Lake Ontario Water Research Articles

Capture-SELEX for Chloramphenicol Binding Aptamers for Labeled and Label-Free Fluorescence Sensing.

Chloramphenicol (CAP) is a potent antibiotic. Due to its side effects, CAP is currently banned in most countries, but it is still found in many food products and in the environment. Developing aptamer-based biosensors for the detection of CAP has interested many researchers. While both RNA and DNA aptamers were previously reported for CAP, they were all obtained by immobilization of the CAP base, which omitted the two chlorine atoms. In this work, DNA aptamers were selected using the library-immobilized method and free unmodified CAP. Three families of aptamers were obtained, and the best one named CAP1 showed a dissociation constant (Kd) of 9.8 μM using isothermal titration calorimetry (ITC). A fluorescent strand-displacement sensor showed a limit of detection (LOD) of 14 μM CAP. Thioflavin T (ThT) staining allowed label-free detection of CAP with a LOD of 1 μM in buffer, 1.8 μM in Lake Ontario water, and 3.6 μM in a wastewater sample. Comparisons were made with previously reported aptamers, and ITC failed to show binding of a previously reported 80-mer aptamer. Due to the small size and well-defined secondary structures of CAP1, this aptamer will find analytical applications for environmental and food monitoring.

Bromine Content Differentiates between Construction and Packaging Foams as Sources of Plastic and Microplastic Pollution

Plastic foams are used to make food packaging, consumer product protective packaging, and building insulation materials–each of which are reported in the environment. This study investigated the contributions of construction and packaging applications to foam plastic litter using visual characteristics and the presence of bromine (Br) from flame retardants as an identifying signature. A foam source library of 86 examples that included building materials and packaging demonstrated that 96% of building materials contained Br while only 5% of foam packaging did, as measured by hand-held X-ray fluorescence (XRF) spectrometry. The XRF enabled the detection of Br in particles down to 1 mm in size, enabling both macro- and microplastic foams to be quantitatively assessed for the relative contributions of construction-based activities and packaging sources to the abundance of foam found on Toronto-area beaches, in tributaries, and in Lake Ontario waters adjacent to Toronto. Beach and surface water surveys revealed 58% and 51% of samples, respectively, contained concentrations of Br consistent with construction foams. This significant proportion highlights a need for greater attention toward the management of construction foam waste, for example, developing and implementing best management practices at active sites to prevent foam litter from entering the environment.

Testing restoration methods for Lake Ontario wetlands at a wetland scale

Sedges and grasses have a competitive advantage over cattails at higher elevations in Great Lakes wetlands where periodic low lake levels result in soils too dry to support cattails. Regulation of Lake Ontario water levels eliminated low lake-level years, resulting in cattail invasion. At a wetland scale at two Lake Ontario sites, we tested restoration methods by dredging channels through cattails, using spoil materials to create mounds suitable for sedge/grass growth, seeding mounds, and controlling cattails (T. × glauca) using methods adapted from experimental studies. Soil moisture and subsidence of mound soils were monitored. Vegetation was sampled pre-restoration and in shoreline sedge/grass meadow, emergent, and mound zones for two years following implementation. Although spoil mounds decreased in elevation at both sites, soil moisture increased more at the site with greater subsidence. Mean percent cover and ramet counts of cattails were reduced in sedge/grass and emergent zones at both sites. Mounds with greater soil moisture held more cattails post-construction. Across years at both sites, Carex lacustris and Calamagrostis canadensis increased in the sedge/grass meadow zone with reduction in Typha; Calamagrostis increased on the mounds. Key factors affecting results were cattail litter and, on the mounds, a second year of seeding with in situ cold, moist stratification, as well as soil moisture related to subsidence. Recommendations for future restorations include conducting more detailed soil surveys to assess potential subsidence, dredging wider and deeper channels to provide spoil for higher mounds, actively controlling invasive species, and conducting additional years of post-restoration data collection.

