Andrew Kindness - Academia.edu (original) (raw)

Papers by Andrew Kindness

Research paper thumbnail of Per and Polyfluoroalkyl Substances Mass Balance Analysis in Ski Wax, Snowmelts, and Soil from Skiing Areas

Research paper thumbnail of Phase Relations and Solubility Modelling in the Cao- SiO2- Al2O3- MgO- SO3-H2O System: For Application To Blended Cementss

MRS Proceedings, 1990

ABSTRACTCement blends are likely to form a large fraction of the materials in the near field of r... more ABSTRACTCement blends are likely to form a large fraction of the materials in the near field of radioactive repositories. Being chemically reactive and slightly soluble, their effect on near field chemistry will be very marked. Predictions of nuclide migration in this zone will therefore depend in part on accurate modelling of cement chemistry.The models being developed require the establishment of correct phase relations in the Cao- SiO2- Al2O3- MgO- SO3-H2O system (the major cement components). More than 40 compatibility experiments were carried out to determine these relationships. Purified cement hydrates were shaken continuously in CO2- free water, for 10 weeks. The results from these experiments together with data from the literature, enabled us to construct a better validated phase relations scheme than has hitherto been possible.Interpretational problems were encountered. Thus, mixtures containing Ca(OH)2, gave rise to the precipitation of metastable phases. This is due to s...

Research paper thumbnail of Application of hydrogeochemical modeling in simulating the transportation of elements in fly ash heap under different disposal systems in South Africa

Physics and Chemistry of the Earth, Parts A/B/C, 2015

Ash heap modelling of South African fly ash from Tutuka was carried out and the duration of trans... more Ash heap modelling of South African fly ash from Tutuka was carried out and the duration of transportation projected for 20 years based on two disposal scenarios, namely; irrigation of ash with rainwater, and irrigation with brines. The hydrogeochemical modeling code, PHREEQC, was applied in the study which gave insights into the speciation, release and transport of elements from the water and brines-fly ash long term interactions. Tutuka ash-water heap model showed a general sharp decrease of total elemental concentrations released during the first 2.5 years simulation as the pH value dropped from 12.6 to 8.7, after which it remained constant and their concentration remained constant up to 20 years. The elements showing this trend included Ca, Mg, Al, Fe, Sr, Zn, Na, K, Li and C(4). Generally, brines caused sharp increase in released concentration of the elements Ca, Mg, S(6) and C(4) for the first 3 years of heap irrigation whereas with water irrigation an opposite trend was observed in which the elemental concentrations decreased. Much of the release chemistry of the elements was closely related to the phase dissolution/precipitation and formation as the major controlling factors. Generally therefore, the modelled leachate quality results revealed that many elements are mobile and move through the ash heap in a progressive leaching pathway. The model could therefore be used to provide reasonable leachate quality from the modelled Tutuka ash heap which may be reaching the ground water. Overall, the ash heap modelling enhanced the understanding of the environmental impacts of ash-water-brines interactions and demonstrated that leachate composition is determined by the following factors; (i) the mass flows from the pores of fly ash, (ii) the surface dissolution of the mineral phases, (iii) the various chemical reactions involved during the ash-brine and ash-water interactions, (iv) the interactions with a gas phase (atmospheric CO 2), (v) the composition of the initial fly ash, and (vi) the leachate flow and hydrodynamics as captured in the conceptual model. Further model validation is recommended with lysimeters to quantatively compare the simulated results against the experimental data and improve on the model.

Research paper thumbnail of Experimental and ab initio infrared intensities in dimethylether: Atomic polar tensors and atomic charges

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 1996

Infrared intensities have been recorded in (CH3)20 over the range 100-3300 cm J and ab initio cal... more Infrared intensities have been recorded in (CH3)20 over the range 100-3300 cm J and ab initio calculations of geometry, frequency and infrared intensity made at the MP2/6-31G* level. The experimental results are compatible with previous data for (CHD2)20 and support the earlier results for (CH3)20 of Blom et al. The more recent data of Rogers appear to be too high. Additivity of vCH infrared intensity, per CH bond, is found in both the experimental and ab initio studies. Overall agreement between the two approaches is quite good. Ab initio based atomic polar tensors and their invariants are listed for representative atoms in dimethyl ether, methane and ethane and their Mulliken and King effective atomic charges compared. Dipole derivatives for the two types of CH bond present are markedly different and are directed away from the bond directions by 14-19 °. Rotation of the permanent dipole moment makes a significant contribution to the vCH stretching intensities in the d 5 species.

