Variability in Particle Mixing Rates in Sediments with Polymetallic Nodules in the Equatorial Eastern Pacific as Determined from Measurements of Excess <Superscript>210</Superscript>Pb     

Kiseong Hyeong  Inah Seo  Hyun-Bok Lee  Chan Min Yoo  Sang-Bum Chi  In Kwon Um 《Ocean Science Journal》2018,53(2):355-368

Radionuclide activities of ²¹⁰Pb and ²²⁶Ra were measured to determine bioturbation coefficients (D_b) in seven sediment cores from the Korean licensed block for polymetallic nodules in the Clarion–Clipperton Fracture Zone. Variability in D_b is considered in the context of the sedimentological, geochemical, and geotechnical properties of the sediments. D_b values in the studied cores were estimated using a steady-state diffusion model and varied over a wide range from 1.1 to 293 cm²/yr with corresponding mixing depths (L) of 26 to 144 cm. When excepting for spurious results obtained from cores where diffusive mixing does not apply, D_b values range from 1.1 to 9.0 cm²/yr with corresponding mixing depths (L) of 26 to 63 cm. Such wide variability in D_b and L values is exceptional in sites with water depths of ～5000 m and is attributed in this study to an uneven distribution of sediment layers with different shear strengths and total organic carbon (TOC) contents, caused by erosion events. The studied cores can be grouped into two categories based on lithologic associations: layers with high maximum shear strength (MSS) and low TOC content, showing a narrow range of D_b values (1.1–9.0 cm²/yr); and layers with low MSS and high TOC content, yielding much higher D_b values of over 30 cm²/yr. The distribution of different lithologies, and the resultant spatial variability in MSS and labile organic matter content, controls the presence and maximum burrowing depth of infauna by affecting their mobility and the availability of food. This study provides a unique case showing that shear strength, which relates to the degree of sediment consolidation, might be an important factor in controlling rates of bioturbation and sediment mixing depths.  相似文献   

Field applicability of self-recovering sustainable liner as landfill final cover   总被引：2，自引：1，他引：1  

Ohjung Kwon  Wanjei Cho 《Environmental Earth Sciences》2011,62(8):1567-1576

Preventing the penetration of rainwater into a landfill site is the main purpose of the final cover in landfill sites. Conventional designs of landfill covers use geotextiles, such as geomembrane and geosynthetic clay liners, and clay liners to lower the permeability of the final cover of landfill sites. However, differential settlement and climatic effects in landfill sites instigate crack development or structural damage inside the final cover. This study therefore investigates the field applicability of a self-recovering sustainable liner (SRSL) as an alternative to the landfill final cover. The SRSL utilizes the precipitation reaction of two chemical materials to form precipitates that fill the pores and thereby lower the overall permeability of the liner. To examine the field applicability of the SRSL system, uniaxial compression tests and laboratory hydraulic conductivity tests were performed under various climatic effects such as wet/dry and freeze/thaw processes. Furthermore, field-scale hydraulic conductivity tests were performed with intentionally induced cracks to demonstrate the self-recovery performance for practical applications. Extensive laboratory and field test results confirmed the capability of the SRSL final cover system to fulfill the strength and hydraulic conductivity requirements, even in harsh field conditions.  相似文献   

Classification of precipitation types using fall velocity-diameter relationships from 2D-video distrometer measurements     

Jeong-Eun Lee  Sung-Hwa Jung  Hong-Mok Park  Soohyun Kwon  Pay-Liam Lin  GyuWon Lee 《大气科学进展》2015,32(9):1277-1290

Fall velocity-diameter relationships for four different snowflake types (dendrite, plate, needle, and graupel) were investigated in northeastern South Korea, and a new algorithm for classifying hydrometeors is proposed for distrometric measurements based on the new relationships. Falling ice crystals (approximately 40 000 particles) were measured with a two-dimensional video disdrometer (2DVD) during a winter experiment from 15 January to 9 April 2010. The fall velocity-diameter relationships were derived for the four types of snowflakes based on manual classification by experts using snow photos and 2DVD measurements: the coefficients (exponents) for different snowflake types were 0.82 (0.24) for dendrite, 0.74 (0.35) for plate, 1.03 (0.71) for needle, and 1.30 (0.94) for graupel, respectively. These new relationships established in the present study (PS) were compared with those from two previous studies. Hydrometeor types were classified with the derived fall velocity-diameter relationships, and the classification algorithm was evaluated using 3× 3 contingency tables for one rain-snow transition event and three snowfall events. The algorithm showed good performance for the transition event: the critical success indices (CSIs) were 0.89, 0.61 and 0.71 for snow, wet-snow and rain, respectively. For snow events, the algorithm performance for dendrite and plate (CSIs = 1.0 and 1.0, respectively) was better than for needle and graupel (CSIs = 0.67 and 0.50, respectively).  相似文献   

