The effect of dietary glycosylated vitamin B-6 on the bioavailability of vitamin B-6 was determined in 4 women. A 44-d metabolic-balance diet study was divided into a preliminary 8-d adjustment period followed by two 18-d experimental periods. The subjects were divided into two groups in a crossover design to compare the effect of low- and high-glycosylated vitamin B-6 diets on the bioavailability of vitamin B-6. The total vitamin B-6 content in the low- and high-glycosylated vitamin B-6 diets was 1.506 mg (8.91 nmol) and 1.897 mg (11.22 μmol), respectively, in which 11 and 22% was the glycosylated form, respectively. Daily 24-h urine specimens were collected by each subject throughout the study; 7- or 8-d fecal collections were made at the end of each experimental period. The four subjects' mean urinary total vitamin B-6 excretion during the low- and high-glycosylated vitamin B-6 periods was 0.76 ± 0.20 and 0.67 ± 0.06 μmol/24 h, respectively; fecal total vitamin B-6 excretion was 2.98 ± 0.43 and 4.56 ± 0.87 μmol/24 h, respectively. Expressed as % of total vitamin B-6 intake, the mean urinary total vitamin B-6 excretion was lower during the high-glycosylated vitamin B-6 period (6.0 ± 0.8%) than during the low-glycosylated vitamin B-6 period (8.5 ± 2.4%); in contrast, their mean fecal vitamin B-6 excretion during the high-glycosylated vitamin B-6 period (40.7 ± 8.2%) was greater than the low-glycosylated vitamin B-6 period (33.6 ± 5.4%). In addition, approximately 11% of ingested glycosylated vitamin B-6 was excreted in urine. These results suggest that dietary glycosylated vitamin B-6 is not completely bioavailable to humans, and the extent of its utilization is not affected by dietary glycosylated vitamin B-6 intake. / Graduation date: 1993

Master of Science / Department of Animal Sciences and Industry / Barry J. Bradford / Dairy cows undergo many homeorhetic adaptations during the transition to lactation. Although many of the physiological processes - including increased lipolysis and postpartum inflammation - are adaptive, exaggerated responses can contribute to metabolic disease and reduced milk production. L-carnitine has been shown to increase hepatic oxidation of fatty acids and reduce hepatic lipid accumulation in early lactation cows; however, L-carnitine is degraded in the rumen. An experiment using 4 ruminally-cannulated Holstein heifers in a split plot design demonstrated that the relative bioavailability of L-carnitine was greater when delivered abomasally than ruminally. There was a dose × route interaction and a route effect for increases in plasma carnitine above baseline, with increases above baseline being greater across all dose levels (1, 3, and 6 g L-carnitine/d) when infused abomasally compared to ruminally. A second experiment used 56 lactating Holstein cows in a randomized complete block design to evaluate 2 rumen-protected products (40COAT and 60COAT) compared to crystalline L-carnitine at doses targeting 3 and 6 g/d carnitine. Although crystalline and 40COAT were effective in linearly increasing carnitine concentrations, only subtle responses were seen for the 60COAT, which were less than that for crystalline carnitine in plasma, milk, and urine. Ineffectiveness of rumen-protected products to increase carnitine concentrations beyond crystalline may have been due to over-encapsulation that hindered liberation of the carnitine and its absorption in the small intestine. Although L-carnitine has the potential to reduce postpartum hepatic lipidosis, effective rumen protection of L-carnitine while maintaining intestinal availability needs further investigation. Plant polyphenols have anti-inflammatory properties and when administered during the transition period, have been shown to increase milk production. An experiment used 122 multiparous Holstein cows in a randomized block design to determine the effect of short term (5-d; SBE5) and long term (60-d; SBE60) administration of Scutellaria baicalensis extract (SBE)on whole-lactation milk yield, 120-d milk component yield, and early lactation milk markers of inflammation. Whole-lactation milk yield was increased for SBE60 compared to control, but was not different for SBE5 compared to control. Greater total pellet intake, milk lactose yield, and reduced SCC during wk 1-9 for SBE60 compared to control, all could have contributed to the observed sustained increase in milk yield. Milk production parameters were not different for SBE5 compared to control. No treatment effects were observed for BCS or milk markers of inflammation (haptoglobin) and metabolic function (β-hydroxybutyrate). Overall, long term administration of S. baicalensis effectively increased milk production, however the mechanism by which this was achieved is unknown. Although routes of administration to effectively achieve their physiological responses were different between L-carnitine (abomasal delivery) and SBE (feeding), both bioactive nutrients can improve the metabolic function of early lactation dairy cows.

