We present 18 years (2001-2018) of aerosol measurements, including organic and elemental carbon (OC and EC), organic tracers (levoglucosan, arabitol, mannitol, trehalose, glucose, and ...2-methyltetrols), trace elements, and ions, at the Birkenes Observatory (southern Norway) - a site representative of the northern European region. The OC/EC (2001-2018) and the levoglucosan (2008-2018) time series are the longest in Europe, with OC/EC available for the PM.sub.10, PM.sub.2.5 (fine), and PM.sub.10-2.5 (coarse) size fractions, providing the opportunity for a nearly 2-decade-long assessment. Using positive matrix factorization (PMF), we identify seven carbonaceous aerosol sources at Birkenes: mineral-dust-dominated aerosol (MIN), traffic/industry-like aerosol (TRA/IND), short-range-transported biogenic secondary organic aerosol (BSOA.sub.SRT ), primary biological aerosol particles (PBAP), biomass burning aerosol (BB), ammonium-nitrate-dominated aerosol (NH.sub.4 NO.sub.3 ), and (one low carbon fraction) sea salt aerosol (SS).
In the present work, we conducted experiments of secondary organic aerosol (SOA) formation from urban cooking and vehicular sources to characterize the mass spectral features of primary organic ...aerosol (POA) and SOA using an high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). Our results showed that the cooking styles have a greater impact on aged COA (cooking organic aerosol) mass spectra than oxidation conditions. However, the oxidation conditions affect the aged HOA (hydrocarbon-like OA) spectra more significantly than vehicle operating conditions. In our study, we use mass spectra similarity analysis and positive matrix factorization (PMF) analysis to establish the POA and SOA mass spectra of these two sources. These mass spectra are used as source constraints in a multilinear engine (ME-2) model to apportion the OA (organic aerosol) sources in the atmosphere. Compared with the traditional ambient PMF results, the improved ME-2 model can better quantify the contribution of POA and SOA from cooking and vehicular sources. Our work, for the first time, establishes the vehicle and cooking SOA source profiles, and can be further used in the OA source apportionment in the ambient atmosphere.
The measurement of elements in PM10 was performed with 1 h time resolution at a rural freeway site during summer 2015 in Switzerland using the Xact1 625 Ambient Metals Monitor. On average the Xact ...elements (without accounting for oxygen and other associated elements) make up about 20 % of the total PM10 mass (14.6 µg m−3). We conducted source apportionment by positive matrix factorisation (PMF) of the
elemental mass measurable by the Xact (i.e. major elements heavier than
Al), defined here as PM10el. Eight different sources were identified in PM10el (elemental PM10) mass driven by the sum of 14 elements (notable elements in brackets): Fireworks-I (K, S, Ba and Cl), Fireworks-II (K), sea salt (Cl), secondary sulfate (S), background dust (Si, Ti), road dust (Ca), non-exhaust traffic-related elements (Fe) and industrial elements (Zn and Pb). The major components were secondary sulfate and non-exhaust traffic-related elements followed by background dust and road dust factors, explaining 21 %, 20 %, 18 % and 16 % of the analysed PM10 elemental mass, respectively, with the factor mass not corrected for oxygen content. Further, there were minor contributions (on the order of a few percent) of sea salt and industrial sources. The regionally influenced secondary sulfate factor showed negligible resuspension, and concentrations were similar throughout the day. The significant loads of the non-exhaust traffic-related and road dust factors with strong diurnal variations highlight the continuing importance of vehicle-related air pollutants at this site. Enhanced control of PMF implemented via the SourceFinder software (SoFi Pro version 6.2, PSI, Switzerland) allowed for a successful apportionment of transient sources such as the two firework factors and sea salt, which remained mixed when analysed by unconstrained PMF.
