Average Particle Number Concentrations Research Articles

Concentrations and origins of ultrafine particles at a major European harbor.

The maritime transport sector poses significant air quality concerns, particularly in nearby cities. Ultrafine particles (UFP, diameter<100nm) are of particular concern due to their potential health impacts. This study measured particle number concentrations (PNC), size distributions (PNSD), and other pollutants including particulate matter (PM), nitrogen oxides (NOX), black carbon (BC), sulfur dioxide (SO2) and ozone (O3), organic markers and trace elements at a major European harbor and an urban background (UB) location. The average PNC at the harbor was 1.8-fold higher than at the UB, with particularly marked differences in the Aitken mode (2.4-fold higher). NOx levels were 10.5-fold higher at the harbor, and NO2, NOX and BC concentrations were 2.0 to 2.9 times greater compared to the UB site. SO2 concentrations were also 1.7-fold higher at the harbor. Two distinct types of PNC peaks were observed: daytime peaks with high Aitken mode particles likely linked to transit ship emissions, and late afternoon/nighttime peaks with higher nucleation mode particles likely linked to thermal power plant emissions, docked cruise ships, and vehicular traffic related to ferry boarding. Source apportionment of PNC-PNSD through Positive Matrix Factorization (PMF) identified four key contributors to PNC at the harbor: Regional recirculation (9%, modes: 100nm and 35nm), Nucleation (30%, mode: 18nm), Coastal background (22%, mode: 75nm), and Ship transit (33%, mode, 35nm). Concentrations of Ti, V, Cr, Ni, Cu, Zn, As, Sb, Pb and Na in the quasi-UFP range were more than twice at the harbor compared to the UB. This study provides insights into UFP concentrations and their sources within a major touristic and commercial harbor, highlighting the complexity of identifying specific contributions from various UFP emission sources in large harbors.

Influence of local meteorology and gaseous pollutant emissions on atmospheric nanoparticle concentrations in a pedestrian way in urban region

The roadside environment is one of the major sources of nanoparticle emission in the urban regions. The complex mixture of different pollutants makes it hard to understand the dynamics and behavior of nanoparticles. The study aims to analyze the dynamics of atmospheric nanoparticles ranging from 10 to 1000 nm along with local meteorological conditions and gaseous pollutants in a pedestrian way at a busy street in Delhi, a megalopolis in India, during all five major seasons of the study area. Nucleation mode particles were higher during the spring season, whereas the contribution of Aitken mode particles dominated the total particle number concentrations in the rest of the seasons. Due to the influence of vehicular sources, rush hour concentrations were higher than during non-rush hours. Thus, the diurnal pattern in particle concentration strongly coincided with emissions associated with the vehicular flow. During the winter season, the average total particle number concentration was observed to be maximum (4.1 × 104 cm−3) with a higher surface area of particles of 3.5 × 10−3 mm2 m−3. Compared to the monsoon season, the concentration of NOX was 5 times higher in winter. The boundary layer height in the study region ranged from 600 to 2400 m during different seasons, and the maximum ventilation coefficient was observed to be > 3000 m2s-1 during summer. Precipitation reduced the concentration of particles by half, from 2.2 x 104 to 1.1 x 104 cm−3, due to wet scavenging. The study revealed that the concentrations of particles depend not only on primary emissions but also are influenced by local meteorology and other co-emitted pollutants. Understanding the dynamics of atmospheric nanoparticles in urban roadside environments as outlined in this study is crucial to devise necessary mitigation measures for people residing near the road in order to reduce health impact and improve air quality.

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.

