Increase In Particle Number Concentration Research Articles

Iron oxide nanoparticle synthesis: Simulation-based comparison of laboratory- and pilot plant-scale spray-flame synthesis

This study analyzes burner scale-dependent effects for iron-oxide nanoparticles synthesis in spray flames through a combined experimental and numerical approach. A laboratory- and a pilot plant-scale synthesis facility generate iron oxide nanoparticles from iron nitrate dissolved in ethanol/2-ethylhexanoic acid solvents on the 0.5 and 15 g/h scale, respectively. Phase Doppler measurements supply initial conditions for spray development in the numerical approach, while in situ OH* chemiluminescence and multi-line nitric oxide laser-induced fluorescence (NO-LIF) thermometry provide experimental data for comparison with simulation results of the pilot plant burner. Ex situ particle sizing by gas adsorption according to Brunauer-Emmet-Teller (BET) and transmission electron microscopy (TEM), along with phase composition determination via X-ray diffraction (XRD), are used to compare products of both burners and the corresponding simulations. The numerical approach employs a Reynolds-averaged Eulerian–Lagrangian description of the flow in combination with a flamelet/progress variable (FPV) combustion and monodisperse particle model to reflect spray-flame synthesis. Despite similar chemiluminescence between experiment and simulation, more significant discrepancies are observed in NO-LIF thermometry and particle sizing. Nanoparticle formation and growth at both burner scales is investigated using the numerical method. Special attention is directed to the high-temperature particle residence time (HTPRT). Notably, the average temperature–time profiles particles experience are almost identical in the burners, although their geometric scales and designs differ substantially. Simulation results show that while the primary particle diameter remains mostly consistent, the pilot-scale burner produces larger particle agglomerates than the laboratory burner. The difference is attributed to an increased particle number concentration during the initial formation of soft agglomerates. The findings demonstrate that, despite retaining a similar HTPRT, the overall flow conditions and liquid spray dispersion, which impact the distribution of the particle number concentration, influence the final agglomerate size.

Los Angeles Basin's air quality transformation: A long-term investigation on the impacts of PM regulations on the trends of ultrafine particles and co-pollutants

This study investigates the long-term trends of ambient ultrafine particles (UFPs) and associated airborne pollutants in the Los Angeles Basin from 2007 to 2022, focusing on the indirect effects of regulations on UFP levels. The particle number concentration (PNC) of UFPs was compiled from previous studies in the area, and associated co-pollutant data, including nitrogen oxides (NOx), carbon monoxide (CO), elemental carbon (EC), organic carbon (OC), and ozone (O3), were obtained from the chemical speciation network (CSN) database. Over the study period, a general decrease was noted in the PNC of UFPs, NOx, EC, and OC, except for CO, the concentration trends of which did not exhibit a consistent pattern. UFPs, NOx, EC, and OC were positively correlated, while O3 had a negative correlation, especially with NOx. Our analysis discerned two distinct sub-periods in pollutant trends: 2007–2015 and 2016–2022. For example, there was an overall decrease in the PNC of UFPs at an annual rate of −850.09 particles/cm3/year. This rate was more pronounced during the first sub-period (2007–2015) at −1814.9 particles/cm3/year and then slowed to −227.21 particles/cm3/year in the second sub-period (2016–2023). The first sub-period (2007–2015) significantly influenced pollutant level changes, exhibiting more pronounced and statistically significant changes than the second sub-period (2016–2022). Since 2016, almost all primary pollutants have stabilized, indicating a reduced impact of current regulations, and emphasizing the need for stricter standards. In addition, the study included an analysis of Vehicle Miles Traveled (VMT) trends from 2007 to 2022 within the Los Angeles Basin. Despite the general increase in VMT, current regulations and cleaner technologies seem to have successfully mitigated the potential increase in increase in PNC. Overall, while a decline in UFPs and co-pollutant levels was observed, the apparent stabilization of these levels underscores the need for more stringent regulatory measures and advanced emission standards.

