Sources Of Submicron Aerosols Research Articles

A 1-year aerosol chemical speciation monitor (ACSM) source analysis of organic aerosol particle contributions from anthropogenic sources after long-range transport at the TROPOS research station Melpitz

Abstract. Atmospheric aerosol particles are a complex combination of primary emitted sources (biogenic and anthropogenic) and secondary aerosol resulting from aging processes such as condensation, coagulation, and cloud processing. To better understand their sources, investigations have been focused on urban areas in the past, whereas rural-background stations are normally less impacted by surrounding anthropogenic sources. Therefore, they are predisposed for studying the impact of long-range transport of anthropogenic aerosols. Here, the chemical composition and organic aerosol (OA) sources of submicron aerosol particles measured by an aerosol chemical speciation monitor (ACSM) and a multi-angle absorption photometer (MAAP) were investigated at Melpitz from September 2016 to August 2017. The location of the station at the frontier between western and eastern Europe makes it the ideal place to investigate the impact of long-range transport over Europe. Indeed, the station is under the influence of less polluted air masses from westerly directions and more polluted continental air masses from eastern Europe. The OA dominated the submicron particle mass concentration and showed strong seasonal variability ranging from 39 % (in winter) to 58 % (in summer). It was followed by sulfate (15 % and 20 %) and nitrate (24 % and 11 %). The OA source identification was performed using the rolling positive matrix factorization (PMF) approach to account for the potential temporal changes in the source profile. It was possible to split OA into five factors with a distinct temporal variability and mass spectral signature. Three were associated with anthropogenic primary OA (POA) sources: hydrocarbon-like OA (HOA; 5.2 % of OA mass in winter and 6.8 % in summer), biomass burning OA (BBOA; 10.6 % and 6.1 %) and coal combustion OA (CCOA; 23 % and 8.7 %). Another two are secondary and processed oxygenated OA (OOA) sources: less oxidized OOA (LO-OOA; 28.4 % and 36.7 %) and more oxidized OOA (MO-OOA; 32.8 % and 41.8 %). Since equivalent black carbon (eBC) was clearly associated with the identified POA factors (sum of HOA, BBOA, and CCOA; R2= 0. 87), eBC's contribution to each of the POA factors was achieved using a multilinear regression model. Consequently, CCOA represented the main anthropogenic sources of carbonaceous aerosol (sum of OA and eBC) not only during winter (56 % of POA in winter) but also in summer (13 % of POA in summer), followed by BBOA (29 % and 69 % of POA in winter and summer, respectively) and HOA (15 % and 18 % of POA in winter and summer, respectively). A seasonal air mass cluster analysis was used to understand the geographical origins of the different aerosol types and showed that during both winter and summer time, PM1 (PM with an aerodynamic diameter smaller than 1 µm) air masses with eastern influence were always associated with the highest mass concentration and the highest coal combustion fraction. Since during wintertime CCOA is a combination of domestic heating and power plant emissions, the summer contribution of CCOA emphasizes the critical importance of coal power plant emissions to rural-background aerosols and its impact on air quality, through long-range transportation.

Chemical characterization and sources of submicron aerosols in Lhasa on the Qinghai–Tibet Plateau: Insights from high-resolution mass spectrometry

In recent years, a great number of studies has been carried out in urban cities regarding urban particulate matter (PM) pollution in China, especially in eastern China. Lhasa, the capital of the Tibet Autonomous Region in western China, is the highest (3650 m a.s.l.) city in China and has notably different lifestyles and PM sources comparing with those in eastern China. However, there is currently a lack of studies on PM pollution in this city. In this study, an Aerodyne high-resolution time-of-flight aerosol mass spectrometer was deployed along with other co-located instruments to explore the chemical characterization of ambient submicron PM (PM1) in Lhasa from 31 August 2019 to 26 September 2019. The mean ambient PM1 mass loading through this study was 4.72 μg m−3. Organic aerosols (OAs) played a dominant role with an average contribution of 82.6% to PM1, followed by 5.4% nitrate, 4.7% ammonium, 3.4% sulfate, 3.1% BC, and 0.7% chloride. The relatively lower contribution from secondary inorganic aerosols (nitrate and sulfate) in this study was distinctly different from that in eastern China, indicating lower fossil fuel usage in this city. Via positive matrix factorization (PMF), organic aerosols were decomposed into four components containing a traffic-related hydrocarbon-like OA (HOA), a cooking-related OA (COA), a biomass burning-related OA (BBOA), as well as an oxygenated OA (OOA). The OOA and COA had higher contributions (34% and 35%, respectively) to total OAs, while the rest accounted for 17% for HOA and 14% for BBOA. However, an increased mass fraction of BBOA (up to 36%) was found during the Sho Dun Festival, suggesting the importance of biomass burning emissions during the religious activities in this city. Frequent new particle formation events were observed during this study and the contribution of chemical species for the particle growth was also explored.

