Fine Particle Number Concentrations Research Articles

Distribution Characteristics of the Number and Mass Concentrations of Respiratory Fine Particles in the Areas Around Coal-fired Power Plants

Distribution Characteristics of the Number and Mass Concentrations of Respiratory Fine Particles in the Areas Around Coal-fired Power Plants

Impact of urban tree arrangement on pedestrian exposure to the size-fractional particulate matter in a city boulevard

Trees act as natural filters that mitigate roadside air pollution. However, the filtration impact of different tree arrangements on traffic pollutants with different particle diameters has rarely been analysed in real street canyon environments. To quantify how roadside tree arrangements impact pedestrian exposure to particle number concentrations (PNCs) of different diameters (0.25–32 μm), in situ field measurements were carried out in a boulevard-type street canyon in the city of Xi'an, China. This study analysed the experimental data of PNCs collected along segments of a pedestrian lane under four typical tree arrangements: open space without trees, a sparse-spaced tree arrangement, a medium-spaced tree arrangement, and a dense-spaced tree arrangement in a street canyon. Our results reveal that the effect of tree arrangement on PNCs depended on the particle diameter. In general, trees can significantly reduce coarse PNC (particles with diameters >2.5 μm) but not the fine PNC. Quantitative analysis showed that a medium-spaced tree arrangement, in which tree crowns are adjacent to each other but do not overlap, is the most capable of reducing PNC, followed by a sparse-spaced tree arrangement, while a the dense-spaced tree arrangement has the least impact. The attenuation effect of trees on the PNCs increased with increasing particle diameter. Moreover, the presence of trees altered the local microclimate, which also affected how exposure to PNCs changed. Our empirical findings further highlight the complexity of how trees affect particulate pollutants in street canyons and provide timely insights for enhancing tree-planning management in cities from the perspective of air quality improvement.

An Experimental Study on the Fine Particle Emissions of Brake Pads According to Different Conditions Assuming Vehicle Deceleration with Pin-on-Disc Friction Test

Fine particles from vehicles occur in a range of particulate matter (PM) sizes and influence the roadside atmosphere. The contribution of fine dust from automobiles to road pollution has reportedly been extremely high. Researchers have estimated that non-exhaust fine dust originating from brakes, tires, clutches, and road surface wear rate is increasing. Several studies have shown that brake pads account for a significant proportion of non-exhaust emissions. In this study, a friction test using vehicle brake pads was carried out with a friction tester to reveal the harmfulness of brake pad particles by the driver’s driving habits. Conditions were made considering the pressure, vehicle speed, and temperature and assuming the amount of deceleration of the vehicle. Particle collection devices were used to analyze the concentration of number and the mass distribution of particles produced in the experiment, with a range from 6 nm to 7.3 μm to gauge the toxicity of particles. The results showed that the number concentration of fine particles tended to increase linearly with changes in vehicle deceleration (braking energy) in the particle diameter region around 0.75–7.3 μm. The number concentration of fine particles tended to increase exponentially in the particle diameter region around 71–120 nm. The rapid occurrence of ultrafine particles in nanometers varied depending on the test conditions.

Source apportionment of fine and ultrafine particle number concentrations in a major city of the Eastern Mediterranean

Ultrafine particles (UFP) are recognized as an emerging pollutant able to induce serious health effects. However, quantitative information regarding the contributions of UFP sources is generally limited. This study evaluates statistical (k-means clustering) and receptor models (Positive Matrix Factorization - PMF) using particle number size distributions (PNSD), along with chemical speciation data, measured at an urban background supersite in Athens, Greece, aiming to characterize their sources. PNSD measurements (10–487 nm) were performed during three distinct periods (warm, cold, and lockdown cold). Traffic and residential biomass burning (BB) produced high UFP number concentrations (NUFP) in the cold period (+107 % compared to summer), while the lockdown restrictions reduced NUFP (−42 %). The five groups produced by cluster analysis that were common among periods were linked to high- and low-traffic, new particle formation (NPF), urban background and regional aerosols. PMF source apportionment identified 5 and 6 factors during warm and cold periods, respectively, indicating that traffic particles dominated NUFP (64–78 % in all periods), while accumulation-mode particles and volume concentrations were controlled by processed aerosol, and especially in the cold periods by BB emissions. A nucleation factor linked to NPF contributed 7–11 % to NUFP. Comparing the two cold periods (business-as-usual, lockdown), important lockdown reductions (−46 %) were seen for fresh traffic contributions to total number concentration (Ntotal). The impact of the source attributed to NPF also eroded (−41 % for Ntotal). Due to the large reduction (−47 % for Ntotal) observed also for the BB source during the lockdown (reduced wood usage due to a milder winter), the relative contributions of all sources did not change considerably (fractional reductions <7 % for Ntotal). The quantitative results, bolstered by source apportionment combining PNSD and online chemical composition measurements, indicate the potential to constrain UFP levels by regulating traffic and residential emissions, with a large upside for population exposure control.

