Integrated ecological risk assessment for the persistent toxic substances in contaminated sediments from the Korean coastal waters: A multiple lines of evidence approach

학위논문 (박사) -- 서울대학교 대학원 : 자연과학대학 지구환경과학부, 2020. 8. 김종성.The coastal ecosystems of Korea are subject to a broad range of adverse impacts from anthropogenic activities. Coastal sediments are particularly vulnerable to pollution by chemicals because they act as terminal sinks for persistent and hydrophobic toxicants. Furthermore, contaminated sediments potentially cause harmful effects on not only benthic animals but also pelagic organisms through sedimentary resuspension and bioturbation processes. Thus, it is crucial to ensure high sediment quality to maintain the environmental health of marine organisms, which can be evaluated using ecological risk assessments (ERA). Complexity of anthropogenic influences on coastal sediments necessitates use of an integrated assessment strategy for effective interpretation and subsequent management of ecological risk associated with chemical contaminants. In this study, an enhanced, the multiple lines of evidence (LOEs) approach for sediment assessment, that combined use of chemical contamination, biological effect, and benthic community structure in the sediment was used to assess spatiotemporal changes and ecological risks of persistent toxic substances (PTSs) including polycyclic aromatic hydrocarbons (PAHs), alkylphenols (APs), and styrene oligomers. Various bioassays, environmental DNA based assessments for benthic microbial communities, and several ecological quality (EcoQ) indices of macrobenthic community structure were also implemented. The concentrations of targeted PTSs in the study areas were generally half that of previous years in recent years. Compared to the inner region, the concentrations of PTSs in sediments from the outer regions were significantly lower. These decreasing trends seemed to be associated with the implementation of pollution control measures and the management of toxic substances in South Korea. Strong aryl hydrocarbon receptor (AhR)- and estrogen receptor (ER)-mediated potencies were documented in the mid-polar and polar fractions of sediment extracts. AhR-mediated potencies in sediments also declined with PAH concentration over the sampling time interval, whereas ER-mediated potencies increased. Thus, over the sampling period, the input of ER agonists appears to have been substantial and continuous, especially in Masan Bay. Potency balance analysis demonstrated that only small portions of AhR- and ER-mediated potencies could be explained by identified known chemicals, including PAHs and APs. Thus, target chemicals were not a major AhR- or ER- agonist in sediments of the study area. Thus, to identify potential toxic chemicals in samples, non-targeted full-scan screening analyses (FSA; GC- and LC-QTOFMS) were performed. As a result, enoxolone was first identified as a novel AhR agonist in the sediment of Masan Bay. Enoxolone had a relative potency of 0.13 compared to benzo[a]pyrene (1.0) in the H4IIE-luc bioassay. Nonylphenols were also detected, with this group being associated with membrane damage influencing the viability of microalgae. Non-polar compounds were strongly associated with inhibiting the bioluminescence of Vibrio fischeri and having lethal effects on the embryos of Danio rerio. Overall, the selected endpoints and FSA demonstrated the toxicological properties of complex environmental mixtures comprehensively. To evaluate the ecological effects of pollutants on benthic