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The Global ETD Search service is a free service for researchers
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Showing 1 to 7 of 7 (0.043 seconds)| 1 |
Historical Deposition and Microbial Redox Cycling of Mercury in Lake Sediments from the Hudson Bay Lowlands, Ontario, CanadaBrazeau, Michelle 17 April 2012 (has links)
The repercussions of climate change are felt worldwide, but Arctic and subarctic regions, where climate warming is expected to be amplified, are especially vulnerable. An episode of mass fish mortality in the Sutton River in the Hudson Bay Lowlands (HBL) of Northern Ontario has elicited the interest of the scientific community. Several lakes were sampled over three years in an effort to better understand and document the changes that may be occurring in these lakes.
This study uses sediment cores to assess the history of mercury (Hg) deposition and to assess changes occurring in autochthonous productivity in these lakes. Sediments deposited after the onset of the industrial revolution contained significantly higher concentrations of Hg, with the highest concentrations found in the most recently deposited sediments. Hg concentrations in these pristine lakes rival those of lakes in heavily urbanized areas, indicating that they are in fact subjected to atmospheric deposition of Hg. There was a large variation in [Hg] of the surface sediments of 13 lakes; underscoring the importance of in situ processes in the fate of atmospherically deposited Hg. Methylmercury (MeHg) concentrations were not correlated with total mercury concentrations (THg), demonstrating how THg is a poor predictor of MeHg; the bioaccumulative neurotoxic form of mercury. The S2 fraction of Rock-Eval® Pyrolysis, C:N ratios and ∂13C signatures were used as proxies of autochthonous carbon and all indicated that the lakes have become increasingly productive, presumably due to warmer water temperatures and longer ice-free seasons.
Additionally, I use molecular techniques to detect and quantify the merA gene in the sediment; a proxy of bacterial mercury resistance involved in redox transformations. In Aquatuk, Hawley and North Raft Lakes, I observed a subsurface increase in merA genes in the sediment core, independently of a control gene and the [THg]. While I have not been able to explain the driving variables of this subsurface increase, I believe that the role of merA within remote lake sediments deserves further work.
Lastly, microcosms were used to measure the production of volatile elemental mercury (Hg(0)) from surface sediments of Aquatuk Lake. I used a combination of analytical and molecular techniques to show that the production of Hg(0) is biogenic and tested the effect of nutrients, pH and ionic strength on the Hg(0) production rates. Ionic strength alone had the greatest impact on Hg(0) production rates, with increased Hg(0) production as ionic strength increases.
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Historical Deposition and Microbial Redox Cycling of Mercury in Lake Sediments from the Hudson Bay Lowlands, Ontario, CanadaBrazeau, Michelle 17 April 2012 (has links)
The repercussions of climate change are felt worldwide, but Arctic and subarctic regions, where climate warming is expected to be amplified, are especially vulnerable. An episode of mass fish mortality in the Sutton River in the Hudson Bay Lowlands (HBL) of Northern Ontario has elicited the interest of the scientific community. Several lakes were sampled over three years in an effort to better understand and document the changes that may be occurring in these lakes.
This study uses sediment cores to assess the history of mercury (Hg) deposition and to assess changes occurring in autochthonous productivity in these lakes. Sediments deposited after the onset of the industrial revolution contained significantly higher concentrations of Hg, with the highest concentrations found in the most recently deposited sediments. Hg concentrations in these pristine lakes rival those of lakes in heavily urbanized areas, indicating that they are in fact subjected to atmospheric deposition of Hg. There was a large variation in [Hg] of the surface sediments of 13 lakes; underscoring the importance of in situ processes in the fate of atmospherically deposited Hg. Methylmercury (MeHg) concentrations were not correlated with total mercury concentrations (THg), demonstrating how THg is a poor predictor of MeHg; the bioaccumulative neurotoxic form of mercury. The S2 fraction of Rock-Eval® Pyrolysis, C:N ratios and ∂13C signatures were used as proxies of autochthonous carbon and all indicated that the lakes have become increasingly productive, presumably due to warmer water temperatures and longer ice-free seasons.
Additionally, I use molecular techniques to detect and quantify the merA gene in the sediment; a proxy of bacterial mercury resistance involved in redox transformations. In Aquatuk, Hawley and North Raft Lakes, I observed a subsurface increase in merA genes in the sediment core, independently of a control gene and the [THg]. While I have not been able to explain the driving variables of this subsurface increase, I believe that the role of merA within remote lake sediments deserves further work.
Lastly, microcosms were used to measure the production of volatile elemental mercury (Hg(0)) from surface sediments of Aquatuk Lake. I used a combination of analytical and molecular techniques to show that the production of Hg(0) is biogenic and tested the effect of nutrients, pH and ionic strength on the Hg(0) production rates. Ionic strength alone had the greatest impact on Hg(0) production rates, with increased Hg(0) production as ionic strength increases.