Master of Science / Department of Human Nutrition / Weiqun Wang / Anthocyanins may prevent chronic diseases such as cancer and cardiovascular disease, however, the anthocyanin metabolites are not well elucidated. We previously selected a purple-fleshed sweet potato clone P40 that contained anthocyanins at up to 7.5 g/kg dry matter, most of which are cyanidin and peonidin derivatives. The main objective of this study is to identify anthocyanin metabolites in the mice fed 20-30% of purple sweet potato P40 (287 mg and 430 mg peonidin-3-glucoside equivalent /kg body weight) diet for 6 weeks. Plasma, liver, and feces were analyzed for anthocyanin metabolites using HPLC/MS and MALDI-TOF-MS. Fifteen hours after consumption of P40 diet, we identified 4 anthocyanin metabolites cyanidin 3,5- diglucoside; cyanidin 3-sophoroside-5-glucoside; cyanidin3-p-hydroxybenzoylsophroside-5-glucoside; and peonidin 3-p-hydroxybenzoylsophroside-5-glucoside in fecal samples. No anthocyanin metabolites were detected in plasma or liver extracts by HPLC/MS or MALDI-TOF-MS. The results indicate that anthocyanin metabolites in fecal samples might provide health benefits for colonic mucosal cells. However, the lack metabolites in both plasma and liver samples suggest a continuous intake of the anthocyanins may be required for systemic benefits due to their quick degradation and low bioavailability.

Wong, Man Wing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 173-188). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgements --- p.v / Table of Contents --- p.vii / List of Tables --- p.xi / List of Figures --- p.xiii / List of Plates --- p.xv / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Definition of Rare earth elements --- p.1 / Chapter 1.2 --- Discovery of REEs --- p.5 / Chapter 1.3 --- Physical and chemical properties of REEs --- p.6 / Chapter 1.4 --- Abundance of REEs on earth --- p.10 / Chapter 1.4.1 --- Bastnasite --- p.11 / Chapter 1.4.2 --- Monazite --- p.14 / Chapter 1.4.3 --- Xenotime --- p.16 / Chapter 1.5 --- Reserves and resources --- p.16 / Chapter 1.5.1 --- World reserves --- p.16 / Chapter 1.5.2 --- REE resources in China --- p.18 / Chapter 1.6 --- Production and demand of REEs --- p.20 / Chapter 1.6.1 --- Production and demand in US --- p.21 / Chapter 1.6.2 --- Production and export in China --- p.23 / Chapter 1.6.3 --- Production in other countries --- p.24 / Chapter 1.7 --- Separation of REEs --- p.24 / Chapter 1.7.1 --- Classical methods --- p.24 / Chapter 1.7.2 --- Modern methods --- p.25 / Chapter 1.7.2.1 --- Ion exchange separation --- p.25 / Chapter 1.7.2.2 --- Solvent extraction --- p.25 / Chapter 1.8 --- Applications --- p.26 / Chapter 1.8.1 --- Alloys --- p.26 / Chapter 1.8.2 --- Permanent magnets --- p.28 / Chapter 1.8.3 --- Catalysts --- p.29 / Chapter 1.8.4 --- Glass additives --- p.30 / Chapter 1.8.5 --- Phosphors in television screens and similar fluorescent surfaces --- p.31 / Chapter 1.8.6 --- Fertilizers and feed additives --- p.32 / Chapter 1.9 --- REEs in the environment --- p.33 / Chapter 1.9.1 --- REEs in soil --- p.33 / Chapter 1.9.2 --- REEs in plants --- p.35 / Chapter 1.10 --- Overview of toxicological studies of REEs --- p.36 / Chapter 1.11 --- Current study --- p.38 / Chapter 1.11.1 --- Thesis outline --- p.3 8 / Chapter 1.11.2 --- Objectives --- p.38 / Chapter 1.11.3 --- Significance --- p.39 / Chapter Chapter 2 --- Phytotoxicity of rare earth elements / Chapter 2.1 --- Introduction --- p.41 / Chapter 2.1.1 --- Ecotoxicity of REEs --- p.41 / Chapter 2.1.2 --- Toxicity tests using higher plants --- p.43 / Chapter 2.1.3 --- Advantages of seed germination and root elongation test --- p.44 / Chapter 2.1.4 --- Selection of species --- p.46 / Chapter 2.1.5 --- Endpoint of test --- p.47 / Chapter 2.1.6 --- Median effect estimates --- p.50 / Chapter 2.1.7 --- Objective --- p.50 / Chapter 2.2 --- Materials and methods --- p.50 / Chapter 2.2.1 --- Test species --- p.51 / Chapter 2.2.2 --- Test chemicals --- p.51 / Chapter 2.2.3 --- Range finding test --- p.51 / Chapter 2.2.4 --- Definitive test --- p.52 / Chapter 2.2.5 --- Statistical analyses --- p.52 / Chapter 2.3 --- Results --- p.53 / Chapter 2.3.1 --- Range finding test --- p.53 / Chapter 2.3.2 --- Definitive test --- p.53 / Chapter 2.3.2.1 --- Germination rate --- p.53 / Chapter 2.3.2.2 --- Root length --- p.55 / Chapter 2.3.2.3 --- Germination index --- p.58 / Chapter 2.3.3 --- The median effective concentration --- p.61 / Chapter 2.4 --- Discussion --- p.62 / Chapter 2.4.1 --- Dose-response curves of REEs --- p.62 / Chapter 2.4.2 --- Relative toxicity of the four REEs --- p.63 / Chapter 2.4.3 --- Mechanism of effect of REEs on seed growth --- p.67 / Chapter 2.4.4 --- Comparison between different endpoints --- p.68 / Chapter 2.4.5 --- Comparison between different species --- p.70 / Chapter 2.4.6 --- Limitations and improvement --- p.71 / Chapter 2.4.7 --- Methods of measuring root length --- p.72 / Chapter 2.5 --- Conclusions --- p.73 / Chapter Chapter 3 --- Growth of tree seedlings in soil treated with rare earth elements / Chapter 3.1 --- Introduction --- p.75 / Chapter 3.2 --- Materials and methods --- p.77 / Chapter 3.2.1 --- Soil --- p.77 / Chapter 3.2.2 --- Tree seedlings --- p.77 / Chapter 3.2.3 --- REEs --- p.78 / Chapter 3.2.4 --- Greenhouse experiment --- p.78 / Chapter 3.2.5 --- Soil analysis --- p.80 / Chapter 3.2.5.1 --- Initial properties --- p.80 / Chapter 3.2.5.2 --- Post harvest analysis --- p.81 / Chapter 3.2.6 --- Plant analysis --- p.83 / Chapter 3.2.7 --- Statistical analysis --- p.83 / Chapter 3.3 --- Results --- p.84 / Chapter 3.3.1 --- Growth --- p.84 / Chapter 3.3.1.1 --- Height --- p.84 / Chapter 3.3.1.2 --- Basal diameter --- p.87 / Chapter 3.3.1.3 --- Biomass --- p.89 / Chapter 3.3.1.4 --- Standing leaf number --- p.92 / Chapter 3.3.1.5 --- Chlorophyll fluorescence --- p.95 / Chapter 3.3.2 --- Tissue contents --- p.97 / Chapter 3.3.2.1 --- REEs concentrations --- p.97 / Chapter 3.3.2.2 --- Nitrogen concentrations --- p.99 / Chapter 3.3.2.3 --- Phosphorus concentration --- p.101 / Chapter 3.3.2.4 --- Mineral concentrations --- p.102 / Chapter 3.3.3 --- Soil --- p.104 / Chapter 3.3.3.1 --- Initial properties --- p.104 / Chapter 3.3.3.2 --- REEs concentrations --- p.106 / Chapter 3.3.3.3 --- Nitrogen and phosphorus concentrations --- p.107 / Chapter 3.3.3.4 --- Mineral concentrations --- p.109 / Chapter 3.4 --- Discussion --- p.110 / Chapter 3.4.1 --- Effects of REEs on growth --- p.110 / Chapter 3.4.2 --- Mechanisms of the effect of REEs --- p.112 / Chapter 3.4.3 --- Nutrient uptake --- p.114 / Chapter 3.4.4 --- Soil nutrient contents --- p.116 / Chapter 3.4.5 --- Comparison between REEs --- p.118 / Chapter 3.4.6 --- Comparison between species --- p.121 / Chapter 3.5 --- Conclusions --- p.123 / Chapter Chapter 4 --- Bioavailability and accumulation of rare earth elements / Chapter 4.1 --- Introduction --- p.124 / Chapter 4.2 --- Materials