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1.
Recent legislation in the European Union (EC/2065/2001) requires that seafood must provide the consumer with information that describes geographical origin and production method. The present studies aimed to establish methods, based on chemical and stable isotopic analysis, that could reliably differentiate between wild and farmed European sea bass (Dicentrarchus labrax). The study measured fatty acid and isotopic compositions (delta13C and delta18O) of total flesh oil, delta15N of the glycerol/choline fraction, and compound-specific analysis of fatty acids (delta13C) by isotope ratio mass spectrometry. The sample set comprised 10 wild and 10 farmed sea bass from England (wild) and Scotland or Greece (farmed). Discrimination was achieved using fatty acid composition with 18:0, 18:2n-6, 20:4n-6, and 22:6n-3 providing the highest contributions for discrimination. Principal component analysis of the data set provided good discrimination between farmed and wild sea bass where factor 1 and factor 2 accounted for 60% of the variation in the data.  相似文献   

2.
Multielemental (C, N, H, S) stable isotope ratio analysis was used as an analytical tool to verify the geographical origin of beef from several European and non-European countries. Beef samples were collected from nine different countries, and the (13)C/(12)C, (15)N/(14)N, (2)H/(1)H, and (34)S/(32)S ratios of defatted beef were measured using isotope ratio mass spectrometry (IRMS). There were highly significant differences in the mean isotopic values of the beef from different countries. The results of discriminant analysis showed that the four isotope ratios were significant for the discrimination of geographical origin and that 84.9% of the samples were correctly assigned to the country of origin (82.2% when cross-validated). Beef was also classified according to geographical origin when additional information on different feeding regimens used in Ireland was included, with 85.0% of the samples correctly allocated and 82.9% cross-validated using the isotopic signatures. All of the Irish beef samples verifiable as pasture-fed beef were correctly classified and then cross-validated.  相似文献   

3.
The use of anabolic substances is prohibited in food-producing animals throughout the European Union. No method is available to reliably detect the misuse of natural hormones in cattle. A method was developed to detect the abuse of testosterone in cattle fattening. Synthesized testosterone is rather depleted in the (13)C/(12)C ratio. Hence, the method is based on gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) analysis of urine. To select testosterone metabolites and endogenous reference compounds (ERC), the concentration of urinary steroids of cattle was investigated. Dehydroepiandrosterone and androst-5ene-3beta,17alpha-diol were chosen as ERCs to show endogenous (13)C/(12)C ratios. Etiocholanolone and 5alpha-androstane-3beta,17alpha-diol were chosen as the most important testosterone metabolites. Other metabolites known from literature like epitestosterone were less promising. In principle, GC/C/IRMS is a nonspecific method because finally carbon dioxide is analyzed. Therefore, a dedicated cleanup procedure for the selected steroids was developed. By means of proposed confidence intervals in the isotopic composition of ERCs and metabolites, the administration of testosterone to cattle could be detected reliably. Differences of up to 11 per thousand on the delta-scale between ERC and testosterone metabolites were found after testosterone administration, whereas endogenous differences did not exceed 2 per thousand.  相似文献   

4.
A comprehensive lignin structure analysis of ten industrially relevant hardwood species is presented. Milled wood lignin (MWL) was isolated from each species using a modified protocol and all milled wood lignin preparations were analyzed through quantitative (13)C NMR spectroscopy, elemental analysis, methoxyl analysis, sugar analysis, and nitrobenzene oxidation. Nitrobenzene oxidation and ozonation were carried out on extractive-free wood, alkali-extracted wood, milled wood lignin, and alkali-extracted lignin. Milled wood lignin isolated by the modified protocol was found to be representative of the total lignin in alkali-extracted wood. Significant variations in lignin structures, such as syringylpropane/guaiacylpropane ratio (S/G ratio), arylglycerol-β-aryl ether (β-O-4), degree of condensation, and elemental and methoxyl contents, were found among the hardwood species studied. These structural variations among species appear to be correlated to a single factor, the syringyl/guaiacyl ratio. A new method to predict the S/G ratio of total lignin in wood was developed, using a calibration line established by the syringaldehyde/vanillin (S/V) ratio (nitrobenzene oxidation) and the S/G ratio ((13)C NMR) of milled wood lignin (MWL).  相似文献   

