Laser cleaning of historical limestone buildings in Bordeaux appraisal using cathodoluminescence and electron paramagnetic resonance

BACKGROUND: Most historical buildings in Bordeaux city are made of limestone. This yellowish-white rock is rather porous and highly sensitive to pollution. As a consequence of local weathering conditions, these buildings present a dark appearance due to the development of a superficial dark grey to black crust. METHODS: For the last decade, a campaign has been underway to clean these buildings. Eleven techniques of surface treatment have been used, including laser beam technology. As a contribution to the study of laser beam effects on stone buildings, two analytical methods have been used on clean versus unclean surfaces: Cathodoluminescence (CL) and Electron Paramagnetic Resonance (EPR), in addition to SEM-EDX and XRD. RESULTS: The black crust is composed of different types of particles: carbon porous micro-particles of industrial origin, atmospheric dust due to the erosion of soils and rocks, alumino-silicate particles from urban pollution; all these particles being cemented by gypsum. DISCUSSION: As far as heritage conservation is concerned, the laser surface treatment not only preserves the original patina of the stone, but also leaves surface smoothness unaltered. CONCLUSIONS AND PERSPECTIVES: CL and EPR data confirm that lasers--with highly controlled parameters--only get rid of the black crust and, thus, reveal the underneath layer, the so-called patina. This patina shows no luminescence, whereas the limestone on which it has grown shows a bright orange emission of CL. This indicates CL to be a fast and easy way to provide a high quality control for the restoration of polluted ancient stones.     

Biomonitoring of the distribution of dust emissions by means of a new SEM/EDX technique

A new application of the Scanning Electron Microscope (SEM) equipped with an Energy Dispersive X-ray Microanalyzer (EDX) has been developed to study the distribution of airborne dust emissions. This technique makes it possible to identify the particles and measure the amount of dust deposition on the surface of the biomonitoring material. Pine bark or needles and moss can easily be used as the study material. A map indicating pollution levels and distribution can be drawn on the basis of the measured data.     

电子束法大气污染治理技术研究

简述了电子束烟气治理技术的发展和现状，介绍了电子束法脱除烟气中的主要污染物ＳＯ２和ＮＯｘ的机制，概述了上海原子核所在电子束烟气交化领域的研究情况和结果。     

Distinct roles of pH and organic ligands in the dissolution of goethite by cysteine

Electron shuttles such cysteine play an important role in Fe cycle and its availability in soils,while the roles of pH and organic ligands in this process are poorly understood.Herein,the reductive dissolution process of goethite by cysteine were explored in the presence of organic ligands.Our results showed that cysteine exhibited a strong reactivity towards goethite-a typical iron minerals in paddy soils with a rate constant ranging from 0.01 to0.1 hr-1.However,a large portion of Fe(Ⅱ) appeare...     

Metallurgical and mechanical characterization of electron beam welded super-duplex stainless steel UNS 32750

This paper addresses the weldability of 6 mm thick plates of super-duplex stainless steel by electron beam welding (EBW) process. Microstructure investigations conducted using optical and SE microscopy showed the presence of large ferrite grains with intra- and inter-granular austenite. Ferrite content studies on the weld zone estimated that there is no significant element partitioning between austenite and ferrite phases. Hardness studies portrayed that the weld hardness is found to be greater than the parent metal which is acquainted due to the solid solution strengthening effect. Tensile results corroborated that the joints obtained by EB welding process have better strength than the base metal. A detailed structure–property relationships has also been carried out through point and line mapping EDAX analysis across the weldment to substantiate the discussions.     

Simultaneous Feammox and anammox process facilitated by activated carbon as an electron shuttle for autotrophic biological nitrogen removal