Comparison of aerosol number size distribution and new particle formation in summer at alpine and urban regions in the Guanzhong Plain, Northwest China

Ultrafine particles play a crucial role in understanding climate change, mitigating adverse health effects, and developing strategies for air pollution control. However, the factors influencing the occurrence and development of new particle formation (NPF) events, as well as the underlying chemical mechanisms, remain inadequately explained. This study compared number concentrations and size distributions of atmospheric ultrafine particles at Xi'an (urban area) and the summit of Mt. Hua (alpine region) in summer to investigate the NPF mechanism and particle growth in both clean and polluted areas of the Guanzhong Plain. The average particle number concentration in Xi'an was significantly higher than that at Mt. Hua. The diurnal variation of total particle number concentration differed between Xi'an and Mt. Hua indicating a divergence in influencing factors. The size distributions in Xi'an varied across different timescales and weather conditions, whereas Mt. Hua exhibited little variation. This stability at Mt. Hua is attributed to its cleaner background atmosphere and the steady influx of aging particles with larger diameters transported from the free atmosphere. In both areas, geometric mean diameters (GMDs) were inversely proportional to particle number concentrations suggesting that increase in particle numbers were primarily due to the generation of smaller particles. The potential governing factors for NPF events differed somewhat between the urban and mountainous stations. In the urban area, intense local stationary and mobile emission sources promoted the growth of newly formed nanoparticles, with ozone-oxidized condensable vapors serving as key precursors. In contrast, at the mountainous station, NPF process were significantly influenced by anthropogenic precursors from long-range transport and locally emitted biogenic organics. The rapid increase in ultrafine particle concentrations primarily poses serious health risks and degrades air quality in urban areas, while also contributing to climate-related effects in alpine regions.

Airborne particulate matter and diesel engine exhaust on infrastructure construction sites in the Copenhagen metropolitan area.

Diesel engine exhaust (DEE) is carcinogenic and potentially hazardous for those working in close proximity to diesel-powered machines. This study characterizes workplace exposure to DEE and its associated particulate matter (PM) during outdoor construction activities. We sampled at 4 construction sites in the Copenhagen metropolitan area. We used portable constant-flow pumps and quartz-fiber filters to quantify personal exposure to elemental carbon (EC), and used real-time instruments to collect activity-based information about particle number and size distribution, as well as black carbon (BC) concentration. Full-shift measurements of EC concentration ranged from < 0.3 to 6.4 µg/m3. Geometric mean (GM) EC exposure was highest for ground workers (3.4 µg/m3 EC; geometric standard deviation, GSD = 1.3), followed by drilling rig operators (2.6 µg/m3 EC; GSD = 1.4). Exposure for non-drilling-rig machine operators (1.2 µg/m3 EC; GSD = 2.9) did not differ significantly from background (0.9 µg/m3 EC; GSD = 1.7). The maximum 15-min moving average concentration of BC was 17 µg/m3, and the highest recorded peak concentration was 44 µg/m3. In numbers, the particle size distributions were dominated by ultrafine particles ascribed to DEE and occasional welding activities at the sites. The average total particle number concentrations (PNCs) measured in near-field and far-field positions across all worksites were 10,600 (GSD = 3.0) and 6,000 (GSD = 2.8)/cm3, respectively. Sites with active drilling rigs saw significantly higher average total PNCs at their near-field stations (13,600, 32,000, and 9,700/cm3; GSD = 2.4, 3.4, and 2.4) than sites without (4,700/cm3; GSD = 1.6). Overall, the DEE exposures at these outdoor construction sites were below current occupational exposure limits for EC (10 µg/m3 in Denmark; 50 µg/m3 in the European Union), but extended durations of exposure to the observed DEE levels may still be a health risk.

Characterizing the Macro and Micro Properties of Precipitation during the Landfall of Typhoon Lekima by Using GPM Observations

Understanding the macro and micro characteristics of precipitation in landfall typhoons is crucial to predicting the path and intensity of tropical cyclones by using numerical models. In this study, we use observations from the Global Precipitation Measurement Mission to analyze the microphysics of convection and stratiform precipitation during the landfall of Typhoon Lekima. The statistical results show that the correlation coefficient of the reflectivity factors of the spaceborne and ground-based radars is 0.77 and that the water content detected by the 18.7 GHz low-frequency vertical channel is positively correlated with the intense-precipitation rate. The storm top height is generally consistent with the location of heavy precipitation. The average near-surface precipitation rate and liquid water content of convective precipitation are higher than those of stratiform precipitation. The average mass-weighted raindrop diameter and particle number concentration of convective (stratiform) precipitation at a distance of 2 km above ground level are 1.52 mm (1.29 mm) and 39.52 (36.44, in decibel scale), respectively. Below the melting layer, there is a significant increase in average particle diameter, indicating that the collision aggregation growth process of raindrops is dominant. These results are potentially helpful in validating and improving microphysics parameterization in numerical models.

