<p>The management and disposal of huge volumes of coal combustion by products such as fly ash has constituted a major challenge to the environment. In most cases due to the inadequate alternative use of coal fly ash, the discarded waste is stored in holding ponds, slag heaps, or stock piled in ash dumps. This practice has raised concerns on the prospect of inorganic metals release to the surface and groundwater in the vicinity of the ash dump. Acceptable scientific studies are lacking to determine the best ash disposal practices. Moreover, knowledge about the mobility patterns of inorganic species as a function of mineralogical association or pH susceptibility of the dry disposed ash dump under natural weathering conditions are scarce in the literature. Fundamental understanding of chemical interactions of dry disposed ash with ingressed CO2 from atmosphere, percolating rain water and brine irrigation within ash disposal sites were seen as key areas requiring investigation. The mineralogical association of inorganic species in the dry disposed ash cores can be identified and quantified. This would provide a basis for understanding of chemical weathering, mineralogical transformations or mobility patterns of these inorganic species in the dry ash disposal scenario. The current study therefore aims to provide a comprehensive characterisation of weathered dry disposed ash cores, to reveal mobility patterns of chemical species as a function of depth and age of ash, with a view to assessing the potential environmental impacts. Fifty-nine samples were taken from 3 drilled cores obtained respectively from the 1 year, 8 year and 20-year-old sections of sequentially dumped,&nbsp / weathered, dry disposed ash in an ash dump site at Tutuka - a South African coal burning power station. The core samples were characterized using standard analytical procedures viz: X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transforms infrared (FTIR) techniques, Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) and Acid neutralisation capacity (ANC) test. A modified sequential extraction (SE) method was used in this study. The chemical partitioning, mobility and weathering patterns in 1 year, 8 year and 20-year-old sections of the ash dump were respectively investigated using this modified sequential extraction scheme. The sequence of the extractions was as follows: (1) water soluble, (2) exchangeable, (3) carbonate, (4) iron and manganese and (5) residual. The results obtained from the 5 steps sequential extraction scheme were validated with the total metal content of the original sample using mass balance method. The distribution of major and trace elements in the different liquid fractions obtained after each step of sequential extraction of the 59 drilled core samples was determined by inductively coupled plasma mass spectrometry (ICPMS). The data generated for various ash core samples were explored for the systematic analysis of mineralogical transformation and change in ash chemistry with ageing of the ash. Furthermore, the data was analyzed to reveal the impact of ingressed CO2 from atmosphere, infiltrating rain water and brine irrigation on the chemistry of ash core samples. Major mineral phases in original ash core samples prior to extraction are quartz (SiO2) and mullite (3Al2O3&middot / 2SiO2). Other minor mineral phases identified were hematite (Fe2O3), calcite (CaCO3), lime (CaO), anorthite (CaAl2Si2O8), mica (Ca (Mg, Al)3 (Al3Si) O10 (OH)2), and enstatite (Mg2Si2O6). X-ray diffraction results show significant loss of crystallinity in the older ash cores. The presence of minor phases of calcite and mica in dry disposed ash cores are attributed to reduction in the pore water pH due to hydration, carbonation and pozzolanic reactions. The X-ray diffraction technique was unable to detect Fe-oxyhydroxide phase and morealuminosilicate phases in ash core samples due to their low abundance and amorphous character. X-ray fluorescence results of the original ash core samples showed the presence of major oxides, such as SiO2, Al2O3, Fe2O3, while CaO, K2O, TiO2, Na2O, MnO, MgO, P2O5, and SO3 occur in minor concentrations. The ratio of SiO2/Al2O3 classified the original core samples prior to extraction as a silico-aluminate class F fly ash. The ternary plot of major elements in 1-year-old ash core samples was both sialic and ferrocalsialic but 8 year and 20-year-old ash core samples were sialic in chemical composition. It is noteworthy that the mass % of SiO2 varies through the depth of the core with an increase of nearly 3 %, to 58 mass % of SiO2 at a depth of 6 m in the 1-year-old core whereas in the case of the 8-year-old core a 2 % increase of SiO2 to a level of 57.5 mass % can be observed at levels between 4-8 m, showing dissolution of major components in the matrix of older ash cores.. The Na2O content of the Tutuka ash cores was low and varied between 0.6-1.1 mass % for 1-year-old ash cores to around 0.6-0.8 mass % for 8-year-old ash cores. Sodium levels were higher in 1-year-old ash cores compared to 8 year and 20-year-old ashcores. Observed trends indicate that quick weathering of the ash (within a year) leached out Na+ from the ash dump. No evidence of Na+ encapsulation even though the ash dump was brine irrigated. Thus the dry disposal ash placement method does not result in a sustainable salt sink for Na-containing species over time. The total content of each of the elements in 1 year and 20-year-old ash cores was normalised with their total content in fresh ash from same power station to show enrichment and depletion factor. Major elements such as K+, Mn showed enrichment in 1-year-old ash cores whereas Al, Si, Na+, Ti, Ca, Mg, S and Fe showed depletion due to over time erosion. Trace elements such as Cr, Sr, P, Ba, Pb, V and Zn showed enrichment but Ni, Y, Zr showed depletion attributed to over time erosion. In 20-year-old ash cores, major elements such as Al, Na+ and Mn showed enrichment while Si, K+, Fe, Mg and Ca showed depletion highlighting their mobility. Trends indicated intensive flushing of major soluble components such as buffering constituents (CaO) by percolating rain water. The 1-year-old and 20-year-old coal ash cores showed a lower pH and greater loss/depletion of the soluble buffering constituents than the 2-week-old placed