Rapid economic growth has led to serious air quality issues in China, which periodically experiences a well-known “haze”. The AIRPRO (AIR Pollution PROcesses in Beijing) consortium brings together ten UK Universities, three UK partner organizations and four major Chinese research institutions to better understand the basic gas and aerosol processes controlling pollution in Beijing, one of the world’s largest megacities of more than 21 million inhabitants. Photo-oxidation in Beijing is highly complex, being initiated by short lived radical species, in the daytime dominated by the hydroxyl radical, OH, and at night by either nitrate (NO3) radicals or ozone. Primary emissions, for example from traffic, industry and domestic cooking/heating are subsequently deposited to surfaces, transformed into secondary pollutants such as O3, NO2, acidic and multifunctional species, many of which are of low volatility and partition to the condensed phase forming secondary organic aerosol (SOA).
A focus of the project is understanding the routes to formation of tropospheric ozone and particulate matter (PM) in Beijing. Ozone is a major air pollutant harmful to human health, agricultural crops and vegetation, and an important greenhouse gas. Understanding, predicting and managing tropospheric ozone levels is a key goal, but is difficult to achieve, as ozone is formed in the atmosphere from the complex oxidation of volatile organic compounds (VOCs) in the presence of NOx and sunlight, on a timescale that in situ chemical processes, deposition and transport all need to be taken into account. A key question is how much ozone is generated in situ from the reaction of peroxy radicals (HO2 and RO2) with NO followed by the photolysis of the generated NO2, compared with transport of ozone from afar. A similar question applies to PM, what is the contribution of primary emissions versus in situ production of secondary organic aerosol via the oxidation of emissions? Recently it was shown that there is a high secondary aerosol contribution to particulate pollution during haze events in China, demonstrating the key role played by chemistry initiated by OH and other species.
Specifically, in this project you will:
(1) Participate in two collaborative field campaigns in Beijing at a highly instrumented site during both summer and winter, when levels of solar radiation, the dominant chemical processes and meteorological processes conditions are expected to differ significantly. You will operate the Leeds FAGE (fluorescence assay by gas expansion) instruments for the in situ measurement of OH, HO2, and organic peroxy radicals, RO2, OH reactivity (a measure of the ability of the urban atmosphere to remove OH radicals) and formaldehyde, as well as a spectralradiometer for the determination of solar-induced photolysis frequencies.
(2) Perform analysis and interpretation of field data collected in Beijing to explore correlations with other species and calculate directly the rate of in situ ozone production for comparison with other instruments. Using a model, you will calculate a steady state OH concentration constrained to measured OH reactivity and OH sources for comparison with the observed OH. Evaluate the importance of nitrous acid, HONO, as a source of OH.
(3) Perform model simulations with the HadGEM3-UKCA chemistry-climate model developed by the UK science community in collaboration with the UK Met Office. By using observations collected during AIRPRO of the sources and sinks of OH and other radicals, for example very detailed speciated measurements of VOCs, you will make the first detailed evaluation of the UKCA chemistry-climate model over Asia. You will quantify the contribution of secondary organic aerosol (SOA) and new particle formation to ambient air pollution in China.
(4) Undertake laboratory studies to further characterize the FAGE instrument, for example to study any potential interferences from species that may be present in the complex environment in Beijing.
You will join an active, thriving and well-funded atmospheric chemistry group within the School of Chemistry. The project will involve collaboration with Dr Lisa Whalley and Dr Dom Spracklen (School of Earth and Environment). You will receive a wide range of training, for example in communication skills, project management, and technology (lasers, vacuum systems, optics, computer controlled data acquisition and numerical calculations). Further details regarding the group and project can be found at: http://www1.chem.leeds.ac.uk/Atmospheric/Field/fage/fage.html
Heard, D.E. and Pilling M.J. (2003), “Measurement of OH and HO2 in the Troposphere”, Chem. Rev., 103, 5163–5198.
Stone, D., L. K. Whalley, D. E. Heard (2012), "Tropospheric OH and HO2 radicals: field measurements and model comparisons", Chem. Soc. Rev., 41, 6348-6404.
Huang, R.-J., Zhang Y., Prevot A.S.H. et al. (2014), “High secondary aerosol contribution to particulate pollution during haze events in China”, Nature, 514, 218-222.
Lu , K. D., et al. (2013), “Missing OH source in a suburban environment near Beijing: observed and modelled OH and HO2 concentrations in summer 2006”, Atmos. Chem. Phys., 13, 1057-1080, 2013.
Lu , K. D., Rohrer F., Hofzumahaus A., et al. (2014), “Nighttime observation and chemistry of HOx in the Pearl River Delta and Beijing in summer 2006”, Atmos. Chem. Phys., 14, 4979-4999, 2014.
Whalley, L.K., , L. J. Carpenter, D. E. Heard et al., (2010) “The chemistry of OH and HO2 radicals in the boundary layer over the tropical Atlantic Ocean”, Atmos. Chem. Phys., 10, 1555-1576.
Whalley, L.K., M.A. Blitz, M. Desservettaz, P.W. Seakins and D. E. Heard (2013), “Reporting the sensitivity of laser-induced fluorescence instruments used for HO2 detection to an interference from RO2 radicals and introducing a novel approach that enables HO2 and certain RO2 types to be selectively measured”, Atmos. Meas. Tech., 6, 3425–3440.