and Methods --- p.126 / Chapter 4.2.1 --- Soil --- p.126 / Chapter 4.2.2 --- Tree seedlings --- p.126 / Chapter 4.2.3 --- Pot experiment --- p.127 / Chapter 4.2.4 --- Chemical speciation of soil --- p.129 / Chapter 4.2.5 --- Statistical analysis --- p.130 / Chapter 4.3 --- Results --- p.130 / Chapter 4.3.1 --- Plant performance --- p.130 / Chapter 4.3.2 --- Tissue contents of La --- p.144 / Chapter 4.3.3 --- Soil --- p.144 / Chapter 4.3.3.1 --- Soil final pH --- p.146 / Chapter 4.3.3.2 --- Soil La contents --- p.146 / Chapter 4.3.4 --- "Association between pH, organic matter and La contents in soil and plant" --- p.149 / Chapter 4.4 --- Discussion --- p.151 / Chapter 4.4.1 --- Growth performance of tree seedling on different soil conditions --- p.151 / Chapter 4.4.2 --- Comparison between growth parameters --- p.152 / Chapter 4.4.3 --- Speciation in soils --- p.154 / Chapter 4.4.4 --- Bioavailability of REEs in soil --- p.155 / Chapter 4.4.5 --- Factors affecting bioavailability of REEs --- p.158 / Chapter 4.4.6 --- Distribution of REEs in plants --- p.162 / Chapter 4.5 --- Conclusions --- p.165 / Chapter Chapter 5 --- General conclusions --- p.167 / Chapter 5.1 --- Summary of major findings --- p.167 / Chapter 5.2 --- Suggestions for further investigation --- p.171 / References --- p.173

Purpose: The aim of this study was to investigate the usefulness of formulation approaches to minimise injection site reactions for poorly soluble drugs. The specific objectives were to modify the injection site reactions by identification of irritant components in the formulation and control of their release kinetics; and to gain understanding of formulation approaches to create a favourable microenvironment in the tissues allowing better tissue tolerance and drug absorption. Methods: Physicochemical properties of the model drug, ricobendazole (RBZ) were characterised using conventional methods. Three formulation approaches to minimise irritancy of the low pH RBZ solution were assessed. An in vitro method using 96-well microplates and a microtiter plate reader was used for detection of drug precipitation on dilution for formulation characterisation. Cellular damage by the formulations was investigated in L929 fibroblasts using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxy phenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) and lactate dehydrogenase (LDH) assays. Tissue tolerance and pharmacokinetics were simultaneously investigated after subcutaneous injection in sheep. A low pH RBZ solution was used as a reference formulation. Results: Preformulation studies showed that RBZ was practically insoluble in water and oils, and was slightly soluble in commonly used co-solvents. Solubility was slightly improved by complexation with hydroxypropyl-β-cyclodextrin (HP-β-CD, K₁:₁ = 311 M⁻�) or a combination of low pH (> 2) with surfactants or co-solvents. A U-shaped pH-solubility profile in aqueous solutions indicated that RBZ is an ampholyte. pKa values measured by absorbance spectroscopy and pH solubility methods were 3.45 and 3.76 (basic) and 9.82 and 9.53 (acidic) respectively. The partition coefficient was 14.3 - 15.2 at pH 6 - 9 and less at higher or lower pH. In aqueous solutions, RBZ showed a V-shaped pH-degradation rate profile and was most stable at pH 4.8. Degradation pathways were identified as hydrolysis and oxidation. Three RBZ injectables (5%) were obtained by modification of the low pH RBZ solution; addition of 