microbial communities, the relative abundance of Planctomycetes could be used as an indicator of sedimentary contamination by PAHs and metals. Based on correlation analyses, cadmium and ER-mediated potencies were more associated with bacterial abundance at the taxonomic level of class compared to other PTSs and metals. EcoQ indices tended to reflect PTS contamination of macrobenthic communities in the region. Ratio-to-mean (RTM) values obtained from the three LOEs indicated that the quality of sediments from the offshore area of the bay had recovered more over the 16-year period compared to inland areas. The RTM values of the benthic indices was similar to those obtained in the chemical analysis; however, changes across the study period were less pronounced. Thus, while chemical concentrations have the potential to decline rapidly, benthic communities require much longer to recover. Other conditions, such as metal contamination and/or hypoxia in bottom water, represent additional anthropogenic pressures on the benthic community. Overall, the present work demonstrated assay- and endpoint-specific variation and sensitivity for the potential toxicity of chemical mixtures in sediments, reaffirming the utility of the multiple LOEs approach in ERA. In conclusion, the characterization of in situ bacterial communities could provide a useful baseline for monitoring and assessing sediment quality in an integrated manner.해양 저서퇴적물은 육상기인오염물질의 최종 종착지이며, 퇴적물 내 장기간 잔류하는 오염물질은 다양한 해양생물에게 해로운 영향을 미친다. 특히, 잔류성 유기오염물질은 생물농축·확대 등을 통해 궁극적으로 인간의 건강까지 위협한다는 점에서 오염퇴적물 생태위해성 평가는 매우 중요하다. 전통적으로 오염퇴적물 평가는 1) 오염물질의 농도, 2) 생물학적 영향, 3) 저서군집 구조의 세가지 측면에서 개별적으로 이루어졌다. 그러나 미지독성물질 또는 기물질의 혼합 영향 등으로 인해 기존의 단편적 오염평가는 생태위해성을 종합적으로 평가하는데 한계가 있었다. 본 연구에서는 생물영향동정 기반의 다중증거 접근법을 이용하여 국내 연안퇴적물 내 유기오염물질의 생태위해성을 통합 평가하였다. 특히, 유기오염물질의 시·공간 변화에 따른 생물영향 특성과 생태위해성을 평가하고, 국내 연안의 우선관리대상물질을 제시하였다. 연구 지역은 육상기인오염물질이 다량으로 유입되는 시화호, 마산만 인근의 특별관리해역과 대도시, 산업단지 등이 밀집된 서해 연안역으로 하였다. 첫째로, 특별관리해역의 저서퇴적물 오염도 평가를 위해 퇴적물 내 다환방향족탄화수소, 알킬페놀류, 스티렌올리고머 화합물의 시·공간적인 농도변화와 분포특성을 파악하였다. 1990년대 말 기채취 된 시료와 최근(2014–15)에 채취한 시료를 동시분석한 결과, 다환방향족탄화수소와 알킬페놀류 화합물 농도는 과거에 비해 최근에 현저히 감소한 것으로 나타났다. 또한 2015년 국내 연안퇴적물에서 최초로 검출되었던 스티렌올리고머의 경우, 과거에도 시화호와 마산만 퇴적물 내에 고농도로 존재했음이 확인되었다. 대체로 지난 20년간 국내 연안퇴적물의 오염도는 감소 추세를 보였는데, 이는 2000년대부터 시행한 연안오염총량관리제와 최근 정착된 유해물질 배출 규제의 정책적 효과로 여겨진다. 한편, 대부분의 유기오염물질은 육상과 인접한 정점에서 상대적으로 높게 검출되었는데, 이는 저서퇴적물의 오염을 저감하기 위해서 육상기인오염물질의 우선관리가 시급함을 시사한다. 둘째로, 저서퇴적물 내 잔류하는 유기오염물질의 생물학적 영향을 파악하기 위해, 시화호와 마산만 퇴적물을 유기추출하고, 화합물의 극성에 따라 분액화 한 후 다양한 생물을 대상으로 노출평가를 수행하였다. 유전자 재조합 세포(H4IIE-luc, MVLN)를 이용한 유기추출액(또는 분액)의 생물활성 반응은 퇴적물 내 유기오염물질의 농도와 유의한 상관관계를 보였다. 하지만 두 세포주의 등가농도 분석결과, 검출된 화합물의 등가농도는 전체 발현된 세포 활성치 보다 매우 낮게 나타났다. 이는 퇴적물 시료 내 미지의 아릴 탄화수소 수용체 또는 에스트로겐 수용체 활성 화합물이 다수 혹은 다량으로 존재함을 시사한다. 해양박테리아의 발광저해도와 제브라피쉬 배아의 치사 영향은 퇴적물 내 존재하는 무극성 화합물에 의한 것으로 확인되었다. 한편, 미세조류의 생리 활성 영향 중, 효소활성은 중극성 화합물의 영향을 받는 것으로 나타났고, 세포막 손상은 주로 극성 화합물(노닐페놀 등)에 기인한 것으로 확인되었다. 퇴적물 내 노닐페놀 농도는 과거에 비해 감소했음에도, 여전히 미세조류의 활성에 부정적인 영향을 미치고 있어 향후 지속적인 모니터링이 요구된다. 종합적으로, 생물학적 영향은 화합물질(종류, 농도)-, 생물 종-, 메커니즘-특이적으로 나타났다. 따라서, 오염퇴적물의 생태위해성을 정확히 평가하기 위해서는 적합한 생물검정법을 선택하는 것이 매우 중요하다. 셋째로, 생물영향동정법을 이용하여 아릴 탄화수소 수용체 활성을 매개하는 미지의 화합물질을 검색하여 유의한 세포활성능을 보이는 물질을 선별하였다. 본 실험을 위하여 비표적 기기분석과 H4IIE-luc 세포 활성 평가를 함께 수행하였다. 그 결과, 퇴적물 내 잔류하는 에녹솔론(피부치료제 성분)이 아릴 탄화수소수용체 활성에 기여했음을 새롭게 밝혀냈다. 에녹솔론은 아릴 탄화수소 수용체와 가장 결합능이 높은 벤조에이피렌과 비교하여 약 10%의 결합능을 가지는 것으로 확인되었다. 따라서 향후 오염퇴적물의 우선관리대상물질 선정에 있어 에녹솔론류 물질의 포함 여부에 대한 검토가 요구된다. 끝으로, 오염퇴적물의 생태위해성 평가를 위해 미생물과 대형저서동물의 군집구조를 살펴보았다. 서해연안 퇴적물 내 미생물 군집구조의 경우, 환경요인(지리적 위치, 염분) 보다는 오염물질 농도 변화에 따라 우점군이 급변하였다. 