other minerals. We find that iron phases increase the affinity and adhesion of 13 C-enriched diss... more other minerals. We find that iron phases increase the affinity and adhesion of 13 C-enriched dissolved molecules to particulate phases -which has been reported to slow bacterial degradation. Further elucidation of the mechanism of interaction between the 2 elements could be achieved through novel instrumental methods, including TEM microscopy and EXAFS spectroscopy which are used to determine the macrostructural arrangement of iron and OM and the chemical environment surrounding iron atoms in sediments. v A PhD is no feat of superhuman intelligence but rather an exercise in persistence, discipline and self-motivation. These have been hard, humbling, trying but amazing years in which I have learned more about myself than I have about sediments, iron or organic matter combined. I could not have gone into this alone and come out the other end without help from a number of people. I would firstly like to thank Yves, my supervisor, who has watched me make every mistake without judgement or repercussion and who has trusted me to take the reins from the very beginning, but has always giving me counsel when I needed it. I would also like to thank Andrew Barber, who once upon a time was my mentee and became a great science partner and a fantastic springboard for ideas. I would also like to thank my present and past lab members whose ebb and flow in the lab maintained an interesting and fun place to work throughout the years: thank you
We provide a detailed description of the hyphenation of an Aurora 1030C high temperature catalyti... more We provide a detailed description of the hyphenation of an Aurora 1030C high temperature catalytic conversion DOC analyzer, a GD-100 CO 2 trap and a continuous flow IRMS, which has made possible the high-throughput, automated measurements of 13 C/ 12 C ratios and DOC concentrations for a wide range of aquatic samples. Precision of 13 C/ 12 C ratios increases exponentially with sample concentration, reaching 0.2‰ or better for high concentration samples (>5 mg L-1), comparable to that obtained in a conventional elemental analyzer-IRMS setup. The system blank contribution is the limiting factor in obtaining maximal performance; optimal system blanks values are on the order of 0.2 μg C with an isotopic signature varying from-20 to-12 ‰ during the lifetime of the combustion column. With appropriate blank correction procedures, accurate analyses (± 0.5‰ or better) can be obtained on concentrations as low as 0.5 mg DOC L-1 , representing the lower limit typically observed in aquatic systems. Sample matrix does not affect reproducibility or accuracy; this method is amenable to both freshwater and seawater samples. Although no certified DOC standards exist for δ 13 C, our two laboratories (Concordia University & University of Ottawa) analyzed a consensus reference material from a deep-ocean environment (CRM Batch 13 Lot # 05-13, Hansell 2013) and found δ 13 C values of-19.9 ± 0.5‰ (n = 4) and-20.6 ± 0.3‰ (n = 3), which corroborates previously reported values for similar samples (
Testosterone doping in sports is detected through the measurement of the carbon isotopic signatur... more Testosterone doping in sports is detected through the measurement of the carbon isotopic signature (δ13C) of testosterone and its metabolites in urine. A critical step in achieving accurate and precise δ13C values during compound‐specific stable carbon isotope analysis (CSIA) is the removal of interfering matrix components. To this end, the World Anti‐Doping Agency (WADA) recommends the use of high‐performance liquid chromatography (HPLC) as a method of sample pretreatment. We provide a description of an automated two‐dimensional HPLC (2D‐HPLC) purification method for urine extracts that has made possible the CSIA of underivatized steroids, requiring only 36 min per sample. Eight urinary steroids including testosterone (T) and dehydroepiandrosterone (DHEA) and four of their metabolites as well as two endogenous reference compounds were collected during HPLC purification. Comparative GC chromatograms are used to contrast the efficiency of two‐dimensional (2D) purification to a previously established 1D‐HPLC method. The 2D purification leads to improved sample purity while simultaneously decreasing the analysis time, allowing for unprecedented sample throughput. Precision of δ13C for all analyzed compounds in negative and positive controls was 0.5‰ or better, which is comparable with the precision of pure reference materials at similar intensities.
β2‐adrenergic agonists having the potential to be misused to enhance performance for their thermo... more β2‐adrenergic agonists having the potential to be misused to enhance performance for their thermogenic and anabolic properties are prohibited in sports. Clenbuterol, ractopamine and zilpaterol are utilised legally or illegally as growth promoters of animals raised for their meat. No withdrawal times are imposed for ractopamine prior to slaughter; residues are detected in meat of treated animals, which constitutes a risk of inadvertent consumption. Insufficient information is available on the fate of ractopamine in humans to implement efficient detection in athletes' urine samples. We have developed a confirmation procedure for total ractopamine in urine following the enzymatic hydrolysis of glucuronides and sulphates and the conversion to tri‐TMS derivative (limit of identification at 0.15 ng/ml). The sulphates were found to form between 85% to 97% of ractopamine excreted in athletes' urine samples analysed routinely or in volunteers following the administration of a micro‐dose of 2.5 μg. Peak levels were reached at 2 to 6 h and decreased rapidly below 1 ng/ml 10 h after dosing. With one exception, the highest level estimated in athletes' samples was 1.2 ng/ml. Zilpaterol was confirmed in a few urine samples collected in the USA and Mexico (highest level 2 ng/ml), while hundreds of athletes' samples were reported to contain clenbuterol by our laboratory over the past 7 years. Most of these cases originated from Mexico (n = 102) and Guatemala (n = 119), often clustered in events during which multiple samples were collected, and for the vast majority, in levels lower than 0.2 ng/ml.
