HR: 1400h
AN: H33C-02    [Abstracts]
TI: An Investigation of the Effects of Body Design on Measurement Accuracy and Optimal Deployment Duration of a Passive Surface Water Flux Meter
AU: * Padowski, J C
EM: JCPadowski@ifas.ufl.edu
AF: Soil and Water Science Department, University of Florida, Gainesville, FL 32611, United States
AU: Jawitz, J W
EM: jawitz@ufl.edu
AF: Soil and Water Science Department, University of Florida, Gainesville, FL 32611, United States
AU: Klammler, H
EM: haki@gmx.at
AF: Research Center for Geophysical and Geological Studies, Federal University of Bahia, Salvador, Brazil
AU: Hatfield, K
EM: khatf@ce.ufl.edu
AF: Department of Civil and Coastal Engineering, University of Florida, Gainesville, FL 32611, United States
AU: Annable, M D
EM: annable@ufl.edu
AF: Department of Environmental Engineering Sciences, University of Florida, Gainesville, FL 32611, United States
AB: Water quality monitoring is essential for evaluating and complying with Total Maximum Daily Loads (TMDL). Conventional methods for gathering water and solute flux data from surface waters involves collecting, compiling and analyzing discrete point measurements to obtain cumulative flux data. The Passive Surface Water Flux Meter (PSFM) is designed to measure water and solute fluxes by automatically integrating instantaneous data in situ; therefore replacing the need for individual sample collections and data processing. A small cartridge within the device contains two types of porous media which simultaneously sorb solutes and release a resident tracer so that solute and water flux may be quantified. The PSFM utilizes the natural pressure gradient created by water flowing around the device. This gradient is used to induce flow through a small cartridge containing sorptive porous media pre-equilibrated with a resident tracer. In general, higher velocities correlate to larger pressure gradients across the cartridge and therefore reduce the amount of time a device can be deployed. However, the magnitude of the pressure gradient depends not only on the velocity of the water but the body design of the device. Body design can be modified to adjust the range of pressure gradients produced. Devices that are more blunt (cylindrical) in nature create higher gradients than more streamlined devices. Therefore, optimal shape and water velocity play an important role in the length of time a PSFM can be deployed and the accuracy of the measurements. Two designs, a blunt (cylindrical) and a streamlined (Joukowsky profile) device, were tested in this study. Laboratory experiments were performed in a large tilting flume to determine maximum deployment times for both devices across velocities ranging from 25-65 cm/s. Optimal deployment time was determined from the amount of resident tracers remaining within the cartridge and accuracy was determined by comparing measurement performance between both devices. Results from these experiments showed that the blunt device provided more accurate water and solute flux measurements at lower velocities, whereas the streamlined shape provided more accurate measurements at higher velocities. Results also indicated that optimal deployment time is dependent on the type of resident tracer as well as device shape. These findings indicate that the shape profile of the PSFM may be adjusted to provide the most accurate cumulative water and solute flux measurements when deployed in flow regimes of known hydrological conditions.
DE: 1871 Surface water quality
DE: 1895 Instruments and techniques: monitoring
SC: Hydrology [H]
MN: 2007 Joint Assembly