The effect of weathering on optically stimulated luminescence dating   总被引：2，自引：0，他引：2  

Gi Young Jeong  Chang-Sik Cheong  Jeong-Heon Choi 《Quaternary Geochronology》2007,2(1-4):117-122

Optically stimulated luminescence (OSL) dating was applied to quartz samples recovered from the gravel sediments of deformed marine terrace at the Suryum site, southeastern Korea, but has yielded stratigraphically inconsistent ages. Micromorphological, chemical, and mineralogical analyses of the gravels indicate the possible influence of chemical weathering on the apparent OSL ages. In the course of weathering after emerging from beach environments, originally permeable gravels underwent infilling by halloysite-rich clays in their voids, export and import of radioactive elements, and loss of mechanical strength with the creation of a porosity within pebbles. Calculation based on the evolution of the weathering profile showed a severe fluctuation of dose rate caused by the change of water content and radioactive element concentrations. Samples recovered from the weathering profile inevitably include quartz grains derived from mechanically weakened pebbles or illuviated from the upper layer, making it difficult to determine the equivalent dose (D_e) values of exclusively depositional quartz sands. Quantitative evaluation of the change of fabric and chemistry of the sediments on the basis of pedologic insight significantly aids in the derivation of OSL ages consistent with geomorphology and other independent age controls.  相似文献   

Screening of extraction methods for Cd and As bioavailability prediction in rhizospheric soil using multivariate analyses     

Sung-Chul Kim  Jae E. Yang  Dong-Kuk Kim  Young-Wook Cheong  Jeffrey Skousen  Yeong-Sang Jung 《Environmental Earth Sciences》2012,66(1):327-335

Heavy metals in tailings and mining wastes from abandoned mines can be released into adjacent agricultural field and bioaccumulated in crops or vegetables. Therefore, prediction of metal bioavailability has become an important issue to prevent adverse effect of bioaccumulated metals on human health. In this study, single and sequential extraction methods were compared using multivariate analysis to predict the bioavailability of Cd and As in contaminated rhizosphere soils. Single extraction using 0.1 M HCl for Cd and 1.0 M HCl for As had an extraction efficiency of 8–12% for soil Cd and 14–17% for soil As compared to total concentration extracted with aqua regia. Using sequential extraction, Fe–Mn-bound Cd (FR3) and residual Cd (FR5) were the dominant fractions representing 43 and 41% of total Cd concentration. For As, the strongly absorbed form (FR2) was the most abundant chemical fraction showing 45–54% of the total As concentration in soil. Multivariate analyses showed that single extraction with HCl and total concentration of Cd and As in soil were significantly correlated to potato and green onion plant tissue metal concentration. Although little information was obtained with multiple regression analysis because of multicollinearity of variables, the result of principle component analysis (PCA) revealed that the highest positive loading was obtained using total concentration of Cd and As in soil in the first principle component (PC1). In addition, total concentration of Cd and As in soil was independently grouped with other chemical fractions by cluster analysis. Therefore, the overall result of this research indicated that total concentrations of Cd and As in rhizosphere soils were the best predictors of bioavailability of heavy metals in these contaminated soils.  相似文献   

Policy solutions in the U.S.     

So-Min Cheong 《Climatic change》2011,106(1):57-70

The paper focuses on relocation, retreat, zoning, insurance, and subsidy as major dimensions of coastal hazard mitigation measures that have resurfaced as potent forces for combating coastal inundation and climate change. It reviews the issues surrounding the practice of these measures and discusses compatibilities of policies, engineering measures, and natural defense. Property rights, development interest, and distorted financial incentives pose as main barriers to coastal relocation and retreat policies in hazard-prone areas. To understand and propose coastal adaptation solutions, the paper recommends place-based studies of local coastal adaptation strategies. Place-based studies offer an in-depth knowledge of local conditions specifically regarding the level of implementation of hazard mitigation policies, and shed light on important trade-offs and synergies of various hazard policies. In addition, coupling existing hazard mitigation policies with coastal management and community management can better inform long-term and comprehensive planning of coastal adaptation.  相似文献   