• The autotrophic nitrogen removal combining Feammox and Anammox was achieved. • Activated carbon can be used as an electron shuttle to enhance Feammox activity. • Fe(III) was reduced to Fe(II) and the secondary Fe(II) mineral (FeOOH) was obtained. • The iron-reducing bacteria and Anammox consortium was enriched simultaneously. Ferric iron reduction coupled with anaerobic ammonium oxidation (Feammox) is a novel ferric-dependent autotrophic process for biological nitrogen removal (BNR) that has attracted increasing attention due to its low organic carbon requirement. However, extracellular electron transfer limits the nitrogen transformation rate. In this study, activated carbon (AC) was used as an electron shuttle and added into an integrated autotrophic BNR system consisting of Feammox and anammox processes. The nitrogen removal performance, nitrogen transformation pathways and microbial communities were investigated during 194 days of operation. During the stable operational period (days 126–194), the total nitrogen (TN) removal efficiency reached 82.9%±6.8% with a nitrogen removal rate of 0.46±0.04 kg-TN/m³/d. The contributions of the Feammox, anammox and heterotrophic denitrification pathways to TN loss accounted for 7.5%, 89.5% and 3.0%, respectively. Batch experiments showed that AC was more effective in accelerating the Feammox rate than the anammox rate. X-ray photoelectron spectroscopy (XPS) analyses showed the presence of ferric iron (Fe(III)) and ferrous iron (Fe(II)) in secondary minerals. X-ray diffraction (XRD) patterns indicated that secondary iron species were formed on the surface of iron-AC carrier (Fe/AC), and Fe(III) was primarily reduced by ammonium in the Feammox process. The phyla Anaerolineaceae (0.542%) and Candidatus Magasanikbacteria (0.147%) might contribute to the Feammox process, and Candidatus Jettenia (2.10%) and Candidatus Brocadia (1.18%) were the dominative anammox phyla in the bioreactor. Overall, the addition of AC provided an effective way to enhance the autotrophic BNR process by integrating Feammox and anammox.     

电子受体对污泥产率的影响

本文通过2个SBR和30次分批实验研究了电子受体（O2、NO3^-）对活性污泥产率系数（真实产率YH和表观产率Yobs）的影响。分批实验采用的基质是多种多样的,所选用的接种污泥是SBR长期培养出来的。实验结果表明,在不同的电子受体（O2、NO3^-）条件下,真实产率YH具有显著的不同,缺氧YH是0.53 mgCOD/mgCOD,而好氧YH是0.68 mgCOD/mgCOD,这是由于不同电子受体需要不同的微生物种群,其细胞产率不同。不过缺、好氧的表观产率Yobs（0.33 g△MLVSS/g△COD和0.35 g△MLVSS/g△COD）的差异并不显著,这是由于好氧污泥的内源呼吸作用更强,有更多的污泥衰减。     

Enhanced removal of Cr(VI) by biochar with Fe as electron shuttles

Biochar is extensively used as an effective soil amendment for environmental remediation. In addition to its strong contaminant sorption capability, biochar also plays an important role in chemical transformation of contaminant due to its inherent redox-active moieties. However, the transformation efficiency of inorganic contaminants is generally very limited when the direct adsorption of contaminants on biochar is inefficient. The present study demonstrates the role of Fe ion as an electron shuttle to enhance Cr(VI) reduction by biochars. Batch experiments were conducted to examine the effects of Fe(III) levels, pyrolysis temperature of biochar, initial solution pH, and biochar dosage on the efficiency of Cr(VI) removal. Results showed a significant enhancement in Cr(VI) reduction with an increase in Fe(III) concentration and a decrease of initial pH. Biochar produced at higher pyrolysis temperatures (e.g., 700°C) favored Cr(VI) removal, especially in the presence of Fe(III), while a higher biochar dosage proved unfavorable likely due to the agglomeration or precipitation of biochar. Speciation analysis of Fe and Cr elements on the surface of biochar and in the solution further confirmed the role of Fe ion as an electron shuttle between biochar and Cr(VI). The present findings provide a potential strategy for the advanced treatment of Cr(VI) at low concentrations as well as an insight into the environmental fate of Cr(VI) and other micro-pollutants in soil or aqueous compartments containing Fe and natural or engineered carbonaceous materials.     

Optimization of the ionization conditions for the trace analysis of PCDD/PCDF with ion trap MS/MS

Commercial ion trap mass spectrometer provides easy-to-operate MS/MS analysis for the determination of PCDD/PCDF. The limit of quantification is appropriately low (0.2 pg for 23478-P5CDF) because all the stages are performed in the trap and sample losses associated with the ion transportation are minimized. However, if excessive ions are injected into the trap, its electrical fields are distorted and an overall reduction in performance arises. Ionization condition is an important parameter as it affects the amount of the total ions produced. If the amount of interfering compounds are negligible, such as standard solution or cleaned-up sample, lower ionization condition (e.g. electron energy: 30 eV, emission current (EC): 150 μA) is preferable. On the contrary, in case excessive interfering ions are coexisting with PCDD/PCDF, such as crude extract or semi-cleaned-up sample, the ionization condition should be high (e.g. electron energy: 90 eV, EC: 350 μA) for the reproductive quantification.     

电子束烟气治理技术的应用

简述了电子束烟气治理技术研究结果基础上的工业规模装置的工艺流程，介绍了１０万ｋＷ级发电机组烟气治理示范装置的主要设计参数及其可行性方案概述。