Objective The Yangtze craton collisional orogeny at ca. extensional events at ca. 1 experienced Paleoproterozoic 1.95-2.0 Ga and post-orogenic 85 Ga related to amalgamation of the Columbia （Nuna） supercontinent （Zh...Objective The Yangtze craton collisional orogeny at ca. extensional events at ca. 1 experienced Paleoproterozoic 1.95-2.0 Ga and post-orogenic 85 Ga related to amalgamation of the Columbia （Nuna） supercontinent （Zhao and Cawood, 2012）. A ca. 2.15 Ga suprasubduction zone ophiolitic melange was recongized in the Archean- Paleoproterozoic Kongling Complex of the northern Yangtze craton （Han et al., 2017）. However, the tectonic evolution in early Paleoproterozoic from 2.4 Ga to 2.2 Ga remains unclear. We report here the presence of a suite of Paleoproterozoic （2.2 Ga） granites in the Huangling dome, northern Yangtze craton, which may provide important insights into crustal growth processes in the craton prior to the assembly of Columbia.展开更多
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 ...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.展开更多
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 ...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.展开更多
The Beiqian site,located in Jimo city,Qingdao,went through three archaeological excavations,and a large number of human and animal bones in the Dawenkou culture and the Zhou Dynasty period were unearthed.By carbon and...The Beiqian site,located in Jimo city,Qingdao,went through three archaeological excavations,and a large number of human and animal bones in the Dawenkou culture and the Zhou Dynasty period were unearthed.By carbon and nitrogen stable isotope analysis,the diet of ancestors is expected to be recovered,and the domesticated plants and animals will be discussed.The investigated results showed that the food structure of ancestors in both periods included food crops,mainly C4 foods,and meat,mainly marine shellfish and livestock.For domestic pigs,they mainly eat C3 plants,and were affected by the lifestyle of ancestors.This study also showed that the diet of ancestors is the shellfish rather than marine fish despite the Beiqian site is located near the shoreline.We can conclude that the diet of ancestors in Dawenkou culture period included millet crops(C4plants),shellfish,marine food,and livestock,representing the lifestyle of farming,domestication,and fishing,supplemented by hunting.In the Zhou dynasty period the meat resource was enriched by domesticated animals and marine fisheries,and the living conditions were significantly improved.展开更多
In the Early Ordovician Zhaogezhuang Section of Tangshan , North China, the Yeli Formation is composed of an entire third-order sequence, with facies ranging from the inner ramp restricted platform and open marine t...In the Early Ordovician Zhaogezhuang Section of Tangshan , North China, the Yeli Formation is composed of an entire third-order sequence, with facies ranging from the inner ramp restricted platform and open marine to the middle and even outer ramps. The Liangjiashan Formation is dominated by highstand system tracts （HST） with predominantly inner ramp grain-shoal and lagoon facies. Analyzing the carbon and oxygen isotope during the whole-rock carbonate reveals the 613C values in the Yeli Formation range from -7.11%o-0.76%o （PDB）, with the mean value at -2.98%0, while the 6180 values range of-9.09%o- -4.65%o with the mean value at -6.12%o. The 613C values in the Liangjiashan Formation range of -1.15%o-0.3%o, and the mean value of -0.57%0; the 61SO values are -8.76%0- -7.48%0, and the mean value is -8.06%o. The 613C values in the Yeli Formation decrease, but at the bottom of the Liangjiashan Formation the values increase steadily. In the middle-upper formation, there is an extended fluctuation between 0- -1.00%o. The 613C trend in the studied section is similar to that of the contemporary sections, except that it has much lower 613C values and a more negative excursion. The correlation between the 613C changes and the eustatic events, as well as the sedimentary facies, indicates that in the Tangshan area, the carbon isotope evolution can be attributabled to the processes of the eutrophic sea/oligotrophic sea, the seafloor organism- mediated oxidation in shallow water and the organic reduction after maximum flooding. The changes in the carbon isotope contents were primarily affected by the regional relative sea level changes. Compared to the other coeval data, the Early Ordovician of the Tang shan area is also severely depleted in 180, with all of the 6180sample values being Delow 5%o, except for one sample with a value ot -4.02%0. Witlt the ancient sea- water having a 6180 value of-5.5%0 （SMOW）, it is reasonable to delineate a temperature of less than 37 C.展开更多
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 a...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.展开更多
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 s...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.展开更多
