Determination of carbon,nitrogen and phosphorus in cattail using cold neutron prompt-gamma activation analysis

Summary A method for the determination of carbon, nitrogen, and phosphorus in cattail using cold neutron prompt-gamma activation analysis (CNPGAA) has been developed and evaluated through the analysis of standard reference materials (SRM). After extensive preparation, approximately 400 mg cattail samples from the lower Apalachicola River floodplain were irradiated in the CNPGAA facility at the National Institute of Standards and Technology (NIST). The results of numerous field samples and two standard reference materials using the nuclear method show favorable comparison to results obtained by a CHNS/O analyzer.     

Determination of carbon, nitrogen, and phosphorus in cattail using thermal neutron prompt gamma activation analysis

A previous study on the determination of carbon, nitrogen, and phosphorus in cattail using cold neutron prompt gamma activation analysis (CNPGAA) demonstrates that the results of numerous cattail samples showed favorable comparison to results from an elemental analyzer (EA) for C and N. However, the results for P overestimated the results from a UV-VIS spectrophotometer because of the interference of chlorine existing in cattail collected from an estuarine environment. To compare to CNPGAA, a method for the determination of C, N, and P in cattail using thermal neutron prompt gamma activation analysis (TNPGAA) has been developed in the TNPGAA facility at the National Institute of Standards and Technology (NIST) and evaluated through the analysis of standard reference materials (SRMs).     

A comparison between cold and thermal neutron prompt gamma activation analysis in the determination of carbon,nitrogen, and phosphorus in cattail

Methods for the determination of total carbon (TC), total nitrogen (TN), and total phosphorus (TP) in cattail (Typha domingensis) using cold and thermal neutron prompt gamma activation analysis (CNPGAA and TNPGAA) have been developed in the CNPGAA and TNPGAA facilities at the National Institute of Standards and Technology (NIST), and evaluated through the analysis of Standard Reference Materials (SRMs) in previous studies. There are major issues that impact the sensitivities of C, N and P using CNPGAA and TNPGAA including the effects of hydrogen content in samples, sample thickness and Compton scattering. However, interference from chlorine (Cl) in cattails has a major impact on the detection of P. This paper compares the effects of hydrogen content, sample thickness and Compton scattering on the sensitivities of C, N, and P between CNPGAA and TNPGAA and provides a resolution to the Cl interference on P in cattail.     

Effects of sample and spectrum characteristics on cold and thermal neutron prompt gamma activation analysis in environmental studies of plants

Previous studies including the development of methods for the determination of carbon, nitrogen, and phosphorus in cattail using cold neutron prompt gamma activation (CNPGAA) and thermal neutron prompt gamma activation analysis (TNPGAA); evaluation of the precision and accuracy of these methods through the analysis of Standard Reference Materials (SRMs); and comparison of the sensitivity of CNPGAA to TNPGAA have been done in the CNPGAA and TNPGAA facilities at the National Institute of Standards and Technology (NIST). This paper integrates the findings from all of these prior studies and presents recommendations for the application of CNPGAA and TNPGAA in environmental studies of plants based on synergistic considerations of the effects of neutron energy, matrix factors such as chlorine content, Compton scattering, hydrogen content, sample thickness, and spectral interferences from Cl on the determination of C, N, and P. This paper also provides a new approach that simulates a sensitivity curve for an element of interest (S), which is a function of hydrogen content (X) and sample thickness (Y) as follows: S = aX + bY + c (where a, b, and c are constants). This approach has provided more accurate results from the analysis of SRMs than traditional methods and an opportunity to use models to optimize experimental conditions.     

In vivo total body chlorine measurements using prompt-gamma neutron activation analysis

Total body chlorine (TBC1) provides an estimate of extracellular water. We have examined the feasibility of measuring TBC1 using the 5.6, 6.1, and 8.6 MeV C1 peaks produced during in vivo prompt-gamma neutron activation (dose<0.3 mSv). In subjects, background interference permitted the use of only the 8.6 MeV peak in C1 analysis. Preliminary analyses of the prompt-gamma spectra for 33 healthy females (ages: 24–40 yr) provided a mean estimate of 0.85 g C1 per kg body weight. It is therefore feasible to measure TBC1 concurrently with body nitrogen using relatively low-dose prompt-gamma neutron activation analysis.     

Development of a procedure for measuring nitrogen by cold neutron prompt gamma-ray activation analysis

An instrument for cold neutron prompt gamma-ray activation analysis (CNPGAA) has been used for the nondestructive determination of nitrogen. The samples were analyzed in an evacuated box to minimize background from neutron capture by atmospheric nitrogen. The system features lower background and lower detection limits than obtainable with the University of Maryland-National Institute of Standards and Technology (NIST) thermal neutron PGAA instrument. CNPGAA has been used to measure nitrogen in standard reference materials which included biological materials and soils; the results are in agreement with certified values. The detection limit for nitrogen in most biological and geological samples is near 1000 mg kg-1.     