Restoration of a Lake Ontario‐connected fen through invasive Typha removal

Lake‐level regulation that began in 1960 eliminated large fluctuations of Lake Ontario water levels, altering coastal wetland plant communities. More than a half century later, the altered hydroperiod supports dense, monotypic stands of invasive cattail (Typha angustifolia and Typha × glauca), which have diminished overall plant community diversity. As a result, Lake Ontario coastal wetlands are less capable of providing many of their traditional ecological functions. One such wetland is Buttonwood Fen, a floating, lake‐connected peatland on Lake Ontario's southern shore near Rochester, NY. We implemented cattail‐control measures from 2016 to 2018 with the goal of decreasing live and dead cattail biomass and increasing cover of native fen taxa. Site manipulation included removal of dead cattail biomass, cutting new cattail growth when rhizome carbohydrate reserves were at their lowest, and hand‐wicking regrowth with herbicide in early fall. Results showed a decrease in live cattail stem density and cover and dead biomass cover, as well as an increase in cover of fen taxa. Although not a replicated study, our results suggest that removing dead cattail biomass and targeted treatment of live cattail stems via cutting and hand‐wicking with glyphosate can reduce cattail and improve site quality.

Characteristics of the Exchange Flow of the Bay of Quinte and Its Sheltered Embayments with Lake Ontario

The nature of the exchange flow between the Bay of Quinte and Lake Ontario has been studied to illustrate the effects of the seasonal onset of stratification on the flushing and transport of material within the bay. Flushing is an important physical process in bays used as drinking water sources because it affects phosphorous loads and water quality. A 2-d analytical model and a 3-dimensional numerical coastal model (FVCOM) were used together with in situ observations of temperature and water speed to illustrate the two-layer nature of the late summer exchange flow between the Bay of Quinte and Lake Ontario. Observations and model simulations were performed for spring and summer of 2018 and showed a cool wedge of bottom water in late summer extending from Lake Ontario and moving into Hay Bay at approximately 3 cm/s. Observed and modelled water speeds were used to calculate monthly averaged fluxes out of the Bay of Quinte. After the thermocline developed, Lake Ontario water backflowed into the Bay of Quinte at a rate approximately equal to the surface outflow decreasing the flushing rate. Over approximately 18.5 days of July 2018, the winds were insufficiently strong to break down the stratification, indicating that deeper waters of the bay are not well mixed. Particle tracking was used to illustrate how Hay Bay provides a habitat for algae growth within the bay.

Wetland vegetation response to record-high Lake Ontario water levels

Lake Ontario water levels were the highest in recorded history in 2017 and 2019, resulting in significant impacts to shoreline properties and observable (but not previously quantified) changes in coastal wetland vegetation. In this study, we assessed differences in coverage of five plant community guilds (submerged aquatic vegetation, Typha, meadow marsh, shrub, and upland) along the shoreline elevation gradient from 12 Lake Ontario coastal wetlands surveyed from 2009 to 2019. This time period included a span of relatively stable water levels (2009–2016), followed by the two high-water years. In general, we found that extreme high water levels led to a decrease in vegetation coverage, most notably at the lower extent of the elevation ranges for the meadow marsh, shrub, and upland vegetation guilds. We also found a modest increase in Typha coverage at the upper extent of its elevation range in 2019, indicating that Typha advanced into the meadow marsh zone during the study period. These findings can be used to calibrate and validate predictive models that inform adaptive management of the new outflow regulation plan for Lake Ontario and can aid in modelling the dynamics of wetland vegetation in relation to predicted changes in Great Lakes water levels due to climate change.

Separation and Preconcentration of Cobalt(II) from Water Samples with Amberlite CG-120 Resin

A selective solid-phase extraction method has been developed for the preconcentration and separation of trace amounts of Co(II). The method was based on the adsorption of Co(II) ions on the Amberlite CG-120 resin. The adsorbed Co(II) ions on the resin were eluted by 4 mol/L HCI and then they were determined by Flame Atomic Absorption Spectrometry (FAAS). Various experimental conditions, such as pH, type and concentration of eluent, the flow rate of sample and eluent solution, amount of resin, and sample volume were investigated to obtain better sensitivity and effective separation of trace levels of the Co(II) ions. Moreover, the interference effects of some ions on the recovery of Co(II) were also investigated. The developed method was applied for the determination of Co(II) ions in drinking and wastewater samples. The enhancement factor (EF) and limit of detection (LOD) values were found to be 25-fold and 9.32 µg/L, respectively. The accuracy of the method was tested by the certified reference material of TMDA-70.2 Lake Ontario Water and there was a good agreement between found and certified values at a 95% confidence level.