An accurate and sensitive method for the simultaneous determination of gibberellic acid（GA3）, gibberellin A4（GA4） and gibberellin A7（GA7） residues in tomato paste was developed by coupling solid phase extraction...An accurate and sensitive method for the simultaneous determination of gibberellic acid（GA3）, gibberellin A4（GA4） and gibberellin A7（GA7） residues in tomato paste was developed by coupling solid phase extraction to high performance liquid chromatography-tandem mass spectrometry（LC-MS/MS） with electrospray ionization based stable isotope dilution analysis（SIDA）. The isotope labeled internal standard can compensate for the losses during the extraction and cleanup steps and for discrimination due to ion suppression. After extraction from methanol, hydrophile lipophilic balance（HLB） solid phase extraction（SPE） column was tested for the capacity of the cleanup of the tomato paste in compared with C18 SPE column which is the common way to the detection of GAs, and the former gained better result. Spiked experiments were performed in the non-contaminated tomato pastes and the recoveries of GA3, GA4 and GA7 were 42.6%―75.0% in external standard method（ESM） and 91.1%―103.8% in internal standard method（ISM） respectively. The validities of this method were investigated and good analytical performance for the three GAs was obtained, including low limits of method detection（2 ng/g for GA3 and GA4, 0.3 ng/g for GA7）, excellent linear dynamic ranges（5―500 ng/g for GA3 and GA4, 1―100 ng/g for GA7） and good relative standard deviation ranges（4.8%―9.4% for the intra-day test and 3.5%―11.9% for the inter-day test）.展开更多
The trophic ecology of the small yellow croaker （Larimichthys polyactis） was studied using stable isotope analyses. Samples were collected from July to September 2009 and 34 individuals from eight sites were examine...The trophic ecology of the small yellow croaker （Larimichthys polyactis） was studied using stable isotope analyses. Samples were collected from July to September 2009 and 34 individuals from eight sites were examined for stable carbon and nitrogen isotopes. Stable carbon isotope ratios （~3C） ranged from -20.67 to -15.43, while stable nitrogen isotope ratios （~SN） ranged 9.18-12.23. The relationship between fi^3C and ~SN suggested high resource partitioning in the sampling area. Significant differences in stable isotope values among the eight sampling sites may be linked to environmental diversities involving various physical processes （such as ocean current, wind and tide） and different carbon sources. Furthermore, the stable isotope ratios may also explain the ontogenetic variability in diet and feeding, because δ13C and δ15N varied significantly with increasing body size. The findings are consistent with other studies on diet analyses in small yellow croaker. It was also demonstrated that stable isotope analysis could be used to estimate the trophic characters of small yellow croaker in feeding patterns and migrating habits.展开更多
As apex predators, sharks are of ecological and conservation importance in marine ecosystems. In this study, trophic positions of sharks were estimated using stable isotope ratios of carbon and nitrogen for five repre...As apex predators, sharks are of ecological and conservation importance in marine ecosystems. In this study, trophic positions of sharks were estimated using stable isotope ratios of carbon and nitrogen for five representative species caught by the Chinese longline fleet in the mid-east Pacific, i.e., the blue shark （Prionace glauca）, the bigeye thresher shark （Alopias superciliosus）, the silky shark （Carcharhinus falciformis）, the scalloped hammerhead （Sphyrna lewini）, and the oceanic whitetip shark （Car-charhinus longimanus）. Of these species, oceanic whitetip shark has the lowest trophic level and mean 815N value （3.9 and 14.93%o± 0.84%o）, whereas bigeye thresher shark has the highest level/values （4.5 and 17.02%o±1.21%o, respectively）. The bigeye thresher shark has significantly higher 515N value than other shark species, indicating its higher trophic position. The blue shark and oceanic whitetip shark has significantly higher 813C values than bigeye thresher shark, silky shark and scalloped hammerhead, possibly due to different diets and/or living habitats. The stable isotope data and stomach content data are highly consistent, suggesting that sta-ble isotope analysis supplements traditional feeding ecology study of sharks, and thus contributes to understanding their trophic linkage.展开更多
This study aims to quantify the effects of different pretreatment methods on the stable carbon isotope values of fatty acids in marine microalgae（Isochrysis zhanjiangenisis）.To identify the effects of sample prepara...This study aims to quantify the effects of different pretreatment methods on the stable carbon isotope values of fatty acids in marine microalgae（Isochrysis zhanjiangenisis）.To identify the effects of sample preparation on theδ^（13）C value and the fatty acid composition,we examined eight types of pretreatment methods including：（a） drying the sample followed by direct methyl esterification using HCl-CH3OH;（b） drying the sample followed by direct methyl esterification using H2SO4-CH3OH;（c） drying the sample by ultrasonic extraction and methylesterification using HCl-CH3OH;（d） drying the sample by ultrasonic extraction and methyl-esterification using H2SO4-CH3OH;（e） fresh sample followed by direct methyl-esterification using HCl-CH3OH;（f） fresh sample followed by direct methyl-esterification using H2SO4-CH3OH;（g） fresh sample with ultrasonic extraction followed by methyl-esterification using HCl-CH3OH,and（h） fresh sample with ultrasonic extraction followed by methylesterification using H2SO4-CH3 OH.The results show that the δ^（13）C values from Groups a-e,g and h fluctuated within 0.3‰,and the δ^（13）C values of Group f were approximately 0.7‰ lower than the other seven groups.Therefore,the different sample pretreatment methods used towards the extraction of fatty acids from marine microalgae may result in different results regarding the stable carbon isotope ratios,and if necessary a correction should be applied.展开更多
