익산지역에서 자동 및 수동채취방식에 따른 강수의 화학적 특성 비교

강공언 한국대기환경학회 2004 한국대기환경학회지 Vol.20 No.3

In order to understand the precipitation acidity and chemical composition of ion species in Iksan area as well as to know the difference of chemical characteristics in precipitation samples from the viewpoint of precipitation sampling method, precipitation samples were collected by wet-only automatic precipitation sampler and hulk manual precipitation sampler in Iksan, from March 2003 to August 2003. The mean pH of precipitation was 5.0. There was a little significant difference in the mean value of pH between automatic and manual sampler. However, pH values of some precipitation samples were lower in automatic sampler than in manual sampler, especially in case of precipitation samples with small rainfall for March 2003. The mean concentrations of each ions in precipitation were generally a little higher in precipitation samples collected by the manual sampler than in those collected by the automatic sampler because of accumulation of dry deposition on the surface of glass funnel installed at the manual sampler during the sampling period of no rainfall. Dominant species determining the acidity of precipitation, were NH₄+ and nss-Ca^(2+) for cations and nss-SO₄^(2-) and NO₃- for anions. The mean concentration of NH₄+ and nss-Ca^(2+)j were 31 μeq/L and 9 μeq/L for the automatic sampler and 40 μeq/L and 16 μeq/L for the manual sampler, respectively. In addition, nss-SO₄^(2-) and NO₃- were 27 μeq/L and 13 μeq/L for the automatic sampler and 32 μeq/L and 17 μeq/L for the manual sampler, respectively. Although the concentrations of the acidifying ions of nss-SO₄^(2-) and NO₃- were about 3 times higher than those for foreign pristine sites, precipitation acidity were estimated to be natural due to the neutralization reaction of the alkaline species of NH₄+ and nss-Ca^(2+) with its higher concentrations. Considering the ratios of nss-SO₄^(2-)/NO₃- and NH₄+/nss-SO₄^(2-), it was found that ammonium sulphate was dominant in Iksan precipitation. The major non-sea salt ions were maximum concentrations for March, but decreased with increasing of precipitation amount.

Regional Scale 산성강하물의 장기변동 특성과 생태계 영향조사

신아윤(Ah-Yoon Shin),성민영(Min-Young Sung),안준영(Joon-Young Ahn),김종춘(Jong-Choon Kim),김정수(Jung-Soo Kim),이석조(Seok-Jo Lee),손정석(Jung-Seok Son),Arun Kumar Reddy Loka 한국환경관리학회 2010 環境管理學會誌 Vol.16 No.2

본 연구의 최종 목적은 전국적으로 지속적인 산성강하물질의 모니터링을 위한 표준화된 측정과 분석을 통한 자료 축적과 연구로 산성강하물에 대한 현상을 이해하고 원인을 규명하며, 산림 생태계를 중심으로 생태계에 미치는 영향을 평가할 수 있는 실측 농도를 근거로 한 국가자료를 지속적으로 확보하고, EANET 자료를 활용하여 우리나라 뿐만 아니라 동아시아 지역 산성강하물의 장기간 변화 경향을 파악하여 습성강하물의 분석 결과 2004~2009년 전국 연평균 pH는 4.8~4.9로 약산성이며 음이온 성분은 SO₄²?가 2.13~3.30 ㎎/L로 가장 높고 양이온 성분은 NH₄?가 0.63~0.85 ㎎/L로 가장 높은 농도로 나타났다. 산성(건성+습성)강하물 침적량 산정결과, 전체 황 침적량은 1.13~2.02 g/㎡ㆍyr이었으며 질소 침적량은 1.29~2.58 g/㎡ㆍyr로 나타났다. This study aims to understand chemical characteristics of wet and dry deposition, and trends of atmospheric concentration and deposition in Korea. To conduct long-term monitoring of acid deposition, rainfall and PM2.5 samples were collected at 38 monitoring sites and analyzed to detect pH, conductivity, and major ionic components including SO₄²?, Cl?, NO₃?, NH₄?, Na?, K?, Ca²? and Mg²?, as well as mass concentration of fine particles (PM2.5). From the analysis, we can observe the trends of acid deposition, deposition amount of each element, and total acid depositions in Korea. The volume weighted annual mean pH of precipitation in Korea was 4.9. The volume weighted annual mean concentrations of SO₄²?, NO₃?, Cl? were 2.21, 1.23, 1.39 ㎎/L respectively, indicating that SO₄²? was the major contributor, followed by NO₃? and Cl?. In the case of cation, annual mean concentration for NH₄?, Na?, K?, Ca²?, Mg²?, and H? are 0.66, 0.67, 0.28, 0.15, 0.11, 0.02 ㎎/L. Annual wet deposition rate for SO₄²?, NO₃?, and NH₄? were 2.61, 1.45, 0.77 g/㎡ㆍyr respectively. The results show that daily averaged mass concentration of PM2.5 is 27.5 ㎍/㎥ and mass concentrations for SO₄²?, NH₄?, and NO₃? are 4.94, 2.00, 2.08 ㎍/㎥ respectively, which account for 18.0%, 7.6% and 7.3% of the total PM2.5 mass concentration individually in the long term monitoring. During the measurement period, deposition velocity for SO₂, HNO₃, aerosol, NO₂, NH₃ was 0.24, 1.42, 0.17, 1.75, 1.75 ㎝/sec. The result shows that annual mean dry deposition rates for SO₂ in 2005~2009 were 0.32, 0.55, 0.56, 0.37, 0.27 S g/㎡ㆍyear, and for HNO₃ were 0.05, 0.11, 0.28, 0.22, 0.20 N g/m²ㆍyear, for NO₂ in 2007~2009 were 0.37, 0.41, 0.35 N g/㎡ㆍyear, and for NH₃ were 0.50, 0.43, and 0.59 N g/㎡ㆍyear. Dry deposition contributed about 29 percent of the total sulfur deposition, and 65 percent of the total nitrogen deposition. Critical load exceedance was estimated for three years (Oct. 2006~Oct. 2009) using mean depositions of nitrogen and sulfur, which shows that the impact of nitrogen was relatively higher than that of sulfur in the capital region and west coastal regions.