5.
An emerging paradigm in soil science suggests microbes can perform ‘N mining’ from recalcitrant soil organic matter (SOM) in conditions of low N availability. However, this requires the production of extracellular structures rich in N (including enzymes and structural components) and thus defies stoichiometric expectation. We set out to extract newly synthesised peptides from the extracellular matrix in soil and compare the amino acid (AA) profiles, N incorporation and AA dynamics in response to labile inputs of contrasting C/N ratio. Glycerol was added both with and without an inorganic source of N (10% 15N labelled NH4NO3) to a soil already containing a large pool of refractory SOM and incubated for 10 days. The resulting total soil peptide (TSP) and extracellular pools were compared using colorimetric methods, gas chromatography, and isotope ratio mass spectrometry. N isotope compositions showed that the extracellular polymeric substance (EPS) contained a greater proportion of products formed de novo than did TSP, with hydrophobic EPS-AAs (leucine, isoleucine, phenylalanine, hydroxyproline and tyrosine) deriving substantially more N from the inorganic source provided. Quantitative comparison between extracts showed that the EPS contained greater relative proportions of alanine, glycine, proline, phenylalanine and tyrosine. The greatest increases in EPS-peptide and EPS-polysaccharide concentrations occurred at the highest C/N ratios. All EPS-AAs responded similarly to treatment whereas the responses of TSP were more complex. The results suggest that extracellular investment of N (as EPS peptides) is a microbial survival mechanism in conditions of low N/high C which, from an evolutionary perspective, must ultimately lead to the tendency for increased N returns to the microbial biomass. A conceptual model is proposed that describes the dynamics of the extracellular matrix in response to the C/N ratio of labile inputs.  相似文献   

6.
Stable carbon isotope ratio analysis (SCIRA) was used to determine the authenticity of commercial Australian orange juices. Thirty-five samples of Valencia (delta(13)C values from -23.8 to -24.7 ppt) and eight samples of Navel juices (delta(13)C values from -24.1 to -24.5 ppt) of known origin were used to establish a decision level before analysis. No significant seasonal variations in (13)C/(12)C ratio were observed. Variations in combustion temperature in the method were also found to be insignificant.  相似文献   

7.
Knowledge about the influence of living roots on decomposition processes in soil is scarce but is needed to understand carbon dynamics in soil. We investigated the effect of dominant deciduous tree species of the Central European forest vegetation, European beech (Fagus sylvatica L.) and European ash (Fraxinus excelsior L.), on soil biota and carbon dynamics differentiating between root- and leaf litter-mediated effects. The influence of beech and ash seedlings on carbon and nitrogen flow was investigated using leaf litter enriched in 13C and 15N in double split-root rhizotrons planted with beech and ash seedlings as well as a mixture of both tree species and a control without plants. Stable isotope and compound-specific fatty acid analysis (13C-PLFA) were used to follow the incorporation of stable isotopes into microorganisms, soil animals and plants. Further, the bacterial community composition was analyzed using pyrosequencing of 16S rRNA gene amplicons. Although beech root biomass was significantly lower than that of ash only beech significantly decreased soil carbon and nitrogen concentrations after 475 days of incubation. In addition, beech significantly decreased microbial carbon use efficiency as indicated by higher specific respiration. Low soil pH probably increased specific respiration of bacteria suggesting that rhizodeposits of beech roots induced increased microbial respiration and therefore carbon loss from soil. Compared to beech δ13C and δ15N signatures of gamasid mites in ash rhizotrons were significantly higher indicating higher amounts of litter-derived carbon and nitrogen to reach higher trophic levels. Similar δ13C signatures of bacteria and fine roots indicate that mainly bacteria incorporated root-derived carbon in beech rhizotrons. The results suggest that beech and ash differentially impact soil processes with beech more strongly affecting the belowground system via root exudates and associated changes in rhizosphere microorganisms and carbon dynamics than ash.  相似文献   

