The Experts below are selected from a list of 243 Experts worldwide ranked by ideXlab platform
Jeffrey P. Chanton - One of the best experts on this subject based on the ideXlab platform.
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Methane Oxidation In Landfill Cover Soils
GeoFlorida 2010, 2010Co-Authors: Jeffrey P. Chanton, Tarek Abichou, Gary R. Hater, Roger B. Green, Jean E. BognerAbstract:Microbial methane oxidation in landfill cover soil is a very effective approach for reducing emissions from landfills. Oxidation of methane may be enhanced by the application of materials present on site, such as yard waste or compost. Engineers require a method to quantify methane oxidation in different types of covers. In this paper we will present a simple, effective stable Isotope Technique for the evaluation of cover soil methane oxidation. The approach exploits systematic variations in the ratio of 13 C/ 12 C in CH4 prior to and following exposure to methane oxidizing microbes in the soil. The action of the bacteria increases this ratio, due to their preference for utilizing 12 CH4 rather than 13 CH4. The shift in the ratio following
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methane oxidation in swedish landfills quantified with the stable carbon Isotope Technique in combination with an optical method for emitted methane
Environmental Science & Technology, 2007Co-Authors: Gunnar Börjesson, Jerker Samuelsson, Jeffrey P. ChantonAbstract:Methane budgets (production = emissions + oxidation + recovery) were estimated for six landfill sites in Sweden. Methane oxidation was measured in downwind plumes with a stable Isotope Technique (Chariton, J. P., et al., Environ. Sci. TechnoL 1999, 33, 3755-3760.) Positions in plumes for Isotope sampling as well as methane emissions were determined with an optical instrument (Fourier Transform InfraRed) in combination with N2O as tracer gas (Galle, B., et al., Environ. Sci. TechnoL 2001, 35,21-25.) Two landfills had been closed for years prior to the measurements, while four were active. Measurements at comparable soil temperatures showed that the two closed landfills had a significantly higher fraction of oxidized methane (38-42% of emission) relative to the four active landfills (4.6-15% of emission). These results highlight the importance of installing and maintaining effective landfill covers and also indicate that substantial amounts of methane escape from active landfills. Based on these results we recommend that the IPCC default values for methane oxidation in managed landfills could be set to 10% for active sites and 20% for closed sites. Gas recovery was found to be highly variable at the different sites, with values from 14% up to 65% of total methane production. The variance can be attributed to different waste management practices.
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methane oxidation in two swedish landfill covers measured with carbon 13 to carbon 12 Isotope ratios
Journal of Environmental Quality, 2001Co-Authors: Gunnar Börjesson, Jeffrey P. Chanton, Bo H. SvenssonAbstract:The release of methane (CH4) from landfills to the atmosphere and the oxidation of CH( in the cover soils were quantified with static chambers and a C-13-Isotope Technique on two landfills in Sweden. One of the landfills had been closed and covered 17 years before this investigation while the other was recently covered. On bath landfills, the tops of the landfills were compared with the sloping parts in the summer and winter. Emitted CH4, captured in chambers, was significantly enriched in C-13 during summer compared with winter (P < 0.0001), and was enriched relative to anaerobic-zone methane, The difference between emitted and anaerobic zone delta C-13-CH4 was used to estimate soil methane oxidation. In summer, these differences ranged from 9 to 26 parts per thousand, and CA(4) oxidation was estimated to be between 41 and 50% of the produced CHI in the new landfill, and between 60 and 94% in the old landfill. In winter, when soil temperature was below 0 degreesC, no difference in delta C-13 was observed between emitted and anaerobic-zone CH4 suggesting that there was no soil oxidation. The temperature effect shown in this experiment suggests that there may be both seasonal and latitudinal differences in the importance of landfill CH4 oxidation. Finally the isotopic fractionation factor to) varied from 1.023 to 1.038 and was temperature dependent, increasing at colder temperatures. Methanotrophic bacteria appeared to have high growth efficiencies and the majority of the methane consumed in incubations did not result in immediate CO2 production.
