Source Of Ultrafine Particles Research Articles

Aerosol particle number concentration, ultrafine particle number fraction, and new particle formation measurements near the international airports in Berlin, Germany – First results from the BEAR study

Studies revealed airports as a prominent source of ultrafine particles (UFP), which can disperse downwind to residential areas, raising health concerns. To expand our understanding of how air traffic-related emissions influence total particle number concentration (PNC) in the airport’s surrounding areas, we conduct long-term assessment of airborne particulate exposure before and after relocation of air traffic from “Otto Lilienthal” Airport (TXL) to Berlin Brandenburg Airport “Willy Brandt” (BER) in Berlin, Germany. Here, we provide insights into the spatial–temporal variability of PNC measured in 16 schools recruited for Berlin-Brandenburg Air Study (BEAR).The results show that the average PNC in Berlin was 7900 ± 7000 cm−3, consistent with other European cities. The highest median PNC was recorded in spring (6700 cm−3) and the lowest in winter (5100 cm−3). PNC showed a bi-modal increase during morning and evening hours at most measurement sites due to road-traffic emissions. A comparison between measurements at the schools and fixed monitoring sites revealed good agreement at distances up to 5 km. A noticeable decline in this agreement occurred as the distance between measurement sites increased. After TXL was closed, PNC in surrounding areas decreased by 30 %. The opposite trend was not seen after BER was re-opened after the COVID-lock-down, as the air traffic has not reached the full capacity yet. The analysis of particle number size distribution data showed that UFP number fraction exhibit seasonal variations, with higher values in spring and autumn. This can be explained by nucleation events, which notably affected PNC.The presented findings will play a pivotal role in forthcoming source attribution and epidemiological investigations, offering a holistic understanding of airports’ impact on airborne pollutant levels and their health implications. The study calls for further investigations of air-traffic-related physical–chemical pollutant properties in areas found further away (> 10 km) from airports.

Cloud response to co-condensation of water and organic vapors over the boreal forest

Abstract. Accounting for the condensation of organic vapors along with water vapor (co-condensation) has been shown in adiabatic cloud parcel model (CPM) simulations to enhance the number of aerosol particles that activate to form cloud droplets. The boreal forest is an important source of biogenic organic vapors, but the role of these vapors in co-condensation has not been systematically investigated. In this work, the environmental conditions under which strong co-condensation-driven cloud droplet number enhancements would be expected over the boreal biome are identified. Recent measurement technology, specifically the Filter Inlet for Gases and AEROsols (FIGAERO) coupled to an iodide-adduct chemical ionization mass spectrometer (I-CIMS), is utilized to construct volatility distributions of the boreal atmospheric organics. Then, a suite of CPM simulations initialized with a comprehensive set of concurrent aerosol observations collected in the boreal forest of Finland during spring 2014 is performed. The degree to which co-condensation impacts droplet formation in the model is shown to be dependent on the initialization of temperature, relative humidity, updraft velocity, aerosol size distribution, organic vapor concentration, and the volatility distribution. The predicted median enhancements in cloud droplet number concentration (CDNC) due to accounting for the co-condensation of water and organics fall on average between 16 % and 22 %. This corresponds to activating particles 10–16 nm smaller in dry diameter that would otherwise remain as interstitial aerosol. The highest CDNC enhancements (ΔCDNC) are predicted in the presence of a nascent ultrafine aerosol mode with a geometric mean diameter of ∼ 40 nm and no clear Hoppel minimum, indicative of pristine environments with a source of ultrafine particles (e.g., via new particle formation processes). Such aerosol size distributions are observed 30 %–40 % of the time in the studied boreal forest environment in spring and fall when new particle formation frequency is the highest. To evaluate the frequencies with which such distributions are experienced by an Earth system model over the whole boreal biome, 5 years of UK Earth System Model (UKESM1) simulations are further used. The frequencies are substantially lower than those observed at the boreal forest measurement site (< 6 % of the time), and the positive values, peaking in spring, are modeled only over Fennoscandia and the western parts of Siberia. Overall, the similarities in the size distributions between observed and modeled (UKESM1) are limited, which would limit the ability of this model, or any model with a similar aerosol representation, to project the climate relevance of co-condensation over the boreal forest. For the critical aerosol size distribution regime, ΔCDNC is shown to be sensitive to the concentrations of semi-volatile and some intermediate-volatility organic compounds (SVOCs and IVOCs), especially when the overall particle surface area is low. The magnitudes of ΔCDNC remain less affected by the more volatile vapors such as formic acid and extremely low- and low-volatility organic compounds (ELVOCs and LVOCs). The reasons for this are that most volatile organic vapors condense inefficiently due to their high volatility below the cloud base, and the concentrations of LVOCs and ELVOCs are too low to gain significant concentrations of soluble mass to reduce the critical supersaturations enough for droplet activation to occur. A reduction in the critical supersaturation caused by organic condensation emerges as the main driver of the modeled ΔCDNC. The results highlight the potential significance of co-condensation in pristine boreal environments close to sources of fresh ultrafine particles. For accurate predictions of co-condensation effects on CDNC, also in larger-scale models, an accurate representation of the aerosol size distribution is critical. Further studies targeted at finding observational evidence and constraints for co-condensation in the field are encouraged.

