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The package PbIso is a free and open R toolbox for commonly used calculations and plots of Pb–Pb isotope data and for generating Pb evolution models. In this paper, we review Pb isotope systematics and the calculations that are commonly used, such as model age, model source μ (238U/204Pb), time-integrated κ (232Th/238U), and initial Pb isotope ratios. These equations are implemented into R functions in the package PbIso. In addition, functions are provided for generating Pb evolution models, paleoisochrons, and isochrons. This allows users to apply calculations to their data in a straightforward way while providing transparency and flexibility of the calculations used. We have implemented some basic features of the PbIso package into an online shiny R application (see https://shereearmistead.github.io/software/pbiso), which makes it easy for users without any R experience to use these calculations with their own data and to generate plots. We have provided a case study from the Superior Province in Canada, showing how different Pb evolution models can be generated in PbIso and compared to Pb isotope data. [ABSTRACT FROM AUTHOR]

We report the discovery of one of the largest ancient (>3.0 Ga) crustal terranes on Earth. Granitoids with crystallization ages >3.0 Ga and/or Sm-Nd depleted mantle model ages ≥3.2 Ga define a -1000 x 100 km belt on the western margin of the Rae craton, Canada, referred to herein as the Perry River terrane (PRT). Zircon U-Pb-Hf-O isotope and whole-rock geochemical data from granitoids show that the PRT is a predominantly juvenile 3.3--3.2 Ga terrane that was partially reworked by more evolved ca. 3.1 Ga magmatism. These findings call for a reassessment of the timing and extent of ancient continental growth on Earth. A global compilation of zircon Hf isotope data from 3.6 to 3.0 Ga igneous rocks reveals clusters of relatively juvenile (initial εHf -2 to +3) rocks at ca. 3.31 and ca. 3.23 Ga, which include samples from the PRT and 13 other terranes worldwide. Other global zircon data sets also document age peaks between 3.3 and 3.2 Ga, and a cluster of broadly chondritic initial εHf values around 3.2 Ga. The 3.3--3.2 Ga period may therefore have been a time of enhanced net continental growth on Earth, and the PRT is one of the largest terranes preserved from that time. Furthermore, zircon Hf isotope data from 3.3--3.1 Ga PRT granitoids and 3.5--3.0 Ga igneous rocks worldwide yield little evidence for parent magmas that interacted with or derived from pre--3.6 Ga continental material. Contrary to some continental-growth models, this latter observation suggests that the volume of continental crust established by 3.6 Ga was relatively small. [ABSTRACT FROM AUTHOR]

Wood Buffalo National Park (WBNP), the largest national park of Canada, has unique and complex ecosystems that depend on specific water quantity and quality. We characterize groundwaters and surface waters in WBNP by determining their chemical compositions and water types, the dominant hydrochemical processes affecting their compositions, and their hydrochemical characteristics in relation to interpreted groundwater flow systems. Total Dissolved Solid concentrations in groundwaters and surface waters range from ≤10 mg/L to ≥300,000 mg/L. Four distinct water type groups are found: (1) Ca-SO4-type waters occur in multiple clusters across the area in outcrop areas of Devonian evaporites; (2) Na-Cl-type waters predominantly occur in the Salt plains region along the central eastern boundary, overlapping evaporite and carbonate-dominated bedrock formations; (3) Ca-HCO3-type waters dominate the Peace-Athabasca Delta-region in the south and most of the central region; and (4) "mixed" waters. Solutes in the waters originate from three main processes: dissolution of halite, dissolution of sulphate minerals, and dissolution of carbonates. The spatial occurrence of hydrochemical characteristics correlate with hypothesized groundwater flow systems, i.e., Ca-SO4 and Na-Cl-type waters coincide with discharge areas of intermediate to regional groundwater flow paths, and Ca-HCO3-type waters overlap with recharge areas. The findings of this study contribute to advancing knowledge on the hydrochemical characteristics of this remote and highly protected region of Alberta, Canada, and are important components of any further, comprehensive assessment of the natural water conditions. [ABSTRACT FROM AUTHOR]

The Isotrace CNRS workgroup in collaboration with National Research Council of Canada has characterized a number of trace element mass fractions and isotope ratios currently not certified in AQUA-1 natural drinking water reference material (NRC Canada). This survey further expands the use of this material as a tool for environmental quality control, method validation, and method development tool for the international community. Simultaneously, the SLRS-6 river water was analyzed as quality control and also in order to compare both water characteristics, which were sampled in the same area but having undergone different treatment. Mass fractions for B, Cs, Li, Ga, Ge, Hf, Nb, P, Rb, Rh, Re, S, Sc, Se, Si, Sn, Th, Ti, Tl, W, Y, Zr, REEs, and six isotopic ratios are proposed for Sr and Pb. Measurements were mostly performed using ICP-MS with various calibration approaches. The results are reported as consensus or indicative values depending on the number of available datasets, with their associated uncertainties. [ABSTRACT FROM AUTHOR]

A freeze-dried bovine muscle-certified reference material (CRM), known as BOTS-1 (DOI: https://doi.org/10.4224/crm.2018.bots-1 ), containing incurred residues of commonly used veterinary drugs was produced and certified for the mass fraction of eight veterinary drug residues. Value assignment was carried out using liquid chromatography tandem mass spectrometry (LC-MS/MS) methods in conjunction with isotope dilution and standard addition approaches involving stable isotope internal standards. Data from the National Research Council of Canada (NRC), Canadian Food Inspection Agency (CFIA), United States Department of Agriculture (USDA), and the Federal Office of Consumer Protection and Food Safety in Germany (BVL) were used for value assignment. Results for two drug residues were also obtained through an international inter-laboratory comparison CCQM-K141/P178 organized under the auspices of the International Bureau of Weights and Measures (BIPM). Quantitative NMR ( 1 H-qNMR) was used to characterize primary standards of all veterinary drugs certified. The certified mass fractions of the veterinary drug residues were 490 ± 100 µg/kg for chlorpromazine, 44 ± 4.4 µg/kg for ciprofloxacin, 3.3 ± 1.4 µg/kg for clenbuterol, 9.5 ± 0.8 µg/kg for dexamethasone, 57 ± 4.8 µg/kg for enrofloxacin, 3.0 ± 0.4 µg/kg for meloxicam, 12.4 ± 1.2 µg/kg for ractopamine, and 2290 ± 120 µg/kg for sulfadiazine with expanded uncertainties quoted (95% confidence) which include the effects due to between-bottle inhomogeneity, instability during long-term storage and transportation, and characterization., (© 2023. Crown.)