20% HP-β-CD, incorporation into a w/o emulsion, and a microemulsion (ME). On dilution with SPB, the onset time of drug precipitation was prolonged and the rate was reduced in the presence of HP-β-CD. The w/o emulsion had a low viscosity (< 60 mPa.s) and exhibited Newtonian flow. Drug release versus the square root of time was linear and the release rate could be adjusted by phase ratio and droplet size. Drug release was found to be by diffusion. A coarse emulsion layer appeared at the interface between the ME and buffer. Drug release from the ME was faster than from the emulsion and was linear with the square root of time. On titration into SPB, the three formulations showed controlling effects on the release of H₃O⁺ compared to the reference formulation. RBZ (0.1 mg/ml) was more toxic to L929 cells than the co-solvent propylene glycol (50 mg/ml). The formulations showed greater cytotoxicity than their vehicles in the order: ME > RBZ solution = emulsion > HP-β-CD. HP-β-CD and emulsion excipients showed little or no cytotoxicity. The MEs exhibited more toxicity in the LDH assay than in the MTS assay. A reversed phase HPLC assay for simultaneous determination of RBZ and its metabolite in sheep plasma using an isocratic system with UV detection was developed and used in the pharmacokinetic studies. Plasma samples were prepared by solid phase extraction. A suitable internal standard was selected by quantitative structure-retention relationships analysis. The composition of a ternary mobile phase was optimised with the assistance of multiple linear regression. The assays were linear over the concentration range 10 - 1000 ng/ml for both analytes (r > 0.999) with satisfactory inter-day and intra-day precision and accuracy (CV < 10%). The recoveries for all analytes were > 96%. A pilot study in sheep suggests that injection of the vehicles (the CD, emulsion and ME) caused virtually no pain on injection or site reactions. Both the reference formulation and its vehicle induced pain on injection and resulted in swollen tissues. Histology after two weeks showed granulation for the formulation, but not the vehicle. In contrast, animals showed virtually no injection site reactions with the ME and emulsion. The HP-β-CD formulation gave transient pain on injection but a two-fold increase in bioavailability compared with the reference. The emulsion produced sustained drug release and increased drug absorption. In the main study, the HP-β-CD vehicle showed good tissue compatibility. Irritation by the HP-β-CD formulation was attributed to the low pH. Cmax, tmax and AUC0-[infinity] for the reference formulation were 1.3 � 0.3 [mu]g/ml, 9.6 � 2.9 h and 36.7 � 9.2 [mu]g�h/ml respectively, while the corresponding data for the HP-β-CD formulation were 2.9 � 0.8 [mu]g/ml, 5.0 � 0.6 h and 54.5 � 15.3 [mu]g�h/ml respectively. The half-life following the injection of the HP-β-CD formulation (5.5 � 2.8 h) was shorter than that of the reference formulation (8.5 � 3.4 h). Conclusions: Injection site reactions may be minimised by identification of irritant components in a formulation and by controlling their release. Controlling the burst release of the poorly water soluble drug RBZ in a low pH solution could improve tissue tolerance and minimise post-injection precipitation, and hence increase drug bioavailability. In addition, HP-β-CD was a useful local injectable carrier which significantly enhanced the absorption of RBZ after subcutaneous injection in sheep.