8.
Abstract

A dual‐inlet isotope ratio mass spectrometer (VG‐SIRA 12, Isotech, Middlewich, England) using sealed‐glass combustion sample preparation and an automated single‐inlet isotope ratio mass spectrometry system (RoboPrep Sample Converter interfaced with a TracerMass Stable Isotope Detector, Europa Scientific, Crewe, England) were compared for δ13C analysis. Two hundred twenty four samples of plant and animal tissue were analyzed for S13C using the two systems. Delta 13C values obtained from the two instruments were highly correlated (r2=0.986, P=0.0001). The slope of the relationship was not different from one nor was the Y‐intercept different from zero (Y=‐0.2 + 1.0X; P=0.86 and P=0.28 for the slope and Y‐intercept, respectively). In addition, samples from two complete experiments were run on both mass spectrometery systems and statistical analyses performed. In both experiments, differences between treatments were detectable using the RoboPrep system that were not detectable using the SIRA 12 system. In all cases mean δ13C values were comparable between the two systems, and coefficients of variation were low; well within acceptable experimental limits.  相似文献   

9.
In addition to the already available information on the authenticity of alpha- (1) and beta-ionone (2) from plant tissues, there is an interest in the stable isotope data of 1 and 2 available by synthesis from citral and acetone, as European Union regulations, in contrast to the United States and other countries, do not allow a product to be declared as 'natural' that has been chemically synthesized (e.g., by using a natural catalyst) from natural educts. Analyses performed by on-line capillary gas chromatography-isotope ratio mass spectrometry in the combustion and pyrolysis modes (HRGC-C/P-IRMS) as well as by elemental analyzers (EA-C/P-IRMS) measuring delta(13)C(V)-PDB and delta(2)H(V)-SMOW values provide for the first time isotope data of such 'natural' 1 and 2 as well as of synthetic and 'ex plant' alpha-ionol (3). The isotope data recorded for synthesized 1 and 2 reflected the influence of the origin of the used citral, whereas that of acetone was less remarkable. For instance, 'natural' 1 ex citral from lemongrass showed, as expected for a C4 plant, an enriched delta(13)C(V)-PDB value of -18.5 per thousand. In addition, the use of synthetic citral resulted in an enriched delta(2)H(V)-SMOW value of -43 per thousand, whereas with citral ex Litsea cubeba and ex lemongrass values of -242 and -232 per thousand, respectively, were recorded. IRMS analyses of 'natural' 2 revealed delta(13)C(V)-PDB and delta(2)H(V)-SMOW values that were nearly identical to that recorded for 'natural' 1. As to both 1 and 2, variations of synthesis conditions led to distinct changes in the delta(13)C(V)-PDB but not the delta(2)H(V)-SMOW values. Synthetic 3 showed delta(13)C(V)-PDB and delta(2)H(V)-SMOW values of -24.5 and -184 per thousand, respectively. These data differed from those found in raspberry fruit under study (n = 8), that is, ranging from -33.6 to -36.6 per thousand for delta(13)C(V)-PDB and from -200 to -225 per thousand for delta(2)H(V)-SMOW. The values determined additionally for 1 and 2 in raspberry fruit samples ranged from -30.3 to -35.1 per thousand and from -176 to -221 per thousand for delta(13)C(V)-PDB and delta(2)H(V)-SMOW, respectively, and thus corresponded to the already known literature information.  相似文献   

10.
陕西关中地区肉牛产地同位素溯源技术初探   总被引：3，自引：1，他引：2  
为应用牛组织中C、N同位素组成的区域分布和同位素指标溯源肉牛产地,本文利用同位素比率质谱仪(IRMS)对陕西关中不同区县来源的牛尾毛样品的1δ3C和1δ5N值进行检测,通过聚类分析,研究陕西关中地区肉牛组织中同位素组成的区域分布情况。结果表明,杨凌区、眉县牛尾毛样品聚为一类;乾县、永寿县样品聚为一类;麟游县样品聚为一类;扶风县、岐山县和凤翔县分类不十分明显,分散在上述3类中。说明陕西关中不同地区肉牛组织中同位素组成存在差异,利用它们可进行肉牛地域的小范围溯源。  相似文献   

