This study was conducted to compare the speciation and behavior of P in soils receiving either different biosolids or inorganic fertilizer, as assessed by sequential chemical extractions, phosphate desorption, and synchrotron X-ray absorption near edge structure (XANES) spectroscopy. The objectives of this study were to i) measure the total amount of organic and inorganic phosphorus removed by chemical extraction method ii) investigate how P desorption kinetics are influenced in biosolids amended soils compared to inorganic fertilizer amended soils; and iii) perform solid state speciation of soil samples before and after chemical extraction and desorption with P K-edge XANES spectroscopy. Soil samples were analyzed that received three different rates of biosolids (16.8, 33.6, and 67.2 Mg ha-1 yr-1) and one inorganic fertilizer application (336 kg N, 224 kg P, and 112 kg K ha-1 yr-1) for 32 years. Both sequential chemical extraction and XANES analysis showed that total amount of P increased in biosolids amended soils (from 5292 to 10945 mg P kg-1) and that it increased with increasing application rate. Sequential chemical extractions showed that the labile portion of total P in inorganic fertilized soil (40 %) was larger than in biosolids applied soils (39 to 27 %). Results from both sequential chemical extraction and XANES analysis showed that NaOH extraction removed the highest amount of P from all biosolids applied soils (from 1857 to 2600 mg P kg-1). <p>The amount of desorbed P decreased as the soil:solution ratio increased from 0.005 to 100 g L-1 for both soils and the desorption was typically higher in inorganic fertilizer applied soil than in biosolids applied soil. The effect of pH on P desorption was pronounced, and desorption was higher at pH 5 than pH 7.5 for both soils. A continuous flow desorption method was also used to measure cumulative P desorption over time. Cumulative P desorption in inorganic fertilizer applied soil (894.5 mg P kg-1) was higher than in the biosolids amended soils (572.9 mg P kg-1) over 20 hr period time. First-order and parabolic diffusion kinetic equations were used to model the desorption data from the continuous flow technique. This revealed that the P desorption rate was faster (and chemically-controlled) at initial stages and slower (and diffusion-limited) at later stages. The desorption rate was much faster in inorganic fertilizer applied soil than in biosolids applied soil.<p>XANES analysis of the fractions removed in sequential chemical extractions suggested that the predominant form of P was poorly crystalline dicalcium phosphate in biosolids applied soils, and labile, sorbed forms as well as some apatite-type calcium phosphate was present in inorganic fertilizer applied soil. The combined results from sequential chemical extraction and XANES analysis indicate that P in inorganic fertilizer and biosolids-applied soils behave differently. There were larger amounts of low crystallinity phosphates in the biosolids samples, and much higher apatite content in the inorganic fertilizer amended soil.

This study was conducted to compare the speciation and behavior of P in soils receiving either different biosolids or inorganic fertilizer, as assessed by sequential chemical extractions, phosphate desorption, and synchrotron X-ray absorption near edge structure (XANES) spectroscopy. The objectives of this study were to i) measure the total amount of organic and inorganic phosphorus removed by chemical extraction method ii) investigate how P desorption kinetics are influenced in biosolids amended soils compared to inorganic fertilizer amended soils; and iii) perform solid state speciation of soil samples before and after chemical extraction and desorption with P K-edge XANES spectroscopy. Soil samples were analyzed that received three different rates of biosolids (16.8, 33.6, and 67.2 Mg ha-1 yr-1) and one inorganic fertilizer application (336 kg N, 224 kg P, and 112 kg K ha-1 yr-1) for 32 years. Both sequential chemical extraction and XANES analysis showed that total amount of P increased in biosolids amended soils (from 5292 to 10945 mg P kg-1) and that it increased with increasing application rate. Sequential chemical extractions showed that the labile portion of total P in inorganic fertilized soil (40 %) was larger than in biosolids applied soils (39 to 27 %). Results from both sequential chemical extraction and XANES analysis showed that NaOH extraction removed the highest amount of P from all biosolids applied soils (from 1857 to 2600 mg P kg-1). <p>The amount of desorbed P decreased as the soil:solution ratio increased from 0.005 to 100 g L-1 for both soils and the desorption was typically higher in inorganic fertilizer applied soil than in biosolids applied soil. The effect of pH on P desorption was pronounced, and desorption was higher at pH 5 than pH 7.5 for both soils. A continuous flow desorption method was also used to measure cumulative P desorption over time. Cumulative P desorption in inorganic fertilizer applied soil (894.5 mg P kg-1) was higher than in the biosolids amended soils (572.9 mg P kg-1) over 20 hr period time. First-order and parabolic diffusion kinetic equations were used to model the desorption data from the continuous flow technique. This revealed that the P desorption rate was faster (and chemically-controlled) at initial stages and slower (and diffusion-limited) at later stages. The desorption rate was much faster in inorganic fertilizer applied soil than in biosolids applied soil.<p>XANES analysis of the fractions removed in sequential chemical extractions suggested that the predominant form of P was poorly crystalline dicalcium phosphate in biosolids applied soils, and labile, sorbed forms as well as some apatite-type calcium phosphate was present in inorganic fertilizer applied soil. The combined results from sequential chemical extraction and XANES analysis indicate that P in inorganic fertilizer and biosolids-applied soils behave differently. There were larger amounts of low crystallinity phosphates in the biosolids samples, and much higher apatite content in the inorganic fertilizer amended soil.

