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351.
Waska H Kim S Kim G Peterson RN Burnett WC 《Journal of environmental radioactivity》2008,99(12):1859-1862
A delayed coincidence counter (RaDeCC), developed to determine ultra-low levels of (223)Ra (half life = 11.1 days) and (224)Ra (half life = 3.6 days) in seawater, was adapted to measure (226)Ra (half life = 1622 years). After pre-concentration of Ra from seawater onto MnO(2)-coated fiber we show in this study that the (226)Ra activity can be determined using the RaDeCC's ability to record alpha decay of its daughters as total counts. For sufficient ingrowth of (222)Rn, the Mn-fiber is hermetically sealed in a column for a few days. Then, the ingrown (222)Rn is circulated through the RaDeCC air-loop system followed by shutting down of the pump and closure of the scintillation cell for equilibration. Counting may be completed within a few hours for seawater samples. Sample measurements with this method agreed well with data obtained using gamma-ray spectrometry. This proves that a set of Ra isotopes ((223)Ra, (224)Ra, and (226)Ra), commonly used for geophysical studies such as mixing rates of different water masses and submarine groundwater discharge, can be efficiently and rapidly measured using the RaDeCC. 相似文献
352.
Simulating mesoscale transport and diffusion of radioactive noble gases using the Lagrangian particle dispersion model 总被引:1,自引:0,他引:1
In order to simulate the impact of mesoscale wind fields and to assess potential capability of atmospheric Lagrangian particle dispersion model (LPDM) as an emergency response model for the decision supports, two different simulations of LPDM with the mesoscale prognostic model MM5 (Mesoscale Model ver. 5) were driven. The first simulation of radioactive noble gas ((85)Kr exponent) emitted during JCO accident occurred from 30 September to 3 October 1999 at Tokai, Japan showed that the first arriving short pulse was found in Tsukuba located at 60km away from the accidental area. However, the released radioactive noble gas was transported back to the origin site about 2 days later due to the mesoscale meteorological wind circulation, enhancing the levels of (85)Kr with the secondary peak in Tsukuba. The second simulation of atmospheric dilution factors (the ratio of concentration to the emission rate, chi/Q), during the underground nuclear test (UNT) performed by North Korea showed that high chi/Q moved to the eastward and extended toward southward in accordance with the mesoscale atmospheric circulations generated by mesoscale prognostic model MM5. In comparison with the measurements, the simulated horizontal distribution patterns of (85)Kr during the JCO are well accord with that of observation in Tsukuba such as the existence of secondary peak which is associated with the mesoscale circulations. However, the simulated level of (85)Kr anomaly was found to be significantly lower than the observations, and some interpretations on these discrepancies were described. Applications of LPDM to two mesoscale emergency response dispersion cases suggest the potential capability of LPDM to be used as a decision support model provided accurate emission rate of accident in case of a large accident. 相似文献
353.
People receive information about visiting places from a variety of sources, and it is important to understand how information
affects recreation experiences. This study examines how different information treatments describing a recreation place influence
perceived crowding and encounter norms. The study location was the Jungmoeri area of Mudeungsan Provincial Park (MPP) in Korea.
Data were collected from 50 college students utilizing a series of simulated moving pictures in a laboratory setting. Respondents
were given information describing three different types of conditions and experiences (nature preserve, transition/buffer,
and developed area), plus a no information control. Results showed that information influenced perceived crowding and encounter
norms. For the range of encounter numbers depicted in the photos, the nature preserve treatment produced higher crowding ratings
and lower tolerances for encounters, the developed area treatment produced lower crowding ratings and higher tolerances, and
the transition/buffer and the control were in between. Information treatments also influence the perceived importance of encounter
numbers, and importance was highest for the nature preserve. Management implications are discussed. 相似文献
354.
Sang-Won Park Sung-Kuk Kim Jeong-Bae Kim Sung-Woo Choi Hilary I. Inyang Shuzo Tokunaga 《Water, Air, & Soil Pollution: Focus》2006,6(1-2):97-110
Halogenated aliphatic compounds (HACs) can be reduced by iron sulfides in aqueous systems. Generally, the thermodynamics and
kinetics of dehalogenation reactions are controlled by the mineralogical and particle surface characteristics of the iron
sulfide, the composition of the HAC and reaction conditions such as component concentrations, pH and Eh. In this theoretical
and experimental investigation of CCl4 and C2Cl6 reduction by FeS and FeS2, the roles of hydrophobic and hydrophilic sites on the iron sulfides were analyzed. Experimental data obtained through zeta
potential measurements, were used along with the Gouy-Chapman model and the simple two-layer surface complexation model to
relate iron sulfide surface hydroxyl densities to the degree of HAC dehalogenation. The surface hydroxyl site densities of
FeS and FeS2 were found to be 0.11 sites/nm2 and 0.21 sites/nm2, respectively. During the dehalogenation reaction process, CCl4 was found to decrease to its first intermediate product CHCl3 within the first 20 hours followed by a slower process of conversion to CH2Cl2. The results also show that FeS is less hydrated (more hydrophobic) than FeS2. For CCl4 and C2Cl6, FeS is a better dehalogenator than FeS2. These results imply that particle surface hydrophobicity is a critical factor in surface-mediated dehalogenation of chlorinated
compounds. 相似文献
355.
Low-level liquid borate wastes have been immobilized with paraffin wax using a concentrate waste drying system (CWDS) in Korean nuclear power plants. The possibility for improving chemical durability of paraffin waste form was suggested in this study. A small amount of low density polyethylene (LDPE) was added to increase the leaching resistance of the existing paraffin waste form. The influence of LDPE on the leaching behavior of waste form was investigated by performing leaching test according to ANSI/ANS-16.1 procedure during 325 days. It was observed that the leaching of nuclides immobilized within paraffin waste form made a marked reduction although little content of LDPE was added to waste form. The acceptance criteria of paraffin waste form associated with leachability index (LI) and compressive strength after the leaching test were fully satisfied with the help of LDPE. 相似文献
356.
Kim N. Dirks Murray D. Johns John E. Hay Andrew P. Sturman 《Atmospheric environment (Oxford, England : 1994)》2002,36(39-40)
Carbon monoxide monitoring using continuous samplers is carried out in most major urban centres in the world and generally forms the basis for air quality assessments. Such assessments become less reliable as the proportion of data missing due to equipment failure and periods of calibration increases. This paper presents a semi-empirical model for the prediction of atmospheric carbon monoxide concentrations near roads for the purpose of interpolating missing data without the need for any traffic or emissions information. The model produces reliable predictions while remaining computationally simple by being site-specifically optimized. The model was developed for, and evaluated at, both a suburban site and an inner city site in Hamilton, New Zealand. Model performance statistics were found to be significantly better than other simple methods of interpolation with little additional computational complexity. 相似文献
357.
Allan Gomez-Flores Gukhwa Hwang Sadia Ilyas Hyunjung Kim 《Frontiers of Environmental Science & Engineering》2022,16(3):31
358.
Lwin Chaw Su Kim Young-Nam Lee Mina Kim Kwon-Rae 《Environmental science and pollution research international》2022,29(42):62807-62821
Environmental Science and Pollution Research - In anthropogenic soils, there have been relatively limited studies focusing on Cr and Ni contaminants because they exhibit less toxic effects to... 相似文献
359.
Kim Young-Nam Lee Keum-Ah Lee Mina Kim Kwon-Rae 《Environmental science and pollution research international》2022,29(58):87555-87567
Environmental Science and Pollution Research - Globally, various types of soil amendments have been used to improve the fertility and quality of soils in agricultural lands. In heavy metal(loid)... 相似文献
360.