Research Fellow - School of Geography, Earth and Environmental Sciences - 97854 - Grade 7

Position Details

School of Geography, Earth and Environmental Sciences

Location: University of Birmingham, Edgbaston, Birmingham UK

Full time starting salary is normally in the range £30,942 to £40,322, with potential progression once in post to £42,792

Grade 7

Full Time/FTC until November 2023

Closing date - 22nd August 2021

Background

The main purpose of the post is to carry out research in the context of the NERC Discovery Science grant Quantifying the light scattering and atmospheric oxidation rate of real organic films on atmospheric aerosol, a collaboration between researchers at Royal Holloway University of London, University of Birmingham, ISIS Neutron Source and the Rutherford Appleton Laboratory (RAL). The postholder will specifically focus on the work package (WP) 2(b) on Neutron Reflection for the oxidation of thin films at the air-water interface and WP 3(a) on Atmospheric Lifetime Modelling. This work is led by Dr Christian Pfrang with WP2(b) being carried out across ISIS, University of Birmingham and Royal Holloway (where work is led by Prof. Martin King and supported by his team), and WP3(a) will benefit from Dr Pfrang's long-term link with project partner Prof. Ulrich Pöschl at the Max-Planck Institute for Chemistry (Mainz, Germany). The research will be intimately linked to the other WPs within this NERC grant that will be carried out by a PostDoc based at Royal Holloway/RAL on Laser trapping and Mie Spectroscopy for the oxidation of thin films at the solid-liquid interface and Radiative transfer modelling both led by Prof. King. The Postholder will also benefit from expertise from the further Co-Is on this grant based at ISIS (Drs Skoda and Welbourn) and RAL (Dr Ward).

Summary of Role

The postholder will be part of the School of Geography, Earth and Environmental Sciences (GEES) at the University of Birmingham, one of the leading research bases for Atmospheric Science in the UK. The successful candidate will be responsible to carry out the following work:

Within WP2(b) on Neutron Reflection for the oxidation of thin films at the air-water interface to (1) measure the chemical kinetic data for the oxidation rate of real atmospheric material at an air-water interface with the key day and night-time atmospheric oxidants: hydroxyl radical (OH), ozone(O3) and nitrate radical (NO3) and (2) measure the film thickness for real atmospheric material at an air-water interface before, during and after chemical oxidation. Real atmospheric material collected in WP1 will be spread via chloroform on an air-water interface on a custom-made Teflon trough in a neutron reflectometer at ISIS pulsed neutron source. The Neutron reflectivity will be measured as a function of momentum transfer whilst the film is oxidised by either OH radicals, O3 or NO3. Neutron reflection is sensitive to the number and type of nuclei under investigation. By mixing D2O and H2O the water sub-phase can achieve a contrast matching the air above the film and the neutron reflection is then only sensitive to the film. The product of the film thickness and neutron scattering length density is the neutron scattering length per unit area and can be used as a kinetic variable for the surface coverage, of the film. The system is very apt for measuring the gas-phase reaction with a surface species and does not suffer from the competing transport and reactive process in aerosol bulk that reaction with pure aerosol with gas-phase oxidants routinely encounters, making the system elegantly simple. Bimolecular rate constants can be measured from fast diffusion-limited values to atmospherically unimportant slow reactions. Drs Pfrang and Skoda have developed a joint neutron reflection infra-red reflection absorption spectroscopy rig at ISIS that provide key complimentary molecular information particularly for the study of chemically complex films.

WP3(a) on Atmospheric Lifetime Modelling will build on Dr Pfrang's established long-term link with project partner, MPIC director Prof. Ulrich Pöschl to develop kinetic model descriptions of real atmospheric surface films for the first time. The models KM-SUB and KM-GAP, co-developed by Dr Pfrang and widely used in the aerosol community (> 200 citations), will be tailored to accommodate data from workpackages 1 and 2 on complex surface real films. Single component films have already been described and interpreted by KM-GAP. Preliminary work on two-component mixtures have revealed clear differences between one- and two-component film lifetimes. The present work will deliver a step change in the understanding how multi-component surface films on atmospheric droplets react with atmospheric oxidants. We are uniquely placed to carry out this challenging model development since we have extensive expertise with KM-GAP and collaborations with world-leading modelling expertise at MPIC via the groups of Prof. Uli Pöschl and Dr Thomas Berkemeier. KM-GAP is a novel kinetic multi-layer model for gas-particle interactions in aerosols and clouds that treats explicitly all steps of mass transport and chemical reaction of semi-volatile species partitioning be- tween gas phase, particle surface and particle bulk. It includes gas phase diffusion, reversible adsorption, surface reactions, bulk diffusion and reaction, as well as condensation, evaporation and heat transfer. The size change of atmospheric particles and the temporal evolution and spatial profile of the concentration of individual chemical species will be modelled along with gas uptake and accommodation coefficients during oxidation. The modelling will initially expand the comparison of two component proxy mixtures. We will then fit 75% of the experimental data (training set) on results from real atmospheric materials (WPs 1&2) using the genetic algorithm approach of Berkemeier. We will predict lifetimes and size changes in a range of atmospheric conditions. Ca. 25% of the experimental data will then be compared to the model predictions and differences will be critically evaluated and variables optimised to establish the predictive power. Sensitivity studies will reveal the most important parameters & conditions in order to establish a parameterisation that can be used as input for larger-scale models at MPIC. Warm clouds and the impact on their Köhler-type behaviour and its modification caused by real surfactant films established by our droplet-level modelling will be targeted since it is likely that the surfactants will be most influential for the cloud droplet formation processes in those clouds. We will be able to propose atmospheric film lifetimes directly constrained by experimental data for the first time. The modified KM-GAP model will allow the film lifetime to be calculated accurately by considering the accommodation, transport and reaction of atmospheric oxidants on a core-shell particle. Although the reactions in WP 2 imply simple kinetics at the air-water interface (i.e. direct reaction with the film) the KM-GAP model will be able to consider the transport in gas and liquid phases of oxidants and products, the reaction chemistry inside and outside the particle and the effect of the particles size on the lifetime. These processes are not considered in current atmospheric models and a short film oxidation lifetime with respect to physical removal of the particle, as indicated in our preliminary work, will demonstrate the key importance of these processes in the atmosphere. The work in WP3(a) will be carried out by the postholder supported by Dr Pfrang and include ca. 10 weeks at Mainz with MPIC and the Pöschl/Berkemeier groups.