Current recommendations for amino acid intake during pregnancy are for a constant amino acid intake throughout. However, the demand for amino acids changes from maternal tissue growth in early gestation to fetal, conceptus and mammary tissue development in late gestation. The availability of amino acids from feed ingredients are based on growing pig data, although recent evidence suggests that mature animals have a greater capacity to digest and absorb amino acids. Therefore, this thesis investigated the threonine requirement of sows in gestation and the availability of threonine (Thr) in common feed ingredients fed directly to sows using the indicator amino acid oxidation technique. The Thr requirement in early gestation was determined to be 5.0 to 6.0 g/d, at least 40% below current recommended Thr requirements, whereas the requirement for Thr in late gestation was determined to be 12.3 to 13.6 g/d, close to 30% above current recommendations. These results suggest that current sow feeding recommendations (i.e. constant level of AA throughout gestation) result in over- and under-feeding AA in early and late gestation, respectively. The metabolic availability of Thr in corn and barley fed to growing pigs was 82.2 and 115.3%, respectively, whereas when fed to pregnant sows, the metabolic availability of Thr in corn and barley was 88.0 and 89.3%, respectively. The > 100% availability of Thr from barley was likely due to the effect of barley on the demand for Thr for production of mucin and mucous proteins. The results indicate that the availability of amino acids from feed ingredients is greater when fed to sows than when fed to growing pigs. In conclusion, current sow amino acid requirement recommendations do not appropriately reflect actual amino acid demand during pregnancy. The deficiency in dietary amino acids during late gestation may result in maternal lean tissue catabolism to support fetal growth. The greater availability of amino acids from feed ingredients in sows may reduce the degree of amino acid deficiency in late gestation under current feeding programs. Application of phase feeding sows during pregnancy will more closely meet the demand for amino acids and may improve sow reproductive longevity. / Nutrition and Metabolism

Colloidal macromolecular organic matter (COM), which makes up a large portion of the bulk dissolved organic matter (DOM) in marine environments, has the capability to modify the bioavailability of potentially toxic metals to aquatic organisms. In order to better understand the bioavailability of some of these metals to estuarine bivalves, American Oysters (Crassostrea virginica) were exposed to different types of natural colloidal (COM) and model (alginic acid, carrageenan, and latex particles) organic biopolymers, tagged with gamma-emitting radioactive metal ions (110mAg, 109Cd, 57Co, 51Cr, 59Fe, 203Hg and 65Zn) or 14C (to sugar OH groups). Natural COM was obtained from Galveston Bay water by 0.5µm filtration, followed by cross-flow ultrafiltration, using a 1kDa ultrafilter, diafiltration and freeze-drying. COM and DOM model compounds were used in the bioavailability experiments at 2 ppm concentrations. Separate 16-hour experiments using varying sizes of latex particles assessed the lowest size of colloids that can be filtered from the water. Results showed that filter-feeding bivalves could efficiently remove particles as small as 0.04µm (40nm) in diameter, with removal halftimes of 2.5 to 5.5 hours, equivalent to filtration rates of about 50±15 ml/hour, or about 3 L d-1 g-1, which are typical values for these oysters. Results of the 20-hour bioavailability experiments demonstrated that oysters could effectively filter metals bound to COM, with the metals bound to alginic acid COM being removed at the highest rates from the water. However, the metals bound to alginic acid were not found in oyster meat in the highest amounts: it was the metals associated with the carrageenan COM. The 14C labeled biopolymer data also showed alginic acid to be removed from the water at the highest rate and, contrary to the metals, was also present in the meat in the greatest amounts. Thus, while previous experiments suggested that the quantity (i.e., concentration) of natural organic matter is important for metal bioavailability, it was shown here that the “quality”, i.e., the type of natural organic matter, is also a factor for controlling bioavailability, removal and incorporation rates of metals to oysters.

