Thesis (Ph. D.)--University of Alaska, 1988. / "February 1989." Includes bibliographical references.

Thesis (Ph.D.)--University of Alberta, 2010. / Title from PDF file main screen (viewed on July 13, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy, [Department of] Earth and Atmospheric Sciences, University of Alberta. Includes bibliographical references.

Master of Science / Division of Biology / Walter K. Dodds / Contrary to the previous notion that a stream acts primarily as the transporter of materials from land to oceans, research has shown that in-stream processing of organic matter and nutrients is significant and relevant at a global scale. Dissolved organic carbon (DOC) is the most abundant form of organic carbon in streams and has been demonstrated as an important source of energy supporting stream food webs. Understanding the dynamics of DOC in streams is, therefore, important in determining the contribution of flowing waters to global carbon storage and release. However, DOC exists as many different compounds, varying in source, composition, and quality. The composition of DOC that ends up in streams is partly controlled by the surrounding watershed, and landscape effects on DOC quality and quantity in streams have been observed. In the North American Tallgrass prairie, woody encroachment has led to changes in riparian vegetation, potentially altering the DOC received by the stream, and making it important to understand rates of DOC transformation as landscape alterations continue. The heterogeneity of the DOC pool makes it difficult to fully describe its components and to measure transformation rates. DOC uptake, or biological use, has been estimated through several methods including in-stream additions of various DOC sources and bottle incubations of stream water and sediments. One problem with addition methods for calculating uptake is that the DOC pool is difficult to replicate and additions of simple compounds or organic leachates do not represent total dissolved organic carbon (TDOC) dynamics. Another potential issue is that additions of a labile compound could potentially alter microbial activity through a priming effect and therefore distort ambient DOC uptake estimates. Finally, uptake parameters are mostly calculated assuming benthic uptake while recent studies have shown that planktonic uptake of DOC can also be significant. We conducted this study with these three considerations in mind. In the first chapter, we describe our use of in situ additions of glucose and bur oak leaf leachate in prairie stream reaches and concentrations of specific components to determine uptake dynamics of various specific DOC components, from a simple sugar to more complex plant compounds. We calculated uptake parameters of glucose and two different oak leaf components. We found that using glucose concentrations rather than TDOC concentrations, as has been done in previous studies, to measure uptake parameters resulted in higher uptake rates, indicating the importance of measuring the specific component added. Through leaf leachate additions, we found that an amino acid like component was consistently taken up faster than a humic-like component. The second chapter addresses the questions of uptake location and priming through a series of recirculating chamber incubations. We found that benthic uptake of leaf leachate was more important than that in the water column. Finally, elevated uptake of one leaf leachate component in the presence of glucose indicated a priming effect on microbial DOC uptake.

Limestone dissolution in karst environments is likely due to geochemistry of the water, the actions of microbial communities, and the effect of water flow. We explored the rate of limestone dissolution and will examine here the microbial communities associated with the limestone. A conduit within the brackish cave, Double Keyhole Spring, on the coast of central west Florida was the site of the experiment. PVC pipes (5cm x 16cm) were filled with crushed limestone that was screened to a 1.9cm – 2.54cm size range. There were three treatments (5 replicates each): Control - sealed autoclaved controls with limestone and conduit water; Low Flow – sealed at one end, with a screen on the other so water contacts the limestone but cannot flow through; High Flow – screen mesh at both ends to allow the flow of conduit water over the limestone in the tube. After 9 months, the samples were retrieved. The Controls showed a loss of 0.33% ± 0.10, Low Flow samples showed a loss of 1.63% ± 0.71, and High Flow samples lost 2.28% ±0.29. Other studies in freshwater conditions found an average mass loss of 2.25% over the same time period under conditions similar to the High Flow sample in this experiment. Q-PCR and LH-PCR were used to estimate microbial density and species richness. The microbial community growing on the limestone samples were found to be significantly different from sediment or water column samples in both diversity and richness. The conclusion of this study is that the archaeal community growing on the limestone is the main biological driver of limestone dissolution in Double Keyhole Spring.