Spatial variability of fine particle number concentration in an urban area: The effect of aspect ratio and vehicular traffic

The condensation particle number counting (CPC) technique was used to measure the number concentration of fine particles (FPs) from 20 to 1000 nm in several monitoring campaigns inside an urban area, with the aim of studying the spatial variability inside the urban area at pedestrian level and its correlation with aspect ratio H/W (height of buildings/street width) and local traffic. The effect of aspect ratio on the FP concentrations was studied in the range of 0 ≤ H/W ≤ 4.04. To study the effect of local traffic on FP concentrations, measurements were carried out in adjacent and with similar geometrics (building height, street width, and aspect ratio) pedestrian and traffic-streets. Vertical profiles were also studied measuring FP concentration in a deep street canyon at heights from 1 to 12 m. The study shows a significant impact of local traffic on FP concentrations (traffic streets 2.7 times higher than pedestrian streets). With the increase of the value of the aspect ratio, FP concentrations exceed European averages. Additionally, It was observed a clear decrease in FP concentrations with height in deep street canyons. These results emphasize the importance of aspect ratio and local traffic when assessing the impact of FPs pollution.

Indoor Exposure and Regional Inhaled Deposited Dose Rate during Smoking and Incense Stick Burning-The Jordanian Case as an Example for Eastern Mediterranean Conditions.

Tobacco smoking and incense burning are commonly used in Jordanian microenvironments. While smoking in Jordan is prohibited inside closed spaces, incense burning remains uncontrolled. In this study, particle size distributions (diameter 0.01-25 µm) were measured and inhaled deposited dose rates were calculated during typical smoking and incense stick-burning scenarios inside a closed room, and the exposure was summarized in terms of number and mass concentrations of submicron (PNSub) and fine particles (PM2.5). During cigarette smoking and incense stick-burning scenarios, the particle number concentrations exceeded 3 × 105 cm-3. They exceeded 5 × 105 cm-3 during shisha smoking. The emission rates were 1.9 × 1010, 6.8 × 1010, and 1.7 × 1010 particles/s, respectively, for incense, cigarettes, and shisha. That corresponded to about 7, 80, and 120 µg/s, respectively. Males received higher dose rates than females, with about 75% and 55% in the pulmonary/alveolar during walking and standing, respectively. The total dose rates were in the order of 1012-1013 #/h (103-104 µg/h), respectively, for PNSub and PM2.5. The above reported concentrations, emissions rates, and dose rates are considered seriously high, recalling the fact that aerosols emitted during such scenarios consist of a vast range of toxicant compounds.

The role of volatile organic compounds in the oxidation-driven fragmentation of soot particles

