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791.
Yiteng Su Lihong Peng Angus Shiue Gui-Bing Hong Zhang Qian 《Journal of the Air & Waste Management Association (1995)》2014,64(7):827-833
Mesoporous MCM-41 was synthesized using cetyltrimethyl ammonium bromide (CTAB) as a cationic surfactant and spent quartz sand as the silica source. Modification of the mesoporous structure to create an absorbent was then completed using 3-aminopropyltrimethoxysilane. Amine-Quartz-MCM (The A-Q-MCM) adsorbents were then characterized by N2 adsorption/desorption, elemental analysis (EA), X-ray fluorescence (XRF), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), as well as the carbon dioxide (CO2) adsorption/desorption performance. In this study, spent quartz sand was utilized to synthesize Quartz-MCM (Q-MCM) and the amine functionalized material, A-Q-MCM, which exhibited a higher uptake of CO2 at room temperature compared with the nongrafted material. The results showed that Q-MCM is similar to MCM-41 synthesized using commercial methods. The surface area, pore volume, and pore diameter were found to be as high as 1028 m2/g, 0.907 cm3/g, and 3.04 nm, respectively. Under the condition of CO2 concentration of 5000 ppm, retention time of 50 cc/min, and the dosage of 1 g/cm3, the mean adsorption capacity of CO2 onto A-Q-MCM was about 89 mg/g, and the nitrogen content of A-Q-MCM was 2.74%. The adsorption equilibrium was modeled well using a Freundlich isotherm.
Implications:In this study, spent quartz sand was utilized to synthesize Q-MCM. The amine functionalized material exhibited a higher uptake of CO2 at room temperature compared with the nongrafted material. The results showed that Q-MCM is similar to MCM-41 synthesized using commercial methods. The adsorption equilibrium was modeled well using a Freundlich isotherm. 相似文献
792.
Quantitative Identification of Disturbance Thresholds in Support of Aquatic Resource Management 总被引:3,自引:0,他引:3
The identification of disturbance thresholds is important for many aspects of aquatic resource management, including the establishment
of regulatory criteria and the identification of stream reference conditions. A number of quantitative or model-based approaches
can be used to identify disturbance thresholds, including nonparametric deviance reduction (NDR), piecewise regression (PR),
Bayesian changepoint (BCP), quantile piecewise constant (QPC), and quantile piecewise linear (QPL) approaches. These methods
differ in their assumptions regarding the nature of the disturbance-response variable relationship, which can make selecting
among the approaches difficult for those unfamiliar with the methods. We first provide an overview of each of the aforementioned
approaches for identifying disturbance thresholds, including the types of data for which the approaches are intended. We then
compare threshold estimates from each of these approaches to evaluate their robustness using both simulated and empirical
datasets. We found that most of the approaches were accurate in estimating thresholds for datasets with drastic changes in
responses variable at the disturbance threshold. Conversely, only the PR and QPL approaches performed well for datasets with
conditional mean or upper boundary changes in response variables at the disturbance threshold. The most robust threshold identification
approach appeared to be the QPL approach; this method provided relatively accurate threshold estimates for most of the evaluated
datasets. Because accuracy of disturbance threshold estimates can be affected by a number of factors, we recommend that several
steps be followed when attempting to identify disturbance thresholds. These steps include plotting and visually inspecting
the disturbance-response data, hypothesizing what mechanisms likely generate the observed pattern in the disturbance-response
data, and plotting the estimated threshold in relation to the disturbance-response data to ensure the appropriateness of the
threshold estimate. 相似文献
793.
Numerous road and railway construction projects include costly mitigation measures to offset the barrier effect produced on local fauna, despite the scarcity of data on the effectiveness of such mitigation measures. In this study, we evaluate the utility of different types of crossing structures. Vertebrate use of 43 transverse crossing structures along the A-52 motorway (north-western Spain) was studied during spring 2001. Research centered on wildlife passages (9), wildlife-adapted box culverts (7), functional passages (6 overpasses, 7 underpasses) and culverts (14), with marble dust being used to record animal tracks. A total of 424 track-days were recorded, with most of the larger vertebrate groups present in the area being detected. All crossing structure types were used by animals, although the intensity of use varied significantly among them (Kruskal-Wallis test, p<0.05); culverts were used less frequently than other structures. Crossing structure type and width were identified as the most important factors in their selection for use. Wildlife passages and adapted culverts allowed crossing by certain species (wild boar, roe deer, Eurasian badger), which do not tend to cross elsewhere. These results highlight the importance of using both mixed-type structures and wildlife passages in reducing the barrier effect of roads. 相似文献
794.
湖南永吉高速公路建设的景观格局影响评价 总被引:3,自引:0,他引:3
利用遥感(RS)、全球定位系统(GPS)与地理信息系统技术(GIS),对湖南省永吉高速公路沿线建设前后的景观进行分类和制图,结合景观结构分析软件Fragstats33和景观生态学方法,从斑块和景观两个层次上研究高速公路建设前后景观格局的变化。结果表明:(1)斑块层次指数中,沿线除公路用地外各景观类型的面积均有所减少,257%的土地转换为公路用地,其中旱地面积减少最多,但是公路建设前后没有改变该区域的优势斑块类型;(2)景观层次指数中,斑块数目和斑块密度的增加与最大斑块指数的减少,都表明景观异质性增加;(3)不同缓冲区分析结果表明:高速公路建设对景观格局的干扰突出表现在距公路较近的500 m缓冲区内。本研究方法在未来路网规划与环境影响评价中具有一定应用前景 相似文献
795.
