Flux-Core Data

The first step is to determine the number of turns needed for the primary winding. For this, the parameters from the core data sheet of the particular core and core material are used. Also, the minimum level of flux density already should have been determined (refer to Appendix D). The equation for determining the number of turns for the primary winding in the CGS System (U.S.) is... 

This study demonstrates the use of multiple-core methods to obtain whole-basin sediment fluxes from a suite of lakes and the application of these data to questions of atmospheric metal deposition. Multiple-core data can be economically produced by integrating longer core sections and reducing the number stratigraphic units for analysis. As few as three 210Pb analyses per core can yield a modern accumulation rate additional samples provide more historical detail. 

The quantity V,(C, - Co) was then plotted versus time t, a line fit to the data by least-square methods, and the amount of material entering the water per unit time determined as the slope. This number was divided by the surface area sampled by the flux box to calculate the flux of material out of the sediment per unit area per time. The error is taken as the standard deviation of the slope and is about 10%. The actual uncertainty must be higher, as will become clear later (Nixon et al., 1980). The last sample points (—30-50 hr) in both the summer and fall sets of flux cores were not used in the calculations. Inclusion of these points often, but not always, resulted in calculation of a higher (or Mn, see Part II) flux. (In some cases a lower flux is calculated.) This suggested that lower O2 levels were beginning to cause changes in pore-water profiles and perhaps reaction distribution in the sediment. For consistency in calculation none of these later sample points were used. These points were arbitrarily included or discarded in previous calculations (Aller, 1977) the present... 

Fig. 10. Amount of and Fe " released from flux-core sediment versus time after collection. Mn increases are approximately linear with time and are plotted relative to the starting concentration in the blank flux boxes (Co, t = 0). Only data from the first 30 hr are used to calculate summer and fall flux rates. Fe increases are plotted relative to the concentration of the first sample taken from the incubated flux core (Co, t = 0). An approximate initial linear rate of increase is assumed and correction for Fe precipitation made in calculating the flux (Section 5.4).

The values for Fe in flux cores are assumed to be 7.5 x lO Vmin at 22°C, and based on a temperature dependence for Fe precipitation rates of 10 times/15°C found by Stumm and Lee (1961), kp 1.6 x 10 Vmin at 15 C. Data of Lewin and Chen (1973) that illustrate Fe precipitation at 10°C in sample bottles of similar size to the flux cores give a calculated... 

Integration of in-core flux mapping data for fuel bumup calculations... 

Figure 10. An example of the use of ( Paxs/ °Thxs) to reconstruct past productivity taken from Chase et al. (in press-a). Data is from a core in the Southern Pacific (AESOPS Station 6 at 61° 52.5 S, 169° 58.3 W). The downcore record of ( Pa/ °Th)xs,o indicates an increase in opal productivity centered at 15 ka. This productivity increase is also seen in the records of two other productivity proxies— the opal accumulation and Ba accumulation rates. Downcore records of these sediment constituents are also shown and have been converted from concentrations to accumulation fluxes by normalizing to the known °Thx, flux.

Table 1. Fluxes of Mn (mmol/m2/d) and As (x10 3 mmol/m2/d) in short-term, duplicate and triplicate incubations of cores at three overlying water oxygen concentrations. A/D no data, - core not incubated,

Table 8 Average PBDE surface concentrations, doubling times, inventories, burdens, surface fluxes, and load rates in sediment from the Great Lakes. Data were from Zhu and Hites [22] and Song et al. [46-48]. The errors are 1 standard error (N = 2- 4) NS indicates that the concentrations did not change significantly with depth in this core ...

Sakurai, T., Suzuki, N., Morita, M., 2002. Examination of dioxin fluxes recorded in dated aquatic-sediment cores in the Kanto region of Japan using multivariate data analysis. 

In most of the 30 porewater profiles examined between 1984 and 1987, sulfate concentrations decreased to < 20 peq/L within 5 cm of the sediment-water interface and remained relatively constant below this depth. These data indicate that sulfate reduction occurs primarily in the upper 5 cm, a contention which is supported by results from laboratory studies in which 35SO was added to intact sediment-water cores. We generally observed steeper sulfate gradients in summer than in winter, and hypothesize that winter gradients are not as steep because microbial activity is reduced. So far, however, we have not found a statistically significant relationship between temperature and sulfate flux. 

The overall heat transfer coefficient U in Eqn. (3) is based on the measured temperature difference between the central axis of the bed and the coolant. It is derived by asymptotic matching of thermal fluxes between the one-dimensional (U) and two-dimensional (kr,eff kw,eff) continuum models of heat transfer. Existing correlations are employed to describe the underlying heat transfer processes with the exception of Eqn. (7), which is a new result for the apparent solid phase conductivity (k g), including the effect of the tube wall. Its derivation is based on an analysis of stagnant bed conductivity data (8, 9), accounting for "central-core" and wall thermal resistances. 

Figure 2 shows the trial network as it is presently configured, including the supporting sub-network of more intensive measurements intended to provide benchmark data for testing the inferential methods. At stations of this special subnetwork (the "CORE" network), data are recorded with finer time resolution, and deposition fluxes are measured using more direct measurement techniques whenever possible. 

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