Acquisition of a Micro X-Ray Fluorescence Spectrometer

Understanding how chemical elements are cycled among various components such as plants, soil, rock, river sediment, and aquifers

To predict how Earth systems will respond to environmental and climate changes, it is essential to understand how chemical elements are cycled among various components such as plants, soil, rock, river sediment, and aquifers. These dynamic changes in Earth’s chemistry underpin many life-supporting processes in Earth’s Critical Zone – a thin near-surface zone where life, soil, water, rock, and air interact. A common problem in these biogeochemical studies is resolving spatial changes in chemical elements at the micrometer scale while preserving the sample. Nondestructive spatial imaging of geochemistry using a µ-XRF instrument will provide a means to resolve small-scale 2- and 3-dimensional changes in chemical composition.

Dr. Gary Stinchcomb, in collaboration with colleagues from the Department of Earth Sciences and CAESER, was awarded an NSF Instrumentation and Facilities grant (NSF EAR I/F) in the amount of $431,158 to acquire a µ-XRF instrument for measuring and mapping the spatial distribution of chemical elements in Earth materials. Stinchcomb and his students intend to use the instrument to map out plant-essential nutrients in modern and fossil soils. Understanding the micron-scale spatial distribution of key nutrients (e.g., P) could lead to breakthroughs in our understanding of how plant roots interact with the surrounding soil minerals (Figure 1).

Micro X-Ray Fluorescence Spectrometer

Figure 1. (LEFT) Boxplot showing significant difference in the mean soil P transfer, m(x)_P, as a function of forest type (CBO – cherry bark oak, PO – post oak). (MIDDLE) Boxplot showing significant difference in the CO2 efflux, FCO2, from the surface of the forest soils. (RIGHT) Petrographic image from the PO soil showing Fe-Mn oxide nodule, a sink for soil P, being occluded by clay (stress cutan). We hypothesize that this process is facilitating preferential P loss in the PO soil. The acquisition of a micro-XRF will allow Memphis researchers to test this and similar hypotheses involving small-scale spatial heterogeneities in soil and Earth materials in genera.

This instrument will also aid groundwater, sedimentology and geoarchaeology research by mapping chemical changes in minerals from aquifer sediments, flood and lake deposits, ancient river channels, and prehistoric rock quarries. Co-Investigators on this proposal include University of Memphis researchers: Dr. Will Jackson, Dr. Dan Larsen, Dr. Deb Leslie, Dr. Ray Lombardi, Dr. Ryan Parish, and Dr. Jenn Pickering.

This instrument, and the proposed Institute of µ-XRF at the University of Memphis, will create opportunities for students and promote diversity and inclusion through summer programs and visiting research fellows. The µ-XRF will foster education and training for students in the economically distressed Delta Regional Authority area, benefiting early career scientists and providing research opportunities for up to 150 students over the next 3-5 years.

Dr. Gary Stitchcomb

For more information on this project, contact Stinchcomb at gstnchcm@memphis.edu.