Isotope Ratio Method Research Articles

Detection of adulteration in Iranian grape molasses added glucose/fructose/sugar beet syrups with 13C/12C isotope ratio analysis method.

Grape molasses (GM), produced from grapes, is a traditional Iranian food and is widely consumed in Iran. However, GM adulteration is among the most widespread illegitimate procedures involving contamination of food with foreign materials, such as adding sugar-water solution, date syrup, sugar beet syrup, and grape sauce. This study used stable carbon 13C/12C isotope ratio analysis method to detect adulteration of GM samples with glucose syrups (GS), fructose syrups (FS), and beet sugar syrups (BS) at the ratio of 0%, 10%, 30%, and 50% (by weight). Physicochemical properties of GM including °Brix, conductivity, specific gravity, pH, moisture content, ash content, hydroxymethyl furfural, sugar content, and rheological properties of samples were investigated. The δ13C isotope ratio of the GM was determined as -26.61%, that of the GS as -13.23%, that of the FS as -13.42%, and that of the BS as -16.58%. The δ13C isotope ratio increased by the addition of adulterant syrups to GM. The addition of each adulterant syrup had a different effect on the physicochemical parameters; however, the °Brix and specific gravity had a positive correlation with the δ13C isotope ratio results. The magnitudes of G' and G" increase with an increase in frequency representing the viscoelastic behavior of samples. The obtained results of this study suggest the use of δ13C isotope ratio method as a fast and accurate method to investigate the adulteration of grape molasses.

Stable isotopes reveal the surface water-groundwater interaction and variation in young water fraction in an urbanized river zone

Based on 30 sampling campaigns on precipitation, river water and groundwater in Qingbaijiang urban catchment, southwest China, this study reports the spatio-temporal evolution of water isotopes under the impacts of human activities. The seasonal variation of groundwater-surface water interaction is quantitatively evaluated by isotope-aid hydrograph separation, and the young water fraction (Fyw) in river water at different spatial locations is estimated based on the seasonal periodicity of isotopes. The results show that the stable isotopes in river water and groundwater in Qingbaijiang urban catchment grow enriched from upstream to downstream, reflecting the transformation of the dominant water source from plateau river water to local precipitation and the influence of evaporation. The operation of water conservancy projects and construction of impervious surface in urban areas increase the evaporation intensity of river water. The results of the end-member mixing analysis (EMMA) demonstrates that the average annual contributions of river water to near-bank groundwater are 60.17%, 23.55% and 24.90% in the upper, middle and lower parts, respectively. The periodic storage and release of water led by the water conservancy projects enhances the groundwater recharge in the upstream river, while the water exchanges between river water and groundwater in the middle and lower parts of the catchment are reduced. The Fyw at 8 river sections of Qingbaijiang River estimated by the isotopic amplitude ratio method ranges from 0.067 to 0.194, with an overall increasing trend from upstream to downstream. The young water fraction is negatively correlated with mean elevation, mean slope and vegetation coverage, while positively correlated with the proportion of anthropogenic land use and the proportion of low-permeable soil. The construction of impervious surfaces and drainage systems in urban and rural areas is an important driver for the elevated young water fraction.

Estimate of Neutron Fluence Using Isotope Ratio Method for ZR-2.5NB Materials Irradiated in the National Research Universal Reactor

Abstract The isotope ratio method (IRM) is a technique used for estimating the energy production in a fission reactor by measuring isotope ratios in nonfuel reactor components. This method has been successfully demonstrated on the estimation of cumulative energy production as well as plutonium production in graphite-moderated and light-water-moderated reactors for nonproliferation purposes. In this paper, IRM was used to estimate neutron fluence in Zr-2.5Nb materials irradiated in fast neutron (FN) irradiation facilities in the National Research Universal (NRU) reactor. Neutron fluence has been shown to be an important parameter for studying irradiation effects on the performance and properties of critical reactor components. Selected isotope ratios of hafnium and iron were used as indicators of the neutron fluence in Zr-2.5Nb sample materials. Correlations between neutron fluence and the indicator element isotope ratios were generated using the reactor physics simulation codes Winfrith improved multigroup scheme (WIMS)-AECL and SCALE/Oak Ridge Isotope GENeration code (ORIGEN). Inductively coupled plasma-mass spectrometry (ICP-MS) was used to obtain accurate measurements of the isotope ratios. Neutron fluence values estimated using IRM, were in good agreement with the values based on measured irradiation power histories of the NRU reactor. This study proposes a potential application of IRM to the estimation of neutron fluence for critical reactor components in heavy-water-moderated reactors such as pressure and calandria tubes in CANDU® reactors.