This thesis examines the production and distribution of dissolved gaseous mercury (DGM) in freshwater ecosystems and its relationship to mercury volatilization. The importance of volatilization was assessed within a multidisciplinary mercury mass balance for Big Dam West Lake (BDW) Kejimkujik Park, Nova Scotia. The magnitude of volatilization was found to be approximately double the direct wet deposition over lake and wetlands, and 27% of the direct wet deposition to the terrestrial catchment. Over the entire basin area the mass of mercury volatilized is 46% of the mass deposited by wet deposition. A new method of continuous (5 minute) DGM analysis was developed and tested. The detection limit for DGM was 20 fmol L-1 with 99% removal efficiency. Control experiments showed that there was no interference due to methyl mercury, which is present in similar concentrations to DGM. Experiments comparing continuous DGM analysis with discrete DGM analysis showed that the results are not significantly affected by typical variations in water temperature (4--30°C), oxidation-reduction potential (135--355 mV), dissolved organic carbon (4.5--10.5 mg L-1), or pH (3.5--7.8). The continuous analysis was within 4.5% of the discrete analysis when compared across 12 samples analyzed in triplicate. Diurnal patterns for dissolved gaseous mercury (DGM) and mercury flux were measured (using this new DGM method and a Teflon flux chamber method) in two lakes with contrasting dissolved organic carbon (DOC) concentrations in Kejimkujik Park, Nova Scotia. Consistently higher DGM concentrations were found in the high DOC lake as compared to the low DOC lake. Cross-correlation analysis indicated that DGM dynamics changed in response to solar radiation with lag-times of 65 and 90 minutes. An examination of current mercury flux models using this quantitative data indicated some good correlations between the data and predicted flux (r ranging from 0.27 to 0.83) but generally poor fit (standard deviation of residuals ranging from 0.97 to 3.38). This research indicates that DOC and wind speed may play important roles in DGM and mercury flux dynamics that have not been adequately accounted for in current predictive models. The distribution of DGM in the water columns of shallow and deep freshwater lakes was investigated in Lake Ontario and several small freshwater lakes. When DGM concentrations were expressed on an areal basis, DGM concentrations above the thermocline in Lake Ontario average 1.5 ng m-2 and in small freshwater lakes it ranged between 0.1 and 0.8 ng m -2. Further, it was demonstrated that the majority of DGM in large freshwater lakes such as Lake Ontario exists below the thermocline where photochemical oxidation and reduction processes cannot occur. The depth profiles indicate that vertical mixing in the water column may alter the DGM concentration in the upper epilimnion, and that turn over in deep lakes may result in a transfer of large concentrations of DGM from the hypolimnion into the epilimnion. In addition, the results indicate that microbial processes may be an important factor regulating DGM in the water column of freshwater lakes, particularly in the hypolimnion. (Abstract shortened by UMI.)

We present two novel stable isotope methods for measuring lake metabolism and compare the results to traditional techniques. The delta 18O method measures planktonic gross primary production (GPP) from dissolved oxygen concentrations, isotopes and respiration (R) and the delta 13C method measures "whole-lake" GPP and R from dissolved oxygen and carbon concentrations and isotopes. All three methods showed GPP was greater than R over the ice-free season and estimates of GPP were not significantly different. There was also no significant difference in R as measured by bottle incubations and the delta13C method. However, the delta 13C method does not account for inputs of external carbon which will result in underestimation of R and overestimation of GPP. In systems with significant allochthonous carbon inputs, the delta13C method cannot be accurate unless these inputs are accounted for. The delta18O method was used to measure metabolic parameters of twenty-one northern temperate lakes and showed GPP dominated over R during the ice-free season. GPP and R were most strongly correlated with lake temperature, which in turn is a function of the amount of solar radiation received by the lake. Our results imply that it is this solar radiation that drives planktonic gross primary productivity, which in turn drives the majority of planktonic respiration. Variation in dissolved organic carbon only explained 8% of the variation in planktonic R, while variation in planktonic GPP explained approximately 80% of the variation in planktonic R. Despite general autotrophy in the lakes, they were generally oversaturated in CO2 during the ice-free season, on average 252+/-25%. However, we found little evidence to conclude that this was the result of an excess of in situ respiration over production. The magnitude of the annual excess of R over GPP was not sufficient to account for the flux to the atmosphere. Moreover, carbon evasion was not a function of respiratory flux, nor did the isotopic signature of dissolved CO2 in the lakes present evidence of respiration. Groundwater inputs of carbon dioxide represent a plausible source for carbon dioxide oversaturation in some but not all of the lakes sampled.