Online Chemical Characterization and Sources of Submicron Aerosol in the Major Mediterranean Port City of Piraeus, Greece

Port cities are affected by a wide array of emissions, including those from the shipping, road transport, and residential sectors; therefore, the characterization and apportionment of such sources in a high temporal resolution is crucial. This study presents measurements of fine aerosol chemical composition in Piraeus, one of the largest European ports, during two monthly periods (winter vs. summer) in 2018–2019, using online instrumentation (Aerosol Chemical Speciation Monitor—ACSM, 7-λ aethalometer). PMF source apportionment was performed on the ACSM mass spectra to quantify organic aerosol (OA) components, while equivalent black carbon (BC) was decomposed to its fossil fuel combustion and biomass burning (BB) fractions. The combined traffic, shipping and, especially, residential emissions led to considerably elevated submicron aerosol levels (22.8 μg m−3) in winter, which frequently became episodic late at night under stagnant conditions. Carbonaceous compounds comprised the major portion of this submicron aerosol in winter, with mean OA and BC contributions of 61% (13.9 μg m−3) and 16% (3.7 μg m−3), respectively. The contribution of BB to BC concentrations was considerable and spatially uniform. OA related to BB emissions (fresh and processed) and hydrocarbon-like OA (from vehicular traffic and port-related fossil fuel emissions including shipping) accounted for 37% and 30% of OA, respectively. In summer, the average PM1 concentration was significantly lower (14.8 μg m−3) and less variable, especially for the components associated with secondary aerosols (such as OA and sulfate). The effect of the port sector was evident in summer and maintained BC concentrations at high levels (2.8 μg m−3), despite the absence of BB and improved atmospheric dispersion. Oxygenated components yielded over 70% of OA in summer, with the more oxidized secondary component of regional origin being dominant (41%) despite the intensity of local sources, in the Piraeus environment. In general, with respect to local sources that can be the target of mitigation policies, this work highlights the importance of port-related activities but also reveals the extensive wintertime impact of residential wood burning. While a separation of the BB source is feasible, more research is needed on how to disentangle the short-term effects of different fossil-fuel combustion sources.

Physiochemistry characteristics and sources of submicron aerosols at the background area of North China Plain: Implication of air pollution control in heating season

Aerosol physiochemistry and sources in the background regions of North China Plain (NCP) remains poorly characterized. Here we present a comprehensive characterization of aerosol composition and sources at an NCP mountain site during heating periods (November 12 to December 24, 2018) using a Quadrupole Aerosol Mass Spectrometer (Q-AMS). The average mass concentration of non-refractory submicron aerosols (NR-PM1) was 22.6 ± 29.9 μg/m3, in which organic aerosol (OA) and nitrate showed comparable contribution of 32.8% and 35.1%, respectively, followed by ammonium (15.3%), sulfate (13.9%) and chloride (2.6%). Secondary inorganic aerosol (SIA) was found to dominated in polluted days (70%) which the aerosol level is 15 times higher than that in clean days which dominated by organics (54%). In addition, organics, nitrate and sulfate showed similar unimodal size distributions peaked at 600–800 nm in polluted days, which appear to be internally mixed that originated from regional transportation of aged aerosol. Whereas, the different size distribution mode of organics with SIA that peaked at smaller particle size (200–300 nm) in cleans days suggested contributions from local emissions. Positive matrix factorization (PMF) and ME2 analysis showed oxidized organic aerosols (OOA) dominated the total OA (64%), while the contribution of the hydrocarbons-like OA (HOA) and biomass burning OA (BBOA) was comparable (15–21%). To evaluate the effect of air pollution control on the background aerosols chemistry, interannual variations in aerosol chemical compositions during heating periods in 2014–2018 were deduced combined with the trajectory cluster analysis. The results showed the aerosol source region was mainly from the urban agglomeration of NCP, which showed the largest decrease in aerosol mass concentration during the past five years. In addition, the aerosol compositions became to be SIA dominated gradually under different air mass influence condition, suggesting the air pollution control is more effective for the reduction of primary emissions than the secondary species.