In this work, the role of volatile organic compounds (VOCs) in soot oxidation and fragmentation was investigated in a lean, premixed CH4 flame. An aerosol generator was used to homogeneously disperse soot with and without VOCs (termed Soot-W and Soot-WO, respectively) into the flame. Because minimal soot was formed in the flame itself, information on the fragmentation of the Soot-W and Soot-WO during the oxidation process was readily captured to determine the role of VOCs in soot fragmentation. The integrated number concentration of fine mode particles and the degree of particle aggregation show that the presence of VOCs suppresses soot aggregate fragmentation, primarily by the mitigating consumption of the neck sites between primary particles due to the decreased specific surface area. The actual oxygen diffusion route and effective pore width between the crystallite structures were determined using the image analysis technique. To determine the characteristic regime of oxygen diffusion, the distribution of effective pore width was studied using high-resolution transmission electron microscopy and image analysis. The estimated effectiveness factor indicates that the presence of VOCs lowers the propensity of internal burning via intra-particle oxygen diffusion, and reduces the extent of primary particle fragmentation, as evidenced by a relatively smaller peak of ultrafine particles. The analysis of the nanostructure of neck sites vs. the bulk discovers significantly more disordered and thus reactive structure at neck sites, explaining the prevalence of aggregate fragmentation over primary particle fragmentation. The finding of the role of VOCs in oxidation-driven fragmentation is beneficial to the optimization of existing models for predicting the number concentration of fine and ultrafine particles. Furthermore, a better understanding of this role may aid in the control of the most harmful fine and ultrafine particle emissions.

Experimental study on the treatment of desulfurization wastewater from coal-fired power plant by spray evaporation.

In this study, a pilot-scale evaporation tower system was built to treat the desulfurization wastewater by spray evaporation. The distribution characteristics of Cl- in the wastewater evaporation process were investigated. Besides, the morphology and physicochemical property of solid evaporation products from desulfurization wastewater were analyzed. In addition, the emission characteristics of fine particulates were evaluated. The results indicated that the increase of salt content in desulfurization wastewater increased the mass concentrations of Cl- in three phases, but the proportions of it remained almost unchanged, which were about 10%, 55%, and 35% in the gas phase, outlet solid phase, and bottom solid phase respectively. The increase of flue gas temperature can improve the content of Cl- in the gas phase, while the increase of wastewater pH inhibited the formation of gaseous HCl. The solid evaporation products from desulfurization wastewater had a prismatic crystal structure, which mainly included the sulfate and chloride salts, and the main elements including O, Na, Mg, S, Cl, K, and Ca. Besides, the peak values of particle size distribution in the bottom solid phase and outlet solid phase were 7.67 and 0.32μm, respectively. For the particulate matters in flue gas, the spray evaporation of desulfurization wastewater can reduce the particle concentration, promote particle agglomeration, reduce the number concentration of fine particles, and improve the removal effect of PM10. When the inlet particle concentration was 7.62g/m3, it can reduce the particle concentration at the tower outlet to 4.59g/m3 and reduce the number and mass concentrations of PM10 after ESP by about 43.8% and 36.8%.

Long-term trends of ultrafine and fine particle number concentrations in New York State: Apportioning between emissions and dispersion

In the past several decades, a variety of efforts have been made in the United States to improve air quality, and ambient particulate matter (PM) concentrations have been used as a metric to evaluate the efficacy of environmental policies. However, ambient PM concentrations result from a combination of source emission rates and meteorological conditions, which also change over time. Dispersion normalization was recently developed to reduce the influence of atmospheric dispersion and proved an effective approach that enhanced diel/seasonal patterns and thus provides improved source apportionment results for speciated PM mass and particle number concentration (PNC) measurements. In this work, dispersion normalization was incorporated in long-term trend analysis of 11–500 nm PNCs derived from particle number size distributions (PNSDs) measured in Rochester, NY from 2005 to 2019. Before dispersion normalization, a consistent reduction was observed across the measured size range during 2005–2012, while after 2012, the decreasing trends slowed down for accumulation mode PNCs (100–500 nm) and reversed for ultrafine particles (UFPs, 11–100 nm). Through dispersion normalization, we showed that these changes were driven by both emission rates and dispersion. Thus, it is important for future studies to assess the effects of the changing meteorological conditions when evaluating policy effectiveness on controlling PM concentrations. Before and after dispersion normalization, an evident increase in nucleation mode particles was observed during 2015–2019. This increase was possibly enabled by a cleaner atmosphere and will pose new challenges for future source apportionment and accountability studies.