Particulate matter (PM) affects visibility, climate, and public health. Organic matter (OM), a uniquely complex portion of PM, can make up more than half of total atmospheric fine PM mass. We ...investigated the effect of aging on secondary organic aerosol (SOA) concentration and composition for wood burning (WB) and coal combustion (CC) emissions, two major atmospheric OM sources, using mid-infrared (MIR) spectroscopy and aerosol mass spectrometry (AMS). For this purpose, primary emissions were injected into an environmental chamber and aged using hydroxyl (diurnal aging) and nitrate (nocturnal aging) radicals to reach an atmospherically relevant oxidative age. A time-of-flight AMS instrument was used to measure the high-time-resolution composition of non-refractory fine PM, while fine PM was collected on PTFE filters before and after aging for MIR analysis. AMS and MIR spectroscopy indicate an approximately 3-fold enhancement of organic aerosol (OA) concentration after aging (not wall-loss corrected). The OM:OC ratios also agree closely between the two methods and increase, on average, from 1.6 before aging to 2 during the course of aging. MIR spectroscopy, which is able to differentiate among oxygenated groups, shows a distinct functional group composition for aged WB (high abundance of carboxylic acids) and CC OA (high abundance of non-acid carbonyls) and detects aromatics and polycyclic aromatic hydrocarbons (PAHs) in emissions of both sources. The MIR spectra of fresh WB and CC aerosols are reminiscent of their parent compounds with differences in specific oxygenated functional groups after aging, consistent with expected oxidation pathways for volatile organic compounds (VOCs) of each emission source. The AMS mass spectra also show variations due to source and aging that are consistent with the MIR functional group (FG) analysis. Finally, a comparison of the MIR spectra of aged chamber WB OA with that of ambient samples affected by residential wood burning and wildfires reveals similarities regarding the high abundance of organics, especially acids, and the visible signatures of lignin and levoglucosan. This finding is beneficial for the source identification of atmospheric aerosols and interpretation of their complex MIR spectra.
The reversible partitioning of glyoxal was studied in simulation chamber experiments for the first time by time-resolved measurements of gas-phase and particle-phase concentrations in ...sulfate-containing aerosols. Two complementary methods for the measurement of glyoxal particle-phase concentrations are compared: (1) an offline method utilizing filter sampling of chamber aerosols followed by HPLC-MS/MS analysis and (2) positive matrix factorization (PMF) analysis of aerosol mass spectrometer (AMS) data. Ammonium sulfate (AS) and internally mixed ammonium sulfate/fulvic acid (AS/FA) seed aerosols both show an exponential increase of effective Henry’s law coefficients (K H,eff) with AS concentration (c AS, in mol kg–1 aerosol liquid water, m = molality) and sulfate ionic strength, I(SO4 2–) (m). A modified Setschenow plot confirmed that “salting-in” of glyoxal is responsible for the increased partitioning. The salting constant for glyoxal in AS is K S CHOCHO = (−0.24 ± 0.02) m –1, and found to be independent of the presence of FA. The reversible glyoxal uptake can be described by two distinct reservoirs for monomers and higher molecular weight species filling up at characteristic time constants. These time constants are τ1 ≈ 102 s and τ2 ≈ 104 s at c AS < 12 m, and about 1–2 orders of magnitude slower at higher c AS, suggesting that glyoxal uptake is kinetically limited at high salt concentrations.
Elemental carbon (EC) or black carbon (BC) in the atmosphere has a strong influence on both climate and human health. In this study, radiocarbon (14C) based source apportionment is used to ...distinguish between fossil fuel and biomass burning sources of EC isolated from aerosol filter samples collected in Beijing from June 2010 to May 2011. The 14C results demonstrate that EC is consistently dominated by fossil-fuel combustion throughout the whole year with a mean contribution of 79% ± 6% (ranging from 70% to 91%), though EC has a higher mean and peak concentrations in the cold season. The seasonal molecular pattern of hopanes (i.e., a class of organic markers mainly emitted during the combustion of different fossil fuels) indicates that traffic-related emissions are the most important fossil source in the warm period and coal combustion emissions are significantly increased in the cold season. By combining 14C based source apportionment results and picene (i.e., an organic marker for coal emissions) concentrations, relative contributions from coal (mainly from residential bituminous coal) and vehicle to EC in the cold period were estimated as 25 ± 4% and 50 ± 7%, respectively, whereas the coal combustion contribution was negligible or very small in the warm period.
