Buffalo Pound Research Articles

Impacts of hydrologic management on the eutrophication of shallow lakes in an intensive agricultural landscape (Saskatchewan, Canada)

Abstract Hydrologic management of shallow lakes is often undertaken to prevent fluctuations in lake level, and to ensure sufficient water volume for economic, domestic, and recreational uses, but there is inconsistent evidence of whether lake‐level stabilisation through hydrological management promotes or hinders eutrophication. Here we used multi‐proxy paleolimnological assessments of water quality (sedimentary carbon, nitrogen, total phosphorus, fossil pigments), and zooplankton community ecology (fossil Cladocera assemblages), combined with Landsat‐derived estimates of lake surface area in two shallow eutrophic lakes, in the Prairies of southern Saskatchewan, Canada, to quantify how 8 decades of contrasting hydrological management strategies (continuous or intermittent) affect primary production and phytoplankton composition. Analysis revealed that irregular hydrological management of Pelican Lake led to sharp increases in primary production concomitant with lake‐level decline. In contrast, continuously managed Buffalo Pound Lake, a drinking water reservoir for regional cities, exhibited slow, persistent eutrophication over decades despite active regulation of water levels. In both lakes, strong correlations of δ 15N values with pigments from diazotrophic cyanobacteria (canthaxanthin) showed that N2‐fixation increased during eutrophication irrespective of the timing of change. Finally, variation in fossil cladoceran density and composition reflected changes in pelagic and littoral habitats (e.g., reduced macrophyte cover) due to changes in both lake level and water quality. Basin comparison shows that while hydrologic management can moderate water quality degradation due to lake‐level change, it does not prevent eutrophication when nutrient influx remains high. Given that regional water availability is forecast to decline in coming decades, we anticipate that continued hydrological management will be unavoidable and will be unable to improve water quality unless nutrient influx is also controlled.

Water Quality and Flow Management Scenarios in the Qu’Appelle River–Reservoir System Using Loosely Coupled WASP and CE-QUAL-W2 Models

The water bodies of the Saskatchewan Prairies suffer multiple stressors, and demand for water is expected to increase. Water quality models can help evaluate water management strategies and risks such as climate change. This study assesses the impact of interbasin water transfers on the water quality of a strategic, eutrophic prairie reservoir that receives poor-quality watershed run-off. A one-dimensional WASP model was used to estimate nutrient transformations in the transfers along a 97 km river channel. The WASP model was then loosely coupled to a two-dimensional CE-QUAL-W2 model of the downstream receiving reservoir. Output from the WASP model was manually transformed into boundary conditions for the CE-QUAL-W2 reservoir model. This method improves on an earlier attempt to estimate nutrient transformations in the transfers using linear regression. Results from the loosely coupled models suggest Buffalo Pound Lake would respond well to the interbasin transfers. The number of threshold exceedances decreased for all modeled water quality variables. Nutrient concentrations were most influenced in the open water season following spring freshet. Any additional reduction of threshold exceedances during winter was minimal in comparison. These results are interesting from a management perspective as increased transfers under winter operations risk ice damage to the river channel.

Comparative Analysis of Empirical and Machine Learning Models for Chla Extraction Using Sentinel-2 and Landsat OLI Data: Opportunities, Limitations, and Challenges

Remote retrieval of near-surface chlorophyll- a (Chla) concentration in small inland waters is challenging due to substantial optical interferences of various water constituents and uncertainties in the atmospheric correction (AC) process. Although various algorithms have been developed to estimate Chla from moderate-resolution terrestrial missions (∼10–60 m), the production of both accurate distribution maps and time series of Chla has proven challenging, limiting the use of remote analyses for lake monitoring. Here, we develop a support vector regression (SVR) model, which uses satellite-derived remote-sensing reflectance spectra ( R r s δ ) from Sentinel-2 and Landsat-8 images as input for Chla retrieval in a representative eutrophic prairie lake, Buffalo Pound Lake (BPL), Saskatchewan, Canada. Validated against in situ Chla from seven ice-free seasons (N ∼ 200; 2014–2020), the SVR model outperformed both locally tuned, R r s δ -fed empirical models (Normalized Difference Chlorophyll Index, 2- and 3-band, and OC3) and Mixture Density Networks (MDNs) by 15–65%, while exhibiting comparable performance to a locally trained MDN, with an error of ∼35%. Comparison of Chla retrieval models, AC processors (iCOR, ACOLITE), and radiometric products (Rayleigh-corrected, surface, and top-of-atmosphere reflectance) showed that the best Chla maps and optimal time series (up to 100 mg m−3) were produced using a coupled SVR-iCOR system.

