Papers by Georges Thériault
Journal of virological methods, 2014
Increasing attention is being paid to the impact of agricultural activities on water quality to u... more Increasing attention is being paid to the impact of agricultural activities on water quality to understand the impact on public health. F-RNA coliphages have been proposed as viral indicators of fecal contamination while porcine teschovirus (PTV) and porcine adenovirus (PAdV) are proposed indicators of fecal contamination of swine origin. Viruses and coliphages are present in water in very low concentrations and must be concentrated to permit their detection. There is little information comparing the effectiveness of the methods for concentrating F-RNA coliphages with concentration methods for other viruses and vice versa. The objective of this study was to compare 5 current published methods for recovering F-RNA coliphages, PTV and PAdV from river water samples concentrated by electronegative nitrocellulose membrane filters (methods A and B) or electropositive Zeta Plus 60S filters (methods C-E). Method A is used routinely for the detection of coliphages (Méndez et al., 2004) and m...
Neurochemical Research, 1989
We have used a cell-free system derived from hamster brain to investigate protein synthesis durin... more We have used a cell-free system derived from hamster brain to investigate protein synthesis during experimental phenylketonuria. In such a system the elongation inhibitor emetine impeded translation in extracts derived from both treated and control animals. On the other hand the initiation inhibitor aurintricarboxylic acid showed no effects on protein synthesis activity of treated hamsters, although it was severely inhibiting in controls. This suggests that initiation is the altered step in brain protein synthesis failure consecutive to phenylketonuria.
The indicator of risk of water contamination by phosphorus (IROWC_P)
was designed to estimate the... more The indicator of risk of water contamination by phosphorus (IROWC_P)
was designed to estimate the level of risk of P contamination in water and how the level of risk has changed over 25 yr
(19812006) in agricultural watersheds of Canada. IROWC_P allows for a qualitative assessment of this risk in
comparison with other regions of eastern and western Canada, and the identification of high to very high risk watersheds
may require on-site assessment and the development of remedial action plans. This study presents an in-depth analysis of
IROWC_P results in the major Great Lakes watersheds of Canada. The risk of water contamination by P remains
acceptable (very low to moderate) in most Great Lakes watersheds, but better management practices (e.g., reduced
fertilization and manure application rates) and improved control of surface runoff may be required in watersheds which
are at increased risk. The Canadian watersheds of the Great Lakes basin showed a 39% reduction in their P applications in
excess of crop requirements between 1981 and 2006 bringing the Ontario provincial P-balance close to equilibrium in 2006.
Vulnerable areas were found south of Kitchener in the Lower Grand River watershed and east of Lake Simcoe.
Physiological and Molecular Plant Pathology, 1992
Accepted for publication ]une 1992( Chitosan, a polymer of#-1,4-o-glucosamine derived from crab-s... more Accepted for publication ]une 1992( Chitosan, a polymer of#-1,4-o-glucosamine derived from crab-shell chitin was applied to tomato plants prior to inoculation with the root pathogen, Fusarium oxysporum f . sp. radicis-lycopersici . Whether chitosan was applied by leaf spraying or root coating, it was found to markedly reduce the number of root lesions caused by the fungus, and to drastically increase the formation of putative physical barriers in infected root tissues . The effect of chitosan on the induction of host cell reactions was observed at concentrations ranging from 0 . 5 to 2 mg ml -' with an optimal effect at 2 mg ml -' . The enhanced protection of tomato roots to fungal attack upon application of chitosan to leaves suggests that chitosan-induced resistance is systemic . Formation of wall oppositions such as papillae and occlusion of xylem vessels with either a network of bubble-like structures or a coating material were among the most typical features of host reactions . In addition, the accumulation of amorphous deposits, probably infused with phenolics from their electron-density, was observed in most intercellular spaces and some host cells . These deposits were often found to interfere with the walls of invading hyphae causing severe alterations . The application of wheat germ agglutinin, a lectin with N-acetylglucosamine-binding specificity, in conjunction with gold-complexed ovomucoid, to tissue sections showed that the walls of severely altered hyphal cells were labelled except in the area closely appressed to host cell walls . This suggests that extracellular chitinases accumulate in the host's cell walls but are not the primary determinants of fungal damage . The possibility that toxic compounds such as phenols and chitosan-induced phytoalexins may be responsible for the observed damage of invading hyphae is discussed .
