Full Title
Organic Carbon Speciation, Decomposition Markers and Processes in Wetland Soils
Student
Nirmala Wijieratne
Supervisors
Ewen Silvester (La Trobe University) and Darren Baldwin (MDFRC)
Funding Body
Department of the Environment, Water, Heritage and the Arts, Commonwealth Environment Research Facilities (CERF) Significant Projects
Duration
TBA
Outcomes
PhD thesis
Summary
The flooding frequency and intensity of wetlands in the lower Murray-Darling basin has decreased in the recent past due to river regulation and climate change effects. Flooding events serve to re-supply the flood plain soils with carbon, nutrients and minerals, as part of the aquatic-terrestrial exchange processes. The effect of the change in frequency and intensity of flooding events on floodplain health is unknown.
This project will examine the soil-flood plain interaction, soil carbon speciation on flooding regimes, soil micro aggregates and the historical record of a floodplain sediment profile to determine the past frequency of flooding events, and the characteristics of the deposited carbon, with the ultimate aim of determining the catchment origins of the organic carbon. Carbon analysis will focus on molecules that are highly stable, and likely to be characteristic of different types of vegetation (e.g. sterols, lipids, etc.).
The work will form part of a larger CERF funded project dealing with carbon dynamics more generally in Yanga Nature reserve (Murrumbidge river), in the lower Murray-Darling basin.
The project work will entail:
(i) Development of extraction, concentration and analysis techniques for identifying and quantifying Organic carbon species such as Carbohydrates (neutral sugars and amino sugars), Proteins(amino acids), Phenols, Lignins, Lipids), Organic N and P species and Potential Plant Biomarkers.
(ii) The identification of biomarker molecules from a range of upper catchment aquatic and terrestrial plants, allowing the development of a library of biomarker compounds.
(iii) Analysis of organic carbon deposits in preserved soil cores from the study area, and cross referencing with biomarker library.
(iv) Dating of sediment cores (210Pb), and development of a natural history model for floodplain soils in the Yanga Nature reserve.
Techniques to be used will include:
· Carbon extraction techniques
· Colorimetric methods
· Chromatographic methods- HPLC, GC-MS, LC-MS
· Spectroscopic methods- Solid state 13C NMR, NEXAFS, IR and 13C-NMR.
· Dating of sediment cores (210Pb)
