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Three study areas of Kwanak campus (Seoul National University), Boeun (Choongbuk) and Gapyung (Kyonggi) were selected and classified according to their bedrock types in order to investigate soil–gas radon concentrations. The mean values of radon concentrations decreased in the order of Gapyung (40BqL–1) > Kwanak campus (30BqL–1) > Boeun (22BqL–1), and decreased in the order of granite gneiss > banded gneiss > granite > black slate–shale > mica schist > shale–limestone > phyllite schist according to bed rock types. Variation in radon emanation with water content in soils and with soil grain size was assessed by the modified Morse (1976) 3min method. Soil–gas radon concentrations increased with increasing water content in the range of less than about 6–16wt.%, but decreased above 6–16wt.%. Radon concentrations also increased with decreasing soil grain size. Radioactivity analysis of radionuclides of 238U series in some soil samples indicated their possible radioactive disequilibrium between 226Ra and 238U due to the differing geochemical behaviour of intermediate radionuclides. Thus, a radioactive isotope geochemical approach should be necessary for soil–gas radon study. 相似文献
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Pascale M. Biron Thomas Buffin-Bélanger Marie Larocque Guénolé Choné Claude-André Cloutier Marie-Audray Ouellet Sylvio Demers Taylor Olsen Claude Desjarlais Joanna Eyquem 《Environmental management》2014,54(5):1056-1073
River systems are increasingly under stress and pressure from agriculture and urbanization in riparian zones, resulting in frequent engineering interventions such as bank stabilization or flood protection. This study provides guidelines for a more sustainable approach to river management based on hydrogeomorphology concepts applied to three contrasted rivers in Quebec (Canada). Mobility and flooding spaces are determined for the three rivers, and three levels of “freedom space” are subsequently defined based on the combination of the two spaces. The first level of freedom space includes very frequently flooded and highly mobile zones over the next 50 years, as well as riparian wetlands. It provides the minimum space for both fluvial and ecological functionality of the river system. On average for the three studied sites, this minimum space was approximately 1.7 times the channel width, but this minimum space corresponds to a highly variable width which must be determined from a thorough hydrogeomorphic assessment and cannot be predicted using a representative average. The second level includes space for floods of larger magnitude and provides for meanders to migrate freely over a longer time period. The last level of freedom space represents exceptional flood zones. We propose the freedom space concept to be implemented in current river management legislation because it promotes a sustainable way to manage river systems, and it increases their resilience to climate and land use changes in comparison with traditional river management approaches which are based on frequent and spatially restricted interventions. 相似文献
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Indigenous bacteria that are resistant to high concentrations of Cr(VI) were isolated from a Cr-contaminated sediment. Sand
column experiments were conducted using the isolated bacteria to investigate microbial effects on Cr(VI) reduction in open
systems that simulated subsurface conditions. The indigenous Cr-resistant bacteria appeared to reduce Cr(VI) in the column
experiments. When 12 mg/L of Cr(VI) was injected into the columns, the removal efficiencies of Cr(VI) by the isolated bacteria
were 39.1%, 62.5%, and 63.6% at 24, 48, and 72 h retention times of Cr(VI) solution, respectively. These results imply that
the linear velocity of groundwater or pore water should be less than 0.63 cm/h for effective removal of Cr(VI) in subsurface
conditions. In comparison, the noninoculated control column did not show a significant variation in dissolved Cr(VI) concentration.
The results indicated that reduction of Cr(VI) was occurring in the column due to the activity of the indigenous bacteria. 相似文献
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Foreword
Foreword 相似文献40.
Bottom sediments of harbors in the South Korea have been long suspected for metal contamination due to ship-based and urban-based activities for the past several decades. A number of areas have been suspected to impair ecosystem services to the local residents and drawn complaints from main stakeholders. Twelve contamination suspected harbors were subject to evaluate the level of contamination of Cr, Ni, Cu, Zn, As, Cd, Pb and Hg. The level of sediment contamination for each metal was evaluated comparing the relative enrichment of a given metal to pollution-insensitive aluminum. Regional background concentration of a given metal was also determined based on its down core measurement and sediment texture. Ecological risk posed by the presence of heavy metals was evaluated using the sediment quality guidelines (SQGs) developed by United States National Ocean and Atmosphere Administration (US NOAA) as benchmarks for evaluating sediment chemistry to aquatic organisms. Cu, Zn, Cd, Pb and Hg in the surface sediment were found to be higher than a factor of 1.5 than background sediments, and the overall metal contaminations of surface sediment can be regarded as medium-high- to high-priority sites in the sense of SQGs. 相似文献