Selenite Stable Isotope Fractionation during Abiotic Reduction by Sodium Sulfide.

Reduction of Se(IV) by sulfur reducing bacteria (SRB) can remove Se from groundwater either by direct respiration or the production of HS and subsequent abiotic reduction. This study examined abiotic Se(IV) reduction by HS to determine the associated Se isotope fractionation. The extent of fractionation was compared to the results with studies of Se(IV) reduction in systems containing microorganisms to assess whether these processes could be distinguished.

A cross scale investigation of galena oxidation and controls on mobilization of lead in mine waste rock.

Galena and Pb-bearing secondary phases are the main sources of Pb in the terrestrial environment. Oxidative dissolution of galena releases aqueous Pb and SO to the surficial environment and commonly causes the formation of anglesite (in acidic environments) or cerussite (in alkaline environments). However, conditions prevalent in weathering environments are diverse and different reaction mechanisms reflect this variability at various scales.

Real-Time XANES Measurement of Se Reduction by Zerovalent Iron in a Flow-through Cell, and Accompanying Se Isotope Measurements.

An anoxic flow-through cell experiment was conducted to examine mechanisms controlling the real-time reduction of selenate (Se(VI)) by zerovalent iron (ZVI), which is commonly used in permeable reactive barriers to treat dissolved contaminants including Se(VI). Changes in selenium (Se) isotope composition were examined by increasing the influent Se concentration over time, thus changing the proportion of Se removed from solution. At the conclusion of the experiment, an anoxic Se-free solution was pumped through the cell to assess the stability of the reaction products.

Fractionation of Selenium during Selenate Reduction by Granular Zerovalent Iron.

Batch experiments were conducted using granular zerovalent iron (G-ZVI) with either ultrapure water or CaCO3 saturated simulated groundwater to assess the extent of Se isotope fractionation in solution under the anaerobic conditions characteristic of many aquifers. G-ZVI is a common remediation material in permeable reactive barriers (PRB) to treat Se-contaminated groundwater, and stable isotopes are a potential tool for assessing removal mechanisms. The solution composition, speciation of Se, and Se isotope ratios were determined during both sets of experiments.