Introducing the novel concept of cumulative concentration roses for studying the transport of ultrafine particles from an airport to adjacent residential areas

Abstract. Airports are often surrounded by urban residential areas, which is both a motivation and challenge for studying their potential impact on local air quality. Airports are a relevant source of ultrafine particles (UFPs), which can pose a risk to human health due to their small size (particle diameter Dp≤100 nm). However, in urban environments, UFPs originate from a multitude of biogenic and anthropogenic sources. Here, we investigate UFPs in close proximity to an airport to disentangle their impact on local air quality from other urban sources. We present observations and analyses of airborne UFP concentrations and size distributions determined at two sites in close proximity to Munich Airport. Therefore, two novel measurement stations were established north and south of the airport but were neither situated on the axis of prevailing wind directions nor impacted by fly overs. This set-up allowed us to explore a mainly advection-driven distribution of UFPs into the most populated adjacent residential areas. The observation period covered a full year from August 2021 to July 2022. We analysed the data set in three steps. (1) First, we derived UFP concentration roses using the wind data as reported at 10 m height at the airport to represent the local wind field. An increase in particle number concentrations and a shift of the modal maximum towards smaller mobility diameters became evident for wind directions, including those approaching from the airport. During the airport's operation hours during the daytime, median particle number concentrations were 2.2- and 1.6-fold compared to nighttime at the northern station and the southern station. However, our data had a high variability, and the direction-based analysis was uncertain due to other potential UFP sources in the surroundings and the assumption of a homogeneous, local wind field. (2) Next, we derived concentration roses employing the airflow observations from the two measuring stations at 5.3 m height. While the annual concentration rose in principle yielded the same conclusions as the first analysis step, a significant seasonal and diurnal variability of UFPs and wind became evident. The influencing factors were likely other urban local UFP sources, an increased surface roughness due to green vegetation, and the atmospheric boundary layer development. (3) In order to assess the possible advection of UFPs from the direction of Munich Airport relative to all other directions over the course of the year, we calculated cumulative concentration roses with both local- and site-scale wind data. Under the assumption of a homogeneous local wind field, the fraction of all UFPs sampled in airflows approaching from the airport's direction was 21 % (N322) and 40 % (S229). Considering a local background, the range of UFP advection from Munich Airport to the adjacent residential areas was up to 10 % in the north and 14 % in the south. It has to be noted that these values highlight the relative magnitude of the maximum impact of the airport on local air quality as they do not distinguish between UFP sources from the airport and other measuring sites. Additionally, they integrate over a time period during which the airport did not reach its full capacity compared to pre-COVID-19 times.

Investigation of RH effect on uncommon limonene ozonolysis products and SOA formation in indoor air with real time measurement techniques

Scientific interest in SOA influence on indoor air quality increases since last 20 years. It is well known, that particles of nano-sized diameter pose a threat for human health causing, among others: eye, upper airway irritation, inflammatory response in cells, worsening asthma, hypertension, diabetes, and central nervous dysfunction. Terpenes are reactive VOCs, commonly emitted in indoor air and considered to be SOA precursors by oxidation reactions. The aim of this study was to investigate the relative humidity influence on i) formation of limonene ozonolysis products and ii) SOA formation process – especially the first steps of it. We managed to determine 4 uncommon limonene ozonolysis products (m/z: 43, 83, 99 and 110) appearing in the PTR-TOF-MS mass spectra with the same frequency as well-known formaldehyde, acetone, acetic acid and formic acid. We also detected m/z 75 and m/z 115 formed under dry conditions and m/z 111 and m/z 125 formed under humid conditions. Detected masses formula is proposed with probability >70 % and the probability is derived from the deviation of the exact mass to the measured one and the isotope distribution. SMPS data analysis allowed us to conclude that RH around 40% increases particle mass concentration, regardless initial limonene concentration. Unfortunately, conclusions about RH influence on particle number concentration are inconsistent. Under low initial terpene concentration, RH around 40% decreases particle number concentration. However, for high initial limonene concentration, RH around 40% caused increase in particle number concentration. Obtained results allowed to conclude, that i) RH influences both particle number and particle mass concentration, ii) initial substrate concentration influences SOA formation altering the RH effect, iii) comparison of results and drawing conclusions is difficult due to different experimental protocols in the literature and due to the number of factors influencing SOA formation initiated by terpene oxidation.