The relative contributions of traffic and non-traffic sources in ultrafine particle formations in Tehran mega city

Emissions of ultrafine particles (UFPs; diameter < 100 nm) are strongly associated with traffic-related emissions and are a growing global concern in urban environments. The aim of this study was to investigate the variations of particle number concentration (PNC) with a diameter > 10 nm at nine stations and understand the major sources of UFPs (primary vs. secondary) in Tehran megacity. The study was carried out in Tehran in 2020. NOx and PNC were reported from a total of nine urban site locations in Tehran and BC concentrations were examined at two monitoring stations. Data from all stations showed diurnal changes with peak morning and evening rush hours. The hourly PNC was correlated with NOx. PNCs in Tehran were higher compared to those of many cities reported in the literature. The highest concentrations were at District 19 station (traffic) and the lowest was at Punak station (residential) such that the average PNC varied from 8.4 × 103 to 5.7 × 104 cm−3. In Ray and Sharif stations, the average contributions of primary and secondary sources of PNC were 67 and 33%, respectively. Overall, we conclude that a decrease in primary emission leads to a decrease in the total concentration of aerosols, despite an increase in the formation of new particles by photo nucleation.

Harnessing AI to unmask Copenhagen's invisible air pollutants: A study on three ultrafine particle metrics

Ultrafine particles (UFPs) are airborne particles with a diameter of less than 100 nm. They are emitted from various sources, such as traffic, combustion, and industrial processes, and can have adverse effects on human health. Long-term mean ambient average particle size (APS) in the UFP range varies over space within cities, with locations near UFP sources having typically smaller APS. Spatial models for lung deposited surface area (LDSA) within urban areas are limited and currently there is no model for APS in any European city. We collected particle number concentration (PNC), LDSA, and APS data over one-year monitoring campaign from May 2021 to May 2022 across 27 locations and estimated annual mean in Copenhagen, Denmark, and obtained additionally annual mean PNC data from 6 state-owned continuous monitors. We developed 94 predictor variables, and machine learning models (random forest and bagged tree) were developed for PNC, LDSA, and APS. The annual mean PNC, LDSA, and APS were, respectively, 5523 pt/cm3, 12.0 μm2/cm3, and 46.1 nm. The final R2 values by random forest (RF) model were 0.93 for PNC, 0.88 for LDSA, and 0.85 for APS. The 10-fold, repeated 10-times cross-validation R2 values were 0.65, 0.67, and 0.60 for PNC, LDSA, and APS, respectively. The root mean square error for final RF models were 296 pt/cm3, 0.48 μm2/cm3, and 1.60 nm for PNC, LDSA, and APS, respectively. Traffic-related variables, such as length of major roads within buffers 100–150 m and distance to streets with various speed limits were amongst the highly-ranked predictors for our models. Overall, our ML models achieved high R2 values and low errors, providing insights into UFP exposure in a European city where average PNC is quite low. These hyperlocal predictions can be used to study health effects of UFPs in the Danish Capital.

