Sediments에서 燐의 溶出 및 除去에 關한 硏究

김우일 全北大學校 大學院 1993 국내석사

Excessive plant growth can be caused by the influx of nurients into surface water bodies. In eutrophic lakes, the sediments can be an important source of phosphate for the growth of phytoplankton. It has been reported that the release rate of phosphate from the sediments is higher in summer than that in winter. Many factors have been asserted to be responsible for this, which are water temperature, dissolved oxygen, pH, particle size distribution, mixing, benthic community, hydraulic retention time, and wind velocity, etc. Exchangeable phosphorus content and sorption capacities of phosphate into sediments are highly correlated with the chemical composition of sediments such as iron, aluminum, and organic matter content, that is affected by the water quality of lakes such as hardness, alkalinity, and pH. The purposes of this study were to assess some environmental factors such as DO, pH, and temperature, affecting the phosphorus release from the sediments collected from Duckjin Pond, at Chonju in South Korea and to estimate the phosphate removal efficiency of several adsorbants such as sand, activated carbon, and activated alumina, etc. The results of this study are summarized as follows. 1. It was founded that the increase of temperature, pH as well as anaerobic conditon can stimulate the release of phosphate from sediments of lakes or dams. PO_4-P and Total phosphorus release rate from sediments with unfiltered subwater in aerobic condition, were noted to be a 34.86mg/㎡.day and 142.95mg/㎡.day, respectively. 2. In removal method of phosphate with adsorbants, phosphate removal dfficiencies were higher for adsorbants coated with alum than for those uncoated. For 1ppm PO_4-P with 5g of adsorbants sand and activated carbon coated with alum in 500mL, removal efficiencies were 66.7% and 92.9% for 5 hours contact time, repectively. But removal efficiency was lower for activated alumina coated with alum than for that uncoated.

A Case-study; How to Achieve Sustainable Beneficial Uses of Marine Sediments in Colombia

Wendy Tatiana Gonzalez Cano Korea Institute of Ocean Science and Technology (K 2023 국내석사

Marine sediments (MSs) are one of the valuable natural resources for humans. By applying various remediation technologies, MSs which are classified as clean and natural or contaminated, including dredged materials, could be successfully transformed into commercially useful products. However, the selection of remediation technologies may still be challenging for decision-makers. This research aims to develop a comprehensive environmental assessment to identify promising ex-situ technologies for MSs in Colombia, and propose management frameworks to achieve sustainable beneficial uses. A novel approach has been proposed to recognize all MSs as potentially exploitable resources in the context of sustainable development. Through various case studies, this research allows the understanding of the mechanisms involved in sediment remediation and promotes the development of new remediation technologies. Further studies have not been reported on this issue in Latin America, including Colombia until now. After evaluating the qualities of marine sediment in Colombia, concentrations of specific harmful heavy metals (HHMs) such as mercury (Hg), zinc (Zn), lead (Pb), and copper (Cu) were found to exceed the environmental standards of various nations expecting adverse effects on water bodies and marine life. Ex-situ technologies were evaluated from cost–benefit analysis and environmental feasibility. Based in the results, the proposed methodology appeared suitable to select remediation technologies. This research identified solidification/stabilization (S/S) as the most suitable technologies for sustainable sediment remediation in Colombia. Sustainable beneficial uses of MSs may offer ample opportunities for environmental enhancement and economic benefits from the point of view of new circular economies. Continuous research and adopting appropriate environmental regulations, such as the London Protocol, 1996 (LP), would contribute to effectively managing all MSs. More innovative and cost-effective technologies to obtain beneficial uses of MSs would still be needed to mitigate global environmental issues such as marine pollution by contaminated sediments. Decision makers may use the environmental assessment tools developed to select optimal remediation technologies and implement sustainable management of MSs by achieving their beneficial uses.

A Comprehensive Laboratory Characterization of Clayey Soils with Different Pore Fluid Chemistry and Physics-Inspired Electrical Conductivity Data Analysis of Seabed Sediments

