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661.
Solid phase reactions of Cr(Ⅵ) with Fe(0) were investigated with spherical-aberration-corrected scanning transmission electron microscopy(Cs-STEM) integrated with X-ray energy-dispersive spectroscopy(XEDS). Near-atomic resolution elemental mappings of Cr(Ⅵ)–Fe(0) reactions were acquired. Experimental results show that rate and extent of Cr(Ⅵ) encapsulation are strongly dependent on the initial concentration of Cr(Ⅵ) in solution. Low Cr loading in nZⅥ(1.0 wt%) promotes the electrochemical oxidation and continuous corrosion of n ZⅥ while high Cr loading(1.0 wt%) can quickly shut down the Cr uptake. With the progress of iron oxidation and dissolution, elements of Cr and O counter-diffuse into the nanoparticles and accumulate in the core region at low levels of Cr(Ⅵ)(e.g., 10 mg/L). Whereas the reacted n ZⅥ is quickly coated with a newly-formed layer of 2–4 nm in the presence of concentrated Cr(Ⅵ)(e.g., 100 mg/L). The passivation structure is stable over a wide range of pH unless pH is low enough to dissolve the passivation layer. X-ray photoelectron spectroscopy(XPS) depth profiling reconfirms that the composition of the newly-formed surface layer consists of Fe(Ⅲ)–Cr(Ⅲ)(oxy)hydroxides with Cr(Ⅵ) adsorbed on the outside surface. The insoluble and insulating Fe(Ⅲ)–Cr(Ⅲ)(oxy)hydroxide layer can completely cover the n ZⅥ surface above the critical Cr loading and shield the electron transfer. Thus, the fast passivation of nZⅥ in high Cr(Ⅵ) solution is detrimental to the performance of nZⅥ for Cr(Ⅵ) treatment and remediation. 相似文献
662.
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664.
采用大肠杆菌吸附-化学还原法,以大肠杆菌(ECCs)为模板、十六烷基三甲基溴化铵为保护剂、抗坏血酸为还原剂,由废含金催化剂制备金纳米线(AuNWs)。采用XRD,SEM,TEM等技术对AuNWs进行表征。研究了AuNWs对罗丹明6G(R6G)和4-巯基苯甲酸(4-MBA)的拉曼散射信号的增强效果。实验结果表明:在制备过程中加入微生物ECCs,可使金回收率提高约20百分点;当溶液pH小于4时,反应2 h后,有大量呈线状的AuNWs聚集沉降,金回收率可达99%1以上。表征结果显示,AuNWs呈多晶结构,晶格间距为0.23 nm。表面增强拉曼散射分析表明,AuNWs对R6G和4-MBA具有良好的拉曼光谱增强性能。 相似文献
665.
中国2000—2010年耕地低效转化的空间特征 总被引:1,自引:0,他引:1
耕地向经济效益相对较低的用地类型转化具有多重社会及生态效应。论文首先将耕地向草地、灌丛地和裸地的转化定义为“耕地低效转化”,然后以GlobeLand30为基础,提取2000—2010年的低效转化耕地,并结合耕地资源禀赋和地形条件,从多尺度、多角度深入揭示了我国耕地低效转化的空间分布特征。结果表明:1)全国总体的耕地低效转化率仅为1.50%,但区域差异明显,空间分布极不均衡;2)耕地低效转化依照地势的三级阶梯呈现明显的区域分异规律,农牧交错带的耕地转化问题最为严重,但耕作条件好、原有耕地比例高的东部地区,耕地低效转化水平一般较低;3)耕地低效转化率大体随海拔和坡度的增加而增加,但会受到地形复杂度的影响。 相似文献
666.
生物膜填料塔处理浓度有机废气的工业应用试验研究 总被引:2,自引:0,他引:2
工业应用试验研究表明,生物膜填料塔处理工业有机废气是可行的,当运行条件控制适当时,净化效率可保持在90%以上,能够实现达标排放,这一成果填补了我国环保工业技术领域的空白,工程技术上接近现阶段国外的技术研究水平。 相似文献
667.