11.
Feedlots in southern Alberta apply composted (CM) or stockpiled (SM) manure with straw (ST) or wood-chip (WD) bedding to cropland, but few studies have examined the effect of manure type and bedding material on carbon composition of these feedlot amendments prior to land application using solid-state 13C NMR-DPMAS (nuclear magnetic resonance-direct polarization, magic angle spinning). The particulate organic matter fraction was extracted from four amendment treatments (CM-ST, CM-WD, SM-ST, SM-WD) to avoid possible paramagnetic interference from considerable mineral soil in the manure from the unpaved feedlot. The hypothesis was that O-alkyl C of POM should be lower for more decomposed manure types (CM than SM) and bedding materials (ST than WD), and that alkyl C, aromatic C, carboxyl C, aromaticity, and alkyl:O-alkyl (A:O-A) ratio should be greater for the more decomposed amendments. The C composition of all feedlot amendments was dominated by aromatic C (8%–14%) and O-alkyl (7%–14%) C and had considerable less contribution from carboxyl (2%–4%) and alkyl C (1%–3%). The manure type hypothesis was supported for O-alkyl C (but not for the other three C groups), aromaticity, but not the A:O-A ratio. The bedding hypothesis was supported for O-alkyl C, aromaticity, and A:O-A ratio, but not for alkyl C, aromatic C, and carboxyl C. A decrease in O-alkyl C, increase in aromaticity, and increase in A:O-A ratio (bedding only) with more decomposed manure types or bedding materials suggested that these 13C NMR parameters may have potential to evaluate the maturity and stability of composted feedlot manures.  相似文献   

12.
The use of solid-phase microextraction (SPME) coupled with isotope ratio mass spectrometry (IRMS) for the analysis of flavor compounds produced by lactic acid bacteria has been evaluated using both liquid and headspace sampling modes. Initially, it was necessary to optimize the conditions for the SPME extraction of flavors-diacetyl and acetoin-in standard aqueous solutions. The effects of salt, headspace versus liquid sampling, and coating phase were tested. Second, the suitability of the coupling of SPME and gas chromatography-combustion interface-IRMS (GC-C-IRMS) for the determination of delta(13)C values was assessed. It is shown that neither the analyte concentration nor the period of fiber exposure has an effect on the delta(13)C values. Finally, having verified that there are no matrix effects from the fermentation medium, it is reported for the first time that flavor compounds can be extracted directly from culture supernatant by SPME and their delta(13)C values can be obtained by GC-C-IRMS.  相似文献   

13.
This paper explores the influence of spatial scale on modelled projections of soil organic carbon (SOC) content. The effect of land use change (LUC) on future SOC stocks was estimated using the Rothamsted Carbon model for a small area of southern Belgium. The study assumed no management change and used a single climate change scenario. Three model experiments were used to identify how data scale affects predicted SOC stocks: (i) using European LUC datasets at a resolution of 10′ and assuming equal distribution of change within the study area, (ii) using more accurate regional data aggregated to the 10’ resolution, and (iii) using the regional data at a spatial resolution of 250 m. The results show that using coarse resolution (10′) data is inappropriate when modelling SOC changes in the study area as only the methods using precise data predict a change in SOC stocks similar to those reported in the literature. This is largely because of differences in model parameterisation. However, precisely locating LUC does not significantly affect the results. The model, using either pan‐European or region‐specific precise data predicts an average SOC increase of 1 t C ha?1 (1990–2050), mainly resulting from afforestation of 13% of agricultural land.  相似文献   

