• Journal of Applied Biological Chemistry
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• 제51권6호
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• pp.262-271
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• 2008

Natural abundances of stable isotopes of nitrogen and carbon (${\delta}^{15}N$ and ${\delta}^{13}C$) are being widely used to study N and C cycle processes in plant and soil systems. Variations in ${\delta}^{15}N$ of the soil and the plant reflect the potentially variable isotope signature of the external N sources and the isotope fractionation during the N cycle process. $N_2$ fixation and N fertilizer supply the nitrogen, whose ${\delta}^{15}N$ is close to 0%o, whereas the compost as. an organic input generally provides the nitrogen enriched in $^{15}N$ compared to the atmospheric $N_2$. The isotope fractionation during the N cycle process decreases the ${\delta}^{15}N$ of the substrate and increases the ${\delta}^{15}N$ of the product. N transformations such as N mineralization, nitrification, denitrification, assimilation, and the $NH_3$ volatilization have a specific isotope fractionation factor (${\alpha}$) for each N process. Variation in the ${\delta}^{13}C$ of plants reflects the photosynthetic type of plant, which affects the isotope fractionation during photosynthesis. The ${\delta}^{13}C$ of C3 plant is significantly lower than, whereas the ${\delta}^{13}C$ of C4 plant is similar to that of the atmospheric $CO_2$. Variation in the isotope fractionation of carbon and nitrogen can be observed under different environmental conditions. The effect of environmental factors on the stomatal conductance and the carboxylation rate affects the carbon isotope fractionation during photosynthesis. Changes in the environmental factors such as temperature and salt concentration affect the nitrogen isotope fractionation during the N cycle processes; however, the mechanism of variation in the nitrogen isotope fractionation has not been studied as much as that in the carbon isotope fractionation. Isotope fractionation factors of carbon and nitrogen could be the integrated factors for interpreting the effects of the environmental factors on plants and soils.

• 생태와환경
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• 제51권1호
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• pp.96-104
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• 2018

안정동위원소비는 전 세계적으로 수생태 환경 연구에서 매우 활발하게 적용되고 있는 분야로써, 국내에서도 2000년대 이후 담수 및 연안 생태계의 먹이망 구조 연구 등 다양한 연구에서 활용되고 있다. 최근에는 기존의 총 조직내의 안정동위원소 분석기법의 한계점을 인지하고 보완하기 위한 방안으로 아미노산의 질소 안정동위원소 분석 기법이 개발되었으며, 이를 활용한 다양한 연구 사례들이 보고됨에 따라 수생태 연구의 활용범위가 급격히 확대되고 있다. 아미노산의 질소 안정동위원소 분석기법의 기술적인 접근성의 한계에 의해 현재까지 국내에서 수생태계 연구를 위해 아미노산의 질소 안정동위원소비를 활용한 연구는 제한적인 실정이지만, 국내 다양한 하천 및 호수 그리고 연안의 환경 변화 특성을 고려할 때, 향후 수생태 환경연구에 있어 그 유용성과 활용 가치가 대단히 높을 것으로 전망된다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2003년도 총회 및 춘계학술발표회
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• pp.63-66
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• 2003

This study applied a hydrogeological field survey and isotope investigation to identify source locations and delineate pathways of groundwater contamination by nitrogen compounds. The infiltration and recharge processes were analyzed with groundwater-level fluctuation data and oxygen-hydrogen stable isotope data. The groundwater flow pattern was investigated through groundwater flow modeling and spatial and temporal variation of oxygen isotope data. Based on the flow analysis and nitrogen isotope data, source types of nitrate contamination in groundwater are identified. Groundwater recharge largely occurs in spring and summer due to precipitation or irrigation water in rice fields. Based on oxygen isotope data and cross-correlation between precipitation and groundwater level changes, groundwater recharge was found to be mainly caused by irrigation in spring and by precipitation at other times. The groundwater flow velocity calculated by a time series of spatial correlations, 231 m/yr, is in good accordance with the linear velocity estimated from hydrogeologic data. Nitrate contamination sources are natural and fertilized soils as non-point sources, and septic and animal wastes as point sources. Seasonal loading and spatial distribution of nitrate sources are estimated by using oxygen and nitrogen isotopic data.

