D. Tech. Environmental, Water and Earth Sciences / Pollution of water sources with heavy metals is currently a global concern due to the detrimental effect of these metals on both human and animal health. To address this issue, biological treatment methods have been seen as the most effective and eco-friendly option of the available treatment processes of wastewater. The aim of this study was to compare the ability of selected bacterial isolates and indigenous protozoan to tolerate nickel and vanadium in wastewater systems in order to determine which group of organisms might play a major role in the removal of nickel and vanadium, even at high concentrations, in wastewater treatment systems.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

In this thesis, column experiments were conducted in order to determine the effect of irrigation with local groundwater on mobilization of lead and zinc in 50 years old sulfate-acid mine tailings. In addition, the influence of soluble oxalic acid, a common rhizosphere organic acid, was assessed by varying its concentration across an environmentally relevant range. In general, metal contaminant dissolution was not affected by the presence of oxalic acid. In both tailings, Zn mobilization was higher than Pb suggesting the presence of more kinetically labile Zn phases, regardless of the treatment used. Lead mobilization was also low because effluent solutions were near to equilibrium conditions with respect to gypsum, preventing Pb dissolution from Pb-sulfate minerals. Geochemical modeling also indicated that lead release was controlled by anglesite and plumbojarosite dissolution. Zinc release appears to be controlled by Zn-talc and goslarite.

Technogenic pollution level with heavy metals (Cr, Pb, Ni, Cu, Zn) of different pedogenesis Luvisols by various physical chemical methods estimated. Their sorption capacity in soils clay fraction (< 0,005 mm) analyzed. The results obtained permitted to carry out the theoretical and experimental modeling of heavy metals sorption in clay fraction of Luvisols. There was determined that it’s heavy metals sorption capacity makes up to 2000 mg kg-1.

No description available.

Weak organic acids and/or their salts were tested as soil washing or flushing agents for the ex- or in-situ remediation of soils polluted by heavy metals. Three soils naturally with heavy metals were used for the tea. / The three soils were characterized as a clay loam, loam and sandy clay loam. Their organic matter, pH, saturated hydraulic conductivity, cation exchange capacity, particle density and heavy metal contents were also characterized. The different retention forms of heavy metals in all 3 soils were studied by sequential extraction. The clay loam was contaminated with Cr, Hg, Mn and Pb while the loam and sandy clay loam were contaminated with Cd, Pb, Cu and Zn. Weak organic adds and/or their salts and chelating agents (EDTA and DTPA) were used at different pH, levels of concentration and leaching time in batch experiments to establish optimum conditions for maximum removal of heavy metals from the three soils. Citrate and tartarate were found to be quite effective, in leaching heavy metals from these soils. The rate of leaching of heavy metals from soils with citrate, tartarate and EDTA was modeled using two-reaction model at a constant pH and temperature. / Three contaminated soils of different textures were flushed in a column at optimum pH with a salt of weak organic acids, namely, citrate, tartarate, citrate+oxalate or a chelating agent such as EDTA and DTPA. The citrate and tartarate (ammonium salts) were found to be quite effective in removing heavy metals from the three contaminated soils while leaching little macronutrients and improving the soil's structure. An in-situ soil remediation simulation was also successfully tested using the sandy clay loam at large scale level in a tub (plastic container) using citrate as a flushing liquid. EDTA and DTPA were effective in removing the heavy metals except for Hg, but these strong chelating agents extracted important quantities of macronutrients from the soil. These chelating agents are also known to pollute the soil by being adsorbed on the soil particles. / A bioremediation process was developed using the fungus Aspergillus niger to produce weak organic acids (mainly citrate and partly oxalate depending on pH) for the leaching of heavy metals from contaminated soils. The fungus was cultivated on the surface of the three contaminated soils for 15 days at 30°C and a pH ≤ 4 to enhance the production of citric acid rather than oxalic acid which hinders Pb leaching. By extrapolating the result, the three contaminated soils were expected to be sufficiently remediated to meet the A category (Quebec clean up criteria for cleaning soils contaminated by heavy metals) after 20 to 25 days of leaching using this technique. / Finally, the leachate, collected following the soil remediation using weak organic acids and/or their salts, EDTA and DTPA was treated effectively using granular activated carbon.