Research paper thumbnail of Immobilisation and fixation of molybdenum (VI) by Portland cement

International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, 1995

Complex impedance measurements have been performed on 14 shaly sand samples, Berea sandstone, and... more Complex impedance measurements have been performed on 14 shaly sand samples, Berea sandstone, and Ottawa sandbentonite packs in a frequency range of 10 Hz to 10 MHz, using both the two-and four-electrode techniques. The dielectric permittivity is found to correlate with the clay volume fraction, the cation exchange capacity, and electrochemical potential of the rock samples and to depend strongly on the salinity of the brine used. Stress and wcttability are shown to have a small influence on the dielectric constant of fully brine-saturated rocks. Empirical correlations between the dielectric constant, frequency, permeability, cation exchange capacity, and porosity arc presented for the shaly sands used in this study.

Research paper thumbnail of Solubility properties of ternary and quaternary compounds in the CaO Al2O3 SO3H2O system

Cement and Concrete Research, 1991

ABSTRACT

Research paper thumbnail of Cement hydrate phase: Solubility at 25°C

Cement and Concrete Research, 1992

ABSTRACT

Research paper thumbnail of Infrared intensities of CH stretching bands in partially deuterated compounds, and effects of conformation and substitution

Journal of Molecular Structure, 1990

Research paper thumbnail of Water chemistry and effect of evapotranspiration on chemical sedimentation on the Mkuze River floodplain, South Africa

Journal of Arid Environments, 2011

The Mkuze Wetland System, forming part of the iSimangaliso World Heritage Site, is South Africa’s... more The Mkuze Wetland System, forming part of the iSimangaliso World Heritage Site, is South Africa’s largest freshwater wetland area and is known to act as a sink for naturally occurring solutes within the landscape. The chemistry of groundwater and porewater samples, collected from two transects on the Mkuze River floodplain, was investigated to identify processes involved in the control of solute concentrations. Results show that solutes in the groundwater become increasingly concentrated under the influence of evapotranspiration, resulting in the saturation, precipitation, and accumulation of less soluble compounds. Trends in porewater chemistry and calculated saturation indices support previously documented mineralogical and sediment geochemical investigations, with CaCO3 and silica precipitation, and Fe-rich smectite neoformation identified as the major controls on solute concentration. The association of these mineral phases with zones of high salinity suggests that mineral precipitation is an active process on the floodplain which results in the progressive development of salinity, particularly in areas dominated by deep-rooted trees. Similarities between geochemical processes documented in the Okavango Delta (Botswana) and those identified in this study suggest that evapotranspiration-induced chemical sedimentation is an important process in southern African wetlands, which has the potential to influence vegetation distribution, hydrological flows, and local topography.

Research paper thumbnail of Electronic submission, calculation and checking of laboratory practical scripts

South African journal of chemistry, 2000

Research paper thumbnail of GenX uptake by wheat and flooded and non-flooded rice: greenhouse experiment

GenX (hexafluoropropylene oxide dimer acid) belongs to the group of per- and poly-fluoroalkyl sub... more GenX (hexafluoropropylene oxide dimer acid) belongs to the group of per- and poly-fluoroalkyl substance (PFAS) compounds introduced to replace perfluorooctanoic acid (PFOA), which has been phased out in industrial and consumer product formulations. While GenX has been investigated in lab animals, there is limited information available regarding its uptake and translocation in wheat and rice. This study reports on a greenhouse experiment in which wheat and rice grown under flooded and non-flooded conditions were exposed to two GenX concentrations in the soil (0.4 mg kg− 1 and 2 mg kg− 1). GenX was analysed in the soil, porewater and shoots using targeted liquid chromatography-tandem mass spectroscopy (LC-MS/MS) analysis. Extractable organic fluorine (EOF) was determined using high-resolution continuum source graphite furnace molecular absorption spectrometry (HR GFMAS). Results showed that different species took up different amounts of GenX. The GenX in rice shoots was found to be 2....

