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  • 1
    Language: English
    In: Rapid Communications in Mass Spectrometry, August 30, 2017, Vol.31(16), p.1333(11)
    Description: Byline: Jing Wei, Minghua Zhou, Harry Vereecken, Nicolas Bruggemann Rationale Chemodenitrification is an important N.sub.2O source in soil; however, knowledge about the production of CO.sub.2 and N.sub.2O from abiotic nitrite-SOM reactions, especially the N.sub.2O isotopic signatures (intramolecular .sub.15N site preference (SP), and I[acute accent].sub.15N.sub.bulk and I[acute accent].sub.18O values), is quite limited at present. Methods N.sub.2O and CO.sub.2 emissions from chemical reactions of nitrite with lignin products were determined with gas chromatography, and their response surfaces as a function of pH from 3 to 6 and nitrite concentration from 0.1 to 0.5 mM were explored with polynomial regression. The intramolecular .sub.15N distribution of N.sub.2O, as well as I[acute accent].sub.15N.sub.bulk and I[acute accent].sub.18O values, were measured with an isotope ratio mass spectrometer coupled to an online pre-concentration unit. The variability in N.sub.2O SP values was tested from pH 3 to 5, and for nitrite concentrations from 0.3 to 0.5 mM. Results Both CO.sub.2 and N.sub.2O emissions varied largely with pH and the structure of lignin products. The highest N.sub.2O emission occurred at pH 4-5 in 4-hydroxy-3,5-dimethoxybenzaldehyde and 4-hydroxy-3,5-dimethoxybenzoic acid treatments, and at pH 3 in the treatments with lignin, 4-hydroxy-3-methoxybenzaldehyde, 4-hydroxy-3-methoxybenzoic acid, 4-hydroxybenzaldehyde, and 4-hydroxybenzoic acid. A wide range of N.sub.2O SP values (11.9-37.40/00), which was pH dependent and not distinguishable from microbial pathways, was observed at pH 3-5. The I[acute accent].sub.15N.sub.bulk and I[acute accent].sub.18O values of N.sub.2O were both in a similar range to that reported for fungal denitrification and bacterial denitrification. Conclusions These results present the first characterization of the isotopic composition of N.sub.2O from chemodenitrification in pure chemical assays. Chemical reactions of nitrite with lignin are pH-dependent and associated with substantial CO.sub.2 and N.sub.2O emissions. The SP values of N.sub.2O derived from chemodenitrification were neither distinguishable from the biotic pathways nor remained stable with varying pH. Therefore, the use of N.sub.2O isotopic signatures for source partitioning is restricted when chemodenitrification is contributing significantly to N.sub.2O emission. CAPTION(S): Table S1. Parameters of the mathematical equations for response surfaces of N2O emission from nitrite reactions with lignin and lignin derivatives. Table S2. Parameters of the mathematical equations for response surface of CO2 emission from nitrite reactions with lignin and lignin derivatives. Figure S1. Structures of lignin and lignin derivatives. The proportion of different units in lignin could shift according to its original plant types, and its degree of hydrolysis could also differ depending on the various extraction processes (Stevenson [38]). Figure S2. The N2O and CO2 emissions from the reaction of 0.01 g organosolv lignin and 5 mL of 0.5 mM nitrite solution in water for 24 h. For sterilized treatment, the vials were sterilized at 170[degrees]C for 6 h in an oven, and nitrite solution was sterilized by passing through a 0.2 I1/4m filter. There was no significant difference (P 〉 0.05) between sterilized and unsterilized treatments. Figure S3. Linear regression of O15Nbulk with I[acute accent]15N[alpha] and I[acute accent]15N[beta] values (a), site preference with I[acute accent]15N[alpha] and I[acute accent]15N[beta] values (b), and I[acute accent]15N[alpha] with I[acute accent]15N[beta] values (n = 41). Figure S4. Paired t test to compare the differences of I[micro]15Nbulk between organosolv and alkali lignin (a), 4-hydroxybenzoic acid and 4-hydroxybenzaldehyde (b), 4-hydroxy-3-methoxybenzoic acid and 4-hydroxy-3-methoxybenzaldehyde (c), and 4-hydroxy-3,5-dimethoxybenzoic acid and 4-hydroxy-3,5-dimethoxybenzaldehyde (d). The box indicates the range of the 25 and 75 percentiles of the data, the line in the box is the median, and the notch lines indicate the 1.5 interquartile range. Figure S5. Paired t test to compare the differences of I[micro]18O between organosolv and alkali lignin (a), 4-hydroxybenzoic acid and 4-hydroxybenzaldehyde (b), 4-hydroxy-3-methoxybenzoic acid and 4-hydroxy-3-methoxybenzaldehyde (c), and 4-hydroxy-3,5-dimethoxybenzoic acid and 4-hydroxy-3,5-dimethoxybenzaldehyde (d). The box indicates the range of the 25 and 75 percentiles of the data, the line in the box is the median, and the notch lines indicate the 1.5 interquartile range. Figure S6. Paired t test to compare the differences of site preference between organosolv and alkali lignin (a), 4-hydroxybenzoic acid and 4-hydroxybenzaldehyde (b), 4-hydroxy-3-methoxybenzoic acid and 4-hydroxy-3-methoxybenzaldehyde (c), and 4-hydroxy-3,5-dimethoxybenzoic acid and 4-hydroxy-3,5-dimethoxybenzaldehyde (d). The box indicates the range of the 25 and 75 percentiles of the data, the line in the