Abstract A new portable in situ flume (PISF) for measuring critical bed shear stress (CBSS) was d... more Abstract A new portable in situ flume (PISF) for measuring critical bed shear stress (CBSS) was developed in this study. The PISF consists of an open bottom sediment erosion chamber and an electrically-driven pump. Unlike most existing in situ flumes with similar designs, the new PISF does not rely on monitoring the flow conditions or particle density in the sediment erosion chamber; instead, it is a pre-calibrated flume. The calibration was performed by first determining CBSS of various selected sediment samples of known particle size and density (using the law of the wall), based on flow velocity-depth profiles measured in a 6 m straight open-channel flume using a Particle Image Velocimetry (PIV) system. These same particles of known CBSS were then used in the new in-situ flume under controlled lab conditions to obtain a series of calibration curves of CBSS vs. pump electrical power. A wide variety of particle types and sizes (simulated sediments) were used in this two-step calibration procedure to widen CBSS measurement range and simulate cohesive force effects. The size of the PISF is much smaller and more practical than other similar devices as lamellar flow conditions are not required and it can be applied to a wide range of sediment types including cohesive sediments.
In temperate urbanized areas where road salting is used for winter road maintenance, the level of... more In temperate urbanized areas where road salting is used for winter road maintenance, the level of chloride in surface waters has been increasing. While a number of studies have shown that the early-life stages of freshwater mussels are particularly sensitive to salt; few studies have examined the toxicity of salt-impacted winter road runoff to the early-life stages of freshwater mussels to confirm that chloride is the driver of toxicity in this mixture. This study examines the acute toxicity of field-collected winter road runoff to the glochidia of wavy-rayed lampmussels (Lampsilis fasciola) (48 h exposure) and newly released juvenile fatmucket mussels (Lampsilis siliquoidea) (<1 week old; 96 h exposure) under different water hardness. The chronic toxicity (28 d) to older juvenile L. siliquoidea (7-12 months old) was also investigated. The 48-h EC50 and 96-h LC50 for L. fasciola glochidia and L. siliquoidea juveniles exposed to different dilutions of road run-off created with moderately hard synthetic water (∼80 mg CaCO3/L) were 1177 (95% confidence interval (CI): 1011-1344 mg Cl-/L) and 2276 mg Cl-/L (95% CI: 1698-2854 mg Cl-/L), respectively. These effect concentrations correspond with the toxicity of chloride reported in other studies, indicating that chloride is likely the driver of toxicity in salt-impacted road-runoff, with other contaminants (e.g., metals, polycyclic aromatic hydrocarbons) playing a de minimis role. Toxicity data from the current study and literature and concentrations of chloride in the surface waters of Ontario were used to conduct a probabilistic risk assessment of chloride to early-life stage freshwater mussels. The assessment indicated that chronic exposure to elevated chloride levels could pose a risk to freshwater mussels; further investigation is warranted to ensure that the most sensitive organisms are protected.
An exploratory study of urban runoff toxicity was undertaken at 14 urban sites, including two sit... more An exploratory study of urban runoff toxicity was undertaken at 14 urban sites, including two sites receiving runoff from major multi-lane divided highways (&gt;100,000 vehicles·day−1). To assess various types of toxicity, a battery of tests was used including Daphnia magna, Microtox™, sub-mitochondrial particles, and the SOS Chromotest (for genotoxicity). The whole data set comprised almost 70 samples and 350 test results, which were reduced to toxicity point values using a toxicity scale. About two fifths of all data did not show any toxic responses, one fifth indicated severe toxicity, one fifth confirmed toxicity, and one fifth potential toxicity. When comparing urban stormwater toxicity to that of multi-lane divided highway (MLDH) runoff, the main difference was noted for the severe toxicity level; almost 20% of MLDH samples were severely toxic compared to 1% of urban stormwater samples. The MLDH data were obtained at the edge of the pavement, and although attenuation of runoff toxicity during transport can be expected, particularly in grassed swales, additional research is required.
