https://repository.kopri.re.kr/handle/201206/9758 2026-04-23T04:49:13Z 2026-04-23T04:49:13Z Lee, Dong？Hun Kim, Jung-Hyun Kang, Sujin Kim, Dahae Shin, Kyung？Hoon https://repository.kopri.re.kr/handle/201206/16614 2026-02-10T04:31:21Z 2025-04-01T00:00:00Z

Title: Evidence of methanogenic activity associated with past fish farming in Lake Soyang, South Korea Authors: Lee, Dong？Hun; Kim, Jung-Hyun; Kang, Sujin; Kim, Dahae; Shin, Kyung？Hoon Abstract: In this study, a 54-cm-long sediment core was collected from an area with a history of fish farming to investigate a potential link between methane production and past aquaculture activities in Lake Soyang, a large artificial lake (ca. 2？110 m water depth, 16.08 km2 in area). Along with bulk elements (carbon and nitrogen), we analyzed specific lipid biomarkers, including n-alkanes, sterols, glycerol dialkyl diethers (DGDs), and glycerol dialkyl glycerol tetraethers (GDGTs). Additionally, we measured the compound-specific carbon isotopic composition (δ13C) of specific lipids, excluding GDGTs. Evidence of prior aquaculture activities was indicated by high total organic carbon content (~ 30 wt%) and elevated concentrations of coprostanol and stigmasterol, reflecting substantial deposition of mixed organic matter (OM) from aquaculture practices, such as fish feed and feces. The δ13C values of sterols (？ 28.4 ± 1.4‰) were relatively enriched compared to those of isoprenoid DGDs, such as archaeol and OH-archaeol (？ 40.0 ± 3.2‰). This suggests that increased acetoclastic methanogenic activities may be closely linked to the assimilation of by-products derived from aquaculture-related OM as potential carbon sources. Our findings highlight the potential importance of methane production within aquaculture systems and the environmental factors influencing this process. These results could inform the development of systematic management strategies to mitigate methane emissions from aquaculture systems.

2025-04-01T00:00:00Z Kang Sujin Kim, Jung-Hyun Ryu Jong-Sik Shin Kyung-Hoon https://repository.kopri.re.kr/handle/201206/16280 2025-10-30T06:14:20Z 2024-02-01T00:00:00Z

Title: Export of aged dissolved organic carbon to the Geum and Seomjin estuaries in South Korea Authors: Kang Sujin; Kim, Jung-Hyun; Ryu Jong-Sik; Shin Kyung-Hoon Abstract: We investigated the source and reactivity of dissolved organic carbon (DOC) in two contrasting Korean estuaries: the Geum, a closed system with a dammed river mouth, and the Seomjin, an open estuary system. The average Delta 14CDOC value in the Geum estuary (-101.8 +/- 38.0 %o) was higher than that in the Seomjin estuary (-176.4 +/- 101.9 %o). The depleted 14C signal in the Seomjin estuary appears to be associated with a high average monthly Q90/Q50 ratio, which is an indicator of base water flow, and a low DOC:sigma B + ratio, which is an indicator of groundwater flow. This suggests that groundwater in the Seomjin watershed passed through a deeper soil column compared with the Geum watershed, transferring older DOC to the river during the base flow season and into the estuary. In contrast, the Geum estuary dam appears to be associated with higher Delta 14CDOC and the export of younger DOC to the estuary due to enhanced primary productivity in the dam reservoir. Our results suggest that input of aged DOC derived from a deeper soil column influenced the estuarine DOC pool in the open Seomjin estuary, and this effect could be dampened by riverine DOC produced in the dam reservoir of the closed Geum estuary.

2024-02-01T00:00:00Z Kang Sujin Kim, Jung-Hyun Ryu Jong-Sik Bong Yeon Sik Shin Kyung-Hoon https://repository.kopri.re.kr/handle/201206/16220 2025-10-27T05:06:05Z 2024-01-01T00:00:00Z