Formation of secondary organic aerosols from Cl-initiated oxidation of anisole: Rapid release of ultrafine particles and organic chlorides

Recent studies have highlighted the increased occurrence of reactive chlorine, drawing significant attention to the process of chlorinated chemical oxidation of oxygenated aromatics emitted from biomass burning (BB) in the formation of secondary organic aerosols (SOA). This study selected an oxygenated aromatic, anisole, as a representative of BB, and investigated the products and mechanisms of its reaction with Cl•, as well as exploring the implications of precursor-to-oxidant ratio ([anisole/Cl2]0), NOx levels, and seed particles on SOA generation. The gas-phase composition, SOA composition, and particle information were determined using a single-photon ionization time-of-flight mass spectrometry (SPIMS), a thermal desorption unit gas chromatography mass spectrometry (TDU-GC/MS), and a scanning mobility particle sizer (SMPS), respectively. Experimental results indicate that within minutes of turning on the ultraviolet (UV) lights, a large quantity of ultrafine particles (UFPs) (diameter <100 nm) is immediately formed. The SOA yield is significantly dependent on [anisole/Cl2]0, decreasing from 66.2% to 20.0% as the [anisole/Cl2]0 increases. Upon oxidation by Cl•, anisole promptly released organic chlorides, including 2-chlorophenol and 2,4,6-trichlorophenol. The addition of NOx decreased the SOA yield, enhanced the role of OH• in the reaction process, and led to the formation of organic nitrogen products, such as C6H5NO3 and C7H7NO4. Furthermore, Cl• primarily initiates reactions through H-abstraction and Cl-substitution, resulting in the oxidation products largely retaining the benzene ring. This provides a potential explanation for the high SOA yield induced by Cl• in this study. Overall, our work suggests that the release of UFPs and organic chlorides can be found in the Cl-initiated oxidation of anisole, which contributes to high SOA yields. Against the backdrop of increasing wildfire frequency due to global warming, it is necessary to consider the contributions and sources of UFPs and organic chlorides caused by the reaction of wildfire emissions with Cl atoms.

A traffic-induced shift of ultrafine particle sources under COVID-19 soft lockdown in a subtropical urban area

During the unprecedented COVID-19 city lockdown, a unique opportunity arose to dissect the intricate dynamics of urban air quality, focusing on ultrafine particles (UFPs) and volatile organic compounds (VOCs). This study delves into the nuanced interplay between traffic patterns and UFP emissions in a subtropical urban setting during the spring-summer transition of 2021. Leveraging meticulous roadside measurements near a traffic nexus, our investigation unravels the intricate relationship between particle number size distribution (PNSD), VOCs mixing ratios, and detailed vehicle activity metrics. The soft lockdown era, marked by a 20–27% dip in overall traffic yet a surprising surge in early morning motorcycle activity, presented a natural experiment. We observed a consequential shift in the urban aerosol regime: the decrease in primary emissions from traffic substantially amplified the role of aged particles and secondary aerosols. This shift was particularly pronounced under stagnant atmospheric conditions, where reduced dilution exacerbated the influence of alternative emission sources, notably solvent evaporation, and was further accentuated with the resumption of normal traffic flows. A distinct seasonal trend emerged as warmer months approached, with aromatic VOCs such as toluene, ethylbenzene, and xylene not only increasing but also significantly contributing to more frequent particle growth events. These findings spotlight the criticality of targeted strategies at traffic hotspots, especially during periods susceptible to weak atmospheric dilution, to curb UFP and precursor emissions effectively. As we stand at the cusp of widespread vehicle electrification, this study underscores the imperative of a holistic approach to urban air quality management, embracing the complexities of primary emission reductions and the resultant shifts in atmospheric chemistry.