아이크 에마누엘 전남대학교 2023 국내박사

본 연구에서는 대표적인 세 가지 점토광물과 다양한 비표면적을 가지는 여섯 개의 점토 시료를 이용하여 이온 농도 및 pH의 간극수 특성 변화에 따른 점토 시료의 지반공학적 거동 변화를 연구하였다. 사용한 시료 AMK, EPK 및 LWK의 3가지는 카올리나이트, YI 및 MI는 일라이트, 그리고 DB는 벤토나이트의 광물학적 특성을 가진다. 지반공학적 특성 분석을 위한 실내 시험으로 침강시험, 에터버그 한계 시험을 실시하였고, 전기 민감도 지수 및 점도 변화를 관찰하였다. 또한 해저 심해 퇴적물의 자료를 물리학적 모델 및 분석으로 심해토의 전기전도도 및 열전도도의 상관관계를 분석하였다. 침강 시험 결과, 낮은 pH 조건 (pH 3)에서 입자의 이온 농도, 광물학적 또는 비표면적에 관계없이 응집된 방식으로 침전된다는 것을 확인하였다. 그러나 알칼리성 조건에서 현탁액은 낮은 이온 농도에서 분산된 형태를, 높은 이온 농도에서는 응집된 형태 모두를 보여준다. 이러한 결과는 낮은 이온 농도에서 pH의 영향이 거동을 지배한다는 것을 암시한다. pH 지배 및 이온 농도 지배 조건의 전이 임계 이온 농도 C*0는 0.0015 M과 0.003 M 사이의 경계에서 관찰되었다. 혼합 침전 모드는 이 임계 이온 농도 경계에서 관찰되었다. 이온 농도 외에도, 광물학적 특성과 비표면적은 pH보다 침전 거동에 큰 영향을 미친다. 본 연구에서는 이러한 침강특성을 예측하기 위하여 새로운 변수를 제안하였다. 제안된 변수들의 상관관계로부터 관찰된 침전 모드와 임계 이온 농도 경계를 확인할 수 있다. 에터버그 한계의 (LL 및 PL)의 경우 광물학적 특성 및 비표면적의 변화에 관계없이 이온 농도가 증가함에 따라 감소하는 경향을 보였다. 기존의 흙 분류 체계가 아닌 소성도와 전기적 민감도에 따라 12개의 하위 분류가 있는 새로운 세립토 분류 체계로 본 연구에서 사용한 6개의 시료를 분류하였다. 새로운 세립토 분류 체계는 시료의 비표면적, 광물학적 특성 및 간극 유체의 상호 작용이 세립토의 소성도와 전기적 민감도를 어떻게 변화시킬 수 있는지 보여준다. 또한 해저 심해 퇴적물의 자료를 활용하여 물리학적 모델 및 분석으로 심해토의 전기전도도 및 열전도도의 상관관계를 분석을 수행하였다. 지반 압축 모델과 Archie의 모델을 활용하여 심해토의 깊이별 간극비 및 전기전도도 변화를 효과적으로 추정하였다. 또한 기하학적 평균 모델은 심해토의 열전도도 예측에 매우 효과적으로 분석되었다. 다중변수 예측모델을 활용하여 Archie 모델의 m 지수와 밀도를 활용하여 심해토의 전기전도도와 열전도도 사이의 관계식을 제안하였다. The purpose of this study is to investigate the effects of pore fluid chemistry (ionic concentrations and pH), mineralogy, and specific surface on the geotechnical behaviour of six clayey soils spanning three mineralogies. The samples are chosen to reflect a wide range of common clay mineralogies; AMK, EPK and LWK for Kaolinite; YI and MI for Illite, then DB for Bentonite. The tests include sedimentation, liquid limit, plastic limit, electrical sensitivity index, viscosity, and lastly a large scale, physics-inspired and data driven electrical and thermal conductivity data analysis of seabed sediments. The laboratory tests constitute different solid volume fractions and strain levels, hence ensuring versed understanding of microscale particle interactions. The sedimentation test results indicates that at low pH condition (pH 3), particles settle in flocculated fashion irrespective of ionic concentration, mineralogy, or specific surface area. However, in the alkaline condition, the suspensions settle both in dispersed (at lower ionic concentrations) and flocculated form (at higher ionic concentrations). This suggests that the influence of pH is dominant at low ionic concentrations. The Critical ionic concentration C*0 at which there is a transition between the pH-controlled and ionic concentration-controlled fabric was observed at the boundary between 0.0015 M and 0.003 M. The mixed sedimentation mode occurred at this critical ionic concentration boundary. Besides ionic concentrations, mineralogy and specific surface area shows great influence on settling behaviour than pH. Sedimentations parameters were innovated to reflect crucial clay sedimentation features. These parameters were able to confirm the observed sedimentation modes and the critical ionic concentration boundaries; ~ 3×10-3 M for AMK and EPK (high specific surface), then C*0 ~ 1.5×10-3 M for LKW and MI (low specific surface) suggesting notable fabric change. DB showed no critical ionic concentrations within the chosen ionic concentrations due to its very high specific surface area. The liquid limit and plastic limit decrease with increasing ionic concentrations irrespective of pH, mineralogy, and specific surface. This suggests that ionic concentration is very pivotal to the plasticity of clay samples. Also, in the newly formulated plasticity chart in the context of pore fluid chemistry, LWK, EPK, AMK and MI plotted in the CL section, while YI plotted in MH category. However, DB classifies as CH at C* ≤ 5×10-2 M and as elastic silt (MH) at ionic concentrations C0 ≥ 0.1 M. The electrical sensitivity was conducted using deionized water, 1.8-M NaCl solution, and kerosene as pore fluids, which are aimed at generating distinct van der Waals and double-layer effects. There are 12 fines groups in the new fine chart as a function of their plasticity (non, low, intermediate, or high) and electrical sensitivity (low, intermediate, or high). The LWK and MI classifies into low plasticity and low electrical sensitivity. The YI grouped into intermediate plasticity and low electrical sensitivity. However, AMK, and EPK categorized into intermediate plasticity and intermediate electrical sensitivity, while DB categorized into high plasticity and high electrical sensitivity. This shows how the interaction between specific surface, mineralogy and pore fluid chemistry can alter the existing plasticity and fines classification. Hence, this study recommends a complementary application of the triad in soil classification system and in electrical sensitivity index. The large scale, physics-inspired and data driven analysis of depth dependent seabed sediments for electrical and thermal conductivity was carried out using several models. Asymptotically correct compaction model and Archie’s equation were very effective in fitting the void ratio and electrical conductivity of the seabed sediment depth profile respectively. The ‘mixing’ models proved very robust in estimating bulk thermal conductivity of seabed sediments, in which the geometric mean model presents the most effective prediction, having the least regression root mean square error (RMSE), least prediction root mean square error (RMSE) and best prediction R-squared. The model prediction and parameter estimation errors were evaluated using statistical tools. The Archie’s cementation exponent (m) was assessed while the seabed sediments were classified using asymptotic void ratio and specific surface area, both of which suggests the predominance of intermediate plasticity sediments. Finally, a robust link between the electrical and thermal conductivity of the seabed sediments was innovated using geotechnical and geophysical properties of the sediments.

