Objectives
This isotopic study explores the mobility patterns of a growing urban population from Notre Dame's Catholic cemetery (1691–1796), located in Montreal (Canada). The site offers a unique ...opportunity to investigate early colonial settlement in Nouvelle France through individual life patterns.
Materials and methods
Stable oxygen isotopic compositions (δ18O) were measured on the enamel of 32 individuals from the Notre Dame collection. Premolars and third molars were selected, as they reflected the δ18O of the drinking water during childhood (2.5–5.5 years) and pre‐adulthood (9.5–15.5 years). Firstly, premolars from three children (4–8 years of age) allowed us to provide a mean δ18O for the water consumed locally (22.7 ± 1.0 ‰ vs. VSMOW). Then, our δ18O were compared with published data from various geographical regions in North America (Eastern Canada and the United States) and Europe (France and the British Isles) to highlight mobility patterns of each individual.
Results
Forty‐eight percent of our sample (14 out of 29 individuals) did not reflect any long‐distance mobility, as all their δ18O reflected Montreal's variation during their lifetime. The remaining (15 out of 29 individuals) experienced mobility within (n = 8) and outside (n = 7) North America and at different phases of their life (five at pre‐adulthood, six at adulthood and four during both phases). Their migration patterns were analyzed according to age, sex, diet and possible ancestry in order to propose some “biographies.”
Discussion
This study highlights high population diversity in early colonial Montreal. Historians wrote that the city was growing, not only with the arrival of Europeans (e.g., young male workers, sailors), but also other groups (e.g., Indigenous people, slaves from North America). Additional analyses (e.g., ancient DNA) will be needed to explore further this phenomenon.
Rationale
Water‐stable isotopes in rainfall are powerful tracers of atmospheric processes at different spatial and temporal scales. However, commercially available rain samplers for isotopic analysis ...are prohibitively expensive, especially for high spatial resolution networks and studies conducted in developing countries. A low‐cost, simple, and robust sampler was designed for event and monthly rainfall samplings.
Methods
Rainfall collectors were built based on existing designs provided in the literature and using easily accessible materials. Event samplers were filled with different volumes of reference water and left for 72 h in laboratory conditions to determine the minimum amount of rainfall to be collected to minimize isotopic fractionation, from both postsampling evaporation and equilibration. Samples were analyzed using dual‐inlet isotope ratio mass spectrometry and cavity ring‐down spectroscopy.
Results
For samples larger than 4% of the bottle's capacity, the evaporative enrichment due to Rayleigh distillation is negligible compared to the overall analytical uncertainty. Using a tube connecting the funnel to the water sample has proved to reduce postsampling evaporation by at least five times. To limit water self‐diffusion, we recommend collecting the largest rainfall amount possible. Under these conditions, these collectors are suitable for rainfall sampling for isotopic analysis.
Conclusions
This low‐cost methodology will enable isotopic sampling of precipitation at high spatial resolutions and democratize the use of isotopes for hydrological studies in developing countries. All instructions for building and using these samplers are made openly accessible to the scientific community so they can be repeated and adapted to the needs of each project.
Hydraulic fracturing is becoming an important technique worldwide to recover hydrocarbons from unconventional sources such as shale gas. In Quebec (Canada), the Utica Shale has been identified as ...having unconventional gas production potential. However, there has been a moratorium on shale gas exploration since 2010. The work reported here was aimed at defining baseline concentrations of methane in shallow aquifers of the St. Lawrence Lowlands and its sources using δ(13)C methane signatures. Since this study was performed prior to large-scale fracturing activities, it provides background data prior to the eventual exploitation of shale gas through hydraulic fracturing. Groundwater was sampled from private (n = 81), municipal (n = 34), and observation (n = 15) wells between August 2012 and May 2013. Methane was detected in 80% of the wells with an average concentration of 3.8 ± 8.8 mg/L, and a range of <0.0006 to 45.9 mg/L. Methane concentrations were linked to groundwater chemistry and distance to the major faults in the studied area. The methane δ(1)(3)C signature of 19 samples was > -50‰, indicating a potential thermogenic source. Localized areas of high methane concentrations from predominantly biogenic sources were found throughout the study area. In several samples, mixing, migration, and oxidation processes likely affected the chemical and isotopic composition of the gases, making it difficult to pinpoint their origin. Energy companies should respect a safe distance from major natural faults in the bedrock when planning the localization of hydraulic fracturation activities to minimize the risk of contaminating the surrounding groundwater since natural faults are likely to be a preferential migration pathway for methane.
Rationale
A method to measure the δ2H and δ18O composition of pore water in soil samples using direct vapour equilibration and laser spectrometry was first described in 2008, and was rapidly adopted. ...Here, we describe an improved setup to measure pore water δ2H and δ18O values through direct vapour equilibration with a laser spectrometer, combining a liquid and a vapour mode for water isotope analyses, and resulting in improved accuracy.
Methods
We first tested new gas sampling bags as part of the equilibration protocol. Then, to assess measurement accuracy, vapour samples from equilibrated liquid waters of known isotope composition were measured in the liquid mode of the analyser using the new setup as well as the manufacturer's vapour mode. Various modes of preparing liquid water standards, namely equilibration, nebulisation, and vapourisation, were tested to determine the best calibration in terms of accuracy. Finally, the proposed modified liquid setup was validated by analysing water vapour equilibrated from soil pore water of a known composition.
