Using geochemical stratigraphy to indicate post-fire sediment and nutrient fluxes into a water supply reservoir, Sydney, Australia

摘要

Wildfire can lead to increased fine-sediment (and associated nutrient) delivery to water bodies downstream of burnt terrain. Burnt soils in the drainage basin of Sydney's principal water supply reservoir show enrichment in nutrient and trace element properties (Ca, Mg, P, K, Zn and Pb) in association with mineralization of organic matter, This work aims to explore the potential for using geochemical tracers to quantify the impact of severe wildfire on downstream sediment dynamics and further, to see if a useful record of changing river basin sediment dynamics is recorded in reservoir sediment. Whilst fire-induced changes in geochemistry appear to offer a useful means for discriminating surface sediment sources with respect to fire severity, comparison with the geochemical stratigraphy of the lake is hampered by variable sedimentation dynamics linked to water level fluctuation and overprinting of source signatures by process-related transformations,. Further exploration of the factors affecting catchment source signatures and linkages within the system are required before the sedimentary record can be used to full advantage.