Interactions between organic matter and mineral matrices are critical to the preservation of soil... more Interactions between organic matter and mineral matrices are critical to the preservation of soil and sediment organic matter. In addition to clay minerals, Fe(III) oxides particles have recently been shown to be responsible for the protection and burial of a large fraction of sedimentary organic carbon (OC). Through a combination of synchrotron X-ray techniques and high-resolution images of intact sediment particles, we assessed the mechanism of interaction between OC and iron, as well as the composition of organic matter co-localized with ferric iron. We present scanning transmission x-ray microscopy images at the Fe L 3 and C K 1 edges showing that the organic matter co-localized with Fe(III) consists primarily of C=C, C=O and C-OH functional groups. Coupling the co-localization results to iron K-edge X-ray absorption spectroscopy fitting results allowed to quantify the relative contribution of OC-complexed Fe to the total sediment iron and reactive iron pools, showing that 25-62% of total reactive iron is directly associated to OC through inner-sphere complexation in coastal sediments, as much as four times more than in low OC deep sea sediments. Direct inner-sphere complexation between OC and iron oxides (Fe-O-C) is responsible for transferring a large quantity of reduced OC to the sedimentary sink, which could otherwise be oxidized back to CO 2 .
β2‐adrenergic agonists having the potential to be misused to enhance performance for their thermo... more β2‐adrenergic agonists having the potential to be misused to enhance performance for their thermogenic and anabolic properties are prohibited in sports. Clenbuterol, ractopamine and zilpaterol are utilised legally or illegally as growth promoters of animals raised for their meat. No withdrawal times are imposed for ractopamine prior to slaughter; residues are detected in meat of treated animals, which constitutes a risk of inadvertent consumption. Insufficient information is available on the fate of ractopamine in humans to implement efficient detection in athletes' urine samples. We have developed a confirmation procedure for total ractopamine in urine following the enzymatic hydrolysis of glucuronides and sulphates and the conversion to tri‐TMS derivative (limit of identification at 0.15 ng/ml). The sulphates were found to form between 85% to 97% of ractopamine excreted in athletes' urine samples analysed routinely or in volunteers following the administration of a micro‐d...
The biogeochemical cycles of iron (Fe) and organic carbon (OC) are strongly interlinked. In ocean... more The biogeochemical cycles of iron (Fe) and organic carbon (OC) are strongly interlinked. In oceanic waters, organic ligands have been shown to control the concentration of dissolved Fe [1], whereas in soils, solid Fe phases provide a sheltering and preservative effect for organic matter [2]. Until now however, the role of iron in the preservation of OC in sediments has not been clearly established. Here we show that 21.5 ± 8.6% of the OC in sediments is directly bound to reactive iron phases, which promote the preservation of OC in sediments. Iron-bound OC represents a global mass of 19 to 45 × 10^15 g of OC in surface marine sediments. This pool of OC is different from the rest of sedimentary OC, with 13C and nitrogen-enriched organic matter preferentially bound to Fe which suggests that biochemical fractionation occurs with OC-Fe binding. Preferential binding also affects the recovery of high molecular weight lipid biomarkers and acidic lignin oxidation products, changing the envi...
The burial and preservation of organic matter (OM) in marine sediments is tightly coupled to the ... more The burial and preservation of organic matter (OM) in marine sediments is tightly coupled to the diagenetic cycles of iron and manganese. Recently, it has been shown that approximately 20% of the sedimentary organic carbon (OC) may be bound to reducible iron oxides (Lalonde et al., 2012). These strong iron-OC complexes, formed within the oxic layer of the sediment, are transferred to the deeper anoxic sediment layers through sedimentation, physical reworking and bioturbation and are metastable over geological timescales. Using longterm (250-day) incubations under various redox and amendment conditions (Fe(II) and dissolved OM (DOM) additions), we examined the effect of iron on the early diagenetic transformations of OM in marine sediments. The fate of fresh, algal-derived DOM was monitored by tracking its stable carbon isotopic signature (δ 13 C). We demonstrate the incorporation of the 13 C-depleted tracer into the sediment through sorption (adsorption and co-precipitation). In the presence of iron oxides, we observed an increased transfer of the dissolved algal material to the solid phase, revealing the role of iron in shuttling DOM from sediment pore waters to sediment particles. Furthermore, we show that the presence of iron has a differential effect on OC and organic nitrogen (ON), with preferential preservation of OC and accelerated degradation of ON in the presence of reactive iron oxide surfaces. Hence, we propose that redox-sensitive metals may regulate the global redox balance through increased carbon preservation as well as exerting a control on the concentration of fixed nitrogen species in marine sediments.