대표적으로 Planctomycetes 미생물군의 경우, 카드뮴과 다환방향족 탄화수소의 농도가 높아질수록 개체군 밀도(상대 풍부도)가 유의하게 감소하는 것으로 나타났다. 마산만 퇴적물 내 대형저서동물 중 가장 우점하는 분류군은 다모류였으며, 특히 내측 정점에서 과거(1998년)와 최근(2015년) 모두 유기오염지시종인 등가시버들갯지렁이가 극우점하였다. 이는 오염원에 인접한 지역에서 일부 대형저서동물이 장기간 지속적인 영향을 받고 있음을 시사한다. 한편 생태지수 분석 결과 마산만 저서퇴적물 오염도는 최근에, 특히 외해에서 현저히 감소한 것으로 확인되었다. 그러나 대형저서동물 군집의 건강도는 오염물질 농도의 급격한 감소 또는 생물학적 영향 저감에도 불구하고, 뚜렷한 증가 추세를 보이지 않았다. 이상의 연구결과를 종합 요약하면, 첫째, 국내 연안 저서퇴적물 내 유기오염물질은 최근 전반적으로 감소했으나, 일부 핫스팟 지역에서 여전히 유의한 생물 영향을 보였다. 둘째, 유기오염물질의 종류와 농도, 대상 생물의 종류와 측정 항목에 따라 저서퇴적물의 오염도 및 생태위해성이 상이하게 평가되었다. 본 연구에서 제시한 다중증거접근법은 기존 퇴적물 오염평가법을 대체할 수 있는 효과적인 오염퇴적물 생태위해성 평가법으로 사료된다. 향후, 저서 퇴적물의 오염도가 심각한 연안 해역을 체계적으로 관리하기 위해서는 지속적인 생태위해성 평가 기법의 개발이 요구된다.CHAPTER. 1. Introduction 1 1.1. Backgrounds 2 1.2. Objectives 11 CHAPTER. 2. Long-term Changes in Distributions of Dioxin-like and Estrogenic Compounds in Sediments of Lake Sihwa, Korea: Revisted Mass Balance 14 2.1. Introduction 15 2.2. Materials and Methods 19 2.2.1. Sampling and sample preparations 19 2.2.2. Instrumental analysis 20 2.2.3. In vitro bioassays 26 2.2.4. Potency balance analysis 29 2.3. Results and Discussion 33 2.3.1. Long-term changes in distributions of PTSs in sediments 33 2.3.2. AhR- and ER-mediated potencies 41 2.3.3. Potency balance 46 CHAPTER. 3. Multiple Bioassays and Target and Non-Targeted Analyses to Characterize Potential Toxicological Effects Associated with Sediments of Masan Bay: Focusing on AhR-mediated Potency 50 3.1. Introduction 51 3.2. Materials and Methods 55 3.2.1. Sampling and sample preparations 55 3.2.2. In vitro bioassays 58 3.2.3. In vivo bioassays 60 3.2.4. Targeted chemical analyses 65 3.2.5. Full-scan screening analyses 68 3.2.6. Toxicological confirmation 73 3.2.7. VirtualToxLab in silico analysis 73 3.3. Results and Discussion 74 3.3.1. AhR-mediated potencies 74 3.3.2. Inhibitions of bioluminescence 80 3.3.3. Inhibition of growth and viability of cells 87 3.3.4. Embryo developmental toxicity 92 3.3.5. Occurrence, distributions, and sources of target analytes 94 3.3.6. Full-scan screening analyses 96 3.3.7. Toxicological confirmation 97 CHAPTER. 4. Integrated Assessment of West Coast of South Korea by Use of Benthic Bacterial Community Structure as Determined by eDNA, Concentrations of Contaminants, and In Vitro Bioassays 101 4.1. Introduction 102 4.2. Materials and Methods 104 4.2.1. Study area and sediment collection 104 4.2.2. Next-generation sequencing and bioinformatics analyses 107 4.2.3. Analyses of chemicals and toxicological tests 109 4.2.4. Statistics analyses 111 4.3. Results and Discussion 113 4.3.1. Description of next-generation sequencing data 113 4.3.2. Spatial distributions of bacterial communities 115 4.3.3. Temporal variation in the bacterial communities 121 4.3.4. Correlation between bacterial communities and environmental variables 125 CHAPTER. 5. Integrated Assessment of Persistent Toxic Substances in Sediments from Masan Bay: Compariosn between 1998 and 2014 128 5.1. Introduction 129 5.2. Materials and Methods 135 5.2.1. Sampling and sample preparations 135 5.2.2. Instrumental analysis 136 5.2.3. In vitro analyses 136 5.2.4. Ecological quality (EcoQ) indices of macrobenthic community 137 5.2.5. Integrated approach: RTM values method 137 5.3. Results and Discussion 139 5.3.1. Distributions of PTSs in sediments 139 5.3.2. In vitro potencies in sediments 145 5.3.3. Macrobenthic community 149 5.3.4. Integrated approach: RTM values 159 CHAPTER. 6. Conclusions 164 6.1. Summary 165 6.2. Environmental implications and Limitations 169 6.3. Future Research Directions 172Docto