Bet-hedging bigmouth buffalo (Ictiobus cyprinellus) recruit episodically over a 127-year timeframe in Saskatchewan

The bigmouth buffalo ( Ictiobus cyprinellus) is an iconic freshwater fish native to North America that is in decline. Recent studies have revealed bigmouth buffalo exhibit a slow pace of life, yet demographic information on bigmouth buffalo outside of North Dakota and Minnesota is lacking. We used otoliths to investigate population demographics of bigmouth buffalo in Canada, and also monitored bigmouth buffalo spawning frequency and reproductive success in the wild. From a sample of 52 fish collected during 2018–2021 we found bigmouth buffalo from the Qu'Appelle system more than 125 years old. Only 13 year classes ranging from 1894–1997 were evident with one year class since 1948, indicating recruitment has been episodic. During the past decade (2013–2022) bigmouth buffalo have spawned only once (May 2013) in Buffalo Pound Lake. This spawning effort culminated in recruitment failure because the water-level recession rate was too rapid. Our findings indicate that bigmouth buffalo spawning attempts as well as recruitment occur within a narrow range of water-level fluctuations that may rarely occur, which is enabled by their supercentenarian lifespan, and has direct implications for the conservation of this species.

Buffalo Pound Lake—Modelling Water Resource Management Scenarios of a Large Multi-Purpose Prairie Reservoir

Water quality models are an emerging tool in water management to understand and inform decisions related to eutrophication. This study tested flow scenario effects on the water quality of Buffalo Pound Lake—a eutrophic reservoir supplying water for approximately 25% of Saskatchewan’s population. The model CE-QUAL-W2 was applied to assess the impact of inter-basin water diversion after the impounded lake received high inflows from local runoff. Three water diversion scenarios were tested: continuous flow, immediate release after nutrient loading increased, and a timed release initiated when water levels returned to normal operating range. Each scenario was tested at three different transfer flow rates. The transfers had a dilution effect but did not affect the timing of the nutrient peaks in the upstream portion of the lake. In the lake’s downstream section, nutrients peaked at similar concentrations as the base model, but peaks arrived earlier in the season and attenuated rapidly. Results showed greater variation among scenarios in wet years compared to dry years. Dependent on the timing and quantity of water transferred, some but not all water quality parameters are predicted to improve along with the water diversion flows over the period tested. The results suggest that it is optimal to transfer water while local watershed runoff is minimal.

Improvement of field fluorometry estimates of chlorophyll a concentration in a cyanobacteria‐rich eutrophic lake

AbstractInstrumented buoys are used to monitor water quality, yet there remains a need to evaluate whether in vivo fluorometric measures of chlorophyll a (Chl a) produce accurate estimates of phytoplankton abundance. Here, 6 years (2014–2019) of in vitro measurements of Chl a by spectrophotometry were compared with coeval estimates from buoy‐based fluorescence measurements in eutrophic Buffalo Pound Lake, Saskatchewan, Canada. Analysis revealed that fluorometric and in vitro estimates of Chl a differed both in terms of absolute concentration and patterns of relative change through time. Three models were developed to improve agreement between metrics of Chl a concentration, including two based on Chl a and phycocyanin (PC) fluorescence and one based on multiple linear regressions with measured environmental conditions. All models were examined in terms of two performance metrics; accuracy (lowest error) and reliability (% fit within confidence intervals). The model based on PC fluorescence was most accurate (error = 35%), whereas that using environmental factors was most reliable (89% within 3σ of mean). Models were also evaluated on their ability to produce spatial maps of Chl a using remotely sensed imagery. Here, newly developed models significantly improved system performance with a 30% decrease in Chl a errors and a twofold increase in the range of reconstructed Chl a values. Superiority of the PC model likely reflected high cyanobacterial abundance, as well as the excitation–emission wavelength configuration of fluorometers. Our findings suggest that a PC fluorometer, used alone or in combination with environmental measurements, performs better than a single‐excitation‐band Chl a fluorometer in estimating Chl a content in highly eutrophic waters.

