• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.23 no.1
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• pp.32-48
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• 2018

The mechanisms of $CH_4$ uptake into and release from the ocean are not well understood due mainly to complexity of the biogeochemical cycle and to lack of regional-scale and/or process-scale observations in the marine boundary layers. Without complete understanding of oceanic mechanisms to control the carbon balance and cycles on a various spatial and temporal scales, however, it is difficult to predict future perturbation of oceanic carbon levels and its influence on the global and regional climates. High frequency, high precision continuous measurements for carbon isotopic compositions from dissolved $CH_4$ in the surface ocean and marine atmosphere can provide additional information about the flux pathways and production/consumption processes occurring in the boundary of two large reservoirs. This paper introduces recent advances on optical instruments for real time $CH_4$ isotope analysis to diagnose potential applications for in situ, continuous measurements of carbon isotopic composition of dissolved $CH_4$. Commercially available, three laser absorption spectrometers - quantum cascade laser spectroscopy (QCLAS), off-axis integrated cavity output spectrometer (OA-ICOS), and cavity ring-down spectrometer (CRDS) are discussed in comparison with the conventional isotope ratio mass spectrometry (IRMS). Details of functioning and performance of a CRDS isotope instrument for atmospheric ${\delta}^{13}C-CH_4$ are also given, showing its capability to detect localized methane emission sources.

• Korean Journal of Ecology and Environment
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• v.52 no.1
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• pp.50-64
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• 2019

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.

• Korean Journal of Heritage: History & Science
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• v.39
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• pp.39-58
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• 2006

This study reviews recent shell midden studies in Korea. With more interest in biological materials, recent shell midden studies have attempted to reconstruct palaeoenvironment, and understand subsistence economy, the formation processes and function of sites and past culture. Especially, one of the major topics in prehistoric Korean shell midden studies is the transitional process from hunter-gatherer to farmer. To solve these questions related with shell middens, new sampling strategies and excavation techniques have been adopted. Analytical methods combined with scientifical technologies also have been introduced to shell middle studies. These methods indude stable isotope analyses(Oxygen isotope and Carbon and Nitrogen isotope analyses) and growth-line analysis, etc.

• Korean Journal of Ecology and Environment
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• v.47 no.2
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• pp.127-134
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• 2014

Organic carbon and nitrogen stable isotope ratios of particulate organic matter (POM) were determined at 7 stations (6 stations in Han river and Paldang dam outflow station) from May to October 2013, in order to understand the origin of POM at the Han river. ${\delta}^{13}C$ values of POM in four stations showed significant seasonal changes season, but ${\delta}^{15}N$ values were enriched in around Kyeongan stream (K). POC, PN and Chl-a concentration showed a similar seasonal pattern in Kyeongan stream, with an apparent decrease from July to August. POC and PN concentration has a higher correlation with Chl-a concentration in Kyeongan stream (K). ${\delta}^{13}C$ and ${\delta}^{15}N$ values of POM has a lighter value during lower Chl-a concentration peroid, compared to other seasons. Our results revealed that Kyeongan stream (K) seemed to be influenced by substantial amount of organic manure or fertilizer input in 2013, compared to the previous year (2012). These results suggest that the analysis of stable isotope ratios is a simple but useful tool for the identification of organic matter origin in aquatic environments.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.2
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• pp.132-136
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• 2011

The Temporal variability in the food chain structure of bacteria in the sedimentary organic matter was investigated using stable isotope and fatty acid. Potential organic matter sources (Land plant, Marine POM, benthic microalgae, Riverine POM), sedimentary organic matter and bacteria were sampled in Gamo largoon and Nanakita estuary. The main objective of the present study was to determine food sources of bacteria along with temporal variability. Land plant (${\delta}^{13}C$ = -26.6‰ and ${\delta}^{15}N$ = 3.6‰) and Riverine POM (${\delta}^{13}C$ = -25.5‰ and ${\delta}^{15}N$ = 8.9‰) were isotopically distinct from benthic microalgae (${\delta}^{13}C$ = -16.3‰ and ${\delta}^{15}N$ = 6.2‰) and Marine POM (${\delta}^{13}C$ = -20.3‰ and ${\delta}^{15}N$ = 10.3‰). ${\delta}^{13}C$ values of sedimentary organic matter showed a distinct gradient in the range of -20.7‰ to -191‰. The stable carbon and nitrogen isotope values of bacteria in the study were -20.8‰ to -18.6‰ for ${\delta}^{13}C$ and 6.5‰ to 8.6‰ for ${\delta}^{15}N$. From this results based on stable isotope measurements showed that in the bacteria was found to be dominated by Marine POM and Benthicmicoralge during 0 to 20 day. Whereas, terrestrial plant and riverine POM showed little in fluence to bacteria during the experiment.

• Korean Journal of Ecology and Environment
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• v.52 no.4
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• pp.358-365
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• 2019

We measured the body composition, including bone mineral density (BMD) and food resource availability using dual energy X-ray absorptiometry and the carbon and nitrogen stable isotope ratios of body condition of 4 anuran species(Hyla japonica, Glandirana rugosa, Pelophylax nigromaculatus, Lithobates catesbeianus) in South Korea. Additionally, the carbon and nitrogen stable isotope ratios were employed to determine the food resource availability of anurans. We figured out the relationship between the body composition, including BMDs and food resource availability. The body composition and BMDs did not differ between male and female while there was difference among the species. Food resource availability and BMDs were the highest in L. catesbeianus, the lowest in H. japonica. BMDs tended to increase with higher food resource availability. Body composition and BMDs, which represent the body condition of an individual, can be used as an ecological indicator to assess the stability of the habitat of anurans.