Canadian Journal of Soil Science
Indicators of risk of water contamination by agricultural pollutants are developed in Canada to a... more Indicators of risk of water contamination by agricultural pollutants are developed in Canada to assess sustainability of agriculture. Crack flow (CF), a key pathway for sub-surface contaminant transport, is part of the transport-hydrology algorithm used in two of these risk indicators. The objective was to develop a methodology for predicting the likelihood of CF in Canadian agricultural soils at the landscape scale. The algorithm considers soil clay content, crack development followed by a runoff event based on water budget, tile drainage, and crops. More than 40% of Canadian farmlands had moderate to very high likelihood of CF, mainly in Manitoba, Ontario and Quebec, due to frequent runoffs on cracked clay soils potentially contributing to groundwater contamination. In Ontario and Quebec, farmlands with high CF likelihood correspond to regions under intensive tile drainage, which increases the risk of lateral translocation of contaminants to surface water bodies. Besides being a c...
In Quebec / Canada, water quality improvement in rural areas greatly depends on the reduction of ... more In Quebec / Canada, water quality improvement in rural areas greatly depends on the reduction of diffuse pollution. Indeed, point source pollution has been reduced significantly in Canada in recent years by creating circumscribed pits for manure and removing animals from stream. Diffuse pollution differs from point source pollution because it is spread over large areas. In agricultural areas, sediment loss by soil and riverbank erosion along with loss of nutrients (phosphorus, nitrogen, etc.) and pesticides from fields represent the main source of non-point source pollution. The factor mainly responsible for diffuse pollution in agricultural areas is surface runoff occurring in poorly drained areas in fields. The presence of these poorly drained areas is also one of the most limiting factors in crop productivity. Thus, a reconciliation of objectives at the farm (financial concern for farmers) and off-farm concerns (environmental concern) is possible. In short, drainage, runoff, eros...
![Research paper thumbnail of Erratum to “Phosphorus algal availability and release potential in suspended and streambed sediments in relation to sediment and catchment characteristics” [AGEE 188 (2014) 169–179]](https://attachments.academia-assets.com/42227854/thumbnails/1.jpg)
Agriculture, Ecosystems & Environment, 2014
Both suspended and streambed sediments from two pairs of streams (intervention outlet and control... more Both suspended and streambed sediments from two pairs of streams (intervention outlet and control outlet, and Branch 14 and Branch 15) in livestock intensive catchments were analyzed for total phosphorus (TP), algal available P (AAP), P fractions and P saturation index (PSI). The variations in sediment P characteristics associated with sediment type and study sites were investigated; and the key variables controlling the variations were explored. Relative to streambed sediments, suspended sediments had significantly higher storage of TP and AAP and greater potential to continue adsorbing P from the water column. The differences between the two groups of sediments mainly resulted from differences in sediment particle size. For both suspended and streambed sediments, concentrations of TP, AAP, organic P (Po) and inorganic P (Pi) were not significantly different between the two catchment outlets, but were significantly higher in Branch 15 than in Branch 14; PSI values were considerably higher in the control outlet than at any of the study sites within the intervention micro-catchment. Sediment properties (e.g., calcium (Ca), aluminum (Al) and organic matter (OM)) and catchment characteristics (e.g., soil M3P status and drainage area) explained 62-87% of the variations in log-transformed TP, AAP, Po, Pi and PSI in suspended sediments, with sediment properties being the main contributor. For streambed sediments, variations in P concentrations and PSI were less well explained (13-56%), and sediment OM was the most importance predictor. Forest area percentage in landscape explained limited (3%) proportion of the variations in streambed sediment P concentrations and PSI.