Differential distribution of authenticity results of different varieties of refined honey based on stable isotope ratio method

Differential distribution of authenticity results of different varieties of refined honey based on stable isotope ratio method

An Improved Method for PWR Fuel Failure Detection Using Cascade-forward Neural Network With Decision Tree

When a fuel rod is damaged, determining the degree of fuel failure makes sense. The operators can decide whether to continue operating the reactor or shut it down based on the severity of the fuel failure. The isotopic ratio of two radioactive fission products (FPs) is a typical technique for evaluating the degree of fuel failure, although this is not applicable in the case of little fuel failure but large tramp uranium mass. The feedforward neural network (FFNN) has been used to identify fuel failures in order to overcome the shortcomings of the isotopic ratio method, although there is still inadequacy in the ability to distinguish between an intact fuel rod and a defective fuel rod with a small defect. In this study, we propose a cascade-forward neural network with a decision tree for fuel failure detection that performs well at classifying the degree of fuel failure and, in particular, at differentiating between an intact fuel rod and a defective fuel rod with a small size defect. The input of the neural network is the specific activity of FPs measured in the coolant. The degree of fuel failure is determined by the neural network’s output, which is labeled using one-hot encoding. The training set is constructed using the Booth-type diffusion model and the first-order kinetic model. The performance of the improved neural network is demonstrated. It is shown that the improved method is more accurate and responsive than the previous neural network when recognizing the onset of fuel failure. Finally, the most important nuclides are determined through the sensitivity analysis, and the neural network is simplified according to the importance of nuclides and the limitation of the radioactive detector in practical application.

Verification of Graphite Isotope Ratio Method Combined With Polynomial Regression for the Estimation of Cumulative Plutonium Production in a Graphite-Moderated Reactor

Verification of Graphite Isotope Ratio Method Combined With Polynomial Regression for the Estimation of Cumulative Plutonium Production in a Graphite-Moderated Reactor

Source analysis of heavy metal pollution in agricultural soil irrigated with sewage in Wuqing, Tianjin

In this study, the contents of heavy metals and Cd and Pb isotope ratios of agricultural soil and potential source samples collected from farmland receiving sewage irrigation in Wuqing District, Tianjin, China were determined. Multiple methods were used for source analysis, including positive matrix factorization (PMF), correlation analysis, principal component analysis (PCA), and the Cd and Pb isotope ratio method. The results showed that agricultural soil was slightly contaminated by heavy metals in the research area, with relatively higher Cd and Pb accumulation levels compared to those of other heavy metals. Four types of pollution sources, including the soil parent material sources, industrial emission sources, agricultural practice sources, and mixed sources of sewage irrigation and transportation were apportioned and quantified by PMF, combined with the results of PCA and correlation analysis. The contribution rates quantified by the Cd and Pb isotope ratio method were similar, suggesting that no single source dominates Pb and Cd pollution. The contribution rates of Pb analyzed by the isotope ratio method were almost identical to those of the PMF model, indicating the rationality of the PMF result. Our results suggested that correlation analysis and PCA should be utilized to provide information for obtaining reasonable results and defining source categories for PMF, whereas the isotope ratio method should be applied to verify the accuracy of source contributions analyzed by PMF.

Identifying the Source of Heavy Metal Pollution and Apportionment in Agricultural Soils Impacted by Different Smelters in China by the Positive Matrix Factorization Model and the Pb Isotope Ratio Method