The role of snow in scavenging aerosol particles: A physical-chemical characterization

The below cloud scavenging of aerosols by snow has been analysed in León (NW Spain). Six snow events were registered over the course of one year of study. Ultrafine and accumulation aerosol particles were measured using a scanning mobility particle sizer spectrometer, while hydrometeors were characterized using a disdrometer. Furthermore, the chemical composition of the melted snow-water samples (soluble and insoluble fractions) was analysed.The scavenging coefficient (λ) showed a great variability among events. An effective washing of particles was observed during the first 30 min of snowfall. The mean change in the scavenging efficiency (%ΔC) of particle number concentration (PNC) and λ coefficient during this time interval were: i) nucleation mode: 36.3 % and 3.02 · 10−4 s−1; ii) Aitken mode: 30.4 % and 2.37 · 10−4 s−1 and iii) accumulation mode: 22.4 % and 1.77 · 10−4 s−1. The range of particle sizes that is less efficiently scavenged by snowfall was observed between 400 and 600 nm. When analyzing the whole snow event, an increase of PNC was observed. Two possible explanations underlie this behaviour: it could be caused by changes in air masses or by the resuspension of aerosol particles scavenged by snowflakes upon reaching the ground. A clear relationship was observed between Ca2+, SO42− and NO3− concentrations of aerosol particles before the snow event and the concentrations registered in the melted snow-water.The largest and smallest changes in aerosol number concentrations were caused by snowflakes of 3 and 6 mm in diameter, respectively. The particle size distributions (PSD) were fitted to log-normal distributions and the parameters were compared before and after snowfall.

Analysis of new particle formation events and comparisons to simulations of particle number concentrations based on GEOS-Chem–advanced particle microphysics in Beijing, China

Abstract. Aerosol particles play important roles in air quality and global climate change. In this study, we analyze the measurements of particle size distribution from 12 March to 6 April 2016 in Beijing to characterize new particle formation (NPF) using the observational data of sulfuric acid, meteorological parameters, solar radiation, and the mass concentration of fine particles (PM2.5, particulate matter with diameters less than 2.5 µm). During this 26 d campaign, 11 new particle formation events are identified with obvious bursts of sub-3 nm particle number concentrations and subsequent growth of these nucleated particles. It is found that sulfuric acid concentration in Beijing does not have a significant difference between NPF event and non-event days. Low relative humidity (RH) and high daily total solar radiation appear to be favorable for the occurrence of NPF events, which is quite obvious in this campaign. The simulations using four nucleation schemes, i.e., H2SO4–H2O binary homogeneous nucleation (BHN), H2SO4–H2O–NH3 ternary homogeneous nucleation (THN), H2SO4–H2O–ion binary ion-mediated nucleation (BIMN), and H2SO4–H2O–NH3–ion ternary ion-mediated nucleation (TIMN), based on a global chemistry transport model (GEOS-Chem) coupled with an advanced particle microphysics (APM) model, are conducted to study the particle number concentrations and new particle formation process. Our comparisons between measurements and simulations indicate that the BHN scheme and BIMN scheme significantly underestimate the observed particle number concentrations, and the THN scheme captures the total particle number concentration on most NPF event days well but fails to capture the noticeable increase in particle number concentrations on 18 March and 1 April. The TIMN scheme has obvious improvement in terms of total and sub-3 nm particle number concentrations and nucleation rates. This study provides a basis for further understanding of the nucleation mechanism in Beijing.