• Bulletin of the Korean Chemical Society
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• 제35권8호
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• pp.2403-2409
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• 2014

Absolute isotope ratio is a critical constituent in determination of atomic weight. To measure the absolute isotope ratio using a mass spectrometer, mass discrimination factor, $f_{MD}$, is needed to convert measured isotope ratio to real isotope ratio of gas molecules. If the $f_{MD}$ could be predicted, absolute isotope ratio of a chemical species would be measureable in absence of its enriched isotope pure materials or isotope references. This work employed gravimetrically prepared isotope mixtures of argon (Ar) to obtain $f_{MD}$ at m/z of 40 in the magnetic sector type gas mass spectrometer (gas/MS). Besides, we compare the nitrogen isotope ratio of nitrogen trifluoride ($NF_3$) with that of nitrogen molecule ($N_2$) decomposed from the same $NF_3$ thermally in order to identify the difference of $f_{MD}$ values in extensive m/z region from 28 to 71. Our result shows that $f_{MD}$ at m/z 40 was $-0.044%{\pm}0.017%$ (k = 1) from measurement of Ar artificial isotope mixtures. The $f_{MD}$ difference in the range of m/z from 28 to 71 is observed $-0.12%{\pm}0.14%$ from $NF_3$ and $N_2$. From combination of this work and reported $f_{MD}$ values by another team, IRMM, if $f_{MD}$ of $-0.16%{\pm}0.14%$ is applied to isotope ratio measurement from $N_2$ to $SF_6$, we can determine absolute isotope ratio within relative uncertainty of 0.2 %.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 2003년도 International Symposium on Clean Environment
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• pp.198-203
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• 2003

The effects of salmon carcasses on forest and stream ecosystems were determined by nitrogen stable isotope analysis in natural streams in Hokkaido, Northern Japan, where numerous chum salmon (Oncoryhncus keta) were migrated upstream ITom ocean to spawn in autumn. The leaves and soils surrounding riparian forest and stream dwelling invertebrates were collected before and after migration. The nitrogen stable isotope ratio $({\delta}^{15}N)$ of riparian vegetation (Salix spp.) were different depending on the presence of salmon and distance from the stream. The $({\delta}^{15}N)$ of stream dwelling invertebrates were different between salmon present and absent stream. This difference was tested using the experiment channel by implanting salmon carcasses. The nitrogen stable isotope ratio of epilithic algae and leaf shredding animals were nearly 3 higher in the salmon implanted treatment suggesting that around 20％ of salmon derived nitrogen was uptake either in algae and leaf shredding invertebrates. These results suggest that the salmon carcasses effects not only on stream primary production but also on primary consumers, which decompose leaves fertilized with nitrogen from carcasses.

• Ocean Science Journal
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• 제42권4호
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• pp.223-230
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• 2007

To understand the origin and biogeochemistry of the organic matter in surface sediments of Lake Shihwa and Lake Hwaong, organic nitrogen, inorganic nitrogen, labile organic carbon, and residual organic carbon contents as well as stable isotope ratios for carbon and nitrogen were determined by KOBr-KOH treatment. Ratios of organic carbon to organic nitrogen $(C_{org}/N_{org})$ (mean = 24) were much higher than ratios of organic carbon to total nitrogen $(C_{org}/N_{tot})$ (mean= 12), indicating the presence of significant amounts of inorganic nitrogen in the surface sediments of both lakes. Stable isotope ratios for organic nitrogen were, on average, $5.2\%_{\circ}$ heavier than ratios of inorganic nitrogen in Lake Shihwa, but those same ratios were comparable in Lake Hwaong. This might be due to differences in the origin or the degree of degradation of sedimentary organic matter between the two lakes. In addition, stable isotope ratios for labile organic carbon were, on average, $1.4\%_{\circ}$ heavier than those for residual organic carbon, reflecting the preferential oxidation of $^{13}C$-enriched organic matter. The present study demonstrates that KOBr-KOH treatment of sedimentary organic matter can provide valuable information for understanding the origin and degradation state of organic matter in marine and brackish sediments. This also suggests that the ratio of $(C_{org}/N_{org})$ and stable isotope ratios for organic nitrogen can be used as indexes of the degree of degradation of organic matter.