The Central Hebei Basin （CHB） is one of the largest sedimentary basins in the North China Craton, extending in a northeast-southwest direction with an area of 〉350 km2. We carried out SHRIMP zircon dating, Hf-in-zi...The Central Hebei Basin （CHB） is one of the largest sedimentary basins in the North China Craton, extending in a northeast-southwest direction with an area of 〉350 km2. We carried out SHRIMP zircon dating, Hf-in-zircon isotopic analysis and a whole-rock geochemical study on igneous and metasedi- mentary rocks recovered from drill holes that penetrated into the basement of the CHB, Two samples of gneissic granodiorite （XG1-1） and gneissic quartz diorite 048-1） have magmatic ages of 2500 and 2496 Ma, respectively. Their zircons also record metamorphic ages of 2.41-2.51 and ～2.5 Ga, respec- tively. Compared with the gneissic granodiorite, the gneissic quartz diorite has higher REE contents and lower Eu/Eu＊ and （La/Yb）n values. Two metasedimentary samples （MG1, H5） mainly contain ～2,5 Ga detrital zircons as well as late Paleoproterozoic metamorphic grains. The zircons of different origins have eHf （2.5 Ga） values and Hf crustal model ages ranging from 0 to 5 and 2.7 to 2,9 Ga, respectively, Therefore, ～2.5 Ga magmatic and Paleoproterozoic metasedimentary rocks and late Neoarchean to early Paleoproterozoic and late Paleoproterozoic tectono-thermal events have been identified in the basement beneath the CHB. Based on regional comparisons, we conclude that the early Precambrian basement beneath the CHB is part of the North China Craton.展开更多
Stratigraphic variations of 18 O/ 16 O ratios of winter accumulated snow at an alpine temperate glacier correspond to temporal patterns of local climatic variations. Although the snow is influenced b...Stratigraphic variations of 18 O/ 16 O ratios of winter accumulated snow at an alpine temperate glacier correspond to temporal patterns of local climatic variations. Although the snow is influenced by percolation and homogenization processes, the isotope stratigraphy in the glacier's accumulation area is not destroyed during the first part of summer. Below the equilibrium line altitude, rapid melting results in isotopic homogenization. Variation of δ 18 O values in the firn are relatively small.展开更多
Marine Isotope Stage 11（MIS 11; ca. 423-362 ka） is generally considered to be the best analogue for the present interglacial（Holocene）, and investigation of it will improve our understanding of current climate var...Marine Isotope Stage 11（MIS 11; ca. 423-362 ka） is generally considered to be the best analogue for the present interglacial（Holocene）, and investigation of it will improve our understanding of current climate variability and assist in predictions of future climate change. However, many recent studies primarily focus on the structure and duration of MIS 11. Little research has focused on climate warmth and stability recorded in the Chinese loess-paleosol sequences（LPS） during the S4 paleosol formation（equivalent to MIS 11）. On the basis of previous work, this study presents a high-resolution record（ca. 75 a/cm） that spans from MIS 1 to MIS 15, as preserved in the thickest known Jingyuan loess section on the western Chinese Loess Plateau（CLP）. This LPS is almost 165 m thick and was sampled from the upper part of L6 to the modern soil at 2-cm depth intervals. Measurements of magnetic susceptibility, mean grain size and ＆gt;63 μm particle content, carbonate content, total organic carbon, and soil color of samples were made to reconstruct the paleoclimate variation, and a grain-size age model was used to constrain the chronological framework. The primary results show that a generally warm-humid climate dominated the S4 paleosol development, but the climate condition was extremely unstable during the whole of MIS 11. Two obviously different climate regimes controlled the MIS 11 climate variation： the early part of MIS 11 was extremely warm and stable, but the latter part was relatively cool（non-glacial） and unstable. This climate pattern was consistent with records on the central CLP and wavelet analysis suggested that it was forced by the 65°N insolation variability modulated by a quasi-100-ka cycle. In addition, a multi-proxy comparative study on the climate conditions during S0 to S5 paleosol development indicates that the period of S4 development might be the warmest interglacial of the past 650 ka. However, the climate condition during S4 development was not the most humid episode as recorded in Xifeng and Luochuan loess sections on the central CLP. On the contrary, it was drier than both the MIS 15 and the present interglacial on the western CLP, which is somewhat similar to the present climate pattern on the central CLP.展开更多
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 magma...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.展开更多