The biogeochemical behaviour of plutonium and americium was investigated in contaminated soils from the UK to help determine possible remediation and management options. Stimulating anoxic sediments from Aldermaston, through the addition of a carbon substrate (glucose), induced reducing conditions resulting in a negligible change in Pu mobility. This was despite a substantial shift in the bacterial profile from a diverse community to one dominated by fermentative Beta proteobacteria and Clostridia. The latter group also includes organisms associated with metal reduction, such as close relatives to Clostridium species, reported previously to facilitate the reduction of Pu(IV) to Pu(III). A sequential extraction was performed on soils from Aldermaston and the Esk Estuary to identify which selected fractions the Pu and Am are most strongly associated with. The majority of Pu was associated with the 'residual fraction': 63.8 – 85.5 % and 91.9 – 94.5 % in the Aldermaston and Esk Estuary soils respectively. Metals associated with this fraction are highly recalcitrant and are unlikely to be released into solution over a significant time span under most geological conditions. The Am was more evenly distributed with the 'organic fraction' being the most dominant. Degradation of organic matter under oxidising conditions may result in mobilization of metals associated with this fraction. The Aldermaston soil was also subjected to bioleaching using a sulfuric acid producing microbial community, which resulted in a maximum 0.18 % of Pu released into solution. However, up to 12.5% of Am was found in solution suggesting Am is more susceptible to mobilization than Pu. The potential for Pu mobilization through abiotic oxidative leaching was investigated using permanganate. Even when carbonate was added to act as a potential complexant for the Pu, less than 1% of the Pu was leached. Greater success was observed when leaching was attempted using citric acid; an estimated 25 – 30% of Pu was released into solution offering a potential route for remediation of Pu-contaminated soils. These data would suggest that the Pu is highly recalcitrant, and may exist in a small particulate form in the Aldermaston soils, possibly in the oxide form, and is unlikely to mobilize under natural biogeochemical conditions.

Calcareous wetlands are rare in New England due to the limited occurrence of limestone-rich bedrock. Because of their great floristic diversity and their support of numerous rare and uncommon plant species, these habitats are targeted for conservation. Little is known about the intricate workings of these ecosystems. This research contributes significantly to understanding the complex biogeochemical relationships that exist between the plant and soil systems in calcareous freshwater wetland environments as a whole. A 3-year field study was initiated in May 1996, to collect data on soils, geochemistry, and hydrology along a 250-m-long transect. Monitoring was concentrated within the rooting zone. Field monitoring and water sampling were conducted biweekly across three growing seasons. Measurements were made for soil-water pH, conductivity, total iron, alkalinity and several dissolved metals. Strong seasonal patterns were observed for several parameters including calcium and iron. Seasonal changes in geochemistry were evaluated using Solmineq.88, a thermodynamic model. In July 1997, soils were sampled adjacent to each replicate instrumentation cluster and standard analyses conducted. Significant differences were measured between the stations for pH, cation exchange capacity, exchangeable calcium, phosphorus, manganese, and biologically available iron. A detailed vegetation analysis was completed in July 1997. High species richness and turnover were measured across the site. Ordination and cluster techniques were used to analyze the vegetation patterns and relate these to environmental site variables. The ordinations suggest that gradients in both soil chemistry (e.g., pH, exchangeable calcium, phosphorus, and iron) and geochemistry (e.g., pH and dissolved calcium) may have strong influences on the vegetation patterns observed in this study. These research results will serve as a baseline for the geochemistry in the greater watershed region, representing a relatively undisturbed system. No fen studies currently exist (for any geographical region) that monitored soil and geochemical parameters throughout the growing season. This research demonstrates the importance of seasonal sampling to describe the cycles present in site biogeochemistry accurately, and it defines several geochemical parameters that strongly influence plant species occurrence and distribution within these environments. This detailed analysis provides valuable information for conservation managers seeking to identify areas for future conservation, preservation, or restoration efforts.