This Postdoctoral Research Fellowship will focus on the two WPs above, but we will support and encourage the postholder to harvest synergies within the research team, with their collaborators and the large atmospheric science research community at Birmingham in particular to get involved in related research activities as a stepping stone to build a successful research career.

The postholder will need to be able to adapt quickly and professionally to the needs of the day, and to be able to cope well and harmoniously with conflicting demands. In delivering this role efficiently and effectively, the postholder will be expected to exercise judgement and to use initiative in being proactive. The postholder should also be willing to participate in intense beamtime experiments (no more than 10 days per year) when overnight stays and shift work at the large-scale facility (e.g. ISIS Neutron Source) may be required.

Main Duties

The post holder will be mainly responsible to carry out the research within the two WPs outlined above, specifically:
- Lead the team and experimental work to carry out the measurements of the chemical kinetic data for the oxidation of real atmospheric material at an air-water interface with the key day and night-time atmospheric oxidants hydroxyl radical (OH), ozone (O3) and nitrate radicals (NO3)
- Lead the team and experimental work to carry out the measurement of the film thickness for real atmospheric material at an air-water interface before, during and after chemical oxidation
- With support from Dr Pfrang and the MPIC team develop kinetic model descriptions of real atmospheric surface films building on the KM-SUB and KM-GAP modelling approaches, tailored to accommodate data from WPs 1 and 2 on complex surface real films
- Develop a model description of the size change of atmospheric particles, the temporal evolution and spatial profile of the concentration of individual chemical species along with gas uptake and accommodation coefficients during oxidation. The modelling will initially expand the comparison of two component proxy mixtures. The postholder should then fit 75% of the experimental data (training set) on results from real atmospheric materials (WPs 1&2) using the genetic algorithm approach of Berkemeier
- Develop model predictions of lifetimes and size changes in a range of atmospheric conditions. Ca. 25% of the experimental data will then be compared to the model predictions and differences will be critically evaluated and variables optimised to establish the predictive power
- Carry out sensitivity studies to reveal the most important parameters & conditions in order to establish a parameterisation that can be used as input for larger-scale models at MPIC
- Develop research objectives and proposals for own or joint research, with assistance of a mentor if required
- Harvest these model descriptions to propose atmospheric film lifetimes directly constrained by experimental data for the first time to establish the importance of these processes in the atmosphere
- Communicate the research findings internally, nationally and internationally
- Organise the research activities (incl. tracking the budget, organising travelling if required and ensure suitable data management and record keeping), liaise with collaborators, contribute to outreach activities that relate to this research, draft reports requested by NERC or the large-scale facilities and organise regular meetings between Co-Is and for the research team at Birmingham
- Co-supervise PhD and MSc students at Birmingham working on projects linked to this NERC grant

Person Specification

Skills
• Ability to run and develop aerosol models such as KM-SUB and KM-GAP
• Ability to write modelling code in Matlab and/or Python
• Ability to carry out experimental work at large-scale facilities
• Very good awareness of current atmospheric chemistry issues
• Ability to work proactively, independently and as part of a team
• Ability to problem solve and use own judgement to make decisions, either independently or after consultation with others
• Ability to manipulate and handle large data sets
• Excellent written and oral communication skills, and ability to communicate effectively
• Excellent organisational skills and ability to prioritise own workload according to changing business needs and daily work constraints

Qualifications
• PhD or near completion, in Chemistry, Physics, Atmospheric Sciences or a closely related field
• UG degree in Chemistry, Physics, Atmospheric Sciences or a closely related field

Knowledge and Experience
• Very good knowledge of atmospheric chemistry and physics
• Knowledge of kinetic modelling of aerosols
• Knowledge of heterogeneous reactions in the atmosphere
• Knowledge of laboratory-based experimental methods in atmospheric chemistry
• Flexibility to take on a wide variety of tasks, taking account of the need to manage competing demands and busy workload
• Ability to work under pressure, to meet deadlines, and deal with large and complex data sets
• Strong team working attitude and experience