Development and validation of an analytical pyrolysis method for detection of airborne polystyrene nanoparticles.

Microplastic is ubiquitous in the environment. Recently it was discovered that microplastic (MP, 1 µm-5 mm) contamination is present in the atmosphere where it can be transported over long distances and introduced to remote pristine environments. Sources, concentration levels, and transportation pathways of MP are still associated with large uncertainties. The abundance of atmospheric MP increases with decreasing particle size, suggesting that nanoplastics (NP, <1µm) could be of considerable atmospheric relevance. Only few analytical methods are available for detection of nanosized plastic particles. Thermoanalytical techniques are independent of particle size and are thus a powerful tool for MP and NP analysis. Here we develop a method for analysis of polystyrene on the nanogram scale using pyrolysis gas chromatography coupled to mass spectrometry. Pyrolysis was performed using a slow temperature ramp, and analytes were cryofocused prior to injection. The mass spectrometer was operated in selected ion monitoring (SIM) mode. A lower limit of detection of 1±1 ng and a lower limit of quantification of 2±2 ng were obtained (for the trimer peak). The method was validated with urban matrices of low (7 µg per sample) and high (53 µg per sample) aerosol mass loadings. The method performs well for low loadings, whereas high loadings seem to cause a matrix effect reducing the signal of polystyrene. This effect can be minimized by introducing a thermal desorption step prior to pyrolysis. The study provides a novel analysis method for qualitative and semi-quantitative analysis of PS on the nanogram scale in an aerosol matrix. Application of the method can be used to obtain concentration levels of polystyrene in atmospheric MP and NP. This is important in order to improve the understanding of the sources and sinks of MP and NP in the environment and thereby identify routes of exposure and uptake of this emerging contaminant.

Gas-to-Particle Partitioning of Products from Ozonolysis of Δ3-Carene and the Effect of Temperature and Relative Humidity.

Formation of oxidized products from Δ3-carene (C10H16) ozonolysis and their gas-to-particle partitioning at three temperatures (0, 10, and 20 °C) under dry conditions (<2% RH) and also at 10 °C under humid (78% RH) conditions were studied using a time-of-flight chemical ionization mass spectrometer (ToF-CIMS) combined with a filter inlet for gases and aerosols (FIGAERO). The Δ3-carene ozonolysis products detected by the FIGAERO-ToF-CIMS were dominated by semivolatile organic compounds (SVOCs). The main effect of increasing temperature or RH on the product distribution was an increase in fragmentation of monomer compounds (from C10 to C7 compounds), potentially via alkoxy scission losing a C3 group. The equilibrium partitioning coefficient estimated according to equilibrium partitioning theory shows that the measured SVOC products distribute more into the SOA phase as the temperature decreases from 20 to 10 and 0 °C and for most products as the RH increases from <2 to 78%. The temperature dependency of the saturation vapor pressure (above an assumed liquid state), derived from the partitioning method, also allows for a direct way to obtain enthalpy of vaporization for the detected species without accessibility of authentic standards of the pure substances. This method can provide physical properties, beneficial for, e.g., atmospheric modeling, of complex multifunctional oxidation products.

An open-hardware community ice nucleation cold stage for research and teaching.

Aerosol particles with rare specific properties act as nuclei for ice formation. The presence of ice nucleating particles in the atmosphere leads to heterogeneous freezing at warm temperatures and thus these particles play an important role in modulating microphysical properties of clouds. This work presents an ice nucleation cold stage instrument for measuring the concentration of ice nucleating particles in liquids. The cost is âˆ¼ $10 k including an external chiller. Using a lower cost heat sink reduces the cost to âˆ¼ $6 k. The instrument is suitable for studying ambient ice nucleating particle concentrations and laboratory-based process-level studies of ice nucleation. The design plans allow individuals to self-manufacture the cold-stage using 3D printing, off-the-shelf parts, and a handful of standard tools. Software to operate the instrument and analyze the data is also provided. The design is intended to be simple enough that a graduate student can build it as part of a course or thesis project. Costs are kept to a minimum to facilitate use in classroom demonstrations and laboratory classes.