The effectiveness of street sweeping as a source control measure for stormwater pollution was tes... more The effectiveness of street sweeping as a source control measure for stormwater pollution was tested at a site in Toronto, using three types of sweepers employed by the City. A paired-plot experimental design was employed along an arterial road with a traffic volume of 26,000 vehicles/day. Typically, after several days of dry weather, one roadway plot was swept by the available sweeper (treated) and the following plot was left unswept (control). After sweeping, sediment on the roadway was sampled on both plots; wet samples were collected by washing off one half of each plot, and dry samples were collected by vacuum cleaning the remaining halves of both plots. Differences between swept and unswept plots were assessed by comparing: (a) conventional sediment quality parameters, total residue mass, and particle sizes for dry sediment samples, and (b) toxicity, conventional water quality parameters, and particle sizes in wet samples. Results were highly variable and contained large uncer...
Water in the urban space has been considered up to now mostly from the perspective of water suppl... more Water in the urban space has been considered up to now mostly from the perspective of water supply, sewage purification and storm water management, with increasing awareness of the necessity of freshwater ecosystems conservation. However there has been little holistic consideration of the freshwater and terrestrial ecosystems for moderation and control of the hydrological cycle in the city. Ecohydrology principles provide a new framework for urban water management where the use of ecosystem properties as an integrating management tool should serve to reduce hydro peaking, improve storm water quality and retention, and convert excess nutrients, pollutants and even sludge in to biomass/bioenergy. In parallel the enhancement of fresh water and green areas in the city space improves human health and quality of life.
Benthic invertebrate assessments can be used to gauge the impact of urban wetweather flows in rec... more Benthic invertebrate assessments can be used to gauge the impact of urban wetweather flows in receiving waters. Experiences from Cemagref in France have shown that standardized benthic indices (e.g. Oligochaete Index of Sediment Bioindication IOBS) can be used to reliably determine the ecological status of urban streams and can be incorporated into the new European Water Framework Directive. The Canadian studies on streams and stormwater ponds using chemical analyses, benthic toxicity testing and benthic community structure comparisons have shown that toxicity was more likely to occur in deeper ponds where fine sediments from urban runoff accumulated. A more comprehensive evaluation of wet-weather flow impacts could be obtained by combining approaches from both countries.
Stormwater treatment by lamellar and conventional clarification, with and without flocculant addi... more Stormwater treatment by lamellar and conventional clarification, with and without flocculant addition, was investigated in Toronto, Ontario, using a pilot-scale rectangular clarifier vessel with removable lamellar plates. During the 2001 to 2003 field seasons, 76 stormwater runoff events were characterized with respect to flow and quality, and further investigated for stormwater treatment. Most stormwater constituent concentrations at this site exceeded those for the U.S. NURP median urban site. A cationic polymeric flocculant dosed at 4 mg/L, with lamellar clarification, provided the best results with a total suspended solids (TSS) removal of 83% at total vessel surface loads up to 36 m/h. The clarification processes produced a concentrated sludge, which was strongly polluted by heavy metals and would require special disposal procedures.
An elutriation apparatus has been proposed for determining the settling velocity distributions of... more An elutriation apparatus has been proposed for determining the settling velocity distributions of suspended solids in combined sewer overflows (CSOs). The apparatus consisted of a series of interconnected cylindrical settling chambers, through which the sample was drawn using a peristaltic pump attached to the outlet of the last settling chamber. Since the diameters of the cylinders were progressively increasing, sediment with different settling velocities settled in different cylinders. By measuring the amount of sediment in each cylinder, the settling velocity distribution was deduced. The apparatus was tested using samples from a CSO outfall in Hamilton, Ontario, Canada. The test results showed that the apparatus performed well for determining settling characteristics of suspended solids and chemical distribution in different settling fractions. The effectiveness of polymer addition to enhance flocculation and settling of CSOs was also tested in this apparatus. The elutriation ap...