Chasing Northern Pike under Ice: Long‐Distance Movements Following Catch‐and‐Release Ice Angling

AbstractCatch‐and‐release ice angling is a popular recreational activity, but little is known about the postrelease behavior of fish in the winter. Cold water temperatures and an ambush hunting strategy may constrain Northern Pike Esox lucius, limiting their postrelease movements to a small area near the capture location. We used manual acoustic telemetry to track 15 Northern Pike ranging from 56 to 98.5 cm total length for up to 7 d after catch‐and‐release ice angling in Buffalo Pound Lake, Saskatchewan, Canada. All of the fish but one moved unexpectedly long distances of several km over the tracking period. For the fish that were tracked over all 7 d, path lengths traveled ranged from 1.4 to 18.4 km. The minimum daily distance traveled ranged from 0 to 4.6 km and varied significantly by tracking day; the fish moved shorter distances on day 4 postrelease. There was a significant interaction between fish size and day postrelease; larger fish moved shorter minimum daily distances and dispersed shorter distances from the release site over the first 2 d of tracking. In contrast, by 5 d after release, both the largest and smallest fish had dispersed the longest distances from the release site and intermediate‐sized fish dispersed the least. The cumulative path length traveled by day 5 of tracking did not reveal any significant size‐based patterns. Our study raises the possibility that relatively large movements may be common for Northern Pike in the winter despite cold water temperatures and their expected foraging behavior. In addition, postrelease behavior varies with fish size. Habitat and space requirements for Northern Pike in the winter can encompass much larger areas and more habitat features than has been previously envisioned.

Seasonality of pCO2 in a hard‐water lake of the northern Great Plains: The legacy effects of climate and limnological conditions over 36 years

AbstractBiogeochemical processes are active year‐round in ice‐covered lakes, such that processes in one season can affect limnological conditions in subsequent seasons. However, the extent and nature of these legacy effects are poorly understood, particularly for the CO2 content of lakes and when considering gas exchange with the atmosphere. Here, we used a unique 36‐yr dataset of weekly limnological measurements of Buffalo Pound Lake in the northern Great Plains to assess seasonal changes in CO2 concentration and flux and determine how dependent lake pCO2 is on limnological conditions of previous seasons. We found that the lake was a net source of CO2 to the atmosphere (mean 18.5 ± 7.4 mol CO2 m−2 yr−1), with spring potentially accounting for the majority (~ 64% ± 20%) of CO2 efflux, assuming ice in spring was permeable to gas exchange (32.9% ± 19.8% if not). Analysis with generalized additive models (GAMs) demonstrated that current and antecedent seasonal conditions combined to explain 72.6% of deviance in spring pCO2, but that the strength of model predictions and the importance of antecedent conditions diminished in GAMs of summer (43.6%) and fall (23.3%) CO2 levels. This research suggests that pCO2 is regulated by a combination of coeval and historical environmental conditions and shows that quantification of seasonal and annual fluxes requires a mechanistic understanding of the legacy effects of preceding time intervals.

Water quality modeling of a prairie river-lake system.

Eutrophication of an under-ice river-lake system in Canada has been modeled using the Water Quality Analysis Simulation Program (WASP7). The model was used to assess the potential effect on water quality of increasing inter-basin transfer of water from an upstream reservoir into the Qu'Appelle River system. Although water is currently transferred, the need for increased transfer is a possibility under future water management scenarios to meet water demands in the region. Output from the model indicated that flow augmentation could decrease total ammonia and orthophosphate concentrations especially at Buffalo Pound Lake throughout the year. This is because the water being transferred has lower concentrations of these nutrients than the Qu'Appelle River system, although there is complex interplay between the more dilute chemistry, and the potential to increase loads by increasing flows. A global sensitivity analysis indicated that the model output for the lake component was more sensitive to input parameters than was the model output of the river component. Sensitive parameters included dissolved organic nitrogen mineralization rate, phytoplankton nitrogen to carbon ratio, phosphorus-to-carbon ratio, maximum phytoplankton growth rate, and phytoplankton death rate. Parameter sensitivities on output variables for the lake component were similar for both summer (open water) and winter (ice-covered), whereas those for the river component were different. The complex interplay of water quality, ice behaviors, and hydrodynamics of the chained river-lake system was all coupled in WASP7. Mean absolute error varied from 0.03-0.08 NH4-N/L for ammonium to 0.5 to1.7mg/L for oxygen, and 0.04-0.13 NO3-N/L for nitrate.

