Dissolved organic matter (DOM) is a key component in the biogeochemical cycling in freshwater ecosystem. However, it has been rarely explored, particularly complex river watershed dominated by natural and anthropogenic sources, such as various effluent facility and livestock. The current research developed a new analytical method for TOC/TN (Total Organic Carbon/Total Nitrogen) stable isotope ratio, and distinguish DOM source using stable isotope value (δ13C-DOC) and spectroscopic indices (fluorescence index [FI] and biological index [BIX]). The TOC/TN-IR/MS analytical system was optimized and precision and accuracy were secured using two international standards (IAEA-600 Caffein, IAEA-CH-6 Sucrose). As a result of controlling the instrumental conditions to enable TOC stable isotope analysis even in low-concentration environmental samples (<1 mgC L-1), the minimum detection limit was improved. The 12 potential DOM source were collected from watershed, which includes top-soils, groundwater, plant group (fallen leaves, riparian plants, suspended algae) and effluent group (pig and cow livestock, agricultural land, urban, industry facility, swine facility and wastewater treatment facilities). As a result of comparing characteristics between 12 sources using spectroscopic indices and δ13C-DOC values, it were divided into four groups according to their characteristics as a respective DOM sources. The current study established the TOC/TN stable isotope analyses system for the first time in Korea, and found that spectroscopic indices and δ13C-DOC are very useful tool to trace the origin of organic matter in the aquatic environments through library database.

Recently, quantitative analyses of food web structure based on carbon and nitrogen stable isotopes are widely applied to environmental assessments as well as ecological researches of various ecosystems, particularly rivers and streams. In the present study, we analyzed carbon and nitrogen stable isotope ratios of POM (both planktonic and attached forms), zooplankton, benthic macroinvertebrates and fish collected from 6 sites located at Nakdong River. Samples were collected from upstream areas of 5 weirs (Sangju, Gangjeong- Goryeong, Dalseong, Hapcheon-Changnyeong, and Changnyeong-Haman Weirs) and one downstream area of Hapcheon-Changnyeong Weir in dry season (June) and after rainy season (September). We suggested ranges of their carbon and nitrogen stable isotope ratios and calculated their trophic levels in the food web to compare their temporal and spatial variations. Trophic levels of organisms were relatively higher in Sangju Weir located at upper part of Nakdong River, and decreased thereafter. However, the trophic levels were recovered at the Changnyeong-Haman Weir, the lowest weir in the river. The trophic level calculated by nitrogen stable isotope ratios showed more reliable ranges when they were calculated based on zooplankton than POM used as baseline. The suggested quantitative ecological information of the majority of biological communities in Nakdong River would be helpful to understand the response of river food web to environmental disturbances and can be applied to various further researches regarding the quantitative approaches for the understanding food web structure and function of river ecosystems as well as restoration.

The nitrogen isotope value in both ammonium and nitrate ion were determined at 9 stations during both June and August 2016, in order to understand the origin of DIN at the Han river. δ15N-NO3 and δ15N-NH4 values in 8 stations (CP, SB, MHC, P4, SJ, SBC, P2, SC) were no significant variation. However δ15N-NO3 and δ15N-NH4 values in KK (Kyeongan stream) showed significant different in comparison with 8 stations, with an apparent increase of nitrogen isotope values. These results indicate that antropogenic nitrogen source influence on KK station. Also the δ13C and δ15N isotope ratio of phytoplankton (Diatom and Cyanobacteria) in KK (Kyeongan stream) showed heavier values, compared to other study stations. These results indicate that nitrogen isotope value in phytoplankton effects by different nitrogen source in study sites. These results suggest that the analysis of stable isotope ratios is a simple but useful tool for the identification of dissolved inorganic nitrogen origin in aquatic environments.

Compound specific isotope analysis of amino acids (CSIA-AAs) is being highlighted as an alternative approach for overcoming some restrictions in application of stable isotope analysis of bulk tissue (SIA) for trophic position (TP) estimation. However, this approach has rarely been applied in Korea. The present study determines TP of two Polychaeta (Nephtyidae and Glyceridae) and two fish species (Platycephalus indicus and Lophius litulon) collected from the Geum River estuary using nitrogen isotope ratio of amino acid and compared with the TP values estimated by SIA. The Polychaeta species, sampled in two sites, showed similar TP between SIA (2.7 and 3.1) and CSIA-AAs (2.6 and 3.1). However, for both fish species, TP values displayed a large difference between SIA (3.1 and 2.3) and CSIA-AAs (3.8 and 3.7). In this study TP values estimated by CSIA-AAs showed more similar to the previously reported gut content analysis of both fishes compared with the results of SIA. Current study suggests the applicability of nitrogen isotope ratio of amino acid to understand coastal ecosystem structure and trophic ecology.

