• Journal of the Mineralogical Society of Korea
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• v.23 no.2
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• pp.107-115
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• 2010

Removal and mineralization of dissolved uranium by bacteria in KURT (KAERI Underground Research Tunnel), Korea Atomic Energy Research Institute (KAERI) was investigated. Two different bacteria, IRB (iron-reducing bacteria) and SRB (sulfate-reducing bacteria) was used, and minerals formed by these bacteria were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Compared to uranyl ions, ferric ions were preferentially reduced by IRB, showing that there is no significant reduction and removal of uranium. However, uranium concentration considerably decreased by addition of Mn(II). Results show that a sulfide mineral such as mackinawite (FeS) is formed by SRB respiration through combination of Fe(II) and S without manganese sulfide formation. In the presence of Mn(II), however, uranium is removed effectively, suggesting that the sorption and incorporation of uranium could be affected by Mn(II) onto the sulide minerals.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.8
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• pp.798-807
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• 2008

Due to economic impairment derived from metal corrosion of pumping station installed around coastal area, it was needed for related cause-effect to be investigated for understanding practical corrosion behavior and providing proper control. This research was thus carried out to determine whether the microbe can influence on metal corrosion along with its control in the laboratory. For this study, groundwater was sampled from the underground pump station(i.e. I Gas Station) where corrosion was observed. Microbial diversity on the samples were then obtained by 16S rDNA methods. From this, microbial populations showing corrosion behaviors against metals were reported as Leptothrix sp.(Iron oxidizing) and Desulfovibrio sp.(Sulfur reducing) Iron oxidizing bacteria were dominantly participating in the corrosion of iron, while sulfate reducing bacteria were more preferably producing precipitate of iron. In case of galvanized steel and stainless steel, iron oxidizing bacteria not only enhanced the corrosion, but also generated its scale of precipitate. Sulfate reducing bacteria had zinc steel corroded greater extent than that of iron oxidizing bacteria. In the inactivation test, chlorine or UV exposure could efficiently control bacterial growth. However as the inactivation intensity being increased beyond a threshold level, corrosion rate was unlikely escalated due to augmented chemical effect. It is decided that microbial corrosion could be differently taken place depending upon type of microbes or materials, although they were highly correlated. It could be efficiently retarded by given disinfection practices.

• Economic and Environmental Geology
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• v.56 no.4
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• pp.421-433
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• 2023

The final disposal of spent nuclear fuel(SNF) from nuclear power plants takes place in a deep geological repository. The metal canister encasing the SNF is made of cast iron and copper, and is engineered to effectively isolate radioactive isotopes for a long period of time. The SNF is further shielded by a multi-barrier disposal system comprising both engineering and natural barriers. The deep disposal environment gradually changes to an anaerobic reducing environment. In this environment, sulfide is one of the most probable substances to induce corrosion of copper canister. Stress-corrosion cracking(SCC) triggered by sulfide can carry substantial implications for the integrity of the copper canister, potentially posing a significant threat to the long-term safety of the deep disposal repository. Sulfate can exist in various forms within the deep disposal environment or be introduced from the geosphere. Sulfate has the potential to be transformed into sulfide by sulfate-reducing bacteria(SRB), and this converted sulfide can contribute to the corrosion of the copper canister. Bentonite, which is considered as a potential material for buffering and backfilling, contains oxidized sulfate minerals such as gypsum(CaSO4). If there is sufficient space for microorganisms to thrive in the deep disposal environment and if electron donors such as organic carbon are adequately supplied, sulfate can be converted to sulfide through microbial activity. However, the majority of the sulfides generated in the deep disposal system or introduced from the geosphere will be intercepted by the buffer, with only a small amount reaching the metal canister. Pyrite, one of the potential sulfide minerals present in the deep disposal environment, can generate sulfates during the dissolution process, thereby contributing to the corrosion of the copper canister. However, the quantity of oxidation byproducts from pyrite is anticipated to be minimal due to its extremely low solubility. Moreover, the migration of these oxidized byproducts to the metal canister will be restricted by the low hydraulic conductivity of saturated bentonite. We have comprehensively analyzed and summarized key research cases related to the presence of sulfates, reduction processes, and the formation and behavior characteristics of sulfides and pyrite in the deep disposal environment. Our objective was to gain an understanding of the impact of sulfates and sulfides on the long-term safety of high-level radioactive waste disposal repository.

