1,720,980 research outputs found
Escherichia coli contamination of rural well water in Alberta, Canada is associated with soil properties, density of livestock and precipitation
Full text linkWaterborne outbreaks of infectious disease continue to be a public health risk, particularly those in areas where testing of private and public small system groundwater systems is left to the owners/overseers of these wells who may not recognize the importance of testing and treatment. Recognizing factors associated with contamination of wells is important for public safety and can encourage well owners/overseers to test regularly and properly maintain drinking water supplies. Tests results for presence/absence of total coliforms and Escherichia coli for private and public untreated well water for the years 2010-2012 (n=56,609) were provided by the Alberta Provincial Laboratory for Public Health. Tests were geolocated with the Alberta Township Survey System and aggregated to the quarter section. Agricultural independent variables were provided by the Canadian Agricultural Census and monthly cumulative precipitation was calculated using Alberta Agriculture and Forestry’s website of weather station data. Overall frequency of E. coli-positive wells in the study was 1.4%. A marginal multivariable logistic regression model was fit using generalized estimating equations to account for repeat testing of some quarter sections. Three significant factors associated with increased E. coli-positive untreated drinking water wells were identified: soil properties (KSat and sand content), animal density and monthly cumulative precipitation
Temporal and Spatial Monitoring of E. coli and Pathogen Indicators in the Shallow Groundwater and Vadose Zone, Abbotsford, British Columbia, Canada
No full textBibliography: p. 53-60Some pages are in colour
Fecal indicator transport in a river-connected alluvial aquifer
No full textBibliography: p. 87-95Some pages are in colour.Includes CD-R containing appendices
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Remediation of a Salt-Affected, Macroporous Soil in Central Alberta, Canada
No full textSalt-affected soil may be characterized by both elevated salinity and sodicity. High salinity levels impair plant growth and result in reduced plant yield. Leaching of salt from affected soil may be utilized to improve plant growth or to meet regulatory soil quality guidelines. As salinity levels decline during the leaching process recalcitrant elevated sodicity levels may result in clay swelling and disruption of soil structure. The accompanying reduction in soil permeability can produce poor soil drainage and reduced plant growth. The focus of this thesis is the remediation of salt-affected soil resulting from produced water releases associated with oil and gas production. Laboratory and field characterization and experiments were conducted on salt-affected soil at a former production facility in central AB, 35 km southwest of Edmonton. The objective of this thesis is to improve remediation outcomes using salt leaching in the relatively dry climate and fine-grained soil conditions typical of the Canadian prairies (CP). In addition, the effect of soil mineralogy on remediation of salt-affected soils is examined by quantifying the effect of gypsum and calcite dissolution on soil saturated paste extract (SPE) salinity and sodicity, as well as saline-sodic effects on hydraulic conductivity due to clay swelling.
Gypsum (CaSO4•2H2O) was added to the soil as a Ca-amendment to ameliorate elevated Na levels. Calcite (CaCO3) occurs naturally in this soil. Sulphate and HCO3 mass in the SPE was compared to that in soil water samples collected from the field using suction lysimeters. Excess sulphate mass attributed to gypsum dissolution was measured in the SPE, while negligible excess calcite dissolution was determined. Excess gypsum dissolution occurred in 30 % of the soil samples. Gypsum dissolution in the saturated paste resulted in an overestimation of electrical conductivity (EC) by 22 % on average and an underestimation of sodium adsorption ration (SAR) by 7.6 % on average. The relative error increased as soil salinity and sodicity approached regulatory guidelines of 3 dS/m for EC and 4 for SAR. Following application of the correction for excess gypsum dissolution, the number of samples that met regulatory guidelines for both EC and SAR increased from 3 to 8, a 167 % increase.
Smectite, a swelling clay, is present in the soil under study, comprising 48 % of the clay-sized (<2 µm) fraction. Laboratory permeameter testing on intact soil cores demonstrated that 46 % of hydraulic conductivity reduction induced by clay swelling during leaching of moderately sodic conditions (SAR = 14) occurs following stabilization of effluent soil salinity. This time-dependent effect is attributed to slow diffusion of a small fraction of salt from smectite-bound pores. Additionally, variable degrees of recovery of hydraulic conductivity were observed upon application of high salinity permeant. This implies that saline-sodic swelling effects on pore structure are not fully reversible. Confined and intact subsoil shows greater sensitivity to saline-sodic induced reduction in hydraulic conductivity than repacked soils used in other research studies. Saline-sodic swelling effects represent a greater hazard to hydraulic conductivity to saline-sodic subsoils than surface soils for a similar swelling clay content.
