No description available.

No description available.

The specific activity of the ('32)P labeled sediment-P taken up by submersed macrophytes was shown to be identical to the specific activity of the sediment mobile P, as measured by isotopic dilution. The mobile P therefore represents the sediment-P available to aquatic macrophytes. / The ability to accurately measure the specific activity of the available sediment-P was applied to problems pertaining to the role of macrophytes in P cycling. The relative contribution of water and sediments in supplying P to macrophytes was measured by growing macrophytes in situ, rooted in ('32)P labeled sediments, and with the shoot in free contact with the unlabeled overlying water. Macrophytes grown in mesotrophic and eutrophic sites derived more than 95% of their P from the sediments alone. When grown in a hypertrophic site, the sediments still supplied 70% of the P. / Rates of P release by macrophytes and significance to their periphyton and surrounding phytoplankton were estimated by using fully labeled plants. The periphyton derived only 6.5% of its P form the macrophytes. Myriophyllum released 0.32 ug.g('-1).h('-1) P, most of which being readily available to phytoplankton. / The high vertical mobility of the available sediment-P was demonstrated both by experimental manipulations and direct observations.

No description available.

The top-down effects of consumers and bottom-up effects of resource availability are important in determining community structure and ecological processes. I experimentally examined the roles of consumers — both detritivores and predators — and habitat context in affecting nutrient cycling using the detritus-based insect community in bromeliad leaf wells. I also investigated the role of multiple resources in limiting plant productivity using meta analyses. The insect community in bromeliads only increased nitrogen release from leaf detritus in the presence of a predator trophic level. When only detritivores were present, the flow of stable isotope-labeled nitrogen from detritus to bromeliads was statistically indistinguishable from that in bromeliads lacking insects. I suggest that emergence of adult detritivores constitutes a loss of nitrogen from bromeliad ecosystems, and that predation reduces the rate of this nutrient loss. Hence, insects facilitate nutrient uptake by the plant, but only if both predators and detritivores are present. Moreover, predators can affect nutrient cycling by influencing the spatial scale of prey turnover. This mechanism results in a pattern opposite to that predicted by classic trophic cascade theory. Increasing habitat complexity can have implications for nutrient cycling by decreasing the foraging efficiency of both predators and their prey, and by affecting the vulnerability of predators to intraguild predation. Along a natural gradient in bromeliad size, I found that, depending on the relationship between community composition and habitat size, habitat complexity interacts with the changing biotic community to either complement or counteract the impact of predators on nutrient uptake by bromeliads. In contrast to the existing emphasis on single-resource limitation of primary productivity, meta-analyses of a database of 653 studies revealed widespread limitation by multiple resources, and frequent interaction between these resources in restricting plant growth. A framework for analyzing fertilization studies is outlined, with explicit consideration of the possible role of multiple resources. I also review a range of mechanisms responsible for the various forms of resource limitation that are observed in fertilization experiments. These studies emphasize that a wider range of predator and nutrient impacts should be considered, beyond the paradigm of single resource limitation or classic trophic cascades.

The synthesis and characterization of two new bulky N,P-monophosphaamidines (also known as C-aminophosphaalkenes) are described. These phosphorus analogues to amidines are shown to exhibit isomerism and tautomerism in solution that is characteristic tothe amidine functional group. In addition, the nature of the P=C-N system is examined using DFT techniques. Metal complexes of the title compounds with Group 6 metal carbonyls (L-M(CO)5, M=Cr,Mo,W) are also described. A new primary phosphane is reported that contains the sterically bulky, 2,6-diisoropylphenyl (Dip) group, along with mono and disilylated derivatives. Also included is the synthesis and characterization of a new bulky N,N',P-monophosphaguanidine. / xxxii, 280 leaves : ill. ; 28 cm.

No description available.

