Sulfate Formation by Photosensitization in Mixed Incense Burning-Sodium Chloride Particles: Effects of RH, Light Intensity, and Aerosol Aging.

Elevated particulate sulfate concentrations have been frequently observed in coastal areas when air masses are influenced by continental emissions, especially combustion sources like biomass burning. We studied the SO2 uptake by laboratory-generated droplets containing incense smoke extracts and sodium chloride (IS-NaCl) under irradiation and found enhanced sulfate production over pure NaCl droplets, attributable to photosensitization induced by constituents in IS. Low relative humidity and high light intensity facilitated sulfate formation and increased the SO2 uptake coefficient by IS-NaCl particles. Aging of the IS particles further enhanced sulfate production, attributable to the enhanced secondary oxidant production promoted by increased proportions of nitrogen-containing CHN and oxygen- and nitrogen-containing CHON species under light and air. Experiments using model compounds of syringaldehyde, pyrazine, and 4-nitroguaiacol verified the enhancements of CHN and CHON species in sulfate formation. This work provides experimental evidence of enhanced sulfate production in laboratory-generated IS-NaCl droplets via enhanced secondary oxidant production triggered by photosensitization in multiphase oxidation processes under light and air. Our results can shed light on the possible interactions between sea salt and biomass burning aerosols in enhancing sulfate production.

Remarkable nucleation and growth of ultrafine particles from vehicular exhaust.

High levels of ultrafine particles (UFPs; diameter of less than 50 nm) are frequently produced from new particle formation under urban conditions, with profound implications on human health, weather, and climate. However, the fundamental mechanisms of new particle formation remain elusive, and few experimental studies have realistically replicated the relevant atmospheric conditions. Previous experimental studies simulated oxidation of one compound or a mixture of a few compounds, and extrapolation of the laboratory results to chemically complex air was uncertain. Here, we show striking formation of UFPs in urban air from combining ambient and chamber measurements. By capturing the ambient conditions (i.e., temperature, relative humidity, sunlight, and the types and abundances of chemical species), we elucidate the roles of existing particles, photochemistry, and synergy of multipollutants in new particle formation. Aerosol nucleation in urban air is limited by existing particles but negligibly by nitrogen oxides. Photooxidation of vehicular exhaust yields abundant precursors, and organics, rather than sulfuric acid or base species, dominate formation of UFPs under urban conditions. Recognition of this source of UFPs is essential to assessing their impacts and developing mitigation policies. Our results imply that reduction of primary particles or removal of existing particles without simultaneously limiting organics from automobile emissions is ineffective and can even exacerbate this problem.

The seasonal variation, characteristics and secondary generation of PM2.5 in Xi'an, China, especially during pollution events.

As an important central city in western China, Xi'an has the worst atmospheric pollution record in China and many measures have been taken to improve the air quality in the past few years. In this study, PM2.5 samples were collected across four seasons from 2017 to 2018 in Xi'an. Organic carbon and elemental carbon, water soluble ions, and elements were monitored to assess the air quality. The average annual PM2.5 concentration was (134.9 ± 48.1 µg/m3), with the highest concentration in winter (188.8 ± 93.2 µg/m3), and lowest concentration in summer (71.2 ± 12.1 µg/m3). The secondary generation of sulfate (SO42-) and nitrate (NO3-) was strong in spring, and secondary organic carbon (SOC) was formed in all seasons. The compositions of PM2.5 changed greatly during a sandstorm occurred and the Spring Festival. The sandstorm played a positive role in removing local pollutant NO3-, but also increased the concentration of SO42-, however both the concentration of SO42- and NO3- greatly increased by secondary generation during Spring Festival. Potential source analysis showed that during the sandstorm, pollutants were transported over a long distance from the northwest of China, whereas it was mainly from the local and surrounded emissions during the Spring Festival. Except Ca2+ and geological dust (GM), the other components in PM2.5 increased significantly on the day of the Spring Festival. During sampling time in Xi'an, the positive matrix factorization (PMF) model analysis showed that PM2.5 mainly came from vehicle emission, coal combustion, and biomass burning.

Secondary organic aerosol formation from straw burning using an oxidation flow reactor.

