Advanced source apportionment of carbonaceous aerosols by coupling offline AMS and radiocarbon size segregated measurements over a nearly two-year period

Abstract. Carbonaceous aerosols are related to adverse human health effects. Therefore, identification of their sources and analysis of their chemical composition is important. The offline AMS technique offers quantitative separation of organic aerosol (OA) factors that can be related to major OA sources either primary or secondary. While primary OA can be more clearly separated into sources, secondary (SOA) source apportionment is more challenging because different sources – anthropogenic or natural, fossil or non-fossil – can yield similar highly oxygenated mass spectra. Radiocarbon measurements provide unequivocal separation between fossil and non-fossil sources of carbon. Here we coupled these two offline methods and analysed the OA and organic carbon (OC) of different size fractions (particulate matter below 10 and 2.5 µm – PM10 and PM2.5, respectively) from the Alpine valley of Magadino (Switzerland) during the years 2013 and 2014 (219 samples). The combination of the techniques gave further insights into the characteristics of secondary OC (SOC) which rather based on the type of SOC precursor and not on the volatility or the oxidation state of OC, as typically considered. Out of the primary sources separated in this study, biomass burning OC was the dominant one in winter with average concentrations of 5.36 ± 2.64 µg m−3 for PM10 and 3.83 ± 1.81 µg m−3 for PM2.5, indicating that wood combustion particles were predominantly generated in the fine mode. The additional information from the size segregated measurements revealed a primary sulphur containing factor, mainly fossil, detected in the coarse size fraction and related to non-exhaust traffic emissions with average yearly PM10 (PM2.5) concentration of 0.20 ± 0.24 µg m−3 (0.05 ± 0.04 µg m−3). A primary biological OC was also detected in the coarse mode peaking in spring and summer with yearly average concentrations for PM10 (PM2.5) 0.79 ± 0.31 µg m−3 (0.24 ± 0.20 µg m−3). The secondary OC was separated into two oxygenated, non-fossil OC factors which were identified based on their seasonal variability (i.e. summer and winter OOC) and a third fossil OOC factor which correlated with fossil OC mainly peaking in winter and spring with PM10 (PM2.5) contributing on average 13 % ± 7 % (10 % ± 9 %) to the total OC. The winter OOC was connected to anthropogenic sources, with PM10 (PM2.5) contributing on average 13 % ± 13 % (6 % ± 6 %) to the total OC. The summer OOC, stemming from oxidation of biogenic emissions was more pronounced in the fine mode with PM10 (PM2.5) contributing on average 43%±12% (75 % ± 44 %) to the total OC. In total the non-fossil OC far dominated the fossil OC throughout all seasons, by contributing on average 75 % ± 24 % to the total OC. The results also suggested that during the cold period the prevailing source was residential biomass burning while during the warm period primary biological sources and secondary organic aerosol from the oxidation of biogenic emissions became important. However, SOC was also formed by aged fossil fuel combustion emissions not only in summer but also during the rest of the year.

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Advanced source apportionment of carbonaceous aerosols by coupling offline AMS and radiocarbon size-segregated measurements over a nearly 2-year period

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-6187-2018 ◽

2018 ◽

Vol 18 (9) ◽

pp. 6187-6206 ◽

Cited By ~ 20

Author(s):

Athanasia Vlachou ◽

Kaspar R. Daellenbach ◽

Carlo Bozzetti ◽

Benjamin Chazeau ◽

Gary A. Salazar ◽

...

Keyword(s):