Morphology and hygroscopicity of nanoplastics in sea spray.

The role of airborne nanoparticles in atmospheric chemistry and public health is largely controlled by particle size, morphology, surface composition, and coating. Aerosol mass spectrometry provides real-time chemical characterization of submicron atmospheric particles, but analysis of nanoplastics in complex aerosol mixtures such as sea spray is severely limited by challenges associated with separation and ionization of the aerosol matrix. Here we characterize the internal and external mixing state of synthetic sea spray aerosols spiked with 150 nm nanoplastics. Aerosols generated from pneumatic atomization and from a sea spray tank are compared. A humidified tandem differential mobility analyzer is used as a size and hygroscopicity filter, resulting in separation of nanoplastics from sea spray, and an inline high-resolution time-of-flight aerosol mass spectrometer is used to characterize particle composition and ionization efficiency. The separation technique amplified the detection limit of the airborne nanoplastics. A salt coating was found on the nanoplastics with coating thickness increasing exponentially with increasing bulk solution salinity, which was varied from 0 to 40 g kg-1. Relative ionization efficiencies of polystyrene and sea salt chloride were 0.19 and 0.36, respectively. The growth-factor derived hygroscopicity of sea salt was 1.4 at 75% relative humidity. These results underscore the importance of separating airborne nanoplastics from sea salt aerosol for detailed online characterization by aerosol mass spectrometry and characterization of salt coatings as a function of water composition. The surface coating of nanoplastic aerosols by salts can profoundly impact their surface chemistry, water uptake, and humidified particle size distributions in the atmosphere.

Airway and systemic biomarkers of health effects after short-term exposure to indoor ultrafine particles from cooking and candles - A randomized controlled double-blind crossover study among mild asthmatic subjects.

BACKGROUND: There is insufficient knowledge about the systemic health effects of exposure to fine (PM2.5) and ultrafine particles emitted from typical indoor sources, including cooking and candlelight burning. We examined whether short-term exposure to emissions from cooking and burning candles cause inflammatory changes in young individuals with mild asthma. Thirty-six non-smoking asthmatics participated in a randomized controlled double-blind crossover study attending three exposure sessions (mean PM2.5 µg/m3; polycyclic aromatic hydrocarbons ng/m3): (a) air mixed with emissions from cooking (96.1; 1.1), (b) air mixed with emissions from candles (89.8; 10), and (c) clean filtered air (5.8; 1.0). Emissions were generated in an adjacent chamber and let into a full-scale exposure chamber where participants were exposed for five hours. Several biomarkers were assessed in relation to airway and systemic inflammatory changes; the primary outcomes of interest were surfactant Protein-A (SP-A) and albumin in droplets in exhaled air - novel biomarkers for changes in the surfactant composition of small airways. Secondary outcomes included cytokines in nasal lavage, cytokines, C-reactive protein (CRP), epithelial progenitor cells (EPCs), genotoxicity, gene expression related to DNA-repair, oxidative stress, and inflammation, as well as metabolites in blood. Samples were collected before exposure start, right after exposure and the next morning. RESULTS: SP-A in droplets in exhaled air showed stable concentrations following candle exposure, while concentrations decreased following cooking and clean air exposure. Albumin in droplets in exhaled air increased following exposure to cooking and candles compared to clean air exposure, although not significant. Oxidatively damaged DNA and concentrations of some lipids and lipoproteins in the blood increased significantly following exposure to cooking. We found no or weak associations between cooking and candle exposure and systemic inflammation biomarkers including cytokines, CRP, and EPCs. CONCLUSIONS: Cooking and candle emissions induced effects on some of the examined health-related biomarkers, while no effect was observed in others; Oxidatively damaged DNA and concentrations of lipids and lipoproteins were increased in blood after exposure to cooking, while both cooking and candle emissions slightly affected the small airways including the primary outcomes SP-A and albumin. We found only weak associations between the exposures and systemic inflammatory biomarkers. Together, the results show the existence of mild inflammation following cooking and candle exposure.

