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991.
Wipfler EL Ness M Breedveld GD Marsman A Van Der Zee SE 《Journal of contaminant hydrology》2004,72(1-4):47-66
Enhanced understanding of light non-aqueous phase liquid (LNAPL) infiltration into heterogeneous porous media is important for the effective design of remediation strategies. We used a 2-D experimental facility that allows for visual observation of LNAPL contours in order to study LNAPL redistribution in a layered porous medium. The layers are situated in the unsaturated zone near the watertable and they are inclined to be able to observe the effect of discontinuities in capillary forces and relative permeabilities. Two experiments were performed. The first experiment consisted of LNAPL infiltration into a fine sand matrix with a coarse sand layer, and the second experiment consisted of a coarse sand matrix and a fine sand layer. The numerical multi-phase flow model STOMP was validated with regard to the experimental results. This model is able to adequately reproduce the experimental LNAPL contours. Numerical sensitivity analysis was also performed. The capillarity contrast between sands was found to be the main controlling factor determining the final LNAPL distribution. 相似文献
992.
Iesce MR Cermola F De Lorenzo F Graziano ML Caliendo B 《Environmental science and pollution research international》2002,9(2):107-109
Irradiation of carboxin (1) with a 500 W UV lamp (filter Pyrex) in CH3CN leads to the products 3, 5-8, 12-14 depending upon the reaction conditions. All photo-products were isolated and characterized. Photooxidation occurred even if unsensitized, while photoalteration was very slow in the absence of oxygen. The main oxygenated-products 3 and 13 were also recovered under biomimetic conditions by exposure of an aqueous solution of 1 to sunlight. 相似文献
993.
Andrea M. Hofmaier Siegfried M. G. Schwirzer Friedrich J. Wiebel Karl-Werner Schramm Martin Wegenke und Antonius A. F. Kettrup 《Umweltwissenschaften und Schadstoff-Forschung》1999,11(1):2-8
Zusammenfassung Polychlorierte aromatische Kohlenwasserstoffe (PHAK), z.B. 2,3,7,8-Tetrachlordibenzo-p-dioxin (TCDD), weisen eine Vielzahl von toxischen Wirkungen und biologischen Effekten auf. Die Substanzklasse der PHAK besitzt
die Eigenschaft der Bindung an ein cytosolisches Rezeptor-Protein, gefolgt von der Synthese bestimmter Genprodukte, u.a. von
Cytochrom P450 1A1 (CYP 1A1). In dieser Arbeit wird ein Bioassay beschrieben, der erlaubt, die Induktion von CYP 1A1 als Summenparameter
für die biologische Wirksamkeit der kritischen, halogenierten Verbindungen in komplexen Umweltmatrizes zu bestimmen. Zur Abtrennung
von Substanzen aus den Extrakten von Umweltproben (z. B. Naturstoffe und polyzyklische aromatische Kohlenwasserstoffe), die
den Bioassay st?ren k?nnen, wurde ein Ein-S?ulen-Clean-up entwickelt. Die biologisch ermittelten TEQ-Werte stimmen gut mit
den Resultaten der chemischen Analytik überein. Der Bioassay in Kombination mit dem Clean-up bietet eine zeitsparende und
kostengünstige M?glichkeit zur Untersuchung von Umweltproben.
相似文献
994.
以改进的化学沉淀法处理硫酸铵废水 总被引:3,自引:0,他引:3
针对MAP化学沉淀法处理氨氮废水中存在的问题。如处理成本高、处理后的废水中磷浓度高,对化学沉淀法进行了改进研究,考察Mg^2+以外的二价金属离子(Ni^2+,Mn^2+,Zn^2+,Cu^2+,Fe^2+)在磷酸根作用下对氨氮的去除效果。针对废水中磷浓度高的问题,进行了MAP沉淀法的条件优化实验。结果表明。通过体系pH值和沉淀剂投加比例的合理控制,可以使在高浓度氨氮废水在出水氨氮浓度达标的同时,实现废水中的氮磷浓度同时控制;针对NaOH作pH调节剂成本过高,而以Ca(OH)2作pH调节剂时,钙离子严重影响MAP沉淀效果。对硫酸铵废水体系提出了CaSO4沉淀——MAP沉淀新工艺。结果表明,这一改进完全可以消除钙离子的影响。实现以石灰取代传统的NaOH调节剂。 相似文献
995.
996.