Spatial variability and health assessment of particle number concentration at different exposure locations near urban traffic arterial: A case study in Xi'an, China

Urban traffic arteries are considered as hot-spots of pollution of particle number concentration (PNC), but the knowledge of spatial variability and exposure levels of PNC with different particle sizes emitted by vehicles is yet less reported. In this paper, PNC in the size range from 6 to 10,000 nm were measured using the Electrical Low-Pressure Impactor Plus (ELPI+) at four sites near high-density traffic in Xi'an, including one traffic, one roadside, and two urban background. The results showed that PNC was highest at the distance closest to the traffic sources, and decreased exponentially with distance. Vehicle exhaust was the primary source of ambient ultrafine particle (UFP), contributing 60.03% and 54.48% of the number concentration of UFP in the clean and haze weathers, respectively. The average PNCs measured at the traffic site were 2.24 and 3.17 times greater than those at the roadside and urban background sites, respectively. Coarse mode particle concentrations exhibited a higher level at the roadside site due to the secondary dust generated by vehicles. An interesting phenomenon that an inverted U-shaped relationship between measured UFP levels and traffic flows was found when the flow was higher than 6000 veh h−1. Strong spatial inhomogeneity for UFP along the urban road, whereas particles larger than 100 nm in diameter tend to similar concentration distributions. The mean respiratory deposition dose (RDD) at four locations was (7.14 ± 1.12) × 105 particles h−1, with the highest (14.61 ± 2.29) × 1010 particles h−1 at the traffic site. Retired people had a higher exposure of UFP compared to children and adults. This improved understanding of the impact of vehicle emissions on the distribution of PNC near-road.

108 Workplace Exposure to Ultrafine Particles, Dust, and Chemicals During Plastic Production with Recycled Plastics

Abstract The plastics industry is a major contributor to the world economy, and in 2019 alone, there were some 480 million metric tons of plastic produced worldwide. Although a great deal of attention has been given to measuring and understanding the extent of plastic in the environment and its associated human exposure, much less is known about the human exposure to plastics during its production. The aim of this study is to characterize in detail the particulate matter (PM) emitted from various processes involved in the manufacturing and recycling of plastics. Here we report our findings from an initial campaign carried out at a Danish plastics factory. Online instruments were used to determine the particle number and mass concentrations for particles in the range of 10nm to 10µm, over the course of five hours, at both near- and far-field positions with respect to activities associated with the processing of plastics, including extruding, thermoforming, mixing, crushing, and rolling. For fine particles (&amp;lt;300nm), the average total particle number concentrations associated with these activities were 3.3x104, 4.0x103, 2.8x104, 3.5x104, and 6.9x104 #/cm3, respectively. Respirable dust concentrations were 13, 7, 9, 7 (calculated), and 12 µg/m3, respectively, and total dust concentrations were similar or slightly higher. These data suggest that the principal contributions to human exposure in the facility are fine and ultrafine particles. In addition to the real-time data and mass concentrations, samples are also analyzed for elemental composition and plastics. This research was supported by FFIKA, a grant from the Danish government.

Critical aspects in occupational exposure assessment with different aerosol metrics in an industrial spray coating process

Engineered Nanomaterials (ENMs) have several uses in various industrial fields and are embedded in a myriad of consumer products. However, there is continued concern over the potential adverse health effects and environmental impacts of ENMs due to their unique physico-chemical characteristics. Currently, there are no specific international regulations for various ENMs. There are also no Occupational Exposure Limits (OEL) regulated by the European Union (EU) for nanomaterials in the form of nano-objects, their aggregates or agglomerates (NOAA). For ENMs the question of which metric to be used (i.e., mass, surface area, number concentrations) to determine the exposure is still not resolved. The aim of this work is to assess the worker exposure by inhalation in an industrial spray coating process by using all three metrics mentioned above. Two target ENMs (N-doped TiO2, TiO2N and AgNPs capped with a quaternized hydroxyethyl-cellulose, AgHEC) generated for industrial-scale spraying processes were considered. Results showed that the averaged particle number concentration (10–100 nm) was below 2.7 104 cm−3 for both materials. The Lung Deposited Surface Area (LDSA) was in the range between 73 and 98 μm2cm−3 and the particle mass concentration (obtained by means of ICP-EOS off-line analysis) resulted below 70 μg m−3 and 0.4 μg m−3 for TiO2 and Ag, respectively. Although, the airborne particles concentration compared well with the NIOSH Recommended Exposure Level (REL) limits the contribution to the background, according to EN 17058 (Annex E) was significant (particularly in the particle number and PM1 mass concentrations). We successfully evaluated the worker exposure by means of the different airborne particles' metrics (number, surface and mass concentrations). We concluded that worker exposure assessment involving ENMs is a complex procedure with requires both real time and off-line measurements and a deep investigation of the background.

