Lignin as a tracer for terrestrial vegetation across the river-estuarine-coastal continuum
Biogeochemical processes in rivers, estuaries and coastal seas play key roles in the global carbon C cycle by controlling the flux of material from land to ocean. It has been estimated that as little as 10% terrestrial organic matter is transferred from rivers to sites of burial in the sediments of continental margins.
However, the following questions are not well understood: i) where the OC matter from? ii) what fraction is decomposed?, iii) where within the river-estuary system is organic matter preserved or sequestered? Established approaches on the sources of organic matter along the river–estuarine continuum include sediment data on bulk carbon-isotope (δ13C) composition in combination with the ratios of carbon to nitrogen providing biological ‘end members’.
Although these approaches broadly estimate marine as compared to terrestrial organic matter, they are insensitive to changing terrestrial vascular plant sources due to a range of confounding factors. This project aims to identify the vascular plant sources encountered along river channels (land to sea) using a molecular biomarker approach to quantitatively understand the source(s), degradation processes and fate of terrestrial particulate organic matter in sediments.
The PhD will focus on the use of lignin as a tracer because it provides the greatest potential due to its ubiquitous presence in all true vascular plants, its relatively high resistance to biotic and abiotic alteration, and retention of source specific characteristic “phenolic fingerprints”.
The project will employ state-of-the-art analytical techniques in organic geochemistry (solid-state 13C NMR, analytical pyrolysis-GC/MS). The successful candidate will be trained in these techniques, the interpretation of the data and will be involved with fieldwork at a range of sites for the collection of samples from a range of UK catchment systems.
Candidates should have a minimum 2:1 undergraduate degree in chemistry or environmental science with a strong focus on analytical chemistry. Candidates with a strong background in analytical chemistry, with experience of organic geochemical analytical techniques, will be preferred.
For further details please contact Dr Chris Vane firstname.lastname@example.org