Experimental and numerical analysis of fine particle and soot formation in a modern 100 MW pulverized biomass heating plant

The formation of soot, organic, and inorganic aerosols has a profound effect on the environmental and technological feasibility of biomass combustion. In this work, the soot and aerosol processes are examined for a modern pulverized wood-burning 100 MWth district heating plant. Experimental data was collected from two locations inside the furnace (30% and 100% thermal loads), including measurements for fine particle (PM1) number size distribution, number concentration, and chemical composition. The experiments were complemented with Computational Fluid Dynamics (CFD) simulations and Plug-Flow Reactor (PFR) modeling. The measurements and modeling are combined in a comprehensive analysis, providing fundamental understanding on the aerosol processes inside the furnace. The wood-powder combustion is efficient under both thermal loads, indicated by the low unburned carbon content in fly-ash, and the low CO, NO and soot emissions (<0.3 mg/Nm3). The fine particles consist mainly of K2SO4, and of lesser amounts of alkali salts (NaCl, KCl), and Ca and Mg compounds (oxides or sulfates). A large concentration of KOH/K2CO3 vapor may exist in the flue gas and play a significant role in the heat exchanger fouling. The applied modeling tools are shown to provide accurate estimations for the composition and formation regions of fine particles inside the industrial biomass furnaces.

Влияние относительной влажности воздуха на счетную концентрацию аэрозольных частиц в герметичном объеме

Investigates the effect of the increase in relative humidity on the change in the number concentration of fine particles suspended in the air in a closed sealed volume. This work was carried out within the scope of a series of works of the SIRIUS international project. The project is aimed at studying the dynamics of aerosol accumulation in the air environment of a sealed inhabited object using methods for assessing the level of aerosol contamination used in cleanroom technology. A qualitative result of the relationship between the number concentration of the airborne particles and the relative humidity inside the sealed volume in the absence of other sources of particle generation was obtained. This result correlates with the experimental data obtained during the SIRIUS four-month isolation experiment and lays the foundation for preparing for new isolation experiments of the SIRIUS project.

Reducing the nanoparticles generated at the wheel\u2013rail contact by applying tap water lubricant at subway train operational velocities

The formation characteristics and the reduction of nanoparticles emitted from wheel–rail contacts at subway-train velocities of 73, 90, and 113 km/h under dry and water-lubricated conditions (using tap water) were studied using a twin-disk rig. The resulting number concentration (NC) of ultrafine and fine particles increased with train velocity under both conditions. Particle generation varied with slip rate under both conditions in both the particle categories. Furthermore, the formation characteristics at 113 km/h under dry conditions showed a notable deviation from those under water-lubricated conditions in three aspects: (i) The maximum NC of ultrafine particles was higher than that of fine particles, (ii) the predominant peak diameter was in the ultrafine particles category, and (iii) the proportion of ultrafine particles was much higher than those of the fine particles. Applying water decreased the NC of ultrafine and fine particles significantly at all tested velocities (by 54–69% and 87–91%, respectively). Adding water increased the NC of particles ≤ 35 nm in diameter, possibly owing to the increase in water vapor and mineral crystals from tap water. Overall, this study provides a reference for researchers aiming to minimize nanoparticle formation at the wheel–rail contacts by applying a lubricant.

Air quality monitoring using mobile low-cost sensors mounted on trash-trucks: Methods development and lessons learned

Air quality monitoring (AQM) is crucial for cities to develop management plans supporting population health. However, there is a dearth of measurements due to the high cost of standard reference instruments. Mobile AQM using low-cost sensors deployed on routine fleets of vehicles can enable the continuous detection of fine-scale pollutant variations in cities at a lower cost. New methods need to be developed to interpret these measurements. This paper presents three such methods. First, we propose a technique to identify aerosol hotspots. Second, we employ techniques published previously to assess the generalizable map of fine and coarse particle number concentrations, to understand qualitatively the contribution of local and regional sources across the region sampled. By using the raw number concentration of differently sized particles from the Optical Particle Counters (OPCs) instead of the noisier mass concentrations, we obtain more robust results. Third, in order to evaluate source signatures in cities, we propose another technique, in which we cluster the entire range of aerosol size-distribution measurements acquired. The properties of each cluster provide insight into the aerosol source characteristics in the sampling environment. We test these methods using a dataset we collected by mounting OPCs on two trash-trucks in Cambridge, Massachusetts.