In order to study the effect of barley, Italian ryegrass (IRG), and legume mixture on nitrogen fixation and transfer to grasses on spring paddy field, an experiment was carried out from Oct. 2006 to June 2007 in Naju, Korea. A split plot design with three replications was used for the experiment. One reference plot was assigned for each treatment to determine nitrogen fixation. Main plots consisted of Chinese milk vetch, crimson clover, forage pea, and hairy vetch with barley, respectively. Subplot treatment were barley or IRG with four seeding ratio of legumes (50:50, 60:40, 70:30, and 80:20). To estimate N fixation by legumes, 15N isotope dilution technique was used. 15N fertilizer [(15NH4)2SO4 solution at 99.8 atom N] was uniformly applied to 600 cm2 in the middle of each plot on April 15, 2007. Plots were harvest by hand on June 8, 2007. Dried sample were ground to a fine power and analyzed for total N isotope N. 15N was determined using elemental analyzer-isotope ratio mass spectrometry. The calculation of N transfer was determined with the isotope dilution method. The content of N was higher in legumes than that in barley or Italian ryegrass. Nitrogen level in forage pea was significantly higher than that of other legumes. There were significantly differences in N content between legumes in IRG mixture. Atom % 15N excess was significantly different in legumes with barley. The 60:40 sub plot had higher (p<0.05) atom % 15N than other seeding ratio treatments. The enrichment ranged from 0 to 0.58. Compared to barley, the enrichment of IRG with its accompanied legumes was higher, ranging from 0.38 to 1.0. The N derived from the atmosphere (Ndfa) ranged from 0% to 49.5% with barley-legume mixture. It ranged from 0 to 60.5% in IRG-legume plots. N transfer from legumes to neighboring grasses was 12.3 to 90.9 kg/ha for barley-legume mixture and 31.7 to 107.8 kg/ha for IRG plots. IRG plots showed higher N transfer for IRG-legume mixture in general based on difference method. Based on 15N dilution method, the N transfer was 0 to 36.1 kg/ha for barley-legume mixture and 0 to 50.6 kg/ha for IRG plots. There was a tendency toward higher N transfer on the difference method than that of the 15N dilution method.

Nitrogen (N) loading from domestic, agricultural and industrial sources can lead to excessive growth of macrophytes or phytoplankton in aquatic environment. Many studies have used nitrogen stable isotope ratios to identify anthropogenic nitrogen in aquatic systems as a useful method for studying nitrogen cycle. In this study to evaluate the precision and accuracy of Kjeldahl processes, two reference materials (IAEA-NO-3, N-1) were analyzed repeatedly. Measured the δ¹⁵N-NO₃and δ¹⁵N-NH₄values of IAEA-NO-3 and IAEA-N-1 were 4.7±0.2‰ and 0.4±0.3‰, respectively, which are within recommended values of analytical uncertainties. Also, we investigated spatial patterns of δ¹⁵N-NO₃and δ¹⁵N-NH₄in effluent plumes from a waste water treatment plant in Han River, Korea. δ¹⁵N-NO₃and δ¹⁵N-NH₄values are enriched at downstream areas of water treatment plant suggesting that dissolved nitrogen in effluent plumes should be one of the main N sources in those areas. The current study clarifies the reliability of Kjeldahl analytical method and the usefulness of stable isotopic techniques to trace the contamination source of dissolved nitrogen such as nitrate and ammonia.

본 연구는 탄소 및 질소 안정동위원소비를 이용하여 하천에서 환경변화의 지표로 활용할 수 있는 부착조류의 먹이원으로서 기여도를 파악하고자 하였다. 연구지역인 탐진강은 지류를 통해 유입되는 외래기원물질의 영향으 로 상류에서 하류로 갈수록 높은 영양염의 농도를 나타 냈으며 이와 더불어 상위섭식자인 어류의 질소 안정동위 원소비의 증가가 관찰되었다. 또한 탐진강에서 채집된 저 서성대형무척추동물과 어류의 δ13C 값이 상류에서 하류 로 이동하면서 무거워지는 경향을 나타내었다. 이는 탐진 강 하류 수역에서 무거운 δ13C 값을 보였던 암석 부착조 류가 먹이원으로서의 기여도가 높아진 결과로 판단된다.

