Contaminants upward migration

If upward migration of contaminants (due to hydrogeological conditions) through the surface barrier is considered likely, a surface barrier can be engineered. For instance, impermeable clays or high-density polyethylene (HDPE)... 

The chemistry of soil contaminants is also an important factor determining the success of a barrier layer. Chemical attack on soil surface covers by low-pH soils, and the deflocculation of clays by oils and tars, may also cause failure of the integrity of the barrier, leading to upward migration of the contaminants (Muller-Kirchenbauer et al., 1988). To minimize the risk of exposure due to barrier failure. Tiller (1992) suggests that surface barriers can be used in conjunction with a less sensitive land use that poses the least risk to public health if the barrier fails. 

Air sparging is the process of introducing compressed air below the VOC- or semi-VOC-contaminated water table, and allowing it to migrate upward into the vadose... 

Figure 11.4 Upward soil migration of f -om a contaminated water table over a 6-month period, (a) The water table height was manipulated, in 0.5cm increments, from 45cm depth up to 30cm depth (over the initial 3 months) and back down to 45cm depth (over the latter 3 months), (b) The water table remained at 45 cm depth for the duration of the experiment. Source-. Ashworth and Shaw (2006b) reproduced with permission from Elsevier.

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