Chemical Analysis of Surface-Level Ozone Exceedances during the 2015 Pan American Games

Surface-level ozone (O3) continues to be a significant health risk in the Greater Toronto Hamilton Area (GTHA) of Canada even though precursor emissions in the area have decreased significantly over the past two decades. In July 2015, Environment and Climate Change Canada (ECCC) led an intensive field study coincident with Toronto hosting the 2015 Pan American Games. During the field study, the daily 1-h maximum O3 standard (80 ppbv) was exceeded twice at a measurement site in North Toronto, once on July 12 and again on July 28. In this study, ECCC’s 2.5-km configuration of the Global Environmental Multi-scale (GEM) meteorological model was combined with the Modelling Air-quality and CHemistry (MACH) on-line atmospheric chemistry model and the Town Energy Balance (TEB) urban surface parameterization to create a new urban air quality modelling system. In general, the model results showed that the nested 2.5-km grid-spaced urban air quality model performed better in statistical scores compared to the piloting 10-km grid-spaced GEM-MACH model without TEB. Model analyses were performed with GEM-MACH-TEB for the two exceedance periods. The local meteorology for both cases consisted of light winds with the highest O3 predictions situated along lake-breeze fronts. For the July 28 case, O3 production sensitivity analysis along the trajectory of the lake-breeze circulation showed that the region of most efficient O3 production occurred in the updraft region of the lake-breeze front, as the precursors to O3 formation underwent vertical mixing. In this updraft region, the ozone production switches from volatile organic compound (VOC)-sensitive to NOx-sensitive, and the local net O3 production rate reaches a maximum. This transition in the chemical regime is a previously unidentified factor for why O3 surface-level mixing ratios maximize along the lake-breeze front. For the July 12 case, differences between the model and observed Lake Ontario water temperature and the strength of lake-breeze opposing wind flow play a role in differences in the timing of the lake-breeze, which impacts the predicted location of the O3 maximum north of Toronto.

Selection of a metal ligand modified DNAzyme for detecting Ni2+

Nickel is a highly important metal, and the detection of Ni2+ using biosensors is a long-stand analytical challenge. DNA has been widely used for metal detection, although no DNA-based sensors were reported for Ni2+. DNAzymes are DNA-based catalysts, and they recruit metal ions for catalysis. In this work, in vitro selection of RNA-cleaving DNAzymes was carried out using a library containing a region of 50 random nucleotides in the presence of Ni2+. To increase Ni2+ binding, a glycyl–histidine-functionalized tertiary amine moiety was inserted at the cleavage junction. A representative DNAzyme named Ni03 showed a high cleavage yield with Ni2+ and it was further studied. After truncation, the optimal sequence of Ni03l could bind one Ni2+ or two Co2+ for catalysis, while other metal ions were inactive. Its cleavage rates for 100 μM Ni2+ reached 0.63 h−1 at pH 8.0. A catalytic beacon biosensor was designed by labeling a fluorophore and a quencher on the Ni03l DNAzyme. Fluorescence enhancement was observed in the presence of Ni2+ with a detection limit of 12.9 μM. The sensor was also tested in spiked Lake Ontario water achieving a similar sensitivity. This is another example of using single-site modified DNAzyme for sensing transition metal ions.

