Determination of Carbon and Nitrogen Isotope Fractions in Asparagine, Aspartic Acid, Threonine and Methionine

The nomenclature for compounds that are modified with isotopes is growing every day. Compounds can be modified with isotopes either individually, in a functional group or groups, or completely with all atomic centers of the element. This diversity of isotope-modified compounds increases the range of researches that can be studied using them. Compounds modified with isotopes of carbon-13 or nitrogen-15 can be converted into carbon monoxide, carbon dioxide and molecular nitrogen. Currently, only the average value of carbon-13 or nitrogen-15 isotopes can be determined. However, by directly determining the atomic share of these isotopes in organic compounds modified with isotopes, information about the isotopic centers of the element can be obtained. The atomic fraction of an element is defined as a single carbon or nitrogen isotope-modified center or centers, or all centers that are isotope-modified with that element at the same time. Carbon-13 or nitrogen-15 isotopes’ atomic fraction can be determined molecularly or with fragment ions of different elemental content, or both. This makes the method self-verifying, increasing the accuracy and reliability of the results obtained. Amino acids, such as asparagine, aspartic acid, methionine, and threonine, are essential for the human body. This proposed method of isotopic analysis will increase the possibilities for scientific research using these compounds.

Recent applications of isotope analysis to forensic anthropology

Isotope analysis has become an increasingly valuable tool in forensic anthropology case-work over the past decade. Modern-day isotopic investigations on human remains have integrated the use of multi-isotope profiles (e.g. C, N, O, H, S, Sr, and Pb) as well as iso-topic landscapes ("isoscapes") from multiple body tissues (e.g. teeth, bone, hair, and nails) to predict possible region-of-origin of unidentified human remains. Together, data from various isotope analyses provide additional lines of evidence for human identification, including a decedent's possible region-of-birth, long-term adult residence, recent travel history, and dietary choices. Here, we present the basic principles of isotope analysis and provide a brief overview of instrumentation, analytical standards, sample selection, and sample quality measures. Finally, we present case studies that reflect the diverse applications of isotope analysis to the medicolegal system before describing some future research directions. As shown herein, isotope analysis is a flexible and powerful geolocation tool that can provide new investigative leads for unidentified human remains cases.

Determination of trophic levels of marine fish in the Yellow Sea and northern East China Sea using nitrogen stable isotope (δ^(15)N) analysis of otoliths

Fish otolithδ^(15) N(δ^(15) N_(oto))is a demonstrated source of information of dietary history for marine fi sh as it is available iN_(oto)lith archives and sedimentary deposits unlike white muscle tissue(WMT).WMT and stomach content data are insufficient for trophic level(TL)data of past fi shes which is important for the changes of marine fi shery resources over long time scales.To determine the correlation betweenδ^(15) N_(oto) and fi sh WMTδ^(15) N(δ^(15) N_(wmt))and the feasibility of usingδ^(15) N_(oto) in characterizing the TLs of marine fi shes,we conducted nitrogen stable isotope analysis(SIA)in the otolith and WMT of 36 marine fi sh species sampled from the Yellow Sea and northern East China Sea in 2011-2014.Bothδ^(15) N_(oto) andδ^(15) N_(wmt) were analyzed using an elemental analyzer coupled with an isotope ratio mass spectrometer(EA-IRMS).Multiple otoliths were combined to make each otolith measurement and were analyzed as-is without a carbonate dissolution pre-processing step.δ^(15) N_(oto) andδ^(15) N_(wmt) comparisons for species in the Yellow Sea and northern East China Sea are currently lacking and would be helpful for both regional studies and for increasing the number of species for whichδ^(15) N_(oto) andδ^(15) N_(wmt) have been compared.Additionally,to determine the relative accuracy of trophic level calculated usingδ^(15) N_(oto),we compared TL calculated fromδ^(15) N_(oto) to traditional trophic level metrics calculated usingδ^(15) N_(wmt).The results showed a positive and highly signifi cant correlation(R=0.780,P<0.001)betweenδ^(15) N_(oto) andδ^(15) N_(wmt).Trophic level estimation using WMT(TL wmt)and otolith(TL oto)showed congruence in our study,which is not entirely surprising given thatδ^(15) N_(oto) was regressed againstδ^(15) N_(wmt) and the resulting regression coefficient was used to convertδ^(15) N_(oto) toδ^(15) N_(wmt) prior to calculating TL oto.This conversion was required in order to be consistent with previousδ^(15) N_(wmt)-based calculations of TL for comparison.TL oto calculations resulted in TL values that were largely within 5%-10%of TL values calculated withδ^(15) N_(wmt).Our fi ndings show thatδ^(15) N_(oto) is a feasible technique for characterizing the TLs of marine fi sh and can also assist in food web and marine ecosystem studies.

