A novel phosphorus (P) adsorbent, ferrihydrite-modified diatomite (FHMD) was developed and characterized in this study. The FHMD was made through surface modification treatments, including NaOH treatment and ferrihydrite deposition on raw diatomite. In the NaOH treatment, surface SiO2 was partially dissolved in the NaOH solution. The dissolved Si contributed to form stable 2-line ferrihydrite, which deposited into the larger mesopores and macropores of the diatomite. The 2-line ferrihydrite not only deposited into the pores of the diatomite but also aggregated on the surface. Filling the larger mesopores and macropores of the diatomite and aggregation on the diatomite surface with 0.24 g Fe/g of 2-line ferrihydrite resulted in a specific surface area of 211.1 m2/g for the FHMD, which is an 8.5-fold increase over the raw diatomite (24.77 m2/g). The surface modification also increased the point of zero charge (pHPZC) values to 10 for the FHMD from 5.8 for the raw diatomite.<p> Effects of the formation process parameters such as concentrations of FeCl2, NaOH, and drying temperature on the formation mechanism and crystalline characteristics of FHMD were studied by using X-ray absorption near-edge structure (XANES) spectroscopy. The spectra were recorded in both the total electron yield (TEY) and the fluorescence yield (FY) modes to investigate the chemical nature of Fe and Si on the surface and in the bulk of ferrihydrite-modified diatomite, respectively. It was found that only the surface SiO2 was partially dissolved in the NaOH solution with stirring and heating, whereas the bulk of diatomite seemed to be preserved. The dissolved Si was incorporated into the structure of ferrihydrite to form the 2-line Si-containing ferrihydrite. The crystalline degree of ferrihydrite increased with the increasing FeCl2 concentration and the Brunauer-Emmett-Teller (BET) specific surface area of FHMD decreased with the increasing FeCl2 concentration. The NaOH solution of higher concentration partially dissolved more surface SiO2 and the crystalline degree of ferrihydrite decreased with the increase in NaOH concentration. The dehydroxylation on the surface of FHMD occurred in the high temperature calcination, causing an energy shift in the Si L-edge spectra to the high energy side and an increase in the crystalline degree of ferrihydrite. In this study, the optimal synthesis conditions for the FHMD with the least crystalline degree and the highest surface area were found to be as the follows: 100 mL of 0.5M FeCl2 solution, 6M NaOH solution and the drying temperature of 50 ºC.<p> Phosphorus adsorption behavior and adsorption mechanism of FHMD were investigated in the research. The Langmuir model best described the P adsorption data for FHMD. Because of increased surface area and surface charge, the maximum adsorption capacity of FHMD at pH 4 and pH 8.5 was increased from 10.2 mg P/g and 1.7 mg P/g of raw diatomite to 37.3 mg P/g and 13.6 mg P/g, respectively. Phosphorus showed the best affinity of adsorption onto FHMD among common anions. K-edge P XANES spectra demonstrate that P is not precipitated with Fe (III) of FHMD, but adsorbed on the surface layer of FHMD.<p> Phosphorus removal from lake water and limiting phosphorus release from sediment by FHMD was examined. Phosphorus removal from lake water proceeded primarily through P adsorption onto the surface of FHMD. When a dose of FHMD of 250 mg/L was applied to lake water, a total phosphorus (TP) removal efficiency of 88% was achieved and a residual TP concentration was 17.0 µg/L which falls within the oligotrophic TP range (3.0-17.7 µg/L). FHMD settled down to the bottom of the 43 cm high cylinder within 6 hours, which suggested that retention time of FHMD in the 5.5 m of Jackfish lake water column was close to the equilibrium time of P adsorption onto FHMD (72 hours). During the 30-day anoxic incubation period, TP concentrations in lake water treated by 400, 500 and 600 mg/L of FHMD showed a slight decrease and maximum TP concentrations remained at levels lower than 15 µg/L. The addition of FHMD resulted in a marked increase in Fe-P fraction, a pronounced decrease in labile-P and organic-P fractions, and stable Al-P, Ca-P and residual-P fractions. The effect of FHMD on limiting P release was comparable with those of the combination of FHMD and alum solutions with logarithmic ratios of Al to mobile P of 0.5 and 0.8. FHMD not only can effectively remove P from lake water but also keep a strong P-binding capacity under anoxic conditions and competition for P with alum at high amounts.<p> The role of gypsum on stabilizing sediment and the optimum dose of gypsum were investigated. The effectiveness of gypsum in stabilizing sediment was proved by the fact that at the same agitation speed, turbidities and soluble reactive P (SRP) concentrations of samples treated with gypsum were much lower than those of sample without gypsum. The optimal thickness of the gypsum layer was found to be 0.8 cm.