Remediation of heavy metals and NAPLs contaminated marine sediments using soil washing and in situ air sparging technology

이준호 韓國外國語大學校 大學院 2012 국내박사

Chapter Ⅰ Distribution of Heavy Metals in the Sediments of Maehyang-ri Shooting Range, West Coast of South Korea This study was conducted to evaluate the heavy metal contamination in the sediments of the Nongdo and Gokdo areas within the Maehyang-ri shooting range. The sediments in the Maehyang-ri inland of (Gokdo) was Sandy (S), whereas Nongdo, at the north side incline was slightly gravelly muddy Sand ((g)mS), containing 12.9% gravel, 47.0% sand, 35.1% silt and 5.0% clay. Copper (Cu) and Pb in Maehyang-ri shooting range sediments were 114.4±5.7 ppm and 362.3±20.5 ppm, respectively. In Nongdo site the sediments contain Cd (22.5±1.9 ppm), Cu (35.5±4.0 ppm), Pb (1,279.0±5.1 ppm) and Zn (403.4±9.8 ppm). The heavy metals were adsorbed in the sediments of the 1st strike shooting range Cu, Pb, Cd, and Cr, according to the reaction concentration in the order of Cu>Cd>Cr>Pb. The leaching equilibrium of Cu was very high 9.0-14.0 mg/g, compared to that of other metals (0.0-2.0 mg/g). And pollution Index in 1st shooting range of 0.10-0.97. Also the reaction speed constant k was in the order of Cu>Pb>Cr>Cd. Background sediments around Maehyang-ri inland (B sample site) showed that equilibrium reached in the range of 1.0-4.5 mg/g, in the order of Cr>Cu>Pb, with the reaction speed constant k, Cr>Cd>Cu>Pb. Chapter Ⅱ Remediation of Heavy Metals-contaminated Marine Sediments of Maehyang-ri Shooting Range Using Soil Washing Technology This study was conducted in order to evaluate heavy metal contamination in within Nongdo, Gokdo and Maehyang-ri shooting range sediments, and the remediation of the sediments through batch reactor scale washing. Cu and Pb contamination of the T1 site (Maehyang-ri shooting range area) sediments was apparent from the observed concentrations of 114.4±5.7 ppm and 362.3±20.5 ppm, respectively, whereas sediments in the Nongdo area were determined to be contaminated with Cd (22.5±1.9 ppm), Cu (35.5±4.0 ppm), Pb (1,279.0±5.1 ppm) and Zn (403.4±9.8 ppm). The extraction of heavy metals reached quasi-equilibrium with in 6 h of shaking with 0.1 N HCl, and 95% and 94% extraction efficiencies were observed for Cu and Pb. This may be due to the effects of mineralogical factors, sediment particle sizes and non-residual fractions such as exchangeable carbonate, Fe-Mn oxide and organics and sulfides. The ethylene diamine tetra acetic (EDTA) acid evaluated more effective extractant than any of the other 5 extractants (citric acid, EDTA, phosphoric acid, potassium phosphate and oxalic acid) tested for removing the heavy metals. The removal efficiency of residual fractions was higher than that of non-residual fraction. The Pb and Zn removal rates of were 92.4% and 94.0%, respectively. Chapter Ⅲ Characteristics of Intertidal Zone Sediments at Maehyang-ri Shooting Range, West Coast of South Korea This study was conducted to evaluate the characteristics of the intertidal sediments between shooting and target area, Maehyang-ri, West Coast of Korea. At site closest to the target, Sandy sediments contain Pb up to 623.9 ppm, twice as much as warning standard. According to relationships, Pb and Cu are relatively strongly adsorbed onto organic substances, which are in turn related to particle sizes, different from Zn and Cd. Based on the average C/N (10), Pb accumulation seems to have resulted to the deposition of sediments from the target island. Results of the analysis of excessive radioactivity Pb (210Pbex) of column sediments indicate a sedimentation rate of 0.42 cm/yr at 5-15 cm, and 2.26 cm/yr at 20-30 cm, suggesting that heavy metal contamination has been leached to about 21 cm from the surface. Chapter Ⅳ Degradation of TPHs, BTEX and PAHs Compounds for NAPLs Contaminated Gomso and Busan Bay Sediments Using In Situ Air Sparging Combined with Soil Vapor Extraction This study was carried out in order to determine the remediation of TPHs, BTEX and PAHs compounds the marine sediments of Mandol, Hajeon, Sangam and Busan, South Korea. For the samples of Mandol to air was continuously injected at 5 L/min for 48 h, and extracted analyze volatile organic compounds (VOCs) while reducing pressure of two vacuum pumps. It took 1.6 h for the detection rate for VOCs to go down to 0 ppm (reduction of 100.0% after 48 h air injection). Total petroleum hydrocarbon (TPH) levels of Mandol, Hajeon, Sangam, and Busan sediments were 2,459, 6,712, 4,348, and 14,278 ppm. Trichloroethylene (TCE) was reduced 99.5% to 100%; perchloroethylene (PCE), 93.2% to 100%, characteristically. These compounds were removed lest in the fine sediments of Busan. The PAHs was reduced in small amounts 1.8% to 34.4%. The removed rated of TCE, PCE, Toluene, Etylebenzene, Xylene, and BTEX are closely related to particle sizes and organic carbon concentration of the sediments (correlation coefficients 0.90 to 0.99), while TPHs and Benzene moderately (0.71 to 0.76). Chapter Ⅴ TVOCs Volatilization and Affected Area Changes for NAPLs contaminated Gomso and Busan Bay Sediments Using In Situ Air Sparging Combined with Soil Vapor Extraction Air Sparging (AS) and Soil Vapor Extraction (SVE) method was applied in situ applied to various