The potential for the widespread contamination of groundwater by Dense Non-aqueous
Liquids (DNAPLs) in South Africa is substantial, because of the extensive production,
transport, utilisation, and disposal of large volumes of DNAPL chemicals. There are a
great number of potential sites where DNAPLs may have been released to the subsurface
in varying quantities. A basic understanding of the nature and occurrence of groundwater
in South Africa aquifer systems is a prerequisite for assessment, monitoring and
management of DNAPL contaminated sites.
The physical properties of an aquifer that have the greatest impact on the fate and
transport of DNAPL contaminants, are the flow rate and flow mechanism present, and the
hydraulic conductivity. The major South African aquifer systems have been classified in
relation to the dominant flow mechanisms and flow characteristics. The majority of the
utilised South African aquifers can be classified as intergranular fractured aquifers. From
the results of this study, which included laboratory experiments and the controlled
injection of a surrogate DNAPL in the field, it is clear that preferential pathways in
fractured rock will determine the flow path of any DNAPL phase contamination.
Aqueous plumes of DNAPL contaminants will also be influenced by these pathways
(dissolving and or diffusing from the NAPL into the water in fractures and matrix) which
can result in spatially variable aqueous plumes in these aquifer systems. The local
variations in fracture strike and dip play a far more important role in DNAPL flow than
the regional fracture dip or groundwater flow directions.
Natural attenuation processes are important consideration under South African
conditions. Relatively high organic carbon in the shallow zones assists in retardation of
the organic contaminants, while the large unsaturated zone, arid climate and high
temperatures leads to significant loss of contaminant mass through volatilization.
Although the National Water and Environmental Acts of South Africa are very clear on
prevention of pollution to, and management of water resources, no guidelines exist on
how to deal with DNAPL contaminated sites. Recommendations have been made
relating to the regulations that are required for:
· Site assessment
· Sampling and monitoring
· Implementation of monitored natural attenuation
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-12122007-081339 |
| Date | 12 December 2007 |
| Creators | Pretorius, Jennifer Anne |
| Contributors | Dr BH Usher |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-12122007-081339/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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