Promoting the removal of fine particles and zero discharge of desulfurization wastewater by spray-turbulent agglomeration

The treatment of fine particles and desulfurization wastewater from coal-fired power plants is an important issue in the field of energy and environment. To promote the removal of fine particles and zero discharge of desulfurization wastewater, a novel treatment technology with the coupling of spray evaporation and turbulent agglomeration was proposed, and the effect of desulfurization wastewater spray on fine particles agglomeration and removal were investigated by experiment. The results showed that the spray-turbulent agglomeration system can effectively promote the agglomeration and removal of fine particles through capillary force and adhesion effect of crystals precipitated from the desulfurization wastewater droplets. After that the fine particles agglomeration efficiency was improved to 39.3%, which was 10.9% higher than single turbulent agglomeration, and the number and mass concentrations of fine particles after ESP reduced about 46.5% and 38.9%, respectively. In addition, the effect of turbulent agglomeration system on the evaporation of desulfurization wastewater was studied by simulation using CFD models, the motion trajectory, evaporation time and motion distance of spray droplets with different sizes were calculated. It indicated that turbulence can increase the relative velocity between droplets and flue gas, thus improving the heat and mass transfer rates of spray droplets in the evaporation process, so as to promote the evaporation of large-size droplets and shorten their motion distance required for complete evaporation. The average motion distance of spray droplets was shortened by 383 and 543 mm respectively at the diameter size of 110 and 120 μm.

Kitchen concentrations of fine particulate matter and particle number concentration in households using biomass cookstoves in rural Honduras

Cooking and heating with solid fuels results in high levels of household air pollutants, including particulate matter (PM); however, limited data exist for size fractions smaller than PM2.5 (diameter less than 2.5 μm). We collected 24-h time-resolved measurements of PM2.5 (n = 27) and particle number concentrations (PNC, average diameter 10–700 nm) (n = 44; 24 with paired PM2.5 and PNC) in homes with wood-burning traditional and Justa (i.e., with an engineered combustion chamber and chimney) cookstoves in rural Honduras.The median 24-h PM2.5 concentration (n = 27) was 79 μg/m3 (interquartile range [IQR]: 44–174 μg/m3); traditional (n = 15): 130 μg/m3 (IQR: 48–250 μg/m3); Justa (n = 12): 66 μg/m3 (IQR: 44–97 μg/m3). The median 24-h PNC (n = 44) was 8.5 × 104 particles (pt)/cm3 (IQR: 3.8 × 104–1.8 × 105 pt/cm3); traditional (n = 27): 1.3 × 105 pt/cm3 (IQR: 3.3 × 104–2.0 × 105 pt/cm3); Justa (n = 17): 6.3 × 104 pt/cm3 (IQR: 4.0 × 104–1.2 × 105 pt/cm3). The 24-h average PM2.5 and particle number concentrations were correlated for the full sample of cookstoves (n = 24, Spearman ρ: 0.83); correlations between PM2.5 and PNC were higher in traditional stove kitchens (n = 12, ρ: 0.93) than in Justa stove kitchens (n = 12, ρ: 0.67). The 24-h average concentrations of PM2.5 and PNC were also correlated with the maximum average concentrations during shorter-term averaging windows of one-, five-, 15-, and 60-min, respectively (Spearman ρ: PM2.5 [0.65, 0.85, 0.82, 0.71], PNC [0.74, 0.86, 0.88, 0.86]).Given the moderate correlations observed between 24-h PM2.5 and PNC and between 24-h and the shorter-term averaging windows within size fractions, investigators may need to consider cost-effectiveness and information gained by measuring both size fractions for the study objective. Further evaluations of other stove and fuel combinations are needed.

