This project will create a new, unique synchrotron-based user facility to examine geologic materials at the micron scale with a focused X-ray beam tuned specifically for lighter elements Na through Ti. This facility is designed and optimized for "tender" (1-8 keV energy) X-ray micro-spectroscopy and imaging applications for Earth Science research, and will complement existing and highly productive "hard" X-ray facilities operating above about 4.5 keV. It will extend to lower energies the X-ray fluorescence (XRF) and X-ray absorption spectroscopy (XAS) capabilities typical of hard X-ray microprobes, as element-specific non-invasive probes of elemental distribution and local physical and electronic structures and states in crystalline and non-crystalline materials. In addition, it will offer advanced capabilities for microbeam extended X-ray absorption spectroscopy (EXAFS) for determination of more detailed local structure around the selected element.
This project will be undertaken by adding new micro-focusing capabilities at an established and proven macro-focused (~1mm spot size) tender-energy XAS beamline at X15B of the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory, and will subsequently transition to the new Tender Energy Spectroscopy (TES) beamline under development at NSLS-II. Its key attributes will be the distinct 1 to 8 keV energy range, user-tunable spot size from about 50 microns to 1 micron, high flux and stability optimized for high-quality and extended XAS, options for both XRF and XAS mapping with rapid scanning, and a helium glove-box sample environment. Performance will improve when transferred to NSLS-II, a state-of-the-art new Synchrotron designed for high brightness applications. These new capabilities are critical for advancing our knowledge of geochemical and biogeochemical processes, in particular those involving lighter elements, and will be openly available for use through the NSLS General User program. Specific applications targeted include the mineral-water interface, nutrients and contaminants, carbonates, paleoclimate, redox processes, high-pressure mineralogy; and health effects of Earth materials.
Phosphorus is an essential nutrient element for all life forms. Phosphate fertilizers are routinely applied to soils to support growth of agricultural crops. Some of this phosphate invariably migrates to streams and rivers, potentially leading to algal blooms that deteriorate the quality of these surface waters. Knowledge of how phosphorus binds on soil particles helps us develop management strategies for maximizing the benefits of phosphorus fertilization in agriculture, reducing the cost of fertilizers to farmers, and preventing detrimental impacts on water quality. This NSF project involved building a state-of-the art X-ray microscope that can be used to image phosphorus and other elements directly on soil particles. The microscope, which was built on an electron accelerator (synchrotron) that produces extremely intense X-rays, is capable of analyzing chemical components of soil phosphorus that are important for predicting and controlling how this nutrient behaves in soils. Our task was to evaluate the quality of data produced by the X-ray microscope on soil samples during initial construction, and also the ease of use of the microscope. Macroscopic X-ray data that we collected at a synchrotron facility in Thailand provided a useful target of data quality for the X-ray microscope. Phosphorus analyses that we performed during the early stages of microscope functioning at the National Synchrotron Light Source (NSLS) did not achieve this target for data quality. However, the X-ray microscope is now being moved to a new synchrotron facility at Brookhaven National Laboratory (NSLS-II) that will provide improved data quality due to the more powerful X-ray beam produced. Some problems encountered with the stability of the X-ray beam during analyses should also go away when the microscope is set up at the new facility. In essence, this project allowed the new X-ray microscope to first be built at the NSLS, so that the transition to the new NSLS-II will be more efficient. Soil scientists can more quickly take advantage of this new, state-of-the art facility and make timely discoveries in phosphorus chemistry of soils that will improve the management of this nutrient for agriculture while also protecting the quality of our nation's water resources.
