分类: 地球科学 >> 大气科学 提交时间: 2024-06-21 合作期刊: 《干旱区科学》
摘要: Methane (CH4) is a potent greenhouse gas that has a substantial impact on global warming due to its substantial influence on the greenhouse effect. Increasing extreme precipitation events, such as drought, attributable to global warming that caused by greenhouse gases, exert a profound impact on the intricate biological processes associated with CH4 uptake. Notably, the timing of extreme drought occurrence emerges as a pivotal factor influencing CH4 uptake, even when the degree of drought remains constant. However, it is still unclear how the growing season regulates the response of CH4 uptake to extreme drought. In an effort to bridge this knowledge gap, we conducted a field manipulative experiment to evaluate the impact of extreme drought on CH4 uptake during early, middle, and late growing stages in a temperate steppe of Inner Mongolia Autonomous Region, China. The result showed that all extreme drought consistently exerted positive effects on CH4 uptake regardless of seasonal timing. However, the magnitude of this effect varied depending on the timing of season, as evidenced by a stronger effect in early growing stage than in middle and late growing stages. Besides, the pathways of CH4 uptake were different from seasonal timing. Extreme drought affected soil physical-chemical properties and aboveground biomass (AGB), consequently leading to changes in CH4 uptake. The structural equation model showed that drought both in the early and middle growing stages enhanced CH4 uptake due to reduced soil water content (SWC), leading to a decrease in NO3–-N and an increase in pmoA abundance. However, drought in late growing stage primarily enhanced CH4 uptake only by decreasing SWC. Our results suggested that seasonal timing significantly contributed to regulate the impacts of extreme drought pathways and magnitudes on CH4 uptake. The findings can provide substantial implications for understanding how extreme droughts affect CH4 uptake and improve the prediction of potential ecological consequence under future climate change.
提交时间: 2017-04-06
摘要: A series of LaCo0.95-xFexPd0.05O3 (x = 0, 0.1, 0.2, 0.3) perovskite-type catalysts have been prepared by a modified sol-gel method. Their structures and physicochemical properties have been studied by powder X-ray diffraction (PXRD), transmission electron
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-04-06
摘要: A series of La1-xBaxCoO3(x = 0, 0.1, 0.2, 0.3) perovskites were synthesized by the modified sol-gel method, and their activities for NO oxidation were investigated as well. The relevant structural characterizations of the prepared catalysts were conducted
分类: 材料科学 >> 材料科学(综合) 提交时间: 2017-03-30
摘要: A series of La1-xBaxCoO3(x = 0, 0.1, 0.2, 0.3) perovskites were synthesized by the modified sol-gel method, and their activities for NO oxidation were investigated as well. The relevant structural characterizations of the prepared catalysts were conducted
分类: 材料科学 >> 材料科学(综合) 提交时间: 2017-03-30
摘要: A series of La1-xBaxCoO3(x = 0, 0.1, 0.2, 0.3) perovskites were synthesized by the modified sol-gel method, and their activities for NO oxidation were investigated as well. The relevant structural characterizations of the prepared catalysts were conducted
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Molybdenum-doped mesoporous SBA-15, mesoporous SBA-15-supported MoO3/SBA-15, and traditional silica-supported MoO3/SiO2 were successfully synthesized. Various techniques, such as XRD, TEM, BET, UV-DRS, Raman, XPS and IR, were used to characterize the above obtained materials. The studies of TEM, XRD and BET confirmed that the highly ordered mesoporous structure of SBA-15 was maintained in the doped Mo-SBA-15 whereas supported MoO3/SBA-15 showed a significant reduction in surface area due to the deposition of MoO3 nanoparticles into the SBA-15 channels. XPS studies revealed that a high concen- tration of Mo5+ species appeared in doped Mo-SBA-15 whereas supported MoO3/SBA-15 and MoO3/SiO2 only contained Mo6+ species. The metathesis reaction of 1-butene and ethene to propene was used to evaluate the catalytic performance of Mo-containing materials. The doped Mo-SBA-15 illustrated a superior catalytic performance over the supported MoO3/SBA-15 and MoO3/SiO2 catalysts. The enhancement of catalytic performance for doped Mo-SBA-15 was assigned to the incorporation of Mo species into the SBA-15 framework. Due to the doping method, Mo-SBA-15 exhibited a well-ordered mesoporous struc- ture, a high surface area, and a high concentration of Mo5+ species, which is beneficial to the catalytic per- formance for metathesis reactions.
