Leaching depth profiles

Figure 12. Ion microprobe depth profiles of lead and thallium in coal fly ash taken before (unextracted) and after solvent leaching with H2O or DMSO...

The ejecta layer was a shallow surface stratum at distances between 1000 and 3000 feet from the crater lip. The radionuclide depth profiles at 1500 feet were studied in detail to determine whether or not any radionuclide had been leached from the surface stratum of radioactivity. At... 

If the Cs/Mn ratios are calculated for the depth profiles at the crater lip stations, as was done for the 20A—1500 foot station, a similar condition is seen. Figure 12 shows the Cs/Mn ratios for ejecta samples collected at several crater lip stations. An increase in 137Cs concentration relative to 54Mn with depth is seen at each crater station. Increases in the ratio with depth represent enrichment of Cs with respect to Mn by rainfall leaching. Cs/Mn ratios of 0.01 to 0.02 are characteristic of the... 

Figure 1. SIMS depth profiles in a simulated nuclear waste glass. Major and minor elemental profiles are shown for fractured surfaces exposed to 25° C aqueous leaching for 2 d (a) and 50 d (b). (Reproduced, with permission, from Ref. 4. Copyright 1980, North-Holland Publishing Co.)...

Figure 2. SIMS depth profiles for a sodium borosilicate glass blank sample, air-exposed only (a), and sample exposed to aqueous leaching at 25°C for 30 min (b).

Figure 3. Comparison of SIMS depth profiles of aqueous leaching of a sodium borosilicate glass, for 30 min (a). Key ----------, 0°C and--------, 25°C. Error func-...

Figure 4. SIMS depth profiles for a borosilicate glass exposed to 0°C aqueous leaching for periods of 5 (-----------------------) and 30 (------) min.

Most recently Puppels and co-workers to determine the concentration of defined NMF component non-invasively in vivo in the SC have pioneered the use of confocal Raman microscopy.84 Figure 18.3 shows depth profiles for the major filaggrin derived components, urea and lactate obtained using this technique. Evidence of leaching from the skin surface is characteristically seen in most profiles and the precipitous drop off in levels of filaggrin derived components deeper in the SC indicates the boundary at which filaggrin hydrolysis is rapidly initiated. 

Figure 12. Hydrogen and sodium (relative to albite) depth profile of several silicates leached at 200°C in deionized water. [After Petit et al., (1989).]...

Figure 6.8 Na (by RBS) and H (by ERD) depth profiles of the surfaces of a sodium borosilicate glass leached in a pH 8 aqueous solution at 70 °C for various times. (From Reference 25.)...

Confocal Raman microscopy was used to study the distribution and redistribution (by leaching) of the fungicide Fluorfolpet FF (5%) and DOP (10-30 wt.%) in PVC films [559]. The technique was also used for depth profiling studies of small surfactant molecules (sodium dodecyl sulfate, SDS) and sulfate anions (804 ) in dry BuA/AA latex films [560]. Other techniques such as ATR-FTIR and step-scan PAS have extensively been used for the same purpose, but have some limitations in the... 

For each of the model compounds, some material will have leached deeper Into the soil than Is shown in the table. The model calculates only the position of maximum concentration. For a compound like DBCP, which has a very weak adsorption interaction with the soil, the concentration profile will be spread out. DBCP would probably be found at low concentrations at the 1017 cm level. For the strongly adsorbed compounds, such as toxaphene and methoxychlor, the concentration peak will be narrow, and the depth of maximum concentration is the depth where most of the material is. 

DBCP. The predictions suggest that DBCP is volatile and diffuses rapidly into the atmosphere and that it is also readily leached into the soil profile. In the model soil, its volatilization half-life was only 1.2 days when it was assumed to be evenly distributed into the top 10 cm of soil. However, DBCP could be leached as much as 50 cm deep by only 25 cm of water, and at this depth diffusion to the surface would be slow. From the literature study of transformation processes, we found no clear evidence for rapid oxidation or hydrolysis. Photolysis would not occur below the soil surface. No useable data for estimating biodegradation rates were found although Castro and Belser (28) showed that biodegradation did occur. The rate was assumed to be slow because all halogenated hydrocarbons degrade slowly. DBCP was therefore assumed to be persistent. 

The soil was loose and contained abundant spores with more genera above 0.4 m (Table 4, Fig. 6), and became denser due to the abrupt increasing in clay concentration below 0.4 m of SL profile (Chen et al. 2002a), which restrained the penetration of spores with leaching of soil water. Consequently, the quantity of spores decreased with depth (Table 4) and the genus became monotonous (Fig. 6). The loose/stiff quality of soil is then a critical factor controlling the penetration of spores. 

Both the Na and K intensities in the K-feldspar profile of Figure 4 are stable with depth indicating a previously documented lack of alkali mobility in the surface layers of feldspars at low temperature (7). In contrast, K increases and Na decreases with depth beneath the obsidian surface demonstrating substantial elemental mobility. The K loss near the surface corresponds to a concentration increase measured in aqueous solution. Sodium profiles in obsidian should exhibit even greater near-surface losses relative to K based on profiles measured by HF leaching (3) and sputter-induced optical emission studies (6). 

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