14.
Glycerol is often added to starches to plasticize the product, but the presence of glycerol may also affect the water content of the samples. To evaluate the effect of glycerol on the sorption properties of starches, waxy maize, rice, and wheat starch were thermomechanically extruded in the presence of glycerol. Sorption isotherms of these extruded samples were ascertained using dynamic vapor sorption (DVS). BET and GAB modeling showed a monolayer (mo) significantly higher for waxy maize than for rice and wheat. Glycerol inclusion changed the model values, indicating reduction in sorption energy at the monolayer and restructuring of the multilayer. An interaction factor (xi) based on weight fraction models was calculated. Differences in xi were obtained when glycerol was added, varying from approximately 0.9 for 5% glycerol to approximately 0.8 for 20% glycerol, supporting the hypothesis of interactions between starch and this polyol.  相似文献   

15.
Abstract

Data on the organic matter composition of vegetation, crop litter, and forest litter of Oi (=L) horizons from several European locations available with the litter compound analysis (LCA) discussed in previous communications are presented. The wet chemical results are discussed in comparison to data as revealed by cross polarization magic angle spinning carbon‐13 nuclear magnetic resonance spectroscopy (CPMAS 13C‐NMR) and pyrolysis‐field ionization mass spectrometry (Py‐FIMS). The LCA of vegetation, crop litter, and forest litter provides much detailed information about the chemical composition of extractable organic matter. Normally, both CPMAS 13C‐NMR and Py‐FIMS confirm the wet chemical results. Our data suggest a moderate chemical variation between the fresh organic residue and the litter. NMR revealed structural information about the non‐extractable organic matter using a combination of wet chemical extraction and CPMAS 13C‐NMR of whole soil. In addition, Py‐FIMS identified specific SOM segments at a qualitative level.  相似文献   

16.
茶树对可溶性有机和无机态氮的吸收与运转特性   总被引：1，自引：0，他引：1  
【目的】 揭示亚热带茶树能否直接吸收利用分子态可溶性有机氮,探讨茶树吸收可溶性有机和无机氮后的运转特性差异。【方法】 采用13C、15N双标记甘氨酸、15N标记硫酸铵和15N标记硝酸钾为同位素示踪剂,采用茶树（黄金桂）幼苗为试验材料进行同位素示踪盆栽试验,用同位素质谱仪测定茶树植株地上和地下部的13C、15N丰度。【结果】 供试土壤施用13C、15N双标记甘氨酸态有机氮后,2 h和6 h茶苗地下部和整株中的13C增量/15N增量比值均接近于1:1的理论值;2 h和6 h茶苗地上部未检出13C增量,而72 h地上部13C增量达0.284 μmol/（g,DW）;施用铵态氮2 h、6 h和72 h茶苗地下部、地上部和整株中的15N增量均极显著高于施用硝态氮和甘氨酸态有机氮;施用铵态氮6 h茶苗地上部15N增量/地下部15N增量比率分别比硝态氮和甘氨酸态有机氮的比率高34.7%和65.0%,72 h茶苗地上部15N增量/地下15N增量比率分别比硝态氮和甘氨酸态有机氮的比率高88.6%和133.0%,差异均达极显著水平。【结论】 黄金桂茶苗具有从土壤中直接吸收利用甘氨酸分子态有机氮的能力,但吸收量不及铵态氮和硝态氮;吸收的可溶性分子态有机氮可以从茶树根系运转至地上部;不同形态氮素在茶树植株体内的迁移能力高低表现为:铵态氮>硝态氮>甘氨酸态氮,该研究结果进一步证明陆地生态系统植物直接吸收利用可溶性有机氮是普遍存在的现象。  相似文献   