Simultaneous stabilization of arsenic, lead, and copper in contaminated soil using mixed waste resources   总被引：1，自引：0，他引：1  

Keun-Young Lee  Deok Hyun Moon  Sang-Ho Lee  Kyoung-Woong Kim  Kyung-Hoon Cheong  Jeong-Hun Park  Yong Sik Ok  Yoon-Young Chang 《Environmental Earth Sciences》2013,69(6):1813-1820

In the present study, stabilization treatment using waste resource stabilizers was performed for soil contaminated with As and heavy metals (Pb and Cu). Calcined oyster shell (COS) and coal mine drainage sludge (CMDS) were used as a mixed stabilizing agent for a wet-curing duration of 28 days. After the stabilization treatment, the treatment process efficiency was evaluated by the results of various batch- and column-leaching tests. Neutral and weak acid extraction methods, such as water-soluble extraction and SPLP, did not exhibit satisfactory results for heavy metal stabilization, even if they showed very low leachability. On the other hand, TCLP and 0.1 M HCl extraction showed that the stabilizers significantly reduced the amount of heavy metals leached from the soil, which strongly supports the thesis that the stabilization treatment is efficient in the acidic leaching conditions that were explored. Specifically, in the 0.1 M HCl extraction, the reduction efficiencies of As, Pb, and Cu leachings were more than 90 %, compared with control experiments. This study demonstrates that the application of waste resources for the stabilization of As and heavy metals is feasible. However, some limitations observed in the experiments should be considered in future studies, such as the mobilization of alkali-soluble elements, and in particular, exchangeable fractions of Cu. In addition, the treatment efficiency can be evaluated by different leaching methods, which suggests that multidirectional approaches are required for the proper evaluation of stabilization treatment.  相似文献   

A three-dimensional multi-level turbulence model for tidal motion     

Xiaobo Chao  N. J. Shankar  Cheong Hin Fatt 《Ocean Engineering》1999,26(11):338

A three-dimensional multi-level turbulence model is developed to simulate tide induced circulation in coastal waters. Based on the bathymetry data, the coastal waters are divided into a number of layers. In every layer, the velocities are integrated along the layer depth. The eddy viscosity and diffusivity are computed from the Prandtl mixing length turbulence model. This multi-level model solves for the water surface elevations and currents in different water depths. Comparison of numerical results with the measured data shows good conformity.  相似文献   

Multilevel finite-difference model for three-dimensional hydrodynamic circulation     

N.J. Shankar  H.F. Cheong  S. Sankaranarayanan 《Ocean Engineering》1997,24(9):785-816

A three-dimensional finite-difference multilevel hydrodynamic model is developed using an explicit scheme on a staggered grid. The model has been tested against four cases, namely (i) wind-induced circulation (ii) density-driven circulation (iii) seiche oscillation in a closed basin and (iv) tide-induced circulation in a open channel. The results obtained in the present study compare well with those obtained from the corresponding analytical solutions under idealised conditions for the above four cases. The model was also tested against the case of circulation induced by wind and Coriolis force and the results obtained are compared with the results of Davies and Owen (1979).  相似文献   

Electrical interferences observed in the Cassini CIRS spectrometer     

Cheong Chan  Shane Albright  Nicolas Gorius  John Brasunas  Don Jennings  F. Michael Flasar  Ronald Carlson  Ever Guandique  Conor Nixon 《Experimental Astronomy》2015,39(2):367-386

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Characteristics of tailings from the closed metal mines as potential contamination source in South Korea   总被引：4，自引：0，他引：4  

Kwang-Koo Kim  Kyoung-Woong Kim  Ju-Yong Kim  In S. Kim  Young-Wook Cheong  Jeong-Sik Min 《Environmental Geology》2001,41(3-4):358-364

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Sr, Nd and Pb Isotopic Systematics of the Cenozoic Basalts of the Korean Peninsula and Their Implications for the Permo-Triassic Continental Collision Boundary     

Kye-Hun Park  Jun-Beom Park  Chang-Sik Cheong  Chang Whan Oh 《Gondwana Research》2005,8(4):529-538

