Characteristics and source apportionment of PM1 emissions at a roadside station

Risk of stroke admission after long-term exposure to PM1: Evidence from a large cohort in South China

BACKGROUND

Limited attention has been paid to the health effects of long-term PM1 exposure on stroke admission. Current investigations exploring the long-term PM exposure effect are largely based on observational studies, and PM generally is not allocated randomly to participants. Using traditional regression models might confuse messaging and hinder policy recommendations for pollution control and disease prevention policies.

METHODS

We conducted a cohort study among 36,271 adults from one of the largest cities in China in 2015 and followed up through 2020. Hazard ratios of stroke admissions following long-term PM1 exposure were estimated via a causal inference approach, marginal structural time-varying Cox proportional hazard model, accounting for multiple confounders. Additionally, several sensitivity analyses and impact modification analyses were carried out.

RESULTS AND DISCUSSION

Associations with 1 μg/m3 increase in long-term PM1 were identified for total (HR, 1.079; 95 %CI, 1.012-1.151) and ischemic stroke admissions (HR, 1.092; 95 %CI, 1.018-1.171). The harmful associations varied with exposure duration, initially increasing and then decreasing. The 2-3 years cumulative exposure was associated with a 3.3-5.4 % raised risk for total stroke. For every 1 μg/m³ increase in long-term PM1 exposure, females exhibited a higher risk of both total and ischemic stroke (13 % and 16 %) than men (4 % and 5 %). Low-exposure individuals (whose annual PM1 concentrations were under the third quartile among the annual concentrations for all the participants) exhibited greater sensitivity to PM1 effects (total stroke: 1.079 vs. 1.107; ischemic stroke: 1.092 vs. 1.116). The results underline the importance of safeguarding low-exposed people in highly polluted areas and suggest that long-term PM1 exposure may increase stroke admission risk, warranting attention to vulnerable groups.

Pollution Characteristics of Heavy Metals in PM1 and Source-Specific Health Risks in the Tianjin Airport Community, China

The airport and its surrounding areas are home to a variety of pollution sources, and air pollution is a recognized health concern for local populated regions. Submicron particulate matter (PM1 with an aerodynamic diameter of <1 mm) is a typical pollutant at airports, and the enrichment of heavy metals (HMs) in PM1 poses a great threat to human health. To comprehensively assess the source-specific health effects of PM1-bound HMs in an airport community, PM1 filter samples were collected around the Tianjin Binhai International Airport for 12 h during the daytime and nighttime, both in the spring and summer, and 10 selected HMs (V, Cr, Mn, Co, Ni, Cu, Zn, As, Cd, and Pb) were analyzed. The indicatory elements of aircraft emissions were certified as Zn and Pb, which accounted for more than 60% of the sum concentration of detected HMs. The health risks assessment showed that the total non-cancer risks (TNCRs) of PM1-bound HMs were 0.28 in the spring and 0.23 in the summer, which are lower than the safety level determined by the USEPA, and the total cancer risk (TCR) was 2.37 × 10-5 in the spring and 2.42 × 10-5 in the summer, implying that there were non-negligible cancer risks in the Tianjin Airport Community. After source apportionment with EF values and PMF model, four factors have been determined in both seasons. Consequently, the source-specific health risks were also evaluated by combining the PMF model with the health risk assessment model. For non-cancer risk, industrial sources containing high concentrations of Mn were the top contributors in both spring (50.4%) and summer (44.2%), while coal combustion with high loads of As and Cd posed the highest cancer risk in both seasons. From the perspective of health risk management, targeted management and control strategies should be adopted for industrial emissions and coal combustion in the Tianjin Airport Community.

Pollutants Concentration during the Construction and Operation Stages of a Long Tunnel: A Case Study of Lowari Tunnel, (Dir–Chitral), Khyber Pakhtunkhwa, Pakistan

Long tunnels with significant overburden, changeable geological conditions, a steep gradient, water infiltration, and heavy traffic flow are susceptible to environmental concerns during both construction and operation. The availability of fresh air and visibility is the most important necessity in excavation for tunnel workers inside the tunnel during the construction phase, as well as those crossing the tunnel during operation. Lowari Tunnel’s tunnel air pollutants were researched. Carbon monoxide (CO), carbon dioxide (CO2), oxygen (O2), hydrogen sulfide (H2S), sulfur dioxide (SO2), nitrogen oxide (NO), ammonia (NH3), nitrogen dioxide (NO2), PM1, PM2.5, PM10, air velocity, dust morphological and particle size distribution analysis are among the parameters under consideration. The findings provide evidence for the development of tunnel air quality.

