Release of Chromium from Soils with Persulfate Chemical Oxidation   总被引：1，自引：0，他引：1  

Kawalpreet Kaur  Michelle Crimi 《Ground water》2014,52(5):748-755

An important part of the evaluation of the effectiveness of persulfate in situ chemical oxidation (ISCO) for treating organic contaminants is to identify and understand its potential impact on metal co‐contaminants in the subsurface. Chromium is a redox‐sensitive and toxic metal the release of which poses considerable risk to human health. The objective of this study was to investigate the impact of persulfate chemical oxidation on the release of chromium from three soils varying in physical‐chemical properties. Soils were treated with unactivated and activated persulfate [activated with Fe(II), Fe(II)‐EDTA, and alkaline pH] at two different concentrations (i.e., 41 mM and 2.1 mM persulfate) for 48 h and 6 months and were analyzed for release of chromium. Results show that release of chromium with persulfate chemical oxidation depends on the soil type and the activation method. Sandy soil with low oxidant demand released more chromium compared to soils with high oxidant demand. More chromium was released with alkaline pH activation. Alkaline pH and high Eh conditions favor oxidation of Cr(III) to Cr(VI), which is the main mechanism of release of chromium with persulfate chemical oxidation. Unactivated and Fe(II)‐activated persulfate decreased pH and at low pH in absence of EDTA chromium release is not a concern. These results indicate that chromium release can be anticipated based on the given site and treatment conditions, and ISCO system can be designed to minimize potential chromium release when treating soils and groundwater contaminated with both organic and metal contaminants.  相似文献   

Phase Resolved High Speed Photometry and Spectroscopy of Pulsars     

Claudio Cumani  Karl-Heinz Mantel 《Experimental Astronomy》2001,11(2):145-150

We describe the implementation of two High Time Resolution modes for ESO's new generation CCD controller FIERA. These new modes have been used to perform phase-resolved high speed photometry and spectroscopy of pulsars with the FORS instruments at the VLT.  相似文献   

The photometric and spectroscopic variability of 1329-294     

R. Haefner  H. Barwig  K. -H. Mantel 《Astrophysics and Space Science》1993,204(2):199-204

Photometric and spectroscopic observations of the poorly documented cataclysmic variable 1329-294 are presented. No definite period neither on a long nor on a short time scale could be derived from the photometric data. The radial velocity curve of the emission lines has been used to improve the known orbital period and to confine the primary mass to a value within the Chandrasekhar limit.Based on observations collected at the European Southern Observatory.  相似文献   

Robe’s problem: its extension to 2+2 bodies     

Bhavneet Kaur  Rajiv Aggarwal 《Astrophysics and Space Science》2012,339(2):283-294

In the problem of 2+2 bodies in the Robe’s setup, one of the primaries of mass m^*₁m^{*}_{1} is a rigid spherical shell filled with a homogeneous incompressible fluid of density ρ ₁. The second primary is a mass point m ₂ outside the shell. The third and the fourth bodies (of mass m ₃ and m ₄ respectively) are small solid spheres of density ρ ₃ and ρ ₄ respectively inside the shell, with the assumption that the mass and the radius of third and fourth body are infinitesimal. We assume m ₂ is describing a circle around m^*₁m^{*}_{1}. The masses m ₃ and m ₄ mutually attract each other, do not influence the motion of m^*₁m^{*}_{1} and m ₂ but are influenced by them. We also assume masses m ₃ and m ₄ are moving in the plane of motion of mass m ₂. In the paper, the equations of motion, equilibrium solutions, linear stability of m ₃ and m ₄ are analyzed. There are four collinear equilibrium solutions for the given system. The collinear equilibrium solutions are unstable for all values of the mass parameters μ,μ ₃,μ ₄. There exist an infinite number of non collinear equilibrium solutions each for m ₃ and m ₄, lying on circles of radii λ,λ′ respectively (if the densities of m ₃ and m ₄ are different) and the centre at the second primary. These solutions are also unstable for all values of the parameters μ,μ ₃,μ ₄, φ, φ′. Such a model may be useful to study the motion of submarines due to the attraction of earth and moon.  相似文献   

Transition metals (Mn,Ni, Co) doping in TiO<Subscript>2</Subscript> nanoparticles and their effect on degradation of diethyl phthalate     

R. Kaur  P. Singla  K. Singh 《International Journal of Environmental Science and Technology》2018,15(11):2359-2368

Transition metal-doped TiO₂ nanoparticles are synthesized by sol–gel method. The as-prepared samples are characterized by various techniques to correlate structural and optical properties with chemical nature of dopants and their effect on photocatalytic degradation of diethyl phthalate esters. X-ray diffraction (XRD) reveals that all the samples are crystalline and exhibit anatase as a major phase. Chemical nature of dopants could not affect the formation of anatase and its volume fraction. The crystallite size of undoped and doped TiO₂ nanoparticles varies between 10 and 12 nm as confirmed by XRD and transmission electron microscope. The lowest optical band gap observed is 2.47 eV in Mn-doped TiO₂. Among all the samples, Ni-doped TiO₂ sample shows better photocatalytic activity and degradation of diethyl phthalate due to its lower crystallite size and higher surface area than those of Mn- and Co-doped TiO₂ samples.  相似文献   

Metasomatism of ferroan granites in the northern Aravalli orogen,NW India: geochemical and isotopic constraints,and its metallogenic significance   总被引：1，自引：0，他引：1  

Parampreet Kaur  Naveen Chaudhri  Albrecht W. Hofmann  Ingrid Raczek  Martin Okrusch  Susanne Skora  Jürgen Koepke 《International Journal of Earth Sciences》2014,103(4):1083-1112

The late Palaeoproterozoic (1.72–1.70 Ga) ferroan granites of the Khetri complex, northern Aravalli orogen, NW India, were extensively metasomatised ~900 Ma after their emplacement, at around 850–830 Ma by low-temperature (ca. 400 °C) meteoric fluids that attained metamorphic character after exchanging oxygen with the surrounding metamorphic rocks. Albitisation is the dominant metasomatic process that was accompanied by Mg and Ca metasomatism. A two-stage metasomatic model is applicable to all the altered ferroan intrusives. The stage I is represented by a metasomatic reaction interface that developed as a result of transformation of the original microcline–oligoclase (An_12–14) granite to microcline–albite (An_1–3) granite, and this stage is rarely preserved. In contrast, the stage II metasomatic reaction front, where the microcline-bearing albite granite has been transformed to microcline-free albite granite, is readily recognisable in the field and present in most of the intrusives. Some of them lack an obvious reaction interface due to the presence of stage II albite granites only. When studied in isolation, these intrusives were incorrectly classified and their tectonic setting was misinterpreted. Furthermore, our results show that the mafic mineralogy of metasomatised granites has a significant impact on the characterisation of such rocks in the magmatic classification and discrimination diagrams. Nevertheless, the stage I metasomatised granites can be appropriately characterised in these diagrams, whereas the characterisation of the stage II granites will lead to erroneous interpretations. The close spatial association of these high heat producing ferroan granites with iron oxide–copper–gold (IOCG), U and REE mineralisation in the region indicates a genetic link between the metasomatism and the mineralisation. World-class IOCG, U and REE deposits are associated with metasomatised ferroan granites, suggesting that such a relationship may act as a critical first-order exploration target for undiscovered mineral deposits.  相似文献