published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

published_or_final_version / Earth Sciences / Master / Master of Philosophy

published_or_final_version / Chemistry / Master / Master of Philosophy

published_or_final_version / Ecology and Biodiversity / Master / Master of Philosophy

Numerous urban soils surrounding industrial and metallurgical facilities in the U.S. are contaminated with metals including lead (Pb), cadmium (Cd), copper (Cu), Zinc (Zn), chromium (Cr), and nickel (Ni). Simplified geochemical mapping requires soil sampling and analysis for the presence of heavy metals from a grid pattern within a geographic area. In this study, a contour map of metal concentrations at two depths was subsequently superimposed over a standard political map to indicate areas of elevated metal concentrations in the soil. Natural levels of Pb, Cd, Cu, Zn, Cr, and Ni in Delaware County soils were determined to be 114.2 mg/kg, 0.14 mg/kg, 29.3 mg/kg, 88.4 mg/kg, 9.0 mg/kg, and 39.8 mg/kg, respectively. The average concentrations of metals found throughout Muncie, 203.9 mg/kg Pb, 39.2 mg/kg Cu, 275.4 mg/kg Zn, 9.7 mg/kg Cr, and 25.0 mg/kg Ni, were compared with natural levels to determine the extent of heavy metal pollution from atmospheric deposition. From the geographic mapping of metal concentrations, the effect of past industrial processes on possible contamination of soils by metals in Muncie, Indiana, was determined. Metals were also be fractionated in order to assess the percentage which is potentially bioavailable. / Department of Natural Resources and Environmental Management

M.Sc. / The study looks into the sediment-bound metals (Fe, Mn, Cu, Cr, Cd, Co, Pb, Ni, Zn and Hg) of the Leeu/Taaibospruit catchment, which is impacted by agricultural, industrial and urban development. A number of chemical procedures, including total metal determination, the Tessier-sequential extraction scheme, the BCR Protocol, evaluation of the % TOC and determination of AVS to SEM ratios were applied to sediment samples collected from eight sites along the two rivers in the study area. Samples were collected during both high flow (summer) and low flow (winter) conditions. Following the chemical characterisation, bioaccumulation testing was conducted by exposing chironomid larvae to the sediment samples collected in from the study sites and determining their metal uptake relative to control specimens in uncontaminated sediments. These bioaccumulation results were then considered in conjunction with the chemical parameters in an attempt to identify any trends and correlations. Significant spatial and temporal differences were found in the metal concentrations from the study area. The total extraction results indicated that abundant amounts of Cr and Fe are present throughout the system. This was expected based on the make-up of the underlying geology. In addition, one of the sites, which is in close proximity to the town of Sasolburg, was identified as a potentially contaminated site. This site had significantly higher concentrations of Zn, Cu, Pb and, most notably, Hg when compared to the other sites. The elevated metal concentrations are most evident in samples collected under low flow conditions, but are also seen in the high flow Hg concentrations. Sequential extractions showed that Fe and Cr are concentrated in the residual phases of the sediment. Copper is largely present in the oxidisable fraction under low flow conditions, but also has considerable residual and reducible chemical forms. Manganese and Zn are distributed among all the different chemical phases and are therefore likely to be readily available for uptake by benthic organisms. The TOC was found to be highest during low flow conditions and at those sites with observable amounts of organic debris from the surrounding reeds and other vegetation. The AVS/SEM ratios were used to predict that due to the formation of insoluble metal sulphides, Cd, Cu, Hg, Ni, Pb and Zn are unlikely to be bioavailable at certain sites, i.e. the contaminated site 1 and at site 5, which only has agricultural impacts. In general, the bioaccumulation of Fe, Co, Ni, Cr and Mn was higher in the test larvae than the control larvae. Bioaccumulation of Cu, Pb, Zn and Hg levels were only higher than the control worms at sites where contamination was suspected to have taken place. Average bioaccumulation factors indicated that Hg is the metal that is most readily available for bioaccumulation, followed by Cu, Zn and Mn. All of these metals were bioconcentrated in the tissues of the test chironomids, while levels of Fe, Ni, Cr and Pb were found to be lower in the organisms than in the sediments. Although many of the chemical fractions were found to correlate significantly with the uptake of the different metals, the best overall correlation existed between the bioaccumulated metal and the total non-residual fraction. In fact, the sum of the first four steps of the Tessier-scheme correlated significantly with the bioaccumulated metal for all elements considered in the calculation, except for Pb. Additionally, the predictions made by the AVS model were found to be useful in justifying the behaviour and accumulation patterns of Hg, Zn and Cu at certain sites. The correlations and bioavailability clearly differed spatially, temporally and among the different elements. It is therefore suggested that prediction of the bioavailability and subsequent uptake of sediment-bound metals will require as many chemical and environmental factors as possible, and should include bioaccumulation and toxicity testing in order to examine the validity and completeness of these predictions.