Bathymetry enhancement by altimetry-derived gravity anomalies in the East Sea (Sea of Japan)   总被引：1，自引：0，他引：1  

Kwang Bae Kim  Yu-Shen Hsiao  Jeong Woo Kim  Bang Yong Lee  Yi Kyun Kwon  Chang Hwan Kim 《Marine Geophysical Researches》2010,31(4):285-298

The gravity-geologic method (GGM) was used to enhance the bathymetry of the East Sea (Sea of Japan) with satellite altimetry-derived free-air gravity anomalies and shipborne depth measurements. By comparison with the bathymetry model of Smith and Sandwell’s (SAS) approach (1994), GGM was found to have an advantage with short wavelength (≤12 km) components, while SAS better predicts longer wavelength (≥25 km) components, despite its dependency on density contrast. To mitigate this limitation, a tuning density contrast of 10.25 g/cm³ between seawater and the seafloor was primarily estimated by the downward continuation method and then validated by the check points method with GGM. Similarly, SAS is limited by the “A” value in low-pass part of the Wiener filter, which defines the effective range of the wavelength components on bathymetry. As a final result, we present an enhanced GGM bathymetry model by integrating all available data.  相似文献   

Some statistical characteristics of large deepwater waves around the Korean Peninsula     

Kyung-Duck Suh  Hyuk-Dong Kwon  Dong-Young Lee 《Coastal Engineering》2010

The relationship between significant wave height and period, the variability of significant wave period, the spectral peak enhancement factor, and the directional spreading parameter of large deepwater waves around the Korean Peninsula have been investigated using various sources of wave measurement and hindcasting data. For very large waves comparable to design waves, it is recommended to use the average value of the empirical formulas proposed by Shore Protection Manual in 1977 and by Goda in 2003 for the relationship between significant wave height and period. The standard deviation of significant wave periods non-dimensionalized with respect to the mean value for a certain significant wave height varies between 0.04 and 0.21 with a typical value of 0.1 depending upon different regions and different ranges of significant wave heights. The probability density function of the peak enhancement factor is expressed as a lognormal distribution, with its mean value of 2.14, which is somewhat smaller than the value in the North Sea. For relatively large waves, the probability density function of the directional spreading parameter at peak frequency is also expressed as a lognormal distribution.  相似文献   

First retrieval of data regarding spatial distribution of Asian dust aerosol from the Geostationary Ocean Color Imager     

Kwon Ho Lee  Joo Hyung Ryu  Jae Hyun Ahn  Young Joon Kim 《Ocean Science Journal》2012,47(4):465-472

Aerosol optical thickness (AOT) was retrieved from the Geostationary Ocean Color Imager (GOCI) on board the Communication, Ocean, and Meteorological Satellite (COMS) for the first time. AOT values were retrieved over the ocean at a spatial scale of 0.5 × 0.5 km² by using the look-up table (LUT)-based separation technique. The radiative transfer model (RTM) was used for different models of atmosphere-ocean environmental conditions, taking into account the realistic variability of scattering and absorption. Ocean surface properties affected by whitecaps and pigment content were also taken into account. The results show that the radiance observed by the GOCI amounts to only 5% of the radiation that penetrated the ocean and, consequently, 95% of the radiation is scattered in the atmosphere or reflected at the ocean surface in the visible wavelengths longer than 0.6 ìm. Within these wavelengths, radiance variations at the top of atmosphere (TOA) due to pigment variations are within 10%, while the radiance variation due to wind speed is considerably higher. For verification of GOCI-retrieved AOTs, comparison between GOCI and ground-based sunphotometer measurement at Gosan, Korea (126.10°E, 33.23°N)) showed good correlation (r = 0.99). The GOCI observations obtained by using the proposed technique showed promising results for the daily monitoring of atmospheric aerosol loading as well as being useful for environmental supervisory authorities.  相似文献   

Fugacity analysis of polycyclic aromatic hydrocarbons between microplastics and seawater     

Hwang Lee  Sein Chang  Seung-Kyu Kim  Jung-Hwan Kwon 《Ocean Science Journal》2017,52(1):43-55

Recently, the accumulation of plastic debris in the marine environment has become a great concern worldwide. Although plastics are biologically and chemically inert, plastic debris has been suspected of causing adverse effects on ecosystems due to the increase in reactivity by size reduction and/or micropollutants associated with plastics. Because of the high sorption capacity of microplastics toward organic micropollutants, it is suspected that microplastics may play roles in the distribution and fate of micropollutants. In order to quantitatively evaluate the “net flow” of environmental contaminants in water-plastic-organism systems, a fugacity analysis was conducted using concentrations of polycyclic aromatic hydrocarbons (PAHs) in open oceans and in polyethylene as a representative material of plastic debris. Ratio of fugacity in polyethylene to that in seawater showed a decreasing trend with increasing partition coefficient between polyethylene and seawater (K_PE/sw). This indicates that phase equilibrium between polyethylene and seawater is not attained for higher molecular weight PAHs. Disequilibrium of high molecular weight PAHs suggests that transfer from seawater to plastic debris is thermodynamically driven and the role of plastic debris as a vector to transfer them to living organisms would be minimal. However, additives may slowly migrate from plastics into the environment causing potentially serious effects on ecosystems.  相似文献   