• Applied Science and Convergence Technology
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• 제24권5호
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• pp.132-135
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• 2015

Schematic of RAON vacuum system is introduced. Vacuum test for superconducting cavity with liquid nitrogen is performed. Schematic plan for RAON vacuum system is introduced and vacuum control system for superconducting cavity test is constructed. Vacuum pressure of cavity is shown as a function of pumping time. The temperature of cavity is shown as a function of cooling time. Outgassing species from cavity is also detected. Detailed experimental procedure is presented to test the cavity vacuum with liquid nitrogen.

• ALGAE
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• 제32권4호
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• pp.349-357
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• 2017

Korean mariculture Undaria pinnatifida was collected during the months of January, February, March, and December of 2010, as well as from January of 2011 to investigate the changes in the carbon and nitrogen stable isotope ratios (${\delta}^{13}C$ and ${\delta}^{15}N$) and heavy metal with respect to it growth and to identify the factors that influence such changes. The blades of U. pinnatifida showed ${\delta}^{13}C$ and ${\delta}^{15}N$ in the range (mean) of -13.11 to -19.42‰ (-16.93‰) and 2.99 to 7.57‰ (4.71‰), respectively. Among samples with the same grow-out period, those that weighed more tended to have higher ${\delta}^{13}C$ suggesting a close association between the carbon isotope ratio and growth rate of U. pinnatifida. Indeed, we found a very high positive linear correlation between the monthly average ${\delta}^{13}C$ and the absolute growth rate in weight ($r^2=0.89$). Nitrogen isotope ratio tended to be relatively lower when nitrogen content in the blade was higher, probably due to the strengthening of isotope fractionation stemming from plenty of nitrogen in the surrounding environment. In fact, a negative linear correlation was observed with the nitrate concentration in the nearby seawaters ($r^2=0.83$). Concentrations of Cu, Cd, Pb, Cr, Hg, and Fe in the blades showed a rapid decrease in their concentration per unit weight in the more mature U. pinnatifida. Specifically, compared to adult samples, Cu, Hg, and Pb were concentrated by 30, 55, and 73 folds, respectively, in the young blades. Therefore, U. pinnatifida tissue ${\delta}^{13}C$ is as an indirect indicator of its growth rate, while ${\delta}^{15}N$ values and heavy metal concentrations serve as tracers that reflect the environmental characteristics.

• 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.

• 생태와환경
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• 제50권4호
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• pp.452-458
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• 2017

본 연구는 암모니아성 질소 및 질산성 질소의 안정동위원소 분석방법을 적용하여, 호소 내 식물플랑크톤 성장에 영향을 미치는 외부 오염원의 기원을 추정함으로써, 효율적인 수질 관리 및 수생태계 기능해석 지원기능을 제공하기 위하여 연구하였다. 남한강, 북한강, 팔당호 지역에 비해서 경안천 지역의 유기물 기원이 뚜렷하게 차이를 보이며, 외부기원 유기물이 높은 영향을 미치는 것으로 여겨진다. 또한 식물플랑크톤(규조류, 남조류)이 자생기원 보다는 외부기원 질소원을 활용하고 있음을 확인하였다. 한강 유역에서 암모니아성 질소 및 질산성 질소의 안정동위원소비를 이용한 유기물 기원 연구는 적용가능 할 것으로 여겨지며, 식물플랑크톤의 탄소 및 질소 동위원소비를 활용하여 그 거동을 추정할 수 있었다. 추후 유역 오염원의 대표 값(end member)의 지속적인 조사를 통하여 자료구축이 이루어져야 할 것이다.