Herein, we use an oxidation flow reactor, Gothenburg: Potential Aerosol Mass (Go: PAM) reactor, to investigate the secondary organic aerosol (SOA) formation from wheat straw burning. Biomass burning emissions are exposed to high concentrations of hydroxyl radicals (OH) to simulate processes equivalent to atmospheric oxidation of 0-2.55 days. Primary volatile organic compounds (VOCs) were investigated, and particles were measured before and after the Go: PAM reactor. The influence of water content (i.e. 5% and 11%) in wheat straw was also explored. Two burning stages, the flaming stage, and non-flaming stages, were identified. Primary particle emission factors (EFs) at a water content of 11% (∼3.89 g/kg-fuel) are significantly higher than those at a water content of 5% (∼2.26 g/kg-fuel) during the flaming stage. However, the water content showed no significant influence at the non-flaming stage. EFs of aromatics at a non-flaming stage (321.8±46.2 mg/kg-fuel) are larger than that at a flaming stage (130.9±37.1 mg/kg-fuel). The OA enhancement ratios increased with the increase in OH exposure at first and decreased with the additional increment of OH exposure. The maximum OA enhancement ratio is ∼12 during the non-flaming stages, which is much higher than ∼ 1.7 during the flaming stages. The mass spectrum of the primary wheat burning organic aerosols closely resembles that of resolved biomass burning organic aerosols (BBOA) based on measurements in ambient air. Our results show that large gap (∼60%-90%) still remains to estimate biomass burning SOA if only the oxidation of VOCs were included.

The paradigm for exceptional iodine capture by nonporous amorphous electron-deficient cyclophanes.

Nuclear power emerges as a beacon of hope in tackling the energy crisis. However, the emission of radioactive iodine originating from nuclear waste and accidents poses a serious danger to nature and human well-being. Therefore, it becomes imperative to urgently develop suitable adsorbents capable of iodine capture and long-term storage. It's generally recognized that achieving high iodine capture efficiency necessitates the presence of electron-rich pores/cavities that facilitate charge-transfer (CT) interactions, as well as effective sorption sites capable of engaging in lone pair interactions with iodine. In this study, an unprecedented iodine capture paradigm by nonporous amorphous electron-deficient tetracationic cycloalkanes in vapor and aqueous solutions is revealed, overturning preconceived notions of iodine trapping materials. A newly reported tetracationic cyclophane, BPy-Box4+, exhibited an exceptional iodine vapor sorption capacity of 3.99 g g-1, remarkable iodine removal efficiency in aqueous media, and outstanding reusability. The iodine capture mechanism is unambiguously elucidated by theoretical calculations and the single-crystal structures of cyclophanes with a gradual increase in iodine content, underlining the vital role of host-guest (1:1 or 1:2) interactions for the enhanced iodine capture. The current study demonstrates a new paradigm for enhanced iodine capture by nonporous amorphous electron-deficient cyclophanes through host-guest complexation.

Detailed Speciation of Semi-Volatile and Intermediate-Volatility Organic Compounds (S/IVOCs) in Marine Fuel Oils Using GC × GC-MS.

Ship emissions contribute substantial air pollutants when at berth. However, the complexity and diversity of the marine fuels utilized hinder our understanding and mapping of the characteristics of ship emissions. Herein, we applied GC × GC-MS to analyze the components of marine fuel oils. Owing to the high separation capacity of GC × GC-MS, 11 classes of organic compounds, including b-alkanes, alkenes, and cyclo-alkanes, which can hardly be resolved by traditional one-dimensional GC-MS, were detected. Significant differences are observed between light (-10# and 0#) and heavy (120# and 180#) fuels. Notably, -10# and 0# diesel fuels are more abundant in b-alkanes (44~49%), while in 120# and 180#, heavy fuels b-alkanes only account for 8%. Significant enhancement of naphthalene proportions is observed in heavy fuels (20%) compared to diesel fuels (2~3%). Hopanes are detected in all marine fuels and are especially abundant in heavy marine fuels. The volatility bins, one-dimensional volatility-based set (VBS), and two-dimensional VBS (volatility-polarity distributions) of marine fuel oils are investigated. Although IVOCs still take dominance (62-66%), the proportion of SVOCs in heavy marine fuels is largely enhanced, accounting for ~30% compared to 6~12% in diesel fuels. Furthermore, the SVOC/IVOC ratio could be applied to distinguish light and heavy marine fuel oils. The SVOC/IVOC ratios for -10# diesel fuel, 0# diesel fuel, 120# heavy marine fuel, and 180# heavy marine fuel are 0.085 ± 0.046, 0.168 ± 0.159, 0.504, and 0.439 ± 0.021, respectively. Our work provides detailed information on marine fuel compositions and could be further implemented in estimating organic emissions and secondary organic aerosol (SOA) formation from marine fuel storage and evaporation processes.

