The role of natural biofilms affecting the water quality in rivers has been the main theme in this study. Firstly, the study developed the capacity of biofilms in retention and/or production of DOC. Secondly, the study also approached the production of the geosmin metabolite by benthic cyanobacterial mats. In the two developed aspects, the structure and function of the biofilms showed their relevance in evaluating the capacity of biofilms on the amelioration of the water quality. The importance of the biofilms on ecological research in running waters has been focus in their capacity of adsorption and transformation of nutrient, and therefore, in the self-purification capacity of streams and rivers. Biofilms are also major sites of carbon cycling in streams and rivers, affecting the water DOC dynamics. Eutrophication of streams and rivers have been also linked with an increase of algal biomass. As a consequence, the massive growth of cyanobacterial mats can cause the production of toxic and nuisance metabolites, like geosmin, a secondary metabolite which causes earthy and musty taste and odor in the water.The first conclusion of this study was that biofilms may play an important role in the retention of water DOC. We elucidated whether biofilms act as sinks or sources of fluvial DOC, depending on their structure and biomass accumulation. Metabolism (extracellular enzymatic activity) and structure (algae, bacteria, C/N content) of light-growth and dark-growth systems were analyzed over a year. Biofilms from the light-growth regime presented monthly variation in DOC uptake/release rates, but the annual average presented higher DOC uptake than dark-growth biofilms. However, the latter had a constant DOC consumption along the year, permitting a maintenance of low water DOC levels. The biofilm structure and the relative contribution of autotrophs and heterotrophs had a relevant implication in the carbon recycling, since metabolic activities were affected by variations in this structure.Geosmin production was related with the massive growth of benthic cyanobacteria (formed mainly by Oscillatoria limosa) in littoral zones, where water velocity was low, warmer temperatures and high nutrient concentration and low N/P ratio. The masses were further detached and drift downstream, being the responsible for the dispersion of geosmin along the river. The high biomass accumulation per surface unit, may cause a nutrient depletion inside the mat, e.g. nitrogen limitation. Structural and functional differences were found in the different fractions of the cyanobacterial mat (attached vs. free-floating). Free-floating mats presented higher biomass and exoenzymatic activities. Otherwise, the low phosphatase/aminopeptidase ratio found in both compartments indicated a nitrogen limitation inside the mats. Microstructural analyses with oxygen and redox microsensors have been useful to understand the function of the different cyanobacterial patches inside the mat. During the dark, Oscillatoria micro-patches aggregated and accumulated in thick masses where some anoxia conditions were found, giving a very low redox potential. This low diffusion could be associated with resource depletion, limiting the nutrient availability and defining the appropriate conditions for the geosmin production.

Zone-coated diesel oxidation catalysts (DOCs) can be used to obtain overall improved performance in oxidation reaction extents. However, why this occurs and under what conditions an impact is expected are unknown. In order to demonstrate why these catalysts work better than their standard counterparts and how significant the improved performance is, the CO oxidation performance over a series of Pt−Pd/Al2O3 catalysts, each with a different distribution of precious metal down the length, while maintaining equivalent totals of precious metal, was modeled. Simulations with different flow rates, ramp rates, steady-state temperatures at the end of the ramp rate, different total precious metal loadings, and CO inlet values were compared. At conversions less than 50%, the most significant differences were noted when the temperature was ramped to just at the CO oxidation light-off point (a typical measure of 50% conversion/oxidation), with catalysts containing more precious metal at the downstream portions leading to better light-off conversion performance. However, in terms of cumulative emissions over a long period of time, a “front-loaded” design proved best. These results are readily explained by decreased CO poisoning and the propagation of the heat derived from the exotherm from the front to the rear of the catalyst. Also, although the trends were the same, regardless of change in the parameter, the impact of different distributions was more apparent under conditions where a catalyst would be challenged, i.e., at low temperature ramp rates, higher CO inlet concentrations, and lower amounts of total catalyst used. At higher ramp rates, the input heat from the entering gas stream played an increasingly important role, relative to conduction associated with the exotherm, dampening the effects of the catalyst distribution. Therefore, although catalysts that are zone-coated with precious metals, or any active sites, could prove better in terms of performance than homogeneously distributed active site catalysts, this improvement is only significant under certain reaction conditions. In a mixture of three reactants, CO, C3H6 and NO oxidation, it was found that a loading a larger amount of active sites in the catalyst middle, maintained better CO and C3H6 oxidation but not NO oxidation, which required the whole catalyst length. A faster light-off conversion was also related to higher amount of precious metal at the catalyst outlet. The CO conversion performance for a variety of distributed precious metal designs was evaluated as a function of exposure time to sulphur and the spatial accumulation profile of sulphur along the monolith length was predicted. The results illustrate that the sulphur accumulates near the catalyst inlet and decreases toward the outlet, resulting in shifting the reaction zones further toward the catalyst outlet. With sulfation, light-off temperatures (T50) increased and the time for back to front reaction propagation also increased. A back loaded catalyst resulted in the best light-off conversion compared to the other catalyst designs and a middle loaded catalyst maintained a higher overall conversion if sulphur poisoning takes place. These catalyst designs were also tested under thermal aging conditions by using a second order sintering model integrated with the CO oxidation reaction model. The spatial normalized dispersion profiles along the monolith showed that the catalyst outlet experienced significant damage relative to the inlet due to sintering. A front loaded catalyst design had the highest catalytic activity due its resistance to sintering.