Assessing the impact of aircraft arrival on ambient ultrafine particle number concentrations in near-airport communities in Boston, Massachusetts

Aircraft emissions contribute to overall ambient air pollution, including ultrafine particle (UFP) concentrations. However, accurately ascertaining aviation contributions to UFP is challenging due to high spatiotemporal variability along with intermittent aviation emissions. The objective of this study was to evaluate the impact of arrival aircraft on particle number concentration (PNC), a proxy for UFP, across six study sites 3–17 km from a major arrival aircraft flight path into Boston Logan International Airport by utilizing real-time aircraft activity and meteorological data. Ambient PNC at all monitoring sites was similar at the median but had greater variation at the 95th and 99th percentiles with more than two-fold increases in PNC observed at sites closer to the airport. PNC was elevated during the hours with high aircraft activity with sites closest to the airport exhibiting stronger signals when downwind from the airport. Regression models indicated that the number of arrival aircraft per hour was associated with measured PNC at all six sites, with a maximum contribution of 50% of total PNC at a monitor 3 km from the airport during hours with arrival activity on the flight path of interest (26% across all hours). Our findings suggest strong but intermittent contributions from arrival aircraft to ambient PNC in communities near airports.

Evidence for the coupling of refill liquids content and new particle formation in electronic cigarette vapors

The size and chemical content of particles in electronic cigarette vapors (e-vapors) dictate their fate in the human body. Understanding how particles in e-vapors are formed and their size is critical to identifying and mitigating the adverse consequences of vaping. Thermal decomposition and reactions of the refill liquid (e-liquid) components play a key role in new particles formation. Here we report the evolution of particle number concentration in e-vapors over time for variable mixtures of refill e-liquids and operating conditions. Particle with aerodynamic diameter < 300 nm accounted for up to 17% (or 780 μg/m3) of e-vapors particles. Two events of increasing particle number concentration were observed, 2–3 s after puff completion and a second 4–5 s later. The intensity of each event varied by the abundance of propylene glycol, glycerol, and flavorings in e-liquids. Propylene glycol and glycerol were associated with the first event. Flavorings containing aromatic and aliphatic unsaturated functional groups were strongly associated with the second event and to a lesser extent with the first one. The results indicate that particles in e-vapors may be formed through the heteromolecular condensation of propylene glycol, glycerol, and flavorings, including both parent chemicals and/or their thermal decomposition products.

New particle formation in coastal New Zealand with a focus on open-ocean air masses

Abstract. Even though oceans cover the majority of the Earth, most aerosol measurements are from continental sites. We measured aerosol particle number size distribution at Baring Head, in coastal New Zealand, over a total period of 10 months to study aerosol properties and new particle formation, with a special focus on aerosol formation in open-ocean air masses. Particle concentrations were higher in land-influenced air compared to clean marine air in all size classes, from sub-10 nm to cloud condensation nuclei sizes. When classifying the particle number size distributions with traditional methods designed for continental sites, new particle formation was observed at the station throughout the year with an average event frequency of 23 %. While most of these traditional event days had some land influence, we also observed particle growth starting from nucleation mode in 16 % of the data in clean marine air, and at least part of this growth was connected to nucleation in the marine boundary layer. Sub-10 nm particles accounted for 29 % of the total aerosol number concentration of particles larger than 1 nm in marine air during the spring. This shows that nucleation in marine air is frequent enough to influence the total particle concentration. Particle formation in land-influenced air was more intense and had on average higher growth rates than what was found for marine air. Particle formation and primary emissions increased particle number concentrations as a function of time spent over land during the first 1–2 d. After this, nucleation seems to start getting suppressed by the pre-existing particle population, but accumulation mode particle concentration keeps increasing, likely due to primary particle emissions. Further work showed that traditional NPF events were favoured by sunny conditions with low relative humidity and wind speeds. In marine air, formation of sub-10 nm particles was favoured by low temperatures, relative humidity, and wind speeds and could happen even during the night. Our future work will study the mechanisms responsible for particle formation at Baring Head with a focus on different chemical precursor species. This study sheds light on both new particle formation in open-ocean air masses coming from the Southern Ocean and local aerosol properties in New Zealand.

