Phase-transforming metamaterial with magnetic interactions.

Solid-solid phase transformations can affect energy transduction and change material properties (e.g., superelasticity in shape memory alloys and soft elasticity in liquid crystal elastomers). Traditionally, phase-transforming materials are based on atomic- or molecular-level thermodynamic and kinetic mechanisms. Here, we develop elasto-magnetic metamaterials that display phase transformation behaviors due to nonlinear interactions between internal elastic structures and embedded, macroscale magnetic domains. These phase transitions, similar to those in shape memory alloys and liquid crystal elastomers, have beneficial changes in strain state and mechanical properties that can drive actuations and manage overall energy transduction. The constitutive response of the elasto-magnetic metamaterial changes as the phase transitions occur, resulting in a nonmonotonic stress-strain relation that can be harnessed to enhance or mitigate energy storage and release under high-strain-rate events, such as impulsive recoil and impact. Using a Landau free energy-based predictive model, we develop a quantitative phase map that relates the geometry and magnetic interactions to the phase transformation. Our work demonstrates how controllable phase transitions in metamaterials offer performance capabilities in energy management and programmable material properties for high-rate applications.

Significantly Accelerated Photosensitized Formation of Atmospheric Sulfate at the Air-Water Interface of Microdroplets.

The multiphase oxidation of sulfur dioxide (SO2) to form sulfate is a complex and important process in the atmosphere. While the conventional photosensitized reaction mainly explored in the bulk medium is reported to be one of the drivers to trigger atmospheric sulfate production, how this scheme functionalizes at the air-water interface (AWI) of aerosol remains an open question. Herein, employing an advanced size-controllable microdroplet-printing device, surface-enhanced Raman scattering (SERS) analysis, nanosecond transient adsorption spectrometer, and molecular level theoretical calculations, we revealed the previously overlooked interfacial role in photosensitized oxidation of SO2 in humic-like substance (HULIS) aerosol, where a 3-4 orders of magnitude increase in sulfate formation rate was speculated in cloud and aerosol relevant-sized particles relative to the conventional bulk-phase medium. The rapid formation of a battery of reactive oxygen species (ROS) comes from the accelerated electron transfer process at the AWI, where the excited triplet state of HULIS (3HULIS*) of the incomplete solvent cage can readily capture electrons from HSO3- in a way that is more efficient than that in the bulk medium fully blocked by water molecules. This phenomenon could be explained by the significantly reduced desolvation energy barrier required for reagents residing in the AWI region with an open solvent shell.

Phase State Regulates Photochemical HONO Production from NaNO3/Dicarboxylic Acid Mixtures.

Field observations of daytime HONO source strengths have not been well explained by laboratory measurements and model predictions up until now. More efforts are urgently needed to fill the knowledge gaps concerning how environmental factors, especially relative humidity (RH), affect particulate nitrate photolysis. In this work, two critical attributes for atmospheric particles, i.e., phase state and bulk-phase acidity, both influenced by ambient RH, were focused to illuminate the key regulators for reactive nitrogen production from typical internally mixed systems, i.e., NaNO3 and dicarboxylic acid (DCA) mixtures. The dissolution of only few oxalic acid (OA) crystals resulted in a remarkable 50-fold increase in HONO production compared to pure nitrate photolysis at 85% RH. Furthermore, the HONO production rates (PHONO) increased by about 1 order of magnitude as RH rose from <5% to 95%, initially exhibiting an almost linear dependence on the amount of surface absorbed water and subsequently showing a substantial increase in PHONO once nitrate deliquescence occurred at approximately 75% RH. NaNO3/malonic acid (MA) and NaNO3/succinic acid (SA) mixtures exhibited similar phase state effects on the photochemical HONO production. These results offer a new perspective on how aerosol physicochemical properties influence particulate nitrate photolysis in the atmosphere.

Quantification and Characterization of Fine Plastic Particles as Considerable Components in Atmospheric Fine Particles.