ash, indicating significant chemical weathering within a year. Based&nbsp / on ANC results the leaching behaviours of Ca, Mg, Na+, K+, Se, Cr, and Sr were found to be controlled by the pH of the leachant indicating high mobility of major soluble species in the ash cores when in contact with slightly acid rain water. Other investigated toxic metals such as As, Mo and Pb showed amphoteric behaviour with respect to the pH of the leachant. Chemical alterations and formation of transient minor secondary mineral phases was found to have a significant effect on the acid susceptibility and depletion pattern of chemical species in the core ash samples when compared to fresh ash. These ANC results correlated well with the data generated from the sequential extraction scheme. Based on sequential extraction results elements, showed noticeable mobility in the water soluble, exchangeable and carbonate fractions due to adsorption and desorption caused by variations in the pore water pH. In contrast, slight mobility of elements in the Fe and Mn, and residual fractions of dry disposed fly ashes are attributed to the co-precipitation and dissolution of minor amount of less soluble secondary phase overtime. The 1-year-old dry disposed ash cores were the least weathered among the 3 drilled ash cores. Therefore low concentration of toxic metals in older ash cores were ascribed to extensive weathering with slower release from residual mineral phases over time. Elements were found to associate with different mineral phases depending on the age or depth of the core samples showing greater heterogeneity in dispersion. For instance the average amount of total calcium in different mineral associations of 1-year-old ash cores is as follows / water soluble (10.2 %), exchangeable (37.04 %), carbonate (37.9 %), Fe and Mn (7.1 %) and residual (2.97 %). The amount of total Na+ in different mineral phases of 1-year-old ash cores followed this trend: water soluble (21 %), exchangeable (11.26 %), carbonate (2.6 %), Fe and Mn (4.7 %) and residual (53.9 %). The non-leachable portion of the total Na+ content (namely that contained in the residual fraction) in the 1-year-old ash core samples under conditions found in nature ranged between 5-91 %. This non-leachable portion of the Na+ showed the metastability of the mineral phases with which residual Na+ associates. Results showed older ash cores are enriched in toxic elements. Toxic elements such as As, B, Cr, Mo and Pb are enriched in the residual fraction of older ash cores. For instance As concentration in the residual fraction varied between 0.0003- 0.00043 mg kg-1 for 1-year-old ash cores to around 0.0003-0.0015 mg kg-1 for 20-year-old ash cores. This suggests that the older ash is enriched in toxic elements hence dust from the ash dump would be toxic to human health. The knowledge of mobility and ecotoxicological significance of coal fly ash is needed when considering its disposal or reuse in the environment. The mobility and ecotoxicology of inorganic metals in coal fly ash are determined by (i) mineralogical associations of inorganic species (ii) in-homogeneity in the ash dumps (iii) long and short term exposure to ingress CO2 and percolating rain water. Management issues such as inconsistent placement of ash in the dumps, poor choice of ash dump site, in-homogeneity in brine irrigation, no record of salt load put on the ash dumps and lack of proper monitoring requires improvement. The thesis provides justification for the use of the modified sequential extraction scheme as a predictive tool and could be employed in a similar research work. This thesis also proved that the dry ash disposal method was not environmental friendly in terms of overall leaching potential after significant chemical weathering. Moreover the study proved that the practice of brine co-disposal or irrigation on ash dumps is not sustainable as the ash dump did not act as a salt sink.</p>

Tortilla sales are projected to exceed 9.5 billion by 2014. However, currently no wheat cultivars have been identified that possess the intrinsic quality attributes needed for the production of optimum quality tortillas. Tortillas made with refined wheat flour low in dietary fiber (DF) are popular in the United States due to their sensory properties. This study explored the use of wheat lines (WL) possessing variations in high molecular weight glutenin allele sub-units (HMW-GS) for production of tortillas and also investigated the use of corn based resistant starches (RS), type II (RS2) and wheat based RS type IV (RS4) to increase DF in tortillas. Tortillas were made with 0-15 percent RS and 100 percent whole white wheat (WW). Flour protein profiles, dough, and tortilla properties were evaluated to determine the effects of the allelic variations and RS substitution on tortilla quality. Sensory properties of tortillas with RS were determined. Variations in HMW-GS composition significantly affected the protein quality and tortilla properties. Flour from WL possessing allelic combinations (2*, 17+18, 7, 2+12), (1, 17+18, 5+10), (2*, 17, 2+12) and (1, 2*, 17+18, 2+12) had 12.8-13.3 percent protein. These WL had extensible doughs and produced large diameter tortillas with superior (greater than or equal to 3.0) flexibility after 16 days compared to control. However, WL with (17+18 and 5+10) and (2*, 17+7, 5) produced extensible doughs, large, but less flexible, tortillas compared to control. WL with (2*,17+18,5+10) and (1,2*,7+9,5+10) produced smaller diameter tortillas, but with superior flexibility compared to control. RS2, WW, and cross-linked-pre-gelatinized RS4 (FiberRite) produced hard, less-extensible doughs and thinner tortillas compared to control, due to high water absorption. Cross-linked RS4 (Fibersym) dough and tortillas were comparable to control. 15 percent of RS2 and RS4 increase DF in control to 6 and 14 percent respectively, compare to control (2.8 percent DF). WW tortillas were less acceptable than control in appearance, flavor and texture, while tortillas with 15 percent Fibersym had higher overall acceptability than control. RS2 negatively affected dough machinability and tortilla shelf stability. However, 15 percent RS4 improved the DF in refined flour tortillas to meet FDA's "good source of fiber claim," without negatively affecting dough/tortilla quality.

