Thermogravimetric Analysis Coupled with Mass Spectrometry and Inductively Coupled Plasma Optical Emission Spectroscopy for Sediment Fingerprinting: Tracing the Sources of Sediment to the Coral Reefs of Montserrat

Hook, Anna and Quinton, John and Tuffen, Hugh (2024) Thermogravimetric Analysis Coupled with Mass Spectrometry and Inductively Coupled Plasma Optical Emission Spectroscopy for Sediment Fingerprinting: Tracing the Sources of Sediment to the Coral Reefs of Montserrat. Masters thesis, Lancaster University.

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Abstract

Coral reef survival is threatened by sediment deposition, particularly those surrounding volcanic islands, where sudden and larger sediment loads enhance threats. Tracing the sources of this sediment is vital for erosion mitigation, land-use and conservation, and is achieved through sediment fingerprinting, a technique with little application to coral reefs. In this study, the novel application of TGA-MS to identify potential tracers was used, alongside ICP-OES, on ghaut and reef samples from the volcanic island of Montserrat in the Caribbean, where knowledge of soil compositions and the effect of recent eruptions is severely understudied. Sediment from within 40 ghauts (steep-sided ephemeral watercourses) in the north-west and 7 coral reefs on the western coast of Montserrat were sampled. For TGA-MS, a heating rate of 10°C/min from ~30°C to 1000°C was used, identifying OM, clay and calcite weight loss percentages, and exsolved H2O and CO2. ICP-OES analysed 11 elemental concentrations: Al, Ca, Cu, Fe, Mg, Mn, Ni, P, Pb, Si and Zn. The three-step method for tracer selection was used, producing a final tracer suit of clay, Fe, Mn and Si, with 100% reclassification accuracy. A MixSIAR unmixing model was applied to 5 marine samples, determining ghauts further south, in close proximity to the Belham River and Soufrière Hills Volcano, were the largest contributors to sediment deposition (>67%). Laboratory analysis and field observations implied the sediment was volcanically derived and particle size analysis indicated the predominant grain size on the reefs were fine sediment <0.5mm in diameter. The inclusion of clay identified that volcanic deposits were transported via terrestrial landscapes prior to deposition. The wider significance of the study is highlighted in terms of land-use planning, erosion mitigation and coral reef conservation, with a particular emphasis on the importance of considering varying processes on catchments experiencing unique processes, such as those of volcanism.