• Journal of the Korean association of regional geographers
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• v.22 no.2
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• pp.439-449
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• 2016

Understanding the variability of the monsoon system requires information about the changes in the past. We revealed the Mid- and Late-Holocene paleo-climate changes and Asian monsoon variations in Korea by the speleothem records from Pyeongchang. To this, we used thicknesses of growth laminae, stable-isotope analysis (carbon, oxygen), and radio-carbon age dating. The speleothem grew between ~4580 yr BP to ~660 yr BP and we identified several weak AM(Asian monsoon) events, such as Middle Bronze Age Cold Epoch, Iron Age Cold Epoch, and Dark Age Cold Period. These events might have occurred relatively early compared to those of other studies.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.59-59
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• 2017

Rice (Oryza sativa L.) is the most important crop and its yield must be improved to feed the increasing global population. Recently developed high-yielding varieties with extra-large sink capacity often have a problem in unstable grain-filling. Therefore, understanding limiting factors for improving grain-filling and controlling them are essential for further improvement of rice grain yield. However, since grain-filling rate was determined by complex sink-source balance, the ability of grain-filling was very difficult to evaluate. Source ability for 'grain' was not only determined by the ability of carbon assimilation in leaves, but also that of carbon translocation from leaves to panicles. Sink strength was determined by the complex carbon metabolism from sucrose degradation to starch synthesis. Hence, to evaluate the grain-filling ability and determine its regulatory steps, the whole picture of carbon flow from photosynthesis at leaves to starch synthesis at grains must be revealed in a metabolite level. In this study, the yield and grain growth rate of three high-yielding varieties, which show high sink capacity commonly, were compared. Momiroman showed lower grain filling rate and slower grain growth rate than the other varieties, Hokuriku 193 and Tequing. To clarify the limiting point in the carbon flow of Momiroman, $CO_2$ labeled by stable isotope ($^{13}C$) was fed to three varieties during ripening period. The ratio of $^{13}C$ left in the stem was higher in Momiroman 24 hours after feeding, suggesting inefficient carbon translocation of Momiroman. More interestingly, $^{13}C$ translocation from soluble fraction to insoluble one in the grain seemed to be slower in Momiroman. To get the further insight in a metabolite level, we are now trying the $^{13}C$ labeling metabolome analysis in the developing grains.

• The Korean Journal of Quaternary Research
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• v.24 no.2
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• pp.35-48
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• 2010

The purpose of this study is to investigate paleoenvironmental conditions of the shallow sea around Jeju Island during the Late Holocene using geochemical contents of the bivalve (Glycymeris albolineata) collected from the Sangmori Shell Mound. The bivalve shell used shows the archaeological age of 2,300 yr BP. Stable carbon and oxygen isotope compositions show that growth rates decreased with aging. Coeval trends of both isotope compositions can be observed: heavier values during winters and lighter values summers except for their young and old growth stages. The seasonality of bivalve shell appear to reflect seasonal variations of paleotemperature as well as paleosalinity. Especially China Coastal Water with low salinity was transported into the southern Jeju Strait from Changjiang River during summer periods. Heavier carbon isotope values during winter indicate higher productivity, and this is supported by high density of phytoplanktons and higher chlorophyll contents during winter time. For accurate interpretation, monitoring of present-day conditions of shallow marine water as well as additional geochemical analysis of the same Recent bivalve may be necessary.

• Economic and Environmental Geology
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• v.40 no.5
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• pp.623-633
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• 2007

Stable isotope and biomarker analyses were carried out for the organic sediments from the exploratory wells in the Jeju Basin in order to understand the characteristics of organic matter. Organic matter in Geobuk-1, Okdom-1, JDZ VII-1 and VII-2 well is predominantly originated from land plants rather than marine algae according to carbon $({\delta}^{13}C_{org})$ and nitrogen $({\delta}^{15}N_{org})$ isotopic compositions. In the Geobuk-1, geochemical characteristics such as carbon $({\delta}^{13}C_{org})$, nitrogen ($({\delta}^{15}N_{org})$ and TOC contents are obviously changed by the depth 2,400 m, which is likely due to the change of origin of organic matter, sedimentary process or sedimentary environments. Analysis of the saturated fraction of the bitumen suggests the contribution of migrated oil to the indigenous bitumen from the samples 2,509, 2,833 and 3,163 m of the JDZ YII-1 and 3,253 m of the Geobuk-1 well. However, this characteristics can be derived from the contribution of the original organic matter. Based on the biomarker analysis, the samples from the Okdom-1 and Geobuk-1 appear to represent sedimentary organic matter of similar composition, that is rotatively immature, and which was probably deposited in the fluvio-deltaic setting with minor offshore marine influence. The samples from JDZ VII-1 appear to have been deposited in a more terrestrially dominated setting.