Catalkaya EC Bali U Sengül F 《Environmental science and pollution research international》2003,10(2):113-120
INTENTION, GOAL, SCOPE, BACKGROUND: Since the intermediate products of some compounds can be more toxic and/or refractory than the original compund itself, the development of innovative oxidation technologies which are capable of transforming such compounds into harmless end products, is gaining more importance every day. Advanced oxidation processes are one of these technologies. However, it is necessary to optimize the reaction conditions for these technologies in order to be cost-effective. OBJECTIVE: The main objectives of this study were to see if complete mineralization of 4-chlorophenol with AOPs was possible using low pressure mercury vapour lamps, to make a comparison of different AOPs, to observe the effect of the existence of other ions on degradation efficiency and to optimize reaction conditions. METHODS: In this study, photochemical advanced oxidation processes (AOPs) utilizing the combinations of UV, UV/H2O2 and UV/H2O2/Fe2+ (photo-Fenton process) were investigated in labscale experiments for the degradation and mineralization of 4-chlorophenol. Evaluations were based on the reduction of 4-chlorophenol and total organic carbon. The major parameters investigated were the initial 4-chlorophenol concentration, pH, hydrogen peroxide and iron doses and the effect of the presence of radical scavengers. RESULTS AND DISCUSSION: It was observed that the 4-chlorophenol degradation efficiency decreased with increasing concentration and was independent of the initial solution pH in the UV process. 4-chlorophenol oxidation efficiency for an initial concentration of 100 mgl(-1) was around 89% after 300 min of irradiation in the UV process and no mineralization was achieved. The efficiency increased to > 99% with the UV/H2O2 process in 60 min of irradiation, although mineralization efficiency was still around 75% after 300 min of reaction time. Although the H2O2/4-CP molar ratio was kept constant, increasing initial 4-chlorophenol concentration decreased the treatment efficiency. It was observed that basic pHs were favourable in the UV/H2O2 process. The results showed that the photo-Fenton process was the most effective treatment process under acidic conditions. Complete disappearance of 100 mgl(-1) of 4-chlorophenol was achieved in 2.5 min and almost complete mineralization (96%) was also possible after only 45 min of irradiation. The efficiency was negatively affected from H2O2 in the UV/H2O2 process and Fe2+ in the photo-Fenton process over a certain concentration. The highest negative effect was observed with solutions containing PO4 triple ions. Required reaction times for complete disappearance of 100 mgl(-1) 4-chlorophenol increased from 2.5 min for an ion-free solution to 30 min for solutions containing 100 mgl(-1) PO4 triple ion and from 45 min to more than 240 min for complete mineralization. The photodegradation of 4-chlorophenol was found to follow the first-order law. CONCLUSION: The results of this study showed that UV irradiation alone can degrade 4-CP, although at very slow rates, but cannot mineralize the compound. The addition of hydrogen peroxide to the system, the so-called UV/H2O2 process, significantly enhances the 4-CP degradation rate, but still requires relatively long reaction periods for complete mineralization. The photo-Fenton process, the combination of homogeneous systems of UV/H2O2/Fe2+ compounds, produces the highest photochemical elimination rate of 4-CP and complete mineralization is possible to achieve in quite shorter reaction periods when compared with the UV/H2O2 process. RECOMMENDATIONS AND OUTLOOK: It is more cost effective to use these processes for only purposes such as toxicity reduction, enhancement of biodegradability, decolorization and micropollutant removal. However the most important point is the optimization of the reaction conditions for the process of concern. In such a case, AOPs can be used in combination with a biological treatment systems as a pre- or post treatment unit providing the cheapest treatment option. The AOP applied, for instance, can be used for toxicity reduction and the biological unit for chemical oxygen demand (COD) removal. 相似文献
997.
Acute toxicity of cadmium to fish Labeo rohita and copepod Diaptomus forbesi pre-exposed to CaO and KMnO4 总被引:5,自引:0,他引:5
96-h LC50 values of cadmium (Cd) to fish Labeo rohita and the copepod Diaptomus forbesi, determined by static bioassays, were, respectively, 89.5 and 10.2 mg/l. LC50 values increased significantly when fish pre-exposed to 100–350 mg/l CaO or 0.5–1.5 mg/l KMnO4 for 4 d and the copepod to 20–70 mg/l CaO or 0.25–1.0 mg/l KMnO4 for same period. The LC50 values also increased when the pre-exposure period of CaO was increased to 12 d at concentration 100 mg/l for fish and 20 mg/l for copepod. All fish died when pre-exposed to 1.5 mg/l KMnO4 for 8 d. But LC50 values of Cd to copepod increased when pre-exposure period of 0.5 mg/l KMnO4 was increased from 4 to 8 d. 相似文献
998.
研究了水溶液中竹炭对 2 ,4-二氯苯酚的吸附特性及其影响因素。结果表明 ,竹炭对 2 ,4-二氯苯酚具有较强的吸附性能 ,吸附效果与竹炭粒径、用量、污染物浓度以及吸附平衡时间和平衡方式有关。 相似文献
999.
为了研究富氧条件下不同泄爆面积对CH4燃烧诱导快速相变的影响,基于自主设计搭建的CH4燃烧诱导快速相变试验台,通过改变富氧系数和泄爆面积对CH4燃烧的压力振荡特性进行研究,分析了不同富氧系数E(0.21,0.3,0.4,0.6)及泄爆面积比(0,0.25,0.5,0.75,1)下CH4燃烧的压力峰值、到达压力峰值的时间及特征时间等参数的变化趋势。结果表明,随富氧系数增大,爆炸压力峰值逐渐增大。富氧系数E=0.21时,压力峰值低于相应的绝热压力,无压力振荡;当E=0.3时,压力峰值低于相应的绝热压力且伴随压力振荡。当E为0.4、0.6时,压力峰值高于相应绝热压力且伴随压力振荡;在泄爆条件下,随富氧系数增加,到达压力峰值的时间逐渐减小。通过分析不锈钢管道中的燃烧诱导快速相变现象,发现泄爆可以有效降低爆炸压力峰值,且随泄爆面积比增大,到达压力峰值的时间提前。 相似文献
1000.