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seasonal variation in methane oxidation in a landfill cover soil as determined by an in situ stable Isotope Technique
Global Biogeochemical Cycles, 2000Co-Authors: Jeffrey P. Chanton, Karen LiptayAbstract:Seasonal variations in the oxidation of methane during its transport across the soil cap of a landfill in Leon County, Florida, were determined in situ with a stable isotopic Technique. The approach contrasted the δ13C values of emitted and anoxic zone CH4 and utilized measurements of the isotopic fractionation factor α, which varied inversely with temperature from 1.025 to 1.049. Anoxic zone CH4 did not vary seasonally and had a δ13C average value of −55.18 ± 0.15‰. Methane emitted from the landfill soil surface and captured in chambers ranged in δ13C from −54‰ in winter, when emission rates were high, to −40‰ in summer, when emission rates were lower. The antipathetic variation between the δ13C of emitted CH4 and the rate of CH4 emission is consistent with control of the emission rate by bacterial oxidation. Our interpretation of the Isotope data indicates that methane oxidation consumed from 3 to 5% of the total flux in winter to a maximum of 43 ± 10% in summer. There was variation in the extent of methane oxidation in soil types, with mulch/topsoil averaging 55 ± 14% and clay averaging 33 ± 13% in summer. The seasonally integrated value for methane oxidation for areas of the landfill covered with mulch/topsoil was 26 ± 4% of the flux toward the soil surface, while for clay soil it was only 14 ± 2%. The overall annual average, which includes both types of soil, was 20 ± 3%. Covering landfills with additional mulch, which can be generated from yard waste, may attenuate methane emission by providing a loose noncompact substrate for bacterial attachment and an environment with moisture, methane, and oxygen. At specific sites within the landfill we studied, temperature was the main factor controlling methane oxidation.
Penni Davila - One of the best experts on this subject based on the ideXlab platform.
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calcium and zinc absorption from lactose containing and lactose free infant formulas
The American Journal of Clinical Nutrition, 2002Co-Authors: Steven A Abrams, Ian J Griffin, Penni DavilaAbstract:BACKGROUND: Calcium absorption is enhanced by the presence of lactose, but the quantitative significance of this effect in infant formulas is uncertain. It is also not known whether lactose affects zinc absorption. OBJECTIVE: We measured the absorption of calcium and zinc from infant formulas by using a multitracer, stable-Isotope Technique. DESIGN: Eighteen full-term infants (aged 8-12 wk at enrollment) were fed 2 partially hydrolyzed whey-protein-based formulas ad libitum for 2 wk per formula. The carbohydrate source was lactose in one formula and glucose polymers in the other (lactose-free). Infants were studied in a blinded crossover fashion after 2 wk of adaptation to each formula. Isotope absorption studies were conducted with a 4-tracer method in which (70)Zn and (44)Ca were provided orally and (67)Zn and (46)Ca intravenously. Zinc and calcium absorption was measured from the fractional excretion of the oral and intravenous Isotopes in urine. RESULTS: Fractional and total calcium absorption was significantly greater from the lactose-containing formula than from the lactose-free formula. For total calcium absorption, the mean difference between formulas was 10.3% (P = 0.002) and 60 mg/d (P = 0.006). For zinc, fractional absorption (32 +/- 11%), total absorption, and intake did not differ significantly between the 2 formulas. CONCLUSIONS: The presence of lactose in a formula based on cow-milk protein increases absorption of calcium but not of zinc. Absorption of calcium from a lactose-free infant formula is, however, adequate to meet the calcium needs of full-term infants when the formula's calcium content is similar to that of lactose-containing, cow-milk-based infant formulas.
Gunnar Börjesson - One of the best experts on this subject based on the ideXlab platform.
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methane oxidation in swedish landfills quantified with the stable carbon Isotope Technique in combination with an optical method for emitted methane
Environmental Science & Technology, 2007Co-Authors: Gunnar Börjesson, Jerker Samuelsson, Jeffrey P. ChantonAbstract:Methane budgets (production = emissions + oxidation + recovery) were estimated for six landfill sites in Sweden. Methane oxidation was measured in downwind plumes with a stable Isotope Technique (Chariton, J. P., et al., Environ. Sci. TechnoL 1999, 33, 3755-3760.) Positions in plumes for Isotope sampling as well as methane emissions were determined with an optical instrument (Fourier Transform InfraRed) in combination with N2O as tracer gas (Galle, B., et al., Environ. Sci. TechnoL 2001, 35,21-25.) Two landfills had been closed for years prior to the measurements, while four were active. Measurements at comparable soil temperatures showed that the two closed landfills had a significantly higher fraction of oxidized methane (38-42% of emission) relative to the four active landfills (4.6-15% of emission). These results highlight the importance of installing and maintaining effective landfill covers and also indicate that substantial amounts of methane escape from active landfills. Based on these results we recommend that the IPCC default values for methane oxidation in managed landfills could be set to 10% for active sites and 20% for closed sites. Gas recovery was found to be highly variable at the different sites, with values from 14% up to 65% of total methane production. The variance can be attributed to different waste management practices.