Organic Carbon ◽

Source Apportionment ◽

Biomass Burning ◽

Organic Aerosol ◽

Anthropogenic Sources ◽

Biogenic Emissions ◽

Carbonaceous Aerosols ◽

Yearly Average ◽

Fine Mode ◽

Pm2.5 Concentration

Abstract. Carbonaceous aerosols are related to adverse human health effects. Therefore, identification of their sources and analysis of their chemical composition is important. The offline AMS (aerosol mass spectrometer) technique offers quantitative separation of organic aerosol (OA) factors which can be related to major OA sources, either primary or secondary. While primary OA can be more clearly separated into sources, secondary (SOA) source apportionment is more challenging because different sources – anthropogenic or natural, fossil or non-fossil – can yield similar highly oxygenated mass spectra. Radiocarbon measurements provide unequivocal separation between fossil and non-fossil sources of carbon. Here we coupled these two offline methods and analysed the OA and organic carbon (OC) of different size fractions (particulate matter below 10 and 2.5 µm – PM10 and PM2.5, respectively) from the Alpine valley of Magadino (Switzerland) during the years 2013 and 2014 (219 samples). The combination of the techniques gave further insight into the characteristics of secondary OC (SOC) which was rather based on the type of SOC precursor and not on the volatility or the oxidation state of OC, as typically considered. Out of the primary sources separated in this study, biomass burning OC was the dominant one in winter, with average concentrations of 5.36 ± 2.64 µg m−3 for PM10 and 3.83 ± 1.81 µg m−3 for PM2.5, indicating that wood combustion particles were predominantly generated in the fine mode. The additional information from the size-segregated measurements revealed a primary sulfur-containing factor, mainly fossil, detected in the coarse size fraction and related to non-exhaust traffic emissions with a yearly average PM10 (PM2.5) concentration of 0.20 ± 0.24 µg m−3 (0.05 ± 0.04 µg m−3). A primary biological OC (PBOC) was also detected in the coarse mode peaking in spring and summer with a yearly average PM10 (PM2.5) concentration of 0.79 ± 0.31 µg m−3 (0.24 ± 0.20 µg m−3). The secondary OC was separated into two oxygenated, non-fossil OC factors which were identified based on their seasonal variability (i.e. summer and winter oxygenated organic carbon, OOC) and a third anthropogenic OOC factor which correlated with fossil OC mainly peaking in winter and spring, contributing on average 13 % ± 7 % (10 % ± 9 %) to the total OC in PM10 (PM2.5). The winter OOC was also connected to anthropogenic sources, contributing on average 13 % ± 13 % (6 % ± 6 %) to the total OC in PM10 (PM2.5). The summer OOC (SOOC), stemming from oxidation of biogenic emissions, was more pronounced in the fine mode, contributing on average 43 % ± 12 % (75 % ± 44 %) to the total OC in PM10 (PM2.5). In total the non-fossil OC significantly dominated the fossil OC throughout all seasons, by contributing on average 75 % ± 24 % to the total OC. The results also suggested that during the cold period the prevailing source was residential biomass burning while during the warm period primary biological sources and secondary organic aerosol from the oxidation of biogenic emissions became important. However, SOC was also formed by aged fossil fuel combustion emissions not only in summer but also during the rest of the year.

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Long-term chemical analysis and organic aerosol source apportionment at 9 sites in Central Europe: Source identification and uncertainty assessment

10.5194/acp-2017-124 ◽

2017 ◽

Cited By ~ 1

Author(s):

Kaspar R. Daellenbach ◽

Giulia Stefenelli ◽

Carlo Bozzetti ◽

Athanasia Vlachou ◽

Paola Fermo ◽

...

Keyword(s):