Water, Air, & Soil Pollution, 2013
Phosphorus (P) release and flux at sedimentwater interface was hypothesized to vary with studied ... more Phosphorus (P) release and flux at sedimentwater interface was hypothesized to vary with studied catchment branches due to differences in water chemistry of recharging groundwater. Stream water, seepage water, groundwater, and resurgence groundwater were collected, and their dissolved reactive P (DRP) concentrations and related water chemistry variables (pH, dissolved oxygen, cations, and anions) were measured to identify P sources in seepage water and resurgence groundwater and to look into their impacts on stream water DRP. Results showed that the groundwatercarried P concentrations were negligible, and, thus, not a direct source of DRP to stream water. However, the upwelling groundwater could contribute to stream water DRP by dissolving calcite-bound P in top sediments of branch 15. The seepage experiment indicated that in branch14, sediment release of reducible P was minimal. Furthermore, the presence of impermeable clay layer over the streambed of branch 14 prevented the transport of water and nutrients from beneath sediments to stream water, further reducing the P flux across the sedimentwater interface. This study revealed that in branch 14, the recharge of anoxic groundwater did not significantly influence stream water P, due directly to its low P concentration, or indirectly to the lack of reducible P and the poor hydrological connectivity in bottom
Water Science & Technology, 2007
The objective of this study is to estimate the soil N flux from the vadose zone to the aquifer of... more The objective of this study is to estimate the soil N flux from the vadose zone to the aquifer of the Wilmot watershed (Prince Edward Island, Canada) for a typical three-year cropping rotation (barley-red clover-potato). A conceptual model estimates that 199-221 tons of N were yearly available for leaching at the watershed scale. A significant portion of this N amount was available for leaching at the end of the crop season representing 80-90% of the annual N balance. Drainage water nitrate concentrations were significantly higher after the potato-rotation year than during the crop season. Low nitrate concentrations were measured at spring thaw indicating that most of the nitrate available from the preceding potato crop season was likely leached at the end of fall or during winter. Early spring ionic exchange membrane sampling show a large availability of nitrate in soil possibly throughout winter as well, resulting from soil N mineralization and nitrification over the winter period. These findings are corroborated by the isotope natural abundance analysis of nitrate in groundwater implying that nitrifiers are significantly active during winter, as well as during the crop season, and that leaching of soil nitrates with seasonal signals takes place whenever recharge is occurring.
Nordic Hydrology, 2007
ABSTRACT A coupled air permeameter-gas chamber has been used to measure both the air permeability... more ABSTRACT A coupled air permeameter-gas chamber has been used to measure both the air permeability and diffusion coefficient of an inert gas through natural ice layers. The apparatus was designed to take sequential measurements of both these parameters for the same sample without any intermediate manipulation of the specimen. In avoiding manipulation, errors related to the structural variations between different replicates are eliminated. The apparatus is portable, allowing measurements to be made directly at the study site. The permeability is directly measured in situ by the air permeameter while gas samples used in the diffusion experiments are collected and subsequently analysed at the laboratory. The validation of the apparatus was accomplished by comparing theoretical values for the permeability of beds of spherical beads with known dimensions. Measured permeability values,for different ice samples vary from 0.005 x 10(-10) to 12.9 x 10(-10) m(2). Mean diffusion coefficients ranged from 0.013 to 0.028 cm(2) s(-1). These values are situated in the range for those found between hard packed snow and loose compacted soil.
Soil Science Society of America Journal, 2002
as flooded soils or sediments, the reading usually stabilizes quickly (several seconds). However,... more as flooded soils or sediments, the reading usually stabilizes quickly (several seconds). However, in transitional Redox potential (E H ) measurement is a reading of voltage differsystem turning from oxidized to more reduced condience between a working electrode such as a Pt electrode and a refertions (350 to Ϫ100 mV) and vice versa, the drift is sigence electrode inserted into the soil or various substrates. This study nificant and may persist over a longer period. In such was conducted to develop a method for continuous, autonomous, and multiple E H measurements using Pt microelectrodes connected to a systems, suggest an overnight stabidata logger. A preliminary field experiment was carried out to assess lization period prior to recording the measurement. the long-term viability of Pt microelectrodes installed in situ. A second Long-term, continuous measurements of redox poexperiment was conducted in the laboratory to test an interface detential would provide insight of the dynamics of changes signed to allow the stabilization of E H measurements. The Pt microin a soil profile when environmental conditions are draselectrodes and reference electrode showed reliable readings during tically modified (e.g., after addition of organic matter, the field trial and generally tested viable at the end of the four month flooding, and fertilization). To achieve this goal, the experiment. However, discrepancies between logged E H measurelong-term viability of electrodes installed in situ needs ments and manually stabilized readings, particularly under moderate to be assessed and an automated, continuous recording reductive conditions, emphasized the necessity to adapt the principle of stabilized E H values must be accessible. Although Pt of manually stabilized readings to the use of a data logger. Laboratory data obtained from pairs of Pt microelectrodes and reference elec-electrodes installed in situ over a long time may become trodes connected to a new homemade interface confirmed that instancontaminated by surface reactions and lose their effitaneous logged measurements led to the underestimation of E H values ciency and accuracy (Bohn, 1971; Devitt et al., 1989), by 140 mV in the critical and unstable range of 0 to 200 mV. Continusome studies demonstrated that electrode performance ous, multiple measurements of stabilized E H using Pt microelectrodes was not significantly impaired by poisoning even after is now feasible using a stabilization interface placed between the micromany months of use (Smith et al., 1978; Austin and electrode and the data logger.
