Postgraduate Profiles

Xin Du

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Thesis: Vertical distribution and geochemical behavior of rare earth elements in intensely weathered soil/regolith profiles.

Lanthanides, also called Rare Earth Elements (REE), are a group of chemically similar elements whose fate and fractionation in natural systems creates geochemical signatures and allows geochemical mechanisms to be deduced. Slight variations in physical and hence chemical properties allow REE to be differentially leached and fractionated during advanced weathering. The proposed research will focus on REE geochemical behavior and vertical distribution in intensely weathered profiles, especially laterite soil/regolith. Petrological and quantitative mineralogical study of the parent material will be conducted to determine the minerals initially controlling REE distribution; mass balance calculations based on immobile elements will be used to determine net gains or losses while weathering indexes, such as CIA, WI and CIW will be calculated for comparison. Chemical speciation will be used to gain insight into pedogenic and biogeochemical cycling of REE, increasing our understanding of REE environmental and ecological effects.

Why my research is important

Due to REE being widely used in agriculture as microelement fertilizers in some regions, the biogeochemical cycling of REE and their environmental and ecological effects are also therefore of great concern. Currently, much attention has been given to REE bio-availability, whereas there has been less research attention given to the geochemical cycling of REE, especially in intensively weathered soil/regolith. As a geochemical tracer, REE is widely utilized in studies of the evolution of petrological systems and assessing soil origin, pedogenesis and soil evolution. Studying the geochemical behavior of REE during intensive weathering will increase our understanding of biogeochemical cycling of REE and their environmental and ecological effects. In addition, the precise sequence of events and fate of REE during weathering is also necessary for us to evaluate the potential of REE fractionation as palaeo-environmental recorders, which is a crucial aspect of research into Earth’s early atmosphere and early life.


Sep 2008

May 2012