In this study, the agricultural soil around Zhuzhou Smelter in Zhuzhou district, Hunan, China and Huludao Zinc Plant in Huludao district, Liaoning, China was selected as the research area to discuss the current situation of heavy metal pollution in the surrounding agricultural soil caused by different smelting plants for soil environmental management and sustainable development of soil resources. Eight elements’ (Cd, Pb, As, Hg, Cr, Ni, Cu, and Zn) contents were measured to assess their pollution risk level and spatial distribution distinction. Correlation analysis, the positive matrix factorization (PMF), and Pb isotope ratio method were employed to analyze the sources of soil heavy metal pollution in the research area. The contents of Cd, Pb, Hg, and Zn in the soil of the two research areas were seriously polluted, and the changes of their spatial content were related to the migration and sedimentation of the smelter waste gas. Four types of pollution sources, including the smelting source, agricultural sources, natural sources, and mixed sources of industrial activity and traffic were identified in both areas by PMF, and the contribution rates of the four pollution sources in both areas were similar. Taking the agricultural soil around Huludao Zinc Plant as an example, the contribution rates of the different pollution sources analyzed by Pb isotope ratio method were the lead smelting source (43.7%), followed by the agricultural source (34.6%), traffic source (14.2%), and natural source (7.5%), which were basically consistent with that of PMF analysis, verifying the reliability of the two methods. The results above showed that the smelters were the main cause of heavy metal pollution in agricultural soils around the two research areas, and the analysis results of element content ratio and smelting source characteristic element contribution rate ratio could provide reference for the analysis of heavy metal pollution in agricultural soil around smelters for soil pollution control decision making.

Radioactive Isotope Ratios as a Novel Method of Ancient Pottery Analysis: Ostrowite Archaeological Site Data

The radioactive isotope content of any geological sample (lithic rock, sand, silt or clay) is characteristic for a specific type of geological material. The use of the isotope ratio method allows each sample to be distinguished in terms of source. In this study the radioactive isotope ratio method has been applied to a set of ceramic pottery specimens from the same multi-layered archaeological site and probably produced from local raw material. The method shows the similarities within the ceramic material used to manufacture the pottery. The variations in the quantitative and qualitative compositions of the basic products (clay, silt, loam, sand, ash and organic admixtures) used in the preparation of the ceramic paste change the isotopic composition and activity ratios. Pottery from each ceramic manufacturing centre, based on the specific composition of the raw materials, have characteristic isotope ratios. Radioactive isotope ratios as fingerprints of ancient ceramic manufacturing centres have not yet been applied as an archaeometric method. The proposed method has been applied to a Striatemulti-phased settlement complex and pottery manufacturing centre in Ostrowite in northern Poland. The earliest pottery to be manufactured in Ostrowite dates to5200-5000 BC, during the existence of the Early Neolithic settlement. Subsequent settlement phases and pottery production horizons are dated to the early Iron Age (approx.800-600 BC), the Roman period (1st to 4th centuries AD) and the Middle Ages (11th to14th centuriesAD). The site has a long tradition and experience in ceramic production.In this study two isotope ratios were applied: 40K/ 228Ac and 226Ra/ 208Tl. The proposed non-destructive archaeometric method allows the analysis of vessel fragments. This study analysed 11 fragments of Neolithic pottery,3 fragments from the early Iron Age, 5fragments from the Roman period, 5 specimens from the medieval period, 3 burned clay samples and 8 raw material samples, all collected from the Ostrowite complex.This pilot study confirm the grouping of the isotope ratio results for each type of the samples, even in terms of similarities with the base clay material collected in this region.

Vitamin A Absorption Determined in Rats Using a Plasma Isotope Ratio Method

ABSTRACTBackgroundBetter methods are needed for determining vitamin A absorption efficiency.ObjectiveOur objective was to measure vitamin A absorption in rats by adapting a plasma isotope ratio method previously used to determine cholesterol absorption.MethodsMale Sprague-Dawley rats [n = 14; 340 ± 16 g (mean ± SD)] received an oral tracer dose of [3H]retinyl acetate in oil plus an intravenous dose of [14C]vitamin A–labeled lymph prepared in a donor rat that had received [14C]retinyl acetate intraduodenally. Blood samples were collected on days 1, 2, 3, 6, 9, and 12, and plasma was analyzed for 3H and 14C; vitamin A absorption was calculated for each sample as (fraction of oral dose/fraction of intravenous dose) × 100. Radioactivity was also measured in feces and urine collected as pools on days 3, 6, 9, and 12 and in liver and remaining carcass on day 12.ResultsVitamin A absorption calculated as the plasma isotope ratio was >100% on day 1, 78% ± 5% on day 6, 76% ± 5% on day 9, and 74% ± 5% on day 12; fitting the data to an exponential function plus a constant predicted an absorption of 75% by day 14. Recovery of the oral dose in feces (day 0 to day 6) was low (6.2% ± 0.84%, n = 10) and the mean isotope ratio in day 9–12 urine pool was lower than that in plasma.ConclusionsThe plasma isotope ratio holds promise for estimating vitamin A absorption, but additional work is needed to determine how long studies need to be and if the doses should be administered simultaneously. For application of this method in humans, artificial chylomicrons labeled with a stable isotope of retinyl acetate could be used for the intravenous dose, with a different isotope required for the oral dose.

