Reactive transport modelling of fertilizer waste in a dual porosity aquifer
| dc.contributor.advisor | Van Tonder, G. J. | |
| dc.contributor.author | Bredenkamp, Brendon | |
| dc.date.accessioned | 2015-10-20T09:33:02Z | |
| dc.date.available | 2015-10-20T09:33:02Z | |
| dc.date.issued | 2011-11-16 | |
| dc.description.abstract | English: The fertilizer production facility had a negative impact on the soil, groundwater and surface water environment due to the handling / storage and production activities at the site. Observations and numerical modelling found the fertilizer product loadings areas as the main source area of contaminants viz. Ca, Mg, NO3, Cl, SO4, EC and TDS. Uncontrolled run-off emanating from the site is a major contributing factor to contaminating the groundwater and surface water resources. A distinct difference could be observed between the geochemical signature of the potential contaminated seepage and that of the groundwater. This geochemical characterisation of the contaminant plume identified an interaction of the leachate and the soil with a high clay (montmorillonite) content, with various cation exchange and sorption processes occurring. Potassium is largely exchanged (for sodium), while phosphates are likely to sorbed on the clay particles. Nitrate is likely to be retarded to a limited extent, especially when redox conditions are conducive to the conservation of the nitrate specie. The elevated contaminant concentrations pose a health risk to potential users and livestock which may ingest the water, especially nitrate concentrations. Numerical modelling was used to validate and develop the site conceptual model. Iterative modelling improved the initial correlation R2 of modelled and observed nitrate concentrations, the correlation improved from 0.29 to 0.64. The model was validated by assuming that horizontal and bedding plan fractures are likely to play a role in contaminant transport (which was not modelled). Artificial recharge (seepage and leachate infiltration) was present at the plant area. Groundwater abstraction from farmers boreholes downstream had an influence on the development of the nitrate plume. Surface water contamination contributed to the current plume geometry and therefore partly responsible for the current plume extent. A secondary groundwater contaminant source was found in the south western part of the study area. Predictive modelling found abstraction of groundwater from site to be the most effective containment measure when compared to a cut-off trench. The groundwater contamination is likely to pose a low current and future risk to groundwater users, as no current groundwater users are found in proximity to the site and the contaminant plume. However a potential surface contaminant risk does occur to down stream surface water bodies during a flood event. | en_ZA |
| dc.description.abstract | Afrikaans: Die kunsmis vervaardigings fasiliteit het 'n negatiewe impak op die grond, grondwater en oppervlakwater omgewing as gevolg van die hantering / stoor-en produksie-aktiwiteite op die terrein. Waarnemings en numeriese modellering het gevind dat die kunsmis laai gebiede die hoof bron van kontaminante nl. Ca, Mg, NO3, Cl, SO4, EC en TDS is. Onbeheerde opervlak water vloei afkomstig van die terrein is 'n groot bydraende faktor tot die besoedeling van die grondwater en oppervlakwater hulpbronne. 'n Duidelike verskil tussen die geochemiese eienskappe van die potensiële besoedelde loog water en die van grondwater kan waargeneem word. Hierdie geochemiese karakterisering van die besoedelings pluim dui aan dat daar „n interaksie tussen die loog water en die grond met 'n hoë klei (montmorilloniet) inhoud geïdentifiseer is. Verskeie katioon-uitruiling en sorpsie prosesse vind plaas. Kalium word grootliks gewissel (met natrium), terwyl fosfate geneig is om op die klei deeltjies te adsorbeer. Nitraat word waarskynlik tot 'n beperkte mate vertraag, veral wanneer redox kondisies bevorderlik is vir die bewaring van die nitraat spesie. Die verhoogde kontaminant konsentrasies skep 'n risiko vir die gesondheid vir potensiële gebruikers en vee wat die water inneem (veral nitraat konsentrasies). Numeriese modellering is gebruik om die terrein konseptuele model te kontroleer en te ontwikkeling. Iteratiewe modellering verbeter die aanvanklike korrelasie R2 van die gemodelleerde en waargeneemde nitraat konsentrasies. Die aanvanklike korrelasie van 0,29 het verbeter na 0,64. Die model is gevalideer deur die veronderstelling dat horisontale en naatvlak frakture geneig is om 'n rol speel in die besoedelings vervoer (wat nie gemodelleer is nie). Kunsmatige aanvulling (loging en infiltrasie) was teenwoordig in die aanleg area. Die onttrekking van grondwater stroom-af van die terrein uit die boere se boorgate het 'n invloed gehad op die ontwikkeling van die nitraat pluim. Oppervlakwaterbesoedeling het grootliks bygedra tot die huidige grondwater besoedelings pluim en dus deels verantwoordelik vir die huidige pluim ontwikkeling. 'n Sekondêre grondwater besoedelings bron is gevind in die suid westelike deel van die studie area. Voorspellende modellering het gevind dat onttrekking van grondwater op terrein die mees effektiewe vorm van pluim inperking is, in vergelyking met 'n afsny sloot. Die grondwater besoedeling het waarskynlik 'n lae huidige en toekomstige risiko in terme van impak op grondwater-gebruikers; aangesien daar geen huidige grondwater gebruikers gevind word in die nabyheid van die terrein en die besoedelings pluim. Daar is egter 'n potensiële oppervlakte besoedelings risiko na benede strome en oppervlakwater liggame tydens' n vloed gebeurtenis. | af |
| dc.identifier.uri | http://hdl.handle.net/11660/1421 | |
| dc.language.iso | en | en_ZA |
| dc.publisher | University of the Free State | en_ZA |
| dc.rights.holder | University of the Free State | en_ZA |
| dc.subject | Dissertation (M.Sc. (Institute for Groundwater Studies))--University of the Free State, 2009 | en_ZA |
| dc.subject | Groundwater -- Pollution -- South Africa | en_ZA |
| dc.subject | Agricultural wastes -- Environmental aspects | en_ZA |
| dc.subject | Groundwater flow | en_ZA |
| dc.subject | Predictive modelling | en_ZA |
| dc.subject | Contaminant risk | en_ZA |
| dc.subject | Surface water | en_ZA |
| dc.subject | Seepage | en_ZA |
| dc.subject | Numerical modelling | en_ZA |
| dc.subject | Contaminant transport | en_ZA |
| dc.subject | Fertilizer related contaminants | en_ZA |
| dc.subject | Nitrate | en_ZA |
| dc.title | Reactive transport modelling of fertilizer waste in a dual porosity aquifer | en_ZA |
| dc.type | Dissertation | en_ZA |