Strontium isotope geochemistry of alluvial groundwater: a tracer for groundwater resources characterisation

International audience(Paris, 29 septembre 2011, n° 2010/24176, X c/ AMF., D. 2012. 204, note D. Martin et M. Françon

The Inherent Tracer Fingerprint of Captured CO2.

Carbon capture and storage (CCS) is the only currently available technology that can directly reduce anthropogenic CO2 emissions arising from fossil fuel combustion. Monitoring and verification of CO2 stored in geological reservoirs will be a regulatory requirement and so the development of reliable monitoring techniques is essential. The isotopic and trace gas composition - the inherent fingerprint - of captured CO2 streams is a potentially powerful, low cost geochemical technique for tracking the fate of injected gas in CCS projects; carbon and oxygen isotopes, in particular, have been used as geochemical tracers in a number of pilot CO2 storage sites, and noble gases are known to be powerful tracers of natural CO2 migration. However, the inherent tracer fingerprint in captured CO2 streams has yet to be robustly investigated and documented and key questions remain, including how consistent is the fingerprint, what controls it, and will it be retained en route to and within the storage reservoir? Here we present the first systematic measurements of the carbon and oxygen isotopes and the trace noble gas composition of anthropogenic CO2 captured from combustion power stations and fertiliser plants. The analysed CO2 is derived from coal, biomass and natural gas feedstocks, using amine capture, oxyfuel and gasification processes, from six different CO2 capture plants spanning four different countries. We find that δ13C values are primarily controlled by the δ13C of the feedstock while δ18O values are predominantly similar to atmospheric O2. Noble gases are of low concentration and exhibit relative element abundances different to expected reservoir baselines and air, with isotopic compositions that are similar to air or fractionated air. The use of inherent tracers for monitoring and verification was provisionally assessed by analysing CO2 samples produced from two field storage sites after CO2 injection. These experiments at Otway, Australia, and Aquistore, Canada, highlight the need for reliable baseline data. Noble gas data indicates noble gas stripping of the formation water and entrainment of Kr and Xe from an earlier injection experiment at Otway, and inheritance of a distinctive crustal radiogenic noble gas fingerprint at Aquistore. This fingerprint can be used to identify unplanned migration of the CO2 to the shallow subsurface or surface

Nitrogen and Carbon Isotopic Dynamics of Subarctic Soils and Plants in Southern Yukon Territory and its Implications for Paleoecological and Paleodietary Studies

We examine here the carbon and nitrogen isotopic compositions of bulk soils (8 topsoil and 7 subsoils, including two soil profiles) and five different plant parts of 79 C3 plants from two main functional groups: herbs and shrubs/subshrubs, from 18 different locations in grasslands of southern Yukon Territory, Canada (eastern shoreline of Kluane Lake and Whitehorse area). The Kluane Lake region in particular has been identified previously as an analogue for Late Pleistocene eastern Beringia. All topsoils have higher average total nitrogen δ15N and organic carbon δ13C than plants from the same sites with a positive shift occurring with depth in two soil profiles analyzed. All plants analyzed have an average whole plant δ13C of −27.5 ± 1.2 ‰ and foliar δ13C of ±28.0 ± 1.3 ‰, and average whole plant δ15N of −0.3 ± 2.2 ‰ and foliar δ15N of ±0.6 ± 2.7 ‰. Plants analyzed here showed relatively smaller variability in δ13C than δ15N. Their average δ13C after suitable corrections for the Suess effect should be suitable as baseline for interpreting diets of Late Pleistocene herbivores that lived in eastern Beringia. Water availability, nitrogen availability, spacial differences and intra-plant variability are important controls on δ15N of herbaceous plants in the study area. The wider range of δ15N, the more numerous factors that affect nitrogen isotopic composition and their likely differences in the past, however, limit use of the modern N isotopic baseline for vegetation in paleodietary models for such ecosystems. That said, the positive correlation between foliar δ15N and N content shown for the modern plants could support use of plant δ15N as an index for plant N content and therefore forage quality. The modern N isotopic baseline cannot be applied directly to the past, but it is prerequisite to future efforts to detect shifts in N cycling and forage quality since the Late Pleistocene through comparison with fossil plants from the same region

A review of the distribution of particulate trace elements in urban terrestrial environments and its application to considerations of risk

We review the evolution, state of the art and future lines of research on the sources, transport pathways, and sinks of particulate trace elements in urban terrestrial environments to include the atmosphere, soils, and street and indoor dusts. Such studies reveal reductions in the emissions of some elements of historical concern such as Pb, with interest consequently focusing on other toxic trace elements such as As, Cd, Hg, Zn, and Cu. While establishment of levels of these elements is important in assessing the potential impacts of human society on the urban environment, it is also necessary to apply this knowledge in conjunction with information on the toxicity of those trace elements and the degree of exposure of human receptors to an assessment of whether such contamination represents a real risk to the city’s inhabitants and therefore how this risk can be addressed

Strontium isotope geochemistry of alluvial groundwater: a tracer for groundwater resources characterisation

