Dry-deposited particles were collected during the passage of an extremely strong dust storm in March, 2010 at a coastal site in Qingdao(36.15°N, 120.49°E), a city located in Eastern China. The size, morphology, and elemental composition of the particles were quantified with a scanning electron microscope equipped with an energy dispersive X-ray instrument(SEM–EDX). The particles appeared in various shapes, and their size mainly varied from 0.4to 10 μm, with the mean diameters of 0.5, 1.5, and 1.0 μm before, during, and after the dust storm, respectively. The critical size of the mineral particles settling on the surface in the current case was about 0.3–0.4 μm before the dust storm and about 0.5–0.7 μm during the dust storm. Particles that appeared in high concentration but were smaller than the critical size deposited onto the surface at a small number flux. The elements Al, Si and Mg were frequently detected in all samples, indicating the dominance of mineral particles. The frequency of Al in particles collected before the dust storm was significantly lower than for those collected during and after the dust storm. The frequencies of Cl and Fe did not show obvious changes, while those of S, K and Ca decreased after the dust arrival. These results indicate that the dust particles deposited onto the surface were less influenced by anthropogenic pollutants in terms of particle number. 相似文献
In order to study their synergistic catalytic effects in toluene degradation, CuMn_2O_4/HTS-1(HTS-1 was a titanium silicon molecular sieve), Cu_(0.7)Mn_2Y_(0.3)O_x/HTS-1 and Cu_(0.7)Mn_2Ce_(0.3)O_x/HTS-1 catalysts were prepared by the impregnation method.The textural properties, redox properties and acidity of the catalysts were characterized by X-ray diffractometer(XRD),transmission electron microscopy(TEM), scanning electron microscopy(SEM), H_2 temperature-programmed reduction(H_2-TPR), X-ray photoelectron spectroscopy(XPS),frustrated total internal reflection(FT-IR), ammonium temperature-programmed desorption(NH_3-TPD) and pyridine adsorption internal reflection(Py-IR) measurements.The potential roles of Lewis acid sites(activating dioxygen) were discussed, and the experimental results indicated that the most efficient route for toluene degradation over Cu_(0.7)Mn_2Ce_(0.3)O_x/HTS-1(toluene conversion rate of 90%(T99) = 295℃) was ascribed to regulation of the synergistic effects of redox properties(activating molecular toluene) and Lewis acid sites(activating dioxygen).The Mars–Van–Krevelen(MVK) model was adopted to describe the reaction process of toluene oxidation, which gave an in-depth view into the toluene degradation over CuMn_2O_4/HTS-1, Cu_(0.7)Mn_2Y_(0.3)O_x/HTS-1 and Cu_(0.7)Mn_2Ce_(0.3)O_x/HTS-1.In addition, the synergistic effects between redox properties and Lewis acid sites were studied in detail. 相似文献
CO2 can be injected into deep saline aquifers for storage, thereby reducing the concentration of CO2 in the atmosphere. When CO2 is injected into the aquifer, salt precipitation may occur, which may impair the injectivity and affect storage safety. In this study, numerical simulation was used to study salt precipitation in heterogeneous anisotropic sandstone aquifers, the feedback effect of salt precipitation on the flow was considered, and the additional pressure increase caused by salt precipitation was evaluated. The results showed that the maximum decrease in formation permeability and the maximum additional pressure buildup caused by salt precipitation reached 88% and 4.91 MPa, respectively. The salinity of the formation water and the maximum additional pressure buildup is approximately proportional when the salinity is low. Once the salinity exceeds a certain value (approximately 20% in this study), the maximum additional pressure buildup increases sharply. As the permeability increases, the additional pressure buildup decreases. When permeability reaches a certain threshold (approximately 5×10?14 m2 in this study), the maximum additional pressure buildup decreases rapidly and changes only slightly as permeability increases. The CO2 injection rate is basically proportional to the maximum additional pressure buildup. When the vertical permeability increases, the additional pressure buildup due to salt precipitation shows a downward trend. The low-permeability interbeds above the CO2 injection well will cause more local salt precipitation near it, which will further cause a greater and wider pressure buildup. The heterogeneity of the formation will greatly enhance salt precipitation, thereby promoting the formation pressure buildup. The formation heterogeneity must be considered in the study of the salt precipitation and its effect on CO2 injection, especially when the formation permeability is low, the CO2 injection rate is high, and the salinity of the formation water is high.