Featured Application: Use of fiber optics to monitor a target on a medical cyclotron. Many medical isotopes can be produced on a small cyclotron. The alignment and profiles of low-energy proton beams from cyclotrons used for medical radioisotope production, such as the TR13 cyclotron at TRIUMF, Canada, cannot be directly quantified during dose delivery with simultaneous constant feedback and sharp spatial resolutions. Doped silica fibers are a potential solution that has been tested at TRIUMF. To measure the effects of irradiation inside an isotope production target, we attached fibers to the outside of an 18O gas target and measured the light output during irradiation. Different dopants, fiber diameters, and target materials were investigated. It was found that 200 µm diameter Ce- and B-doped fibers produce signals linearly proportional to the beam current. This only deviated when the target was moved such that the beam was steered into the target wall, increasing the production of prompt radiation and causing the beam current to decrease but the fiber signal to increase. With the technique described here, the beam can be monitored on the target, including its steering and its overall alignment with the target. [ABSTRACT FROM AUTHOR]

The abundance of ungulate populations may fluctuate in response to several limiting factors, including climate, diseases, and predation. In the northern Richardson Mountains, Canada, Dall sheep (Ovis dalli dalli) have undergone a major decline in the past decades and predation by grizzly bears (Ursus arctos) and wolves (Canis lupus) was suspected as a leading cause. To better understand the relationship between these three species located in this rugged and remote ecosystem, we relied on a combination of indirect methods. We investigated the apparent role of predation on the Dall sheep population using spatial ecology and stable isotopes. We examined seasonal variation in predation risk, focusing on how it may affect Dall sheep habitat use and sexual segregation, and we evaluated the proportion of Dall sheep in the diet of both predators using stable isotopes. The movements of the three species were monitored by satellite telemetry. Dall sheep habitat use patterns were analyzed using topographical features, greenness index, land cover, and apparent predation risk. The diets of grizzly bears and wolves were examined using a Bayesian mixing model for carbon and nitrogen stable isotopes. We found that Dall sheep habitat use varied seasonally, with different patterns for ewes and rams. Exposure to grizzly bear risk was higher for rams during summer, while ewes were further exposed to wolf apparent predation risk during winter. The importance of safe habitats for ewes was reflected in space use patterns. Stable isotopes analyses suggested that the diet of grizzly bears was largely from animal sources, with mountain mammals comprising about one quarter. Wolves mostly fed on both aquatic browsers and mountain mammals. Diet variation between individual predators suggested that some individuals specialized on mountain mammals, likely including Dall sheep. We conclude that grizzly bear and wolf apparent predation risk are important in driving Dall sheep habitat use and play a role in sexual segregation. Overall, this study presents an innovative combination of indirect methods that could be applied elsewhere to better understand predator-prey dynamics in remote ecosystems. [ABSTRACT FROM AUTHOR]

Phosphogypsum (PG) is a by-product of phosphorus fertilizer that is typically stacked near production sites. Phosphogypsum contains trace elements and naturally occurring radioactive materials which may be hazardous to the surrounding environment. Phosphogypsum stack reclamation typically involves placing a soil cap and seeding grass to create a barrier for reducing environmental impacts; using woody species is uncommon. This study used three soil treatments with grass and woody species to determine whether mixing PG with soil affects soil chemical properties, and metal and radionuclide concentrations in tissue. None of the elements in soil was above Canadian guidelines for industrial land use. Aluminum, beryllium, chromium, copper, iron, magnesium, manganese, nickel, and vanadium were significantly higher in both study and reference sites than in pure PG; cadmium, calcium, fluoride, and strontium were significantly higher in pure PG. There was a poor correlation between soil and plant concentrations for most elements indicating trace elements were not in a bioavailable form. Trace elemental concentrations in plant tissue generally differed significantly with vegetation type but not within similar species. Trace elements and isotopes in PG were not high enough to affect plant growth. Among the isotopes, 222 Ra emissions differed significantly with vegetation covers; activity of 226 Ra in pure PG was above Canadian guidelines, but lower in vegetation tissue. This study suggests 15 cm soil mixed with PG can be used for PG stack revegetation when fast-growing Salix and Populus species are used in reclamation., (© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