Journal of Geophysical Research: Biogeosciences, 2012
Most natural freshwater lakes are net greenhouse gases (GHG) emitters. Compared to natural system... more Most natural freshwater lakes are net greenhouse gases (GHG) emitters. Compared to natural systems, human perturbations such as watershed wood harvesting and long term reservoir impoundment lead to profound alterations of biogeochemical processes involved in the aquatic cycle of carbon (C). We exploited these anthropogenic alterations to describe the C dynamics in five lakes and two reservoirs from the boreal forest through the analysis of dissolved carbon dioxide (CO 2), methane (CH 4), oxygen (O 2), and organic carbon (DOC), as well as total nitrogen (TN) and phosphorus (TP). Dissolved and particulate organic matter, forest soil/litter and leachates, as well as dissolved inorganic carbon (DIC) were analyzed for elemental and stable isotopic compositions (atomic C:N ratios, δ 13 C org , δ 13 C inorg and δ 15 N tot). We found links between the export of terrestrial OM to these systems and the dissolved CO 2 and O 2 concentrations in the water column, as well as CO 2 fluxes to the atmosphere. All systems were GHG emitters, with greater emissions measured for systems with larger inputs of terrestrial OM. The differences in CO 2 concentrations and fluxes appear controlled by bacterial activity in the water column and the sediment. Although we clearly observed differences in the aquatic C cycle between natural and perturbed systems, more work on a larger number of water bodies, and encompassing all four seasons should be undertaken to better understand the controls, rates, as well as spatial and temporal variability of GHG emissions, and to make quantitatively meaningful comparisons of GHG emissions (and other key variables) from natural and perturbed systems.
We provide a detailed description of the hyphenation of an Aurora 1030C high temperature catalyti... more We provide a detailed description of the hyphenation of an Aurora 1030C high temperature catalytic conversion DOC analyzer, a GD-100 CO 2 trap and a continuous flow IRMS, which has made possible the highthroughput, automated measurements of 13 C/ 12 C ratios, and DOC concentrations for a wide range of aquatic samples. Precision of 13 C/ 12 C ratios increases exponentially with sample concentration, reaching 0.2‰ or better for high concentration samples (>5 mg L-1), comparable to that obtained in a conventional elemental analyzer-IRMS setup. The system blank contribution is the limiting factor in obtaining maximal performance; optimal system blanks values are on the order of 0.2 μg C with an isotopic signature varying from-20 to-12‰ during the lifetime of the combustion column. With appropriate blank correction procedures, accurate analyses (±0.5‰ or better) can be obtained on concentrations as low as 0.5 mg DOC L-1 , representing the lower limit typically observed in aquatic systems. Sample matrix does not affect reproducibility or accuracy; this method is amenable to both freshwater and seawater samples. Although no certified DOC standards exist for δ 13 C, our two laboratories analyzed a consensus reference material from a deep-ocean environment (CRM Batch 13 Lot # 05-13, Hansell 2013) and found δ 13 C values of-19.9 ± 0.5‰ (n = 4) and-20.6 ± 0.3‰ (n = 3), which corroborates previously reported values for similar samples (Bouillon et al. 2006; Lang et al. 2007; Panetta et al. 2008) and is consistent with its marine origin.
Detection and quantification of the amorphous phase of etoricoxib bulk drug substances, a selecti... more Detection and quantification of the amorphous phase of etoricoxib bulk drug substances, a selective cycloogenase-2 inhibitor used for the treatment of osteoarthritis, rheumatoid arthritis, and dental pain, was carried out using modulated differential scanning calorimetry (MDSC), dynamic mechanical analysis (DMA), and Raman spectroscopy. Detection of amorphous content in pharmaceutical powders by DMA is a special application of dynamic mechanical spectroscopy. DMA was found to be a sensitive technique, able to detect the presence of an amorphous phase in a crystalline phase at concentrations as low as 0.5%. The limit of detection (LOD) determined for DMA was 2.5%. In comparison, Raman spectroscopy and MDSC had LOD values of 2% and 5% amorphous, respectively.
Organic carbon (OC) depleted in 13 C is a widely used tracer for terrestrial organic matter (OM) ... more Organic carbon (OC) depleted in 13 C is a widely used tracer for terrestrial organic matter (OM) in aquatic systems. Photochemical reactions can, however, change δ 13 C of dissolved organic carbon (DOC) when chromophoric, aromatic-rich terrestrial OC is selectively mineralized. We assessed the robustness of the δ 13 C signature of DOC (δ 13 C DOC ) as a tracer for terrestrial OM by estimating its change during the photobleaching of chromophoric DOM (CDOM) from 10 large rivers. These rivers cumulatively account for approximately one-third of the world's freshwater discharge to the global ocean. Photobleaching of CDOM by simulated solar radiation was associated with the photochemical mineralization of 16 to 43 % of the DOC and, by preferentially removing compounds depleted in 13 C, caused a 1 to 2.9 ‰ enrichment in δ 13 C in the residual DOC. Such solarradiation-induced photochemical isotopic shift could bias the calculations of terrestrial OM discharge in coastal oceans towards the marine end-member. Shifts in terrestrial δ 13 C DOC should be taken into account when constraining the terrestrial end-member in global calculation of terrestrially derived DOM in the world ocean.