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Historical Deposition and Microbial Redox Cycling of Mercury in Lake Sediments from the Hudson Bay Lowlands, Ontario, CanadaBrazeau, Michelle January 2012 (has links)
The repercussions of climate change are felt worldwide, but Arctic and subarctic regions, where climate warming is expected to be amplified, are especially vulnerable. An episode of mass fish mortality in the Sutton River in the Hudson Bay Lowlands (HBL) of Northern Ontario has elicited the interest of the scientific community. Several lakes were sampled over three years in an effort to better understand and document the changes that may be occurring in these lakes.
This study uses sediment cores to assess the history of mercury (Hg) deposition and to assess changes occurring in autochthonous productivity in these lakes. Sediments deposited after the onset of the industrial revolution contained significantly higher concentrations of Hg, with the highest concentrations found in the most recently deposited sediments. Hg concentrations in these pristine lakes rival those of lakes in heavily urbanized areas, indicating that they are in fact subjected to atmospheric deposition of Hg. There was a large variation in [Hg] of the surface sediments of 13 lakes; underscoring the importance of in situ processes in the fate of atmospherically deposited Hg. Methylmercury (MeHg) concentrations were not correlated with total mercury concentrations (THg), demonstrating how THg is a poor predictor of MeHg; the bioaccumulative neurotoxic form of mercury. The S2 fraction of Rock-Eval® Pyrolysis, C:N ratios and ∂13C signatures were used as proxies of autochthonous carbon and all indicated that the lakes have become increasingly productive, presumably due to warmer water temperatures and longer ice-free seasons.
Additionally, I use molecular techniques to detect and quantify the merA gene in the sediment; a proxy of bacterial mercury resistance involved in redox transformations. In Aquatuk, Hawley and North Raft Lakes, I observed a subsurface increase in merA genes in the sediment core, independently of a control gene and the [THg]. While I have not been able to explain the driving variables of this subsurface increase, I believe that the role of merA within remote lake sediments deserves further work.
Lastly, microcosms were used to measure the production of volatile elemental mercury (Hg(0)) from surface sediments of Aquatuk Lake. I used a combination of analytical and molecular techniques to show that the production of Hg(0) is biogenic and tested the effect of nutrients, pH and ionic strength on the Hg(0) production rates. Ionic strength alone had the greatest impact on Hg(0) production rates, with increased Hg(0) production as ionic strength increases.
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Le mercure en Arctique, de l’environnement à la santé humaine : photodéméthylation aquatique, bioaccessibilité alimentaire et interactions avec le microbiome intestinal humainGirard, Catherine 09 1900 (has links)
No description available.
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The Effect of Aluminium Industry Effluents on Sediment Bacterial CommunitiesGill, Hardeep 19 October 2012 (has links)
The goal of this project was to develop novel bacterial biomarkers for use in an industrial context. These biomarkers would be used to determine aluminium industry activity impact on a local ecosystem. Sediment bacterial communities of the Saguenay River are subjected to industrial effluent produced by industry in Jonquière, QC. In-situ responses of these communities to effluent exposure were measured and evaluated as potential biomarker candidates for exposure to past and present effluent discharge. Bacterial community structure and composition between control and affected sites were investigated. Differences observed between the communities were used as indicators of a response to industrial activity through exposure to effluent by-products. Diversity indices were not significantly different between sites with increased effluent exposure. However, differences were observed with the inclusion of algae and cyanobacteria. UniFrac analyses indicated that a control (NNB) and an affected site (Site 2) were more similar to one another with regard to community structure than either was to a medially affected site (Site 5) (Figure 2.4). We did not observe a signature of the microbial community structure that could be predicted with effluent exposure. Microbial community function in relation to bacterial mercury resistance (HgR) was also evaluated as a specific response to the mercury component present in sediments. Novel PCR primers and amplification conditions were developed to amplify merP, merT and merA genes belonging to the mer-operon which confers HgR (Table 5.6). To our knowledge, the roles of merP and merT have not been explored as possible tools to confirm the presence of the operon. HgR gene abundance in sediment microbial communities was significantly correlated (p < 0.05) to total mercury levels (Figure 3.4) but gene expression was not measurable. We could not solely attribute the release of Hg0 from sediments in bioreactor experiments to a biogenic origin. However, there was a 1000 fold difference in measured Hg0 release between control and affected sites suggesting that processes of natural remediation may be taking place at contaminated sites (Figure 3.7). Abundance measurements of HgR related genes represent a strong response target to the mercury immobilized in sediments. Biomarkers built on this response can be used by industry to measure long term effects of industrially derived mercury on local ecosystems. The abundance of mer-operon genes in affected sites indicates the presence of a thriving bacterial community harbouring HgR potential. These communities have the capacity to naturally remediate the sites they occupy. This remediation could be further investigated. Additional studies will be required to develop biomarkers that are more responsive to contemporary industrial activity such as those based on the integrative oxidative stress response.
