[Transmission of Coronavirus via Aerosols and Influence of Environmental Conditions on Its Transmission].

The COVID-19 pandemic has endangered human health and production since 2019. As an emerging disease caused by SARS-CoV-2, its potential transmissibility via aerosols has caused heated debate. This work summarizes the current research findings on virus aerosol generation, aerodynamic properties, and environmental influencing factors on their survivability in order to elucidate coronavirus transmission via aerosols. The occurrence and distinction of SARS-CoV-2, SARS-CoV-1, and MERS-CoV in real atmospheric environments are summarized. The deficiencies of existing research and directions for necessary future research on confirming the airborne transmission mechanism of coronavirus as well as the need for multidisciplinary research are discussed.

[Characteristics of Condensable Particulate Matter in Ultra-low Emission Coal-Fired Power Plants].

The condensable particle matter (CPM) from coal-fired power plants has attracted significant attention for its potential influence on air quality. The knowledge of CPM emissions from coal-fired power plants is limited. In this study, CPM was collected at the inlet and outlet of wet flue gas desulfurization (WFGD) and the outlet of wet electrostatic precipitator (WESP) using in-direct dilution method. Both mass concentration and water-soluble ions of CPM were analyzed after sampling. The gas precursors were measured at the same time. We showed that gas precursors such as HCl, HNO3, SO3, and NH3 significantly contributed to CPM from coal-fired power plants. As the temperature of flue gas decreased, these gas precursors were observed to form CPM. The major components of CPM were water-soluble ions such as SO42-, Cl-, NO3-, and NH4+. WFGD and WESP could reduce the CPM gas precursors. Therefore, CPM concentrations after WFGD and WESP of the five tested coal-fired power plants were reduced by 27% and 45%, respectively. In addition, the condensation of SO3 increased SO42- concentration but reduced Cl- and NO3- contents. Finally, SO42- was found to be the major water-soluble ion of CPM.

[Measuring the Condensable Particle Matter from a Stationary Source].

With the retrofitting of coal-fired power plants and steel plants for ultra-low-emission control, the concentration of filterable particles (FPM) from these sources is decreasing gradually. The condensable particle matter (CPM) draws more attention. The understanding of CPM emission concentration and chemical characteristics is still limited. There has been no standard determination method of CPM in China until now. In this study, three methods, including the dry impinger method (US EPA method 202), indirect dilution method, and direct dilution method, are discussed and compared in measuring CPM emissions from coal-fired power plants, coke-making plants and sintering plants. The results show that method 202 overestimates the emissions of CPM, due to the fact that the gaseous HCl or SO2 dissolves into condensable liquid and cannot be completely eliminated by N2 purging after sampling. Instead, CPM measured using the indirect dilution method better represents its real emission levels into the atmosphere.

[Effect of a Wet Flue Gas Desulphurization System on the Emission of PM2.5 from Coal-Fired Power Plants].

Wet flue gas desulphurization (WFGD) is wildly used to control SO2 emission from coal-fired power plants. The influence of WFGD on particulate matter (PM) emission has recently drawn significant public attentions in China. In this study, PM2.5 was collected at both the inlet and outlet from three WFGD units, including a single scrubber lime-stone-gypsum FGD unit, a cascade scrubber lime-stone-gypsum FGD unit, and a seawater FGD unit. PM2.5 mass concentrations and their chemical compositions were analyzed. A method to calculate the addition and removal ratios is proposed according to the concertation of PM2.5 components, such as Ti, Pb, Cr, and V. The results indicate that the removal ratio was similar between the three WFGD units (77.1% on average). However, the addition ratio varied significantly. The performance of the cascade scrubber lime-stone-gypsum FGD unit was best, with a lower addition ratio of 8.6%, which is attributed to the weaker evaporation of desulphurization slurry droplets in their second tower under the low temperature of the flue gas. The addition ratio of the seawater FGD unit was also low (23.9%) because of its low concentration of solids in the seawater. The addition ratio of the single scrubber lime-stone-gypsum FGD system was highest, with a value of 162.3%, which was probably due to the low efficiency of the de-mister.

Regulating structural dimensionality and emission colors by organic conjugation between SmIII at a fixed distance.

The conjugation of bridging bis(diphenylphosphine oxide) alkane or arene ligands was found to control the structural dimensionality and the emission color of complexes from reactions with SmIII(hfac)3(H2O)2 (hfac- = hexafluoroacetylacetonato) while retaining the SmSm distances. Bis(diphenylphosphine oxide)-1,4-butane (L1) affords a one-dimensional (1D) ribbon {Sm(hfac)3(L1)}∞ (1) that emits red color, while bis(diphenyl-phosphinoyl)-1,4-benzene (L2) results in a two-dimensional (2D) network {Sm(hfac)2(CF3COO)(L2)3}∞ (2) and near-white emission, but bis(diphenyl-phosphinoyl)-9,10-anthracene (L3) forms a zero-dimensional (0D) cyclic structure {Sm(hfac)3(L3)}2 (3) with strong ππ interactions that emit green color. Noticeably, the conjugation change is accompanied by a configurational change of coordination from trans for 1 and 2 to cis for 3. The color change is associated with the superposition of ligand and Sm based electronic band energies and their intensities. Such white light emission by a single compound having contributions from different building components is quite rare.