Thesis (M. Tech.: Biotechnology)-Dept. of Biotechnology and Food Technology, Durban University of Technology, 2008. xiv, 103 leaves : ill. / Phytoremediation is an emerging technology where specially selected and engineered metal-accumulating plants are used for bioremediation. Amaranthus dubius (marog or wild spinach) is a popular nutritious leafy vegetable crop which is widespread especially in the continents of Africa, Asia and South America. Their rapid growth and great biomass makes them some of the highest yielding leafy crops which may be beneficial for phytoremediation. This study was undertaken to evaluate the potential of A. dubius for the phytoremediation of Chromium (Cr), Mercury (Hg), Arsenic (As), Lead (Pb), Copper (Cu) and Nickel (Ni). Locally gathered soil and plants of A. dubius were investigated for the metals from a regularly cultivated area, a landfill site and a sewage site. Metals were extracted from the samples using microwave-digestion and analyzed using Inductively Coupled Plasma – Mass Spectroscopy (ICP-MS). Further experiments were conducted with plants from locally collected seeds of A. dubius, in a tunnel house under controlled conditions. The mode of phytoremediation, the effect of the metals on the plants, the ability of the plant to extract metals from soil (Bioconcentration Factor - BCF), and the ability of the plants to move the metals to the aerial parts of the plants (Translocation Factor - TF) were evaluated for the different metals. Finally, A. dubius was micro-propagated in a tissue culture system with and without exposure to the metal, and the effect was studied by electron microscopy.

Heavy metal contamination of mangroves is of critical concern due to its accumulative and adverse effects in aquatic ecosystems. This study was undertaken to investigate the effects of mercury (Hg ), lead (Pb ), copper (Cu ) and zinc (Zn ) on plant responses, specifically growth and productivity, in Avicennia marina (Forssk.) Vierh. A. marina plants were grown for twelve months in pots contaminated with Hg +, Pb +, Cu2+ and Zn2+ at concentrations of 0, 40, 80, 120 and 160 ppm (1 ppm = 1 (agmf1). Accumulation and distribution of the heavy metals in shoot and root tissues were determined using atomic absorption spectroscopy (Perkin-Elmer Model 303) while secretion of the heavy metals from leaves was studied using scanning electron microscopy and energy dispersive X-ray microanalysis. I hypothesized that heavy metals have deleterious effects on plant growth and that they are absorbed by roots and secreted from salt glands present on the leaves. SEM X-ray microanalyses confirmed secretion of Cu + and Zn + ions as well as salt (NaCl) from glandular structures on both the adaxial and abaxial surfaces of leaves; however Hg2+ and Pb2+ were not detected in the secretion. Ion concentrations were significantly higher in plant roots than in shoots, particularly at 160 ligml"1 for all heavy metals. In addition, toxic levels of Hg and Pb were detected in the shoot tissue; however, Cu2+ and Zn2+ were within the normal ion concentration in the shoots. Plant height, number of leaves, biomass accumulation and chlorophyll content were significantly lower at 160 ugml" than the control values for all heavy metals. Carbon dioxide exchange, transpiration and leaf conductance generally decreased with increasing metal concentration. CO2 exchange at a concentration of 160 (J-gmf1 was significantly lower than the control for all metals. CO2 exchange at 160 ugml"1 for Hg2+, Pb2+, Cu2+ and Zn were 49.6 %, 55 %, 47.6 % and 63.6 % respectively lower than the control values. Photosystem II (PS II) quantum yield, photochemical efficiency of PSII (Fv/Fm) and electron transport rate (ETR) through PS II generally decreased with increasing concentration for all heavy metals. XV This study has shown that A. marina experiences dose-dependent stress responses to Cu2+, Zn2+, Hg2+ and Pb2+ in shoot and root tissue at a concentration of 160 lagmi"1, evidenced by decreases in growth and photosynthetic performance. The results also ~)A- "7-1- 9-1- "J-\-indicate that CuZT, Znz\ HgZT and PbZT are taken up by roots and transported to shoots. In addition, only Cu and Zn are secreted via the glands while Hg and Pb accumulate within the shoots. / Thesis (M.Sc.)-University of KwaZulu-Natal, 2008.