Ozonolysis of α-Pinene and Δ3-Carene Mixtures: Formation of Dimers with Two Precursors.

The formation of secondary organic aerosol (SOA) from the structurally similar monoterpenes, α-pinene and Δ3-carene, differs substantially. The aerosol phase is already complex for a single precursor, and when mixtures are oxidized, products, e.g., dimers, may form between different volatile organic compounds (VOCs). This work investigates whether differences in SOA formation and properties from the oxidation of individual monoterpenes persist when a mixture of the monoterpenes is oxidized. Ozonolysis of α-pinene, Δ3-carene, and a 1:1 mixture of them was performed in the Aarhus University Research on Aerosol (AURA) atmospheric simulation chamber. Here, ∼100 ppb of monoterpene was oxidized by 200 ppb O3 under dark conditions at 20 °C. The particle number concentration and particle mass concentration for ozonolysis of α-pinene exceed those from ozonolysis of Δ3-carene alone, while their mixture results in concentrations similar to α-pinene ozonolysis. Detailed offline analysis reveals evidence of VOC-cross-product dimers in SOA from ozonolysis of the monoterpene mixture: a VOC-cross-product dimer likely composed of the monomeric units cis-caric acid and 10-hydroxy-pinonic acid and a VOC-cross-product dimer ester likely from the monomeric units caronaldehyde and terpenylic acid were tentatively identified by liquid chromatography-mass spectrometry. To improve the understanding of chemical mechanisms determining SOA, it is relevant to identify VOC-cross-products.

Acute health effects from exposure to indoor ultrafine particles-A randomized controlled crossover study among young mild asthmatics.

Particulate matter is linked to adverse health effects, however, little is known about health effects of particles emitted from typical indoor sources. We examined acute health effects of short-term exposure to emissions from cooking and candles among asthmatics. In a randomized controlled double-blinded crossover study, 36 young non-smoking asthmatics attended three exposure sessions lasting 5 h: (a) air mixed with emissions from cooking (fine particle mass concentration): (PM2.5 : 96.1 µg/m3 ), (b) air mixed with emissions from candles (PM2.5 : 89.8 µg/m3 ), and c) clean filtered air (PM2.5 : 5.8 µg/m3 ). Health effects (spirometry, fractional exhaled Nitric Oxide [FeNO], nasal volume and self-reported symptoms) were evaluated before exposure start, then 5 and 24 h after. During exposures volatile organic compounds (VOCs), particle size distributions, number concentrations and optical properties were measured. Generally, no statistically significant changes were observed in spirometry, FeNO, or nasal volume comparing cooking and candle exposures to clean air. In males, nasal volume and FeNO decreased after exposure to cooking and candles, respectively. Participants reported additional and more pronounced symptoms during exposure to cooking and candles compared to clean air. The results indicate that emissions from cooking and candles exert mild inflammation in asthmatic males and decrease comfort among asthmatic males and females.

Emissions of soot, PAHs, ultrafine particles, NOx, and other health relevant compounds from stressed burning of candles in indoor air.

Burning candles release a variety of pollutants to indoor air, some of which are of concern for human health. We studied emissions of particles and gases from the stressed burning of five types of pillar candles with different wax and wick compositions. The stressed burning was introduced by controlled fluctuating air velocities in a 21.6 m3 laboratory chamber. The aerosol physicochemical properties were measured both in well-mixed chamber air and directly above the candle flame with online and offline techniques. All candles showed different emission profiles over time with high repeatability among replicates. The particle mass emissions from stressed burning for all candle types were dominated by soot (black carbon; BC). The wax and wick composition strongly influenced emissions of BC, PM2.5 , and particle-phase polycyclic aromatic hydrocarbons (PAHs), and to lower degree ultrafine particles, inorganic and organic carbon fraction of PM, but did not influence NOx , formaldehyde, and gas-phase PAHs. Measurements directly above the flame showed empirical evidence of short-lived strong emission peaks of soot particles. The results show the importance of including the entire burn time of candles in exposure assessments, as their emissions can vary strongly over time. Preventing stressed burning of candles can reduce exposure to pollutants in indoor air.