<p>The management and disposal of huge volumes of coal combustion by products such as fly ash has constituted a major challenge to the environment. In most cases due to the inadequate alternative use of coal fly ash, the discarded waste is stored in holding ponds, slag heaps, or stock piled in ash dumps. This practice has raised concerns on the prospect of inorganic metals release to the surface and groundwater in the vicinity of the ash dump. Acceptable scientific studies are lacking to determine the best ash disposal practices. Moreover, knowledge about the mobility patterns of inorganic species as a function of mineralogical association or pH susceptibility of the dry disposed ash dump under natural weathering conditions are scarce in the literature. Fundamental understanding of chemical interactions of dry disposed ash with ingressed CO2 from atmosphere, percolating rain water and brine irrigation within ash disposal sites were seen as key areas requiring investigation. The mineralogical association of inorganic species in the dry disposed ash cores can be identified and quantified. This would provide a basis for understanding of chemical weathering, mineralogical transformations or mobility patterns of these inorganic species in the dry ash disposal scenario. The current study therefore aims to provide a comprehensive characterisation of weathered dry disposed ash cores, to reveal mobility patterns of chemical species as a function of depth and age of ash, with a view to assessing the potential environmental impacts. Fifty-nine samples were taken from 3 drilled cores obtained respectively from the 1 year, 8 year and 20-year-old sections of sequentially dumped,&nbsp / weathered, dry disposed ash in an ash dump site at Tutuka - a South African coal burning power station. The core samples were characterized using standard analytical procedures viz: X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transforms infrared (FTIR) techniques, Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) and Acid neutralisation capacity (ANC) test. A modified sequential extraction (SE) method was used in this study. The chemical partitioning, mobility and weathering patterns in 1 year, 8 year and 20-year-old sections of the ash dump were respectively investigated using this modified sequential extraction scheme. The sequence of the extractions was as follows: (1) water soluble, (2) exchangeable, (3) carbonate, (4) iron and manganese and (5) residual. The results obtained from the 5 steps sequential extraction scheme were validated with the total metal content of the original sample using mass balance method. The distribution of major and trace elements in the different liquid fractions obtained after each step of sequential extraction of the 59 drilled core samples was determined by inductively coupled plasma mass spectrometry (ICPMS). The data generated for various ash core samples were explored for the systematic analysis of mineralogical transformation and change in ash chemistry with ageing of the ash. Furthermore, the data was analyzed to reveal the impact of ingressed CO2 from atmosphere, infiltrating rain water and brine irrigation on the chemistry of ash core samples. Major mineral phases in original ash core samples prior to extraction are quartz (SiO2) and mullite (3Al2O3&middot / 2SiO2). Other minor mineral phases identified were hematite (Fe2O3), calcite (CaCO3), lime (CaO), anorthite (CaAl2Si2O8), mica (Ca (Mg, Al)3 (Al3Si) O10 (OH)2), and enstatite (Mg2Si2O6). X-ray diffraction results show significant loss of crystallinity in the older ash cores. The presence of minor phases of calcite and mica in dry disposed ash cores are attributed to reduction in the pore water pH due to hydration, carbonation and pozzolanic reactions. The X-ray diffraction technique was unable to detect Fe-oxyhydroxide phase and morealuminosilicate phases in ash core samples due to their low abundance and amorphous character. X-ray fluorescence results of the original ash core samples showed the presence of major oxides, such as SiO2, Al2O3, Fe2O3, while CaO, K2O, TiO2, Na2O, MnO, MgO, P2O5, and SO3 occur in minor concentrations. The ratio of SiO2/Al2O3 classified the original core samples prior to extraction as a silico-aluminate class F fly ash. The ternary plot of major elements in 1-year-old ash core samples was both sialic and ferrocalsialic but 8 year and 20-year-old ash core samples were sialic in chemical composition. It is noteworthy that the mass % of SiO2 varies through the depth of the core with an increase of nearly 3 %, to 58 mass % of SiO2 at a depth of 6 m in the 1-year-old core whereas in the case of the 8-year-old core a 2 % increase of SiO2 to a level of 57.5 mass % can be observed at levels between 4-8 m, showing dissolution of major components in the matrix of older ash cores.. The Na2O content of the Tutuka ash cores was low and varied between 0.6-1.1 mass % for 1-year-old ash cores to around 0.6-0.8 mass % for 8-year-old ash cores. Sodium levels were higher in 1-year-old ash cores compared to 8 year and 20-year-old ashcores. Observed trends indicate that quick weathering of the ash (within a year) leached out Na+ from the ash dump. No evidence of Na+ encapsulation even though the ash dump was brine irrigated. Thus the dry disposal ash placement method does not result in a sustainable salt sink for Na-containing species over time. The total content of each of the elements in 1 year and 20-year-old ash cores was normalised with their total content in fresh ash from same power station to show enrichment and depletion factor. Major elements such as K+, Mn showed enrichment in 1-year-old ash cores whereas Al, Si, Na+, Ti, Ca, Mg, S and Fe showed depletion due to over time erosion. Trace elements such as Cr, Sr, P, Ba, Pb, V and Zn showed enrichment but Ni, Y, Zr showed depletion attributed to over time erosion. In 20-year-old ash cores, major elements such as Al, Na+ and Mn showed enrichment while Si, K+, Fe, Mg and Ca showed depletion highlighting their mobility. Trends indicated intensive flushing of major soluble components such as buffering constituents (CaO) by percolating rain water. The 1-year-old and 20-year-old coal ash cores showed a lower pH and greater loss/depletion of the soluble buffering constituents than the 2-week-old placed ash, indicating significant chemical weathering within a year. Based&nbsp / on ANC results the leaching behaviours of Ca, Mg, Na+, K+, Se, Cr, and Sr were found