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  • Author or Editor: Q. Xu x
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Summary  

Air samples were collected at a downtown site in Beijing from January to July 2004 and analyzed by instrumental neutron activation analysis (INAA) combined with organic solvent extraction method for the concentrations and distributions of extractable organohalogens (EOX), including extractable organochlorinated (EOCl), organobrominated (EOBr) and organoiodinated compounds (EOI). The concentrations of EOX were increasing in the order of EOCl >> EOBr ~ EOI in both gaseous and particulate phase. EOCl accounted for 75.8-100% and 83.7-100% of EOX in particulate and gaseous phase, respectively, suggesting that EOCl was the major component of the organohalogens in the atmosphere. In the plots of the logarithm of the EOX concentrations versus the reciprocal temperature, their linear relations were observed for EOCl (R = -0.9), for EOBr (R = -0.6) and EOI (R = -0.7) in gaseous phase, which indicated that the concentrations of EOCl, EOBr and EOI in gaseous phase exhibited a strong temperature dependence, i.e., their concentrations increased with increasing of temperature.

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Abstract  

In our invention, FCC (fluid catalytic cracking) dry gas could be used to react with benzene without any special purification, and more than 90% ethylene was converted to ethylbenzene. The phenomenon of carbon deposition over catalyst surface was obvious and leads to a deactivation of catalyst, so it is important to study the behavior of carbon deposition of catalyst during alkylation of benzene. The influence of several factors such as temperature, reaction time, reactant concentration of the amount and the kinetics of carbon deposition were investigated, during which carbon depositing rate equations were obtained for different reactant.

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The combustion behavior of Shuangya Mountain (SYM) coal dust has been investigated by means of TG in this paper. The reaction fraction can be obtained from isothermal TG data. The regressions of g(), an integral function of vs. t for different reaction mechanisms were performed. The mechanism of nucleation and nuclei growth is determined as the controlling step of the coal dust combustion reaction by the correlation coefficient of the regression, and the kinetic equation of the SYM coal dust combustion reaction has been established.

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Abstract  

The synthesis of superheavy elements is now a hot topic in nuclear physics. Alpha-decay and spontaneous fission are two main decay modes in heavy and superheavy regions. Theoretical studies on alpha radioactivity and spontaneous fission can provide useful information for experiments. We investigate the alpha-decay and spontaneous fission of heavy and superheavy nuclei with different models. This includes the alpha-decay energies, alpha decay half-lives, and half-lives of spontaneous fission. The theoretical alpha-decay half-lives are in good agreement with experimental ones. The calculated half-lives of spontaneous fission are in reasonable agreement with present data. The properties of unknown nuclei are predicted.

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Abstract  

Although Ir anomaly has been discovered in a number of C/T boundaries in the world, no positive results of this anomaly in Permian/Triassic (P/Tr) boundary were given. There are many well-developed P/T sections in South China. One of representative sections is located at the Baoqing quarry, Meishan Town, Changxin County, Zhejiang Province. Ir, Os, Re, Au, Pt, Cu and Mo were determined by the radiochemical procedure developed in our laboratory. (1) Besides those accessible by INAA. The results reveal that the refractory siderophile and other chalcophile elements have certain enrichment near and at the boundary layer. However, the Ir/Au and other element abundance ratios fail to accord with the extraterrestrial values. The nature of the boundary event was discussed in terms of elemental geochemistry.

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Abstract  

The concentrations of 14 elements, including Ir, Au, Co, Cr, Fe, Sr, Rb, K, Ta, Zn, Sb, Ba, Sc and Se, in the Wuxi fallen ice were determined by neutron activation analysis. The experimental results show that the relative concentration ratios of Ir/Co, Ir/Cr and Ir/Sc etc. in the ice water (0.0069, 0.00024 and 0.11, respectively) are quite close to those of Type C1 chondrite (0.0102, 0.00021 and 0.092, respectively), which implies that the fallen ice might be a piece of extraterrestrial substance.

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Abstract  

The acidity of mesoporous materials FeSiMCM-41, LaSiMCM-41, SiMCM-41, AlSiMCM-41 and HAlSiMCM-41 has been investigated by microcalorimetric studies of the adsorption of ammonia and temperature programmed ammonia desorption method. In the initial stage, the acid strength sequence is SiMCM-41>HAlSiMCM-41>AlSiMCM-41>FeSiMCM-41>LaSiMCM-41, in agreement with that found for microporous molecular sieves materials. A small number of strong acid sites of SiMCM-41 may result from the aluminum impurity contained in the silica source material. The acid density sequence is HAlSiMCM-41>AlSiMCM-41>FeSiMCM-41>LaSiMCM-41SiMCM-41 and can be explained by the studies of existing states of trivalent atoms in these samples reported in previous work. Since some NH3-TPD plots of these samples show the profiles that could not be back to baseline at elevated temperature, the technique of microcalorimetric adsorption is preferable in studying these samples.

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Abstract  

The sorption of Eu(III) on calcareous soil as a function of pH, humic acid (HA), temperature and foreign ions was investigated under ambient conditions. Eu(III) sorption on soil was strongly pH dependent in the observed pH range. The effect of ionic strength was significant at pH < 7, and not obvious at pH > 8. The type of salt cation used had no visible influence on Eu(III) uptake on soil, however at low pH values, the influence of anions was following the order: Cl ≈ NO3  > ClO4 . In the presence of HA, the sorption edge obviously shifted about two pH units to the lower pH, whilst in range of pH 6–7, the sorption of Eu(III) decreased with increasing pH because a considerable amount of Eu(III) was present as humate complexes in aqueous phase, then increased again at pH > 11. The results indicated that the sorption of Eu(III) on soil mainly formed outer-sphere complexes and/or ion exchange below pH ~7; whereas inner-sphere complexes and precipitation of Eu(OH)3(s) may play main role above pH ~8.

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Abstract  

The paper presents the results of determination of extractable organohalogens (EOX) by instrumental neutron activation analysis (INAA), and polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) by gas chromatography (GC), in atmospheric precipitation in Shanghai, China, from January to August 2005. The results showed that EOCI was the major component of organohalogens in precipitation. A significant correlation between the concentrations of EOBr and EOI was observed (r 2 = 0.75), which suggested that EOBr and EOI in precipitation might mainly come from the same sources. There were no clear seasonal trends for the concentrations of EOX. The concentrations of ΣPCBs ranged from 0.2–2.8 ng/l, with the dominant PCBs containing 3 to 5 chlorine atoms. HCH was the predominant pesticide in precipitation, accounting for over 80% of total OCPs, in which β-HCH took 28%–72% of total HCH. Also, there may be an evidence for significantly historical usage of DDT.

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Abstract  

Yaozhou Kiln at Lidipo and Shangdian are two independent porcelain kiln groups of Yaozhou kiln series in Shanxi Province. Both of them were consisted of some individual porcelain kilns. The samples of 20 pieces of porcelain sherds produced in Shangdian and 43 pieces of porcelain sherds made in Lidipo sites which produced in Kin Dynasty (1115–1234 A.D.) have been collected. The main chemical compositions in body were determined by X-ray fluorescence (XRF). The contents of trace elements were measured using neutron activation analysis (NAA). Principal component analysis (PCA) and stepwise discriminant analysis were used to study the provenance characteristic of these samples. The results indicated that the main components and trace elements in the specimen can be used to reveal the provenance characteristic.

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