The impact of atmospheric oxidation on hygroscopicity and cloud droplet activation of inorganic sea spray aerosol.

Sea spray aerosol (SSA) contributes significantly to natural aerosol particle concentrations globally, in marine areas even dominantly. The potential changes of the omnipresent inorganic fraction of SSA due to atmospheric ageing is largely unexplored. In the atmosphere, SSA may exist as aqueous phase solution droplets or as dried solid or amorphous particles. We demonstrate that ageing of liquid NaCl and artificial sea salt aerosol by exposure to ozone and UV light leads to a substantial decrease in hygroscopicity and cloud activation potential of the dried particles of the same size. The results point towards surface reactions on the liquid aerosols that are more crucial for small particles and the formation of salt structures with water bound within the dried aerosols, termed hydrates. Our findings suggest an increased formation of hydrate forming salts during ageing and the presence of hydrates in dried SSA. Field observations indicate a reduced hygroscopic growth factor of sub-micrometre SSA in the marine atmosphere compared to fresh laboratory generated NaCl or sea salt of the same dry size, which is typically attributed to organic matter or sulphates. Aged inorganic sea salt offers an additional explanation for such a measured reduced hygroscopic growth factor and cloud activation potential.

New Particle Formation and Growth from Dimethyl Sulfide Oxidation by Hydroxyl Radicals.

Dimethyl sulfide (DMS) is produced by plankton in oceans and constitutes the largest natural emission of sulfur to the atmosphere. In this work, we examine new particle formation from the primary pathway of oxidation of gas-phase DMS by OH radicals. We particularly focus on particle growth and mass yield as studied experimentally under dry conditions using the atmospheric simulation chamber AURA. Experimentally, we show that aerosol mass yields from oxidation of 50-200 ppb of DMS are low (2-7%) and that particle growth rates (8.2-24.4 nm/h) are comparable with ambient observations. An HR-ToF-AMS was calibrated using methanesulfonic acid (MSA) to account for fragments distributed across both the organic and sulfate fragmentation table. AMS-derived chemical compositions revealed that MSA was always more dominant than sulfate in the secondary aerosols formed. Modeling using the Aerosol Dynamics, gas- and particle-phase chemistry kinetic multilayer model for laboratory CHAMber studies (ADCHAM) indicates that the Master Chemical Mechanism gas-phase chemistry alone underestimates experimentally observed particle formation and that DMS multiphase and autoxidation chemistry is needed to explain observations. Based on quantum chemical calculations, we conclude that particle formation from DMS oxidation in the ambient atmosphere will most likely be driven by mixed sulfuric acid/MSA clusters clustering with both amines and ammonia.

Emissions of ultrafine particles from five types of candles during steady burn conditions.

Emissions from candles are of concern for indoor air quality. In this work, five different types of pillar candles were burned under steady burn conditions in a new laboratory scale system for repeatable and controlled comparison of candle emissions (temperature ~25°C, relative humidity ~13%, O2 >18%, air exchange rate 1.9 h-1 ). Burn rate, particle number concentrations, mass concentrations, and mode diameters varied between candle types. Based on the results, the burning period was divided in two phases: initial (0-1 h) and stable (1-6 h). Burn rates were in the range 4.4-7.3 and 4.7-7.1 g/h during initial and stable phase, respectively. Relative particle number emissions, mode diameters, and mass concentrations were higher during the initial phase compared to the stable phase for a majority of the candles. We hypothesize that this is due to elevated emissions of wick additives upon ignition of the candle together with a slightly higher burn rate in the initial phase. Experiments at higher relative humidity (~40%) gave similar results with a tendency toward larger particle sizes at the higher relative humidity. Chemical composition with respect to inorganic salts was similar in the emitted particles (dry conditions) compared to the candlewicks, but with variations between different candles.

Reflection on two Ambio papers by P. J. Crutzen on ozone in the upper atmosphere : This article belongs to Ambio's 50th Anniversary Collection. Theme: Ozone Layer.

