Periodic Reporting for period 1 - MOCHA (Molecular Characterisation of Anthropogenic Secondary Organic Aerosols.)
Reporting period: 2017-09-01 to 2019-08-31
Atmospheric aerosols have a large impact on Earth’s climate and human health. However, there is of a lack of detailed information on their sources and chemical composition. Research efforts in this area need to focus on organic matter, which dominates aerosol composition and is comprised of thousands of individual chemical compounds. Only a small fraction (<20% by mass) of the organic matter has been characterised at the molecular level. The major portion of the unknown species are secondary organic aerosols (SOA), which are formed in the atmosphere from chemical processing of organic compounds emitted from both natural and anthropogenic (man-made) sources.
The overall aim of the MOCHA project was to utilize state-of-the-art analytical tools for the Molecular Characterisation of Anthropogenic Secondary Organic Aerosols.
The scientific research objectives were:
1. To characterise the molecular composition of organic aerosols in ambient urban air.
2. To assess the relative importance of the various sources of organic aerosols.
3. To characterise the molecular composition of SOA generated from important anthropogenic precursors.
4. To identify the key chemical species and processes leading to anthropogenic SOA formation.
These research objectives have been achieved through a novel combination of field measurements, atmospheric simulation chamber studies and laboratory-based chemical analysis. A particular emphasis was placed on aerosols produced from domestic solid fuel burning, which is a dominant source of air pollution across Europe. Detailed chemical characterisation of aerosols showed that emissions from the combustion of solid fuels (coal, peat and wood) contained at least 2000 individual organic compounds. Comparison with samples collected in three rural towns showed that over 90% of the compounds could be attributed to coal/peat/wood combustion, confirming that air quality in these locations is overwhelmingly dominated by domestic solid fuel burning. Furthermore, high concentrations of toxic polycyclic aromatic hydrocarbons (PAHs) were determined in the ambient air samples, highlighting the urgent need for introduction of policies to reduce solid fuel combustion for the protection of public health.
The overall aim of the MOCHA project was to utilize state-of-the-art analytical tools for the Molecular Characterisation of Anthropogenic Secondary Organic Aerosols.
The scientific research objectives were:
1. To characterise the molecular composition of organic aerosols in ambient urban air.
2. To assess the relative importance of the various sources of organic aerosols.
3. To characterise the molecular composition of SOA generated from important anthropogenic precursors.
4. To identify the key chemical species and processes leading to anthropogenic SOA formation.
These research objectives have been achieved through a novel combination of field measurements, atmospheric simulation chamber studies and laboratory-based chemical analysis. A particular emphasis was placed on aerosols produced from domestic solid fuel burning, which is a dominant source of air pollution across Europe. Detailed chemical characterisation of aerosols showed that emissions from the combustion of solid fuels (coal, peat and wood) contained at least 2000 individual organic compounds. Comparison with samples collected in three rural towns showed that over 90% of the compounds could be attributed to coal/peat/wood combustion, confirming that air quality in these locations is overwhelmingly dominated by domestic solid fuel burning. Furthermore, high concentrations of toxic polycyclic aromatic hydrocarbons (PAHs) were determined in the ambient air samples, highlighting the urgent need for introduction of policies to reduce solid fuel combustion for the protection of public health.
Aerosols generated from the controlled combustion of various solid fuels (coal, peat and wood) were sampled from the flue of a chimney and compared with those collected in residential areas of three rural towns with known air quality problems. Chemical analysis performed using Ultra High Resolution Mass Spectrometry (UHRMS) showed that each of these samples contained thousands of individual organic compounds. The highly complex nature of these samples was broken down with the use of advanced data analytical tools to elucidate the following:
• Typically, around 45% of compounds contained only Carbon, Hydrogen and Oxygen (CHO family), while 55% contained Sulfur and/or Nitrogen (CHON, CHOS, CHONS families).
• A high proportion (55-95%) of all species were aromatic compounds.
• Wood combustion produced the most oxidized compounds, followed by coal and peat.
• Although there are a large number of common species in the various fuel types, some of molecular formulae can be used to distinguish between coal, peat and wood combustion.
Further off-line chemical analysis was performed using advanced chromatographic techniques for the identification and quantification of a range of target compounds. Large amounts of established combustion marker compounds such as nitroaromatics, phenolic compounds, lignin-type compounds, PAHs and anhydrosugars (i.e. levoglucosan) were detected in all samples. Good progress was also made in identifying candidate marker compounds for each fuel type, although, further work is needed in this area.
A series of simulation chamber experiments was also conducted on two key compounds (2,5-dimethylfuran and -valerolactone) emitted by combustion of biomass and other solid fuels. A state-of-the-art online analytical technique (FIGAERO-CIMS) was used to identify the oxidation products and chemical mechanisms for their formation have been proposed. These simulation chamber experiments have generated novel information on the reaction pathways for anthropogenic SOA formation that can be incorporated into atmospheric models dealing with both air quality and climate.
