dominate speciation sulfide concentrations > 10-4.3 M neutral pH. Conversion As(OH)30 anionic may...

Solid-phase associations of chromium were examined in core materials collected from a full-scale, zerovalent iron permeable reactive barrier (PRB) at the U.S. Coast Guard Support Center located near Elizabeth City, NC. The PRB was installed 1996 to treat groundwater contaminated with hexavalent chromium. After eight years operation, remains effective reducing concentrations Cr average values >1500 microg L(-1) hydraulically upgradient <1 within and downgradient PRB. Chromium removal occurs...

Geochemical and microbiological factors that control long-term performance of subsurface permeable reactive barriers were evaluated at the Elizabeth City, North Carolina, Denver Federal Center, Colorado, sites. These ground water treatment systems use zero-valent iron filings (Peerless Metal Powders Inc.) to intercept remediate chlorinated hydrocarbon compounds Center (funnel-and-gate system) overlapping plumes hexavalent chromium hydrocarbons City (continuous wall system). Zero-valent both...

Geologic carbon sequestration has the potential to cause long-term reductions in global emissions of dioxide atmosphere. Safe and effective application technology requires an understanding risks quality underground sources drinking water. In particular, concern is warranted regarding for CO2 leakage through geological features abandoned wells that may result detrimental perturbations subsurface geochemistry. Reaction path kinetic models indicate geochemical shifts caused by are closely...

Abstract Abiotic degradation of chlorinated solvents by reactive iron minerals such as sulfides, magnetite, green rust, and other Fe( II )‐containing has been observed in both laboratory field studies. These form under iron‐ sulfate‐reducing conditions which are commonly found permeable barriers ( PRBs ), enhanced reductive dechlorination ERD ) treatment locations, landfills, aquifers that chemically reducing. The objective this review is to synthesize current understanding abiotic minerals,...

In a shallow, fjord-like estuary, the Upper and Lower Basins of Pettaquamscutt River (Rhode Island) each contain water columns stratified into oxic anoxic plus sulfidic layers. Both iron monosulfides pyrite from just below oxic-anoxic interface down to sediment-water interface. Concentrations increase with increasing depth in columns, but concentrations are relatively constant depth. Suspended is present only as framboids, whereas underlying sediments dominantly framboids also euhedral...

A field study was conducted to evaluate the performance of a ferrous iron based in situ redox zone for treatment dissolved phase Cr(VI) plume at former industrial site. The created by injecting blend 0.2 M sulfate and sodium dithionite into path within shallow medium fine sand unconfined aquifer formation. Monitoring data collected over period 1020 days after more than 100 m linear groundwater flow through indicated sustained from initial concentrations between 4 8 mg/L less 0.015 mg/L....

Perchlorate salts of potassium and ammonium are the primary oxidants in pyrotechnic mixtures, yet insufficient information is available regarding relationship between fireworks displays environmental occurrence perchlorate. Here we document changes perchlorate concentrations surface water adjacent to a site from 2004 2006. Preceding displays, ranged 0.005 0.081 μg/L, with mean value 0.043 μg/L. Within 14 h after fireworks, spiked values ranging 24 1028× baseline value. A maximum...

A 30-month performance evaluation of a pilot permeable reactive barrier (PRB) consisting mixture leaf compost, zero-valent iron (ZVI), limestone, and pea gravel was conducted at former phosphate fertilizer manufacturing facility in Charleston, SC. The PRB is designed to remove heavy metals arsenic from groundwater by promoting microbially mediated sulfate reduction sulfide-mineral precipitation metal sorption. Performance monitoring showed effective treatment As, Pb, Cd, Zn, Ni...

Permeable reactive barriers (PRBs) are used for groundwater remediation at contaminated sites worldwide. This technology has been efficient appropriate treating organic and inorganic contaminants using zero-valent iron (ZVI) as a reductant material. Continued development of the over years suggests that robust understanding PRB performance mechanisms involved is still lacking. Conflicting information in scientific literature downplays critical role ZVI corrosion various pollutants....

Research Article| December 01, 1998 Pyrite formation in the water column and sediments of a meromictic lake Neil S. Suits; Suits 1Department Geosciences, Pennsylvania State University, University Park, 16802 Search for other works by this author on: GSW Google Scholar Rick T. Wilkin Author Article Information Publisher: Geological Society America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print 0091-7613 Geology (1998) 26 (12): 1099–1102....

Linked tectonic, geochemical, and biologic processes lead to natural arsenic contamination of groundwater in Holocene alluvial aquifers, which are the main threat human health around world. These groundwaters commonly found a long distance from their ultimate source arsenic, where chemical weathering As‐bearing minerals occurs. We propose “GBH‐As” model that ties together all important biologic, hydrologic cause As release terrestrial deposits. Processes highlighted by can explain movement...