CONTAMINATION OF CHALK GROUNDWATER BY CHLORINATED SOLVENTS - CASE-STUDY OF DEEP PENETRATION BY NONAQUEOUS PHASE LIQUIDS

The transport behaviour of chlorinated solvents, both In the aqueous p hase and as a dense non-aqueous phase liquid (DNAPL), in fissured micr oporous aquifers is reviewed. The presence of DNAPL in. aquifers is es pecially serious as it is likely to be the main subsurface source of c ontamination and, given the slow rates of dissolution in groundwater, may persist for decades. However, the identification and quantificatio n of DNAPLs III fractured aquifers present many practical problems and are often. not-achievable A case study of a Chalk site which had been contaminated. by chlorinated solvents demonstrated that the use of; r ange of techniques, including depth profiling of solvent porewater con centrations in cored boreholes, can provide clear evidence for the pre sence of DNAPL at depth, although DNAPL, was not itself observed. Theo retical considerations and field observations confirmed that DNAPL mov ement is via fractures rather than through the microporous matrix.