Agriculture Reference
In-Depth Information
Olivier - Arsenite
Column 301
0.6
0.4
Measured
M6 = K
e
, k
1
, k
2
, k
3
M7 = K
e
, k
1
, k
2
, k
i
M8 = k
1
, k
2
, k
3
, k
i
M9 = K
e
, k
1
, k
2
, k
3
, k
i
0.2
0.0
0
20
40
60
Pore Volume (V/V
o
)
FIGURE 6.24
Comparison of second-order model simulations using several model versions for describing
the arsenite breakthrough curve (BTC) from Olivier soil. The arrow indicates pore volumes
when flow interruptions occurred.
prediction capability of SOM in describing Cu mobility in strongly reactive
calcareous soils. The strongest Cu retention was observed in the surface
soil layer having 2.76% CaCO
3
in comparison to the subsurface layer having
1.18% CaCO
3
. Based on the Cu BTC results shown in Figure 6.25, recovery
in the effluent was only 27% of that applied. Such low Cu recovery in the
effluent was not surprising for this calcareous surface soil. In contrast Cu
recovery was 60% of that applied for the subsurface soil. Rodriguez-Rubio
et al. (2003) suggested that Cu was preferentially retained in calcareous soils
through precipitation of CuO, Cu
2
(OH)
2
CO
3
, or Cu(OH)
2
and by adsorption
on soil carbonates. Elzinga and Reeder (2002) used extended x-ray absorp-
tion fine-structure (EXAFS) spectroscopy to characterize Cu adsorption
complexes at the calcite surface. They observed that Cu occupied Ca sites in
the calcite structure, and formed inner-sphere Cu adsorption complexes at
calcite surfaces. EXAFS results revealed that the precipitation of malachite
(Cu
2
(OH)
2
CO
3
) did not take place in Cu/calcite suspensions at Cu concentra-
tion of 5.0 μM and 10.0 μM.
The solid curves in Figure 6.25 are simulations using the SOM model.
Comparison of calculated BTCs and measured Cu effluent concentrations
illustrates the capability of the SOM model in predicting Cu mobility in
the surface and subsurface columns. Simulations using a linear model are
also given in Figure 6.25, indicated by the dashed curves. The linear model
Search WWH ::
Custom Search