to be controlled by the pH of the leachant indicating high mobility of major soluble species in the ash cores when in contact with slightly acid rain water. Other investigated toxic metals such as As, Mo and Pb showed amphoteric behaviour with respect to the pH of the leachant. Chemical alterations and formation of transient minor secondary mineral phases was found to have a significant effect on the acid susceptibility and depletion pattern of chemical species in the core ash samples when compared to fresh ash. These ANC results correlated well with the data generated from the sequential extraction scheme. Based on sequential extraction results elements, showed noticeable mobility in the water soluble, exchangeable and carbonate fractions due to adsorption and desorption caused by variations in the pore water pH. In contrast, slight mobility of elements in the Fe and Mn, and residual fractions of dry disposed fly ashes are attributed to the co-precipitation and dissolution of minor amount of less soluble secondary phase overtime. The 1-year-old dry disposed ash cores were the least weathered among the 3 drilled ash cores. Therefore low concentration of toxic metals in older ash cores were ascribed to extensive weathering with slower release from residual mineral phases over time. Elements were found to associate with different mineral phases depending on the age or depth of the core samples showing greater heterogeneity in dispersion. For instance the average amount of total calcium in different mineral associations of 1-year-old ash cores is as follows / water soluble (10.2 %), exchangeable (37.04 %), carbonate (37.9 %), Fe and Mn (7.1 %) and residual (2.97 %). The amount of total Na+ in different mineral phases of 1-year-old ash cores followed this trend: water soluble (21 %), exchangeable (11.26 %), carbonate (2.6 %), Fe and Mn (4.7 %) and residual (53.9 %). The non-leachable portion of the total Na+ content (namely that contained in the residual fraction) in the 1-year-old ash core samples under conditions found in nature ranged between 5-91 %. This non-leachable portion of the Na+ showed the metastability of the mineral phases with which residual Na+ associates. Results showed older ash cores are enriched in toxic elements. Toxic elements such as As, B, Cr, Mo and Pb are enriched in the residual fraction of older ash cores. For instance As concentration in the residual fraction varied between 0.0003- 0.00043 mg kg-1 for 1-year-old ash cores to around 0.0003-0.0015 mg kg-1 for 20-year-old ash cores. This suggests that the older ash is enriched in toxic elements hence dust from the ash dump would be toxic to human health. The knowledge of mobility and ecotoxicological significance of coal fly ash is needed when considering its disposal or reuse in the environment. The mobility and ecotoxicology of inorganic metals in coal fly ash are determined by (i) mineralogical associations of inorganic species (ii) in-homogeneity in the ash dumps (iii) long and short term exposure to ingress CO2 and percolating rain water. Management issues such as inconsistent placement of ash in the dumps, poor choice of ash dump site, in-homogeneity in brine irrigation, no record of salt load put on the ash dumps and lack of proper monitoring requires improvement. The thesis provides justification for the use of the modified sequential extraction scheme as a predictive tool and could be employed in a similar research work. This thesis also proved that the dry ash disposal method was not environmental friendly in terms of overall leaching potential after significant chemical weathering. Moreover the study proved that the practice of brine co-disposal or irrigation on ash dumps is not sustainable as the ash dump did not act as a salt sink.</p>

The current study therefore aims to provide a comprehensive characterisation of weathered dry disposed ash cores, to reveal mobility patterns of chemical species as a function of depth and age of ash, with a view to assessing the potential environmental impacts. Fifty-nine samples were taken from 3 drilled cores obtained respectively from the 1 year, 8 year and 20-year-old sections of sequentially dumped, weathered, dry disposed ash in an ash dump site at Tutuka - a South African coal burning power station.

Philosophiae Doctor - PhD / The management and disposal of huge volumes of coal combustion by products such as fly ash has constituted a major challenge to the environment. In most cases due to the inadequate alternative use of coal fly ash, the discarded waste is stored in holding ponds, slag heaps, or stock piled in ash dumps. This practice has raised concerns on the prospect of inorganic metals release to the surface and groundwater in the vicinity of the ash dump. Acceptable scientific studies are lacking to determine the best ash disposal practices. Moreover, knowledge about the mobility patterns of inorganic species as a function of mineralogical association or pH susceptibility of the dry disposed ash dump under natural weathering conditions are scarce in the literature. Fundamental understanding of chemical interactions of dry disposed ash with ingressed CO2 from atmosphere, percolating rain water and brine irrigation within ash disposal sites were seen as key areas requiring investigation. The mineralogical association of inorganic species in the dry disposed ash cores can be identified and quantified. This would provide a basis for understanding of chemical weathering, mineralogical transformations or mobility patterns of these inorganic species in the dry ash disposal scenario. The current study therefore aims to provide a comprehensive characterisation of weathered dry disposed ash cores, to reveal mobility patterns of chemical species as a function of depth and age of ash, with a view to assessing the potential environmental impacts. Fifty-nine samples were taken from 3 drilled cores obtained respectively from the 1 year, 8 year and 20-year-old sections of sequentially dumped, weathered, dry disposed ash in an ash dump site at Tutuka - a South African coal burning power station. The core samples were characterized using standard analytical procedures viz: X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transforms infrared (FTIR) techniques, Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) and Acid neutralisation capacity (ANC) test. A modified sequential extraction (SE) method was used in this study. The chemical partitioning, mobility and weathering