Source Apportionment ◽

Central Europe ◽

Organic Aerosol ◽

Epidemiological Studies ◽

Alpine Valley ◽

Enhanced Production ◽

Inorganic Species ◽

Yearly Average ◽

Average Factor

Abstract. Long-term monitoring of the organic aerosol is important for epidemiological studies, validation of atmospheric models, and air quality management. In this study, we apply a recently developed filter-based offline methodology of the aerosol mass spectrometer to investigate the regional and seasonal differences of contributing organic aerosol sources. We present offline-AMS measurements for particulate matter smaller than 10 μm 9 stations in central Europe with different exposure characteristics for the entire year of 2013 (819 samples). The focus of this study is a detailed source apportionment analysis (using PMF) including in-depth assessment of the related uncertainties. Primary organic aerosol (POA) is separated in three components: hydrocarbon-like OA which is related to traffic emissions (HOA), cooking OA (COA), and biomass-burning OA (BBOA). We observe enhanced production of secondary organic aerosol (SOA) in summer, following the increase in biogenic emissions with temperature (summer oxygenated OA, SOOA). In addition, a SOA component was extracted that correlated with anthropogenic secondary inorganic species which is dominant in winter (winter oxygenated OA, WOOA). A factor (SC-OA) explaining sulfur-containing fragments (CH3SO2+), which has an event-driven temporal behavior, was also identified. The relative yearly average factor contributions range for HOA from 3 to 15 %, for COA from 3 to 31 %, for BBOA from 11 to 61 %, for SC-OA from 5 to 23 %, for WOOA from 14 to 28 %, and for SOOA from 14 to 40 %. The uncertainty of the relative average factor contribution lies between 5 and 9 % of OA. At the sites north of the alpine crest, the sum of HOA, COA, and BBOA (POA) contributes less to OA (POA/OA = 0.3) than at the southern alpine valley sites (0.6). BBOA is the main contributor to POA with 88 % in alpine valleys and 43 % north of the alpine crest. Furthermore, the influence of primary biological particles (PBOA), not resolved by PMF, is estimated and could contribute significantly to OA in PM10.

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Time dependent source apportionment of submicron organic aerosol for a rural site in an alpine valley using a rolling PMF window

10.5194/acp-2020-1263 ◽

2020 ◽

Author(s):

Gang Chen ◽

Yulia Sosedova ◽

Francesco Canonaco ◽

Roman Fröhlich ◽

Anna Tobler ◽

...

Keyword(s):

Source Apportionment ◽

Biomass Burning ◽

Role Model ◽

Organic Aerosol ◽

Temporal Variations ◽

Time Dependent ◽

Rural Site ◽

Oxidation Processes ◽

Rolling Mechanism ◽

Yearly Average

Abstract. We have collected one year of aerosol chemical speciation monitor (ACSM) data in Magadino, a village located in the south of the Swiss Alpine region, which is one of the most polluted areas in Switzerland. We analysed the mass spectra of organic aerosol (OA) by positive matrix factorization (PMF) using Source Finder Professional (SoFi Pro) to retrieve the origins of OA. Therein, we deployed the rolling algorithm to account for the temporal changes of the source profiles, which is closer to the real world. As the first ever application of rolling PMF analysis for a rural cite, we resolved two primary OA factors (traffic-related hydrocarbon-like OA (HOA) and biomass burning OA (BBOA)), one local OA (LOA) factor, a less oxidized oxygenated OA (LO-OOA) factor, and a more oxidized oxygenated OA (MO-OOA) factor. HOA showed stable contributions to the total OA through the whole year ranging from 8.1–10.1 %, while the contribution of BBOA showed a clear seasonal variation with a range of 8.3–27.4 % (highest during winter, lowest during summer) and a yearly average of 17.1 %. The OOA was represented by two factors (LO-OOA and MO-OOA) throughout the year. OOA contributed 71.6 % of the OA mass, varying from 62.5 % (in winter) to 78 % (in spring and summer). The uncertainties (σ) for the modelled OA factors (i.e., rotational uncertainty and statistical variability of the sources) varied from ±4 % (LOA) to a maximum of ±40 % (LO-OOA). Considering the fact that BBOA and LO-OOA (showing influences of biomass burning in winter) had significant contributions to the total OA mass, we suggest a reduction and control of the residential heating as a mitigation strategy for better air quality and lower PM levels in this region. In Appendix A, we conducted a head-to-head comparison between the conventional seasonal PMF analysis and the rolling mechanism. It showed similar or slightly improved results in terms of mass concentrations, correlations with external tracers and factor profiles of the constrained POA factors. The rolling results show smaller scaled residuals and enhanced correlations between OOA factors and corresponding inorganic salts than those of the seasonal solutions, was most likely because the rolling PMF analysis can capture the temporal variations of the oxidation processes for OOA sources. Specifically, the time dependent factor profiles of MO-OOA and LO-OOA can well explain the temporal viabilities of two main ions for OOA factors, m/z 44 (CO2+) and m/z 43 (mostly C2H3O+). This rolling PMF analysis therefore provides a more realistic source apportionment (SA) solution, with time-dependent OA sources. The rolling results show also good agreement with offline Aerodyne aerosol mass spectrometer (AMS) SA results from filter samples, except for winter. This is likely because the online measurement is capable of capturing the fast oxidation processes of biomass burning sources. This study demonstrates the strengths of the rolling mechanism and provides a comprehensive criterion list for ACSM users to obtain reproducible SA results and is a role model for similar analyses of such world-wide available data.

