• Title/Summary/Keyword: chemical elements

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Biodiversity of Microalgae and Their Elemental Components from Veeranam Lake, Tamilnadu, India

  • Sivakumar, K.;Senthilkumar, R.
    • Korean Journal of Ecology and Environment
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    • v.41 no.2
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    • pp.128-136
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    • 2008
  • An attempt was made in the Veeranam freshwater lake with the objectives to collect, identify, describe and document the algae occurring from March 2007 to August 2007. Qualitative and quantitative characterization of phytoplankton and analysis of physico-chemical parameters of water samples were carried out at monthly intervals during the study period in the western and eastern sides of the lake. It was found that the phytoplankton community embraced 68 genera belonging to four classes viz., Bacillariophyceae (40), Chlorophyceae (22), Cynophyceae (4) and Euglenophyceae (2). There were significant influences of various physico-chemical parameters on the phytoplankton population density. Commonly occurred genera, Oscillatoria (Cyanophyceae), Navicula (Bacillariophyceae) and Scenedesmus (Chlorophyceae), were subjected to energy dispersive spectroscopic analysis (EDS). They were found to accumulate different elements such as Zn, P, S, Ca, Mg, Fe, N, Si, Cl and Mn. Among these the member Cyanophyceae contained Zn, P, Mg, Ca, Mn, S and N. Bacillariophyceae Si, Zn, Mg, Cl, N, Fe, and Ca. Chlorophyceae Ca, Mg, N, Fe, Cl, Zn, Si and Mn. Thus these observations would determine the chemical dialogue between the cell structures and role of the elements. Further, it gives the clue about the phytoplankton growth requirements.

One Step Electrodeposition of Copper Zinc Tin Sulfide Using Sodium Thiocyanate as Complexing Agent

  • Sani, Rabiya;Manivannan, R.;Victoria, S. Noyel
    • Journal of Electrochemical Science and Technology
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    • v.9 no.4
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    • pp.308-319
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    • 2018
  • Single step electrodeposition of $Cu_2ZnSnS_4$ (CZTS) for solar cell applications was studied using an aqueous thiocyanate based electrolyte. The sodium thiocyanate complexing agent was found to decrease the difference in the deposition potential of the elements. X-ray diffraction analysis of the samples indicates the formation of kesterite phase CZTS. UV-vis studies reveal the band gap of the deposits to be in the range of 1.2 - 1.5 eV. The thickness of the deposit was found to decrease with increase in pH of the electrolyte. Nearly stoichiometric composition was obtained for CZTS films coated at pH 2 and 2.5. I-V characterization of the film with indium tin oxide (ITO) substrate in the presence and the absence of light source indicate that the resistance decrease significantly in the presence of light indicating suitability of the deposits for solar cell applications. Results of electrochemical impedance spectroscopic studies reveal that the cathodic process for sulfur reduction is the slowest among all the elements.

Anatomical, Chemical, and Topochemical Characteristics of Transgemic Poplar Down-regulated with O-methyltransferase

  • Wi, Seung Gon;Lee, Kwang Ho;Park, Byung Dae;Park, Young Goo;Kim, Yoon Soo
    • Journal of the Korean Wood Science and Technology
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    • v.32 no.3
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    • pp.15-24
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    • 2004
  • The present work was undertaken to investigate the anatomical and chemical characteristics of transgenic poplar down-regulated with antisense OMT gene. Also the distribution of lignin in transgenic poplar trees was investigated at cellular level. No visible abnormal phenotype was observed in the fibers and vessel elements of transgenic poplar. Any marked differences in the staining intensities of Wiesner and Mäule color reaction were not identified in the transgenic poplar. TEM micrographs did not show any staining intensities in the cell walls stained with KMnO4. Interestingly, the UV spectroscopy of semi-thin sections exhibited a distinct decrease of lignin absorption at 280 nm in the vessel walls, indicating transgenic poplar wood with lower amount of guaiacyl lignin in vessel elements. Chemical composition of antisense OMT poplar was almost identical to that of wild-type poplar. Klason lignin content of transgenic poplar did not show any significant difference from that of the controls. The solid state NMR spectra revealed the transgenic poplar with only slightly more syringyl lignin than the control. The present work showed that antisense OMT gene constructed in the poplar was not enough to reduce the overall content of Klason lignin, and suggested that the expression of transformation was confined to vessel walls.

