不同地域牛尾毛中稳定同位素指纹差异分析

利用同位素比率质谱仪测定来自黑龙江省安达市青肯泡乡和火石山乡、内蒙古太仆寺旗、河北省张家口市和三河市、山东省德州市和聊城市7个地域牛尾毛中的δ13C、δ15N和δ2H值,比较分析了不同地域来源牛尾毛中稳定同位素指纹特征差异,探讨不同地域来源牛尾毛中稳定同位素组成差异、影响因素及地域差异的范围,为牛肉及其产品同位素指纹溯源技术在实际中的应用提供指导。各区域牛尾毛中δ13C值表现为:黑龙江省安达市青肯泡乡(-14.83‰±2.12)、河北省三河市(-14.20‰±1.19)、山东省德州市(-14.16‰±2.51)和山东省聊城市(-15.78‰±1.08)>黑龙江省安达市火石山乡(-18.87‰±1.69)、内蒙古太仆寺旗(-19.29‰±2.43)和河北省张家口市(-19.83‰±1.92);δ15 N值为:黑龙江省安达市火石山乡(8.07‰±0.95)>内蒙古太仆寺旗(5.73‰±0.85)、河北省张家口市(6.65‰±1.45)>黑龙江省安达市青肯泡乡(4.60‰±0.41)、河北省三河市(4.24‰±0.75)、山东省德州市(4.18‰±0.96)和山东省聊城市(4.90‰±0.46);δ2H值为:河北省三河市(-87.78‰±1.99)、山东省德州市(-87.91‰±3.19)和山东省聊城市(-89.24‰±2.90)>河北省张家口市(-94.07‰±3.38)>黑龙江省安达市火石山乡(-97.05‰±3.41)、内蒙古太仆寺旗(-97.55‰±2.79)>黑龙江省安达市青肯泡乡(-102.25‰±2.99)。不同地域来源牛尾毛中稳定碳、氮、氢同位素指纹差异及地域差异范围取决于不同地域喂养牛的饲料组成、地域海拔和纬度的差异程度。     

稳定性氮同位素技术研究太湖梅梁湾区域营养盐差异

稳定同位素技术通常用于指示外源输入对环境的影响,采用该技术分析了太湖北部不同湖区悬浮颗粒有机物和浮游动物的碳氮稳定同位素比值的差异。结果表明,不同粒径的悬浮颗粒有机物和浮游动物稳定同位素比值存在显著的季节变化,夏季普遍高于冬季,其中δ13C高3.19‰~7.21‰,δ15N高4.20‰~9.36‰。各有机物δ13C不能有效区分各湖区的环境差异,而δ15N在各湖区存在显著差异。δ15N聚类分析显示,河口区由于受外源输入的影响,其δ15N显著低于其他湖区,单独聚为一类,而交汇处和湖心区影响较小,同河口区存在显著差异。整体来讲,总颗粒有机物和浮游动物δ15N同水体TP浓度呈显著正相关,同总溶解性无机氮浓度、铵根离子浓度呈显著负相关。可见,太湖北部悬浮颗粒有机物和浮游动物δ15N受环境营养盐差异的影响强烈,悬浮颗粒有机物δ15N可以作为指示湖区区域差异的有效指标。     

Estimating symbiotic N2 fixation in Robinia pseudoacacia

Estimating symbiotic di‐nitrogen (N₂) fixation is challenging, especially when working with woody N₂ fixers in field trials. Fortunately, isotope methods based on ¹⁵N natural abundance or on ¹⁵N artificial enrichment (dilution method) make it possible to estimate the proportion of nitrogen derived from the atmosphere (Ndfa) in N₂‐fixing species. These methods have been extensively used in the field for herbaceous species, much less for tree species such as alder and acacia, and rarely for black locust (Robinia pseudoacacia). The objectives of this study were to characterize the fixation potential of black locust in a plantation by using the two ¹⁵N isotope methods in the field, and to document values of isotope fractionation occurring during N₂ fixation (the B value). B values were estimated both by growing trees on an N‐free medium in controlled conditions (B_lab) and by making Ndfa calculated with the natural abundance method converge with Ndfa calculated with the ¹⁵N dilution method in the field (B_field). The two methods gave consistent estimates of the B value. B values ranging between –1.4 and –3.2‰ were found, varying with the age of the plant material. Up to 76% of the N in the black locust trees came from the atmosphere, representing more than 45 kg N ha^?1 over five years and confirming that black locust may be well adapted to N‐poor soils.     

