[Show abstract][Hide abstract] ABSTRACT: In this study we investigated the transport of nalidixic acid-resistant Escherichia coli (E. coli NAR) and bromide (Br¯) through two soils, a sandy loam (SL) and clay loam (CL). Soils were repacked in columns (45 cm length × 22 cm diameter) and subjected to physical (freeze/thaw, and wet/dry cycles) and biological (by earthworms, Eisenia fetida) weathering for 12 months. Saturated flow conditions were maintained using a tension infiltrometer. Tests were carried out at either 5 or 20 °C. After steady-state flow conditions were established, a suspension containing E. coli NAR and Br¯ was sprayed onto the surface of soil columns. Leachate was sampled at three depths, 15, 30 and 45 cm. Time to maximum concentration (Cmax) of E. coli NAR was greater for SL at all depths. Both tracers had rapid breakthrough curves (BTCs) shortly after the suspension injection followed by prolonged tailing indicating the presence of preferential pathways and thus soil heterogeneity regenerated after the induced physical and biological weathering. About 40% of the E. coli NAR and 79% of the Br¯ leached through the entire 45 cm soil columns during the experiments. Leaching with cold water (5 °C) led to lower hydraulic conductivity and flow rate and consequently enhanced bacterial filtration for both soils. Very low values for the detachment coefficient for E. coli NAR at 5 °C suggest an irreversible process of bacterial attachment in heterogeneous soils. BTCs were well described by the mobile-immobile model (MIM) in HYDRUS-1D. Soil texture/structure and temperature had a significant effect on the model’s fitted parameters.
Journal of Hydrology 03/2015; 522. · 2.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Cultivating native lands may alter soil phosphorus (P) distribution and availability. The present study aimed to determine the distribution of P in soil aggregates for different long-term land management practices. The partitioned P in labile (L), Fe/Al-bound, Ca-bound, organic pools, and total P in four aggregate size fractions were determined for five land uses (forest, vineyard after 30 years, wetland, alfalfa, and wheat cultivated soil after 20 years). Both native land uses (forest and wetland) were distinguished by high and low amounts of large macro- and micro-aggregates, respectively, compared with disturbed soils (vineyard, alfalfa, and wheat soils). Labile P in large macro-aggregates were higher in native land use when compared with the other land uses, which led to increasing lability of P and accelerated water pollution. Soils under native conditions sequestered more Ca-bound P in large macro-aggregates than the soils in disturbed conditions. Conversion of native lands to agricultural land caused enhanced organic P storage in aggregates smaller than the 2 mm from 31.0 to 54.3 %. Soils under forest had 30 % total P more than the vineyard for the aggregates >2 mm after 30 years land use change. However, the amount of P in smaller (<2 mm) sized aggregates was increased by 29 % for the vineyard when compared with the forest. The P storage as bound Ca particles for the large macro-aggregates had negative correlation with the micro-aggregates.
Environmental Monitoring and Assessment 06/2014; 186(10). · 1.68 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this study the least limiting water range (LLWR) and associated measurements (water content at field capacity, θFC, wilting point, θPWP, air filled porosity, θAFP, and mechanical resistance, θSMR) were tested on two soils of clay loam (CL) and sandy loam (SL), each under long-term cultivation with either wheat (Triticum aestivum L.) or alfalfa (Medicago sativa). Water content at field capacity (θFC) and wilting point (θPWP) decreased slightly with an increase in bulk density (Db) in clay loam soils under wheat and alfalfa, whereas in sandy loam soils under the same cultivation, both values of θFC and θPWP strongly increased by increments of Db. The variation of LLWR was negatively related to Db in clay loam soils under wheat and alfalfa cultivation. The LLWR