Isotopic analysis based on terahertz spectrum

As a new promising detection technology in the terahertz research field,the terahertz time-domain spec-troscopy(THz-TDS)has very broad application potential in many fields because its advantage on the characteristic spectrum,wide spectrum and non-destructive analysis of interested substances.In this paper,the terahertz absorption spectra of gases mixed with 12 CO and 13 CO in the spec-trum range of 0.5–2.5 THz are measured by terahertz time-domain spectroscopy for the first time.Several isotopo-logues can be clearly distinguished based on the difference in their rotational energies and the consequent terahertz spectrum.The experimental results show that 12 CO and 13 CO have obvious characteristic absorption peaks in the spectrum range of 0.5–2.5 THz due to the difference in rotational energy,and the rotational constant B can be calculated according to the experimental values to distin-guish the two gaseous isotopologues.The frequency posi-tions of the characteristic absorption peak measured by this experiment and the rotation constant B calculated accord-ing to the experimental values are compared with those previous theoretical calculations and experimental results,and they are in good agreement.This result lays a foun-dation for developing more sophisticated terahertz instru-ments to the detection of different isotopologues.

Melt extraction and mineralization: A case study from the Shuangjianzishan supergiant Ag-Pb-Zn deposit(208 Mt), Inner Mongolia, NE China

The supergiant Shuangjianzishan(SJZ) Ag-Pb-Zn deposit is in the southern segment of the Great Hinggan Range(SGHR), northeast China. Previous studies suggest the ore-forming material and fluid originated from the magmatic system, and the mineralization age was consistent with the diagenetic age. However,the relationship between granitic magmatism and mineralization is still unclear in the SJZ. In this study, CH-O-He-Ar and in-situ S-Pb isotope analyses were conducted to determine the sources of ore-forming fluids and metals, which were combined with geochemistry data of SJZ granitoids from previous studies to constrain the relationship between the magmatism and the mineralization. The C-H-O-He-Ar-S-Pb isotopic compositions suggested the SJZ ore-forming material and fluids were derived from a magmatic source, which has mixed a small amount of mantle-derived materials. In addition, the disseminated sulfide from the syenogranite has comparable S-Pb isotopic composition with the sulfide minerals from ore veins,suggesting that the generation of the SJZ ore-forming fluids has a close relationship with the syenogranite magmatism. Combining with the geochemical characters of the syenogranite, the authors proposed that the mantle-derived fingerprint of the SJZ ore-forming fluid might be caused by the parent magma of the syenogranite, which was derived from partial melting of the juvenile lower crust, and underwent the residual melts segregated from a crystal mush in the shallow magma reservoir. The extraction of the syenogranite parent magma further concentrated the fertilized fluids, which was crucial to mineralization of the SJZ Ag-Pb-Zn deposit.