Particulate organic emissions from incense-burning smoke: Chemical compositions and emission characteristics.

Incense burning is a common practice in Asian cultures, releasing hazardous particulate organics. Inhaling incense smoke can result in adverse health effects, yet the molecular compositions of incense-burning organics have not been well investigated due to the lack of measurement of intermediate-volatility and semi-volatile organic compounds (I/SVOCs). To elucidate the detailed emission profile of incense-burning particles, we conducted a non-target measurement of organics emitted from incense combustion. Quartz filters were utilized to trap particles, and organics were analyzed by a comprehensive two-dimensional gas chromatography-mass spectrometer (GC × GC-MS) coupled with a thermal desorption system (TDS). To deal with the complex data obtained by GC × GC-MS, homologs are identified mainly by the combination of selected ion chromatograms (SICs) and retention indexes. SICs of 58, 60, 74, 91, and 97 were utilized to identify 2-ketones, acids, fatty acid methyl esters, fatty acid phenylmethyl esters, and alcohols, respectively. Phenolic compounds contribute the most to emission factors (EFs) among all chemical classes, taking up 24.5 % ± 6.5 % of the total EF (96.1 ± 43.1 µg g-1). These compounds are largely derived from the thermal degradation of lignin. Biomarkers like sugars (mainly levoglucosan), hopanes, and sterols are extensively detected in incense combustion fumes. Incense materials play a more important role in shaping emission profiles than incense forms. Our study provides a detailed emission profile of particulate organics emitted from incense burning across the full-volatility range, which can be used in the health risk assessments. The data processing procedure in this work could also benefit those with less experience in non-target analysis, especially GC × GC-MS data processing.

Secondary aerosol formation in incense burning particles by O3 and OH oxidation via single particle mixing state analysis.

Incense burning is a common religious activity that emits abundant gaseous and particulate pollutants into the atmosphere. During their atmospheric lifetime, these gases and particles are subjected to oxidation, leading to the formation of secondary pollutants. We examined the oxidation of incense burning plumes under O3 exposure and dark condition using an oxidation flow reactor connected to a single particle aerosol mass spectrometer (SPAMS). Nitrate formation was observed in incense burning particles, mainly attributable to the ozonolysis of nitrogen-containing organic compounds. With UV on, nitrate formation was significantly enhanced, likely due to HNO3/HNO2/NOx uptake triggered by OH chemistry, which is more effective than ozone oxidation. The extent of nitrate formation is insensitive to O3 and OH exposure, possibly due to the diffusion limitation on interfacial uptake. The O3-UV-aged particles are more oxygenated and functionalized than O3-Dark-aged particles. Oxalate and malonate, two typical secondary organic aerosol (SOA) components, were found in O3-UV-aged particles. Our work reveals that nitrate, accompanied by SOA, can rapidly form in incense-burning particles upon photochemical oxidation in the atmosphere, which could deepen our understanding of air pollution caused by religious activities.

Real-time chemical characterization of single ambient particles at a port city in Chinese domestic emission control area - Impacts of ship emissions on urban air quality.

The domestic emission control area (DECA) policy has been implemented in China since 2017. However, its impact on ship emissions and in turn urban air quality is still unclear. In this study, real-time single particle measurements were carried out at a site in urban Guangzhou, about 1 km downwind of Huangpu Port, the largest maritime transport hub in southern China, in the summer of 2020 using a single particle aerosol mass spectrometer (SPAMS). During the campaign, the hourly averaged number fraction of ship emitted particles, using vanadium as a chemical indicator, varied from 0 to 14% with an average of 2 ± 1%. Ship emitted single particles contain organic carbon (OC), elemental carbon (EC), metals, sulfate and nitrate. More than 95% of ship emitted particles were sulfate-containing particles and the relative peak areas (RPAs) of sulfate and vanadium in the hourly average mass spectra of ship emitted particles were highly correlated (R2 = 0.85), suggesting the potential contribution of ship emissions to sulfate production in coastal cities. The relative abundance of OC and EC-related components in ship emitted particles varied and it was likely attributed to the different blending fluids used in the production of low sulfur fuels. The results from this study provide evidence for evaluating the effectiveness of the current regulations and guidance for future policy-making regarding the low sulfur fuel quality regulation and multiple-component control strategies.