Research paper thumbnail of The use of silver as a selective precipitant for 129I in radioactive waste management

Waste Management, 1990

I-~9I is one of the more hazardous nuclides occurring in radioactive waste. In the form of I-, it... more I-~9I is one of the more hazardous nuclides occurring in radioactive waste. In the form of I-, its most likely speciation, it is poorly sorbed on most geologic media. Several workers have suggested the use of silver to precipitate I as the insoluble AgI, in a cemented waste form, or as a "getter." The efficacy of this procedure is examined by experiment, in conjunction with thermodynamic predictions. The addition of AgNO3 to Portland cement leads to coprecipitation with C-S-H, with low Ag solubilities (-10 Itg/ L); 2-3 orders of magnitude lower than predicted (from AgzO). AgI is stable in these matrices, with low aqueous I concentrations (<2 mg/L). In 85% BFS-15% OPC pastes, AgI is unstable due to redox and complexation reactions, with much I-passing into solution; concentrations up to 900 mg/L were observed. It is shown that repository conditions, on closure, are also likely to induce solubilisation of I-from AgI. It is concluded that the use of Ag is unlikely to significantly improve the immobilisation properties of the near field for radioiodine.

Research paper thumbnail of Corrosion behaviour of steel in high alumina cement mortar cured at 5,25 and 55 �C: chemical and physical factors

Journal of Materials Science, 1996

The corrosion behaviour of embedded steel was related to the composition of the pore phase in equ... more The corrosion behaviour of embedded steel was related to the composition of the pore phase in equilibrium with the hydrated phases and the porosity of the high alumina cement mortars subsequent to curing at 5, 25 and 55~ The corrosion of reinforcements was evaluated by electrochemical techniques. The effect on corrosion of 3% by weight of cement of NaCI, added during the mixing process, and of the accelerated carbonation of mortars in CO2 atmosphere were also determined. The pH value and the chemical composition of pore fluid of plain high alumina cement (HAC) mortar cured at all three temperatures suggested that the embedded steel was in a passivated state. The resistance of HAC to carbonation and its greater potential for chloride binding by chloroaluminate formation are believed to make HAC inherently more protective to steel, relative to normal Portland cement, during ingress of chloride from external sources. High corrosion rates reported in literature for steel embedded in HAC may be attributable to bad practice, not to lack of passivity.

Research paper thumbnail of Laser ablation of soft tissue using a cryogenically cooled ablation cell

Journal of Analytical Atomic Spectrometry, 2002

ABSTRACT

Research paper thumbnail of Method Development for Flow Adsorption and Removal of Lead and Copper in Contaminated Water Using Electrospun Nanofibers of Chitosan Blend

Analytical Letters, 2011

... a b * , Andrew Kindness a , Brenda Moodley a &amp;amp;amp;amp; Leslie Petrik b pages 1937... more ... a b * , Andrew Kindness a , Brenda Moodley a &amp;amp;amp;amp; Leslie Petrik b pages 1937-1955. ... Res. 341 : 2098 – 2107 . [CrossRef], [PubMed], [Web of Science ®] View all references; Sagheer 2009; Abdou et al. 20081. Abdou , ES , A. Khaled , SA Nagy , A. Maher , and Z. Elsabee . 2008 . ...

Research paper thumbnail of Equilibrium and Kinetic Studies for Extracting Cu, Mn, and Fe From Pulp Wastewater onto a C-18 Column with Acetylacetone Complexing Ligand

Analytical Letters, 2011

A preconcentration procedure using solid phase extraction of heavy metals in pulp wastewater is r... more A preconcentration procedure using solid phase extraction of heavy metals in pulp wastewater is reported. The procedure was optimized by using model solutions of selected heavy metals to investigate the effect of matrix constituents. Equilibrium studies highlighted the bonding and adsorption characteristics. The metal recoveries after spiking pulp waste filtrate with Cu, Ni, and Pb each at 0.1 and 0.2 ppm was 120, 91, and 93%, respectively. The Freundlich adsorption isotherms with correlation coefficients (R 2) 0.612, 0.810, and 0.750, showed a better fit compared to Langmuir isotherm values of 0.277, 0.389, and 0.272 for Cu, Mn, and Fe, respectively.