<p> Combined application of FHMD and gypsum to P control was investigated in the research. It was found in the 30-day incubation of lake water and sediment treated by FHMD and gypsum that no P release seemed to occur regardless of oxic or anoxic conditions. In order to investigate the 120-day effects of FHMD and gypsum on the P control under anoxic and agitation conditions a lab-scale artificial aquarium was established in an environmental chamber. Daily oscillation of a metal grid did not yield the sediment resuspension due to the gypsum stabilization. The combined application of FHMD and gypsum resulted in a 1 g/L increase in the SO42- concentration in the 120-day aquarium compared with that in the control aquarium; however it did not affect the total kjeldahl nitrogen (TKN) concentrations in both the control aquarium and the 120-day aquarium. The addition of FHMD and gypsum enhanced total alkalinity in the 120-day aquarium, thereby improving buffering capacity of lake water. Under anoxic conditions and sediment resuspension conditions, relative to a large increase in total P (TP) concentrations in the control aquarium, TP concentrations in the 120-day aquarium stayed relatively stable, fluctuating within the range of 9.1-13.3 µg/L. Relative to control sediment, Fe-P was significantly enhanced during the 60-day incubation; however, Fe-P did not appear to increase significantly in the second 60-day incubation. Labile-P and organic-P decreased with sediment depths in both control aquarium and test aquariums; however, Al-P, Ca-P and residue-P increased with sediment depth. Lower Al-P is observed in treatment aquariums than in control sediment.<p> As an effective P adsorbent, FHMD showed a high adsorption capacity as well as a significantly higher affinity for P than other anions. A combined application of FHMD and gypsum effectively reduced sediment resuspension and maintained TP levels within the oligotrophic range under anoxic conditions in the laboratory-scale artificial aquarium.

Graduation date: 1992

Graduation date: 1990

The goal of this work is to contribute to the understanding eutrophication in large rivers with a detailed study of the Grand River, an impacted river in highly agricultural and urbanized Southern Ontario. It focuses on the role of nitrogen (N) and phosphorus (P) in the distribution and abundance of benthic submersed macrophytes, which are important actors in river N and P cycles. Chapter 1 uses data from the Provincial Water Quality Monitoring Network to examine seasonal, long term and spatial patterns in total P (TP), soluble reactive P (SRP), nitrate and nitrite (NO3- + NO2-) and ammonium (NH4+). The monitoring of many sites in the Grand River began in 1965, and I examine data from the period from 1965 to 2009. The monitoring program began prior to the Canada-USA ban on the use of phosphate in detergents, which came into effect in 1973, and also before major improvements to municipal waste water treatment. The phosphate ban is analyzed as an example of a whole-system nutrient manipulation experiment, and the seasonal and long term response of the river system, from headwaters to mouth, is examined. TP and SRP declined over the monitoring period, with the greatest response found in TP, which declined by 120 µg/l/y immediately downstream of the of the watershed’s largest treatment plant in the years 1972-1975. Thereafter, TP and SRP continued to decline over most of the lower river, with rates of decline in nutrient concentration accelerating with distance from the wastewater treatment plants (WWTPs). NO3+NO2 increased during the monitoring period in the upper portion of the river with the highest increase of 158 µg-N/l/y observed in the 10 year period of 1975-1985. It did not change in response to WWTP upgrades that occurred in the early 1970s. WWTPs were a clear source of TP, SRP and NH4+ to the river system, but not NO3 +NO2 , and the continual increase in NO3 +NO2 was due to increases in diffuse sources. The seasonal and spatial data suggest that non-point sources of N and P dominate in the Grand River watershed. However, the largest WWTP in the region at Kitchener is an important source of nutrients, and was an especially large source of P prior to changes in detergent standards and wastewater treatment. The submersed macrophyte biomass in the Grand River was examined as a function of proximity to WWTPs in chapter 2. Spatial surveys were conducted in 2007 and 2009 on three reaches of approximately 10 km in length each, with two reaches having an upstream and downstream section, separated by a WWTP. Macrophyte patches were mapped, biomass was estimated, and plants were analyzed for N and P. Tissue N and P were compared to published thresholds for evidence of nutrient limitation. Biomass was greater downstream of the WWTPs than upstream in both reaches and both years, indicating that nutrient loading leads to increased biomass downstream, evidence that even in a heavily agricultural watershed, point sources have a demonstrable effect on macrophyte biomass. Depth was important in explaining some of the variation, while