A Suitability Study on the Indicator Isotopes for Graphite Isotope Ratio Method (GIRM)

The Graphite Isotope Ratio Method (GIRM) can verify non-proliferation of nuclear weapon by estimating the total plutonium production in a graphite-moderated reactor. Using the reactor, plutonium is generated and accumulated through the 238U neutron capture reaction, and impurities in the graphite are converted to nuclides due to the nuclear reaction. Therefore, the amount of plutonium production and concentration of the impurities are correlated. However, the plutonium production cannot be predicted using only the absolute concentration of the impurities. It can only be predicted when the initial concentration of the impurities is obtained because the concentration, at a certain time, depends on it. Nevertheless, the ratios of the isotopes in an element are known regardless of the impurity of an element in the graphite moderator. Thus, the correlation between the isotope ratio and amount of plutonium produced helps predict plutonium production in a graphite-moderated reactor. Boron, Lithium, Chlorine, Titanium, and Uranium are known as indicator elements in the GIRM. To assess whether the correlation between the indicator isotope and amount of plutonium produced is independent of the initial concentration of the impurities, four different impurity compositions of graphite were used. 10B/11B, 36Cl/35Cl, 48Ti/49Ti, and 235U/238U had a consistent correlation with the cumulative plutonium production, regardless of the initial impurity concentration of the graphite, because these isotopes were not generated through the nuclear reaction of other elements. On the other hand, the correlation between 6Li/7Li and plutonium production depended on the initial concentration of the impurities in graphite. Although 7Li can be produced through the neutron capture reaction of 6Li, the (n, α) reaction of 10B was the major source of 7Li. Therefore, the initial concentration of 10B affected the production of 7Li, making Li unsuitable as an indicator element for the GIRM.

Determining the Impact of Riparian Wetlands on Nutrient Cycling, Storage and Export in Permeable Agricultural Catchments

The impact of riparian wetlands on the cycling, retention and export of nutrients from land to water varies according to local environmental conditions and is poorly resolved in catchment management approaches. To determine the role a specific wetland might play in a catchment mitigation strategy, an alternative approach is needed to the high-frequency and spatially detailed monitoring programme that would otherwise be needed. Here, we present a new approach using a combination of novel and well-established geochemical, geophysical and isotope ratio methods. This combined approach was developed and tested against a 2-year high-resolution sampling programme in a lowland permeable wetland in the Lambourn catchment, UK. The monitoring programme identified multiple pathways and water sources feeding into the wetland, generating large spatial and temporal variations in nutrient cycling, retention and export behaviours within the wetland. This complexity of contributing source areas and biogeochemical functions within the wetland were effectively identified using the new toolkit approach. We propose that this technique could be used to determine the likely net source/sink function of riparian wetlands prior to their incorporation into any catchment management plan, with relatively low resource implications when compared to a full high-frequency nutrient speciation and isotope geochemistry-based monitoring approach.

Methodology for the assessment of added/free sugar intake in epidemiological studies.

High-sugar intake has been linked to increased risk of diseases but an accurate assessment of added/free sugar intake has always been a challenge in research. This review summarizes the methodologies for assessing added/free sugar intake reported in recent literature. Four different methods for added/free sugar-intake assessment are discussed, including the carbon isotope ratio (δC) method, Food Patterns Equivalent Database, disaggregation method and the 10-step systematic method. These methods have different strengths and limitations in terms of requirement for background knowledge, flexibility to sugar definition, level of subjectivity, accuracy and needs for recalculation/modification when used in different countries or food products. Although advances have been made in the methodologies for assessing added/free sugar intake, accurate assessment continues to be difficult. Of the methods reviewed, the 10-step systematic method could be a simpler method to provide relatively accurate estimation of added/free sugar intake. Further improvements or combining with other methods may allow more accurate and flexible estimation. Development of a completely objective biomarker for added/free sugar intake is unlikely to be achievable, therefore future research may need to focus on developing correction equations for use with biomarkers such as δC to improve their specificity to added/free sugar intake.