Research paper thumbnail of (Anthracen-9-ylmethyl)diethylamine at 100 K

Acta Crystallographica Section E Structure Reports Online, 2004

Research paper thumbnail of A preliminary analysis of water chemistry of the Mkuze Wetland System, KwaZulu-Natal: a mass balance approach

Water SA, 2004

The Mkuze Wetland System in northern KwaZulu-Natal constitutes an important source of freshwater ... more The Mkuze Wetland System in northern KwaZulu-Natal constitutes an important source of freshwater to Lake St Lucia. The St Lucia System, including both the Mkuze Wetland System and Lake St Lucia, is recognised as a Wetland of International Importance under the Ramsar Convention. The long-term survival of Lake St Lucia depends on an adequate supply of freshwater. Consequently, the role of the Mkuze Wetland System in water quality enhancement is essential. In order to investigate the water chemistry of this system, water samples were collected throughout the study area from surface water, groundwater, pan and reed swamp sites, as well as a rainwater sample. These were analysed for chloride, sodium, potassium, calcium, magnesium, iron and silicon. Four main water bodies were identified using the multivariate techniques, classification and ordination. Of these four groups, two represented the major water sources to the system, these being the Mkuze River and floodplain and the Mbazwane System. The third represented outflow into Lake St Lucia, while the fourth represented scattered ground and surface water samples some distance away from the main watercourses. The solute concentrations of the two water sources were compared using a mass-balance approach. Chloride was identified as a conserved solute and the increasing chloride concentration from the less concentrated inflows (especially the Mbazwane System) to the concentrated outflow into Lake St Lucia, is considered to reflect evapotranspiration. By considering chloride to be conserved, the degree of evaporative enrichment was estimated in the Mkuze Wetland System and used to determine the percentage of solutes retained in the swamp. The wetland was found to be an important sink for calcium (~50% retention), potassium (~70% retention) and silicon (~80% retention), with magnesium and sodium being retained to a lesser extent. The TDS value supports these findings as it is lower than expected in the outflow by a similar percentage to the magnesium and sodium retention. The removal of solutes by the Mkuze Wetland System, not only has far-reaching implications for Lake St Lucia in maintaining a freshwater supply, but could also have significant impacts on the ecology and geomorphology of the Mkuze System itself. The fate of solutes and the processes of solute retention are subjects of ongoing research.

Research paper thumbnail of EOF and target PFAS analysis in surface waters affected by sewage treatment effluents in Berlin, Germany

Analytical and Bioanalytical Chemistry

Per- and polyfluoroalkyl substances (PFAS) are emerging organic pollutants and can occur in surfa... more Per- and polyfluoroalkyl substances (PFAS) are emerging organic pollutants and can occur in surface and groundwater. To identify the degree of pollution in surface water with PFAS, often targeted HPLC–ESI–MS/MS has been employed in which commonly 30–40 compounds are analyzed. However, other PFAS and organofluorines remain undetected. We sampled surface water of the river Spree and the Teltow Canal in Berlin, Germany, which are affected by the effluent discharge of wastewater treatment plants. Here, we employed high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS-GFMAS) for measuring extractable organofluorines (EOF) and compared in a mass balance approach the total fluorine to the identified and quantified PFAS from the targeted analysis. The analysis highlights that the EOF are in the range expected for an urban river system (Winchell et al. in Sci Total Environ 774, 2021). However, downstream of an effluent discharge, the EOF increased by one ...

Research paper thumbnail of A preliminary investigation into the stability of inorganic arsenic species in laboratory solutions simulating sediment pore water

South African Journal of Chemistry, 2016

A simple method to preserve arsenic species in simulated pore water was investigated. Synthetic p... more A simple method to preserve arsenic species in simulated pore water was investigated. Synthetic pore water containing high levels of Fe, Mn and S (as sulfide, S 2-) were synthesized and spiked with different arsenic species. Arsenite [As(III)], arsenate [As(V)], dimethylarsinate [(CH 3) 2 AsO 2-, DMA], monomethylarsonate [(CH 3)AsO 3 2-, MMA], monothioarsenate(V) species (AsO 3 S 3-, MTA) and tetrathioarsenate(v) species (AsS 4 3-, TTA) in different combinations were used. Disodium ethylenediamine tetraacetate (EDTA) and temperature was used to preserve speciation. Solutions were analyzed at intervals of one day, week, month and 2 months after preparation. Samples were analyzed by HPLC-ICP-MS using an ion exchange column and ammonium carbonate buffer. Samples containing Fe and Mn spiked with As(III), As(V), DMA, MMA showed adequate species preservation for two months when EDTA was added. The total As in samples containing Fe, Mn and S 2was preserved over 60 days however, speciation was not preserved. Samples spiked with synthesized mono-and tetra-thioarsenate(V) species showed immediate degradation of the mono-and tetra-thioarsenic species into unidentified AsS species. The results show that while EDTA may be adequate to preserve As species containing high Fe and Mn concentrations, the combination of EDTA and temperature was not successful in preserving As speciation in samples containing sulfides.