Treatment of urban stormwater by clarification, with flocculant addition, was studied in Toronto,... more Treatment of urban stormwater by clarification, with flocculant addition, was studied in Toronto, Canada using a pilot-scale clarifier with removable lamellar plates. Almost 90 stormwater runoff events were characterised at the study site and found fairly polluted. The previous research phase indicated good treatability of this stormwater by lamellar clarification with flocculant addition (total suspended solids, TSS, removal of 84%, at a surface load of 15 m/h), but there were concerns about cleaning plates after storm events. With the aid of numerical modelling, hydraulic improvements to the clarifier inlet zone were retrofitted in 2004 and permitted the removal of the lamellar pack without a loss in treatment efficiency. In the modified clarifier, a cationic polymeric flocculant dosage of 4 mg/L with conventional clarification provided a TSS removal of 77%, at surface loads up to 43 m/h. The use of the polymer did not increase the acute toxicity of the treated effluent. The clari...
Urban stormwater and combined sewer overflow (CSO) discharges are important sources of sediment a... more Urban stormwater and combined sewer overflow (CSO) discharges are important sources of sediment and contaminants (trace metals, PAHs, nutrients and road salts), and cause changes in flow, sediment, chemical and thermal regimes of receiving waters. Over the past several years, benthic conditions of streams representing a range of exposure environments were assessed in Hamilton, Toronto, Oshawa and Kingston, Ontario. Studies progressed from initial surveys of sediment contaminant levels, sediment toxicity and benthic invertebrate community structure to more spatially intensive sampling and experimental approaches that included the use of artificial substrates, in situ water toxicity tests and measurements of contaminant bioaccumulation. Results showed that while sediments and some biota at sites exposed to wet-weather discharges were often contaminated with metals and PAHs and enriched with nutrients, significant biological degradation measured by sediment toxicity or depauperated ben...
Impacts of urban development on a small creek with an on-stream stormwater pond, which was built ... more Impacts of urban development on a small creek with an on-stream stormwater pond, which was built to mitigate the effects of a 13-ha commercial plaza on creek flows, were assessed by investigations of the creek-pond system hydrology, water and sediment chemistry and toxicity, and benthic communities. The hydrology and conventional pollutant loadings of this system were dominated by the creek catchment (4.5 km2), which contributed more than 95% of the total flow; the rest was contributed by the plaza runoff which was less polluted than typical residential runoff. Conventional bioassays (Daphnia magna, Microtox™) did not indicate any confirmed acute toxicity in the creek flow, plaza drainage, or pond outflow. However, sediments accumulated in the pond were rather polluted and several sediment bioassays (including Sediment Microtox™) indicated their severe toxicity. In benthic community assessments, taxa richness and total counts of benthic organisms did not change much when moving from...
A rational-based physical descriptive model (PDM) has been developed to predict the levels of Esc... more A rational-based physical descriptive model (PDM) has been developed to predict the levels of Escherichia coli in water at a beach with dynamic conditions in the Greater Toronto Area (GTA), Ontario, Canada. Bacteria loadings in the water were affected not only by multiple physical factors (precipitation, discharge, wind, etc.), but also by cumulative effects, intensity, duration and timing of storm events. These may not be linearly related to the observed variations in bacteria levels, and are unlikely to be properly represented by a widely used multiple linear regression model. In order to account for these complex relationships, the amounts of precipitation and nearby creek discharge, the impact of various time-related factors, lag time between events and sample collection, and threshold for different parameters were used in determining bacteria levels. This new comprehensive PDM approach improved the accuracy of the E. coli level predictions in the studied beach water compared to...
Urban stormwater management practices impact existing aquatic habitats and create new ones in sto... more Urban stormwater management practices impact existing aquatic habitats and create new ones in stormwater ponds and wetlands. The former case is reviewed and discussed with respect to habitat structure, flow regime, water quality, food sources, and biotic interactions. The latter case is documented by a case study of a stormwater management facility in the Toronto area. The study found that the quality of habitat created in the facility was poor, because of chemical contamination of water and sediment accumulated in the facility. Such contamination could have been avoided by the implementation of pollution source controls, which were recommended in the original design.
