排序方式: 共有41条查询结果,搜索用时 15 毫秒
21.
We describe the oldest tracks of web-footed birds from the Early Cretaceous in South Korea. The tracks are characterized
by a wide divarication angle and a long reversed hallux. The web is semipalmate and restricted to the proximal portion of
the three forward digits. The tracks from the Early Cretaceous in South Korea are smaller than those of the Late Cretaceous,
therefore confirming the trend of size increasing in the early evolution of birds as shown by skeletal fossils. The discovery
of web-footed tracks with abundant non-web-footed tracks indicates that there was a considerable diversification of shore
birds as early as the Early Cretaceous.
Received: 4 November 1999 / Accepted in revised form: 28 February 2000 相似文献
22.
Kim KH Baek SO Choi YJ Sunwoo Y Jeon EC Hong JH 《Environmental monitoring and assessment》2006,118(1-3):407-422
In this study, concentrations of major aromatic VOCs were determined from landfill gas (LFG) at a total of five municipal
landfill sites in Korea including Nan Ji (NJ), Woon Jung (WJ), Sam Poong (SP), Hoei Chun (HC), and No Hyung (NH). The concentration
levels of those VOC were found to be significantly different, mainly as a function of such a parameter as landfill aging.
The VOC concentrations measured from the unclosed landfill sites (e.g., WJ) were characterized by exceedingly high values
above a few tens of ppm. However, the results of the abandoned site (e.g., SP) were about three orders of magnitude lower
than the others so as to merely exceed the typical ambient concentration levels. It was most striking to find a systematic
dominance of toluene over other aromatic VOC under most circumstances. The LFG flux values of all aromatic VOC and the four
specific major ones (termed as BTEX: benzene, toluene, ethylbenzene, and xylene) were also computed for each vent pipe from
all study sites using their concentrations and the concurrently determined environmental parameters. The results, if calculated
in terms of the average BTEX quantity emitted per vent pipe, showed that the magnitude of their emissions can vary substantially,
with the values ranging from 0.05 (SP) to 49.2 kg yr−1 (WJ in wintertime). The LFG flux values of aromatic VOC, when compared to the contribution of non-methane hydrocarbons (NMHC),
were able to explain a constant, but minor, proportion of the LFG carbon budget. 相似文献
23.
Polybrominated diphenyl ethers in blood from Korean incinerator workers and general population 总被引:1,自引:0,他引:1
This study was conducted to examine PBDE exposure in Koreans, with a special focus on incinerator workers due to their potential for occupational exposure to PBDEs. A total of 92 blood samples from 30 incinerator workers, 51 nearby residents and 11 controls were analyzed. The mean total PBDE concentration calculated from the 13 most concentrated congeners for all samples was 16.84+/-7.48 ng/g lipid, which was somewhat higher concentration than in other countries except North America and Canada. The PBDE levels and congener profiles detected in incinerator workers were not distinctly different from those found in the general population. In all groups tested, BDE-47 was dominant (mean contribution=32.5%) followed by BDE-153 (23.6%) and relatively high portions of BDE-183 (16.5%) were found. No strong trend was observed between PBDE levels and a number of key biological factors examined in this study, however, weak correlations were observed in PBDE levels measured against dietary habits, particularly in fish consumption frequency and gender. Overall, our data suggest that the occupational exposure of incinerator workers to PBDEs can be considered minor, while other lifestyle factors can have a greater contribution to PBDE exposure. 相似文献
24.
Removal of As(III) and As(V) using iron-rich sludge produced from coal mine drainage treatment plant
Jung-Seok Yang Young-Soo Kim Sang-Min Park Kitae Baek 《Environmental science and pollution research international》2014,21(18):10878-10889
To test the feasibility of the reuse of iron-rich sludge (IRS) produced from a coal mine drainage treatment plant for removing As(III) and As(V) from aqueous solutions, we investigated various parameters, such as contact time, pH, initial As concentration, and competing ions, based on the IRS characterization. The IRS consisted of goethite and calcite, and had large surface area and small particles. According to energy dispersive X-ray spectroscopy mapping results, As was mainly removed by adsorption onto iron oxides. The adsorption kinetic studies showed that nearly 70 % adsorption of As was achieved within 1 h, and the pseudo-second-order model well explained As sorption on the IRS. The adsorption isotherm results agreed with the Freundlich isotherm model, and the maximum adsorption capacities for As(III) and As(V) were 66.9 and 21.5 mg/g, respectively, at 293 K. In addition, the adsorption showed the endothermic character. At high pH or in the presence of phosphate, the adsorption of As was decreased. When the desorption experiment was conducted to reuse the IRS, 85 % As was desorbed with 1.0 N NaOH. In the column experiment, adsorbed As in real acid mine drainage was 43 % of the maximum adsorbed amount of As in the batch test. These results suggested that the IRS is an effective adsorbent for As and can be effectively applied for the removal of As in water and wastewater. 相似文献
25.
Described here is a sauropod tooth from the Early Cretaceous of South Korea, similar to Brachiosaurus. The crown of the tooth is beveled off lingually so that when worn it presents a chisel-like edge. This find confirms the presence of a brachiosaurid in East Asia during the Early Cretaceous. 相似文献
26.