稻田沟渠-湿地系统的碳氮稳定同位素组成特征

由于稳定同位素在特定污染源中具有特定的组成,在污染物质迁移转化过程中作为示踪剂而广泛应用。针对目前农业面源污染较为严重的现状,该文利用碳氮稳定同位素研究了灌区内外源物输入对稻田沟渠-湿地系统的贡献。结果表明,水中颗粒性有机物(particulate organic matter,POM)由于受到光照、营养物质不同导致POM在各采样点组成不同,δ13C变化范围较大,均值为-27.8‰,与大型水生植物和浮游植物接近,此类植物可能是POM的主要来源。水中δ13CDIC(dissolved inorganic carbon,DIC)与浮游植物呈线性相关,浮游动物δ13C与浮游植物存在一定相关性,而浮游植物与POM之间不存在显著性差异,说明研究区内浮游动物对內源有机碳的利用主要是取食浮游植物低持斜聿愠粱?δ13C值变化范围在-27.2‰～-21.8‰之间,明显高于水体POM含量,说明表层沉积物存在比颗粒有机物更富集碳的藻类与陆源碎屑等物质。各采样点颗粒有机物δ15N值的范围3.1‰～4.2‰,平均值为3.6‰,其中湿地δ15N高于其他采样点。沉积物δ15N平均值为-0.6‰,与大气中N2较为接近。     

Short‐term sequestration of slurry‐derived carbon and nitrogen in temperate grassland soil as assessed by 13C and 15N natural abundance measurements

Land application of animal wastes from intensive grassland farming has caused growing environmental problems during the last decade. This study aimed to elucidate the short‐term sequestration of slurry‐derived C and N in a temperate grassland soil (Southwest England) using natural abundance ¹³C and ¹⁵N stable isotope techniques. Slurry was collected from cows fed either on perennial ryegrass (C3) or maize (C4) silages. 50 m³ ha^—1 of each of the obtained C3 or C4 slurries (δ¹³C = —30.7 and —21.3‰, δ¹⁵N = +12.2 and + 13.8 ‰, respectively) were applied to a C₃ soil with δ¹³C and δ¹⁵N values of —30.0 ± 0.2‰ and + 4.9 ± 0.3‰, respectively. Triplicate soil samples were taken from 0—2, 2—7.5, and 7.5—15 cm soil depth 90 and 10 days before, at 2 and 12 h, as well as at 1, 2, 4, 7, and 14 days after slurry application and analyzed for total C, N, δ¹³C, and δ¹⁵N. No significant differences in soil C and N content were observed following slurry application using conventional C and N analysis techniques. However, natural abundance ¹³C and ¹⁵N isotope analysis allowed for a sensitive temporal quantification of the slurry‐derived C and N sequestration in the grassland soil. Our results showed that within 12 hours more than one‐third of the applied slurry C was found in the uppermost soil layer (0—2 cm), decreasing to 18% after 2 days, but subsequently increasing to 36% after 2 weeks. The tentative estimate of slurry‐derived N in the soil suggested a decrease from 50% 2 hours after slurry application to only 26% after 2 weeks, assuming that the increase in δ¹⁵N of the slurry plots compared to the control is proportional to the amount of slurry‐incorporated N. We conclude that the natural abundance tracer technique can provide a rapid new clue to the fate of slurry in agricultural C and N budgets, which is important for environmental impacts, farm waste management, and climate change studies.     