types. Sediments to check total volatile organic compounds (TVOCs) volatilization and degrees of the affected area. The sediments are Sand, sandy Silt, Silt, and Clay. Smaller size have reduced porosity affected completely. Air was continuously suctioned through vacuum at 5 L/min (pressure is more relevant here) for 48 h, and extracted air was analysed while reducing the pressure of the vacuum. It took complete removal of volatile organic carbon (VOCs) reduction of 100.0% for 48 h. TVOCs generated by deserving all VOCs through heating the sediment samples was 16.690 to 69.735 mg/m3 and TVOCs was removed rate 98.0% to 99.8%. Chapter Ⅵ Measurement of Radius of Influence Caused by a Combined Method of In Situ Air Sparging and Soil Vapor Extraction in the Intertidal Sediments of Gomso Bay, West Coast of South Korea The outer layer of Mandol area is predominantly characterized by sand (S) (average particle size, 1.789 Φ), whereas that of Hajeon area is predominantly characterized by sandy silt (sZ) (average particle size, 5.503 Φ), and that of Sangam area by (Z) (average particle size, 5.835Φ) located in Simwon-myeon, Gochang-gun, Jeonnam, South of Korea. Mandol core sample consisted of 1.60-3.41 Φ (average, 2.30 Φ) sand and muddy sand, and its water content was on average 15.10%. Hajeon core sample consisted of 1.31-4.44 Φ (average, 3.11 Φ) muddy sand, sandy silt, muddy sandy, and muddy sandy gravel, and its water content was on average 19.77%. Lastly Sangam core sediment particles consisted of (-)0.18-(+)5.45 Φ (average, 4.20 Φ), and its water content was on average 19.43%. At Mandol site, during 48h in Mandol, H2S or combustible gas were not detected, and 0.1-2.0 ppm VOC was detected at the monitoring well for the intial 30 min. At SVE wells 1-4, CO2 and O2 varied by 850 ppb (690-1,540ppm), and 0.5% (20.4-20.9%), respectively. At Hajeon site during 48 h, CO2 and O2 varied from 580-1,250 ppm, and 20.6-20.9%, respectively. At Sangam site, 10 min after the air was injected, the air flow did not appear to respond with the sediments, but the air was extracted, indicating a phenomenon called short circulation. At Mandol site, this study assumed an oxygen concentration of 20.6% as the effective concentration, and effective radius of influence (ROI) was estimated to be 128.0 cm. At Hajeon site the ROI was estimated to be 85.7cm. The reason for their effective ROI being rather small seems to be caused by a thin aquifer and thin screens of sparging well. Chapter Ⅶ Clean-up NAPLs of Gomso Bay from Sandy Sediments by In Situ Air Sparging Combined with Soil Vapor Extraction Aim of this study is pollutants flow such as NAPLs are removing. Sediment samples collected from Mandol area were almost entirely composed of sand (99.91%), with the remaining fraction determined to be silt. This sand sample included NAPLs clean-up by in situ air sparging (IAS) combined with soil vapor extraction (SVE) using saturated zone. The average particle size was 1.779 Φ, ranging from 1.518-1.895 Φ and showing a good distribution. Multiple probes were placed above a laboratory scale 2-dimensional reactor (transparent acryl plastic, 60×60×5 cm), and it was determined that H2S began to increase after 115 h, rising to a maximum concentrations of 1 ppm. VOCs was detected between 20 h and 44 h. LEL, CH4 concentration, 0.1-0.3% was observed after 20 h. O2 increased by 0.7%. TVOCs concentrations were determined to be the following: air zone, 0.0119 mg/m3. Non-volatile contaminants seem to have remained in the sediments. At ‘T9 bottom’, the determined concentration of TPH was 89.29 ppm, showing that about 15.4% of TPH seem to be remain in sediments. The highest concentrations of TCE were observed for the A6 port at 398.51 ppm. BTEX, like TCE, appeared to remain within the sediments to some degree, with the highest concentration within the A6 port determined to be 62.98 ppm. Chapter Ⅷ Modeling of Radius of Influence in Sediments by In Situ Air Sparging Laboratory study of In situ air sparging (IAS) flow for a ground-water saturated sediment zone was conducted. Five average modal diameter grains AMG: 0.33, 0.34, 1.38, and 3.89 mm diameter grains were used. Air flow for AMG 1.38 and 3.89 mm sedimentary grains exhibited pervasive air flow patterns, forming a symmetrical cone of influence around the injection point. The maximum areas of influence are 37.0%/m2, and 40.3%/m2 for AMG 1.38 and AMG 3.89 mm grains, respectively. Changes in the characteristics of the sediment, and the swept volume of injected air during air sparging (AS) were also investigated. The results demonstrated that particle movement reduced both the radius of influence (ROI) and the swept volume of injected air. In this case study EXP-1 (AMG 0.34, 1.38, 3.89 mm), EXP-2 (AMG 0.62 mm), and EXP-3 (AMG 0.33 mm) showed the greatest reduction in ROI and swept volume of air, 33.4-40.3%, 37.6%, and 44.0%, respectively. This constant, Cs is the most important determinant in the successful application of IAS, and some experimental and theoretical work, such as slug tests or field tracer tests, have to be carried out in the field prior to performing IAS of contamination sites. The remediated zone is necessarily reduced in size when sediment particles are transported during IAS with soil vapor extraction (SVE).