Commuter Exposure to Black Carbon, Fine Particulate Matter and Particle Number Concentration in Ferry and at the Pier in Istanbul

This paper presents measurements and analyses of the concentrations of black carbon (BC), particle number concentration (PNC), and PM2.5 (≤2.5 μm) while commuting by ferries in Istanbul. In this context, exposures to the mentioned pollutants were estimated for car ferry, fast ferry, and at the piers, and for two travel routes, for a total of 89 trips. BC, PNC, and PM2.5 measurements were simultaneously performed in a ferry and at the piers, and the correlation between pollutant concentrations, meteorological parameters, and environmental factors were analyzed. The mean concentrations for all pollutants in car ferry were lower than the average concentrations in fast ferry. The concentration ratios of fast ferry to car ferry for BC, PNC, and PM2.5 were 6.4, 1.2, and 1.3, respectively. High variability in the concentrations was observed at the piers and in ferry during berthing. The highest mean concentrations (±standard deviation) of BC (14.3 ± 10.1 µg m−3) and PNC (42,005 ± 30,899 pt cm−3) were measured at Yalova pier. The highest mean concentration (±standard deviation) of PM2.5 (26.1 ± 11.5) was measured at Bostancı pier. It was observed that the main external sources of BC, PNC, and PM2.5 at the piers were road transport, residential heating, and shipping activity. There were no significant correlations between BC, PNC, and PM2.5 in fast ferry, while BC was positively correlated with PNC (r = 0.61, p &lt; 0.01) and PM2.5 (r = 0.76, p &lt; 0.01) in car ferry. At the piers, significant relations between pollutants and meteorological variables were observed. It was noticed that there was no significant difference between summer and winter in ferry and at the pier concentrations of BC, PNC, and PM2.5 except for Yenikapı pier and Bakırköy pier. The highest total exposure to PNC and PM2.5 was in car ferry mode, while the highest total exposure to BC was in fast ferry mode.

Respiratory tract deposition of inhaled roadside ultrafine refractory particles in a polluted megacity of South-East Asia

Recent studies demonstrate that Black Carbon (BC) pollution in economically developing megacities remain higher than the values, which the World Health Organization considers to be safe. Despite the scientific evidence of the degrees of BC exposure, there is still a lack of understanding on how the severe levels of BC pollution affect human health in these regions. We consider information on the respiratory tract deposition dose (DD) of BC to be essential in understanding the link between personal exposure to air pollutants and corresponding health effects.In this work, we combine data on fine and ultrafine refractory particle number concentrations (BC proxy), and activity patterns to derive the respiratory tract deposited amounts of BC particles for the population of the highly polluted metropolitan area of Manila, Philippines. We calculated the total DD of refractory particles based on three metrics: refractory particle number, surface area, and mass concentrations. The calculated DD of total refractory particle number in Metro Manila was found to be 1.6 to 17 times higher than average values reported from Europe and the U.S. In the case of Manila, ultrafine particles smaller than 100 nm accounted for more than 90% of the total deposited refractory particle dose in terms of particle number.This work is a first attempt to quantitatively evaluate the DD of refractory particles and raise awareness in assessing pollution-related health effects in developing megacities. We demonstrate that the majority of the population may be highly affected by BC pollution, which is known to have negative health outcomes if no actions are taken to mitigate its emission. For the governments of such metropolitan areas, we suggest to revise currently existing environmental legislation, raise public awareness, and to establish supplementary monitoring of black carbon in parallel to already existing PM10 and PM2.5 measures.

Passive exposure to pollutants from conventional cigarettes and new electronic smoking devices (IQOS, e-cigarette) in passenger cars.

Smoking in car interiors is of particular concern because concentrations of potentially harmful substances can be expected to be high in such small spaces. To assess the potential exposure for occupants, especially children, we performed a comprehensive evaluation of the pollution in 7 passenger cars while tobacco cigarettes and new electronic smoking products (IQOS, e-cigarette) were being smoked. We collected data on the indoor climate and indoor air pollution with fine and ultrafine particles and volatile organic compounds while the cars were being driven. Smoking of an IQOS had almost no effect on the mean number concentration (NC) of fine particles (>300 nm) or on the PM2.5 concentration in the interior. In contrast, the NC of particles with a diameter of 25-300 nm markedly increased in all vehicles (1.6-12.3 × 104/cm3). When an e-cigarette was vaped in the interior, 5 of the 7 tested cars showed a strong increase in the PM2.5 concentration to 75-490 μg/m3. The highest PM2.5 levels (64-1988 μg/m3) were measured while tobacco cigarettes were being smoked. With the e-cigarette, the concentration of propylene glycol increased in 5 car interiors to 50-762 μg/m3, whereby the German indoor health precaution guide value for propylene glycol was exceeded in 3 vehicles and the health hazard guide value in one. In 4 vehicles, the nicotine concentration also increased to 4-10 μg/m3 while the e-cigarette was being used. The nicotine concentrations associated with the IQOS and e-cigarette were comparable, whereas the highest nicotine levels (8-140 μg/m3) were reached with tobacco cigarettes. Cigarette use also led to pollution of the room air with formaldehyde (18.5-56.5 μg/m3), acetaldehyde (26.5-141.5 μg/m3), and acetone (27.8-75.8 μg/m3). Tobacco cigarettes, e-cigarettes, and the IQOS are all avoidable sources of indoor pollutants. To protect the health of other non-smoking passengers, especially that of sensitive individuals such as children and pregnant women, these products should not be used in cars.