Seasonal Variation in Stable Isotope Ratios of Cow Milk in Vilnius Region, Lithuania.

Simple SummaryThe composition of milk is fundamentally dependent on the feeding of the cows, and thereby on a particular environment. However, stable isotope composition is not always constant in the environment and can even change in the same area. Thus, the aim of this study was to better understand the impact of water and food sources on oxygen, carbon, and nitrogen stable isotope ratio (18O/16O, 13C/12C, and 15N/14N) distribution and fractionation in cow milk in different seasons of the year. Cow milk, drinking water, feed, and precipitation water were collected for three years from the same location. Overall, combined δ18O, δ13C, and δ15N analysis of cow milk provides valuable information about the amount of variation in stable isotope ratios in natural samples. This study can be helpful for studies of milk product authentication.Various studies have shown that stable isotope analysis has the potential to verify the geographic origin of foods and drinks. However, stable isotope composition is not always constant in the environment and can even change in the same area. Dairy products are of particular interest as a group of foods that play an important role in feeding the population. The composition of milk is fundamentally dependent on the feeding of the cows, and thereby on a particular environment. To better understand the amount of variation in δ18O, δ13C, and δ15N values in the milk from the same area, we measured stable isotope ratios in cow milk water, artesian water, and precipitation (δ18O) as well as in bulk milk samples (δ13C and δ15N) collected in 2014–2016. Different water and food sources were available during the winter (artesian water only and dry grass) and summer (artesian water and fresh grass), and spring and autumn seasons reflected transitional periods. Oxygen stable isotope ratios in milk water were relatively lower in winter and transitional seasons and higher in summer, showing the dependence on the main water source. δ13C values reflected particular food sources. This study shows the applicability of the stable isotope ratio method in linking cow milk to specific environments and reveals the amount of variation in stable isotope ratios in the same area. These results could be valuable for other studies on geographical origin determination of dairy products.

典型城市单元的土壤重金属溯源方法与实证研究

PDF HTML阅读 XML下载 导出引用 引用提醒 典型城市单元的土壤重金属溯源方法与实证研究 DOI: 10.5846/stxb201809121963 作者: 作者单位: 中国科学研生态环境研究中心城市与区域生态国家重点实验室,中国科学研生态环境研究中心城市与区域生态国家重点实验室,吉林大学新能源与环境学院,中国科学院生态环境研究中心,中国科学院生态环境研究中心,中国科学院生态环境研究中心,广东省环境科学研究院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划（2018YFC1800301，2017YFC0505702）；国家自然科学基金项目（41877509，41571478）；广东省应用型科技研发专项（2016B020240008） Source apportionment methods of soil heavy metals in typical urban units: an empirical study Author: Affiliation: Research Center for Eco-Environmental Sciences,CAS,,,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:随着城市化进程的不断深入，土壤中重金属污染现状及其治理情况越来越受到重视，而查明污染源是有效治理污染的前提。源解析技术目前已广泛的应用于环境受体重金属来源解析实践中，总结了近年来土壤重金属成因分析的常用方法及原理，并提出了一种将多种方法相配合使用的方法体系。选取珠三角某市城郊农田作为研究对象，结果表明，Cd、Pb、Cu、Zn、As存在含量超过国家农用地筛选值的情况，其中Cd超标率高达60.1%。农业活动、工业生产、交通源和自然母质均对研究区土壤重金属的累积产生一定的贡献。正定矩阵因子分析法（PMF，Positive Matrix Factorization）模型模拟的Cd、Ni、Zn和Hg预测值与实测值线性拟合r2均大于90%，其余元素r2均大于60%，呈现出很好的相关性，满足研究需要。PMF模型和铅同位素比值法计算得到的交通及农业对土壤Pb累积的贡献率之和分别为86.0%和84.8%，PMF模型和物质流分析法计算得到的农业对土壤Cd的贡献率分别为86.7%和79.7%，结果均比较接近。结果表明正定矩阵因子法、同位素比值分析法，物质流分析法能很好的联用应用于土壤重金属源解析研究。 Abstract:With the deepening of urbanization, increasing attention has been paid to the status quo and control of heavy metal pollution in soil; however, identifying pollution sources is the premise of effective pollution control. Source analysis has been widely used to evaluate heavy metals in environmental receptors. In this paper, the common methods and principles of source analysis of soil heavy metals pollution in recent years are summarized, and a system combining various methods is proposed. A typical farmland in the Pearl River Delta was selected as a case area. The results indicated that (1) concentrations of Cd, Pb, Cu, Zn, and As in some soil samples were greater than the filter capacity of agricultural land according to the Soil Environmental Quality of China, especially cadmium, which reached 60.1%; and (2) the accumulation of heavy metals in soils was related to the overuse of fertilizers for industrial production, traffic pollution, and soil parent material. (3) The results of the correlation analysis implied that the r2 values of Cd, Ni, Zn, and Hg were more than 90%, and the r2 values of other heavy metals were more than 60%, which indicates that there were significant correlations between the values of the measured and predicted heavy metals. (4) The contribution rates of the sum of transportation and agriculture to soil Pb accumulation through the PMF model and Pb stable isotope ratio method were 86.0% and 84.8%, respectively. The contribution rates of agriculture to soil Cd through the PMF model and material flow analysis were 86.7% and 79.7%, respectively. (5) The results indicate that the positive matrix factor, isotope ratio analysis, and material flow analysis methods can be well combined to study the source of heavy metals in soil. 参考文献 相似文献 引证文献