A complex soup of assorted dissolved organic compounds can be found in lakes, rivers and oceans. ... more A complex soup of assorted dissolved organic compounds can be found in lakes, rivers and oceans. Some of this organic matter (OM) is associated to mineral phases and the composition of the dissolved organic compound mixture is largely dictated by the adsorption efficacy and availability of mineral surfaces. In sediments, about 90% of the OM is bound - to some
The burial and preservation of organic matter (OM) in marine sediments is tightly coupled to the ... more The burial and preservation of organic matter (OM) in marine sediments is tightly coupled to the diagenetic cycles of iron and manganese. Recently, it has been shown that approximately 20% of the sedimentary organic carbon (OC) may be bound to reducible iron oxides . These strong iron-OC complexes, formed within the oxic layer of the sediment, are transferred to the deeper anoxic sediment layers through sedimentation, physical reworking and bioturbation and are metastable over geological timescales. Using longterm (250-day) incubations under various redox and amendment conditions (Fe(II) and dissolved OM (DOM) additions), we examined the effect of iron on the early diagenetic transformations of OM in marine sediments. The fate of fresh, algal-derived DOM was monitored by tracking its stable carbon isotopic signature (δ 13 C). We demonstrate the incorporation of the 13 C-depleted tracer into the sediment through sorption (adsorption and co-precipitation). In the presence of iron oxides, we observed an increased transfer of the dissolved algal material to the solid phase, revealing the role of iron in shuttling DOM from sediment pore waters to sediment particles. Furthermore, we show that the presence of iron has a differential effect on OC and organic nitrogen (ON), with preferential preservation of OC and accelerated degradation of ON in the presence of reactive iron oxide surfaces. Hence, we propose that redox-sensitive metals may regulate the global redox balance through increased carbon preservation as well as exerting a control on the concentration of fixed nitrogen species in marine sediments.
1] Most natural freshwater lakes are net greenhouse gas (GHG) emitters. Compared to natural syste... more 1] Most natural freshwater lakes are net greenhouse gas (GHG) emitters. Compared to natural systems, human perturbations such as watershed wood harvesting and long-term reservoir impoundment lead to profound alterations of biogeochemical processes involved in the aquatic cycle of carbon (C). We exploited these anthropogenic alterations to describe the C dynamics in five lakes and two reservoirs from the boreal forest through the analysis of dissolved carbon dioxide (CO 2 ), methane (CH 4 ), oxygen (O 2 ), and organic carbon (DOC), as well as total nitrogen and phosphorus. Dissolved and particulate organic matter, forest soil/litter and leachates, as well as dissolved inorganic carbon were analyzed for elemental and stable isotopic compositions (atomic C:N ratios, d 13 C org , d 13 C inorg and d 15 N tot ). We found links between the export of terrestrial organic matter (OM) to these systems and the dissolved CO 2 and O 2 concentrations in the water column, as well as CO 2 fluxes to the atmosphere. All systems were GHG emitters, with greater emissions measured for systems with larger inputs of terrestrial OM. The differences in CO 2 concentrations and fluxes appear controlled by bacterial activity in the water column and the sediment. Although we clearly observed differences in the aquatic C cycle between natural and perturbed systems, more work on a larger number of water bodies and encompassing all four seasons should be undertaken to better understand the controls, rates, and spatial as well as temporal variability of GHG emissions, and to make quantitatively meaningful comparisons of GHG emissions (and other key variables) from natural and perturbed systems.
We provide a detailed description of the hyphenation of an Aurora 1030C high temperature catalyti... more We provide a detailed description of the hyphenation of an Aurora 1030C high temperature catalytic conversion DOC analyzer, a GD-100 CO2 trap and a continuous flow IRMS, which has made possible the high-throughput, automated measurements of 13C/12C ratios, and DOC concentrations for a wide range of aquatic samples. Precision of 13C/12C ratios increases exponentially with sample concentration, reaching 0.2‰ or better for high concentration samples (>5 mg L-1), comparable to that obtained in a conventional elemental analyzer-IRMS setup. The system blank contribution is the limiting factor in obtaining maximal performance; optimal system blanks values are on the order of 0.2 µg C with an isotopic signature varying from -20 to -12‰ during the lifetime of the combustion column. With appropriate blank correction procedures, accurate analyses (±0.5‰ or better) can be obtained on concentrations as low as 0.5 mg DOC L-1, representing the lower limit typically observed in aquatic systems. ...