Tracing the source of cooking oils with an integrated approach of using stable carbon isotope and Fatty Acid abundance

We report a new approach to identify swill-cooked oils that are recycled from tainted food and livestock waste from commercial vegetable and animal oils by means of carbon isotope values and relative abundance of fatty acids. We test this method using 40 cooking oil samples of different types with known sources. We found significant differences in both total organic carbon isotope as well as compound-specific isotope values and fatty acid C(14)/C(18) ratios between commercial vegetable oils refined from C(3) plants (from -35.7 to -27.0‰ and from 0 to 0.15) and animal oils (from -28.3 to -14.3‰ and from 0.1 to 0.6). Tested swill-cooked oils, which were generally refined by mixing with animal waste illegally, fall into a narrow δ(13)C/fatty acid ratio distribution: from -25.9 to -24.1‰ and from 0.1 to 0.2. Our data demonstrate that the index of a cross-plotting between fatty acid δ(13)C values and C(14)/C(18) ratios can be used to distinguish clean commercial cooking oils from illegal swill-cooked oils.     

Species-dependent partitioning of C and N stable isotopes between arbuscular mycorrhizal fungi and their C3 and C4 hosts

Natural ¹³C and ¹⁵N abundances of mycorrhizal fungi are increasingly used in ecology but reference data on arbuscular mycorrhizal fungi (AMF) are scarce. In experiments with nine phylogenetically dispersed AMF strains inoculated on leek (C3 plant) and sorghum (C4) in pot cultures, we measured the ¹³C/¹²C and ¹⁵N/¹⁴N ratios in shoots, roots, AMF spores as well as carbon isotope signature of the C16:1ω5 fatty acid (FA), which is diagnostic for AMF. Spore δ¹³C values varied among AMF strains on any given host. They were significantly lower than shoot δ¹³C for sorghum (−2.5‰ on average) while for leek, no clear C isotope partitioning between spores and host shoots was observed. The FA C16:1ω5 fatty acids were more ¹³C-depleted than spores, without correlation with spore δ¹³C values. For both, sorghum and leek, spore δ¹⁵N was higher (+1–2‰ on average) than for shoots. We found no evidence that isotopic partitioning between the partners drives ¹³C and ¹⁵N abundances in plant–AMF symbiosis. Mycorrhizal roots displayed relatively high δ¹³C typical for heterotrophic organs, and not a mix between AMF and plant signatures. Interestingly, inoculation slightly decreased shoot δ¹³C on leek but not on sorghum, as compared with non-mycorrhizal plants, suggesting that AMF improved the plant's water status, a parameter affecting the δ¹³C of C3 but not C4 plants. Phylogenetically closer AMF displayed more similar spore δ¹³C and induced similar ¹³C and ¹⁵N abundances on leek shoots, but this observation was not confirmed for sorghum. Plant and AMF isotopic abundances hardly correlated with other parameters related to plant development, mineral nutrition or root mycorrhizal colonisation, and these correlations were never consistent between sorghum and leek. Thus, isotopic abundances in plant–AMF symbiosis were rather constrained by each AMF/plant interaction. Nevertheless, our data provide a valuable reference for future investigations of AMF communities and AM symbiosis in situ.     

Botanical origin causes changes in nutritional profile and antioxidant activity of fermented products obtained from honey

Honey as rich source of enzymatic and nonenzymatic antioxidants serves as health-promoting nutrient in the human body. Here, we present the first time a comparative study of nutritional profiles (e.g., acidities, sugar, organic acid profile, total polyphenolic, flavonoid content) for different unifloral, multifloral honeys and their fermented products, in correlation with their antioxidant activity. Additionally, an optimized method for HPLC separation of organic acids from honey was established. The total phenolic content of honey samples varied widely among the honey types compared to fermented products. High amounts of total flavonoids were quantified in heather honey, followed by raspberry, multifloral, black locust, and linden honey. A positive correlation between the content of polyphenols, flavonoids, and antioxidant activity was observed in honey samples. After fermentation, the flavonoid content of dark honey fermented products decreased significantly. Black locust and linden honeys are more suitable for fermentation because the decrease in antioxidant substances is less pronounced.     

