Synthesis of large arrays of well-aligned carbon nanotubes on glass

Free-standing aligned carbon nanotubes have previously been grown above 700 degreesC on mesoporous silica embedded with iron nanoparticles. Here, carbon nanotubes aligned over areas up to several square centimeters were grown on nickel-coated glass below 666 degreesC by plasma-enhanced hot filament chemical vapor deposition. Acetylene gas was used as the carbon source and ammonia gas was used as a catalyst and dilution gas. Nanotubes with controllable diameters from 20 to 400 nanometers and lengths from 0. 1 to 50 micrometers were obtained. Using this method, large panels of aligned carbon nanotubes can be made under conditions that are suitable for device fabrication.     

CO2作天然气地下储气库垫层气的可行性分析

用CO2作地下储气库垫层气,可以节省沉积资金,实现碳隔离储存及减少温室效应,是解决天然气工业发展和火力发电等产生环保问题的一个双赢研究项目.通过研究CO2的热力性质及其来源,提出了CO2作储库垫层气的可行性,确定了CO2作为垫层气的最佳热力学条件,为今后我国碳隔离储存和储气库建设运行提供了理论依据.     

Probing c60

Experiments involving the laser vaporization of graphite have indicated that one particular duster of carbon, C(60), is preeminently stable; this special stability may be evidence that C(60) can readily take the form of a hollow truncated icosahedron (a sort of molecular soccerball). If true, this structure for C(60) would be the first example of a spherical aromatic molecule. In fact, because of symmetry properties unique to the number 60, it may be the most perfecty spherical, edgeless molecule possible. Its rapid formation in condensing carbon vapors and its extreme chemical and photophysical stability may have far-reaching implications in a number of areas, particularly combustion science and astrophysics. For these reasons C(60) and other dusters of carbon have continued to be the subject of intense research. This article provides a short review of the many new experimental probes of the properties of C(60) and related carbon dusters.     

秸秆循环利用与土壤碳循环关系

[目的]为了研究秸秆还田过程中在不同的外界环境下碳的转化形式。[方法]通过控制土壤湿度、还田方式、秸秆还田量、培养天数等影响因素,测定土壤中微生物呼吸产生的CO2、土壤有机质、还田率及损失率,来衡量还田的效果。[结果]在人为控制外界条件下,秸秆中的碳更多地转化为有机质,同时减少温室气体中碳的转化。[结论]在土壤湿度45%、粉碎还田、还田量67%、培养天数20 d的条件下,还田效果最佳。     

High-performance carbon nanotube fiber

With their impressive individual properties, carbon nanotubes should form high-performance fibers. We explored the roles of nanotube length and structure, fiber density, and nanotube orientation in achieving optimum mechanical properties. We found that carbon nanotube fiber, spun directly and continuously from gas phase as an aerogel, combines high strength and high stiffness (axial elastic modulus), with an energy to breakage (toughness) considerably greater than that of any commercial high-strength fiber. Different levels of carbon nanotube orientation, fiber density, and mechanical properties can be achieved by drawing the aerogel at various winding rates. The mechanical data obtained demonstrate the considerable potential of carbon nanotube assemblies in the quest for maximal mechanical performance. The statistical aspects of the mechanical data reveal the deleterious effect of defects and indicate strategies for future work.     