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Six-year source apportionment of submicron organic aerosols from near-continuous measurements at SIRTA (Paris area, France)

10.5194/acp-2019-515 ◽

2019 ◽

Author(s):

Yunjiang Zhang ◽

Olivier Favez ◽

Jean-Eudes Petit ◽

Francesco Canonaco ◽

Francois Truong ◽

...

Keyword(s):

Source Apportionment ◽

Biomass Burning ◽

Ambient Air ◽

Carbonaceous Aerosols ◽

Time Resolved ◽

Pronounced Increase ◽

Paris Area ◽

Multi Wavelength ◽

High Concentrations

Abstract. Organic aerosol (OA) particles are recognized as key factors influencing air quality and climate change. However, highly-time resolved year-round characterizations of their composition and sources in ambient air are still very limited due to challenging continuous observations. Here, we present an analysis of long-term variability of submicron OA using the combination of Aerosol Chemical Speciation Monitor (ACSM) and multi-wavelength aethalometer from November 2011 to March 2018 at a background site of the Paris region (France). Source apportionment of OA was achieved via partially constrained positive matrix factorization (PMF) using the multilinear engine (ME-2). Two primary OA (POA) and two oxygenated OA (OOA) factors were identified and quantified over the entire studied period. POA factors were designated as hydrocarbon-like OA (HOA) and biomass burning OA (BBOA). The latter factor presented a significant seasonality with higher concentrations in winter with significant monthly contributions to OA (18–33 %) due to enhanced residential wood burning emissions. HOA mainly originated from traffic emissions but was also influenced by biomass burning in cold periods. OOA factors were distinguished between their less- and more-oxidized fractions (LO-OOA and MO-OOA, respectively). These factors presented distinct seasonal patterns, associated with different atmospheric formation pathways. A pronounced increase of LO-OOA concentrations and contributions (50–66 %) was observed in summer, which may be mainly explained by secondary OA (SOA) formation processes involving biogenic gaseous precursors. Conversely high concentrations and OA contributions (32–62 %) of MO-OOA during winter and spring seasons were partly associated with anthropogenic emissions and/or long-range transport from northeastern Europe. The contribution of the different OA factors as a function of OA mass loading highlighted the dominant roles of POA during pollution episodes in fall and winter, and of SOA for highest springtime and summertime OA concentrations. Finally, long-term trend analyses indicated a decreasing feature (of about 200 ng m−3 yr−1) for MO-OOA, very limited or insignificant decreasing trends for primary anthropogenic carbonaceous aerosols (BBOA and HOA, along with the fossil fuel and biomass burning black carbon components), and no trend for LO-OOA over the 6+-year investigated period.

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Sources of organic aerosols in Europe: a modeling study using CAMx with modified volatility basis set scheme

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-15247-2019 ◽

2019 ◽

Vol 19 (24) ◽

pp. 15247-15270 ◽

Cited By ~ 3

Author(s):

Jianhui Jiang ◽

Sebnem Aksoyoglu ◽

Imad El-Haddad ◽

Giancarlo Ciarelli ◽

Hugo A. C. Denier van der Gon ◽

...

