Improvement of composition and property prediction techniques for for Secondary Organic Aerosol (SOA)

Lead Research Organisation: University of Manchester
Department Name: Earth Atmospheric and Env Sciences


Aerosol particles remain highly uncertain contributors to climate change, influencing climate directly by the scattering and absorption of solar radiation and indirectly through their role as cloud condensation nuclei. Atmospheric loading of particulate matter also has serious implications for urban air quality. Historically, it was assumed that aerosol particles were composed only of inorganic material. However, it has been found that organic components may constitute a substantial fraction of the aerosol composition, ranging from 20-60% of the fine particulate matter depending on the location. Condensed organic material is either directly emitted (primary) or formed in-situ by condensation and transformation of low-volatility and semi-volatile products derived from photo-oxidation of anthropogenic and biogenic volatile organic compounds (secondary organic aerosol:SOA). Gas-to-aerosol partitioning, or creation of SOA, is key to determining the chemical composition and loading of aerosol particles. A detailed knowledge of the formation, properties and transformation of SOA is therefore required to evaluate its impact on atmospheric processes, climate and human health. However, organic material can comprise many thousands, as yet largely unidentified, compounds with a vast range of properties. As a consequence, the chemical and physical processes associated with secondary organic aerosol (SOA) formation are complex and varied, and a quantitative and predictive understanding of SOA formation does not exist and therefore represents a major research challenge in atmospheric science!

Key uncertainties associated with our understanding of SOA formation have been identified. A compound will partition to the particulate phase if its equilibrium vapour pressure is low enough. This is dependent on the pure component vapour pressure, which can further decrease if the compound undergoes condensed phase reactions in the aerosol phase, enhancing gas/particle partitioning. Unfortunately, uncertainties associated with pure component vapour pressures and effective volatility of mixtures are enough to cause uncertainties in aerosol mass spanning up to 4 orders of magnitude. Vapour pressure predictive techniques are largely based on atmospherically irrelevant compounds used within industrial engineering and there is a large gap concerning the rates and importance of postulated relevant condensed phase reactions which we cannot even elucidate on using current analytical laboratory techniques.

In this proposal we aim to address these fundamental uncertainties via

1) Measurement of pure component vapour pressures using our well-established and validated method of Knudsen Effusion Mass Spectrometry. The resulting data will be assimilated into the Dortmund Databank (DDB) and new model revisions will be carried out by our industrial partner.

2) Directly link chemical composition to volatility within mixtures for the first time

3) Assess the complexity required to truly capture the SOA formation in atmospheric models.

Planned Impact

The primary non-academic end-users of the proposed programme output in the UK would be the Met Office via existing links between the PI and the UKCA Climate- Chemistry-Community-Aerosol model, a joint NCAS-Met Office programme funded by NCAS, GMR and DEFRA.The impacts of aerosol on climate are still credited with the largest uncertainty in climate forcing and a large part of the radiatively active boundary layer sub-micron aerosol burden is organic. Prior to the proposed work, accurate model descriptions of aerosol formation are unavailable & our study of those properties dictating gas/particle partitioning of organic compounds will be inform such a climate-focused goal. Other international non-academic agencies conducting IPCC simulations would be best placed to use the same reduced complexity SOA formalisms as supplied to the Met Office. Other specific non-academic end users includes the Dortmund Databank Consortium (DDB), who will benefit from a study of compounds not covered in their existing databases and predictive software (see letter of support - DDB) and the British Aerosol Manufacturers Association (see letter of support - BAMA). This scarcity of data causes empirically constrained predictive models to remain inaccurate and unevaluated when applied to atmospheric systems. The DDB is the largest data bank for experimental data on pure components and mixtures and available via distributed software, online (e.g. www.stn- and in printed form. Customers of DDB include about 50 chemical and engineering companies throughout the world as well as university and research institutions.

A number of academic communities are identified as having an interest in this work, ranging from atmospheric scientists through to physicists. The atmospheric community will benefit from provision of a comprehensive set of fundamental property measurements, development of novel instrumentation and improved predictive models. Dissemination of knowledge through distributed software, printed reference material via collaboration with industrial partners, and online tools developed in this project will vastly increase our ability to benefit researchers in other fields indirectly. We will disseminate results from this work through presentations at conferences in the UK and abroad, through research papers in high profile journals, through our network of collaborators and associates, and the online tools developed in this project (discussed shortly) .

At UoM we will use a Science Communicator in residence, Katherine Harrison to help us to distil the results from this work into a variety of documents that can be used by lay people at various levels of science literacy. A considerable effort will be directed to schools and teachers, where a public lecture will be developed to present the main results to schools and the general public, many times over the course of the 3 years of this project. We will also have a significant presence at UK Science Festivals, where we will present talks at a suitable level. We will also, in collaboration with Harrison, a former school teacher, write articles for schools and teachers and develop resource packs for this group. Furthermore, we will continue to work closely with the University media centres to ensure that all good news stories are broadcast effectively.