Numerical Study for CH4 Production from Gas Hydrate-Bearing Sediments via CO2 Injection

Yu, Shuman ProQuest Dissertations & Theses Rensselaer Polytec 2021 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

CH4 production from gas hydrate-bearing sediments has been considered as a potential measure to supplement global hydrocarbon resources. Natural gas hydrates, solid compounds of gas and water, are often found in the pores of sediments under deepwater or permafrost regions, where hydrate stability conditions of high pressure and low temperature exist. CH4 production from gas hydrate-bearing sediments requires a phase change of the solid gas hydrates and has been deemed possible by depressurization through a well. However, the method tends to lower geomechanical stability of the sediments and consequently, to date, only a few short-term trials of field-scale gas production were successful. Moreover, future hydrocarbon production is overshadowed by growing concerns for its adverse environmental impacts. Therefore, there is a pressing need for an innovative energy strategy that replenishes dwindling supplies of hydrocarbons while maintaining geomechanical stability and achieving carbon neutrality.CO2 injection into gas hydrate-bearing sediments may potentially accomplish the aforementioned objective. As CO2 hydrates are usually more stable than CH4 hydrates, injected CO2 could destabilize CH4 hydrates in the sediments to release out CH4 gas for production while forming solid CO2 hydrates in the newly available pore of the host sediments. In this way, it would effectively maintain the geomechanical stability of the sediments during CH4 production and, at the same time, store CO2 as solid hydrates permanently in the sediments. However, the process is yet to be fully understood as it involves interactions of various multi-physical and chemical processes including generation of immiscible CH4–CO2 fluid mixture in sea water, evolution of chemical reaction kinetics of CH4–CO2 hydrate mixture, heat emission and absorption from hydrate formation and dissociation, respectively, and stress redistribution caused by spatial and temporal developments in CH4–CO2 mixed hydrate-bearing sediments.This research has developed a novel, coupled thermo-hydro-chemo-mechanical formulation that captures the complex processes and has investigated the behavior of CH4 hydrate-bearing sediments subjected to CO2 injection. There are mainly four contributions. Firstly, several additional processes caused by generation of CH4–CO2 fluid mixture have been incorporated such as fluid viscosity change and molar fraction induced diffusion. Secondly, formation of CH4–CO2 hydrate mixture has been taken into account, along with its effect on thermal, hydrological, chemical and mechanical processes. Thirdly, the applicability of the formulation has been validated through simulations of existing laboratory tests of CO2 injection into CH4 hydrate-bearing soil. Fourthly, the efficiency of CH4 production and CO2 storage and its geomechanical impact by CO2 injection in natural gas hydrate-bearing sediments have been thoroughly discussed. The outcome of this research provides valuable insights into the prospect of the revolutionary energy strategy that satisfies conflicting interests, unlocking the new source of hydrocarbon energy while managing geo-risk and environmental sustainability for future generations.

한강 밤섬 및 인근 수계 바닥 퇴적층에서의 미세플라스틱 퇴적 특성 연구

김규원 동국대학교 일반대학원 2025 국내석사

Since plastic began to be used in the 1950s, its production has increased every year, and it is predicted that approximately 1.1 billion tons of plastic will be produced by 2050. Consequently, the amount of plastic released into the environment is also expected to increase. Plastics released into the environment undergo physical, chemical, and biological degradation, turning into microplastics. Initially defined in 2004 as particles smaller than 20 mm, microplastics were redefined in 2008 to refer to plastic particles smaller than 5 mm, a definition still accepted today. Microplastics are widely found in the atmosphere, sediments, soil, freshwater, and even in living organisms, including humans. When microplastics accumulate in soil, they affect its physical and chemical properties, such as structure, density, pH, and electrical conductivity (EC). Moreover, they can cause changes in microbial communities, and pose risks to organisms like fish, birds, and humans through ingestion. Approximately 80% of microplastics are generated from land-based activities, and over 90% of microplastics entering the ocean are transported through rivers. In addition to the volume that enters the ocean, a significant amount is also deposited, with about 70-90% of microplastics predicted to accumulate in sediments. While research on microplastics has increased globally since the 2010s, studies on microplastics in South Korea remain limited. This study aims to investigate the sediments of Bam Island, a Ramsar-Designated wetland expected to have minimal anthropogenic pollution, and the surrounding Han River bed. The objectives of this study are to: 1) assess the distribution of the number and mass of microplastics in Han River sediments, 2) analyze the correlation between sediment physicochemical properties and microplastic distribution, and 3) estimate the total amount of microplastics deposited in the Han River. The sampling was conducted from June 28 to July 1, before the onset of the rainy season. Sediment samples were collected between the Upper Bam Island (Latitude: 37.5358, Longitude: 126.9353) and Down Bam Island (Latitude: 37.5305, Longitude: 126.9212). A total of 9 grab sample sites and 15 core sample sites were selected. Core samples were taken to a maximum depth of 60 cm and stored until analyzed by dividing them into upper, middle, and deep layers. The collected sediments were analyzed for pH, EC, LOI, TAN, TKN, bulk density, and MUD. For microplastic analysis, the samples underwent four preprocessing steps: drying, density separation, organic matter removal, and filtration. The preprocessed microplastic samples were then analyzed using FT-IR spectroscopy to determine the number, size, and polymer type, and the mass of microplastics in each sediment sample was measured using TED-GC/MS. Based on the results of the physicochemical analysis of the sediments, Scheffe's test was conducted to identify significant differences each location and depths. LOI showed a significant difference between the DB, UB and DB, MB. While MUD exhibited a significant difference between DB and MB. TAN and TKN, which are closely related to LOI, also showed significant differences, with DB differing from both UB and MB. Microplastics were detected in the sediments across all sampling sites, with quantities ranging from a minimum of 6.2 particles g-1 to a maximum of 192.4 particles g-1. The major polymer types identified were PS, PP, Polyester, Polyacryl, and PE, which were compared along with the category "Other" (representing the combined total of polymer types not classified as major). The average number of particles for each polymer type was analyzed as follows: PS 2.2 particles g-1, PP 13 particles g-1, Polyester 12.1 particles g-1, Polyacryl 0.3 particles g-1, PE 19 particles g-1, and Other 1.6 particles g-1. The average number of microplastics by size was: 20-45 μm 19.6 particles g-1, 45-100 μm 18.4 particles g-1, 100-300 μm 8.9 particles g-1, and over 300 μm 1.5 particles g-1, indicating that smaller microplastic particles were more abundant. In the comparison between riverbed sediments and inland Bam Island sediments, more microplastics were detected in the riverbed, suggesting that microplastics introduced from the river are likely suspended around Bam Island. It is possible to quantified the number, shape, and size of microplastics by using FT-IR, it is difficult to determine the actual amount of microplastics introduced into the environment. To complement this, mass and MP particles comparisons were conducted using TED-GC/MS analysis. Microplastic mass ranged from a minimum of 0.9 μg g-1 to a maximum of 62.96 μg g-1 across all sampling sites. The average mass by depth was 12.7 μg g-1 in the upper layer, 6.8 μg g-1 in the middle layer, and 4.2 μg g-1 in the lower layer, with the mass in the upper layer being more than twice as high. A comparative analysis of microplastic numbers and mass revealed that a higher number of polymer particles does not directly correspond to a higher mass. Instead, the size and density that varies with polymer types are critical factors. Microplastics showed a positive correlation with LOI, and the same positive correlation was observed with MUD too. This suggests that the formation of biofilms on the surface of microplastics by microorganisms may change their physical and chemical properties, making them more likely to adsorption to clay. Another hypothesis is that the slower flow of the river allows microplastics to settle and accumulate along with smaller particles as the current weakens. The final goal of this study was to estimate the total amount of microplastics in Bam Island sediments, which was found to range between 9,991 and 17,346 tons. This estimation was based on the average mass of microplastics. However, the limited number of sampling sites and even the sampling sites were concentrated around Bam Island. Further research, including upstream and midstream locations of the Han River, is necessary for a more detailed analysis.