The negative effects of air pollution, especially fine particulate matter (PM2.5, particles with an aerodynamic diameter of ≤2.5 µm), on human health, climate, and ecosystems are causing significant concern. Nevertheless, little is known about the contributions of emerging pollutants such as plastic particles to PM2.5 due to the lack of continuous measurements and characterization methods for atmospheric plastic particles. Here, we investigated the levels of fine plastic particles (FPPs) in PM2.5 collected in urban Shanghai at a 2 h resolution by using a novel versatile aerosol concentration enrichment system that concentrates ambient aerosols up to 10-fold. The FPPs were analyzed offline using the combination of spectroscopic and microscopic techniques that distinguished FPPs from other carbon-containing particles. The average FPP concentrations of 5.6 µg/m3 were observed, and the ratio of FPPs to PM2.5 was 13.2% in this study. The FPP sources were closely related to anthropogenic activities, which pose a potential threat to ecosystems and human health. Given the dramatic increase in plastic production over the past 70 years, this study calls for better quantification and control of FPP pollution in the atmosphere.

Determining the elasto-adhesion length by void collapse in ultra-soft materials.

The elasto-adhesion length (lEA) is a materials property that describes the size scale where the relative importance of adhesion and elastic forces transitions for defined structures and functions. Conventional approaches for determining lEA require independent measurements of the critical energy release rate (Gc) and Young's modulus (E). Herein, we introduce a new method to obtain lEA, only relying upon visual inspection. This method relies upon the introduction of a controlled void within a soft material, for example an ultra-soft hydrogel as studied here. The geometry of the void within the hydrogel is tuned to control the relative strength of adhesion and elastic energy, and a relationship between the observed equilibrium configuration of the void and lEA is derived. We validate this new method with independent force-based contact adhesion tests. This method allows for the easy measurement of lEA for difficult-to-handle soft materials and can be amended for various chemistries and materials.

Cavitation induced fracture of intact brain tissue.

Nonpenetrating traumatic brain injuries (TBIs) are linked to cavitation. The structural organization of the brain makes it particularly susceptible to tears and fractures from these cavitation events, but limitations in existing characterization methods make it difficult to understand the relationship between fracture and cavitation in this tissue. More broadly, fracture energy is an important, yet often overlooked, mechanical property of all soft tissues. We combined needle-induced cavitation with hydraulic fracture models to induce and quantify fracture in intact brains at precise locations. We report here the first measurements of the fracture energy of intact brain tissue that range from 1.5 to 8.9 J/m2, depending on the location in the brain and the model applied. We observed that fracture consistently occurs along interfaces between regions of brain tissue. These fractures along interfaces allow cavitation-related damage to propagate several millimeters away from the initial injury site. Quantifying the forces necessary to fracture brain and other soft tissues is critical for understanding how impact and blast waves damage tissue in vivo and has implications for the design of protective gear and tissue engineering.

Geometry-controlled instabilities for soft-soft adhesive interfaces.

Soft materials interfaces can develop complex morphologies, such as cavities or finger-like features, during separation as a result of a mechanical instability. While the onset and growth of these instabilities have been investigated previously for interfaces between rigid and soft materials, no existing predictive model provides insight for controlling the separation morphology associated with these instabilities when both "sides" of the interface are soft. Here, we expand previous models to account for the geometry and materials properties of two soft materials that form an interface. The total compliance of the system, which depends nonlinearly on the thickness of each contacting soft material, plays a primary role in governing the morphology of the separating interface. We validate this model with experimental measurements using a series of soft elastomers with varying layer thicknesses and fixed materials properties, in order to emphasize the geometry alone can give rise to the observed differences in the interface separation process. This model also demonstrates that the degree of geometric asymmetry, or the ratio of the layer thicknesses that form an interface, influences the stress experienced in either layer, thus providing a rich means of controlling how unstable interface separations develop and propagate. This framework is a powerful tool to understand and control adhesion mechanisms in fields ranging from biology to soft robotics, and provides intuition for engineering a separation mode for a desired end result.

Absolute determination of chemical kinetic rate constants by optical tracking the reaction on the second timescale using cavity-enhanced absorption spectroscopy.

