Sedimentation rate versus time

Shoiild the particles have a tendency to cohere slightly during sedimentation, each sampling time, representing a different nominal detention time in the clarifier, will produce different suspended-sohds concentrations at similar rates. These data can be plotted as sets of cui ves of concentration versus settling rate for each detention time by the means just described. Scale-up will be similar, except that detention time will be a factor, and both depth and area of the clarifier will influence the results. In most cases, more than one combination of diameter and depth will be capable of producing the same clarification result. 

Plot of oceanic water depth versus sediment burial velocity (burial velocity is equal to sedimentation rate when the latter is constant over time and diagenetic loss is minimal). Source From Boudreau, B. P. (1997). Diagenetic Modeis and Their implementation. Springer-Verlag, p. 164. 

The data from a representative study of the disappearance of chlorpyrifos from an EPA-14 sediment/water system (p=0.20, fraction sorbed = 0.94) is illustrated in Figure 3. Comparison with Figure 1 shows that once sorptive equilibrium is achieved (t>14,000 minutes) the disappearance rate is first order for both the water and sediment phases. Also, the aqueous disappearance rate constant calculated from the slope of the linear portion of the natural log aqueous concentration versus time plot is 0.5 0.2 x 10 min, which is similar to the values measured in sediment-free EPA-14 supernatant (Table II). A plot summarizing two experiments using EPA-23 sediment is shown in Figure 4. The value of calculated from the... 

Figure 5. Overall sedimentation rates (a) and sedimentation rates of organic C, P, Zn, Cu, and Mn (b-f respectively) versus time (at 15- and 28-m depth). Lake Greifen overturn occurs in December-January.

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).

FIG U RE 10.8 Historical atmospheric loading of Cesium-137 versus time rates of accumulation of Cesium-137 and Lead-210 in Fox River sediments. (Adapted from LimnoTech. 2002a. Measurement of Burial Rates and Mixing Depths Using High Resolution Radioisotope Cores in the Lower Fox River, for the Fox River Group, Report prepared for the Fox River Group. Ann Arbor, MI, January.)... 

FIGURE 10.9 Historical records of sales/production of PCBs versus time rates of accumulation in Lake Ontario sediments (From Eisenreich, S.J., P.D. Capel, J.A. Robbins, and R. Bourbonniere. 1989. Environ. Sci. TechnoL, 23 1116-1126 Adapted from Schwarzenbach, R.P., P.M. Gschwend, and D.M. Imboden. 1993. Environmental Organic Chemistry, 2nd ed. John Wiley and Sons, Hoboken, NJ. With permission). 

Figure 20 Progress of intramolecular sulfurization of malabaricatriene (I) with depth in anoxic Cariaco basin sediments. Plot of the ratio of the concentrations of I to the sum of the concentrations of I + V (see Figure 19 for structures) as a function of sediment depth. The progress of transformation of I-V with increasing sediment depth is indicated by the steady decrease in the relative abundance of the precursor lipid (I). Inset plot of In ([ ]/([ ] + [V])) versus sediment age (= time), used to empirically determine the first-order rate constant for sulfur incorporation...

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