The aims of the project were twofold. The initial objective of the study, based on previous results, was to develop an economically viable methodology for immobilizing yeast cells for the treatment of heavy metal-laden waste water. The non-viable yeast cross-linked by 13% (w/v) formaldehyde/1N HNO₃ exhibited satisfactory mechanical strength and rigidity in a continuous-flow column operation. No apparent disruption of the biomass after repeated use was observed. The cost of immobilizing 1kg dry yeast pellets was estimated at less than US$I. Zn uptake capacity of FA-cross-linked pellets, on batch trials, remained similar to that of raw yeast, reflecting that the immobilizing procedure did not hinder its metal removing capacity. In column studies, cation metals were effectively removed by the yeast pellets from aqueous solution at natural pHs, and then recovered completely by washing the pellets in situ with O.1M HCl. The recovered metals were concentrated in such small volumes that recycling or precipitation of them was facilitated. The metal uptake capacity of the regenerated biomass remained constant in comparison with cycle 1, indicating that reuse of the yeast would be possible. In the case of Cr⁶⁺, a gradual breakthrough curve of Cr in the column profile was noted, with a simultaneous reduction of Cr⁶⁺ to Cr³⁺. However, Cr⁶⁺ in the effluent can be markedly minimised either by accumulation onto the biomass or reduction to its trivalent form. Desorption of bound Cr⁶⁺ with either alkali or salt could not accomplish the regeneration of the biomass. A combination of reduction and desorption with FA/HNO₃ appeared promising in regeneration of the saturated biomass at 4°C. The metal sorption capacities of the yeast pellets, on a batch or a fixed-bed system are relatively lower than that of documented sorbents. Apparently more of the yeast pellets would be required for treating a certain volume of waste effluent, than with other sorbents. Therefore Azolla filiculoides was examined as a suitable sorbent for this purpose. This constitutes the second part of the project. Azolla filiculoides, a naturally-abundant water fern, was screened for its metal sorption and recovering capacities, mechanical stability, flow-permeability and reusability. The azolla biomass appeared to have fulfilled the required mechanical criteria during the repeated sorption-desorption column operations. It is water-insoluble and appears flexible under pressure when rinsed with water. These characters are of crucial importance in a continuous-flow system since a column can be operated at high flow rates without apparent compact of the biomass and pressure loss. Therefore, immobilization of the biomass can be avoided. The sorption isotherm data, obtained from batch removal of Cr⁶⁺, showed that the sorption process was effective, endothermic and highly pH dependent. Considerable amounts of Cr⁶⁺ were accumulated at the optimum pHs of 2-2.5. Column sorption of Cr⁶⁺ at a low flow rate and pH of 2.5 showed optimum performance with a total Cr uptake of 50.4mg/g at 60% saturation of the biomass. Removal of Cr⁶⁺ from an electroplating effluent using an azolla column was deemed reasonably satisfactory, although the uptake declined slightly. Desorption of bound Cr⁶⁺ with various desorbents was incomplete, which resulted in a low regeneration efficiency of about 50%. However, removal and recovery of Cr³⁺ using the azolla column was than that of Cr⁶⁺. Desorption of Cr³⁺ from the spent biomass column was accomplished with the recovery of 80% using O.5N H₂SO₄, The regeneration efficiencies for Cr³⁺ removal were up to 90% and demonstrated that the biomass is reusable. Cation metal uptake capacities of azolla, obtained either from batch or column experiments, are reasonably high in comparison with other sorbents. The uptake of Ni or Zn ions from solution is pH dependent showing the optimum pH of around 6 to 6.5, under the current experimental conditions. The sorption kinetics for cation metals was rapid with about 80% of the bound Ni ions being taken up in the first 10 min. The character of rapid binding is extremely important in a column sorption process, especially on a large scale since it favours an optimum uptake of metals at high flow rates. The Ni or Zn uptakes in column sorption were not markedly affected when the flow rates were increased from 80mllh up to 800ml/h for the 5g biomass used. The cation heavy metals removed from waste effluents were recovered in a concentrated solution of small volume. The desorption of bound Ni and Zn ions from the saturated biomass was accomplished with either O.2N HCl or H₂SO₄ that resulted in recoveries of more than 95%. The metals recovered, in the case of Ni and Zn, are identical to that of plating agents ego nickel sulphate or chloride, so that recycling of the metals is possible. An effluent-free, closed loop of Ni or Zn treatment system was proposed, whereby the Ni or Zn ions can be recycled to the plating bath whilst the purified water is fed back to the rinse tanks. Ca and Mg ions, commonly present in the electroplating effluents, appeared to affect sorption of heavy metals by azolla when metal concentrations were relatively low, presumedly through its competitive binding for the shared sites on surfaces of azolla. The data obtained from column sorption of Ni and Zn follows the BDST model well, enabling the application of the model to predicting design parameters for scale-up of the biosorption column system. It is interesting that the values of metal uptake, expressed in molar quantities, obtained on respective single-metal solutions and the multiple metal system, are similar, implying that the mechanisms involved in the sorption of all metal cations are similar and that the binding sites on surfaces of azolla are probably shared by all cation metals. The surface of the biomass provides sites for metal binding estimated in the range of 0.45-0.57mmol/g, based on the current experiments. The biomass has a surface area of 429 m²/g and water retention of 14.3 ml/g. The functional groups on the surface of azolla were partially identified using chemical modification and metal binding comparison. Among the functional groups examined, carboxyl groups, provided by amino acids and polysaccharides, appeared to play an important role in metal cation binding. The infrared spectra of the samples support this conclusion.

