Wantong Zhang,Xiuping Tao,Zhengyi Hu,Enze Kang,Zhongqing Yan,Xiaodong Zhang,Jinzhi Wang
Alpine peatlands are recognized as a weak or negligible source of nitrous oxide (N 2 O). Anthropogenic activities and climate change resulted in the altered water table (WT) levels and increased nitrogen (N) deposition, which could potentially transition this habitat into a N 2 O emission hotspot. However, the underlying mechanism related with the effects is still uncertain. Hence, we conducted a mesocosm experiment to address the response of growing-season N 2 O emissions and the gene abundances of nitrification (bacterial amoA ) and denitrification ( narG , nirS , norB and nosZ ) to the increased N deposition (20 kg N ha −1 yr −1 ) at two WT levels (WT − 30 , 30 cm below soil surface; WT 10 , 10 cm above soil surface) in the Zoige alpine peatland, Qinghai-Tibetan Plateau. The results showed that the WT did not affect N 2 O emissions, and this was attributed with the limitation of soil NO 3 − . The higher WT level increased denitrification ( narG and nirS gene abundance) resulting in the depletion of soil NO 3 − , but the consequent NO 3 − deficiency further limited denitrification, while the WT did not affect nitrification (bacterial amoA gene abundance). Meanwhile, the N deposition increased N 2 O emissions, regardless of WT levels. This was associated with the N-deposition induced increase in denitrification-related gene abundances of narG , nirS , norB and nosZ at WT − 30 and narG at WT 10 . Additionally, the N 2 O emission factor assigned to N deposition was 1.3 % at WT − 30 and 0.9 % at WT 10 , respectively. Our study provided comprehensive understanding of the mechanisms referring N 2 O emissions in response to the interactions between climate change and human disturbance from this high-altitude peatland.
The binding behavior between soy protein isolate (SPI) and homologous ketones was examined in this study. Three ketones (2-hexanone, 2-heptanone, and 2-octanone) with different carbon chain lengths were selected to investigate the interaction mechanism between SPI and ketones, and three ketones with positional isomers, namely 2-nonanone, 3-nonanone, and 4-nonanone, were used to construct different steric effect. Ultraviolet, fluorescence, and circular dichroism results showed that ketones induced the conformational perturbations of SPI, weakening the polarity of the environment in which the chromogenic group was located and triggering the quenching of SPI intrinsic fluorescence. Hydrophobic site competition experiments revealed that the presence of steric hindrance hindered the collision of compounds with SPI active site. The optimal binding locus for ketones within the SPI structure was determined by molecular docking, and two key amino acids, LYS412 and ASN484, were found. The calculated binding energy (-25.682 ∼ -17.952 kcal mol −1 ) and steric energy (7.883 ∼ 14.894 kcal mol −1 ) of ketones showed that steric effects played a negative role in the binding of SPI to flavor compounds, but this role was weaker than hydrophobic interactions and hydrogen bonding. The improved understanding of the role of carbon chain lengths and steric hindrance on ketone retention could support the flavor product designer or scientists to optimize flavor retention and delivery.
The growing demand for lithium-based materials stems predominantly from the rapid proliferation of renewable energy technologies. Given the growing demand for lithium, extracting the metal from salt lake brines has gained significant research attention. While positively charged nanofiltration (NF) membranes exhibit promising Mg2+/Li+ separation efficacy, the interfacial polymerization technique remains constrained by the inherent permeability-selectivity trade-off. This study optimized the microstructure and surface properties of the polyamide (PA) separation layer by regulating the additional amount of 3-aminobenzenesulfonamide (ABSA) based on the principle of hydrophilic steric dynamic equilibrium. The best-performing membrane, with 0.05 ABSA added, was the polyethylenimine (PEI)/trimesoyl chloride (TMC) NF membrane sample (PEI/ABSA-0.05-TMC), which retained 93.7% of Mg2+ and 28.4% of Li+. Compared to the PEI-TMC NF membrane without ABSA addition, water flux was increased from 12.5 L·m–2·h–1·bar–1 to 17.7 L·m–2·h–1·bar–1, MWCO was adjusted from 584 to 487 Da, and the corresponding separating factor of SLi,Mg increased from 8.51 to 13.3. Throughout prolonged experimental trials, the PEI/ABSA-0.05-TMC NF membrane demonstrated sustained separation stability. This work establishes a robust framework for optimizing NF membranes, providing a strategic pathway toward Mg2+/Li+ separation technologies.
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