We report a new spectroscopic platform coupled to an atmospheric simulation chamber for the direct determination of chemical rate constants with high accuracy at a second time-scale resolution. These developed analytical instruments consist of an incoherent broadband cavity enhanced absorption spectrometer using a red light emitting diode (LED) emitting at ∼662 nm (LED-IBBCEAS) associated with a multipass cell direct absorption spectrometer (MPC-DAS) coupled to an external cavity quantum cascade laser (EC-QCL) operating in the mid-infrared region at approximately 8 µm (EC-QCL-MPC-DAS). Spectrometers were employed to investigate the NO3-initiated oxidation of four selected volatile organic compounds (VOCs) for the determination of the corresponding rate constants with a dynamic range of 5 orders of magnitude (from 10-11 to 10-16 cm3 molecule-1 s-1). Rate constants of (6.5 ± 0.5) × 10-15, (7.0 ± 0.4) × 10-13, and (5.8 ± 0.5) × 10-16 cm3 molecule-1 s-1 for propanal, isoprene and formaldehyde, respectively, were directly determined by fitting the measured concentration-time profiles of NO3 and VOCs (measured using a proton transfer reaction time-of-flight mass spectrometer, PTR-ToF-MS) to chemical models based on the FACSIMILE simulation software (version 4.2.50) at 760 torr and 293 ± 2 K. The obtained rate constants are in good agreement with the most recent recommendations of the IUPAC (International Union of Pure and Applied Chemistry). In addition, a rate constant of (2.60 ± 0.30) × 10-11 cm3 molecule-1 s-1 for the oxidation of 2-methoxyphenol by NO3 radicals was first determined using the absolute kinetic method. Compared to the mostly used indirect relative rate method, the rate constant uncertainty is reduced from ∼20% to ∼12%. The results demonstrated the high potential of using modern spectroscopic techniques to directly determine the chemical reaction rate constants.

Chest physiotherapy for pneumonia in adults.

BACKGROUND: Despite conflicting evidence, chest physiotherapy has been widely used as an adjunctive treatment for adults with pneumonia. This is an update of a review first published in 2010 and updated in 2013. OBJECTIVES: To assess the effectiveness and safety of chest physiotherapy for pneumonia in adults. SEARCH METHODS: We updated our searches in the following databases to May 2022: the Cochrane Central Register of Controlled Trials (CENTRAL) via OvidSP, MEDLINE via OvidSP (from 1966), Embase via embase.com (from 1974), Physiotherapy Evidence Database (PEDro) (from 1929), CINAHL via EBSCO (from 2009), and the Chinese Biomedical Literature Database (CBM) (from 1978). SELECTION CRITERIA: Randomised controlled trials (RCTs) and quasi-RCTs assessing the efficacy of chest physiotherapy for treating pneumonia in adults. DATA COLLECTION AND ANALYSIS: We used standard methodological procedures expected by Cochrane. MAIN RESULTS: We included two new trials in this update (540 participants), for a total of eight RCTs (974 participants). Four RCTs were conducted in the United States, two in Sweden, one in China, and one in the United Kingdom. The studies looked at five types of chest physiotherapy: conventional chest physiotherapy; osteopathic manipulative treatment (OMT, which includes paraspinal inhibition, rib raising, and myofascial release); active cycle of breathing techniques (which includes active breathing control, thoracic expansion exercises, and forced expiration techniques); positive expiratory pressure; and high-frequency chest wall oscillation. We assessed four trials as at unclear risk of bias and four trials as at high risk of bias. Conventional chest physiotherapy (versus no physiotherapy) may have little to no effect on improving mortality, but the certainty of evidence is very low (risk ratio (RR) 1.03, 95% confidence interval (CI) 0.15 to 7.13; 2 trials, 225 participants; I² = 0%). OMT (versus placebo) may have little to no effect on improving mortality, but the certainty of evidence is very low (RR 0.43, 95% CI 0.12 to 1.50; 3 trials, 327 participants; I² = 0%). Similarly, high-frequency chest wall oscillation (versus no physiotherapy) may also have little to no effect on improving mortality, but the certainty of evidence is very low (RR 0.75, 95% CI 0.17 to 3.29; 1 trial, 286 participants). Conventional chest physiotherapy (versus no physiotherapy) may have little to no effect on improving cure rate, but the certainty of evidence is very low (RR 0.93, 95% CI 0.56 to 1.55; 2 trials, 225 participants; I² = 85%). Active cycle of breathing techniques (versus no physiotherapy) may have little to no effect on improving cure rate, but the certainty of evidence is very low (RR 0.60, 95% CI 0.29 to 1.23; 1 trial, 32 participants). OMT (versus placebo) may improve cure rate, but the certainty of evidence is very low (RR 1.59, 95% CI 1.01 to 2.51; 2 trials, 79 participants; I² = 0%). OMT (versus placebo) may have little to no effect on mean duration of hospital stay, but the certainty of evidence is very low (mean difference (MD) -1.08 days, 95% CI -2.39 to 0.23; 3 trials, 333 participants; I² = 50%). Conventional chest physiotherapy (versus no physiotherapy, MD 0.7 days, 95% CI -1.39 to 2.79; 1 trial, 54 participants) and active cycle of breathing techniques (versus no physiotherapy, MD 1.4 days, 95% CI -0.69 to 3.49; 1 trial, 32 participants) may also have little to no effect on duration of hospital stay, but the certainty of evidence is very low. Positive expiratory pressure (versus no physiotherapy) may reduce the mean duration of hospital stay by 1.4 days, but the certainty of evidence is very low (MD -1.4 days, 95% CI -2.77 to -0.03; 1 trial, 98 participants). Positive expiratory pressure (versus no physiotherapy) may reduce the duration of fever by 0.7 days, but the certainty of evidence is very low (MD -0.7 days, 95% CI -1.36 to -0.04; 1 trial, 98 participants). Conventional chest physiotherapy (versus no physiotherapy, MD 0.4 days, 95% CI -1.01 to 1.81; 1 trial, 54 participants) and OMT (versus placebo, MD 0.6 days, 95% CI -1.60 to 2.80; 1 trial, 21 participants) may have little to no effect on duration of fever, but the certainty of evidence is very low. OMT (versus placebo) may have little to no effect on the mean duration of total antibiotic therapy, but the certainty of evidence is very low (MD -1.07 days, 95% CI -2.37 to 0.23; 3 trials, 333 participants; I² = 61%). Active cycle of breathing techniques (versus no physiotherapy) may have little to no effect on duration of total antibiotic therapy, but the certainty of evidence is very low (MD 0.2 days, 95% CI -4.39 to 4.69; 1 trial, 32 participants). High-frequency chest wall oscillation plus fibrobronchoscope alveolar lavage (versus fibrobronchoscope alveolar lavage alone) may reduce the MD of intensive care unit (ICU) stay by 3.8 days (MD -3.8 days, 95% CI -5.00 to -2.60; 1 trial, 286 participants) and the MD of mechanical ventilation by three days (MD -3 days, 95% CI -3.68 to -2.32; 1 trial, 286 participants), but the certainty of evidence is very low. One trial reported transient muscle tenderness emerging after OMT in two participants. In another trial, three serious adverse events led to early withdrawal after OMT. One trial reported no adverse events after positive expiratory pressure treatment. Limitations of this review were the small sample size and unclear or high risk of bias of the included trials. AUTHORS' CONCLUSIONS: The inclusion of two new trials in this update did not change the main conclusions of the original review. The current evidence is very uncertain about the effect of chest physiotherapy on improving mortality and cure rate in adults with pneumonia. Some physiotherapies may slightly shorten hospital stays, fever duration, and ICU stays, as well as mechanical ventilation. However, all of these findings are based on very low certainty evidence and need to be further validated.