It is crucial that tools are developed to ensure benefits for a wide-range of end-users becomes sustainable beyond the duration of the project. To this end, a novel data portal will be constructed and hosted at UoM that provides access to continually updated peer reviewed data derived from this program, a blog, introductory material (see above) and maintains consistent in-house data stewardship and continual support. The incorporation of modeling tools improved in this project within an informatics suite, developed under a separate NERC grant, linked to this portal will be tailored to provide a useful online teaching resource.
Description In this grant we have focused on an area of research that was once in the grasp solely of physical chemists and demonstrated huge implications for atmospheric aerosol science. Not only that, we have helped foster an international community to better understand this challenging area of research that impacts on how we better predict air-quality and climate of the future.
Exploitation Route The focus of this project has impacts in many other fields. By exploiting the development of a novel web-portal on another NERC grant, we hope developments made here can be used by others.
Sectors Chemicals,Environment,Pharmaceuticals and Medical Biotechnology

Description As a follow on from a previous NERC grant, we have used this work to create an international community now focused on resolving the critically important issue of aerosol volatility. Our work has been referenced in numerous studies prescribing the dangers of uncertainty in prediction PM mass loadings, for example.
First Year Of Impact 2013
Title UManSysProp 
Description UManSysProp is an online facility for calculating the properties of individual organic molecules, ensemble mixtures and aerosol particles. Built using open source chemical informatics, and currently hosted at the University of Manchester, the facilities are provided via: a browser-friendly web-interface. a programmer friendly JSON API that enables you to call our suite of tools from your own code. access to the source code GitHub respository for all predictive techniques provided on the site. 
Type Of Material Computer model/algorithm 
Year Produced 2015 
Provided To Others? Yes  
Impact The facility is too new for assessing any impact, through appropriate reference to our description paper. Nonetheless, we receive roughly 800 users per month on the site already and is being used as a focal point for a NERC international network grant starting this year [2016]. 
Title New online and open source facility for predicting the properties of organic molecules and mixtures. 
Description UManSysProp is an online facility for calculating the properties of individual organic molecules, ensemble mixtures and aerosol particles. Built using open source chemical informatics, and currently hosted at the University of Manchester, the facilities are provided here via: a browser-friendly web-interface. a programmer friendly JSON API that enables you to call our suite of tools from your own code. access to the source code behind all predictive techniques provided on the site. 
Type Of Technology Webtool/Application 
Year Produced 2016 
Impact There have been 1800 unique users within its first 9 months of deployment, including 4 references since the paper release. 
Description Pi in the Sky at the Museum of Science and Industry, Manchester 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact In conjunction with STEM and MOSI, 'Pi in the Sky' combined the technology of Raspberry Pi with weather monitoring, giving teachers and pupils some great ideas for projects they could set up themselves in STEM clubs or lessons. The day started with an introductory talk on the links between air quality and weather and an explanation on the equipment that would enable the students to measure and observe weather variables. Using the Raspberry Pi, pupils then built the 'Weather Pi' stations to measure temperature, pressure and relative humidity, with the support of the Atmospheric Scientists. Pupils were given information on how to interpret the results and were encouraged to discuss the measurements from the constructed 'Weather Pi' stations. Following lunch and time to explore the museum, students had a go at creating their very own clouds.

When asked about what they enjoyed during the day, pupils said:

"I enjoyed using Raspberry Pi the most ....which I haven't had the privilege of using before. Also, I would now love to have one at home."
"I liked the enthusiasm and knowledge of the visit leaders."
"It was interesting, fun and got everybody involved."
"I enjoyed doing the cloud experiment and being able to walk around the museum."
"I enjoyed taking part in experiments and finding out how to do different things."
Year(s) Of Engagement Activity 2013
Description iTech 2013 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact I helped to organise the inaugural 'iTech: design your future' event with STEM, at MOSI during National Science and Engineering Week 2014, with support from the Knowledge Transfer Network. 30 schools attended from across Greater Manchester bringing a total of 170 pupils, aged 11-14, and 30 teachers to the event. The event combined workshop zones, showcase zones (which included the RaspberryPi weather station and a presentation of our research), gallery zone and keynote speeches. iTech will become a yearly event with 2015 planned to be even bigger and better than the hugely successful 2014 venture.

On the day, pupils said that they learnt about:

"The careers and opportunities computer science and technology open up."

"How important computers are and how they have changed over the years."

"There is a massive future in STEM."

Pupils also said:

"The workshop really shows pupils the interesting side to computer science and technology which our National Curriculum denies us."

"I found talking to the pros very useful."

"I really get a lot from these experiences."

Teachers also had some very positive feedback:

"Our students really enjoyed it and it really enthused them about aiming higher."

"Thank you, it was very worthwhile for our students."
Year(s) Of Engagement Activity 2014