Keyword(s):

Air Quality ◽

Source Apportionment ◽

Biomass Burning ◽

Agricultural Waste ◽

Organic Aerosols ◽

Basis Set ◽

Anthropogenic Sources ◽

Wood Burning ◽

Gasoline Vehicles

Abstract. Source apportionment of organic aerosols (OAs) is of great importance to better understand the health impact and climate effects of particulate matter air pollution. Air quality models are used as potential tools to identify OA components and sources at high spatial and temporal resolution; however, they generally underestimate OA concentrations, and comparisons of their outputs with an extended set of measurements are still rare due to the lack of long-term experimental data. In this study, we addressed such challenges at the European level. Using the regional Comprehensive Air Quality Model with Extensions (CAMx) and a volatility basis set (VBS) scheme which was optimized based on recent chamber experiments with wood burning and diesel vehicle emissions, and which contains more source-specific sets compared to previous studies, we calculated the contribution of OA components and defined their sources over a whole-year period (2011). We modeled separately the primary and secondary OA contributions from old and new diesel and gasoline vehicles, biomass burning (mostly residential wood burning and agricultural waste burning excluding wildfires), other anthropogenic sources (mainly shipping, industry and energy production) and biogenic sources. An important feature of this study is that we evaluated the model results with measurements over a longer period than in previous studies, which strengthens our confidence in our modeled source apportionment results. Comparison against positive matrix factorization (PMF) analyses of aerosol mass spectrometric measurements at nine European sites suggested that the modified VBS scheme improved the model performance for total OA as well as the OA components, including hydrocarbon-like (HOA), biomass burning (BBOA) and oxygenated components (OOA). By using the modified VBS scheme, the mean bias of OOA was reduced from −1.3 to −0.4 µg m−3 corresponding to a reduction of mean fractional bias from −45 % to −20 %. The winter OOA simulation, which was largely underestimated in previous studies, was improved by 29 % to 42 % among the evaluated sites compared to the default parameterization. Wood burning was the dominant OA source in winter (61 %), while biogenic emissions contributed ∼ 55 % to OA during summer in Europe on average. In both seasons, other anthropogenic sources comprised the second largest component (9 % in winter and 19 % in summer as domain average), while the average contributions of diesel and gasoline vehicles were rather small (∼ 5 %) except for the metropolitan areas where the highest contribution reached 31 %. The results indicate the need to improve the emission inventory to include currently missing and highly uncertain local emissions, as well as further improvement of VBS parameterization for winter biomass burning. Although this study focused on Europe, it can be applied in any other part of the globe. This study highlights the ability of long-term measurements and source apportionment modeling to validate and improve emission inventories, and identify sources not yet properly included in existing inventories.

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The impact of biomass burning and aqueous-phase processing on air quality: a multi-year source apportionment study in the Po Valley, Italy

10.5194/acp-2019-274 ◽

2019 ◽

Cited By ~ 1

Author(s):

Marco Paglione ◽

Stefania Gilardoni ◽

Matteo Rinaldi ◽

Stefano Decesari ◽

Nicola Zanca ◽

...

Keyword(s):

Air Quality ◽

Source Apportionment ◽

Biomass Burning ◽

Organic Aerosol ◽

Cold Season ◽

World Health ◽

Rural Site ◽

Urban Site ◽

Urban Background ◽

Po Valley

Abstract. The Po Valley (Italy) is a well-known air quality hotspot characterized by Particulate Matter (PM) levels well above the limit set by the European Air Quality Directive and by the World Health Organization, especially during the colder season. In the framework of the Emilia-Romagna regional project SUPERSITO, the southern Po Valley submicron aerosol chemical composition was characterized by means of High-Resolution Aerosol Mass Spectroscopy (HR-AMS) with the specific aim of organic aerosol (OA) characterization and source apportionment. Eight intensive observation periods (IOPs) were carried out over four years (from 2011 to 2014) at two different sites (Bologna, BO, urban background and San Pietro Capofiume, SPC, rural background), to characterize the spatial variability and seasonality of the OA sources, with a special focus on the cold season. On the multi-year basis of the study, the AMS observations show that OA accounts for an average 45 ± 8 % (ranging 33–58 %) and 46 ± 7 % (ranging 36–50 %) of the total non-refractory submicron particle mass (PM1-NR) at the urban and at the rural site, respectively. Primary organic aerosol (POA) comprises biomass burning (23 ± 13 % of OA) and fossil fuel (12 ± 7 %) contributions with a marked seasonality in concentration. As expected, the biomass burning contribution to POA is more significant at the rural site (urban/rural concentrations ratio of 0.67), but it is also an important source of POA at the urban site during the cold season, with contributions ranging from 14 to 38 % of the total OA mass. Secondary organic aerosol (SOA) contribute to OA mass to a much larger extent than POA at both sites throughout the year (69 ± 16 % and 83 ± 16 % at urban and rural, respectively), with important implications for public health. Within the secondary fraction of OA, the measurements highlight the importance of biomass burning ageing products during the cold season, even at the urban background site. This biomass burning SOA fraction represents 14–44 % of the total OA mass in the cold season, indicating that in this region a major contribution of combustion sources to PM mass is mediated by environmental conditions and atmospheric reactivity. Among the environmental factors controlling the formation of SOA in the Po Valley, the availability of liquid water in the aerosol was shown to play a key role in the cold season. We estimate that organic fraction originating from aqueous reactions of biomass burning products (bb-aqSOA) represents 21 % (14–28 %) and 25 % (14–35 %) of the total OA mass and 44 % (32–56 %) and 61 % (21–100 %) of the SOA mass at the urban and rural sites, respectively.