PM1.0-Nitrite Heterogeneous Formation Demonstrated via a Modified Versatile Aerosol Concentration Enrichment System Coupled with Ion Chromatography.

Particulate nitrite is a critical source of hydroxyl radicals; however, it lacks high-resolution methods due to its low abundance and stability to explore its formation mechanism. In this study, a modified versatile aerosol concentration enrichment system (VACES) coupled with ion chromatography (IC) was used to measure particulate NO2- hourly online and achieve a lowered detection limit of 10-3 µg m-3. VACES-IC was used to observe a high- and low-concentration events of PM1.0-NO2- in Shanghai, corresponding to the ambient-level concentrations of 0.34 and 0.05 µg m-3, respectively. The morning peak concentrations of NO2- even exceeded 3σ (standard deviation) in the high-concentration event due to the reduction of NO2 by aerosol SO32- based on kinetics and regression analysis. This implies that controlling SO2 emissions would be an effective strategy to decrease morning NO2- concentrations, correspondingly reducing the kinetic formation of SO42- by 20.8-34.8%. However, after sunrise, NO2- formation was primarily attributed to NO2 hydrolysis at pH 4.97-6.14. In the low-concentration event, NO2 hydrolysis also accounted for an overwhelming proportion (∼90%) of NO2- formation. This work estimates the contribution of different paths to particulate NO2- formation based on newly established high-resolution measurements.

Au nanoring arrays as surface enhanced Raman spectroscopy substrate for chemical component study of individual atmospheric aerosol particle.

