In this study, total As (T-As) levels in superpermafrost groundwater at a site in the High Arctic doubled over the course of the summer thaw. This increase was not due to snow input, as levels in snow were negligible. This increase in T-As did not correspond with a decrease in Eh, nor a rise in soluble Fe(II). It did, however, correspond with a shift in As speciation from arsenate to arsenite suggestive of reducing conditions. In the absence of predominant reducing conditions, the highly alkaline nature of the melting snow and concomitant large input of HCO3- may have played an important role in the increase of As in groundwater during the summer thaw. <p>Laboratory studies found that dissolved As (D-As) release under anaerobic conditions depended on the organic matter content of soil, with organic soils releasing D-As under reducing conditions and mineral soils sequestering D-As. In temperate soils, the release of D-As from organic soils is greatly accelerated due to the activity of anaerobic microbes. In northern soils, the same phenomenon may occur, with greater microbiological activity in organic soils where there is more labile C and nutrients than in mineral soil. <p>The sequestration of As in mineral soil is postulated to have occurred due to preferential sorption of arsenite to ferrihydrite or possibly to green rust minerals present under anaerobic conditions. Supporting this, arsenite sequestration occurred to a greater extent compared to arsenate, which is in agreement with the relative affinities of these two species for ferrihydrite. <p>Evidence from this study suggests that the As cycle on Truelove Lowland is dominated by the desorption of As due to HCO3- input each year during the spring melt linked to the sorption of As to ferrihydrite or green rust present in underlying mineral soils. The sequential thawing of the soils active layer and large inputs of HCO3- are unique to northern environments. Thus, this delicate balance of two sorbing processes should be born in mind in northern development. Large inputs of soluble organic matter or nutrients could cause increased solubilization and mobility of D-As during the summer thaw when soils become flooded.

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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

The study of long-term climatic change in the Arctic, a region both particularly sensitive to the effects of a warming climate and an important driver of global climate, is pertinent to understanding the rates and magnitude of current ecosystem changes. Analyses on geological time frames provide insight into the variability of Arctic climate, allowing a contextualized understanding of recent ecosystem changes that have been documented across the Arctic. Lake CF8, a mid-Arctic lake on Clyde Foreland, Baffin Island, contains a unique sedimentary archive of the present and last two interglacial periods, due to past non-erosive glaciation patterns, providing an opportunity to study interglacial climate trends. Diatom assemblages were analyzed through the organic sediment record of the past three interglacials. Trends in the ontogeny of this lake were revealed: the early, post-glacial environment was dominated by species of the colonial Fragilaria genera, which transitioned into high relative abundances of tychoplanktonic Aulacoseira species. Benthic/periphytic taxa, such as Psammothidium marginulatum, tended to increase in relative abundance in the mid- to late-interglacial periods. The ecological interpretation of this pattern is examined in this study, and suggests that climate drives the succession of the diatom community primarily through indirect effects on lake ice and pH. The extent of ice cover likely plays a large role in the biotic community of this lake; the diatom assemblages within the past ~ 50 years indicate increasing littoral habitat complexity with a peak in Eunotia species and a slightly acidic pH, which is discussed in relation to changing habitat availability associated with decreasing ice cover. In-lake production was examined through the use of spectrally-inferred chlorophyll a trends, which also indicate elevated production in the past ~ 50 years. As climate change becomes an increasingly significant threat to the stability of Arctic ecosystems, interest in paleoclimate records that extend into past, non-anthropogenically mediated warm periods, is increasing. This sediment record extends our understanding of past environmental trends beyond the longest records in this part of the Arctic, the Greenland ice core records, and enhances our understanding of the variability of Arctic climate. / Thesis (Master, Biology) -- Queen's University, 2009-05-06 17:04:38.302

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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