We here reflect on two important articles on stratospheric ozone depletion written by P. J. Crutzen (1974) and P. J. Crutzen and D. H. Ehhalt (1977) in the early 1970s. These articles provide a clear description of the stratosphere and the most important chemical reactions involved in stratospheric ozone depletion. They present modeling results and provide recommendations for future research on stratospheric ozone depletion caused by chloro-fluoro-carbons, supersonic transport, nitrous oxide, and nuclear explosions. These two articles represent the beginning of a scientific era, which led to discovery of the Antarctic ozone hole and political action in the form of the Montreal Protocol and its amendments.

The reaction of isotope-substituted hydrated iodide I(HO)- with ozone: the reactive influence of the solvent water molecule.

We report an investigation of the reaction of isotope-substituted hydrated iodide I(HO)- with ozone 16O3 to examine the involvement of the water molecules in the oxidation reactions that terminate with the formation of IO3-. Experimentally, we studied the reaction in the gas phase as elementary reactions using a radio-frequency (RF) ion-trap combined with a quadrupole mass spectrometer (QMS). In approximately 1.2% of the reactions of I(HO)- and 16O3, the 18O atom is found to appear in iodine oxide anions, thus giving evidence for a close involvement of the water molecule in a non-negligible number of the reactions towards IO3-. As a part of the experimental investigation, the reaction rate constant for the exchange reaction I(HO)- + HO → I(HO)- + HO at 300 K was found to be (1.3 ± 0.1) × 10-8 cm3 s-1. Quantum chemical calculations are exploited to establish the energetic difference between I(HO)- and I(HO)-.

Reconciling atmospheric water uptake by hydrate forming salts.

Magnesium and calcium chloride salts contribute to the global atmospheric aerosol burden via emission of sea spray and mineral dust. Their influence on aerosol hygroscopicity and cloud forming potential is important but uncertain with ambiguities between results reported in the literature. To address this, we have conducted measurements of the hygroscopic growth and critical supersaturation of dried, size selected nano-particles made from aqueous solution droplets of MgCl2 and CaCl2, respectively, and compare experimentally derived values with results from state-of-the-art thermodynamic modelling. It is characteristic of both MgCl2 and CaCl2 salts that they bind water in the form of hydrates under a range of ambient conditions. We discuss how hydrate formation affects the particles' water uptake and provide an expression for hydrate correction factors needed in calculations of hygroscopic growth factors, critical super-saturations, and derived κ values of particles containing hydrate forming salts. We demonstrate the importance of accounting for hydrate forming salts when predicting hygroscopic properties of sea spray aerosol.

Hydration of Atmospheric Molecular Clusters III: Procedure for Efficient Free Energy Surface Exploration of Large Hydrated Clusters.

Sampling the shallow free energy surface of hydrated atmospheric molecular clusters is a significant challenge. Using computational methods, we present an efficient approach to obtain minimum free energy structures for large hydrated clusters of atmospheric relevance. We study clusters consisting of two to four sulfuric acid (sa) molecules and hydrate them with up to five water (w) molecules. The structures of the "dry" clusters are obtained using the ABCluster program to yield a large pool of low-lying conformer minima with respect to free energy. The conformers (up to ten) lowest in free energy are then hydrated using our recently developed systematic hydrate sampling technique. Using this approach, we identify a total of 1145 unique (sa)2-4(w)1-5 cluster structures. The cluster geometries and thermochemical parameters are calculated at the ωB97X-D/6-31++G(d,p) level of theory, at 298.15 K and 1 atm. The single-point energy of the most stable clusters is calculated using a high-level DLPNO-CCSD(T0)/aug-cc-pVTZ method. Using the thermochemical data, we calculate the equilibrium hydrate distribution of the clusters under atmospheric conditions and find that the larger (sa)3 and (sa)4 clusters are significantly more hydrated than the smaller (sa)2 cluster or the sulfuric acid (sa)1 molecule. These findings indicate that more than five water molecules might be required to fully saturate the sulfuric acid clusters with water under atmospheric conditions. The presented methodology gives modelers a tool to take the effect of water explicitly into account in atmospheric particle formation models based on quantum chemistry.