Chemical composition and sources of submicron aerosol in a coastal city of China: Results from the 2017 BRICS summit study

Chemical compositions of non-refractory submicron aerosol (NR-PM1) were measured via an Aerodyne Aerosol Chemical Speciation Monitor at the coastal city Xiamen during the 2017 BRICS summit from August 10 to September 10. Mean hourly concentration of NR-PM1 was 13.55 ± 8.83 μg m−3 during the study period, decreasing from 18.83 μg m−3 before-BRICS to 13.02 μg m−3 in BRCIS I and 8.42 μg m−3 in BRICS II. Positive matrix factor analyses resolved four organic aerosols (OA): a hydrocarbon-like OA (HOA, 14.78%), a cooking-related OA (COA, 28.21%), a biomass burning OA (BBOA, 18.00%), and an oxygenated OA (OOA, 39.22%). The contributions of local pollutants like nitrate and HOA reduced, while the proportions of sulfate and OOA increased during the control episodes. The diurnal patterns of NR-PM1 species and OA components in each episode were characterized. The results showed that BC, nitrate, COA, and HOA had peaks in the morning and evening, which became less obvious under the emission control. Moreover, the diurnal variations of all species in Ep 3 with emission control were much flatter due to the effect of transport. Backward trajectories analysis confirmed the long-range transport of air masses from the continent, which resulted in the high proportions of sulfate (43.69%) and OOA (50.28%) in Ep 3. Our study implies the significant effect of emission control on reducing primary pollutants, but the formation of particles during the long-range transport need to be paid more attention when set the air quality control strategies in coastal cities.

Chemical composition and sources of submicron aerosols in winter at a regional site in Beijing-Tianjin-Hebei region: Implications for the Joint Action Plan

The Ministry of Environmental Protection released a Joint Action Plan for Control of Air Pollution (Hereafter, Joint Action Plan, JAP), to reduce PM2.5 concentrations in the Beijing-Tianjin-Hebei region (BTH) during the winter of 2017. To investigate the effectiveness of the controls, we deployed an aerosol chemical speciation monitor and collected filter samples at Xianghe, a representative site for the BTH, to characterize the aerosol composition during the implementation of the JAP. Those results were compared with earlier data obtained from a literature survey and reanalysis of studies in the BTH. During several pollution episodes in the control period, the major aerosol types changed relative to the earlier studies from sulfate, oxygenated organic aerosol, and coal combustion organic aerosol to nitrate and biomass burning organic aerosol. The dominant secondary inorganic aerosol species during the JAP changed from sulfate to nitrate, and the main source for primary organic aerosol switched from coal combustion to biomass burning. These changes can be explained by the fact that the JAP controls targeted coal combustion and SO2 but not biomass burning or NOx emissions. Our evaluation of the control measures provides a scientific basis for developing new policies in the future.

Chemical characterization and sources of submicron aerosols in the northeastern Qinghai–Tibet Plateau: insights from high-resolution mass spectrometry

Abstract. An Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was deployed along with other online instruments to study the highly time resolved chemistry and sources of submicron aerosols (PM1) at Waliguan (WLG) Baseline Observatory, a high-altitude (3816 m a.s.l.) background station located at the northeast edge of the Qinghai–Tibet Plateau (QTP), during 1–31 July 2017. The average PM1 mass concentration during this study was 9.1 µg m−3 (ranging from 0.3 to 28.1 µg m−3), which was distinctly higher than those (2.0–5.7 µg m−3) measured with the Aerodyne AMS at other high-elevation sites in the southern or central QTP. Sulfate showed a dominant contribution (38.1 %) to PM1 at WLG followed by organics (34.5 %), ammonium (15.2 %), nitrate (8.1 %), BC (3.0 %) and chloride (1.1 %). Accordingly, bulk aerosols appeared to be slightly acidic throughout this study, mainly related to the enhanced sulfate contribution. All chemical species peaked at the accumulation mode, indicating the well-mixed and highly aged aerosol particles at WLG from long-range transport. Positive matrix factorization (PMF) on the high-resolution organic mass spectra resolved four distinct organic aerosol (OA) components, including a traffic-related hydrocarbon-like OA (HOA), a relatively fresh biomass burning OA (BBOA), an aged biomass burning OA (agBBOA) and a more-oxidized oxygenated OA (OOA). On average, the two relatively oxidized OAs, OOA and agBBOA, contributed 34.4 % and 40.4 % of organics, respectively, while the rest were 18.4 % for BBOA and 6.8 % for HOA. Source analysis for air masses showed that higher mass concentrations of PM1 and enhanced contributions of sulfate and biomass-burning-related OA components (agBBOA + BBOA) were from the northeast of the WLG with shorter transport distance, whereas lower PM1 mass concentrations with enhanced OOA contribution were from the west after long-range transport, suggesting their distinct aerosol sources and significant impacts of regional transport on aerosol mass loadings and chemistry at WLG.