Pothole wetlands are ubiquitous throughout the Prairie Pothole Region and since 1900, 40-70% of potholes in the region have been drained to increase agricultural production. This thesis describes factors influencing spatial and temporal variations in wetland water quality and characteristics of drainage water. Research was conducted at Smith Creek watershed, southeastern Saskatchewan, where there has been controversy over recent renewed efforts to drain wetlands. Following snowmelt in 2009, 67 wetlands were sampled to determine whether spatial variations in wetland water quality were attributable to land cover, permanence classes, and surface drainage characteristics. Wetlands with cropped uplands had greater TP and K than wetlands with wooded and grassed uplands; TP, TDN, and DOC were higher in seasonally than permanently ponded wetlands; and salts were lower in wetlands with wooded uplands compared to wetlands with cropped and grassed uplands. Measurements of water quality of one permanently ponded wetland over a 20 week period in 2008 showed that the wetland acted as a solute trap. Variations in salts and DOC were influenced by hydrological processes such as runoff, evaporation, and shallow groundwater seepage, whereas variations in nitrogen, phosphorus, and bacteria were influenced by biotic, sorption, and hydrological processes. The experimental drainage of this wetland in November 2009 demonstrated that its water quality was an important control of drainage water quality. Further, the wetland ditch acted as a simple conduit, i.e., little solutes loss or gain occurred along it. In spring 2009, water quality along seven ditches and five natural connections that form between wetlands (termed spills) was compared. Concentrations of most solutes were similar, except TDN, DOC, HCO₃^-, K⁺, and Ca²⁺ that were higher in ditches than spills. Minimal changes in water quality along ditches and spills occurred, likely due to the low temperatures occurring in spring that restrict biotic processing and sorption. Notably, because ditches connect wetlands to streams, as opposed to spills that connect adjacent wetlands, ditches have a greater potential to contribute to downstream solute loading. Wetland drainage efficiency and wetland water quality were deemed the factors critical to determining solute exports via ditches. Results of wetland water quality and drainage characteristics can be useful to future modeling exercises and could be used to inform wetland drainage practices and policies.

Lindner, Murphy, and Wingenbach (2002), noted that agricultural education's core is communication because it is the component that spreads a variety of ideas to a large group of people and is the essential form of education needed for scholarship. Research is needed to ensure that agricultural education students are taught to write, effectively and efficiently, an argument paper that establishes the following components: coherence, audience awareness, argument, summary, sources, and grammar. The purpose of this descriptive study was to determine if the writing competencies of the Doc@Distance graduate students have changed or improved based on the recommendations made in a previous study. A census of the Doc@Distance students was taken for this study. Thirty students submitted an argument writing sample that they wrote during the orientation week of their program in August 2003. The conclusions of this study found that 68.8% of the 2004 Doc@Distance Cohort suggested inadequacy in writing an argument paper, and 71.4% of the 2007 Doc@Distance Cohort suggested inadequacy in writing an argument paper. Ending Cohort `04 demonstrated weakness in coherence, argument, summary, and grammar. Beginning Cohort `07 demonstrated weakness in coherence, audience awareness, summary, and grammar. As a result of this study, it is recommended that a follow-up study be conducted on Cohort `07 in two years to determine if writing abilities for argument papers have changed and to assess the overall changes in argument-writing for this cohort. It is recommended that a study be conducted on Cohort `10 upon admission to determine their argument-writing ability. Ending Cohort `07 and Beginning Cohort `10 should be tested to determine if a difference exists between students completing the program and students entering the program. It is recommended that undergraduate agricultural education students be tested to determine their argument-writing competencies. It is recommended to compare and contrast on-campus agricultural education students and distance education students at Texas A&M University. Finally, it is recommended that Cohorts `07 and `10 be evaluated on their competencies to write data reports, narratives, and informative and research analysis papeers.

