Urea formation from carbon dioxide and ammonia at atmospheric pressure

Urea synthesis, currently the largest use of carbon dioxide in organic synthesis, is conventionally operated at high pressure and high temperature. Here, we report for the first time that urea forms at atmosphere and ambient temperatures by negative corona discharge in gas phase. The conversion of CO₂ and yields of a solid mixture of urea and ammonium carbamate, which was identified by the ¹³C NMR spectrum, rise with reducing temperatures and increasing molar ratios of NH₃/CO₂ and discharge frequencies. The conversion of carbon dioxide was found to be 82.16?% at 20?°C and 1?atm with a molar flow ratio of n(NH₃)/n(CO₂) of 2.5. High pressure and high temperature as energy inputs are not necessary.     

Variation characteristics of atmospheric methane and carbon dioxide in summertime at a coastal site in the South China Sea

● Diurnal patterns of CH₄ and CO₂ are clearly extracted using EEMD. ● CH₄ and CO₂ show mid-morning high and evening low patterns during sea breezes. ● Wind direction significantly modulates the diurnal variations in CH₄ and CO₂. Methane (CH₄) and carbon dioxide (CO₂) are the two most important greenhouse gases (GHGs). To examine the variation characteristics of CH₄ and CO₂ in the coastal South China Sea, atmospheric CH₄ and CO₂ measurements were performed in Bohe (BH), Guangdong, China, in summer 2021. By using an adaptive data analysis method, the diurnal patterns of CH₄ and CO₂ were clearly extracted and analysed in relation to the sea breeze (SB) and land breeze (LB), respectively. The average concentrations of CH₄ and CO₂ were 1876.91 ± 31.13 ppb and 407.99 ± 4.24 ppm during SB, and 1988.12 ± 109.92 ppb and 421.54 ± 14.89 ppm during LB, respectively. The values of CH₄ and CO₂ during SB basically coincided with the values and trends of marine background sites, showing that the BH station could serve as an ideal site for background GHG monitoring and dynamic analysis. The extracted diurnal variations in CH₄ and CO₂ showed sunrise high and sunset low patterns (with peaks at 5:00–7:00) during LB but mid-morning high and evening low patterns (with peaks at 9:00) during SB. The diurnal amplitude changes in both CH₄ and CO₂ during LB were almost two to three times those during SB. Wind direction significantly modulated the diurnal variations in CH₄ and CO₂. The results in this study provide a new way to examine the variations in GHGs on different timescales and can also help us gain a better understanding of GHG sources and distributions in the South China Sea.     

拉萨市大气中碳颗粒物的浓度变化及特征

利用STAPLEX大流量分级采样器于2014年8—12月采集拉萨市城区大气颗粒物84个样品,测定不同粒径上有机碳(OC)和元素碳(EC)的质量浓度,定性分析二次有机碳(SOC),基于碳质组分和~(14)C值得到其来源.结果表明,不同粒径的OC质量浓度呈双峰分布,较高峰出现在0.49μm粒径段,次高峰出现在1.5—3.0μm粒径段(8—9月)和3.0—7.2μm粒径段(11—12月);EC主要分布在0.49μm粒径段.OC/EC比值为4.15—33.80,表明拉萨大气颗粒物存在二次有机碳.研究表明,拉萨市碳质颗粒物的主要污染源是燃煤、机动车尾气、生物质燃烧和地面扬尘、生物质燃烧和地面扬尘是OC的主要来源,燃煤和机动车尾气则是EC的主要来源.     

太湖流域近地表大气二氧化碳本底体积分数观测研究

基于2003年1月至2005年6月用气相色谱法对太湖流域近地表大气中二氧化碳本底体积分数的监测资料,对太湖流域近地表大气二氧化碳体积分数的变化特征进行了分析研究。结果表明:在观测时段内,太湖流域近地表大气二氧化碳体积分数平均值为(413.7±19.2)×10-6,且呈上升的趋势,主要受人类活动、工农业生产和交通运输业发展的影响;二氧化碳体积分数季节变化明显,冬春季高,夏秋季低,冬季出现峰值,平均体积分数为(417.8±3.7)×10-6,夏季出现谷值,平均体积分数为(400.8±14.7)×10-6,一年中最高值(424.0±1.1)×10-6出现在12月份,最低值(387.7±1.4)×10-6出现在8月份,主要受源汇强度变化影响;二氧化碳体积分数日变化基本呈双峰态,这是源汇强度变化和边界层稳定程度相互作用的结果。     

