||Automated Long-Term Remote Monitoring of Sediment-Water Interfacial Flux.
B. K. Lien ;
C. G. Enfield
||National Risk Management Research Lab., Cincinnati, OH. Office of Research and Development.; Pegasus Technical Services, Cininnati, OH.
Water transport ;
Sediment-water interface ;
Flow sensor ;
Flow measurement ;
Field tests ;
Spatial variation ;
Temporal variation ;
Advective flux meter
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||Advective flux across the sediment-water interface is temporally and spatially heterogeneous in nature. For contaminated sediment sites, monitoring spatial as well as temporal variation of advective flux is of importance to proper risk management. This project was conducted to develop a ruggedized advective flux meter capable of unattended long-term remote monitoring of the sediment-water interfacial flux. The flux meter, based on the heat-pulse technique, is capable of quantitatively measuring bi-directional seepage flux from 0 to 8 cm/day with the current configuration. The system has automatic data acquisition, real time data display, and signal display/analysis capability. A remotely controlled monitoring module was included to permit system monitoring and modification over the internet. The instrument has undergone several calibrations to establish relations between the flow rate and the heat-pulse travel time. For very low flow rates, an alternate approach was adopted based on the ratio of temperature rises. Using this approach, it is possible to accurately interpret flow rates down to zero flow conditions. Depending on the magnitude, flow rate can be derived as a function of peak temperature arrival time or as a ratio of rise in temperature on both sides of the heater. Using these two methods, reliable measurements can be made over a wide bi-directional range of flows. In the field operation, the flow across the sediment-water interface is isolated by a dome chamber and funneled through a flow sensor where the flow rate is measured. The advective flux through the sediment-water interface, in terms of the vertical Darcy velocity, is calculated by Divigin the Flow rate through the flow sensor by the cross-section area of the dome.
||Prepared in cooperation with Pegasus Technical Services, Cininnati, OH.
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