The Effect of Emission Control on the Submicron Particulate Matter Size Distribution in Hangzhou during the 2016 G20 Summit

A number of observational and modeling studies have been conducted in China to study the effectiveness of radical short-term emission control measures with regard to air quality improvement. However, none of them have focused on the effect on submicron aerosols. Measurements on the size distribution of particles as small as 3 nm were conducted before, during and after the source emission control period for the 2016 G20 Summit held in Hangzhou, a megacity in eastern China. The measurement provided a unique opportunity to gain insight into the sources of submicron aerosols in Hangzhou and the effectiveness of radical emission control strategies. A WRF-Chem simulation suggested that the sources inside the emission control region contributed more than 70% to PM1 in Hangzhou from September 2 to 7, 2016, even under the strictest control scheme. Source restrictions on emissions from coal-fired power plants, on-road vehicles and industrial VOCs resulted in concentration decreases for PM1, PM0.01 and PM0.1, respectively. New particle formation (NPF) events, which were not suppressed completely by the emission control, enhanced the maximum PM0.01 concentration, at around 11:00 AM, by a factor of 4 compared to non-NPF days. Even during the strictest emission control period, two PM1 episodes still occurred due to the dominance of subsidence airflows, a low wind speed, and a weak vertical temperature gradient.

Characterization of submicron aerosols at a suburban site in central China

We have characterized the chemical composition and sources of submicron aerosol (PM1) at a suburban site in Xinzhou in central China using an Aerosol Chemical Speciation Monitor from July 17 to September 5, 2014. The average (±1σ) PM1 concentration was 35.4 (±20.8) μg/m3 for the entire study period, indicating that Xinzhou was less polluted compared to the megacities in the North China Plain (NCP). The PM1 was mainly composed of organic aerosol and sulfate, on average accounting for 33.1% and 32.4%, respectively, followed by nitrate (14.4%) and ammonium (11.8%). Higher sulfate and lower nitrate contributions than those in megacities in the NCP elucidated an important emission source of coal combustion in central China. Three organic aerosol (OA) factors, i.e., hydrocarbon-like OA (HOA), semi-volatile oxygenated OA (SV-OOA) and low-volatility OOA (LV-OOA), were identified using positive matrix factorization. Secondary OA (=SV-OOA + LV-OOA) dominated OA, on average accounting for 82%, indicating that OA at the Xinzhou site was overall oxidized. We also observed relatively similar aerosol bulk composition and OA composition at low and high mass loading periods, and also from the different source areas, indicating that aerosol species were homogeneously distributed over a regional scale near the site for most of the time during this study. Slightly higher mass concentrations and sulfate contributions from the southern air masses were likely due to the transport from the polluted cities, such as Taiyuan to the south. In addition, the daily variation of PM1 in Xinzhou resembled that observed in Beijing, indicating that the wide-scale regional haze pollution often influences both the NCP and the central China.

Characteristics and sources of submicron aerosols above the urban canopy (260 m) in Beijing, China, during the 2014 APEC summit

Abstract. The megacity of Beijing has experienced frequent severe fine particle pollution during the last decade. Although the sources and formation mechanisms of aerosol particles have been extensively investigated on the basis of ground measurements, real-time characterization of aerosol particle composition and sources above the urban canopy in Beijing is rare. In this study, we conducted real-time measurements of non-refractory submicron aerosol (NR-PM1) composition at 260 m at the Beijing 325 m meteorological tower (BMT) from 10 October to 12 November 2014, by using an aerosol chemical speciation monitor (ACSM) along with synchronous measurements of size-resolved NR-PM1 composition near ground level using a high-resolution time-of-flight aerosol mass spectrometer (HR–ToF–AMS). The NR-PM1 composition above the urban canopy was dominated by organics (46 %), followed by nitrate (27 %) and sulfate (13 %). The high contribution of nitrate and high NO3− / SO42− mass ratios illustrates an important role of nitrate in particulate matter (PM) pollution during the study period. The organic aerosol (OA) was mainly composed of secondary OA (SOA), accounting for 61 % on an average. Different from that measured at the ground site, primary OA (POA) correlated moderately with SOA, likely suggesting a high contribution from regional transport above the urban canopy. The Asia–Pacific Economic Cooperation (APEC) summit with strict emission controls provides a unique opportunity to study the impacts of emission controls on aerosol chemistry. All aerosol species were shown to have significant decreases of 40–80 % during APEC from those measured before APEC, suggesting that emission controls over regional scales substantially reduced PM levels. However, the bulk aerosol composition was relatively similar before and during APEC as a result of synergetic controls of aerosol precursors. In addition to emission controls, the routine circulations of mountain–valley breezes were also found to play an important role in alleviating PM levels and achieving the "APEC blue" effect. The evolution of vertical differences between 260 m and the ground level was also investigated. Our results show complex vertical differences during the formation and evolution of severe haze episodes that are closely related to aerosol sources and boundary-layer dynamics.