In metamorphic rocks, mineral species react over a range of pressure–temperature conditions that do not necessarily overlap. Mineral equilibration can occur at varied points along the metamorphic pressure–temperature (PT) path, and thus at different times. The sole or dominant use of zircon isotopic compositions to constrain the evolution of metamorphic rocks might then inadvertently skew geological interpretations towards one aspect or one moment of a rock's history. Here, we present in-situ U–Pb/Sm–Nd isotope analyses of the apatite crystals extracted from two meta-igneous rocks exposed in the Saglek Block (North Atlantic craton, Canada), an Archean metamorphic terrane, with the aim of examining the various signatures and events that they record. The data are combined with published U–Pb/Hf/O isotope compositions of zircon extracted from the same hand-specimens. We found an offset of nearly ca. 1.5 Gyr between U-Pb ages derived from the oldest zircon cores and apatite U–Pb/Sm–Nd isotopic ages, and an offset of ca. 200 Ma between the youngest zircon metamorphic overgrowths and apatite. These differences in metamorphic ages recorded by zircon and apatite mean that the redistribution of Hf isotopes (largely hosted in zircon) and Nd isotopes (largely hosted in apatite within these rocks), were not synchronous at the hand-specimen scale (≤~0.001 m3). We propose that the diachronous redistribution of Hf and Nd isotopes and their parent isotopes was caused by the different PT conditions of growth equilibration between zircon and apatite during metamorphism. These findings document the latest metamorphic evolution of the Saglek Block, highlighting the role played by intra-crustal reworking during the late-Archean regional metamorphic event. [ABSTRACT FROM AUTHOR]

Abstract: The Balloon-borne Experiment with a Superconducting Spectrometer (BESS) was flown from Lynn Lake, Manitoba, Canada in August, 2000, during the maximum solar modulation period, with an average residual atmospheric overburden of 4.3g/cm2. Precise spectral measurements of cosmic ray hydrogen isotopes from 0.178GeV/n to 1.334GeV/n were made during the 28.7h of flight. This paper presents the measured energy spectra and their ratio, 2H/1H. The results are also compared with previous measurements and theoretical predictions. [Copyright &y& Elsevier]

Background: Leucine has been suggested to improve athletic performance. Therefore, the branched-chain amino acids (BCAAs), especially leucine, are popular as dietary supplements in strength- training athletes; however, the intake of leucine in excess of requirements raises concerns regarding adverse effects. Currently, the tolerable upper intake level (UL) for leucine is unknown. Objective: The objective of the current study was to determine the UL for leucine in adult men under acute dietary conditions. Design: Five healthy adults (20-35 y) each received graded step- wise increases in leucine intakes of 50, 150, 250, 500, 750, 1000, and 1250 mg • kg-1 d-1, which corresponded to the Estimated Average Requirement (EAR) and the EAR X3, X5, X10, X15, X20, and X25 in a total of 29 studies. The UL of leucine was identified by the measurement of plasma and urinary biochemical variables and changes in leucine oxidation by using L-[l-l3C]-leucine. Results: A significant increase in blood ammonia concentrations above normal values, plasma leucine concentrations, and urinary leucine excretion were observed with leucine intakes >500 mg •-1 d-1. The oxidation of L-[l-13C]-leucine expressed as label tracer oxidation in breath (F13CO2), leucine oxidation, and a-ketoisocaproic acid (KIC) oxidation led to different results: a plateau in (F13CO2) observed after 500 mg • kg-1 d-1, no clear plateau observed in leucine oxidation, and KIC oxidation appearing to plateau after 750 mg • kg-1 d-1. Conclusion: On the basis of plasma and urinary variables, the UL for leucine in healthy adult men can be suggested at 500 mg • kg-1 d-1' or ~35 g/d as a cautious estimate under acute dietary conditions. This trial was registered at clinicaltrials.gov as NCT00972582. [ABSTRACT FROM AUTHOR]

We report the activity measured in rainwater samples collected in the Greater Sudbury area of eastern Canada on 3, 16, 20, and 26 April 2011. The samples were γ-ray counted in a germanium detector and the isotopes 131I and 137Cs, produced by the fission of 235U, and 134Cs, produced by neutron capture on 133Cs, were observed at elevated levels compared to a reference sample of ice water. These elevated activities are ascribed to the accident at the Fukushima Dai-ichi nuclear reactor complex in Japan that followed the 11 March 2011, earthquake and tsunami. The activity levels observed at no time presented health concerns. [ABSTRACT FROM AUTHOR]

Background: Plant sterol (PS) supplementation is increasingly ac-cepted as a dietary strategy to lower plasma cholesterol concentra-tions. However, information is scarce about the effect of increased PS intake in potentially vulnerable groups, such as phytosterolemia heterozygotes (HET). Objective: This study assessed the responsiveness of circulating PS and lipid concentrations and cholesterol kinetics (absorption and synthesis) to daily PS supplementation in HET (ABCG8 S107X mutation) compared with a healthy control cohort. Design: A double-blind, randomized, crossover, placebo-controlled study was conducted in 10 HET and 15 control subjects. The par-ticipants had a mean (±SEM) age of 34 ± 2 y and a BM1 (in kg/m2) of 29.9 ±1.1 and consumed ∼ 1.6 g PS or placebo capsules daily with supper for 4 wk. Cholesterol absorption and synthesis were assessed by using [13C]cholesterol and deuterium oxide, respec-tively. Results: Plasma LDL-cholesterol concentrations decreased (P = 0.006) in both groups after PS supplementation (HET: 2.73 ± 0.19 mmol/L; control: 3.11 ± 0.19 mmol/L) compared with placebo (HET: 3.12 ± 0.20 mmol/L; control: 3.50 ± 0.21 mmol/L), whereas PS concentrations (campesterol+ß-sitosterol) increased (P = 0.03) in both groups after PS supplementation (HET: 39.72 ± 6.05 /¡mol/L; control: 24.03 ± 1.65 /¡mol/L) compared with placebo (HET: 27.32 ± 3.80 /&um;mol/L; control: 21.12 ± 2.05 /(mol/L). Cho-lesterol absorption efficiency decreased (P = 0.010) by ∼22% and ∼17% and synthesis rates increased (P = 0.040) by ∼20% and ∼24% in the HET and control groups, respectively, in response to PS consumption compared with placebo. Conclusion: These data suggest that heterozygosity for the ABCG8 S107X mutation does not influence the action of dietary PS on circu-lating cholesterol concentrations but may affect sterol absorption. This trial was registered at clinicaltrials.gov as NCT01102647. [ABSTRACT FROM AUTHOR]