other minerals. We find that iron phases increase the affinity and adhesion of 13 C-enriched diss... more other minerals. We find that iron phases increase the affinity and adhesion of 13 C-enriched dissolved molecules to particulate phases -which has been reported to slow bacterial degradation. Further elucidation of the mechanism of interaction between the 2 elements could be achieved through novel instrumental methods, including TEM microscopy and EXAFS spectroscopy which are used to determine the macrostructural arrangement of iron and OM and the chemical environment surrounding iron atoms in sediments. v A PhD is no feat of superhuman intelligence but rather an exercise in persistence, discipline and self-motivation. These have been hard, humbling, trying but amazing years in which I have learned more about myself than I have about sediments, iron or organic matter combined. I could not have gone into this alone and come out the other end without help from a number of people. I would firstly like to thank Yves, my supervisor, who has watched me make every mistake without judgement or repercussion and who has trusted me to take the reins from the very beginning, but has always giving me counsel when I needed it. I would also like to thank Andrew Barber, who once upon a time was my mentee and became a great science partner and a fantastic springboard for ideas. I would also like to thank my present and past lab members whose ebb and flow in the lab maintained an interesting and fun place to work throughout the years: thank you
We provide a detailed description of the hyphenation of an Aurora 1030C high temperature catalyti... more We provide a detailed description of the hyphenation of an Aurora 1030C high temperature catalytic conversion DOC analyzer, a GD-100 CO 2 trap and a continuous flow IRMS, which has made possible the high-throughput, automated measurements of 13 C/ 12 C ratios and DOC concentrations for a wide range of aquatic samples. Precision of 13 C/ 12 C ratios increases exponentially with sample concentration, reaching 0.2‰ or better for high concentration samples (>5 mg L-1), comparable to that obtained in a conventional elemental analyzer-IRMS setup. The system blank contribution is the limiting factor in obtaining maximal performance; optimal system blanks values are on the order of 0.2 μg C with an isotopic signature varying from-20 to-12 ‰ during the lifetime of the combustion column. With appropriate blank correction procedures, accurate analyses (± 0.5‰ or better) can be obtained on concentrations as low as 0.5 mg DOC L-1 , representing the lower limit typically observed in aquatic systems. Sample matrix does not affect reproducibility or accuracy; this method is amenable to both freshwater and seawater samples. Although no certified DOC standards exist for δ 13 C, our two laboratories (Concordia University & University of Ottawa) analyzed a consensus reference material from a deep-ocean environment (CRM Batch 13 Lot # 05-13, Hansell 2013) and found δ 13 C values of-19.9 ± 0.5‰ (n = 4) and-20.6 ± 0.3‰ (n = 3), which corroborates previously reported values for similar samples (
Testosterone doping in sports is detected through the measurement of the carbon isotopic signatur... more Testosterone doping in sports is detected through the measurement of the carbon isotopic signature (δ13C) of testosterone and its metabolites in urine. A critical step in achieving accurate and precise δ13C values during compound‐specific stable carbon isotope analysis (CSIA) is the removal of interfering matrix components. To this end, the World Anti‐Doping Agency (WADA) recommends the use of high‐performance liquid chromatography (HPLC) as a method of sample pretreatment. We provide a description of an automated two‐dimensional HPLC (2D‐HPLC) purification method for urine extracts that has made possible the CSIA of underivatized steroids, requiring only 36 min per sample. Eight urinary steroids including testosterone (T) and dehydroepiandrosterone (DHEA) and four of their metabolites as well as two endogenous reference compounds were collected during HPLC purification. Comparative GC chromatograms are used to contrast the efficiency of two‐dimensional (2D) purification to a previously established 1D‐HPLC method. The 2D purification leads to improved sample purity while simultaneously decreasing the analysis time, allowing for unprecedented sample throughput. Precision of δ13C for all analyzed compounds in negative and positive controls was 0.5‰ or better, which is comparable with the precision of pure reference materials at similar intensities.
β2‐adrenergic agonists having the potential to be misused to enhance performance for their thermo... more β2‐adrenergic agonists having the potential to be misused to enhance performance for their thermogenic and anabolic properties are prohibited in sports. Clenbuterol, ractopamine and zilpaterol are utilised legally or illegally as growth promoters of animals raised for their meat. No withdrawal times are imposed for ractopamine prior to slaughter; residues are detected in meat of treated animals, which constitutes a risk of inadvertent consumption. Insufficient information is available on the fate of ractopamine in humans to implement efficient detection in athletes' urine samples. We have developed a confirmation procedure for total ractopamine in urine following the enzymatic hydrolysis of glucuronides and sulphates and the conversion to tri‐TMS derivative (limit of identification at 0.15 ng/ml). The sulphates were found to form between 85% to 97% of ractopamine excreted in athletes' urine samples analysed routinely or in volunteers following the administration of a micro‐dose of 2.5 μg. Peak levels were reached at 2 to 6 h and decreased rapidly below 1 ng/ml 10 h after dosing. With one exception, the highest level estimated in athletes' samples was 1.2 ng/ml. Zilpaterol was confirmed in a few urine samples collected in the USA and Mexico (highest level 2 ng/ml), while hundreds of athletes' samples were reported to contain clenbuterol by our laboratory over the past 7 years. Most of these cases originated from Mexico (n = 102) and Guatemala (n = 119), often clustered in events during which multiple samples were collected, and for the vast majority, in levels lower than 0.2 ng/ml.