Research paper thumbnail of Per and Polyfluoroalkyl Substances Mass Balance Analysis in Ski Wax, Snowmelts, and Soil from Skiing Areas

Research paper thumbnail of Phase Relations and Solubility Modelling in the Cao- SiO2- Al2O3- MgO- SO3-H2O System: For Application To Blended Cementss

MRS Proceedings, 1990

ABSTRACTCement blends are likely to form a large fraction of the materials in the near field of r... more ABSTRACTCement blends are likely to form a large fraction of the materials in the near field of radioactive repositories. Being chemically reactive and slightly soluble, their effect on near field chemistry will be very marked. Predictions of nuclide migration in this zone will therefore depend in part on accurate modelling of cement chemistry.The models being developed require the establishment of correct phase relations in the Cao- SiO2- Al2O3- MgO- SO3-H2O system (the major cement components). More than 40 compatibility experiments were carried out to determine these relationships. Purified cement hydrates were shaken continuously in CO2- free water, for 10 weeks. The results from these experiments together with data from the literature, enabled us to construct a better validated phase relations scheme than has hitherto been possible.Interpretational problems were encountered. Thus, mixtures containing Ca(OH)2, gave rise to the precipitation of metastable phases. This is due to s...

Research paper thumbnail of Application of hydrogeochemical modeling in simulating the transportation of elements in fly ash heap under different disposal systems in South Africa

Physics and Chemistry of the Earth, Parts A/B/C, 2015

Ash heap modelling of South African fly ash from Tutuka was carried out and the duration of trans... more Ash heap modelling of South African fly ash from Tutuka was carried out and the duration of transportation projected for 20 years based on two disposal scenarios, namely; irrigation of ash with rainwater, and irrigation with brines. The hydrogeochemical modeling code, PHREEQC, was applied in the study which gave insights into the speciation, release and transport of elements from the water and brines-fly ash long term interactions. Tutuka ash-water heap model showed a general sharp decrease of total elemental concentrations released during the first 2.5 years simulation as the pH value dropped from 12.6 to 8.7, after which it remained constant and their concentration remained constant up to 20 years. The elements showing this trend included Ca, Mg, Al, Fe, Sr, Zn, Na, K, Li and C(4). Generally, brines caused sharp increase in released concentration of the elements Ca, Mg, S(6) and C(4) for the first 3 years of heap irrigation whereas with water irrigation an opposite trend was observed in which the elemental concentrations decreased. Much of the release chemistry of the elements was closely related to the phase dissolution/precipitation and formation as the major controlling factors. Generally therefore, the modelled leachate quality results revealed that many elements are mobile and move through the ash heap in a progressive leaching pathway. The model could therefore be used to provide reasonable leachate quality from the modelled Tutuka ash heap which may be reaching the ground water. Overall, the ash heap modelling enhanced the understanding of the environmental impacts of ash-water-brines interactions and demonstrated that leachate composition is determined by the following factors; (i) the mass flows from the pores of fly ash, (ii) the surface dissolution of the mineral phases, (iii) the various chemical reactions involved during the ash-brine and ash-water interactions, (iv) the interactions with a gas phase (atmospheric CO 2), (v) the composition of the initial fly ash, and (vi) the leachate flow and hydrodynamics as captured in the conceptual model. Further model validation is recommended with lysimeters to quantatively compare the simulated results against the experimental data and improve on the model.

Research paper thumbnail of Experimental and ab initio infrared intensities in dimethylether: Atomic polar tensors and atomic charges

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 1996

Infrared intensities have been recorded in (CH3)20 over the range 100-3300 cm J and ab initio cal... more Infrared intensities have been recorded in (CH3)20 over the range 100-3300 cm J and ab initio calculations of geometry, frequency and infrared intensity made at the MP2/6-31G* level. The experimental results are compatible with previous data for (CHD2)20 and support the earlier results for (CH3)20 of Blom et al. The more recent data of Rogers appear to be too high. Additivity of vCH infrared intensity, per CH bond, is found in both the experimental and ab initio studies. Overall agreement between the two approaches is quite good. Ab initio based atomic polar tensors and their invariants are listed for representative atoms in dimethyl ether, methane and ethane and their Mulliken and King effective atomic charges compared. Dipole derivatives for the two types of CH bond present are markedly different and are directed away from the bond directions by 14-19 °. Rotation of the permanent dipole moment makes a significant contribution to the vCH stretching intensities in the d 5 species.

