“…When distinguishing the different layers and their potential for degradation, inconsistent data are reported. In some publications degradation of contaminants is reported only to occur in the soil layer (Johnson et al, 2000), others report that in the unsaturated zone degradation of contaminants may occur as well (Börger and Poll, 1998;Gooddy et al, 2001), but significantly less effective Johnson et al, 1998). For the saturated zone no or ineffective degradation processes were observed (Börger and Poll, 1998;Johnson et al, 1998).…”