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Brian Kelleher
B.Sc., Ph.D. (University of Limerick)
Lecturer, Analytical/Physical Chemistry

Molecular Mechanisms of Natural Processes

My research interests include the molecular-level characterisation of natural organic matter (NOM) so as to describe natural processes in the environment. The interactions of soil, sediment, and dissolved organic matter in the environment have a major influence on natural processes such as climate change and human activities such as agriculture and the transport of pollutants. Current investigations include:

• The transformations of terrestrial carbon in a marine setting and its ultimate impact on concentrations of atmospheric CO2;
• Stress induced molecular and ecological changes in soil autotrophs: carbon capture and novel compound prospecting;
• The chemical and physical characteristics of marine pockmarks;
• The chemical nature of freshwater and marine dissolved organic matter (DOM).

Our research lab now includes the only Compound Specific Stable Isotope Ratio Mass Spectrometer (CS-IRMS) dedicated to environmental analysis in Ireland. The CS-IRMS is hyphenated to traditional GC-MS and provides C, N and H isotopic ratios of compounds in NOM. The lab also includes LC-MS (TOF) and custom built environmental chambers that we use to isotopically label microbes and plants. The use of isotopes allows us to identify functioning microbes in the environment by employing Stable Isotope Probing (SIP) (this work is carried out by our collaborators in Queens University Belfast) and also provides the means to assess the chemistry of specific molecular pathways such as photosynthesis through CS-IRMS and NMR. We are now trying to apply these techniques to assess the potential for biofuels from marine microorganisms. We are also employing this analytical equipment to learn more about marine processes such as the transformations of carbon within pockmark areas. Through the use of biomarkers in marine sediments and cores we can provide evidence of past climates and environmental conditions and also shed light on degradation processes leading to methane production.

A scanning electron micrograph of a Diatom, a unicellular alga, discovered while studying gas hydrate sediments in the Gulf of Mexico, 2002.

Recent Publications

1. Simpson, Andre J.; Simpson, Myrna J.; Smith, Emma; Kelleher, Brian P.. Microbially Derived Inputs to Soil Organic Matter: Are Current Estimates Too Low? Environmental Science & Technology (2007), 41(23), 8070-8076.
2. Kelleher, B. P., Simpson, A. J., R. E. Rogers, J. Dearman, W. L. Kingery. Effects of natural organic matter from sediments on the growth of marine gas hydrates. Marine Chemistry, 103(3-4), 237-249, 2007. Kelleher, B. P and Simpson, A. J., Humic Substances in Soils: Are they really chemically distinct? Environmental Science and Technology, 40(15), 4605-4611, 2006.
3. Simpson, A. J., Kingery, W. L., Simpson, M. J. Kelleher, B. P. The Application of 1H HR-MAS NMR to the study of clay-organic associations in synthetic complexes and whole soils. , Langmuir, 22(10), 4498-4503, 2006.
4. Kelleher, B. P. Simpson, M. J. and Simpson, A. J. Assessing the fate and transformation of plant residues in the terrestrial environment using HR MAS spectroscopy. Geochimica et Cosma Acta, 70(16), 4080-4094, 2006.