庙岛群岛毗邻海域秋季底栖食物网潜在碳来源贡献及对碳汇渔业的思考

陆架边缘海是全球海洋重要的碳汇区域,而近岸岛屿毗邻海域作为最具代表性的边缘海域,具有来自海洋与陆地的不同碳来源,在碳循环和海洋碳汇中发挥着重要作用。本研究基于碳氮稳定同位素方法,利用贝叶斯混合模型,分析2020年秋季庙岛群岛毗邻海域底栖食物网中不同碳来源(浮游植物、大型藻类、悬浮颗粒有机物和底质有机物)对主要消费者类群(水生底栖无脊椎动物、杂食性鱼类、底栖食性鱼类和肉食性鱼类)的相对贡献,并以此对海洋碳汇和碳汇渔业展开了讨论。结果显示,庙岛群岛毗邻海域秋季底栖食物网生物类群的潜在碳来源主要为藻类(包括浮游植物和大型藻类)和海底底质有机质(SOM),但悬浮颗粒有机物(POM)的贡献较低。碳来源主要以内源性碳(海源)为主。由于大型藻类对水生底栖无脊椎动物的贡献明显高于鱼类,在碳汇渔业的指导下,合理科学地进行藻类增养殖,并通过贝类或以贝藻为食的鱼类混和养殖可能增加碳汇能力,从而促进碳汇渔业的发展。

Mass-Spectrometric Method of Measurement of Isotopic Content of Nitrogen in Organic Compounds

Nitrogen-15 isotope-modified compounds are widely used in medicine, pharmacology, agriculture and various fields of science and their nomenclature is gradually increasing. Their widespread use depends on the availability of inexpensive and simple isotope analysis methods. The present article is an attempt to determine the nitrogen-15 isotope content directly in organic compounds without their conversion. The general principle of possibility of determination of the isotopes of nitrogen directly in organic compounds is proposed. Based on the study of mass-spectra of Carbamide Carbonyldiamide, isocyanic acid and nitrobenzene the mass peaks are selected, by which it is possible to determine the atomic fraction of the isotopes of nitrogen. The respective formulas are proposed.

Metallurgy at the Crossroads: New Analyses of Copper-based Objects at Tianshanbeilu, Eastern Xinjiang, China

Tianshanbeilu is the largest Bronze Age site in eastern Xinjiang, China. Stretching across the entire second millennium BC, it performed a prominent role in connecting the Hexi corridor, Central China and the steppe. A further insight into the metallurgical tradition and the metal supply network is of vital importance to improve our understanding of its multi-connected nature. This paper offers a new set of chemical and isotopic data on the copper-based objects at Tianshanbeilu, including alloying elements, trace elements(impurities) and lead isotopes. Combining the concentrations of arsenic and antimony reveals that arsenic was introduced to copper partially due to the use of specific minerals tethrahedrite-tennantite. Lead isotopes demonstrate that multiple sources of copper were employed at Tianshanbeilu and a majority of them are characterized by common lead, which appears rather different from those of the Central Plains and the Hexi corridor, but highly consistent with local ores. Surprisingly, one object at Tianshanbeilu contains the well-known highly radiogenic lead. This object undoubtedly marks the westernmost boundary of the distribution of the highly radiogenic lead. We also anticipate that more lead isotopic analyses in NW China will further contribute to the study of the highly radiogenic lead in Central China.

Developing an authentication approach using SPME-GC-IRMS based on compound-specific δ^(13)C analysis of six typical volatiles in wine

An analytical method using gas chromatography isotope ratio mass spectrometry(GC-IRMS)combined with solid phase micro-extraction(SPME)was developed to measure the 613C values of six typical volatiles commonly occurring in wine(isoamyl acetate,2-octanone,limonene,2-phenylethanol,ethyl octanoate and ethyl decanoate)for the first time.SPME selected with a divinylbenzene/carboxen/polydimethylsiloxane fiber was combined with the GC-IRMS for pretreatment optimization.The optimized SPME parameters of extraction time,extraction temperature and salt concentration were 40 min,40℃ and 10%,respectively.The 613C values measured by SPME-GC-IRMS were in good agreement with those measured via elemental analyzer(EA)-IRMS and GC-IRMS.The differences range from 0.02‰to 0.44‰ with EA-IRMS and from 0 to 0.28‰ with GC-IRMS,indicating the high accuracy of the method.This newly established method measured the precision within 0.30‰ and was successfully validated to discriminate imported real wine samples with identical label but amazing price differences from different importers.

