The participation degree of community residents has become a yardstick to measure the community governance system and governance capacity in China. Since 2000, China has vigorously promoted community ...construction. The related research literature on community construction in China is also showing an explosive growth trend. Knowledge map refers to the analysis of complex domain knowledge through data mining, information processing, knowledge measurement, chart drawing, etc., so as to achieve the purpose of understanding the dynamic development law of knowledge domain through diagrams. In the face of complex knowledge fields, we can use knowledge maps to combine various information to obtain relational networks and analyze problems from the perspective of “relationships.” Knowledge map is widely used in intelligent search, intelligent question and answer, and other fields. Using the intelligent decision support framework based on knowledge map can help us more clearly find the problems existing in the traditional decision support system and provide corresponding solutions. Combining big data, knowledge map, and other large-scale knowledge analysis and modeling technologies with decision support systems can strengthen the ability of problem analysis and processing and form a knowledge and relationship network. This paper provides direction and theoretical support for the research and development of community construction and governance in China in the future.
The tremendous reservoir of soil organic carbon (SOC) in wetlands is being threatened by water-table decline (WTD) globally. However, the SOC response to WTD remains highly uncertain. Here we examine ...the under-investigated role of iron (Fe) in mediating soil enzyme activity and lignin stabilization in a mesocosm WTD experiment in an alpine wetland. In contrast to the classic 'enzyme latch' theory, phenol oxidative activity is mainly controlled by ferrous iron Fe(II) and declines with WTD, leading to an accumulation of dissolvable aromatics and a reduced activity of hydrolytic enzyme. Furthermore, using dithionite to remove Fe oxides, we observe a significant increase of Fe-protected lignin phenols in the air-exposed soils. Fe oxidation hence acts as an 'iron gate' against the 'enzyme latch' in regulating wetland SOC dynamics under oxygen exposure. This newly recognized mechanism may be key to predicting wetland soil carbon storage with intensified WTD in a changing climate.
Constructing highly efficient nonprecious electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is essential to improve the efficiency of overall water splitting, ...but still remains lots of obstacles. Herein, a novel 3D peony flower-like electrocatalyst was synthesized by employing Mo–Ni2S3/NF nanorod arrays as scaffolds to in situ growth ultrathin NiFe LDH nanosheets (Mo-Ni2S3@NiFe LDH). As expected, the novel peony flower-like Mo–Ni2S3@NiFe LDH displays superior electrocatalytic activity and stability for both OER and HER in alkaline media. Low overpotentials of only 228 mV and 109 mV are required to achieve the current densities of 50 mA cm−2 and 10 mA cm−2 for OER and HER, respectively. Additionally, the material remarkably accelerates water splitting with a low voltage of 1.54 V at 10 mA cm−2, which outperforms most transition metal electrodes. The outstanding electrocatalytic activity benefits from the following these features: 3D peony flower-like structure with rough surface provides more accessible active sites; superhydrophilic surfaces lead to the tight affinity between electrode with electrolyte; metallic Ni substrate and highly conductive Mo–Ni2S3 nanorods scaffold together with offer fast electron transfer; the nanorod arrays and porous Ni foam accelerate gas bubble release and ions transmission; the strong interfacial effect between Mo-doped Ni3S2 and NiFe LDH shortens transport pathway, which are benefit for electrocatalytic performance enhancement. This work paves a new avenue for construction and fabrication the 3D porous structure to boost the intrinsic catalytic activities for energy conversion and storage applications.
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•Peony flower-like Mo-Ni2S3@NiFe LDH microstructure was designed and fabricated.•The special structure enhances charge/mass transport and electrolyte adsorption.•This electrocatalyst presents superior electrocatalytic activity for OER and HER.•This electrocatalyst displays excellent water splitting activity and stability.