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Six-year source apportionment of submicron organic aerosols from near-continuous highly time-resolved measurements at SIRTA (Paris area, France)

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-14755-2019 ◽

2019 ◽

Vol 19 (23) ◽

pp. 14755-14776 ◽

Cited By ~ 8

Author(s):

Yunjiang Zhang ◽

Olivier Favez ◽

Jean-Eudes Petit ◽

Francesco Canonaco ◽

Francois Truong ◽

...

Keyword(s):

Source Apportionment ◽

Biomass Burning ◽

Ambient Air ◽

Carbonaceous Aerosols ◽

Time Resolved ◽

Pronounced Increase ◽

Paris Area ◽

Range Transport ◽

High Concentrations

Abstract. Organic aerosol (OA) particles are recognized as key factors influencing air quality and climate change. However, highly time-resolved long-term characterizations of their composition and sources in ambient air are still very limited due to challenging continuous observations. Here, we present an analysis of long-term variability of submicron OA using the combination of an aerosol chemical speciation monitor (ACSM) and a multiwavelength Aethalometer from November 2011 to March 2018 at a peri-urban background site of the Paris region (France). Source apportionment of OA was achieved via partially constrained positive matrix factorization (PMF) using the multilinear engine (ME-2). Two primary OA (POA) and two oxygenated OA (OOA) factors were identified and quantified over the entire studied period. POA factors were designated as hydrocarbon-like OA (HOA) and biomass burning OA (BBOA). The latter factor presented a significant seasonality with higher concentrations in winter with significant monthly contributions to OA (18 %–33 %) due to enhanced residential wood burning emissions. HOA mainly originated from traffic emissions but was also influenced by biomass burning in cold periods. OOA factors were distinguished between their less- and more-oxidized fractions (LO-OOA and MO-OOA, respectively). These factors presented distinct seasonal patterns, associated with different atmospheric formation pathways. A pronounced increase in LO-OOA concentrations and contributions (50 %–66 %) was observed in summer, which may be mainly explained by secondary OA (SOA) formation processes involving biogenic gaseous precursors. Conversely, high concentrations and OA contributions (32 %–62 %) of MO-OOA during winter and spring seasons were partly associated with anthropogenic emissions and/or long-range transport from northeastern Europe. The contribution of the different OA factors as a function of OA mass loading highlighted the dominant roles of POA during pollution episodes in fall and winter and of SOA for highest springtime and summertime OA concentrations. Finally, long-term trend analyses indicated a decreasing feature (of about −175 ng m−3 yr−1) for MO-OOA, very limited or insignificant decreasing trends for primary anthropogenic carbonaceous aerosols (BBOA and HOA, along with the fossil-fuel and biomass-burning black carbon components) and no statistically significant trend for LO-OOA over the 6-year investigated period.

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Organic aerosol source apportionment in Zurich using an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS) – Part 2: Biomass burning influences in winter

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-8037-2019 ◽

2019 ◽

Vol 19 (12) ◽

pp. 8037-8062 ◽

Cited By ~ 15

Author(s):

Lu Qi ◽

Mindong Chen ◽

Giulia Stefenelli ◽

Veronika Pospisilova ◽

Yandong Tong ◽

...