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.

Assessment of the applicability of a model for aviation-related ultrafine particle concentrations for use in epidemiological studies

Background and objectivesIn recent years it has been shown that aircraft emissions are a dominant source of ultrafine particles in the surroundings of airports. However, health effects of long-term (monthly to yearly) exposure to these particles are unknown. As part of an integrated research program into the health risks of ultrafine particles around Schiphol Airport, the applicability of the dispersion model STACKS+ to assess long-term exposure to ultrafine particles from aviation was assessed. MethodologyA detailed comparison between modelled and measured particle number concentrations (PNC) due to aircraft emissions was carried out at ten locations in the surroundings of Schiphol Airport during two six-month periods in 2017 and 2018. In order to deduce the contribution of aviation to measured PNC, we applied a fitting method of the sum of the modelled contributions from aviation, the modelled contributions from traffic on main roads and the contributions from outside the study area estimated from the measurements, to the measured total PNC. The analysis yielded scaling factors and uncertainty estimates for each of the main contributions. We then subtracted the estimated background and modelled contributions of road traffic from the total measured PNC and took the remainder as an approximation of the measured contribution from aviation to PNC. We compared it to the modelled contribution from aviation, based on the averaged values for the six-month periods. ResultsBoth six-month averaged modelled and measured PNC due to aircraft emissions (i.e., adjusted for background) showed a large range at the monitoring locations representative for population exposure (from close to zero to 10 000 particles/cm3). Spearman and Pearson correlation coefficients between model and measurement results were high (>0.83). ConclusionsThe applied approach enabled us to obtain a robust estimate of the contribution of aviation to the measured PNC. The dispersion model is able to determine the spatially varying average concentrations due to aircraft emissions in residential areas over periods of 6 months, allowing for application in epidemiological studies into long-term exposure.

The Role of Sulfur Emission from the Petroleum Industry on Ultrafine Particle Number Concentration in Singapore

Ultrafine particles, defined as particles with a diameter (dp) smaller than 100 nm, serve as an important component of cloud condensation nuclei, in addition to impacting human health. The dominant sources of ultrafine particles include traffic emissions and nucleation. Singapore is a tropical city that hosts petrochemical industries. To identify the sources of ultrafine particles, a year-long observation of the number size distribution was conducted in Singapore in 2018 and 2019. The concentrations of CO, CO2, CH4, and SO2 were also monitored. The particle number concentration during the southwest monsoon season was high, while that during the northeast monsoon period was relatively low. The CO concentration increased during the morning traffic rush hours, which was associated with relatively minor enhancements in ultrafine particle number concentration. The events for a high number concentration of the Aitken mode particles (dp < 50 nm) were identified during high SO2 concentration periods. The SO2 concentration was high during the afternoon because the sea breeze transported the emissions from the coastal industrial area to the observation site. The enhancements in CH4 from its background level (ΔCH4) and SO2 had a quasi-inverse relationship, as the major emission sources of these two chemical species were different. The particle number concentration (dp > 50 nm) correlated with the enhancements in CO concentration (ΔCO) for CH4-dominant air masses, suggesting that incomplete combustion processes, such as traffic emission, are important for the size range. Conversely, the number concentration of the Aitken mode particles (dp < 50 nm) increased for SO2-dominant air masses, suggesting the importance of industrial plume.

Traffic, marine ships and nucleation as the main sources of ultrafine particles in suburban Shanghai, China

The NMF algorithm assigns PNSD to multiple sources at two Shanghai suburban sites. Main sources of UFPs linked to respiratory deposition are traffic nucleation and emissions, marine ship emissions and photochemical nucleation and growth.