The means through which microbes and plants contribute to soil organic carbon (SOC) accumulation remain elusive due to challenges in disentangling the complex components of SOC. Here we use amino ...sugars and lignin phenols as tracers for microbial necromass and plant lignin components, respectively, and investigate their distribution in the surface soils across Mongolian grasslands in comparison with published data for other grassland soils of the world. While lignin phenols decrease, amino sugars increase with SOC contents in all examined grassland soils, providing continental-scale evidence for the key role of microbial necromass in SOC accumulation. Moreover, in contrast to clay's control on amino sugar accumulation in fine-textured soils, aridity plays a central role in amino sugar accrual and lignin decomposition in the coarse-textured Mongolian soils. Hence, aridity shifts may have differential impacts on microbial-mediated SOC accumulation in grassland soils of varied textures.
How to improve the corrosion resistance and icing-delay ability of metal in practice is still a big challenge. Herein, a ZnO surface with superhydrophobicity was fabricated by combining anodic ...oxidation and surface modification on zinc substrate. The effects of topographies and chemical composition on surface wettability were discussed in detail. The water contact angle and roll-off angle on the optimal superhydrophobic ZnO surface is about 161.0° and 5°, respectively. The results reveal the self-cleaning property, the corrosion resistance and icing-delay ability of the as-prepared sample were improved due to the superhydrophobic treatment. The method adopted here is facile and the cost is low, which is believed to afford a new idea for the design and construction of superhydrophobic surface on metal-based materials and broaden its potential application in anti-corrosion and icing-delay fields.
•Copper mesh with superhydrophobicity and superoleophilicity was fabricated.•The mesh exhibited low adhesive self-cleaning and striking loading capacity.•The copper mesh could be applied to separate ...oil–water mixture.•The superhydrophobic copper mesh exhibits superior corrosion resistance.
A copper mesh with superhydrophobicity and superoleophilicity was fabricated via thermal oxidation and subsequent surface modification. After surface treatment, the copper mesh exhibited self-cleaning properties, striking loading capacities, and superior anticorrosion. In addition, the copper mesh could be used in a separator for separating oil from oily water with high efficiency. The presented approach may provide a promising strategy for the design and construction of superhydrophobic-superoleophilic materials which can be used for separating oil from oily water.
The Ganges–Brahmaputra (G-B) River system transports over a billion tons of sediment every year from the Himalayan Mountains to the Bay of Bengal and has built the world’s largest active sedimentary ...deposit, the Bengal Fan. High sedimentation rates drive exceptional organic matter preservation that represents a long-term sink for atmospheric CO₂. While much attention has been paid to organic-rich fine sediments, coarse sediments have generally been overlooked as a locus of organic carbon (OC) burial. However, International Ocean Discovery Program Expedition 354 recently discovered abundant woody debris (millimeter- to centimeter-sized fragments) preserved within the coarse sediment layers of turbidite beds recovered from 6 marine drill sites along a transect across the Bengal Fan (∼8°N, ∼3,700-m water depth) with recovery spanning 19 My. Analysis of bulk wood and lignin finds mostly lowland origins of wood delivered episodically. In the last 5 My, export included C₄ plants, implying that coarse woody, lowland export continued after C₄ grassland expansion, albeit in reduced amounts. Substantial export of coarse woody debris in the last 1 My included one wood-rich deposit (∼0.05 Ma) that encompassed coniferous wood transported from the headwaters. In coarse layers, we found on average 0.16 weight % OC, which is half the typical biospheric OC content of sediments exported by the modern G-B Rivers. Wood burial estimates are hampered by poor drilling recovery of sands. However, high-magnitude, low-frequency wood export events are shown to be a key mechanism for C burial in turbidites.
•CH3I was analyzed in isooctane for methoxyl quantification and isotope analysis.•Lignin phenols allow for quantification of methoxyl yields.•Lignin oxidation and methoxyl quantification reveal ...structure of buried lignin.•Methoxyl content increases with loss of cellulose in early diagenesis.•Demethoxylation leads to CH3I yields below detection in bituminous coal.
