Solar cycle variability, ozone, and climate

Results from a global climate model including an interactive parameterization of stratospheric chemistry show how upper stratospheric ozone changes may amplify observed, 11-year solar cycle irradiance changes to affect climate. In the model, circulation changes initially induced in the stratosphere subsequently penetrate into the troposphere, demonstrating the importance of the dynamical coupling between the stratosphere and troposphere. The model reproduces many observed 11-year oscillations, including the relatively long record of geopotential height variations; hence, it implies that these oscillations are likely driven, at least in part, by solar variability.     

Thunderstorms: an important mechanism in the transport of air pollutants

Acid deposition and photochemical smog are urban air pollution problems, and they remain localized as long as the sulfur, nitrogen, and hydrocarbon pollutants are confined to the lower troposphere (below about 1-kilometer altitude) where they are short-lived. If, however, the contaminants are rapidly transported to the upper troposphere, then their atmospheric residence times grow and their range of influence expands dramatically. Although this vertical transport ameliorates some of the effects of acid rain by diluting atmospheric acids, it exacerbates global tropospheric ozone production by redistributing the necessary nitrogen catalysts. Results of recent computer simulations suggest that thunderstorms are one means of rapid vertical transport. To test this hypothesis, several research aircraft near a midwestern thunderstrom measured carbon monoxide, hydrocarbons, ozone, and reactive nitrogen compounds. Their concentrations were much greater in the outflow region of the storm, up to 11 kilometers in altitude, than in surrounding air. Trace gas measurements can thus be used to track the motion of air in and around a cloud. Thunderstorms may transform local air pollution problems into regional or global atmospheric chemistry problems.     

黄酒酿造酵母菌发酵过程的有机酸代谢研究

以大米糖化液为培养基,以酵母菌JH301、JH183及安琪黄酒专用干酵母AQ为代表菌株,研究酵母菌在红曲黄酒发酵过程中的乙醇发酵水平、酸代谢变化规律及其产酸组成。结果表明,在发酵过程中酵母菌发酵液总酸均呈先快速增加、pH值快速下降到酵母适宜生长值区间后趋于平缓的趋势,各酵母菌的产酸曲线均符合Log-Modified模型;酵母菌间的产酸水平与产乙醇能力存在差异,产酸水平与产乙醇能力呈负相关。发酵15d后,酵母菌产乙醇水平高低依次为酵母菌JH301、AQ和JH183,体积分数分别为15.8%、14.8%和12.4%,差异均达极显著水平(P0.01)。产酸水平高低依次为酵母菌JH183、AQ和JH301,分别为4.57、3.54、3.26g·L~(-1),差异均达极显著水平(P0.01)。酵母菌在发酵程中酸代谢的主要产物为乳酸、乙酸和琥珀酸,分别占有机酸总量的(77.08±0.60)%、(17.22±0.60)%、(5.70±0.67)%。     

Rethinking organic aerosols: semivolatile emissions and photochemical aging

Most primary organic-particulate emissions are semivolatile; thus, they partially evaporate with atmospheric dilution, creating substantial amounts of low-volatility gas-phase material. Laboratory experiments show that photo-oxidation of diesel emissions rapidly generates organic aerosol, greatly exceeding the contribution from known secondary organic-aerosol precursors. We attribute this unexplained secondary organic-aerosol production to the oxidation of low-volatility gas-phase species. Accounting for partitioning and photochemical processing of primary emissions creates a more regionally distributed aerosol and brings model predictions into better agreement with observations. Controlling organic particulate-matter concentrations will require substantial changes in the approaches that are currently used to measure and regulate emissions.     

Carbon monoxide balance in nature

Consideration of the steady-state equations for stable carbon monoxide and for radioactive carbon monoxide in the troposphere leads to the conclusion that carbon monoxide is produced at a rate of 5x10(15) grams per year, a value some 25 times greater than the rate of carbon monoxide production from combustion. The concomitant residence time for carbon monoxide is 0.1 year, in agreement with a previous estimate of Weinstock. Hydroxyl radicals are shown to account for both the production of this large amount of carbon monoxide by methane oxidation and for its removal by carbon monoxide oxidation. The average concentration of hydroxyl radicals in the troposphere required to achieve this effect is 2.3x10(6) molecules per cubic centimeter, with a daytime concentration of twice that. Levy and McConnell, McElroy, and Wofsy have deduced concentrations of hydroxyl radicals in the troposphere of the same magnitude from purely photochemical considerations, in support of this model.     