Accurate Determination of Zr Isotopic Ratio in Zircons by Femtosecond Laser Ablation MC-ICP-MS with “Wet” Plasma Technique

This work evaluates the use of femtosecond laser ablation multiple collector inductively coupled plasma mass spectrometry(fs-LA-MC-ICP-MS) for Zr isotopic analysis in zircons. The mass fractionation caused by instrumental mass discrimination was corrected by a combination of internal correction using Sr as an internal standard(coming from a NIST SRM 987 standard solution) and external correction using a matrix-matched standard. Several important instrument parameters were investigated, such as the effect of the addition of N;and "wet" plasma condition, the mass fractionation behaviors between Zr isotopes and Sr isotopes, the position effect in laser ablation cell and the effect of laser ablation parameters(laser spot size and energy density). The Zr isotope compositions of seven zircons(GJ-1, 91500, Ple?ovice, Rak-17, Paki, Aus and Mala) were determined by the developed fs-LAMC-ICP-MS and thermal ionization mass spectrometry(TIMS). Our fs-LA-MC-ICP-MS results for Zr isotope compositions agreed with TIMS analyses within analytical uncertainties, indicating the presented method is a suitable tool to resolve isotopic zoning in natural zircons. The results also suggest that GJ-1, 91500, Ple?ovice, Paki, Aus and Mala had the homogenous Zr isotope composition and could be considered as the potential candidates for the Zr isotope analysis in zircons, except Rak-17 which presented the large Zr isotope variation.

A new analytical mode and application of the laser ablation inductively coupled plasma mass spectrometer in the earth sciences

We proposed a new laser analytical mode,which used the high-frequency laser ablation to deliberately obtain the peak-shape signal profile,combined with the linear regression calibration(LRC)method to calculate elemental or isotopic ratios.In order to assess the performance of the new laser analytical mode for the application in the field of earth science,we systematically investigated the elemental quantitative analysis with high spatial resolution(10μm),rapid U-Pb dating in zircons and accurate Sr-Hf isotope analysis in geological samples.The new high-frequency laser analysis technology(20 Hz,100 pulses)reduced the limit of detection(LOD)of 25 elements to 0.005-0.16μg g^(-1) with crater diameters of 10μm,which are significantly lower(decrease to 2-20%)than previous researches.The quantitative analysis of five silicate glass reference materials showed that the precision and accuracy of the 25 trace elements(with the concentration ranging from 0.17 to 683μg g^(-1))were better than 16% and 15%,respectively.The new methods raised the analytical throughput of zircon U-Pb dating,Sr isotope ratios and Hf isotope ratios to 250 analyses per hour,144 analyses per hour and 120 analyses per hour in theory,while the analytical accuracy and precision were not affected.The detailed investigations showed that the proposed new laser analytical mode has good application effects in the field of earth sciences.

Identification of a female murder victim found in Burgenland,Austria in 1993

In 1993,the skeletal remains of a female corpse were found in Burgenland,Austria.Initial identification of the approximately 25–35-year-old female appeared impossible,but the case was reopened 23 years later.By applying biogeochemical isotope methods to her body tissues,the geographical origin of the unknown corpse could be predicted.The results of the C,N,S,H,Sr,and Pb isotope analyses suggested that the female did not originate from Europe and most likely spent her youth in the northern Caribbean.Using these findings,the police were able to identify the woman within 2 weeks.The female came from the Dominican Republic and resided in Austria for only a short period before she was murdered.This case shows that isotope biogeochemistry investigations can provide the police with crucial information that enables unknown persons to be identified.

