Metals sorption in soils is influenced by several factors, including pH, ionic strength, the presence of ionic composition or organic ligands, total amount of metals, and adsorbent loading. These conditions should be considered when evaluating metal sorption capacity of soil material or when applying laboratory results to field conditions. Metal sorption experiments were conducted on Bertie sandy and Starr-Dyke clay loam soils from long-term field studies in which soils received annual applications of copper-rich pig manure for 16 years. Adsorption of Cd, Cu, Pb, and Zn as affected by different background electrolytes at various concentrations was investigated. Electrolytes were Na+, Ca2+, or Al3+ in perchlorate solution, and their concentrations ranged from 0.001 to 0.5 molc L-1. Increasing ionic strength decreased metal adsorption capacity. Electrolyte cation composition had a greater effect on adsorption than did electrolyte concentration. The order of sensitivity to cation composition of the electrolyte was Zn > Cd > Cu > Pb, and this effect was greater in Bertie sandy loam than Starr-Dyke clay loam soils. Little difference in Cu and Pb adsorption was observed between Na+ and Ca2+ in background solution. Most added Cu was adsorbed at low concentrations regardless of pH, but at high concentrations Cu sorption was strongly related to solution pH. Increases in pH resulted in greater Cu sorption due to pH-dependent negative charges and precipitation. The USEPA recommends that soil systems receiving high metal loading rates be maintained at pH 6.5 or above because of the increased metal adsorption. However, pig manure applications to the Bertie soil resulted in greater Cu in soil solution than in control (no manure) soil at pH > 6.5 due to soluble organic matter. Using the Langmuir equation to determine adsorption maxima for soil systems does not always give adequate estimates of adsorption and values from the equations are highly dependent upon soil environmental parameters. Given the limitations in prediction of adsorption maxima, and given that the amount of nonsorbed metal is as important as the adsorbed amount, the isolines of metal remaining in soil solution were provided with a given set of soil environmental factors. / Ph. D.

The major constraints to food production in West Africa are related to the lack of suitable lands. Consequently, farmers incorporate organic amendments and wastewater to improve their yields. Within some limits, such wastes enhance soil fertility and can improve its physical properties. However, the advantages of using organic waste as fertilizer and soil amendment should be assessed with possible environmental and toxicological impacts due to the potential presence of heavy metals. The objective of this study was to assess the effect of organic amendments on heavy metal distribution in soils and vegetables in market gardens in Senegal. Organic amendments and soils samples were collected from four sites in eastern and southern Senegal. Samples were analyzed for physicochemical properties including particle size, total heavy metals, carbon content, nutrients, and pH. A sequential extraction procedure was conducted to determine heavy metal sinks. Results showed that sites were sandy in nature, low to medium in organic carbon content (8300 to 36600 mg kg-1), and had pH ranging from 5 to 7.9. The sequential extraction procedure showed that metals were distributed in the more stable soil fractions: Fe-Mn oxide, organic and residual. The highest soil metal concentrations in soils were found in Pikine and Rufisque sites. Plant samples were collected from these two sites and analyzed for total metal content. Results showed that all metal concentrations in soils, organic amendments, and vegetables were within the safe limits proposed by the World Health Organization, with the exception of Cd, Pb and Zn levels in vegetables. / Master of Science

No description available.

The purpose of this research was to determine the influence of extended dosing of zinc on the carbon cycling and biomass characteristics of freshwater epilithon. Experiments were conducted in artificial streams continuously dosed with 0.00, 0.05, or 1.00 mg Zn liter⁻¹ for 20 to 30 days during summer and fall, 1984 and 1985. Repeated measurement of epilithon structure and function included estimates of ¹⁴C-glucose respiration, ¹⁴C-glutamate respiration, O₂ and CO₂ flux rates, ash-free dry weight (AFDW), protein, carbohydrate, and algal pigment concentrations, and total and zinc-tolerant colony forming units. An increase in epilithic glucose respiration per unit biomass consistently occurred 5 to 10 days after dosing with 1.0 mg Zn liter⁻¹ was started. At the same time significantly lower epilithon biomass occurred in the high dosed streams relative to controls in 3 out of 4 studies. Although algal pigment concentrations were lowest in the high dose streams at the midpoint of the studies, the chlorophyll a-to-pheophytin a ratio remained high, indicating that the minimal algal population was not senescing in situ. After 30 days, the epilithon dosed with 1.0 mg Zn liter⁻¹ had higher AFDW, protein, and carbohydrate concentrations than the other treatments. By 20 days, the high zinc treatment showed evidence of more total and zinc-tolerant colony forming units and lower rates of O₂ and CO₂ flux than epilithon from control streams. The high rates of glucose respiration were characteristic of epilithic communities stressed by 1.0 mg Zn liter⁻¹, and this response was not apparently due to in situ senescence of zinc-sensitive cells; the results suggested that epilithic biomass was washed out of the systems, not being degraded in situ. The development of unique epilithon communities that are acclimated to prolonged zinc exposure is evident in the eventual recolonization of the artificial surfaces, glucose respiration rates that are comparable to controls, and presence of zinc-tolerant heterotrophs. / Ph. D.

