Department of Geography and Environmental Studies

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Browsing Department of Geography and Environmental Studies by browse.metadata.advisor "Brink, I. C."

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    The potential use of wetland plant species within a renosterveld setting for the phytoremediation of glyphosate and fertiliser
    (Stellenbosch : Stellenbosch University, 2018-12) Jacklin, Dylan Michael; De Waal, Jan; Brink, I. C.; Stellenbosch University. Faculty of Arts and Social Sciences. Dept. of Geography & Environmental Studies.
    ENGLISH ABSTRACT: In South Africa, fertiliser and herbicide pollutants resulting from various agricultural practices lead to a degradation of surface freshwater and groundwater quality. Nitrogen and phosphorous, and glyphosate derived from agricultural fertiliser and herbicide applications, respectively, significantly contribute to watercourse toxicity. Adjacent to many of the surface freshwater systems are some of the South Africa’s most productive agricultural fields, which convert the surrounding natural ecosystems in favour of the crops produced. As a result, the degradation of natural vegetation and deterioration of freshwater quality is observed. The critically endangered status of some Renosterveld vegetation types is the product of agricultural expansion, nutrient loading through fertilisation and the spraying of herbicides. The characteristics of phytoremediation provide an attractive alternative for the pollutant biofiltration of freshwater aquatic ecosystems. A buffer of Renosterveld vegetation along river corridors may be a solution for agricultural pollutant remediation prior to entering the watercourses. As a result of its successful uptake and metabolism capabilities of fertilisers and herbicides, inexpensiveness, aesthetic advantages and long-term use, it has become a remediation technology of choice in developing countries. The utilisation of wetland plants occurring within Renosterveld vegetation for pollutant extraction from agricultural practices will increase river corridor biodiversity, creating indigenous refuges, and facilitating habitat connectivity. Considering this, the study aims to delineate the potential use of wetland plant species indigenous to Renosterveld for the effective removal of agricultural pollutants. The evaluation of plant species’ pollutant removal efficiency in comparison to unvegetated soil will substantiate its use in vegetative buffer strips. The potential use of indigenous species as an alternative to invasive alien plant (IAP) species, currently considered successful phytoremediators, will aid in conserving the Renosterveld ecoregion. An experimental phytoremediation system was designed and constructed under laboratory conditions to investigate the pollutant removal potential of indigenous vegetation. Five pollutant parameters, namely ammonia, nitrate, soluble reactive phosphorous and two glyphosate concentrations (0.7 and 225 mg/L), were selected to reflect environmental stresses on 14 indigenous wetland species. The high but non-lethal glyphosate dosage strength was selected by means of a dual species dilution series experiment, where two plant species were subjected to ten different glyphosate concentrations. The dosage strength was selected at a concentration where plants did not display signs of mortality. Effluent analyses indicated the exceptional removal efficiencies of the indigenous wetland species across both fertiliser and herbicide pollutants, with the two most beneficial species identified as the species selected for this test aquic Phragmites australis and Cyperus textilis. The unvegetated soil control further exhibited efficient pollutant removal. However, indigenous vegetation consistently displayed greater pollutant removal than the unvegetated soil control. When compared to the IAP and Palmiet (Prionium serratum) multi-plant community assemblage, the indigenous species indicated similar pollutant removal efficiencies, justifying the use of indigenous plant species over the alien invasive equivalent. Phytoremediation presented significant potential for the utilisation of non-invasive wetland plant species in agricultural pollutant remediation, ameliorating freshwater aquatic ecosystems, and aiding the conservation of the already fragmented landscape.