• 제목/요약/키워드: chemical elements

검색결과 1,274건 처리시간 0.026초

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

  • Sivakumar, K.;Senthilkumar, R.
    • 생태와환경
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    • 제41권2호
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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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    • 제9권4호
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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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    • 제32권3호
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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.

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

  • 강대호;정수군;구인선
    • 대한화학회지
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    • 제47권6호
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    • pp.645-658
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    • 2003
  • 이 연구는 제 7차 교육과정에 의한 화학 II 교과서의 탐구영역을 제 7차 과학 교육 과정에서 제시한 탐구 요소들에 의해 분석하였다. 연구의 목적은 화학 II 교과서의 탐구영역이 제 7차 과학 교육과정을 얼마나 반영하는지 알아보고 현장 탐구학습의 교육적 시사점을 찾고자 하였다. 전체적으로 보았을 때, 기초 탐구요소들은 분류를 제외하고는 제 7차 화학 II교과서에 대체로 찰 반영되어 있었으나, 통합탐구 요소들은 자료해석이 거의 절반을 차지하고, 결론도출, 자료변환 등을 제외한 통함 탐구요소들은 이주 낮은 비율을 나타내고 있다. 탐구활동 요소들도 조사의 비율 이 전체 탐구활동의 100/0미만이고, 과제연구는이주적고, 견학은나타나지 않았다 제 7차과학 교육과정에서는 고학년의 탐구학습 일수록 다양한 통합탐구 요소와 탐구활동을 강조하고 있으므로 현장의 탐구학습에서는 이러한 화학 R 교과서의 미흡한 점을 보완할 수 있는 방향으로 탐구학습을 운영하여야 할 것이다.

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

  • 이상인;임현석;황병철
    • 한국재료학회지
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    • 제26권10호
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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
    • 한국지하수토양환경학회:학술대회논문집
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    • 한국지하수토양환경학회 2004년도 임시총회 및 추계학술발표회
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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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추출크로마토그래피와 유도결합플라스마 원자방출분광법을 이용한 이산화우라늄분말 중 미량금속불순물 분석 (Determination of the Trace Elements in $UO_2$ Powder by ICP-AES Directyl Coupled with Extraction Chromatography)

  • 최광순;이창헌;표형열;한선호;서무열;엄태윤;이계호
    • 대한화학회지
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    • 제37권9호
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    • pp.813-819
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    • 1993
  • $UO_2$ 분말에 미량 함유되어 있는 금속불순물들을 신속하게 정량하고 분석과정에서 발생되는 폐액의 양을 줄이기 위하여, 우라늄용액으로부터 미량금속불순물들을 분리함과 동시에 ICP-AES로 분석할 수 있는 장치를 구성하였다. 미량금속불순물들을 분리하기 위하여, 폴리에틸렌으로 제작한 분리컬럼(내경 : 0.7cm, 길이 : 7 cm)에 TBP(tri-n-butyl phosphate)를 입힌 테프론 분말(약 $330\;{\mu}m$)을 충진하고, 분리컬럼의 출구를 ICP-AES의 시료주입구에 연결시켰다. $UO_2$ 분말에 미량 함유되어 있는 몰리브덴을 비롯한 11개 원소를 분리와 동시에 정량할 수 있었으며, 이들 원소들에 대한 회수율은 용매추출법에서와 거의 동일한 $91{\sim}110%$로서 핵연료 제조공정의 품질관리에 적용이 가능하였다.

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

  • 정명채;정문영;최연왕
    • 자원환경지질
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    • 제37권1호
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    • pp.21-33
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    • 2004
  • 이 연구의 목적은 국내의 휴폐광 금속광산의 중금속 오염을 종합적으로 평가하는 것이다. 그 동안 정부와 지방자치단체 및 개별 연구자에 의해 이루어진 휴폐광 금속광산의 중금속 오염도를 종합적으로 조사한 결과, 주요 오염물질은 광미를 포함한 광산폐기물이었다. 이들로부터 다양한 유독성 물질, 특히 As, Cd, Cu, Pb 및 Zn 등이 바람과 물에 의해 하부 수계로 이동되어 환경문제를 일으키고 있다. 그 결과 많은 광산들 주변에서 다량의 As 및 중금속이 검출되었으며, 일부는 토양환경보전법의 우려기준 및 대책기준을 초과하고 있다. 초과 항목 중에서는 비소의 초과 빈도가 가장 높았으며 그 다음으로 Cd, Cu, Pb, Zn 등의 오염 빈도도 높은 편이었다. 국가에서 지속적인 광해방지사업을 시행함에도 불구하고 아직도 많은 광산에서 오염물질이 배출되고 있는 실정이다. 특히, 다양한 추출법을 적용하여 오염물질의 추출량을 조사한 결과, 광미 및 토양은 지구화학적 특성을 잘 반영하고 있다. 종합적으로 볼 때, 정부주도로 휴폐광산의 관리를 위한 전담기구의 설치가 필요하다.

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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    • 제11권2호
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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.

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

  • 위수민
    • 자원환경지질
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    • 제29권2호
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    • pp.171-182
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    • 1996
  • 제 4기 전곡현무암은 추가령 열곡대내의 한탄강유로를 따라 길게 분포하고 있으며 이대성 외 (1983)에 의하면 대략 10-20 m정도의 두께를 가지고 있다. 전곡현무암의 암석분화 과정을 밝히기 위해 57개의 시료가 채취 되었으며, 이중 16개의 시료에 대한 주성분 및 미량원소의 화학분석이 실시되었다. 분석된 시료들의 화학조성에 의하면 전곡현무암은 알칼리계열의 현무암으로 특징지워지며, MgO를 제외한 주성분원소의 변화범위가 미량원소에 비하여 상당히 좁은 영역을 나타낸다. 분별결정작용 모델을 정량적으로 시험하기 위해서 Multiple linear regression을 사용하였다. 주성분원소와 반정으로 산출되는 광물의 화학조성을 사용하여 계산된 결과는 전곡현무암의 화학조성의 변화는 감람석, 사장석, 휘석, 자철석이 56 : 25 : 17 : 2의 비율로 분별정출되어 분화된 것으로 설명할 수 있다. 그러나 위의 결과를 가지고 미량원소의 함량을 계산하면 불호정 (incompatible) 원소의 계산치는 딸암석의 실제 함량에 미치지 못한다. 이러한 점으로 미루어 전곡현무암의 화학조성의 변화는 광물들의 단순한 분별정출 작용만으로는 설명하기가 어렵다. 따라서 전곡현무암의 화학조성의 변화는 약간 다른 정도의 부분용융에 의해 불호정 원소의 초기치가 다른 것들이 분별정출과정을 겪었거나, 혹은 RTF과정에 의한 불호정원소의 부화가능성을 배제할 수 없음을 시사한다.

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