Characterization and sources of trace elements in PM1 during autumn and winter in Qingdao, Northern China

Atmospheric sub-micrometer particles (PM₁, particles with an aerodynamic diameter ≤ 1.0 μm) monitoring in Qingdao, a coastal city in Northern China, was conducted for two consecutive years from November 1, 2018 to January 31, 2019 (hereafter referred to as OP_2018-2019) and from October 28, 2019 to January 20, 2020 (hereafter referred to as OP_2019-2020). The results showed that compared with OP_2018-2019, the concentrations of V, Ni, As, Pb, and Cd in PM₁ in OP_2019-2020 decreased by 61.9%, 31.4%, 49.2%, 25.4%, and 27.1%, respectively. For the indicators of ship emission sources, a significant reduction in V (73.3%) and Ni (22.1%) concentrations were observed after the implementation of the updated Domestic Emission Control Area (DECA 2.0) policy for ships since January 1, 2019 proposed by the Ministry of Transportation. This result demonstrated that the implementation of the DECA 2.0 policy had a significant effect on reducing ship emissions. The Field Emission Scanning Electron Microscope analysis identified the impact of ship emission sources, while the inconsistent distribution of V and Ni revealed other potential sources of Ni. The V/Ni ratios during the pre-policy and post-policy periods decreased by 40.7%. Along with the further implementation of the domestic coastal ship pollution control zone policy, V/Ni ratio should be cautiously used as a parameter for ship emission sources. The positive matrix factorization method identified five source factors: coal combustion/biomass burning (47.8%), crustal sources (21.2%), vehicle exhaust/road dust (15.1%), industrial emissions (11.1%), and ship emissions (4.9%). The contribution rates of ship emission sources before and after the DECA 2.0 policy were analyzed and found to be 5.6% and 3.4%. The potential source contribution factor analysis of As showed that the potential emission source areas were significantly reduced in OP_2019-2020, which might be related to the coal fired cleanup operations conducted in Beijing-Tianjin-Hebei and surrounding areas.

Uncertainty investigation of plume-chasing method for measuring on-road NOx emission factors of heavy-duty diesel vehicles

The plume-chasing method has shown great advantages in measuring on-road emission factors (EFs) compared with regulatory methods like dynamometer and portable emission measurement systems (PEMS). In this study, a new on-board measurement system incorporating ultrasonic anemometers and solid-state Lidar was developed to investigate the uncertainties of on-road emission factors measured by plume-chasing method due to variables such as on-road wind velocity, chasing speed, chasing distance, and turbulent kinetic energy (TKE). A series of PEMS-chasing experiments for heavy-duty diesel vehicles (HDDVs) were conducted on both highways and local roadways in Beijing, China. Our analysis demonstrated that the differences in EF estimations between concurrent plume-chasing and PEMS measurement decreased with increasing chasing speed as a result of greater vehicle-induced TKE in the wake between HDDV and the mobile platform, whereas the effect of chasing distance on EF estimations appeared insignificant within the tested distance range (12-22 m). In the case of strong crosswinds, overprediction of chasing-based EFs was observed due to convective plume mixing from surrounding vehicular sources. The findings of this study contribute greatly to interpret emission factors measured by the plume-chasing method, and also calls for a future study to develop real-time EF correction algorithms for large-scale mobile chasing measurements.

Decreasing concentrations of carbonaceous aerosols in China from 2003 to 2013

Carbonaceous aerosols were characterized in 19 Chinese cities during winter and summer of 2013. Measurements of organic carbon (OC) and elemental carbon (EC) levels were compared with those from 14 corresponding cities sampled in 2003 to evaluate effects of emission changes over a decade. Average winter and summer OC and EC decreased by 32% and 17%, respectively, from 2003 to 2013, corresponding to nationwide emission control policies implemented since 2006. The extent of carbon reduction varied by season and by location. Larger reductions were found for secondary organic carbon (SOC, 49%) than primary organic carbon (POC, 25%). PM_2.5 mass and total carbon concentrations were three to four times higher during winter than summer especially in the northern cities that use coal combustion for heating.

Chemical and toxicological characterization of particulate emissions from diesel vehicles

This paper presents a detailed chemical and toxicological characterization of the diesel particulate matter (PM) emitted from diesel vehicles running on a chassis dynamometer under different driving conditions. Chemical analyses were performed to characterize the contents of organic carbon (OC), elemental carbon (EC), and 31 polycyclic aromatic hydrocarbons (PAHs) in the collected PM samples. The OC-EC analysis results revealed that PM emissions from diesel vehicles in this study were dominated by OC and that the emission of vehicles equipped with diesel particulate filters had high OC/EC ratios. The PAH analysis results revealed that 4- and 5-ring PAHs were the dominant PAHs in the OC fraction of the PM samples. Particle toxicity was evaluated through three toxicological markers in human A549 cells, namely (1) acellular 2,7-dichlorofluorescein (DCFH) for oxidative potential, (2) interleukin-6 (IL-6) for inflammation, and (3) glutathione (GSH) for antioxidation after exposure. Statistical analyses revealed that vehicle sizes have statistically significant effects on the concentrations of the markers. Correlation analysis between PAHs and toxicological markers revealed that significant correlations existed between specific compounds and markers. Our results can be used as a reference by policy makers to formulate emission control strategies and as a dataset for other modeling studies.