patterns in 1 year, 8 year and 20-year-old sections of the ash dump were respectively investigated using this modified sequential extraction scheme. The sequence of the extractions was as follows: (1) water soluble, (2) exchangeable, (3) carbonate, (4) iron and manganese and (5) residual. The results obtained from the 5 steps sequential extraction scheme were validated with the total metal content of the original sample using mass balance method. The distribution of major and trace elements in the different liquid fractions obtained after each step of sequential extraction of the 59 drilled core samples was determined by inductively coupled plasma mass spectrometry (ICPMS). The data generated for various ash core samples were explored for the systematic analysis of mineralogical transformation and change in ash chemistry with ageing of the ash. Furthermore, the data was analyzed to reveal the impact of ingressed CO2 from atmosphere, infiltrating rain water and brine irrigation on the chemistry of ash core samples. Major mineral phases in original ash core samples prior to extraction are quartz (SiO2) and mullite (Al2O3·2SiO2). Other minor mineral phases identified were hematite (Fe2O3), calcite (CaCO3), lime (CaO), anorthite (CaAl2Si2O8), mica (Ca (Mg, Al)3 (Al3Si) O10 (OH)2), and enstatite (Mg2Si2O6). X-ray diffraction results show significant loss of crystallinity in the older ash cores. The presence of minor phases of calcite and mica in dry disposed ash cores are attributed to reduction in the pore water pH due to hydration, carbonation and pozzolanic reactions. The X-ray diffraction technique was unable to detect Fe-oxyhydroxide phase and morealuminosilicate phases in ash core samples due to their low abundance and amorphous character. X-ray fluorescence results of the original ash core samples showed the presence of major oxides, such as SiO2, Al2O3, Fe2O3, while CaO, K2O, TiO2, Na2O, MnO, MgO, P2O5, and SO3 occur in minor concentrations. The ratio of SiO2/Al2O3 classified the original core samples prior to extraction as a silico-aluminate class F fly ash. The ternary plot of major elements in 1-year-old ash core samples was both sialic and ferrocalsialic but 8 year and 20-year-old ash core samples were sialic in chemical composition. It is noteworthy that the mass % of SiO2 varies through the depth of the core with an increase of nearly 3 %, to 58 mass % of SiO2 at a depth of 6 m in the 1-year-old core whereas in the case of the 8-year-old core a 2 % increase of SiO2 to a level of 57.5 mass % can be observed at levels between 4-8 m, showing dissolution of major components in the matrix of older ash cores.. The Na2O content of the Tutuka ash cores was low and varied between 0.6-1.1 mass % for 1-year-old ash cores to around 0.6-0.8 mass % for 8-year-old ash cores. Sodium levels were higher in 1-year-old ash cores compared to 8 year and 20-year-old ashcores. Observed trends indicate that quick weathering of the ash (within a year) leached out Na+ from the ash dump. No evidence of Na+ encapsulation even though the ash dump was brine irrigated. Thus the dry disposal ash placement method does not result in a sustainable salt sink for Na-containing species over time. The total content of each of the elements in 1 year and 20-year-old ash cores was normalised with their total content in fresh ash from same power station to show enrichment and depletion factor. Major elements such as K+, Mn showed enrichment in 1-year-old ash cores whereas Al, Si, Na+, Ti, Ca, Mg, S and Fe showed depletion due to over time erosion. Trace elements such as Cr, Sr, P, Ba, Pb, V and Zn showed enrichment but Ni, Y, Zr showed depletion attributed to over time erosion. In 20-year-old ash cores, major elements such as Al, Na+ and Mn showed enrichment while Si, K+, Fe, Mg and Ca showed depletion highlighting their mobility. Trends indicated intensive flushing of major soluble components such as buffering constituents (CaO) by percolating rain water. The 1-year-old and 20-year-old coal ash cores showed a lower pH and greater loss/depletion of the soluble buffering constituents than the 2-week-old placed ash, indicating significant chemical weathering within a year. Based on ANC results the leaching behaviours of Ca, Mg, Na+, K+, Se, Cr, and Sr were found to be controlled by the pH of the leachant indicating high mobility of major soluble species in the ash cores when in contact with slightly acid rain water. Other investigated toxic metals such as As, Mo and Pb showed amphoteric behaviour with respect to the pH of the leachant. Chemical alterations and formation of transient minor secondary mineral phases was found to have a significant effect on the acid susceptibility and depletion pattern of chemical species in the core ash samples when compared to fresh ash. These ANC results correlated well with the data generated from the sequential extraction scheme. Based on sequential extraction results elements, showed noticeable mobility in the water soluble, exchangeable and carbonate fractions due to adsorption and desorption caused by variations in the pore water pH. In contrast, slight mobility of elements in the Fe and Mn, and residual fractions of dry disposed fly ashes are attributed to the co-precipitation and dissolution of minor amount of less soluble secondary phase overtime. The 1-year-old dry disposed ash cores were the least weathered among the 3 drilled ash cores. Therefore low concentration of toxic metals in older ash cores were ascribed to extensive weathering with slower release from residual mineral phases over time. Elements were found to associate with different mineral phases depending on the age or depth of the core samples showing greater heterogeneity in dispersion. For instance the average amount of total calcium in different mineral associations of 1-year-old ash cores is as follows; water soluble (10.2 %), exchangeable (37.04 %), carbonate (37.9 %), Fe and Mn (7.1 %) and residual (2.97 %). The amount of total Na+ in different mineral phases of 1-year-old ash cores followed this trend: water soluble (21 %), exchangeable (11.26 %), carbonate (2.6 %), Fe and Mn (4.7 %) and residual (53.9 %). The non-leachable portion of the total Na+ content (namely that contained in the residual fraction) in the 1-year-old ash core samples under conditions found in nature ranged between 5-91 %. This non-leachable portion of the Na+ showed the metastability of the mineral phases with which residual Na+ associates. Results