Modelling volatility of growth rate in atmospheric carbon dioxide concentrations in a Bayesian approach

Atmospheric gases, such as carbon dioxide, ozone, methane, nitrous oxide, and etc., create a natural greenhouse effect and cause climate change. Therefore, modelling behavior of these gases could help policy makers to control greenhouse effects. In a Bayesian framework, we analyse and model conditional variance of growth rate in atmospheric carbon dioxide concentrations (ACDC) using monthly data from a subset of the well known Mauna Loa atmosphere carbon dioxide record. The conditional variance of ACDC monthly growth rate is modelled using the autoregressive conditional heteroscedasticity (ARCH), generalized ARCH model (GARCH) and a few variants of stochastic volatility (SV) models. Smooth transition ARCH and GARCH models are shown to be able to capture the dynamics in the conditional variance in ACDC level growth rate and to improve the forecast performance of ACDC growth rate.     

大气CO2含量升高对稻田水体微量元素流失的潜在影响

日益增多的研究表明,大气CO2含量升高能显著影响陆地生态系统的土壤微量元素状况,但有关湿地生态系统水体微量元素状况的相关研究非常少.为此,本研究借助我国稻田FACE(Free Air CO2 Enrichment)试验(位于江苏省江都市,始于2004年),于2007年对稻田水体中过滤性铁、过滤性锰和总锌的变化进行了动态监测.结果表明:大气CO2含量升高提高了稻田水体中过滤性铁,总锌及返青期、分蘖期和拔节期过滤性锰的质量浓度,但降低了孕穗期过滤性锰的质量浓度,与对照相比,FACE田块过滤性铁、总锌质量浓度平均提高了21.12%、50.20%;过滤性锰在返青期、分蘖期和拔节期平均提高了13.27%,孕穗期降低了18.03%;不同施氮水平下,过滤性铁、过滤性锰和总锌质量浓度差异不显著.上述结果还表明,大气CO2含量增高可能通过田间排水尤其是由水稻生长前期暴雨而导致的洪涝来加重稻田生态系统微量养分流失的风险.     

Photosynthetic carbon dioxide fixation in zooxanthellae

The carbon-fixation patterns of freshly isolated zooxanthellae from the hermatypic coral Acropora formosa were examined during a 15 min exposure to sodium mosa were examined during a 15 min exposure to sodium [¹⁴C]bicarbonate. The labelling pattern during the first 60 s exposure showed that the C₃ carbon-fixation pathway is the major route for photosynthetic carbon fixation in Symbiodinium sp. 3-Phosphoglyceric acid, which constituted >50% of the label after 5 s, steadily decreased over the first 60 s. Hexose phosphates, aspartate, malate and glucose were the other main products during the first 60 s. Over longer periods, significant amounts of the organic acids succinate, aspartate and glutamate were found in the extract along with glucose; but no glycerol.     

大气气溶胶中的氮:化学形态与同位素特征研究进展

氮是大气气溶胶的重要组成部分.气溶胶中的氮组分参与大气中的光化学反应,进而改变大气组成,影响气候变化与人类健康.同时,大气中过量的颗粒氮改变了氮素的自然循环,当它们沉降到地表时对陆地和水生生态系统产生深远的影响.本文综述了近年来气溶胶氮组分的研究进展,按其化学形态分别阐述了气溶胶中无机氮和有机氮的来源及其相关大气化学过程等,同时探讨了气溶胶中氮的同位素特征,指出该研究领域的薄弱环节并对其研究前景进行了展望.     