Modeling Deep Ocean Water and Sediment Dynamics in the Eastern Pacific Ocean Using Actinium-227 and Other Naturally Occurring Radioisotopes

Kemnitz, Nathaniel James ProQuest Dissertations & Theses University of Sout 2022 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

The disequilibrium that occurs within the U and Th-decay series in marine environments can be exploited to give rates of transport of dynamic processes. To provide the most accurate transport rates, the radiotracer should have the following characteristics: (1) the radiotracer should be easily sampled and measured; (2) the source function and geochemical behavior of the radiotracer should be well understood; (3) the radiotracer’s half-life should be on the same order as the process being investigated. This dissertation will utilize the distribution of 227Ac on the basin-scale range in the North- and Southeast Pacific in order to provide rates of transport of other solutes. The half-life of 227Ac (t1/2=21.8 y) is well suited for this scale and its geochemical behavior has been well-studied throughout the last few decades. The GEOTRACES program protocol for sampling and measuring Ac and Ra in the water column has led to multiple 227Ac profiles throughout the world’s oceans. This dissertation will utilize U and Th-decay series equilibria to establish 227Ac bottom fluxes that can provide insight into transport rates and circulation pathways in the Northeastern Pacific Ocean.227Ac is directly produced by decay of 231Pa (t1/2=32.8 ky). 231Pa is scavenged from the water column by falling particulates that carry it to sediments, where it decays to its more soluble daughter. A fraction of this 227Ac diffuses out of deep-sea sediments and is transported vertically and horizontally as it decays in the water column. The water column distribution of excess 227Ac (227Acex) was measured along the U.S. GEOTRACES Meridional Transect (GP15) from Alaska to Tahiti in fall 2018. To constrain its benthic input, cores from 5 stations near the northern half of the GP15 transect were collected in the summer of 2017 (C-Disk-IV transect stations 23-50°N). The GP15 transect parallels the C-Disk-IV cruise track in the Northeast Pacific, offset by a few hundred km.Five sediment cores along the C-Disk-IV transect were measured and modeled with the objective of characterizing the behavior of 227Ac, 228Ra, and 226Ra and their fluxes into the overlying water column. Solid phase profiles of these isotopes were measured, and reaction-transport models were applied that incorporate effects of molecular diffusion, bioturbation, sedimentation, distribution coefficient (kd), and fraction of each isotope released to pore water by parent decay (called F). Good fits to the 226Ra profiles showed F values of 57-83% and sedimentation rates of 0.10 – 0.40 cm kyr-1 for C-Disk-IV sediments. The 228Ra profiles were difficult to measure due to high counting uncertainties, but F values obtained from 228Ra profiles were similar to 226Ra values. Most solid phase 226Ra profiles showed a large deficiency compared to 230Th in the upper 15cm of sediments, while the 228Ra profiles showed a modest deficiency relative to its 232Th parent in the top 3cm of sediments. F values for 227Ac had a much larger range than the Ra isotopes, ranging from 5 - 94% for C-Disk-IV sediments. About half of the 227Ac profiles showed a large deficiency relative to 231Pa in the upper few cm of sediments, while the other half showed a very small deficiency. Sediment composition, loss of surficial material, non-steady state behavior, and non-local bioturbation transport of sediments might explain the discrepancy between the two types of 227Ac profiles. It is noteworthy that 230Th budgets indicate significant sediment winnowing at sites with low F values, perhaps indicating that exhumation of formerly buried sediment plays some role.Two independent approaches were used to quantify the source function of 227Ac and 228Ra in the Northeast Pacific: (1) use of solid phase profiles with a reaction-transport model, as well as integrated downcore daughter-parent deficiency; and (2) direct measurement of fluxes based on core incubation. The two independent methods agree within uncertainty, and the average 227Ac and 228Ra sediment fluxes for the Northeast Pacific are 90 ± 20 and 600 ± 200 dpm m-2 yr-1. The 226Ra sediment flux was only determined by the former approach, and the flux calculated in this study is similar to previous work in the North Pacific. The average sediment flux for 226Ra along the C-Disk-IV cruise is 1300 ± 10 dpm m-2-yr-1, which is over 2x higher than the water column inventory of 226Ra in this region (600 dpm m-2-yr-1). 227Ac fluxes for the southern half of the GP15 transect were calculated by estimating F and using 231Pa measurements in the upper few cm of sediments.Profiles of 227Ac and 231Pa were measured and modeled in the water column along the GP15 transect. Along the GP15 transect, 227Ac and 231Pa are typically near equilibrium between 0-3000m depths, and below this horizon, 227Ac is often in excess over its parent. Excess 227Ac (227Acex) generally increases in activity with increasing depth and the highest concentrations of 227Acex are contained within the bottom 1000m. The highest concentrations of 227Acex in the Eastern Pacific are found near the center of the Northeast Pacific Basin (NEPB) and south of 10˚S. These areas are dominated by low sedimentation and high 231Pa activity in sediments. Along the southern leg of the GP15 transect (Sta.19 - 37), some elevated activities of 227Acex are found at mid-depths (~2600m). These areas appear to be influenced by hydrothermal activity from the East Pacific Rise (EPR), due to the proximity of δ3He anomalies and 227Acex activities at those depths, although maxima in the two tracers are not perfectly coincident.Three types of 227Acex profiles were found in the water column along the GP15 transect: (1) an expected, exponential decrease of 227Acex away from the seafloor; (2) a well-mixed 500m thick bottom layer with very little 227Acex above; (3) and lastly, an unexpected, erratic distribution of 227Acex that has local maxima in 227Acex overlying bottom waters of lower concentration. The first type of 227Acex profile is found toward the northern end of the GP15 transect (Sta.6 – 10). These profiles can be generated if water circulation is flowing along a constant depth, where the 227Ac bottom source is constant. If vertical diffusion of 227Acex is constant, it should produce an 227Acex distribution that is exponentially decreasing away from the seafloor due to the combination of diffusion and radioactive decay. This is the most ideal profile and can be used to find apparent vertical eddy diffusivity rates (Kz), if the bottom is flat, or inclined with a constant slope. The apparent vertical diffusivity will be affected by both diapycnal and isopycnal transport, in situations where the isopycnals and/or the bottom topography are inclined.The second type of 227Acex profile found along the GP15 transect shows nearly constant 227Acex activities within the bottom few hundred meters. These profiles are found in the middle of the Northeast Pacific (30˚ - 40˚N) and indicate that the bottom ~500 meters are rapidly mixed, reflecting the density structure. Above this benthic layer, little 227Acex is found, indicating low vertical transport. Profiles in the southern half of the GP15 transect show the 3rd type of 227Acex profile: an erratic distribution of 227Acex in the bottom few hundred meters that correlates with the depth distribution of regional topographic features. The irregularity appears to reflect high density stratification, coupled with inputs from irregular topography in the Southeast Pacific that produces localized maxima in the 227Acex source function at multiple depths, which then travels horizontally along isopycnals, mimicking the complex source function.Horizontal advection of 227Acex is significant in some parts of the transect, as shown by comparing the integrated decay of 227Acex in the water column to the benthic source: between 40˚ - 30˚N and 10˚ - 0˚N, water column decay is smaller than benthic input and south of 10˚S, it is larger than benthic input. Areas where horizontal advection does not produce a significant effect are: north of 40°N, between 30˚ - 10˚N, and near the equator. In these areas, water column decay is comparable to benthic input. This pattern is consistent with predictions from an inverse model in the Northeast Pacific (Hautala, 2018) that indicates deep-water advection is strongest between 40˚ - 30˚N and circulation is moving in a west-east direction (along 150˚W). North of 40˚N, the model suggests that circulation is moving in a north-south direction.The last chapter of thesis focuses on sedimentary dynamics in the Santa Monica Basin (SMB) during the last 250 years, with an emphasis on the last 40 years. Mass accumulation rates (MAR) for the deepest and lowest oxygen-containing parts of the SMB basin have been remarkably consistent during the past century, averaging 17.1 ± 0.6 mg cm-2 yr-1. However, MAR were slower prior to ~ 1900 CE (~10.5 mg cm-2 yr-1). The increase in sedimentation rate towards the recent occurs at about the time previous studies predicted an increase in siltation and the demise of a shelly shelf benthic fauna on the SMB shelf. The post-1900 CE constancy of sedimentation through a period of massive urbanization in Los Angeles is surprising.