Fate and transport of tritium in the Laurentian Great Lakes system

A mass balance modelling approach was used to help understand the movement and impacts of tritium discharged from Canada Deuterium Uranium (CANDU) reactor facilities into Lake Ontario. A concentration-time model, previously developed, is updated in this study. Historical and projected tritium concentrations for Lake Ontario waters are presented. A model calculated accident scenario (10 times highest accidental release) indicates the importance of dilution to the dispersion of tritium; a “modelled” release in 2016 has tritium levels declining by the year 2030 to “previous 2016 levels”. As part of the mass balance approach, lake-bottom sediments were considered as potential radionuclide “sinks”. Tritium porewater results were noted as perturbations at depth in both short (30–50 cm cores) and long sediment core profiles (to 300 cm). These change in tritium concentrations with depth may have been due to CANDU emissions (as the most likely source) over time, based on records of accidental releases of tritiated coolant water. However, the exact process (advection and/or diffusion) responsible for the penetration of tritium into the lake bottom requires additional physical and hydrogeological characterization of the lake bottom sediments.

Solid phase extraction and preconcentration of some metal ions using Schiff base immobilised silica gel followed by ICP-OES

ABSTRACTIn this study, a simple and efficient solid phase extraction procedure was developed for simultaneous separation and preconcentration of Ba, Cd, Co, Cu, Mn and Ni. The methodology was based on preconcentration of the target analytes on N,N’-bis(4-methoxysalicylidene)-1,3-propanediamine modified silica gel prior to inductively coupled plasma optic emission spectrometry detection. The experimental conditions were as follows: pH of sample 5.00; sample and eluent flow rates 3 mL min−1; sample volume 25 mL; eluent 0.5 mol L−1 HNO3; eluent volume 3.0 mL. Preconcentration factor was achieved as 33.3 for Ba, Co, Mn; 83.3 for Cd, Ni; 166.7 for Cu. Limits of detection were found as 0.33, 0.26, 0.27, 0.36, 0.27 and 0.19 µg L−1 for Ba, Cd, Co, Cu, Mn and Ni, respectively. The relative standard deviations of 2.6–3.8% were obtained via nine parallel analyses. The suggested procedure was successfully validated by the analysis of TMDA-53.3 Lake Ontario water and ERM-CA022a soft drinking water certified reference materials and applied to various natural water samples.

Photointerpretation analysis of plant communities in Lake Ontario wetlands following 65 years of lake-level regulation

Abstract Regulation of Lake Ontario water levels since the St. Lawrence Seaway began operation in the early 1960s reduced the range of lake-level fluctuations and resulted in alteration of wetland plant communities, especially invasion of sedge/grass meadow marsh by cattails. A new regulation plan was implemented in January 2017 that seeks to restore some of the natural range in lake levels to benefit the environment. An adaptive management process accompanied the new Plan 2014, requiring before-after data for evaluation. Aerial photographs from 2014/2015 were obtained from existing sources for 16 wetlands previously assessed from 2001 photographs, and photointerpretation was used to re-map the vegetation types from the earlier study. The updated data set provides further information on wetland response to lake-level regulation. Overall, area of Meadow Marsh decreased from 2001 to 2014/2015 in most wetlands. In some cases, losses were due to increased Cattail abundance and in others to Mixed Emergent abundance. Although area of Cattail did increase at half the sites, expansion landward into Meadow Marsh was likely limited to an upper elevation with drier soils that had not been flooded for at least 15 years. Waterward expansion of Cattail was slow because it occurs by formation of vegetatively-expanding floating mats. The updated data set can now serve as a baseline for future adaptive management evaluations, including response to extreme high lake levels in 2017 and future low lake levels that Plan 2014 should allow during periods of low water supply.

