New methods for studying atmospheric soot

  • Supervisors: Dr. James Allan
    Dr. Paul Williams
    Prof. Hugh Coe
    Prof. Gordon McFiggans
  • External Supervisors:

  • Contact:

    James Allan james.allan@manchester.ac.uk

  • CASE Partner: Cambustion Ltd., Cambridge, UK

Application deadline: 3 February 2017

Introduction:

Black Carbon (BC) particles, or soot, is produced by combustion such as open fires and diesel engines and is a major component of atmospheric pollution. This is both harmful to human health and has a highly potent effect on climate, particularly on regional scales, where it can inhibit cloud formation and cause snow melt when it settles. Studies indicate that BC may be responsible for observed regional climate trends such as the weakening of the Indian monsoon, however the magnitudes of these effects are highly uncertain. This is partly because of the diversity and complexity of the sources and nature of the BC in the atmosphere. Predicting how a soot particle interacts with weather and climate requires knowledge of a complex range of properties including size, shape, composition and the presence of other material in the particles, such as organic matter, but this is difficult because the particles tend to be very small, typically tens to hundreds of nanometers in size. However, new measurement technologies are coming available that will allow us to study these on a level not previously possible.

Project Summary:

In recent years, the Centre for Atmospheric Science (CAS) has built up a comprehensive suite of state-of-the-art instruments for measuring various detailed aspects of soot, such as its composition, size, shape, mixing state and optics, as well as developed models designed to identify sources and predict their effects. The challenge is to apply combinations of measurements to atmospheric and laboratory-generated aerosols in such a way as to test and develop models of microphysical behaviour and to provide data suitable for use in studies of air quality and climate. Instruments used to measure composition, shape and size include the Single Particle Soot Photometer (SP2), Soot Particle Aerosol Mass Spectrometer (SP-AMS) and Centrifugal Particle Mass Analyser (CPMA). Measuring the optical properties (i.e. how dark the particles are) as a function of wavelength is also important in determining their effects and instruments for this include the Photoacoustic Soot Spectrometer (PASS) and Cavity Attenuated Phase Shift Single Scattering Albedometer (CAPS-SSA). There will also be opportunities to explore emerging techniques, such as the Aerodynamic Aerosol Classifier (AAC) and the new Williamson scanning electron microscope facility.

The work will concern the development of novel techniques of exploring the complexity of BC, such as combing measurements like the CPMA and SP2 in series to derive black carbon mass fraction on a per-particle basis. To this end, you will be working closely with Cambustion (as a CASE partner) in order to develop new and exciting methods of applying the existing instrumentation to further elucidate important properties of BC aerosols and improve the quality of existing instruments and metrology. This will also include work at Cambustion’s laboratories in Cambridge, with an opportunity to work with instrumentation currently under development. As well as developing new instruments, this will also allow new insights into important BC processes.

As part of this work, you may also be performing measurements of aerosols in polluted regions of the atmosphere. This may include measurements at ground stations and also measurements on board the Facility for Airborne Atmospheric Measurement (FAAM) BAe-146 research aircraft. Because the field experiments are usually run on a collaborative basis, there will be opportunities to collaborate with other organisations such as the Met Office. There will also be the opportunity to make detailed measurements of aerosols produced under controlled laboratory conditions, utilising a 1.9 litre light-duty diesel engine as part of the facilities at CAS and also the potential to make measurements at other institutes, studying other sources such as wood burning and jet engines.

References:

Liu et al. (2015): The effect of complex black carbon microphysics on the determination of the optical properties of brown carbon, http://dx.doi.org/10.1002/2014GL062443

Bond et al. (2013): Bounding the role of black carbon in the climate system: A scientific assessment, http://dx.doi.org/10.1002/jgrd.50171

Liu et al. (2013): Ambient black carbon particle hygroscopic properties controlled by mixing state and composition, http://dx.doi.org/10.5194/acp-13-2015-2013

Liu et al. (2014): Size distribution, mixing state and source apportionment of black carbon aerosol in London during wintertime, http://dx.doi.org/10.5194/acp-14-10061-2014

McMeeking et al. (2010): Black carbon measurements in the boundary layer over western and northern Europe, http://dx.doi.org/10.5194/acp-10-9393-2010

Olfert and Collings (2005): New method for particle mass classification - the Couette centrifugal particle mass analyzer, http://dx.doi.org/10.1016/j.jaerosci.2005.03.006

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