Eileen Gallacher

Eileen Gallacher


I graduated in 2015 from the UEA with an integrated Master’s degree in Natural Science. My academic background combines studies in climate science and atmospheric chemistry, with a strong theme of analytical chemistry throughout. I wrote my Masters thesis on ozone-depleting CFCs, and co-authored a paper which included most of my findings, alongside a much more comprehensive study carried out by scientists at the UEA and elsewhere.

My research interests continue the theme of my undergraduate degree; chemistry-climate interactions, and though my research experience so far is mostly limited to studying physical and chemical reactions in the atmosphere, here I have the chance to learn more about biochemical processes in the terrestrial biosphere.

I am interested in studying stable isotopes in the context of investigative chemistry and am genuinely fascinated by the extent and potential of their application. I first met stable isotopes in this context during my undergraduate degree and initially pursued my interest through to a brief postgraduate research studentship where I was looking at clumping within CO2 isotopes as a proxy to reconstruct paleo sea temperatures. I have since been working as a teacher, teaching chemistry at a secondary boarding school. I have a passion for scuba diving and promoting conservation of aquatic life (namely the seaweed Posidonia Oceanica) and spent several years teaching scuba diving in the Balearic Islands prior to my academic life.

Eileen Gallacher

Geosciences, Resources and Environmental Risk

PhD title: Isotopic fingerprints of carbonyl sulfide (COS) in atmosphere and biosphere

Measurements of stable isotopes of carbonyl sulfide (COS) form the basis of my PhD project. COS is such an interesting compound because of its potential role in reducing the uncertainty of gross photosynthetic rates and the capacity of the terrestrial biosphere to remove anthropogenic carbon dioxide from the atmosphere1.

I will be using state of the art isotope ratio mass spectrometers both at the UEA and Utrecht University in the Netherlands to distinguish between COS sinks including photosynthesis and soil uptake, and to quantify the contribution of COS to stratospheric sulfate aerosol, where COS influences stratospheric ozone chemistry and the Earth’s radiation budget2 .

Over half of anthropogenic carbon dioxide is removed from the atmosphere by the terrestrial biosphere and the oceans3.  As atmospheric concentrations of CO2 have increased, so too has the capacity of terrestrial plants to remove CO2 via photosynthesis. However, difficulties surrounding measurements of terrestrial Global Primary Production (GPP; fixing of atmospheric CO2 into organic matter) result in large uncertainties in the capacity of the terrestrial carbon sink, which inevitably feed forward into global climate modelling4.

COS is chemically analogous to CO2, and as such is assimilated by terrestrial plants in the same way as CO25. However, COS is not released back into the atmosphere during respiration and therefore COS measurements can be used to estimate photosynthesis rates6. There is an excellent blog written by Maartin Krol explaining all about this here.

I will measure tropospheric and stratospheric air samples in order to calculate reaction-specific isotope signatures7 to distinguish between COS sinks, and subsequently use this information to improve global GPP estimates to a higher level of certainty and verify the stratospheric COS budget.


    Leedham Elvidge et al. 2018. Evaluation of stratospheric age of air from CF4, C2F6, C3F8, CHF3, HFC-125, HFC-227ea and SF6; implications for the calculations of halocarbon lifetimes, fractional release factors and ozone depletion potentials. Atmospheric Chemistry and Physics 18(5).

    Laube, et al. 2016. Tropospheric observations of CFC-114 and CFC-114a with a focus on long-term trends and emissions. Atmospheric Chemistry and Physics 16(23).