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The Effect of Aluminium Industry Effluents on Sediment Bacterial CommunitiesGill, Hardeep 19 October 2012 (has links)
The goal of this project was to develop novel bacterial biomarkers for use in an industrial context. These biomarkers would be used to determine aluminium industry activity impact on a local ecosystem. Sediment bacterial communities of the Saguenay River are subjected to industrial effluent produced by industry in Jonquière, QC. In-situ responses of these communities to effluent exposure were measured and evaluated as potential biomarker candidates for exposure to past and present effluent discharge. Bacterial community structure and composition between control and affected sites were investigated. Differences observed between the communities were used as indicators of a response to industrial activity through exposure to effluent by-products. Diversity indices were not significantly different between sites with increased effluent exposure. However, differences were observed with the inclusion of algae and cyanobacteria. UniFrac analyses indicated that a control (NNB) and an affected site (Site 2) were more similar to one another with regard to community structure than either was to a medially affected site (Site 5) (Figure 2.4). We did not observe a signature of the microbial community structure that could be predicted with effluent exposure. Microbial community function in relation to bacterial mercury resistance (HgR) was also evaluated as a specific response to the mercury component present in sediments. Novel PCR primers and amplification conditions were developed to amplify merP, merT and merA genes belonging to the mer-operon which confers HgR (Table 5.6). To our knowledge, the roles of merP and merT have not been explored as possible tools to confirm the presence of the operon. HgR gene abundance in sediment microbial communities was significantly correlated (p < 0.05) to total mercury levels (Figure 3.4) but gene expression was not measurable. We could not solely attribute the release of Hg0 from sediments in bioreactor experiments to a biogenic origin. However, there was a 1000 fold difference in measured Hg0 release between control and affected sites suggesting that processes of natural remediation may be taking place at contaminated sites (Figure 3.7). Abundance measurements of HgR related genes represent a strong response target to the mercury immobilized in sediments. Biomarkers built on this response can be used by industry to measure long term effects of industrially derived mercury on local ecosystems. The abundance of mer-operon genes in affected sites indicates the presence of a thriving bacterial community harbouring HgR potential. These communities have the capacity to naturally remediate the sites they occupy. This remediation could be further investigated. Additional studies will be required to develop biomarkers that are more responsive to contemporary industrial activity such as those based on the integrative oxidative stress response.
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The Effect of Aluminium Industry Effluents on Sediment Bacterial CommunitiesGill, Hardeep January 2012 (has links)
The goal of this project was to develop novel bacterial biomarkers for use in an industrial context. These biomarkers would be used to determine aluminium industry activity impact on a local ecosystem. Sediment bacterial communities of the Saguenay River are subjected to industrial effluent produced by industry in Jonquière, QC. In-situ responses of these communities to effluent exposure were measured and evaluated as potential biomarker candidates for exposure to past and present effluent discharge. Bacterial community structure and composition between control and affected sites were investigated. Differences observed between the communities were used as indicators of a response to industrial activity through exposure to effluent by-products. Diversity indices were not significantly different between sites with increased effluent exposure. However, differences were observed with the inclusion of algae and cyanobacteria. UniFrac analyses indicated that a control (NNB) and an affected site (Site 2) were more similar to one another with regard to community structure than either was to a medially affected site (Site 5) (Figure 2.4). We did not observe a signature of the microbial community structure that could be predicted with effluent exposure. Microbial community function in relation to bacterial mercury resistance (HgR) was also evaluated as a specific response to the mercury component present in sediments. Novel PCR primers and amplification conditions were developed to amplify merP, merT and merA genes belonging to the mer-operon which confers HgR (Table 5.6). To our knowledge, the roles of merP and merT have not been explored as possible tools to confirm the presence of the operon. HgR gene abundance in sediment microbial communities was significantly correlated (p < 0.05) to total mercury levels (Figure 3.4) but gene expression was not measurable. We could not solely attribute the release of Hg0 from sediments in bioreactor experiments to a biogenic origin. However, there was a 1000 fold difference in measured Hg0 release between control and affected sites suggesting that processes of natural remediation may be taking place at contaminated sites (Figure 3.7). Abundance measurements of HgR related genes represent a strong response target to the mercury immobilized in sediments. Biomarkers built on this response can be used by industry to measure long term effects of industrially derived mercury on local ecosystems. The abundance of mer-operon genes in affected sites indicates the presence of a thriving bacterial community harbouring HgR potential. These communities have the capacity to naturally remediate the sites they occupy. This remediation could be further investigated. Additional studies will be required to develop biomarkers that are more responsive to contemporary industrial activity such as those based on the integrative oxidative stress response.
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