increased up to Db, equal to 1.56 Mg m−3 (when θFC = θ10kPa) and to 1.60 Mg m−3 (when θFC = θ33kPa) in sandy loam under alfalfa, and 1.42 Mg m−3 (both values of θFC) in sandy loam under wheat; LLWR then declined sharply with increasing Db. The highest value of LLWR was observed in the ranges of 0.034–0.167 cm3 cm−3 (when θFC = θ10kPa) and of 0.034–0.119 cm3 cm−3 (when θFC = θ33kPa) in clay loam under wheat. The lowest value of LLWR was observed in between 0.137 and 0.151 cm3 cm−3 (when θFC = θ10kPa) and between 0.087 and 0.111 cm3 cm−3 (when θFC = θ33kPa) in sandy loam under wheat. Linear regressions (Stepwise) showed that LLWR (when θFC = θ10kPa) was related to bulk density, clay, calcium carbonate (CaCO3) and organic carbon (OC) contents (r2 = 0.79). Considering θFC = θ33kPa, LLWR was related to bulk density, clay and OC contents (r2 = 0.48)
Agricultural Water Management 04/2014; 136:34–41. · 2.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The combined effects of two soil textures and two types of crop management were investigated using lithium and bromide tracers transport under saturated flow conditions. Leaching tests were carried out through intact columns of two soils, a clay loam (CL) and sandy loam (SL), each cropped with either wheat (Triticum aestivam) (W) or alfalfa (Medicago sativa) (A) for 11 years. A saturated steady state flow condition was established using tap water prior to injecting a pulse of 0.005 M LiBr solution onto the surface of the soil columns. Breakthrough curves (BTCs) for leached Br− and Li+ in the soil columns (especially under alfalfa cultivation) exhibited an early arrival time and greater concentrations, indicating preferential flow effects. Relative 5% arrival times were 0.07, 0.11, 0.24 and 0.31 for CL-A, SL-A, CL-W, and SL-W, respectively; its smaller values confirmed the higher possibility of preferential flow under alfalfa than under wheat. The Br− concentration was higher than the Li+ concentration. With the exception of soils under alfalfa (CL-A and SL-A), the peak of the BTCs for Br− occurred earlier than that for Li+, by about 0.4 and 1.2 pore volumes for the CL-W and SL-W cases, respectively. Clay loam soil under alfalfa showed higher Br− and Li+ concentration levels when compared to sandy loam soil under alfalfa crop production. In the soils under alfalfa cultivation, structural cracks, root channels, and earthworm burrows were the cause of higher leached concentrations for both tracers when compared to the soil under wheat. Therefore, alfalfa-induced changes in soil structure lead to continuous macropores, a result of the decomposition of penetrating roots. Our results show that agricultural-management practices (i.e. the type of cropping) can play an important role in making groundwater vulnerable to leached solutes.
[Show abstract][Hide abstract] ABSTRACT: Dye tracing field data were collected in small, steep streams in Ontario and used to calculate longitudinal dispersion coefficients for these headwater streams. A predictive equation for longitudinal dispersion coefficient is developed using combined data sets from 5 steeper head - water streams and 24 milder and larger rivers. The predictive equation relates the longitudinal dispersion coefficient to hydraulic and geometric parameters of the stream and has been developed using multiple regression analysis. The newly developed equation shows impressive accuracy of predictions for longitudinal dispersion coefficient (R2 = 0.86, RMSE = 25, Nash-Sutcliffe coefficient Ens = 0.86 and Index of Agreement D = 0.96) for both small, steep headwater streams as well as large, mild rivers. The Froude number has been introduced as a third key parameter to capture the effect of slope of the reach – in addition to the aspect ratio and bed material surface roughness – on the longitudinal dispersion coefficient. The pronounced improvement in the accuracy of the prediction is due to the addition of the Froude number to capture the effect of the slope of the reach on longitudinal dispersion coefficient. This article is protected by copyright. All rights reserved.
