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Utility of bromide and heat tracers for aquifer characterization affected by highly transient flow conditions
Author(s) -
Ma Rui,
Zheng Chunmiao,
Zachara John M.,
Tonkin Matthew
Publication year - 2012
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2011wr011281
Subject(s) - tracer , aquifer , thermal conductivity , hydraulic conductivity , thermal conduction , calibration , plume , thermal diffusivity , materials science , environmental science , soil science , mechanics , geology , thermodynamics , geotechnical engineering , groundwater , soil water , composite material , physics , statistics , mathematics , nuclear physics
A tracer test using both bromide and heat tracers conducted at the Integrated Field Research Challenge site in Hanford 300 Area (300A), Washington, provided an instrument for evaluating the utility of bromide and heat tracers for aquifer characterization. The bromide tracer data were critical to improving the calibration of the flow model complicated by the highly dynamic nature of the flow field. However, most bromide concentrations were obtained from fully screened observation wells, lacking depth‐specific resolution for vertical characterization. On the other hand, depth‐specific temperature data were relatively simple and inexpensive to acquire. However, temperature‐driven fluid density effects influenced heat plume movement. Moreover, the temperature data contained “noise” caused by heating during fluid injection and sampling events. Using the hydraulic conductivity distribution obtained from the calibration of the bromide transport model, the temperature depth profiles and arrival times of temperature peaks simulated by the heat transport model were in reasonable agreement with observations. This suggested that heat can be used as a cost‐effective proxy for solute tracers for calibration of the hydraulic conductivity distribution, especially in the vertical direction. However, a heat tracer test must be carefully designed and executed to minimize fluid density effects and sources of noise in temperature data. A sensitivity analysis also revealed that heat transport was most sensitive to hydraulic conductivity and porosity, less sensitive to thermal distribution factor, and least sensitive to thermal dispersion and heat conduction. This indicated that the hydraulic conductivity remains the primary calibration parameter for heat transport.