Preferential CO oxidation in H2-rich stream over Au/CeO_2 catalysts prepared via modified deposition–precipitation

Theerathad Sakwarathorn,Sangobtip Pongstabodee,Apanee Luengnaruemitchai 한국공업화학회 2011 Journal of Industrial and Engineering Chemistry Vol.17 No.4

Preferential CO oxidation in a H_2-rich stream over Au/CeO_2 catalysts prepared via modified deposition–precipitation by using different precipitating agents at various pH values was investigated in this research work. The prepared catalysts were characterized by XRD, TEM, XRF, BET, TPR, UV–vis, and FTIR. The experimental results showed that the Au/CeO_2 catalysts prepared by using NaOH as a precipitating agent at pH 7 expressed the highest catalytic activities (complete conversion and 51% selectivity at 40℃)due to its well-dispersed nano-size Au particles on the support surface with narrower particle size distribution. When adding CO_2 to the feed stream, the catalytic performance was decreased dramatically due to the formation of the formate species. The co-addition of CO_2 and H_2O in the feedstream had a less negative effect on the CO oxidation compared to the effect of CO_2 alone. Water can attack and decompose the carbonate intermediate; the accumulation of the formate species on the active sites of the catalysts is then decreased and the catalytic performance is improved. After in situ thermal regeneration under 5%oxygen in helium at 110℃ for 2 h, more active sites for the preferential CO oxidation reaction were recovered since the oxygen reacted with the formate species to form CO_2. In addition, the Au/CeO_2catalysts exhibited good stability during the tested time in this study.

Precipitation–deposition assisted fabrication and characterization of nano-sized zinc manganite

N.M. Deraz,Ahmed A. Abdeltawab,M.M. Selim,O. El-Shafey,A.A. El-Asmy,Salem S Al-Deyab 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.5

Catalytic and structural investigations of nano-sized zinc manganite (ZnMn2O4) powders have been determined. These manganites were prepared by precipitation–deposition route followed by heating at 400, 600, and 800℃. The final products were characterized X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray (EDX). The catalytic activity of the as prepared systems was measured by the hydrogen peroxide decomposition in aqueous solution over the solid surface at 30–50℃. The results showed that the calcination temperature affects the different characteristics of the investigated solids.