Notes for a History of Gas Geochemistry

During ancient times,human interest in naturally-occurring gases was religious,while it was scientific in the historical age and industrial in modern times.Gases were also utilized for practical purposes and more than 3000 years before present day,Chinese populations made use of methane for salt extraction while in the 17th century it was observed that native Americans ignited methane seepages.The development of human thinking on gases followed the fundamental steps that characterized the natural sciences during the 18th century scientific revolution that was based on significant improvements in analytical methods.These improvements are still ongoing while present-day scientific publications evidence the spread of the field of interest and more cooperation with geophysical sciences to solve common interest problems.The existence of proper meetings and dedicated scientific journals confirms that gas geochemistry has ended this pioneering phase to enter a more mature condition.

Contribution of Hydrogeochemical and Isotopic Tools to the Management of Upper and Middle Cheliff Aquifers

In the alluvial aquifers of Upper and Middle Cheliff(North-West Algeria), the groundwater quality is deteriorating. The objective of this study was to characterize the physical and chemical properties of these aquifers;and to evaluate the groundwater quality and its appropriateness for drinking and agricultural use. An investigation was carried out by estimating of the physiochemical parameters(Ca^2+, Mg^2+, Na^+, K^+, Cl^-, SO4^2-, HCO3^-, NO3^-, Br^- and TDS) to identify the chemical characteristics of groundwater. Morever, the isotopic composition was examined to identify the sources of recharge of these aquifers. The groundwater geochemistry for the high water level(May, 2012 and June, 2017) and low water level(November, 2012 and October, 2017) was studied. Accordingly, water samples from 39 water sampling points were collected(October, 2017 and June, 2018), for the purpose of analyzing stable isotopes(18O, 2H). The results show that the groundwater is mainly characterized by Ca-Cl and Na-Cl type. The chemical quality of the water is from fair to poor with the presence of nitrates used in agricultural and urban discharge. Also, the Br/Cl ratio gives indications on the origin of the salinity. This salinity is due to the leaching of chlorinated fertilizers, the dissolution of evaporite deposits and the rise of deep salty water by the fault of Chellif. While, the diagram of δ2H=f(δ18O) indicates that the origin of the recharge of these aquifers is the Atlantic and Mediterranean oceanic meteoric rainwater.

Geochemistry of the Mesoproterozoic Intrusions, Geochronology and Isotopic Constraints on the Xiaonanshan Cu-Ni Deposit along the Northern Margin of the North China Craton

Mesoproterozoic magma events in the Bayan Obo rift belt have remained poorly constrained and as a result, the Late Paleoproterozoic–Mesoproterozoic tectonic evolution of the rift belt has remained unclear. By a multiple-facetted regional geological investigation of this belt, we have resolved the stratigraphic sequence and geochronology of the Bayan Obo Group and made new discoveries including a three-stage mantle-derived magmatic sequence. Zircon and baddeleyite dating of Xiaonanshan hornblende pyroxenite emplaced into the Bayan Obo Group yields 207Pb/206Pb ages of ca. 1.34 and 1.33 Ga. The geochronological, geochemistry, Hf isotopic analyses place an important constraint on ages of the Late Paleoproterozoic–Mesoproterozoic strata and the evolution of the rift belt. Our field observations and U-Pb dating results suggest that mineralization is genetically related to Mesoproterozoic magmatism in North China Craton, i.e., 1.33–1.34 Ga. The δ34SV-CDT values of sulphide from the ore-bearing ultra-/mafic samples are about 6.2‰, whereas the 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values vary in the ranges of 17.598–18.115, 15.496–15.501, and 37.478–37.952, respectively. The Late Paleozoic mafic gabbro and acidic granite porphyry intrusions are possible to bimodal magmatic event related to the extensional tectonic setting of the Central Asia in this period.