https://repository.kopri.re.kr/handle/201206/11601 2026-04-23T04:48:12Z 2026-04-23T04:48:12Z Kang, Sujin Kim, Jung-Hyun Joe, Young Jin Jang, Kwangchul Nam, Seung-il Shin, Kyung-Hoon https://repository.kopri.re.kr/handle/201206/13636 2022-07-08T01:06:54Z 2021-07-01T00:00:00Z

Title: Long-term environmental changes in the Geum Estuary (South Korea): Implications of river impoundments Authors: Kang, Sujin; Kim, Jung-Hyun; Joe, Young Jin; Jang, Kwangchul; Nam, Seung-il; Shin, Kyung-Hoon Abstract: We investigated a sediment core collected from the Geum Estuary through sedimentological and geochemical analyses. Three lithological units were classified based on sedimentological characteristics. Unit 1 and Unit 3 were geochemically distinct, while Unit 2 was the transitional phase between them. The geochemical results suggest that the contribution of terrestrial organic carbon (OC) to the sedimentary OC pool in the coarse-grained Unit 1 was lesser than that of fine-grained Unit 3. The excess activity (210Pbex) and the sedimentation rate indicate that Unit 1 corresponded to 1977 Common Era (CE). Since the first dam construction on the Geum River began in 1975 CE, the deposition of Unit 1 in the Geum Estuary is likely associated with river impoundments, which reduce the delivery of fine-grained sediment and terrestrial OC to the estuary. This study highlights the role of river impoundments in altering the sedimentary OC and thus the sedimentary environment in the estuary.

2021-07-01T00:00:00Z Jang, Kwangchul Ahn, Youngkyu Joe, Young Jin Braun, Carmen A. Joo, Young Ji Kim, Jung-Hyun Bayon, Germain Forwick, Matthias Vogt, Christoph Nam, Seung-il https://repository.kopri.re.kr/handle/201206/13003 2022-03-24T07:15:11Z 2021-06-01T00:00:00Z

Title: Glacial and environmental changes in northern Svalbard over the last 16.3 ka inferred from neodymium isotopes Authors: Jang, Kwangchul; Ahn, Youngkyu; Joe, Young Jin; Braun, Carmen A.; Joo, Young Ji; Kim, Jung-Hyun; Bayon, Germain; Forwick, Matthias; Vogt, Christoph; Nam, Seung-il Abstract: The reconstruction of past ice sheet extents and dynamics in polar regions is essential for understanding the global climate system and obtaining more reliable predictions of future climate change. Here, we present a multi-proxy dataset integrating the Nd isotopic compositions (εNd) of paired detrital and authigenic iron oxide fractions, grain size distributions, organic geochemistry, and mineral assemblages in a glacimarine sediment core (core HH17-1085-GC) retrieved from the continental shelf off northern Svalbard. Our results indicate variability in sediment provenance and chemical weathering patterns since the last deglaciation, allowing us to distinguish a succession of distinct paleoclimate events: 1) a general retreat of the Svalbard-Barents Sea Ice Sheet (SBIS) from the continental shelf before ca. 16.3 ka BP; 2) an intense episode of meltwater discharge related to massive glacier loss between ca. 12.1 ？ 9.9 ka BP; and 3) a period of reduced meltwater input between ca. 9.9 and ca. 2.7 ka BP followed by 4) a phase of glacier re-advance over the last two millennia. Evidence for the prolonged supply of radiogenic detrital εNd and dolomite at the site of core HH17-1085-GC indicates that the onset of deglaciation offshore northeastern Svalbard may have occurred at least 1 ka later than that at the northwestern shelf, which can be further evaluated by obtaining a more precise end-member determination for the northeastern source with a quantitative εNd dataset from Nordaustrandet. In the context where both polar sea-ice and oceanic circulation are expected to have played minor roles in determining the εNd composition of sedimentary Fe oxyhydroxide phases, the evidence for pronounced Nd isotopic decoupling between paired authigenic and detrital signatures (？εNd) at ca. 15.2 and 14.1 ka BP is interpreted as reflecting chemical weathering changes following the retreat of the SBIS on northern Svalbard, probably corresponding to punctual episodes of glacial re-advances. Our findings provide a better understanding of the deglacial history of northern Svalbard during and after the last deglaciation and highlight the utility of Nd isotopes as a proxy for reconstructing paleo-cryosphere changes.

2021-06-01T00:00:00Z Nam, Seung-il https://repository.kopri.re.kr/handle/201206/13168 2022-03-24T07:15:42Z 2021-05-01T00:00:00Z

Title: Changes in environments and coastal geomorphology of Svalbard fjords, Arctic Authors: Nam, Seung-il

2021-05-01T00:00:00Z Du, Young Eun Bae, Eun Seo Lim, Yeonjung Cho, Jang-Cheon Nam, Sang-Jip Shin, Jongheon Lee, Sang Kook Nam, Seung-il Oh, Dong-Chan https://repository.kopri.re.kr/handle/201206/13608 2022-07-07T06:44:20Z 2021-04-01T00:00:00Z

Title: Svalbamides A and B, Pyrrolidinone-Bearing Lipodipeptides from Arctic Paenibacillus sp. Authors: Du, Young Eun; Bae, Eun Seo; Lim, Yeonjung; Cho, Jang-Cheon; Nam, Sang-Jip; Shin, Jongheon; Lee, Sang Kook; Nam, Seung-il; Oh, Dong-Chan Abstract: Two new secondary metabolites, svalbamides A (1) and B (2), were isolated from a culture extract of Paenibacillus sp. SVB7 that was isolated from surface sediment from a core (HH17-1085) taken in the Svalbard archipelago in the Arctic Ocean. The combinational analysis of HR-MS and NMR spectroscopic data revealed the structures of 1 and 2 as being lipopeptides bearing 3-amino-2-pyrrolidinone, d-valine, and 3-hydroxy-8-methyldecanoic acid. The absolute configurations of the amino acid residues in svalbamides A and B were determined using the advanced Marfey's method, in which the hydrolysates of 1 and 2 were derivatized with l- and d- forms of 1-fluoro-2,4-dinitrophenyl-5-alanine amide (FDAA). The absolute configurations of 1 and 2 were completely assigned by deducing the stereochemistry of 3-hydroxy-8-methyldecanoic acid based on DP4 calculations. Svalbamides A and B induced quinone reductase activity in Hepa1c1c7 murine hepatoma cells, indicating that they represent chemotypes with a potential for functioning as chemopreventive agents.

2021-04-01T00:00:00Z