구인구직의 공간적 미스매치 현상의 특성 분석

학위논문 (석사)-- 서울대학교 환경대학원 : 환경계획학과, 2015. 2. 이희연.매년 정부는 일자리를 늘리고, 고용환경을 개선하기 위해 다양한 정책을 수립하고 있다. 하지만 이런 정부의 노력에도 불구하고, 실업난은 줄어들지 않고 있다. 과거에는 단순히 일자리가 부족해서 실업이 발생되는 경우가 많았다면, 최근에는 구인구직이 공간적, 직종별로 서로 일치하지 않아서 실업이 발생하는 경우가 많아지고 있다. 이는 일자리가 전국적으로 퍼져 있음에도 불구하고, 구직자들의 학력수준이 높아지면서 구직자들이 단순히 임금수준만을 고려하는 것이 아니라 근무지역, 근무시간, 근무환경 등의 다양한 조건을 고려해서 선호하는 일자리로 점점 더 몰려들기 때문이다. 특히 구직자들의 구직 선호조건의 가장 큰 비중을 차지하고 있는 것이 근무지역이라는 점을 고려해보면 구인구직의 공간 미스매치 현상이 앞으로 더욱 더 심화될 것으로 예상된다. 그러나 구인구직의 미스매치에 관한 국내 연구는 매우 미흡하다. 특히 구인구직의 공간 미스매치에 관한 연구는 거의 이루어지지 못하고 있다. 구인구직의 미스매치로 인한 실업이 증가하고 있다는 점을 고려해 볼 때, 이에 대한 연구가 필요하다. 본 연구에서는 구인구직의 공간 미스매치 현상을 분석하여 실업을 발생시키는 다양한 요인들에 대한 이해를 넓히고, 실업을 해소하는데 필요한 정보를 도출하는데 목적을 두었다. 본 연구를 위해 한국고용정보원의 「워크넷 구인구직 자료」와 「산업직업별 고용조사」자료를 활용하였으며, 광역경제권을 단위로 2008년부터 2013년까지를 분석기간으로 하였다. Armstrong & Taylor(1981)와 오오하시(2006)의 방법을 적용하여 지역 간 미스매치와 직업 간 미스매치를 분석하였다. 또한 일자리를 단순히 전체 일자리가 아닌 일자리 유형별로 구인구직의 미스매치 현상이 어떠한 특성을 보이는 지를 분석하였다. 본 연구의 분석결과를 살펴보면 다음과 같다. 2008～2013년 동안 지역 간 미스매치와 직업 간 미스매치로 인한 실업의 비중이 급격히 증가하는 것으로 나타났다. 일자리 유형별로 살펴보면 대졸 이상, 고숙련 일자리에서의 지역 간 미스매치는 전국적으로 매우 낮게 나타나지만, 고졸 이하, 저숙련 일자리에서는 지역별로 다른 양상을 보이고 있다. 충청권, 동남권, 호남권에서 지역 간 미스매치가 높게 나타나고 있으며, 이는 이들 지역의 경우 고졸이하, 저숙련 구직자들이 해당 광역경제권 내의 특정 지역을 선호하기 때문에 실업이 발생하고 있는 것이다. 따라서 구직자들이 직종을 유지한 채로 지역을 옮겨서 구직활동을 한다면 실업상태에서 벗어날 수 있다. 구직 인원과 구인 인원이 가장 많은 지역은 수도권이다. 그러나 수도권에서는 지역 간 미스매치가 거의 나타나지 않고 있다. 이는 수도권에서는 고졸 이하, 저숙련 구직자들을 포함한 모든 구직자들의 구직반경이 넓어서 선호하는 직종을 찾기 위해 서울, 인천, 경기도 관계없이 구직활동을 하기 때문이다. 수도권에서 직업 간 미스매치가 높게 나타나고 있으며, 이는 수도권에서는 직종 자체를 옮겨야 실업상태에서 벗어날 수 있음을 시사한다. 다음으로 일자리 유형별로 직업 간 미스매치를 분석하여 어떠한 방식으로 직종을 옮겨야 실업 상태에서 벗어날 수 있는 지를 분석하였다. 그 결과 대졸 이상, 고숙련 일자리에서는 직업 간 미스매치가 낮게 나타나는 반면에 고졸 이하, 저숙련 일자리에서 직업 간 미스매치가 높게 나타나고 있다. 이는 해당 일자리 내부의 대부분 직종에서 대졸 이상, 고숙련 구직자들이 대졸 이상, 고숙련 구인 인원보다 많기 때문에 해당 일자리 내부에서 직종을 이동하여 구직활동을 하더라도 실업상태에서 벗어날 수 없는 것이다. 따라서 대졸 이상, 고숙련 구직자들이 학력과 숙련도를 낮추어 고졸 이하, 저숙련 일자리를 얻기 위한 구직활동을 해야 실업상태에서 벗어 날 수 있음을 말해준다. 본 연구 결과를 통해 지역별, 일자리 유형별로 실업을 유발하는 주된 구조적 실업 요인이 다르다는 것을 알 수 있었다. 본 연구는 향후 실업문제를 해소하기 위해 단순히 전국적으로 일률적인 실업 해소 계획을 세우기보다는 지역별, 일자리 유형별로 구인구직의 미스매치 차이를 고려한 차별화된 실업 대책이 필요하다는 정책적 시사점을 도출하였다.제 1 장 서 론 1 1. 연구 배경 및 목적 1 1) 연구의 배경 1 2) 연구의 목적 3 2. 연구 범위 및 내용 4 1) 연구의 범위 4 2) 연구의 내용 5 제 2 장 이론적 배경 및 선행연구 고찰 8 1. 이론적 배경 8 1) 미스매치의 종류 8 2) 공간 미스매치 가설 9 3) 미스매치의 측정 및 모형 10 2. 선행연구 고찰 13 1) 구조적 미스매치에 관한 실증 분석 13 2) 공간 미스매치에 관한 실증 분석 14 제 3 장 분석 틀과 분석 방법 19 1. 분석 틀 19 2. 지역 간 미스매치 분석 방법 20 3. 직업 간 미스매치 분석 방법 24 제 4 장 지역 간 미스매치 분석 27 1. 일자리 유형별 구인‧구직‧실업자 수 추이 27 2. 학력‧숙련도에 따른 직종별 지역 간 미스매치 분석 28 3. 소결 35 제 5 장 직업 간 미스매치 분석 36 1. 수도권의 일자리 유형별 구인‧구직‧실업자수 추이 36 2. 학력‧숙련도별 직업 간 미스매치 분석 37 3. 소결 41 제 6 장 결론 및 시사점 42 1. 결론 42 2. 시사점 및 향후 과제 43 참고문헌 45 Abstract 48Maste

