[en] Highlights: • The CeO₂-SH catalyst showed >97% conversion of NO_x at 230–450 °C. • The resistance to Na and K of the CeO₂ catalyst was enhanced significantly. • Surface sulfate species bind to Ce⁴⁺ improve the N₂ selectivity in NH₃-SCO. -- Abstract: A series of CeO₂ catalysts prepared with sulfate (S) and nitrate (N) precursors by hydrothermal (H) and precipitation (P) methods were investigated in selective catalytic reduction of NO_x by NH₃ (NH₃-SCR). The catalytic activity of CeO₂ was significantly affected by the preparation methods and the precursor type. CeO₂-SH, which was prepared by hydrothermal method with cerium (IV) sulfate as a precursor, showed excellent SCR activity and high N₂ selectivity in the temperature range of 230–450 °C. Based on the results obtained by temperature-programmed reduction (H₂-TPR), transmission infrared spectra (IR) and thermal gravimetric analysis (TGA), the excellent performance of CeO₂-SH was correlated with the surface sulfate species formed in the hydrothermal reaction. These results indicated that sulfate species bind with Ce⁴⁺ on the CeO₂-SH catalyst, and the specific sulfate species, such as Ce(SO₄)₂ or CeOSO₄, were formed. The adsorption of NH₃ was promoted by these sulfate species, and the probability of immediate oxidation of NH₃ to N₂O on Ce⁴⁺ was reduced. Accordingly, the selective oxidation of NH₃ was enhanced, which contributed to the high N₂ selectivity in the SCR reaction. However, the location of sulfate on the CeO₂-SP catalyst was different. Plenty of sulfate species were likely deposited on CeO₂-SP surface, covering the active sites for NO oxidation, which resulted in poor SCR activity in the test temperature range. Moreover, the resistance to alkali metals, such as Na and K, was improved over the CeO₂-SH catalyst

[en] Perovskite-type oxide La_0.6Ce_0.4CoO₃ and its doped Ag catalysts were prepared and their catalytic performances were evaluated for the direct decomposition of NO and the selective reduction of NO with propene in the presence of oxygen. A noticeable enhancement in activity was achieved by doping Ag and the optimum Ag loading was 1%. The effects of H₂O, SO₂, CO₂ and O₂ on the performances of Ag/La_0.6Ce_0.4CoO₃ catalysts for NO decomposition were also investigated. The resistance against H₂O and SO₂ appears satisfactory. The inhibition by CO₂ is strong, although it is reversible. Oxygen did not inhibit the NO decomposition reaction but significantly promoted it. Compared with other perovskite-type oxides reported previously, higher conversions were obtained over the present catalysts for the NO reduction by propene. We speculate that the decomposition of NO is the predominant process even in the presence of propene. The catalysts were characterized by N₂-adsorption, XRD, XPS and NO-TPD and some explanations were put forward

[en] Catalytic performance of Sn/Al₂O₃ catalysts prepared by impregnation (IM) and sol-gel (SG) method for selective catalytic reduction of NO_x by propene under lean burn condition were investigated. The physical properties of catalyst were characterized by BET, XRD, XPS and TPD. The results showed that NO₂ had higher reactivity than NO to nitrogen, the maximum NO conversion was 82% on the 5% Sn/Al₂O₃ (SG) catalyst, and the maximum NO₂ conversion reached nearly 100% around 425C. Such a temperature of maximum NO conversion was in accordance with those of NO_x desorption accompanied with O₂ around 450C. The activity of NO reduction was enhanced remarkably by the presence of H₂O and SO₂ at low temperature, and the temperature window was also broadened in the presence of H₂O and SO₂, however the NO_x desorption and NO conversion decreased sharply on the 300ppm SO₂ treated catalyst, the catalytic activity was inhibited by the presence of SO₂ due to formation of sulfate species (SO₄^2-) on the catalysts. The presence of oxygen played an essential role in NO reduction, and the activity of the 5% Sn/Al₂O₃ (SG) was not decreased in the presence of large oxygen