Thesis (MSc) -- University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Shrews are excellent bioindicators of environmental heavy metal pollution. This is due to their diets and the high rate of consumption at which these small mammals consume their prey. Shrews feed mostly on earthworms, and earthworms accumulate high levels of heavy metals in their bodies. Biomarkers measure responses to environmental pollution in the bodies of exposed organisms. Cellular biomarkers give an indication of responses to pollutants at levels of pollutant exposure that are not yet lethal to the organism. This study was prompted by concern that the number of shrews in the Stellenbosch region was declining. For the present study, shrews (Myosorex varius and Crocidura jlavescens) from the Stellenbosch region were sampled. The levels of Cd and Pb in their bodies were analysed in order to ascertain whether or not these two heavy metals, which occur in the environment as a result of various anthropogenic activities, are present in the food chain of the shrews. In the laboratory, shrews were fed live control and metal exposed earthworms from laboratory cultures. The earthworms had been exposed to either Cd or Pb in these cultures over a number of generations. This was performed to determine whether the presence of the metals in the body of the shrews, had resulted from metal accumulation from the earthworms which were fed to the shrews. Cellular biomarkers were used to determine the cellular response to the metals and membrane integrity and DNA integrity were investigated. This was done by exposing the cells of the shrews and ofBALB/c mice to metal salt solutions of Cd, Pb and Zn in vitro. Membrane integrity was tested by cell leaching techniques viz. the LDH assay and the trypan blue assay. DNA integrity was determined by using the comet assay as a biomarker of exposure. The results of the study show that the shrews in the immediate Stellenbosch region are exposed to lower levels of Cd and even lower levels of Pb than shrews from a site 16km out of the town of Stellenbosch. The cellular responses induced by metal exposure of laboratory mice show that the metals are indeed cytotoxic and genotoxic to the cells of small mammals. Cd and Pb were found to be more cytotoxic than Zn, while Zn was more genotoxic than either CqorPb. / AFRIKAANSE OPSOMMING: Skeerbekke is uitstekende bioindikatore van swaarmetaalbesoedeling in die omgewing. Dit is as gevolg van hul dieët en die hoë koers waarteen hierdie klein soogdiere hul prooi verorber. Skeerbekke voed meestalop erdwurms, en erdwurms akkumuleer hoë vlakke van swaarmetale in hul liggaam. Biomerkers meet response as gevolg van omgewingsbesoedeling in die liggame van blootgestelde organismes. Sellulêre biomerkers gee 'n aanduiding van response op besoedelingstowwe by vlakke wat nog nie dodelik is vir die organisme nie. Die studie is aangespoor deur die bekommernis dat die getal van skeerbekkies in Stellenbosch besig is om te daal. In die studie is skeerbekke (Myosorex varius en Crocidura flavescens) van die Stellenbosch omgewing gevang en die vlakke van Cd en Pb in hul liggame gemeet om vas te stelof die twee swaarmetale, wat in die omgewing beland as gevolg van verskeie antropogeniese aktiwiteite, teenwoordig is in die voedselketting van die skeerbekke. Die skeerbekke is in die laboratorium met lewende kontrole en metaalblootgestelde erdwurms uit kulture in die laboratorium gevoer. Die erdwurms is aan Cd en Pb oor baie generasies blootgestel in hierdie kulture. Dit is gedoen om vas te stelof die teenwoordigheid van die metale in die liggame van die skeerbekke 'n oorsaak is van metaalakkumuleering as gevolg van die erdwurms waarmee hulle gevoer is. Sellulêre biomerkers is gebruik om sellulêre respons op die metale op die membraanintegriteit en DNA-integriteit vas te stel. Dit is gedoen deur die selle van skeerbekke so wel as BALB/c muise in vitro bloot te stel aan metaalsoutoplossings van Cd, Pb en Zn. Membraanintegriteit is getoets deur selmembraan permeabiliteit tegnieke nl. die LDH en tripaan blou toetse. DNA-integriteit is getoets deur die komeettoets te gebruik. Die resultate van die studie dui daarop dat die skeerbekke van Stellenbosch aan laer vlakke van Cd, en nóg laer vlakke van Pb blootgestel is as die skeerbekke van 'n perseel 16km buite die dorp. Die sellulêre response geïndusseer deur blootstelling aan metale by die laboratoriummuise het aangetoon dat die metale inderdaad skadelik is vir die selmembraan en die DNA van die selle van die muise. Cd en Pb is meer toksies vir die selmembraan as Zn, terwyl Zn weer meer toksies is vir die DNA-integriteit as Cd en Pb.

