Journal
WATER RESEARCH
Volume 205, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.watres.2021.117657
Keywords
Eutrophic waters; Arsenic oxidation; Nanobubble; Hypoxia remediation; Arsenic metabolism functional genes; Hydroxyl radicals
Funding
- National Key R&D Program of China [2017YFA0207204, 2018YFD0800305]
- National Natural Science Foundation of China [42007339, 21377003]
- Fundamental Research Funds for the Central Universities [SWU119009]
- Strategic Priority Research Program of the Chinese Academy of Sciences [XDA09030203]
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The application of interfacial oxygen (O-2) nanobubble technology was found to effectively reduce dissolved arsenic levels caused by algal-induced hypoxia and promote the conversion of As(III) to less toxic species. The manipulation by O-2 nanobubbles of microbial and geochemical reactions shows potential for remediating sediment arsenic pollution.
The arsenic (As)-bearing eutrophic waters may suffer from the dual conditions of harmful algal blooms and release of As, driven by algal-induced hypoxia/anoxia. Here, we investigate the use of interfacial oxygen (O-2) nanobubble technology to combat the hypoxia and control As exposure in simulated mesocosm experiments. It was observed that remediation of algal-induced hypoxia at the sediment-water interfaces (SWI) by application of O-2 nanobubbles reduced the level of dissolved As from 23.2 mu g L-1 to <10 mu g L-1 and stimulated the conversion of As(III) to the less toxic As(V) (65-75%) and methylated As (10-15%) species. More than half of the oxidation and all the methylation of As(III) resulted from the manipulation by O-2 nanobubbles of microbes responsible for As(III) oxidation and methylation. Hydroxyl radicals were generated during the oxidation of reductive substances at the SWI in darkness, and should be dominant contributors to As(III) abiotic oxidation. X-ray absorption near-edge structure (XANES) spectroscopic analysis demonstrated that surface sediments changed from being sources to acting as sinks of As, due to the formation of Fe-(hydr)oxide. Overall, this study suggests that interfacial O-2 nanobubble technology could be a potential method for remediation of sediment As pollution through the manipulation of O-2-related microbial and geochemical reactions.
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