A Whole-Lake Experiment to Determine the Effects of Winter Droughts on Shallow Lakes

Lake-level fluctuations are common in the North American Great Plains region, where large-scale climate systems (El Nino, the Pacific Decadal Oscillation) and periodic droughts cause substantial hydrologic variability in both summer and winter. To date, most such research has focused on the effects of summer droughts on prairie lake ecosystems; therefore, we studied the impact of water-level decline during winter on ecosystem structure and function. Specifically, we hypothesized that lower lake levels during winter would increase anoxia, freezing and scouring of benthos, fish kills, herbivory by zooplankton, and nutrient release from sediments. In addition, we tested the hypothesis that winter droughts may initiate a switch between alternative stable states (turbid, clear). Physical, chemical, and biological variables were monitored from 1996 to 2001 in both Wascana Lake, which experienced a 50% decline in lake level, and Buffalo Pound Lake, where water levels were constant. A combination of before-after-control-impact (BACI) and multivariate analyses showed that drawdown resulted in elevated NH4-N concentrations following reinundation; otherwise there were few detectable effects on lake water chemistry (PO4-P, NO3-N, total dissolved nitrogen, total dissolved carbon) or pelagic food web structure (phytoplankton, zooplankton), and the experimental lake remained in a macrophyte-rich state. There was, however, a 2.5-fold increase in macrophyte abundance and a shift from a community dominated by Ceratophyllum demersum before drawdown to one composed of Potamogeton pectinatus after manipulation. Overall, the lack of substantial dewatering effects suggests that lakes of the northern Great Plains may be resilient to severe winter conditions, possibly because of the recruitment of fish from regional metapopulations during summer. Further, our results indicate that lower water levels during winter likely promote the buffer mechanisms that reinforce a macrophyte-rich, clear-water state in shallow prairie lakes.

Influence of Natural Organic Matter (NOM) on the Speciation of Aluminum during Water Treatment

Natural organic matter (NOM) is a term collectively used to describe the complex matrix of organic material present in natural waters. The impact of NOM on the speciation of aluminum at Buffalo Pound water treatment plant was evaluated in the present study using fulvic acid. The first stage of the study was to conduct aluminum (Al) speciation experiments (using background dissolved organic carbon levels present in the raw water) at the pilot scale water treatment plant located within the main plant changing the aluminum sulfate (alum) dose from 68 mg L-1 (yearly average dose of the main plant) to 34 mg L-1. The second stage of the study was to conduct jar tests at various alum/DOC ratios. Pilot scale speciation study showed that when the alum/DOC ratio was 5.3, most of the total aluminum in the filtered water was in the form of particulate aluminum. Such an increased particulate aluminum level did not increase the finished water turbidity. Soluble organic aluminum also increased compared to the level in raw water when the alum/DOC ratio was 5.3. Al speciation study conducted during jar testing showed that organically bound aluminum increased from 8 μg L-1 (raw water) to 15 μg L-1 in the finishedwater when the alum/DOC = 1.37. Jar test results also showed that an alum/DOC of at least 7.3 should be maintained in the main plant in order to meet the proposed operating guidelines of 100 μg L-1 of total aluminum by Health Canada given the conditions that finished water soluble aluminum levels may be in the range of 35–40 μg L-1.