Stable Carbon and Nitrogen Isotopes in a Peat Profile Are Influenced by Early Stage Diagenesis and Changes in Atmospheric CO2 and N Deposition

In this study, we test whether the δ(13)C and δ(15)N in a peat profile are, respectively, linked to the recent dilution of atmospheric δ(13)CO(2) caused by increased fossil fuel combustion and changes in atmospheric δ(15)N deposition. We analysed bulk peat and Sphagnum fuscum branch C and N concentrations and bulk peat, S. fuscum branch and Andromeda polifolia leaf δ(13)C and δ(15)N from a 30-cm hummock-like peat profile from an Aapa mire in northern Finland. Statistically significant correlations were found between the dilution of atmospheric δ(13)CO(2) and bulk peat δ(13)C, as well as between historically increasing wet N deposition and bulk peat δ(15)N. However, these correlations may be affected by early stage kinetic fractionation during decomposition and possibly other processes. We conclude that bulk peat stable carbon and nitrogen isotope ratios may reflect the dilution of atmospheric δ(13)CO(2) and the changes in δ(15)N deposition, but probably also reflect the effects of early stage kinetic fractionation during diagenesis. This needs to be taken into account when interpreting palaeodata. There is a need for further studies of δ(15)N profiles in sufficiently old dated cores from sites with different rates of decomposition: These would facilitate more reliable separation of depositional δ(15)N from patterns caused by other processes. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11270-011-1001-8) contains supplementary material, which is available to authorized users.     

Use of 13C and 15N natural abundance techniques to characterize carbon and nitrogen dynamics in composting and in compost-amended soils

Isotope fractionation during composting may produce organic materials with a more homogenous δ¹³C and δ¹⁵N signature allowing study of their fate in soil. To verify this, C, N, δ¹³C and δ¹⁵N content were monitored during nine months covered (thermophilic; >40 °C) composting of corn silage (CSC). The C concentration reduced from 10.34 to 1.73 g C (g ash)⁻¹, or 83.3%, during composting. Nitrogen losses comprised 28.4% of initial N content. Compost δ¹³C values became slightly depleted and increasingly uniform (from −12.8±0.6‰ to −14.1±0.0‰) with composting. Compost δ¹⁵N values (0.3±1.3 to 8.2±0.4‰) increased with a similar reduced isotope variability.The fate of C and N of diverse composts in soil was subsequently examined. C, N, δ¹³C, δ¹⁵N content of whole soil (0-5 cm), light (<1.7 g cm⁻³) and heavy (>1.7 g cm⁻³) fraction, and (250-2000 μm; 53-250 μm and <53 μm) size separates, were characterized. Measurements took place one and two years following surface application of CSC, dairy manure compost (DMC), sewage sludge compost (SSLC), and liquid dairy manure (DM) to a temperate (C₃) grassland soil. The δ¹³C values and total C applied (Mg C ha⁻¹) were DM (−27.3‰; 2.9); DMC (−26.6‰; 10.0); SSLC (−25.9‰; 10.9) and CSC (−14.0‰; 4.6 and 9.2). The δ¹³C of un-amended soil exhibited low spatial (−28.0‰±0.2; n=96) and temporal (±0.1‰) variability. All C₄ (CSC) and C₃ (DMC; SSLC) composts, except C₃ manure (DM), significantly modified bulk soil δ¹³C and δ¹⁵N. Estimates of retention of compost C in soil by carbon balance were less sensitive than those calculated by C isotope techniques. One and two years after application, 95 and 89% (CSC), 75 and 63% (SSLC) and 88 and 42% (DMC) of applied compost C remained in the soil, with the majority (80-90%) found in particulate (>53 μm) and light fractions. However, C₄ compost (CSC) was readily detectable (12% of compost C remaining) in mineral (<53 μm) fractions. The δ¹⁵N-enriched N of compost supported interpretation of δ¹³C data. We can conclude that composts are highly recalcitrant with prolonged C storage in non-mineral soil fractions. The sensitivity of the natural abundance tracer technique to characterize their fate in soil improves during composting, as a more homogeneous C isotope signature develops, in addition to the relatively large amounts of stable C applied in composts.     