农田碳汇管理策略及其效果评价

目前增加农田生态系统的碳储量的措施主要有：减少碳损失,包括提高能源利用率,减少水土流失和提高水肥利用率;增加土壤有机碳,包括调整耕作制度,使用有机肥料,应用深根作物和增加土壤中微团聚体的含量。在分析各种策略与措施的基础上,笔者认为以下几种农田碳汇管理措施有效且较容易推广。①实施土地用途转换管理：把低产及土壤退化严重的农田变成草地或森林;集约管理农田,实行农林复合、林草复合经营方式;在区域或地区尺度变单一土地利用方式为承担不同人类需要的多种土地利用方式等。②调整耕作制度：免耕不仅使土壤团聚体的数量和稳定性增加,从而减少了团聚体内部有机质的分解作用;还能有效地抑制土壤的过度通气,减少有机碳的氧化降解,防止土壤侵蚀;此外,免耕土壤有机碳的平均滞留时间比常规耕作土壤增加了约1倍。轮作能提高土壤固碳效率,在轮作中加入豆科作物或豆科牧草更可增加土壤有机质汇集,是实现土壤蓄存碳潜力的重要途径。提高复种指数,降低休耕频率可以提高作物产量并增加土壤作物残茬和根的有机质输人,从而增加土壤中有机碳的含量。③改善经营与管理：有机肥或有机肥和化肥配合施用,能显著提高土壤有机碳含量．应当优先选择;人为改变土壤的水分条件可以调节土壤排放温室气体的总量、组成及其产生的潜在温室效应;残茬和土壤有机质库的增加,可以改善植物的水分利用效率和营养再循环能力,减少养分流失,加强碳汇集。④依托技术进步：如改良作物品种,有计划地抓紧培育具有对高温、干旱等极端气候及病虫害有抗性的品种,确保在新的生态环境中产量不断提高,扩大碳的吸收存储。此外,采用新型节能的农机部件对拖拉机等农业动力机械进行改装,也可减少农田碳排放,增加农田碳汇的潜力。     

从国际经验看中国农业温室气体减排路径

2020年,中国提出“二氧化碳排放力争于2030年前达到峰值,努力争取2060年前实现碳中和”。当前农业温室气体减排蕴藏着巨大潜力,是确保碳达峰、碳中和目标实现的重要支撑。本文明确了农业需要减排甲烷、氧化亚氮等温室气体,并分析了农业温室气体的主要成因以及中国农业温室气体减排在宏观、产业、微观上面临的挑战。在介绍发达国家及联合国粮农组织在温室气体减排的举措和经验后,指出中国农业温室气体减排具体路径的方向,包括绿色生物制造、种业基因编辑、垂直农业、植物蛋白、精准农业、农业大数据等,这些方向可以实现经济效益和绿色发展的共存,可以更大程度、更为持久地动员市场主体参与到农业温室气体减排活动中。     

The xenon record of extinct radioactivities in the Earth

Analyses of xenon from well gas rich in carbon dioxide reveal a large excess of radiogenic xenon-129 from the decay of extinct iodine-129. Smaller excesses observed in the heavy xenon isotopes are from fission. These results place narrow limits on any age difference between the earth and the oldest meteorites. The occurrence of excess radiogenic xenon-129 in well gas also suggests that any quantitative degassing of existing solid materials to form the atmosphere must have been limited to a very early period of the earth's history, approximately the first 10(8) years. Alternatively, this observation is consistent with a model of the earth's continuous, but still incomplete, degassing since its time of formation.     

生物质炭输入对土壤有机碳库和CO_2排放的影响研究进展

由于生物质炭的碳化学结构主要以芳香碳为主,具有高度的生物化学和热稳定性,可长期保存于土壤中而不被土壤微生物所分解,因此其在增加土壤碳库容量、稳定土壤有机碳库以及维持土壤碳平衡方面发挥着重要作用。本研究综述了生物质炭输入对活性有机碳、腐殖质特性以及有机碳矿化特征的影响,较详细地分析了生物质炭输入对土壤CO_2通量的影响效果及其机制,最后展望了该方向今后的研究重点。     

Modeling temperature and moisture dependent emissions of carbon dioxide and methane from drying dairy cow manure

Greenhouse gas emissions due to biological degradation processes of animal wastes are significant sources of air pollution from agricultural areas. The major environmental controls on these microbe-induced gas fluxes are temperature and moisture content. The objective of this study was to model the effects of temperature and moisture content on emissions of CO₂ and CH₄ during the ambient drying process of dairy manure under controlled conditions. Gas emissions were continuously recorded over 15 d with paired fully automated closed dynamic chambers coupled with a Fourier Transformed Infrared gas analyzer. Water content and temperature were measured and monitored with capacitance sensors. In addition, on days 0, 3, 6, 9, 12 and 15, pH, moisture content, dissolved organic carbon and total carbon (TC) were determined. An empirical model derived from the Arrhenius equation confirmed high dependency of carbon emissions on temperature and moisture content. Results indicate that for the investigated dairy manure, 6.83% of TC was lost in the form of CO₂ and 0.047% of TC was emitted as CH₄. Neglecting the effect of temperature, the moisture contents associated with maximum gas emissions were estimated as 0.75 and 0.79 g·g⁻¹ for CO₂ and CH₄, respectively.     