Seasonal Impacts of Solar UV Radiation on Photosynthesis of Phytoplankton Assemblages in the Coastal Waters of the South China Sea

We carried out experiments to evaluate seasonal changes in the impacts of UV radiation (UVR, 280–400 nm) on photosynthetic carbon fixation of phytoplankton assemblages. Surface water samples were obtained in the coastal area of the South China Sea, where chlorophyll a ranged 0.72–3.82 μg L⁻¹. Assimilation numbers (photosynthetic carbon fixation rate per chl a) were significantly higher during summer 2005 than those in spring and winter 2004. The mean values obtained under photosynthetically active radiation (PAR) were 2.83 (spring 2004), 4.35 (winter 2004) and 7.29 μg C (μg chl a)⁻¹ h⁻¹ (summer 2005), respectively. The assimilation numbers under PAR + UVR were 1.58, 2.71 and 5.28 μg C (μg chl a)⁻¹ h⁻¹, for spring, winter and summer, respectively. UVR induced less inhibition of photosynthesis during summer 2005 than during the other seasons, in spite of the higher UVR during summer. The seasonal differences in the productivity and photosynthetic response to UV were mainly due to changes in water temperature, while irradiance and vertical mixing explained >80% of the observed variability. Our data suggest that previous studies in the SCS using UV-opaque vessels might have overestimated the phytoplankton production by about 80% in spring, 61% in winter and 38% in summer.     

Activation cross sections for generation of long-lived radionuclides

The feasibility of measuring total body carbon (TBC) based on prompt-gamma activation analysis (PGAA) of the human body was examined. Preliminary analyzes for 33 healthy pre-menopausal women indicated a range of TBC values (7.1±4.4 kg) which translated to 17.1±6.5 kg body fat (27.9%±7.9% of body weight). An advantage of the PGAA measurement is that fat mass can be obtained simultaneous with that of total body protein mass, both indices serving as useful body composition markers of the nutritional status.     

Transformation and source of nutrients in the Changjiang Estuary

The concentrations of phosphate(PO43-),ammonium,nitrite,nitrate,silicate,dissolved organic nitrogen(DON),dissolved organic phosphorus(DOP),particulate phosphorus(PP)and particulate nitrogen(PN)along the salinity gradient were measured in the Changjiang Estuary in April 2007.The behavior of nutrient species along the continuum from the freshwater to the coastal zone is discussed.In the mixing zone between the riverine and marine waters,nitrate and phosphate behave non-conservatively,while silicate behaves conservatively.Nutrient import was quantified from the river load.Nutrient export to the sea was quantified from river discharge and from the salinity-nutrient gradient in the outer estuary.Using these data,a nitrogen and phosphorus budget was made.The internal estuarine fluxes played an important role in the nutrient estuarine fluxes,which accounted for approximately 41%of the nitrogen flux and 45%of the phosphorus flux.The mixing experiments in the laboratory generally reproduced well the inorganic process affecting nutrient dynamics in the Changjiang Estuary,indicating that the primary P and N transformation processes were phosphate and nitrate desorption along the salinity gradient.     

Phosphorus fractions and phosphate sorption characteristics in relation to the sediment compositions of shallow lakes in the middle and lower reaches of Yangtze River region, China

Phosphorus is recognized as the most critical nutrient limiting lake productivity. The trophic status and development of lake systems are also influenced by the phosphorus content and fractions and phosphate sorption characteristics of the lake sediments. The phosphorus fractions and phosphate sorption characteristics of sediments in shallow lakes from the middle and lower reaches of Yangtze River region in China were investigated. The results show that the phosphorus contents in the sediments ranged from 217.8 to 1640 mg kg(-1); inorganic phosphorus (IP) was the major fraction of total phosphorus (TP); phosphorus bound to Al, Fe, Mn oxides, and hydroxides (Fe/Al-P), and calcium bound phosphorus (Ca-P) were the main fractions of IP. Phosphate sorption on the sediments mainly occurred within 2 h and then reached equilibrium in 10 h. The phosphate sorption rate was closely related to the concentration of fine particles. The phosphate sorption capacity ranged from 128.21 to 833.33 mg kg(-1), showing a significant correlation with the contents of Fe, Fe+Al, total organic carbon (TOC), cationic exchange capacity, total nitrogen, TP, Ca, IP, and the ratio of P/(Al+Fe), and it was higher in the sediments of eutrophic lakes than in mesotrophic lakes. Phosphate was mainly sorbed onto Fe and Al particles. The phosphate sorption efficiency ranged from 26.74 to 312.50 L kg(-1), and had a strong positive correlation with Fe content. For the eutrophic lake sediments, there were no significant relationships between the phosphate sorption efficiency and the selected physical and chemical parameters. But for the mesotrophic lake sediments, the phosphate sorption efficiency was found to be positively related to the contents of Al and Fe+Al.     