해저퇴적물의 방사성핵종 분포와 거동

박규준 慶北大學校 大學院 2004 국내박사

Concentrations of radionuclides in sediment and seawater samples in the East Sea (Japan Sea) adjacent to Yangnam, Korea were measured and data on the physical and chemical properties of the sediments were collected. The concentrations of ^(137)Cs and ^(239+240)Pu in the sediment samples were in the range of <minimum detectable activity (MDA)-7.19 ㏃/㎏-dry and 0.12-1.91 ㏃/㎏-dry, respectively. The ratio of ^(239+240)Pu/^(137)Cs was 0.27 in the coastal sea of Korea. The concentration of ^(40)K in the sediment was in the range of 393-920 ㏃/㎏-dry. ^(7)Be was not detected in the sediment. The natural radionuclides of Thorium series, ^(208)Tl, ^(212)Pb, and ^(212)Bi, and Uranium series, ^(214)Pb and ^(214)Bi, were detected. The concentrations of the artificial radionuclides, ^(137)Cs and ^(239+240)Pu, and the natural radionuclides of Thorium series were linearly correlated with particle size, total organic carbon (TOC), H, N, and S contents of the sediment. The adsorption of the radionuclides would increase with decreasing of particle size and increasing of organic contents in marine sediments because organic materials and fine particles have a large cation exchange capacity (CEC) and readily adsorb cations. The ^(137)Cs and ^(239+240)0Pu concentrations in the sediment samples were well fitted to a multiple regression equation with TOC contents and particle size distributions. This result suggests that organic matter and/or particle size distribution play an important role in determining the ^(137)Cs and ^(239+240)Pu concentration. The distribution coefficients, which indicate the degree of adsorption, of ^(137)Cs and ^(239+240)Pu to sediments were in the range of (2.06-23.5) × 10^(3) and (1.93-22.5) × 10^(4), respectively, which are in good agreement with the recommended distribution coefficient for cesium and plutonium in sediments from IAEA (1985). They are strongly dependent on particle size and TOC content. The ^(137)Cs concentrations in seawater were not greatly changed with depth but the ^(239+240)Pu concentrations in seawater were increased with seawater depth because Pu exists predominantly Pu(VI) oxidation state in seawater, which has the heavy molecular mass.