A field irrigation experiment was conducted to increase leaching rates under naturally dry climate conditions. Supplementing natural precipitation with irrigation resulted in varying degrees of leaching from good to negligible, depending on the soil moisture condition. Efficient and timely leaching in fine-grained, macroporous soil is complicated by complex interaction between preferential flow in macropores and saline pore water stored within the soil matrix. Infiltration and drainage result in mixing of fresh water infiltrated through macropores with saline pore water within the aggregated soil matrix. Good leaching efficiency was achieved using repeated cycles of irrigation and drainage. In contrast, under continuous matrix-saturated moisture conditions, persistent fresh water flow in macropores bypassed the saline soil matrix resulting in negligible leaching efficiency. Control of infiltration and drainage cycles to produce good leaching efficiency are well suited to automated irrigation. Soil moisture conditions should be cycled between field capacity and saturation for optimal salt leaching
Evaluating the Effectiveness of Bioretention Systems for Managed Aquifer Recharge in Cold Climates
No full textBioretention systems are a low impact development (LID) technology being utilized to mitigate the flooding and contamination impacts of urbanization on stormwater runoff. These systems are difficult to monitor in cold climates using traditional water-budget techniques when surface temperatures drop below freezing. A bioretention system in the Town of Okotoks, Alberta Canada was investigated to address four objectives. 1) Develop a method to monitor the system year-round. 2) Investigate seasonal changes in the infiltration and recharge characteristics of the system. 3) Determine if there was evidence of nutrient leaching from the system. 4) Develop a technique to estimate recharge from the system. The site was instrumented using a paired monitoring well set-up that allowed for characterization of the local groundwater mound induced by recharging waters. The solution of Hantush was used to calculate the recharge rates required to produce observed groundwater mounding heights and estimate the recharge produced by the bioretention system on a per-event basis. The method overestimated recharge by a factor of three compared to estimates obtained using the water budget technique, but could be corrected by finding an appropriate K value to match the water budget data. The system was estimated to recharge 2500 m3 of stormwater over two years. Winter snow-melt events produced recharge volumes comparable to those induced by a 4.5 mm summer precipitation event. Recharge volumes were found to be strongly correlated with precipitation magnitude, groundwater mound height, and the duration of the mounding event, and had no significant correlation with antecedent soil moisture. Nitrate leeching was observed beneath the bioretention system, with aquifer nitrate concentrations reaching 3.8 mg/L. While bioretention systems are effective at recharging aquifers in cold climates, groundwater plays an important role in the function of these treatment-infiltration systems and care must be taken to ensure nitrogen contamination does not lead to adverse ecological impacts for wildlife or humans. Future work should look at decreasing the uncertainty in recharges estimates associated with this method and accounting for the impact of heterogeneous and anisotropic aquifers with time-variant infiltration rates and recharge pond geometries at surface
A Mesocosm Study of Bioretention Functionality Under Frozen Conditions
No full textUrbanization interrupts the natural hydrologic cycle through the development of large impervious areas that prevent infiltration and introduce contaminants to stormwater. Bioretention is a green stormwater management strategy designed to restore natural hydrologic conditions in urban areas by promoting infiltration and removing contaminants at the source. Bioretention technology has proven to be effective in warm climates, but questions remain regarding how the systems perform in cold climates. This study investigated how bioretention systems function under frozen conditions using 24 mesocosm cells in Okotoks, Alberta. The mesocosm cells were lined and had three types of media, three types of vegetation, and two different impervious to pervious ratios. Media types included two typical bioretention media as well as an experimental mixture of clay loam and woodchips. Simulated spring melt events were conducted at the end of March 2021 and March 2022, with an additional event included at the beginning of March 2022 to observe the influence of midwinter melts on bioretention performance. Datasets were analyzed to compare frozen performance among the different design parameters and simulated events, and were also compared to unfrozen conditions using existing datasets from a separate study conducted at the site. The results of this study showed an average 80% decrease in infiltration rate under frozen conditions relative to unfrozen, with significant difference in infiltration rate depending on media type. The findings show that hydrologic performance is largely based on media type, and more specifically, the ability of the media to support preferential flow under frozen conditions. Preferential flow also limited the effects of refreezing midwinter meltwater, as no significant difference in infiltration rate was seen following the midwinter melt event. Nutrient performance was comparable between frozen and unfrozen conditions, with most cells leaching relatively low concentrations of nutrients. Nutrient removal was largely dependent on media type, but plant nutrient uptake also appeared to play an important role. Overall, the results of this study showed that bioretention systems function well under frozen conditions, but the reduced infiltration rates and effects of preferential flow must be taken into consideration when designing the systems
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