Trophic structure of fish communities is fundamental for ecosystem-based fisheries management, and trophic spectrum classifies fishes by their positions in food web, which provides a simple summary on the trophic stru...Trophic structure of fish communities is fundamental for ecosystem-based fisheries management, and trophic spectrum classifies fishes by their positions in food web, which provides a simple summary on the trophic structure and ecosystem function. In this study, both fish biomass and abundance trophic spectra were constructed to study the spatial and seasonal variations in the trophic structure of demersal fish assemblages in Jiaozhou Bay, China. Data were collected from four seasonal bottom trawl surveys in Jiaozhou Bay from February to November in 2011. Trophic levels(TLs) of fishes were determined by nitrogen stable isotope analysis. This study indicated that most of these trophic spectra had a single peak at trophic level(TL) of 3.4–3.7, suggesting that demersal fish assemblages of Jiaozhou Bay were dominated by secondary consumers(eg. Pholis fangi and Amblychaeturichthys hexanema). The spatial and seasonal variations of trophic spectra of Jiaozhou Bay reflected the influence of fish reproduction, fishing pressure and migration of fishes. Two-way analysis of variance(ANOVA) showed that seasonal variations in trophic spectra in Jiaozhou Bay were significant(P <0.05), but variations among different areas were not significant( P >0.05). The trophic spectrum has been proved to be a useful tool to monitor the trophic structure of fish assemblages. This study highlighted the comprehensive application of fish biomass and abundance trophic spectra in the study on trophic structure of fish assemblages.展开更多
Allochthonous organic matter plays an important role in nutrient cycling and energy mobilization in freshwater ecosystems. However, the subsidies of this carbon source in floodplain ecosystems have not yet well unders...Allochthonous organic matter plays an important role in nutrient cycling and energy mobilization in freshwater ecosystems. However, the subsidies of this carbon source in floodplain ecosystems have not yet well understood. We used a Bayesian mixing model and stable isotopes （613C and 815N） of primary food resources and dominant molluscs species, to estimate the relative importance of allochthonous carbon sources for consumers in a representative sub-lake of Poyang Lake during a prolonged dry season. Our study inferred that terrestrial-derived carbon from Carex spp. could be the primary contributor to snails and mussels in Dahuchi Lake. The mean percentage of allochthonous food resources accounted for 35%- 50% of the C incorporated by these consumers. Seston was another important energy sources for benthic consumers. However, during the winter and low water-level period, benthic algae and submerged vegetation contributed less carbon to benthic consumers. Our data highlighted the importance of terrestrial organic carbon to benthic consumers in the wetlands of Poyang Lake during the prolonged dry period. Further, our results provided a perspective that linkages between terrestrial and aquatic ecosystems might be facilitated by wintering geese via their droppings.展开更多
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 availabil...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.展开更多
Surface lake sediments, 28 from Hoh XU, 24 from northeastern China, 99 from Lake Bosten, 31 from Ulungur and 26 from Heihai were collected to determine δ13C and δ18O values. Considering the impact factors, conductiv...Surface lake sediments, 28 from Hoh XU, 24 from northeastern China, 99 from Lake Bosten, 31 from Ulungur and 26 from Heihai were collected to determine δ13C and δ18O values. Considering the impact factors, conductivity, alkalinity, pH, TOC, C/N and carbonate-content in the sediments, CI, P, S, and metal element ratios of Mg/Ca, Sr/Ca, Fe/Mn of bulk sediments as environmental variables enable evaluation of their influences on δ13C and δ18O using principal component analysis （PCA） method. The closure and residence time of lakes can influence the correlation between δ13C and δ18O. Lake water will change from fresh to brackish with increasing reduction and eutrophication effects. Mg/Ca in the bulk sediment indicates the characteristic of residence time, Sr/Ca and Fe/Mn infer the salinity of lakes. Carbonate formation processes and types can influence the 6~3C--~1So correlation. ~180 will be heavier from Mg-calcite and aragonite formed in a high-salinity water body than calcite formed in freshwater conditions. When carbonate content is less than 30%, there is no relationship with either 613C or 6180, and also none between δ13C and δ18O. More than 30%, carbonate content, however, co-varies highly to δ13C and δ18O, and there is also a high correlation between δ13C and δ18O. Vegetation conditions and primary productivity of lakes can influence the characteristics of δ13C and δ18O, and their co-variance. Total organic matter content （TOC） in the sediments is higher with more terrestrial and submerged plants infilling. In northeastern and northwestern China, when organic matter in the lake sediments comes from endogenous floating organisms and algae, the δ13C value is high. δ13C is in the range of-4‰ to 0‰ when organic matter comes mainly from floating organisms （C/N〈6）; in the range of-4‰ to 8‰ when organic matter comes from diatoms （C/N=6 to 8）; and -8‰ to -4‰ when organic matter comes from aquatic and terrestrial plants （C/N〉8）.展开更多
基金supported by the funded project of the China Geological Survey(grants No.12120113061700,121201009000150013 and DD20160029)
文摘Objective The Yangtze craton collisional orogeny at ca. extensional events at ca. 1 experienced Paleoproterozoic 1.95-2.0 Ga and post-orogenic 85 Ga related to amalgamation of the Columbia （Nuna） supercontinent （Zhao and Cawood, 2012）. A ca. 2.15 Ga suprasubduction zone ophiolitic melange was recongized in the Archean- Paleoproterozoic Kongling Complex of the northern Yangtze craton （Han et al., 2017）. However, the tectonic evolution in early Paleoproterozoic from 2.4 Ga to 2.2 Ga remains unclear. We report here the presence of a suite of Paleoproterozoic （2.2 Ga） granites in the Huangling dome, northern Yangtze craton, which may provide important insights into crustal growth processes in the craton prior to the assembly of Columbia.