Coastal outwelling of organic carbon from mangrove wetlands contributes to near-shore productivity and influences biogeochemical cycling of elements. I used a flume to measure fluxes of dissolved organic carbon (DOC) between a mangrove forest and adjacent tidal creek along Shark River, Florida. Shark River’s hydrology is influenced by diurnal tides and seasonal rainfall and wind patterns. Samplings were made over multiple tidal cycles in 2003 to include dry, wet, and transitional seasons. Surface water [DOC], temperature, salinity, conductivity and pH were significantly different among all sampling periods. [DOC] was highest during the dry season (May), followed by the wet (October) and transitional (December) seasons. Net DOC export was measured in October and December, inferring the mangrove forest is a source of DOC to the adjacent tidal creek during these periods. This trend may be explained by high rates of rainfall, freshwater inflow and subsequent flushing of wetland soils during this period of the year.

I havet finns det flertalet olika bakteriearter, alltså en hög diversitet vilket teoretiskt sett borde betyda en hög funktionalitet. I denna studie har vi undersökt hur bakteriers funktionalitet och diversitet påverkas av förändrad salthalt. Två marina bakteriesamhällen har studerats och jämförts, dels ett Skagerraksamhälle samt ett Östersjösamhälle. Dessa två samhällen utsattes gradvis för hög respektive låg salthalt och efter avslutat experiment hade Skagerraksamhället en låg salthalt dvs Östersjöbetingelse och Östersjösamhället övergått till hög salthalt (Skagerrakbetingelse). Resultatet av detta blev att både funktionalitet och diversitet påverkades, vilket analyserades med Eco-plattor och DGGE (Denaturing Gradient Gel Electrophoresis). Bakterieantalet ökade respektive sänktes i Skagerrak- respektive Östersjö-samhället. Då Östersjösamhället fick en högre salthalt ledde detta till att funktionaliteten sänktes och en tidigare icke dominant art blev dominant. För Skagerraksamhället som fick en sänkt salthalt bedömdes funktionaliteten ha ökat i och med att en ny kolkälla nyttjades. Dock såg diversiteten ut att vara lägre, möjligtvis p.g.a. en förändring av dominanta och icke dominanta bakterier i samhället. Det är däremot inte möjligt att utifrån denna studie dra slutsatsen att en hög diversitet automatiskt ger en hög funktionalitet. / In the sea there is a high diversity of different microorganisms, especially bacteria. In other studies it has been shown that salinity is an important factor forming the bacterial communities. In this study we have investigated how diversity and functionality is affected by changing salinity. Bacterial communities from Skagerrak and the Baltic Sea were used in the study. In the Skagerrak community the bacteria live in an environment with high salinity and low DOC (dissolved organic carbon) concentration and the Baltic communitiy has a low salinity and a high DOC concentration. We made a salinity change between these communities to see how that would affect the communities. The diversity, genotype variation, and functionality of the bacteria were studied using DGGE-analysis and Eco-plates respectively. The results showed that the two communities were affected by the salinity change. The bacterial counts decreased and increased, in the Baltic and Skagerrak communities respectively, in relation to the salinity change and a diversity change was seen in the DGGE-analysis (Denaturing Gradient Gel Electrophoresis). The original Baltic and Skagerrak communities showed different functionality traits. Over time, along the experiment, the functionality changed and the communities showed different functionality at the end of the experiment. But we can’t definitely say that high diversity always gives high functionality.