Keyword(s):

Electrospray Ionization ◽

Source Apportionment ◽

Mass Spectrometer ◽

Biomass Burning ◽

Time Of Flight ◽

Organic Aerosol ◽

Climate Impacts ◽

Ionization Time ◽

Flight Mass Spectrometer ◽

Tof Ms

Abstract. Real-time, in situ molecular composition measurements of the organic fraction of fine particulate matter (PM2.5) remain challenging, hindering a full understanding of the climate impacts and health effects of PM2.5. In particular, the thermal decomposition and ionization-induced fragmentation affecting current techniques has limited a detailed investigation of secondary organic aerosol (SOA), which typically dominates OA. Here we deploy a novel extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS) during winter 2017 in downtown Zurich, Switzerland, which overcomes these limitations, together with an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS) and supporting instrumentation. Positive matrix factorization (PMF) implemented within the Multilinear Engine (ME-2) program was applied to the EESI-TOF-MS data to quantify the primary and secondary contributions to OA. An 11-factor solution was selected as the best representation of the data, including five primary and six secondary factors. Primary factors showed influence from cooking, cigarette smoke, biomass burning (two factors) and a special local unknown event occurred only during two nights. Secondary factors were affected by biomass burning (three factors, distinguished by temperature and/or wind direction), organonitrates, monoterpene oxidation, and undetermined regional processing, in particular the contributions of wood combustion. While the AMS attributed slightly over half the OA mass to SOA but did not identify its source, the EESI-TOF-MS showed that most (>70 %) of the SOA was derived from biomass burning. Together with significant contributions from less aged biomass burning factors identified by both AMS and EESI-TOF-MS, this firmly establishes biomass burning as the single most important contributor to OA mass at this site during winter. High correlation was obtained between EESI-TOF-MS and AMS PMF factors where specific analogues existed, as well as between total signal and POA–SOA apportionment. This suggests the EESI-TOF-MS apportionment in the current study can be approximately taken at face value, despite ion-by-ion differences in relative sensitivity. The apportionment of specific ions measured by the EESI-TOF-MS (e.g., levoglucosan, nitrocatechol, and selected organic acids) and utilization of a cluster analysis-based approach to identify key marker ions for the EESI-TOF-MS factors are investigated. The interpretability of the EESI-TOF-MS results and improved source separation relative to the AMS within this pilot campaign validate the EESI-TOF-MS as a promising approach to source apportionment and atmospheric composition research.

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Simultaneous aerosol mass spectrometry and chemical ionisation mass spectrometry measurements during a biomass burning event in the UK: insights into nitrate chemistry

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-4093-2018 ◽

2018 ◽

Vol 18 (6) ◽

pp. 4093-4111 ◽

Cited By ~ 9

Author(s):

Ernesto Reyes-Villegas ◽

Michael Priestley ◽

Yu-Chieh Ting ◽

Sophie Haslett ◽

Thomas Bannan ◽

...

Keyword(s):