A panel study on the acute respiratory effects of ambient particles of different sizes on children in Shanghai

Objective: To explore the association between size-fractionated particle number concentrations (PNC) and respiratory health in children. Methods: From November 2018 to June 2019, there were 65 children aged 6-9 years from an elementary school in shanghai recruited in this panel study with three rounds of follow-up. The forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), and exhaled nitric oxide (FeNO) levels were measured and buccal mucosa samples of children were collected at each follow-up visit. The level of PNC, temperature and humidity of the elementary school was monitored from 3 days before each physical examination to the end of the physical examination. The linear mixed effects model was used to analyze the association between PNC and indicators of respiratory health in children. Results: Linear mixed effects model analysis revealed that, at lag 2 day, an interquartile range increase in PNC for particles measuring 0.25-0.40 μm was associated with the absolute changes in FVC, FEV1 and abundance-based coverage estimator (ACE) about -60.15 ml (95%CI:-88.97 ml, -31.32 ml), -34.26 ml (95%CI:-63.22 ml, -5.31 ml), -6.00 (95%CI:-9.15, -2.84) and percentage change in FeNO about 12.10% (95%CI: 3.05%, 21.95%), respectively. These adverse health effects increased with the decrease of particle size. Conclusion: The short-term exposure to particulate matter is associated with reduced lung function, buccal microbe diversity and higher airway inflammation level among children. These adverse health effects may increase with the decrease of particle size.

Numerical simulation on the growth of polydisperse fine SiO2 particles by water vapor condensation

The three-stage model was utilized to analyze the law of grown particle size distribution for amplification of polydisperse SiO2 particles in actual water vapor environment. The predicted results demonstrate that the dispersity is narrowed compared with experimental data and the difference between them is large at higher level of supersaturation. Moreover, representative affecting factors on particle growth are discussed. Specifically, the increase of particle number concentration is the significantly negative effect on the particle growth. It leads to the failure of nucleation of small size particles and condensation on large size particles resulting in the several times reduction of arithmetic mean droplet size. Additionally, the improvement of the peak of initial particle size and inlet gas flow temperature on the condition of heating gas flow is not beneficial to particle growth. Besides, the reduction of surface tension of liquid phase can improve the growth strongly at lower level of supersaturation.

Association of Long-Term Air Pollution with Prevalence and Incidence of Distal Sensorimotor Polyneuropathy: KORA F4/FF4 Study.

Background:Air pollution contributes to type 2 diabetes and cardiovascular diseases, but its relevance for other complications of diabetes, in particular distal sensorimotor polyneuropathy (DSPN), is unclear. Recent studies have indicated that DSPN is also increasingly prevalent in obesity.Objectives:We aimed to assess associations of air pollutants with prevalent and incident DSPN in a population-based study of older individuals with high rates of type 2 diabetes and obesity.Methods:Cross-sectional analyses on prevalent DSPN were based on 1,075 individuals 62–81 years of age from the German Cooperative Health Research in the Region of Augsburg (KORA) F4 survey (2006–2008). Analyses on incident DSPN included 424 individuals without DSPN at baseline (KORA F4), of whom 188 had developed DSPN by the KORA FF4 survey (2013–2014). Associations of annual average air pollutant concentrations at participants’ residences with prevalent and incident DSPN were estimated using Poisson regression models with a robust error variance adjusting for multiple confounders.Results:Higher particle number concentrations (PNCs) were associated with higher prevalence [risk ratio (RR) per interquartile range (IQR) (95% CI: 1.01, 1.20)] and incidence [1.11 (95% CI: 0.99, 1.24)] of DSPN. In subgroup analyses, particulate (PNC, , , , and ) and gaseous (, ) pollutants were positively associated with prevalent DSPN in obese participants, whereas corresponding estimates for nonobese participants were close to the null [e.g., for an IQR increase in PNC, (95% CI: 1.05, 1.31) vs. 1.06 (95% CI: 0.95, 1.19); ]. With the exception of , corresponding associations with incident DSPN were positive in obese participants but null or inverse for nonobese participants, with [e.g., for PNC, (95% CI: 1.08, 1.51) vs. 1.03 (95% CI: 0.90, 1.18); ].Discussion:Both particulate and gaseous air pollutants were positively associated with prevalent and incident DSPN in obese individuals. Obesity and air pollution may have synergistic effects on the development of DSPN. https://doi.org/10.1289/EHP7311

