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针对污水处理过程中存在的难降解有机物问题,介绍了芬顿的概念和特点,探讨了均相芬顿氧化在原位产生芬顿试剂的机理及应用.目前均相芬顿氧化技术总体可归纳为超声-芬顿氧化技术、微波-芬顿氧化技术、光-芬顿氧化技术、电-芬顿氧化技术.这些技术的应用能促进有机物的降解,提高芬顿技术的处理效率.通过介绍芬顿氧化技术降解废水中污染物的机理,综述了均相芬顿氧化技术在废水处理中的应用,分析了各种方法的适用范围和优缺点. 相似文献
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Convergence or divergence in desertification risk? Scale-based assessment and policy implications in a Mediterranean country 总被引:1,自引:0,他引:1
This paper explores changes (1990–2000) in two environmental indexes with the aim of providing empirical evidence on regional and local convergence in an increasing-impact phenomenon such as Land Degradation (LD) in Italy. Convergence analysis for ESAI (Environmental Sensitive Area Index) and LVI (Land Vulnerability Index) was developed at five different geographical scales. Results indicate that territorial disparities in land vulnerability tend to increase during the investigated period following a defined spatial pattern that depends on land quality, the environmental context and the economic performance of regional systems. Finally, the implications this process has on policy strategies aimed at mitigating desertification risk are discussed. 相似文献
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针对传统同质点探测方法检验效率低以及在地物区分度不明显地区探测结果包含过多异质点的问题,提出融合似然比检验(LRT)与Bootstrap区间估计的同质点探测方法,通过模拟和实验对该方法进行验证,并对鄂尔多斯某煤矿地表形变进行探测和验证。研究结果表明:相比于传统方法,融合似然比检验(LRT)与Bootstrap区间估计的同质点探测方法具有较高的拒绝率和稳定的拒绝率标准差,比较适合地物区分度不明显的野外矿区同质点探测;在实验矿区发现1处明显下沉,最大累计沉降为-128.9 mm,通过与实测水准比较,发现实测水准结果与基于本文方法的DS-InSAR结果基本一致,2者均方根误差和平均绝对误差分别为14.4,12.0 mm。研究结果可实现对矿区的非接触、大范围、长时间监测,为DS-InSAR中同质点选取提供新思路。 相似文献
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Samaratunga SS Nishimoto J Tabata M 《Environmental science and pollution research international》2008,15(1):27-30
BACKGROUND, AIMS AND SCOPE: Chromium enters into the aquatic environment as a result of effluent discharge from steel works, electroplating, leather tanning industries and chemical industries. As the Cr(VI) is very harmful to living organisms, it should be quickly removed from the environment when it happens to be contaminated. Therefore, the aim of this laboratory research was to develop a rapid, simple and adaptable solvent extraction system to quantitatively remove Cr(VI) from polluted waters. METHODS: Aqueous salt-solutions containing Cr(VI) as CrO4(2-) at ppm level (4-6 ppm) were prepared. Equal volumes (5 ml) of aqueous and organic (2-PrOH) phases were mixed in a 10 ml centrifuge tube for 15 min, centrifuged and separated. Concentrations of Cr(VI), in both the aqueous and organic phases, were determined by atomic absorption spectrometry. The effects of salt and acid concentrations, and phase-contact time on the extraction of Cr(VI) were investigated. In addition, the extraction of Cr(VI) was assessed in the presence of tetramethylammonium chloride (TMAC) in 2-PrOH phase. Effects of some other metals, (Cd(II), Co(II), Cu(II), Ni(II) and Zn(II)), on the extraction of Cr(VI) were also investigated. RESULTS AND DISCUSSION: The Cr(VI) at ppm level was extracted quantitatively by salting-out the homogeneous system of water and 2-propanol(2-PrOH) using chloride salts, namely CaCl2 or NaCl, under acidic chloride media. The extracted chemical species of Cr(VI) was confirmed to be the CrO3Cl-. The ion-pair complex extracted into the organic phase was rationalized as the solvated ion-pair complex of [2-PrOH2+, CrO3Cl-]. The complex was no longer stable. It implied the reaction between extracted species. Studies revealed that salts and acid directly participated in the formation of the above complex. Use of extracting agents (TMAC) didn't show any significant effect on the extraction of Cr(VI) under high salting-out conditions. There is no significant interference effect on the extraction of Cr(VI) by the presence of other metals. The Cr(VI) in the organic phase was back-extracted using an aqueous ammonia solution (1.6 mol dm(-3)) containing 3 mol dm(-3) NaCl. The extraction mechanism of Cr(VI) is also discussed. CONCLUSIONS: Salting-out of homogeneous mixed solvent of 2-propanol can be employed to extract Cr(VI) quantitatively, as an ion-pair of [2-PrOH2+ * CrO3Cl-] solvated by 2-PrOH molecules. Then, the complex becomes 'solvent-like' and is readily separated into the organic phase. The increase of Cl- ion concentration in the aqueous phase favors the extraction. The 2-PrOH, salts and acid play important roles in the extraction process. There is no need to use an extracting agent at a high salting-out condition. RECOMMENDATIONS AND PERSPECTIVES: Chromium(VI) must be quickly removed before it enters into the natural cycle. As the 2-PrOH is water-miscible in any proportion, ion-pairing between 2-PrOH2+ and CrO3Cl- becomes very fast. As a result, Cr(VI) can easily be extracted. Therefore, the method is recommended as a simple, rapid and adaptable method to quickly separate Cr(VI) from aqueous samples. 相似文献
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Denis Gingras Kaz Adamowski Paul J. Pilon 《Journal of the American Water Resources Association》1994,30(1):55-67
ABSTRACT: When nonparametric frequency analysis was performed on 183 stations from Ontario and Quebec, unimodal and multimodal maximum annual flood density functions were discovered. In order to determine generating mechanisms, a monthly partitioning of the annual maximum floods was undertaken. The timing of the floods revealed that the unimodal distributions reflected a single flood generating mechanism while the multi-modal densities reflected two or more mechanisms. Based on the division of the flood series by mechanisms, nine homogeneous regions were delineated. L-moment distributional homogeneity tests along with smaller standard errors for the regional equations supported the delineation. 相似文献
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结合矿井通风系统中通风机分支系统实际,依据可靠性工程理论中Markov过程理论及相关知识,探讨了矿井通风机系统可靠性分析的新方法;推导出了通风机系统的可靠度及首次故障前平均寿命的计算公式;结合现场实际,进行了实例验证;根据通风机系统可靠性各项主要指标数据,分析了影响通风机系统可靠性的因素.为现场通风技术管理人员进一步掌握矿井通风机的可靠性运行状况提供了参考依据. 相似文献
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利用模拟软件Fluent6.3建立二维模型并进行合理设置,对多孔介质中的煤矿低浓度瓦斯燃烧进行数值模拟,研究了均匀型和渐变型燃烧器中的温度分布和NOx生成情况,以及三种不同渐变型多孔介质组合燃烧器中的温度分布和NOx生成情况。结果表明,渐变型多孔介质燃烧器的温度分布比均匀型燃烧器更加均匀;同一瓦斯当量比和流速下,渐变型多孔介质燃烧器的NOx产生量比均匀型燃烧器低很多,有利于减少污染物排放;三种不同渐变型多孔介质组合的温度分布和NOx生成有着不同特点,燃烧器设计时,可根据不同需求选取不同组合形式,综合考虑各因素,组合一燃烧特性最佳。 相似文献