Journal of Water and Climate Change, 2014
This study investigated the effects of climate change (CC) on water redistribution in a microwate... more This study investigated the effects of climate change (CC) on water redistribution in a microwatershed of a lowland agricultural area of the Bras d'Henri River in the temperate cold climate of Quebec, Canada. A Water Flow and Balance Simulation Model (WaSiM-ETH) was used to simulate the hydrology using current climatic conditions and land use characteristics, applying Richards' equation.
Journal of Hydrology, 2010
Large scale assessment 25 Preferential flow 26 Risk assessment 27 2 8 s u m m a r y 29 Indicators... more Large scale assessment 25 Preferential flow 26 Risk assessment 27 2 8 s u m m a r y 29 Indicators of risk of water contamination (IROWCs) by agricultural contaminants are developed to assess 30 sustainability of agriculture. Burrow flow (BF) is part of the transport hydrology algorithm used in IRO-31
Journal of Geophysical Research, 2001
We investigated soil and snow cover gas concentrations at two agricultural sites (St-Lambert; Cha... more We investigated soil and snow cover gas concentrations at two agricultural sites (St-Lambert; Chapais) in Quebec, Canada, during winter 1998-1999. Both sites showed frozen and unfrozen soils and complex snow cover structure. At St-Lambert we measured higher average concentrations of N20 (35 to 62/•L L -•) and CO2 (3 to 19 mL L -•) below the frozen soil surface of plots subjected to a treatment of pig slurry than in the 1 1 control plot (N20 , 9 to 30/•L L-; CO2, 3 to 7.5 mL L-). The lack of vertical gaseous concentration gradients in the snowpack was due to the trapping of accumulating gas below the impermeable frozen soil layer. Soil gas concentrations decreased sharply when soil warmed to the freezing point. At the same time, the snow cover was isothermal. N20 could have been lost at spring thaw through gaseous emissions and/or dissolved in meltwaters and leached to the drainage system. High N20 fluxes were measured using closed chambers (215 ng m -2 s -•, slurry treatment; 55 ng m -2 s -•, control) as soon as snow ablation was completed, but became negligible 2 days later, suggesting that emissions were the result of passive degassing rather than of increased biological activity. At Chapais, N20 and CO2 accumulated in the unfrozen soil surface below a thick (0.1 m) basal ice layer. The basal ice layer and the continuous ice layer above it were impermeable to gas diffusion, as demonstrated by the accumulation of a tracer gas (Ar, >50 mL L -•) introduced by a diffuser into the soil. The existence of a basal ice layer is uncommon in eastern Canada. The occurrence of such a phenomenon may increase with climate change due to more frequent rain events during the cold season and affect the dynamics of winter gas emissions from soils. 23,061 23,062 VAN BOCHOVE ET AL.: ICE LAYERS AND FROZEN SOIL
Journal of Environment Quality, 2012
The indicator of risk of water contamination by phosphorus (IROWC_P) modified was designed to est... more The indicator of risk of water contamination by phosphorus (IROWC_P) modified was designed to estimate for the first time where the risk of water P contamination by agriculture is high, and how this risk is changing over 25 years in agricultural watersheds of Canada. The IROWC_P source component integrates four models of soil P water desorption for dominant and subdominant agricultural soil series of Canada with the cumulative P_Balance for each geographical unit. The transporthydrology component (T_H) connects surface runoff, drainage and erosion yearly estimates with the most relevant parameters relating agricultural lands to their hydrologic network. Best linear combinations of T_H explaining significantly the variations of P concentrations monitored at watershed outlets across the country were found for Western (r=0,55) and Eastern (r=0,44) Canada. IROWC_P values distributed in 282 watersheds over six Census years showed that 24% of the watersheds were at high to very high risk of P water contamination in 2006 and that 62% switched to worst risk classes from 1981 to 2006. Results also demonstrated that BMPs have positive impacts on risk mitigation but that more efforts have to be carried on to reverse risk of water contamination by P from agriculture.