Impact of the closure of Berlin-Tegel Airport on ultrafine particle number concentrations on the airfield

Airports contribute substantially to ultrafine particle (UFP; &amp;lt;100 nm) concentrations on a local scale. These UFPs, which derive mainly from combustion processes, are generated during take-off and landing of aircraft, during aircraft movements on the tarmac, when engines and turbines are started, and by vehicles transporting goods and people on the airfield. UFPs are considered particularly harmful to human health as their small size enables them to pass far into the human body. This study investigates the extent to which particle number concentrations (PNCs) sized 7–2,000 nm respond to the cessation of air traffic due to the closure of a major airport. PNCs and wind data were monitored with a 5 s resolution at one location on the airfield of Berlin-Tegel Airport (TXL). The station was located 600 –640 m east of the runways and thus downwind of the runways for the predominant wind direction. Observations took place 24 h per day every day for about 3 weeks before and 3 weeks after the closure of the airport. During the measurement campaign, a total of 2,507 take-offs and landings took place. Including all wind directions, this study shows 30 %–40% lower PNCs on average, 2.5-fold lower maximum values as well as a 3-fold lower PNC spread after the closure of the airport. These differences are evident only during the day with active flight operations, and not during the nighttime flight ban. Downwind of the airfield, differences are even higher. After the closure of the airport, average PNCs drop by 70%, maxima by 85%, and variability is reduced by almost 90%. 70% lower and 30% less frequent PNC peaks occur downwind of the airport after flight operations are discontinued. This unique natural experiment allows for relatively clear conclusions about the relevance of airport operations on PNCs in the airfield area. The measurements carried out before and after the closure allow a direct comparison of the PNCs during airport operations and without any. Thus, our study reveals the change in UFP concentration that can be achieved through a reduction in flight operations.

Utility of outdoor central site monitoring in assessing exposure of school children to ultrafine particles

Epidemiological studies investigating the association between daily particle exposure and health effects are frequently based on a single monitoring site located in an urban background. Using a central site in epidemiological time-series studies has been established based on the premises of low spatial variability of particles within the areas of interest and hence the adequacy of the central sites to monitor the exposure. This is true to a large extent in relation to larger particles (PM2.5, PM10) that are typically monitored and regulated. However, the distribution of ultrafine particles (UFP), which in cities predominantly originate from traffic, is heterogeneous. With increasing pressure to improve the epidemiology of UFP, an important question to ask is, whether central site monitoring is representative of community exposure to this size fraction of particulate matter; addressing this question is the aim of this paper. To achieve this aim, we measured personal exposure to UFP, expressed as particle number concentration (PNC), using Philips Aerasense Nanotracers (NT) carried by the participants of the study, and condensation particle counters (CPC) or scanning mobility particle sizers (SMPS) at central fixed-site monitoring stations. The measurements were conducted at three locations in Brisbane (Australia), Cassino (Italy) and Accra (Ghana). We then used paired t-tests to compare the average personal and average fixed-site PNC measured over the same 24-h, and hourly, periods. We found that, at all three locations, the 24-h average fixed-site PNC was no different to the personal PNC, when averaged over the study period and all the participants. However, the corresponding hourly averages were significantly different at certain times of the day. These were generally times spent commuting and during cooking and eating at home. Our analysis of the data obtained in Brisbane, showed that maximum personal exposure occurred in the home microenvironment during morning breakfast and evening dinner time. The main source of PNC for personal exposure was from the home-microenvironment. We conclude that the 24-h average PNC from the central-site can be used to estimate the 24-h average personal exposure for a community. However, the hourly average PNC from the central site cannot consistently be used to estimate hourly average personal exposure, mainly because they are affected by very different sources.