Monolayer-ordered gold nanoring arrays were prepared by ion-sputtering method and used as surface enhanced Raman spectroscopy (SERS) substrates to test the individual atmospheric aerosols particle. Compared to other methods used for testing atmospheric aerosols particles, the collection and subsequent detection in our work is performed directly on the gold nanoring SERS substrate without any treatment of the analyte. The SERS performance can be tuned by changing the depth of the gold nanoring cavity as originating from coupling of dipolar modes at the inner and outer surfaces of the nanorings. The electric field exhibits uniform enhancement and polarization in the ordered Au nanoring substrate, which can improve the accuracy for detecting atmospheric aerosol particles. Combined with Raman mapping, the information about chemical composition of individual atmospheric aerosols particle and distribution of specific components can be presented visually. The results show the potential of SERS in enabling improved analysis of aerosol particle chemical composition, mixing state, and other related physicochemical properties.

Satellite-Based Estimates of Wet Ammonium (NH4-N) Deposition Fluxes Across China during 2011-2016 Using a Space-Time Ensemble Model.

Wet NH4-N deposition plays a significant role in the ecosystem safety in China, and thus it is highly imperative to estimate the national wet NH4-N deposition flux accurately. In this study, a new methodology named space-time ensemble machine-learning model was first applied to constrain the high-resolution NH4-N deposition fluxes over China based on the satellite data, assimilated meteorology, and various geographical covariates. A small gap between site-based cross-validation (CV) R2 value (0. 73) and 10-fold CV R2 value (0.76), along with remarkable improvement in predictive accuracy (0.76) compared with previous studies (0.61), demonstrated the strong prediction capability of the space-time ensemble model in data mining. The higher wet NH4-N deposition fluxes mainly occurred in North China Plain (NCP), Sichuan Basin, Hunan, Jiangxi, and Guangdong provinces, whereas other regions retained the lower values. In addition, the wet NH4-N deposition fluxes, removing the precipitation effect in some major developed regions (e.g., Beijing and Shanghai) of China, displayed gradual increases from 2011 to 2014, while they suffered from dramatic decreases during 2014-2016, which was due to the strict implementation of the Action Plan for Air Pollution Prevention and Control (APPC-AP). The high-quality NH4-N deposition data sets are greatly useful to assess the potential ecological risks.

Photochemical Oxidation of Water-Soluble Organic Carbon (WSOC) on Mineral Dust and Enhanced Organic Ammonium Formation.

Water-soluble organic carbon (WSOC), which is closely related to biogenic emissions, is of great importance in the atmosphere for its ubiquitous existence and rich abundance. Levoglucosan, a typical WSOC, is usually considered to be stable and thus used as a tracer of biomass burning. However, we found that levoglucosan can be photo-oxidized on mineral dust, with formic acid, oxalic acid, glyoxylic acid, 2,3-dioxopropanoic acid, dicarbonic acid, performic acid, mesoxalaldehyde, 2-hydroxymalonaldehyde, carbonic formic anhydride, and 1,3-dioxolane-2,4-dione detected as main products. Further, we observed the heterogeneous uptake of NH3 promoted by the carboxylic acids stemming from the photocatalytic oxidation (PCO) of levoglucosan. The mineral-dust-initiated PCO of levoglucosan and enhanced heterogeneous uptake of NH3, which are highly influenced by irradiation and moisture conditions, were for the first time revealed. The reaction mechanisms and pathways were studied in detail by diffuse reflection infrared Fourier transform spectroscopy (DRIFTS), high-pressure photon ionization time-of-flight mass spectrometry (HPPI-ToF-MS) and flow reactor systems. Diverse WSOC constituents were studied as well, and the reactivity toward NH3 is related to the number of hydroxyl groups of the WSOC molecules. This work reveals a new precursor of secondary organic aerosols and provides experimental evidence of the existence of organic ammonium salts in atmospheric particles.

Complexation of Fe(III)/Catechols in atmospheric aqueous phase and the consequent cytotoxicity assessment in human bronchial epithelial cells (BEAS-2B).