Waterborne carbon (C) forms an active and significant part of the global C cycle, which is important in theArctic where greater temperature increases and variability are anticipated relative to the rest of the globe withpotential implications for the C cycle. Understanding and quantification of the current processes governing themovement of C by connecting terrestrial and marine systems is necessary to better estimate future changes ofwaterborne C. This thesis investigates how the sub-arctic landscape influences the waterborne carbon exportby combining data-driven and modeling methods across spatial and temporal scales. First, a study of the stateof total organic carbon monitoring in northern Scandinavia was carried out using national-scale monitoringdata and detailed data from scientific literature. This study, which highlights the consistency in land cover andhydroclimatic controls on waterborne C across northern Scandinavia, was combined with three more detailedstudies leveraging field measurements and modeling. These focused on the Abisko region to provide insightto processes and mechanisms across scales. The thesis highlights that the governing transport mechanismsof dissolved organic and inorganic carbon (DOC and DIC respectively) are fundamentally different due todifferences in release rates associated with the nature of their terrestrial sources (geogenic and organic matterrespectively). As such, the DIC mass flux exhibits a high flow-dependence whereas DOC is relatively flowindependent.Furthermore, these investigations identified significant relationships between waterborne C andbiogeophysical as well as hydroclimatic variables across large to small spatial scales. This thesis demonstratesthat both surface and sub-surface hydrological processes (such as flow pathway distributions) in combinationwith distributions of C sources and associated release rates are prerequisite for understanding waterborne Cdynamics in northern streams. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Submitted. Paper 4: Accepted.</p>

Zone-coated diesel oxidation catalysts (DOCs) can be used to obtain overall improved performance in oxidation reaction extents. However, why this occurs and under what conditions an impact is expected are unknown. In order to demonstrate why these catalysts work better than their standard counterparts and how significant the improved performance is, the CO oxidation performance over a series of Pt−Pd/Al2O3 catalysts, each with a different distribution of precious metal down the length, while maintaining equivalent totals of precious metal, was modeled. Simulations with different flow rates, ramp rates, steady-state temperatures at the end of the ramp rate, different total precious metal loadings, and CO inlet values were compared. At conversions less than 50%, the most significant differences were noted when the temperature was ramped to just at the CO oxidation light-off point (a typical measure of 50% conversion/oxidation), with catalysts containing more precious metal at the downstream portions leading to better light-off conversion performance. However, in terms of cumulative emissions over a long period of time, a “front-loaded” design proved best. These results are readily explained by decreased CO poisoning and the propagation of the heat derived from the exotherm from the front to the rear of the catalyst. Also, although the trends were the same, regardless of change in the parameter, the impact of different distributions was more apparent under conditions where a catalyst would be challenged, i.e., at low temperature ramp rates, higher CO inlet concentrations, and lower amounts of total catalyst used. At higher ramp rates, the input heat from the entering gas stream played an increasingly important role, relative to conduction associated with the exotherm, dampening the effects of the catalyst distribution. Therefore, although catalysts that are zone-coated with precious metals, or any active sites, could prove better in terms of performance than homogeneously distributed active site catalysts, this improvement is only significant under certain reaction conditions. In a mixture of three reactants, CO, C3H6 and NO oxidation, it was found that a loading a larger amount of active sites in the catalyst middle, maintained better CO and C3H6 oxidation but not NO oxidation, which required the whole catalyst length. A faster light-off conversion was also related to higher amount of precious metal at the catalyst outlet. The CO conversion performance for a variety of distributed precious metal designs was evaluated as a function of exposure time to sulphur and the spatial accumulation profile of sulphur along the monolith length was predicted. The results illustrate that the sulphur accumulates near the catalyst inlet and decreases toward the outlet, resulting in shifting the reaction zones further toward the catalyst outlet. With sulfation, light-off temperatures (T50) increased and the time for back to front reaction propagation also increased. A back loaded catalyst resulted in the best light-off conversion compared to the other catalyst designs and a middle loaded catalyst maintained a higher overall conversion if sulphur poisoning takes place. These catalyst designs were also tested under thermal aging conditions by using a second order sintering model integrated with the CO oxidation reaction model. The spatial normalized dispersion profiles along the monolith showed that the catalyst outlet experienced significant damage relative to the inlet due to sintering. A front loaded catalyst design had the highest catalytic activity due its resistance to sintering.

Zugl.: Hohenheim, Univ., Diss., 2006.

Zugl.: Leipzig, Universiẗat, Diss., 1999.