Sr, Nd and Pb isotopic compositions of the Cenozoic basalts were analyzed from Baengnyeongdo Island, Jeongok, Ganseong, and Jejudo Island of Korea. They reveal relatively enriched Sr and Nd isotopic compositions (⁸⁷Sr/⁸⁶Sr = 0.703300.70555, ¹⁴³Nd/¹⁴⁴Nd = 0.512980.51256) compared with MORB.²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb values of all the analyzed Korean basalts lie above the Northern Hemisphere Reference Line (NHRL) defined by Hart (1984). Pb isotopic compositions of basalts from Jejudo Islands (²⁰⁶Pb/²⁰⁴Pb = 18.6119.12, ²⁰⁷Pb/²⁰⁴Pb = 15.5415.69, ²⁰⁸Pb/²⁰⁴Pb = 38.9839.72) are significantly more radiogenic than the rest (²⁰⁶Pb/²⁰⁴Pb = 17.7218.03, ²⁰⁷Pb/²⁰⁴Pb = 15.4415.58, ²⁰⁸Pb/²⁰⁴Pb = 37.7738.64). The Cenozoic Korean basalts thus can be divided into two groups based on their Sr, Nd and Pb isotopic compositions. The north group reveals mixing between DMM and EM1 while the south group displays DMM-EM2 mixing. Such a distribution is the same as Chinese Cenozoic basalts and it can be interpreted that the subcontinental lithospheric mantle under Korea represents simple lateral continuation of the South and North China Blocks. We suggest that Korean continental collision zone cross the Korean Peninsula through the region between the north and south basalt groups of Korea.  相似文献   

Geochemical and Sr–Nd–Pb isotopic investigation of Triassic granitoids and basement rocks in the northern Gyeongsang Basin, Korea: Implications for the young basement in the East Asian continental margin     

Chang-Sik Cheong  Sung-Tack Kwon  Hee Sagong 《Island Arc》2002,11(1):25-44

Abstract We present chemical and Sr–Nd–Pb isotopic compositions of three Triassic (226–241 Ma) calc‐alkaline granitoids (the Yeongdeok granite, Yeonghae diorite and Cheongsong granodiorite) and basement rocks in the northern Gyeongsang basin, south‐eastern Korea. These plutons exhibit typical geochemical characteristics of I‐type granitoids generated in a continental magmatic arc. The Yeongdeok and Yeonghae plutons have similar initial Sr, Nd and Pb isotope ratios (⁸⁷Sr/⁸⁶Sr_initial = 0.7041 ~ 0.7050, ?_Nd(t) = 2.3 ~ 4.0, ²⁰⁶Pb/²⁰⁴Pb_feldspar = 18.22 ~ 18.34), but distinct rare earth element patterns, suggesting that the two plutons formed from partial melting of a similar source material at different depths. The Cheongsong pluton has slightly more enriched Sr–Nd–Pb isotopic compositions (⁸⁷Sr/⁸⁶Sr_initial = 0.7047 ~ 0.7065, ?_Nd(t) = 3.9 ~ 2.8, ²⁰⁶Pb/²⁰⁴Pb_feldspar = 18.24 ~ 18.37) than the other two plutons. The Nd model ages of the basement rocks (1.1 ~ 1.4 Ga) are slightly older than those of the plutons (0.6 ~ 1.0 Ga). The initial Sr and Nd isotopic ratios of the plutons can be modeled by the mixing between the mid‐oceanic ridge basalt‐like depleted mantle component and the crustal component represented by basement rocks, which is also supported by Pb isotope data. The Sr and Nd isotope data from granitoids and basement rocks suggest that the Gyeongsang basin, the Hida belt and the inner zone of south‐western Japan share relatively young basement histories (middle Proterozoic), compared with those (early Proterozoic to Archean) of the Gyeonggi and Yeongnam massifs and the Okcheon belt. The Nd isotope data of basement rocks suggest that the Hida belt might be better correlated with the basement of the Gyeongsang basin than the Gyeonggi massif, the Okcheon belt or the Yeongnam massif, although it may represent an older continental margin of East Asia than the Gyeongsang basin considering its slightly older Nd model ages.  相似文献