Heterogeneous nucleation experiments bridging the scale from molecular ion clusters to nanoparticles

Generation, investigation, and manipulation of nanostructured materials are of fundamental and practical importance for several disciplines, including materials science and medicine. Recently, atmospheric new particle formation in the nanometer-size range has been found to be a global phenomenon. Still, its detailed mechanisms are mostly unknown, largely depending on the incapability to generate and measure nanoparticles in a controlled way. In our experiments, an organic vapor (n-propanol) condenses on molecular ions, as well as on charged and uncharged inorganic nanoparticles, via initial activation by heterogeneous nucleation. We found a smooth transition in activation behavior as a function of size and activation to occur well before the onset of homogeneous nucleation. Furthermore, nucleation enhancement for charged particles and a substantial negative sign preference were quantitatively detected.     

Particle formation by ion nucleation in the upper troposphere and lower stratosphere

Unexpectedly high concentrations of ultrafine particles were observed over a wide range of latitudes in the upper troposphere and lower stratosphere. Particle number concentrations and size distributions simulated by a numerical model of ion-induced nucleation, constrained by measured thermodynamic data and observed atmospheric key species, were consistent with the observations. These findings indicate that, at typical upper troposphere and lower stratosphere conditions, particles are formed by this nucleation process and grow to measurable sizes with sufficient sun exposure and low preexisting aerosol surface area. Ion-induced nucleation is thus a globally important source of aerosol particles, potentially affecting cloud formation and radiative transfer.     

Methylhydroxycarbene: tunneling control of a chemical reaction

Chemical reactivity is conventionally understood in broad terms of kinetic versus thermodynamic control, wherein the decisive factor is the lowest activation barrier among the various reaction paths or the lowest free energy of the final products, respectively. We demonstrate that quantum-mechanical tunneling can supersede traditional kinetic control and direct a reaction exclusively to a product whose reaction path has a higher barrier. Specifically, we prepared methylhydroxycarbene (H(3)C-C-OH) via vacuum pyrolysis of pyruvic acid at about 1200 kelvin (K), followed by argon matrix trapping at 11 K. The previously elusive carbene, characterized by ultraviolet and infrared spectroscopy as well as exacting quantum-mechanical computations, undergoes a facile [1,2]hydrogen shift to acetaldehyde via tunneling under a barrier of 28.0 kilocalories per mole (kcal mol(-1)), with a half-life of around 1 hour. The analogous isomerization to vinyl alcohol has a substantially lower barrier of 22.6 kcal mol(-1) but is precluded at low temperature by the greater width of the potential energy profile for tunneling.     

The sulfur cycle

Even granting our uncertainties about parts of our model of the sulfur cycle, we can draw some conclusions from it: 1) Man is now contributing about one half as much as nature to the total atmospheric burden of sulfur compounds, but by A.D. 2000 he will be contributing about as much, and in the Northern Hemisphere alone he will be more than matching nature. 2) In industrialized regions he is overwhelming natural processes, and the removal processes are slow enough (several days, at least) so that the increased concentration is marked for hundreds to thousands of kilometers downwind. 3) Our main areas of uncertainty, and ones that demand immediate attention because of their importance to the regional air pollution question, are: (i) the rates of conversion of H(2)S and SO(2) to sulfate particles in polluted as well as unpolluted atmospheres; (ii) the efficiency of removal of sulfur compounds by precipitation in polluted air. And for a better understanding of the global model we need to know: (i) the amount of biogenic H(2)S that enters the atmosphere over the continents and coastal areas; (ii) means of distinguishing man-made and biogenic contributions to excess sulfate in air and precipitation; (iii) the volcanic production of sulfur compounds, and their influence on the particle concentration in the stratosphere; (iv) the large-scale atmospheric circulation patterns that exchange air between stratosphere and troposphere (although absolute amounts of sulfate particles involved are small relative to the lower tropospheric burden); (v) the role of the oceans as sources or sinks for SO(2).     

Role of deep cloud convection in the ozone budget of the troposphere

Convective updrafts in thunderstorms prolong the lifetime of ozone (O(3)) and its anthropogenic precursor NOx [nitric oxide (NO) + nitrogen dioxide (NO(2))] by carrying these gases rapidly upward from the boundary layer into a regime where the O(3) production efficiency is higher, chemical destruction is slower, and surface deposition is absent. On the other hand, the upper troposphere is relatively rich in O(3) and NOx from natural sources such as downward transport from the stratosphere and lightning; convective overturning conveys the O(3) and NOx toward the Earth's surface where these components are more efficiently removed from the atmosphere. Simulations with a three-dimensional global model suggest that the net result of these counteractive processes is a 20 percent overall reduction in total tropospheric O(3). However, the net atmospheric oxidation efficiency is enhanced by 10 to 20 percent.     

