Abstract. Weekly PM 2.5 samples were collected for one year (1999)(2000) in Beijing and Shanghai and the carbonaceous species analyzed to investigate and compare their time series patterns and possible sources in the two biggest cities of China. Weekly carbonaceous concentrations varied in wide ranges with 8.6-59 µg m −3 for OC and 1.5-25.4 µg m −3 for EC in Beijing, and with 5.1-38.4 µg m −3 for OC and 2.3-13.0 µg m −3 for EC in Shanghai. Similar weekly and seasonal variations of OC and EC concentrations were found in each city though major combustion sources presented source-dependent emission characteristics and seasonal differences in emission amount for carbonaceous species. Both OC and EC maintained much higher concentrations in late fall through winter, probably due to enhanced emissions coupled with unfavorable meteorological conditions. In Beijing, the 14 C analysis of limited samples suggested there was a significant contribution (33-48%) of modern carbon to the total fine carbonaceous PM burden with higher fractions in the harvest seasons. The high mass ratios of excessive potassium to EC in both Beijing and Shanghai also indicated that biomass burning had important contribution to fine carbonaceous particles.

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This paper presents an experimental study on the effect of randomly distributed fibres on enhancing the liquefaction resistance of sand. A series of undrained cyclic triaxial compression tests and hollow cylinder torsional shear tests were conducted on saturated sand samples with and without fibres. The influencing factors (including fibre length, fibre content and relative density), which are closely related to the liquefaction resistance of sand, were investigated. The test results indicated that samples reinforced with randomly distributed fibres can sustain many more loading cycles than can samples without fibres before liquefaction occurs; that is, the inclusion of fibres can effectively improve the liquefaction resistance of sand. The liquefaction resistance increased with increasing fibre length and fibre content. The reinforcement effect is found to be significant in both medium dense samples and loose samples. The results from triaxial tests and hollow cylinder shear tests were similar, indicating that the different loading conditions in the two types of tests will not influence the reinforcement effect of randomly distributed fibres.

In a geological repository for disposal of high-level radioactive waste, gas breakthrough is an important phenomenon during a gas migration process in the saturated engineered barrier. In this paper, gas injection, swelling pressure, water permeability, and water retention tests were conducted on saturated compacted GaoMiaoZi (GMZ) bentonite to investigate the gas breakthrough mechanism. Results show that, for saturated GMZ bentonite tested under rigid boundary conditions, the gas breakthrough pressure is significantly larger than the swelling pressure and slightly lower than the gas entry pressure obtained from the water retention characteristic and the van Genuchten model. Gas breakthrough pressure deviates from the swelling pressure and approaches the calculated gas entry pressure as the dry density increases. Mechanical and capillary effects are both important to the gas migration process for specimens with lower dry densities, and the capillary effect becomes more important with the increase of dry density. The desaturation and shrinkage of the specimen will result in unexpectedly high and disordered interfacial gas flux. For specimens with higher dry densities, gas will only flow through interconnected larger pores, then result in minor desaturation–shrinkage of the specimen. Finally, a new model with consideration of both mechanical and capillary effects is proposed, which can accurately predict gas breakthrough pressure for a GMZ bentonite specimen.

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