Particulate matter (PM) pollution is a severe environmental problem in the Beijing–Tianjin–Hebei (BTH) region in North
China. PM studies have been conducted extensively in Beijing, but the
chemical ...composition, sources, and atmospheric processes of PM are still
relatively less known in nearby Tianjin and Hebei. In this study, fine PM
in urban Shijiazhuang (the capital of Hebei Province) was characterized using
an Aerodyne quadrupole aerosol chemical speciation monitor (Q-ACSM) from
11 January to 18 February in 2014. The average mass concentration of
non-refractory submicron PM (diameter <1 µm, NR-PM1) was
178±101 µg m−3, and it was composed of 50 % organic aerosol
(OA), 21 % sulfate, 12 % nitrate, 11 % ammonium, and 6 % chloride.
Using the multilinear engine (ME-2) receptor model, five OA sources were
identified and quantified, including hydrocarbon-like OA from vehicle
emissions (HOA, 13 %), cooking OA (COA, 16 %), biomass burning OA (BBOA,
17 %), coal combustion OA (CCOA, 27 %), and oxygenated OA (OOA, 27 %).
We found that secondary formation contributed substantially to PM in episodic
events, whereas primary emissions were dominant (most significant) on average.
The episodic events with the highest NR-PM1 mass range of
300–360 µg m−3 were comprised of 55 % of secondary species. On the
contrary, a campaign-average low OOA fraction (27 %) in OA indicated the
importance of primary emissions, and a low sulfur oxidation degree
(FSO4) of 0.18 even at RH >90 % hinted at insufficient
oxidation. These results suggested that in Shijiazhuang in wintertime fine PM
was mostly from primary emissions without sufficient atmospheric aging,
indicating opportunities for air quality improvement by mitigating direct
emissions. In addition, secondary inorganic and organic (OOA) species
dominated in pollution events with high-RH conditions, most likely due to
enhanced aqueous-phase chemistry, whereas primary organic aerosol (POA)
dominated in pollution events with low-RH and stagnant conditions. These
results also highlighted the importance of meteorological conditions for PM
pollution in this highly polluted city in North China.
Gasoline direct injection (GDI) vehicles have recently been identified as a
significant source of carbonaceous aerosol, of both primary and secondary
origin. Here we investigated primary emissions ...and secondary organic aerosol
(SOA) from four GDI vehicles, two of which were also retrofitted with a
prototype gasoline particulate filter (GPF). We studied two driving test
cycles under cold- and hot-engine conditions. Emissions were characterized by
proton transfer reaction time-of-flight mass spectrometry (gaseous
non-methane organic compounds, NMOCs), aerosol mass spectrometry (sub-micron
non-refractory particles) and light attenuation measurements (equivalent
black carbon (eBC) determination using Aethalometers) together with
supporting instrumentation. Atmospheric processing was simulated using the
PSI mobile smog chamber (SC) and the potential aerosol mass oxidation flow
reactor (OFR). Overall, primary and secondary particulate matter (PM) and
NMOC emissions were dominated by the engine cold start, i.e., before thermal
activation of the catalytic after-treatment system. Trends in the
SOA oxygen to carbon ratio (O : C) for OFR and SC were
related to different OH exposures, but divergences in the H : C remained
unexplained. SOA yields agreed within experimental variability between the
two systems, with a tendency for higher values in the OFR than in the SC (or,
vice versa, lower values in the SC). A few aromatic compounds dominated the
NMOC emissions, primarily benzene, toluene, xylene isomers/ethylbenzene and
C3-benzene. A significant fraction of the SOA was explained by those
compounds, based on comparison of effective SOA yield curves with those of
toluene, o-xylene and 1,2,4-trimethylbenzene determined in our OFR, as well
as others from literature. Remaining discrepancies, which were smaller in the
SC and larger in the OFR, were up to a factor of 2 and may have resulted from
diverse reasons including unaccounted precursors and matrix effects. GPF
retrofitting significantly reduced primary PM through removal of refractory
eBC and partially removed the minor POA fraction. At cold-started conditions
it did not affect hydrocarbon emission factors, relative chemical composition
of NMOCs or SOA formation, and likewise SOA yields and bulk composition
remained unaffected. GPF-induced effects at hot-engine conditions
deserve attention in further studies.