Freshwater methane emissions offset the continental carbon sink

Inland waters (lakes, reservoirs, streams, and rivers) are often substantial methane (CH(4)) sources in the terrestrial landscape. They are, however, not yet well integrated in global greenhouse gas (GHG) budgets. Data from 474 freshwater ecosystems and the most recent global water area estimates indicate that freshwaters emit at least 103 teragrams of CH(4) year(-1), corresponding to 0.65 petagrams of C as carbon dioxide (CO(2)) equivalents year(-1), offsetting 25% of the estimated land carbon sink. Thus, the continental GHG sink may be considerably overestimated, and freshwaters need to be recognized as important in the global carbon cycle.     

Missing mass in collisional debris from galaxies

Recycled dwarf galaxies can form in the collisional debris of massive galaxies. Theoretical models predict that, contrary to classical galaxies, these recycled galaxies should be free of nonbaryonic dark matter. By analyzing the observed gas kinematics of such recycled galaxies with the help of a numerical model, we demonstrate that they do contain a massive dark component amounting to about twice the visible matter. Staying within the standard cosmological framework, this result most likely indicates the presence of large amounts of unseen, presumably cold, molecular gas. This additional mass should be present in the disks of their progenitor spiral galaxies, accounting for a substantial part of the so-called missing baryons.     

Carbon dioxide exchange between air and seawater: no evidence for rate catalysis

It has been suggested that enzymatic catalysis plays a major role in regulating the mass transport of carbon dioxide from the atmosphere into the oceans. Evidence for this mechanism was not found in a series of gas exchange experiments in which the gas transfer rate coefficients for samples obtained from various natural seawaters, with and without the addition of carbonic anhydrase, were compared with those from artificial seawater. Wind-induced turbulence appears to be the major factor controlling the ocean's response to anthropogenic increases in atmospheric carbon dioxide.     

我国露地与设施番茄生产的温室气体排放比较

为比较我国不同栽培方式(露地与设施)及不同省份番茄生产的温室气体排放差异,基于生命周期法,遵循农田生态系统的全环式路径,根据《全国农产品成本收益资料汇编—2020》数据,对我国露地与设施番茄的温室气体排放及碳评价指标进行了测算和比较分析。结果显示：我国露地、设施番茄生产系统的平均温室气体排放量分别为4 630.09、8 697.52 kg CO₂e·hm^-2,设施比露地高87.85%;露地番茄的主要温室气体排放源为化肥,而设施番茄的主要温室气体排放源为农膜和化肥;露地番茄的净温室气体排放为负、碳生态效率大于1,对生态环境具有正外部性,而设施番茄的净温室气体排放为正、碳生态效率小于1,具有负环境外部性;土地碳强度、碳生产效率、碳经济效率方面,设施种植的可持续性均低于露地种植。各省份露地、设施番茄温室气体排放量分别在2 849.24～7 524.61、5 788.83～13 779.69 kg CO₂e·hm^-2之间,最高省份分别是最低省份的2.64、2.38倍,露地、设施番茄的温室气体排放、构成、固碳...     

The 1986 lake nyos gas disaster in cameroon, west Africa

The sudden, catastrophic release of gas from Lake Nyos on 21 August 1986 caused the deaths of at least 1700 people in the northwest area of Cameroon, West Africa. Chemical, isotopic, geologic, and medical evidence support the hypotheses that (i) the bulk of gas released was carbon dioxide that had been stored in the lake's hypolimnion, (ii) the victims exposed to the gas cloud died of carbon dioxide asphyxiation, (iii) the carbon dioxide was derived from magmatic sources, and (iv) there was no significant, direct volcanic activity involved. The limnological nature of the gas release suggests that hazardous lakes may be identified and monitored and that the danger of future incidents can be reduced.     