Research paper thumbnail of Immobilisation and fixation of molybdenum (VI) by Portland cement

International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, 1995

Complex impedance measurements have been performed on 14 shaly sand samples, Berea sandstone, and... more Complex impedance measurements have been performed on 14 shaly sand samples, Berea sandstone, and Ottawa sandbentonite packs in a frequency range of 10 Hz to 10 MHz, using both the two-and four-electrode techniques. The dielectric permittivity is found to correlate with the clay volume fraction, the cation exchange capacity, and electrochemical potential of the rock samples and to depend strongly on the salinity of the brine used. Stress and wcttability are shown to have a small influence on the dielectric constant of fully brine-saturated rocks. Empirical correlations between the dielectric constant, frequency, permeability, cation exchange capacity, and porosity arc presented for the shaly sands used in this study.

Research paper thumbnail of Solubility properties of ternary and quaternary compounds in the CaO Al2O3 SO3H2O system

Cement and Concrete Research, 1991

ABSTRACT

Research paper thumbnail of Cement hydrate phase: Solubility at 25°C

Cement and Concrete Research, 1992

ABSTRACT

Research paper thumbnail of Infrared intensities of CH stretching bands in partially deuterated compounds, and effects of conformation and substitution

Journal of Molecular Structure, 1990

Research paper thumbnail of Water chemistry and effect of evapotranspiration on chemical sedimentation on the Mkuze River floodplain, South Africa

Journal of Arid Environments, 2011

The Mkuze Wetland System, forming part of the iSimangaliso World Heritage Site, is South Africa’s... more The Mkuze Wetland System, forming part of the iSimangaliso World Heritage Site, is South Africa’s largest freshwater wetland area and is known to act as a sink for naturally occurring solutes within the landscape. The chemistry of groundwater and porewater samples, collected from two transects on the Mkuze River floodplain, was investigated to identify processes involved in the control of solute concentrations. Results show that solutes in the groundwater become increasingly concentrated under the influence of evapotranspiration, resulting in the saturation, precipitation, and accumulation of less soluble compounds. Trends in porewater chemistry and calculated saturation indices support previously documented mineralogical and sediment geochemical investigations, with CaCO3 and silica precipitation, and Fe-rich smectite neoformation identified as the major controls on solute concentration. The association of these mineral phases with zones of high salinity suggests that mineral precipitation is an active process on the floodplain which results in the progressive development of salinity, particularly in areas dominated by deep-rooted trees. Similarities between geochemical processes documented in the Okavango Delta (Botswana) and those identified in this study suggest that evapotranspiration-induced chemical sedimentation is an important process in southern African wetlands, which has the potential to influence vegetation distribution, hydrological flows, and local topography.

Research paper thumbnail of Electronic submission, calculation and checking of laboratory practical scripts

South African journal of chemistry, 2000

Research paper thumbnail of GenX uptake by wheat and flooded and non-flooded rice: greenhouse experiment

GenX (hexafluoropropylene oxide dimer acid) belongs to the group of per- and poly-fluoroalkyl sub... more GenX (hexafluoropropylene oxide dimer acid) belongs to the group of per- and poly-fluoroalkyl substance (PFAS) compounds introduced to replace perfluorooctanoic acid (PFOA), which has been phased out in industrial and consumer product formulations. While GenX has been investigated in lab animals, there is limited information available regarding its uptake and translocation in wheat and rice. This study reports on a greenhouse experiment in which wheat and rice grown under flooded and non-flooded conditions were exposed to two GenX concentrations in the soil (0.4 mg kg− 1 and 2 mg kg− 1). GenX was analysed in the soil, porewater and shoots using targeted liquid chromatography-tandem mass spectroscopy (LC-MS/MS) analysis. Extractable organic fluorine (EOF) was determined using high-resolution continuum source graphite furnace molecular absorption spectrometry (HR GFMAS). Results showed that different species took up different amounts of GenX. The GenX in rice shoots was found to be 2....