Delhi, the capital of India, suffers from heavy local emissions as well as regional transport of air pollutants, resulting in severe aerosol loadings. To determine the sources of these pollutants, we ...have quantified the mass concentrations of 26 elements in airborne particles, measured by an online X-ray fluorescence spectrometer with time resolution between 30 min and 1 h. Measurements of PM10 and PM2.5 (particulate matter <10 μm and < 2.5 μm) were conducted during two consecutive winters (2018 and 2019) in Delhi. On average, 26 elements from Al to Pb made up ~25% and ~19% of the total PM10 mass (271 μg m−3 and 300 μg m−3) in 2018 and 2019, respectively. Nine different aerosol sources were identified during both winters using positive matrix factorization (PMF), including dust, non-exhaust, an S-rich factor, two solid fuel combustion (SFC) factors and four industrial/combustion factors related to plume events (Cr-Ni-Mn, Cu-Cd-Pb, Pb-Sn-Se and Cl-Br-Se). All factors were resolved in both size ranges (but varying relative concentrations), comprising the following contributions to the elemental PM10 mass (in % average for 2018 and 2019): Cl-Br-Se (41.5%, 36.9%), dust (27.6%, 28.7%), non-exhaust (16.2%, 13.7%), S-rich (6.9%, 9.2%), SFC1 + SFC2 (4%, 7%), Pb-Sn-Se (2.3%, 1.66%), Cu-Cd-Pb (0.67%, 2.2%) and Cr-Ni-Mn (0.57%, 0.47%). Most of these sources had the highest relative contributions during late night (22:00 local time (LT)) and early morning hours (between 03:00 to 08:00 LT), which is consistent with enhanced emissions into a shallow boundary layer. Modelling of airmass source geography revealed that the Pb-Sn-Se, Cl-Br-Se and SFC2 factors prevailed for northwest winds (Pakistan, Punjab, Haryana and Delhi), while the Cu-Cd-Pb and S-rich factors originated from east (Nepal and Uttar Pradesh) and the Cr-Ni-Mn factor from northeast (Uttar Pradesh). In contrast, SFC1, dust and non-exhaust were not associated with any specific wind direction.
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•Quantified highly time-resolved elements in PM10 and PM2.5 in Delhi during winters•Source apportionment was improved combining receptor model and trajectory analysis.•Major PM10 elemental constituents were Cl, S and crustal elements (Si, Ca, Ti, Fe).•Northwest and east were the most influential source regions for various sources.
Source apportionment of organic carbon (OC) and elemental carbon (EC) from PM1 (particulate matter with a diameter equal to or smaller than 1 μm) in Beijing, China was carried out using radiocarbon ...(14C) measurement. Despite a dominant fossil-fuel contribution to EC due to large emissions from traffic and coal combustion, nonfossil sources are dominant contributors of OC in Beijing throughout the year except during the winter. Primary emission was the most important contributor to fossil-fuel derived OC for all seasons. A clear seasonal trend was found for biomass-burning contribution to OC with the highest in autumn and spring, followed by winter and summer. 14C results were also integrated with those from positive matrix factorization (PMF) of organic aerosols from aerosol mass spectrometer (AMS) measurements during winter and spring. The results suggest that the fossil-derived primary OC was dominated by coal combustion emissions whereas secondary OC was mostly from fossil-fuel emissions. Taken together with previous 14C studies in Asia, Europe and USA, a ubiquity and dominance of nonfossil contribution to OC aerosols is identified not only in rural/background/remote regions but also in urban regions, which may be explained by cooking contributions, regional transportation or local emissions of seasonal-dependent biomass burning emission. In addition, biogenic and biomass burning derived SOA may be further enhanced by unresolved atmospheric processes.
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