river width and orientation were not important. Even though macrophyte biomass was elevated downstream of the WWTPs, there was no strong evidence of N or P limitation upstream based on tissue concentrations and a laboratory determined critical nutrient threshold, and I hypothesize that the nutrient limitation affecting biomass occurs earlier in the growing season, before peak biomass. This suggests that the eutrophication process in rivers is distinct from that in lakes, and future work should view eutrophication in rivers in the context of seasonal succession. Drivers of seasonal and inter-annual variability in submersed macrophyte biomass were examined in chapter 3 with a multi-year, reach-scale spatial survey of three reaches near the WWTPs of Waterloo and Kitchener. Biomass differed among reaches, years and sites, and showed distinct seasonal patterns. The reach downstream of the WWTPs had the highest biomass, and peak biomass came soonest in the growing season, while the upstream reach had the smallest and latest peak biomass. Weather was significantly correlated to both the quantity and the time of the peak biomass, with higher temperatures associated with larger and earlier peak biomass and precipitation and higher flow associated with later and lower peak biomass. Therefore, the eutrophication response in rivers can depend on weather, and these drivers of variation should be accounted for when forecasting responses to future changes in nutrient loading. The effect of nitrogen discharged by WWTPs on the riverine submersed macrophyte community, and the suitability of macrophyte tissues as indicators of point source impact, were quantified in chapter 4 using δ15N as a tracer of WWTP effluent impact. Macrophytes and water for NO3- and NH4+ concentration and isotope analysis was collected by canoe along two 10 km reaches of the river, up and downstream of two WWTPs. Macrophytes incorporated effluent nitrogen into their tissues downstream of the WWTPs, using effluent NH4+ rather than NO3-. Impacts of the effluent on macrophytes can be traced as far as 10 km downstream, while daytime chemical evidence of the plume disappeared much sooner. The δ15N-NH4+ value rapidly increased downstream of the WWTP, changing in one instance from +13‰ to +31‰ over 1 km, with macrophyte δ15N values changing from +6‰ to +24‰ over 5 km, while δ15N- NO3- values showed no such change. These data lead to the conclusion that riverine submersed macrophytes record the influence of WWTP effluent, specifically effluent NH4+, but that using two end-member mixing models to determine N sources would be inappropriate in such dynamic environments. Nitrogen cycle processes such as nitrification and denitrification are influenced by dissolved oxygen (DO) and rapid transformations occur in environments with strong DO gradients. Because development of dense macrophyte beds in eutrophic rivers has the potential to greatly alter daily oxygen cycling, producing strong redox potentials, macrophytes could influence microbial nitrogen cycling. In Chapter 5, nitrogen uptake by macrophytes using a 15N-NH4+ tracer and N2O production was investigated using in situ chamber incubations upstream and downstream of a WWTP. NH4+ uptake occurred in chambers, while measurable net N2O production occurred in some chambers only. Neither N2O production nor NH4+ uptake differed between chambers with and without PO43- addition, nor did they differ between light and dark treatments. NH4+ uptake was higher at the upstream site, indicating that above the WWTP there was NH4+ demand in the macrophyte community. NH4+ uptake was a hyperbolic function of mean chamber NH4+ concentration. Turnover time for the macrophyte N pool due to NH4+ uptake was as long as 47 d, while the turnover of the dissolved NH4+ pool was as rapid as 14 h. Because net uptake was a small fraction of gross uptake, calculated release rates were almost as high as uptake rates, again indicating rapid NH4+ cycling. Eutrophication of rivers has elements that make it a process distinct from that in lakes. I showed that, in the Grand River, N and P were both high in concentration throughout the river, with a distinct increase downstream of the largest WWTPs in the watershed. The biomass of benthic submersed macrophytes was elevated below the WWTPs, but there was no evidence of nutrient limitation upstream during the time of peak biomass. Macrophyte biomass development followed a seasonal pattern, but was also influenced by seasonal temperature and precipitation patterns. Thus, the riverine eutrophication process has an important seasonal component, much as the plants themselves do, peaking in the summer and senescing in the fall. As part of the eutrophication response, macrophytes altered the chemical cycles of nutrients that fuel their growth. Though changes in benthic biomass themselves are part of riverine eutrophication, this thesis provides evidence that changes in macrophyte biomass produces chemical and ecological changes that are characteristic of increased trophic conditions.