Interactions between organic matter and mineral matrices are critical to the preservation of soil... more Interactions between organic matter and mineral matrices are critical to the preservation of soil and sediment organic matter. In addition to clay minerals, Fe(III) oxides particles have recently been shown to be responsible for the protection and burial of a large fraction of sedimentary organic carbon (OC). Through a combination of synchrotron X-ray techniques and high-resolution images of intact sediment particles, we assessed the mechanism of interaction between OC and iron, as well as the composition of organic matter co-localized with ferric iron. We present scanning transmission x-ray microscopy images at the Fe L 3 and C K 1 edges showing that the organic matter co-localized with Fe(III) consists primarily of C=C, C=O and C-OH functional groups. Coupling the co-localization results to iron K-edge X-ray absorption spectroscopy fitting results allowed to quantify the relative contribution of OC-complexed Fe to the total sediment iron and reactive iron pools, showing that 25-62% of total reactive iron is directly associated to OC through inner-sphere complexation in coastal sediments, as much as four times more than in low OC deep sea sediments. Direct inner-sphere complexation between OC and iron oxides (Fe-O-C) is responsible for transferring a large quantity of reduced OC to the sedimentary sink, which could otherwise be oxidized back to CO 2 .
β2‐adrenergic agonists having the potential to be misused to enhance performance for their thermo... more β2‐adrenergic agonists having the potential to be misused to enhance performance for their thermogenic and anabolic properties are prohibited in sports. Clenbuterol, ractopamine and zilpaterol are utilised legally or illegally as growth promoters of animals raised for their meat. No withdrawal times are imposed for ractopamine prior to slaughter; residues are detected in meat of treated animals, which constitutes a risk of inadvertent consumption. Insufficient information is available on the fate of ractopamine in humans to implement efficient detection in athletes' urine samples. We have developed a confirmation procedure for total ractopamine in urine following the enzymatic hydrolysis of glucuronides and sulphates and the conversion to tri‐TMS derivative (limit of identification at 0.15 ng/ml). The sulphates were found to form between 85% to 97% of ractopamine excreted in athletes' urine samples analysed routinely or in volunteers following the administration of a micro‐d...
The biogeochemical cycles of iron (Fe) and organic carbon (OC) are strongly interlinked. In ocean... more The biogeochemical cycles of iron (Fe) and organic carbon (OC) are strongly interlinked. In oceanic waters, organic ligands have been shown to control the concentration of dissolved Fe [1], whereas in soils, solid Fe phases provide a sheltering and preservative effect for organic matter [2]. Until now however, the role of iron in the preservation of OC in sediments has not been clearly established. Here we show that 21.5 ± 8.6% of the OC in sediments is directly bound to reactive iron phases, which promote the preservation of OC in sediments. Iron-bound OC represents a global mass of 19 to 45 × 10^15 g of OC in surface marine sediments. This pool of OC is different from the rest of sedimentary OC, with 13C and nitrogen-enriched organic matter preferentially bound to Fe which suggests that biochemical fractionation occurs with OC-Fe binding. Preferential binding also affects the recovery of high molecular weight lipid biomarkers and acidic lignin oxidation products, changing the envi...
The burial and preservation of organic matter (OM) in marine sediments is tightly coupled to the ... more The burial and preservation of organic matter (OM) in marine sediments is tightly coupled to the diagenetic cycles of iron and manganese. Recently, it has been shown that approximately 20% of the sedimentary organic carbon (OC) may be bound to reducible iron oxides (Lalonde et al., 2012). These strong iron-OC complexes, formed within the oxic layer of the sediment, are transferred to the deeper anoxic sediment layers through sedimentation, physical reworking and bioturbation and are metastable over geological timescales. Using longterm (250-day) incubations under various redox and amendment conditions (Fe(II) and dissolved OM (DOM) additions), we examined the effect of iron on the early diagenetic transformations of OM in marine sediments. The fate of fresh, algal-derived DOM was monitored by tracking its stable carbon isotopic signature (δ 13 C). We demonstrate the incorporation of the 13 C-depleted tracer into the sediment through sorption (adsorption and co-precipitation). In the presence of iron oxides, we observed an increased transfer of the dissolved algal material to the solid phase, revealing the role of iron in shuttling DOM from sediment pore waters to sediment particles. Furthermore, we show that the presence of iron has a differential effect on OC and organic nitrogen (ON), with preferential preservation of OC and accelerated degradation of ON in the presence of reactive iron oxide surfaces. Hence, we propose that redox-sensitive metals may regulate the global redox balance through increased carbon preservation as well as exerting a control on the concentration of fixed nitrogen species in marine sediments.