To investigate the possibility of discrimination between organic and non-organic rice using stable isotope nitrogen of natural abundance, organic rice of 17 samples and non-organic rice of 13 samples grown at adjoining organic rice field were collected in 2008. Rice was grinded into brown rice, milled rice and hull, and samples were analysed for nitrogen and δ¹⁵N at NICEM. Authors also made inquiries about N source for both farmers who conduct organic- and non-organic rice cultivation. In order to know whether the δ¹⁵N can be used in discrimination between organic and non-organic rice, discriminant analysis were made with SPSS and logistic method. 1. Organic farmers used manure, rice bran, used mushroom culture, fermented fertilizer (company products), and oil cake, but non-organic farmers applied compound fertilizer. Rice straws were remained in organic rice field while moved out in non-organic field. 2. There were difference in δ¹⁵N among organic rice and its byproduct(7.760‰ in hull, 6.720‰ in rice), but significant difference was not found between them. And the trend was same between province. Non-organic rice showed similar results. 3. Significant difference of δ¹⁵N were found between organic rice and non-organic rice (p＜0.01) and between hull of organic rice and that of non-organic rice hull (p＜0.05). δ¹⁵N seemed to be useful criteria for discrimination of organic and non-organic rice. 4. When applied discrimination analysis of SPSS and logistic, there were significant difference between organic rice, non-organic rice and its byproducts except brown rice and hull in SPSS method. Hull can be used as the most useful component for unknown sample prediction with 83.3% probability.

밀과 보리에 있어서 종자크기와 질소영양이 수분리용효율과 탄소동위원소차별에 미치는 영 향을 조사하여 탄소동위원소차별, 수분이용효율, 질소영양간의 상호작용를 구명하고저 종자크기가 영과당 각각 44mg과 22mg인 춘파형 밀과 보리 한 품종을 직경이 15.3cm인 폿트에서 2본씩 재식, m2 당 질소 10g과 32g 비율로 시용하여 수분이용효율에 관련된 형질과 탄소동위원소차별을 조사하였다. 두 종자크기와 두 질소 시비량을 평균한 건물중은 절간신장기에는 보리가 밀보다 105% 컸던 반면 개화기에는 보리보다 출수가 3일 늦은 밀이 보리보다 16% 많았다. 절간신장기과 개화기에 있어서 보리에 비하여 밀에서 건물중에 미치는 대립종자의 영향이 컸었다. 다질소구가 소질소구에 비하여 개화기에 있어서 밀과 보리의 건물중이 각각 40%와 31% 높았다. 절간신장기와 개화기에 있어서 수분이용효율은 보리가 밀보다 각각 35%와 20% 많았고, 지상부의 탄소동위원소차별은 밀보다 보리가 생육기와 식물체 부위에 따라 2.0~3.6% 적었다. 종자크기가 수분이용효율에 미치는 영향은 뚜렷한 경향이 없었고 탄소동위원소차별에도 유의한 영향을 주지 않았다. 절간신장기에 있어서 수분이용효율은 질소영양에 의하여 영향을 받지 않았으나 개화기에 있어서는 소질소구에 비하여 다질소구에서 밀과 보리가 각각 2%와 7% 컸었다. 두 맥종과 두 종자크기를 평균한 탄소동위원소차별은 생육시기에 관계없이 다질소구에서 소질소구보다 약 2.5% 낮았다. 탄소동위원소차별은 절간신장기에는 수분이용효율과 유의한 상관관계가 없었으나 개화기에 있어서는 부의 상관이 있었다.리고 질소시용량이 적을수록 높은 경향이었으며 아밀로스함량은 재배유형과 비종간에는 큰 차가 없었으나, 시비량간에 있어서는 질소시용량과 비례하여 증감하는 경향을 보였다. 5. 쌀의 N, K함량은 완효성 비료가 속효성 비료보다 높고 질소시용률이 많을수록 높았으나, Mg함량은 질소시용량이 많을수록 높았으며 기계이앙에서는 속효성 비료가, 그리고 건답직파에서는 완효성 비료가 높게 함유하였고, Na함량은 완효성 비료의 시용에서 보다 높게 함유하였다. 또한 Mg/K비을은 속효성 비료가 완효성 비료보다 높았고 기계 이앙보다는 건답직파에서 높게 나타났다. 그러나 N/K비율은 완효성 비료가 높았다. 6. 쌀의 외관상 미질은 완효성 비료보다는 속효성 비료 시용에서 그리고 질소시용량이 적을수록 우수하였으나, 밥맛 검정은 재배유형간에는 기계이앙이 건답직파보다 우수하였고, 비종간에는 속효성 비료보다는 완효성 비료에서, 그리고 질소의 감비보다는 100%시용구에서 보다 우수한 경향을 보였다. 따른 분얼체계와 동신엽, 동신분얼의 수량성은 표준구와 50%증비구는 0, 1, 2, 11, 3, 21, 12, 22, 4, C의 순위였으나 100%증비구에서는 주간보다 1차분얼의 1이 무겁고 3보다 11이 무거웠다.섭취하였고, 탄수화물은 농촌지역 여고생이 대도시 지역 여고생에 비하여 유의적으로 많이 섭취하였다. 지역별 여고생의 에너지섭취 비율은 탄수화물 : 단백질 : 지방의 섭취 비율이 대도시 60.75% : 16.4% 22.9%이며, 중소도시가 62.7% : 15.7% : 21.5%,농촌이66.8% : 14. l% : 19.1%이었다. 영양지식의 정확도나 인지도는 영양소 섭취와