Addressing the challenges of E-cigarette safety profiling by assessment of pulmonary toxicological response in bronchial and alveolar mucosa models

Limited toxicity data on electronic cigarette (ECIG) impede evidence-based policy recommendations. We compared two popular mixed fruit flavored ECIG-liquids with and without nicotine aerosolized at 40 W (E-smoke) with respect to particle number concentrations, chemical composition, and response on physiologically relevant human bronchial and alveolar lung mucosa models cultured at air–liquid interface. E-smoke was characterized by significantly increased particle number concentrations with increased wattage (25, 40, and 55 W) and nicotine presence. The chemical composition of E-smoke differed across the two tested flavors in terms of cytotoxic compounds including p-benzoquinone, nicotyrine, and flavoring agents (for example vanillin, ethyl vanillin). Significant differences in the expression of markers for pro-inflammation, oxidative stress, tissue injury/repair, alarm anti-protease, anti-microbial defense, epithelial barrier function, and epigenetic modification were observed between the flavors, nicotine content, and/ or lung models (bronchial or alveolar). Our findings indicate that ECIG toxicity is influenced by combination of multiple factors including flavor, nicotine content, vaping regime, and the region of respiratory tree (bronchial or alveolar). Toxic chemicals and flavoring agents detected in high concentrations in the E-smoke of each flavor warrant independent evaluation for their specific role in imparting toxicity. Therefore, multi-disciplinary approaches are warranted for comprehensive safety profiling of ECIG.

An estimate of the exposure-response relationship between traffic-related ultrafine particles and systolic blood pressure

Exposure to traffic-related air pollution (TRAP) is associated with adverse health outcomes, including hypertension and elevated blood pressure; however, the nature of the exposure-response functions for these associations is not well established. In a previous three-exposure, three-period crossover trial we showed that using portable HEPA filters to reduce indoor infiltration of TRAP was significantly effective in preventing short-term average increases in systolic blood pressure (SBP). We measured particle number concentrations (PNC), black carbon (BC) concentrations, and room temperatures continuously during the trial, and we measured participant blood pressures every 10 minutes. We then examined the relationship between SBP and PNC. A total of 1321 SBPs arising from 76 participants were analyzed. The average age of the participants was 60 years, 79% were female, 77% were Asian, and 17% were White. None had serious health conditions. The average SBP was 120.0 mmHg and the average particle number concentration (PNC) was 13,000 particles/cm3, ranging from 860 to 99,000 particles/cm3. A linear mixed model was used to fit a curvilinear relationship between SBP and PNC. The model included BC concentrations and room temperatures as covariates, as well as a random intercept to account for the interdependence of multiple SBPs recorded from each participant. The resulting adjusted model, yielding statistically significant regression coefficients (p &lt; 0.001), can be written as: SBP = 117.54 + 1.22 (PNC/5000) - 0.059 (PNC/5000)2, which implies that SBP increases by 1.22 mmHg for every 5000 particles/cm3 increase in PNC but tapers off at higher levels of PNC. For example, at 5000 particles/cm3 the average SBP is expected to be 118.7 mmHg, but it increases to 121.0 mmHg at 15,000 particles/cm3 and to 124.5 mmHg at 30,000 particles/cm3. The results of the present study suggest an exposure-response function for SBP and PNC.

Experimental characterization of ultrafine particle emissions from a light-duty diesel engine equipped with a standard DPF

A detailed experimental characterization of the particle emissions of a EURO 5 light-duty Diesel engine, equipped with a wall flow Diesel Particulate Filter (DPF), is presented. Particle Size Distributions (PSDs) in the range from 4.5 up to 160 nm have been measured at the engine exhaust by means of a Scanning Mobility Particle Sizer, during both DPF accumulation and regeneration phase. During accumulation, the size-dependent DPF removal efficiency has been evaluated by PSDs measurements at both inlet and outlet of the filter. The maximum efficiency was found in the range 10-40 nm. Nevertheless, the DPF ensures a strong reduction in the emissions for the sub-23 nm nanoparticles too, with an efficiency between 91–95%. Unless for the warm-up phase, the engine operating conditions do not have a great impact on the particles emitted due to the high DPF removal efficiency. The measurements carried out during the regeneration phase evidenced that particle emissions strongly depend on DPF temperature. Actually, once the soot burnout temperature is reached, soot oxidation starts and a great amount of particles in terms of PN is released. Overall, PSDs showed an increase in particle number concentration up to two order of magnitude with respect to the emissions measured during the accumulation phase.