17.
In this paper we describe the GCTE global Soil Organic Matter Network (SOMNET) before focusing on the European network of long-term sites. We then select two examples from the European site network and demonstrate how such data can be used to (a) track long-term changes in soil organic matter, (b) evaluate and compare soil organic matter models, and (c) make rough estimates of the potential for carbon (C) sequestration in soils at the regional (European) level. Our simple calculations based on only two long-term experiments suggest that amendment of arable soils with 10 Mg ha−1 of organic manure could lead to an increase in current total European soil C stock to 30 cm of about 4.8% over 90 yr, a scenario with limited potential for sequestering C. Similarly, afforestation through natural woodland regeneration of 30% of current arable land (surplus to requirements by 2010) could lead to an increase in current total European soil C stock of 12.4% over 100 yr. This is equivalent to 43 Tg C yr−1 or 3.8% of anthropogenic CO2–C emissions from Europe. If temporary C storage in standing woody biomass is included in the estimate, the amount of C sequestered is quadrupled and could account for 15.28% of Europe's annual CO2–C emissions. This is equivalent to 2.8% of annual global anthropogenic CO2–C emissions. These calculations are presented to demonstrate a simple technique for estimating rough C sequestration potentials but they do suggest some potential to sequester C in European agricultural soils. As a result, a more sophisticated approach using statistical relationships derived from a large number of long-term experiments was developed. The need for balancing the effects of these scenarios on soil C against other environmental considerations is discussed. Methods for improving estimates of the potential for soil C sequestration using the European site network are also discussed.  相似文献   

18.
黑土、栗钙土和潮土胡敏酸分子结构的差异性分析   总被引：2，自引：0，他引：2  
郑殷恬  赵红  赵楠  吕贻忠 《土壤》2011,43(5):804-808
以北方典型的黑土、栗钙土和潮土提取的胡敏酸为研究对象,通过元素分析、傅里叶红外光谱仪及13C核磁共振仪对三者进行结构分析。不同胡敏酸的各种元素含量略有差别,各种官能团含量也不同。元素分析结果来看H/C原子比潮土最高,栗钙土次之,黑土最少;O/C的原子比三者没有明显的差别;C/N比呈现由高到低的次序分别为黑土、栗钙土、潮土。3种胡敏酸的红外光谱吸收峰相似,但吸收强度有差别,如3 352 cm-1和2 931 cm-1处潮土和栗钙土信号强度相当,黑土较低,而在2 580 cm-1处三者信号差异不明显,1 720,1 620,1 420,1 220 cm-1这4个吸收峰信号强弱均为黑土最强,栗钙土次之,潮土最弱。而从核磁共振图谱可以看出潮土结构中含有更多的多糖和蛋白质类结构单元;黑土有机质含量高,芳香化程度也较高。  相似文献   

19.
An improved procedure for determining (13)C and (2)H isotope ratios, using gas chromatography-isotope ratio mass spectrometry (GC-IRMS), has been developed for identifying the addition of low cost commercial sugar syrups to apple juices and related products. Isotopic techniques are commonly used to identify the addition of low cost sugars to fruit juices and are difficult to circumvent as it is not economically viable to change the isotopic ratios of the sugars. The procedure utilizes the derivative hexamethylenetetramine, which is produced through chemical transformation of a sugar degradation product and provides position-specific (13)C and (2)H ratios that relate to the parent sugar molecule. The new procedure has advantages over methods using nitro-sugar derivatives in terms of analysis time and sensitivity. The differences between the delta(2)H per thousand and delta(13)C per thousand values of the 100 authentic apple juices and beet and cane commercial sugar syrups permit their addition to be reliably detected.  相似文献   

20.
Peat land has been considered as an alternative type of land for agricultural development especially in the tropics. In the present study, the N-supplying capacity, one of the most important soil properties in terms of crop production, of peat soils was examined. Ten peat soil samples were collected from Indonesia, Malaysia, and Japan. Gross N mineralization in the soil samples was estimated using a zero-order model, and kinetic parameters of mineralization were determined using a simple type model. Soil organic matter composition was investigated using 13C CPMAS NMR. Mineralization potential ( N 0), apparent activation energy ( E a), and mineralization rate constant ( k ) ranged between 571–2,445 mg kg−1, 281–8,181 J mol−1, and 0.009–0.020 d−1, respectively. Although none of the parameters showed a significant correlation with the soil C/N ratio, a negative correlation was observed between the k value and the ratio of the proportion of alkyl C in total C to that of O -alkyl C estimated by 13C CPMAS NMR. The latter suggested that the k values were higher in the peat soils relatively rich in readily decomposable organic matter including carbohydrates.  相似文献   

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