Abstract: Geochemical and isotopic monitoring allows determination of CO2 presence in the subsurface through the sampling of produced fluids and gases at production and/or monitoring wells. This is demonstrated by data from 22 months of monitoring at the Pembina Cardium CO2 Monitoring Pilot in central Alberta, Canada. Eight wells centered around two CO2 injectors were sampled monthly between February 2005 and February 2007. Stable isotope analyses of the samples revealed that changes in the δ13CCO2 values in produced gas as well as changes in the δ18O values of the produced fluids indicate CO2 presence and identify trapping mechanisms at select production wells. Using equilibrium isotope exchange relationships and CO2 solubility calculations, fluid and gas saturations in the pore space in excess of that occupied by oil were calculated. We demonstrate that stable isotope measurements on produced fluids and gases at the Pembina Cardium CO2 storage site can be used to determine both qualitatively and quantitatively the presence of CO2 around the observation well, given that the injected CO2 is isotopically distinct. [Copyright &y& Elsevier]

We present a short overview of the rare isotope facility at TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics. Plans for the future are also presented. [ABSTRACT FROM AUTHOR]

The article examines the measures undertaken by the government of Canada during the international shortage of medical isotopes, after it discovered the shutdown of the reactor in Chalk River, Ontario that included the termination of Linda Keen as chief executive officer and president of the Canadian Nuclear Safety Commission. The forced resignation of Keen provoked an international debate on the interference of the government in an independent agency. However, the Federal Court sided with the government as it dismissed the appeal made by Keen.

Neotropical migratory songbirds typically breed in temperate regions and then travel long distances to spend the majority of the annual cycle in tropical wintering areas. Using stable-isotope methodology, we provide quantitative evidence of dual breeding ranges for 5 species of Neotropical migrants. Each is well known to have a Neotropical winter range and a breeding range in the United States and Canada. However, after their first bout of breeding in the north, many individuals migrate hundreds to thousands of kilometers south in midsummer to breed a second time during the same summer in coastal west Mexico or Baja California Sur. They then migrate further south to their final wintering areas in the Neotropics. Our discovery of dual breeding ranges in Neotropical migrants reveals a hitherto unrealized flexibility in life-history strategies for these species and underscores that demographic models and conservation plans must consider dual breeding for these migrants. [ABSTRACT FROM AUTHOR]

Defining management units is basic to the sound management of resources. Walrus (Odobenus rosmarus rosmarus) are hunted throughout their range in Canada and are subject to other human activities requiring management decisions. Current management units are based on a comprehensive review and a stock assessment completed in the mid 1990s. Between 1993 and 2004, satellite-linked radio tags provided information on the movements of walrus in Canada's High Arctic. These data were incorporated with other information that has become available since 1995 to reassess walrus management units in Canada. Tagging data and other information suggest that some finer discrimination of walrus populations is needed as a precautionary approach and to formulate testable hypotheses. Specifically, the previous North Water/Baffin Bay walrus stock may be considered to be three stocks: Baffin Bay, west Jones Sound, and Penny Strait-Lancaster Sound stocks. The Foxe Basin population appears to comprise two stocks (North Foxe Basin and Central Foxe Basin) rather than one. Previously suspected subdivisions in the Hudson Bay-Davis Strait population are substantiated by isotopic evidence although sampling on a finer geographic scale is required before this stock can be partitioned. There is new evidence to support the previously postulated separation of the walrus in the Southern and Eastern Hudson Bay stock from all others, but no evidence to warrant subdivision. [ABSTRACT FROM AUTHOR]

We compared the carbon isotope composition of ecosystem-respired CO2 (δ13CR) from 11 forest ecosystems in Canada and the USA and examined differences among forest δ13CR responses to seasonal variations in environmental conditions from May to October 2004. Our experimental approach was based on the assumption that variation in δ13CR is a good proxy for short-term changes in photosynthetic discrimination and associated shifts in the integrated ecosystem-level intercellular to ambient CO2 ratio (ci/ca). We compared δ13CR responses for three functional groups: deciduous, boreal and coastal forests. The δ13CR values were well predicted for each group and the highest R² values determined for the coastal, deciduous and boreal groups were 0.81, 0.80 and 0.56, respectively. Consistent with previous studies, the highest correlations between δ13CR and changes in environmental conditions were achieved when the environmental variables were averaged for 2, 3 or 4 days before δ13CR sample collection. The relationships between δ13CR and environmental conditions were consistent with leaf-level responses, and were most apparent within functional groups, providing support for our approach. However, there were differences among groups in the strength or significance, or both, of the relationships between δ13CR and some environmental factors. For example, vapor pressure deficit (VPD) and soil temperature were significant determinants of variation in δ13CR in the boreal group, whereas photosynthetic photon flux (PPF) was not; however, in the coastal group, variation in δ13CR was strongly correlated with changes in PPF, and there was no significant relationship with VPD. At a single site, comparisons between our δ13CR measurements in 2004 and published values suggested the potential application of δ13CR measurements to assess year-to-year variation in ecosystem physiological responses to changing environmental conditions, but showed that, in such an analysis, all environmental factors influencing carbon isotope discrimination during photosynthetic gas exchange must be considered. [ABSTRACT FROM AUTHOR]

