Biogeochemical processes affecting selenium cycling in wetlands

Masscheleyn, Patrick H.; Patrick, W. H.

doi:10.1002/etc.5620121207

Cited by 106 publications

(50 citation statements)

References 34 publications

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“…In a study on Se(VI) reduction to Se(0) in a water–sediment system, Tokunaga et al (1996) found that 60% of the newly formed Se(0) in sediment during an experiment was reoxidized to Se(IV) and Se(VI) at Day 2 after collection. In a flooded sediment system at pH 7, Masscheleyn and Patrick (1993) reported that the boundary between Se(VI) and Se(IV) is at an Eh of about 250 to 285 mV, and between Se(IV) and Se(0), at an Eh of about −10 to −40 mV. In this study, the redox potential in the water column and water–sediment system increased during the experiments (Fig.…”

Section: Resultssupporting

confidence: 57%

Fate of Colloidal‐Particulate Elemental Selenium in Aquatic Systems

2004

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Bacterial reduction of selenate [Se(VI)] to elemental Se [Se(0)] is considered an effective bioremediation technique to remove selenium (Se) from agricultural drainage water. However, the fate of the newly formed Se(0) in aquatic systems is not known when it flows out of the treatment system. A set of laboratory experiments was conducted to determine the fate of the colloidal-particulate Se(0) in a water column and in a water-sediment system. Results showed that the newly formed colloidal-particulate Se(0) followed two removal pathways in aquatic systems: (i) flocculation-sedimentation to the bottom of the water and (ii) oxidation to selenite [Se(IV)] and Se(VI). During 58 d of the experiments, 51% of the added Se(0) was precipitated to the bottom of the water and 47% was oxidized to Se(IV) in the water column. In the water-sediment system, Se(IV) in the water accounted for 21 to 25% of the added Se(0). Adsorption of Se(IV) to the bottom sediment resulted in a relatively low amount of Se(IV) in the water. This study indicates that the newly formed Se(0) may be an available form of Se for uptake by organisms if it flows to aquatic systems from a treatment site. Therefore, an effective bioremediation system for removing Se from drainage water must reduce Se(VI) to Se(0) and remove Se(0) directly from the drainage water.

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Section: Resultssupporting

confidence: 57%

Fate of Colloidal‐Particulate Elemental Selenium in Aquatic Systems

2004

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“…Rapid sequence reduction of Se(VI) to Se(0) can also be explained by the redox potential of the rice straw solution. Masscheleyn and Patrick (1993) reported that a sequence reduction from Se(VI) to Se(IV) and then to Se(0) at a given pH was related to the redox potential. In a flooded sediment system at pH 7, Se(VI) reduced to Se(IV) at a redox potential of 250 to 285 mV, and Se(IV) reduced to Se(0) at redox potentials of −10 to −40 mV (Masscheleyn and Patrick, 1993).…”

Section: Discussionmentioning

confidence: 99%

“…Masscheleyn and Patrick (1993) reported that a sequence reduction from Se(VI) to Se(IV) and then to Se(0) at a given pH was related to the redox potential. In a flooded sediment system at pH 7, Se(VI) reduced to Se(IV) at a redox potential of 250 to 285 mV, and Se(IV) reduced to Se(0) at redox potentials of −10 to −40 mV (Masscheleyn and Patrick, 1993). In this study, the redox potential in the rice straw solution dropped rapidly to levels that were much lower than −40 mV.…”

Section: Discussionmentioning

confidence: 99%

“…The biogeochemistry of Se in the aquatic system is quite complicated, because Se can exist in four oxidation states (−II, 0, IV, and VI). The major features affecting the movement and solubility of Se are associated with changes in those species (Cooke and Bruland, 1987; Jayaweera and Biggar, 1996; Masscheleyn et al, 1990; Masscheleyn and Patrick, 1993). Selenate is the most oxidized form of Se, and is highly soluble in water (Elrashidi et al, 1987; Mikkelsen et al, 1989b).…”

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Characterization of Selenate Removal from Drainage Water Using Rice Straw

Zhang

Frankenberger²

2003

J of Env Quality

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Removal of selenium (Se) from agricultural drainage water is very important for protecting wildlife in wetland systems. We conducted a series of experiments on selenite [Se(IV)] adsorption and selenate [Se(VI)] reduction to determine Se removal from drainage water amended with 1000 microg/L of Se(VI) or Se(IV) and 5 g of rice (Oryza sativa L.) straw. Under sterile conditions, the added Se(IV) was not adsorbed to the rice straw within 2 d of the experiment and the added Se(VI) was not reduced within 14 d. In contrast, added Se(VI) in a nonsterile rice-straw solution was reduced rapidly, from 930 microg/L at Day 3 to 20 microg/L at Day 5, with an increase in unprecipitated elemental Se [Se(0)] and total Se(0). In the last several days of the experiments, unprecipitated Se(0) was the major Se form in the rice-straw solution, with a small amount of organic Se(-II). This study showed that Se removal from drainage water in the presence of rice straw involves a two-step process. The first is the microbial reduction of Se(VI) to Se(IV) and then to colloidal Se(0). The second is flocculation and precipitation of colloidal Se(0) to the bottom of the experimental flasks and the surface of rice straw.

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“…At low levels of redox potential in drainage water, bacteria reduced NO − 3 and Se(VI) effectively. Nitrate is a competitive electron acceptor affecting Se(VI) reduction because of its similar redox potential in aquatic systems (Masscheleyn and Patrick, 1993). In a batch study on the effect of NO − 3 on Se(VI) reduction to Se(0) in drainage water by rice straw, Zhang and Frankenberger (2003b) found that a level of 100 mg L −1 of NO − 3 in drainage water had little effect on Se(VI) reduction to Se(0).…”

Section: Discussionmentioning

confidence: 99%

Removal of Selenate in Simulated Agricultural Drainage Water by a Rice Straw Bioreactor Channel System

Zhang

Frankenberger

2003

J of Env Quality

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Removal of selenium (Se) from agricultural drainage water is important in protecting wetland wildlife. Three flow-through bioreactor channel systems (BCSs), each with three channels filled with rice (Oryza sativa L.) straw, were set in the laboratory to determine removal of selenate [Se(VI)] (1020 microg L(-1)) from drainage water with a salinity of 10.4 dS m(-1), a pH of 8.1, and a nitrate (NO3-) range of 0 to 100 mg L(-1). Results showed that the rice straw effectively reduced Se(VI) during 122 to 165 d of the experiments. Calculation of Se mass in the three BCSs showed that 89.5 to 91.9% of the input Se(VI) was reduced to red elemental Se [Se(0)], where 96.6 to 98.2% was trapped in the BCSs. Losses of each gram of rice straw were almost equal to the removal of 1.66 mg of Se from the drainage water as a form of red Se(0), indicating that rice straw is a very effective organic source for removing Se(VI) from drainage water.

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Biogeochemical processes affecting selenium cycling in wetlands

Cited by 106 publications

References 34 publications

Fate of Colloidal‐Particulate Elemental Selenium in Aquatic Systems

Fate of Colloidal‐Particulate Elemental Selenium in Aquatic Systems

Characterization of Selenate Removal from Drainage Water Using Rice Straw

Removal of Selenate in Simulated Agricultural Drainage Water by a Rice Straw Bioreactor Channel System

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