Concern over excess phosphorus (P) input and loading in some soils of the Canadian prairie region has led to a need for a better understanding of the fate of added manure and fertilizer P. Information on the effects of manure application over long term (i.e., years) and short term (i.e., weeks, months) as related to management practices and manure form is still lacking. Knowledge of the P forms and species present in soil following application of manure and inorganic P fertilizers, and linking this to potential P availability and mobility is needed to make sound P management recommendations. The objective of this thesis project was to assess the speciation of soil P in different manures and inorganic fertilizer-amended Saskatchewan soils as affected by time, presence and absence of plants, landscape position, soil type, and management practices including rate and placement. Three studies were conducted (growth chamber and field-based experiments) to study P behavior in soils. These studies closely followed a time scale, beginning with speciation and fate followed over the very short-term (i.e., days to weeks) to a short-term period (i.e., months to a year) following amendment application, and finally the effects of repeated annual manure additions made over the long term (i.e., 11 years). Soils used in this study were loamy textured Brown and Black Chernozems. Solid cattle manure (SCM) and liquid hog manure (LHM) were applied at low and high rates in the very short-term and long-term studies. The low rate of SCM and LHM application was 7.6 T ha-1 yr-1 (dry weight) and 37,000 L ha-1 yr-1, respectively which was equivalent to approximately 100 kg total N ha-1 yr-1 application (agronomic N rate). The high rate was four times this amount. Inorganic fertilizer (mono-ammonium phosphate blended with urea) at rate of 54 kg N ha-1 and 12 kg P ha-1 and SCM at rate of 60 T ha-1 were applied in the short-term study. A sequential chemical extraction procedure was used to fractionate P in very short-term and short-term studies and different soil test phosphorus (STP) methods were used to determine effects on the labile P in the long-term study. Changes in P speciation with time and their relative proportions in fertilizered soils were also assessed using the synchrotron-based X-ray absorption near-edge structure (XANES) spectroscopy in all studies. This study has revealed that manure, especially SCM elevates labile P over all time frames examined. Over the very short-term (i.e., weeks to a month), P was added as manure tends to remain in labile forms like brushite and adsorbed P that is accessible to plants for uptake. In the manure band (months to a year), manure P was relatively unchanged over a period of months while in the mono-ammonium phosphate (MAP) fertilizer band, adsorbed and Ca-P was readily formed from fertilizer P. Aging over several years (one to eleven years), along with high soil pH and high Ca:P ratio enhanced formation of more stable Ca-P minerals like apatite, especially in SCM amended soil. Overall, the unique combined use of wet chemical analysis and synchrotron-based techniques in this thesis research has improved our understanding of fate and transformation of P added to prairie soils. It is suggested that future studies of fate of applied P in soil also utilize a combination of wet chemical and spectroscopic techniques, as this was shown to be a rewarding approach.

The fate and mobility of boric acid in the environment is largely controlled by adsorption reactions with soil organic matter and soil minerals to form surface complexes (Marzadori et al., 1991; Su and Suarez, 1995; Yermiyahu et al., 1995; Peak et al., 2002). The effects of humic acid (HA) and dissolved CO2 on boric acid adsorption on amorphous (am)-Al(OH)3 were investigated as their influence on sorption is potentially important. Although a model system was used in the studies, the findings should be generally useful to better understand the mobility and bioavailability of boric acid in the soil ecosystems.<p>In this dissertation, boric acid adsorption on pure am-Al(OH)3 and 5% w/w HA coated am-Al(OH)3 were investigated both as a function of pH (4.5 11) and initial boric acid concentration (0 4.5 mmol L-1). Batch adsorption isotherm experiments were also conducted with samples exposed to atmospheric CO2 and anaerobic (N2) conditions to examine the effects of dissolved CO2 on boric acid adsorption. Both the pH envelope and the adsorption isotherm experiments showed that the HA coating on am-Al(OH)3 and the presence of dissolved CO2 decreased boric acid adsorption. <p>Raman spectroscopy and boron (B) K-edge X-ray Absorption Near Edge Structure (XANES) spectroscopy were used to investigate the coordination of boric acid adsorbed at mineral/water interfaces. The Raman spectroscopy was less successful than expected as there were difficulties in identifying B bands in the 5% w/w HA coated am-Al(OH)3 samples.<p>The B K-edge XANES spectroscopy yielded better results. The XANES spectra of boric acid adsorption samples showed that both trigonal BO3 and tetrahedral BO4 coordinated complexes are present on the pure and HA coated mineral surfaces. At pH 7.0 and 9.2, the adsorption of boric acid on am-Al(OH)3 is predominantly inner-sphere trigonal complexes; with minor amounts of inner-sphere tetrahedral complexes. Both macroscopic and spectroscopic experiments revealed that the combination of HA coating on am-Al(OH)3 and dissolved CO2 decreased boric acid adsorption compared to adsorption on pure am-Al(OH)3.<p>The discoveries in this dissertation contribute significantly in understanding the effects of HA and dissolved CO2 has on boric acid adsorption in the environment. Since B speciation and the stability of am-Al(OH)3 mineral and HA changes with pH, the bioavailability of B is expected to change as well with pH. The adsorption on boric acid on am-Al(OH)3 and/or HA coated am-Al(OH)3 is expected to decrease the amount of boric acid available to plants. Therefore the nutrient management regimen will have to be modified for soils that are high in natural organic matter, carbonate and/or aluminum hydroxyl species.