Investigation of partition coefficients and fingerprints of atmospheric gas- and particle-phase intermediate volatility and semi-volatile organic compounds using pixel-based approaches.

Ambient gas- and particle-phase intermediate volatility and semi-volatile organic compounds (I/SVOCs) of Beijing were analyzed by a thermal desorption comprehensive two-dimensional gas chromatography quadrupole mass spectrometry (TD-GC × GC-qMS). A pixel-based scheme combing the integration-based approach was applied for partition coefficients estimation and fingerprints identification. Blob-by-blob recognition was firstly utilized to characterize I/SVOCs from the molecular level. 412 blobs in gas-phase and 460 blobs in particle-phase were resolved, covering a total response of 47.5% and 43.5%. A large pool of I/SVOCs was found with a large diversity of chemical classes in both gas- and particle-phase. Acids (8.5%), b-alkanes (5.8%), n-alkanes (C8-C25, 5.3%), and aromatics (4.4%) were dominant in gas-phase while esters (7.0%, including volatile chemical product compounds, VCPs), n-alkanes (C9-C34, 5.7%), acids (4.6%), and siloxanes (3.6%) were abundant in particle-phase. Air pollutants were then evaluated by a two-parameter linear free energy relationship (LFER) model, which could be further implemented in the two-dimensional volatility basis set (2D-VBS) model. Multiway principal component analysis (MPCA) and partial least squares-discriminant analysis (PLS-DA) implied that naphthalenes, phenol, propyl-benzene isomers, and oxygenated volatile organic compounds (OVOCs) were key components in the gas-phase under different pollution levels. This work gives more insight into property estimation and fingerprints identification for complex ambient samples.

[Chemical Characteristics and Source Apportionment of Organic Aerosols in Atmospheric PM2.5 in Winter in Beijing].

To explore the concentrations, characteristics, and sources of organic aerosols in winter in Beijing, atmospheric fine particulate matter (PM2.5) samples were collected from November 10, 2016 to December 10, 2016. One hundred and twenty-nine particulate organic matters (POM) were quantified by gas chromatography-mass spectrometry, accounting for approximately 9.3%±1.2% of the total concentration of organic matter. The most abundant class was sugar, among which levoglucosan alone accounted for 18% of the quantified organic matter mass. The next most abundant classes were alkanoic acids, normal alkanes, dicarboxylic acids, and polycyclic aromatic hydrocarbons. The influence of winter heating and biomass burning emissions on organic aerosols in winter in Beijing was analyzed by the characteristics of the molecular markers in the POM. Compared with those during the non-heating period, the concentrations and proportions of hopane species, which are tracers for fossil fuels, increased in the organic matters during the heating period. Moreover, the influence of coal burning emissions on the distribution of hopane species was enhanced. The species with the maximum concentration and carbon predominance index in n-alkanes also reflected the influence of enhanced fossil fuel emissions. The results of the concentration-weighted trajectory model for levoglucosan, a tracer for biomass combustion, suggested that straw burning pollution in the surrounding areas of Beijing would affect the composition of organic aerosols in Beijing via airmass transport. A molecular marker-based chemical mass balance model was used to apportion the sources of organic carbon in the winter of 2016 in Beijing, and the results were compared with those of research in 2006 to quantify the changes in the source contributions over 10 years. The contribution of motor vehicles increased significantly in 2016 compared with that in 2006, whereas the contribution of coal burning and wood burning decreased to a large extent. The contribution of cooking emissions could not be ignored. Therefore, the control of motor vehicle and cooking emissions is of great importance to reduce the problem of PM2.5 pollution in winter in Beijing.

Secondary aerosol formation from a Chinese gasoline vehicle: Impacts of fuel (E10, gasoline) and driving conditions (idling, cruising).

