•Stepwise chemical procedure for multi-sulfur species recovery from a single sample.•(Multi-)isotope analysis of purified sulfur species.•New insights into sulfur biogeochemical cycle from multi ...S-pools analysis.
Deciphering the role of sulfur in biogeochemical cycles strongly relies on its stable isotope composition, which ultimately depends on the ability to quantitatively recover different sulfur species from geological samples. For decades most studies have been restricted to the 34S/32S composition of bulk samples, using simple methods based on the analysis of SO2 released by sample combustion combined to mass spectrometry. The wet chemistry procedures required to selectively extract specific sulfur species were generally avoided due to their tediousness and inefficiency for some complex matrices, especially when targeting organic sulfur. With the recent advent of multi-isotope studies (investigating the minor sulfur stable isotopes 33S and 36S) which rely either on the analysis of sulfur as SF6, or on the use of secondary ion or multi-collector inductively coupled plasma mass spectrometry, wet chemistry-based preparation procedures were brought back to the stage with a renewed interest in developing procedures better adapted to the investigation of specific sulfur species.
Here we propose a new stepwise chemical procedure for the quantitative recovery and multi-isotope analysis of organic sulfur from both solvent soluble (total lipid extract) and insoluble (kerogen) fractions, based on a wet oxidation by sodium hypochlorite. This procedure also allows the multi-isotope analysis of inorganic sulfur species (elemental sulfur, sulfates and sulfides) in the same sample. Its application to different well-known petroleum source rocks and to an oil demonstrates its relevance for disentangling the interactions between the different sulfur pools and for shedding new light on the sulfur biogeochemical cycle.
The Early Triassic is generally portrayed as a time of various, high ecological stresses leading to a delayed biotic recovery after the devastating end-Permian mass extinction. This interval is ...notably characterized by repeated biotic crises (e.g., during the late Smithian), large-scale fluctuations of the global carbon, nitrogen and sulfur cycles as well as harsh marine conditions including a combination of ocean acidification, anoxia, extreme seawater temperatures and shifting productivity. Observations from different paleolatitudes suggest that sulfidic (H2S-rich) conditions may have developed widely during the Early Triassic, possibly reaching up to ultra-shallow environments in some places. However, the existence and the spatio-temporal extent of such redox swings remain poorly constrained. In order to explore Early Triassic paleoceanographic redox changes and their potential influences on the biotic recovery, we analyzed multiple sulfur isotopes (32S, 33S, 34S, and 36S) of sedimentary pyrite and carbonate associated sulfate (δ34SCAS) from the Mineral Mountains section, Utah. Sediments from this section were mainly deposited in shallow waters and span the Smithian and lower Spathian. We report a 68‰ range of variations in δ34Spy associated with Δ33Spy varying from −0.01‰ to +0.12‰, whereas the δ34SCAS varies between +19.5‰ and + 34.8‰. We interpret the observed signal of multiple sulfur isotopes as reflecting the operation of pore-water synsedimentary microbial sulfate reduction in open system with respect to sulfates before the late Smithian, evolving to a closed system, sulfate limited, Rayleigh-type distillation across the Smithian/Spathian boundary (SSB) and immediately after the SSB. We argue that this marked change is driven by the effectiveness of the connection between the sedimentary pore waters and the overlying water column, which is, in this case, controlled by the local sedimentological conditions such as the bioturbation intensity and the sedimentation rate. Therefore, our results suggest that changes in the sulfur cycle before and across the SSB at Mineral Mountains is probably a local consequence of the loss of the mixed sedimentary layer during the late Smithian extinction event, as opposed to reflecting the development of a lethal anoxic ocean at the global scale.