To determine the sources and sinks of atmospherically deposited Pb at a forested watershed (Plastic Lake) in central Ontario, Canada, Pb pools and fluxes through upland, wetland and lake compartments were measured during 2002/2003 and compared with previous measurements taken between 1989 and 1991. In 2002/2003, annual bulk deposition of Pb was 0.49 mg m−2 compared with 1.90–1.30 mg m−2 in 1989–1991. Annual Pb concentrations in stream water draining the upland part of the catchment were very low (0.04 μg l−1) and were approximately half those measured in 1989–1991 (0.11–0.08 μg l−1). Leaching losses in stream water were small and mass balance estimates indicate almost complete retention (>95%) of atmospherically deposited Pb in upland soils. In contrast, annual Pb concentrations in stream water draining a wetland were between 0.38 and 0.77 μg l−1, with the highest concentration occurring in 2002/2003 and mass balance calculations indicate that the wetland is a net source of Pb in all measured years. Lead concentrations in the lake outflow were low and the average Pb concentration measured in 2002/2003 (0.09 μg l−1) was approximately half the value recorded in 1989–1991 (0.19 μg l−1 both years). Annual mass balance estimates indicate that the lake retained between 2.47 mg m−2 (1989/1990) and 1.42 mg m−2 (2002/2003) and that in 2002/2003 68% of the Pb input to the lake is derived from the terrestrial catchment. These estimates are higher than sediment core records, which indicate around 18 mg m−2 Pb was retained in sediment during the 1990s. Nevertheless, Pb concentrations decrease with sediment depth and 206Pb/207Pb concentrations increase with depth, a pattern also observed in mineral soils that reflects the substantial contribution of anthropogenic Pb to the watershed. Lead isotope data from soil and sediment indicate a recent anthropogenic Pb signal (206Pb/207Pb ∼ 1.185) in upper soils and sediments and an older anthropogenic signal (206Pb/207Pb ∼ 1.20) in deeper soil and sediment. Lead isotope data in sediment and vegetation indicate that practically all the Pb cycled in the forest at Plastic Lake is anthropogenic in origin. [ABSTRACT FROM AUTHOR]

The lowering of the water table resulting from peatland drainage may dramatically alter C and N cycling in peatland ecosystems, which contain one-third of the total terrestrial C. In this study, tree annual ring width and C (δ13C) and N (δ15N) isotope ratios in soil and plant tissues (tree foliage, growth rings, and understory foliage) in a black spruce-tamarack (Picea mariana-Larix laricina) mixed-wood forest were examined to study the effects of drainage on tree growth and C and N dynamics in a minerotrophic peatland in west-central Alberta, Canada. Drainage increased the δ15N of soil NH4+ from a range of +0.6‰ to +2.9‰ to a range of +4.6‰ to +7.0‰ most likely through increased nitrification following enhanced mineralization. Plant uptake of 15N-enriched NH4+ in the drained treatment resulted in higher plant δ15N (+0.8‰ to +1.8‰ in the drained plots and -3.9‰ to -5.4‰ in the undrained plots), and deposition of litterfall N enriched with 15N increased the δ15N of total soil N in the surface layer in the drained (+2.9‰) as compared with that in the undrained plots (+0.6‰). The effect of drainage on foliar δ13C was species-specific, i.e., only tamarack showed a considerably less negative foliar δ13C in the drained (-28.1‰) than in the undrained plots (-29.1‰), indicating improved water use efficiency (WUE) by drainage. Tree ring area increments were significantly increased following drainage, and δ13C and δ15N in tree growth rings of both species showed responses to drainage retrospectively. Tree-ring δ13C data suggested that drainage improved WUE of both species, with a greater and more prolonged response in tamarack than in black spruce. Our results indicate that drainage caused the studied minerotrophic peatland to become a more open ecosystem in terms of C and N cycling and loss. The effects of forested peatland drainage or drying on C and N balances deserve further research in order to better understand their roles in future global change. [ABSTRACT FROM AUTHOR]

An extensive study of peridotitic sulfide inclusion bearing diamonds and their prospective harzburgitic host rocks from the 53 Ma Panda kimberlite pipe, Ekati Mine, NWT Canada, has been undertaken with the Re–Os system to establish their age and petrogenesis. Diamonds with peridotitic sulfide inclusions have poorly aggregated nitrogen (<30% N as B centers) at N contents of 200–800 ppm which differs from that of chromite and silicate bearing diamonds and indicates residence in the cooler portion of the Slave craton lithospheric mantle. For most of the sulfide inclusions, relatively low Re contents (average 0.457 ppm) and high Os contents (average 339 ppm) lead to extremely low 187Re/188Os, typically << 0.05. An age of 3.52 ± 0.17 Ga (MSWD = 0.46) and a precise initial 187Os/188Os of 0.1093 ± 0.0001 are given by a single regression of 11 inclusions from five diamonds that individually provide coincident internal isochrons. This initial Os isotopic composition is 6% enriched in 187Os over 3.5 Ga chondritic or primitive mantle. Sulfide inclusions with less radiogenic initial Os isotopic compositions reflect isotopic heterogeneity in diamond forming fluids. The harzburgites have even lower initial 187Os/188Os than the sulfide inclusions, some approaching the isotopic composition of 3.5 Ga chondritic mantle. In several cases isotopically distinct sulfides occur in different growth zones of the same diamond. This supports a model where C–O–H–S fluids carrying a radiogenic Os signature were introduced into depleted harzburgite and produced diamonds containing sulfides conforming to the 3.5 Ga isochron. Reaction of this fluid with harzburgite led to diamonds with less radiogenic inclusions while elevating the Os isotope ratios of some harzburgites. Subduction is a viable way of introducing such fluids. This implies a role for subduction in creating early continental nuclei at 3.5 Ga and generating peridotitic diamonds. [ABSTRACT FROM AUTHOR]