화산섬 연안 지하수 및 해수 중 pH의 조절 요인에 관한 연구

학위논문 (박사)-- 서울대학교 대학원 : 지구환경과학부, 2015. 8. 김규범.The oceans are being acidified as a result of oceanic uptake of anthropogenic CO2, and global surface pH levels have already decreased by more than 0.1 units since preindustrial times. This ocean acidification may have critical consequences for marine ecosystems and biogeochemical cycles. In addition to ocean acidification driven by rising atmospheric CO2 levels, some coastal regions have experienced more rapid declines in their seawater pH than that in the open ocean as a result of anthropogenic nutrient inputs through river water and groundwater discharge. Although a number of studies have dealt with coastal pH changes related to river water discharge, studies on the effects of coastal groundwater discharge, which has recently been recognized as an important pathway for nutrients, organic matter, and other trace elements, are limited. Therefore, in this study, I aimed to investigate the pH changes in coastal groundwater itself and evaluate the effects of this groundwater discharge on coastal seawater pH. In order to evaluate pH changes in coastal groundwater, pH (NBS scale), dissolved inorganic carbon (DIC), total alkalinity (TAlk), and δ13C-DIC were measured in groundwater of a subterranean estuary (STE) in Hwasun Bay, which is located in the southwestern part of Jeju Island that lies off the coast of South Korea. This site was chosen because the amount of submarine groundwater discharge (SGD), which includes a substantial amount of submarine fresh groundwater discharge (SFGD), is large in this area and thus water is exchanged actively between the land and ocean through a sandy sediment layer. In the STE of Hwasun, the pH values (7.4±0.2) of fresh groundwater increased sharply to ~10 and then behaved conservatively in the mixing zone between alkalified fresh groundwater and seawater. Similar patterns were observed for pH at Samyang on the northern coast and at Iho on the northwestern coast of the island. The distributions of DIC, TAlk, δ13C-DIC, Ca2+, and Mg2+ in coastal groundwater of Hwasun, along with the results from laboratory experiments on sediment columns, suggest that the increase of pH in this STE is associated with the adsorption of protons (protonation) onto sandy sediments, rather than other geochemical processes. The laboratory experiments that used sediment samples from five different sites (Hwasun, Samyang, Hyeobjae, Hamdeok, and Pyoseon) on Jeju Island showed that the protonation (1) is a common occurrence for various sediments, (2) increases pH effectively for low salinity (salinity <10) groundwater, and (3) depends on the relative amount of transition metal (i.e., Fe, Ti, and Mn) oxides. The chamber experiments at the interface of seawater and groundwater of Hwasun Bay indicate that there is direct seepage of high pH water into the ocean. This increase in pH leads to the corresponding uptake of CO2 from the atmosphere. Thus, these results suggest that the reaction between groundwater and coastal sediments should be considered as an important driver of pH change that regulates the magnitude of chemical species in coastal groundwater seeping into the ocean at the volcanic island of Jeju. The effect of protonation of sediments occurs throughout the entire coast of Jeju beach sediments. However, in some STEs where the loading of organic matter is substantial and the residence time of SGD is long enough to allow organic matter to decompose, the decreases in pH down to 7.7 and the increases in DIC up to 2.5 mmol kg-1 were observed. Therefore, the pH in coastal groundwater of this volcanic island is controlled mainly by two factors, namely, protonation and organic matter oxidation. In order to evaluate the effect of SGD on the coastal ocean, variations in pH of coastal seawaters in Hwasun Bay off the volcanic island of Jeju were measured. This bay is situated in the oligotrophic open ocean. In this region, salinities of all coastal waters depend primarily on SGD because of the lack of any contributions from the river or stream waters. A significant increase in pH along the lower-salinity plume zone was observed, and this zone was extended 0.5 km horizontally where it encompassed the waters from the bottom to the surface (<15m water depth). The observed data for the entire bay-water column showed a significant negative correlation (r2 = 0.82) between salinity and pH. A simple two-endmember (submarine groundwater and offshore seawater) mixing model showed that this pH increase was caused by enhanced biological production, which resulted from the SGD-driven nutrient inputs rather than from the groundwater dilution itself. Since a number of local and regional studies have shown that SGD-driven fluxes of nutrients are comparable to or higher than riverine fluxes, these results from an SGD-dominated environment suggest that SGD may have a significant influence on coastal biogeochemical changes such as acidification, deoxygenation, and eutrophication. The change in pH of coastal groundwater discharge and the associated transport of substances (i.e., nutrients, organic matter, and inorganic carbon) may have a great impact on the coastal ecosystem and biogeochemistry of volcanic islands standing in oligotrophic ocean, which is very vulnerable to ongoing acidification. Therefore, the results presented here provides a good starting point for investigating the various effect of SGD on coastal ocean acidification over different temporal and spatial scales.Abstract ···························································································· ⅰ Table of contents ·································································································· ⅴ List of tables ········································································································· ⅷ List of figures ······································································································· ⅹ 1. Introduction ····························································································· 1 1.1. Coastal ocean pH ························································································· 1 1.2. Coastal groundwater pH ·············································································· 5 1.3. Objectives ···································································································· 8 2. Materials and methods ················································································ 14 2.1. Study areas ································································································· 14 2.1.1. General features of Jeju Island ························································ 14 2.1.2. Hwasun Bay ···················································································· 15 2.1.3. Other sites in Jeju Island ································································· 16 2.2. Sampling methods ····················································································· 19 2.2.1. Coastal groundwater ······································································· 19 2.2.2. Seeping groundwater ······································································· 21 2.2.3. Coastal seawater ·············································································· 21 2.2.4. Sediment samples for laboratory experiments ································ 22 2.3. Analytical methods ···················································································· 27 2.3.1. Salinity and pH ··············································································· 27 2.3.2. DIC and TAlk ·················································································· 27 2.3.3. δ13C-DIC ························································································· 29 2.3.4. Major cations (Ca2+ and Mg2+) ························································ 29 2.3.5. Nutrients ·························································································· 30 2.3.6. Major elements of sediment samples ·············································· 30 2.4. Laboratory experiments ············································································· 38 2.4.1. Effect of salinity on protonation of sandy sediments ······················ 38 2.4.2. Protonation extent of various sediments ········································· 38 2.4.3. Long-term capacity of protonation ················································· 39 3. Results ············································································································· 40 3.1. Coastal groundwater ·················································································· 40 3.1.1. Hwasun Bay ···················································································· 40 3.1.2. Other sites in Jeju Island ································································· 40 3.2. Seeping groundwater ················································································· 42 3.3. Coastal seawater ························································································ 43 3.4. Major elements of sediment samples ························································· 45 4. Discussion ······································································································· 57 4.1. Coastal groundwater ··················································································· 57 4.1.1. Protonation in Hwasun Bay sediments ············································ 57 4.1.1.1. Change in pH caused by protonation of sandy sediments ····· 57 4.1.1.2. Effect of salinity on protonation of sandy sediments ············ 59 4.1.1.3. Protonation extent of various sediments ······························· 60 4.1.1.4. Long-term capacity of protonation ········································ 61 4.1.2. Factors controlling pH change in coastal groundwater at Jeju Island ···················································································································· 62 4.1.3. pH in seeping groundwater ······························································ 63 4.2. Coastal seawater ························································································· 82 4.2.1. pH change associated with groundwater dilution ···························· 82 4.2.2. pH change associated with biological production ···························· 83 5. Summary and conclusions ···································································· 95 References ·································································································· 98 Abstract (in Korean) ··············································································· 109Docto

