Fluctuation trace, generalized

Figure 2.7 Illustration showing a generalized representative fluctuation trace with the definitions of parameters used in equation 2.15 shown.

Nearly all trace elements show depth-related trends, with minor fluctuations (Fig. 3). The elements that increase with depth in porewaters from both sites are B, Cr, Li, Mo, Pb, and Ni. Concentrations are mostly higher in the Drax porewaters in a comparable manner to the major ions. Arsenic and Se are similar to each other in the porewaters from the two sites. Concentrations are lower than the other elements considered here and both elements show a general increase with depth in the Drax porewaters whereas at Meaford there is not a clear depth trend. The Ba concentrations decrease with depth in the Drax samples in a comparable manner to the NO, and CD depth trends and there is also a similar reversal of the depth trend between 2 and 3 m. The fact that the trends appear similar suggests that at least some of the Ba may be derived from the surface. In the Meaford samples Ba does not decrease with depth, but neither do NO and CD, and therefore there is further support for a possible surface-derived component in the Drax porewaters. The Ba concentrations at Meaford fluctuate and do not vary consistently with depth making interpretation difficult. The Sr porewater concentrations in the Meaford samples do show a more consistent depth relationship suggesting dissolution from the ash, whereas at Drax, below the surface zone, values are approximately constant, which could... 

While detailed transport calculations of trace constituent distributions in the troposphere are not generally available, a number of simple box models have been fitted to measurements of seasonal fluctuations in carbon dioxide and ozone and tropospheric distributions of fission debris. These box models may not accurately represent the physical processes responsible for tropospheric motions and mixing, but the parameters used in the model do provide reasonable estimates of macroscopic mixing rates in the troposphere. 

A typical schematic inlet stream temperature history is shown in Fig. 1. The temperatures were recorded on the oscillograph at a chart speed of 4 in./sec. Since the cool-down period was generally 20 sec or more in duration, much of the significance of the temperature fluctuations observed is lost on the time scale used in Fig. 1 therefore, actual temperature traces for typical time increments are reproduced in Fig. 2. From Fig. 1 it is evident that the temperature-time trace is initially very smooth, but fluctuates with time thereafter. A few seconds after the admission of fluid into the test section, saturation temperature appears momentarily. As the test section gradually cools down, liquid appears more frequently and persists for longer periods. These phenomena can be readily seen from the sequence of temperature traces shown in Fig. 2. From these observations, the following mechanisms of two-phase flow are postulated for pressurized cool-dowm. 

Contamination generally poses the most important problem in ultra-trace analysis. It causes fluctuations of the blank values, thus defining the lower limits of detection, but also introduces systematic inaccuracies. Tracer techniques can be used to study the sources of contamination reagent blanks, vessel walls, airborne pollutants, etc. 

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