文摘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.
文摘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.
基金supported by the National Social Science Fund(Grant Nos.11CKG004 and 11AZD116)Natural Science Foundation of Shandong Province(Grant No.ZR2012BQ025)Innovation Fund of Shandong University(Grant No.IFYT12038)
文摘The Beiqian site,located in Jimo city,Qingdao,went through three archaeological excavations,and a large number of human and animal bones in the Dawenkou culture and the Zhou Dynasty period were unearthed.By carbon and nitrogen stable isotope analysis,the diet of ancestors is expected to be recovered,and the domesticated plants and animals will be discussed.The investigated results showed that the food structure of ancestors in both periods included food crops,mainly C4 foods,and meat,mainly marine shellfish and livestock.For domestic pigs,they mainly eat C3 plants,and were affected by the lifestyle of ancestors.This study also showed that the diet of ancestors is the shellfish rather than marine fish despite the Beiqian site is located near the shoreline.We can conclude that the diet of ancestors in Dawenkou culture period included millet crops(C4plants),shellfish,marine food,and livestock,representing the lifestyle of farming,domestication,and fishing,supplemented by hunting.In the Zhou dynasty period the meat resource was enriched by domesticated animals and marine fisheries,and the living conditions were significantly improved.
基金supported by the National Natural Science Foundation of China(No.41372039)
文摘In the Early Ordovician Zhaogezhuang Section of Tangshan , North China, the Yeli Formation is composed of an entire third-order sequence, with facies ranging from the inner ramp restricted platform and open marine to the middle and even outer ramps. The Liangjiashan Formation is dominated by highstand system tracts （HST） with predominantly inner ramp grain-shoal and lagoon facies. Analyzing the carbon and oxygen isotope during the whole-rock carbonate reveals the 613C values in the Yeli Formation range from -7.11%o-0.76%o （PDB）, with the mean value at -2.98%0, while the 6180 values range of-9.09%o- -4.65%o with the mean value at -6.12%o. The 613C values in the Liangjiashan Formation range of -1.15%o-0.3%o, and the mean value of -0.57%0; the 61SO values are -8.76%0- -7.48%0, and the mean value is -8.06%o. The 613C values in the Yeli Formation decrease, but at the bottom of the Liangjiashan Formation the values increase steadily. In the middle-upper formation, there is an extended fluctuation between 0- -1.00%o. The 613C trend in the studied section is similar to that of the contemporary sections, except that it has much lower 613C values and a more negative excursion. The correlation between the 613C changes and the eustatic events, as well as the sedimentary facies, indicates that in the Tangshan area, the carbon isotope evolution can be attributabled to the processes of the eutrophic sea/oligotrophic sea, the seafloor organism- mediated oxidation in shallow water and the organic reduction after maximum flooding. The changes in the carbon isotope contents were primarily affected by the regional relative sea level changes. Compared to the other coeval data, the Early Ordovician of the Tang shan area is also severely depleted in 180, with all of the 6180sample values being Delow 5%o, except for one sample with a value ot -4.02%0. Witlt the ancient sea- water having a 6180 value of-5.5%0 （SMOW）, it is reasonable to delineate a temperature of less than 37 C.
基金Supported by the National Key Basic Research Development Program of China(973 Program)(No.2015CB453303)the National Science Foundation for Young Scientists of China(No.41606195)。
文摘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.
基金supported by Chinese NSF project(42130114)the strategic priority research program(B)of CAS(XDB41000000)the pre-research Project on Civil Aerospace Technologies No.D020202 funded by Chinese National Space Administration(CNSA).
文摘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.