Constructing rainfall depth-frequency curves considering a linear trend in rainfall observations     

Lynn Seo  Tae-Woong Kim  Minha Choi  Hyun-Han Kwon 《Stochastic Environmental Research and Risk Assessment (SERRA)》2012,26(3):419-427

Comprehensive flood prevention plans are established in large basins to cope with recent abnormal floods in South Korea. In order to make economically effective plans, appropriate design rainfalls are critically determined from the rainfall depth-frequency curves which take the occurrence of abnormal floods into consideration. Conventional approaches to construct the rainfall depth-frequency curves are based on the stationarity assumption. However, this assumption has a critical weak aspect in that it cannot reflect non-stationarities in rainfall observations. As an alternative, this study suggests the non-stationary Gumbel model (NSGM) which incorporates a linear trend of rainfall observations into rainfall frequency analysis to construct the rainfall depth-frequency curves. A comparison of various schemes employed in the model found that the proposed NSGM permits the estimation of the distribution parameters even when shifted in the future by using linear relationships between rainfall statistics and distribution parameters, and produces more acceptable estimates of design rainfalls in the future than the conventional model. The NSGM was applied at several stations in South Korea and then expected the design rainfalls to increase by up to 15–30% in 2050.  相似文献   

Derivative‐Assisted Classification of Fractured Zones Crossing a Deep Borehole     

Sung‐Hoon Ji  Dae Hyoung Lee  In Wook Yeo  Kyoung‐Woo Park  Yong‐Kwon Koh 《Ground water》2014,52(1):145-155

In this study, the derivative analysis using the derivative of drawdown with respect to log‐time was utilized to determine candidates for hydraulic conductor domains (HCDs). At a 500‐m deep borehole in the study site, the fractured rocks crossing the borehole were first classified in fractured and nonfractured zones by core logging and geophysical loggings, such as acoustic televiewing, density, and flow loggings. After conducting the hydraulic tests such as constant head withdrawal and recovery tests at the fractured zones and the nonfractured zones, the derivative analyses were carried out, of which the results were evaluated to determine the candidates for HCDs. For the nonfractured zones, the diagnostic plot has only a big hump indicating poor connection of the background fractures to the permeable geologic media, while those of the candidates for HCDs show various flow regimes. On the basis of these results, the candidates for HCDs among the fractured zones were determined. From discussion on the results, the combination of the spacing analysis and derivative analysis following a hydraulic test is recommended for determining the candidates for HCDs rather than other geophysical loggings.  相似文献   

Understanding of the Common Land Model performance for water and energy fluxes in a farmland during the growing season in Korea   总被引：1，自引：0，他引：1  

Minha Choi  Seung Oh Lee  Hyojung Kwon 《水文研究》2010,24(8):1063-1071

The Common Land Model (CLM) is one of the most widely used land surface models (LSMs) due to the practicality of its simple parameterization scheme and its versatility in embracing a variety of field datasets. The improved assessment of land surface water and energy fluxes using CLM can be an alternative approach for understanding the complex land–atmosphere interactions in data‐limited regions. The understanding of water and energy cycles in a farmland is crucial because it is a dominant land feature in Korea and Asia. However, the applications of CLM to farmland in Korea are in paucity. The simulations of water and energy fluxes by CLM were conducted against those from the tower‐based measurements during the growing season of 2006 at the Haenam site (a farmland site) in Korea without optimization. According to the International Geosphere–Biosphere Programme (IGBP) land cover classification, a homogeneous cropland was selected initially for this study. Although the simulated soil moisture had a similar pattern to that of the observed, the former was relatively drier (at 0·1 m³ m^?3) than the latter. The simulated net radiation showed good agreement with the observed, with a root mean squared error (RMSE) of 41 W m^?2, whereas relatively large discrepancies between the simulation and observation were found in sensible (RMSE of 66 W m^?2) and latent (RMSE of 60 W m^?2) heat fluxes. On the basis of the sensitivity analysis, soil moisture was more receptive to land cover and soil texture parameterizations when compared to soil temperature and turbulent fluxes. Despite the uncertainty in the predictive capability of CLM employed without optimization, the initial performance of CLM suggests usefulness in a data‐limited heterogeneous farmland in Korea. Further studies are required to identify the controls on water and energy fluxes with an improved parameterization. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献