Determination of trace elements in the nanometer, ultrafine, fine, and coarse particulate matters in an area affected by light vehicular emissions in the city of Rio de Janeiro

The objective of this work was to determine the trace element composition in the nanometric, ultrafine, fine, and coarse particulate matters (PM) found in the surrounding area of the UERJ Chemical Technology Applications Institute, using a MSP 120 MOUDI II cascade impactor. After acid extraction, the elements were analyzed via ICP-OES, and the results obtained were treated statistically. The average concentrations of the nanometric, ultrafine, fine, and coarse particles were 11.8, 8.2, 7.7, and 7.1 μg m^-3, respectively. The total average concentration of Cd, Ni, Pb, Cr, and Fe complied with the air quality standards recommended by US EPA and WHO. When compared with other locations, the PM fractions found in this study were 1.1 to 346 times greater. Through the calculation of Pearson's correlation coefficient, a high correlation was observed between most of the trace elements studied, especially in the ultrafine, fine, and coarse fractions, which suggests that they are probably caused by the same sources of vehicular emissions. The enrichment factor was calculated to estimate the possible sources. Since Cd, Cu, Pb, and Mo are enriched by anthropic sources, they are probably influenced by vehicular emissions, in particular the wear on tires and brakes, and the burning of fossil fuel.

Characterization of ambient PM1 at a suburban site of Agra: chemical composition, sources, health risk and potential cytotoxicity

The present study was conducted at a University campus of Agra to determine concentrations of crustal and trace elements in submicron mode (PM₁) particles to reveal sources and detrimental effects of PM₁-bound metals (Cr, Cd, Mn, Zn, As, Co, Pb, Cu and Ni) in samples collected in the foggy (1 December 2016-17 January 2017) and non-foggy periods (1 April 2016-30 June 2016). Samples were collected twice a week on preweighed quartz fibre filters (QM-A 47 mm) for 24 h using Envirotech APM 577 (flow rate 10 l min^-1). Mass concentration of PM₁ was 135.0 ± 28.2 and 54.0 ± 18.5 µg/m³ during foggy and non-foggy period, respectively; crustal and trace elements were 13 and 4% during foggy and 11 and 3% in the non-foggy period. Source identification by PCA (principal component analysis) suggested that biomass burning and coal combustion was the prominent sources in foggy period followed by resuspended soil dust, industrial and vehicular emission, whereas in non-foggy period resuspended soil dust was dominant followed by biomass burning and coal combustion, industrial and vehicular emissions. In both episodes, Mn has the highest Hq (hazard quotient) value and Cr has the highest IlcR (Incremental Lifetime Cancer Risk) value for both adults and children. In vitro cytotoxicity impact on macrophage (J774) cells was also tested using MTT assay which revealed decreasing cell viability with increasing particle mass.

Chemical characterization, sources and potential health risk of PM2.5 and PM1 pollution across the Greater Athens Area

With the principal aim to assess the typical Mediterranean profile of the PM_2.5 and PM₁ pollution, three intensive monitoring campaigns took place simultaneously within different types of environment across an urban location of the basin. Focusing on the PM components with numerous anthropogenic sources and increased potential health risk, the samples were chemically analyzed for 20 p.m.-bound Polycyclic Aromatic Hydrocarbons (PAHs). Carbonaceous and ionic constituents were quantified as well. In order to uncover the spatiotemporal variation of the PM profile the key sources were identified, the seasonal effects and the role of the prevailing mesoscale atmospheric circulation were evaluated and most importantly the potential health risk was estimated. In general, the pollution status of the basin was the result of a complex interaction between the local and external input with Particulate Organic Matter (POM) and Secondary Inorganic Aerosols (SIA) being the main aerosols' components. PM₁ was a better indicator of the anthropogenic emissions while according to the results of factor analysis the co-existence of various combustion sources was determinant. Chemically, the maxima of the ΣPAHs, the differentiation of their structure in accordance with their molecular weight and the distribution of the individual compounds confirmed the significance of the emission sources. Similarly, the estimated carcinogenicity/mutagenicity was emission-dependent with the maximum contribution coming from B[a]P, IndP, B[ghi]Per, B[e]P and B[b]F. Seasonally, the highest potential health risk of the PAHs' mixture was recorded during the cold season while meteorologically, it was mostly associated with the south flow.