showed older ash cores are enriched in toxic elements. Toxic elements such as As, B, Cr, Mo and Pb are enriched in the residual fraction of older ash cores. For instance As concentration in the residual fraction varied between 0.0003- 0.00043 mg kg-1 for 1-year-old ash cores to around 0.0003-0.0015 mg kg-1 for 20-year-old ash cores. This suggests that the older ash is enriched in toxic elements hence dust from the ash dump would be toxic to human health. The knowledge of mobility and ecotoxicological significance of coal fly ash is needed when considering its disposal or reuse in the environment. The mobility and ecotoxicology of inorganic metals in coal fly ash are determined by (i) mineralogical associations of inorganic species (ii) in-homogeneity in the ash dumps (iii) long and short term exposure to ingress CO2 and percolating rain water. Management issues such as inconsistent placement of ash in the dumps, poor choice of ash dump site, in-homogeneity in brine irrigation, no record of salt load put on the ash dumps and lack of proper monitoring requires improvement. The thesis provides justification for the use of the modified sequential extraction scheme as a predictive tool and could be employed in a similar research work. This thesis also proved that the dry ash disposal method was not environmental friendly in terms of overall leaching potential after significant chemical weathering. Moreover the study proved that the practice of brine co-disposal or irrigation on ash dumps is not sustainable as the ash dump did not act as a salt sink. / South Africa

A procedure to evaluate the leaching properties of radionuclides from irradiated graphite waste has been developed by combining ANSI 16.1 (USA) and NEN 7345 (Netherlands) standardised diffusion leaching techniques. The ANSI 16.1 standard has been followed to the acquire the leachates and to determine the leach rate/ diffusion coefficient and NEN 7345 standard technique has been used to determine the diffusion mechanism of radionuclides. The investigation employs simulated Drigg groundwater as a leachant using semi-dynamic technique for the production of leachate specimens. From gamma spectroscopy analysis the principal radionuclides present in terms of activity were 60Co, 137Cs, 134Cs, 155Eu, 133Ba and 46Sc. The dominant radionuclides are 60Co, 134Cs and 133Ba which together account for about 91 % of the total activity. The 91 % can be broken down into 73.4 % 60Co, 9.1 % 134Cs and 8.1 % 133Ba. Analysis of total beta and total beta without tritium activity release from Magnox graphite was measured using liquid scintillating counting. Preliminary results show that there is an initial high release of activity and decreases when the leaching period increases. This may be due to the depletion of contaminants which were absorbed by the internal pore networks and the surface. During the leaching test approximately 275.33 ± 18.20 Bq of 3H and 106.26 ± 7.01 Bq of 14C was released into the leachant within 91 days. Irradiation induced damages to the nuclear graphite crystal structure have been shown to cause disruption of the bonding across the basal planes. Moreover, the closures of Mrozowski cracks have been observed in nuclear graphite, the bulk property are governed by the porosity, in particular, at the nanometre scale. Therefore, knowledge of the crystallite structure and porosity distribution is very important; as it will assist in understand the affects of irradiated damage and location and the mechanism of the leaching of radionuclides. The work reported herein contributed several key findings to the international work on graphite leaching to offer guidance leading toward obtaining leaching data in the future: (a) the effective diffusion coefficient for 14C from graphite waste has been determined. The diffusion process for 14C has two stages resulting two different values of diffusion coefficient, i.e., for the fast and slow components; (b) the controlling leaching mechanism for 3H radionuclide from graphite is shown to be surface wash–off; and for that of 14C radionuclide the initial controlling leaching mechanism is surface wash-off following by diffusion which is the major transport mechanism ; (c) The weight loss originates from the open pore structure which has been opened up by radiolytic oxidation; at the higher weight losses much of the closed porosity in the graphite has been opened. The investigation indicates that weigh loss has a major influence on the leaching of elements from the irradiated graphite; and (d) the analysis of the pores in nuclear graphite can be categorised into three types. These three types of pores are: (1) small pores narrow which are slit-shaped pores in the binder phase or matrix, (2) gas evolution pores or gas entrapment pores within the binder phase or matrix and (3) lenticular pores which are large cracks within the filler particles. It is shown in this thesis that by using tomography to study the morphology of the different pores coupled with the distribution of impurities an understanding of the role of porosity in leaching is possible.

Paleosols from the Bahamas and the Northern Mariana Islands (CNMI) are closely related to past atmospheric circulation and dust load. In the Bahamas the sources of insoluble residue (IR) must be allogenic because the islands consist of almost pure carbonates. The Al2O3:TiO2 ratio was used to establish the provenance of the IR of the paleosols. Comparisons of this ratio from Bahamian paleosols, North African dust, Lesser Antilles ash and North American loess reveal that the African dust is the major contributor to the IR, with a potential minor volcanic input from the Lesser Antilles. The contribution of the North American loess to the IR was not determined because of geochemical similarities with the North African dust. The study of two outcrops in Eleuthera indicate that paleosols can act as aquicludes. The Bahamian samples were collected on a roughly north-south transect in order to establish the climatic influence on paleosol properties. Even though there is a marked climatic gradient in the Bahamas, the paleosol geochemistry shows no trend that could be related to paleoclimate. While previous studies indicated that the source of insoluble residues in the soils of CNMI is carbonate dissolution, the present study shows that atmospheric deposition of ash from the Mariana arc and dust from the Asian continent may play a significant role in paleosol formation.

