Agriculture Reference
In-Depth Information
Adsorbed S (µg/g)
Concentration c (µg/cm 3 )
0
20
40
60
80
100
0
10
20
30
40
50
60
70
0
0
10
5
10
20
30
10
Clay
10
40
Clay
50
15
20
20
50
Sand
Sand
20
30
30
30
40
Loam
40
40
Loam
50 h
30
40
50
50
50 h
60
60
FIGURE 9.9
Solute concentration and amount of solute sorbed versus soil depth in a three-layered soil
profile with first-order kinetic retention reactions.
with time in the clay layer in comparison to the other two layers. Such a slow
adsorption resulted in a decrease of solute concentration with soil depth in
the clay layer. In contrast, a somewhat uniform distribution was observed for
the sand layer accompanied by an increase in the loam layer. Solute trans-
port during infiltration and water redistribution was investigated for several
other combinations of soil layer stratifications and the results indicated that
solute transport through multilayered soil was significantly influenced by
the order in which the soil layers are stratified. Another example is presented
in Figures  9.10 and 9.11 from a greenhouse lysimeter study of a Windsor
soil. Secondary treated wastewater was applied to the soil twice weekly for
25 weeks. Solution samples were collected and analyzed for N, and the soil-
water pressure head was monitored frequently at different depths in this
three-layered soil. Model predictions agreed well with pressure head data
with depth and time, as well as gravimetrically determined soil water con-
tent with depth for the two soils. Model predictions of nitrate concentration
shown, in Figure 9.11 with depth and time were adequate except for interme-
diate soil depths (30 and 45 cm). Predictions of ammonium were consistently
higher than measured results for all depths (data not shown).
Examples of experimental and predicted BTC results based on miscible
displacements from packed soil columns having two layers are shown in
Figures 9.12 and 9.13. Predictions and experimental BTC results for tritium
shown in Figure  9.13 (solid and dashed lines) for a sand-clay and clay-
sand sequence indicate a good match of the experimental data. All input
Search WWH ::




Custom Search