Page 343 - Soil and water contamination, 2nd edition

330 Soil and Water Contamination

2-
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of O , NO , and SO from pristine groundwater (Hunter et al., 1998). However, redox-
2 3 4
+
sensitive cations (Fe(II), Mn(II), and NH ) and organic micro-pollutants in the leachate
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plume are also subject to retardation , which hampers their advective and dispersive transport
across the plume fringe (Griffioen, 1999). Van Breukelen and Griffioen (2004) performed a
detailed study of the hydrochemical gradients at the top fringe of the Banisveld landfill leachate
plume, the Netherlands. In the period 1998–2001, the top of the plume rose by approximately
0.6 m in response to intensified drainage by a nearby brook. Figure 17.23 shows the depth
profiles of some solutes including redox-sensitive species sampled in 2001 (Van Breukelen and
Griffioen, 2004). Due to upward advective transport induced by the increased drainage and
differential retardation, the fronts of cations are clearly separated in space. The following cation
+
+
+
2+
2+
2+
fronts follow the conservative tracer front: 1) Na , 2) NH , and K , and 3) Ca , Mg , Fe ,
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+
2+
and Mn . Thus, cation exchange results in the spatial separation of NH and in particular
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