Results
The δ2H and δ18O measurements were found to be more accurate by the modified liquid mode than by the factory‐setup vapour mode. The strong and non‐linear dependence of measured δ2H and δ18O values on H2O concentration in vapour mode, especially at concentrations equal to the vapour pressure saturation typically found in laboratories, is problematic for corrections. Regarding calibration and standards, the use of two equilibrated liquid water standards was found to best calibrate measurements in the modified liquid setup. Finally, the modified liquid mode setup and its calibration, as described here, were shown to be appropriate for soil pore water analysis.
Conclusions
The proposed modified setup results in more precise δ2H and δ18O soil pore water values than the usual protocols. An average standard deviation of 0.04‰ for δ18O values and 0.3‰ for δ2H values, based on 228 soil sample analyses, was obtained.
Rationale
We address here the selection, preparation, calibration, storage, and use of carbonate and water working standards (WSs) for stable H, C, and O isotope measurements requiring the best ...possible precision and accuracy vs international reference materials (iRMs). This may be of interest for laboratories working intensively in the domains of the carbon and water cycles and of paleoclimate.
Methods
Defining a WS for stable C and O isotope studies requires combining mineralogical, physical, chemical (low Mg‐ and trace‐carbonate), and isotopic measurements to select a carbonate fit for purpose; for water, two distinct deionized or distilled waters, with high and low δ2H and δ18O values, respectively, are normally used. In both cases, a strict protocol must be followed to properly qualify the WS vs the current international isotopic scales, and much attention must be paid to calculating rigorous estimates of final uncertainties on these scales.
Results
Two specific protocols for the selection of carbonate and water WSs are detailed. Equations for a proper estimate of uncertainties are proposed.
Conclusions
The selection of WSs involves a preselection of potentially suitable materials based on initial estimates of their mineralogical, chemical, and isotopic properties and long‐term stability, based on literature or previous measurements. Their precise characterization vs international isotopic scales requires a thorough analytical work in a correct sequence. When properly carried out, the proposed protocols should permit WSs to be obtained, defined vs the VSMOW and VPDB scales, with uncertainties comparable with those achieved for the characterization of iRMs.
Due to anthropogenic emissions and changes in land use, trees are now exposed to atmospheric levels of CO₂ that are unprecedented for 650,000 y Lüthi et al. (2008) Nature 453:379–382 (thousands of ...tree generations). Trees are expected to acclimate by modulating leaf–gas exchanges and alter water use efficiency which may result in forest productivity changes. Here, we present evidence of one of the strongest, nonlinear, and unequivocal postindustrial increases in intrinsic water use efficiency (iWUE) ever documented (+59%). A dual-isotope tree-ring analysis (δ
13C and δ
18O) covering 715 y of growth of North America’s oldest boreal trees (Thuja occidentalis L.) revealed an unprecedented increase in iWUE that was directly linked to elevated assimilation rates of CO₂ (A). However, limited nutrient availability, changes in carbon allocation strategies, and changes in stomatal density may have offset stem growth benefits awarded by the increased iWUE. Our results demonstrate that even in scenarios where a positive CO₂ fertilization effect is observed, other mechanisms may prevent trees from assimilating and storing supplementary anthropogenic emissions as above-ground biomass. In such cases, the sink capacity of forests in response to changing atmospheric conditions might be overestimated.
Radiogenic (87Sr/86Sr) and stable (δ88/86Sr) strontium isotope compositions spanning a calendar year are reported for rivers from across subarctic Canada that drain contrasting lithologies ranging ...from Precambrian bedrock (Koksoak, Great Whale and La Grande rivers of Northern Quebec) to carbonate and clastic Phanerozoic sedimentary rocks of the Western Interior Platform (Nelson River, of central and western Canada). The 87Sr/86Sr isotopic compositions of the river waters reflect the underlying geology, with rivers draining the Precambrian Shield having higher 87Sr/86Sr ratios (0.727–0.734) than the Phanerozoic dominated Nelson River (0.713). The stable strontium isotope values (δ88/86Sr) range from 0.26 to 0.39‰, with the values for the Nelson River overlapping those of the other three. Rivers that have not been developed for hydroelectric power show a seasonal variation in the 87Sr/86Sr ratios, whereas those that have been diverted or dammed show little or no seasonal variation due to increased residence time of their water in hydroelectric reservoirs. The three rivers from Northern Quebec show discrete ranges in their 87Sr/86Sr and δ88/86Sr isotope compositions that correlate with the Ca/Sr and Na/Sr ratios of the river water. These correlations are interpreted to reflect differential chemical weathering of felsic versus mafic source rocks and/or of surficial sediment vs bedrock sources.
•River impoundment (damming) alters the Sr isotope composition of rivers.•Spring meltwater plumes alter the Sr isotope composition of the rivers.•Stable Sr isotope compositions and river chemistry reflect the bedrock geology.•Stable Sr isotope compositions of boreal rivers reflect silicate vs carbonate weathering.
PDF
