• 한국재료학회지
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• 제25권10호
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• pp.543-546
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• 2015

$TiO_2$ nanowires were grown by thermal oxidation of TiO powder in an oxygen and nitrogen gas environment at $1000^{\circ}C$. The ratio of $O_2$ to $N_2$ in an ambient gas was changed to investigate the effect of the gas ratio on the growth of $TiO_2$nanowires. The oxidation process was carried out at different $O_2$/$N_2$ ratios of 0/100, 25/75, 50/50 and 100/0. No nanowires were formed at $O_2$/$N_2$ ratios of less than 25/75. When the $O_2$/$N_2$ ratio was 50/50, nanowires started to form. As the gas ratio increased to 100/0, the diameter and length of the nanowires increased. The X-ray diffraction pattern showed that the nanowires were $TiO_2$ with a rutile crystallographic structure. In the XRD pattern, no peaks from the anatase and brookite structures of $TiO_2$were observed. The diameter of the nanowires decreased along the growth direction, and no catalytic particles were detected at the tips of the nanowires which suggests that the nanowires were grown with a vapor-solid growth mechanism.

• 환경위생공학
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• 제21권3호
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• pp.15-26
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• 2006

As traffic in city-centre around the world continues to increase, so levels of atmospheric pollutants continue to rise. High concentrations of NOx can have negative effects on human health, and we must find new ways to reduce their levels in the air we breathe. Nitrogen oxide gas (NOx), consisting of nitrogen monoxide (NO) and nitrogen dioxide $(NO_2)$ produced using $O_3$ oxidation, at a low concentration corresponding to that on roads as a result of exhaust from automobiles, was carried out to evaluate the removal characteristics of NOx through a laboratory-scale biofilter packed with soil as a packing material. A mixture media (yellow soil (30%): soil (40%): compost (10%): a used briquet (20%)) was applied. After about 1day of operation, the removal efficiency for $NO_2$ in all experiments with a constant condition ($25^{\circ}C$ and water humidity (60%)) was over 98%. The retention times of the section between phase I and phase II for formation and reduction of $NO_3$ NO and $NO_2$ on the initial $NO_3$ concentration was 50min $(O_3:195\;ppb),\;55min\;(O_3:925\;ppb),\;65min\;(O_3:1743\;ppb),\;70min\;(O_3:2616\;ppb),\;75min\;(O_3:3500\;ppb)$, respectively The soil biofilter system is a unique technology that purifies urban air by utilizing the natural processes that take place in the soil. Although some of the processes are quite complex, they can broadly be summarized as adsorption onto soil particles, dissolution into soil pore water, and biochemical.

• Preventive Nutrition and Food Science
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• 제12권3호
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• pp.181-184
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• 2007

Effect of aqueous chlorine dioxide ($ClO_{2}$) treatment on quality change of mackerel during storage was examined. Mackerel treated with 0, 5, 10, and 50 ppm of $ClO_{2}$ solution, respectively was stored at $4^{\circ}C$. $ClO_{2}$ treatment decreased populations of aerobic bacteria in mackerel during storage. The number of total aerobic bacteria of mackerel treated with 50 ppm $ClO_{2}$ increased from 2.45 to 3.44 log CFU/g after 9 days of storage, while that of the control increased from 3.47 to 4.72 log CFU/g. The pH values of mackerel increased during storage, with no significant changes among treatments. Volatile basic nitrogen values of mackerel were decreased by $ClO_{2}$ treatment. Quality of mackerel treated with $ClO_{2}$ was better than that of the control during storage based on sensory evaluation. These results indicate that aqueous $ClO_{2}$ treatment could be useful for improving the microbial safety and qualities of mackerel.

• 한국대기환경학회지
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• 제24권1호
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• pp.16-29
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• 2008

