Professor Dwayne Heard

Profile

I received my D Phil from the University of Oxford in 1990, having worked with Gus Hancock in the Physical Chemistry Laboratory. I then undertook postdoctoral work at SRI International, Menlo Park, California, with David Crosley, before moving to Macquarie University in 1992 as a Lecturer in Chemistry, where I also worked in Brian Orr’s laboratory.  I came to Leeds in March 1994, initially as a Royal Society University Research Fellow.

Responsibilities

• Head of Atmospheric, Planetary and Theoretical Chemistry research group

Research interests

Personal Research Page

Overview: Atmospheric Chemistry and Astrochemistry

My research spans both Atmospheric Chemistry and Astrochemistry.  For Earth’s atmosphere, we aim to improve the accuracy of chemical mechanisms contained in numerical models which are used to predict future changes in climate change and air quality, and which drive all legislative controls on emissions. The future well-being of Earth’s atmosphere relies on a detailed understanding of the chemistry responsible for the oxidation of man-made and natural emissions. Further afield, over 200 molecules have now been observed in space, for example in dense molecular clouds and other interstellar environments, and we aim to understand the chemical pathways leading to their formation and destruction. We focus on the kinetics of gas-phase reactions of radical species with complex organic molecules (COMs).

Methods:

Field measurements of OH and other radicals, OH reactivity and formaldehyde in the atmosphere on ground and airborne platforms, and comparison with model calculations
State-of-the-art field instruments using laser-induced fluorescence spectroscopy at low pressure (FAGE) have been developed for quantitative measurement of the hydroxyl radical (OH, which drives much of the chemistry of the atmosphere), other radicals (HO2, RO2) and the reactive intermediate formaldehyde, from both ground-based mobile laboratories and the NERC FAAM BAe-146 instrumented aircraft. Since 1996 we have participated in over 30 field campaigns worldwide (UK, Europe, Arctic, Antarctica, China, Asia, Africa, Australia and Cape Verde) spanning pristine, remote environments to heavily polluted mega-cities. Measurements are compared with calculations from a range of models, including a box model utilising the detailed Master Chemical Mechanism, which was developed at Leeds and contains around17,000 reactions and 7,000 chemical species. The level of agreement between field measurements and models is an excellent test of how well we understand the chemistry of our atmosphere for these different environments. We have also developed a field instrument to measure directly the chemical reactivity of OH, a measure of the chemical complexity of the local environment.

Laboratory studies of chemical kinetics and photochemistry in both the gas phase and on the surface of aerosols
Each reaction in an atmospheric model requires a rate coefficient and branching ratio for the products to be specified as a function of temperature and pressure, and also wavelength in the case of photochemical reactions. In the well-equipped Dainton kinetics laboratory, we use laser flash-photolysis combined with a variety of laser spectroscopic probes to study the details of key chemical and photochemical atmospheric processes, many of which involve free-radicals. Using a pulsed Laval nozzle we are able to access temperatures are low as 30 K which are representative of interstellar and stellar outflow environments as well as the atmosphere of other planets and moons, for example, Titan. Heterogeneous chemistry on the surface of aerosols is an important component of chemical models, and we are measuring both the uptake and production of radicals and other intermediates at the surface of aerosols of different sizes and chemical composition.

Kinetic and mechanistic studies using The Leeds Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC)
HIRAC enables us to study mechanistic details of the oxidative chemistry and photochemistry of our atmosphere whilst controlling the chemical composition and conditions (e.g. temperature and pressure). Using a variety of state-of-the art instruments we are able to detect both stable species and free-radicals, including OH, HO2 and RO2, and comparison with model predictions again confirms our mechanistic understanding. HIRAC also provides an ideal medium in which to calibrate field instruments under realistic conditions and is a testbed to develop new instrumentation.

The work is supported by the National Centre for Atmospheric Science (NCAS) which is based in Leeds and funded by NERC. Much of the work is performed in collaboration with colleagues here in Chemistry and also in the School of Earth and Environment as part of the Institute for Climate and Atmospheric Science (ICAS). Our research is highly collaborative, and we have very close links with other atmospheric groups within the University and across the wider UK and international community. 

I am Editor of the textbook “Analytical Techniques for Atmospheric Measurement” which was published by Blackwell.

Enquiries are welcome from motivated applicants from all around the world for those interested in PhD or postdoctoral opportunities.

Qualifications

• D Phil in Physical Chemistry, University of Oxford
• BA and MA in Chemistry, University of Oxford

Professional memberships

• Fellow of the Royal Society of Chemistry
• Fellow of the Higher Education Academy

Student education

I teach Physical Chemistry at all undergraduate levels.

Research groups and institutes

• Atmospheric and Planetary Chemistry