Thesis (PhD (Botany and Zoology)) -- University of Stellenbosch, 2006. / Metals are natural elements of the earth crust usually present at low concentrations in all soils. Although many metals such as cobalt, copper, iron and zinc are essential to living organisms, at elevated concentrations most metals are toxic to organisms living in and on soils. Elevated concentrations of metals are caused either by anthropogenic deposition following remobilisation from the earth crust or are of natural origin. Ultramafic soils do not only pose unfavourable living conditions such as drought and poor organic content, these soils are also characterized by extremely high concentrations of a range of metals known to be toxic under normal circumstances. Ultramafic soils are of high ecological importance as a high proportion of endemic organisms, especially plants, live on these soils. As it is known that earthworms do occur in ultramafic soils, the aims of the present study were to investigate the abilities of earthworms to survive in these soils and the influences of elevated chromium, cobalt, copper, manganese and nickel levels. For the evaluation of the metal background conditions, soils originating from ultramafic rocks of the Barberton Greenstone Belt, Mpumalanga, South Africa were collected and different fractions representing different levels of bioavailability were analyzed for arsenic, chromium, cobalt, copper, manganese and nickel. To assess the mobile, readily available metal fraction, i.e. Ca2+- exchangeable metal cations, a 0.01 mol/L CaCl2 extraction was performed. To investigate the mobilisable metal fraction, representing the amount of easily remobilisable complexed and carbonated metal ions, a DTPA (di-ethylene-triamine-pentaacetic acid) extraction was conducted. In relation to non-ultramafic or anthropogenic contaminated soils, a far lower proportion of metals were extractable by the above mentioned extraction methods. To investigate the availability and effects of these metals on earthworms, two ecophysiologically different species were employed. Aporrectodea caliginosa and Eisenia fetida were long-term exposed to the ultramafic soils collected at the Barberton region and a control soil from a location at Stellenbosch with a known history of no anthropogenic metal contamination. The responses to the ecological stress originating in the ultramafic soils were measured on different levels of earthworm organisation. As endpoints affecting population development, cocoon production, fecundity and viability were evaluated. On individual level, growth, metal body burden and tissue distribution were investigated. As endpoints on subcellular level, the membrane integrity was assessed by the neutral red retention assay, the mitochondrial activity was measured by the MTT colorimetric assay and as a biomarker for the DNA integrity, the comet assay was performed. Focussing on manganese and nickel, the uptake by E. fetida of these metals was investigated with the exclusion of soil related properties using an artificial aqueous medium to draw comparisons to the uptake of these metals in natural soils. The possible development of resistance towards nickel was tested by exposing pre-exposed (for more than 10 generations) E. fetida specimens to ultramafic soils with concentrations of more than 4000 mg/kg nickel. The results showed that, except on the endpoint survival, which was less sensitive than all other bioassays, significant responses to the ultramafic challenge were observed in all earthworm bioassays and on all levels of organisation. The sensitivity of the responses of the earthworms towards the ultramafic conditions was not predictable by the level of organisation. The two species showed different strategies of metal elimination. In A. caliginosa, metals such as nickel, manganese and chromium were transported to the posterior section and the posterior section was subsequently pushed off by autotomization. In E. fetida, metals such as chromium and nickel were sequestered in storage compartments in the coelomic cells or fluid. Other metals, such as cobalt, were not taken up at elevated concentrations. Although an increased accumulation of nickel was observed in E. fetida specimens pre-exposed to nickel, development of resistance or cross resistance was not observed in this species. In contrast, pre-exposed specimen exposed to elevated concentrations of nickel showed a higher sensitivity in terms of survival, indicating the absence of acclimatisation or even genetic adaptation. A comparison of the two species employed indicated that A. caliginosa was less suited for the assessment of the ultramafic soils due to the high individual variation in metal body burden, the mass loss observed and the slow reproduction rate even in the control soils. This happened despite the fact that A. caliginosa was a soil dwelling species supposed to be better adapted to the soil substrate than the litter dwelling E. fetida. The toxicity of the ultramafic soils was not necessarily related to total or environmentally available amounts of the selected metals. Thus, it can be speculated that either these soils contained unidentified toxicants with resulting interactions between toxicants playing an important role or earthworms were able to remobilize metals occurring in these soils. As the singular application of an ecotoxicological endpoint did not give reliable results, especially seen over the duration of the exposures, it can be concluded that, when studying soils with such a complex composition, the utilisation of endpoints addressing different levels of organisation is necessary for the assessment of toxic stress emerging from these ultramafic soils.

