https://repository.kopri.re.kr/handle/201206/11925 Thu, 16 Apr 2026 00:06:58 GMT 2026-04-16T00:06:58Z https://repository.kopri.re.kr/handle/201206/13822 Title: Reductive Transformation of Hexavalent Chromium in Ice Decreases Chromium Toxicity in Aquatic Animals Authors: Kim, Bo-Mi; Kim, Bomi; Nam, Sang-Eun; Eom, Hye-Jin; Lee, Somyeong; Kim, Kitae; Rhee, Jae-Sung Abstract: In this study, the toxicity of hexavalent chromium [Cr(VI)] reduced by citric acid in ice was measured using representative aquatic model invertebrates (i.e., rotifer, water flea, amphipod, and polychaete) and a vertebrate (zebrafish) by analyzing short- and/or long-term endpoints that are frequently applied to each animal. Cr(VI) reduction in the presence of citric acid was markedly enhanced in the ice phase compared to that in an aqueous solution through the freeze concentration effect. The highly concentrated Cr(VI) and citric acid in ice grain boundaries were also confirmed using in situ cryogenic confocal Raman spectroscopy. Overall, exposure to Cr(VI) resulted in higher acute and/or chronic effects on aquatic animals, such as drastic mortality, growth inhibition, and decrease in offspring number, whereas the animals were increasingly tolerant to Cr(VI) that was reduced in the ice phase. Sublethal concentrations of Cr(VI) significantly decreased the antioxidant capacity in the aquatic animals. However, when the same concentrations of Cr(VI) were reduced in ice, these treatments showed no modulation or increase in the antioxidant defense system. Taken together, our results suggest that Cr(VI) reduction into Cr(III) was successfully achieved in ice and that this methodology can decrease the actual toxicity of Cr(VI) in aquatic animals. Tue, 15 Mar 2022 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/13822 2022-03-15T00:00:00Z https://repository.kopri.re.kr/handle/201206/13825 Title: Frozen Hydrogen Peroxide and Nitrite Solution: The Acceleration of Benzoic Acid Oxidation via the Decreased pH in Ice Authors: Ahn, Yong-Yoon; Kim, Jungwon; Kim, Kitae Abstract: We investigated benzoic acid oxidation via the reaction of hydrogen peroxide (H2O2) and nitrite (NO2 -). The oxidation of benzoic acid by reactive nitrous acid (HONO) was negligible, and the reactivity of the H2O2/NO2- system decreased with a decrease in temperature under aqueous conditions. However, freezing markedly accelerated the chemical reaction. Based on Raman microscope measurements, concentrated species were confirmed in certain regions of the ice. We proposed that the change in nitrite speciation (accordingly, a decrease in the pH below pKa), derived from the freezing concentration effect, was the reason for the accelerated reactions. The oxidation characteristics of the system were monitored under varying conditions, such as initial pH, dosage ratio, benzoic acid concentration, and reaction with various benzene derivatives. The ultrahigh-performance liquid chromatography/electrospray ionization/mass spectrometry (UHPLC/ESI/MS) measurement showed that peroxynitrous acid (HOONO)-mediated oxidation generated hydroxylated and nitrated byproducts. Additionally, decarboxylated products were detected, indicating direct electron transfer from the organic compounds to HOONO. As freezing is a global phenomenon, and H2O2 and NO2- are ubiquitous in the environment, the transformation of aromatic compounds with H2O2/NO2- in cold environments must be considered in environmental chemistry. Tue, 15 Feb 2022 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/13825 2022-02-15T00:00:00Z https://repository.kopri.re.kr/handle/201206/13342 Title: Study of Physical and Chemical Properties of Ice surfaces at Low Temparature Authors: 강헌 Tue, 01 Feb 2022 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/13342 2022-02-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/13823 Title: Freeze-Thaw Cycle-Enhanced Transformation of Iodide to Organoiodine Compounds in the Presence of Natural Organic Matter and Fe(III) Authors: Du, Juanshan; Kim, Kitae; Min, Dae Wi; Choi, Wonyong Abstract: The formation of organoiodine compounds (OICs) is of great interest in the natural iodine cycle as well as water treatment processes. Herein, we report a pathway of OIC formation that reactive iodine (RI) and OICs are produced from iodide oxidation in the presence of Fe(III) and natural organic matter (NOM) in frozen solution, whereas their production is insignificant in aqueous solution. Moreover, thawing the frozen solution induces the further production of OICs. A total of 352 OICs are detected by Fourier transform ion cyclotron resonance mass spectrometry in the freeze-thaw cycled reactions of Fe(III)/I-/humic acid solution, which are five times as many as OICs in aqueous reactions. Using model organic compounds instead of NOM, aromatic compounds (e.g., phenol, aniline, o-cresol, and guaiacol) induce higher OIC formation yields (10.4-18.6%) in the freeze-thaw Fe(III)/I-system than those in aqueous (1.1-2.1%) or frozen (2.7-7.6%) solutions. In the frozen solution, the formation of RI is enhanced, but its further reaction with NOM is hindered. Therefore, the freeze-thaw cycle in which RI is formed in the frozen media and the resulting RI is consumed by reaction with NOM in the subsequently thawed solution is more efficient in producing OICs than the continuous reaction in frozen solution. Tue, 18 Jan 2022 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/13823 2022-01-18T00:00:00Z