[ES] El principal objetivo de esta tesis fue evaluar el valor nutritivo de la pulpa granulada de remolacha (PR) producida en diferentes zonas azucareras de España. Inicialmente se caracterizó la composición química de PR procedentes del norte y sur de España, cosechadas en invierno y verano, respectivamente. Se compararon la composición química y el contenido de ácidos grasos y aminoácidos de 12 muestras de PR, agrupadas según su procedencia. La composición de la materia seca (MS) de la PR, se caracteriza por un bajo contenido en proteína cruda (8.7%), dentro del 62% de la fibra neutro detergente (FND), pero rica en FND (39.4%) y fibra soluble en detergente neutro (45.7%), y bajo en grasa bruta (1.2%) y almidón (0.9%). El análisis de componentes principales (CP) de los principales principios inmediatos indicó que ya los dos primeros CP explican el 62% de la variabilidad en la composición de la PR. Los valores de los autovectores de los CP indicaron un importante peso del contenido en almidón y FND en el primer CP y del contenido en cenizas en el segundo CP. Posteriormente se determinó la digestibilidad de un pienso control con sustitución de 20% de PR de cinco orígenes distintos, y su posible efecto en el valor nutritivo de estas PR para conejos de engorde. Se utilizaron 90 conejos de 42 días de edad con 1.49 ± 0.208 kg de peso vivo, alojados en jaulas metabólicas individuales y con alimentación ad libitum. La digestibilidad de los componentes de los piensos se determinó por el método convencional in vivo de recolección fecal total. La digestibilidad de cada una de las pulpas de remolacha se determinó mediante el método de sustitución. No se apreció efecto de la sustitución de componentes del pienso control por el 20% de PR de diferentes procedencias en el consumo voluntario de los conejos. La inclusión de PR en las dietas aumentó la digestibilidad de materia seca (MS), materia orgánica, energía bruta y de todas las fracciones fibrosas, y disminuyó la digestibilidad de la proteína bruta. Respecto al efecto de la procedencia, se observaron diferencias significativas (P<0.05) en la digestibilidad de todas las fracciones fibrosas, siendo la PR recolectada en verano la de mayor digestibilidad. El origen de la PR también afectó su valor nutritivo, con valores de energía digestible entre 11.8 y 14.5 MJ/kg MS y de proteína digestible entre 38 y 66 g/kg MS. Finalmente, para evaluar el efecto del nivel de inclusión de pulpa de remolacha, con o sin melaza, sobre el rendimiento del crecimiento, se utilizaron un total de 470 conejos de 28 días de edad, con 612.2 ± 103.4 gr. de peso vivo. Los animales fueron asignados aleatoriamente a cinco tratamientos dietéticos: Control, sin pulpa de remolacha; PR20 y PR40, con 20 y 40% de pulpa de remolacha sin melaza, respectivamente; y PRM20 y PRM40, con 20 y 40% de pulpa de remolacha con melaza, respectivamente. El consumo diario de alimento (CDA) y la ganancia media diaria (GMD) se controlaron a los 28, 49 y 59 días de edad. También se determinaron las características de la canal y del tracto digestivo a los 59 días de edad. La mortalidad y la morbilidad fueron controladas diariamente. La mortalidad durante el período de crecimiento fue mayor en los grupos PRM que en los PR (+9.2%; P<0,05). A mayor inclusión de PR, con o sin melaza, menor CDA y GMD de los animales, así como el rendimiento a la canal, la proporción de hígado y el porcentaje de grasa disecable de sus canales. Sin embargo, la mejor eficiencia alimenticia durante los últimos 10 días se obtuvo con el grupo PRM40. Respecto a los parámetros digestivos, cuanto mayor fue la inclusión de pulpa de remolacha, con o sin melaza, mayor el peso del tracto gastrointestinal vacío y ciego. De hecho, una mayor inclusión de pulpa de remolacha disminuyó el pH y la materia seca, y disminuyó el contenido total de ácidos grasos volátiles del ciego, más rico en ácido acético, pero más pobre en propiónico, isobutirico, isovalérico y valérico. / [CA] L'objectiu principal d'aquesta tesi era avaluar el valor nutritiu de la polpa granulada de remolatxa (PR) produïda en diferents zones de sucre d'Espanya. La composició química de PR del nord i del sud d'Espanya, recol·lectada a l'hivern i l'estiu, respectivament. Es va comparar la composició química i el contingut d'àcids grassos i aminoàcids de 12 mostres de PR, agrupades segons el seu origen. La matèria seca (MS) del PR es caracteritza per un baix contingut de proteïna crua (8,7%), dins del 62% de la fibra detergent neutra (FND), però ric en FND (39,4%) i fibra soluble en detergent neutre (45,7%) i baix en greixos bruts (1,2%) i midó (0,9%). L'anàlisi principal de components (CP) dels principals principis immediats va indicar que els dos primers CP ja expliquen el 62% de la variabilitat en la composició del PR. Els valors autovector CP van indicar un pes important del contingut de midó i FND al primer CP i del contingut de cendra al segon CP. Posteriorment, la digestibilitat d'un aliment de control es va determinar amb una substitució del 20% de PR de cinc orígens diferents i el seu possible efecte sobre el valor nutritiu d'aquests PR per engreixar conills. Es van utilitzar conills de 90 42 dies amb 1,49 ± 0,208 kg de pes corporal, allotjats en gàbies metabòliques individuals i amb alimentació ad libitum. La digestibilitat dels components dels pinsos va ser determinada pel mètode in vivo convencional de recol·lecció fecal total. La digestibilitat de cadascuna de les púlps de remolatxa es va determinar mitjançant el mètode de substitució. No hi va haver cap efecte apreciat de substituir els components de l'alimentació de control per un 20% de PR de diferents fonts sobre el consum voluntari de conills. La inclusió de PR en dietes va augmentar la digestibilitat de la matèria seca (MS), la matèria orgànica, l'energia crua i totes les fraccions fibroses i va disminuir la digestibilitat de la proteïna crua. Pel que fa a l'efecte de l'origen, es van observar diferències significatives (P < 0,05) en la digestibilitat de totes les fraccions fibroses, i el PR recollit a l'estiu és