• Journal of Soil and Groundwater Environment
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• v.8 no.2
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• pp.9-18
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• 2003

Sampling of waters from each stage of treatment system (Successive Alkalinity Producing System; SAPS), tailings seepage, and spring near the Hanchang coal mine of Kangwon Province were carried out seasonally and analyzed to evaluate the source and possible path of groundwater contamination by acid mine drainage (AM). Sulfur isotope compositions were measured to identify the origin of groundwater contaminations and the sulfate reduction processes in the SAPS. Low pH and high metal concentration of spring water indicates possibility of the groundwater contamination by AMD. Removal efficiency of acidity of the SAPS was 18.17 g/$\textrm{m}^2$/day on an average and the metal removal efficiency was almost 100%, which was higher than those of other treatment systems. However, no appreciable decrease of sulfur content and almost similar sulfur isotope compositions of water from each stage of the treatment system may suggest incomplete or very poor sulfate reduction by sulfate reducing bacteria. Chemical and sulfur isotope compositions showed that spring water was contaminated by seepage from mine tailings. And seepage of stonewall, a part of treatment system was affected by both tailings seepage and mine adit drainage. In this study site, the treatment system was constructed for the only AMD from mine adit not for tailings seepages, which resulted in the groundwater contamination from tailing seepages. Similar situation is expected in other abandoned coal mine areas.

• Economic and Environmental Geology
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• v.40 no.5
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• pp.575-585
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• 2007

Microbial control of the geochemical behavior of heavy metals (Cd, Cu, Pb, and Zn) and As in contaminated subsurface soil and sediment was investigated through activation of indigenous bacteria with lactate under anaerobic condition for 25 days. The results indicated that dissolved Cd, Pb and Zn were microbially removed from solutions, which was likely due to the formation of metal sulfides after reduction of sulfate by indigenous sulfate-reducing bacteria. Soils from the Dukeum mine containing a large amount of sulfate resulted in complete removal of dissolved As after 25 days by microbial activities, while there were gradual increases in dissolved As concentration in soils from the Hwabuk mine and sediments from the Dongducheon industrial area which showed low $SO_4{^2-}$ concentrations. Addition of appropriate carbon sources and sulfate to contaminated geological media may lead to activation of indigenous bacteria and thus in situ stabilization of the heavy metals; however, potential of As release into solution after the amendment should be preferentially investigated.

• Journal of Conservation Science
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• v.29 no.2
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• pp.187-196
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• 2013

This study is on the corrosion of iron objects caused by sulfides in undersea environment. The corrosion state of objects in seawater and their damage state after underwater and left in highly humid air were studied. The samples of this study were four iron objects which had been taken out from undersea mud layer located in Taean Mado, Chungcheongnamdo. SEM-EDS and XRD analyse on the objects to check whether they have sulfides or not. The result of analysis suggested that the major component of corrosion product generated in undersea deposit soil is sulfur(S) and iron sulfide(FeS) is formed as sulfide. However, there was no clear corrosion on the surface of objects which was exposed to sea water because of the impact of concretion which covered the surface. In order to check the damage status of iron objects after they had been taken out of sea water, exposure tests in high humidity environment and dehumidified environment were done on the corrosion products. The result of the test suggested that the oxidization of iron sulfide corrosion product makes iron sulfate ($FeSO_4$) and sulfuric acid ($H_2SO_4$) and they can cause secondary corrosion of iron objects. Therefore, it is believed that the iron sulfide corrosion product of iron objects taken out from underwater environment should be removed by all means and the keeping environment of the iron objects should also maintain dehumidified state.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.10 no.1
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• pp.1-7
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• 2005

Tidal flats have been regarded to carry out transformation and removal of land-derived organic matter, and this purifying capability of organic matter by tidal flats is one of very important reasons for their conservation. However, integral biogeochemical studies on production and decomposition of organic matter by benthic microbes in tidal flats have been absent in Korea, although the information is indispensable to quantification of the purifying capability. Our major goals in this multidisciplinary research were to understand major biogeochemical processes and rates mediated by diverse groups of microbes dominating material cycles in the tidal flats, and to assess the contribution of benthic microbes to removal of organic matter and nutrients in the tidal flats. Our study sites were Ganghwa and Incheon north-port tidal flats that had been regarded as naturally well reserved and organically polluted, respectively. Our research group measured over 3 years primary production, biomass and community structure of primary producers, abundance and production of bacteria, enzyme activities, distribution of protozoa and protozoan grazing rates, rates of denitrification and sulfate reduction, early sediment diagenesis, primary production and respiration based on oxygen microelectrode. We analyzed major features of each biogeochemical process and their interactions. The results are compiled in the following articles in this special issue: An (2005), Hwang and Cho (2005), Mok et at. (2005), Na and Lee (2005), Yang et at. (2005), and Yoo and Choi (2005).