The present project aimed at measuring plant heavy metal uptake as a function of transpiration rates and dissolved heavy metal level in the soil solution. Two experiment was conducted separately in two season (Spring and Fall 2000). In these two experiments, young wheat plants ( Triticum aestivum) were irrigated with nine different solutions containing Cd and Zn. The study was conducted in two chambers where relative humidity was controlled to obtain two different levels of transpiration rates. Each control chambers contained 27 pots filled with sand and seeded with wheat plants, each nine triplicated pots receiving a different treatment: three Cd treatments with levels of 0.01, 0.10, and 0.50 mg/L; one Zn treatment with level of 25mg/L and four treatment combinations of Cd/Zn with levels of 0.01 Cd/25Zn, 0.10Cd/25ZN, 0.50Cd/25Zn and 0.50Cd/50Zn mg/L. The transpiration rate of the plants was monitored over a period of 30 days, measured from the emergence of the plants by weighing the pots daily. On day 15 and 30, three plants were removed from each pot, to weigh their dry matter production and to analyze their heavy metal uptake. (Abstract shortened by UMI.)

Despite improved liner design, there are still reported incidences of landfill leachate, rich in heavy metals, percolating through to groundwater and threatening ecosystems. This thesis introduces the concept of segregating municipal solid wastes (MSW) according to their major heavy metals and their metal's adsorption compatibility. Each segregated portion can be disposed in a different landfill compartment to minimize leaching of these heavy metals with the greatest bioactive impact. The validity of the concept was evaluated by batch and column retention mobility studies using copper (Cu) alone or with either lead (Pb) or cadmium (Cd) in solutions bearing various pHs. This was supported by selective sequential extraction (SSE) to determine the affinity to specific liner fractions. The following summarizes the procedure used. / Beforehand, a soil column test using sand with 5 and 10% bentonite was conducted to develop an equation predicting liner permeability, k , under simulated field conditions. The column permeability test revealed that a liner with 5% bentonite resulted in a k value which respected the North American criteria of 10-5 m/s. / In the batch experiments, solutions with Cu alone or with Cd or Pb, adjusted to pH of 3.7, 5.5 or 7.5, were applied to sand liners with 0%, 5% or 10% bentonite, having CEC's of 2.0, 6.4, and 10.8 (cmol(+) kg-1 ), respectively. Bentonite, pH and Pb significantly affected Cu adsorption. Cu was adsorbed by the liners at pH <6.5 whereas Cu precipitated at pH >6.5. Cu retention was higher in the presence of Cd than in that of Pb, at all combinations of CEC and pH. Competition between metals was greater in liners with lower CEC and therefore fewer adsorption sites. Limiting Pb in a landfill compartment can improve Cu adsorption at pH's below the precipitating threshold. / In the SSE procedure, the liner samples were centrifuged, decanted from their solutions and each adsorption fraction analyzed for Cu content. Results indicated that the carbonate fraction adsorbed more Cu, and that Pb significantly increased the mobility of Cu due to competition for exchangeable sites. / In the final soil column test using a sand liner with 5% bentonite, the leachate had an initial pH of 3.7. The leaching test confirmed the compatibility of Cu with Cd. The leaching of Cu was greater in the presence of Pb. Total metals in leachate was greater for the Cu-Cd solutions than for the Cu-Pb, because of Cd's relatively high mobility. The sequential extraction results showed again that the carbonate fraction dominated metal adsorption. Total heavy metal leaching followed the order of Cu/Cd > Cu/Pb > Cu alone. / Thus, disposing MSW in landfill compartments based on their heavy metal compatibility can minimize migration of heavy metals.