HR: 15:25h
AN: H23G-08 INVITED     [Abstracts]
TI: Microsensors to the Model Forecasts: Multiscale Embedded Networked Sensing of Nutrients in the Watershed
AU: * Harmon, T C
EM: tharmon@ucmerced.edu
AF: University of California Merced, School of Engineering P.O. Box 2039, Merced, CA 95340 United States
AB: Hydrologic and water quality observatories are being planned with a vision of enhancing our ability to better understand, forecast and adaptively manage both water quantity and quality. To adequately cover these spatially and temporally variable systems, distributed, embedded sensor networks must be designed with the proper mix (multimodality) of sensors to quantify key system properties, including temperature and chemical distributions, as well as mass and energy fluxes, and to do so across multiple scales. Given resource limitations, process models need to be coupled to the sensor network to interpolate between sensor data. This work focuses on the spatially distributed flux of nutrients, specifically nitrate, in surface-subsurface environments. It begins at the sensor level, describing the development and testing of nitrate microsensors that are scaleable to large, dense sensor networks required to cover heterogeneous watersheds, including associated soil and sediment systems. First and second generation miniature and inexpensive nitrate sensors (ion selective electrodes) fabricated by depositing conducting polymers on carbon substrates are presented in the context of laboratory and field tests. While these sensors are limited to relatively short deployments (4-8 weeks), there are potential strategies for overcoming this problem. Scale-up to one- and three-dimensional soil/sediment sensor arrays is discussed in the context of two deployments: (1) a groundwater quality protection network, where recycled wastewater that is potentially high in nitrate is being used for agricultural irrigation, and (2) nonpoint source nitrate pollution in rivers and groundwater in agricultural watersheds. Recent hardware (wireless transceivers) and software advancements (e.g., network topology design and debugging, energy management) intended for networks spanning 100s of m in space are outlined in these examples. The discussion extends to sensor form factor, in situ calibration, network spatial design, calibration and data integrity, complimentary modes of sensing and integrated sensing and modeling, concluding with an assessment of current limitations and a proposal of possible strategies for overcoming these limitations.
DE: 1848 Monitoring networks
DE: 1894 Instruments and techniques: modeling
DE: 1895 Instruments and techniques: monitoring
DE: 4894 Instruments, sensors, and techniques
SC: Hydrology [H]
MN: Fall Meeting 2005