Mercury biomagnifies in aquatic foodwebs in freshwater lakes, and common loons ( Gavia immer) breeding in eastern Canada can be exposed to reproductively toxic concentrations of mercury in their fish prey. We assessed the bioaccumulation and biomagnification of mercury in juvenile and adult common loons, and their preferred prey: yellow perch ( Perca flavescens) in Kejimkujik National Park (KNP), Nova Scotia by measuring mercury levels and stable isotope ratios in tissues. Total mercury levels and stable-carbon (δ13C) and nitrogen isotope ratios (δ15N) were determined in composite whole-fish samples from lakes in KNP and blood samples from juvenile and adult loons captured on lakes in KNP and southern New Brunswick. Geometric mean mercury concentrations were 0.15 and 0.38 μg/g (wet wt.) in small (9-cm fork length) and large (17-cm fork length) yellow perch, and were 0.43 and 2.7 μg/g (wet wt.) in blood of juvenile and adult common loons, respectively. Mercury concentrations in perch and loons were positively associated with body mass and δ15N values. Juvenile loons and large yellow perch had similar mercury levels and δ15N values, indicating similar trophic status despite their 22-fold difference in body mass. Mercury concentrations were higher in yellow perch and common loons in acidic lakes. Our findings highlight the importance of both chemical and ecological factors in understanding mercury biomagnification in lakes and associated risks to fish-eating wildlife. [ABSTRACT FROM AUTHOR]

Abstract: Surface water samples were collected from 55 sites in the Great Lakes Basin and analyzed for the presence of perchlorate using HPLC/MS/MS with an isotopically enriched internal standard. Sites included areas impacted by heavy industry, urbanization, agriculture and atmospheric deposition. Perchlorate was detected at several of the sites at concentrations close to the method detection limit (0.2μg/l). Despite these low concentrations, its presence was confirmed by sample concentration and determination of the isotopic ratio of perchlorate. The presence of perchlorate at two of the sites was related to a fireworks display which had occurred prior to sampling. The other detections of perchlorate were in rivers/creeks draining watersheds which had high density livestock and crop farming activity. We suspect the two are related. To our knowledge, these are the first reported concentrations of perchlorate in Canadian surface waters. [Copyright &y& Elsevier]

Many Phanerozoic time-scale boundaries are characterized by oceanic anoxia and mass extinction events with the deposition of black shale. The Re-Os isotope system in black shale can be used to provide depositional ages for these rocks, thus yielding direct radiometric ages for time-scale boundaries. We demonstrate that the Re-Os black shale geochronometer can yield precise ages useful for time-scale research through study of the Devonian-Mississippian boundary within the Exshaw Formation, Canada. The Re-Os date determined places the Devonian-Mississippian boundary at 361.3 ± 2.4 Ma (2σ including λ uncertainty, model 1, mean square of weighted deviates = 1.2), in accord with recent calibration interpolated from U-Pb zircon dates (360.7 ± 0.7 Ma) for the Hasselbachtal section, Germany. [ABSTRACT FROM AUTHOR]

Moonmilk, which is often seen coating walls in temperate caves, is a porous secondary calcite deposit composed of an aggregate of microcrystalline calcite and water. This study, based on moonmilk deposits found in Caverne de l'Ours, Ottawa Valley region, proposes a model for its formation based on the calcite and water isotope chemistry and evaluates its use as a climatic proxy. In Caverne de l'Ours, non-calcitic mineral inclusions protrude from the bedrock (Grenville marble) into the moonmilk, while others are entirely enclosed within the moonmilk. This observation suggests a mechanism of bedrock dissolution and reprecipitation for the formation of moonmilk, which is controlled by the changing seasonal climate in the cave. The δ18O of the moonmilk interstial water indicates that the condensation of water vapour occurs mostly in winter and spring. The condensation of water vapour on the surface of the walls allows for the dissolution of the Grenville marble and releases ions necessary for the precipitation of moonmilk. The δ18O and δ13C of calcite and δ18O of the moonmilk interstitial water indicate that precipitation of moonmilk occurs during summer and fall. During these seasons, the relative humidity in the cave decreases resulting in moonmilk growth through the slow evaporation of calcite-saturated water. A comparison of the δ18O record of moonmilk from caves in Gaspésie (Canada) and from Aven d'Orgnac (France) shows that this material retains temperature information valuable for paleoclimatic reconstructions. [ABSTRACT FROM AUTHOR]

The South Mountain Batholith (SMB) of southwestern Nova Scotia is a large, highly differentiated, peraluminous, granitic batholith in which the average A/CNK (mol Al2O3/mol(CaO + Na2O + K2O)) increases from 1.16 to 1.23 with chemical evolution. We use vector analysis of variations solely in Al2O3–(CaO + Na2O + K2O) space to assess the fractionation, assimilation, fluid, and source controls on the peraluminosity of the SMB. With increasing chemical evolution, Al2O3 decreases, CaO decreases sharply, Na2O is approximately constant, and K2O increases in the early and middle stages but decreases in the most evolved stage. Initial 87Sr/86Sr and 143Nd/144Nd isotopic ratios for granites and average Meguma Supergroup country rocks suggest an upper limit of ~33% of wall-rock contamination for the most evolved rocks, if the most primitive rocks are uncontaminated. The trend of chemical evolution of the SMB through Al2O3–(CaO + Na2O + K2O) space is the resultant of all input vectors (processes). In the early stages, those processes are fractional crystallization of plagioclase ± K-feldspar ± cordierite ± biotite and contamination by country rocks. In the later stages, those processes are fractionation of plagioclase ± K-feldspar ± andalusite ± muscovite, further contamination by country rocks, and selective partitioning of Ca–Na–K into aqueous fluid phases. Clear geochemical evidence for variation in the source composition is lacking. [ABSTRACT FROM AUTHOR]