Chassis dynamometer experiments were conducted to investigate the effect of vehicle speed and usage of ethanol-blended gasoline (E10) on formation and evolution of gasoline vehicular secondary organic aerosol (SOA) using a Gothenburg Potential Aerosol Mass (Go: PAM) reactor. The SOA forms rapidly, and its concentration exceeds that of primary organic aerosol (POA) at an equivalent photochemical age (EPA) of ~1 day. The particle effective densities grow from 0.62 ± 0.02 g cm-3 to 1.43 ± 0.07 g cm-3 with increased hydroxyl radical (OH) exposure. The maximum SOA production under idling conditions (4259-7394 mg kg-fuel-1) is ~20 times greater than under cruising conditions. There was no statistical difference between SOA formation from pure gasoline and its formation from E10. The slopes in Van Krevelen diagram indicate that the formation pathways of bulk SOA includes the addition of both alcohol/peroxide functional groups and carboxylic acid formation from fragmentation. A closure estimation of SOA based on bottom-up and top-down methods shows that only 16%-38% of the measured SOA can be explained by the oxidation of measured volatile organic compounds (VOCs), suggesting the existence of missing precursors, e.g. unmeasured VOCs and probably semivolatile or intermediate volatile organic compounds (S/IVOCs). Our results suggest that applying parameters obtained from unified driving cycles to model SOA concentrations may lead to large discrepancies between modeled and ambient vehicular SOA. No reduction in vehicular `SOA production is realized by replacing normal gasoline with E10.

Successive Passage In Vitro Led to Lower Virulence and Higher Titer of A Variant Porcine Epidemic Diarrhea Virus.

A highly virulent porcine epidemic diarrhea virus (PEDV) appeared in China and spread rapidly to neighbor countries, which have led to great economic losses to the pig industry. In the present study, we isolated a PEDV using Vero cells and serially propagated 100 passages. PEDV SDSX16 was characterized in vitro and in vivo. The viral titers increased to 107.6 TCID50/mL (100th) by serial passages. The spike (S) gene and the whole gene of the SDSX16 virus was fully sequenced to assess the genetic stability and relatedness to previously identified PEDV. Along with successive passage in vitro, there were 18 nucleotides (nt) deletion occurred in the spike (S) gene resulting in a deletion of six amino acids when the SDSX16 strain was passaged to the 64th generation, and this deletion was stable until the P100. However, the ORF1a/b, M, N, E, and ORF3 genes had only a few point mutations in amino acids and no deletions. According to growth kinetics experiments, the SDSX16 deletion strain significantly enhanced its replication in Vero cells since it was passaged to the 64th generation. The animal studies showed that PEDV SDSX16-P10 caused more severe diarrhea and vomiting, fecal shedding, and acute atrophic enteritis than SDSX16-P75, indicating that SDSX16-P10 is enteropathogenic in the natural host, and the pathogenicity of SDSX16 decreased with successive passage in vitro. However, SDSX16-P10 was found to cause lower levels of cytokine expression than SDSX16-P75 using real-time PCR and flow cytometry, such as IL1ß, IL6, IFN-ß, TNF-α, indicating that SDSX16-P10 might inhibit the expression of cytokines. Our data indicated that successive passage in vitro resulted in virulent attenuation in vivo of the PEDV variant strain SDSX16.

[Epidemiological survey of high-risk human papillomavirus among 2501 woman].

OBJECTIVE: To survey the prevalence of high-risk human papillomavirus (HPV) in woman in Guangzhou during the period from 2013 to 2014. METHODS: A total of 2501 women in Guangzhou seeking medical attention in our hospital underwent high-risk HPV genotype screening of cervical specimens using real-time PCR. RESULTS: The prevalence of high-risk HPV infection among the women was 14.85% (146/983) in the year 2013, similar to the rate of 14.56% (221/1518) in 2014 (Χ(2)=0.041, P=0.839); no significant differences were found in the high-risk HPV infection rates between different age groups in either 2013 (Χ(2)=2.916, P=0.572) or 2014 (Χ(2)=6.494, P=0.165). The constituent ratio of the 13 types of high-risk HPV showed no significant difference between 2013 and 2014 (Χ(2)=11.872, P=0.452). The 13 HPV genotypes detected, listed in a descending order of the constituent ratios, included HPV-52, -16, -58, -56, -39, -51, -68, -59, -31, -35, -18, -33 and -45 in 2013, and were HPV-52, -16, -58, -68, -18, -51, -56, -39, -31, -33, -59, -35 and-45 in 2014. CONCLUSION: We report a high prevalence of high-risk HPV among women in Guangzhou, which suggests the necessity of screening for high-risk HPV-DNA among women at all ages for prevention and early detection of cervical cancer.