Intestinal β-carotene bioconversion in humans is determined by a new single-sample, plasma isotope ratio method and compared with traditional and modified area-under-the-curve methods

The vitamin A value (bioefficacy) of provitamin A carotenoids is determined by absorption of the carotenoid (bioavailability) and its subsequent conversion to retinol (bioconversion). Here we show that intestinal bioconversion of β-carotene can be estimated based on analysis of a single plasma sample collected 6 h after subjects ingest a test dose of stable isotope-labeled β-carotene from the ratio of retinyl esters to retinyl esters plus β-carotene. Plasma isotope ratio predictions of bioconversion ranged from 50 to– 93% (mean 76%) for 45 healthy young adults with low vitamin A stores. Results were the same as predictions made by a traditional area-under-the-curve method calculated from 0 to– 8 h or a modified area-under-the-curve method calculated from 0 to– 12 h. The modified method may provide better estimates of bioconversion between 8 and 24 h after ingestion of a carotenoid dose when stable isotopes cannot be used due to cost or logistics. Furthermore, because the plasma isotope ratio method requires only one blood sample and no isolation of triglyceride-rich lipoproteins, its use will facilitate estimation of provitamin A carotenoid bioconversion in human subjects and especially children, in whom repeated blood sampling is not feasible.

A Simple Plasma Retinol Isotope Ratio Method for Estimating β-Carotene Relative Bioefficacy in Humans: Validation with the Use of Model-Based Compartmental Analysis

Background: Provitamin A carotenoids are an important source of dietary vitamin A for many populations. Thus, accurate and simple methods for estimating carotenoid bioefficacy are needed to evaluate the vitamin A value of test solutions and plant sources. β-Carotene bioefficacy is often estimated from the ratio of the areas under plasma isotope response curves after subjects ingest labeled β-carotene and a labeled retinyl acetate reference dose [isotope reference method (IRM)], but to our knowledge, the method has not yet been evaluated for accuracy.Objectives: Our objectives were to develop and test a physiologically based compartmental model that includes both absorptive and postabsorptive β-carotene bioconversion and to use the model to evaluate the accuracy of the IRM and a simple plasma retinol isotope ratio [(RIR), labeled β-carotene-derived retinol/labeled reference-dose-derived retinol in one plasma sample] for estimating relative bioefficacy.Methods: We used model-based compartmental analysis (Simulation, Analysis and Modeling software) to develop and apply a model that provided known values for β-carotene bioefficacy. Theoretical data for 10 subjects were generated by the model and used to determine bioefficacy by RIR and IRM; predictions were compared with known values. We also applied RIR and IRM to previously published data.Results: Plasma RIR accurately predicted β-carotene relative bioefficacy at 14 d or later. IRM also accurately predicted bioefficacy by 14 d, except that, when there was substantial postabsorptive bioconversion, IRM underestimated bioefficacy. Based on our model, 1-d predictions of relative bioefficacy include absorptive plus a portion of early postabsorptive conversion.Conclusion: The plasma RIR is a simple tracer method that accurately predicts β-carotene relative bioefficacy based on analysis of one blood sample obtained at ≥14 d after co-ingestion of labeled β-carotene and retinyl acetate. The method also provides information about the contributions of absorptive and postabsorptive conversion to total bioefficacy if an additional sample is taken at 1 d.