Journal of Geophysical Research: Biogeosciences, 2012
Most natural freshwater lakes are net greenhouse gases (GHG) emitters. Compared to natural system... more Most natural freshwater lakes are net greenhouse gases (GHG) emitters. Compared to natural systems, human perturbations such as watershed wood harvesting and long term reservoir impoundment lead to profound alterations of biogeochemical processes involved in the aquatic cycle of carbon (C). We exploited these anthropogenic alterations to describe the C dynamics in five lakes and two reservoirs from the boreal forest through the analysis of dissolved carbon dioxide (CO 2), methane (CH 4), oxygen (O 2), and organic carbon (DOC), as well as total nitrogen (TN) and phosphorus (TP). Dissolved and particulate organic matter, forest soil/litter and leachates, as well as dissolved inorganic carbon (DIC) were analyzed for elemental and stable isotopic compositions (atomic C:N ratios, δ 13 C org , δ 13 C inorg and δ 15 N tot). We found links between the export of terrestrial OM to these systems and the dissolved CO 2 and O 2 concentrations in the water column, as well as CO 2 fluxes to the atmosphere. All systems were GHG emitters, with greater emissions measured for systems with larger inputs of terrestrial OM. The differences in CO 2 concentrations and fluxes appear controlled by bacterial activity in the water column and the sediment. Although we clearly observed differences in the aquatic C cycle between natural and perturbed systems, more work on a larger number of water bodies, and encompassing all four seasons should be undertaken to better understand the controls, rates, as well as spatial and temporal variability of GHG emissions, and to make quantitatively meaningful comparisons of GHG emissions (and other key variables) from natural and perturbed systems.
We provide a detailed description of the hyphenation of an Aurora 1030C high temperature catalyti... more We provide a detailed description of the hyphenation of an Aurora 1030C high temperature catalytic conversion DOC analyzer, a GD-100 CO 2 trap and a continuous flow IRMS, which has made possible the highthroughput, automated measurements of 13 C/ 12 C ratios, and DOC concentrations for a wide range of aquatic samples. Precision of 13 C/ 12 C ratios increases exponentially with sample concentration, reaching 0.2‰ or better for high concentration samples (>5 mg L-1), comparable to that obtained in a conventional elemental analyzer-IRMS setup. The system blank contribution is the limiting factor in obtaining maximal performance; optimal system blanks values are on the order of 0.2 μg C with an isotopic signature varying from-20 to-12‰ during the lifetime of the combustion column. With appropriate blank correction procedures, accurate analyses (±0.5‰ or better) can be obtained on concentrations as low as 0.5 mg DOC L-1 , representing the lower limit typically observed in aquatic systems. Sample matrix does not affect reproducibility or accuracy; this method is amenable to both freshwater and seawater samples. Although no certified DOC standards exist for δ 13 C, our two laboratories analyzed a consensus reference material from a deep-ocean environment (CRM Batch 13 Lot # 05-13, Hansell 2013) and found δ 13 C values of-19.9 ± 0.5‰ (n = 4) and-20.6 ± 0.3‰ (n = 3), which corroborates previously reported values for similar samples (Bouillon et al. 2006; Lang et al. 2007; Panetta et al. 2008) and is consistent with its marine origin.
Detection and quantification of the amorphous phase of etoricoxib bulk drug substances, a selecti... more Detection and quantification of the amorphous phase of etoricoxib bulk drug substances, a selective cycloogenase-2 inhibitor used for the treatment of osteoarthritis, rheumatoid arthritis, and dental pain, was carried out using modulated differential scanning calorimetry (MDSC), dynamic mechanical analysis (DMA), and Raman spectroscopy. Detection of amorphous content in pharmaceutical powders by DMA is a special application of dynamic mechanical spectroscopy. DMA was found to be a sensitive technique, able to detect the presence of an amorphous phase in a crystalline phase at concentrations as low as 0.5%. The limit of detection (LOD) determined for DMA was 2.5%. In comparison, Raman spectroscopy and MDSC had LOD values of 2% and 5% amorphous, respectively.
Organic carbon (OC) depleted in 13 C is a widely used tracer for terrestrial organic matter (OM) ... more Organic carbon (OC) depleted in 13 C is a widely used tracer for terrestrial organic matter (OM) in aquatic systems. Photochemical reactions can, however, change δ 13 C of dissolved organic carbon (DOC) when chromophoric, aromatic-rich terrestrial OC is selectively mineralized. We assessed the robustness of the δ 13 C signature of DOC (δ 13 C DOC ) as a tracer for terrestrial OM by estimating its change during the photobleaching of chromophoric DOM (CDOM) from 10 large rivers. These rivers cumulatively account for approximately one-third of the world's freshwater discharge to the global ocean. Photobleaching of CDOM by simulated solar radiation was associated with the photochemical mineralization of 16 to 43 % of the DOC and, by preferentially removing compounds depleted in 13 C, caused a 1 to 2.9 ‰ enrichment in δ 13 C in the residual DOC. Such solarradiation-induced photochemical isotopic shift could bias the calculations of terrestrial OM discharge in coastal oceans towards the marine end-member. Shifts in terrestrial δ 13 C DOC should be taken into account when constraining the terrestrial end-member in global calculation of terrestrially derived DOM in the world ocean.