중국 산동 지방의 캠브리아기 미생물초

학위논문 (박사)-- 서울대학교 대학원 : 지구환경과학부, 2014. 2. 최덕근.During the Cambrian, a typical epeiric platform (North China Platform) formed on the Sino-Korean Block. Various reefs formed on the platform since the Cambrian Series 2. The Cambrian Series 2 reefs (Zhushadong Formation) comprise various thrombolites that consist of Epiphyton, Kordephyton, tube-shaped microbe, Bija, Tarthinia, Renalcis, Amgaina, and Razumovskia. Compared with the Cambrian Series 3 reefs on the same platform (Zhangxia Formation), the Zhushdong thrombolites yield more diverse calcified microbes than that of the Zhangxia Formation, although the reefs were much smaller. The difference was most likely due to changes in depositional environments (abundant siliciclastic input and tidal effects vs. stable carbonate platform) and global changes within reefal environments (end-Cambrian Series 2 extinction of archaeocyaths and calcified microbes). The Furongian (late Cambrian) reefs are characterized by maze-like maceriate reefs that form several bioherms and biostromes. Among them, there is an extensive biostromal microbialite (10–20 m in thickness and over 6,000 km2 in area) which is overlain by grainstones. The lower part of the biostromal microbialite is characterized by flat-bedded megastructure that deposited during sea-level highstand. With rapid rise in sea level, the microbialites caught up with the sea-level rise in the topographic highs, forming domal megastructures, whereas the domal microbialites deposited together with abundant non-microbial sediment in topographic lows. Subsequent deposition and migration of coarse-grained non-microbial sediment during sea-level rise progressively terminated the entire microbialites. Microfacies analysis was done on the maze-like maceriate reefs of the Furongian succession. The maze-like maceria structure was formed by siliceous sponge spicule networks and microbial components including microstromatolites, Girvanella, and Tarthinia. The Cambrian Series 3 and Furongian reefs were compared. The Cambrian Series 3 reefs are characterized by thrombolites and dendrolites, which were mainly constructed by calcified microbe Epiphyton and Renalcis. On the other hand, many of the Furongian reefs are maze-like maceriate reefs formed by siliceous sponges and some calcified microbes including Girvanella and Tarthinia, and columnar stromatolites mainly constructed by Girvanella. The Cambrian Series 3 and Furongian are separated by a major geologic event that occurred across the series boundary, characterized by positive carbon and sulfur isotope excursion (Steptoean Positive Carbon Isotope Excursion), eustatic sea-level drop, extinction and diversification of organisms, and increase in characteristic sedimentary facies. Reefs were also greatly affected by the eventcalcified microbe Epiphyton and Renalcis greatly decreased, which were later gradually substituted by sponge-microbial association and calcified microbes (mostly Girvanella).ABSTRACT……………………………………………………………………………………i CHAPTER 1 Calcified microbial reefs in the Cambrian Series 2 of the North 1 China Platform: implications on the evolution of Cambrian calcified microbes Abstract………………………………...………………………………………………….1 1.1. Introduction………………………………………………………….………………2 1.2. Geological setting…………………………...………………………………………6 1.3. Methods…………………………...…………………………………………………6 1.4. Microbial reefs in the Zhushadong Formation………………………………………7 1.4.1. Macro- and mesoscale characteristics………………………………………………7 1.4.2. Microscale characteristics…………………………………………………………14 1.5. Discussion……………………………………………………………………………26 1.5.1. Calcified microbes in the Cambrian of the North China Platform…………………26 1.5.2. Controls on diversification of calcified microbes…………………………………28 1.6. Conclusions…………………………………………………………………………34 1.7. References……………………………………………………………………………35 CHAPTER 2 Demise of an extensive biostromal microbialite in the Furongian (late Cambrian) Chaomidian Formation, Shandong Province, China Abstract………………………………...………………………………………………43 2.1. Introduction…………………………………………………………………………44 2.2. Geological setting……………………………………………………………………45 2.3. The microbialite bed and the overlying grainstone………………………………47 2.3.1. Microbialite…………………………………………………………………………49 2.3.2. Microbialite-grainstone boundary…………………………………………………61 2.3.3. Grainstone deposit…………………………………………………………………64 2.4. Discussion……………………………………………………………………………65 2.5. Conclusions…………………………………………………………………………68 2.6. References……………………………………………………………………………68 CHAPTER 3 Furongian (late Cambrian) sponge–microbial maze-like reefs in the North China Platform Abstract…………………………………………………………………………………77 3.1. Introduction…………………………………………………………………………78 3.2. Geological setting and depositional environments…………………………………79 3.3. Methods………………………………………………………………………………82 3.4. Microbialites…………………………………………………………………………82 3.4.1. Microbial components………………………………………………………………88 3.4.2. Siliceous sponges…………………………………………………………………92 3.4.3. Occurrence of microbial components and sponges…………………………………93 3.4.4. Interpretations………………………………………………………………………96 3.5. Discussion……………………………………………………………………………98 3.6. Conclusions…………………………………………………………………………102 3.7. References…………………………………………………………………………102 CHAPTER 4 Transition in reefal environments and their relationship to the major geological event during the middle to late Cambrian: a review and new view Abstract………………………………...………………………………………………111 4.1. Introduction………………………………………………………………………112 4.2. Cambrian Series 3 (middle Cambrian) reefs……………………………………113 4.2.1. Eastern Sino-Korean Block (Zhangxia Formation)………………………………123 4.2.2. Virginia, USA (Shady Dolomite)…………………………………………………124 4.3. Furongian (late Cambrian) reefs…………………………………………………125 4.3.1. Eastern Sino-Korean Block (Chaomidian Formation)……………………………127 4.3.2. Great Basin, Laurentia (Bonanza King and Nopah formations)…………………128 4.4. Changes in the reefal environments………………………………………………129 4.5. Events across the middle–late Cambrian boundary……………………………132 4.5.1. Carbon and sulfur isotope excursions……………………………………………133 4.5.2. Eustatic sea-level change…………………………………………………………135 4.5.3. Biotic changes……………………………………………………………………137 4.5.4. Sedimentary facies………………………………………………………………140 4.6. Discussion…………………………………………………………………………142 4.7. Conclusions…………………………………………………………………………145 4.8. References…………………………………………………………………………146 ACKNOWLEDGEMENTS…………………………………………………………….165 ABSTRACT IN KOREAN………………………………………………………………166Docto