Nitrous acid (HONO) can be produced by heterogenous reactions of nitrogen dioxide on surface materials and direct emission from combustion sources. However, a little is known of indoor HONO levels or the relationship between residential HONO, NO, and $NO_2$ concentrations in occupied houses. Therefore, we measured simultaneously NO, $NO_2$, and HONO concentrations in living room of an apartment using continuous analyzers to study the production of HONO (June $22{\sim}30$, 2006). The 4-min average concentrations of indoor NO, $NO_2$, and HONO were 4.3 (range: $0.4{\sim}214.3$), 10.3 ($2.0{\sim}87.3$), and 1.8 ppb ($0.3{\sim}7.7$), respectively. Peak levels of HONO up to 7.7 ppb and 24-hr averages as high as 1.7 ppb were measured. In agreement with previous studies, indoor HONO concentrations increased during operation of an unvented gas range. Examination of the observed kinetics suggests that the secondary production of indoor HONO, possibly as a result of heterogeneous reactions involving $NO_2$ and $H_2O$ is associated with $[NO_2]^2[H_2O]\;(r^2=0.88)$ rather than with $[NO][NO_2][H_2O]\;(r^2=0.75)$. Three combustion experiments at nighttime were also carried out to investigate the effects of vented combustion on the HONO, NO, and $NO_2$ concentrations. It was found to release HONO for $10{\sim}15$ minutes after NO and $NO_2$ source was turned off, and peak values were finally attained. Compared to unvented combustion, peak $NO_2$ and HONO concentrations were 3.2 and 2.0 times lower at weak vented combustion (air flow: $340\;m^3/hr$) and 4.9 and 2.4 times lower at strong vented combustion (air flow: $540\;m^3/hr$), respectively, emphasizing importance of operating ventilation hood fan during combustion to improve indoor air quality.

• 한국토양비료학회지
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• 제46권4호
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• pp.288-295
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• 2013

Nitrogen dioxide ($NO_2$) gas damage on vegetable crops commonly occurs in plastic film houses where relatively large amounts of $NO_3{^-}$ are applied in acid soils. In acid soils, $HNO_2$ can be formed from the $NO_2{^-}$ accumulated during denitrification, and $NO_2$ can be evolved from the chemical self-decomposition of $HNO_2$. In this study, $NO_2$ gas production and its detrimental effects on plants were investigated in soils of various conditions to elucidate the mechanisms involved in the gas production. A silty loam soil was amended with $NO_3{^-}$ (500 mg N $kg^{-1}$) and glucose, and pH and moisture of the soil were adjusted respectively to 5.0 and 34.6% water holding capacity (WHC) with 0.01 M phosphate buffer. The soil was placed in a 0.5-L glass jar with strawberry leaf or $NO_2$ gas absorption badge in air space of the jar, and the jar was incubated at $30^{\circ}C$. After 4-5 days of incubation, dark burning was observed along the outside edge of strawberry leaf and $NO_2$ production was confirmed in the air space of jar. However, when the soil was sterilized, $NO_2$ emission was minimal and any visible damage was not found in strawberry leaf. In the soil where water or $NO_3{^-}$ content was reduced to 17.3% WHC or 250 mg N $kg^{-1}$, $NO_2$ production was greatly reduced and toxicity symptom was not found in strawberry leaf. Also in the soil where glucose was not amended, $NO_2$ production was significantly reduced. In soil with pH of 6.5, $NO_2$ was evolved to the level causing damage to strawberry leaf when the soil conditions were favorable for denitrification. However, compared to the soil of pH 5.0, the $NO_2$ production and its damage to plants were much less serious in pH 6.5. Therefore, the production of $NO_2$ damaging plants might be occurred in acid soils when the conditions are favorable for denitrification.

• 보존과학회지
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• 제31권4호
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• pp.403-409
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• 2015

석록(Malachite)과 석청(Azurite)은 대표적인 구리계통 안료이며, 고대부터 벽화에 널리 사용되어왔다. 사찰 등의 벽화는 외부환경에 노출되어 있으므로 대기가스의 영향으로 인해 채색층 손상이 발생될 수 있다. 본 연구에서는 대기가스가 토벽화에 채색된 석록과 석청에 미치는 영향을 파악하기 위하여 의사시편을 제작하고 대기가스($NO_2$, $CO_2$, $SO_2$)에 의한 물질변화 양상을 분석하였다. 실험 결과, 석록과 석청은 $CO_2$와 $SO_2$환경에서 눈에 띄는 변화를 나타내지 않았으나 $NO_2$환경에서는 큰 변화를 보였다. 특히 $NO_2$의 농도가 높아질수록 안료층의 박락현상이 두드러졌으며, 주사전자현미경 상에서는 안료입자에 기공이 형성되면서 더 작은 입자로 부스러지는 현상이 함께 관찰되었다. 또한 $NO_2$환경에 노출시킨 석록의 경우에는 XRD분석에서 새로운 화합물(Rouaite : dicopper(nitrate(V) trihydroxide, $Cu_2(NO_3)(OH)_3$))이 동정되어 $NO_2$가스가 석록과 석청에 대하여 화학적 변화를 동반한 박락 및 변색 현상을 일으킨다는 사실을 확인할 수 있었다.