The fate and mobility of boric acid in the environment is largely controlled by adsorption reactions with soil organic matter and soil minerals to form surface complexes (Marzadori et al., 1991; Su and Suarez, 1995; Yermiyahu et al., 1995; Peak et al., 2002). The effects of humic acid (HA) and dissolved CO2 on boric acid adsorption on amorphous (am)-Al(OH)3 were investigated as their influence on sorption is potentially important. Although a model system was used in the studies, the findings should be generally useful to better understand the mobility and bioavailability of boric acid in the soil ecosystems.<p>In this dissertation, boric acid adsorption on pure am-Al(OH)3 and 5% w/w HA coated am-Al(OH)3 were investigated both as a function of pH (4.5 11) and initial boric acid concentration (0 4.5 mmol L-1). Batch adsorption isotherm experiments were also conducted with samples exposed to atmospheric CO2 and anaerobic (N2) conditions to examine the effects of dissolved CO2 on boric acid adsorption. Both the pH envelope and the adsorption isotherm experiments showed that the HA coating on am-Al(OH)3 and the presence of dissolved CO2 decreased boric acid adsorption. <p>Raman spectroscopy and boron (B) K-edge X-ray Absorption Near Edge Structure (XANES) spectroscopy were used to investigate the coordination of boric acid adsorbed at mineral/water interfaces. The Raman spectroscopy was less successful than expected as there were difficulties in identifying B bands in the 5% w/w HA coated am-Al(OH)3 samples.<p>The B K-edge XANES spectroscopy yielded better results. The XANES spectra of boric acid adsorption samples showed that both trigonal BO3 and tetrahedral BO4 coordinated complexes are present on the pure and HA coated mineral surfaces. At pH 7.0 and 9.2, the adsorption of boric acid on am-Al(OH)3 is predominantly inner-sphere trigonal complexes; with minor amounts of inner-sphere tetrahedral complexes. Both macroscopic and spectroscopic experiments revealed that the combination of HA coating on am-Al(OH)3 and dissolved CO2 decreased boric acid adsorption compared to adsorption on pure am-Al(OH)3.<p>The discoveries in this dissertation contribute significantly in understanding the effects of HA and dissolved CO2 has on boric acid adsorption in the environment. Since B speciation and the stability of am-Al(OH)3 mineral and HA changes with pH, the bioavailability of B is expected to change as well with pH. The adsorption on boric acid on am-Al(OH)3 and/or HA coated am-Al(OH)3 is expected to decrease the amount of boric acid available to plants. Therefore the nutrient management regimen will have to be modified for soils that are high in natural organic matter, carbonate and/or aluminum hydroxyl species.