Environmental risk factors of incident distal sensorimotor polyneuropathy: Results from the prospective population-based KORA F4/FF4 study

Distal sensorimotor polyneuropathy (DSPN) is a common condition in older populations with high prevalence of obesity and type 2 diabetes. We hypothesised that the risk of DSPN is increased by multiple ubiquitous environmental risk factors, particularly in people with obesity. This study was based on 423 individuals aged 62–81 years without DSPN who participated in the population-based Cooperative Health Research in the Region of Augsburg (KORA) F4 survey (2006–2008) in Southern Germany. During 6.5 years of follow-up, 188 participants developed clinical DSPN as assessed by the Michigan Neuropathy Screening Instrument. Environmental exposures, including air temperature, surrounding greenness (assessed with the normalized difference vegetation index [NDVI]), long-term road traffic noise and air pollution, were assessed at participants' residences. The cumulative risk index (CRI) evaluated the joint effects of co-occurring exposures on DSPN risk based on effect estimates from multi-exposure Poisson regression models. The models were adjusted for age, sex, height, waist circumference, smoking, alcohol consumption, physical activity, education and neighbourhood socioeconomic status. In the entire cohort, the co-occurrence of an interquartile range (IQR) decrease in temperature of the warm season and NDVI in a 100-m buffer and of an IQR increase in night-time average traffic noise and in annual average particle number concentration (PNC) was positively associated with incident DSPN (CRI [95 % CI] 1.39 [1.02, 1.91]). Effect estimates for exposure combinations were generally higher in individuals with obesity (CRI 1.34–2.01) than in those without obesity (CRI 0.90–1.33). The four-exposure model showed a twofold increased risk of DSPN among obese (CRI [95 % CI] 2.01 [1.10, 3.67]), but not among non-obese individuals (CRI [95 % CI] 1.18 [0.83, 1.67]). Thus, ubiquitous environmental exposures jointly augment the risk of DSPN in the older population. Lower air temperature in the warm season, less greenness, and higher noise levels and ultrafine particle concentrations identified people with obesity as a particularly vulnerable subgroup.

Size Distribution and Source Appointment of Road Particles During Winter in Tianjin

The significant role of traffic emissions mixed from various sources in urban air pollution has been widely recognized. However, the corresponding contributions to the roadside particle distribution are poorly understood due to the mixed impacts of various sources. Particle number concentrations of different sizes at the roadside in Nankai District of Tianjin were continuously monitored using a portable aerosol particle spectrometer during the morning rush hour (07:30-09:20) from Nov. 9, 2018 to Jan. 6, 2019. Characteristic and influencing factors of particle size distributions were discussed combined with temperature and relative humidity data, while potential sources of particles at the roadside were identified based on size distribution analysis. The results showed that the average total particle number concentrations were 502 cm-3, and the concentrations of the accumulation mode and coarse mode were 500 cm-3 and 2 cm-3, respectively. The distribution of number concentrations at the roadside was unimodal and primarily concentrated at 0.25-0.50 μm, with peak sizes at 0.28-0.30 μm. The same distribution trend of particle number concentration and difference in the concentration in the same segment size were observed at different periods. Vehicle activity level was the main influencing factor of road particulate matter concentration on different weekdays; the probability of the high value of road particulate matter concentration was reduced by a reasonable combination of the vehicle tail numbers. Temperature and relative humidity were both found to be positively correlated with the number concentration of particles. With the increase in temperature and relative humidity, the total and peak particle number concentration showed an overall upward trend. In addition, the peak particle size increased from 0.28-0.30 μm to 0.35-0.40 μm when relative humidity was higher than 80%. Three sources, including road dust, brake and tire wear, and the aging particles from vehicle exhaust, were identified using positive matrix factorization in this study. Road dust contributed 8.6% of the total number concentration, which mainly consisted of particles with sizes above 5.00 μm. Brake and tire wear contributed 2.8% of the total number concentration of particles with a size range of 0.80-4.00 μm. The aging particles from vehicle exhaust contributed the most (88.5%), with a peak at 0.25-0.65 μm. The sources of roadside particles were mainly related to vehicle activity, whereas temperature and relative humidity also affected the particle number size distribution.

