This proposal addresses the challenge of robustly and efficiently measuring processes and structures associated with soil hydrogeology and subsurface biogeochemistry at coastal interfaces. We will develop NMR sensors capable of performing high-resolution measurements of soil properties from the pore-scale to the site-scale. With current technology, shallow NMR measurements are frequently limited by insufficient signal and excess noise. Next generation detection modules will be developed for high-sensitivity, noise-immunity and robust performance across a wide range of environmental conditions. Sensor configurations will include non-invasive surface modules as well as in-situ probes. These tools will be designed for limited-access manual surveying and eventually for remote monitoring. The Phase 1 tasks will establish the feasibility of sensors that have significantly enhanced sensitivity (signal amplitude) and noise-immunity. We will design a functional prototypes of a unilateral magnet sensor that can be used for non-invasive profiling in the upper 30cm, an in-situ probe for depth profiling of several meters, and hardware/software architectures for noise-rejection. We will test the technology at local field sites and, in the final month, will carry out demonstrations at a coast interface site of current interest to DOE Office of Science. Completion of this technology in Phase 2 and beyond will deliver robust and efficient soil sensors for both small- and large-scale site characterization. NMR measurements will allow efficient determination of key soil parameters that cannot be easily measured by other methods, and which are key to controlling groundwater flow and storage. For the DOE coastal systems initiative, these measurements will be of critical value to improve biogeochemical and reactive transport models related to nutrient loading and cycling, processes that have profound effect on ecosystems, coastal economies, and global climate. Characterization of shallow soils is also a critical challenge in commercial markets of environmental management and geotechnical engineering and this technology will be readily transitioned for those complementary commercial purposes.
