No abstract

[1] The 2008 M w 7.9 Wenchuan earthquake is a result of ongoing India-Tibet collision and reflects the growth of the Longmen Shan fold-and-thrust belt. In this paper, we construct a 3-D structural model of the geometry of the coseismic faults and related structures of the Wenchuan earthquake by integrating geological investigations, relocated aftershocks, and seismic reflection profiles. In the 3-D structural model, the differences between the southern and northern segments of the rupture are highlighted. The structural transition zone between the two segments contains a major geometric segment boundary, reflecting differences in the structural configuration of the thrust ramp and the tectonic evolution of the fault system, which appears to have localized significant damage from Anxian to Beichuan. Within the northern segment, we identify a transverse structure across which the Beichuan fault plunges under the Tangwangzhai syncline. This boundary corresponds to a marked change in the nature of the surface rupture and is illuminated by a microearthquake sequence perpendicular to the Longmen Shan thrust belt. In the southern segment, our investigations confirm that uplift due to active faulting and folding is largely responsible for the areas of steepest topography. On the basis of this association, the southwestern segment of the Longmen Shan, south of the Wenchuan earthquake, is likely active and presents a significant earthquake hazard, despite the lack of historical earthquakes in this region. This study illustrates the importance of building 3-D models to study active faulting and folding, as well as to assess earthquake hazard.

For understanding the environmental behavior and toxicity of Ag nanoparticles (Ag-NPs), a quantitative method for characterizing the AgNPs in soils and sediments is urgently needed. In this study, we validated a previously developed extraction method by optimizing the extraction of silver nanoparticles from soil and sediment samples to which engineered AgNPs had been added. The samples were analyzed by single particle inductively coupled plasma mass spectrometry (SP-ICP-MS). Initially, different extraction conditions were evaluated to validate the optimal extraction procedure. Then the optimal extraction procedure was applied to environmental soil and sediment samples spiked with AgNPs. The extraction data for Ag-NPs with sizes below 30 nm was not shown due to the particle size detection limit of the SP-ICP-MS method (∼20 nm). The number concentrations of Ag particles extracted from different environmental soils and sediments matrices were in the range of (12 ± 1–23 ± 1) × 107 particles/g soil. Similarly, 53.4–100.0% of the particulate Ag mass was recovered. For the relatively low Ag mass recovery of Guiyu agricultural soil, the Ag mass recovery shows great improvement (from 53.4 to 105.8%) by the soil dilution using SiO2. The optimal method was validated to be feasible for extracting Ag-NPs from environmental soils and sediments, except for the soil with high soil organic matter (SOM) content. The SiO2 dilution of soil provides a promising way to promote the extraction of Ag-NPs in soil (or sediment) with high SOM content, which could further promote the study on the environmental behavior and toxicity of Ag-NPs in soil and sediment environment.

The oxidation of alcohols is a kind of very important reaction in industry and has caused great concern in recent years, especially with molecular oxygen as the oxidant. Among various catalysts reported in the literature, Au/CeO2 exhibits excellent catalytic performance in the oxidation of alcohols, with aldehydes as the target product. However, there is still not a clear consensus regarding the nature of the active sites of Au/CeO2 related catalysts. In this contribution, three distinctly different Au species supported on CeO2 nanorods (CeO2-NR) were prepared (viz., isolated single Au atoms (Au-SA), Au nanoclusters (Au-NC), and Au nanoparticles (Au-NP)); their catalytic performances in the aerobic oxidation of alcohols was comparatively investigated in order to discriminate the active sites in Au/CeO2. A series of characterization results combining with DFT calculation illustrates that the performance of Au/CeO2 catalysts in alcohol oxidation is closely related to the size of Au species and the concentration of oxygen vacancies (Ov), where the interfacial [O–Ov–Ce–O–Au] sites between Au species and CeO2 support play an important role in catalyzing the alcohol oxidation. The oxygen vacancies in CeO2 facilitate the adsorption of alcohol and the dissociation of the O–H bond, whereas the adjacent Au3+/Au+ species can promote the elimination of β-hydride in the alkoxide intermediate. As the Au-SA/CeO2-NR catalyst is provided with abundant active [O–Ov–Ce–O–Au] sites, it exhibits much higher activity in the oxidation of alcohols, in comparison with Au-NC/CeO2-NR and Au-NP/CeO2-NR. The insight shown in this work should be helpful in understanding the catalysis of interfacial sites between metal and an oxide support and developing better catalysts for the oxidation of alcohols.