• Environmental Engineering Research
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• 제24권3호
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• pp.443-448
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• 2019

The present study was conducted to compare the voltage generation in two-chamber microbial fuel cells (MFCs) with a biocathode where nitrate and oxygen are used as a terminal electron acceptors (TEA) and to investigate the nitrogen removal and the electrochemical characteristics depending on the separators of the MFCs for denitrification. The maximum power density in a biocathode MFC using an anion exchange membrane (AEM) was approximately 40% lower with the use of nitrate as a TEA than when using oxygen. The MFC for denitrification using an AEM allows acetate ($CH_3COO^-$) as a substrate and nitrate ($NO_3{^-}$) as a TEA to be transported to the opposite sides of the chamber through the AEM. Therefore, heterotrophic denitrification and electrochemical denitrification occurred simultaneously at the anode and the cathode, resulting in a higher COD and nitrate removal rate and a lower maximum power density. The MFC for the denitrification using a cation exchange membrane (CEM) does not allow the transport of acetate and nitrate. Therefore, as oxidation of organics and electrochemical denitrification occurred at the anode and at the cathode, respectively, the MFC using a CEM showed a higher coulomb efficiency, a lower COD and nitrate removal rate in comparison with the MFC using an AEM.

• 한국지하수토양환경학회지:지하수토양환경
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• 제27권2호
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• pp.87-98
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• 2022

This study aims to prepare a technical protocol for identifying the source of nitrate in water using nitrogen (δ¹⁵N) and oxygen (δ¹⁸O) stable isotope ratios. The technical processes for nitrate sources identification are composed of site investigation, sample collection and analysis, isotope analysis, source identification using isotope characteristics, and source apportionment for multiple potential sources with the Bayesian isotope mixing model. Characteristics of various nitrate potential sources are reviewed, and their typical ranges of δ¹⁵N and δ¹⁸O are comparatively analyzed and summarized. This study also summarizes the current knowledge on the dual-isotope approach and how to correlate the field-relevant information such as land use and hydrochemical data to the nitrate source identification.

• 한국작물학회지
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• 제45권2호
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• pp.128-133
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• 2000

This study was carried out to investigate the effect of forms and levels of nitrogen fertilizer on plant growth and essential oil production of Agastache rugosa. Calcium nitrate had more influenced on length and width of leaves and lateral branch length than did urea. When nitrogen fertilizer level was increased from 12 kgN/I0a to 24kgN/I0a, plant growth was stimulated and dry matter of leaf and inflorescence were increased. Top dry matter of plant with calcium nitrate treatment (38.4 g) was heavier than that of urea treatment (32.8 g). Interactions among accession and nitrogen form and nitrogen rate were not significantly different for top dry matter. The forms and rate of nitrogen fertilizer did not affect estragole content. The estragole contents was higher in leaf (91.8%) than that of inflorescence (81.3%). While the essential oil content was not affected by different nitrogen forms, nitrogen level affected the essential oil contents positively by increasing dry matter. Essential oil yield was not affected by accession or nitrogen form, but by nitrogen rate. With increasing N application from 12kgN/I0a to 24 kgN/I0a, essential oil yield was increased by 95.8 %.

• 대한환경공학회지
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• 제35권9호
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• pp.654-659
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• 2013

본 연구에서는 액상당밀을 외부탄소원으로 이용하는 탈질미생물 Pseudomonas sp. KY1의 탈질능력을 확인하고 최적의 C/N 비율을 도출하였다. 회분식 실험 결과, C/N 비율 3/1에서 $0.0263hr^{-1}$의 유사1차반응상수가 도출되었고, 이 비율에서 100 mg-N/L의 초기 질산성질소는 실험시작 후 약 100시간 이내에 약 80%의 제거율을 보였다. C/N 비율 3/1의 컬럼 실험에서 초기 질산성질소 농도 100 mg-N/L의 오염수(유속 0.3 mL/min)는 실험시작 후 172시간(35 PV) 이후부터 실험 종료 시(62 PV)까지 최대 95%의 탈질효율을 보였고, 이 비율에서 2차 오염원으로 작용할 수 있는 잔류당밀의 농도를 최소화(125~180 mg-COD/L) 할 수 있었다.