Three experiments were conducted to determine the efficacy of an <i>Escherichia coli</i> 6-phytase (Quantum phytase) in laying hens fed corn-soybean meal based diets. In experiment 1, the Escherichia coli 6-phytase (Quantum) was evaluated for its efficacy in a 40-wk laying hen production trial. A total of 1080 White Leghorn hens were fed mash corn-soybean meal (CSM) based diets containing 0.35%, 0.25% or 0.15% of non-phytate phosphorus (NPP) with the 0.25% and 0.15% diets containing 200, 400 and 600 U/kg of exogenous phytase. Only minor differences in production characteristics were found between the 0.35% and 0.25% treatments regardless of phytase addition, indicating that 0.25% NPP resulted in P intake that was at or above the hens requirement. In contrast, the hens fed the 0.15% NPP diet without phytase supplementation had significantly reduced production performance in comparison to the 0.35% treatment. The addition of phytase to the 0.15% diet improved these production characteristics to levels equal to or better than the 0.35% diet. The results indicated that Quantum phytase was efficacious in CSM-based diets fed to White Leghorn laying hens and can be used to reduce the need for diet supplementation with inorganic phosphorus. In experiment 2, the effect of Quantum phytase on nutrient digestibility and bone ash in laying hens fed CSM-based diets was investigated. A total of 108 White Leghorn hens were fed CSM-based diets containing 0.35%, 0.25% or 0.15% NPP with the 0.25% and 0.15% diets containing 200, 400 or 600 U/kg of exogenous phytase. A linear reduction in phytate digestibility, ileal protein digestibility and soluble P was reported with increasing levels of exogenous phytase in the 0.25% diet. Tibial bone ash percentage was higher in 61-wk-old hens fed 0.25% diets supplemented with 200 or 400 U/kg phytase. Overall, the Quantum phytase was not efficacious in improving nutrient digestibility in laying hens fed CSM-based diets deficient in NPP. In experiment 3, the impact of dietary Ca and P level on the efficacy of an E. coli-derived 6-phytase and the apparent digestibility of various nutrients was investigated in White Leghorn laying hens fed CSM-based diets. A total of 384 White Leghorn hens were fed CSM-based diets containing four levels of Ca (2.5, 3.5, 4.5 or 5.5%), two levels of NPP (0.15 or 0.30%), and two levels of phytase (300 or 600 U/kg feed). Increasing dietary Ca caused a decrease in AMEn, duodenal protein digestibility, Ca and phytate digestibility, percentage soluble P in feces and the percentage of poor quality eggs, while significantly increasing bone ash and hen-housed and hen-day egg production. The higher level of NPP (0.30%) decreased AMEn, fecal protein, Ca and P digestibility, and hen-housed and hen-day egg production, while increasing fecal soluble P and egg specific gravity in comparison to the lower NPP level. The higher level of dietary phytase (600 U/kg feed) significantly increased AMEn, phytate and P digestibility, soluble P in feces, and hen-day and hen-housed egg production, while significantly reducing the percentage of soft shelled, cracked and broken eggs. Overall, dietary phytase, Ca and NPP levels, either as main effects or in an interactive manner, can affect apparent nutrient digestibility and production traits in laying hens fed CSM-based diets.