Ultrafine particle number concentration and its size distribution during Diwali festival in megacity Delhi, India: Are 'green crackers' safe?

Since the air pollution and noise generated from fireworks are related to air quality and human health, the regulatory bodies had implemented the eco-friendly "Green Crackers" in megacity Delhi, India, to celebrate Diwali 2019 with the permission of a specific time slot (8:00 p.m. to 10:00 p.m.). The present study was conducted on a residential educational institute campus to evaluate the particle number size distribution (PNSD) of green cracker emissions. During the Diwali event period, the high peak of particle number concentration (PNC) reached 1.7×105 # cm-3 with a geometric mean diameter (GMD) of ∼44nm. The average PNC increment on Diwali day was 138% and 97% compared to pre (October 26, 2019) and post (October 28, 2019) Diwali period, respectively, including 468%, 142%, 65%, 75% on pre-Diwali and 485%, 110%, 32%, 26% on post- Diwali 2019 period in terms of Nucleation mode (10nm<Dp<20nm), Small Aitken mode (20nm<Dp<50nm), Large Aitken mode (50nm<Dp<100nm), and Accumulation mode (100nm<Dp<1000nm), respectively. Unlike traditional firework emissions, green crackers had a high UFP/Ntotal ratio of 0.72, including Nucleation mode-0.35, Aitken mode-0.30, and Accumulation mode 0.35, distinguishing it from other pre-and post-Diwali particle number size distribution-dN/dlogDp curves. These observations indicate that green crackers emit more particles with smaller diameters than traditional crackers. Recommendations for using green crackers for Diwali celebrations may be an option if lower size-diameter particle emission could be controlled by changing the material composition of the green crackers. More research studies need to be conducted to assess atmospheric emissions of green crackers and their health impacts to evaluate whether they are better or worse than traditional crackers.

Contribution of traffic-originated nanoparticle emissions to regional and local aerosol levels

Abstract. Sub-50 nm particles originating from traffic emissions pose risks to human health due to their high lung deposition efficiency and potentially harmful chemical composition. We present a modeling study using an updated European Aerosol Cloud Climate and Air Quality Interactions (EUCAARI) number emission inventory, incorporating a more realistic, empirically justified particle size distribution (PSD) for sub-50 nm particles from road traffic as compared with the previous version. We present experimental PSDs and CO2 concentrations, measured in a highly trafficked street canyon in Helsinki, Finland, as an emission factor particle size distribution (EFPSD), which was then used in updating the EUCAARI inventory. We applied the updated inventory in a simulation using the regional chemical transport model PMCAMx-UF over Europe for May 2008. This was done to test the effect of updated emissions at regional and local scales, particularly in comparison with atmospheric new particle formation (NPF). Updating the inventory increased the simulated average total particle number concentrations by only 1 %, although the total particle number emissions were increased to a 3-fold level. The concentrations increased up to 11 % when only 1.3–3 nm sized particles (nanocluster aerosol, NCA) were considered. These values indicate that the effect of updating overall is insignificant at a regional scale during this photochemically active period. During this period, the fraction of the total particle number originating from atmospheric NPF processes was 91 %; thus, these simulations give a lower limit for the contribution of traffic to the aerosol levels. Nevertheless, the situation is different when examining the effect of the update closer spatially or temporally or when focusing on the chemical composition or the origin of the particles. For example, the daily average NCA concentrations increased by a factor of several hundred or thousand in some locations on certain days. Overall, the most significant effects – reaching several orders of magnitude – from updating the inventory are observed when examining specific particle sizes (especially 7–20 nm), particle components, and specific urban areas. While the model still has a tendency to predict more sub-50 nm particles compared to the observations, the most notable underestimations in the concentrations of sub-10 nm particles are now overcome. Additionally, the simulated distributions now agree better with the data observed at locations with high traffic densities. The findings of this study highlight the need to consider emissions, PSDs, and composition of sub-50 nm particles from road traffic in studies focusing on urban air quality. Updating this emission source brings the simulated aerosol levels, particularly in urban locations, closer to observations, which highlights its importance for calculations of human exposure to nanoparticles.