Shock synthesis of amino acids in simulated primitive environments

A mixture of gases roughly simulating the primitive terrestrial atmosphere has been subjected to shock heating followed by a rapid thermal quench. Under strictly homogeneous conditions there is a very high efficiency of 5 x 10(10) molecules per erg of shock-injected energy for production of alpha-amino acids. Calculations suggest that rapid quenching bypasses the usual thermochemical barrier. The product of energy flux and efficiency implies the unexpected conclusion that shocks occurring on atmospheric entry of cometary meteors and micrometeorites and from thunder may have been the principal energy sources for pre-biological organic synthesis on the primitive earth.     

Heterogeneous atmospheric aerosol production by acid-catalyzed particle-phase reactions

According to evidence from our laboratory, acidic surfaces on atmospheric aerosols lead to potentially multifold increases in secondary organic aerosol (SOA) mass. Experimental observations using a multichannel flow reactor, Teflon (polytetrafluoroethylene) film bag batch reactors, and outdoor Teflon-film smog chambers strongly confirm that inorganic acids, such as sulfuric acid, catalyze particle-phase heterogeneous reactions of atmospheric organic carbonyl species. The net result is a large increase in SOA mass and stabilized organic layers as particles age. If acid-catalyzed heterogeneous reactions of SOA products are included in current models, the predicted SOA formation will be much greater and could have a much larger impact on climate forcing effects than we now predict.     

不同贮藏方式对赣南纽荷尔脐橙果实品质的影响

【目的】研究机械冷库（Mcs）、山区水冷贮藏库（Ecvs）和通风贮藏库（Vws）对赣南纽荷尔脐橙(Citrus sinensis Osbeck‘Newhall’)果实的贮藏效果,为优化柑橘贮藏条件及贮藏库的改良提供理论依据。【方法】将商业成熟度的纽荷尔脐橙果实分别放置于3种不同类型的生产贮藏库,持续跟踪贮藏库的环境参数变化;运用气相色谱仪、红外线CO2分析仪等设备,分析贮藏果实的生理和生化指标,并进行感官评价。【结果】在贮藏期内,3种贮藏库内部环境参数持续变化,Mcs内部温度和相对湿度分别维持在2.1-11.2℃和64.4%-99.0%之间。随着气温升高,Mcs内部与运输或货架期环境的温差逐渐加大,与Vws、Ecvs存在显著差异。Vws与Ecvs内部温度和相对湿度的皮尔森系数分别达到0.80以上,变化趋势一致,但是,比较两种贮藏库相同时刻的温度和相对湿度,Ecvs延缓库内部温度升高,维持库内相对湿度的能力优于Vws。同时,Mcs内部CO2和乙烯浓度显著高于其他贮藏库。果实可滴定酸和可溶性固形物含量随着贮藏期的延长逐渐下降,而且果实可滴定酸比可溶性固形物下降更剧烈。在105 d(days of storage,DOS)后,Ecvs贮藏果实的可滴定酸含量显著高于Vws和Mcs贮藏果实,而果实可溶性固形物含量在各贮藏方式之间无显著性差异。果实的柠檬酸和苹果酸浓度在135 DOS显著下降,3种贮藏方式之间,果实柠檬酸和苹果酸的浓度存在差异,在65 DOS后,Ecvs贮藏果实柠檬酸和苹果酸浓度高于Mcs、Vws贮藏果实。在135 DOS前,Mcs维持果实硬度、可溶性糖、Vc效果明显优于Ecvs和Vws;但是在160 DOS,Mcs贮藏果实的硬度、可溶性糖和Vc损耗加剧,其含量显著低于Ecvs贮藏的果实。此外,果实的乙醇、乙醛、甲醇的浓度在105 DOS显著升高,3种贮藏方式之间,Mcs贮藏果实在160 DOS的乙醇积累量(723.02 μg•L-1)显著高于Ecvs、Vws贮藏果实,果实风味品质降低。Ecvs、Vws贮藏果实感官满意度随贮藏期延长不断波动,而Mcs贮藏果实感官满意度先升高后逐渐下降,在160 DOS显著低于Vws和Ecvs贮藏的果实。【结论】贮藏库与运输、货架期环境的温差,贮藏库内气体成份,尤其是乙烯,显著影响果实有机酸、乙醇、乙醛和甲醇的含量,导致不同贮藏库的果实品质和感官满意度的差异。Mcs贮藏果实在135 DOS品质出现劣变,Ecvs贮藏果实寿命可延长至160 DOS,而Vws贮藏果实品质在65 DOS后显著下降,不适于长期贮藏脐橙。     

Cellulose to sugars: new path gives quantitative yield

Cellulosic residues that had been treated with a small amount of chemical solvent under room conditions were quantitatively saccharified on enzyme hydrolysis. This treatment can be used to obtain simple sugars for the production of alcohol and other chemicals.     