The traffic signature on the vertical PM profile: Environmental and health risks within an urban roadside environment

In an attempt to investigate the traffic-impacted vertical aerosols profile and its relationship with potential carcinogenicity and/or mutagenicity, samples of different sized airborne particles were collected in parallel at the 1st and 5th floor of a 19 m high building located next to one of the busiest roads of Athens. The maximum daily concentrations were 65.9, 42.5 and 38.5 μg/m³, for PM₁₀, PM_2.5 and PM₁, respectively. The vertical concentration ratio decreased with increasing height verifying the role of the characteristics of the area (1st/5th floor: 1.21, 1.13, 1.09 for PM₁₀, PM_2.5 and PM₁, respectively). Chemically, strengthening the previous hypothesis, the collected particles were mainly carbonaceous (68%-93%) with the maximum budget of the polyaromatic hydrocarbons being recorded near the surface (1st/5th floor: 1.84, 1.07, 1.15 for PM₁₀, PM_2.5 and PM₁, respectively). The detected PM-bound PAHs along with the elements as well as the carbonaceous and ionic constituents were used in a source apportionment study. Exhaust and non-exhaust emissions, a mixed source of biomass burning and high temperature combustion processes (natural gas, gasoline/diesel engines), sea salt, secondary and soil particles were identified as the major contributing sources to the PM pollution of the investigated area. With respect to the health hazards, the calculation of the Benzo[a]Pyrene toxicity equivalency factors underlined the importance of the height of residence in buildings for the level of the exposure (1st/5th floor: B[a]P_TEQ: 1.82, 1.12, 1.10, B[a]P_MEQ: 1.85, 1.13, 1.09 for PM₁₀, PM_2.5 and PM₁, respectively). Finally, despite its verified significance as a surrogate compound for the mixture of the hydrocarbons (its contribution up to 72%, 79% on the level of the 1st and 5th floor, respectively), the importance of the incorporation of PAH species in addition to B[a]P when assessing PAH toxicity was clearly documented.

Particulate Matter Produced by Micro-Scale Biomass Combustion in an Oxygen-Lean Atmosphere

This article extends earlier research by the authors that was devoted to the experimental evaluation of ultra-fine particles produced by the laboratory combustion of beechwood samples. These particles can have severe influence on human health. The current paper presents a parametrical study carried out to assess the influence of the composition of the atmosphere and the temperature on the production of ultra-fine particles during the micro-scale combustion process. The paper presents a laboratory procedure that incorporate the thermogravimetric analysis (TGA) and detailed monitoring of the size distribution of the produced fine particles. The study utilises the laboratory scale identification of the formation and growth of the fine particles during the temperature increase of beech wood samples. It also compares the particle emissions produced by beech heartwood and beech bark. The size of the emitted particles is very strongly influenced by the concentration of light volatiles released from the heated wood sample. From the experimental study, decreasing oxygen content in the atmosphere generally results in higher particulate matter (PM) production.

Chemical characterization and quantitativ e assessment of source-specific health risk of trace metals in PM1.0 at a road site of Delhi, India

This study presents the concentration of submicron aerosol (PM_1.0) collected during November, 2009 to March, 2010 at two road sites near the Indian Institute of Technology Delhi campus. In winter, PM_1.0 composed 83% of PM_2.5 indicating the dominance of combustion activity-generated particles. Principal component analysis (PCA) proved secondary aerosol formation as a dominant process in enhancing aerosol concentration at a receptor site along with biomass burning, vehicle exhaust, road dust, engine and tire tear wear, and secondary ammonia. The non-carcinogenic and excess cancer risk for adults and children were estimated for trace element data set available for road site and at elevated site from another parallel work. The decrease in average hazard quotient (HQ) for children and adults was estimated in following order: Mn > Cr > Ni > Pb > Zn > Cu both at road and elevated site. For children, the mean HQs were observed in safe level for Cu, Ni, Zn, and Pb; however, values exceeded safe limit for Cr and Mn at road site. The average highest hazard index values for children and adults were estimated as 22 and 10, respectively, for road site and 7 and 3 for elevated site. The road site average excess cancer risk (ECR) risk of Cr and Ni was close to tolerable limit (10^-4) for adults and it was 13-16 times higher than the safe limit (10^-6) for children. The ECR of Ni for adults and children was 102 and 14 times higher at road site compared to elevated site. Overall, the observed ECR values far exceed the acceptable level.

Predicting PM10 concentration in Seoul metropolitan subway stations using artificial neural network (ANN)

The indoor air quality of subway systems can significantly affect the health of passengers since these systems are widely used for short-distance transit in metropolitan urban areas in many countries. The particles generated by abrasion during subway operations and the vehicle-emitted pollutants flowing in from the street in particular affect the air quality in underground subway stations. Thus the continuous monitoring of particulate matter (PM) in underground station is important to evaluate the exposure level of PM to passengers. However, it is difficult to obtain indoor PM data because the measurement systems are expensive and difficult to install and operate for significant periods of time in spaces crowded with people. In this study, we predicted the indoor PM concentration using the information of outdoor PM, the number of subway trains running, and information on ventilation operation by the artificial neural network (ANN) model. As well, we investigated the relationship between ANN's performance and the depth of underground subway station. ANN model showed a high correlation between the predicted and actual measured values and it was able to predict 67∼80% of PM at 6 subway station. In addition, we found that platform shape and depth influenced the model performance.