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methane oxidation in two swedish landfill covers measured with carbon 13 to carbon 12 Isotope ratios
Journal of Environmental Quality, 2001Co-Authors: Gunnar Börjesson, Jeffrey P. Chanton, Bo H. SvenssonAbstract:The release of methane (CH4) from landfills to the atmosphere and the oxidation of CH( in the cover soils were quantified with static chambers and a C-13-Isotope Technique on two landfills in Sweden. One of the landfills had been closed and covered 17 years before this investigation while the other was recently covered. On bath landfills, the tops of the landfills were compared with the sloping parts in the summer and winter. Emitted CH4, captured in chambers, was significantly enriched in C-13 during summer compared with winter (P < 0.0001), and was enriched relative to anaerobic-zone methane, The difference between emitted and anaerobic zone delta C-13-CH4 was used to estimate soil methane oxidation. In summer, these differences ranged from 9 to 26 parts per thousand, and CA(4) oxidation was estimated to be between 41 and 50% of the produced CHI in the new landfill, and between 60 and 94% in the old landfill. In winter, when soil temperature was below 0 degreesC, no difference in delta C-13 was observed between emitted and anaerobic-zone CH4 suggesting that there was no soil oxidation. The temperature effect shown in this experiment suggests that there may be both seasonal and latitudinal differences in the importance of landfill CH4 oxidation. Finally the isotopic fractionation factor to) varied from 1.023 to 1.038 and was temperature dependent, increasing at colder temperatures. Methanotrophic bacteria appeared to have high growth efficiencies and the majority of the methane consumed in incubations did not result in immediate CO2 production.
S Fairweather-tait - One of the best experts on this subject based on the ideXlab platform.
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Can a double Isotope method be used to measure fractional zinc absorption from urinary samples?
European Journal of Clinical Nutrition, 1997Co-Authors: A Rauscher, S Fairweather-taitAbstract:Objective: This study was designed to test whether fractional absorption calculated from urinary enrichment of stable Isotopes of zinc accurately reflects true absorption measured by faecal monitoring. Design: The two Techniques were directly compared in volunteers, whereby each subject acted as his/her own control. Setting: Volunteers were healthy adults, living at home, who were taking part in a larger study on zinc. They attended the local hospital for Isotope administration. Subjects: Fifteen volunteers were recruited, seven of whom had non-insulin dependent diabetes mellitus. All completed the study, but five did not carry out a complete faecal collection. Interventions: Each subject received an oral and i.v. dose of different stable Isotopes of zinc with breakfast. Faecal and urinary enrichment with the Isotopes was measured. Results: There was no significant correlation between the two measures of absorption. Conclusions: The double label stable Isotope Technique for determining zinc absorption from measurements of urinary enrichment does not reliably predict true zinc absorption (measured by faecal and urinary monitoring) in a heterogenous group of adults given relatively low doses of stable Isotopes of zinc. Sponsorship: This work was funded by the European Commission (Training and Mobility Programme).
Peter Kastenmayer - One of the best experts on this subject based on the ideXlab platform.
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dephytinisation of soyabean protein isolate with low native phytic acid content has limited impact on mineral and trace element absorption in healthy infants
British Journal of Nutrition, 2004Co-Authors: Lena Davidsson, Peter Kastenmayer, Ekhard E Ziegler, Peter Van Dael, Denis BarclayAbstract:Infant formulas based on soyabean protein isolate are often used as an alternative to cows'-based formulas. However, the presence of phytic acid in soya formulas has raised concern about the absorption of trace elements and minerals from these products. The aim of the present study was to evaluate mineral and trace element absorption from regular and dephytinised soya formula in healthy infants. Soyabean protein isolate with a relatively low native content of phytic acid was used for production of a regular soya formula (300 mg phytic acid/kg liquid formula) and an experimental formula was based on dephytinised soya protein isolate (<6mg phytic acid/kg liquid formula). Using a crossover study design, apparent mineral and trace element absorptions were measured by a stable Isotope Technique based on 72 h faecal excretion of non-absorbed stable Isotopes (Zn, Fe, Cu and Ca) and by the chemical balance Technique (Mn, Zn, Cu and Ca) in nine infants (69-191 d old). Fe absorption was also measured by erythrocyte incorporation 14d after intake. The results from the present study demonstrated that Zn absorption, measured by a stable Isotope Technique, was significantly greater after dephytinisation (mean value 16.7 v. 22.6%; P=0.03). No other statistically significant differences between the two formulas were observed. The nutritional benefit of dephytinisation was marginal in the present study. Based on these results, the use of soyabean protein isolate with low native content of phytic acid should be promoted for production of soya formulas and adequate addition of ascorbic acid to enhance Fe absorption should be ensured in the products.