Ultrafine Particles in Viennese Gastronomy after Introduction of a National Smoking Ban

Background: Ultrafine particles have a substantial influence on the pathogenesis of diseases from ambient air pollution including personal and indoor tobacco smoke. In public rooms such as gastronomy venues without complete smoking ban, the main source of ultrafine particles is cigarette smoke. Objectives: In accordance with the research question if the legislative smoking ban reduced ultrafine particle pollution in Viennese bars, cafés and pubs, the effectiveness of this ban for the protection of nonsmokers was evaluated. As a further objective, the comparison with the ultrafine particle concentrations in smoking and non-smoking areas before and after the general smoking ban was relevant, whereby the data from the survey period April to October 2019 were used. Hereby, the effectiveness of the measure could be derived from the direct comparison of the earlier and the current recordings. Methods: 2 years after the national Non-Smoking Protection Law in November 2019 had gone into force, the indoor exposures with ultrafine particles were surveyed in 22 Viennese bars/discotheques, 5 cafés and 12 pubs/restaurants and bars. By unannounced and undercover measurements over 20 minutes each, these well frequented gastronomy locations were investigated between October 2021 and February 2022. The concentration of ultrafine particles (PNC, pt/cm³), the corresponding diameter (10 - 300 nm) and lung deposited surface area (LDSA) were recorded via Miniature Diffusion Size Classifier (miniDiSC®) in all three types of locations. Results: The ultrafine particle loadings in 2021/22 in the three location types were not significantly different any more. Two years after the ban the median PNC (pt/cm³) was 19,751 in bars, 18,854 in cafés and 19,357 in pubs. The average diameter (AD, nm) was 54.17 in bars, 44.27 in cafés and 52.08 in pubs. For average LDSA (µm²/cm³), the values were 51.65 in bars, 35.76 in cafés, and 60.71 in pubs. 2019 data had shown significantly higher median values for PNC (pt/cm³) for smoking locations at 72,802 versus non-smoking areas at 27,776 and non-smoking locations at 18,854. Similarly, smoking locations showed significantly higher values for AD (nm) at 78 versus non-smoking areas at 62 and non-smoking locations at 52. For average LDSA (µm²/cm³), smoking locations also had the highest values at 402.0 versus non-smoking areas at 108.0 and non-smoking locations at 51.9. From comparison of data, it was possible to derive the UFP concentrations above which a hospitality indoor area - regardless of its declared status - may be classified as polluted by nanoparticles (tobacco smoke): For PNC, 34,435 pt/ cm³, for average diameter 67.45 nm and for LDSA 163.68 µm²/cm³ are proposed as cut-off values. Conclusion: The national smoking ban significantly improved air quality in Viennese hospitality venues. Two years after the ban ultrafines were comparably low and not significantly different between bars, cafés and pubs, whether they were used before for smoking or not. The decrease of ultrafine particle pollution was attributed to regular non-smoking in localities. Some outliers of the present investigation after the smoking ban indicated, that control of compliance with the law has to be continued.

Real world ultrafine particle emission factors for road-traffic derived from multi-year urban flux measurements using eddy covariance

Mixed fleet particle number emission factors as derived from 3 years of size-resolved particle flux observations show about 2/3 of emission in the nucleation mode &lt;30 nm. Long-term monitoring helps to understand variation in emission factors.

Nucleation of jet engine oil vapours is a large source of aviation-related ultrafine particles

Large airports are a major source of ultrafine particles, which spread across densely populated residential areas, affecting air quality and human health. Jet engine lubrication oils are detectable in aviation-related ultrafine particles, however, their role in particle formation and growth remains unclear. Here we show the volatility and new-particle-formation ability of a common synthetic jet oil, and the quantified oil fraction in ambient ultrafine particles downwind of Frankfurt International Airport, Germany. We find that the oil mass fraction is largest in the smallest particles (10-18 nm) with 21% on average. Combining ambient particle-phase concentration and volatility of the jet oil compounds, we determine a lower-limit saturation ratio larger than 1 × 105 for ultra-low volatility organic compounds. This indicates that the oil is an efficient nucleation agent. Our results demonstrate that jet oil nucleation is an important mechanism that can explain the abundant observations of high number concentrations of non-refractory ultrafine particles near airports.