[Show abstract][Hide abstract] ABSTRACT: Saturated hydraulic conductivity (
), among other soil hydraulic properties, is important and necessary in water and mass transport models and irrigation and drainage studies. Although this property can be measured directly, its measurement is difficult and very variable in space and time. Thus pedotransfer functions (PTFs) provide an alternative way to predict the
from easily available soil data. This study was done to predict the
in Khuzestan province, southwest Iran. Three Intelligence models including (radial basis function neural networks (RBFNN), multi layer perceptron neural networks (MLPNN)), adaptive neuro-fuzzy inference system (ANFIS) and multiple-linear regression (MLR) to predict the
were used. Input variable included sand, silt, and clay percents and bulk density. The total of 175 soil samples was divided into two groups as 130 for the training and 45 for the testing of PTFs. The results indicated that ANFIS and RBFNN are effective methods for
prediction and have better accuracy compared with the MLPNN and MLR models. The correlation between predicted and measured
values using ANFIS was better than artificial neural network (ANN). Mean square error values for ANFIS, ANN, and MLR were 0.005, 0.02, and 0.17, respectively, which shows that ANFIS model is a powerful tool and has better performance than ANN and MLR in prediction of
[Show abstract][Hide abstract] ABSTRACT: After rapid urban expansion in Ontario, post-World War II, there followed a lengthy period of time where only minimal infrastructure maintenance occurred. Now, however, most of that infrastructure is approaching the end of its predicted life expectancy, and has started failing at an unprecedented rate. The combination of low maintenance and the increasing age of water distribution infrastructure has resulted in increasing rates of pipe failures. To assign priorities for repair/replacement, artificial neural network modelling is employed. Eight independent variables are employed, namely pipe length, diameter, age, break category, soil type, pipe material, the year of Cement Mortar Lining (if implemented), and the year of Cathodic Protection (if implemented), to determine the importance of different factors influencing the pipe failure rate. The results in application to the distribution system in Etobicoke, Ontario demonstrate that ANN models have very strong predictive capabilities (R2=0.94) when compared with the multiple linear regression method (R2=0.75) to assist rehabilitation planning.
Canadian Water Resources Journal 03/2013; 38(1):24-33. · 1.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Highlights
► Monitored chloride concentrations in the Highland Creek watershed of Toronto for 4 years. ► Preferential flow via “urban karst” highly influenced chloride concentrations in baseflow. ► The rate of increase in chloride concentration is consistent with the rate of urban development. ► Mass balance showed about 40% of the applied road salt enters the shallow aquifer system. ► To meet drinking guidelines would require 50% reduction in mass of salt entering the aquifer.
Journal of Hydrology 02/2013; 479:159–168. · 2.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The applicability of the Qualitative Habitat Evaluation Index (QHEI) as a planning and design tool for stream assessments in southern Ontario was evaluated. QHEI assessments were made at 50 Ontario sites where benthic data were available or collected. QHEI was correlated to % Ephemeroptera-Plecoptera-Trichoptera (%EPT), Hilsenhoff Biotic Index (HBI) and Taxa Richness. QHEI reference ranges of >67.5, 52.5 to 67.5, and <52.5 were determined for Exceptional, Good, and Marginal/Poor habitats, respectively. Predictive regression equations were developed for stream assessment and rehabilitation design. However, only about 50% of the variance in biologic indices is explained by geomorphic stressors within the stream. Further improvement of QHEI and refinement of reference ranges specific to Ontario regions will require further data collection and modelling.
Canadian Water Resources Journal 01/2013; 36(2):149-158. · 1.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study was carried out to investigate the transport of Escherichia coli NAR and bromide (Br) through repacked (R) and weathered (W) soil columns. A suspension containing E. coli NAR and Br were leached and the effluent from the weathered soil columns had greater contaminant concentrations than that from the repacked soil columns. The time to the concentration peak of (C(max)) E. coli NAR and Br increased in the order CL-W < SL-W < SL-R < CL-R. The breakthrough sequence suggests the formation of a heterogeneous soil pore network induced by weathering and the importance of accelerated flow in the weathered columns. The dual-permeability model in HYDRUS-1D software was used to simulate the E. coli NAR and Br transport parameters by inverse modeling. Parameters of the attachment-detachment model were calculated using the dual-permeability model parameters fitted to the BTCs of E. coli NAR. A greater attachment coefficient associated with soil repacking and the finer textured clayey soil demonstrated the importance of adsorbent site and smaller pore spacing in these treatments. Smaller attachment and adsorption isotherm coefficients in weathered soil columns suggest the need for further research to validate this as a predictive model for the risks for vadose zone contaminant transport.
Journal of Environmental Management 05/2012; 107:147-58. · 3.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: s u m m a r y This study was conducted to assess the role of the regeneration of soil structure by physical weathering of soils in columns on the transport of Nalidixic acid-resistant Escherichia coli strain (E. coli NAR) and also Bromide (Br). Leaching experiments were carried out at steady-state flow conditions, under a suction head of 5 cm, through columns of repacked and weathered clay loam (CL) and sandy loam (SL) soils. A pulse-type boundary condition was used and breakthrough curves for bacteria and Br were obtained at three depths during a 24 h leaching experiment. Observed data were analyzed employing the mobile–immobile water (MIM) models for repacked or weathered soil columns using HYDRUS-1D code. Both models described well the effluent concentrations. Calibration of the models to match the observed breakthrough curves of Br and E. coli NAR resulted in a smaller value of dispersivity for the later. For bac-teria, the fitted attachment and straining coefficients increased with the clay content of the soil. Earlier peaks in the breakthrough curves were observed for the weathered soil columns. This was attributed to increased pore connectivity associated with weathering. In contrast the balanced and symmetrical shape of the breakthrough curves from the repacked soil columns indicates that leaching occurred mainly through matrix flow. Ó 2012 Elsevier B.V. All rights reserved.