Annual ambient atmospheric mercury speciation measurement from Longjing,a rural site in Taiwan

The main purpose of this study was to monitor ambient air particulates and mercury species [RGM, Hg(p), GEM and total mercury] concentrations and dry depositions over rural area at Longjing in central Taiwan during October 2014 to September 2015. In addition, passive air sampler and knife-edge surrogate surface samplers were used to collect the ambient air mercury species concentrations and dry depositions, respectively, in this study. Moreover, direct mercury analyzer was directly used to detect the mercury Hg(p) and RGM concentrations. The result indicated that: (1) The average highest RGM, Hg(p), GEM and total mercury concentrations, and dry depositions were observed in January, prevailing dust storm occurred in winter season was the possible major reason responsible for the above findings. (2) The highest average RGM, Hg(p), GEM and total mercury concentrations, dry depositions and velocities were occurred in winter. This is because that China is the largest atmospheric mercury (Hg) emitter in the world. Its Hg emissions and environmental impacts need to be evaluated. (3) The results indicated that the total mercury ratios of Kaohsiung to that of this study were 5.61. This is because that Kaohsiung has the largest industry density (~60 %) in Taiwan. (4) the USA showed average lower mercury species concentrations when compared to those of the other world countries. The average ratios of China/USA values were 89, 76 and 160 for total mercury, RGM and Hg(p), respectively, during the years of 2000–2012.     

Long-term organic fertilizer-induced carbonate neoformation increases carbon sequestration in soil

Environmental Chemistry Letters - Soil carbon is major driver of climate in the long term because soil can either decrease global warming by carbon sequestration or increase warming by...     

Recent advances in the photocatalytic reduction of carbon dioxide

Fossil fuels are currently the major energy source and are rapidly consumed to supply the increasing energy demands of mankind. CO₂, a product of fossil fuel combustion, leads to climate change and will have a serious impact on our environment. There is an increasing need to mitigate CO₂ emissions using carbon–neutral energy sources. Therefore, research activities are devoted to CO₂ capture, storage and utilization. For instance, photocatalytic reduction of CO₂ into hydrocarbon fuels is a promising avenue to recycle carbon dioxide. Here we review the present status of the emission and utilization of CO₂. Then we review the photocatalytic conversion of CO₂ by TiO₂, modified TiO₂ and non-titanium metal oxides. Finally, the challenges and prospects for further development of CO₂ photocatalytic reduction are presented.     

吉林西部不同开发年份盐碱水田土壤有机碳和碳酸盐的季节动态

水稻土是中国主要的耕作土壤,在陆地土壤碳循环研究中具有重要现实意义。针对吉林西部水田土壤的特征,将无机碳库纳入土壤碳库研究,以典型灌区前郭县为例,野外采集盐碱地和已开发5、15、25、35、55年的5种不同水田表层土壤,建立实验样地,在水稻生长的幼苗期、分蘖期、长穗期和结实期采集土壤样品,用TOC仪分别测试表层土壤有机碳和碳酸盐含量,分析其季节动态规律和开发年份特征。结果表明：吉林西部盐碱水田土壤有机碳呈现“减-增-减”的季节变化规律,水稻生长的幼苗期和分蘖期有机碳含量下降,长穗期含量上升,结实期含量下降,碳酸盐季节变化规律与其相反,二者季节变化呈显著负相关;经历一个生长季后,开发5、15、25、35、55年的土壤有机碳含量分别增加了2.98%、3.53%、3.66%、2.72%、2.30%,碳酸盐含量分别增加了4.07%、2.15%、1.08%、1.61%、11.36%,说明研究区水田生长期具有碳汇作用;与未开发盐碱地相比,开发的5、15、25、35、55年生长季土壤平均总碳量分别增加了89.81%、121.03%、137.22%、188.28%,有机碳含量分别增加了284.28%、392.00%、456.37%、559.08%、666.06%,碳酸盐含量分别降低了13.49%、22.84%、32.23%、43.53%、62.40%;开发年份越长,水田土壤总碳和有机碳含量越高,碳酸盐含量越低;总碳的增加来自有机碳的增加;盐碱地开发有利于土壤碳汇。水稻生长期温度和降雨量影响土壤有机碳和碳酸盐季节变化。     