Stable carbon, nitrogen, and oxygen isotope analysis as a potential tool for verifying geographical origin of beef

Stable isotope analysis of organic elements such as carbon and nitrogen has been employed as a powerful tool for provenance determination of food materials, because isotopic compositions of the materials reflect many factors in natural environment. In this study, we examined carbon, nitrogen, and oxygen isotope signatures of beef from Australia, Japan, and USA, in order to confirm the method as a potential tool for verifying geographical origin of beef commercially distributed in Japan. Defatted dry matter of beef from USA was characterized by higher carbon isotopic composition (-13.6 per thousand to -11.1 per thousand) than that from Japan (-19.6 per thousand to -17.0 per thousand) and Australia (-23.6 per thousand to -18.7 per thousand). That from Australia was characterized by higher oxygen isotopic composition (+15.0 per thousand to +19.4 per thousand) than that from Japan (+7.3 per thousand to +13.6 per thousand) and USA (+9.5 per thousand to +11.7 per thousand). The oxygen isotopic composition in Japanese beef showed a positive correlation with the isotopic composition of cattle drinking water, the difference in which is clearly latitude dependent. These results suggest that a comparison of carbon, nitrogen, and oxygen isotopic compositions is applicable as a potential tool to discriminate the provenance of beef not only between different countries (i.e. Australia, Japan, and USA) but also among different regions within Japan.     

Determination of Phosphorous and Nitrogen in the Sediment of Lake ‘pamvotis’ (Greece)

Abstract

Phosphorous and nitrogen nutrients in the sediment of the lake Pamvotis were determined by standard methods of analysis. The pore water of the sediment was also analyzed for orthophosphate, ammonia and nitrate content. The results give evidence that nutrient phosphorus content of the sediment is increased at the summer periods and with nitrogen content being available during the whole year gives eutrophic behavior in the lake waters. However, the winter rains reduce the phosphorous content during the spring months. The phosphorus is introduced into the lake by agricultural runoffs and by trenches from urban areas. Several isolated events originating from activities of the inhabitants of the small island and the human activities around the lake give rise to temporary pollution of the lake waters.     

COHN analysis: Body composition measurements based on the associated particle imaging and prompt-gamma neutron activation analysis techniques

The measurement of the body’s carbon (C), oxygen (O), hydrogen (H), and nitrogen (N) content can be used to calculate the relative amounts of fat, protein, and water. A system based on prompt-gamma neutron activation analysis (PGNAA), coupled with the associated particle imaging (API) technique, is being developed for this purpose. A compact D, T neutron generator (∼10⁷ n/s output) with an internal alpha-particle detector is used. The counting system consists of 6 shielded bismuth germanate (BGO) detectors (10.2 cm × 10.2 cm × 10.2 cm) operated with fast-timing electronics to detect only gamma-rays within a 100 ns time window following a trigger pulse generated by the alpha detector. The body can be scanned from the shoulders to the knees within about 30 min, with the equivalent whole-body dose <0.4 mSv. The cumulative gamma-ray spectra in the 2 MeV to 8 MeV region is collected and analyzed for multiple peaks attributed to body C,O,H, and N. Measurement precision for each element, based on tissue-equivalent phantoms, are in the 2–5% range, which are sufficient for population studies in adults. Further improvements are needed to extend the measurements to pediatric clinical research studies.     

Catalytic oxidation with air of cyclohexanone to dicarboxylic acids on synthetic carbons. Effect of supported metals and solvents

The oxidation with air of cyclohexanone was conducted in the presence of synthetic carbons catalysts. The effect of carbon activation treatment (CO2 or air burnoff), phosphorus additive, platinum loading, and nature of the solvent (water or water/acetic acid mixture) were studied. Cyclohexanone oxidation at 140 degrees C yielded a mixture of C6, C5, and C4 dicarboxylic acids. Air activated carbons, including those containing phosphorus or those supporting platinum, resulted in a higher yield of adipic acid. The activity and selectivity was associated with the oxygenated functional groups, essentially carbonyl/quinone groups, created during air activation of the carbon. The incorporation of phosphorus into the carbon increased slightly the selectivity to 34.3%, probably because this additive increased the density of oxygenated functional groups. The deposition of platinum by impregnation and liquid-phase reduction with formaldehyde increased the reaction rate and improved the selectivity to adipic acid, where the highest figure was 38.8%. It was suggested that platinum contributed to molecular oxygen activation. In contrast platinum deposition by cationic exchange followed by reduction under H2 resulted often in a detrimental effect probably because the density of the oxygenated groups on carbon is decreased upon H2 reduction in the presence of platinum. When the oxidation of cyclohexanone was carried out in mixtures of water/acetic acid, the selectivity given by the different samples were quite close and generally smaller than those obtained in water which indicates that acetic acid interacts with the oxygenated surface functional groups responsible for the activity and selectivity. Oxidation experiments with methyl-labeled 4-methylcyclohexanone indicated that glutaric acid was produced by oxidative decarbonylation of both the C1 and C2 carbon atoms of the molecule.     

