The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Kyung-hoon Shin - One of the best experts on this subject based on the ideXlab platform.
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Dual carbon isotope (δ13C and Δ14C) characterization of particulate organic carbon in the Geum and Seomjin estuaries, South Korea
Marine pollution bulletin, 2019Co-Authors: Sujin Kang, Jung-hyun Kim, Jong-sik Ryu, Kyung-hoon ShinAbstract:We investigated the source, composition, and reactivity of particulate organic carbon (POC) in two contrasting Korean estuary systems, a closed estuary (Geum) (i.e., with an estuary dam at the river mouth) and an open (Seomjin) estuary. A dual isotope (δ13CPOC and Δ14CPOC) approach was applied to surface water samples collected along a salinity gradient in August 2016. Our results indicate that phytoplankton-derived POC was the main contributor to the total POC pool in the reservoir of the Geum estuary, while terrestrial-derived POC predominated the upper Seomjin estuary. A simple binary mixing model using Δ14CPOC revealed a higher modern POC contribution (87-90%) in the Geum estuary reservoir than that (77%) of the upper Seomjin estuary. Accordingly, it appears that an estuary dam can alter the source and reactivity of POC in a reservoir, which can be transferred to the adjacent coastal ecosystem.
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Multimedia distributions, bioaccumulation, and trophic transfer of microcystins in the Geum River Estuary, Korea: Application of compound-specific isotope analysis of amino acids.
Environment international, 2019Co-Authors: Dokyun Kim, Seongjin Hong, Hyuntae Choi, Bohyung Choi, Jaeseong Kim, Jong Seong Khim, Hodong Park, Kyung-hoon ShinAbstract:Abstract To determine distributions, bioaccumulation, and trophic transfer of freshwater cyanobacterial toxins such as microcystins (MCs), surface water, suspended solids, sediments, and coastal organisms were collected from seven stations in inner and outer regions of the estuary dam in the Geum River Estuary in June and July 2017. Concentrations of MC variants (MC-LR, -RR, and -YR) in the multimedia samples were analyzed using a HPLC-MS/MS. Trophic position (TP) of organisms (fish, bivalve, gastropod, decapod, and polychaete) was determined by nitrogen stable isotope analyses of both bulk tissues and amino acids. From July to August 2017, great concentrations of MCs were detected in discharged freshwater ranging from 0.4 to 75 μg L−1. Considerable amounts of MCs are delivered to the Geum River Estuary in summer season. MCs spread far away as dissolved phases (18.7–49.5 ng L−1) in July when large amount of freshwater was discharged during the rainy season. Concentrations of MCs in marine organisms varied among species, ranging from 40 to 870 ng g−1 dw. Bioaccumulated MCs tend to decrease with increasing TP of organisms, suggesting that MCs are biodiluted through the marine food web. Compound-specific isotope analysis (nitrogen of amino acids) provides more reliable TPs compared with those by bulk isotope analysis in a closed estuary (such as the Geum River Estuary) with large fluctuations in the isotope ratio of primary producers.
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Temporal variation in riverine organic carbon concentrations and fluxes in two contrasting estuary systems: Geum and Seomjin, South Korea
Environment international, 2019Co-Authors: Sujin Kang, Jung-hyun Kim, Daun Kim, Hyeongseok Song, Jong-sik Ryu, Giyoung Ock, Kyung-hoon ShinAbstract:Abstract In this study, surface water samples were collected at sites located in the lowest reaches of closed (Geum) (i.e. with an estuary dam at the river mouth) and open (Seomjin) estuary systems between May 2016 and May 2018. We analyzed concentrations and stable isotopes of particulate organic carbon (POC) and dissolved organic carbon (DOC) to assess OC sources, to estimate fluxes of riverine OC, and to assess some of the factors driving OC exports in these two contrasting Korean estuary systems. Our geochemical results suggest that the contribution of the phytoplankton-derived POC to the total POC pool was larger in the Geum River than in the Seomjin River. Notably, a heavy riverine algae bloom occurred in the Geum River in August 2016, resulting in a high carbon isotopic composition (−19.4‰) together with low POC/PN ratio (