The fungicide chlorothalonil (1,3-tetrachloroisophthalonitrile) is widely used in cranberry production in Massachusetts. Its partition constant, $\rm K\sb{DOC},$ with aquatic humic substances isolated from cranberry bog water was assessed in this study. Elemental analysis of humic substances indicated differences in C, H, N, and O that were consistent with published elemental ratios of aquatic humic substances. Infrared spectra were also similar with respect to C=O stretching of carboxyl and ketonic groups and showed evidence of aromatic C=C stretching. Ultrafiltration of humic acids showed 53% greater than 10,000 molecular weight cut off (MWCO). The fulvic acid fraction had 71% less than 10,000 MWCO. UV absorbance ratios at 400 and 254 nm were 0.23 and 0.16 for humic and fulvic acid, respectively indicating a more aromatic structure than Aldrich humic acid from soil. Base titration showed a charge at pH 8 of 7.5 and 13 meq g-$\rm C\sp{-1}$ for humic and fulvic acid, respectively. Measurements of the TCIN Henry's constant were made using gas-purge techniques. The value obtained, $5 \times 10\sp{-5}$ kPa $\rm m\sp3$ $\rm mol\sp{-1}$ (s = $1.7 \times 10\sp{-5},$ n = 4), was consistent with calculated values from solubility and vapor pressure. Log $\rm K\sb{DOC}$ values for fulvic and humic acid measured using gas-purge techniques were 4.3 (s = 0.6) and 4.5 (s = 0.8), respectively. These values were greater than reported $\rm K\sb{OC}$ values by as much as 1.5 orders of magnitude, suggesting that $\rm K\sb{OC}$ values may underestimate TCIN solubility enhancement in cranberry bog water. TCIN binding to aquatic humic substances corresponds to increased solubility in aqueous systems and potentially toxic levels in the presence of sorbent. Solubility in water, based on the measured $\rm K\sb{DOC}$ values, could increase by 200% with waters containing 35 mg $\rm l\sp{-1}$ DOC. Measured DOC of cranberry bog waters was in the 1 to 30 mg $\rm l\sp{-1}$ range.

Atmosphere-biosphere exchange plays a key role in the global cycles of water and carbon. Air pollution can alter these processes and induce climate perturbations and feedbacks. Surface ozone (O3) is an air pollutant and greenhouse gas that is toxic to plants, reducing their growth and ability to regulate water loss. Past controlled experiments have shown that O3 degrades a plant's water-use efficiency (WUE), which is the ratio of carbon uptake in photosynthesis to water loss in transpiration. This has potentially significant implications for terrestrial water cycle and precipitation, but no studies have evaluated the O3 effect on WUE in complete ecosystems. We aim to quantify the impact of O3 on WUE across a wide array of ecosystems. Meteorological and biological data was obtained from 23 FLUXNET flux tower sites, which use the eddy covariance method to derive hourly fluxes of carbon dioxide (CO2), water vapor (H2O), and O3 between the atmosphere and ecosystem. Across a broad range of sites, we find a significant negative relationship between daily anomalies of stomatal O3 flux (FS, O3) and WUE that explains 1-3% of WUE variability. The largest impacts occur in locations and species with high stomatal conductance, such as broadleaf forests, humid climates, or irrigated crops, rather than where surface O3 concentrations are highest. Past long-term studies have also found similar O3 impacts (1-3%) on WUE, indicating a consistent response across a pool species and ecosystems. / A Thesis submitted to the Department of Earth, Ocean, & Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / Spring Semester 2016. / March 23, 2016. / Ecosystems, FLUXNET, Natural environments, Stomatal ozone flux, Water-use efficiency / Includes bibliographical references. / Christopher D. Holmes, Professor Directing Thesis; Stephanie Pau, Committee Member; Vasu Misra, Committee Member; Jon Ahlquist, Committee Member.