为探讨煤矿企业员工不安全行为影响因子的相互关系,基于行为安全模型,从管理者、班组长和一线员工3个角度进行分析,确定了对行为安全有关键影响的因子群。在此基础上,采用决策试验与评价实验室(DEMATEL)方法,研究构建行为影响因子之间的依赖关系矩阵,揭示安全投入程度、安全监管机构能力、安全处罚适当性等因子对员工行为方式的影响程度,并形成煤矿员工行为方式影响因子的四分图。结果表明:安全投入程度是煤矿员工行为方式的主要影响因子和原因因子,管理者行为影响因子均是其原因因子,管理者的行为方式对企业安全状况有较大影响。 相似文献
796.
797.
Jumin Hao Mei-Juan Han Songman Han Xiaoguang Meng Tsan-Liang Su Qingwu K. Wang 《环境科学学报(英文版)》2015,36(10):152-162
Arsenic (As) is one of the most toxic contaminants found in the environment. Development of novel detection methods for As species in water with the potential for field use has been an urgent need in recent years. In past decades, surface-enhanced Raman scattering (SERS) has gained a reputation as one of the most sensitive spectroscopic methods for chemical and biomolecular sensing. The SERS technique has emerged as an extremely promising solution for in-situ detection of arsenic species in the field, particularly when coupled with portable/handheld Raman spectrometers. In this article, the recent advances in SERS analysis of arsenic species in water media are reviewed, and the potential of this technique for fast screening and field testing of arsenic-contaminated environmental water samples is discussed. The problems that remain in the field are also discussed and an outlook for the future is featured at the end of the article. 相似文献
798.
Single and joint stress of acetochlor and Pb on three agricultural crops in
northeast China 总被引:10,自引:0,他引:10
In order to evaluate ecological risk of agrochemicals in agricultural environment, single and joint toxic effects of an important herbicide and a typical heavy metal on root elongation of crops were investigated. Seeds of the three crops including wheat (Triticum aestivum), Chinese cabbage (Brassica pekimensis) and soybean (Glycine max) as the main crops in northeast China were exposed to acetochior as a herbicide and lead (Pb) as a heavy metal using the pot-culture method, and meadow brown soil as one of the main soils distributed in northeast China was applied in the investigation. The results indicated that the interactive effects of the two pollutants on root elongation of the three crops were very complicated although they had markedly significant (P〈0.01) linear interrelationships based on the regression analyses. When the concentration of added Pb^2+ reached 200 mg/kg, acetochlor and Pb had an antagonistic effect on the inhibition of root elongation of the three crops. However, acetochlor and Pb had significantly (P〈0.05) synergic effects on the inhibition of root elongation when concentration of added Pb^2+ was up to 1000 mg/kg. At the low concentration of added Pb, joint toxicity of acetochlor and Pb was more dependent on the concentration of Pb. Among the three crops, wheat was the most sensitive to the toxicity of Pb and Chinese cabbage was the most sensitive to the toxicity of acetochlor. 相似文献
799.
800.
Peng Du Xing Li Yanling Yang Zhaoyang Su Hang Li Nan Wang Tingting Guo Tingting Zhang Zhiwei Zhou 《环境科学学报(英文版)》2019,31(8):82-92
To alleviate ultrafiltration(UF) membrane fouling, the pre-coagulation of poly-aluminum chloride(PACl) with the aid of chitosan(CTS) was conducted for synthetic humic acid–kaolin water treatment. Pre-coagulation of three molecular weights(MW) CTSs(50–190 kDa(CTSL), 190–310 kDa(CTSM) and 310–375 kDa(CTSH)) was optimized with slow-mixing speeds of 30, 60 and 90 r/min, respectively. The removal efficiency and floc properties as well as membrane fouling were analyzed, and were compared to results obtained by conventional coagulation with PACl. Results showed that variations in floc properties could be ascribed to the coagulation mechanisms of CTS_L/CTS_M/CTS_H at different slow-mixing speeds, resulting in reduced UF membrane fouling. Specifically, at the low speed of 30 r/min, all three CTS types produced flocs with similar properties, while CTSLresulted in the lowest removal efficiency and aggravated irreversible fouling. At the appropriate speed of 60 r/min, CTSMgenerated the most compact flocs with the combined effects of bridging and path mechanisms. The compact cake layer formed could alleviate irreversible fouling,which was beneficial for prolonging the operation of the UF membrane. At the high speed of90 r/min, CTSHformed fragile flocs and aggravated irreversible membrane fouling. We considered membrane fouling to be affected by floc properties and the resultant removal efficiency, which was governed by the MW of the CTS used and the slow-mixing speed applied as well. 相似文献