Effects of source emission and window opening on winter indoor particle concentrations in the severe cold region of China

Indoor particles are affected by both indoor particle sources and outdoor particles penetrating into the indoor environment. Some human behaviors such as opening windows, cooking, and smoking influence indoor air quality strongly. Indoor particle sources increase the indoor particle concentrations by generating considerable amounts of particulate matters. Opening windows can increase the exchange efficiency of indoor and outdoor particles. In this study, the effects of indoor particle source emission and opening a window on indoor particle concentrations were estimated for the severe cold region of China using tests in a room-size chamber. Indoor and outdoor fine particulate matter (PM2.5) mass concentrations and particle number concentrations from 0.3 to 10 μm were measured simultaneously in different test conditions. An indoor source was simulated using an aerosol generator to discharge dust, which was intercepted by indoor air conditioners. Indoor particle concentrations increased rapidly when the indoor source was active, and longer emission time led to greater growth. After ending indoor particle emission, indoor particle concentrations decreased due to infiltration and deposition, and opening the window can promote that decrease. Decay rates were greater for 2.5–10 μm particles because loss by gravitational settling is dominant for larger particles. When the window was opened, particle decay rates became extremely high; up to 19.09 h−1 for 2.5–10 μm particles and up to 9.73 h−1 for PM2.5.

Impact from local sources and variability of fine particle number concentration in a coastal sub-urban site

Particle number (PN) concentration was measured in coastal sub-urban site in Crete, Greece, between September 2013 and August 2014. Outdoor data were obtained for 173 sampling days with particle number size distribution measured in the size range 5.5–350.4 nm. Ambient concentrations varied considerably during the campaign with local sources playing a dominant role on temporal fluctuations. In particular, domestic heating was identified as the main anthropogenic activity that produces ultrafine particles with the higher PN concentrations measured on cold months among the measured periods. In turn, investigation of the impact of wind direction has shown that east direction was associated with elevated ultrafine PN concentrations, whilst, the monthly variability during warm periods was linked with the frequency of east-originated winds. Elevated concentrations were attributed to aviation/shipping emissions transported from the nearby airport and port. On the contrary, city-originated (southwest) winds were not associated with a pattern of increased ultrafine PN concentrations. In addition, diurnal profiles demonstrated that local traffic during rush hours (06:00–09:00 and 19:00–22:00) is responsible for increased PN concentrations for these parts of the day. However, the influence from vehicular emissions to ambient PN concentrations was lower compared to emissions from domestic heating. The seasonal variability between weekends/weekdays was also associated with traffic profile. Overall, 23 new particle formation (NPF) events were identified through the present campaign with growth rate (GR) vary between 0.75 and 5.87 nm/h and formation rate (JD) vary between 0.0005 and 0.2454 cm−3 s−1. The majority of NPF events started in the morning and after rush hours highlighting the role played by precursor gases from traffic emissions for urban sites. Moreover, the majority of the NPF events presented a west/north/northwest prevailing wind direction suggesting that fresh sea breeze air is a key factor for the formation of new particles in the under study site. Lastly, moderate positive correlations with meteorological variables found between temperature and GR, relative humidity and JD, solar radiation and GR whereas moderate negative correlation found between wind speed and JD.