NIR Spectroscopy: An Alternative for Soil Analysis

Advances in laboratory instrumentation and chemometrics provide alternatives to traditional methods of conducting soil chemical analysis. One of these is infrared diffuse reflectance spectroscopy in the near-infrared spectral range (NIRS). Herein we report the results of a multinational study to develop useful calibrations associating NIRS spectra with laboratory-measured results for total soil carbon (C), total soil nitrogen (N), δ¹³C, and δ¹⁵N from a single soil site in Mexico subjected to zero- and conventional-tillage regimens with and without crop residues and crop rotations of maize and wheat across 16 years. Modified partial least squares regression (MPLS) was used to obtain useful NIR predictions for total soil C and N, with ratio performance deviation (RPD) values of 6.8 and 2.6, respectively. Corresponding multiple correlation coefficients (RSQs) for C and N were 0.98 and 0.85, with standard errors of prediction (SEPs) of ±0.45 g C kg^–1 and ±0.09g Nkg^–1, respectively. The generation of δ¹⁵N and δ¹³C models produced different NIR recordings in soils with and without crop residues. Application of discriminant partial least squares (DPLS) statistics to the NIR spectral data allowed us to discriminate soils with and without residues. The prediction confidence for stable isotopes was 90% (internal validation) and 94% (external validation). Modified partial least squares regression was used to estimate δ¹⁵N and δ¹³C. Ratio performance deviation, RSQ, and SEP values obtained for δ¹³C and δ¹⁵N were 2.44 and 3.57, 0.83 and 0.81, ±0.5‰ (parts per thousand) and ±0.45‰ in soils with residues and 2.5 and 3.8, 0.93 and 0.92, and ±0.2‰ and ±0.23‰ in soils without residues, respectively. Overall, results obtained with NIRS were comparable to those obtained using conventional analytical methods, a finding that has wide relevance to agricultural soils and environmental studies in tropical locations. However, further testing is necessary to confirm that the calibration models are neither site nor instrument specific.     

Effect of different fertilizers on nitrogen isotope composition and nitrate content of Brassica campestris

The effect of different fertilizers on the δ(15)N value, nitrate concentration, and nitrate reductase activity of Brassica campestris and the δ(15)N value of soil has been investigated through a pot experiment. The δ(15)N mean value of B. campestris at the seedling stage observed in the composted chicken treatment (+8.65‰) was higher than that of chemical fertilizer treatment (+5.73‰), compost-chemical fertilizer (+7.53‰), and control check treatment (+7.86‰). There were significantly different δ(15)N values (p < 0.05) between B. campestris cultivated with composted chicken manure treatment and with chemical fertilizer treatment. The similar results were also found at the middle stage and the terminal stage. The variation of δ(15)N value in soil for different treatments was smaller than that of B. campestris, which was +6.71-+8.12‰, +6.83-+8.24‰, and +6.85-8.4‰, respectively, at seedling stage, middle stage, and terminal stage. With the growth of B. campestris, the nitrate content decreased in all treatments, and the nitrate reductase activity in B. campestris increased except for the CK. Results suggested that the δ(15)N values of B. campestris and soil were more effected by the fertilizer than by the dose level, and the δ(15)N value analysis could be used as a tool to discriminate the B. campestris cultivated with composted manure or chemical fertilizer.     