Potential arsenic toxicity in different geologic environments is dependent on total arsenic concentration and arsenic bioavailability. It is important to identify the geologic environments that may sequester arsenic because these systems can act as long-term sources for arsenic as well as retard transport and limit toxicity. Bioavailability is defined as the readiness of a compound or element to be taken up by organisms (Gregorich et al., 2001), while potential bioavailability is possible uptake of a compound or element by organisms. The objective of this research is to quantify the potential bioavailability of arsenic in laboratory microcosms and in different geologic environments in the Nueces and San Antonio River Watersheds, Texas, using a chelating resin as an infinite sink. To assess the applicability of chelating resins to estimate potential arsenic bioavailability in the field, iron-loaded DOWEX M4195 resin was used to extract arsenic from solutions and sediments (pond sediment, river sediment, and ephemeral stream sediment). The average percentage of arsenic sorbed from solution was 66% ± 0.16. Competition studies between arsenate, phosphate, and vanadate suggest there is moderate competition, reducing overall arsenic sorption to the resin in the presence of competing ions. Iron-loaded resin was then exposed to sediment samples spiked with increasing amounts of arsenic over 15, 30, 60 and 90 days. Results of the sediment study showed 1) increased arsenic sorption to the resin over time, 2) small variations of potential bioavailable arsenic among geologically different sediments, and 3) evidence of arsenic sequestration. Field devices that housed iron-loaded resin were used to extract potentially bioavailable arsenic from sediment in six different geologic environments (i.e. lake, river, perennial stream, ephemeral stream, pond, and wetland) in the watersheds over a twenty-eight day period. The wetland (15.7 mmol As/g wet resin) and perennial stream sediments (11.0 mmol As/g wet resin) represented the maximal and minimal calculated potential bioavailability, respectively. However, the potentially bioavailable index calculated from mmol As/g wet resin extracted from field environments and mmol As/ g sediment in digested samples showed sequestration would be high in the wetland environment and high bioavailability in the perennial stream and river environments.

Benthic uptake of mercury (Hg) governs bioavailability to fish yet there are still large gaps in our knowledge of what mediates this process. Without this information it is difficult to ascertain where Hg accumulation in the foodweb will be greatest. In the St. Lawrence River Area of Concern (AOC) at Cornwall, one contaminated zone (Zone 1) shows elevated Hg in yellow perch (Perca flavescens) and their prey items compared to those from other zones in the AOC. Greater availability of Hg to benthos due to unique physical features (large deposition of woodfibre deposits) of Zone 1 is hypothesized to account for this observation. In this study, amphipods (Gammarus fasciatus) and (Echinogammarus ischnus) were collected in Zone 1 using artificial substrates between June-September 2007, and Hg concentrations compared to those obtained in sediments and porewaters of surficial sediments, as well as methane gas evasion rates. Methylmercury (MeHg) concentrations in amphipods were significantly related to porewater total Hg (THg) and MeHg concentrations. No parallel relationship was found for sediment Hg concentrations or methane bubbling rates from sediments. Spatial and temporal trends in Hg bioavailability were evident from significant relationships with water column depth and temperature. Water column depth was associated with higher MeHg concentrations in amphipods and porewaters. Concentrations of porewater MeHg were above the detection limit in all of the June samples, the month which also coincided with highest amphipod MeHg concentrations. Finally, sediment organic matter may be influencing patterns of MeHg availability in Zone 1, and displayed a negative relationship to amphipod MeHg. Although bubbling from contaminated sediments did not directly correlate with amphipod Hg uptake, future studies should look at the influence of bubbling on the redistribution of contaminated sediment particles within the zone. / Thesis (Master, Biology) -- Queen's University, 2008-12-30 23:34:20.287

No description available.