Are glyoxal and methylglyoxal critical to the formation of a missing fraction of SOA (Secondary Organic Aerosol)?: (Pho-SOA).

Lead Research Organisation: University of York
Department Name: Chemistry


Atmospheric aerosols are ubiquitous in the Earth's atmosphere. They are made up of complex colloidal mixtures of liquid and solid particulate matter and understanding their chemical and physical properties is crucial in elucidating their environmental and health impacts. However, despite much scientific effort over the last decade, the true impact of aerosols on the Earth's atmosphere is yet to be elucidated owing to large uncertainties and lack of fundamental knowledge on their sources, composition (hence physical properties) and formation mechanisms. Recent experimental findings indicate organic aerosols (OA) are predominantly secondary in nature and can account for a significant fraction (10-70%) of total ambient atmospheric aerosol. However, current models significantly underestimate SOA (Secondary Organic Aerosol) production and their rate of formation. Accretion or oligomerization reactions of light weight volatiles such as glyoxal (GLY, CHOCHO) and methylglyoxal (MGLY, CH3COCHO), which have been shown to be a potentially important source of global SOA, have been proposed to justify such disagreement. The magnitude, type (reversible or irreversible) and mechanism of particle growth owing to alfa-dicarbonyls are still substantial questions. The aim of this project is to quantitatively demonstrate the hypothesis that heterogeneous uptake of GLY and MGLY in aerosols can explain a significant fraction of the missing SOA in models. To address this, the project will carry out an extensive series of outdoor chamber experiments (in the highly instrumented European Photoreactor, EUPHORE) that will address the main limitations of previous studies. The experimental work will be supported by detailed chamber simulations using the Master Chemical Mechanism (MCM15). GLY or MGLY will either be introduced directly into the chamber or generated in-situ by the reaction of OH + alkynes. The chamber experiments will be carried out in the presence (and absence) of natural solar radiation in EUPHORE in order to investigate whether heterogeneous reactive uptake of these dicarbonyl compounds and SOA growth is photochemically activated (photosensitized) and relative humidity dependent. The gas and aerosol phase evolution of the precursor and oxidation products, together with HOx radicals (OH + HO2) will be monitored using novel chemical ionisation reaction (time-of-flight and quadrupole) mass spectrometry (CIR-MS), Aerosol Time of Flight Mass Spectrometry (ATOFMS), Fourier Transform Ion Cyclotron resonance Mass Spectrometry (FT-ICR-MS), liquid chromatography-ion trap mass spectrometry (LC-MSn) and laser induced fluorescence (LIF). Model sensitivity simulations using the MCM coupled to a representation of absorptive gas-to-aerosol partitioning incorporating parameterisations from the findings of this study, will be carried out in order to investigate the atmospheric implications of SOA formation via heterogeneous uptake of dicarbonyl compounds for urban environment where aromatics compounds (significant sources of dicarbonyls) have been proposed as key urban SOA sources.
Description Glyoxal and methylglyoxal represent two of the most common end products of the cycle of oxidation of volatile organic compounds. They are thought to play a key role in formation of atmospheric particles, through secondary chemistry and cloud processing. This project aimed to understand the mechanisms by which these chemicals can form aerosol and potentially change aerosol properties such as forming cloud droplets. We used a combination of simulations chamber experiments at the European PhotoReactor in Valencia and laboratory studies of detailed chemistry. We identified key chemical processes that lead to aerosol formation, discovered new reaction routes and also determined that sunlight plays a key role in the formation of aerosol from these chemicals.
Exploitation Route This work has been cited 13 times so far. There is increasing evidence of photo-initiated chemistry within aerosol particles and this work identifies new mechanisms for this process.
Sectors Environment

Description Used to create an undergraduate min research project for third year chemists.
First Year Of Impact 2013
Sector Education
Impact Types Societal