Estimation of inhaled airborne particle number concentration by subway users in Seoul, Korea

Exposure to airborne particulate matter (PM) causes several diseases in the human body. The smaller particles, which have relatively large surface areas, are actually more harmful to the human body since they can penetrate deeper parts of the lungs or become secondary pollutants by bonding with other atmospheric pollutants, such as nitrogen oxides. The purpose of this study is to present the number of PM inhaled by subway users as a possible reference material for any analysis of the hazards to the human body arising from the inhalation of such PM. Two transfer stations in Seoul, Korea, which have the greatest number of users, were selected for this study. For 0.3-0.422 μm PM, particle number concentration (PNC) was highest outdoors but decreased as the tester moved deeper underground. On the other hand, the PNC between 1 and 10 μm increased as the tester moved deeper underground and showed a high number concentration inside the subway train as well. An analysis of the particles to which subway users are actually exposed to (inhaled particle number), using particle concentration at each measurement location, the average inhalation rate of an adult, and the average stay time at each location, all showed that particles sized 0.01-0.422 μm are mostly inhaled from the outdoor air whereas particles sized 1-10 μm are inhaled as the passengers move deeper underground. Based on these findings, we expect that the inhaled particle number of subway users can be used as reference data for an evaluation of the hazards to health caused by PM inhalation.

Source apportionment of size-fractionated particles during the 2013 Asian Youth Games and the 2014 Youth Olympic Games in Nanjing, China

In this study, samples of size-fractionated particulate matter were collected continuously using a 9-size interval cascade impactor at an urban site in Nanjing, before, during and after the Asian Youth Games (AYG), from July to September of 2013, and the Youth Olympic Games (YOG), from July to September of 2014. First, elemental concentrations, water-soluble ions including Cl^-, NO₃^-, SO₄^2-, NH₄⁺, K⁺, Na⁺ and Ca²⁺, organic carbon (OC) and elemental carbon (EC) were analysed. Then, the source apportionment of the fine and coarse particulate matter was carried out using the chemical mass balance (CMB) model. The average PM₁₀ concentrations were 90.4±20.0μg/m³ during the 2013 AYG and 70.6±25.3μg/m³ during the 2014 YOG. For PM_2.1, the average concentrations were 50.0±12.8μg/m³ in 2013 and 34.6±17.0μg/m³ in 2014. Investigations showed that the average concentrations of particles declined significantly from 2013 to 2014, and concentrations were at the lowest levels during the events. Results indicated that OC, EC, sulfate and crustal elements have significant monthly and size-based variations. The major components, including crustal elements, water-soluble ions and carbonaceous aerosol accounted for 75.3-91.9% of the total particulate mass concentrations during the sampling periods. Fugitive dust, coal combustion dust, iron dust, construction dust, soil dust, vehicle exhaust, secondary aerosols and sea salt have been classified as the main emissions in Nanjing. The source apportionment results indicate that the emissions from fugitive dust, which was the most abundance emission source during the 2013 AYG, contributed to 23.0% of the total particle mass. However, fugitive dust decreased to 6.2% of the total particle mass during the 2014 YOG. Construction dust (14.7% versus 7.8% for the AYG and the YOG, respectively) and secondary sulfate aerosol (9.3% versus 8.0% for the AYG and the YOG, respectively) showed the same trend as fugitive dust, suggesting that the mitigation measures of controlling particles from the paved roads, construction and industry worked more efficiently during the YOG.

Chemical profiles of urban fugitive dust PM2.5 samples in Northern Chinese cities

Urban fugitive dust PM2.5 samples were collected in 11 selected cities in North China, and 9 ions (SO4(2-), NO3(-), Cl(-), F(-), Na(+), NH4(+), K(+), Mg(2+), and Ca(2+)) and 22 elements (Si, Al, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Br, Rb, Sr, Sn, Sb, Ba, and Pb) were determined to investigate chemical profiles of PM2.5. The coefficient of divergence (CD) was used to compare the similarities of the chemical profiles for fugitive dust among three regions in North China, and the results showed that their composition are quite similar. Total water soluble ions occupied 9.3% and 10.0% on average of road dust and construction dust, respectively, indicating that most of the materials in urban fugitive dust samples were insoluble. Ca(2+) was the most abundant cation and SO4(2-) dominated in anions. Soil dust loading was calculated to occupy 70.8% and 83.6% in road dust and construction dust, respectively. Ca, Si, Fe, and Al were the most abundant elements in all the samples, and Ca was absolutely the most abundant specie among the 22 detected elements in construction dust samples. Chemical species ratios were used to highlight the characteristics of urban fugitive dust by comparing with other types of aerosols. High Ca/Al ratio was a good marker to distinguish urban fugitive dust from Asian dust and Chinese loess. In addition, low K(+)/K and NO3(-)/SO4(2-), and high Zn/Al and Pb/Al ratios were good indicators to separate urban fugitive dust from desert dust, Chinese loess, or urban PM2.5 samples.