Sensitized near infrared emission through supramolecular d → f energy transfer within an ionic Ru(ii)-Er(iii) pair.

The newly synthesized ionic triple salt Ru-Er, {[RuII(bpy)2(dbim)][ErIII(hfac)4][CF3COO]·H2O} (bpy = 2,2'-bipyridine; hfac- = hexafluoroacetylacetonate; dbim = 2,2'-dibenzimidazole) exhibits near-infrared (NIR) emission at 1535 nm by intermolecular Ru → Er (d → f) energy transfer across supramolecular interactions when pumped within the Ru(ii) 3MLCT band. It is the first such observation for a transition metal-lanthanide ionic pair.

[Evaluation and Development of a Weighing Chamber by Using Saturated MgCl2 Solution].

In recent years, China has suffered a lot from atmospheric particles. Many studies of particles are based on filters. As a result, the accuracy of filter weighing is of great importance. A weighing chamber (1.2 m×0.6 m×0.8 m) was developed and evaluated using saturated MgCl2 solution with a self-made flow control system to maintain constant relative humidity (RH). By evaluating the mass change of blank and aerosol-enriched filters after weighing in different RH, we selected RH of 30%-40% as the range for the proper constant RH. To reach a constant RH, 20 L·min-1 dry air was put through a RH-constant chamber with MgCl2 solution in it. Then, the RH-constant air was put continually into the weighing chamber. After the weighing chamber reached stable RH, the flow rate was adjusted to 5 L·min-1 to maintain the RH. Throughout a one-month test, the weighing chamber maintained 30.1%-34.0% RH while the outside RH changed a lot. We weighed 60 filters with this weighing chamber after equilibration for 24 hours. The standard deviation after three times' weighing was no more than 0.02 mg. compared to other methods, the RH-controlling method of this weighing chamber was simple, stable, easy to maintain, and cost effective.

Enhancing the efficiency of planar heterojunction perovskite solar cells via interfacial engineering with 3-aminopropyl trimethoxy silane hydrolysate.

The interfacial compatibility between compact TiO2 and perovskite layers is critical for the performance of planar heterojunction perovskite solar cells (PSCs). A compact TiO2 film employed as an electron-transport layer (ETL) was modified using 3-aminopropyl trimethoxy silane (APMS) hydrolysate. The power conversion efficiency (PCE) of PSCs composed of an APMS-hydrolysate-modified TiO2 layer increased from 13.45 to 15.79%, which was associated with a significant enhancement in the fill factor (FF) from 62.23 to 68.04%. The results indicate that APMS hydrolysate can enhance the wettability of γ-butyrolactone (GBL) on the TiO2 surface, form a perfect CH3NH3PbI3 film, and increase the recombination resistance at the interface. This work demonstrates a simple but efficient method to improve the TiO2/perovskite interface that can be greatly beneficial for developing high-performance PSCs.

[Development and Performance Evaluation of a Supermicron Particle Generation System for Aerosol Instrument Calibration].

Accurate calibration of aerosol measurement instruments is critical for ensuring the data quality when sampling ambient particulate matter (PM) or those from emission sources. A system for calibrating these instruments was set up, which included an ultrasonic device to generate polydisperse supermicron particles, a chamber, and an aerodynamic particle spectrometer to measure particle size distribution. We verified its performance in stably generated testing aerosol with good spatial uniformity, controlled size distributions and concentrations. The testing aerosol generated had a lognormal distribution. A PM10 and PM2.5 two-stage virtual impactor was calibrated using this online method. Collection efficiencies of PM10 and PM2.5 stages calibrated by an off-line method using monodisperse particles were also used for comparison. The results from two different methods were consistent with each other. Though the off-line method has been widely used to calibrate PM samplers, it suffers from long experimental duration (2-3 days for calibrating one sampler). In contrast, the online method allows for a rapid calibration (less than half a day for calibrating one sampler).

[Application of a Two-stage Virtual Impactor in Measuring of PM10 and PM2.5 Emissions from Stationary Sources].

Recently, the Ministry of Environmental Protection of China started the development of emission inventories in fifteen Chinese cities. It includes the esmission of PM10 and PM2.5 from stationary sources. However, there is no national standard method in China for stationary source PM10 and PM2.5 sampling. In this study, a two-stage virtual impactor was developed for sampling PM10 and PM2.5 from stationary sources. Its performance was evaluated for four types of sataionary sources, i.e., coal-fired power plant, waste incineration, circulating fluid bed, and converter steelmaking. These four tested emission sources were equipped with high efficiency PM control devices. PM2.5 mass concentrations measured in the chimneys of these emission sources were (0.93±0.03), (3.3±0.65), (0.59±0.04), and (0.15±0.04) mg·m-3, respectively, while the PM10 mass concentrations were (1.13±0.11), (6.9±0.86), (1.12±0.16), and (0.43±0.15) mg·m-3, respectively.