C. Vollmann - One of the best experts on this subject based on the ideXlab platform.
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Composition of the root essential oils of several Geum species and related members of the subtribus geinae (rosaceae)
Flavour and Fragrance Journal, 1995Co-Authors: C. Vollmann, W. ScbultzeAbstract:The root essential oils of several members of the genera Geum, Waldsteinia and Coluria, together representing the subtribus Geinae, were analysed by GC-MS. The qualitative composition of these oils was relatively similar with eugenol and some pinane derivatives, e.g. myrtanals, myrtenal, myrtanols and myrtenol, as characteristic constituents. The oils differed considerably concerning the quantitative composition, e.g. two groups of Geum species could be observed, one with a high (>65%) and one with a low (
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Composition of the essential oil from the underground parts of Geum reptans L. (Rosaceae)
Flavour and Fragrance Journal, 1995Co-Authors: Wulf Schultze, C. VollmannAbstract:The essential oil isolated from underground parts of Geum reptans L. (Rosaceae) was analysed by GC and GC-MS. The composition of the oil has not been described until now. In total, 111 components were identified, representing 91% of the oil. The main classes of the compounds present are monoterpenoids (20.5%) and fatty acids (52%) with linolenic acid as the predominant constituent (18.3%). The differences in oil composition between lowland and alpine Geum species are discussed.
Dongseok Shin - One of the best experts on this subject based on the ideXlab platform.
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Effects of Coordinated Operation of Weirs and Reservoirs on the Water Quality of the Geum River
Water, 2017Co-Authors: Jung Ahn, Kang Jung, Dongseok ShinAbstract:Multifunctional weirs can be used to maintain water supply during dry seasons and to improve downstream water quality during drought conditions through discharge based on retained flux. Sixteen multifunctional weirs were recently constructed in four river systems as part of the Four Rivers Restoration Project. In this study, three multifunctional weirs in the Geum River Basin were investigated to analyze the environmental effects of multifunctional weir operation on downstream flow. To determine seasonal vulnerability to drought, the basin was evaluated using the Palmer Drought Severity Index (PDSI). Furthermore, the downstream flow regime and the effect on water quality improvement of a coordinated dam–multifunctional weir operation controlled by: (a) a rainfall–runoff model; (b) a reservoir optimization model; and (c) a water quality model, were examined. A runoff estimate at each major location in the Geum River Basin was performed using the water quality model, and examined variation in downstream water quality depending on the operational scenario of each irrigation facility such as dams and weirs. Although the water quality was improved by the coordinated operation of the dams and weirs, when the discharged water quality is poor, the downstream water quality is not improved. Therefore, it is necessary to first improve the discharged water quality on the lower Geum River. Improvement of the water quality of main stream in the Geum River is important, but water quality from tributaries should also be improved. By applying the estimated runoff data to the reservoir optimization model, these scenarios will be utilized as basic parameters for assessing the optimal operation of the river.
Sujin Kang - One of the best experts on this subject based on the ideXlab platform.
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Dual carbon isotope (δ13C and Δ14C) characterization of particulate organic carbon in the Geum and Seomjin estuaries, South Korea
Marine pollution bulletin, 2019Co-Authors: Sujin Kang, Jung-hyun Kim, Jong-sik Ryu, Kyung-hoon ShinAbstract:We investigated the source, composition, and reactivity of particulate organic carbon (POC) in two contrasting Korean estuary systems, a closed estuary (Geum) (i.e., with an estuary dam at the river mouth) and an open (Seomjin) estuary. A dual isotope (δ13CPOC and Δ14CPOC) approach was applied to surface water samples collected along a salinity gradient in August 2016. Our results indicate that phytoplankton-derived POC was the main contributor to the total POC pool in the reservoir of the Geum estuary, while terrestrial-derived POC predominated the upper Seomjin estuary. A simple binary mixing model using Δ14CPOC revealed a higher modern POC contribution (87-90%) in the Geum estuary reservoir than that (77%) of the upper Seomjin estuary. Accordingly, it appears that an estuary dam can alter the source and reactivity of POC in a reservoir, which can be transferred to the adjacent coastal ecosystem.