Lead concentrations and Pb isotope ratios were measured in the forest floor, mineral soil and vegetation at a white pine and a sugar maple stand in a woodland in south central Ontario. Lead concentrations decreased and 206Pb/207Pb ratios increased with mineral soil depth reflecting the mixing of pollution and natural Pb sources. Lead concentrations and 206Pb/207Pb ratios at 20–30 cm depth were ∼6–7 mg/kg and 1.31–1.32, respectively. Assuming an integrated 206Pb/207Pb ratio in deposition over time of 1.18, estimated from lichen measurements and published data for the region, approximately 65% of Pb in the surface (0–1 cm) mineral soil is from anthropogenic sources. Approximately 90% of pollution Pb is found in the 0–10 cm soil layer (Ah) and less than 3% of the pollution Pb is present in the forest biomass and mull-type forest floor combined. Despite low Pb concentrations in vegetation (<2.5 mg/kg), we estimate that between 65 and 100% of the Pb in vegetation and ∼75% of the Pb in the forest floor is from pollution sources. In total, the pollution Pb burdens at the pine and maple stands are estimated to be 860 and 750 mg/m2, respectively. [Copyright &y& Elsevier]

Presents a study that examined neodymium isotope geochemistry of felsic volcanic and intrusive rocks from the Yukon-Tanana terrane (YTT) in the Finlayson Lake region, Yukon, Canada. Geological setting of the YTT in the Finlayson Lake region; Geochemical attributes of the intrusive rocks; Systematics of the neodymium isotopes.

Perennial ice from caves on and to the east of the Canadian Great Divide yield δ[sup 18]O and δD values, which are unusually high measurements when compared with the average precipitation for the region. Furthermore, these ice data fall below and along lines of lower slope than the Global Meteoric Water Line. To explain the observed relationships, we propose the following process. A vapour-ice isotopic fractionation mechanism operates on warm-season vapour when it precipitates as hoar ice on entering the caves. The subsequent fall of hoar to the cave floor through mechanical overloading, along with ice derived from ground-water seepage (with a mean annual isotopic composition), results in massive ice formation of a mixed composition. This mixed composition is what is observed in the characteristic relationships found here. Such findings suggest that a warm versus cold climate interpretation for ancient cave ice may be the opposite of that found in the more familiar polar and glacial ice cores. [ABSTRACT FROM AUTHOR]

Natural mineral-rich springs which attract moose Alces alces and white-tailed deer Odocoileus virginianus were studied in a small area in central Canada. The spring water was particularly rich in Na and Cl but also contained levels of K, Ca, Mg, HCO3 and Mn higher than nearby stream water. In a selection experiment near a natural spring, aqueous solutions of NaCI, NaHCO3 and Na2SO4 were consumed consistently by the animals while salts of K, Ca and Mg were not. Isotope analysis indicates that the spring waters are part of a modern and probably localized flow system. Evaporite minerals and extensive fractures in the local sedimentary bedrock appear to account for the salt content of the spring waters. [ABSTRACT FROM AUTHOR]

Presents an abstract which deals with Nd isotopes in clastic 600-75 Ma sedimentary rocks from miogeocline of Alberta and British Columbia used to constrain the importance of proximal changes in provenance and develop miogeoclinal for Nd isotopes for input to Cordilleran terranes. History of sedimentation and basin development; Average effects of sedimentation; Indication from the result of the study.

Honey from Apis mellifera is a useful and inexpensive biomonitor for mapping metal distributions in urban centers. The sampling resolution of a biomonitoring survey (e.g., city versus global scale) determines which geochemical processes are reflected in the results. This study presents Pb isotopic compositions and metal concentrations in honey from around the world, sampled at varying resolutions: honey from Canada (n = 21), the United States (n = 111), Belgium (n = 25), and New Zealand (n = 10), with additional samples from Afghanistan, Brazil, Cuba, Germany, Liberia, Taiwan, and Turkey. Honey was sampled at high resolution in two uniquely different land-use settings (New York Metro Area and the Hawaiian island of Kaua'i), at regional-scale resolution in eastern North America (including the Great Lakes region), and Pb isotopic compositions of all samples were compared on a global scale. At high sampling resolution, metal concentrations in honey reveal spatially significant concentration gradients: in New York City, metals associated with human activity and city infrastructure (e.g., Pb, Sb, Ti, V) are more concentrated in honey collected within the city compared to honey from upstate New York, and metal concentrations in honey from Kaua'i suggest polluting effects of nearby agricultural operations. At lower resolution (regional and global scales), lead isotopic compositions of honey are more useful than metal concentrations in revealing large-scale Pb processes (e.g., the enduring legacy of global leaded gasoline use throughout the twentieth century) and the continental origin of the honey. Lead isotopic compositions of honey collected from N. America (especially from the eastern USA) are more radiogenic ( 206 Pb/ 207 Pb: 1.132-1.253, 208 Pb/ 206 Pb: 2.001-2.129) compared to European honey, and honey from New Zealand, which has the least radiogenic isotopic compositions measured in this study ( 206 Pb/ 207 Pb: 1.077-1.160, 208 Pb/ 206 Pb: 2.090-2.187). Thus, biomonitoring using honey at different resolutions reflects differing processes and, to some extent, a honey terroir defined by the Pb isotopic composition. The data presented here provide important (and current) global context for future studies that utilize Pb isotopes in honey. Moreover, this study exhibits community science in action, as most of the honey was collected by collaborators around the world, working directly with local apiarists and hobby beekeepers., (Copyright © 2021 Elsevier Inc. All rights reserved.)