Journal of Hydrology 03/2012; · 2.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Knowledge of the transport and deposition behavior for pathogenic Escherichia coli is needed to assess contamination and protect water resources. We evaluated the effects of repacked (R) and physically and biologically weathered (PBW) columns of sandy loam and clay loam soils on the transport and retention of E. coli and bromide under saturated and unsaturated flow conditions. PBW soil columns were weathered outdoors by exposure to wetting, drying, freezing and thawing cycles during the winter of 2008 and spring and summer of 2009. These physically weathered soil columns were subjected to additional 6months of biological weathering by 20 earthworms placed onto each soil columns. Nalidixic acid-resistant E. coli (E. coli NAR) and bromide (Br) were employed as pulse tracers and their temporal and spatial variabilities were monitored in the leachate samples. The flow regimes (inlet suction 0 for saturated and 5hPa for unsaturated) were controlled using a tension infiltrometer. Cumulative percentage and maximum concentrations (Cmax) of Br and E. coli NAR and filtration coefficients (λf) of E. coli NAR were assessed. In the repacked soil columns, average bacterial concentration and Cmax in leachate were lower, likely due to enhanced pollutant/soil particle interactions at low water fluxes. The largest λf occurred in the repacked clay loam soil. Accelerated water velocities through preferential flow pathways were likely responsible for the smaller filtration coefficients in the PBW columns. Unsaturated flow conditions resulted in larger λf values for E. coli NAR and smaller Cmax values for both tracers.
[Show abstract][Hide abstract] ABSTRACT: A decline in the water quality of Lake Simcoe, Ontario has been observed over the past few decades. This decline has been attributed to excessive loading of the limiting nutrient phosphorus. Atmospheric deposition of phosphorus is a major non-point source contributing 25–50% of the total phosphorus (TP) load entering Lake Simcoe. The objectives of this study were to quantify seasonal variability of atmospheric TP deposition on Lake Simcoe and to estimate spatial distribution patterns of atmospheric TP deposition on Lake Simcoe. Based on the 1995–2007 period of records, on average 35% of the annual bulk atmospheric TP load occurs in the spring, while the summer, autumn and winter account for 45%, 13% and 7%, respectively. The autumn and winter loads are more or less consistent and exhibit little change much from year to year; however, the summer load can vary greatly. Spatially, the Northwest and Southeast quadrants of the lake show the highest atmospheric TP deposition during the spring and summer months. Most of the soils with the highest vulnerability for wind erosion are located in these quadrants and the dominant winds blow in the NW–SE direction.
Journal of Great Lakes Research 01/2011; 37:15-25. · 1.77 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Possible trends of climate (temperature, precipitation, and potential evapotranspiration (PET)) for Regina, Saskatchewan are described, premised on comparisons of both projections from historical data and calculations from use of four general circulation models (GCMs). Results derived from GCMs of CGCM3.1, CCSM3, HadGEM1 and MIROC3.2, along with a series of storylines describing the relationships between the forces driving greenhouse gas and aerosol emissions during the 21st century, are employed which demonstrate increasing trends in temperature and precipitation. Unlike the identifiable and divergent projections of mean annual temperatures, there are relatively small differences in total annual precipitation projections using a number of projected scenarios of emissions. Further, although the projections indicate higher rates of precipitation are expected, there will not be increased water availability due to greater projected increases in PET, translating to there being less water available in the next century.Les tendances climatiques possibles (température, précipitations et évapotranspiration potentielle) pour Régina, Saskatchewan, sont décrites; elles sont fondées sur des comparaisons de projections tirées de données historiques et des calculs de l'utilisation de quatre modèles de circulation générale (MCG). Les résultats utilisés proviennent des modèles de circulation générale CGCM3,1, CCSM3, HadGEM1 et MIROC3,2, en plus d'une série de synopsis décrivant les relations entre les forces à la base des gaz à effet de serre et les émissions aérosols durant le 21e siècle, ce qui démontre les tendances accélérées dans les températures et les précipitations. Contrairement aux projections identifiables et divergentes des moyennes de températures annuelles, il existe des différences relativement faibles dans les projections de précipitations annuelles en utilisant quelques scénarios d'émissions projetées. De plus, bien que les projections indiquent que des taux de précipitation supérieurs sont prévus, ils n'augmenteront pas la disponibilité de l'eau en raison des plus grandes augmentations projetées d'évapotranspiration potentielle; le résultat sera donc une diminution de la disponibilité d'eau au cours du prochain siècle.
