Retention of immobile Se(0) in flow-through aquifer column systems during bioreduction and oxic-remobilization

DOI: 10.1016/j.scitotenv.2022.155332

Authors: Mallory S. Ho (University of Helsinki) , Gianni F. Vettese (University of Helsinki) , Katherine Morris (University of Manchester) , Jonathan R. Lloyd (University of Manchester) , Christopher Boothman (University of Manchester) , William R. Bower (University of Helsinki) , Samuel Shaw (University of Manchester) , Gareth T. W. Law (University of Helsinki)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Science Of The Total Environment

State: Published (Approved)
Published: April 2022
Diamond Proposal Number(s): 21441

Abstract: Selenium (Se) is a toxic contaminant with multiple anthropogenic sources, including 79Se from nuclear fission. Se mobility in the geosphere is generally governed by its oxidation state, therefore understanding Se speciation under variable redox conditions is important for the safe management of Se contaminated sites. Here, we investigate Se behavior in sediment groundwater column systems. Experiments were conducted with environmentally relevant Se concentrations, using a range of groundwater compositions, and the impact of electron-donor (i.e., biostimulation) and groundwater sulfate addition was examined over a period of 170 days. X-Ray Absorption Spectroscopy and standard geochemical techniques were used to track changes in sediment associated Se concentration and speciation. Electron-donor amended systems with and without added sulfate retained up to 90% of added Se(VI)(aq), with sediment associated Se speciation dominated by trigonal Se(0) and possibly trace Se(-II); no Se colloid formation was observed. The remobilization potential of the sediment associated Se species was then tested in reoxidation and seawater intrusion perturbation experiments. In all treatments, sediment associated Se (i.e., trigonal Se(0)) was largely resistant to remobilization over the timescales of the experiments (170 days). However, in the perturbation experiments, less Se was remobilized from sulfidic sediments, suggesting that previous sulfate-reducing conditions may buffer Se against remobilization and migration.

Journal Keywords: Contaminated land; Geological disposal; Biostimulation; XAS; Sequential extraction

Subject Areas: Environment, Earth Science, Chemistry


Instruments: I20-Scanning-X-ray spectroscopy (XAS/XES)

Added On: 27/04/2022 10:10

Documents:
1-s2.0-S0048969722024251-main.pdf

Discipline Tags:

Desertification & Pollution Earth Sciences & Environment Natural disaster Geology Geochemistry

Technical Tags:

Spectroscopy X-ray Absorption Spectroscopy (XAS) Extended X-ray Absorption Fine Structure (EXAFS) X-ray Absorption Near Edge Structure (XANES)