This paper investigates impacts of the creation of Marine Protected Areas (MPAs), in both economic and biological perspectives. The economic indicator is defined as the sum of discounted benefits ...derived from exploitation of the resource in the fishery sector, assumed to be optimally managed. The biological indicator is taken as the stock density of the resource. The basic fishery model (C.W. Clark, Mathematical Bioeconomics: The Optimal Management of Renewable Resources, second ed., John Wiley and Sons, New York, 1990) will serve as a convenient benchmark in comparing results with those that are derived from a model of two patchy populations (cf. R. Hannesson, Marine reserves: what would they accomplish, Mar. Resour. Econ. 13 (1998) 159). In the latter, a crucial characteristic is the migration coefficient with describes biological linkages between protected and unprotected areas. A set of situations where both economic and biological criteria are enhanced, after introducing a MPA, is presented. These results are obtained with the help of numerical simulations.
Nitrogen and hydrogen isotopic compositions together with N, K, Rb, Cs and H sub(2)O contents were measured on several high-pressure (HP) to ultrahigh- pressure (UHP) metasediments from the Schistes ...Lustres nappe (western Alps) and on unmetamorphosed sedimentary protoliths from the Apennines (Italy). These samples represent a sequence of pelagic sediments subducted to different depths down to 90 km along a 'cold' geothermal gradient (~8 degree C/km). Nitrogen isotopic composition ( delta super(15)N between +2.6 and +4.8ppm) does not show any specific evolution with increasing metamorphic conditions and can be considered constant during subduction. Large variations of the N content (between 169 and 1721 ppm N) together with K, Rb and Cs content are observed but the constancy of K/N (14), K/Rb (385) and K/Cs (10190) molar ratios in protoliths and metamorphic rocks indicates that none of these fluid-mobile elements was lost through devolatilization processes. This suggests that fluid circulation was limited to sample scale and that the rocks behaved as closed systems during subduction. This interpretation is also supported by the small range of delta D values (from-54.1 to-78.0ppm). The present results indicate that N, K, Rb and Cs were retained in the subducted sedimentary veneer at least down to the depth locus of island arc magmatism. Based on the correlation between N and K contents, the flux of sedimentary N recycled in subduction zones is estimated at 7.6x10 super(11) g/yr. Mass balance calculations strongly support the fact that nitrogen is efficiently recycled to the deeper mantle.
Characteristic features of in situ diamonds can be used to retrace diamond formation during ultrahigh pressure (UHP) metamorphism of the Kokchetav Massif, Kazakhstan. These features include the ...nitrogen aggregation state in diamond, dissolution features observed on diamond surfaces, and the carbon and nitrogen isotopic composition of the diamonds. The minerals in which the diamonds are included provide additional information and support the view that at least some of the Kokchetav microdiamonds are the products of prograde or peak UHP metamorphism. The coexistence of diamond and graphite is evaluated within this framework.
In this work we deal with the design of the robust feedback control of wastewater treatment system, namely the activated sludge process. This problem is formulated by a nonlinear ordinary ...differential system. On one hand, we develop a robust analysis when the specific growth function of the bacterium $\mu$ is not well known. On the other hand, when also the substrate concentration in the feed stream s sub(in) is unknown, we provide an observer of system and propose a design of robust feedback control in term of recycle rate, in order to keep the pollutant concentration lower than an allowed maximum level s sub(d).