An Analysis of Inquiry Area in the Chemistry(II) Textbooks by the Inquiry Elements Based on the 7th Science Curriculum (제7차 과학교육과정의 탐구 요소들에 의한 화학(II) 교과서의 탐구 영역 분석)

  • Kang, Dae-Ho;Jeong, Soo-Goon;Koo, In-Sun
    • Journal of the Korean Chemical Society
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    • v.47 no.6
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    • pp.645-658
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    • 2003
  • This study was carried out to analyze inquiry area of the chemistry (II) textbooks which were published by the 7th curriculum. The study attempts to analyze the degree to which chemistry (II) textbooks reflected the guidelines of the 7th science curriculum and propose educational suggestions for the inquiry learning. The analysis of the inquiry area was carried out based on the suggested inquiry elements of the 7th science curriculum. Overall, for the analysis of inquiry elements, basic inquiry elements except classifying suggested by the 7th science curriculum were well reflected on the textbooks. However, for the integrated inquiry elements, interpreting data takes almost half of the total integrated inquiry elements. Other integrated inquiry elements except drawing conclusion and transforming data were reflected less than ten percent. Investigation was also reflected less than ten percent of all inquiry activity. And inquiry activities were limited in terms of variety with few projects and no field trip. The main essence of the 7th science curriculum is the emphasis on total inquiry learning through various integrated inquiry elements and inquiry activities for higher grade students. Thus it is suggested that teachers provide inquiry learning which can supplement the textbook.

Effect of Micro-Alloying Elements on Recrystallization Behavior of Carbon Steels at Different Strain Rates (변형률 속도에 따른 탄소강의 재결정 거동에 미치는 미량 합금 원소의 영향)

  • Lee, Sang-In;Lim, Hyeon-Seok;Hwang, Byoungchul
    • Korean Journal of Materials Research
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    • v.26 no.10
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    • pp.535-541
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    • 2016
  • The present study deals with the effects of micro-alloying elements such as Ni, V, and Ti on the recrystallization behavior of carbon steels at different strain rates. Eight steel specimens were fabricated by varying the chemical composition and reheating temperature; then, a high-temperature compressive deformation test was conducted in order to investigate the relationship of the microstructure and the recrystallization behavior. The specimens containing micro-alloying elements had smaller prior austenite grain sizes than those of the other specimens, presumably due to the pinning effect of the formation of carbonitrides and AlN precipitates at the austenite grain boundaries. The high-temperature compressive deformation test results indicate that dynamic recrystallization behavior was suppressed in the specimens with micro-alloying elements, particularly at increased strain rate, because of the pinning effect of precipitates, grain boundary dragging and lattice misfit effects of solute atoms, although the strength increased with increasing strain rate.

Comparison of USEPA Digestion Methods for Trace Metal Analysis Using SRM

  • Shin, Mi-Young;Yoon, Hyeon;Kim, Youn-Tae;Yoon, Cheol-Ho;Woo, Nam-Chil
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • 2004.09a
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    • pp.223-226
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    • 2004
  • The importance of a proper sample preparation and analysis technique has getting attention due to the complicity of toxic elements of interest from environmental samples depend on analytical purposes. It is critical to use proper analytical method to evaluate trace elements concentration in many environmental samples especially for making remediation decisions. Therefore, it is critical to apply a proper sampling and analytical method such as EPA publication SW-846 (Test Methods for Evaluating Solid Waste, Physical/chemical Methods). The objective of this study was to compare the USEPA Methods 3050B, modified 3050B, 305 la, and KBSI method (modified EPA 3052 Method) in term of recovery rate of metals. The NIST SRM (Montana soil) was used to compare the extraction and digestion efficiency. After sample has been collected the analysis were achieved by ICP-MS (Elan 6100, Perkin Elmer) as well as ICP-AES (Ultima 2C, JY) for trace elements and major elements.

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Determination of the Trace Elements in $UO_2$ Powder by ICP-AES Directyl Coupled with Extraction Chromatography (추출크로마토그래피와 유도결합플라스마 원자방출분광법을 이용한 이산화우라늄분말 중 미량금속불순물 분석)

  • Choi, Kwang-Soon;Lee, Chang-Heon;Pyo, Hyung-Yeal;Han, Sun-Ho;Suh, Moo-Yul;Eom, Tae-Yoon;Lee, Gae-Ho
    • Journal of the Korean Chemical Society
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    • v.37 no.9
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    • pp.813-819
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    • 1993
  • An ICP-AES system directly connected with a separation column was used in order to determine the trace elements in $UO_2$ powder promptly and reduce the volume of the waste solution. The outlet of a separation column, which was filled with Teflon powder ($330\;{\mu}m$) coated with tri-n-butyl phosphate (TBP) as extractant, was directly connected with sample injection tube of ICP-AES. Eleven elements including molybdenum in $UO_2$ powder were separated and determined simultaneously. Recoveries of these elements were $91{\sim}110%$ and these results were agreed with those of solvent extraction methods. This method was applicable to quality control in manufacturing nuclear fuel.