M. Tech. (Department of Biotechnology, Faculty of Engineering and Technology) Vaal University of Technology / The Klip River has suffered severe anthropogenic effects from industrial, agricultural, mining and domestic activities. As a result harmful contaminants such as heavy metals have accumulated in the river, causing microorganisms inhabiting the environment to develop mechanisms to protect them from the harmful effects of the contaminants. The current study deals with the isolation and characterization of heavy metal resistant bacteria isolated from the Klip River Catchment. Water and sediment samples were collected from 6 sites of the Klip River, and the Vaal Barrage (control). In-situ parameters, such as pH, turbidity, salinity, conductivity, temperature and dissolved oxygen were determined. Lead, iron, cadmium, nickel, zinc and copper concentrations of water were determined by atomic absorption spectroscopy. For bacterial analysis sediment and water samples were collected in sterile glass jars and bottles respectively. Heavy metal resistant bacterial isolates were screened on heavy metal constituted Luria Bertani (LB) agar. Biochemical profiles of the isolates were constructed using the API 20E® strips, antibiotic susceptibility tests were done and growth studies were carried out using spectrophotometric methods. The isolates were identified using 16SrDNA sequencing and alignment. A partial sequence of the copper resistance gene pcoA was amplified from strains Lysinibacillus sp. KR25 [KJ935917], and Escherichia coli KR29 [KJ935918]. The pcoR gene was amplified from E. coli (KR29) and the partial sequence for the chromate resistance gene chrB, was amplified from Pseudomonas sp. KR23 [KJ935916]. The gene fragments were then sequenced and translated into protein sequences. The partial protein sequences were aligned with existing copper and chromate resistance proteins in the Genbank and phylogenetic analysis was carried out. The physico-chemical properties of the translated proteins were predicted using the bioinformatics tool Expasy ProtParam Program. A homology modelling method was used for the prediction of secondary structures using SOPMA software, 3D-protein modelling was carried out using I-TASSER. Validation of the 3D structures produced was performed using Ramachandran plot analysis using MolProbity, C-score and TM-scores. Plasmid isolation was also carried out for both the wild type strains and cured derivatives and their plasmid profiles were analysed using gel electrophoresis to ascertain the presence of plasmids in the isolates. The cured derivatives were also plated on heavy metal constituted media. Antibiotic disc diffusion tests were also carried out to ascertain whether the antibiotic resistance determinants were present on the plasmid or the chromosome. The uppermost part of the Klip River had the lowest pH and thus the highest levels of heavy metal concentrations were recorded in the water samples. Turbidity, salinity and specific conductivity increased measurably at Site 4 (Henley on Klip Weir). Sixteen isolates exhibiting high iron and lead resistance (4 mM) were selected for further studies. Antibiotic susceptibility tests revealed that the isolates exhibited multi-tolerances to drugs such as Ampicillin (10 μg/ml), Amoxcyllin (10 μg/ml), Cephalothin acid (30 μg/ml), Cotrimoxazole (25 μg/ml), Neomycin (30 μg/ml), Streptomycin (10 μg/ml), Tetracycline (30 μg/ml), Tobramycin (10 μg/ml) and Vancomycin (30 μg/ml). Growth studies illustrated the effect of heavy metals on the isolates growth patterns. Cadmium and chromium inhibited the growth of most of the microorganisms. The following strains had high mean specific growth rates; KR01, KR17, and KR25, therefore these isolates have great potential for bioremediative applications. Using 16SrDNA sequencing the isolates were identified as KR01 (Aeromonas hydrophila), KR02 (Bacillus sp.), KR04 (Bacillus megaterium), KR06 (Bacillus subtilis), KR07 (Pseudomonas sp), KR17 (Proteus penneri), KR18 (Shewanella), KR19 (Aeromonas sp.), KR22 (Proteus sp.), KR23 (Pseudomonas sp.), KR25 (Lysinibacillus sp.), KR29 (Escherichia coli), KR44 (Bacillus licheniformis) and KR48 (Arthrobacter sp.). Three heavy metal resistance genes were detected from three isolates. The pcoA gene was amplified from strains Lysinibacillus sp KR25, and Escherichia coli KR29; pcoR gene from E. coli KR29 and the chrB gene, from Pseudomonas sp. KR23. The genes encoding for heavy metal resistance and antibiotic resistance were found to be located on the chromosome for both Pseudomonas sp. (KR23) and E.coli (KR29). For Lysinibacillus (KR25) the heavy metal resistance determinants are suspected to be located on a mobile genetic element which was not detected using gel electrophoresis. The translated protein sequence for pcoA_25 showed 82% homology with the copper resistant protein form Cronobacter turicensis [YP003212800.1]. Sequence comparisons between the pcoR partial protein sequence found in E. coli KR29 showed 100% homology with 36 amino acids (which was 20% of the query cover) from a transcriptional regulatory protein pcoR found in E. coli [WP014641166.1]. For the chrB partial protein sequence detected in Pseudomonas sp. (KR23), 97% of the query sequence showed 99% homology to a vitamin B12 transporter btuB in Stenotrophus sp. RIT309.