Analysis of Trends in Water Quality of Buffalo Pound Lake

In this study various methods were used to understand the temporal behaviour of specific water quality variables of Buffalo Pound Lake in Saskatchewan. Various techniques were employed in trend determination and exponential smoothing techniques were employed in the modelling of fourteen water quality variables. Most of the variables were serially correlated, making the determination of the magnitude of trends unattainable at the 10% level of significance. The only variables with a statistically significant magnitude of trend were available nitrogen (−0.0066 mg/l.yr) and pH (−0.0072/yr). Upward trends in available phosphorus and silica, downward trends in chlorophyll α and sulfate were significant (p < 0.10), according to the Spearman Rank test. Temperature, dissolved oxygen, total dissolved solids, total suspended solids (upward) and colour were not significant (p > 0.10) using the Spearman Rank correlation coefficient. The Spearman Rank correlation coefficient for total phosphorus, and total suspended solids and colour (p < 0.18), suggest that these variables may be reporting the correct direction of the trend at least 82% of the time. Determination of time series models for each variable using exponential smoothing techniques yielded a variety of responses. Adequate models were obtained for temperature, dissolved oxygen, available nitrogen and total suspended solids based on the evaluation of forecast residuals. Models for total dissolved solids, pH and sulfate appeared on the borderline in their ability to predict effectively. No exponential smoothing models could be developed for available phosphorus and fecal coliforms.

Characterisation and concentration profile of aluminium during drinking-water treatment

An aluminium(Al) characterisation study was conducted at a surface water treatment plant (Buffalo Pound Water Treatment Plant (BPWTP) in Moose Jaw, Saskatchewan, Canada) to understand better the effect of alum coagulant on various Al fractions. The raw water source for BPWTP is Buffalo Pound Lake water. The Al sources at BPWTP are: • present naturally Al in the raw water and • Al derived due to use of alum as a coagulant. Seasonal evaluations of Al at BPWTP showed that raw lake water total concentrations were highly variable. Suspended (filterable) Al was the predominant species of raw water total Al. Organic-bound or organo-Al complex Al appeared to be the predominant species of dissolved Al in both raw and treated water during the September to November 1997 Al characterisation study. However, during October to December 1998, inorganic Al dominated dissolved Al content. Characterisation of Al at BPWTP showed that the use of (liquid) Al sulphate (alum) did not increase the concentration of total Al levels. This was because: • alum coagulation was practised at pH 7, at which the Al is least soluble • clarifier and filtration units effectively removed particulate Al and • granular activated carbon (GAC) was capable of removing part of the organic dissolved Al. The study showed that BPWTP would be able to comply with the requirement of Health Canada Guideline value (for conventional treatment plants) for Al of less than 100 ?g/ l as total Al. Turbidity and dissolved organic carbon of the raw water influenced the applied alum dose at BPWTP. WaterSA Vol.28(1) 2002: 99-106

Factors influencing residual aluminium levels at the Buffalo Pound Water Treatment Plant, Saskatchewan, Canada

One of the current concerns for water treatment plants using alum as a coagulant is elevated concentration of residual aluminium in finished water. The objective of the study is to examine the seasonal variations and factors influencing residual aluminium at the Buffalo Pound Water Treatment Plant (BPWTP). Analysis of BPWTP data for two years related to seasonal variations of total/dissolved aluminium levels showed that much of the raw water total aluminium were in particulate form. Raw water particulate aluminium is correlated well (r2 = 0.79 for 1996 and r2 = 0.82 for 1997) with raw water total suspended solids indicating much of the particulate aluminium is derived from the suspended solids present in raw water. An analysis of eight-year data on total/dissolved aluminium, turbidity, dissolved organic carbon and applied alum dosage showed that dissolved organic carbon present in the raw water played a major role in controlling efficacy of alum coagulation at BPWTP. The data showed that when alum/DOC ratio is less than 7, insufficient alum addition led to incomplete coagulation resulting in colloidal material mostly consisting of organic aluminium in particulate form. Hence particulate aluminium increased in treated water. But this increase in particulate aluminium did not increase the turbidity of treated water. This indicated that an adequate alum dose in response to dissolved organic carbon change is important in minimising residual aluminium in treated water at BPWTP.