In a constructed treatment wetland applied to domestic wastewaters, long term studies and increased operational experience indicate that phosphorus removal is variable or inconsistent, especially in cold-climate applications. These inconsistencies can be attributed to the complexity of phosphorus removal mechanisms, and the lack of consideration of these complexities in the design, installation and operation of these treatment systems. Sorption of phosphorus to the wetland media is generally considered to be the major removal mechanism. The research described in this thesis was conducted to determine the most suitable material for application in a constructed wetland and a post wetland-filter to treat phosphorus in wastewater effluents, taking advantage of sorption processes. The present work was conducted at lab (bench) scale. Three potential sorptive media were studied in the research program, namely gravel, slag and clinker. Several methods for media analysis were investigated as potential screening tools for media selection. To determine the various forms of phosphorus in the media, sequential extraction tests were considered to be most relevant and useful for this research. Batch testing and flow cell testing along with sequential extraction tests were conducted to predict the sorption capacity and performance of the media for the long term (10+ years) removal of phosphorus. The protocols developed in this thesis permitted a rigorous assessment of the media and should be applied in any assessment of sorptive media to select the best medium. Gravel showed some sorption of phosphorus although it was not sufficient to meet the regulatory limits for the effluent concentration. Clinker and slag showed high sorption capacity as compared to gravel and the observed effluent concentration was below the regulatory limits. All three media showed the presence of background phosphorus, with clinker having the highest amount of background phosphorus. However, except gravel, clinker and slag did not show any significant amount of phosphorus being leached out during low phosphorus loading conditions. Taking all factors under consideration, slag and clinker were identified as good media for phosphorus removal. Media that have proven to have high sorption capacities and also retention capabilities should be considered for applications where phosphorus removal is the prime objective. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2007-12-10 11:40:49.657 / NSERC

Hydraulic retention time (HRT) might contribute to the substantial variation in phosphorus-chlorphyll and chlorophyll-zooplankton models because rapid flushing might depress plankton development. However, for a world-wide data set. HRT was not correlated with chlorophyll. Total phosphorus had no effect on chlorphyll when hypereutrophic sites were considered separately, but chlorophyll was negatively related to HRT. Short term HRT, averaged over periods up to one month, was not correlated with chlorophyll, or zooplankton biomass, in seven impoundments on the St. Lawrence and Ottawa Rivers. The size distribution of algae was not affected by HRT. The proportion of rotifer to total zooplankton biomass was positively related to HRT, but this trend disappeared when nauplius biomass was removed from the total. These results indicate that rapid flushing does not necessarily reduce planktonic biomass and that short term HRT is not useful for the prediction and management of planktonic biomass in these systems.

The success of enhanced biological phosphorus removal depends on the constant availability of volatile fatty acids (VFAs). To reduce costs of purchasing external carbon, waste streams would be a preferred source for nutrient removal. VFAs were shown to vary in the incoming sewage and fermentate from primary sludge (PS). Another available source of organic to generate VFAs is waste activated sludge (WAS). The effect of solids retention time and biomass concentration, as well as the effect of temperature and requirement for mixing on generation of VFA from the fermentation of WAS were investigated. It was found that VFA yields from sludge fermentation increased with SRT. At the longest SRT of 10 days improved biomass degradation resulted in the highest soluble to total COD ratio and the highest VFA yield. WAS fermentation was found highly temperature-dependent. The overall VFA–COD concentration in the non-mixed reactors was much lower than the mixed reactors. The study of fermentation of PS, WAS and a mixture of WAS and PS demonstrated that PS fermentation predictably generated a significantly higher amount of soluble COD than WAS. Co-fermentation of WAS with PS enhanced soluble COD production and increased the release of phosphate and ammonium. Fermentation of combined PS and WAS sludge generated a concentration of phosphate high enough to allow phosphorus recovery as struvite The effect of using glycerol as an external carbon source in biological phosphorus removal was investigated. Using glycerol directly resulted in the failure of the process which maintained enhanced biological phosphorus removal. When glycerol was co-fermented with waste activated sludge, significant VFA production was observed. By 2 | P a g e supplying the system with the VFA-enriched supernatant of the fermentate, biological phosphorus removal was enhanced. It was concluded that, if glycerol was to be used as external carbon source for biological phosphorous removal, the effective approach was to ferment glycerol with waste activated sludge. According to the cost analysis, the economic benefit of WAS fermentation can be demonstrated in three ways: 1) cost saving in external carbon addition; 2) cost saving in sludge handling; 3) revenue from phosphorus. At current condition, the value of the recovered P product is insignificant relative to the cost of chemicals that required for recovery and capital cost of the facilities. However, P recovery becomes important when the sustainability take into account.