This study presents strontium isotope and major ion data of shallow groundwater and river water from the Ile du Chambon catchment, located on the Allier river in the Massif Central (France). There are large variations in the major-element contents in the surface- and groundwater. Plotting of Na vs. Cl contents and Ca, Mg, NO₃, K, SO₄, HCO₃, Sr concentrations reflect water–rock interaction (carbonate dissolution for Ca, Mg, HCO₃ and Sr because the bedrock contains marly limestones), agricultural input (farming and fertilising) and sewage effluents (for NO₃, K, SO₄), although some water samples are unpolluted. Sr contents and isotope ratios (⁸⁷Sr/⁸⁶Sr vary from 0.70892 to 0.71180 along the hydrological cycle) in the groundwater agree with previous work on groundwater in alluvial aquifers in the Loire catchment. The data plot along three directions in a ⁸⁷Sr/⁸⁶Sr v. 1/Sr diagram as a result of mixing, involving at least three geochemical signatures–Allier river water, and two distinct signatures that might be related to different water-rock interactions in the catchment. Mixing proportions are calculated and discussed. The alluvial aquifer of the Ile du Chambon catchment is considered, within the Sr isotope systematic, in a larger scheme that includes several alluvial aquifers of the Loire Allier catchment.</p> <p style='line-height: 20px;'><b>Keywords: </b>: Loire river, major and trace elements, Sr isotopic ratio, alluvial aquifer, hydrolog

Characterization of coal from the Mariovo basin, Macedonia – Insights from organic geochemical and sulphur isotopic data.

Data detailed petrographic study of coal from the Mariovo basin in Macedonia suggests circulation of fluids mobilizing metals from different origins (basement, volcanism ?) during burial. Sulphur isotopic data on organic matter and pyrite indicate dominantly marine-derive fluids and processus of bacterial reduction of sulphates

Seasonality in the Δ³³S measured in urban aerosols highlights an additional oxidation pathway for atmospheric SO₂

Sulfates present in urban aerosols collected worldwide usually exhibit significant non-zero Δ33S signatures (from −0.6&thinsp;‰ to 0.5&thinsp;‰) whose origin still remains unclear. To better address this issue, we recorded the seasonal variations of the multiple sulfur isotope compositions of PM10 aerosols collected over the year 2013 at five stations within the Montreal Island (Canada), each characterized by distinct types and levels of pollution. The δ34S-values (n=&thinsp;155) vary from 2.0&thinsp;‰ to 11.3&thinsp;‰ (±0.2&thinsp;‰, 2σ), the Δ33S-values from −0.080&thinsp;‰ to 0.341&thinsp;‰ (±0.01&thinsp;‰, 2σ) and the Δ36S-values from −1.082&thinsp;‰ to 1.751&thinsp;‰ (±0.2&thinsp;‰, 2σ). Our study evidences a seasonality for both the δ34S and Δ33S, which can be observed either when considering all monitoring stations or, to a lesser degree, when considering them individually. Among them, the monitoring station located at the most western end of the island, upstream of local emissions, yields the lowest mean δ34S coupled to the highest mean Δ33S-values. The Δ33S-values are higher during both summer and winter, and are &lt;&thinsp;0.1&thinsp;‰ during both spring and autumn. As these higher Δ33S-values are measured in “upstream” aerosols, we conclude that the mechanism responsible for these highly positive S-MIF also occurs outside and not within the city, at odds with common assumptions. While the origin of such variability in the Δ33S-values of urban aerosols (i.e. −0.6&thinsp;‰ to 0.5&thinsp;‰) is still subject to debate, we suggest that oxidation by Criegee radicals and/or photooxidation of atmospheric SO2 in the presence of mineral dust may play a role in generating such large ranges of S-MIF.</p

Seasonality in the Δ&lt;sup&gt;33&lt;/sup&gt;S measured in urban aerosols highlights an additional oxidation pathway for atmospheric SO&lt;sub&gt;2&lt;/sub&gt;

International audienceSulfates present in urban aerosols collected worldwide usually exhibit significant non-zero 33 S signatures (from −0.6 ‰ to 0.5 ‰) whose origin still remains unclear. To better address this issue, we recorded the seasonal variations of the multiple sulfur isotope compositions of PM 10 aerosols collected over the year 2013 at five stations within the Montreal Island (Canada), each characterized by distinct types and levels of pollution. The δ 34 S-values (n = 155) vary from 2.0 ‰ to 11.3 ‰ (±0.2 ‰, 2σ), the 33 S-values from −0.080 ‰ to 0.341 ‰ (±0.01 ‰, 2σ) and the 36 S-values from −1.082 ‰ to 1.751 ‰ (±0.2 ‰, 2σ). Our study ev-idences a seasonality for both the δ 34 S and 33 S, which can be observed either when considering all monitoring stations or, to a lesser degree, when considering them individually. Among them, the monitoring station located at the most western end of the island, upstream of local emissions, yields the lowest mean δ 34 S coupled to the highest mean 33 S-values. The 33 S-values are higher during both summer and winter, and are < 0.1 ‰ during both spring and autumn. As these higher 33 S-values are measured in "up-stream" aerosols, we conclude that the mechanism responsible for these highly positive S-MIF also occurs outside and not within the city, at odds with common assumptions. While the origin of such variability in the 33 S-values of urban aerosols (i.e. −0.6 ‰ to 0.5 ‰) is still subject to debate, we suggest that oxidation by Criegee radicals and/or photooxi-dation of atmospheric SO 2 in the presence of mineral dust may play a role in generating such large ranges of S-MIF