Mass Spectrometry ◽

Source Apportionment ◽

Biomass Burning ◽

Organic Aerosol ◽

Oxides Of Nitrogen ◽

Night Time ◽

Aerosol Mass ◽

Ionisation Mass Spectrometry ◽

Chemical Ionisation ◽

Ionisation Mass

Abstract. Over the past decade, there has been an increasing interest in short-term events that negatively affect air quality such as bonfires and fireworks. High aerosol and gas concentrations generated from public bonfires or fireworks were measured in order to understand the night-time chemical processes and their atmospheric implications. Nitrogen chemistry was observed during Bonfire Night with nitrogen containing compounds in both gas and aerosol phases and further N2O5 and ClNO2 concentrations, which depleted early next morning due to photolysis of NO3 radicals and ceasing production. Particulate organic oxides of nitrogen (PONs) concentrations of 2.8 µg m−3 were estimated using the m ∕ z 46 : 30 ratios from aerosol mass spectrometer (AMS) measurements, according to previously published methods. Multilinear engine 2 (ME-2) source apportionment was performed to determine organic aerosol (OA) concentrations from different sources after modifying the fragmentation table and it was possible to identify two PON factors representing primary (pPON_ME2) and secondary (sPON_ME2) contributions. A slight improvement in the agreement between the source apportionment of the AMS and a collocated AE-31 Aethalometer was observed after modifying the prescribed fragmentation in the AMS organic spectrum (the fragmentation table) to determine PON sources, which resulted in an r2 =  0.894 between biomass burning organic aerosol (BBOA) and babs_470wb compared to an r2 =  0.861 obtained without the modification. Correlations between OA sources and measurements made using time-of-flight chemical ionisation mass spectrometry with an iodide adduct ion were performed in order to determine possible gas tracers to be used in future ME-2 analyses to constrain solutions. During Bonfire Night, strong correlations (r2) were observed between BBOA and methacrylic acid (0.92), acrylic acid (0.90), nitrous acid (0.86), propionic acid, (0.85) and hydrogen cyanide (0.76). A series of oxygenated species and chlorine compounds showed good correlations with sPON_ME2 and the low volatility oxygenated organic aerosol (LVOOA) factor during Bonfire Night and an event with low pollutant concentrations. Further analysis of pPON_ME2 and sPON_ME2 was performed in order to determine whether these PON sources absorb light near the UV region using an Aethalometer. This hypothesis was tested by doing multilinear regressions between babs_470wb and BBOA, sPON_ME2 and pPON_ME2. Our results suggest that sPON_ME2 does not absorb light at 470 nm, while pPON_ME2 and LVOOA do absorb light at 470 nm. This may inform black carbon (BC) source apportionment studies from Aethalometer measurements, through investigation of the brown carbon contribution to babs_470wb.

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Remote sensing of soot carbon – Part 1: Distinguishing different absorbing aerosol species

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-13607-2015 ◽

2015 ◽

Vol 15 (9) ◽

pp. 13607-13656 ◽

Cited By ~ 4

Author(s):

G. L. Schuster ◽

O. Dubovik ◽

A. Arola

Keyword(s):

Refractive Index ◽

Optical Properties ◽

Iron Oxide ◽

South America ◽

Biomass Burning ◽

Southern Africa ◽

Refractive Indices ◽

Carbonaceous Aerosols ◽

Fine Mode ◽

Soot Carbon

Abstract. We describe a method of using the aerosol robotic network (AERONET) size distributions and complex refractive indices to retrieve the relative proportion of carbonaceous aerosols and iron oxide minerals. We assume that soot carbon has a spectrally flat refractive index, and that enhanced imaginary indices at the 440 nm wavelength are caused by brown carbon or hematite. Carbonaceous aerosols can be separated from dust in imaginary refractive index space because 95% of biomass burning aerosols have imaginary indices greater than 0.0042 at the 675–1020 nm wavelengths, and 95% of dust has imaginary refractive indices of less than 0.0042 at those wavelengths. However, mixtures of these two types of particles can not be unambiguously partitioned on the basis of optical properties alone, so we also separate these particles by size. Regional and seasonal results are consistent with expectations. Monthly climatologies of fine mode soot carbon are less than 1.0% by volume for West Africa and the Middle East, but the southern Africa and South America biomass burning sites have peak values of 3.0 and 1.7%. Monthly-averaged fine mode brown carbon volume fractions have a peak value of 5.8% for West Africa, 2.1% for the Middle East, 3.7% for southern Africa, and 5.7% for South America. Monthly climatologies of iron oxide volume fractions show little seasonal variability, and range from about 1.1 to 1.7% for coarse mode aerosols in all four study regions. Finally, our sensitivity study indicates that the soot carbon retrieval is not sensitive to the component refractive indices or densities assumed for carbonaceous and iron oxide aerosols, and differs by only 15.4% when these parameters are altered from our chosen baseline values. The associated soot carbon absorption aerosol optical depth (AAOD) does not vary at all when these parameters are altered, however, because the retrieval is constrained by the AERONET optical properties.

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