Hydroclimatological Drivers of Extreme Floods on Lake Ontario

AbstractThis study examines the hydrologic and climatic conditions that precede major flood events on Lake Ontario, with the purpose of understanding the potential for seasonal forecasts to inform lake level management. Seven late spring/early summer flood events are identified since 1949, including the record‐breaking flood of 2017. The surface climate, atmospheric circulation, and antecedent lake levels for the preceding winter and spring seasons are examined. Results suggest that flood events are caused by different combinations of high, initial wintertime water levels across all of the Great Lakes, anomalously wet winters across the entire Great Lakes basin, and wet spring conditions, particularly in the eastern part of the basin. Wet winters that precede flood events are often associated with La Niña conditions, while wet springs are often associated with a westward shift of the North Atlantic Subtropical High. As the critical drawdown period for Lake Ontario occurs in the fall, before the onset of anomalous winter or spring/summer inputs, a generalized additive model was used to predict April–August maximum monthly average Lake Ontario water levels using November levels for all Great Lakes, a nonlinear response to the wintertime Niño 3.4 index, and scenarios of April–May overbasin precipitation. The Niño 3.4 index significantly improves lake level predictions, suggesting that an El Niño‐Southern Oscillation signal may be useful for lake level management. Future work needed to verify the use of El Niño‐Southern Oscillation for Lake Ontario flood forecasting and to link the North Atlantic Subtropical High to predictions of springtime Great Lakes climate is discussed.

Ligandless, Task-Specific Ionic Liquid-Based Ultrasound-Assisted Dispersive Liquid–Liquid Microextraction for the Determination of Cobalt Ions by Electrothermal Atomic Absorption Spectrometry

ABSTRACTLigandless, task-specific ionic liquid based ultrasound-assisted dispersive liquid–liquid microextraction (TSIL-USA-DLLME) was used for preconcentration of cobalt ions in food and water samples and in vitamin supplements before analysis by electrothermal atomic absorption spectrometry. The reported method is free of toxic volatile organic solvents and does not require the use of a back-extraction step. The dispersion of extractant was achieved with the use of ultrasound. A TSIL, trioctylmethylammonium thiosalicylate (TOMATS), was served as both the extraction and complexing agent. After microextraction, the TOMATS phase was separated by centrifugation and dissolved in ethanol before analysis. Selected parameters affecting the microextraction including the pH of the sample, the volume of the ionic liquid, the ultrasonication time, centrifugation parameters, and the influence of ionic strength were optimized. The limit of detection was 0.011 ng mL−1 for cobalt ions. The achieved preconcentration factor was 24. The relative standard deviations for the determination of analyte in the real samples were 3–24%. The accuracy of this method was evaluated by the extraction and determination of the analyte in several certified reference materials including INCT-SBF-4 (soya bean flour), INCT-TL-1 (tea leaves), ERM-CAO11b (hard drinking water), INCT-MPH-2 (mixed Polish herbs), TMDA-54.5 (Lake Ontario Water), and NIST 1643e. The measured cobalt contents were in satisfactory agreement with the certified concentrations based on Student’s t-test at the 95% confidence level. The presented method has been successfully applied for the determination of analyte in real samples that include tea, lake water, and vitamin supplements.

Determination of fluorine in herbs and water samples by molecular absorption spectrometry after preconcentration on nano-TiO2 using ultrasound-assisted dispersive micro solid phase extraction

This work presents ultrasound-assisted dispersive micro solid phase extraction (USA DMSPE) for preconcentration of fluorine (F) in water and herb samples. TiO2 nanoparticles (NPs) were used as an adsorbent. The determination with slurry sampling was performed via molecular absorption of calcium monofluoride (CaF) at 606.440 nm using a high-resolution continuum source electrothermal absorption spectrometry (HR-CS ET MAS). Several factors influencing the efficiency of the preconcentration technique, such as the amount of TiO2, pH of sample solution, ultrasonication and centrifugation time and TiO2 slurry solution preparation before injection to HR-CS ET MAS, were investigated in detail. The conditions of detection step (wavelength, calcium amount, pyrolysis and molecule-forming temperatures) were also studied. After extraction, adsorbent with the analyte was mixed with 200 μL of H2O to prepare a slurry solution. The concentration limit of detection was 0.13 ng mL−1. The achieved preconcentration factor was 7. The relative standard deviations (RSDs, %) for F in real samples were 3–15%. The accuracy of this method was evaluated by analyses of certified reference materials after spiking: INCT-MPH-2 (Mixed Polish Herbs), INCT-SBF-4 (Soya Bean Flour), ERM-CAO11b (Hard Drinking Water) and TMDA-54.5 (Lake Ontario Water). The measured F contents in reference materials were in satisfactory agreement with the added amounts, and the recoveries were found to be 97–109%. Under the developed extraction conditions, the proposed method has been successfully applied for the determination of F in real water samples (lake, sea, tap water) and herbs.

