Browsing by Subject "Resin"

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    Climate and Land Use Change Impacts on N-Loads in Iowa Rivers and Remediation of Tile Water with an Anion-Exchange Resin
    (2017-12) Wolf, Kari
    This research was conducted to (1) better understand the underlying reasons for a continuous increase in nitrate loads in the Gulf of Mexico, and (2) if an industrial anion resin can be used at a field scale to reduce N losses from tile-drained watersheds to the rivers. The first objective was accomplished through statistical analyses of climate and land use change impacts on streamflow, baseflow, flow weighted nitrate-N concentrations (FWNC) and nitrate-N-loads in three major rivers of Iowa. The rivers included the Des Moines River, the Iowa River, and the Raccoon River. The results from this analysis showed that natural log of annual streamflow, baseflow, and N-loads were primarily controlled by the precipitation in the corresponding watersheds. For streamflow and baseflow, this precipitation corresponded to the current years as well as previous year precipitation. Previous year precipitation reflected the lack or excess presence of stored water in the soil and its consequences in terms of increased or decreased overland flow, infiltration, and percolation processes. For N loads, the precipitation effect was limited to one-year precipitation for the Des Moines and the Iowa Rivers and two-year precipitation for the Raccoon River. There were individual years when streamflow, baseflow, and N loads were impacted by up to three previous years’ precipitation. Effect of land use change, in terms of increased soybean area, had no effect on annual streamflow, annual baseflow, annual flow-weighted N concentrations or annual N-loads in all three rivers. Additional regression analysis of FWNC and N-loads from 1987-2001 showed no effect of N fertilizer use as an explanatory variable for any of the three watersheds. Statistical analysis of the combined annual data from all three rivers showed that there was a unique relationship between the natural log of streamflow, the baseflow, and the N-yield (N-loads/watershed area) versus the precipitation. The precipitation effects were both in terms of current year precipitation and the previous year precipitation. The coefficient of determination (R2) of Ln(streamflow), Ln(baseflow) and Ln(N load) with precipitation for the combined data were 0.74, 0.70 and 0.54, respectively. Limited scatter in the N-yield data at a given annual precipitation level over three rivers suggested that variation in annual precipitation has much bigger impact on N losses than the differences in cultural or cropping practices between the three river watersheds over the study period. Considering that there has been a 10-15% increase in precipitation in the Upper Midwestern United States in recent years, the combined N Yield relationship with precipitation would suggest that the recent increases in N-loads or increased hypoxic area in the Gulf of Mexico are likely due to increased precipitation. Statistical analysis of N-loads over a shorter period of time (1987-2001) also showed that changes in fertilizer use had no effect on river N-loads. Regression analysis of monthly streamflow, baseflow, N-loads and FWNC concentration showed that natural log of streamflow, baseflow, and N-loads were generally linearly related to precipitation in a given month and a few prior months. In some cases earlier in the season, these variables were also related to previous year’s precipitation, an indication that some of the past water stored in the soil both above and below the drain tile is interacting with current months precipitation and affecting the streamflow and baseflow. In most cases, there was no effect of soybean area on natural log of monthly streamflow, baseflow, or N-loads. A field test on the use of anion exchange resin to remediate tile water for nitrate showed that nitrate adsorption by the resin is instantaneous. The efficiency of the resin to retain nitrate varied 7-46%. This efficiency generally decreased with time due to the presence of sulfate, bicarbonates, and organic anions in tile water, which competed with nitrate ions for adsorption to the resin. In some instances, nitrate concentration in the percolating water was higher than the tile water most likely due to the expulsion of adsorbed nitrate ions on the resin by sulfate ion in the tile water. The results also showed that potassium chloride (KCl) is an effective resin-regenerating agent and provides a means to recycle wastewater as KNO3 fertilizer back on land. Although the use of anion exchange resin is an attractive alternative to passive technologies like bioreactors, saturated buffers, control drainage, etc. for remediating nitrate in tile water, it also presents some challenges in its use under field conditions. These challenges include the fouling up of the resin by sediment, sulfate, bicarbonate, and organic anions in tile water; costs associated with buying of resin and regenerating salt (KCl versus NaCl); need for a large volume of clean water for cleaning of resin; and the difficulty of treating large volume of tile water in-situ. However, the feasibility study shows that small-scale units similar to home water softener can be developed for individual homes in rural area where groundwater may be high in NO3-N concentration and NO3-N remediation is needed.
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    Origin, composition, and role of antimicrobial plant resins collected by honey bees, Apis mellifera
    (2014-05) Wilson, Michael Bradley
    The use of plant resins in nest building by honey bees, Apis mellifera, is an oft ignored, but critical behavior to bee health. Termed `propolis' by beekeepers, deposited resins in the nest have many positive physiological effects on the colony. Honey bees are feral and abundantly managed in many regions of the United States, from the Sonoran Desert to icy Minnesota, yet a diversity of very different resinous plants exist in every environment they call home. We know very little about what resinous plants bees utilize in these different regions, or what benefits bees might derive from specific plants. It is thought that the antimicrobial properties inherent in resins, which are complex mixtures of phenolic and isoprenoid compounds, are important drivers of their derived benefits to bees. The research herein focuses on creating better methods to track resin forager behavior, and then using those methods to discover the botanical sources of bee-foraged resins, while also exploring how resins from different plants directly affect the growth of two bee pathogens, the gram-positive bacteria Paenibacillus larvae and the fungus Ascophaera apis. I found that individual resin foragers can be chemically tracked to their resinous plant targets using metabolomic methods that hold great advantages over traditional chemical analyses, and that there is much diversity in the ability of resins from different Populus spp. to inhibit the in vitro growth of P. larvae and A. apis. I go on to further explore the benefits of different resins and find that propolis from Fallon, NV was particularly active against P. larvae and A. apis out of samples from 12 different regions in the U.S. Finally, I used bioassay-guided fractionation against P. larvae to isolated several flavanone-3-alkyl esters from NV propolis that displayed very high activity (IC50 = 17 µM to 68 µM) against P. larvae and A. apis. Re-examination of data from my previous studies indicated that these compounds were strong contributors to overall anti-P. larvae activity in regional propolis samples, and that Populus spp. are likely the botanical sources of these compounds.
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    Seasonal benefits of a natural propolis envelope to honey bee immunity and colony health
    (Company of Biologists, 2015) Borba, Renata S.; Klyczek, Karen K.; Mogen, Kim L.; Spivak, Marla
    Honey bees, as social insects, rely on collective behavioral defenses that produce a colony-level immune phenotype, or social immunity, which in turn impacts the immune response of individuals. One behavioral defense is the collection and deposition of antimicrobial plant resins, or propolis, in the nest. We tested the effect of a naturally constructed propolis envelope within standard beekeeping equipment on the pathogen and parasite load of large field colonies, and on immune system activity, virus and storage protein levels of individual bees over the course of a year. The main effect of the propolis envelope was a decreased and more uniform baseline expression of immune genes in bees during summer and autumn months each year, compared with the immune activity in bees with no propolis envelope in the colony. The most important function of the propolis envelope may be to modulate costly immune system activity. As no differences were found in levels of bacteria, pathogens and parasites between the treatment groups, the propolis envelope may act directly on the immune system, reducing the bees’ need to activate the physiologically costly production of humoral immune responses. Colonies with a natural propolis envelope had increased colony strength and vitellogenin levels after surviving the winter in one of the two years of the study, despite the fact that the biological activity of the propolis diminished over the winter. A natural propolis envelope acts as an important antimicrobial layer enshrouding the colony, benefiting individual immunity and ultimately colony health.