High-Precision Direct Determination of the ^(87)Sr/^(86)Sr Isotope Ratio of Bottled Sr-Rich Natural Mineral Drinking Water Using MC-ICP-MS

Strontium has four naturally occurring stable isotopes,84Sr,86Sr,87Sr,and 88Sr,with abundances of 0.56,9.87,approximately 7.04,and 82.53 atomic %,respectively.The 87Sr/86Sr isotope ratio is variable due to the addition of radiogenic 87Sr produced by the beta decay of 87Rb with a half-life of 4.88 ± 0.05 Ga.Thus,

Application of Stable Isotope Techniques in Studies of Carbon and Nitrogen Biogeochemical Cycles of Ecosystem

Stable isotope techniques have been proved useful as tools for studying the carbon (C) and nitrogen (N) biogeochemical cycles of ecosystem. This paper firstly introduced the basic principles and the distribution characteristics of stable isotope, then reviewed the recent advances and applications of stable isotope in the C and N biogeochemical cycles of ecosystem. By applying the 13 C natural abundance technique, ecologists are able to understand the photosynthetic path and CO 2 fixation of plants, the CO 2 exchange and C balance status of ecosystem, the composition, distribution and turnover of soil organic C and the sources of organic matter in food webs, while by using the 13 C labeled technique, the effects of elevated CO 2 on the C processes of ecosystem and the sources and fate of organic matter in ecosystem can be revealed in detail. Differently, by applying the 15 N natural abundance technique, ecologists are able to analyze the biological N 2 -fixation, the N sources of ecosystem, the N transformation processes of ecosystem and the N trophic status in food webs, while by using the 15 N labeled technique, the sources, transformation and fate of N in ecosystem and the effects of N input on the ecosystem can be investigated in depth. The applications of both C and N isotope natural abundance and labeled techniques, combined with the elemental, other isotope ( 34 S) and molecular biomarker information, will be more propitious to the investigation of C and N cycle mechanisms. Finally, this paper concluded the problems existed in current researches, and put forward the perspective of stable isotope techniques in the studies on C and N biogeochemical cycles of ecosystem in the future.

The Representation of the Chemical Elements’ Isotopes by the Neutron Excess Content

A more compact representation of the Segré chart of nuclides can be obtained replacing the isotopic neutron with the corresponding neutron excess number;a first sight inspection of all the natural isotopes is produced. The resulting representation shows a built-inorder in the organization of the nuclear components into the nuclei of the natural isotopes, sustained by the relevant role of the magic numbers. The interpretation, on the identical foot, of the nuclear instability of Tc, Pm and of the elements following Bi is suggested. The present representation reminds the spheron model of the nuclear structure suggested by L. Pauling. The alpha decay paths of radioactive isotopes are shown, side by side to the low energy nuclear transmutations (LENR). Representations of the artificial isotopes of the chemical elements and of the stellar nucleosynthesis processes are also proposed.

About Radiation in ^natGd for Neutron Capture Therapy

In the present work, based on publications dedicated to ^natGd natural gadolinium isotopes, characteristics of secondary particles are analysed in details for various neutron-induced reactions. Characteristics of the secondary particles produced in these reactions that make significant contribution to absorbed dose are estimated. It is also established that the main contribution to the absorbed dose is made by secondary particles produced in interactions of neutrons and ^155Gd and ^157Gd isotopes. From comparison of gamma-radiation spectra it is defined that the amount of γ-quanta with energies 0-400 keV （i.e. effective γ-quanta） produced in the （n,γ）-reaction by ^155Gd is higher than that by ^157Gd. Compared spectra of other particles （internal conversion electrons, Auger electrons, x-ray radiation） have shown that earlier used average values of their energy must be defined more precisely. When biological objects are irradiated for approximately 30 minutes by epithermal neutrons in the ^natGd NCT （Gadolinium-based neutron-capture therapy）, one should take into account energies of secondary particles produced by ^152Gd, ^154Gd, ^156Gd, ^158Gd and ^160Gd isotopes as they have high linear energy transfer （LET）. It is demonstrated that when combined, all these secondary particles can make significant contribution to the absorbed dose at neutron-irradiation of biological objects by the ^natGd NCT technique.