Highway runoff is a significant source of contaminants entering many freshwater systems. To provi... more Highway runoff is a significant source of contaminants entering many freshwater systems. To provide information on effects of highway runoff on aquatic biota, runoff samples were collected from three sites representing different classes of highways with low, intermediate and high traffic intensities. Samples were analysed for chloride, trace metals and polycyclic aromatic hydrocarbons (PAHs). Runoff from a major multilane divided highway, with the highest traffic intensity, contained the highest levels of chloride (45–19,135 mg/L) and metals. Runoff solids from this highway contained the highest levels of PAHs (19.7–2142 mg/kg). PAHs were also high (9.83–237 mg/kg and 26.4–778 mg/kg) at the intermediate and low traffic intensity sites, respectively. High concentrations of potent mutagens and carcinogens such as benzo(a)pyrene (0.414–124.62 μg/g) and indeno-pyrene (0.549–50.597 μg/g) were measured in the particulate phase of all runoff samples. Chloride concentrations of winter and e...
The Terraview-Willowfield Stormwater Management Facility (TWSMF) receives inputs of multiple cont... more The Terraview-Willowfield Stormwater Management Facility (TWSMF) receives inputs of multiple contaminants, including metals, polycyclic aromatic hydrocarbons (PAHs), road salt, and nutrients, via highway and residential runoff. Contaminant concentrations in runoff are seasonally dependent, and are typically high in early spring, coinciding with the snowmelt. In order to investigate the seasonal fluctuations of contaminant loading and related changes in toxicity to benthic invertebrates, overlying water and sediment samples were collected in the fall and spring, reflecting low and high contaminant loading, respectively, and four-week sediment toxicity tests were conducted with Hyalella azteca. The effects of metals and PAHs are discussed here; the effects of salts, nutrients, and water quality are discussed in a companion paper. Survival and growth of Hyalella after exposure to fall samples were variable: survival was significantly reduced (64-74% of controls) at three out of four si...
Abstract A new portable in situ flume (PISF) for measuring critical bed shear stress (CBSS) was d... more Abstract A new portable in situ flume (PISF) for measuring critical bed shear stress (CBSS) was developed in this study. The PISF consists of an open bottom sediment erosion chamber and an electrically-driven pump. Unlike most existing in situ flumes with similar designs, the new PISF does not rely on monitoring the flow conditions or particle density in the sediment erosion chamber; instead, it is a pre-calibrated flume. The calibration was performed by first determining CBSS of various selected sediment samples of known particle size and density (using the law of the wall), based on flow velocity-depth profiles measured in a 6 m straight open-channel flume using a Particle Image Velocimetry (PIV) system. These same particles of known CBSS were then used in the new in-situ flume under controlled lab conditions to obtain a series of calibration curves of CBSS vs. pump electrical power. A wide variety of particle types and sizes (simulated sediments) were used in this two-step calibration procedure to widen CBSS measurement range and simulate cohesive force effects. The size of the PISF is much smaller and more practical than other similar devices as lamellar flow conditions are not required and it can be applied to a wide range of sediment types including cohesive sediments.
