Field tracer tests

Dispersion has often been treated as a constant parameter, with values of the dispersivity on the order of centimeters (Perkins and Johnston, 1963). For typical shallow groundwater flow velocities, this places dispersive transport on the same order as diffusion. However, extensive field tracer tests have demonstrated that dispersion is much more effective than these values would indicate and, furthermore, that effective dispersivity tends to increase with the scale of the tracer test (GeUiar, 1986 Schwartz, 1977 Sudicky and Frind, 1981). This behavior derives from the fundamentally quasifractal nature of hydraulic heterogeneity... 

Standard tracer tests are typically used at relatively small field scales. Estimates of dispersivity at scales larger than several hundred of meters usually rely on different methods, either using historical contamination data or exploiting natural variations in the chemistry of natural recharge of the aquifer. However, estimates of advection and dispersion based on data from contaminant plumes or environmental tracer measurements are less reliable than field tracer tests, since there is a larger uncertainty in the location and the intensity of source zone. Often, there is also an inadequate number of sampling points. 

Quantification of injection fluids effects to Mindanao Geothermal Production Field productivity through a series of tracer tests,... 

FIerras, E.B. 2004. The Naphthalene Disulfonate Tracer Test in the Mahanagdong Field, Leyte. Proceedings, 25th Annual PNOC-EDC Geothermal Conference. 2005. 

Williams, G.M. et al., The influence of organics in field migration experiments. Part 1. In situ tracer tests and preliminary modeling, Radiochimica Acta, 52/53, 463, 1991. 

Transferability of the results from this study to the Cape Cod natural gradient tracer test will provide information about the validity of laboratory experiments in providing information about onsite processes. Although actual values for some of the physical parameters determined in the laboratory may not apply to an aquifer because of scale differences between laboratory and field, conceptually realistic models such as the profile side-pore diffusion model may be able to simulate onsite transport conditions more accurately. 

The tracer test was carried out in a single realization of the heterogeneous hydraulic conductivity field. There are number of other realizations satisfying the same statistical properties, each potentially yielding different aL values. Since Equation 15.9 yields a theoretical value that represents the average over all possible realizations of the K field, one could expect the value of a single realization to be different. 

Tracer materials are defined as any product included in the test substance that can be recovered analytically for determining the drift from the application. This may be the active ingredient in an actual tank mix, or it may be a material added to the tank mix for subsequent detection. The selection of an appropriate tracer for assessing deposition rates in the field is critical to the success of a field study. Tracer materials such as low-level active ingredient products, colored dyes, fluorescent dyes, metallic salts, rare earth elements and radioactive isotopes have been used with varying degrees of success in the field. An appropriate tracer should have the following characteristics ... 

When a tracer is considered, it is important to evaluate its performance with respect to these criteria, especially stability during exposure and storage/analysis. Normal practice involves conducting weathering tests where field collectors are treated with known amounts of the tracer and an assessment is made of weathering, extraction and storage stability under conditions pertaining to the intended use. The characteristics of the tracer allow it to be applied uniformly over the application area. Typically, application monitors are used to verify both the application rate and the uniformity of the application. 

Figure E6.7.5. Tracer curves fit to the field tests at x = 25 km, downstream of Kearney, by the reactor model provided in Figure E6.7.4.

To describe a zone of potential effect, information about the initial concentration of the effluent, its dilution in the receiving water, and the extent of the 1% plume is required. Some pulp mills calculate a range of concentrations from the outfall to the 1% effluent plume boundary. Tracer studies and additional conductivity measurements taken during field work can support previous plume delineation studies to identify the areas in the receiving waters having effluent concentrations greater than 1 %. The zone of potential effect for a sublethal test result can then be mapped onto the 1 % effluent plume based on where the effluent concentrations are... 

Catalytic Oxidation of Carbon Monoxide. - This reaction has been used by several authors as a simple test reaction in the field of catalytic oxidation. Hirota et al.115 conclude from tracer experiments that this follows an oxidation-reduction mechanism in which lattice oxygen is used. In the mechanism proposed, two neighbouring (V=0) groups are successively reduced by CO and are then simultaneously reoxidized. 

From the OPCW proficiency tests, it can be seen that from the seventh OPCW proficiency test (spring 2000) onward, Tracer has been the only FTIR technique for which use has been reported. Four laboratories have used this technique. At least two other laboratories working in the field of CWC... 

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