Transient variation of aerosol size distribution in an underground subway station

As the number of people using rapid transit systems (subways) continues to rise in major cities worldwide, increasing attention has been given to the indoor air quality of underground stations. This study intended to observe the change of PM distribution by size in an underground station with PSDs installed located near the main road in downtown Seoul, as well as to examine causes for the changes. The results indicate that the PM suspended in the tunnel flowed into the platform area even in a subway station where the effect of train-induced wind is blocked by installed PSDs, as this flow occurred when the PSDs were opened. The results also indicate that coarse mode particles generated by mechanical friction in the tunnel, such as that between wheels and rail, also flowed into the platform area. The PM either settled or was re-suspended according to size and whether the ventilation in the platform area was in operation or if the platform floor had been washed. The ventilation system was more effective in removing PM of smaller sizes (fine particles) while the wash-out performed after train operations had stopped reduced the suspension of coarse mode particles the next morning. Despite installation of the completely sealed PSDs, inflow of coarse mode particles from the tunnel seems unavoidable, indicating the need for measures to decrease the PM generated there to lower subway user exposure since those particles cannot be reduced by mechanical ventilation alone. This research implicate that coarse PM containing heavy metals (generated from tunnel side) proliferated especially during rush hours, during which it is very important to control those PM in order to reduce subway user exposure to this hazardous PM.

A multivariate study for characterizing particulate matter (PM(10), PM(2.5), and PM(1)) in Seoul metropolitan subway stations, Korea

Given that around eight million commuters use the Seoul Metropolitan Subway (SMS) each day, the indoor air quality (IAQ) of its stations has attracted much public attention. We have monitored the concentration of particulate matters (PMx) (i.e., PM10, PM2.5, and PM1) in six major transfer stations per minute for three weeks during the summer, autumn, and winter in 2014 and 2015. The data were analyzed to investigate the relationship between PMx concentration and multivariate environmental factors using statistical methods. The average PM concentration observed was approximately two or three times higher than outdoor PM10 concentration, showing similar temporal patterns at concourses and platforms. This implies that outdoor PM10 is the most significant factor in controlling indoor PM concentration. In addition, the station depth and number of trains passing through stations were found to be additional influences on PMx. Principal component analysis (PCA) and self-organizing map (SOM) were employed, through which we found that the number of trains influences PM concentration in the vicinity of platforms only, and PMx hotspots were determined. This study identifies the external and internal factors affecting PMx characteristics in six SMS stations, which can assist in the development of effective IAQ management plans to improve public health.

Temporal variations of PM1 major components in an urban street canyon

Seasonal changes in the levels of PM1 and its main components (organic carbon (OC), elemental carbon (EC), SO4 (2-), NO3 (-) and NH4 (+)) were studied in an urban street canyon in southeastern Spain. Although PM1 levels did not show an evident seasonal cycle, strong variations in the concentrations of its major components were observed. Ammonium sulfate, the main secondary inorganic compound, was found to be of regional origin. Its formation was favored during summer due to increased photochemical activity. In contrast, the concentrations of particulate ammonium nitrate, which is thermally unstable, were highest in winter. Although traffic emissions are the dominant source of EC in the city, variations in traffic intensity could not explain the seasonal cycle of this component. The higher EC concentrations during the cold months were attributed to the lower dispersion conditions and the increase in EC emissions. Special attention has been given to variations in organic carbon levels since it accounted for about one third of the total PM1 mass. The concentrations of both total OC and secondary OC (SOC) were maxima in winter. The observed seasonal variation in SOC levels is similar to that found in other southern European cities where the frequency of sunny days in winter is high enough to promote photochemical processes.