基金Supported by the Project of Chinese Academy of Inspection and Quanrantine(No.2010JK001)the Project of Xinjiang Entry-exit Inspection and Quarantine Bureau, China(No.2010XK0033)
文摘An accurate and sensitive method for the simultaneous determination of gibberellic acid（GA3）, gibberellin A4（GA4） and gibberellin A7（GA7） residues in tomato paste was developed by coupling solid phase extraction to high performance liquid chromatography-tandem mass spectrometry（LC-MS/MS） with electrospray ionization based stable isotope dilution analysis（SIDA）. The isotope labeled internal standard can compensate for the losses during the extraction and cleanup steps and for discrimination due to ion suppression. After extraction from methanol, hydrophile lipophilic balance（HLB） solid phase extraction（SPE） column was tested for the capacity of the cleanup of the tomato paste in compared with C18 SPE column which is the common way to the detection of GAs, and the former gained better result. Spiked experiments were performed in the non-contaminated tomato pastes and the recoveries of GA3, GA4 and GA7 were 42.6%―75.0% in external standard method（ESM） and 91.1%―103.8% in internal standard method（ISM） respectively. The validities of this method were investigated and good analytical performance for the three GAs was obtained, including low limits of method detection（2 ng/g for GA3 and GA4, 0.3 ng/g for GA7）, excellent linear dynamic ranges（5―500 ng/g for GA3 and GA4, 1―100 ng/g for GA7） and good relative standard deviation ranges（4.8%―9.4% for the intra-day test and 3.5%―11.9% for the inter-day test）.
基金Supported by the Special Research Fund for the National Non-profit in East China Sea Fisheries Research Institute (No. 2009M01)
文摘The trophic ecology of the small yellow croaker （Larimichthys polyactis） was studied using stable isotope analyses. Samples were collected from July to September 2009 and 34 individuals from eight sites were examined for stable carbon and nitrogen isotopes. Stable carbon isotope ratios （~3C） ranged from -20.67 to -15.43, while stable nitrogen isotope ratios （~SN） ranged 9.18-12.23. The relationship between fi^3C and ~SN suggested high resource partitioning in the sampling area. Significant differences in stable isotope values among the eight sampling sites may be linked to environmental diversities involving various physical processes （such as ocean current, wind and tide） and different carbon sources. Furthermore, the stable isotope ratios may also explain the ontogenetic variability in diet and feeding, because δ13C and δ15N varied significantly with increasing body size. The findings are consistent with other studies on diet analyses in small yellow croaker. It was also demonstrated that stable isotope analysis could be used to estimate the trophic characters of small yellow croaker in feeding patterns and migrating habits.
基金Li Yunkai was supported by the National Natural Science Foundation of China (No.41206124)Ph.D.Programs Foundation of Ministry of Education of China (No.201 23104120001)+3 种基金the ‘Chen Guang’ Project of Shanghai Municipal Education Commission (No.D8004-10-0206)the Shanghai Education Development Foundation (No.B-8102-10-0084)Zhu Jiangfeng and Dai Xiaojie were supported by the National Natural Science Foundation of China (No.41106118)the Scientific Observing and Experimental Station of Oceanic Fishery Resources, Ministry of Agriculture, China
文摘As apex predators, sharks are of ecological and conservation importance in marine ecosystems. In this study, trophic positions of sharks were estimated using stable isotope ratios of carbon and nitrogen for five representative species caught by the Chinese longline fleet in the mid-east Pacific, i.e., the blue shark （Prionace glauca）, the bigeye thresher shark （Alopias superciliosus）, the silky shark （Carcharhinus falciformis）, the scalloped hammerhead （Sphyrna lewini）, and the oceanic whitetip shark （Car-charhinus longimanus）. Of these species, oceanic whitetip shark has the lowest trophic level and mean 815N value （3.9 and 14.93%o± 0.84%o）, whereas bigeye thresher shark has the highest level/values （4.5 and 17.02%o±1.21%o, respectively）. The bigeye thresher shark has significantly higher 515N value than other shark species, indicating its higher trophic position. The blue shark and oceanic whitetip shark has significantly higher 813C values than bigeye thresher shark, silky shark and scalloped hammerhead, possibly due to different diets and/or living habitats. The stable isotope data and stomach content data are highly consistent, suggesting that sta-ble isotope analysis supplements traditional feeding ecology study of sharks, and thus contributes to understanding their trophic linkage.
基金The State Oceanic Public Welfare Project of China under contract Nos 2012418012-02 and 201305002
文摘This study aims to quantify the effects of different pretreatment methods on the stable carbon isotope values of fatty acids in marine microalgae（Isochrysis zhanjiangenisis）.To identify the effects of sample preparation on theδ^（13）C value and the fatty acid composition,we examined eight types of pretreatment methods including：（a） drying the sample followed by direct methyl esterification using HCl-CH3OH;（b） drying the sample followed by direct methyl esterification using H2SO4-CH3OH;（c） drying the sample by ultrasonic extraction and methylesterification using HCl-CH3OH;（d） drying the sample by ultrasonic extraction and methyl-esterification using H2SO4-CH3OH;（e） fresh sample followed by direct methyl-esterification using HCl-CH3OH;（f） fresh sample followed by direct methyl-esterification using H2SO4-CH3OH;（g） fresh sample with ultrasonic extraction followed by methyl-esterification using HCl-CH3OH,and（h） fresh sample with ultrasonic extraction followed by methylesterification using H2SO4-CH3 OH.The results show that the δ^（13）C values from Groups a-e,g and h fluctuated within 0.3‰,and the δ^（13）C values of Group f were approximately 0.7‰ lower than the other seven groups.Therefore,the different sample pretreatment methods used towards the extraction of fatty acids from marine microalgae may result in different results regarding the stable carbon isotope ratios,and if necessary a correction should be applied.