An RCT of acute health effects in COPD-patients after passive vape exposure from e-cigarettes.

Background: E-cigarette use has been shown to have short-term acute effects among active users but less is known of the acute passive effects, particularly among individuals with existing respiratory diseases. Objective: To investigate local and systemic effects of short-term passive vape exposure among patients with mild or moderate chronic obstructive pulmonary disease (COPD). Methods: In a double-blinded crossover study 16 non-smoking COPD-patients (mean age 68) were randomly exposed for 4 h to passive vape (median PM2.5: 18 µg/m3 (range: 8-333)) and clean air (PM2.5 < 6 µg/m3) separated by 14 days. Particles were measured using an ultrafine particle counter (P-TRAK) and a scanning mobility particle sizer (SMPS). Health effects including Surfactant Protein-A (SP-A) and albumin in exhaled air, spirometry, FeNO, and plasma proteins were evaluated before, right after, and 24 hours after exposure. Participants reported symptoms throughout exposure sessions. Data were analyzed using mixed models. Results: SP-A in exhaled air was negatively affected by exposure to vape and several plasma proteins increased significantly. Throat irritation was more pronounced during passive vape exposure, while FVC and FEV1 decreased, however, not significantly. Conclusions: SP-A in exhaled air and some plasma proteins were affected by passive vape in patients with COPD indicating inflammation, showing that passive vape exposure is potentially harmful.

Reply to the 'Comment on "Atmospheric chemistry of iodine anions: elementary reactions of I-, IO-, and IO with ozone studied in the gas-phase at 300 K using an ion trap"' by D. Britz, Phys. Chem. Chem. Phys., 2019, 21, C9CP03851E.

We reply to the comment by Dieter Britz on two recent papers in Physical Chemistry Chemical Physics. The comment presents a valuable, however, less flexible, alternative to the analysis performed in these papers and as such has no impact on any of the scientific results reported in the two publications.

Sea Spray Aerosol Formation: Laboratory Results on the Role of Air Entrainment, Water Temperature, and Phytoplankton Biomass.

Sea spray aerosol (SSA) emission is a complex process affected by various controlling factors. This work seeks to deconvolute some of this complexity in a controlled laboratory setting using a plunging jet by varying three key parameters, one at a time: (1) air entrainment rate, (2) seawater temperature, and (3) biomass of phytoplankton. The production of SSA is found to vary linearly with air entrainment rate. By normalizing the production flux to air entrainment rate, we observe nonlinear variation of the production efficiency of SSA with seawater temperature with a minimum around 6-10 °C. For comparison, SSA was also generated by detraining air into artificial seawater using a diffuser demonstrating that the production efficiency of SSA generated using a diffuser decreases almost linearly with increasing seawater temperature, and the production efficiency is significantly higher than that for SSA generated using a plunging jet. Finally, by varying the amount of phytoplankton biomass we demonstrate that SSA particle production varies nonlinearly with the amount of biomass in seawater.

Corrigendum: Effect of Aerosolization and Drying on the Viability of Pseudomonas syringae Cells.

[This corrects the article DOI: 10.3389/fmicb.2018.03086.].

The reaction of hydrated iodide I(H2O)- with ozone: a new route to IO2- products.

We report on an experimental characterization of the isolated reaction of hydrated iodide I(H2O)- with ozone O3 at room temperature performed using a radio-frequency ion trap combined with a quadrupole mass spectrometer. Contrary to the oxidation reaction of the bare I- ion, the hydrated iodide I(H2O)- primarily reacts to form I- and IO2- with significant absolute reaction rate constants of 2.0 ± 0.3 × 10-10 cm3 molecule-1 s-1 and 2.5 ± 0.3 × 10-10 cm3 molecule-1 s-1 while direct pathways to IO- and IO3- are much weaker. Quantum chemical calculations indicate that in aqueous phase and for atmospherically relevant temperatures, the presence of hydrated iodides are favored over bare I- ions, thus suggesting that the chemistry of the hydrated ions is relevant for understanding and modeling atmospheric processes at the air-water interface.