Limnological succession in reservoirs: a paleolimnological comparison of two methods of reservoir formation

Analysis of diatoms, algal pigments, and chironomids in sediment cores from two otherwise similar prairie reservoirs demonstrated that differences in reservoir formation (river valley impoundment versus lake inundation) and hydrological regime (variable versus stable water level) resulted in distinct patterns of aquatic community change. Lake Diefenbaker, a 500-km2 reservoir created by damming the South Saskatchewan River in 1968, experiences water level fluctuations of 6 m·year-1. In contrast, impoundment of Buffalo Pound Lake in 1952 flooded a natural lake, raised mean water levels ~2.0 m, and reduced water level fluctuations from ~3 to &lt;1 m·year-1. Comparison of fossil records showed that reservoir formation did not inevitably lead to eutrophication. Lake Diefenbaker exhibited typical reservoir ontogeny with three trophic periods, including an initial ~4-year period of eutrophy, a decade of mesotrophy, and a gradual shift to modern productive conditions. Planktonic taxa dominated diatom communities at all times, whereas benthic chironomid and algal remains were rare. In contrast, pigment analyses suggested that phytoplankton standing crops declined after impoundment in Buffalo Pound Lake but that chironomid and macrophyte populations expanded. Such site specificity in trophic development appears to result from differences in the extent of inundation (500 versus ~5 km2) and the magnitude of subsequent water level fluctuations (6.3 versus &lt;1 m).

Factors influencing residual aluminium levels at the Buffalo Pound Water Treatment Plant, Saskatchewan, Canada

One of the current concerns for water treatment plants using alum as a coagulant is elevated concentration of residual aluminium in finished water. The objective of the study is to examine the seasonal variations and factors influencing residual aluminium at the B uffalo P ound W ater Treatment Plant ( BPWTP ). Analysis of BPWTP data for two years related to seasonal variations of total/dissolved aluminium levels showed that much of the raw water total aluminium were in particulate form. Raw water particulate aluminium is correlated well ( r 2 = 0.79 for 1996 and r 2 = 0.82 for 1997) with raw water total suspended solids indicating much of the particulate aluminium is derived from the suspended solids present in raw water. An analysis of eight-year data on total/dissolved aluminium, turbidity, dissolved organic carbon and applied alum dosage showed that dissolved organic carbon present in the raw water played a major role in controlling efficacy of alum coagulation at BPWTP . The data showed that when alum/ DOC ratio is less than 7, insufficient alum addition led to incomplete coagulation resulting in colloidal material mostly consisting of organic aluminium in particulate form. Hence particulate aluminium increased in treated water. But this increase in particulate aluminium did not increase the turbidity of treated water. This indicated that an adequate alum dose in response to dissolved organic carbon change is important in minimising residual aluminium in treated water at BPWTP .

Limnological succession in reservoirs: a paleolimnological comparison of two methods of reservoir formation

Analysis of diatoms, algal pigments, and chironomids in sediment cores from two otherwise similar prairie reservoirs demonstrated that differences in reservoir formation (river valley impoundment versus lake inundation) and hydrological regime (variable versus stable water level) resulted in distinct patterns of aquatic community change. Lake Diefenbaker, a 500-km2 reservoir created by damming the South Saskatchewan River in 1968, experiences water level fluctuations of 6 m·year-1. In contrast, impoundment of Buffalo Pound Lake in 1952 flooded a natural lake, raised mean water levels ~2.0 m, and reduced water level fluctuations from ~3 to <1 m·year-1. Comparison of fossil records showed that reservoir formation did not inevitably lead to eutrophication. Lake Diefenbaker exhibited typical reservoir ontogeny with three trophic periods, including an initial ~4-year period of eutrophy, a decade of mesotrophy, and a gradual shift to modern productive conditions. Planktonic taxa dominated diatom communities at ...