New particle formation at a peri-urban agricultural site

New Particle Formation (NPF) is a major source of ultrafine particles that affect both air quality and climate. Despite emissions from agricultural activities having a strong potential to lead to NPF, little is known about NPF within agricultural environments. The aim of the present study was to investigate the occurrence of NPF events at an agricultural site, and any potential relationship between agricultural emissions and NPF events. A field campaign was conducted for 3 months at the FR-Gri-ICOS site (France), at an experimental farm 25 km west of Paris city centre.16 NPF events have been identified from the analysis of particle number size distributions; 8 during the daytime, and 8 during the night-time. High solar radiation and ozone mixing ratios were observed during the days NPF occurred, suggesting photochemistry plays a key role in daytime NPF. These events were also associated with higher levels of VOCs such as isoprene, methanol, or toluene compared to non-event days. However, ammonia levels were lower during daytime NPF events, contributing to the hypothesis that daytime NPF events were not related to agricultural activities.On the other hand, temperature and ozone were lower during the nights when NPF events were observed, whereas relative humidity was higher. During these nights, higher concentrations of NO2 and ammonia were observed. As a result, agricultural activities, in particular the spreading of fertiliser on surrounding crops, are suspected to contribute to night-time NPF events.Finally, all the identified NPF events were also observed at SIRTA monitoring station 20 km from the FR-Gri ICOS site, showing that both night-time and daytime NPF events were regional processes. We hypothesise that night-time NPF may be related to fertiliser spreading over a regional scale, as opposed to the local activities at the farm. To our knowledge, this is the first time night-time NPF has been observed in the agricultural context.

The effectiveness of the coagulation sink of 3–10 nm atmospheric particles

Abstract. As a major source of ultrafine particles, new particle formation (NPF) occurs frequently in various environments. However, the survival of new particles and the frequent occurrence of NPF events in polluted environments have long been perplexing, since new particles are expected to be scavenged by high coagulation sinks. Towards solving these problems, we establish an experimental method and directly measure the effectiveness of the size-dependent coagulation sink of monodisperse 3–10 nm particles in well-controlled chamber experiments. Based on the chamber experiments and long-term atmospheric measurements from Beijing, we then discuss the survival of new particles in polluted environments. In the chamber experiments, the measured coagulation sink of 3–10 nm particles increases significantly with a decreasing particle size, whereas it is not sensitive to the compositions of test particles. Comparison between the measured coagulation coefficient with theoretical predictions shows that almost every coagulation leads to the scavenging of one particle, and the coagulation sink exceeds the hard-sphere kinetic limit due to van der Waals attractive force. For urban Beijing, the effectiveness of the coagulation sink and a moderate or high (e.g., &gt; 3 nm h−1) growth rate of new particles can explain the occurrence of measured NPF events; the moderate growth rate further implies that, in addition to gaseous sulfuric acid, other gaseous precursors also contribute to the growth of new particles.

Non-linear models for black carbon exposure modelling using air pollution datasets

Black carbon (BC) is a product of incomplete combustion, present in urban aerosols and sourcing mainly from road traffic. Epidemiological evidence reports positive associations between BC and cardiovascular and respiratory disease. Despite this, BC is currently not regulated by the EU Air Quality Directive, and as a result BC data are not available in urban areas from reference air quality monitoring networks in many countries. To fill this gap, a machine learning approach is proposed to develop a BC proxy using air pollution datasets as an input. The proposed BC proxy is based on two machine learning models, support vector regression (SVR) and random forest (RF), using observations of particle mass and number concentrations (N), gaseous pollutants and meteorological variables as the input. Experimental data were collected from a reference station in Barcelona (Spain) over a 2-year period (2018–2019). Two months of additional data were available from a second urban site in Barcelona, for model validation. BC concentrations estimated by SVR showed a high degree of correlation with the measured BC concentrations (R2 = 0.828) with a relatively low error (RMSE = 0.48 μg/m3). Model performance was dependent on seasonality and time of the day, due to the influence of new particle formation events. When validated at the second station, performance indicators decreased (R2 = 0.633; RMSE = 1.19 μg/m3) due to the lack of N data and PM2.5 and the smaller size of the dataset (2 months). New particle formation events critically impacted model performance, suggesting that its application would be optimal in environments where traffic is the main source of ultrafine particles. Due to its flexibility, it is concluded that the model can act as a BC proxy, even based on EU-regulatory air quality parameters only, to complement experimental measurements for exposure assessment in urban areas.

Evolution of size-segregated aerosol concentration in NW Spain: A two-step classification to identify new particle formation events