Disentangling the Microphysical Effects of Fire Particles on Convective Clouds Through A Case Study.

Aerosol emissions from forest fires may impact cloud droplet activation through an increase in particle number concentrations (“the number effect”) and also through a decrease in the hygroscopicity κ of the entire aerosol population (“the hygroscopicity effect”) when fully internal mixing is assumed in models. This study investigated these effects of fire particles on the properties of simulated deep convective clouds (DCCs), using cloud‐resolving simulations with the Weather Research and Forecasting model coupled with Chemistry for a case study in a partly idealized setting. We found that the magnitude of the hygroscopicity effect was in some cases strong enough to entirely offset the number/size effect, in terms of its influence on modeled droplet and ice crystal concentrations. More specifically, in the case studied here, the droplet number concentration was reduced by about 37% or more due solely to the hygroscopicity effect. In the atmosphere, by contrast, fire particles likely have a much weaker impact on the hygroscopicity of the pre‐existing background aerosol, as such a strong impact would occur only if the fire particles mixed immediately and uniformly with the background. We also show that the differences in the number of activated droplets eventually led to differences in the optical thickness of the clouds aloft, though this finding is limited to only a few hours of the initial development stage of the DCCs. These results suggest that accurately and rigorously representing aerosol mixing and κ in models is an important step toward accurately simulating aerosol‐cloud interactions under the influence of fires.

Enhanced New Particle Formation Above the Marine Boundary Layer Over the Yellow Sea: Potential Impacts on Cloud Condensation Nuclei

AbstractAircraft measurements of aerosols were conducted over the Yellow Sea and the East China Sea from February 14 to March 10, 2013, during the Aerosol Radiative Forcing in East Asia 2013 Winter campaign. Ground‐based measurements of aerosols were also conducted on Fukue Island (32.8°N, 128.7°E), located near the boundary of the Yellow Sea and the East China Sea. The aircraft measurements revealed large increases in particle number concentrations in the nucleation mode (2.5–10 nm and up to ~105 cm−3) at altitudes of ~0.5–3 km over the Yellow Sea. This was attributed to enhanced new particle formation (NPF) above the marine boundary layer over the Yellow Sea. The number ratios of Aitken‐mode (10–90 nm) or accumulation‐mode (&gt;90 nm) particles to black carbon particles (tracer for primary emissions) were used to quantify the effects of NPF on particle number concentrations. We estimated that NPF increased median Aitken‐mode particle number concentrations by an order of magnitude at altitudes of ~1–3 km over the Yellow Sea. Synchronized aircraft and ground‐based data suggest that vertical transport of Aitken‐mode particles formed over the Yellow Sea led to a large variability in the particle growth events observed on Fukue Island. A shift of sea surface temperature near Fukue Island and the resultant promotion of vertical mixing are probably the key mechanisms responsible for this complex feature. Evolution of accumulation‐mode particles was observed farther downwind over the East China Sea, suggesting significant impacts of NPF on the regional distributions of cloud condensation nuclei.

Particle and Carbon Dioxide Concentration Levels in a Surgical Room Conditioned with a Window/Wall Air-conditioning System.