Environmental assessment on electrokinetic remediation of multimetal-contaminated site: a case study 总被引:1,自引:0,他引:1
Do-Hyung Kim Jong-Chan Yoo Bo-Ram Hwang Jung-Seok Yang Kitae Baek 《Environmental science and pollution research international》2014,21(10):6751-6758
In this study, an environmental assessment on an electrokinetic (EK) system for the remediation of a multimetal-contaminated real site was conducted using a green and sustainable remediation (GSR) tool. The entire EK process was classified into major four phases consisting of remedial investigations (RIs), remedial action construction (RAC), remedial action operation (RAO), and long-term monitoring (LTM) for environmental assessment. The environmental footprints, including greenhouse gas (GHG) emissions, total energy used, air emissions of criteria pollutants, such as NOx, SOx, and PM10, and water consumption, were calculated, and the relative contribution in each phase was analyzed in the environmental assessment. In the RAC phase, the relative contribution of the GHG emissions, total energy used, and PM10 emissions were 77.3, 67.6, and 70.4 %, respectively, which were higher than those of the other phases because the material consumption and equipment used for system construction were high. In the RAO phase, the relative contributions of water consumption and NOx and SOx emissions were 94.7, 85.2, and 91.0 %, respectively, which were higher than those of the other phases, because the water and electricity consumption required for system operation was high. In the RIs and LTM phases, the environmental footprints were negligible because the material and energy consumption was less. In conclusion, the consumable materials and electrical energy consumption might be very important for GSR in the EK remediation process, because the production of consumable materials and electrical energy consumption highly affects the GHG emissions, total energy used, and air emissions such as NOx and SOx. 相似文献
27.
Optimizing Agricultural Best Management Practices in a Lake Erie Watershed 总被引:1,自引:0,他引:1 下载免费PDF全文
Jongcheol Pyo Sang‐Soo Baek Minjeong Kim Sanghun Park Hyuk Lee Jin‐Sung Ra Kyung Hwa Cho 《Journal of the American Water Resources Association》2017,53(6):1281-1292
Implementing agricultural best management practices (BMPs) is influenced by a balance of desired environmental outcomes, economic feasibility, and stakeholder familiarity, the latter taken to be related to BMP acceptability. To explore this balance, we developed a multi‐objective decision support system for allocating BMP type and placement by coupling the Soil and Water Assessment Tool with a nondominated sorted genetic algorithm that minimizes total phosphorus (TP) yields from agricultural hydrologic response units (HRUs) and costs, while using stakeholder BMP familiarity as a constraint; conventional tillage, no tillage, nutrient management, riparian buffers, and contour cropping were explored. Using constraints representing current conditions, the optimization resulted in 59.6 to 81.0% reduction in agricultural TP yield from HRUs at costs ranging between US $0.8 and US $5.3 million. The constrained optimization tended to select mostly single BMPs or at most two BMPs for a given HRU due to these BMPs having higher acceptability to stakeholders. In contrast, the unconstrained case, representing full familiarity, selected 2‐ and 3‐BMP applications. There was little difference in costs between the constrained and unconstrained cases below an 80% TP yield reduction; however, significant differences were found at larger reductions, supporting the value of stakeholder education and extension efforts. Editor's note : This paper is part of the featured series on SWAT Applications for Emerging Hydrologic and Water Quality Challenges. See the February 2017 issue for the introduction and background to the series. 相似文献
28.
The removal characteristics of arsenate using micellar-enhanced ultrafiltration (MEUF) were investigated. Among four different cationic surfactants used, hexadecylpyridinium chloride (CPC) showed the highest removal efficiency of arsenic (96%), and the removal efficiency with hexadecyltrimethylammonium bromide (CTAB) was 94%. But the removal efficiency with benzalkonium chloride (BC) was the lowest (57%) due to higher critical micelle concentration (CMC) of BC than those of other surfactants. Over 80% of arsenic was removed with octadecylamine acetate (ODA). On the effect of solution pH on the arsenic removal, since the valance of arsenate decreases from trivalent to monovalent as pH decreases, the removal was reduced at lower pH. The presence of 0.45mM of nitrate and 0.01mM of phosphate reduced the removal efficiency by 5-8%. This decrease was because of the competition between the arsenate, nitrate and phosphate for the binding sites of the surfactant micelle. Similar decrease in the removal of arsenate was observed with CPC, CTAB and ODA in the presence of these anions. In cross-flow filtration, the removal efficiency of arsenic was similar to that in the dead-end system. However, the decline in flux was less than that in dead-end filtration. In order to lower the concentration of the surfactant in the effluent, the effluent was treated with powdered activated carbon (PAC) before discharging to the environment. Over 98% surfactant was removed with 1gl(-1) of PAC. In conclusions, the MEUF is considered as a feasible process using CPC or CTAB to remove the arsenate from groundwater compared with the other solid based adsorbent processes. 相似文献
29.
30.
In this study, a new empirical equation for the transverse dispersion coefficient has been developed based on the hydraulic
and geometric parameters in natural streams using a regression technique. First, a total of 32 data sets in 16 streams were
collected. Among those sets, 16 sets were used for deriving the new equation, and the other 16 sets were used for verifying
the equation. Then, through dimensional analysis, it was found that the normalized transverse dispersion coefficient is associated
with several parameters such as sinuosity, aspect ratio, and a friction term. The robust least square method was applied to
estimate regression coefficients. The newly proposed equation was proven to be superior in explaining the dispersion characteristics
of natural streams more precisely compared to the existing equations. 相似文献