Real-time measurements of particles in the 15–736 nm range have been obtained by a Scanning Mobility Particle Sizer to characterize the evolution of particle size distribution and new particle formation (NPF) events in an urban background area. The annual, weekly and diurnal variations of the modal (nucleation (Nnuc), Aitken (NAit) and accumulation (Nacc)) particle concentrations were characterised. The NAit and Nacc registered their maximums in cold months during rush hours, in the morning (0600–0900 UTC) and in the afternoon (1700–2000 UTC), while the maximums for Nnuc were reached in warm months during midday hours. NAit, Nacc and Ntotal showed a significant negative correlation with wind speed and a different relationship with the planetary boundary layer (PBL) height by periods. In the warm period, a positive significant correlation between PBL and Nnuc was registered, indicating that the higher dispersion promoted by a high PBL causes favourable conditions for the occurrence of NPF events (a low polluted atmosphere). NPF processes are one of the main sources of ultrafine particles (<100 nm) in the warm period. After a visual-based classification, 45 NPF events of type Ia (strong and with a good confidence level) were identified and analysed, occurring primarily between 1100 and 1500 UTC, mainly in spring and summer. In addition, a two-step method was developed for identifying NPF events: cluster analysis followed by discriminant analysis. The application of discriminant analysis to one of the clusters, grouping 93 days, enabled us to identify 55 of the 56 NPF events days included in the cluster. This method is a valuable tool for identifying NPF events quickly and effectively.

An indicator for sulfuric acid–amine nucleation in atmospheric environments

New particle formation (NPF) occurs frequently in various atmospheric environments and it is a major source of ultrafine particles. This study proposes an indicator, I, for the occurrence of NPF in the atmosphere based on the mechanism of H2SO4–amine nucleation. It characterizes the synergistic effects of the governing factors for H2SO4–amine nucleation, including H2SO4 concentration, amine concentrations, the stability of H2SO4–amine clusters, and aerosol surface area concentration. Long-term measurements in urban Beijing were used to validate this indicator. Good consistency was found between this indicator and the occurrence of NPF. NPF was usually observed with I > 1 for typical conditions in urban Beijing. The derivation and expressions of I also indicate a good positive association between the H2SO4 dimer concentration and NPF, as also verified by measurements. I was shown to be also applicable in urban Shanghai.Copyright © 2021 American Association for Aerosol Research

Health effects of short-term exposure to ultrafine particles around Amsterdam Schiphol airport

Background: Studies have shown elevated concentrations of ultrafine particles (UFP) near airports. Little is known about the health effects of UFP, particularly from aviation. We evaluated the health effects of short-term exposure to UFP around Schiphol Airport, The Netherlands. Methods: We conducted three studies, with different designs: 1. Observational study with 191 schoolchildren in residential areas near Schiphol, including weekly lung function and exhaled NO measurements at school (161 children) and daily lung function and symptom recording at home (all 191 children). 2. Controlled exposure study with 21 healthy adults, including 2-5 repeated 5-hour exposures in a mobile laboratory directly next to Schiphol, with pre and post measurements of lung function, exhaled NO, electrocardiography and blood pressure. 3. Toxicological study with human bronchial epithelial cells (Calu-3), using UFP collected directly next to Schiphol as well as UFP collected from a turbine engine, and assessment of cell viability, cytotoxicity and inflammatory potential. Results: In children, we found statistically significant associations between exposure to UFP and an increase in daily respiratory symptoms and bronchodilator use. These associations were observed for UFP from aviation as well as UFP from road traffic, based on particle size distribution. In the adults study, exposure to UFP from aviation was associated with a decline in lung function (FVC) and a prolongation of the QTc interval (ECG). UFP from road traffic was associated with an increase in systolic blood pressure. In Calu-3 cells, exposure to UFP resulted in cell damage and release of pro-inflammatory markers, with no significant differences in reactivity between the different sources of UFP. Conclusions: Together these studies show that short-term increased exposure to UFP, as occurs around Schiphol, is associated with acute health effects. We found no indications that effects of UFP from aviation are substantially different from those of UFP from road traffic.

Wintertime new particle formation and its contribution to cloud condensation nuclei in the Northeastern United States

Abstract. Atmospheric particles can act as cloud condensation nuclei (CCN) and modify cloud properties and precipitation and thus indirectly impact the hydrological cycle and climate. New particle formation (NPF or nucleation), frequently observed at locations around the globe, is an important source of ultrafine particles and CCN in the atmosphere. In this study, wintertime NPF over the Northeastern United States (NEUS) is simulated with WRF-Chem coupled with a size-resolved (sectional) advanced particle microphysics (APM) model. Model-simulated variations in particle number concentrations during a 2-month period (November–December 2013) are in agreement with corresponding measurements taken at Pinnacle State Park (PSP), New York, and Appalachian State University (APP), North Carolina. We show that, even during wintertime, regional nucleation occurs and contributes significantly to ultrafine-particle and CCN number concentrations over the NEUS. The model shows that, due to low biogenic emissions during this period, wintertime regional nucleation is solely controlled by inorganic species and the newly developed ternary ion-mediated nucleation scheme is able to capture the variations in observed particle number concentrations (ranging from ∼200 to 20 000 cm−3) at both PSP and APP. Total particle and CCN number concentrations dramatically increase following NPF events and have the highest values over the Ohio Valley region, where elevated [SO2] is sustained by power plants. Secondary particles dominate particle number abundance over the NEUS, and their fraction increases with altitude from ≳85 % near the surface to ≳95 % in the upper troposphere. The secondary fraction of CCN also increases with altitude, from 20 %–50 % in the lower boundary layer to 50 %–60 % in the middle troposphere to 70 %–85 % in the upper troposphere.