치아우식 위험도 분석에 있어 간소화한 Cariogram 모델의 유효성 평가

학위논문 (박사)-- 서울대학교 대학원 : 치의과학과 치과보존학 전공, 2013. 8. 손호현.Objectives Modification and correction of individual caries risk factors is essential for dental caries management. The risk assessment models should be simple to apply and be acceptable and convenient for patients. The objectives of this study were to assess the caries risk among young adult dental patients and to compare the caries risk profiles obtained from the simplified Cariogram models and the conventional Cariogram model. Material and Methods Data required for a caries risk assessment with the Cariogram were collected from 80 young adult patients (mean: 23 ± 3.3 years old). Three different simplified Cariogram models were produced with exclusion of either or both salivary secretion rate and lactobacilli count: group 1, conventional modelgroup 2, both salivary secretion rate and lactobacilli count excludedgroup 3, salivary secretion rate excludedgroup 4, lactobacilli count excluded. Results With conventional Cariogram model, the mean chance of avoiding caries was 55.5%, and the susceptibility sector was 13.5%, the diet sector was 13.3%, the bacteria sector was 11.8%, the circumstance sector was 5.7%. The mean chance of avoiding caries in group 1 (55.5%) was not significantly different from those in groups 2 and 3. Also four caries-related sectors of the Cariogram (diet, bacteria, susceptibility and circumstance) in group 1 were not significantly different than in groups 2 and 3. Group 4 showed significant differences from group 1 in the mean chance of avoiding caries, and the diet, susceptibility and circumstance sectors (p < 0.05). Significant correlations were detected between all risk factors and their corresponding risk sectors (p < 0.05). Also there were significant correlations between each risk factor and the chance of avoiding caries, except for the amount of plaque, in groups 1, 2, and 3 (p < 0.05). Conclusions Dental patients in this study had a medium risk of caries and the dominant sector was the susceptibility sector. The simplified Cariogram model without salivary secretion rate and lactobacilli count did not significantly change the outcome produced from the conventional model. However, single exclusion of lactobacilli count noticeably changed the caries risk profile.I. Introduction 1 II. Materials and methods 4 III. Results 8 IV. Discussion 10 V. References 14 Figures 17 Tables 21 국문초록 29Docto

Second-line glucose-lowering drugs added to metformin and the risk of hospitalization for heart failure: A nationwide cohort study

AIM: To compare the risks of hospitalization for heart failure (HHF) associated with sulfonylurea (SU), dipeptidyl peptidase-4 inhibitor (DPP-4i), and thiazolidinedione (TZD) as add-on medications to metformin (MET) therapy using the data of Korean adults with type-2 diabetes from the Korean National Health Insurance database. METHODS: We identified 98,383 people who received SU (n = 42,683), DPP-4i (n = 50,310), or TZD (n = 5,390) added to initial treatment of MET monotherapy in patients with type-2 diabetes. The main outcome was the hospitalization for HHF. Hazard ratios for HHF by type of second-line glucose-lowering medication were estimated by Cox-proportional hazard models. Sex, age, duration of MET monotherapy, Charlson Comorbidity Index and additional comorbidities, and calendar year were controlled as potential confounders. RESULTS: The observed numbers (rate per 100,000 person-years) of HHF events were 1,129 (658) for MET+SU users, 710 (455) for MET+DPP-4i users, and 110 (570) for MET+TZD users. Compared to that for MET+SU users (reference group), the adjusted hazard ratios for HHF events were 0.76 (95% confidence interval 0.69-0.84) for MET+DPP-4i users and 0.96 (95% confidence interval 0.79-1.17) for MET+TZD users. CONCLUSION: DPP-4i as an add-on therapy to MET may lower the risks of HHF compared with SU.ope