This study examined the consequences of the opening and operation of a new highway north of Richmond, Virginia with respect to contamination of the aquatic environment with heavy metals (Zn, Cd, and Pb), and the effects of these metals on the biota of roadside streams. Sixteen sites located on six small, soft-water streams that were crossed by the highway, encompassing six reference sites located upstream of the highway, six sites located directly at the highway, and four sites located downstream of the highway, were sampled over a two and a half year period, allowing both spatial and temporal analyses. Traffic densities on the highway averaged about 12,000 vehicles per day (vpd). Significant increases in the metals concentrations of sediment, benthic invertebrates, fish whole-bodies, and fish tissues (liver, kidney, and bone) were noted over the course of the study, although the increase varied in magnitude, and were not always consistent. Sediment metals concentrations followed a dynamic plateau. Fish whole-body concentrations of Cd and Pb increased steadily over the course of the study. Spot-sampling for the same parameters along another nearby, more heavily traveled highway (50,000 vpd) indicated that increases in metals concentrations in the different ecosystem components at the study streams would have been greater had there been more traffic. A number of biotic parameters were investigated to determine whether metals contamination was affecting the biological integrity of the study sites. These were: benthic macroinvertebrate diversity and density; the percentage of the aquatic insect community that was composed of chironomids; and fish community diversity, density, and biomass. Only benthos density, the percent chironomids, and fish species diversity showed changes that could be related to metals contamination. Indications from spot sampling along the more heavily traveled highway were that if more contamination had been experienced, more biotic parameters would have been disturbed, and to a larger extent. Fish community structure analyses using the Pinkham-Pearson coefficient of similarity indicated that fish community structure became increasingly altered at highway sites, and to a lesser degree downstream sites, over the study period. / Ph. D. / incomplete_metadata

published_or_final_version / Geography and Geology / Master / Master of Philosophy

M.Sc. / The increase in industrialisation, mining and agricultural activity along rivers could have a detrimental effect on aquatic environments unless the dangers of pollutants are not taken notice of. Metal ions and industrial effluent have become a source of pollution in the watercourses of South Africa. Pollutants generally have negative effects on the physiology of aquatic biota in polluted waters. The effects of copper and industrial effluent by the exposure of the clawed toad, Xenopus laevis and Tilapia sparrmanii are presented in this study. An experimental static-renewal system with an exposure time of 96 hours was followed at 25±1°C. After copper and effluent exposure, several physiological changes occurred in the two aquatic organisms. The sublethal effects that occurred include changes in hatching, survival, behaviour, growth impairment and developmental limitations. The results of the present study suggest that lethal endpoints can be used as indicators in detecting and evaluating the effects of aquatic pollution, caused by copper and effluent. Individual variation, however, could hamper the conclusions made but the study of aquatic organisms is of practical importance when conducting experimental studies in a laboratory and does not have the same impact as during field studies. Apart from the exposure to sublethal concentrations of copper and effluent, computational derivations of LC50, NOEC values and 95% confidence limits were made. The obtained concentrations were used as assumptions that pollutants should not exceed for the protection of aquatic life. Statistically different differences were found between the chosen derived variables of control and experimental organisms. The advantages of FETAX solution over borehole water can be attributed to the bioavailability of pollutants, which appears to be much less in those solutions. The predicted NOEC values provide some information regarding the concentrations at which no effects will be observed and the Target Water Quality Ranges (TWGR) for water were used to determine if the diluent was correct.