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Environmental Assessment of Heavy Metals Anna Abandoned Metalliferous Mine in Korea (국내 휴/폐광 금속황산 주변의 중금속 환경오염 평가)

  • 정명채;정문영;최연왕
    • Economic and Environmental Geology
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    • v.37 no.1
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    • pp.21-33
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    • 2004
  • The objective of this study is to review of environmental assessment of heavy metals derived from various metalliferous mines in Korea. As a results of national wide research for heavy metal contaminations in the vicinity of metalleferous mines, the main contaminants are mine waste materials including tailings. From the materials, toxic elements including As, Cd, Cu, Pb and Zn can be dispersed into downstream through wind and water. Thus, soils around the mines contain elevated levels of those elements, which are over the guide values for environmental regulation of soils in Korea. Arsenic is one of the most important elements contaminated by mining activities, to a less extent, Cd, Cu, Pb and Zn. In spite of remediation works for some metal mines by the government, there are still lots of abandoned mines which are necessary for reclamation of mining sites. This study also includes that metal concentrations in soils and tailings can be varied upon various decomposition methods including 0.1N HC1 and aqua regia and sequential extraction scheme, with differences in each element, too. This may be due to geochemical characteristics of the elements, such as solubility, mobility and chemical forms in the geochemical environment. Finally, it is suggested that a certain organization should be runned by Korean government for management of abandoned mines.

Chemical Properties of Indoor Individual Particles Collected at the Daily Behavior Spaces of a Factory Worker

  • Ma, Chang-Jin;Kang, Gong-Unn;Sakai, Takuro
    • Asian Journal of Atmospheric Environment
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    • v.11 no.2
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    • pp.122-130
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    • 2017
  • The main purpose of the study was to clarify the properties of individual particles collected at each behavior space of a factory worker. The samplings of size-segregated ($PM_{2.1-1.1}$ and $PM_{4.7-3.3}$) indoor particles were conducted at three different behavior spaces of a factory worker who is engaged in an auto parts manufacturing plant (i.e., his home, his work place in factory, and his favorite restaurant). Elemental specification (i.e., relative elemental content and distribution in and/or on individual particles) was performed by a micro-PIXE system. Every element detected from the coarse particulate matters of home was classified into three groups, i.e., a group of high net-counts (Na, Al, and Si), a group of intermediate net-counts (Mg, S, Cl, K, and Ca), and a group of minor trace elements (P, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Pb). The results of EF for $PM_{4.7-3.3}$ in home indicated that several heavy metals were generated from the sources within the house itself. An exceptional feature shown in the individual particles in workplace is that Cr, Mn, and Co were clearly detected in both fine and coarse particles. Cluster analysis suggested that the individual coarse particles ($PM_{4.7-3.3}$) collected at the indoor of factory were chemically heterogeneous and they modified with sea-salt, mineral, and artificially derived elements. The principal components in individual coarse particles collected at restaurant were sea-salt and mineral without mixing with harmful trace elements like chromium and manganese. Compared to the indoor fine particles of home and restaurant, many elements, especially, Cl, Na, Cr, Mn, Pb, and Zn showed overwhelmingly high net-counts in those of factory.

Geochemical Characteristics of the Quaternary Jungok Basalt in Choogaryong Rift Valley, Mid-Korean Peninsula (추가령 열곡대에 분포하는 전곡현무암의 지화학적 특성)

  • Wee, Soo-Meen
    • Economic and Environmental Geology
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    • v.29 no.2
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    • pp.171-182
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    • 1996
  • Quaternary Jungok basalts are distributed along the old Hantan river in Mid-Korean Peninsula. They were flowed out from Mt. Ori and Upland (680 m), and they formed narrow and long basalt plateau showing the layers of 10 to 20 meters in thickness and about 95 km in length. Fifty seven samples were collected from the study area, and sixteen rock samples were selected and analysed for major and trace elements. The analyzed samples have alkalic composition and show a relatively restricted variation in major element chemistry (except MgO), as comparing to the that of trace element. Based on major element chemistry, a quantitative modelling of fractional crystallization by multiple linear regression method suggests that the chemical evolution of the evolved rocks can be generated by fractionation of olivine, plagioc1ase, clinopyroxene, and magnetite in proportion of 56 : 25 : 17 : 2, respectively. The calculated trace element abundances by mineral proportions estimated from major element modelling, however, underestimate the incompatible element concentrations in the evolved rocks. According to the incompatible element abundances, simple fractional crystallization process has difficulty to explain the chemical variation of the evolved rocks. It seems that the other processes, which enrichment of incompatible elements can occure without concomitant changes in major element compositions, are needed in order to explain the chemical variation of the Jungok basalts. Thus, the major elements and compatible trace elements variations of the Jungok basalts are due to fractional crystallization, but the incompatible elements variation is due to fractional crystallization superimposed on already varying concentrations caused by slightly different degrees of melting of the same source, and/or due to periodic replenishment, tapping and fractionation(RTF) processes.

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