A novel phosphorus (P) adsorbent, ferrihydrite-modified diatomite (FHMD) was developed and characterized in this study. The FHMD was made through surface modification treatments, including NaOH treatment and ferrihydrite deposition on raw diatomite. In the NaOH treatment, surface SiO2 was partially dissolved in the NaOH solution. The dissolved Si contributed to form stable 2-line ferrihydrite, which deposited into the larger mesopores and macropores of the diatomite. The 2-line ferrihydrite not only deposited into the pores of the diatomite but also aggregated on the surface. Filling the larger mesopores and macropores of the diatomite and aggregation on the diatomite surface with 0.24 g Fe/g of 2-line ferrihydrite resulted in a specific surface area of 211.1 m2/g for the FHMD, which is an 8.5-fold increase over the raw diatomite (24.77 m2/g). The surface modification also increased the point of zero charge (pHPZC) values to 10 for the FHMD from 5.8 for the raw diatomite.<p> Effects of the formation process parameters such as concentrations of FeCl2, NaOH, and drying temperature on the formation mechanism and crystalline characteristics of FHMD were studied by using X-ray absorption near-edge structure (XANES) spectroscopy. The spectra were recorded in both the total electron yield (TEY) and the fluorescence yield (FY) modes to investigate the chemical nature of Fe and Si on the surface and in the bulk of ferrihydrite-modified diatomite, respectively. It was found that only the surface SiO2 was partially dissolved in the NaOH solution with stirring and heating, whereas the bulk of diatomite seemed to be preserved. The dissolved Si was incorporated into the structure of ferrihydrite to form the 2-line Si-containing ferrihydrite. The crystalline degree of ferrihydrite increased with the increasing FeCl2 concentration and the Brunauer-Emmett-Teller (BET) specific surface area of FHMD decreased with the increasing FeCl2 concentration. The NaOH solution of higher concentration partially dissolved more surface SiO2 and the crystalline degree of ferrihydrite decreased with the increase in NaOH concentration. The dehydroxylation on the surface of FHMD occurred in the high temperature calcination, causing an energy shift in the Si L-edge spectra to the high energy side and an increase in the crystalline degree of ferrihydrite. In this study, the optimal synthesis conditions for the FHMD with the least crystalline degree and the highest surface area were found to be as the follows: 100 mL of 0.5M FeCl2 solution, 6M NaOH solution and the drying temperature of 50 ºC.<p> Phosphorus adsorption behavior and adsorption mechanism of FHMD were investigated in the research. The Langmuir model best described the P adsorption data for FHMD. Because of increased surface area and surface charge, the maximum adsorption capacity of FHMD at pH 4 and pH 8.5 was increased from 10.2 mg P/g and 1.7 mg P/g of raw diatomite to 37.3 mg P/g and 13.6 mg P/g, respectively. Phosphorus showed the best affinity of adsorption onto FHMD among common anions. K-edge P XANES spectra demonstrate that P is not precipitated with Fe (III) of FHMD, but adsorbed on the surface layer of FHMD.<p> Phosphorus removal from lake water and limiting phosphorus release from sediment by FHMD was examined. Phosphorus removal from lake water proceeded primarily through P adsorption onto the surface of FHMD. When a dose of FHMD of 250 mg/L was applied to lake water, a total phosphorus (TP) removal efficiency of 88% was achieved and a residual TP concentration was 17.0 µg/L which falls within the oligotrophic TP range (3.0-17.7 µg/L). FHMD settled down to the bottom of the 43 cm high cylinder within 6 hours, which suggested that retention time of FHMD in the 5.5 m of Jackfish lake water column was close to the equilibrium time of P adsorption onto FHMD (72 hours). During the 30-day anoxic incubation period, TP concentrations in lake water treated by 400, 500 and 600 mg/L of FHMD showed a slight decrease and maximum TP concentrations remained at levels lower than 15 µg/L. The addition of FHMD resulted in a marked increase in Fe-P fraction, a pronounced decrease in labile-P and organic-P fractions, and stable Al-P, Ca-P and residual-P fractions. The effect of FHMD on limiting P release was comparable with those of the combination of FHMD and alum solutions with logarithmic ratios of Al to mobile P of 0.5 and 0.8. FHMD not only can effectively remove P from lake water but also keep a strong P-binding capacity under anoxic conditions and competition for P with alum at high amounts.