On the use of an explicit chemical mechanism to dissect peroxy acetyl nitrate formation.

Peroxy acetyl nitrate (PAN) is a key component of photochemical smog and plays an important role in atmospheric chemistry. Though it has been known that PAN is produced via reactions of nitrogen oxides (NOx) with some volatile organic compounds (VOCs), it is difficult to quantify the contributions of individual precursor species. Here we use an explicit photochemical model--Master Chemical Mechanism (MCM) model--to dissect PAN formation and identify principal precursors, by analyzing measurements made in Beijing in summer 2008. PAN production was sensitive to both NOx and VOCs. Isoprene was the predominant VOC precursor at suburb with biogenic impact, whilst anthropogenic hydrocarbons dominated at downtown. PAN production was attributable to a relatively small class of compounds including NOx, xylenes, trimethylbenzenes, trans/cis-2-butenes, toluene, and propene. MCM can advance understanding of PAN photochemistry to a species level, and provide more relevant recommendations for mitigating photochemical pollution in large cities

Heterogeneous N2O5 reactions on atmospheric aerosols at four Chinese sites : improving model representation of uptake parameters

Heterogeneous reactivity of N2O5 on aerosols is a critical parameter in assessing NOx fate, nitrate production, and particulate chloride activation. Accurate measurement of its uptake coefficient (gamma N2O5) and representation in air quality models are challenging, especially in the polluted environment. With an in situ aerosol flow-tube system, the gamma N2O5 was directly measured on ambient aerosols at two rural sites in northern and southern China. The results were analyzed together with the gamma N2O5 derived from previous field studies in China to obtain a holistic picture of gamma N2O5 uptake and the influencing factors under various climatic and chemical conditions. The field-derived or measured gamma N2O5 was generally promoted by the aerosol water content and suppressed by particle nitrate. Significant discrepancies were found between the measured gamma N2O5 and that estimated from laboratory-determined parameterizations. An observation-based empirical parameterization was derived in the present work, which better reproduced the mean value and variability of the observed gamma N2O5. Incorporating this new parameterization into a regional air quality model (WRF-CMAQ) has improved the simulation of N2O5, nitrogen oxides, and secondary nitrate in the polluted regions of China.Peer reviewe

Polluted dust promotes new particle formation and growth

Peer reviewe

A synergistic ozone-climate control to address emerging ozone pollution challenges

Tropospheric ozone threatens human health and crop yields, exacerbates global warming, and fundamentally changes atmospheric chemistry. Evidence has pointed toward widespread ozone increases in the troposphere, and particularly surface ozone is chemically complex and difficult to abate. Despite past successes in some regions, a solution to new challenges of ozone pollution in a warming climate remains unexplored. In this perspective, by compiling surface measurements at ∼4,300 sites worldwide between 2014 and 2019, we show the emerging global challenge of ozone pollution, featuring the unintentional rise in ozone due to the uncoordinated emissions reduction and increasing climate penalty. On the basis of shared emission sources, interactive chemical mechanisms, and synergistic health effects between ozone pollution and climate warming, we propose a synergistic ozone-climate control strategy incorporating joint control of ozone and fine particulate matter. This new solution presents an opportunity to alleviate tropospheric ozone pollution in the forthcoming low-carbon transition.This study was supported by the Research Grants Council of Hong Kong Special Administrative Region via General Research Funds (HKBU 15219621 and PolyU 15212421) and a Theme-based Research Scheme (T24-504/17-N). The authors acknowledge the support of the Australia–China Centre on Air Quality Science and Management. R.S. acknowledges support from ANID/FONDAP/1522A0001. D.S. thanks the program of Coordination for the Improvement of Higher Education Personnel (CAPES) (436466/2018-0). X.X. acknowledges funding from the Natural Science Foundation of China (41330422) and the Chinese Academy of Meteorological Sciences (2020KJ003). K.L. is supported by the Natural Science Foundation of China (42205114), Jiangsu Carbon Peak and Neutrality Science and Technology Innovation fund (BK20220031), and the Startup Foundation for Introducing Talent of NUIST. We sincerely appreciate all the organizations and programs introduced in the section “experimental procedures” for freely providing ozone data. We thank Dr. Owen Cooper (University of Colorado, Boulder, and NOAA) for insightful guidance and discussion. No organization or program will be responsible for the results generated from their data.Peer reviewe

Bioinspired C/TiO₂ photocatalyst for rhodamine B degradation under visible light irradiation

