Free convection of a dusty‐gas flow along a semi‐infinite vertical cylinder

An analysis is performed to study the free convection of a dusty‐gas flow along a semi‐infinite isothermal vertical cylinder. The governing equations of the flow problem are transformed into non‐dimensional form and the resulting nonlinear, coupled parabolic partial differential equations have been solved numerically using an implicit finite difference scheme of Crank–Nicholson type. The flow variables such as gas–velocity, dust‐particle velocity and temperature, shearing stress and heat transfer coefficients are calculated numerically for various parameters occurring in the problem. It is observed that due to the presence of dust particles, the gas velocity is found to decrease. Copyright © 2009 John Wiley & Sons, Ltd.     

论卤盐养生（8）

卤盐（包括食盐）是中国矿物药的重要组成部分。从文化价值、临床应用和情志调摄3个方面诠释了卤盐的养生学意义,并全面、详细地阐述了食盐对中国古代文化的四大贡献、6种盐类的现代临床应用价值以及盐湖旅游的6项要素;列举了160多个盐湖卤水的主要化学成分、矿化度或微量元素;摘录了论述卤盐主治功用的古今文献。本文分期刊出。     

Determination of Pd,Rh, Pt,Au in road dust by electrothermal vaporization inductively coupled plasma mass spectrometry with slurry sampling

Inductively coupled plasma mass spectrometry coupled with ultrasonic slurry sampling electrothermal vaporization (USS-ETV-ICP-MS) has been applied to determine Pd, Rh, Pt and Au in 0.5% m/v slurries of several road dust samples. 2% m/v ammonium pyrrolidine dithiocarbamate (APDC) was used as the modifier to enhance the ion count. The influence of instrument operating conditions, slurry preparation and interferences on the ion count was reported. This method has been applied to the determination of Pd, Rh, Pt and Au in BCR 723 Road Dust and NIST SRM 2709 San Joaquin Soil reference materials and two road dust samples collected locally. The analysis results of the standard reference materials agreed with the certified values. Precision between sample replicates was better than 10% for all the determinations. The method detection limits estimated from standard addition curves were 0.9, 0.4, 0.6 and 0.4 ng g⁻¹ for Pd, Rh, Pt and Au, respectively, in original dust samples.     

Efficient Synthesis of Aryl Hydroxylactams by Reducing Imides With Activated Zinc Dust

A series of aryl hydroxylactams (2a, 2b, 2d–2g, 2i–2k, 2m, and 2n) was synthesized by partially reducing aryl cyclic imides in moderate to excellent yields with activated zinc dust alone in acetic acid. This method was regiospecific and can be employed as an alternative for reported methods to partially reduce aryl cyclic imides.     

Influence of Interfacial Tension on Seeded Calcium Carbonate Scale Precipitation: Effect of Adsorbed Asphaltenes

Clay particles with adsorbed asphaltenes, which are commonly found in produced water, have been used as seed particles during precipitation of calcium carbonate in order to determine whether such particles may influence the kinetics of precipitation. The results show that the presence of the adsorbed asphaltenes accelerates the precipitation, and there is also a significant difference between different types of adsorbed asphaltenes. The adsorption of asphaltenes at the seed surface leads to a significant increase in the interfacial tension between the seed surface and the aqueous solution, and calcium carbonate therefore precipitates at the seed surface in order to reduce this high interfacial tension.     

Investigation of the solubilization of car-emitted Pt,Pd and Rh in street dust and spiked soil samples

A sequential extraction procedure (three-step), proposed by the Standards, Measurements and Testing Programme (formerly BCR) of the European Union, was applied to street dust and spiked soil samples for the determination of PGEs. Analyses were carried out using inductively coupled plasma-mass spectrometry (ICP-MS). The results indicate that up to 5% from Pt, 70% from Pd and 14% from Rh are in mobile forms in street dust. The results for the soil samples spiked with crushed catalytic converter are significantly lower indicating that PGEs are oxidised more efficiently in natural conditions. Additionally Pt and Pd bound to humic acids were investigated.     