Inorganic arsenic speciation in water samples by miniaturized solid phase microextraction using a new polystyrene polydimethyl siloxane polymer in micropipette tip of syringe system

The polymer, polystyrene polydimethyl siloxane was loaded into the micropipette tip of the syringe system as an adsorbent to developed miniaturized solid phase microextraction. Standard solutions of arsenate and arsenite were passed through the adsorbent loaded in micropipette tip to check the adsorption behaviors. It was observed that arsenate adsorbed on the polystyrene polydimethyl siloxane in the pH rang of 6–8, while arsenite was directly passed through the micropipette tip of syringe system. The adsorbed arsenate in micropipette tip of syringe system were eluted by 1.0M hydrochloric acid. The total inorganic arsenic contents were obtained by the addition of oxidizing agent potassium permanganate into the studied samples before passing to the micropipette tip of syringe system. Arsenite concentration in water samples were measured by subtracting arsenate from total inorganic arsenic concentration. Different characteristics which effect the determination of arsenate specie like amount of adsorbent, adsorption capacity, pH, pulled and pushed cycles for adsorption and desorption, volume of sample, eluent type and it volume were also studied in detail. Enrichment factor and detection limit of arsenate by desired method were 218 and 6.9ngL−1 respectively. The relative standard deviation was 4.1% (n=10, C=0.12µgL−1). Accuracy of the desired technique was confirmed by analysis of the CRMs (Lake Ontario Water TM-28.3 and Riverine Water NRCC-SLRS-4). Desired technique was significantly useful for determination of the total arsenic, arsenate, and arsenite contents in different natural water samples.

Mark Retention of Calcein in Cisco and Bloater

AbstractSince 2012, a multi‐agency initiative to restore these native forage species has been under way. Evaluating the restoration success of Cisco Coregonus artedi and Bloater C. hoyi in Lake Ontario waters requires methods to identify stocked fish. However, juvenile Cisco and Bloater are fragile; thus, mass marking techniques that reduce the handling of individual fish are required and have not previously been evaluated. In 2014–2015 we evaluated the usefulness of calcein (SE‐MARK) as a marker on bony structures, including the otolith. Juvenile Bloater and Cisco (14, 100, 128 d old) were immersed in a calcein bath at 5,000 mg/L of water for 4 min to apply the chemical marker. Observations of the marking retention were evaluated 8 d following the treatment. All fish immersed in calcein had strong brilliant marks (rating scale 3) on all bony structures including scales, fin rays, jaw bones, and vertebrate. The otolith was the only hard structure that did not show a brilliant marking due to the opaque nature of the structure. Our results suggest that calcein produces a strong discernable mark on hard bony structures of Cisco and Bloater; however, long‐term retention needs further study.

Schiff base immobilized silica gel framework as an efficient sorbent for preconcentration of Pb and Zn ions in aqueous media

A novel preconcentration method for Pb and Zn ions using a column packed with Schiff base modified silica gel is described. The method was based on the sorption of analytes on N,N'-bis(4-methoxysalicylidene)-1,3-propanediamine modified silica gel and elution with HNO$_{3}$ prior to flame atomic absorption analysis. The parameters pH, flow rate, sample volume, eluent volume, and concentration were optimized using a central composite design. The detection limits were 10.0 $\mu $g L$^{-1}$ for Pb and 1.1 $\mu $g L$^{-1}$ for Zn. The suggested procedure was validated with Lake Ontario water as a certified reference material and recovery percentages were 101.8% for Pb and 98.2% for Zn. The application of the method was performed on snow, tap, bottled, mineral, and lake water samples and recovery percentages were in the range of 96.7%-101.6% and 96.4%-98.4% for Pb(II) and Zn(II), respectively.