Examining the Microbial Degradation of Naphthenic Acids Using Stable Isotope Analysis of Carbon and Nitrogen

Naphthenic acids (NAs) are a complex group of naturally occurring oil sands constituents that constitute a significant portion of the dissolved organic carbon (DOC) pool available for microbial degradation in the process-related waste water associated with oil sands mine sites. One approach to understanding the biological fate of oil sands process-derived carbon and nitrogen in aquatic reclamation of the mine sites involves the use of stable isotope analyses. However, for stable isotope analyses to be useful in such field-based assessments, there is a need to determine how microbial degradation of a complex mixture of NAs might change the stable isotope values (δ ¹³C, δ ¹⁵N). In batch cultures and semi-continuous laboratory microcosms, utilization of a commercial mixture of NAs by oil sands-derived microbial cultures resulted in microbial biomass that was similar or slightly ¹³C enriched (1.4‰ to 3.0‰) relative to the DOC source, depending on the length of incubation. Utilization of a NA-containing extract of oil sands processed water resulted in greater ¹³C enrichment of microbial biomass (8.5‰) relative to the DOC source. Overall, the δ ¹³C of the DOC comprised of complex mixtures of NAs showed minimal change (?0.5‰ to ?0.1‰) during the incubation period whereas the δ ¹³C of the dissolved inorganic carbon (DIC) was more variable (?5.0‰ to +5.4‰). In tests where the concentration of available nitrogen was increased, the final biomass values were ¹⁵N enriched (3.8‰ to 8.4‰) relative to the initial biomass. The isotope trends established in this study should enhance our ability to interpret field-based data from sites with hydrocarbon contamination, particularly in terms of carbon source utilization and ¹⁵N enrichment.     

Quantitative high-performance liquid chromatography analyses of flavonoids in Australian Eucalyptus honeys

Flavonoids of nine Australian monofloral Eucalyptus honeys have been analyzed and related to their botanical origins. The mean content of total flavonoids varied from 1.90 mg/100 g of honey for stringybark (E. globoidia) honey to 8.15 mg/100 g of honey for narrow-leaved ironbark (E. crebra) honey, suggesting that species-specific differences occur quantitatively among these Eucalyptus honeys. All of the honey samples analyzed in this study have a common flavonoid profile comprising tricetin (5,7,3',4',5'-pentahydroxyflavone), quercetin (3,5,7,3',4'-pentahydroxyflavone), and luteolin (5,7,3',4'-tetrahydroxyflavone), which, together with myricetin (3,5,7,3',4',5'-hexahydroxyflavone) and kaempferol (3,5,7,4'-tetrahydroxyflavone), were previously suggested as floral markers for European Eucalyptus honeys. Thus, flavonoid analysis could be used as an objective method for the authentication of the botanical origin of Eucalyptus honeys. Moreover, species-specific differences can also be found in the composition of honey flavonoid profiles. Among these honeys, bloodwood (E. intermedia) honey contains myricetin and tricetin as the main flavonoid compounds, whereas there is no myricetin detected in yapunyah (E. ochrophloia), narrow-leaved ironbark (E. crebra), and black box (E. largiflorens) honeys. Instead, these types of Eucalyptus honeys may contain tricetin, quercetin, and/or luteolin as their main flavonoid compounds. Compared to honeys from other geographical origins, the absence or minor presence of propolis-derived flavonoids such as pinobanksin, pinocembrin, and chrysin in Australian honeys is significant. In conclusion, these results demonstrate that a common flavonoid profile exists for all of the Eucalyptus honeys, regardless of their geographical origins; the individual species-specific floral types of Eucalyptus honey so common in Australia could be possibly differentiated by their flavonoid profile differences, either qualitatively or quantitatively or both.     

Intramolecular carbon isotope distribution of acetic acid in vinegar

Compound-specific carbon isotope analysis of acetic acid is useful for origin discrimination and quality control of vinegar. Intramolecular carbon isotope distributions, which are each carbon isotope ratios of the methyl and carboxyl carbons in the acetic acid molecule, may be required to obtain more detailed information to discriminate such origin. In this study, improved gas chromatography-pyrolysis-gas chromatography-combustion-isotope ratio mass spectrometry (GC-Py-GC-C-IRMS) combined with headspace solid-phase microextraction (HS-SPME) was used to measure the intramolecular carbon isotope distributions of acetic acid in 14 Japanese vinegars. The results demonstrated that the methyl carbons of acetic acid molecules in vinegars produced from plants were mostly isotopically depleted in (13)C relative to the carboxyl carbon. Moreover, isotopic differences (δ(13)C(carboxyl) - δ(13)C(methyl)) had a wide range from -0.3 to 18.2‰, and these values differed among botanical origins, C3, C4, and CAM plants.     