Indoor and Outdoor Levels and Sources of Submicron Particles (PM1) at Homes in Edmonton, Canada

Exposure to submicron particles (PM1) is of interest due to their possible chronic and acute health effects. Seven consecutive 24-h PM1 samples were collected during winter and summer 2010 in a total of 74 nonsmoking homes in Edmonton, Canada. Median winter concentrations of PM1 were 2.2 μg/m(3) (interquartile range, IQR = 0.8-6.1 μg/m(3)) and 3.3 μg/m(3) (IQR = 1.5-6.9 μg/m(3)) for indoors and outdoors, respectively. In the summer, indoor (median 4.4 μg/m(3), IQR = 2.4-8.6 μg/m(3)) and outdoor (median 4.3 μg/m(3), IQR = 2.6-7.4 μg/m(3)) levels were similar. Positive matrix factorization (PMF) was applied to identify and apportion indoor and outdoor sources of elements in PM1 mass. Nine sources contributing to both indoor and outdoor PM1 concentrations were identified including secondary sulfate, soil, biomass smoke and environmental tobacco smoke (ETS), traffic, settled and mixed dust, coal combustion, road salt/road dust, and urban mixture. Three additional indoor sources were identified i.e., carpet dust, copper-rich, and silver-rich. Secondary sulfate, soil, biomass smoke and ETS contributed more than 70% (indoors: 0.29 μg/m(3), outdoors: 0.39 μg/m(3)) of measured elemental mass in PM1. These findings can aid understanding of relationships between submicron particles and health outcomes for indoor/outdoor sources.

Further insights into the composition, source, and toxicity of PAHs in size-resolved particulate matter in a megacity in China

Concentrations of particulate matter with an aerodynamic diameter less than 10 μm (PM10 ) and PM with an aerodynamic diameter less than 2.5 μm (PM2.5 ), and 16 polycyclic aromatic hydrocarbons (PAHs) were measured. The average concentrations of PM10 and PM2.5 reached 209.75 μg/m(3) and 141.87 μg/m(3) , respectively, and those of ΣPAHs were 41.46 ng/m(3) for PM10 and 36.77 ng/m(3) for PM2.5 . The mass ratio concentrations were 219.23 μg/g and 311.01 μg/g in PM10 and PM2.5 , respectively. Three sources and their contributions for PAHs were obtained. For individual input mode, diesel exhaust contributed 46.77% (PM10 ) and 41.12% (PM2.5 ) for mass concentration and 48.69% (PM10 ) and 39.47% (PM2.5 ) for mass ratio concentration; gasoline exhaust contributed 31.02% (PM10 ) and 39.47% (PM2.5 ) for mass concentration and 28.95% (PM10 ) and 36.46% (PM2.5 ) for mass ratio concentration; and coal combustion contributed 22.22% (PM10 ) and 19.41% (PM2.5 ) for mass concentration and 22.36% (PM10 ) and 15.89% (PM2.5 ) for mass ratio concentration. For combined input mode, the same source categories were obtained. Source contributions to PM10 and PM2.5 were diesel exhaust (40.70% and 36.64%, respectively, for mass concentration; 49.19% and 38.47%, respectively, for mass ratio concentration), gasoline exhaust (35.09% and 38.47%, respectively, for mass concentration; 32.50% and 33.43%, respectively, for mass ratio concentration), and coal combustion (24.21% and 24.89%, respectively, for mass concentration; 18.31% and18.17%, respectively, for mass ratio concentration). Source risk assessment showed that vehicle emission was a significant contributor. The findings can help elucidate sources of PAHs and provide evidence supporting further applications of the Unmix model and additional studies about PAHs. Environ Toxicol Chem 2015;34:480-487. © 2014 SETAC.

Diurnal concentrations variations, size distributions for ambient air particles and metallic pollutants (Cr, Mn, Ni, Cd, Pb) during summer season at a traffic area

This study characterized and discussed particulate ambient air particulate concentrations and seasonal variations for PM18, PM10, PM2.5, and PM1 during June 2013-July 2013 at this traffic sampling site. In addition, this study also characterized the ambient air particulates size distributions by using MOUDI-100S4 sampler to collect 1-day the ambient suspended particles (PM18, PM10, PM2.5, and PM1) at this sampling site. In addition, the study also showed that the main pollutants contributions were from traffic and residual areas. As for the pollutants seasonal concentrations variations, the results indicated that the average particle concentrations orders were all displayed as daytime > nighttime for PM18, PM10, PM2.5 and PM1 at this characteristic sampling site. The results further indicated that the mean highest of metal concentrations in this study indicated that the average metal concentration were all displayed as Mn > Cr > Ni > Pb > Cd for PM18, PM10, PM2.5 and PM1 on daytime and nighttime at this characteristic sampling site.