Canadian Journal of Soil Science, 2007
Canadian Journal of Soil Science, 2010
Development of a method for estimating the likelihood of crack flow in Canadian agricultural soil... more Development of a method for estimating the likelihood of crack flow in Canadian agricultural soils at the landscape scale. Can. J. Soil Sci. 90: 129Á149. Indicators of risk of water contamination by agricultural pollutants are developed in Canada to assess sustainability of agriculture. Crack flow (CF), a key pathway for sub-surface contaminant transport, is part of the transport-hydrology algorithm used in two of these risk indicators. The objective was to develop a methodology for predicting the likelihood of CF in Canadian agricultural soils at the landscape scale. The algorithm considers soil clay content, crack development followed by a runoff event based on water budget, tile drainage, and crops. More than 40% of Canadian farmlands had moderate to very high likelihood of CF, mainly in Manitoba, Ontario and Quebec, due to frequent runoffs on cracked clay soils potentially contributing to groundwater contamination. In Ontario and Quebec, farmlands with high CF likelihood correspond to regions under intensive tile drainage, which increases the risk of lateral translocation of contaminants to surface water bodies. Besides being a component of risk indicators of water contamination by phosphorus and coliforms, the CF algorithm and maps can be used to identify areas at risk of subsurface water contamination. Best management practices, adapted to reduce CF can then be targeted to these areas.
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Papers by Georges Thériault
was designed to estimate the level of risk of P contamination in water and how the level of risk has changed over 25 yr
(19812006) in agricultural watersheds of Canada. IROWC_P allows for a qualitative assessment of this risk in
comparison with other regions of eastern and western Canada, and the identification of high to very high risk watersheds
may require on-site assessment and the development of remedial action plans. This study presents an in-depth analysis of
IROWC_P results in the major Great Lakes watersheds of Canada. The risk of water contamination by P remains
acceptable (very low to moderate) in most Great Lakes watersheds, but better management practices (e.g., reduced
fertilization and manure application rates) and improved control of surface runoff may be required in watersheds which
are at increased risk. The Canadian watersheds of the Great Lakes basin showed a 39% reduction in their P applications in
excess of crop requirements between 1981 and 2006 bringing the Ontario provincial P-balance close to equilibrium in 2006.
Vulnerable areas were found south of Kitchener in the Lower Grand River watershed and east of Lake Simcoe.
was designed to estimate the level of risk of P contamination in water and how the level of risk has changed over 25 yr
(19812006) in agricultural watersheds of Canada. IROWC_P allows for a qualitative assessment of this risk in
comparison with other regions of eastern and western Canada, and the identification of high to very high risk watersheds
may require on-site assessment and the development of remedial action plans. This study presents an in-depth analysis of
IROWC_P results in the major Great Lakes watersheds of Canada. The risk of water contamination by P remains
acceptable (very low to moderate) in most Great Lakes watersheds, but better management practices (e.g., reduced
fertilization and manure application rates) and improved control of surface runoff may be required in watersheds which
are at increased risk. The Canadian watersheds of the Great Lakes basin showed a 39% reduction in their P applications in
excess of crop requirements between 1981 and 2006 bringing the Ontario provincial P-balance close to equilibrium in 2006.
Vulnerable areas were found south of Kitchener in the Lower Grand River watershed and east of Lake Simcoe.