Stable isotope ratio method for the characterisation of the poultry house environment

ABSTRACTStable isotope analysis was applied to describe the poultry house environment. The poultry house indoor environment was selected for this study due to the relevant health problems in animals and their caretakers. Air quality parameters including temperature, relative humidity, airflow rate, NH3, CO2 and total suspended particles, as well as mean levels of total airborne bacteria and fungi count, were measured. Carbon isotope ratios (13C/12C) were obtained in size-segregated aerosol particles. The carbon (13C/12C) and nitrogen (15N/14N) isotope ratios were measured in feed, litter, scrapings from the ventilation system, feathers and eggs. Additionally, the distribution of δ13C and δ15N values in different tissues of the chicken was examined. The airborne bacteria and fungi extracted from the air filters collected from poultry farms were grown in the laboratory in media with known isotope values and measured for stable isotope ratios. Analysis of isotope fractionation between microorganisms and their media indicated the applicability of stable isotope analysis in bulk samples for the identification of source material. The analysed examples imply that stable isotope analysis can be used to examine the indoor environment along with its biology and ecology, and serve as an informative bioanalytical tool.

The occurrence and sources of heavy metal contamination in peri-urban and smelting contaminated sites in Baoji, China.

Atmospheric deposition, soil, plant, ore, and coal cinder samples were collected and analyzed to determine heavy metal concentrations in a typical peri-urban industrial area of Baoji. The lead isotope ratio method was employed to trace the source and dispersion of atmospheric heavy metal contamination. Results showed that concentrations of lead, zinc, cadmium, and copper in atmospheric deposition significantly exceed soil background levels and Chinese soil environmental quality standards. The most polluted sites were located in the downwind direction of the smelter, which confirmed this site to be the major pollution source for this area. The other source of heavy metals in this area is a power plant. The investigation into lead isotopes revealed compositions in atmospheric deposition samples were similar to those in ores and coal cinders identifying smelting as the predominant pollution source of lead with the power plant having a minimal effect. Similar isotopic compositions were also found in plants, indicating that the major source of lead in plants was derived from atmospheric deposition, although some evidence was found to suggest uptake from the soil to the roots as an additional contaminant pathway.

Source identification of nitrate by means of stable nitrogen isotopes in the river Daugava and loads of nitrogen to the Gulf of Riga

ABSTRACTNitrogen isotope ratio of nitrate provides a powerful tool to investigate nitrate sources and cycling mechanisms. Although the use of an isotope ratio method for 15N/14N allows identifying the nitrate sources in rivers by estimating a seasonal variation of N-NO3 concentration, however, there are some restrictions. Nitrification, the conversion of NH4+ to NO3-, can proceed with significant nitrogen isotope fractionation, preferentially accumulating 14N in the produced NO3-, and can make it difficult to identify the nitrate source with a high proportion of the isotope δ15N. However, the uptake and assimilation of NH4+ and NO3- have the capability of affecting isotopic compositions of riverine nitrogen compounds, and this may hinder the determination of whether the impact of the nitrate source with a high proportion of the isotope δ15N reduces. In addition, this study demonstrates that nitrate nitrogen concentration may correlate with δ15NNO3 values both positively and negatively. Such correlations are the result of isotope effects during nitrogen transformation processes (e.g. nitrification and assimilation) and isotopic variability in the various nitrate sources. A comparison of NO3- concentration and δ15NNO3 can be used to further distinguish mixing from biological processing. However, in order to get a more precise answer regarding the nitrate sources, it would be useful to take both the data of nitrogen isotopes and data of oxygen isotopes present in nitrates.