Effects of ions on water structure: a low-field (1) H T1 NMR relaxometry approach

Aqueous salt solutions play an important role in nature because of their effects on environmental biogeochemical processes and on structural properties of biomolecules. Upon dissolution, salts split in ions that are solvated. Water in hydration shells is subjected to molecular motions that can be monitored by (1) H T1 NMR relaxometry. This technique allowed the evaluation of the nature of the interactions between water and ions via variable temperature experiments. Examination of relaxometry properties of aqueous solutions at variable salt concentrations allowed acknowledgement of the role played by ions in either structuring or destructuring water aggregates. A mathematical model has been applied on six environmentally relevant salts: NaCl, KCl, CaCl2 , CaCO3 , NaNO3 , and NH4 NO3 . It was linear only for the concentration dependence of KCl-R1 . This model accorded with the one reported in literature where it has been considered valid only for diluted solutions. However, in the present study, the range of linearity for KCl was extended up to the saturation point. The model was modified for NaCl, CaCl2 , and CaCO3 by using it as an exponential form in order to account for the nonlinearity of the R1 -versus-concentration curves. Nonlinearity was explained by the nonnegligible ion-ion interactions occurring as concentration was increased. Finally, further modification was needed to account for the asymmetric distribution of water around nitrate (in NaNO3 and NH4 NO3 ) and ammonium (in NH4 NO3 ). This study is preliminary to the comprehension of the diffusion mechanisms of ions in water solutions at the equilibrium condition with solid surfaces such as soils and biochar-amended soils. Copyright © 2014 John Wiley & Sons, Ltd

Biochar, soil fertility, and environment

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conformational redistribution of honey components following different storage conditions

The present study aims at the investigation of the changes in water distribution among the organic components of selected honey samples following honey storage at different temperatures. Results, achieved by application of fast field cycling NMR relaxometry, revealed that the organic constituents were homogeneously distributed within the whole samples stored at room temperature. Conversely, after four months of refrigeration at 4°C, the organic systems were included in persistent clusters, as a consequence of the water release due to the larger stability of the intramolecular interactions over the intermolecular ones. The new conformational arrangements of the honey constituents entailed enhancement of honey moisture content. For this reason, it can be suggested that honey refrigeration prior to storage at room temperature may be detrimental for its long-term storage. In fact, higher risk of fermentation may occur once the sample is warmed after the first refrigeration step

Biochar Effects on Ce Leaching and Plant Uptake in Lepidium sativum L. Grown on a Ceria Nanoparticle Spiked Soil

The increasing use of nanoparticles is causing a threat to the environment and humans. The aim of this work was to evaluate the effects of the quenching procedure of biochar production on the biochar capacity to retain the CeO2 nanoparticle (CeO2NP) in soil. The effects on Lepidium sativum L. (watercress) were considered. Two biochars were produced from fir wood pellets under the same pyrolysis conditions but with different quenching procedures: dry quenching and wet quenching. The two biochars (BCdryQ and BCwetQ) were separately added to a CeO2NP-spiked soil (1000 mg kg−1) at the dose 5%DW and placed in 12 lysimeters under controlled conditions. Lepidium sativum L. seeds were sowed on each lysimeter. The lysimeters were irrigated once a week for 7 weeks, and the leachates were collected. At the end of the experiment, the aboveground biomass was harvested; the total number of plants and the number of plants at the flowering stage were counted, and the height of the tallest plant and the total dry biomass were measured. The data showed that the quenching procedure influences the CeO2NP retention in soil, and BCdryQ can reduce the leaching of the nanoparticles. Biochar significantly increased the flowering in plants, and BCwetQ reduced the biomass production. This work highlights the importance of the biochar production process for soil applications. The production settings are crucial in determining the efficacy of the product for its ultimate use

Effect of pruning-derived biochar on heavy metals removal and water dynamics

Biomass-derived biochar is considered as a promising heavy metal adsorbent, due to abundance of polar functional groups, such as carboxylic, hydroxyl, and amino groups, which are available for heavy metal removal. The aims of this study were to evaluate the effectiveness of an orchard pruning-derived biochar in removing some heavy metals (through the evaluation of isotherms) and to study water dynamics at the solid-liquid interface as affected by heavy metal adsorption (through an innovative nuclear magnetic resonance (NMR) relaxometry approach). Both isotherms and NMR spectra revealed that Pb and Cr showed a good affinity for the biochar surface (Pb > Cr), while Cu was less affine. Accordingly, higher amounts of Pb and Cr were adsorbed by biochar as compared to those of Cu in the single systems. In binary systems (i.e., when two metals were applied simultaneously), Pb showed the highest inhibition of the adsorption of the other two metals, whereas the opposite was evidenced when Cu was used; the competitive adsorption was also strongly influenced by the metal residence time on biochar surface. In ternary systems (i.e., when all metals were applied simultaneously), even in the presence of high amounts of Pb and Cr, considerable adsorption of Cu occurred, indicating that some biochar adsorption sites were highly specific for a single metal

Conformational Redistribution of Honey Components following Different Storage Conditions

The present study aims at the investigation of the changes in water distribution among the organic components of selected honey samples following honey storage at different temperatures. Results, achieved by application of fast field cycling NMR relaxometry, revealed that the organic constituents were homogeneously distributed within the whole samples stored at room temperature. Conversely, after four months of refrigeration at 4°C, the organic systems were included in persistent clusters, as a consequence of the water release due to the larger stability of the intramolecular interactions over the intermolecular ones. The new conformational arrangements of the honey constituents entailed enhancement of honey moisture content. For this reason, it can be suggested that honey refrigeration prior to storage at room temperature may be detrimental for its long-term storage. In fact, higher risk of fermentation may occur once the sample is warmed after the first refrigeration step

Hydration and water holding properties of cross-linked lignite humic acids

Lignite and lignite humic acids, which are used as soil amendments sometimes, are supposed to improve soil properties such as water holding capacity. The structure of those materials is composed of various organic molecules stabilized mostly byweak interactions. Therefore, excess ofwater causes only partial swelling, but most of the physical structure is destabilized. This accelerates the desiccation and hampers their application as natural hydrogel-like substances. In order to stabilize the structure of lignite humic acids and improve the water holding capacity, we applied formaldehyde cross-linking procedure based on covalent coupling of aromatic humic acids moieties. By combining the 1H NMR relaxometry and methods of thermal analysis, the kinetics and degree of hydration, water distribution and moisture uptake were investigated. It was found that cross-linking induced a reduction in moisture sorption capacity at lowrelative humidity and an increase at higher relative humidity,which was attributed to the separation of functional groups and decreasing of structural compactness after crosslinking. As a result, the cross-linked humic acids, exhibited faster water uptake and approximately three-fold higher water holding capacity in comparison with the parental sample. The distribution of relaxation times of water protons in swollen humic acids revealed the unification of pore size distribution upon cross-linking. Although the improved hydration of cross-linked lignite humic acids already resembles the hydration of some hydrophilic polymers, the water holding capacity is still belowthe capacity of classical hydrogels. Nevertheless, the lowprice of lignite, sorption properties and its overall positive affect on soil quality and productivity give a promise in application of this material both in agriculture and remediation technologies