M. Tech. (Chemistry, Faculty of Applied and Computer Science), Vaal University of Technology / The abundance of agricultural waste materials has led to its use as adsorbents for trace metal adsorption. The raw Macadamia nutshell (RMN) powder was treated with a hydrochloric acid solution to obtain acid modified Macadamia nutshells (AMM), and with sodium hydroxide solution to obtain base modified Macadamia nutshells (BMM). Then, the AMM and BMM materials were grafted with 0.5 M, 1 M, and 2 M acrylic acid. The different AMM grafted materials were labelled 0.5 GAM, 1 GAM and 2 GAM representing the different grafting ratios. The same naming order was followed for the BMM grafted materials, that is, 0.5 GBM, 1 GBM and 2 GBM corresponding to different concentrations used. The prepared Macadamia based adsorbents were characterized using Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), carbon, hydrogen, nitrogen and sulphur (CHNS) analysis, powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) analysis. The determination of surface properties such as the point of zero charge (pHPZC), bulk density and the surface negative charge was accomplished with appropriate wet chemistry methods. The adsorption of selected trace metals (Cu(II), Cd(II), Co(II), and Cr(VI)) was done in batch experiments. Atomic absorption spectroscopy (AAS) was used for the determination of metal ions concentrations and total Cr. The ultraviolet-visible (UV–Vis) spectroscopy was used for the determination of Cr(VI) concentration remaining in solution after adsorption. The RMN, AMM, and BMM adsorbents showed potential in removing more than 45% Cu(II) ions, but less than 30% for both Cd(II) and Co(II) ions. However, more than 90% removal of Cr(VI) ions was achieved with the same adsorbents. Consequently, only the adsorption of Cr(VI) was further investigated in the study due to the higher removal efficiency displayed by the Macadamia based biosorbents. The optimum adsorption conditions for the RMN, AMM, and BMM materials were found to be pH 2, 100 mg/L initial concentration of Cr(VI), 600 min contact time and 0.2 g adsorbent mass. The ideal conditions for the 0.5 GAM and 0.5 GBM were found to be pH 2, 25 mg/L initial concentration of Cr(VI), 180 min contact time, and 0.15 g adsorbent mass. The optimum temperature was found to be 40℃ for all materials. A volume of 20 mL was used for all batch experiments. The RMN, AMM, BMM, 0.5 GBM, and 0.5 GAM adsorption mechanisms were better described by the Langmuir isotherm which predicted a monolayer sorption process. The kinetic data fitted better to the pseudo second-order rate model which signified a chemisorption type of interaction. The thermodynamic parameters showed that the adsorption reaction was feasible, spontaneous and endothermic. The Macadamia based materials showed greater potential as adsorbents for the adsorption of Cr(VI) ions from aqueous solution compared to the other selected trace metal ions [Cd(II), Cu(II) and Co(II)].

No description available.

This study examines the waste of cotton gins as a potential alternative energy source, on account of its heat content, availability, and low emission rates. To confirm that this potential energy source meets minimum industrial fuel standards, this research has carried out an investigation of some important physical characteristics and toxic element analysis of cotton gin waste. Using cotton gin waste as fuel is an attractive solution to the problems of disposing of a surplus agricultural waste as well as supplementing fuel must meet both environmental emission standards and industrial fuel standards, the physical and chemical characteristics of cotton gin waste and its toxic element concentrations are important for its objective evaluation as a fuel. Constituent components, moisture contents, and ash contents of four separate parts of cotton gin waste were determined and evaluated closely following the American Society for Testing and Materials (ASTM) test methods. The three most toxic heavy metals, Arsenic (As), Chromium (Cr), and Lead (Pb), chosen for quantitative analysis were determined by using an inductively coupled plasma atomic emission spectrometry and a microwave oven sample digestion method.