Fine particulate matter in the indoor air of barbeque restaurants: elemental compositions, sources and health risks

Cooking is a significant source of indoor particulate matter that can cause adverse health effects. In this study, a 5-stage cascade impactor was used to collect particulate matter from 14 restaurants that cooked with charcoal in Kocaeli, the second largest city in Turkey. A total of 24 elements were quantified using ICP-MS. All of the element contents except for Mn were higher for fine particles (PM2.5) than coarse particles (PM>2.5), and the major trace elements identified in the PM2.5 included V, Se, Zn, Cr, As, Cu, Ni, and Pb. Principle component analysis (PCA) and enrichment factor (EF) calculations were used to determine the sources of PM2.5. Four factors that explained over 77% of the total variance were identified by the PCA. These factors included charcoal combustion, indoor activities, crustal components, and road dust. The Se, As, Cd, and V contents in the PM2.5 were highly enriched (EF>100). The health risks posed by the individual metals were calculated to assess the potential health risks associated with inhaling the fine particles released during charcoal cooking. The total hazard quotient (total HQ) for a PM2.5 of 4.09 was four times greater than the acceptable limit (i.e., 1.0). In addition, the excess lifetime cancer risk (total ELCR) for PM2.5 was 1.57×10(-4), which is higher than the acceptable limit of 1.0×10(-6). Among all of the carcinogenic elements present in the PM2.5, the cancer risks resulting from Cr(VI) and As exposure were the highest (i.e., 1.16×10(-4) and 3.89×10(-5), respectively). Overall, these results indicate that the lifetime cancer risk associated with As and Cr(VI) exposure is significant at selected restaurants, which is of concern for restaurant workers.

Characterization of aerosol associated non-polar organic compounds using TD-GC-MS: a four year study from Delhi, India

Aerosol associated Non-Polar Organic Compounds (NPOCs)--25 n-alkanes, 17 Polycyclic Aromatic Hydrocarbons (PAHs), and 3 Isoprenoid hydrocarbons--have been identified and quantified in PM10 samples collected over four years in time sequence (2006-2009), using Thermal Desorption Gas Chromatography Mass Spectrometry, in Delhi region. Established organic markers, associated diagnostic parameters, and molecular diagnostic ratios were used to assess and discern the contributing biogenic, petrogenic and pyrogenic sources to NPOCs. Analysis show that anthropogenic contributions to NPOCs exhibit increase from 2006 to 2009. Distribution profiles of NPOCs were significantly affected by change in season. Lower concentrations of NPOCs during summer months, and higher during winter, once scaled to Planetary Boundary Layer height, suggests that contributing sources were most active during summer months. During monsoon season high mass fractions of Total n-alkanes (ppm), Total PAHs (ppm), and Black carbon (BC) % alludes at the role of differential washout process involving hydrophilic and hydrophobic fractions of ambient aerosols. Significantly high, four year average concentrations of TPAH and BC signify the dominance of pyrogenic source contributions to PM10. High correlation between monthly mean concentrations of TPAH and BC (R(2)=0.75) suggests that besides common emission source, they are also contributed, individually, by exclusive independent sources.

Vertical characteristics of levels and potential sources of water-soluble ions in PM₁₀ in a Chinese megacity

To investigate the vertical characteristics of ions in PM10 as well as the contributions and possible locations of their sources, eight water-soluble ions were measured at four heights simultaneously along a meteorological tower in Tianjin, China. The total ion concentrations showed a general decreasing trend with increasing height, ranging from 64.94μgm(-3) at 10m to 44.56μgm(-3) at 220m. NH4(+), SO4(2-) and NO3(-) showed higher height-to-height correlations. In addition, relationships between ions are discussed using Pearson correlation coefficients and hierarchical clustering analysis (HCA), which implied that, for each height, the correlations among NH4(+), SO4(2-) and NO3(-) were higher. Finally, sources were identified qualitatively by the ratio of certain ions and quantitatively by principal component analysis/multiple linear regression (PCA/MLR) and positive matrix factorisation (PMF). Secondary sources played a dominant role for PM10 and water-soluble ions at four heights and became more important at greater heights (the percentage contributions were 43.04-66.41% for four heights by PCA/MLR and 46.93-67.62% by PMF). Then, the redistributed concentration field (RCF) combined with PCA/MLR and PMF was applied, which indicated the high potential source regions. The vertical characteristics of the levels, relationships, source contributions and locations would support the effective management of the water-soluble ions in particulate matter.

Applied investigation on the interaction of hazardous elements binding on ultrafine and nanoparticles in Chinese anthracite-derived fly ash

A multifaceted instrumental approach was employed to determine the chemistry and mineralogy of pulverized-coal-combustion fly ashes from two Chinese power plants. Techniques included traditional optical microscopy, X-ray diffraction, and chemical analysis along with a variety of electron beam methods. The aim is to demonstrate and bring together the wide variety of procedures dealing with F as the key element of concern, and determining its location in the mineral nanoparticles. The Hg content of the Anwen (Songzao coalfield) fly ashes is higher than that of the Diandong (East Yunnan) fly ashes, possibly owing to the greater C and Cl in the Anwen fly ashes. Both fly ash sources contain a variety of amorphous and nano-crystalline trace-element-bearing particles, both associated with multi-walled carbon nanotubes and as particles independent of carbons.