• 대한환경공학회지
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• 제27권3호
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• pp.330-336
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• 2005

본 연구에서는 촉매공정의 질소산화물 제거 성능을 향상시키기 위하여 배기가스에 오존을 주입하였다. 배기가스에 오존을 주입하면 배기가스에 포함되어 있는 NO의 일부가 $NO_2$로 빠르게 산화되며, NO와 $NO_2$ 혼합물은 촉매반응기에서 $N_2$로 환원된다. 오존의 발생을 위해 유전체 장벽 방전 반응기가 사용되었고 촉매로는 상용 $V_2O_5-WO_3/TiO_2$ 촉매가 사용되었다. 질소산화물의 환원제는 암모니아였다. 촉매반응기 전단의 $NO_2$ 함량은 오존 주입량에 의해 변화될 수 있었으며, $NO_2$ 함량 변화가 촉매의 질소산화물 저감성능에 미치는 영향에 대해 살펴보았다. $NO_2$ 함량이 촉매반응기의 성능에 미치는 영향은 다양한 조건에서 수행되었는데, 주요 변수로 선정한 것은 반응온도, 초기 $NO_x$ 농도, 암모니아 농도, 그리고 배기가스 유량이었다. 오존주입에 의한 $NO_2$ 함량 증가는 촉매공정의 질소산화물 제거 성능을 크게 향상시킬 수 있었으며, 이러한 성능 향상 효과는 반응온도가 낮을수록 두드러졌다. 본 연구의 오존 주입 방법은 기존 촉매 공정의 개선에 크게 유용할 것으로 판단된다.

• 대한임베디드공학회논문지
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• 제11권5호
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• pp.299-304
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• 2016

As public interest in air quality and environment problem is increasing, many researches are being carried out the gas measurement system. Especially, Non-dispersive infrared (NDIR) measurements using Beer-Lambert gas sensing principle with very high selectivity and long life time are noted for reliable method. It is possible to detect various gases such as carbon dioxide (CO2), carbon monoxide (CO), and nitrogen dioxide (NO2), but many researches are mostly concentrated on CO2 sensor. The multi-gas measuring instrument is high price and unwieldy, therefore it is not suitable for wide area required numerous instrument. So we study the NDIR multi-gas measurement system for air quality based on wireless sensor network, and experiment the realized measurement system.

• 한국응용과학기술학회지
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• 제33권1호
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• pp.110-117
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• 2016

기존 연구에서는 스크러버를 이용한 $NO_2$ 를 제거하기 위해 암모니아 수용액을 적용한다. 하지만 암모니아는 독성 및 악취가 강해 실선 적용에 어려움이 따를 수 있어, 암모니아를 대체할 수 있는 물질을 찾기 위해 이 연구를 진행하였다. 대체 물질로는 수산화나트륨(NaOH), 티오황산나트륨($Na_2S_2O_3$), 요소(Urea)를 사용하였다. 세정액을 제외한 모든 부분은 기존 암모니아를 적용한 실험의 최적 조건과 동일하게 진행하였다. 그 결과 실험에 사용된 세 가지 물질 중 두 물질은 암모니아 용액과 대체가 가능한 것으로 사료되었으며, 최적조건은 각각 NaOH 2.5 %, $Na_2S_2O_3$ 5.0 % 에서 가장 높은 효율을 나타냈다. Urea는 효율이 일정하게 지속되지 않아 대체 물질로는 적합하지 않음을 확인 할 수 있었다.

• 한국환경보건학회지
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• 제24권2호
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• pp.134-144
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• 1998

A comprehensive air quality monitoring was carried out to investigate the criteria concentration of air pollutant in indoor of subway stations of Seoul City. The samples were collected twice per year (the first and the second half of the year) at each sampling point from February to September in 1997. Sampling point of subway stations was ticket office and platform. The measurement of indoor air pollutants such as sulfur dioxide(SO$_2$), nitrogen dioxide(NO$_2$), carbon monoxide(CO), carbon dioxide(CO$_2$), total suspended particulate(TSP) was performed to determine the indoor air quality. Heavy metals(Pb, Cd, Cu, Cr, As, Hg) were also measured together with those air pollutants. The annual average concentration of CO$_2$ and TSP in subway stations were relatively high while those of heavy metals were within 10% of environmental recommended standard concentration in all stations. As results of regression analysis between line and line of air factors, the concentrations of CO, CO$_2$, TSP, Pb, Cd, Cr and Cu were highly correlated, but those of $SO_2, NO_2$ and Hg were not correlated. As results of regression analysis between ticket office and platform, the concentrations of heavy metals such as Cr and Cu were highly correlated. Results of oneway analysis of variance between the first and the second half of the year air factors also indicated that CO, CO$_2$, Cd, Cu, Hg were significant($\alpha$=0.01), respectively. The average contration of total suspended particulate(TSP) in subway line No. 1 was shown high concentration(200 $\mu g/m^3\cdot$ day) level.