메탄화 반응을 위한 Ni-Co 이원 금속 촉매의 제조와 특성 분석

강미영(Mi Yeong Kanga),김우영(Woo Young Kim),조원준(Won Jun Cho),이종협(Jong Heop Yia) 한국가스학회 2009 한국가스학회지 Vol.13 No.5

일산화탄소, 수소와 같은 친환경 연료용 가스를 이용하여 메탄화 반응을 거쳐 합성 가스를 생성하였다. 이를 위한 촉매로 상용 알루미나에 담지된 Ni-Co 이원 금속을 증착침전법을 사용하여 제조하였으며 제조된 촉매의 촉매 활성 비교를 위하여 Ni, Co 단일 금속 촉매를 동일한 방법으로 제조하였다. 제조한 촉매를 TEM, XRD, TPR 분석을 실시하여 각각의 촉매 특성을 확인하였고 메탄화 반응을 진행하여 합성 가스 전환율을 측정하였다. 증착침전법으로 제조한 촉매의 경우, 금속 입자가 작은 크기로 분산된 것을 확인하였다. Ni, Co 두 금속이 담지된 이원 촉매는 Ni, Co가 각각 담지된 단일 금속 촉매에 비해 더욱 높은 활성을 나타내었으며 TPR 분석 결과, 이는 두 금속의 공존으로 인한 상호 작용을 통해 활성 수소를 보다 증가시켰기 때문으로 나타났다. Synthetic natural gas was producd by the reaction of carbon monoxide and hydrogen via methanation. Ni-Co bimetallic catalyst supported on Al2O3 for methanation was prepared using deposition-precipitation method. For the comparison, Ni, Co monometallic catalyst was prepared using the same method. The prepared catalysts were characterized by TEM, XRD and TPR and applied to methanation reaction. The catalysts prepared using deposition-precipitation method showed the high metal dispersion. The activity of Ni-Co bimetallic catalyst was higher than that of Ni, Co monometallic catalyst. TPR measurements indicated that Ni-Co bimetallic catalyst had more active hydrogen species than Ni, Co monometallic catalyst due to the synergetic effect in the presence of Ni and Co.

Correlation of tree ring growths of four major species with climate changes in South Korea

Thi-Hoan Luong,이계한,장경수,임형우,최우정 한국산림과학회 2013 Forest Science And Technology Vol.9 No.4

Annual tree rings of Pinus densiflora, Quercus variabilis, Larix leptolepis, and Cryptomeria japonica were analyzed toexamine the correlations of annual ring growth of these species with environmental variables. In all four species, annualring area was increased over time and affected by integration of climate changes and atmospheric pollutants in the forestecosystem. C. japonica ring growth was larger than that of other species. The annual growth rings of P. densiflora andC. japonica increased with increasing temperature (p < 0.05). The significant impacts of NO2 concentration on annual ringgrowth of C. japonica (p < 0.05) might reflect the nitrogen deposition. The relation of CO2 concentration with annual ringgrowth of C. japonica (p < 0.001) could suggest that annual ring growth of C. japonica decreased with increasing CO2concentration, probably due to stomatal closure. The effects of SO2 concentration on annual ring area of P. densiflora,L. leptolepis, and C. japonica (p < 0.05) along with the correlation of O3 concentration with ring growth of P. densiflora(p < 0.05) could be due to acid deposition. The relationships of precipitation pH with annual ring growth of P. densiflora (p< 0.05) and Q. variabilis (p < 0.01) might reflect the change of nutrient cycles in the forest ecosystem. Therefore, annualring growths of four tree species depended on environmental factors in the study area. Integrated effects of climate changeand atmosphere pollutants on tree growth in the study might reflect the problem of acidification in the forest ecosystem.

Gold Nanoparticles Grafted Mesoporous Silica: A Highly Efficient and Recyclable Heterogeneous Catalyst for Reduction of 4-Nitrophenol

Akansha Mehta,Manu Sharma,Ashish Kumar,Soumen Basu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.9

Synthesis of gold nanoparticles dispersed uniformly on mesoporous silica (mAu/SiO2) by homogeneous deposition–precipitation (HDP) method is used as an effective catalyst for reduction of 4- nitrophenol to 4-aminophenol. Silica provides support and surface area to increase the catalytic activity of gold. X-ray photon spectroscopy revealed binding energy of Au 4f7/2 (~84.0 eV) and Au 4f5/2 (~87.7 eV) which support the formation of Au0 on SiO2 surface. Au/SiO2 showed Langmuir type-IV isotherms which are the characteristic features of mesoporous materials furthermore, pore size decreases with incorporation of Au NP's on SiO2 surface. The enhancement is due to the strong interaction of Au0 with silica support. The catalytic conversion was studied by UV-Visible spectroscopy and high performance liquid chromatography (HPLC) quantification method, which shows conversion of nitro group into amino group. In addition, the catalyst was easily separated and reused. The reusability of the catalyst exhibited better reduction of the 4-nitrophenol to 4- aminophenol even after 10 consecutive cycles. In comparison to trisodium citrate capped pure gold nanoparticles mAu/SiO2 catalysts showed very good catalytic activity toward nitrophenol reduction. Here we conclude that embedment of metal catalysts like Au into high surface area support like silica is a positive step toward development of novel heterogeneous catalysts.