[en] Field measurements were conducted to determine the characteristics of non-methane hydrocarbons (NMHCs) emitted from open burning of wheat straw and maize stover, two major agricultural residues in China. The headfire ignition technique was used with sampling downwind from the agricultural fire. Fifty-two NMHC species were quantified using gas chromatography/mass spectrometry. A carbon mass balance method was used to determine NMHC emission factors. The emission factors of the total speciated NMHCs from wheat straw and maize stover are 1690 ± 580 mg kg^-1 and 1590 ± 430 mg kg^-1, respectively. Propane, n-pentane, 2,3-dimethylbutane, 2-methylpentane, propene, benzene and toluene are the main species, together accounting for 55.3%-68.0% of the total NMHCs. On the basis of measured emission factors and the published maximum incremental reactivity values for NMHCs, we estimated the ozone forming potential (OFP) of speciated NMHCs. The results indicate that propene, 1-butene, isoprene, toluene and m,p-xylene have high OFP values and account for about 50% of the total OFP. Alkenes played the most important role in potential ozone formation, followed by aromatics and alkanes.

[en] Highlights: • Sensor with high linearity and stability was selected to build sensor network. • Systematical variation of sensor sensitivity was corrected and unified through pre-calibration. • Sensors were classified into four main working status by a statistical analysis method. • With data quality control, the sensor networks show potential in identifying illegal emission sources. Low-cost air quality sensor networks have been increasingly used for high spatial resolution air quality monitoring in recent years. Ensuring data reliability during continuous operation is critical for these sensor networks. Using particulate matter sensor as an example, this study reports a data quality control method, including sensor selection, pre-calibration, and online inspection. It was used in developing and operating the dense low-cost particle sensor networks in two Chinese cities. Firstly, seven mainstream sensors were tested and one model of particle sensor was selected due to its better linearity and stability. For a batch of sensors of the same model, although they were calibrated after manufactured, there are differences in response toward the same concentration of pollutants. The systematical variation of sensors was corrected and unified through pre-calibration. After deploying them in the field, a data analysis method is established for online inspecting their working status. Using data from these sensors, it evaluates parameters such as intraclass correlation coefficients and normalized root mean square error. These two metrics help to construct a two-dimensional coordinate system and to classify sensors into four status, including normal, fluctuation, hotspots, and malfunction. During a one-month operation in the two cities, 8 (out of 82) and 10 (out of 59) sensors with suspected malfunctions were screened out for further on-site inspection. Moreover, the sensor networks show potential in identifying illegal emission sources that cannot be typically detected by sparse regulatory air quality monitoring stations.

[en] Intake fractions, an emissions-intake relationship for primary pollutants, are defined and are estimated in order to make simple estimates of health damages from air pollution. The sulfur dioxide (SO₂) and total suspended particles (TSP) intake fractions for five cities of China are estimated for the four main polluting industries-electric power generation, mineral (mostly cement) products industry, chemical process industry and metallurgical industry (mainly iron and steel smelting). The Industrial Source Complex Long Term (ISTLT3) model is used to simulate the spatial distribution of incremental ambient concentrations due to emissions from a large sample of site-specific sources. Detailed population distribution information is used for each city. The average intake fractions within 50 km of these sources are 4.4x10^-6 for TSP, and 4.2x10^-6 for SO₂, with standard deviations of 8.15x10^-6 and 9.16x10^-6, respectively. They vary over a wide range, from 10^-7 to 10^-5. Although the electric power generation has been the focus of much of the air pollution research in China, our results show that it has the lowest average intake fraction for a local range among the four industries, which highlights the importance of pollutant emissions from other industrial sources. Sensitivity analyses show how the intake fractions are affected by the source and pollutant characteristics, the most important parameter being the size of the domain. However, the intake fraction estimates are robust enough to be useful for evaluating the local impacts on human health of primary SO₂ and TSP emissions. An application of intake fractions is given to demonstrate how this approach provides a rapid population risk estimate if the dose-response function is linear without threshold, and hence can help in prioritizing pollution control efforts. (author)

