지하수공내 존재하는 철산화 박테리아와 중금속분포특성

Abstract

Abstract

Characteristics of the heavy metal distribution and Fe-oxidizing bacteria in the groundwater well

Cho, Sang Seob Advisor : Prof. Park, Cheon-Young Dept. of Energy & Resources Engineering Graduate School, Chosun University

The objective of this study was to investigate the mineralogical and geochemical through distribution of heavy metals on the interrelation between groundwater and Fe scale in the study area. The ground water and Fe scale samples were collected from area A(ground water at Chosun University) and area B(ground water in Industrial area) in Gwang-ju. It was discovered that the pH of the sample from area A ranged of 6.09 to 7.37, which is neutral. In an Eh-pH diagram, Fe3+ was shown to be the dominant Fe ion species dissolved in the ground water. As a result of calculating the saturation index of the ground water species, it was discovered that gibbsite, goethite, and hematite were oversaturated. Fe2O3 was a major element in Fe scale from area A and its content ranged from 8.77 wt.% to 79.14 wt.%. SiO2, S, Al2O3, MnO, MgO, Na2O, K2O and TiO2 showed up as trace elements. In this content of the main elements and heavy metal elements in a vertical distribution, all of them decreased as depth increased. The heavy metal content of the Fe scale are presented as follows: Cr(max of 94,400 mg/kg), Ni(max of 7,250 mg/kg), Zn(max of 10,000 mg/kg), Mo(max of 2,930 mg/kg), Cu(max of 1,410 mg/kg) and Co(max of 87 mg/kg). When their mean values were compared, they were enriched in the following order: Cr > Ni > Zn > Mo > Cu > Co. Fe scale from area A had a very high content of Cr and in particular, the content was high at the stainless steel pipe while it was low at the submerged motor. As a result of XRD analysis in the Fe scale, it was detected the amorphous iron-hydroxide, goethite, quartz, and kaolinite. It was predicted from the saturation indexes that goethite and kaolinite would be deposited because of oversaturation and it was proved that the goethite was oversaturated through the XRD analysis. As a result of the SEM analysis in the Fe scale, it was interpreted that the Leptothrix species has a pip-structure and the Gallionella species has a spiral structure. On the surfaces of the structures, iron-hydroxide with a framboidal structure was formed. The twisted structure which was interpreted to be related to the Gallionella species from area A at all depths. The pH of the ground water from area B ranged from 6.77 to 8.15. In Eh-pH diagram, it can be seen that the Fe3+ ion was the most dominant among the Fe ions. As a result of Piper's diagram, it was plotted between temporary hardness and permanent hardness, and was classified as Ca-HCO3 type ground water. In calculating the saturation index, it was discovered that gibbsite, goethite, and hematite were oversaturated. The main elements of the Fe scale from area B were Fe2O3, SiO2, and S while Al2O3, MnO, MgO, Na2O, K2O and TiO2 were minor elements. The Fe2O3 content ranged from 58.57 to 75.73wt.% and the SiO2 content ranged from 5.8 to 16.175wt.%. As a result of displaying the element contents of the Fe scale in a vertical distribution, the Fe2O3 content increased as depth increased, and the amount of SiO2, Al2O3, MgO and CaO decreased as depth increased. In particular, in the SS ground water well, when the As content increased, the Fe2O3 content also increased. As a result of the SEM analysis on the Fe scale, lath shapes and lamellar shapes made of Fe2O3 were observed. In conducting XRD analysis these Fe scales, lepidocrocite and goethite were observed. Form the ground water species from area B, twisted stalks attached by Fe hydroxide of spherical particles were observed.