Associations between modeled residential outdoor and measured personal exposure to ultrafine particles in four European study areas

Land use regression (LUR) models for Ultrafine Particles (UFP) have been developed to assess health effects of long-term average UFP exposure in epidemiological studies. Associations between LUR modeled residential outdoor and measured long-term personal exposure to UFP have never been evaluated, adding uncertainty in interpretation of epidemiological studies of UFP. Our aim was to assess how predictions of recently developed LUR models for UFP compared to measured average personal UFP exposure in four European areas.Personal UFP exposure was measured in 154 adults from Basel (Switzerland), Amsterdam and Utrecht (the Netherlands), Norwich (United Kingdom), and Turin (Italy). Subjects performed three 24-h exposure measurements by carrying a real-time monitor measuring particles between 10 and 300 nm (MiniDisc). Subjects reported whereabouts and indoor sources of UFP in questionnaires. In Basel and the Netherlands contemporaneously residential outdoor UFP concentrations were monitored. Area-specific LUR models were applied to model residential outdoor UFP concentrations. Associations between modeled and measured UFP concentrations were assessed with linear regression.LUR model predictions were significantly associated with median but not mean personal UFP exposures, likely because of the high impact of indoor peaks on mean personal exposures. Regression slopes (±se) combined for the four areas were 0.12 ± 0.04 for median and −0.06 ± 0.17 for mean personal exposure. The LUR model explained variance of the median personal exposure less than variance of residential outdoor measurements. Associations did not change when personal exposure was calculated for the time spent at home or when presence of indoor sources was incorporated in the regression models. Regression slopes for measured residential outdoor versus personal exposure were smaller for UFP (0.16 ± 0.04) than for simultaneously measured PM2.5 and soot (0.32 ± 0.10 and 0.43 ± 0.06).Our findings provide some support for the use of LUR models to estimate long-term exposure to ambient generated UFP in epidemiological studies.

Traffic-induced multicomponent ultrafine particle microphysics in the WRF v3.6.1 large eddy simulation model: General behaviour from idealised scenarios at the neighbourhood-scale

Traffic is the key source of ultrafine particles (UFPs, particulate matter with a diameter less than 0.1 μm or 100 nm) in most urban areas. The traffic-generated UFPs vented out from an urban street mix with overlying ‘urban background air’ and are diluted whilst also undergoing change due to condensation/evaporation and other aerosol microphysics. Traffic-generated UFPs are comprised of a complex mixture of semi-volatile compounds (SVOCs) with volatility varying over many orders of magnitude, resulting in size-dependent particle composition. This study coupled the multicomponent microphysics (involving condensation/evaporation) of UFPs with the WRF v3.6.1 (Weather Research and Forecasting) large eddy simulation model (i.e. WRF-LES-UFP), and used this modelling system to investigate the general behaviour of UFPs on the neighbourhood scale (10-1000 m; transport times of few minutes) for idealised scenarios. The model captures the horizontal dispersion of UFPs downwind into the neighbourhood scale and vertical mixing with urban background air. Evaporation decreases the mode size of UFPs venting into the urban boundary layer from street-level. The neighbourhood-scale evolution of UFPs is, therefore, a combination of the effects of emissions, mixing with background, and condensation/evaporation. Total UFP number concentration and total mass concentrations scale linearly with the emission rate or the background concentration, demonstrating numerical conservation of the scheme. The linearity is less pronounced for the number concentration of smaller particles (UFP diameter less than 100 nm) with respect to UFP size and concentrations of those organic compounds with a time scale comparable to the dilution time scale (in the order of minutes), reflecting the effects (altering the particle sizes) due to condensation/evaporation.