Sources of submicron aerosol during fog-dominated wintertime at Kanpur

The main objective of this atmospheric study was to determine the major sources of PM1 (particles having aerodynamic diameter <1.0 μm) within and near the city of Kanpur, in the Indo-Gangetic Plain. Day and night, 10 h long each, filter-based aerosol samples were collected for 4 months (November 2009 to February 2010) throughout the winter season. These samples were subjected to gravimetric and quantitative chemical analyses for determining water-soluble ions (NH4 (+), F(-), Cl(-), NO3 (-), and SO4 (2-)) using an ion chromatograph and trace elements using an inductively coupled plasma-optical emission spectrometer. The mean PM1 mass concentrations were recorded as 114 ± 71 μg/m(3) (day) and 143 ± 86 μg/m(3) (night), respectively. A significantly higher diurnal contribution of ions (NH4 (+), F(-), Cl(-), NO3 (-), and SO4 (2-)) in PM1 mass was observed during the fog-affected days and nights throughout the winter season, for which the average values were recorded as 38.09 ± 13.39 % (day) and 34.98 ± 12.59 % (night), respectively, of the total PM1 mass. This chemical dataset was then used in a source-receptor model, UNMIX, and the model results are described in detail. UNMIX provided a maximum number of five source factors, including crustal material, composite vehicle, secondary aerosol, coal combustion, and iron/steel production and metallurgical industries, as the dominant air pollution sources for this study.

Spatial variation of chemical composition and sources of submicron aerosol in Zurich during wintertime using mobile aerosol mass spectrometer data

Abstract. Mobile measurements of PM1 (particulate matter with an aerodynamic diameter &lt;1 μm) chemical composition using a quadrupole aerosol mass spectrometer and a multi-angle absorption photometer were performed using the PSI mobile laboratory during winter 2007/2008 and December 2008 in the metropolitan area of Zurich, Switzerland. Positive matrix factorization (PMF) applied to the organic fraction of PM1 yielded 3 factors: Hydrocarbon-like organic aerosol (HOA) related to traffic emissions; organic aerosol from wood burning for domestic heating purposes (WBOA); and oxygenated organic aerosol (OOA), assigned to secondary organic aerosol formed by oxidation of volatile precursors. The chemical composition of PM1 was assessed for an urban background site and various sites throughout the city. The background site is dominated by secondary inorganic and organic species (57 %), BC, HOA, and WBOA account for 15 %, 6 %, and 12 %, respectively. As for the other sites, HOA is important along major roads (varying between 7 and 14 % of PM1 for different sites within the city, average all sites 8 %), domestic wood burning makes up between 8–15 % of PM1 for different sites within the city (average all sites 10.5 %). OOA makes up the largest fraction of organic aerosol (44 % on average). A new method allows for the separation and quantification of the local fraction of PM1 emitted or rapidly formed in the city, and the fraction of PM1 originating from the urban background. The method is based on simultaneous on-road mobile and stationary background measurements and the correction of small-scale meteorological effects using the ratio of on-road sulfate to stationary sulfate. Especially during thermal inversions over the Swiss plateau, urban background concentrations contribute substantially to particulate number concentrations (between 40 and 80 % depending on meteorological conditions and emissions, 60 % on average) as well as to the mass concentrations of PM1 components measured on road in downtown Zurich (between 30 and 90 %, on average 60 % for black carbon and HOA, and between 90 and 100 % for WBOA, OOA, and the measured inorganic components). The results emphasize, on a scientific level, the advantage of mobile measurements for distinguishing local from regional air pollution research, and on a political level, the importance of regional collaboration for mitigating air pollution issues.