The petrogenesis of the Pridoli to Early Lochkovian granites in the Miramichi Highlands of New Brunswick, Canada, is controversial. This study focuses on the Pridoli Nashwaak Granite (biotite granite and two-mica granite). In situ trace elements and O and Hf isotopes in zircon, coupled with O isotopes in quartz, are used to reveal its magmatic sources and evolution processes. In the biotite granite, inherited zircon cores have broadly homogenous δ18OZrc ranging from +6.7‰ to 7.4‰, whereas magmatic zircon rims have δ18OZrc of +6.3‰ to 7.2‰ and εHf(t) of −0.39 to −5.10. The Hf and Yb/Gd increase with decreasing Th/U. Quartz is isotopically equilibrated with magmatic zircon rims. The biotite granite is interpreted to be solely derived by partial melting of old basement rocks of Ganderia and fractionally crystallized at the fO2 of 10−21 to 10−10 bars. The two-mica granite has heterogeneous inherited zircon cores (δ18OZrc of +5.2‰ to 9.9‰) and rims (δ18OZrc of +6.2‰ to 8.7‰), and εHf(t) of −11.7 to −1.01. The two-mica granite was derived from the same basement, but with supracrustal contamination. This open-system process is also recorded by Yb/Gd and Th/U ratios in zircon and isotopic disequilibrium between magmatic zircon rims and quartz (+10.3 ± 0.2‰). [ABSTRACT FROM AUTHOR]

Little is known about how forests adjust their gas-exchange mode while atmospheric CO 2 rises globally and air quality changes regionally. The present study aims at addressing this research gap for boreal spruce trees growing in three different regions of Canada, submitted to distinct levels of atmospheric emissions, by examining the amount of carbon gained per unit of water lost in trees, i.e., the intrinsic water use efficiency (iWUE). Under pristine air quality conditions, middle-to long-term trends passed from no-reaction mode to passive strategies due to atmospheric CO 2 , and short-term iWUE variations mostly ensue from year-to-year climatic conditions. In contrast, in trees exposed to pollutants from a copper smelter and an oil-sands mining region, air quality deterioration generated swift, long-term iWUE rises immediately at the onset of operations. In this case, the very active foliar strategy sharply reduced the intra-foliar CO 2 (Ci) pressure. Statistical modeling allowed identifying emissions as the main trigger for the iWUE swift shifts; subsequent combined effects of emissions and rising CO 2 led to passive foliar modes in the recent decades, and short-term variations due to climatic conditions appeared all along the series. Overall, boreal trees under different regional conditions modified their foliar strategies mostly without changing their stem growth. These findings underline the potential of acidifying emissions for prompting major iWUE increases due to lowering the stomatal apertures in leaves, and the combined influence of rising CO 2 in modulating other foliar responses. A fallout of this research is that degrading air quality may create true divergences in the relationship between tree-ring isotopes and climatic conditions, an impact to consider prior to using isotopic series for paleo-climatic modeling. Image 1 • IWUE was determined for boreal trees submitted to distinct levels of atmospheric emissions. • Trees from remote stands rise iWUE proportionally with atmospheric pCO 2. • IWUE trends of exposed stands depart from regular pCO 2 -induced reactions. • Trees modified their foliar strategies without changing their stem growth. • Modeling underlines the individual and combined influences of pCO 2 and acidifying pollutants. Gas exchange strategies of forests exposed to acidifying emissions create major divergences from responses to pCO 2 and climatic conditions, a concern for modeling global C and water cycles. [ABSTRACT FROM AUTHOR]

The article reports on the closure of the National Research Universal (NRU) in Ontario, Canada due to its scheduled maintenance resulting to the cancellation of tests for cancer and heart disease because of shortage of medical isotopes. The maintenance includes the installation of safety-related equipment, including upgrades to the reactor cooling pumps. These reactor supplies 60% of the molybdenum isotopes used in medical applications worldwide. MDS Nordion company, a life-sciences firm and molybdenum supplier stated that it expects shortages of the radioisotope until mid-January in 2008.

We report exceptional preservation of fossil wood buried deeply in a kimberlite pipe that intruded northwestern Canada's Slave Province 53.3±0.6 million years ago (Ma), revealed during excavation of diamond source rock. The wood originated from forest surrounding the eruption zone and collapsed into the diatreme before resettling in volcaniclastic kimberlite to depths >300 m, where it was mummified in a sterile environment. Anatomy of the unpermineralized wood permits conclusive identification to the genus Metasequoia (Cupressaceae). The wood yields genuine cellulose and occluded amber, both of which have been characterized spectroscopically and isotopically. From cellulose δ(18)O and δ(2)H measurements, we infer that Early Eocene paleoclimates in the western Canadian subarctic were 12-17°C warmer and four times wetter than present. Canadian kimberlites offer Lagerstätte-quality preservation of wood from a region with limited alternate sources of paleobotanical information.

Eggs of glaucous gulls (Larus hyperboreus), black-legged kittiwakes (Rissa tridactyla), thick-billed murres (Uria lomvia) and black guillemots (Cepphus grylle) were collected from several sites throughout the Canadian Arctic. Samples were analyzed for organochlorines as well as mercury and selenium. Glaucous gulls breeding at sites in the High Arctic showed higher levels of organochlorine contamination than those in the western Low Arctic. This was likely due to dietary differences among colonies as suggested by stable isotope data, although different overwintering areas may also play a role. Levels of sigmaPCB, sigmaDDT, sigmaCHLOR, sigmaCBz and dieldrin were significantly lower in thick-billed murres from Prince Leopold Island in the High Arctic compared with colonies in the eastcrn Low Arctic. This difference was likely due to the combined effects of different atmospheric deposition patterns in the High and Low Arctic and different overwintering areas since murres from Prince Leopold Island may winter farther north than murres from the other colonies sampled. Eggs from colonies at higher latitudes generally contained higher concentrations of mercury. The trophic and dietary differences/similarities suggested by stable-nitrogen and carbon isotope data in this study were useful in explaining the spatial patterns of contaminant concentrations observed among colonies of seabirds such as the glaucous gull and the black-legged kittiwake where variation in latitudinal atmospheric deposition patterns and different overwintering grounds did not appear to be confounding factors.