Title: Contribution of carbonate-derived dissolved inorganic carbon into autochthonous particulate organic carbon in two small temperate Korean rivers (Geum and Seomjin) Authors: Kang Sujin; Kim, Jung-Hyun; Ryu Jong-Sik; Bong Yeon Sik; Shin Kyung-Hoon Abstract: In this study, we estimated the contributions of carbonate mineral weathering to dissolved inorganic carbon (DIC) and carbonate-derived DIC to autochthonous particulate organic carbon (POC) in two temperate Korean rivers. We combined stoichiometric and stable carbon isotopic approaches to calculate the contribution of autochthonous POC, considering diverse riverine DIC sources. We collected surface water samples from May 2016 to May 2018 and analyzed the major ion composition of rivers along with the concentrations and stable carbon isotopes of DIC. Our estimates showed that the relative abundances of carbonate mineral weathering (0.41 +/- 0.11 in the Geum River and 0.43 +/- 0.07 in the Seomjin River) were only slightly lower than those of silicate mineral weathering (0.59 +/- 0.1 in the Geum River and 0.57 +/- 0.07 in the Seomjin River). The resulting percentage contributions of DIC derived from the carbonate mineral weathering to riverine autochthonous POC, if we consider the additional DIC sources of atmospheric and soil-derived CO2, were 10 +/- 3 % in the Geum River and 2 +/- 1 % in the Seomjin River. The calculated annual fluxes of carbonate-derived DIC for 2016-2018 were 23.2 +/- 0.3 Gg C yr(-1) in the Geum River and 1.1 +/- 0.4 Gg C yr(-1) in the Seomjin River. Moreover, the calculated annual fluxes of carbonate-derived POC were 3.6 +/- 0.5 Gg C yr(-1) in the Geum River and 0.1 +/- 0.7 Gg C yr(-1) in the Seomjin River. Accordingly, our study provides the first insight into the contribution of carbonate-derived DIC to riverine autochthonous POC in small temperate Korean river systems, dominated by silicate rocks.

2024-01-01T00:00:00Z Paradis Sarah Diesing Markus Gies Hannah Haghipour Negar Narman Lena Magill Clayton Wagner Thomas Galy Valier V. Hou Pengfei Zhao Meixun Kim, Jung-Hyun Shin Kyung-Hoon Lin Baozhi Liu Zhifei Wiesner Martin G. Stattegger Karl Chen Jianfang Zhang Jingjing Eglinton Timothy I. https://repository.kopri.re.kr/handle/201206/16438 2025-11-06T08:25:53Z 2024-01-01T00:00:00Z

Title: Unraveling Environmental Forces Shaping Surface Sediment Geochemical "Isodrapes" in the East Asian Marginal Seas Authors: Paradis Sarah; Diesing Markus; Gies Hannah; Haghipour Negar; Narman Lena; Magill Clayton; Wagner Thomas; Galy Valier V.; Hou Pengfei; Zhao Meixun; Kim, Jung-Hyun; Shin Kyung-Hoon; Lin Baozhi; Liu Zhifei; Wiesner Martin G.; Stattegger Karl; Chen Jianfang; Zhang Jingjing; Eglinton Timothy I. Abstract: As major sites of carbon burial and remineralization, continental margins are key components of the global carbon cycle. However, heterogeneous sources of organic matter (OM) and depositional environments lead to complex spatial patterns in sedimentary organic carbon (OC) content and composition. To better constrain the processes that control OM cycling, we focus on the East Asian marginal seas as a model system, where we compiled extensive data on the OC content, bulk isotopic composition (delta 13C and Delta 14C), total nitrogen, and mineral surface area of surficial sediments from previous studies and new measurements. We developed a spatial machine learning modeling framework to predict the spatial distribution of these parameters and identify regions where sediments with similar geochemical signatures drape the seafloor (i.e., "isodrapes"). We demonstrate that both provenance (44%-77%) and hydrodynamic processes (22%-53%) govern the fate of OM in this margin. Hydrodynamic processes can either promote the degradation of OM in mobile mud-belts or preserve it in stable mud-deposits. The distinct isotopic composition of OC sources from marine productivity and individual rivers regulates the age and reactivity of OM deposited on the sea-floor. The East Asian marginal seas can be separated into three main isodrapes: hydrodynamically energetic shelves with coarser-grained sediment depleted in OC, OM-enriched mud deposits, and a deep basin with fine-grained sediments and aged OC affected by long oxygen exposure times and petrogenic input from rivers. This study confirms that both hydrodynamic processes and provenance should be accounted for to understand the fate of OC in continental margins. Plain Language Summary This study focuses on carbon cycle processes occurring in marine sediments of the East Asian marginal seas. We compiled extensive data on the organic carbon content and composition of surface sediments in these seas and developed a machine learning model to predict their spatial patterns and identify the environmental conditions that drive their distribution. We found that the spatial distribution of organic matter is governed by the resuspension of different grain size fractions due to water current intensity as well as the contrasting origin of the organic matter (marine, terrestrial, and rock-derived) that influences its reactivity. We also identified three main areas where sediments with similar composition drape the seafloor: shelves with strong bottom current with less organic matter, mud deposits rich in organic matter, and a deep basin with aged organic matter. Understanding the factors that control the distribution of organic matter in these areas is important for accurately assessing their contribution to the global carbon cycle.

2024-01-01T00:00:00Z