[Characteristics of Water-Soluble Inorganic Ions in PM2.5 Emitted from Coal-Fired Power Plants].

To characterize the primary PM2.5 emission from coal-fired power plants in China, and to quantitatively evaluate the effects of flue gas denitrification and desulfurization on PM2.5 emission, a pulverized coal fired (PC) power plant and a circulating fluidized bed (CFB) plant were selected for measuring the mass concentration and water-soluble ion composition of PM2.5 in flue gas. The results showed that the mass concentration of PM2.5 generated from the CFB was much higher than that from the PC, while the mass concentrations of PM2.5 emitted from these two plants were very similar, because the CFB was equipped with an electrostatic-bag precipitator (EBP) with higher PM2.5 removal efficiency than the common electrostatic precipitator (ESP). Although the total concentration of water-soluble ions in PM2.5 generated from the PC was lower than that from the CFB, the total concentration of water-soluble ions in PM2.5 emitted from the PC was much higher than that from the CFB, which implied that PM2.5 emission from the PC was greatly affected by the flue gas treatment installations. For example, the flue gas denitrification system produced H2SO4 mist, part of which reacted with the excessive NH3 in the flue gas to form NH4HSO4 in PM2.5 and to increase the acidity of PM2.5. In addition, the escaping of desulfurization solution during the flue gas desulfurization process could also introduce NH4+ and SO2- into PM2.5. Therefore, although the main water-soluble ions in PM2.5 generated from both of the plants were Ca2+ and SO(4)2-, the major cation was changed to NH4+ when emitted from PC.

Switchable sensitizers stepwise lighting up lanthanide emissions.

Analagous to a long-ranged rocket equipped with multi-stage engines, a luminescent compound with consistent emission signals across a large range of concentrations from two stages of sensitizers can be designed. In this approach, ACQ, aggregation-caused quenching effect of sensitizers, would stimulate lanthanide emission below 10(-4) M, and then at concentrations higher than 10(-3) M, the "aggregation-induced emission" (AIE) effect of luminophores would be activated with the next set of sensitizers for lanthanide emission. Simultaneously, the concentration of the molecules could be monitored digitally by the maximal excitation wavelengths, due to the good linear relationship between the maximal excitation wavelengths and the concentrations {lg(M)}. This model, wherein molecules are assembled with two stages (both AIE and ACQ effect) of sensitizers, may provide a practicable strategy for design and construction of smart lanthanide bioprobes, which are suitable in complicated bioassay systems in which concentration is variable.

[Sampling methods for PM2.5 from stationary sources: a review].

The new China national ambient air quality standard has been published in 2012 and will be implemented in 2016. To meet the requirements in this new standard, monitoring and controlling PM2,,5 emission from stationary sources are very important. However, so far there is no national standard method on sampling PM2.5 from stationary sources. Different sampling methods for PM2.5 from stationary sources and relevant international standards were reviewed in this study. It includes the methods for PM2.5 sampling in flue gas and the methods for PM2.5 sampling after dilution. Both advantages and disadvantages of these sampling methods were discussed. For environmental management, the method for PM2.5 sampling in flue gas such as impactor and virtual impactor was suggested as a standard to determine filterable PM2.5. To evaluate environmental and health effects of PM2.5 from stationary sources, standard dilution method for sampling of total PM2.5 should be established.

Walkable dual emissions.

Walkable dual emissions, in which the emission bands of the walker reversibly cross or leave those of the stationary ones depending on temperature and concentration, have been demonstrated in cyclic dimeric lanthanide complexes [Ln(hfac)3(PAnPO2)]2 (Ln = Eu(III), Tb(III); hfac(-) = hexafluoroacetylacetonate; PAnPO2 = 9,10-bis(diphenylphosphino) anthracene dioxide), providing a concept model for signals exchanging and dispatching. Additionally, good linear relationships are observed between the maximum emission bands of the walker vs the concentrations {lg(M)} and the measurement temperatures (K), implying such materials could be served as potential concentration and temperature sensors.

The overall reaction process of ozone with methacrolein and isoprene in the condensed phase.

The reaction of isoprene and methacrolein with ozone was investigated at different stages in the condensed phase at temperatures from 15 to 265 K by IR spectroscopy. The results revealed the following overall reaction process: the generation of primary ozonide (POZ), then its decomposition, and finally conversion into secondary ozonide (SOZ), which supported the Criegee mechanism. In the POZ and SOZ of isoprene, ozone cyclo-added preferentially to the double-bond that is not substituted by the methyl group. For methacrolein, the mainly detected SOZ is claimed to be MACSII formed by recombination of the intermediate CH(2)OO radical with aldehyde carbonyl of methylglyoxal in stead of the ketone carbonyl group. Theoretical calculations were performed at the B3LYP//MP2/6-311++G (2d, 2p) level to analyze the resulting spectrum. The good agreement between the calculated infrared spectra of POZ and SOZ and the experimental spectra supports the above-described findings.