To better address how Mid-Ocean Ridge Basalt (MORB) sulfur isotope composition can be modified by assimilation and/or by immiscible sulfide fractionation, we report sulfur (S), chlorine (Cl) and ...copper (Cu) abundances together with multiple sulfur isotope composition for 38 fresh basaltic glasses collected on the Pacific-Antarctic ridge. All the studied glasses - with the exception of 8 off-axis samples - exhibit relatively high Cl/K, as the result of pervasive Cl-rich fluid assimilation. This sample set hence offers an opportunity to document both the upper mantle S isotope composition and the effect of hydrothermal fluids assimilation on the S isotope composition of erupted basalts along segments that are devoid of plume influence. Delta super(33)S and Delta super(36)S yield homogenous values within error of Canyon Diablo Troilite (CDT), whereas delta super(34)S are variable, ranging between -1.57 plus or minus 0.11ppt and +0.60 plus or minus 0.10ppt with a mean value of -0.64 plus or minus 0.40ppt (1 sigma , versus V-CDT). The geographic distribution of delta super(34)S follows a spike-like pattern, with local super(34)S-enrichments by up to +1.30ppt compared to a low- delta super(34)S baseline. As hydrothermal massive sulfides are characterized by relative super(34)S-enrichments, such first-order variability can be accounted for by hydrothermal sulfide assimilation, a process that would occur for a subset of samples (n = 10). Excluding these particular samples, the mean delta super(34)S is significantly less variable, averaging at -0.89 plus or minus 0.11ppt (1 sigma , n = 28), a value that we suggest to be representative of the average MORB source value for Pacific-Antarctic basalts. Weak trends between delta super(34)S and super(206)Pb/ super(204)Pb are displayed by such uncontaminated samples suggesting the recycled oceanic crust to have a modest impact on the S budget of the mantle. Their positive signs, however, suggest the depleted mantle to have a delta super(34)S of -1.40 plus or minus 0.50ppt. The sub-chondritic super(34)S/ super(32)S value that was previously observed for the South-Atlantic mantle is here extended to the Pacific-Antarctic domain. Such a feature cannot originate from oceanic crust recycling and substantiates the concept of a core-mantle fractionation relict.
In order to better investigate the compositions and the origins of fluids associated with diamond growth, we have carried-out combined noble gas (He and Ar), C and N isotope, K, Ca and halogen (Cl, ...Br, I) determinations on fragments of individual microinclusion-bearing diamonds from the Panda kimberlite, North West Territories, Canada. The fluid concentrations of halogens and noble gases in Panda diamonds are enriched by several orders of magnitude over typical upper mantle abundances. However, noble gas, C and N isotopic ratios (
3He/
4He
=
4–6
Ra,
40Ar/
36Ar
=
20,000–30,000, δ
13C
=
−4.5‰ to −6.9‰ and δ
15N
=
−1.2‰ to −8.8‰) are within the worldwide range determined for fibrous diamonds and similar to the mid ocean ridge basalt (MORB) source value. The high
36Ar content of the diamonds (>1
×
10
−9
cm
3/g) is at least an order of magnitude higher than any previously reported mantle sample and enables the
36Ar content of the subcontinental lithospheric mantle to be estimated at ∼0.6
×
10
−12
cm
3/g, again similar to estimates for the MORB source. Three fluid types distinguished on the basis of Ca–K–Cl compositions are consistent with carbonatitic, silicic and saline end-members identified in previous studies of diamonds from worldwide sources. These fluid end-members also have distinct halogen ratios (Br/Cl and I/Cl). The role of subducted seawater-derived halogens, originally invoked to explain some of the halogen ratio variations in diamonds, is not considered an essential component in the formation of the fluids. In contrast, it is considered that large halogen fractionation of a primitive mantle ratio occurs during fluid–melt partitioning in forming silicic fluids, and during separation of an immiscible saline fluid.
We study a selection method for a Nash feedback equilibrium of a one-dimensional linear-quadratic nonzero-sum game over an infinite horizon. By introducing a change in the time variable, one obtains ...an associated game over a finite horizon T > 0 and with free terminal state. This associated game admits a unique solution which converges to a particular Nash feedback equilibrium of the original problem as the horizon T goes to infinity.
Ozone exhibits large and mass independent isotopic fractionations (MIF) in oxygen isotope ratios relative to molecular di-oxygen (O2) from which it is formed. An interpretation of this effect was ...proposed based on the behavior of the indistinguishable isotopes 16O in scattering processes. We report here an experiment aimed at testing one of the predictions of this model.
O3 was formed by high frequency discharge in O2 with pressures ranging between 1.6 and 38 Torr. The isotopic evolution of the closed O2 reservoir was monitored during its distillation taking place during the continuous removal of ozone by condensation. Its composition evolves from a mass independent to a mass dependent fractionation along with the decrease in pressure. The isotopic pathways defined by this evolution in the 3 isotopes diagram are in quantitative agreement with the theoretical prediction of the disappearance of MIF with the increase of the complex lifetime stabilized as ozone.
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