Enhanced Inorganic Redox Reactions in Ice and its Environmental Implications
Doctor This study is directed to understanding the redox reactions of inorganic compounds trapped in ice and related environmental implications. The redox chemical reactions in the environment are an important part in environmental chemistry and provide basic information for preserving and remediati...
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| Format: | Thesis |
| Language: | English |
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포항공과대학교
2012
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| Online Access: | http://postech.dcollection.net/jsp/common/DcLoOrgPer.jsp?sItemId=000001387003 https://oasis.postech.ac.kr/handle/2014.oak/1630 |
| Summary: | Doctor This study is directed to understanding the redox reactions of inorganic compounds trapped in ice and related environmental implications. The redox chemical reactions in the environment are an important part in environmental chemistry and provide basic information for preserving and remediating the affected environment. The mobility, toxicity, bioavailability, and environmental fate of inorganic elements are influenced by their redox speciation. Chemical mechanisms and processes of inorganic species have been extensively investigated in aquatic environment but those in ice have rarely to our knowledge been studied despite their importance in the environment, especially in the cold regions (e.g., upper troposphere, permafrost, polar/high latitude environment, and midlatitudes during winter season) where freeze-thaw cycles take place.1. The formation of dissolved iron from iron oxide particles in ice was investigated as a new pathway for a bioavailable iron production. The dissolution experiments were carried out under dark condition (in both the absence and presence of various organic complexing ligands). In acidic pH conditions (pH 2, 3, and 4), the dissolution of iron oxides was greatly enhanced in the ice phase compared to that in water. The dissolved iron from iron oxides was mainly in the ferric form, which indicates that the dissolution is not a reductive process. The extent of dissolved iron was affected by the presence and kind of organic complexing ligands and the type of iron oxides.2. The formation of bio-available iron (Fe(II)aq) from the dissolution of iron oxide particles was investigated in ice phase under both UV and visible light irradiation. The photoreductive dissolution of iron oxides proceeded slowly in aqueous solution (pH 3.5) but was significantly accelerated in polycrystalline ice with subsequently releasing more bioavailable ferrous iron upon thawing. The enhanced photogeneration of Fe(II)aq in ice was confirmed regardless of the type of iron oxides [hematite (α-Fe2O3),, ... |
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