Recent research has shown that the complexation of metals-organics plays an important role in atmospheric particulate matter, whose health effects should be taken into account. This work investigates the interactions between catechols (CAs), i.e., 4-nitrocatechol (4NC) and 4-methylcatechol (4MC), and transition metals (i.e., Fe) in the aqueous phase dark reaction. The formation of Fe/CAs complexes and secondary organics products are analyzed by UV-Vis spectroscopy, stopped-flow spectroscopy, high-resolution mass spectrometry and Raman spectroscopy, while the insoluble particulate matter formed from the CAs/Fe mixtures are characterized by the FTIR, X-ray photoelectron spectroscopy (XPS) and thermogravimetric-quadrupole-mass spectrometry (TG-Q-MS). On the basis of the density functional theory (DFT) calculation and experimental results, the possible formation pathways for the complexes of Fe(III) with 4NC (a proxy for organics) are proposed. The Fe/CAs complexes and organics products perhaps have significant sources of light absorption which play an important role in influencing the intensity of atmospheric radiation and particulate phase photochemistry. Besides, the cytotoxicity is tested as a function of concentrations for CAs/Fe mixtures in BEAS-2B cells. Our results show that CAs/Fe mixtures have strong association with cytotoxicity, indicating the mixtures have potential influence to human health.

Klarite as a label-free SERS-based assay: a promising approach for atmospheric bioaerosol detection.

Detecting atmospheric bioaerosols in a quantitative way is highly desirable for public health and safety. This work demonstrates that surface-enhanced Raman spectroscopy (SERS) is a simple and rapid analytical technique for the detection of atmospheric bioaerosols, on a Klarite substrate. For both simulated and ambient bioaerosols, this detection assay results in an increase in the enhancement factor of the Raman signal. We report a strong SERS signal generated by bioaerosols containing living Escherichia coli deposited on Klarite. Furthermore, we demonstrate that SERS mapping can be used to estimate the percentage of airborne, living Escherichia coli. Moreover, Klarite provides differently distinct SERS spectra at different bacterial growth phases, indicating its potential to identify changes occurring in the bacterial envelope. Finally, we applied SERS for the rapid detection of Escherichia coli in ambient bioaerosols without using time-consuming and laborious culture processes. Our results represent rapid, culture-free and label-free detection of airborne bacteria in the real-world environment.

Unexpectedly Increased Particle Emissions from the Steel Industry Determined by Wet/Semidry/Dry Flue Gas Desulfurization Technologies.

"Ultralow-emission" standards have started to be implemented for steel plants in China. Flue gas desulfurization (FGD) systems integrating desulfurization and dedusting, common end-of-pipe technologies before the stacks, have been a key process for controlling the complexity of sintering flue gas to meet ultralow-emission requirements. This study reports comprehensive analysis of the influence of wet/semidry/dry FGD systems on particulate emissions via a field investigation of five typical sinter plants equipped with various FGD devices. The size distribution and mass concentration of particulate matter (PM) are adjusted to different ranges by these FGD systems. Chemical analysis of the PM compositions shows that 20-95% of the mass of inlet PM is removed by FGD systems, while it is estimated that approximately 17, 63, 59, and 71% of the outlet PMs are newly contributed by desulfurizers and their byproducts for the tested wet limestone, wet ammonia, semidry circulating fluidized bed, and activated coke FGD systems, respectively. The newly contributed compositions of PM2.5 emitted from these FGD systems are dominated by CaSO4, (NH4)2SO4, CaSO4 + CaO, and coke carbon, respectively. These results suggest that the deployment of FGD technology should be comprehensively considered to avoid additional negative impacts from byproducts generated in control devices on the atmosphere.

Primary Particulate Matter Emitted from Heavy Fuel and Diesel Oil Combustion in a Typical Container Ship: Characteristics and Toxicity.

Container ships have been widely recognized as an important emission source within maritime transport. Heavy fuel oil (HFO) and diesel oil (DO) are the two most commonly used fuels. This study reports the characteristics and toxicities of particulate matter (PM) emissions from HFO and DO combustion in a typical container ship. The PM number size distribution possesses a bimodal structure with peaks at ∼20 nm and ∼100 nm. The PM2.5 emission factors (EFs) are 3.15 ± 0.39 and 0.92 ± 0.02 g/kg fuel for HFO and DO, respectively. The benzo[a]pyrene equivalent carcinogenic potency (BaPeq) of 16 polycyclic aromatic hydrocarbons contained in HFO and DO PM2.5 is approximately 0.81 ± 0.10 and 0.12 ± 0.04 mg/kg fuel, respectively. BaPeq concentration shows an increasing tendency with decreased PM size. The reactive oxygen species activity and cytotoxicity of HFO PM2.5 samples are ∼2.1 and ∼2.5 times higher than those of DO PM2.5 samples, respectively. These health risks are both significantly attributed to the BaPeq content in PM2.5 with correlations of 0.86-0.92. Furthermore, the examined biological effects are much greater than those of atmospheric PM2.5 collected in Shanghai. Our results imply that better fuel quality is important for improving air quality and reducing health risks.