Aluminum Speciation during Drinking Water Treatment

Abstract Aluminum is one of the trace inorganic metals present in drinking water. Aluminum present in alum (a widely used coagulant for water treatment) as well as naturally occurring aluminum in raw water is transformed into various forms (speciation) during drinking water treatment. Speciation of aluminum during drinking water treatment is essential to understand the behavior of aluminum and aluminum species removal during water treatment and also to identify the factors influencing residual aluminum in treated waters. In this connection, an aluminum speciation study was conducted at the Buffalo Pound water treatment plant. Aluminum was fractionated into eight different forms (total, soluble + colloidal, soluble, organic, inorganic, particulate, suspended, and colloidal aluminum). Speciation results showed that raw lake water total aluminum concentrations were highly variable, and almost all of the raw water particulate aluminum (predominant species of total aluminum) was present in suspended form. Soluble aluminum levels throughout the plant (raw to treated) were less than 50 µg/L and most of the soluble aluminum was in organic form. The study showed that granular activated carbon was capable of removing soluble aluminum in organic form. Residual aluminum present in treated water consisted of mostly particulate and organic forms of aluminum. Raw water particulate aluminum correlates well (R2 = 0.90) with raw water turbidity, implying that removal of turbidity from raw water will reduce particulate aluminum in treated waters. Similarly the organic fraction of residual aluminum was influenced by the high dissolved organic carbon present in the raw water. As the soluble aluminum concentrations were less than 50 µg/L, the plant would not have any difficulty to meet a guideline value for aluminum in treated waters in the range of 0.1 to 0.2 mg/L as dissolved aluminum.

Biotoxicity of mercury as influenced by mercury(II) speciation

Integration of physicochemical procedures for studying mercury(II) speciation with microbiological procedures for studying the effects of mercury on bacterial growth allows evaluation of ionic factors (e.g., pH and ligand species and concentration) which affect biotoxicity. A Pseudomonas fluorescens strain capable of methylating inorganic Hg(II) was isolated from sediment samples collected at Buffalo Pound Lake in Saskatchewan, Canada. The effect of pH and ligand species on the toxic response (i.e., 50% inhibitory concentration [IC50]) of the P. fluorescens isolated to mercury were determined and related to the aqueous speciation of Hg(II). It was determined that the toxicities of different mercury salts were influenced by the nature of the co-ion. At a given pH level, mercuric acetate and mercuric nitrate yielded essentially the same IC50s; mercuric chloride, on the other hand, always produced lower IC50s. For each Hg salt, toxicity was greatest at pH 6.0 and decreased significantly (P = 0.05) at pH 7.0. Increasing the pH to 8.0 had no effect on the toxicity of mercuric acetate or mercuric nitrate but significantly (P = 0.05) reduced the toxicity of mercuric chloride. The aqueous speciation of Hg(II) in the synthetic growth medium M-IIY (a minimal salts medium amended to contain 0.1% yeast extract and 0.1% glycerol) was calculated by using the computer program GEOCHEM-PC with a modified data base. Results of the speciation calculations indicated that complexes of Hg(II) with histidine [Hg(H-HIS)HIS+ and Hg(H-HIS)2(2+)], chloride (HgCl+, HgCl2(0), HgClOH0, and HgCl3-), phosphate (HgHPO4(0), ammonia (HgNH3(2+), glycine [Hg(GLY)+], alanine [Hg(ALA)+], and hydroxyl ion (HgOH+) were the Hg species primarily responsible for toxicity in the M-IIY medium. The toxicity of mercuric nitrate at pH 8.0 was unaffected by the addition of citrate, enhanced by the addition of chloride, and reduced by the addition of cysteine. In the chloride-amended system, HgCl+, HgCl2(0), and HgClOH0 were the species primarily responsible for observed increases in toxicity. In the cysteine-amended system, formation of Hg(CYS)2(2-) was responsible for detoxification effects that were observed. The formation of Hg-citrate complexes was insignificant and had no effect on Hg toxicity.

The Distribution of Mercury in the Sediments of Eight Saskatchewan Lakes

AbstractEight lakes located in the southern half of Saskatchewan were sampled in May and June, 1987, to determine the concentration and spatial distribution of mercury in their surface sediments. Katepwa and Buffalo Pound lakes had maximum total mercury sediment concentrations of 0.158 and 0.100 μg · g−1 dry weight respectively, while in the other six lakes the mercury concentration was never greater than 0.04 μg · g−1 dw. Despite this difference in mercury concentration in the sediments of the lakes, walleye sampled from them have high mercury concentrations exceeding 0.5 μ · g−1 (wet weight).