分类: 材料科学 >> 材料科学(综合) 提交时间: 2017-05-09
摘要: For exploring more types of suitable polymeric membranes for application in alkaline fuel cells (AFCs), a series of 1,2-dimethylimidazolium functionalized poly(arylene ether sulfone)s containing 4-phenyl- pyridine units in the main chain (named as DIm-PPYPAES) were firstly synthesized as anion exchange membranes (AEMs) in this work. Proton nuclear magnetic resonance (1H NMR) and Fourier transform infrared (FT-IR) spectroscopy were employed to characterize and confirm the chemical structure of the synthesized copolymers and the derived membranes. The DIm-PPYPAES membranes with different ionized levels ranging from 1.15 meq. g 1 to 1.77 meq. g 1, exhibited good thermal stability, solubility behavior and a relatively high level of hydroxide conductivity. The highest hydroxide conductivity of 83.35 mS cm 1 at 80 C was achieved for the DIm-PPYPAES-4 membrane with a moderate IEC of 1.77 meq. g 1. Moreover, after 15 days of treatment with a 2 M NaOH solution at 60 C, the DIm-PPYPAES membrane still exhibited relatively high ionic conductivity even above 10 mS cm 1 at 30 C and retained their integrated shapes.
分类: 生物学 >> 植物学 >> 植物生态学和植物地理学 提交时间: 2016-05-04
摘要: Bioenergy crop cultivation on former peat extraction areas is a potential after-use option that provides a source of renewable energy while mitigating climate change through enhanced carbon (C) sequestration. This study investigated the full C and greenhouse gas (GHG) balances of fertilized (RCG-F) and nonfertilized (RCG-C) reed canary grass (RCG; Phalaris arundinacea) cultivation compared to bare peat (BP) soil within an abandoned peat extraction area in western Estonia during a dry year. Vegetation sampling, static chamber and lysimeter measurements were carried out to estimate above- and belowground biomass production and allocation, fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) in cultivated strips and drainage ditches as well as the dissolved organic carbon (DOC) export, respectively. Heterotrophic respiration was determined from vegetation-free trenched plots. Fertilization increased the above- to belowground biomass production ratio and the autotrophic to heterotrophic respiration ratio. The full C balance (incl. CO2, CH4 and DOC fluxes from strips and ditches) was 96, 215 and 180 g C m−2 yr−1 in RCG-F, RCG-C and BP, respectively, suggesting that all treatments acted as C sources during the dry year. The C balance was driven by variations in the net CO2 exchange, whereas the combined contribution of CH4 and DOC fluxes was 2 eq ha−1 yr−1 in RCG-F, RCG-C and BP, respectively. The CO2 exchange was also the dominant component of the GHG balance, while the contributions of CH4 and N2O were 2 uptake through adequate water and nutrient supply is a key prerequisite for ensuring sustainable high yields and climate benefits in RCG cultivations established on organic soils following drainage and peat extraction.
分类: 生物学 >> 生物物理学 >> 细胞生物学 提交时间: 2016-05-12
摘要: The fatty alk(a/e)ne biosynthesis pathway found in cyanobacteria gained tremendous attention in recent years as a promising alternative approach for biofuel production. Cyanobacterial aldehyde-deformylating oxygenase (cADO), which catalyzes the conversion of C-n fatty aldehyde to its corresponding Cn-1 alk(a/e)ne, is a key enzyme in that pathway. Due to its low activity, alk(a/e)ne production by cADO is an inefficient process. Previous biochemical and structural investigations of cADO have provided some information on its catalytic reaction. However, the details of its catalytic processes remain unclear. Here we report five crystal structures of cADO from the Synechococcus elongates strain PCC7942 in both its iron-free and iron-bound forms, representing different states during its catalytic process. Structural comparisons and functional enzyme assays indicate that Glu144, one of the iron-coordinating residues, plays a vital role in the catalytic reaction of cADO. Moreover, the helix where Glu144 resides exhibits two distinct conformations that correlates with the different binding states of the di-iron center in cADO structures. Therefore, our results provide a structural explanation for the highly labile feature of cADO di-iron center, which we proposed to be related to its low enzymatic activity. On the basis of our structural and biochemical data, a possible catalytic process of cADO was proposed, which could aid the design of cADO with improved activity.