基金supported by the Major State Basic Research Program of the People's Republic of China(Grant No.2012CB416600)the National Natural Science Foundation of China(Grant No.40672127)the Key Program of the Ministry of Land and Resources of China(Grant Nos.1212010811033,12120113013700)
文摘The Central Hebei Basin （CHB） is one of the largest sedimentary basins in the North China Craton, extending in a northeast-southwest direction with an area of 〉350 km2. We carried out SHRIMP zircon dating, Hf-in-zircon isotopic analysis and a whole-rock geochemical study on igneous and metasedi- mentary rocks recovered from drill holes that penetrated into the basement of the CHB, Two samples of gneissic granodiorite （XG1-1） and gneissic quartz diorite 048-1） have magmatic ages of 2500 and 2496 Ma, respectively. Their zircons also record metamorphic ages of 2.41-2.51 and ～2.5 Ga, respec- tively. Compared with the gneissic granodiorite, the gneissic quartz diorite has higher REE contents and lower Eu/Eu＊ and （La/Yb）n values. Two metasedimentary samples （MG1, H5） mainly contain ～2,5 Ga detrital zircons as well as late Paleoproterozoic metamorphic grains. The zircons of different origins have eHf （2.5 Ga） values and Hf crustal model ages ranging from 0 to 5 and 2.7 to 2,9 Ga, respectively, Therefore, ～2.5 Ga magmatic and Paleoproterozoic metasedimentary rocks and late Neoarchean to early Paleoproterozoic and late Paleoproterozoic tectono-thermal events have been identified in the basement beneath the CHB. Based on regional comparisons, we conclude that the early Precambrian basement beneath the CHB is part of the North China Craton.
文摘Stratigraphic variations of 18 O/ 16 O ratios of winter accumulated snow at an alpine temperate glacier correspond to temporal patterns of local climatic variations. Although the snow is influenced by percolation and homogenization processes, the isotope stratigraphy in the glacier's accumulation area is not destroyed during the first part of summer. Below the equilibrium line altitude, rapid melting results in isotopic homogenization. Variation of δ 18 O values in the firn are relatively small.
基金joint supported by the National Natural Science Foundation of China (41401226, 41271024)the China Postdoctoral Science Foundation (2015M570865)
文摘Marine Isotope Stage 11（MIS 11; ca. 423-362 ka） is generally considered to be the best analogue for the present interglacial（Holocene）, and investigation of it will improve our understanding of current climate variability and assist in predictions of future climate change. However, many recent studies primarily focus on the structure and duration of MIS 11. Little research has focused on climate warmth and stability recorded in the Chinese loess-paleosol sequences（LPS） during the S4 paleosol formation（equivalent to MIS 11）. On the basis of previous work, this study presents a high-resolution record（ca. 75 a/cm） that spans from MIS 1 to MIS 15, as preserved in the thickest known Jingyuan loess section on the western Chinese Loess Plateau（CLP）. This LPS is almost 165 m thick and was sampled from the upper part of L6 to the modern soil at 2-cm depth intervals. Measurements of magnetic susceptibility, mean grain size and ＆gt;63 μm particle content, carbonate content, total organic carbon, and soil color of samples were made to reconstruct the paleoclimate variation, and a grain-size age model was used to constrain the chronological framework. The primary results show that a generally warm-humid climate dominated the S4 paleosol development, but the climate condition was extremely unstable during the whole of MIS 11. Two obviously different climate regimes controlled the MIS 11 climate variation： the early part of MIS 11 was extremely warm and stable, but the latter part was relatively cool（non-glacial） and unstable. This climate pattern was consistent with records on the central CLP and wavelet analysis suggested that it was forced by the 65°N insolation variability modulated by a quasi-100-ka cycle. In addition, a multi-proxy comparative study on the climate conditions during S0 to S5 paleosol development indicates that the period of S4 development might be the warmest interglacial of the past 650 ka. However, the climate condition during S4 development was not the most humid episode as recorded in Xifeng and Luochuan loess sections on the central CLP. On the contrary, it was drier than both the MIS 15 and the present interglacial on the western CLP, which is somewhat similar to the present climate pattern on the central CLP.
基金supported financially by the China Geological Survey project [DD20160123 (DD-16-049, D1522), DD20160050, DD20190370]the Fundamental Research Funds for the Central Universities (310827171122)the National Natural Science Foundation of China (Grant 41672068)。
文摘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.