The potential of hyperspectral images and partial least square regression for predicting total carbon,total nitrogen and their isotope composition in forest litterfall samples

Purpose

The main objective of this study was to examine the potential of using hyperspectral image analysis for prediction of total carbon (TC), total nitrogen (TN) and their isotope composition (δ¹³C and δ¹⁵N) in forest leaf litterfall samples.

Materials and methods

Hyperspectral images were captured from ground litterfall samples of a natural forest in the spectral range of 400–1700 nm. A partial least-square regression model (PLSR) was used to correlate the relative reflectance spectra with TC, TN, δ¹³C and δ¹⁵N in the litterfall samples. The most important wavelengths were selected using β coefficient, and the final models were developed using the most important wavelengths. The models were, then, tested using an external validation set.

Results and discussion

The results showed that the data of TC and δ¹³C could not be fitted to the PLSR model, possibly due to small variations observed in the TC and δ¹³C data. The model, however, was fitted well to TN and δ¹⁵N. The cross-validation R² _cv of the models for TN and δ¹⁵N were 0.74 and 0.67 with the RMSE_cv of 0.53% and 1.07‰, respectively. The external validation R² _ex of the prediction was 0.64 and 0.67, and the RMSE_ex was 0.53% and 1.19 ‰, for TN and δ¹⁵N, respectively. The ratio of performance to deviation (RPD) of the predictions was 1.48 and 1.53, respectively, for TN and δ¹⁵N, showing that the models were reliable for the prediction of TN and δ¹⁵N in new forest leaf litterfall samples.

Conclusions

The PLSR model was not successful in predicting TC and δ¹³C in forest leaf litterfall samples using hyperspectral data. The predictions of TN and δ¹⁵N values in the external litterfall samples were reliable, and PLSR can be used for future prediction.

     

Amino acid 15N in long-term bare fallow soils: influence of annual N fertilizer and manure applications

Long‐term dynamics of amino acids (AAs), from a bare fallow soil experiment (established in 1928 at INRA‐Versailles, France), were examined in unamended control (Con) plots and plots treated with ammonium sulphate (Amsul), ammonium nitrate (Amnit), sodium nitrate (Nanit) or with animal manure (Man). Topsoil (0–25 cm) from 1929, 1963 and 1997 was analysed for C, N and ¹⁵N content and distribution of 18 amino acids recovered after acid hydrolysis with 6 m HCl. With time, soil N, C and AA content were reduced in Con, Amsul, Amnit and Nanit, but increased in Man. However, the absolute N loss was 3–11 times larger in Man than Nanit, Amsul, Amnit and Con, due to the much higher N annual inputs applied to Man. From 1929 to 1997 in Con, Amsul, Amnit and Nanit the whole soil and non‐hydrolysable‐N pool δ¹⁵N increased associated with the loss of N (indicative of Rayleigh ¹⁵N^/14N fractionation). No δ¹⁵N change from 1929 to 1997 was found in the hydrolysable AA‐N (HAN) pool. Fertilizer N inputs aided stabilization of soil AA‐N, as AA half‐life in the mineral N fertilizer treatments increased from 34 years in 1963 to 50 years in 1997. The δ¹⁵N values of alanine and leucine reflected both source input and ¹⁵N^/14N fractionation effects in soils. The δ¹⁵N increase of ornithine (～6‰) was similar to the whole soil. The δ¹⁵N change of phenylalanine in Con (decrease of 7‰) was related to its proportional loss since 1929, whereas for Amsul, Amnit, Nanit and Man it was associated with isotope effects caused by the fertilizer inputs. However, the soil δ¹⁵N value of most individual amino acids (IAAs) did not significantly change over nearly 70 years, even with mineral or organic N inputs. We conclude for these bare fallow systems that: (i) δ¹⁵N changes in the whole soil and non‐hydrolysable AA pool were solely driven by microbial processes and not by the nature of fertilizer inputs, and (ii) without plant inputs, the δ¹⁵N of the HAN pool and (most) IAAs may reflect the influence of plant–soil interactions from the previous (arable cropping) rather than present (fallow) land use on these soil δ¹⁵N values.     