Environmental Science and Pollution Research - Understanding whether and how urban innovation offers a sound solution to the dilemma of urban green development is a crucial response to mitigate the... 相似文献
Environmental Science and Pollution Research - Meteorological factors, which are periodic and regular in a long run, have an unignorable impact on human health. Accurate health risk prediction... 相似文献
• The optimum SCR activity was realized by tuning the acid pretreatment.• Optimized catalysts showed NOx conversion above 90%.• The NH3 and NO adsorption capacity of Al-O3-Fe is stronger than Fe-O3-Fe.• The formation of almandine consumes Fe3+ and Al3+ and weakens their interaction. Red mud (RM), as an alkaline waste, was recently proved to be a promising substitute for the SCR catalyst. Dealkalization could improve the acidity and reducibility of red mud, which were critical for SCR reaction. However, the dealkalization effect depended on the reaction between acid solution and red mud. In this study, we realized the directional control of the chemical state of active sites through tuning the acid pretreatment (dealkalization) process. The pretreatment endpoint was controlled at pH values of 3–5 with diluted nitric acid. When the pH values of red mud were 3 and 5 (CRM-3 and CRM-5), activated catalysts showed NOx conversion above 90% at 275°C–475°C. The high initial reaction rate, Ce3+/(Ce3+ + Ce4+) ratio, and surface acidity accounted for the excellent SCR performance of CRM-5 catalyst. Meanwhile, more Fe3+ on the CRM-3 surface improved the NH3 adsorption. There was a strong interaction between Al and Fe in both CRM-5 and CRM-3 catalysts. DFT results showed that the adsorption capacity of the Al-O3-Fe for NH3 and NO is stronger than that of Fe-O3-Fe, which enhanced the NOx conversion of the catalyst. However, the almandine was formed in CRM-4, consumed part of Fe3+ and Al3+, and the interaction between Al and Fe was weakened. Also, deposited almandine on the catalyst surface covered the active sites, thus leading to lower NH3-SCR activity. 相似文献
Environmental Science and Pollution Research - The bioavailable trace metals are closely related to environmental safety and human health, which might have different source characteristics from the... 相似文献
Aiming at the problems of complex environment and serious dust pollution in large open-pit coal yards, a dust suppression gel with a dual network structure was prepared by modifying the soluble starch and sodium alginate with iron ions. The changes of functional groups, thermal stability, and morphology structure before and after the reaction were analyzed by FTIR, TG-DSC, and SEM, and the formation mechanism of the dual network was revealed by XPS. Furthermore, the water absorption and water retention experiments proved that the dual network structure is more conducive to water retention than the single-layer network. According to molecular dynamics simulations and contact angle experiments, gel and adsorbed water molecules can approach coal dust molecules on their own to contact, wet, and combine with coal dust. The adhesion test proved that the dust suppression gel with iron ions had better adhesion to dust. The anti-freezing test shows that the dust suppression gel has good anti-freezing performance. The antifreeze test shows that the dust suppression gel still has excellent freeze–thaw resistance at the test temperature of??-20℃. The mechanical property test shows that the dust suppressant gel can prevent the product from being damaged by external force. The acid and alkali resistance experiments showed that the acid and alkali resistance of the gel was improved under the condition of iron ion modification, and the flying of coal powder was effectively prevented. This research provides a new theoretical idea for coal dust control in complex environment.