<p> The role of gypsum on stabilizing sediment and the optimum dose of gypsum were investigated. The effectiveness of gypsum in stabilizing sediment was proved by the fact that at the same agitation speed, turbidities and soluble reactive P (SRP) concentrations of samples treated with gypsum were much lower than those of sample without gypsum. The optimal thickness of the gypsum layer was found to be 0.8 cm.<p> Combined application of FHMD and gypsum to P control was investigated in the research. It was found in the 30-day incubation of lake water and sediment treated by FHMD and gypsum that no P release seemed to occur regardless of oxic or anoxic conditions. In order to investigate the 120-day effects of FHMD and gypsum on the P control under anoxic and agitation conditions a lab-scale artificial aquarium was established in an environmental chamber. Daily oscillation of a metal grid did not yield the sediment resuspension due to the gypsum stabilization. The combined application of FHMD and gypsum resulted in a 1 g/L increase in the SO42- concentration in the 120-day aquarium compared with that in the control aquarium; however it did not affect the total kjeldahl nitrogen (TKN) concentrations in both the control aquarium and the 120-day aquarium. The addition of FHMD and gypsum enhanced total alkalinity in the 120-day aquarium, thereby improving buffering capacity of lake water. Under anoxic conditions and sediment resuspension conditions, relative to a large increase in total P (TP) concentrations in the control aquarium, TP concentrations in the 120-day aquarium stayed relatively stable, fluctuating within the range of 9.1-13.3 µg/L. Relative to control sediment, Fe-P was significantly enhanced during the 60-day incubation; however, Fe-P did not appear to increase significantly in the second 60-day incubation. Labile-P and organic-P decreased with sediment depths in both control aquarium and test aquariums; however, Al-P, Ca-P and residue-P increased with sediment depth. Lower Al-P is observed in treatment aquariums than in control sediment.<p> As an effective P adsorbent, FHMD showed a high adsorption capacity as well as a significantly higher affinity for P than other anions. A combined application of FHMD and gypsum effectively reduced sediment resuspension and maintained TP levels within the oligotrophic range under anoxic conditions in the laboratory-scale artificial aquarium.

Phosphorus flowing via rivers into the Baltic Sea is a major source of nutrients, and in some cases the limiting factor for the growth of algae which causes the phenomenon known as eutrophication. Remote sensing of phosphorus, here using Landsat TM-data, can help to give a better understanding of the process of eutrophication. Since Landsat TM-data is used, this could form a basis for further spatio-temporal analysis in the Baltic Sea region. A method originally described and previously applied for a Chinese river is here transferred and applied to three different rivers flowing into the Baltic Sea. The results show that by measuring the proxy variables of Secchi Depth and Chloryphyll-a the remote sensing model is able to explain 41% of the variance in total- phosphorus for the rivers Dalälven, Norrström and Gavleån without any consideration taken to CDOM, turbidity or other local features.

none

none

Plants containing condensed tannins (CT) represent an alternative feed resource for ruminants. However, limited information regarding nutrient disappearance from these plants is available. Two experiments were conducted to evaluate phosphorus (P) and other nutrient disappearance from plants containing CT. In the first experiment, nutrient disappearance from three native Texas species (Acacia angustissima var. hirta, Desmodium paniculatum, Smilax bona-nox, and Medicago sativa as control) were evaluated using the mobile nylon bag technique. For the second experiment, ruminal degradation parameters, ruminal and post-ruminal disappearance of P and other nutrients from a browse containing CT (Quercus virginiana) were compared to species without CT (Cynodon dactylon cv. Tifton 85, and Medicago sativa). Results from the first experiment indicate that the proportion of nutrient that disappeared during rumen, pepsin/HCl, or intestinal incubation differed among plant species and nutrient evaluated (P<0.05) and did not appear to be directly related to relative CT concentrations. Dry matter (DM), inorganic matter (IM), and organic matter (OM) disappearance were greater (P