Influence of Regional Pollution Outflow on Particle Number Concentration and Particle Size in Airshed of Guangzhou, South China

A measurement campaign of particle number concentration and size distribution was conducted at urban (SYSU) and suburban (Panyu) areas of Guangzhou, South China, during 16 January to 3 February 2020 before and during the Chinese New Year (CNY) holiday. Average particle number concentration (PNC) was 6.3 × 103 cm-3 and 9.7 × 103 cm-3, respectively, at urban and suburban sites, indicating the severe particulate matter (PM) pollution. The PNC in the region was influenced by monsoon and the land–sea breeze systems. During monsoon seasons, PM pollution occurred at a regional scale affecting the urban and suburban areas as indicated by the high PNC correlation (r value = 0.70), but the PNCs were lower than that during land-sea breeze period (with lower PNCM1/PNCLSB1 and PNCM2/PNCLSB2 ratios) due to the higher atmospheric dispersion. There is a strong local emission (mainly vehicular emissions) in both urban and suburban areas which was significantly lowered during the CNY period due to reduced human activities. The PM pollution was found to be significantly influenced by local emissions (dominated by Aitken mode particles) and new particle formation (NPF) process (dominated by nucleation mode particles). NPF event was found to be associated with a higher N10-25/H2SO4 proxy ratio during the low wind speed condition.

CE Coupled to ICP-MS and Single Particle ICP-MS for Nanoparticle Analysis.

Capillary electrophoresis (CE) can be used for the separation of nanoparticles (NPs). Coupling of CE to inductively coupled plasma mass spectrometry (ICP-MS) or single particle (sp)-ICP-MS enhances the analytical performance and capabilities of the method compared to CE with a standard detector (ultraviolet visible spectroscopy), in particular for trace analysis of metals or metal-containing compounds. spICP-MS is a method for NP analysis, where a standard ICP-MS setup is used with fast time-resolved detection in order to obtain information on individual NPs. Here we describe a method for the separation and detection of silver and gold NPs using CE-ICP-MS and CE-spICP-MS with reversed electrode polarity stacking mode (REPSM) for online preconcentration. CE-spICP-MS allows obtaining the average size, size distribution, elemental composition, and particle number concentration (PNC) of NPs in addition to a CE separation profile in a single run. Moreover, CE-spICP-MS can be used in some cases to separate NPs with different coatings.

Formation of cluster mode particles (1–3 nm) in preschools

This study is the first study that reports the cluster particle (1–3 nm) formation (CPF) in two modern preschools located in Nur-Sultan city of Kazakhstan from October 28 to November 27, 2019. The average particle number concentration and mode diameter values during major CPF events in Preschool I and Preschool II were found to be 1.90 × 106 (SD 6.43 × 106) particles/cm3 and 1.60 (SD 0.85) nm, and 1.11 × 109 (SD 5.46 × 109) particles/cm3 and 2.16 (SD 1.47) nm, respectively. The ultraviolet PM concentration reached as high as 7 μg/m3 in one of the measurement days. The estimated emission rate in Preschool I for CPF events was 9.57 × 109 (SD 1.92 × 109) particles/min. For Preschool II, the emission rate was 7.25 × 109 (SD 12.4 × 109) particles/min. We identified primary cluster particles (CPs) emitted directly from the sources such as candle burning, and secondary CPs formed as a result of the oxidation of indoor VOCs or smoking VOCs. The secondary CPs are likely to be SOA. Indoor VOCs were mainly emitted during cleaning activities as well as during painting and gluing. Indoor VOCs are the controlling factors in the CPF events. Changes in the training and cleaning programs may result in significant reductions in the exposure of the children to CPs.