L'étude des nanoagrégats métalliques supportés sur des oxydes est d'une importance primordiale autant au niveau fondamental que technologique, notamment dans le domaine de l'énergie. Les nanoparticules à base de platine supportées sur alumine Gamma sont largement utilisées comme catalyseurs hétérogènes ultradispersés, en particulier sous atmosphère réductrice d'hydrogène. Leur réactivité et leur sélectivité sont intimement liés à la géométrie locale et à la densité électronique des sites actifs. Ces dernières sont particulièrement ardues à définir, étant donnée la très faible taille des agrégats étudiés (environ 0.8 nm de diamètre). La spectroscopie XANES (X-Ray Absorption Near Edge Structure), nécessitant un rayonnement synchrotron, est un des outils les plus appropriés pour étudier ces systèmes, en particulier in situ, à l'échelle atomique. En effet les spectres XANES sont influencés par la géométrie locale et la symétrie de l'environnement des atomes (en particulier les angles entre les liaisons), le degré d'oxydation, les types de liaisons mis en jeu, et la structure électronique du système. Tous ces facteurs sont néanmoins difficiles à différencier et même à interpréter. Il est donc impossible de déduire de manière précise la structure des particules métalliques par la seule expérience, sans aucune comparaison avec des spectres simulés. La mise en place de modèles théoriques devient alors nécessaire. Nous mettons donc en oeuvre une approche associant expériences XANES haute résolution in situ et simulations quantiques, ces dernières visant à la proposition de modèles structuraux pertinents, à la quantification de la réactivité des agrégats et au calcul des caractéristiques spectrales pour comparaison à l'expérience. L'identification de la morphologie des particules, de l'interaction métal-support et du taux de couverture en H est ainsi rendue possible par l'association de l'expérience et du calcul. La bibliothèque de modèles existants de particules monométalliques de Pt supportées sur de l'alumine Gamma avec ou sans hydrogène adsorbé, est complétée par des modèles hydrogénés sur la face (110) et par des modèles de différentes tailles hydrogénés sur la face (100). Cette bibliothèque devenue assez complète a permis une étude de l'influence de la taille des particules, de leur morphologie, de leur structure électronique, des différentes face de l'alumine Gamma, ainsi que du taux de couverture en hydrogène sur la signature des spectres XANES. Cette première étude des catalyseurs monométalliques de platine, se conclue par la discrimination de certaines morphologies, mais surtout la quantification du taux de couverture en hydrogène des particules. Ensuite, des modèles de particules bimétalliques platine – étain supportés sur la face (100) de l'alumine Gamma sont élaborés avec adsorption d'hydrogène. Ces modèles permettent de mieux comprendre l'influence de l'étain sur la morphologie, les propriétés électroniques et l'interaction avec le support et l'hydrogène de ces agrégats. Différentes compositions ont été explorées, ce qui a apporté des informations sur la dilution du platine par l'étain. L'adsorption d'hydrogène a alors été étudiée sur des agrégats de Pt10Sn3 supportées sur la face (100) de l'alumine Gamma. Bien que de nombreux paramètres ne sont pas encore pris en compte dans ces modèles, la comparaison à l'expérience permet déjà d'avoir une première approximation sur la description de systèmes bimétalliques. / The study of metallic nanoclusters supported on oxides is of paramount fundamental and technological importance, particularly in the field of energy. The nanoparticles based on platinum supported on gamma alumina are widely used as highly dispersed heterogeneous catalysts especially under reducing hydrogen atmosphere. Their reactivity and selectivity are intimately related to the local geometry and the electronic density of active sites. These are particularly difficult to define, given the very small size of the studied particles (about 0.8 nm in diameter). XANES (X-Ray Absorption Near Edge Structure) spectroscopy requiring synchrotron radiation, is one of the most appropriate tools to study these systems, especially in situ, at the atomic scale. Indeed the XANES spectra are influenced by the geometry and symmetry of the atoms local environment (especially angles between bonds), the degree of oxidation, the bond types involved, and the electronic structure of the system . All these factors are nevertheless difficult to differentiate and even to interpret. It is therefore impossible to infer accurately the structure of the metal particles by experience alone, without any comparison with simulated spectra. The establishment of theoretical models becomes necessary. We are implementing an approach that combines high-resolution XANES experiments in situ and quantum simulations, the latter aimed at proposing relevant structural models to quantify the reactivity of the particles and calculating spectral characteristics for comparison to experiment. The identification of the clusters morphologies, the metal-support interaction and the hydrogen coverage is made possible combining experiments and quantum calculations. The library of existing monometallic Pt particles models supported on Gamma alumina with or without adsorbed hydrogen, is refined. New models considering the two main surface of Gamma alumina, the particle size and hydrogen adsorption are developed. This extended library of models enabled a study of the effect of particle size, morphology, electronic structure, different alumina faces, and the hydrogen coverage on the signature of XANES spectra. This first study of monometallic platinum catalysts, concludes with the discrimination of the morphologies, but especially with the quantification of the hydrogen coverage of the particles for each temperature and hydrogen pressure experimental condition. Then, models of bimetallic Platinum-tin particles supported on the (100) Gamma alumina face are performed with hydrogen adsorption. These models provide insights into the effect of tin on the morphology, the electronic properties and the interaction with the support and hydrogen of these clusters. Different compositions were explored, which provided information on the dilution of platinum by tin. The adsorption of hydrogen was then studied on Pt10Sn3 clusters supported on the (100) face of alumina. Although many parameters are not yet included in these models, the comparison to the experience already provides a first approximation to the description of bimetallic systems.