不同放牧强度下荒漠草原土壤有机碳及其δ~(13)C值分布特征

以内蒙古短花针茅荒漠草原为研究对象,通过测定不同载畜率下土壤部分理化性质、土壤有机碳含量和δ~(13)C值.探讨随放牧强度增加土壤有机碳深度分布和δ~(13)C值的组成差异特征.结果显示:随深度增加.有机碳含量呈线性急剧降低,变化范围在16.17～6.26 g/kg之间,而土壤有机碳的δ~(13)C值不断增大.变化范围在-22.5‰～-14.3‰.放牧对土壤有机碳的影响主要在0-20 cm土层,且放牧强度越大,有机碳含量越低,有机质分解程度越大,δ~(13)C值越偏正,δ~(13)C值的深度变化特征还表明.土壤剖面形成发育过程中当地气候和植被发生了很大的变化,可能实现了由C_4植物占优势向C_3植物占优势的变迁.     

不同氮肥处理对土壤和番茄中稳定性氮同位素丰度的影响

采用盆栽番茄的方式,根据氮肥类型和施用量,设置8种肥料处理（以纯氮计）：C1（有机肥,9.5g）、CU1（有机肥、化肥均为4.75g）、U1（化肥,9.5g）、C2（有机肥,19g）、CU2（有机肥、化肥均为9.5g）、U2（化肥,19g）、C3（有机肥,29g）、CK（不施肥料）,分析各处理的土壤、番茄叶片和果实δ15N的变化,比较不同部位δ15N的差异.结果表明,（1）施用有机肥能显著提高土壤、叶片和果实的δ15N（P ＜0.05）,而施用化肥则显著降低其δ15N（P＜0.05）.纯有机肥（C1、C2、C3）处理番茄叶片和果实δ15N分别为6.02‰ ～ 12.75‰和4.69‰～8.24‰,纯化肥（U1、U2）处理为2.83‰～5.53‰和2.66‰ ～4.50‰,纯有机肥处理δ15N显著高于纯化肥处理.（2）番茄植株不同部位δ15N的比较结果为老叶＞新叶＞新茎＞果实＞老茎＞侧根＞主根,表明氮素由根部吸收经过茎的运输到达叶片和果实的过程中,15N逐步富集.（3）建议将利用氮稳定同位素技术鉴别番茄果实纯有机肥和纯化肥处理的δ15N的阈值设定为5‰,有机种植检测可以借鉴此法设定相应的临界值,以鉴别有机种植和非有机种植.研究结果表明通过氮稳定同位素技术可以区分植物中氮素的来源,从而得知作物生长过程中的施肥情况,为有机食品检测提供有效方法.     

Nitrogen Isotope Ratios of Synthetic and Organic Sources of Nitrate Water Contamination in Spain

This work aims to identify the sources of nitrogencontamination in nitrate vulnerable zones (NVZs) of Spain by means of the nitrogen isotope method. Three categories of nitrogen sources (synthetic fertilisers, animal wastes, and sludges and effluents from waste-water treatment plants) from three NVZs were analysed for their nitrogen isotopic composition (δ¹⁵N) in order to assess the applicability of the method to the identification of these N sources. The mean δ¹⁵N values were: +1.48‰ for synthetic fertilisers, +15.98‰ for animal wastes and +11.52‰ for sludges and effluents. The synthetic fertiliser sources were significantly different from the organic sources and so, the method can be used for their identification. The highest variability was found within the animal waste category. The range of values found for the different kinds of animal wastes (+5.86 to +36.74) was very wide and overlappedthe range found for sludges and effluents from waste-water treatmentplants (+4.57 to +20.18). Accordingly, these two nitrogen sources areisotopically indistinguishable.