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calcium bioavailability from a calcium and sulfate rich mineral water compared with milk in young adult women
The American Journal of Clinical Nutrition, 1995Co-Authors: Francois Couzy, Peter Kastenmayer, M Vigo, Jennifer Clough, R Munozbox, Denis BarclayAbstract:Some mineral waters have a high calcium content and may contribute a significant part of the human daily requirements. Calcium bioavailability from a calcium- and sulfate-rich mineral water (CS-W) containing 11.2 mmol Ca/L (467 mg/L) was compared with that from milk in nine healthy young women. Calcium absorption was measured in the fasting state with a dual-label stable-Isotope Technique. Fractional absorption rates from milk and CS-W were 25.0 ± 6.7% and 23.8 ± 4.8% (x ± SD), respectively, and did not differ significantly (P = 0.05). Urine was collected for 36 h after the administration of the oral stable Isotope while the subjects consumed a controlled diet and a quantity of milk or CS-W providing 25 mmol (1000 mg) Ca. No significant difference was found in the excretion of calcium, nor in the excretion of the two stable Isotopes. Mean urinary sulfate excretion was significantly increased by 35% when the CS-W was consumed. No significant correlation was found between 36-h urinary excretion of the intravenous calcium tracer and sulfate, sodium, or urine volume. Therefore, calcium from the CS-W was as well absorbed and retained as that from milk, and no calciuric effect of sulfate was found, showing that such mineral waters can be valuable dietary sources of calcium.
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iron bioavailability studied in infants the influence of phytic acid and ascorbic acid in infant formulas based on soy isolate
Pediatric Research, 1994Co-Authors: Lena Davidsson, Peter Kastenmayer, Serge Hercberg, Pilar Galan, F Cherouvrier, Marcel Alexandre Juillerat, Richard F HurrellAbstract:ABSTRACT: The influence of phytic acid and ascorbic acid content of soy formula on iron (Fe) bioavailability was investigated in infants by analysis of the incorporation of stable Isotopes of Fe into red blood cells 14 d after administration using a double stable Isotope Technique. Paired comparisons were made with each infant acting as his or her own control. The geometric mean fractional Fe incorporation into red blood cells increased from 5.5 to 6.8% (p<0.05) when soy formula with the native content of phytic acid was compared with a 83% dephytinized formula. A more pronounced effect was shown with soy formula containing no phytic acid; the mean fractional Fe incorporation increased from 3.9 (native phytic acid) to 8.7% (zero phytic acid; p < 0.001). A significant (p < 0.01) effect was also demonstrated when the Fe:ascorbic acid molar ratio in the native phytate-containing formula was increased from 1:2.1 to 1:4.2; mean fractional Fe incorporation increased from 5.9 to 9.6%. These results demonstrate that the Fe bioavailability from soy-based infant formulas can be similarly increased by either removing phytic acid or increasing the ascorbic acid content.
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a double stable Isotope Technique for measuring iron absorption in infants
British Journal of Nutrition, 1994Co-Authors: Peter Kastenmayer, Lena Davidsson, Pilar Galanz, Francise Cherouvrier, Serge Hercberg, Richard F HurrellAbstract:: A stable Isotope Technique has been developed which uses 57Fe and 58Fe as labels and which enables the simultaneous measurement of Fe absorption from two test meals in infants. The method was evaluated by measuring Fe absorption from a commercial whey-adjusted infant formula in nine healthy infants aged 13-25 weeks. Each infant was fed 210 ml formula, labelled with either 57Fe or 58Fe, on four consecutive mornings, in random order. The total Fe content in each feed was 2.5 mg Fe; either as 2.5 mg 57Fe, or 0.6 mg 58Fe plus 1.9 mg Fe with normal isotopic composition. Isotopic enrichment of Fe in erythrocytes was measured by thermal ionization mass spectrometry 14 d after the last administration, and Fe absorption was calculated based on Isotope ratio shifts, total circulating Fe and intake of each Isotope. Geometric mean absorption for the 57Fe and 58Fe labels was 6.72 and 6.58% respectively, and the absorption of the two Isotopes was not significantly different (Student's paired t test). By this Technique, paired comparisons of Fe absorption can be obtained and systematic studies of the influence of dietary factors on Fe absorption during infancy can be conducted.