In temperate urbanized areas where road salting is used for winter road maintenance, the level of... more In temperate urbanized areas where road salting is used for winter road maintenance, the level of chloride in surface waters has been increasing. While a number of studies have shown that the early-life stages of freshwater mussels are particularly sensitive to salt; few studies have examined the toxicity of salt-impacted winter road runoff to the early-life stages of freshwater mussels to confirm that chloride is the driver of toxicity in this mixture. This study examines the acute toxicity of field-collected winter road runoff to the glochidia of wavy-rayed lampmussels (Lampsilis fasciola) (48 h exposure) and newly released juvenile fatmucket mussels (Lampsilis siliquoidea) (<1 week old; 96 h exposure) under different water hardness. The chronic toxicity (28 d) to older juvenile L. siliquoidea (7-12 months old) was also investigated. The 48-h EC50 and 96-h LC50 for L. fasciola glochidia and L. siliquoidea juveniles exposed to different dilutions of road run-off created with moderately hard synthetic water (∼80 mg CaCO3/L) were 1177 (95% confidence interval (CI): 1011-1344 mg Cl-/L) and 2276 mg Cl-/L (95% CI: 1698-2854 mg Cl-/L), respectively. These effect concentrations correspond with the toxicity of chloride reported in other studies, indicating that chloride is likely the driver of toxicity in salt-impacted road-runoff, with other contaminants (e.g., metals, polycyclic aromatic hydrocarbons) playing a de minimis role. Toxicity data from the current study and literature and concentrations of chloride in the surface waters of Ontario were used to conduct a probabilistic risk assessment of chloride to early-life stage freshwater mussels. The assessment indicated that chronic exposure to elevated chloride levels could pose a risk to freshwater mussels; further investigation is warranted to ensure that the most sensitive organisms are protected.
An exploratory study of urban runoff toxicity was undertaken at 14 urban sites, including two sit... more An exploratory study of urban runoff toxicity was undertaken at 14 urban sites, including two sites receiving runoff from major multi-lane divided highways (&gt;100,000 vehicles·day−1). To assess various types of toxicity, a battery of tests was used including Daphnia magna, Microtox™, sub-mitochondrial particles, and the SOS Chromotest (for genotoxicity). The whole data set comprised almost 70 samples and 350 test results, which were reduced to toxicity point values using a toxicity scale. About two fifths of all data did not show any toxic responses, one fifth indicated severe toxicity, one fifth confirmed toxicity, and one fifth potential toxicity. When comparing urban stormwater toxicity to that of multi-lane divided highway (MLDH) runoff, the main difference was noted for the severe toxicity level; almost 20% of MLDH samples were severely toxic compared to 1% of urban stormwater samples. The MLDH data were obtained at the edge of the pavement, and although attenuation of runoff toxicity during transport can be expected, particularly in grassed swales, additional research is required.
The effectiveness of street sweeping as a source control measure for stormwater pollution was tes... more The effectiveness of street sweeping as a source control measure for stormwater pollution was tested at a site in Toronto, using three types of sweepers employed by the City. A paired-plot experimental design was employed along an arterial road with a traffic volume of 26,000 vehicles/day. Typically, after several days of dry weather, one roadway plot was swept by the available sweeper (treated) and the following plot was left unswept (control). After sweeping, sediment on the roadway was sampled on both plots; wet samples were collected by washing off one half of each plot, and dry samples were collected by vacuum cleaning the remaining halves of both plots. Differences between swept and unswept plots were assessed by comparing: (a) conventional sediment quality parameters, total residue mass, and particle sizes for dry sediment samples, and (b) toxicity, conventional water quality parameters, and particle sizes in wet samples. Results were highly variable and contained large uncer...
Water in the urban space has been considered up to now mostly from the perspective of water suppl... more Water in the urban space has been considered up to now mostly from the perspective of water supply, sewage purification and storm water management, with increasing awareness of the necessity of freshwater ecosystems conservation. However there has been little holistic consideration of the freshwater and terrestrial ecosystems for moderation and control of the hydrological cycle in the city. Ecohydrology principles provide a new framework for urban water management where the use of ecosystem properties as an integrating management tool should serve to reduce hydro peaking, improve storm water quality and retention, and convert excess nutrients, pollutants and even sludge in to biomass/bioenergy. In parallel the enhancement of fresh water and green areas in the city space improves human health and quality of life.
Benthic invertebrate assessments can be used to gauge the impact of urban wetweather flows in rec... more Benthic invertebrate assessments can be used to gauge the impact of urban wetweather flows in receiving waters. Experiences from Cemagref in France have shown that standardized benthic indices (e.g. Oligochaete Index of Sediment Bioindication IOBS) can be used to reliably determine the ecological status of urban streams and can be incorporated into the new European Water Framework Directive. The Canadian studies on streams and stormwater ponds using chemical analyses, benthic toxicity testing and benthic community structure comparisons have shown that toxicity was more likely to occur in deeper ponds where fine sediments from urban runoff accumulated. A more comprehensive evaluation of wet-weather flow impacts could be obtained by combining approaches from both countries.