Papilio paris butterfly wings were replicated by a sol-gel method and a calcination process, which could take advantage of the spatial features of the wing to enhance their photocatalytic properties. Hierarchical structures of P. paris-carbon-TiO2 (PP-C-TiO2) were confirmed by SEM observations. By applying the Brunauer-Emmett-Teller method, it was concluded that in the presence of wings the product shows higher surface area with respect to the pure TiO2 made in the absence of the wings. The higher specific surface area is also beneficial for the improvement of photocatalytic property. Furthermore, the conduction and valence bands of the PP-C-TiO2 are more negative than the corresponding bands of pure TiO2, allowing the electrons to migrate from the valence band to the conduction band upon absorbing visible light. That is, the presence of C originating from wings in the PP-C-TiO2 could extend the photoresponsiveness to visible light. This strategy provides a simple method to fabricate a high-performance photocatalyst, which enables the simultaneous control of the morphology and carbon element doping

<span style="mso-bidi-language:HI">Purification and characterization of trehalose-6-phosphate synthase from <i><span style="mso-bidi-language:HI">Saccharomycopsis </span></i><i><span style="mso-bidi-font-family:Arial;mso-bidi-language:HI">fibuligera </span></i><span style="mso-bidi-language:HI">A<span style="mso-bidi-font-family:Arial; mso-bidi-language:HI">11 </span></span></span>

289-294Mutant <span style="mso-bidi-font-family: Arial;mso-bidi-language:HI">A11, a mutant of Saccharomycopsis fibuligera Sdu with low acid and neutral trehalase was found to <span style="mso-bidi-font-family:Arial; mso-bidi-language:HI">accumulate over 18% (w/w) trehalose <span style="mso-bidi-font-family:Arial;mso-bidi-language: HI">from starch in its cells. In this study, trehalose-6-phosphate synthase <span style="mso-bidi-font-family: Arial;mso-bidi-language:HI">(Tps1) was purified to homogeneity from this mutant, with a 30-fold increase in the specific enzyme activity, as compared to the concentrated cell-free extract, from initial cells. The molecular mass of the purified enzyme as determined by SDS-PAGE was 66 <span style="mso-bidi-font-family:Arial;mso-bidi-language: HI">kDa. The optimum pH and temperature of the purified enzyme were 6.6 and 37°C, respectively. The enzyme was activated by Ca<span style="mso-bidi-font-family: Arial;mso-bidi-language:HI">2<span style="mso-bidi-language: HI">+, K+ and Mg2+, with K+ showing the highest activation at 35 mM. On the other hand, Mn<span style="mso-bidi-font-family:Arial;mso-bidi-language: HI">2+, Cu<span style="mso-bidi-font-family: Arial;mso-bidi-language:HI">2<span style="mso-bidi-language: HI">+, Fe3+, Hg2+ and Co<span style="mso-bidi-font-family:Arial;mso-bidi-language: HI">2+ inhibited the enzyme. The enzyme was also strongly inhibited by protease inhibitors such as iodoacetic acid, EOTA and PMSF. </span

Application of Ni/MgO catalysts in the pyrolysis of bituminous coal

Carbon pyrolysis is one of the essential ways to improve carbon energy utilization and reduce environmental pollution. The main product of carbon pyrolysis process is tar, and improving tar yield can not only increase the resource utilization efficiency, but also reduce the pollution to the environment. Therefore, this paper investigates the application of Ni/MgO catalyst in the pyrolysis process of bituminous coal. The experimental results show that Ni/MgO catalyst can effectively activate small molecule radicals and make them combine with prominent molecule radicals stably to improve the tar yield. Meanwhile, when it is under the pyrolysis gas environment, pyrolysis temperature reaches 570 ℃, gas flow rate is 375 ml/min, and the catalyst is selected to be filled in the upper layer, the activation effect of Ni/MgO catalyst is more prominent, and it can significantly increase the tar yield and the proportion of light oil. Ni/MgO catalyst had the best effect in tar yield increase compared to other catalysts, but the performance was average in fair oil percentage increase. The catalyst could also reduce the number of aliphatics in the tar and increase the proportion of non-aliphatics, improving the tar quality

Impact Load Identification Algorithm of Helicopter Weapon Pylon Based on Time-Domain Response Signal

Accurately identifying the peak value of impact load acting on the helicopter structure during weapon launch is of great significance to the design and finalization of weapon pylons. Firstly, a method of standardized preprocessing load signal is proposed by analyzing the vibration response and the characteristics of the impact load. Then, the test model of the weapon pylon is designed, and the position of the strain gauge is determined; the static load calibration test and the ground impact test are carried out on the test model. Next, the time-domain response measured by the strain gauge is filtered and de-noised. Impact load is processed by a standardized method. The response and load are used to train BP neural network and the mapping relationship between response and load is established. The impact load generated by a specific weapon is statistically processed to obtain the normalized average load time history, and the identified standard load is converted back to the original load pattern. Finally, the network that meets the error requirements is tested. Both the standardized pattern and the original pattern have high identification accuracy, which shows that an effective load identification model can be established based on the time-domain response signal and the standardized processed load signal