Canadian Journal of Civil Engineering 08/2010; 37(9):1247-1260. · 0.41 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The discovery of vast quantities of hydrocarbons during exploration of the Mackenzie Delta has led to the detection of numerous anomalous deep holes in various delta channels in the past four decades. The proposed pipeline crossing from the Mackenzie Delta to northern Alberta has renewed interest in studying the stability of these deep holes. The main goal of this research project was to study ice-covered flow velocity and bed shear stress distributions using a previously calibrated computational fluid dynamics (CFD) model for a 30 m deep hole in the East Channel of the Mackenzie Delta to provide an initial assessment of its stability. In this study, a previously developed 3D CFD model using the FLUENT code with the renormalization group theory (RNG) k-ε turbulence closure model with nonequilibrium wall functions was adapted to represent ice-covered flow conditions for the study reach. The numerical model was applied to simulate four flow conditions (500, 720, and 1000 m3/s along with a moving ice cover during a flow rate of 720 m3/s). Results indicated that a single vortex was formed near the inner bend above the hole and deposition may be a key process occurring during ice-covered flow conditions.L'exploration du delta du Mackenzie à la suite de la découverte de vastes quantités d'hydrocarbures a mené à la détection de plusieurs fosses d'affouillement profondes anormales dans les divers canaux du delta au cours des quarante dernières années. Le franchissement proposé du pipeline du delta du Mackenzie au nord de l'Alberta a renouvelé l'intérêt de vérifier la stabilité de ces fosses profondes. Le principal objectif de ce projet de recherche était d'étudier la vitesse d'écoulement sous couvert de glace et les distributions des contraintes de cisaillement du lit en utilisant un modèle numérique de la dynamique des fluides étalonné pour une fosse profonde de 30 m dans le canal Est du delta du Mackenzie afin de fournir une évaluation initiale de sa stabilité. Dans cette étude, un modèle numérique tridimensionnel de la dynamique des fluides, développé antérieurement, utilisant le code FLUENT et le modèle de turbulence k-ε « RNG » muni de fonctions de non équilibre des parois, a été adapté de manière à représenter les conditions d'écoulement sous couvert de glace pour la portée de l'étude. Le modèle numérique a ensuite été appliqué pour simuler quatre conditions d'écoulement (500, 720, 1000 m3/s de même qu'un couvert de glace se déplaçant avec un écoulement de 720 m3/s). Les résultats indiquent qu'un seul vortex s'est formé près de la portion interne du coude du fleuve au-dessus de la fosse d'affouillement et que la déposition peut être un processus important survenant durant les conditions d'écoulement sous couvert de glace.
Canadian Journal of Civil Engineering 04/2009; 36(5):791-800. · 0.41 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A new method is developed to integrate empirical data and watershed properties with geographic information systems (GIS) tools to prioritize the sensitivities of streams to deterioration arising from adverse stormwater effects. A risk-based decision-making process based on fuzzy logic methodology is employed, using a broad spectrum of parameters to evaluate stream systems, to rank susceptibility to adverse stormwater effects, and to establish management priorities. The methodology is applied to Grindstone Creek and Highland Creek, two systems with varying susceptibility to the effects of erosion. A comparison of results shows that Highland Creek has a greater risk than Grindstone Creek. Overall, the fuzzy logic methodology was found to be an effective tool for evaluating and prioritizing streams that are susceptible to adverse stormwater effects to establish management priorities.
Canadian Water Resources Journal 01/2009; 34(3):205-228. · 1.22 Impact Factor