This thesis describes studies and research conducted as part of the development, standardization, and validation of a new laboratory protocol for measuring the bioaccumulation of sediment-associated contaminants in freshwater organisms. The test species used in this method are the oligochaete Lumbriculus variegatus, the mayfly nymph Hexagenia spp., and the juvenile fathead minnow Pimephales promelas. Bioaccumulation methods in the literature were critically reviewed to properly guide the development and standardization of methods. This enabled data gaps to be addressed and the conditions and exposure techniques of the new method to be standardized, properly justified, and based on experimental evidence. Method development included the investigation of the effect of the density of organisms on bioaccumulation in the three test species. The importance of standardizing loading density to total organic carbon (TOC) in sediment was demonstrated, as was the appropriateness of using a ratio of TOC to organism dry weight of 27:1 as a standard loading density for the different test species. To validate the new method and assess the relative effectiveness of the three test species for accumulating different contaminants, a variety of field-contaminated sediments were tested, representing a range of contaminants, levels of contamination, and physical properties of sediment. It was observed that differences in bioaccumulation between the three species may, but do not always, exist, and can vary with contaminant and sediment type. It was also demonstrated that estimates of bioaccumulation, such as biota-sediment accumulation factors (BSAFs), can be species- and site-specific, supporting the need and use of standardized bioaccumulation methods and test species to facilitate comparisons across sites or over time. Comparisons of laboratory- and field-based estimates of bioaccumulation further validated the new laboratory method. Good agreement was observed between laboratory and field estimates for fish, while bioaccumulation was higher in laboratory-exposed invertebrates compared to mussels caged in situ. The laboratory method generally overestimated the relative bioavailability of contaminants compared to the field, but provides a conservative estimate of bioaccumulation. A kinetic study investigated the uptake and elimination of PCBs in the three test species and demonstrated that a 28-d test duration was a sufficient standard for both invertebrate species to reach steady-state concentrations. There was conflicting evidence of whether steady-state concentrations were truly reached in the fish and uncertainty remains as to the appropriateness of a 28-d test for these organisms, for which additional testing is necessary.

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A study of suspended sediment transport dynamics was undertaken in the West River at Cape Bounty, Melville Island, Nunavut. Hydrometerological conditions and sediment transport were measured over three seasons in order to characterize suspended sediment transport and grain size characteristics in relation to catchment and channel snowpack. Catchment snow water equivalence was measured at the beginning of the season, and discharge, suspended sediment concentration (SSC) and grain size were measured at high temporal resolution through the runoff period to evaluate diurnal-, event- and seasonal-scale discharge-suspended sediment and grain size hysteresis. In addition, two models of a time-integrated suspended sediment trap, modified from Philips et al. (2000), were deployed in both streams to assess the representativeness of the captured sediment. The West stream discharge was dominated by the snowmelt peak in all three seasons. From 54-96% of suspended sediment was transported during this short period, although hysteresis relationships indicate that delivery of sediment and water were not synchronous and interannual relationships suggest disproportionate increases in sediment discharge with increased catchment snowpack. Clockwise and counter-clockwise suspended sediment hysteresis relationships were apparent and associated with lesser and greater snowpack, respectively. Additionally, grain size hysteresis suggested variable sediment sources during the season. Assessment of the time-integrated suspended sediment trap in the East and West streams illustrated that the captured material was not representative of the ambient stream conditions. Captured mass was typically two orders of magnitude less than expected iii capture rates (<1%) and that the captured sediment was significantly coarser than the ambient stream suspended sediment load. Investigations of suspended sediment transfer in this small, High Arctic catchment reveal that sediment transport increased with increased catchment snowpack, but delivery of water and sediment were not synchronous during the nival discharge event suggesting changing sediment accessibility during the season. An attempt to collect a time-integrated suspended sediment sample that would incorporate variability in the character and magnitude of sediment delivery provided an unrepresentative sample, but results indicate that a detailed examination of hydraulic relationships between the trap and ambient conditions could ultimately lead to the development of a more representative trap. / Thesis (Master, Geography) -- Queen's University, 2007-09-16 10:03:25.925

Using a sediment budget approach, suspended sediment transport dynamics were studied over the 2010 summer runoff season in the 8 km2 West River catchment at the Cape Bounty Arctic Watershed Observatory (CBAWO), Melville Island, Nunavut. Research was carried out in an effort to determine the longer term impacts and response of recent (2007-8) active layer detachments (ALD) on the river system. In 2010, measured ALD inflows contributed 4.7% of the measured sediment yield, a decrease of 13.3% from 2007 when they initially formed. This indicates that while they continue to supply sediment to the main river, the impact they have on sediment fluxes, and hence the sediment budget has diminished, with time. Results from the sediment budget indicate that connectivity and the sediment delivery ratio within the system have also decreased with time. Sediment budget analysis shows that in response to this additional sediment, the West River progressively stores more sediment throughout the season, storing as much as 85% of sediment inflows during baseflow. Sediment was preferentially deposited within the channel, with coarser material deposited in the upper reaches, and finer material deposited in the lower reaches. Similarly, the transported and stored sediment became progressively finer with time, indicating the importance that river competence and wetted perimeter have on sediment transport as the larger sediment was entrained earlier in the season under higher flow conditions when the sediment was accessible, and finer sediment transported later in the season due to decreased competence and reduced accessibility of sediment. This sediment storage is expected to replenish sediment in the channel that is eroded during peak discharge in spring, and also dampens the effects that disturbances have on the sediment budget through storage. Sediment stored in the channel towards the end of the season does not contribute to sediment yield and may prove to be an important source of sediment in future years under late summer rainfall events. / Thesis (Master, Geography) -- Queen's University, 2011-12-08 16:31:48.633

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Mercury-contaminated sediments are found in many locations throughout North America and the world. Release of Hg from such sediments and subsequent biological uptake can result in biomagnification in associated ecosystems. This study focused specifically on a stabilization technique involving the addition of reactive media to the sediment matrix to immobilize Hg and reduce its bioavailability. A series of batch and column experiments was conducted over a range of physical and geochemical conditions to evaluate the propensity of a diverse set of reactive media to stabilize Hg in sediment with high organic carbon and clay content. The additives, selected to promote adsorption and precipitation of Hg, included natural attapulgite (palygorskite) clay, organically-modified clay, elemental sulfur, a strong reductant, and mixtures thereof. The results of the batch experiments indicated that addition of reactive media to the sediment led to substantially lower aqueous concentrations of Hg relative to untreated sediment. The stabilization of Hg was observed to be dependent on mass of added reagent, with generally greater treatment observed for the higher masses of reagent evaluated. Aqueous concentrations of Hg were reduced from > 800 ng L-1 in control samples to < 50 ng L-1 in treated samples for all of the reactive media at the highest mass proportions evaluated. The effectiveness of Hg stabilization using the sulfur-based blends was strongly affected by contact with atmospheric oxygen, with better treatment observed in oxygen-limited conditions. The results of the column tests showed that relatively low concentrations of Hg (< 50 ng L-1) were leached from untreated sediment, maintained under anoxic conditions, with steadily percolating water. However, increased concentrations of Hg (> 200 ng L-1) were observed in column effluent collected from the untreated sediment following flow interruption. This release of high concentrations of Hg was not observed for the columns containing treated sediment after stagnation. Particularly low Hg concentrations were maintained in effluent collected from the sulfur-based treatment mixtures (< 40 ng Hg L-1) for the entirety of the experimental duration, regardless of flow perturbations.

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