Improve NMR estimation of water content and distribution in unsaturated bedrocks

<p>Nuclear magnetic resonance (NMR) has been widely used in near-surface geophysics due to its direct sensitivity to water. As a field form of NMR, borehole NMR has been applied to in situ hydrological investigations for decades. However, the recent implementations of borehole NMR to unsaturated zones face challenges due to the complex geology. Due to the fast operation speed and unsaturated conditions in critical zones, the raw NMR signals often suffer from limited relaxation time ranges and low signal to noise ratios. Such low quality of raw data can induce artifacts during inversion and following data interpretations. This study investigates the long-overdue evaluations of how the low borehole NMR data quality affects water distribution estimation in unsaturated zones. A synthetic analysis based on lab NMR data was first performed to simulate the inversion errors induced by the low-quality borehole NMR data. Lab NMR measurements were conducted on carbonate and shale samples from a well that has a corresponding borehole NMR profile. In order to match the low signal-to-noise ratio and data size of the low-quality borehole NMR data, lab NMR data points were reduced, deadtime was increased and normally distributed noise was added.  The inversion results of the synthetic data reveal that the low signal to noise ratio leads to an overestimation of signals at lower relaxation time while the limited relaxation time range does not significantly affect the total water estimation. To improve the water estimation from the low-quality borehole data, a peak decomposition and peak fusion method were then applied to the synthetic data. Relaxation time distribution of both lab and synthetic data were decomposed into multiple normally distributed peaks. The first peak with the shortest relaxation time from lab NMR was used to substitute the first peak of the synthetic borehole NMR relaxation time distribution. After peak decomposition and fusion, the predicted water contents were closer to lab NMR than original synthetic data. This study reveals the mispredictions of water distribution due to the low data quality of borehole NMR. The success of improving water content estimation on the synthetic study has clear implications that the peak decomposition and peak fusion method can be applied to actual borehole NMR data to improve water content and distribution estimation in unsaturated zones.   </p>

Fabrication of lignocellulosic biomass paper containing nanofibrillated biomass

Fibrillated cellulose has been frequently used for making nanopapers and thin films. However, limited work has been carried out in the construction of such materials using native lignocellulosic biomass. Making papers from fibrillated biomass allows complete utilization of whole plant material and may reduce chemical and energy consumption. Ultra-friction grinding was used to directly fibrillate knife-milled poplar into micro- to nano-sized biomass fibers. Papers were made using the fibrillated biomass containing nanofibrillated biomass and their mechanical properties were tested. Biomass papers made via press-drying had higher tensile strength than papers made by air-drying. A higher press-drying temperature of 180 °C produced stronger papers than at 150 °C. Guar gum substantially increased the strength of the press-dried papers in comparison to cationic starch. Press-drying increased the thermogravimetric peak decomposition temperature by 13 °C in comparison to air-drying.

Thermal stability of N-heterocycle-stabilized iodanes – a systematic investigation

The thermal stability of pseudocyclic and cyclic N-heterocycle-stabilized (hydroxy)aryl- and mesityl(aryl)-λ3-iodanes (NHIs) through thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) is investigated. Peak decomposition temperatures (T peak) were observed within a wide range between 120 and 270 °C. Decomposition enthalpies (ΔH dec) varied from −29.81 to 141.13 kJ/mol. A direct comparison between pseudocyclic and cyclic NHIs revealed high T peak but also higher ΔH dec values for the latter ones. NHIs bearing N-heterocycles with a high N/C-ratio such as triazoles show among the lowest T peak and the highest ΔH dec values. A comparison of NHIs with known (pseudo)cyclic benziodoxolones is made and we further correlated their thermal stability with reactivity in a model oxygenation.

Possible effects of irrigation with wastewater on the clay mineralogy of some Australian clayey soils: laboratory study

Potassium is common in a wide variety of wastewaters and in some wastewaters is present at several hundred to several thousand mg L–1. Potassium is taken up by expandable clays leading to its fixation and illitisation of smectitic and vermiculitic layers. Hence the addition of wastewaters to soils may lead to mineralogical changes in the soils that affect their physico-chemical properties. Winery wastewater was equilibrated with clay-rich soils from Southern Australia. X-ray diffraction patterns and chemical composition of clays extracted from untreated and treated soils were determined. In three of the four soils, shifts in peak positions occurred towards more illitic components along with increases in K and sometimes also Mg and Na contents of soil clays. Peak decomposition showed trends towards the formation of interstratifications of illite with smectite at the expense of smectite and an alteration of poorly crystallised illite into its more well-ordered forms. The results show that illitisation may occur as a result of the addition of K-rich wastewaters to clayey soils.