[en] Spinel Co₃O₄ octahedra synthesized by a facile redox-precipitation method were investigated for the complete oxidation of methane. XRD analysis showed that the spinel structural Co₃O₄ octahedra had a relatively strong (1 1 1) diffraction peak as compared with that of the irregular shaped Co₃O₄ nanoparticles prepared by a conventional precipitation method. The results of methane combustion test demonstrated that the Co₃O₄ octahedra had no catalytic activity at 300-500 deg. C, while the Co₃O₄ irregular nanoparticles were highly active at the same reaction conditions. HRTEM studies revealed that the Co₃O₄ octahedra were predominantly exposed by the low Miller-index {1 1 1} facets with the lowest surface energy, and the Co₃O₄ irregular nanoparticles were exposed by various crystal facets. The results exhibited that the {1 1 1} facets with the low surface energy of the Co₃O₄ octahedra resulted in the inert catalytic activity in the methane oxidation reaction

[en] The selective catalytic reduction (SCR) of NO by hydrocarbon is an efficient way to remove NO emission from lean-burn gasoline and diesel exhaust. In this paper, a thermally and hydrothermally stable Al-Ce-pillared clay (Al-Ce-PILC) was synthesized and then modified by SO₄^2-, whose surface area and average pore diameter calcined at 773 K were 161 m²/g and 12.15 nm, respectively. Copper-impregnated Al-Ce-pillared clay catalyst (Cu/SO₄^2-/Al-Ce-PILC) was applied for the SCR of NO by C₃H₆ in the presence of oxygen. The catalyst 2 wt% Cu/SO₄^2-/Al-Ce-PILC showed good performance over a broad range of temperature, its maximum conversion of NO was 56% at 623 K and remained as high as 22% at 973 K. Furthermore, the presence of 10% water slightly decreased its activity, and this effect was reversible following the removal of water from the feed. Py-IR results showed SO₄^2- modification greatly enhanced the number and strength of Broensted acidity on the surface of Cu/SO₄^2-/Al-Ce-PILC, which played a vital role in the improvement of NO conversion. TPR and XPS results indicated that both Cu⁺ and isolated Cu²⁺ species existed on the optimal catalyst, mainly Cu⁺, as Cu content increased to 5 wt%, another species CuO aggregates which facilitated the combustion of C₃H₆ were formed. (author)

[en] Along with the rapid development of oil industries internationally, petroleum prospecting and exploitation activities are growing intensively. Especially in China, with the fastest economic growth in the world and shortage of petroleum resources, we are leading the practices of petroleum deep exploitation. Obviously, the risk of damage to the natural environment from these activities is high. Oil contamination in soils and groundwater is becoming a big issue along with pesticide pollution, which makes organic pollution prevention and control (OPPC) much more complex. In this paper, based on recent research on oil-contaminated soil at home and abroad, we make comments on the remediation technologies for polluted soil, emphasizing bioremediation techniques and degradation mechanisms in order to push forward research into bound organic pollution prevention and control (OPPC), especially in China.

[en] Atmospheric environmental quality in China has been improving due to a variety of programs implemented by the Chinese government in recent decades. However, air pollution is still serious because of rapid socioeconomic development and increased energy consumption. Atmospheric environmental problems appear to be complex and regional in nature, and China's climate is aggravated by global climatic change. Air pollution originates from multiple sources and the effect on public human health will increase. The influence of acid rain in southern China will be long term, and the impact of climate change will rise. In order to reduce the adverse effects of air pollutants on the environment, the total number of emission sources from major industry, fine particle pollutants, SO₂ emissions from power plants and the vehicle exhaust must be lowered and strictly controlled. The energy structure will affect the quality of the atmosphere for a long time. Increased energy efficiency, optimization of energy structure and the generation of a sustainable consumption and production patterns will provide opportunities to resolve regional and the global environmental problems