el que té la màxima digestibilitat. L'origen del PR també va afectar el seu valor nutritiu, amb valors d'energia digeribles entre 11,8 i 14,5 MJ / kg MS i proteïna digestible entre 38 i 66 g / kg MS. Finalment, sobre el rendiment del creixement, es van utilitzar un total de 470 conills de 28 dies, amb 612,2 ± 103,4 gr. de pes viu. Els animals van ser assignats aleatòriament a cinc tractaments dietètics: control, sense polpa de remolatxa; PR20 i PR40, amb polpa de remolatxa 20 i 40% sense melassa, respectivament; i PRM20 i PRM40, amb polpa de remolatxa de melassa del 20 i del 40%, respectivament. El consum diari d'aliments (CDA) i el benefici mitjà diari (GMD) es van controlar als 28, 49 i 59 dies d'edat. També es van determinar les característiques del canal i del tracte digestiu als 59 dies d'edat. La mortalitat i la morbiditat es controlaven diàriament. La mortalitat durant el període de creixement va ser superior als grups PRM que a la PR (+ 9,2%; P < 0,05). Com més gran sigui la inclusió de PR, amb o sense melassa, el CDA inferior i el GMD dels animals, així com el rendiment al canal, la proporció de fetge i el percentatge de greixos dissecables als vostres canals. Tanmateix, la millor eficiència alimentària durant els darrers deu dies es va obtenir amb el grup PRM40. Pel que fa als paràmetres digestius, com més gran sigui la inclusió de la polpa de remolatxa, amb o sense melassa, més gran sigui el pes del tracte gastrointestinal buit i cec. De fet, una major inclusió de la polpa de remolatxa va disminuir el pH i la matèria seca i va disminuir el contingut total d'àcids grassos volàtils al cec, més ric en àcid acètic, però més pobre en propionic, isobutiric, isoval I valeric, independentment de la temporada, proporciona un alt contingut de fibra, soluble i insoluble, tot i que no és una font important de proteïnes, aminoàcids o àcids grassos. / [EN] The main objective of this thesis was to evaluate the nutritional value of granulated beet pulp (PR) produced in different sugar-growing areas of Spain. Initially the chemical composition of PR from the north and south of Spain, harvested in winter and summer, respectively, was characterized. The chemical composition and fatty acid and amino acid content of 12 PR samples, grouped according to their origin, were compared. The composition of the dry matter (DM) of the PR is characterized by a low crude protein content (8.7%), within 62% of neutral detergent fiber (NDF), but rich in NDF (39.4%) and fiber. soluble in neutral detergent (45.7%), and low in crude fat (1.2%) and starch (0.9%). The analysis of principal components (PC) of the main immediate principles indicated that the first two PCs already explain 62% of the variability in the composition of the PR. The values of the CP eigenvectors indicated an important weight of the starch and NDF content in the first CP and the ash content in the second CP. Subsequently, the digestibility of a control feed with 20% replacement of PR from five different origins was determined, and its possible effect on the nutritional value of these PR for fattening rabbits. Ninety 42-day-old rabbits with 1.49 ± 0.208 kg live weight were used, housed in individual metabolic cages and fed ad libitum. The digestibility of feed components was determined by the conventional in vivo method of total fecal collection. The digestibility of each of the beet pulps was determined using the substitution method. No effect was seen of replacing components of the control feed with 20% PR from different sources on the voluntary consumption of the rabbits. The inclusion of PR in the diets increased the digestibility of dry matter (DM), organic matter, gross energy and all fibrous fractions, and decreased the digestibility of crude protein. Regarding the effect of origin, significant differences (P<0.05) were observed in the digestibility of all fibrous fractions, with the PR collected in summer being the one with the highest digestibility. The origin of PR also affected its nutritional value, with digestible energy values between 11.8 and 14.5 MJ/kg DM and digestible protein between 38 and 66 g/kg DM. Finally, to evaluate the effect of the level of inclusion of beet pulp, with or without molasses, on growth performance, a total of 470 rabbits of 28 days of age were used, with 612.2 ± 103.4 gr. live weight. The animals were randomly assigned to five dietary treatments: Control, without beet pulp; PR20 and PR40, with 20 and 40% beet pulp without molasses, respectively; and PRM20 and PRM40, with 20 and 40% beet pulp with molasses, respectively. Daily feed intake (DAI) and average daily gain (ADG) were monitored at 28, 49 and 59 days of age. The characteristics of the carcass and digestive tract were also determined at 59 days of age. Mortality and morbidity were monitored daily. Mortality during the growth period was higher in the PRM than in the PR groups (+9.2%; P<0.05). The greater the inclusion of PR, with or without molasses, the lower the ADC and ADG of the animals, as well as the carcass yield, the proportion of liver and the percentage of dissectable fat in their carcasses. However, the best feed efficiency during the last 10 days was obtained with the PRM40 group. Regarding the digestive parameters, the greater the inclusion of beet pulp, with or without molasses, the greater the weight of the empty and blind gastrointestinal tract. In fact a greater inclusion of beet pulp decreased the pH and dry matter, and decreased the total content of volatile fatty acids of the caecum, richer in acetic acid, but poorer in propionic, isobutyric, isovaleric and valeric acids. Regarding the effect of the harvest season on the chemical characteristics of granulated sugar beet pulp, regardless of the season, it provides high fiber content, soluble and insoluble, although it is not an important source of protein / Arce Cabrera, ON. (2024). Utilización de pulpa granulada de remolacha en la alimentación de conejos en cebo [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/206201

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