An isotope study of the accumulation mechanisms of high-sulfur gas from the Sichuan Basin, southwestern China

The mechanism of hydrogen sulfide(H_2S) generation plays a key role in the exploration and development of marine high-sulfur natural gas, of which the major targets are the composition and isotope characteristics of sulfur-containing compounds.Hydrocarbon source rocks, reservoir rocks, natural gases and water-soluble gases from Sichuan Basin have been analyzed with an online method for the content of H_2S and isotopic composition of different sulfur-containing compounds. The results of comparative analysis show that the sulfur-containing compounds in the source rocks are mainly formed by bacterial sulfate reduction(BSR), and the sulfur compounds in natural gas, water and reservoir are mainly formed by thermal sulfate reduction(TSR). Moreover, it has been shown that the isotopically reversion for methane and ethane in high sulfur content gas is caused by TSR. The sulfur isotopic composition of H_2S in natural gas is inherited from the gypsum or brine of the same or adjacent layer,indicating that the generation and accumulation of H_2S have the characteristics of either a self-generated source or a near-source.

Biochar application significantly increases soil organic carbon under conservation tillage:an 11-year field experiment

Biochar application and conservation tillage are significant for long-term organic carbon(OC)sequestration in soil and enhancing crop yields,however,their effects on native soil organic carbon(native SOC)without biochar carbon sequestration in situ remain largely unknown.Here,an 11-year field experiment was carried out to examine different biochar application rates(0,30,60,and 90 Mg ha^(−1))on native SOC pools(native labile SOC pool I and II,and native recalcitrant SOC)and microbial activities in calcareous soil across an entire winter wheat-maize rotation.The proportions of C_(3) and C_(4)-derived native SOC mineralization were quantified using soil basal respiration(SBR)combined with 13C natural isotope abundance measurements.The results showed that 39-51%of the biochar remained in the top 30 cm after 11 years.Biochar application rates significantly increased native SOC and native recalcitrant SOC contents but decreased the proportion of native labile SOC[native labile SOC pool I and II,dissolved organic carbon(DOC),and microbial biomass carbon(MBC)].Biochar application tended to increase the indicators of microbial activities associated with SOC degradation,such as SBR,fluorescein diacetate hydrolysis activity,and metabolic quotient(qCO_(2)).Meanwhile,higher biochar application rates(B60 and B90)significantly increased the C_(4)-derived CO_(2) proportion of the SBR and enhanced C_(4)-derived native SOC mineralization.The effect of the biochar application rate on the content and proportion of native SOC fractions occurred in the 0-15 cm layer,however,there were no significant differences at 15-30 cm.Soil depth also significantly increased native labile SOC pool Ⅰ and Ⅱ contents and decreased qCO_(2).In conclusion,the biochar application rate significantly increased native SOC accumulation in calcareous soil by enhancing the proportion of native recalcitrant SOC,and biochar application and soil depth collectively influenced the seasonal turnover of native SOC fractions,which has important implications for long-term agricultural soil organic carbon sequestration.

comCompetition for resources is ameliorated by niche differentiation between Solidago virgaurea life-history stages in the Arctic

Aims competition has been shown to modify the niche breadth of coex-isting species,but within-species interactions have received little attention.Establishing small juvenile individuals and established,larger,sexually reproducing adult individuals represent two life-his-tory stages within species.We investigated the nitrogen and carbon resource use of adult and juvenile individuals and similarity of sym-biotic fungal community composition in these two plant life stages.We used the plant Solidago virgaurea growing in a simplified system in the low Arctic as model species.Methods Isotopic signatures(foliarδ15N and foliarδ13c)were analysed to characterize nitrogen acquisition and water-use efficiency of the plants.Symbiotic root fungal community composition was esti-mated by cloning and sequencing small subunit ribosomal RNA gene.Important Findings The isotopic signatures differed significantly between the life stages,indicating that the establishing juvenile cohort used relatively more amino acids or gained N through mycorrhizal symbiosis in com-parison to the established adult plants.Symbiotic fungal commu-nities did not differ between the two plant cohorts suggesting a possibility that the plants shared the same mycorrhizal network.We conclude that competition-mediated differences in plant resource use may create niche differentiation between the two life-history stages and enable them to coexist.