• 분석과학
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• 제31권3호
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• pp.122-133
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• 2018

본 연구에서는 광주지역 민방위비상급수시설 101 개소를 대상으로 2006년부터 2016년까지 11년 동안 측정한 지하수 수질자료를 통계적으로 분석하였으며, 각 시설별로 먹는물 수질기준 초과횟수와 평균농도 분석 및 경향성 분석을 실시하고, 그 분석결과를 이용하여 4 개의 오염등급으로 구분하였다. 또한 이를 바탕으로 토지이용 현황별로 각 항목의 지하수 오염도를 평가하였다. 통계적으로 유의한 민방위 비상급수 15 개 항목에 대한 수질기준초과횟수, 평균농도분석, 경향성분석의 세가지 오염지시인자를 분석하여 합산한 결과 Turbidity (51.5 %) > Color (32.7 %) > Nitrate nitrogen (28.7 %) > Hardness (25.7 %) 순으로 오염 지시율이 상대적으로 높게 평가되었다. 오염등급 분석결과 안전(0)부터 오염심각(3)까지 오염등급이 다양하게 분포한 Turbidity, Color, Nitrate nitrogen의 3 개 항목을 제외하면 12 개 항목의 수질 오염등급은 전체의 25 %는 '오염가능한 등급(1)'으로, 75%는 '안전한 등급(0)'으로 평가되었다. QGIS를 이용하여 오염 지시율이 높게 평가된 4 개 항목(Turbidity, Color, Nitrate nitrogen, Hardness)은 오염지도에 작성하여 오염등급을 시각화하였다.

• 한국식품영양과학회지
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• 제26권4호
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• pp.606-613
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• 1997

멸치에 일정량의 식염, 아질산염, 질산염 및 아스코르브산을 첨가하여 숙성시키면서, NA생성에 미치는 영향에 대해 조사한 결과는 다음과 같다. pH는 담금직 후 7.1에서 숙성 110일 후 5.5로 산성화되었다. TMAO 질소는 숙성 중 감소한 반면, TMA 및 DMA질소는 증가하였다. 아질산염 첨가구는 숙성 중 NDMA 함랑이 증가하였고, 아스코르브산 첨가구는 NDMA 생성이 억제되었다. 모델계 실험 결과, 멸치젓의 니트로소화 최적 pH는 3.8이었고, 아스코르브산은 NDMA생성을 크게 억제시킨 반면 thiocyanate는 촉진시켰다. 본 실험 결 과, 멸치젓 자체에는 NDMA가 거의 검출되지 않았으나, 질산염이나 아질산염의 함량이 많은 물질과 함께 섭취된다면 위내에서 NDMA가 생성될 가능성이 충분한 것으로 판단되었다.

• Journal of Microbiology and Biotechnology
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• 제30권8호
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• pp.1235-1243
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• 2020

The use of microalgal biomass as feedstock for biofuels has been discussed for decades as it provides a sustainable approach to producing fuels for the future. Nonetheless, its feasibility has not been established yet and various aspects of biomass applications such as CO₂ biofixation should also be explored. Therefore, in this study, the CO₂ biofixation and lipid/carbohydrate production potential of Chlorella sp. ABC-001 were examined under various nitrogen concentrations. The highest biomass productivity and CO₂ biofixation rate of 0.422 g/l/d and 0.683 g/l/d, respectively, were achieved under a nitrogen-rich condition (15 mM nitrate). Carbohydrate content was generally proportional to initial nitrate concentration and showed the highest value of 41.5% with 15 mM. However, lipid content showed an inverse relationship with nitrogen supplementation and showed the highest value of 47.4% with 2.5 mM. In consideration as feedstock for biofuels (bioethanol, biodiesel, and biogas), the sum of carbohydrate and lipid contents were examined and the highest value of 79.6% was achieved under low nitrogen condition (2.5 mM). For lipid-based biofuel production, low nitrogen supplementation should be pursued. However, considering the lower feasibility of biodiesel, pursuing CO₂ biofixation and the production of carbohydrate-based fuels under nitrogen-rich condition might be more rational. Thus, nitrogen status as a cultivation strategy must be optimized according to the objective, and this was confirmed with the promising alga Chlorella sp. ABC-001.