Winter’s Hawk: Red-tails on the Southern Plains by Jim Lish

Reviewed by: Winter’s Hawk: Red-tails on the Southern Plains by Jim Lish James A. Hewlett Winter’s Hawk: Red-tails on the Southern Plains. By Jim Lish. Norman: University of Oklahoma Press, 2015. xi + 163 pp. Illustrations, map, references, index. $24.95 paper. Approximately 15 miles northwest of Rochester, New York, the southern shore of Lake Ontario bends slightly to the southeast near Braddock Bay before continuing its eastward expanse toward Sodus Point. This innocuous feature on the map is unlikely to give anyone pause for thought, but for a red-tail hawk traversing the shoreline, a pause is exactly what this geographical twist demands. Carried by the southwest winds that develop during the warming days of early summer, thousands [End Page 146] of juvenile red-tailed hawks are pushed to the northeast from their Ohio Valley nesting grounds and then funneled into Braddock Bay as the cold Lake Ontario waters shut down the thermals that the hawks rely on for their migration. For naturalists and researchers, Braddock Bay’s geographical location makes it one of the prime locations in North America to observe the mass migration of a variety of raptor species. As a biologist studying red-tailed hawks, I have had the great fortune of having access to the natural treasure that exists along the shores of Lake Ontario. While my tenure observing and studying this raptor has spanned the last 10 years, this pales in comparison to the more than 50 years that Jim Lish has spent observing red-tails on the tallgrass prairies of Oklahoma. Like western New York, the Southern Plains are a unique geographical destination for a mass migration of red-tails moving along a flyway that stretches from Alaska and Canada, south along the Great Plains, and into Mexico. Every winter, red-tail hawks migrate south, often pushed along Arctic fronts sweeping out of Canada, to winter in the Southern Plains. Lish’s observations, focused primarily in his home state of Oklahoma, include some of the highest densities of wintering red-tailed hawks ever reported. Observers traveling through portions of western Oklahoma during peak months may find wintering red-tails in densities of one per mile. Lish combines basic biology with classic natural history and nature writing to engage the reader in a story that is both entertaining and educational. His passion for Buteo, and the depth of experience he has gained through years of observation and study, drive a narrative that will appeal to a broad audience. Scholars of natural history will at times recognize a style similar to the works of Aldo Leopold, and a structure resembling many classic 19th-century works. The hand-drawn color plates of a classic natural history work have been replaced here by over 180 color photographs that capture the characteristics and behavior of North America’s most abundant hawk species. While some of the most engaging photographs include hawks posing on a variety of perch substrates, Lish clearly understands the need to utilize underside views of the raptors in flight—a view most commonly experienced in the field and used to identify birds of prey. A two-page, scaled, side-by-side comparison of 24 adult and juvenile red-tailed hawks of various races is a highlight of the text, and is at the core of a lengthy discussion of the variation that exists within Oklahoma’s wintering population. Winter’s Hawk is a must-read for anyone interested in red-tailed hawks, but it will appeal to all readers with an interest in ornithology, nature photography, and natural history. James A. Hewlett Department of Science and Technology Finger Lakes Community College Canandaigua, New York Copyright © 2016 Center for Great Plains Studies, University of Nebraska–Lincoln

Covalent linking DNA to graphene oxide and its comparison with physisorbed probes for Hg2+ detection

Graphene oxide (GO) has attracted extensive research interest as a platform for DNA adsorption and biosensor development. While most researchers use simple physisorption of fluorescently labeled DNA, covalent sensors are less susceptible to non-specific probe displacement and minimize false positive results. In this work, three thymine-rich DNA probes of different lengths are modified on their 3′-end with an amino group for covalent conjugation to GO. They also each contain an internally labeled fluorophore so that Hg2+ binding can lead to a large distance increase between the fluorophore and the GO surface for fluorescence signaling. Hg2+-dependent fluorescence signaling from the covalent sensors are compared with that from the non-covalent sensors in terms of sensitivity, selectivity, signaling kinetics, and continuous monitoring. The covalent sensors are much more stable and resistant to non-specific probe displacement, while still retaining high sensitivity and similar selectivity. The detection limits are 16.3 and 20.6nM Hg2+, respectively, for the covalent and non-covalent sensors, and detection of spiked Hg2+ in Lake Ontario water is demonstrated.