Stormwater treatment by lamellar and conventional clarification, with and without flocculant addi... more Stormwater treatment by lamellar and conventional clarification, with and without flocculant addition, was investigated in Toronto, Ontario, using a pilot-scale rectangular clarifier vessel with removable lamellar plates. During the 2001 to 2003 field seasons, 76 stormwater runoff events were characterized with respect to flow and quality, and further investigated for stormwater treatment. Most stormwater constituent concentrations at this site exceeded those for the U.S. NURP median urban site. A cationic polymeric flocculant dosed at 4 mg/L, with lamellar clarification, provided the best results with a total suspended solids (TSS) removal of 83% at total vessel surface loads up to 36 m/h. The clarification processes produced a concentrated sludge, which was strongly polluted by heavy metals and would require special disposal procedures.
An elutriation apparatus has been proposed for determining the settling velocity distributions of... more An elutriation apparatus has been proposed for determining the settling velocity distributions of suspended solids in combined sewer overflows (CSOs). The apparatus consisted of a series of interconnected cylindrical settling chambers, through which the sample was drawn using a peristaltic pump attached to the outlet of the last settling chamber. Since the diameters of the cylinders were progressively increasing, sediment with different settling velocities settled in different cylinders. By measuring the amount of sediment in each cylinder, the settling velocity distribution was deduced. The apparatus was tested using samples from a CSO outfall in Hamilton, Ontario, Canada. The test results showed that the apparatus performed well for determining settling characteristics of suspended solids and chemical distribution in different settling fractions. The effectiveness of polymer addition to enhance flocculation and settling of CSOs was also tested in this apparatus. The elutriation ap...
Treatment of urban stormwater by clarification, with flocculant addition, was studied in Toronto,... more Treatment of urban stormwater by clarification, with flocculant addition, was studied in Toronto, Canada using a pilot-scale clarifier with removable lamellar plates. Almost 90 stormwater runoff events were characterised at the study site and found fairly polluted. The previous research phase indicated good treatability of this stormwater by lamellar clarification with flocculant addition (total suspended solids, TSS, removal of 84%, at a surface load of 15 m/h), but there were concerns about cleaning plates after storm events. With the aid of numerical modelling, hydraulic improvements to the clarifier inlet zone were retrofitted in 2004 and permitted the removal of the lamellar pack without a loss in treatment efficiency. In the modified clarifier, a cationic polymeric flocculant dosage of 4 mg/L with conventional clarification provided a TSS removal of 77%, at surface loads up to 43 m/h. The use of the polymer did not increase the acute toxicity of the treated effluent. The clari...
Urban stormwater and combined sewer overflow (CSO) discharges are important sources of sediment a... more Urban stormwater and combined sewer overflow (CSO) discharges are important sources of sediment and contaminants (trace metals, PAHs, nutrients and road salts), and cause changes in flow, sediment, chemical and thermal regimes of receiving waters. Over the past several years, benthic conditions of streams representing a range of exposure environments were assessed in Hamilton, Toronto, Oshawa and Kingston, Ontario. Studies progressed from initial surveys of sediment contaminant levels, sediment toxicity and benthic invertebrate community structure to more spatially intensive sampling and experimental approaches that included the use of artificial substrates, in situ water toxicity tests and measurements of contaminant bioaccumulation. Results showed that while sediments and some biota at sites exposed to wet-weather discharges were often contaminated with metals and PAHs and enriched with nutrients, significant biological degradation measured by sediment toxicity or depauperated ben...