Lignin is a major structural plant biochemical and biogeochemical compound present in peat and lignite. Its monomeric (phenolic) and polymeric structures include varying amounts of ether-bonded methyl groups (i.e., methoxy or OCH3). These methoxy groups are generally underused targets for both structural characterization and isotopic analyses. We analyzed the quantity and C and H isotopic composition of methoxy groups within a range of substrates including lignin phenols, lignin, wood, peat, lignite, and sub-bituminous and bituminous coal. We used the Zeisel method to cleave the ether bonds with hydroiodic acid to yield iodomethane which can be analyzed by gas chromatography (GC). Finding inconsistent transfer and isotope effects associated with room temperature headspace injections, we instead used isooctane as a solvent for the iodomethane analyte (the liquid method). Using the liquid method, we obtained a linear response by GC-flame ionization detection (GC-FID) for iodomethane and a linear calibration and 85 ± 6% recovery of methyl from methoxy groups from solid standards of phenolic compounds of known stoichiometry. We introduced quantification via lignin phenolic compounds to calibrate both analytical and experimental yield. Methyl yields provided structural information and confirmed that lignin oxidation products (LOPs) from copper oxide oxidation underestimate the number of methoxy-bearing phenols (yield < 0.3 of expected based on stoichiometry); in combination the two approaches provide structural information and quantification. We found that concentrations of methyl from methoxy groups in geologic sediments (lignite, sub-bituminous and bituminous coal) initially increase with diagenesis as lignin to cellulose ratio increases, and then decline to low concentrations during coalification, offering new possibilities for characterizing the transformation of peat and lignite. We assessed an array of plant biochemicals and established that natural and synthetic methoxy groups span a broad range of dual stable carbon and hydrogen isotopic compositions indicating scope for biogeochemical and forensic applications.
Abstract
Sphagnum
wetlands are global hotspots for carbon storage, conventionally attributed to the accumulation of decay-resistant litter. However, the buildup of mineral-associated organic carbon ...(MAOC) with relatively slow turnover has rarely been examined therein. Here, employing both large-scale comparisons across major terrestrial ecosystems and soil survey along
Sphagnum
gradients in distinct wetlands, we show that
Sphagnum
fosters a notable accumulation of metal-bound organic carbon (OC) via activating iron and aluminum (hydr)oxides in the soil. The unique phenolic and acidic metabolites of
Sphagnum
further strengthen metal-organic associations, leading to the dominance of metal-bound OC in soil MAOC. Importantly, in contrast with limited MAOC sequestration potentials elsewhere, MAOC increases linearly with soil OC accrual without signs of saturation in
Sphagnum
wetlands. These findings collectively demonstrate that
Sphagnum
acts as an efficient ‘rust engineer’ that largely boosts the rusty carbon sink in wetlands, potentially increasing long-term soil carbon sequestration.
Background
Future ecosystem structure and function will largely depend on root responses to climate change. However, few studies have explored the responses of root production and decomposition to ...simultaneous warming and altered precipitation in high-latitude and high-altitude ecosystems.
Methods
Using ingrowth core and root bag methods, we investigated root production and decomposition dynamics from 2013 to 2015 in a full-factorial warming (control, 1.5 ~ 1.8 °C warming) and precipitation (dry (−50% precipitation), ambient, and wet (+50% precipitation)) experiment established in 2011 in a Tibetan alpine grassland.
Results
Warming and precipitation effects on root production were independent. Dry plus warming treatments increased root production, while wet treatments did not significantly affect root production. In contrast, root decomposition accelerated along the increasing precipitation gradient. Warming tended to decrease root decomposition under dry treatments but did not affect root decomposition under wet treatments. The different responses of root production among the treatments were mainly driven by changes in soil moisture, whereas those of root decomposition were mainly due to the changes in the root carbon nitrogen ratio, soil microbial biomass and soil moisture.
Conclusions
Given that altered precipitation had contrasting effects on root production and decomposition, our findings indicate that root-derived carbon may accumulate in soils on the Tibetan Plateau where precipitation decreases but not in the areas with projected increasing precipitation under future warming.
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