基金Supported by the National Natural Science Foundation of China(No.41006083)the Shandong Provincial Natural Science Foundation,China(No.ZR2010DQ026)+1 种基金the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20120132130001)the Fundamental Research Funds for the Central Universities(No.201262004)
文摘Trophic structure of fish communities is fundamental for ecosystem-based fisheries management, and trophic spectrum classifies fishes by their positions in food web, which provides a simple summary on the trophic structure and ecosystem function. In this study, both fish biomass and abundance trophic spectra were constructed to study the spatial and seasonal variations in the trophic structure of demersal fish assemblages in Jiaozhou Bay, China. Data were collected from four seasonal bottom trawl surveys in Jiaozhou Bay from February to November in 2011. Trophic levels(TLs) of fishes were determined by nitrogen stable isotope analysis. This study indicated that most of these trophic spectra had a single peak at trophic level(TL) of 3.4–3.7, suggesting that demersal fish assemblages of Jiaozhou Bay were dominated by secondary consumers(eg. Pholis fangi and Amblychaeturichthys hexanema). The spatial and seasonal variations of trophic spectra of Jiaozhou Bay reflected the influence of fish reproduction, fishing pressure and migration of fishes. Two-way analysis of variance(ANOVA) showed that seasonal variations in trophic spectra in Jiaozhou Bay were significant(P <0.05), but variations among different areas were not significant( P >0.05). The trophic spectrum has been proved to be a useful tool to monitor the trophic structure of fish assemblages. This study highlighted the comprehensive application of fish biomass and abundance trophic spectra in the study on trophic structure of fish assemblages.
基金Supported by the National Natural Science Foundation of China(Nos.41471088,41301077)
文摘Allochthonous organic matter plays an important role in nutrient cycling and energy mobilization in freshwater ecosystems. However, the subsidies of this carbon source in floodplain ecosystems have not yet well understood. We used a Bayesian mixing model and stable isotopes （613C and 815N） of primary food resources and dominant molluscs species, to estimate the relative importance of allochthonous carbon sources for consumers in a representative sub-lake of Poyang Lake during a prolonged dry season. Our study inferred that terrestrial-derived carbon from Carex spp. could be the primary contributor to snails and mussels in Dahuchi Lake. The mean percentage of allochthonous food resources accounted for 35%- 50% of the C incorporated by these consumers. Seston was another important energy sources for benthic consumers. However, during the winter and low water-level period, benthic algae and submerged vegetation contributed less carbon to benthic consumers. Our data highlighted the importance of terrestrial organic carbon to benthic consumers in the wetlands of Poyang Lake during the prolonged dry period. Further, our results provided a perspective that linkages between terrestrial and aquatic ecosystems might be facilitated by wintering geese via their droppings.
文摘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.
基金provided by China NSFC grant (41173015, 41202093)the Chinese Ministry of Education Supervision of Ph.D. Degree Fund (20100211110020)
文摘Surface lake sediments, 28 from Hoh XU, 24 from northeastern China, 99 from Lake Bosten, 31 from Ulungur and 26 from Heihai were collected to determine δ13C and δ18O values. Considering the impact factors, conductivity, alkalinity, pH, TOC, C/N and carbonate-content in the sediments, CI, P, S, and metal element ratios of Mg/Ca, Sr/Ca, Fe/Mn of bulk sediments as environmental variables enable evaluation of their influences on δ13C and δ18O using principal component analysis （PCA） method. The closure and residence time of lakes can influence the correlation between δ13C and δ18O. Lake water will change from fresh to brackish with increasing reduction and eutrophication effects. Mg/Ca in the bulk sediment indicates the characteristic of residence time, Sr/Ca and Fe/Mn infer the salinity of lakes. Carbonate formation processes and types can influence the 6~3C--~1So correlation. ~180 will be heavier from Mg-calcite and aragonite formed in a high-salinity water body than calcite formed in freshwater conditions. When carbonate content is less than 30%, there is no relationship with either 613C or 6180, and also none between δ13C and δ18O. More than 30%, carbonate content, however, co-varies highly to δ13C and δ18O, and there is also a high correlation between δ13C and δ18O. Vegetation conditions and primary productivity of lakes can influence the characteristics of δ13C and δ18O, and their co-variance. Total organic matter content （TOC） in the sediments is higher with more terrestrial and submerged plants infilling. In northeastern and northwestern China, when organic matter in the lake sediments comes from endogenous floating organisms and algae, the δ13C value is high. δ13C is in the range of-4‰ to 0‰ when organic matter comes mainly from floating organisms （C/N〈6）; in the range of-4‰ to 8‰ when organic matter comes from diatoms （C/N=6 to 8）; and -8‰ to -4‰ when organic matter comes from aquatic and terrestrial plants （C/N〉8）.