One of the most important functions of air conditioning systems in operating rooms is to protect occupants against pathogenic agents transported by air. This protection is done by simultaneously controlling the air distribution, temperature, humidity, filtration and infiltration from other areas etc. Due to their low price, simple installation, operation and maintenance, window/wall air conditioning system have largely been used in operating rooms in Brazil, even if these types of equipment only recirculate the air inside the room without appropriate filtration and renovation with outdoor air. In this context, this work aims to analyse the performance of the window/wall air conditioning systems on indoor air ventilation in operating rooms by measuring particle number concentrations and carbon dioxide concentrations during different surgical procedures, in a single surgical room and in the nearby areas (corridor) for two cases: single surgery and two subsequent surgeries. In addition, the efficiency of the analysed air conditioning system was evaluated by comparing the ventilation level calculated in the surgical room with the ventilation required in order to maintain the carbon dioxide concentration within acceptable levels. The results showed that this type of air conditioning system is not appropriate for use in operating rooms since it cannot provide an adequate level of ventilation. The CO2 concentrations during surgeries, in fact, significantly exceeded acceptable values and a simultaneous increase in particle number concentration was observed. The results also showed that there is a high risk of contamination between subsequent surgeries in the same surgical room, due to residues of contaminants transported by the particles emitted during the surgeries that were not removed from the operating room by the air conditioning system. The particle number concentration measured in the second surgery, in fact, was approximately six times higher than in the first surgery.

Occupational exposure to LTA Nanozeolites: strategies of exposure monitoring and toxicity evaluation

Nanozeolites (NZs) are increasingly used in several sectors, but very few data are available on their toxicity. Therefore in this study we aimed to apply a standardized strategy to assess the occupational exposure integrated to an in vitro model useful to evaluate potential toxic effects in the case study of LTA-NZs.Particle number concentration (PNC) values greater than the background significant level were highlighted during the production process phase of LTA NZs. The increase of PNC in the typical size range of produced NZs (around 100nm) and the presence of airborne NZs and their agglomerates in the workplace were confirmed by both real-time (CPC and FMPS) and off-line (ICP-MS and SEM-EDX) data analysis.We also investigated the potential cyto-genotoxicity of NZs produced in the factory, on human alveolar cells (A549) exposed to 10-100μg/mL. We evaluated cell viability/apoptosis by cytofluorimetric assay, membrane damage by LDH release and DNA damage by Fpg-comet assay. We found a slight increase of apoptotic cell % at 50 and 100μg/mL. We found slight, statistically significant, direct DNA damage and slight oxidative DNA damage.These findings represent the first data integrating exposure characterization and potential genotoxicity of NZs and highlight the need to perform further studies to confirm such results.

Associations between size-fractionated particle number concentrations and COPD mortality in Shanghai, China

BackgroundFew studies have investigated respiratory effects of particulate matter air pollution using a full range of particle size distribution. ObjectivesTo explore the short-term associations between size-fractionated particle number concentration (PNC) and chronic obstructive pulmonary disease (COPD) mortality. MethodsWe conducted a time-series study to explore the associations between size-fractionated PNC and daily COPD mortality in the Pudong New Area of Shanghai, China, from 2014 to 2016. We evaluated particle size distribution from 0.01 μm to 10 μm, which was segregated into 7 ranges to better explore the size-dependent associations. We used over-dispersed generalized additive models to estimate the associations after controlling for time trends, temperature, humidity, day of the week and holidays. ResultsA total of 5430 deaths due to COPD were identified during the study period. For size ranges from 2.5 – 10 μm, 1–2.5 μm to 0.3–1 μm, there were stronger associations between PNC and COPD mortality, but the associations were statistically insignificant. However, for the smaller size ranges from 0.3 to 0.01 μm, the associations became statistically significant and the magnitude of association remained stable. An interquartile range increase in PNC at lag 0–1 day for size ranges 0.01–0.03 μm, 0.03–0.05 μm, 0.05–0.1 μm and 0.1–0.3 μm was associated with increments of 4.44% (95% CI: 1.16%, 7.73%), 4.31% (95% CI: 1.16%, 7.47%), 4.22% (95% CI: 1.05%, 7.40%), and 4.28% (95% CI: 0.48%, 8.09%) in COPD mortality, respectively. ConclusionThis study suggested that particles below 0.3 μm in diameter might be mainly responsible for the adverse effect of particulate air pollution on CDPD mortality in Shanghai, China.