• 한국환경보건학회지
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• 제46권6호
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• pp.646-654
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• 2020

Objectives: Users of parks or children's play facilities have pointed to pets' bowel movements as the most serious problem when using them. In prior studies, a very low detection rate of parasites (eggs) in sand flooring materials has been found. Even though feces have been identified, no parasites (eggs) have been detected. Method: A standard solution of nitrate nitrogen was used to verify the reliability of a new nitrogen analysis method. The linearity, precision, and accuracy of the nitrate nitrogen analysis method were verified. Using this method, the pollution distribution of the sand flooring material and the degree of pollution at each point were investigated. Results: As a result of the verification of the nitrogen analysis method, the linearity was found to be good at r2=0.999 when distilled water is mixed in a standard substance solution. The standard substance additive solution r2=0.968 was found to be good. Precision represented 0.01 to 0.06% RSD for peak height. The recovery rate was 92.4 to 104.0 percent, indicating high accuracy. According to the same method of analysis, the flooring material sand at a general amusement facility with the largest number of concealed spaces was nitrate nitrogen 6.1 times higher than at the entrance of the playground. Also, in a comparison between clean sand and sandy flooring, the average nitrogen concentration of the sand flooring material was 24.4-167 times higher than pure sand. Conclusions: As such, no parasites (eggs) were detected at all points under investigation, but the sand flooring was exposed to animal fecal contamination. Therefore, the management of nitrogenous components should allow accurate identification of animal fecal contamination so that the timing of sand replacement can be managed hygienically and safely.

• Journal of Microbiology and Biotechnology
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• 제11권2호
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• pp.179-185
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• 2001

Nitrate grown cells of cyanobacterium Plectonema boryanum, transferred to nitrogen stress, evolved nitrogenase catalyzed $H_2$ under microaerophilic condition. Nitrogen ($N_2$) in gs phase, low light intensity, and reducing substances in incubation phase stimulated $N_2$fixation ($H_2\;evolution$). Cyanobacterium grew slowly under microaerobic condition with a low intracellular ammonia pool. Nitrogen sources (${NO_3}^-,{NH_4}^+,\;and\;CH_3NH_3$) inhibited nitrogenase and glutamine synthetase (GS) transferase activity, and methylamine behaved like an ammonical nitrogen source. Depletion of molybdenum (Mo) and addition of tungsten (W) in the incubation medium inhibited $H_2$ evolution, Cyanobacterium was able to take up nitrate and expressed nitrate reductase (NR) activity under microaerophilic condition at an extremely slow rate.

• Journal of Nutrition and Health
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• 제10권4호
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• pp.111-115
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• 1977

Vegetables and fruits purchased from several markets in Seoul from July to October in 1977 were analyzed to know the level of nitrate-and nitrite-nitrogen accumulation in relation to a public health. Radishes and chinese cabbages utilized mainly as pickled vegetables in Korea resulted in the highest concentration of nitrate-nitrogen. Some of the levels for radishes and chinese cabbages were notably high and exceeded a recommended upper limit of 300 ppm $No_{3}-N$, and thus these levels would render these samples unsafe for use. The levels in some of vegetables other than radish and chinese cabbage, e.g., spinach, lettuce, green onion, cabbage were relatively high and considered to be unsafe for use in feeding infants, where as those of green pepper, bean sprouts and parsely were very low and safe. And also the levells in fruits were very low and safe. Nitrite-nitrogen contents in all tested vegetables and fruits ranged to trace and appeared not to be accumulated in fresh vegetables and fruits. Stems and roots of radishes and chinese cabbages accumulated approximately 2 fold more nitrate-nitrogen than leaves in 5 samples of each vegetable tested.