Mount agung eruption provides test of a global climatic perturbation

The Mount Agung volcanic eruption in 1963 provides the best-documented global radiative perturbation to the earth's atmosphere currently available. Data on stratospheric aerosols produced by this eruption have been used as input to a model for the atmospheric thermal structure. The computed magnitude, sign, and phase lag of the temperature changes in both the stratosphere and the troposphere are in good agreement with observations, providing evidence that the climatic response to a global radiative perturbation is significant, as well as support for the use of theoretical models to predict climatic effects.     

Efficient atmospheric cleansing of oxidized organic trace gases by vegetation

The biosphere is the major source and sink of nonmethane volatile organic compounds (VOCs) in the atmosphere. Gas-phase chemical reactions initiate the removal of these compounds from the atmosphere, which ultimately proceeds via deposition at the surface or direct oxidation to carbon monoxide or carbon dioxide. We performed ecosystem-scale flux measurements that show that the removal of oxygenated VOC via dry deposition is substantially larger than is currently assumed for deciduous ecosystems. Laboratory experiments indicate efficient enzymatic conversion and potential up-regulation of various stress-related genes, leading to enhanced uptake rates as a response to ozone and methyl vinyl ketone exposure or mechanical wounding. A revised scheme for the uptake of oxygenated VOCs, incorporated into a global chemistry-transport model, predicts appreciable regional changes in annual dry deposition fluxes.     

砧木和覆膜对爱媛28果实营养品质的影响

【目的】探索砧木和覆膜对爱媛28果实内在品质及营养功能成分的影响,以期为进一步优化其栽培技术提供参考。【方法】分别以枳和卡里佐枳橙为砧木,设置4个处理,即枳+不覆膜、枳+覆膜、卡里佐枳橙+不覆膜、卡里佐枳橙+覆膜,测定不同处理的果实基础品质及糖、有机酸、类黄酮、酚酸、氨基酸和异味物质含量。【结果】不覆膜条件下,相比卡里佐枳橙砧,枳砧果实的可溶性固形物、可滴定酸含量和维生素C含量分别高9.78%、8.20%和4.84%,总糖含量、有机酸总量和总类黄酮含量显著高于卡里佐枳橙（P<0.05,下同）,分别比卡里佐枳橙砧果实高18.65%、27.93%和10.64%;但总酚含量和总氨基酸含量显著低于卡里佐枳橙砧;同时,枳砧爱媛28果实的异味物质乙醇和乙醛含量显著低于卡里佐枳橙砧果实。相比不覆膜,覆膜处理下,爱媛28果实中可溶性固形物含量、有机酸总量和总酚含量均显著增加,其中枳砧果实的上述3个指标分别增加9.90%、5.20%和66.12%,卡里佐枳橙砧分别增加9.78%、5.64%和28.88%。覆膜处理下,2种砧木处理的果实中异味物质乙醛和乙醇含量均显著降低,其中,枳砧分别减少15.58%和9.01%,卡里佐枳橙砧分别减少37.17%和11.76%;此外,枳砧果实的总氨基酸含量显著增加,卡里佐枳橙砧果实的总氨基酸含量显著减少。【结论】生产上爱媛28以枳作为砧木,其果实的综合品质明显优于卡里佐枳橙砧,且通过覆膜可进一步改良爱媛28的果实营养品质,提升风味。     

pH对厨余垃圾发酵产酸特性影响的研究

采用锥形瓶反应器及室内培养方法,研究了pH对厨余垃圾酸化的影响。结果表明,酸化产物的组成与pH有关,乳酸和乙酸在不同的pH值下总为主要产物;pH>7时,明显有丙酸生成;酸化的最佳pH值为7,此条件下VFA的产量最高可达35.1gVFA·L-1,总固体(TS)的去除率高达65.3%。     

减压对冬枣采后生理生化变化的影响

 以冬枣果实为试材 ,研究了减压对枣果贮藏生理生化变化的影响。结果表明 ,减压有效地保持了枣果的硬度和VC 含量 ,降低了果肉中乙醇、乙醛含量和枣果呼吸强度 ,抑制了抗坏血酸氧化酶和乙醇脱氢酶的活性 ,减慢了内源乙烯的释放速率。但是 ,减压对阻止果肉褐变无明显效果。     

溶液中有机酸碱的广义氧化还原电极电势及应用

 根据广义氧化还原理论，给出溶液中部分有机酸碱的电极电势。利用这些电势，定量地比较酸碱的氧化性和还原性的强弱；定量地判断反应的方向和计算反应的平衡常数。有机化学反应得到进一步系统化。