Facile Synthesis, Characterization and Photocatalytic Activity of MWCNT-Supported Metal Sulfide Composites under Visible Light Irradiation

Zhu, Lei,Meng, Ze-Da,Oh, Won-Chun The Korean Ceramic Society 2012 한국세라믹학회지 Vol.49 No.2

This paper reported a simple deposition-precipitation method, introducing the metal (Ni, Ag and Sn) and $Na_2S{\cdot}5H_2O$ to preparedispersion metal sulfide nanoparticles on the surface of the Multi-walled carbon nanotube for synthesis of CNT-$M_xS_y$ ($NiS_2$, $Ag_2S$, SnS) composite photocatalysts. The characterization of the prepared CNT-$M_xS_y$ ($NiS_2$, $Ag_2S$, SnS) composites was performed by X-ray diffraction, scanning electron microscopy with energy dispersive X-ray analysis and BET analysis. Furthermore, the MB degradation rate constant for CNT-SnS composite was $5.68{\times}10^{-3}$ under visible light irradiation, which was much higher than the corresponding values for other samples. The detailed formation and photocatalytic mechanism are also provided here.

The construction of the Ni/La2O2CO3 nanorods catalysts with enhanced low-temperature CO2 methanation activities

Hui Yang,Xueying Wen,Siyuan Yin,Yixin Zhang,Cai-e Wu,Liang Xu,Jian Qiu,Xun Hu,Leilei Xu,Mindong Chen 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.128 No.-

In this work, the La(OH)3 nanorods were successfully synthesized by precisely regulating the parametersof the hydrothermal method. Then, a series of Ni-based CO2 methanation catalysts were fabricated via theincipient-wetness impregnation and deposition–precipitation methods by employing the La(OH)3 nanorodsas the supports. The influences of the support morphology and the preparation method on the metalsupportinteraction, Ni dispersion, and the surface basicity were carefully investigated based on varioustechniques, such as XRD, SEM, H2-TPR, CO2-TPD, XPS, ect. It was found that the rod-shaped La(OH)3 supportedcatalyst prepared by the deposition–precipitation method performed the optimum activity andstability. The reason for this could be derived from the confinement effect of the crystal plane of therod-shaped support, which would promote the formation of the strong metal-support interaction andthe construction of the Ni-La interface with high activity. Furthermore, the online-tandem TG-MS andin-situ DRIFTS technologies were used to investigate the thermal decomposition performance of the catalystprecursors in the calcination process and the reaction intermediates of the CO2 methanation. Therefore, the fundamental roles of support morphology and catalyst preparation method were expectedto direct the advancement of the Ni-based nanostructured catalysts with outstanding low-temperatureperformances.

Effects of magnetic field on calcium carbonate precipitation: Ionic and particle mechanisms

Seung Koo Song,Nelson Saksono,Misri Gozan,Setijo Bismo,Elsa Krisanti,Roekmijati Widaningrum 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.5

There are two most widely reported mechanisms to study the effect of magnetic fields on calcium carbonate (CaCO3) precipitate, namely ionic and particle mechanisms. The effects are most debatable because they are contrary to each other. This study explored the effects of both mechanisms in CaCO3 deposit and total CaCO3 precipitation using ionic and particle methods. The ionic method showed reductions in CaCO3 deposit and total precipitation rate of CaCO3, whereas the particle method showed the opposite results. The particle number decreased and the average particle diameter of CaCO3 deposit increased in the ionic method. Meanwhile in the particle method, the particle number increased, average particle diameter decreased and particle aggregation of CaCO3 was observed. XRD measurement on all deposits showed that the crystal deposit was mostly of calcite and the traces of vaterite. However, the amount of the crystal in the particle method was observed to be less than that in the ionic method, indicating that CaCO3 deposit was more amorphous. Particle mechanism decreased the Ca2+ ion concentration in solution during magnetization, and ionic mechanism reduced scale (CaCO3) formation after magnetization and separation processes. This method could be applied for decreasing water hardness and prevent the formation of scaling.