Research paper thumbnail of The use of silver as a selective precipitant for 129I in radioactive waste management

Waste Management, 1990

I-~9I is one of the more hazardous nuclides occurring in radioactive waste. In the form of I-, it... more I-~9I is one of the more hazardous nuclides occurring in radioactive waste. In the form of I-, its most likely speciation, it is poorly sorbed on most geologic media. Several workers have suggested the use of silver to precipitate I as the insoluble AgI, in a cemented waste form, or as a "getter." The efficacy of this procedure is examined by experiment, in conjunction with thermodynamic predictions. The addition of AgNO3 to Portland cement leads to coprecipitation with C-S-H, with low Ag solubilities (-10 Itg/ L); 2-3 orders of magnitude lower than predicted (from AgzO). AgI is stable in these matrices, with low aqueous I concentrations (<2 mg/L). In 85% BFS-15% OPC pastes, AgI is unstable due to redox and complexation reactions, with much I-passing into solution; concentrations up to 900 mg/L were observed. It is shown that repository conditions, on closure, are also likely to induce solubilisation of I-from AgI. It is concluded that the use of Ag is unlikely to significantly improve the immobilisation properties of the near field for radioiodine.

Research paper thumbnail of Corrosion behaviour of steel in high alumina cement mortar cured at 5,25 and 55 �C: chemical and physical factors

Journal of Materials Science, 1996

The corrosion behaviour of embedded steel was related to the composition of the pore phase in equ... more The corrosion behaviour of embedded steel was related to the composition of the pore phase in equilibrium with the hydrated phases and the porosity of the high alumina cement mortars subsequent to curing at 5, 25 and 55~ The corrosion of reinforcements was evaluated by electrochemical techniques. The effect on corrosion of 3% by weight of cement of NaCI, added during the mixing process, and of the accelerated carbonation of mortars in CO2 atmosphere were also determined. The pH value and the chemical composition of pore fluid of plain high alumina cement (HAC) mortar cured at all three temperatures suggested that the embedded steel was in a passivated state. The resistance of HAC to carbonation and its greater potential for chloride binding by chloroaluminate formation are believed to make HAC inherently more protective to steel, relative to normal Portland cement, during ingress of chloride from external sources. High corrosion rates reported in literature for steel embedded in HAC may be attributable to bad practice, not to lack of passivity.

Research paper thumbnail of Laser ablation of soft tissue using a cryogenically cooled ablation cell

Journal of Analytical Atomic Spectrometry, 2002

ABSTRACT

Research paper thumbnail of Method Development for Flow Adsorption and Removal of Lead and Copper in Contaminated Water Using Electrospun Nanofibers of Chitosan Blend

Analytical Letters, 2011

... a b * , Andrew Kindness a , Brenda Moodley a &amp;amp;amp;amp; Leslie Petrik b pages 1937... more ... a b * , Andrew Kindness a , Brenda Moodley a &amp;amp;amp;amp; Leslie Petrik b pages 1937-1955. ... Res. 341 : 2098 – 2107 . [CrossRef], [PubMed], [Web of Science ®] View all references; Sagheer 2009; Abdou et al. 20081. Abdou , ES , A. Khaled , SA Nagy , A. Maher , and Z. Elsabee . 2008 . ...

Research paper thumbnail of Equilibrium and Kinetic Studies for Extracting Cu, Mn, and Fe From Pulp Wastewater onto a C-18 Column with Acetylacetone Complexing Ligand

Analytical Letters, 2011

A preconcentration procedure using solid phase extraction of heavy metals in pulp wastewater is r... more A preconcentration procedure using solid phase extraction of heavy metals in pulp wastewater is reported. The procedure was optimized by using model solutions of selected heavy metals to investigate the effect of matrix constituents. Equilibrium studies highlighted the bonding and adsorption characteristics. The metal recoveries after spiking pulp waste filtrate with Cu, Ni, and Pb each at 0.1 and 0.2 ppm was 120, 91, and 93%, respectively. The Freundlich adsorption isotherms with correlation coefficients (R 2) 0.612, 0.810, and 0.750, showed a better fit compared to Langmuir isotherm values of 0.277, 0.389, and 0.272 for Cu, Mn, and Fe, respectively.