자연 토양과 퇴적물의 Black Carbon에 대한 다환방향족탄화수소(PAHs)의 흡착 및 탈착 특성 : Sorption and Desorption Behaviors of Polycyclic Aromatic Hydrocarbon on

쳔민펑 경북대학교 대학원 2007 국내석사

Contaminant distribution is integral to environmental evaluations of contaminated sediments and soil on every level. Serious health concerns arise when polycyclic aromatic hydrocarbons (PAHs) are present as environmental pollutants due to their carcinogencity and mutagenicity. To fully assess sorption of hydrophobic organic compounds in natural soil and sediment system is still challenging despite the attention it has received over the years. In addition to the complexity of sediments or soils, several factors relevant to the role of black carbon in sorption of hydrophobic organic compounds in various environmental systems contribute to such difficulties. Note that for the purposes of this research, black carbon (BC) is defined as carbonaceous materials including soots, chars, charcoal, coke as well as coal and kerogen. The heterogeneity of black carbon, the diverse origins of black carbon as well as the lack of standardization in definition, identification, and analytical techniques are the factors contributing to difficulties in fully understanding sorption processes. A wet chemical oxidation method was used for isolation and quantification of BC. The various chemical-treatment steps of the BC isolation procedure have potential to impact on BC surface and adsorptive properties. Sorption and desorption characteristics of PAHs in black carbon isolated from natural soil and various lake-sediments were investigated. Black carbon show higher distribution coefficient than predicted based on dissolution of PAH in untreated soil and sediments. Lake sediment black carbon shows higher sorption capacity and more nonlinearity than original sediment on sorption isotherm; it is different form natural soil black carbon, natural soil black carbon shows smaller sorption capacity than untreated soil. It was the result of the difference on BET surface and organic carbon content. In terms of R2 values, MTCFOKM was the best fitting the data in both sorption and desorption kinetics. In addition, the Langmuir model was the best fitting the data in sorption isotherm. To characterize the difference of desorption-resistance in soil/sediment and black carbon, cyclic sorption/desorption studies were conducted. Effect of contact time on sorption isotherm of PAHs was investigated. The results indicated the sorption constant increased as the contact time increased, but the nonlinearity N decreased as the contact time increased. The increase in sorption was attributed to contact time. Effect of initial concentration on the sorption and desorption behaviors of PAHs was also investigated. Sorption and desorption constants were decreased as initial concentration increased. Effect of aging time on desorption kinetics on original soil/sediments and black carbon were also investigated. The desorption equilibrium concentration in solid phase, desorption constant and desorption resistance of PAHs increased consistently with the increasing aging time.

DISTRIBUTION OF PCDD/FS, PCBS, AND PCNS IN COASTAL SEDIMENTS COLLECTED FROM MAJOR INDUSTRIAL BAYS IN SOUTH KOREA

Ji-Young Son Graduate School of UNIST 2018 국내석사

Polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs), polychlorinated biphenyls (PCBs), and polychlorinated naphthalenes (PCNs) are persistent organic pollutants (POPs), and they are unintentionally emitted into the environment from incomplete combustion or thermal processes. Since the 1980s, productions and uses of technical mixture of PCBs and PCNs have been very popular such as transformer, insulators, paints, plasticizers, and capacitors. In particular, marine sediments are considered as the final sink of POPs. Those toxic compounds may enter the marine organisms and be accumulated in the human body through the food chain. So far, various researches on PCDD/Fs and PCBs in the sediments have been carried out in Korea; however, there have been only a few studies on PCNs in the sediments. Therefore, the aims of this study were to investigate the levels, patterns, spatial distributions, and to identify the major sources of PCDD/Fs, PCBs, and PCNs in bays located within or near the industrial areas in South Korea. In this study, the sediment samples were collected in Gwangyang, Jinhae, Busan, and Ulsan bays in March and April 2016. There were 16 sampling sites in the Gwangyang Bay (GY1-16), 20 sites in Jinhae Bay (JH1-20), 18 sites in the Busan Bay (BS1-18), and 15 sites in the Ulsan Bay (US1-15). The target compounds were 17 PCDD/Fs, 18 PCBs (dl-PCBs and indicator PCBs), and 15 PCNs (75 PCNs for 14 sediment samples). The sediment samples were extracted using accelerated solvent extraction system (ASE), and the extracts were purified by multilayer silica gel and alumina columns. PCDD/Fs, PCBs, and PCNs were analyzed using gas chromatography/high resolution mass spectrometry (GC/HRMS). The concentrations of PCDD/Fs, PCBs, PCNs in sediments ranged from 0.18 pg TEQ/g to 19.80 pg TEQ/g. The highest TEQ concentration was observed near the wastewater treatment plant in Jinhae Bay, which seemed to be due to the effluent discharge. The concentrations in this study were comparable or lower than those of other countries, and the levels of PCDD/Fs and PCBs were lower than those of the previous studies in Korea. The correlation analysis between TOC contents and concentrations of PCDD/Fs (R2=0.67, p<0.01), PCBs (R2=0.44, p<0.01), and PCNs (R2=0.45, p<0.01) indicated positive correlations. Generally, the concentrations in the inner part were higher than those in the outer part, which is due to the industrial complexes. Therefore, the concentrations of PCDD/Fs, PCBs, PCNs might be influenced by various industries. The concentrations of PCDD/Fs and PCBs have decreased compared with those obtained from the previous studies in Korea. However, this study has been the first comprehensive study for PCNs with high resolution monitoring in industrial bays. On the basis of this study, it could be possible to understand the spatial distributions and major sources of PCDD/Fs, PCBs, and PCNs in industrial bays.