2026-B20 Linking Tree Emissions to Atmospheric Chemistry: BVOC Reactivity under Rising CO₂

PROJECT HIGHLIGHTS

  • Diverse skillset development, including experimental instrumentation and coding 
  • Field studies at the BIFoR FACE facility 
  • Use of atmospheric chemical modelling to translate findings to climate impact 

Overview

Atmospheric chemical processing determines the link between emissions to the air and atmospheric composition, which in turn affects climate and health. The biosphere is the largest source of organic compounds to the atmosphere, with trees dominating production of biogenic volatile organic compounds (BVOCs) such as isoprene and monoterpenes. VOCs go on to form ozone (harmful to human health, crop yields and ecosystems) and fine particles (again, harmful to health, and impacting climate through scattering of radiation and influencing cloud formation).   

There are two key uncertainties in BVOC emissions. First, the totality of BVOC emissions is poorly understood. Many thousands of species are formed and attempts to characterise them individually face large gaps:  bottom-up estimates indicate differences of up to 50% between individually measured species and the total concentration known to be present! This matters because BVOC loading determines the pool of reactive organic material available to form atmospheric particles. In addition, oxidation cycles are initiated by reagents such as OH, where alkene ozonolysis is a major source of OH and ozone sinks. Key questions include: What is the total BVOC population present in key environments? What is the contribution of alkene-ozone reactions to OH formation and subsequent particle formation? 

Secondly, we know that tree VOC emissions change with plant stress, e.g. temperature, but do not know how BVOC emissions will respond to increased atmospheric CO2. For example, will BVOC emissions track the increases in net primary productivity and tree growth observed under enhanced CO2? How will environmental change – increasing CO2 levels – affect BVOC production from forests? 

This studentship will focus on characterising BVOC emissions using complementary top-down and bottom-up methodologies. An emerging top-down approach to tackling the complexity of atmospheric chemical systems is to directly measure integrated properties, which will achieved with the Total Ozone Reactivity System developed here at the University of Birmingham. Alongside the top-down approach, a bottom-up approach using mass spectrometry will quantify the emissions of key known BVOCs, such as isoprene and total mono- and sesquiterpenes. The result will be a full view of BVOC emissions from oak trees under both ambient and enhanced CO2 conditions.  

Case funding

This project is not suitable for CASE funding

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This studentship will involve laboratory, field, and modelling work. In the laboratory, the student will optimize the Total Ozone Reactivity System (TORS) for measurements of trace volatile organic compounds (VOCs). This will involve testing sensitivity limits for various VOCs, under both controlled (single compound) and ambient (branch sampling) conditions. Integral to the field work portion of the PhD is a summer field campaign at the BIFoR FACE facility, one of the world’s largest climate change facilities monitoring the impact of rising CO2 on a mature ecosystem. Proof-of-concept measurements at BIFoR FACE have already demonstrated feasibility. The student will use the optimized TORS instrumentation in the field environment, alongside mass spectrometry measurements, to quantify how changes in CO2 impact VOC emissions from oak trees. The experimental data will be supported by atmospheric box modelling, comparing observations with model predictions.  

DRs will be awarded CENTA Training Credits (CTCs) for participation in CENTA-provided and ‘free choice’ external training. One CTC can be earned per 3 hours training, and DRs must accrue 100 CTCs across the three and a half years of their PhD.  

During this PhD you will gain an integrated set of technical, analytical and professional skills. You will be trained in cutting-edge instrumentation (Total Ozone Reactivity System, mass spectrometry), in both laboratory and field environments (including deployment at BIFoR FACE), and in coding (Python and globally recognised modelling codes). You will acquire skills in experimental design, trace VOC measurement, and atmospheric box modelling/data analysis. In addition, you will develop transferable capabilities: scientific writing and presentation; communicating complex ideas to diverse audiences; project management; and time/data management. Opportunities to attend seminars, workshops, conferences, and public engagement will further support your career readiness. 

Not applicable.

Year 1: Laboratory experiments, measuring key unknown reaction rate coefficients for ozone reactivity with identified terpene emissions from oak trees 

Year 2: Further optimization of instrumentation, ensuring full testing and sensitivity analysis prior to a summertime field campaign at the BIFoR FACE facility 

Year 3: Analysis of fieldwork results, with integration into and comparison with Master Chemical Mechanism and AtChem model for understanding impact of atmospheric chemical networks. 

Norby, R. J., et al., (2024) ‘Enhanced woody biomass production in a mature temperate forest under elevated CO2’, Nature Climate Change, 14, pp. 983-988. doi: 10.1038/s41558-024-02090-3 

Sommariva, R., et al., (2020) ‘An instrument for in situ measurement of total ozone reactivity’, Atmospheric Measurement Techniques, 13 (3), pp.1655-1670. doi: 10.5194/amt-13-1655-2020 

Di Carlo, P., et al., (2004) ‘Missing OH Reactivity in a Forest: Evidence for Unknown Reactive Biogenic VOCs’, Science, 304 (5671), pp. 722-725. doi: 10.1126/science.1094392 

Further details and How to Apply

Project contact details: Dr Julia Lehman, [email protected] 

To apply to this project: 

  • You must include a CV with the names of at least two referees (preferably three) who can comment on your academic abilities.  
  • Please submit your application and complete the host institution application process via: https://sits.bham.ac.uk/lpages/LES068.htm.   Please select the PhD Geography and Environmental Science (CENTA) 2026/27 Apply Now button. The CENTA Studentship Application Form 2026 and CV can be uploaded to the Application Information section of the online form.  Please quote 2026-B20when completing the application form.  

 Applications must be submitted by 23:59 GMT on Wednesday 7th January 2026. 

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