Impacts of urban development on a small creek with an on-stream stormwater pond, which was built ... more Impacts of urban development on a small creek with an on-stream stormwater pond, which was built to mitigate the effects of a 13-ha commercial plaza on creek flows, were assessed by investigations of the creek-pond system hydrology, water and sediment chemistry and toxicity, and benthic communities. The hydrology and conventional pollutant loadings of this system were dominated by the creek catchment (4.5 km2), which contributed more than 95% of the total flow; the rest was contributed by the plaza runoff which was less polluted than typical residential runoff. Conventional bioassays (Daphnia magna, Microtox™) did not indicate any confirmed acute toxicity in the creek flow, plaza drainage, or pond outflow. However, sediments accumulated in the pond were rather polluted and several sediment bioassays (including Sediment Microtox™) indicated their severe toxicity. In benthic community assessments, taxa richness and total counts of benthic organisms did not change much when moving from...
A rational-based physical descriptive model (PDM) has been developed to predict the levels of Esc... more A rational-based physical descriptive model (PDM) has been developed to predict the levels of Escherichia coli in water at a beach with dynamic conditions in the Greater Toronto Area (GTA), Ontario, Canada. Bacteria loadings in the water were affected not only by multiple physical factors (precipitation, discharge, wind, etc.), but also by cumulative effects, intensity, duration and timing of storm events. These may not be linearly related to the observed variations in bacteria levels, and are unlikely to be properly represented by a widely used multiple linear regression model. In order to account for these complex relationships, the amounts of precipitation and nearby creek discharge, the impact of various time-related factors, lag time between events and sample collection, and threshold for different parameters were used in determining bacteria levels. This new comprehensive PDM approach improved the accuracy of the E. coli level predictions in the studied beach water compared to...
Urban stormwater management practices impact existing aquatic habitats and create new ones in sto... more Urban stormwater management practices impact existing aquatic habitats and create new ones in stormwater ponds and wetlands. The former case is reviewed and discussed with respect to habitat structure, flow regime, water quality, food sources, and biotic interactions. The latter case is documented by a case study of a stormwater management facility in the Toronto area. The study found that the quality of habitat created in the facility was poor, because of chemical contamination of water and sediment accumulated in the facility. Such contamination could have been avoided by the implementation of pollution source controls, which were recommended in the original design.
Highway runoff is a significant source of contaminants entering many freshwater systems. To provi... more Highway runoff is a significant source of contaminants entering many freshwater systems. To provide information on effects of highway runoff on aquatic biota, runoff samples were collected from three sites representing different classes of highways with low, intermediate and high traffic intensities. Samples were analysed for chloride, trace metals and polycyclic aromatic hydrocarbons (PAHs). Runoff from a major multilane divided highway, with the highest traffic intensity, contained the highest levels of chloride (45–19,135 mg/L) and metals. Runoff solids from this highway contained the highest levels of PAHs (19.7–2142 mg/kg). PAHs were also high (9.83–237 mg/kg and 26.4–778 mg/kg) at the intermediate and low traffic intensity sites, respectively. High concentrations of potent mutagens and carcinogens such as benzo(a)pyrene (0.414–124.62 μg/g) and indeno-pyrene (0.549–50.597 μg/g) were measured in the particulate phase of all runoff samples. Chloride concentrations of winter and e...
The Terraview-Willowfield Stormwater Management Facility (TWSMF) receives inputs of multiple cont... more The Terraview-Willowfield Stormwater Management Facility (TWSMF) receives inputs of multiple contaminants, including metals, polycyclic aromatic hydrocarbons (PAHs), road salt, and nutrients, via highway and residential runoff. Contaminant concentrations in runoff are seasonally dependent, and are typically high in early spring, coinciding with the snowmelt. In order to investigate the seasonal fluctuations of contaminant loading and related changes in toxicity to benthic invertebrates, overlying water and sediment samples were collected in the fall and spring, reflecting low and high contaminant loading, respectively, and four-week sediment toxicity tests were conducted with Hyalella azteca. The effects of metals and PAHs are discussed here; the effects of salts, nutrients, and water quality are discussed in a companion paper. Survival and growth of Hyalella after exposure to fall samples were variable: survival was significantly reduced (64-74% of controls) at three out of four si...
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