A complex soup of assorted dissolved organic compounds can be found in lakes, rivers and oceans. ... more A complex soup of assorted dissolved organic compounds can be found in lakes, rivers and oceans. Some of this organic matter (OM) is associated to mineral phases and the composition of the dissolved organic compound mixture is largely dictated by the adsorption efficacy and availability of mineral surfaces. In sediments, about 90% of the OM is bound - to some
The burial and preservation of organic matter (OM) in marine sediments is tightly coupled to the ... more The burial and preservation of organic matter (OM) in marine sediments is tightly coupled to the diagenetic cycles of iron and manganese. Recently, it has been shown that approximately 20% of the sedimentary organic carbon (OC) may be bound to reducible iron oxides . These strong iron-OC complexes, formed within the oxic layer of the sediment, are transferred to the deeper anoxic sediment layers through sedimentation, physical reworking and bioturbation and are metastable over geological timescales. Using longterm (250-day) incubations under various redox and amendment conditions (Fe(II) and dissolved OM (DOM) additions), we examined the effect of iron on the early diagenetic transformations of OM in marine sediments. The fate of fresh, algal-derived DOM was monitored by tracking its stable carbon isotopic signature (δ 13 C). We demonstrate the incorporation of the 13 C-depleted tracer into the sediment through sorption (adsorption and co-precipitation). In the presence of iron oxides, we observed an increased transfer of the dissolved algal material to the solid phase, revealing the role of iron in shuttling DOM from sediment pore waters to sediment particles. Furthermore, we show that the presence of iron has a differential effect on OC and organic nitrogen (ON), with preferential preservation of OC and accelerated degradation of ON in the presence of reactive iron oxide surfaces. Hence, we propose that redox-sensitive metals may regulate the global redox balance through increased carbon preservation as well as exerting a control on the concentration of fixed nitrogen species in marine sediments.
1] Most natural freshwater lakes are net greenhouse gas (GHG) emitters. Compared to natural syste... more 1] Most natural freshwater lakes are net greenhouse gas (GHG) emitters. Compared to natural systems, human perturbations such as watershed wood harvesting and long-term reservoir impoundment lead to profound alterations of biogeochemical processes involved in the aquatic cycle of carbon (C). We exploited these anthropogenic alterations to describe the C dynamics in five lakes and two reservoirs from the boreal forest through the analysis of dissolved carbon dioxide (CO 2 ), methane (CH 4 ), oxygen (O 2 ), and organic carbon (DOC), as well as total nitrogen and phosphorus. Dissolved and particulate organic matter, forest soil/litter and leachates, as well as dissolved inorganic carbon were analyzed for elemental and stable isotopic compositions (atomic C:N ratios, d 13 C org , d 13 C inorg and d 15 N tot ). We found links between the export of terrestrial organic matter (OM) to these systems and the dissolved CO 2 and O 2 concentrations in the water column, as well as CO 2 fluxes to the atmosphere. All systems were GHG emitters, with greater emissions measured for systems with larger inputs of terrestrial OM. The differences in CO 2 concentrations and fluxes appear controlled by bacterial activity in the water column and the sediment. Although we clearly observed differences in the aquatic C cycle between natural and perturbed systems, more work on a larger number of water bodies and encompassing all four seasons should be undertaken to better understand the controls, rates, and spatial as well as temporal variability of GHG emissions, and to make quantitatively meaningful comparisons of GHG emissions (and other key variables) from natural and perturbed systems.
We provide a detailed description of the hyphenation of an Aurora 1030C high temperature catalyti... more We provide a detailed description of the hyphenation of an Aurora 1030C high temperature catalytic conversion DOC analyzer, a GD-100 CO2 trap and a continuous flow IRMS, which has made possible the high-throughput, automated measurements of 13C/12C ratios, and DOC concentrations for a wide range of aquatic samples. Precision of 13C/12C ratios increases exponentially with sample concentration, reaching 0.2‰ or better for high concentration samples (>5 mg L-1), comparable to that obtained in a conventional elemental analyzer-IRMS setup. The system blank contribution is the limiting factor in obtaining maximal performance; optimal system blanks values are on the order of 0.2 µg C with an isotopic signature varying from -20 to -12‰ during the lifetime of the combustion column. With appropriate blank correction procedures, accurate analyses (±0.5‰ or better) can be obtained on concentrations as low as 0.5 mg DOC L-1, representing the lower limit typically observed in aquatic systems. ...
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Papers by Karine Lalonde