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Temporal variation in riverine organic carbon concentrations and fluxes in two contrasting estuary systems: Geum and Seomjin, South Korea
Environment international, 2019Co-Authors: Sujin Kang, Jung-hyun Kim, Daun Kim, Hyeongseok Song, Jong-sik Ryu, Giyoung Ock, Kyung-hoon ShinAbstract:Abstract In this study, surface water samples were collected at sites located in the lowest reaches of closed (Geum) (i.e. with an estuary dam at the river mouth) and open (Seomjin) estuary systems between May 2016 and May 2018. We analyzed concentrations and stable isotopes of particulate organic carbon (POC) and dissolved organic carbon (DOC) to assess OC sources, to estimate fluxes of riverine OC, and to assess some of the factors driving OC exports in these two contrasting Korean estuary systems. Our geochemical results suggest that the contribution of the phytoplankton-derived POC to the total POC pool was larger in the Geum River than in the Seomjin River. Notably, a heavy riverine algae bloom occurred in the Geum River in August 2016, resulting in a high carbon isotopic composition (−19.4‰) together with low POC/PN ratio (
Gea-jae Joo - One of the best experts on this subject based on the ideXlab platform.
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Large weir construction causes the loss of seasonal habitat in riverine wetlands: a case study of the Four Large River Projects in South Korea
Ecological Engineering, 2020Co-Authors: Ji Yoon Kim, Jun Nishihiro, Gea-jae JooAbstract:Abstract From 2009 to 2012, South Korea carried out national-wide construction projects in four rivers; sixteen large-weirs were constructed to control flood risk and to secure water resources. Environmental impact assessment of the weir construction evaluated conditional changes by comparing post-survey records with pre-construction periods. However, the ecological assessment for the weir construction in a long-term perspective has been still limited. In this study, we compared the long-term dynamics of riverine habitat in two construction sites (Nakdong River and Geum River), and one reference site (Seomjin River) in South Korea using 33-years database of satellite imagery. We classified 30 m-grid riverine habitats into three temporal types (i.e., permanent water, seasonal water, and non-flooded habitat) based on annual flooding frequency and its temporal trend was compared. After weirs construction, the area of permanent water was increased (Nakdong R.: +36.0%, Geum R.: +10.9%); seasonal habitat and non-flooded habitat were decreased (Nakdong R: −36.5% and −37.4%; Geum R: −22.9% and −28.2%, respectively). And annual flux of habitat transitions into different habitat types has been decreased only in weir construction sites. Among different habitat transition categories, habitat change into permanent water was the highest during the weir construction periods. Our long-term analysis of riverine habitat can be used to understand temporal changes and recovery after weir construction and channel dredging.
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Distribution pattern of Pectinatella magnifica (Leidy, 1851), an invasive species, in the Geum River and the Nakdong River, South Korea
Journal of Ecology and Environment, 2014Co-Authors: Gea-jae Joo, Ji Yoon Kim, Myeoung-seop Byeon, Dong-gyun Hong, Jung-soo Gim, Jong-yun ChoiAbstract:We conducted a distributional survey of Pectinatella magnifica, an invasive species, in the Geum River and the Nakdong River from July 12 to July 25, 2014. The spacing between the study sites was 10 km along the main channels for the Geum River (n = 12, 120 km) and the Nakdong River (n = 38, 380 km) from the estuarine barrage to upper part of main channel. Pectinatella magnifica was detected along the riparian zone (within 100 m) at each of the study sites. Presence rate of P. magnifica in Geum River and Nakdong River was 25% and 32.6%, respectively. The colony number of P. magnifica at Geum River (9.5 ± 3.1 colony/m, n = 3) was over 94 fold higher than that in the Nakdong River (0.1 ± 0.1 colony/m, n = 16). The Total length distribution of P. magnifica had a truncated bell shape at each rivers (mean length: 14.0 ± 1.2 cm for Geum River (n = 32), and 16.8 ± 1.4 cm for Nakdong River (n = 52)). These findings could provide basic information regarding the distribution pattern of P. magnifica in a new invasion area.