Pressurised solvent extraction of nitrated derivatives of polycyclic aromatic hydrocarbons from roadside dust

An analytical method based upon the pressurised solvent extraction and gas chromatography and mass spectrometry (GC-MS) for analysis of nitrated derivatives of polycyclic aromatic hydrocarbons (nitro-PAHs) in roadside dust has been developed. Five nitro-PAHs (1-nitronaphthalene, 1-nitropyrene, 9-nitroanthracene, 2-nitrofluorene, 6-nitrochrysene) were chosen for this study because of their variable physical properties and effect on human health. Experiments with spiked inert matrix were used for the best extraction conditions finding. Different extraction conditions (temperature, pressure, solvents and duration of extraction cycle) were examined. The highest recoveries were observed at the extraction pressure of 14?MPa, temperature of 100°C and two cycles of 5?min extraction time, when dichloromethane was used as an extraction solvent. These conditions were applied to the extraction of nitro-PAHs from roadside dust. After extraction the nitro-PAHs fraction was isolated by the silica gel column chromatography. The GC-MS detector was used for analyses of the extracts. Recoveries of nitro-PAHs after extraction from roadside dust ranged from 60% for 9-nitroanthracene to 108% for 6-nitrochrysene.     

Application of the Combustion Method in a Closed Flask to the Lead Determination in Atmospheric Aerosols

Abstract

The destruction of the filter for metal determination in atmospheric aerosols is an important step in the analysis. Nowadays the decomposition of this kind of sample has not been completely solved, so it is interesting to study new methods for filter sample attack. In the present work the application of the combustion method in a closed flask for mixed cellulose esters filter decomposition for lead determination is proposed. For this purpose optimum operating conditions as stopper flask design, sample size, flask volume, shaking time and volume and concentration of absorbing solution are established, and accuracy and precision of the proposed method using AAS for the measurements is given. The results obtained by the closed flask combustion are compared with those found by wet attack with HNO₃. The method proposed is rapid, has low reagent contamination and no loss of lead by volatilization or by amalgamation occurs. This method shows an accuracy and a precision in good agreement with the standard method.     

Preconcentration of cobalt using Amberlyst 36 as a solid-phase extractor and its determination in various environmental samples by flame atomic absorption spectrometry

A new and simple column-solid-phase extraction method has been developed to separate and preconcentrate trace cobalt in water and soil prior to its determination by flame atomic absorption spectrometry (FAAS). Different factors such as pH of sample solution, sample volume, amount of resin, flow rate of aqueous solution, volume and concentration of eluent, and matrix effects for preconcentration were optimized. Under optimized experimentally established conditions, an analytical detection limit of 0.44?µg?L^?1, precision (RSD) of 1.9%, enrichment factor of 200, and capacity of resin of 82?mg?g^?1 were obtained. The method was applied for cobalt determination by FAAS in tap water, natural drinking water, soil, and roadside dust samples. The accuracy of the method is confirmed by analysing standard reference material (Montana Soil, SRM 2711).     

A re-examination of platinum-group element concentrations in the environmental certified reference material BCR-723

A detailed statistical examination of replicated data used to certify platinum-group elements (PGEs) in environmental reference material BCR-723 is presented. Certification of Pt, Pd, and Rh concentrations in BCR-723 was based on 16, eight, and nine accepted data sets, respectively. Each accepted data set contained six replicated measurements for each PGE, and the statistical properties of these concentration data were examined, i.e. 96 for Pt, 48 for Pd, and 54 for Rh. This level of investigation has received limited attention but is critical in furthering our understanding of PGE variability and representativeness. Concentrations of Pt, Pd, and Rh were shown to differ significantly between accepted data sets. Palladium and Pt differed in their quantification between detection techniques. Additionally, Pd and Pt concentrations varied significantly between laboratories using a similar definitive method (inductively coupled plasma-isotope dilution mass spectrometry). The distribution of Pd concentrations was found to be bimodal, with a secondary population exhibiting a contamination signal of about 15%. The secondary population, not previously reported in BCR-723, is likely a measurement artifact and not due to a nugget effect. Comparisons of BCR-723 with other environmental media from Europe, i.e. airborne particulate matter, tunnel dust, and road-deposited sediment, indicated that Pd is uncommonly low in BCR-723 (6.0?ng?g^?1) and is generally not representative in terms of its distribution relative to Pt and Rh. Serious consideration should be given to developing a new PGE certified environmental reference material.