Prompt gamma-ray activation analysis for certification of sulfur in fuel oil SRMs

A combination of cold neutron prompt gamma-ray activation analysis (CNPGAA) and thermal neutron (TN) PGAA was used to determine sulfur in fuel oils to develop a method to provide values for certification. CNPGAA was used to measure S/H mass ratios, and TNPGAA to measure hydrogen mass fractions. Measurements were combined to determine sulfur mass fractions (with expanded uncertainties) of 2.159 ± 0.072 % for SRM 1622e, 0.7066 ± 0.0120 % for SRM 1619b, and 0.1266 ± 0.0030 % for SRM 1617b, in agreement with certified values. The results validate the method as suitable for certification of sulfur at mass fractions ≥0.1 %.

     

Neutron scattering by hydrogen in cold neutron prompt gamma-activation analysis

The effects of neutron scattering by hydrogen within targets for cold neutron prompt -ray activation analysis (CNPGAA) have been characterized. For most targets studied, the probability for neutron absorption, and hence CNPGAA sensitivities (counts·s^–1·mg^–1), decrease with increasing H content and with target thickness. Comparisons with results from thermal neutron PGAA indicate that the effects of cold neutron scattering differ from those of thermal neutron scattering. CNPGAA sensitivities for l/v nuclides show similar sensitivity decreases, while Sm sensitivities show smaller decreases.     

Differences in the stable isotope signatures of seabird egg membrane and albumen – implications for non‐invasive studies

In many bird species, egg membranes can be obtained non‐invasively after the chicks have hatched, and stable isotope analysis of egg membranes can be used to study the diet and foraging distribution of these birds during egg formation. It has been suggested that the enrichment factors of albumen and egg membranes differ for ¹³C, but are similar for ¹⁵N. In this study, we compared carbon and nitrogen stable isotopes of the membranes and albumen of individual eggs of three wild seabird species, the Southern Rockhopper penguin Eudyptes chrysocome, the Imperial shag Phalacrocorax atriceps albiventer, and the Thin‐billed prion Pachyptila belcheri. We also included chicken eggs for comparison. Egg membranes were generally enriched in ¹³C, compared with albumen. The difference varied between species, with 2.1‰ in Rockhopper penguins, 1.6‰ in Imperial shags, but only 0.5‰ in Thin‐billed prions and 0.4‰ in chicken eggs. Egg membranes were slightly enriched in ¹⁵N in Imperial shags (0.9‰) and chickens (0.5‰), compared with albumen, while there was no difference for Thin‐billed prions and Rockhopper penguins. The isotopic values of carbon and nitrogen were correlated between albumen and egg membranes of individual eggs, suggesting that egg membranes can be used reliably to investigate trophic differences between individuals, seasons or colonies. Species‐specific mathematical corrections could be used to compare results across studies that use different egg components. Copyright © 2009 John Wiley & Sons, Ltd.     

Educational Web site: Radioisotopic methods of determining body composition

We have designed a Web site intended to inform the general public aboutexisting nuclear technologies based on the measurement of radioisotopes inthe human body. The presentation is focused on the concept of radioisotopemeasurements for determination of body composition (bone, muscle, water, fat),and the risks, benefits, and clinical applications of these techniques. Procedurescovered are ⁴⁰K whole body counting, delayed-gamma neutron activation,prompt-gamma neutron activation, and dual-energy X-ray absorptiometry. Theinformation presented is tailored for the nonscientific public, in order topromote familiarity with and understanding of the basic concepts of radioisotopemeasurements in the human body. Further development of the site will includegreater scientific detail, suitable for student instruction or for continuingeducation requirements of various certification programs.     

MBBR两种填料对养猪废水脱氮除磷效果对比

为了探讨移动床生物膜反应器中不同填料对废水脱氮除磷效果的影响,采用碳纤维球和聚乙烯塑料两种不同悬浮填料进行对比试验。在不同运行条件下,分别测定氨氮、总氮、总磷、COD等指标,对比挂膜和脱氮除磷效果。结果表明,碳纤维球填料挂膜速度快,在不同运行条件下均比聚乙烯塑料填料对COD、NH4+-N、TN、TP等的去除效果好,去除率分别可达91.2%、98.0%、77.5%、68.1%。这说明比表面积大、孔隙率高的填料挂膜更快,挂膜量更多,更有利于实现同时生物脱氮除磷。