Chen B Li Y Huang GH Huang Y Li Y 《Journal of environmental science and health. Part. B》2004,39(4):613-626
A GIS-aided pesticide loss model (PeLM) was developed to simulate pesticide losses through surface runoff and sediment transport in watershed systems. The PeLM could tackle the movement of eroded soil along with surface runoff as well as the pesticide losses in adsorbed and dissolved phases. The contributions of different soil types in the sediment were also examined. The model was applied to the Kintore Creek Watershed of southern Ontario, Canada. The simulation results were verified through observed data, indicating a correlation level of 0.89-0.98. The results also showed that clay particles usually held the largest share of contributions to pesticide losses through soil erosion. This study is significant in the efforts for modeling nonpoint source pollution in watershed systems. It provides useful information and support for the related decisions of watershed management. 相似文献
668.
Xi Haiyan Cai Qiang He Miao Shi Hanchang 《Frontiers of Environmental Science & Engineering in China》2007,1(3):381-384
This research describes a fast detection method on the basis of enzyme-linked immunosorbent assay (ELISA) for Escherichia coli in drainage of wastewater treatment plants. Optimized conditions such as the reaction format (sandwich or direct), the concentrations
of diluted horseradish peroxidase (HRP)-E. coli conjugate, and anti-HPR antibody and pretreatment of E. coli were studied. Those results showed that the linear range of detection for E. coli was 10 cfu/mL-6 × 104 cfu/mL. Compared with conventional methods, it is a convenient and sensitive detection method with low cost.
Translated from Environmental Science, 2005, 26(5): 128–131 [译自: 环境科学] 相似文献
669.
Nowadays, more people tend to spend their recreational time in large national parks, and trace metal(loid)s in soils have attracted long-term attention due to their possible harm to human health. To investigate the pollution levels, potential sources and health risks of trace metal(loid)s in road soils, a total of eight trace metal(loid)s (including As, Cd, Cr, Cu, Ni, Pb, Zn and Hg) from 47 soil samples along roads were studied in the Huangshan National Park in Southeast China. The results showed that the concentrations of As, Cd, Pb, Zn and Hg appeared different degrees of pollution compared with their corresponding background values. According to the pollution indices, Hg and Cd were recognized as significant pollutants presenting moderate to high ecological risk. Combining principal component analysis and positive matrix factorization model, the results showed that traffic, industrial, agricultural and natural sources were the potential origins of trace metal(loid)s in this area, with contribution rates of 39.93%, 25.92%, 10.53% and 23.62%, respectively. Non-carcinogenic risks were all negligible, while the carcinogenic risk of As was higher than the limit (1 10−6). Moreover, children were more susceptible to trace metal(loid)s by ingestion which appeared to be a more important exposure pathway than dermal contact and inhalation. The contribution rates of different sources to non-carcinogenic risks and carcinogenic risks were similar among children and adults, while traffic and industrial sources have a significant impact on health risks. This study will give more insights to control the environmental risks of trace metal(loid)s in national parks. 相似文献
670.
The microscopic reaction mechanisms of diphenylether (DPE) and 4-bromodiphenylether (4-BrDPE) with nitrous acid (HNO(2)) in the absence of O(2) have been explored by the 355nm laser flash photolysis. It was proposed that OH radical, from the photolysis of HNO(2), added to DPE forms the C(12)H(10)O-OH adduct while added to 4-BrDPE forms the 4-BrDPE-OH and 4-BrOH-DPE adducts. The first-order decay rate constants of the C(12)H(10)O-OH adduct, 4-BrDPE-OH adduct and 4-BrOH-DPE adduct were measured to be (1.86+/-0.14)x10(5)s(-1), (2.19+/-0.04)x10(5)s(-1) and (1.56+/-0.03)x10(5)s(-1), respectively. The final photolysis products of DPE and HNO(2) identified by GC/MS analysis were phenol, o-hydroxydiphenylether, p-hydroxydiphenylether and p-nitrodiphenylether, while the final photolysis product of 4-BrDPE and HNO(2) identified by LC/MS analysis was mainly the dimer. 相似文献