Research paper thumbnail of (Anthracen-9-ylmethyl)diethylamine at 100 K

Acta Crystallographica Section E Structure Reports Online, 2004

Research paper thumbnail of A preliminary analysis of water chemistry of the Mkuze Wetland System, KwaZulu-Natal: a mass balance approach

Water SA, 2004

The Mkuze Wetland System in northern KwaZulu-Natal constitutes an important source of freshwater ... more The Mkuze Wetland System in northern KwaZulu-Natal constitutes an important source of freshwater to Lake St Lucia. The St Lucia System, including both the Mkuze Wetland System and Lake St Lucia, is recognised as a Wetland of International Importance under the Ramsar Convention. The long-term survival of Lake St Lucia depends on an adequate supply of freshwater. Consequently, the role of the Mkuze Wetland System in water quality enhancement is essential. In order to investigate the water chemistry of this system, water samples were collected throughout the study area from surface water, groundwater, pan and reed swamp sites, as well as a rainwater sample. These were analysed for chloride, sodium, potassium, calcium, magnesium, iron and silicon. Four main water bodies were identified using the multivariate techniques, classification and ordination. Of these four groups, two represented the major water sources to the system, these being the Mkuze River and floodplain and the Mbazwane System. The third represented outflow into Lake St Lucia, while the fourth represented scattered ground and surface water samples some distance away from the main watercourses. The solute concentrations of the two water sources were compared using a mass-balance approach. Chloride was identified as a conserved solute and the increasing chloride concentration from the less concentrated inflows (especially the Mbazwane System) to the concentrated outflow into Lake St Lucia, is considered to reflect evapotranspiration. By considering chloride to be conserved, the degree of evaporative enrichment was estimated in the Mkuze Wetland System and used to determine the percentage of solutes retained in the swamp. The wetland was found to be an important sink for calcium (~50% retention), potassium (~70% retention) and silicon (~80% retention), with magnesium and sodium being retained to a lesser extent. The TDS value supports these findings as it is lower than expected in the outflow by a similar percentage to the magnesium and sodium retention. The removal of solutes by the Mkuze Wetland System, not only has far-reaching implications for Lake St Lucia in maintaining a freshwater supply, but could also have significant impacts on the ecology and geomorphology of the Mkuze System itself. The fate of solutes and the processes of solute retention are subjects of ongoing research.

Research paper thumbnail of EOF and target PFAS analysis in surface waters affected by sewage treatment effluents in Berlin, Germany

Analytical and Bioanalytical Chemistry

Per- and polyfluoroalkyl substances (PFAS) are emerging organic pollutants and can occur in surfa... more Per- and polyfluoroalkyl substances (PFAS) are emerging organic pollutants and can occur in surface and groundwater. To identify the degree of pollution in surface water with PFAS, often targeted HPLC–ESI–MS/MS has been employed in which commonly 30–40 compounds are analyzed. However, other PFAS and organofluorines remain undetected. We sampled surface water of the river Spree and the Teltow Canal in Berlin, Germany, which are affected by the effluent discharge of wastewater treatment plants. Here, we employed high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS-GFMAS) for measuring extractable organofluorines (EOF) and compared in a mass balance approach the total fluorine to the identified and quantified PFAS from the targeted analysis. The analysis highlights that the EOF are in the range expected for an urban river system (Winchell et al. in Sci Total Environ 774, 2021). However, downstream of an effluent discharge, the EOF increased by one ...

Research paper thumbnail of A preliminary investigation into the stability of inorganic arsenic species in laboratory solutions simulating sediment pore water

South African Journal of Chemistry, 2016

A simple method to preserve arsenic species in simulated pore water was investigated. Synthetic p... more A simple method to preserve arsenic species in simulated pore water was investigated. Synthetic pore water containing high levels of Fe, Mn and S (as sulfide, S 2-) were synthesized and spiked with different arsenic species. Arsenite [As(III)], arsenate [As(V)], dimethylarsinate [(CH 3) 2 AsO 2-, DMA], monomethylarsonate [(CH 3)AsO 3 2-, MMA], monothioarsenate(V) species (AsO 3 S 3-, MTA) and tetrathioarsenate(v) species (AsS 4 3-, TTA) in different combinations were used. Disodium ethylenediamine tetraacetate (EDTA) and temperature was used to preserve speciation. Solutions were analyzed at intervals of one day, week, month and 2 months after preparation. Samples were analyzed by HPLC-ICP-MS using an ion exchange column and ammonium carbonate buffer. Samples containing Fe and Mn spiked with As(III), As(V), DMA, MMA showed adequate species preservation for two months when EDTA was added. The total As in samples containing Fe, Mn and S 2was preserved over 60 days however, speciation was not preserved. Samples spiked with synthesized mono-and tetra-thioarsenate(V) species showed immediate degradation of the mono-and tetra-thioarsenic species into unidentified AsS species. The results show that while EDTA may be adequate to preserve As species containing high Fe and Mn concentrations, the combination of EDTA and temperature was not successful in preserving As speciation in samples containing sulfides.