Effect of relative humidity and the presence of aerosol particles on the α-pinene ozonolysis.

The α-pinene ozonolysis under the different environmental conditions were observed in a smog chamber. The second-order rate constant (k) was determined to be (7.25±0.06)×10-17cm3/(molecule·sec) under 20% of relative humidity (RH) and room temperature. RH showed a marked influence on the α-pinene ozonolysis. The value of k increased with RH increase, which was 1.6 times faster at RH=80% than that at RH=20%. Additionally, the value of k apparently changed in the presence of the aerosol particles. The diesel soot increased the k value. The fly ash prohibited the reaction, however, H2SO4-treated fly ash promoted the reaction. The information of products gained using FT-IR and SPAMS showed that pinonic acid, 10-hydroxy-pinonic acid and pinic acid could be generated during the α-pinene ozonolysis. Water molecules could take part in the formation of the products, and play a vital role in the degradation of α-pinene. The atmospheric residence time calculation showed that the ozonolysis in the atmosphere is an important way of the α-pinene consumption as compared to that reacted with OH during daytime. The results suggested that the degradation of α-pinene via the ozonization in the atmosphere may be affected greatly by RH, as well as the presence of aerosol particles. The ozonolysis reaction may be an important way of the α-pinene consumption during daytime.

Observation and analysis of atmospheric volatile organic compounds in a typical petrochemical area in Yangtze River Delta, China.

Volatile organic compounds (VOCs) are a kind of important precursors for ozone photochemical formation. In this study, VOCs were measured from November 5th, 2013 to January 6th, 2014 at the Second Jinshan Industrial Area, Shanghai, China. The results showed that the measured VOCs were dominated by alkanes (41.8%), followed by aromatics (20.1%), alkenes (17.9%), and halo-hydrocarbons (12.5%). The daily trend of the VOC concentration showed a bimodal feature due to the rush-hour traffic in the morning and at nightfall. Based on the VOC concentration, a receptor model of Positive Matrix Factorization (PMF) coupled with the information related to VOC sources was applied to identify the major VOC emissions. The result showed five major VOC sources: solvent use and industrial processes were responsible for about 30% of the ambient VOCs, followed by rubber chemical industrial emissions (23%), refinery and petrochemical industrial emissions (21%), fuel evaporations (13%) and vehicular emissions (13%). The contribution of generalized industrial emissions was about 74% and significantly higher than that made by vehicle exhaust. Using a propylene-equivalent method, alkenes displayed the highest concentration, followed by aromatics and alkanes. Based on a maximum incremental reactivity (MIR) method, the average hourly ozone formation potential (OFP) of VOCs is 220.49 ppbv. The most significant source for ozone chemical formation was identified to be rubber chemical industrial emissions, following one by vehicular emission. The data shown herein may provide useful information to develop effective VOC pollution control strategies in industrialized area.

Characteristics of the pollutant emissions in a tunnel of Shanghai on a weekday.

Tunnel displays a typical semi-closed environment, and multitudes of the pollutants tend to accumulate. The samples of gaseous pollutants and particulate matter (PM) were collected from the Xiangyin tunnel at Shanghai to investigate the characteristics of the pollutant emissions. The results indicated that both gaseous pollutants and PM exhibited much higher concentrations during the rush hours in the morning and at night due to vehicle emission. Two peaks of the PM concentration were observed in the scope of 0.7-1.1 and 3.3-4.7 µm, accounting for 14.6% and 20.3% of the total concentrations, respectively. Organic matter (OM), EC, and many water-soluble ions were markedly higher at the rush hours in the morning than those at night, implicating comprehensive effects of vehicle types and traffic volume. The particle number concentrations exhibited two peaks at Aitken mode (25 nm and 100 nm) and accumulation mode (600 nm), while the particle volume concentration displayed high values at the accumulation mode (100-500 nm) and coarse mode (2.5-4.0 µm). The peak around 100 nm was detected in the morning rush hours, but it diminished with the decrease of the traffic volume. Individual-particle analysis revealed that main particles in the tunnel were Fe-rich particles, K-rich particles, mineral particles, Ca-S rich particles and Al-Si particles. The particles collected at the rush hours displayed marked different morphologies, element concentrations and particle sizes compared to the ones collected at the non-rush period. The data presented herein could shed a light on the feature of vehicle emissions.