Carbon monoxide in rainwater

Concentrations of carbon monoxide in rainwater collected at widely diverse locations show up to a 200-fold supersaturation relative to the partial pressure of the gas in the atmosphere. These results indicate the existence of an additional natural source of carbon monoxide not heretofore considered. Production of carbon monoxide in clouds is tentatively attributed to the photochemical oxidation of organic matter or the slight dissociation of carbon dioxide induced by electrical discharges, or both. Methane concentrations measured in the same rainwater show that the partitioning of this gas, unlike that of carbon monoxide, is very close to a state of equilibrium.     

基于行业标准的木材生产作业系统碳排放

以现行林业行业标准为基础,核算标准工序下木材生产的综合能耗量,并以此计算木材生产作业系统的温室气体排放量.结果表明：在基本条件下机械化木材生产的碳排放在9.4050~12.3488 kg/m3,其中木材运材碳排放最大,约占65.3%~74.7%;其次为集材段（拖拉机占12.2%~15.7%,索道占11.0%~14.3%）;碳排放作业过程还受气温、海拔及林型、蓄积量等的影响,尤其是采伐工序,平均条件下的油锯采伐碳排放是基本条件下的2.22倍.虽然木材运输在平均条件下的碳排放是基本条件的1.5倍,但由于木材运输阶段所占的排放比例最大,因此在实际生产中,提高车辆的使用率与尾气排放技术对降低木材生产的碳排放具有重大意义;从碳排放角度看,油锯采伐—索道集材—绞盘机装车—柴油车运材—水运到材为最优作业模式.研究结果可为森工作业过程中合理选择木材生产作业方式提供科学依据.     

Annealing c60+: synthesis of fullerenes and large carbon rings

Laser vaporization of graphite generates C(60)(+) cluster ions that are fullerenes and a mixture of roughly planar polycyclic polyyne ring isomers. Experimental studies of the annealing of the non-fullerene C(60)(+) ions indicate that they can be converted (in the gas phase) into the fullerene and an isomer that appears to be a large monocyclic ring. Some fragmentation is associated with conversion to the fullerene geometry, but the majority of the non-fullerene C(60)(+) isomers are cleanly converted into an intact fullerene. The emergence of the monocyclic ring (as the clusters are annealed) suggests that this is a relatively stable non-spheroidal form of these all carbon molecules. The estimated activation energies for the observed structural interconversions are relatively low, suggesting that these processes may play an important role in the synthesis of spheroidal fullerenes.     

川西高山树线交错带海拔梯度上土壤有机碳稳定性特征

高山树线交错带是高海拔地带对环境变化最为敏感的生态系统之一,土壤有机碳库及其稳定性在生态系统变化中具有显著指示作用。通过物理-化学方法对土壤不同活性有机碳进行连续分级分离,研究土壤有机碳不同组分在海拔环境梯度下分布特征及稳定性。结果表明,高山树线交错带土壤有机碳主要集中在物理分级组分（≥0.02 mm）,且粒径越大有机碳含量越高,即主要以颗粒态有机碳形式存在,占比均高于98%;在<0.02 mm有机-无机复合体中有机碳采用化学分级分离,这部分有机碳占比低于土壤总有机碳2%,且主要以腐殖质（胡敏素）形式存在（占土壤总有机碳0.6%~0.8%）,腐殖质占有机碳比例远低于一般土壤;随着海拔升高,土壤有机碳总量上升,颗粒态有机碳（物理分级组分）比例升高,胡敏素类腐殖质比例下降。因此,川西高海拔树线交错带的高寒土壤有机碳,主要以不稳定有机碳（POC）形式存在,随着温度上升（海拔降低）将导致土壤矿质化和腐殖化加剧,有机碳总量下降,土壤不稳定性组分（物理分级组分）降低,土壤稳定性（腐殖化比例）上升。     

Modified phases of diamond formed under shock compression and rapid quenching

Two modified forms of carbon were quenched by a rapid-cooling technique from graphite sheets shock-compressed to 65 gigapascals and 3700 K. One form, ;;n-diamond," which was obtained from the most rapidly cooled part, has a crystal structure close to that of cubic diamond. The other form, found in the relatively slow-cooled part, was comparable to an i-carbon prepared by an ion-beam technique. The n-diamond is interpreted as a metastable form, the same as hexagonal diamond, converted from graphite through a martensitic transition, for which either the region or the path may be different from that of hexagonal diamond. The second form was found to be produced through reconstruction.