Cardiovascular and Metabolic Diseases Etiology Research Center (CMERC) cohort: study protocol and results of the first 3 years of enrollment

Although the etiologies of cardiovascular disease (CVD) are widely understood, the goal of finding a globally effective solution for preventing CVD is unrealistic. Therefore, we aimed to conduct a community-based prospective study on the prevention and management of CVD in Korean adults. This study was designed to recruit 8,000 healthy adults over the course of 5 years. The baseline assessment includes a wide range of established CVD risk factors, including demographic characteristics, medical history, health behaviors, psychological conditions, body size and composition, blood pressure, the augmentation index, carotid ultrasonography, an electrocardiogram, and biochemical indicators, as well as some novel factors, such as social network characteristics, exposure to environmental pollutants, inflammatory markers, hemostatic markers, and immunosenescence markers. Annual telephone interviews and follow-up health examinations at 5-year intervals after the baseline assessment are planned to collect information on changes in health status and its determinants. Additionally, indirect follow-up using secondary data sources will be conducted to obtain information on health services utilization and death. So far, more than 6,000 adults have been enrolled during the first three and a half years, and almost all participants have been tracked by annual telephone follow-up surveys. The data have been uploaded to iCReaT, the clinical research information management system of the Korea National Institute of Health.ope

Antimicrobial effect of medical adhesive composed of aldehyded dextran and ε-Poly(L-Lysine).

Infection of surgical wounds is a severe problem. Conventional tissue reattachment methods have limits of incomplete sealing and high susceptibility to infection. Medical adhesives have several advantages over traditional tissue reattachment techniques, but still have drawbacks, such as the probability of infection, low adhesive strength, and high cytotoxicity. Recently, a new medical adhesive (new-adhesive) with high adhesive strength and low cytotoxicity, composed of aldehyded dextran and ε-poly(L-lysine), was developed. The antimicrobial activity of the new-adhesive was assayed using agar media and porcine skin. In the agar diffusion method, inoculated microorganisms that contacted the new-adhesive were inactivated, but this was not dependent on the amount of new-adhesive. Similar to the agar media results, the topical antimicrobial effect of new-adhesive was confirmed using a porcine skin antimicrobial assay, and the effect was not due to physical blocking based on comparison with the group whose wounds were wrapped.ope

Inter-Rater Reliability of Carotid Intima-Media Thickness Measurements in a Multicenter Cohort Study

Objectives: Carotid intima-media thickness (CIMT) and the presence of carotid artery plaque are widely used as preclinical markers of atherosclerosis. Due to operator dependency in measuring CIMT, it is important to evaluate the reliability of measuring CIMT and plaque between centers in a multicenter study. The purpose of this study is to evaluate the inter-rater reliability of CIMT and plaque presence among three clinical centers of the Cardiovascular and Metabolic Disease Etiology Research Center (CMERC). Methods: Twenty people without known cardiovascular disease (age 37-64) were enrolled during 2014-2015, and their left and right carotid arteries were examined repeatedly with ultrasonography for CIMT measurements at three clinical centers according to a predetermined protocol. Maximum and mean values of CIMT at distal common carotid artery were recorded. Plaque presence at a carotid artery was checked by an operator. The reliability of CIMT and carotid plaque presence was assessed using an intraclass correlation coefficient (ICC) and kappa statistics, respectively. Results: Calculated ICC was 0.647 (95% CI: 0.487-0.779) for maximum CIMT, and 0.758 (95% CI: 0.632-0.854) for mean CIMT. In Bland Altman plot, most observed values were distributed within mean difference ±1.96 SD ranges. Kappa statistics of plaque presence between two centers were 0.304 (center 1 and 2), 0.507 (center 1 and 3), and 0.606 (center 2 and 3), respectively, while Fleiss kappa for overall agreement was 0.445. Conclusions: The inter-rater reliability of CIMT measurements among three clinical centers turned out to be high, and the agreement of measuring carotid plaque presence was fair.ope

Cohort Profile: The Cardiovascular and Metabolic Diseases Etiology Research Center Cohort in Korea

Mortalities from cardiovascular disease in Korea have decreased markedly over the past three decades. The major cardiovascular and metabolic risk factors, however, remain prevalent, and their burden on health is large. The Cardiovascular and Metabolic Diseases Etiology Research Center (CMERC) planned a cohort study in order to identify novel risk factors and to develop evidence-based prevention strategies of cardiovascular and metabolic diseases. The CMERC deliberately designed two prospective cohorts, a community-based general population cohort (the CMERC cohort) and its sister cohort (a hospital-based high-risk patient cohort), covering a broad spectrum of cardiovascular and metabolic diseases. This paper describes the CMERC cohort study of community-dwelling adults aged 30 to 64 years. A total of 8097 adults completed baseline measurement between 2013 and 2018. Baseline measurements assessed socio-demographic factors, medical history, health-related behaviors, psychological health, social network and support, anthropometry, body composition, and resting blood pressure and comprised electrocardiography, carotid artery ultrasonography, fasting blood analysis, and urinalysis. Both active follow-up through an annual telephone survey and a 5-year on-site health examination survey and passive follow-up through secondary data linkage with national databases, such as national death records, have been applied. Researchers interested in collaborative research may contact the corresponding author.ope