box is the median, and the notch lines indicate the 1.5 interquartile range. Figure S7. Paired t test to compare the differences of I[acute accent]15N[alpha] between organosolv and alkali lignin (a), 4-hydroxybenzoic acid and 4-hydroxybenzaldehyde (b), 4-hydroxy-3-methoxybenzoic acid and 4-hydroxy-3-methoxybenzaldehyde (c), and 4-hydroxy-3,5-dimethoxybenzoic acid and 4-hydroxy-3,5-dimethoxybenzaldehyde (d). The box indicates the range of the 25 and 75 percentiles of the data, the line in the box is the median, and the notch lines indicate the 1.5 interquartile range. Figure S8. Paired t test to compare the differences of I[acute accent]15N[beta] between organosolv and alkali lignin (a), 4-hydroxybenzoic acid and 4-hydroxybenzaldehyde (b), 4-hydroxy-3-methoxybenzoic acid and 4-hydroxy-3-methoxybenzaldehyde (c), and 4-hydroxy-3,5-dimethoxybenzoic acid and 4-hydroxy-3,5-dimethoxybenzaldehyde (d). The box indicates the range of the 25 and 75 percentiles of the data, the line in the box is the median, and the notch lines indicate the 1.5 interquartile range.
    Keywords: Ph – Environmental Aspects ; Nitrogen Oxides – Environmental Aspects ; Lignin – Environmental Aspects
    ISSN: 0951-4198
    E-ISSN: 10970231
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  • 2
    In: Nature, 2016, Vol.536(7617), p.E1
    Description: In their study, Evaristo et al.1 collected an extensive data set on the basis of which they statistically determined the isotopic compositions of the plant water source (δ 18Ointersect and δ 2Hintersect, called respectively δ 18Ointercept and δ 2Hintercept in their paper) as the x and y coordinates in (δ 18O, δ 2H) space of the intersection between the local meteoric water line (LMWL) and the plant xylem water 'evaporation line' (EL) for a range of climates and vegetation types.
    Keywords: Isotopes ; Groundwater ; Groundwater Recharge ; Stream Flow ; Precipitation ; Botany ; Flowers & Plants;
    ISSN: 0028-0836
    E-ISSN: 1476-4687
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  • 3
    In: Magnetic Resonance in Chemistry, December 2016, Vol.54(12), pp.975-984
    Description: Magnetic impurities are ubiquitous in natural porous media such as sand and soil. They generate internal magnetic field gradients because of increased magnetic susceptibility differences between solid and liquid phase in the pore space and because of the presence of magnetic centers. These internal gradients accelerate NMR relaxation rates and thus might limit the possibility of pore space characterization using NMR. In this study, we investigate the effects of coating the surface of natural sands by the antiferromagnetic iron oxyhydroxide goethite on NMR relaxation and diffusion properties. We found a non‐quadratic dependence of the relaxation time distributions on the echo time indicating that the relaxation experiments were not performed in the fast diffusion limit, while the weak dependence on the external magnetic field strength is explained by the preponderance of the surface relaxation over the effect of diffusion in internal gradients. The surface to volume ratio of the pore space, determined by NMR diffusimetry ((S/V)) remains approximately constant, whereas the same quantity, determined from gas adsorption ((S/V)) increases proportional to the coating density. This is because gas adsorption measures surface roughness on sub‐nanometer scale, whereas NMR diffusimetry averages over structures smaller than few microns. This has consequences for the calculation of the surface relaxivities. The usage of the (S/V) leads to constant values, whereas the usage of (S/V) leads to apparently decreasing relaxivities with increasing coating, which is unrealistic. Copyright © 2016 John Wiley & Sons, Ltd. The diffusion length scale of water in a porous medium composed of sand coated by goethite particles controls both, the surface to volume ratio determined by NMR diffusometry and the relaxation rates. These increase with coating but approach an upper limit when particle distances are shorter than the diffusion lengths. The combination of both yields constant surface relaxivities.
    Keywords: Nmr ; 1 H ; Nmr Relaxometry ; Pfg Nmr ; Surface Relaxivity ; Magnetic Coating ; Porous Media ; Fast Diffusion Limit
    ISSN: 0749-1581
    E-ISSN: 1097-458X
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  • 4
    In: Ecohydrology, September 2018, Vol.11(6), pp.n/a-n/a
    Description: Editors of several journals in the field of hydrology met during the General Assembly of the European Geosciences Union—EGU in Vienna in April 2017. This event was a follow‐up of similar meetings held in 2013 and 2015. These meetings enable the group of editors to review the current status of the journals and the publication process and to share thoughts on future strategies. Journals were represented at the 2017 meeting by their editors, as shown in the list of authors. The main points on invigorating hydrological research through journal publications are communicated in this joint editorial published in the above journals.
    Keywords: Hydrology;
    ISSN: 1936-0584
    E-ISSN: 1936-0592
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