In order to elucidate further details of the species and processes leading to anthropogenic SOA formation, a field measurement campaign was conducted during winter in Cork city. Results obtained during one night-time pollution event indicated the presence of a large number of oxidised and nitrated aromatic species such as phenols, nitrophenols, nitroaromatics, nitro-PAHs etc. The results thus indicate that aromatic hydrocarbons and PAHs are key sources of anthropogenic SOA in locations strongly affected by biomass or solid fuel burning.
Overall, the unique information obtained from this combined field and laboratory study is expected to contribute to a greatly improved understanding of the composition, sources and processes leading to organic aerosol formation in the atmosphere, and in turn, the impact of SOA on human health and climate.
The results have been presented at three international conferences and form the basis of four research publications. Communication of the project results to the general public has been achieved through the project website, social media and a short film.
• Typically, around 45% of compounds contained only Carbon, Hydrogen and Oxygen (CHO family), while 55% contained Sulfur and/or Nitrogen (CHON, CHOS, CHONS families).
• A high proportion (55-95%) of all species were aromatic compounds.
• Wood combustion produced the most oxidized compounds, followed by coal and peat.
• Although there are a large number of common species in the various fuel types, some of molecular formulae can be used to distinguish between coal, peat and wood combustion.
Further off-line chemical analysis was performed using advanced chromatographic techniques for the identification and quantification of a range of target compounds. Large amounts of established combustion marker compounds such as nitroaromatics, phenolic compounds, lignin-type compounds, PAHs and anhydrosugars (i.e. levoglucosan) were detected in all samples. Good progress was also made in identifying candidate marker compounds for each fuel type, although, further work is needed in this area.
A series of simulation chamber experiments was also conducted on two key compounds (2,5-dimethylfuran and -valerolactone) emitted by combustion of biomass and other solid fuels. A state-of-the-art online analytical technique (FIGAERO-CIMS) was used to identify the oxidation products and chemical mechanisms for their formation have been proposed. These simulation chamber experiments have generated novel information on the reaction pathways for anthropogenic SOA formation that can be incorporated into atmospheric models dealing with both air quality and climate.
In order to elucidate further details of the species and processes leading to anthropogenic SOA formation, a field measurement campaign was conducted during winter in Cork city. Results obtained during one night-time pollution event indicated the presence of a large number of oxidised and nitrated aromatic species such as phenols, nitrophenols, nitroaromatics, nitro-PAHs etc. The results thus indicate that aromatic hydrocarbons and PAHs are key sources of anthropogenic SOA in locations strongly affected by biomass or solid fuel burning.
Overall, the unique information obtained from this combined field and laboratory study is expected to contribute to a greatly improved understanding of the composition, sources and processes leading to organic aerosol formation in the atmosphere, and in turn, the impact of SOA on human health and climate.
The results have been presented at three international conferences and form the basis of four research publications. Communication of the project results to the general public has been achieved through the project website, social media and a short film.
The research programme conducted in this project represents a highly original and innovative approach to significantly improve our understanding of organic aerosols in the urban environment. By integrating field measurements and simulation chamber experiments, MOCHA tackled this scientific challenge from both observational and experimental perspectives, while also ‘bridging the gap” between real-world and laboratory studies. A key innovative aspect of this research was the measurement strategy, which employs two of the most powerful (online and offline) techniques available for determining the chemical composition of organic aerosols at the molecular level. Indeed, this project almost certainly represents the first time that FIGAERO-CIMS and UHRMS have been used together. Furthermore, this combination has provided vast quantities of unique and valuable data to deliver unprecedented insights into the key components of anthropogenic SOA and mechanisms for its formation. This research has therefore delivered significant progress beyond state-of-the-art, with the results being highly useful to the wider research community.
The wider societal implications of this research are centred in the linked areas of climate change, air quality and human health. The research highlights the dominant contribution of solid fuel burning to air pollution in towns and cities. The new information generated on the sources and chemical nature of the particulate pollution provides a better understanding of the impact of aerosols on health and climate. This forms a scientific bases for policy makers to introduce efficient measures for the improvement of air quality at the national and European level, that will also help to mitigate climate change. In particular, the results of MOCHA will be directly relevant to the goals of the “2020 Climate Action Strategy” and “2020 Sustainable Development Goals” of the European Union and the “Convention on Climate Change” of the United Nations.
The wider societal implications of this research are centred in the linked areas of climate change, air quality and human health. The research highlights the dominant contribution of solid fuel burning to air pollution in towns and cities. The new information generated on the sources and chemical nature of the particulate pollution provides a better understanding of the impact of aerosols on health and climate. This forms a scientific bases for policy makers to introduce efficient measures for the improvement of air quality at the national and European level, that will also help to mitigate climate change. In particular, the results of MOCHA will be directly relevant to the goals of the “2020 Climate Action Strategy” and “2020 Sustainable Development Goals” of the European Union and the “Convention on Climate Change” of the United Nations.