煤矸石风化物不同粒级中重金属镉含量及其形态变化

对抚顺西露天矿煤矸石山表层煤矸石风化母岩进行多点取样,风化物筛分成>2 mm、2～0.25 mm和<0.25 mm等3个粒级,分析测定了矸石山表层母岩及其风化物不同粒级中Cd含量及其形态变化特征.结果表明:煤矸石母岩及其风化物中cd含量超过土壤环境质量2级标准,页岩、泥岩及其风化物pH值7.2～8.6,但燃后泥岩pH值4.9.碳质页岩2～0.25 mm粒级风化物中Cd损失最多,为73.6%;<0.25 mm细粒级Cd损失较少,为17.0%,这与细颗粒的表面吸附作用有关;泥岩及其各粒级风化物Cd元素不易损失,其Cd含量变化也相对较小;但燃后泥岩风化物中的Cd较容易损失.煤矸石风化物各样品类型中的Cd均以残渣态为主,可还原态和弱酸可提取态所占比例次之,可氧化态所占比例最小.弱酸可提取态Cd在细颗粒风化物中所占比例较高.     

Using a CHN analyzer to reduce carbonate interference in particulate organic carbon analyses

Using a CHN analyzer at a reduced temperature (720°C), the organic carbon of particulates taken from water is oxidized while little, if any, dissociation of carbonate occurs. When necessary for increased precision or for samples with a high CaCO₃ content, the small interference of carbonate with organic C determinations can be quantified by running representative samples at different oxidation time intervals and interpolating to time zero. By running replicates, one at 720°C and one at 1100°C, data on organic and inorganic carbon and on nitrogen are obtained with the analyzer.     

Vole response to unintentional changes in the chemistry of GM poplars

Summary.  There is an increased interest for the use of GM trees in forestry and several commercially promising lines are now available. However, the ecological implications of the use of GM trees, e.g. effects on non-target natural enemies, have rarely been explored. The aim of this study was to determine if modification of non-defensive traits in GM poplars unintentionally can influence plant chemistry in a way that has consequences for palatability to voles. In a greenhouse experiment, we used two lines, SPS33A and SPS26, of GM hybrid poplars (Populus tremula x tremuloides) with 1.5 and 4 times, respectively, over-expression sucrose-phosphate synthase (SPS). This enzyme plays a central role in sucrose synthesis, affecting cold acclimation, mesophyll sucrose content and biomass production. As a control we used the isogenic unmodified wild type. Stems of these poplars were presented to bank voles and field voles in cafeteria experiments. The concentration of condensed tannins was higher in leaves of lines SPS33A and SPS26 than in the isogenic wild-type and the concentration of nitrogen was higher in line SPS33A than in both the wild-type and line SPS26. Although the bank voles consumed slightly less bark from SPS33A, there were no significant differences in the preference of bank vole or field vole for the different poplar lines. This indicates that the changes in plant chemistry were insufficient to produce any strong herbivore response or that alteration in tannins and nitrogen counteracted each other. Still, changes in the interactions between mammalian herbivores and GM trees are important to consider in future cost-benefits analyses of GM trees.     

Optimal sequestration of carbon dioxide and phosphorus in soils by gypsum amendment

Gypsum has been applied as a natural fertilizer and soil amendment for centuries in agriculture for providing crop nutrients such as Ca and S, and for improving soil physical properties. Recently, gypsum has been tested for sequestrating CO₂ from the air and for capturing soluble phosphates in the soil, through formation of insoluble calcium phosphates and carbonates. However, the environmental factors controlling these sequestration processes have not been systemically studied. Here, we calculate optimal conditions of sequestration using chemical equilibrium modeling. Our results show that CO₂ carbonation is effective at pH higher than 8.5 at atmospheric concentration. The removal of P is higher than 80 % for pH higher than 6.4, when Ca and P are at stoichiometric ratio. Also, placement of gypsum in subsoil is more effective for CO₂ capture than applying it on soil surface since soil pores often contain higher concentrations of CO₂ due to the soil respiration process. Overall, increases in medium pH, gypsum application rate, or CO₂ partial pressure can increase the effectiveness of the amendment.     

惠州绿化乔木叶片及其叶面降尘对大气SO2污染的生物监测

采用常规采样及碱片挂片法同步监测广东省惠州市大气SO2体积分数,用ICP-AES测定了惠州市不同功能区的2种主要绿化树种大叶榕(Ficus virens Ait var.sublanceolata(Miq.) Corner)、紫荆(Bauhinia blakeana)叶片及其叶面降尘的硫质量分数。结果表明,不同功能区植物叶片和降尘的硫质量分数差异显著,其综合污染指数(PI)以商业交通区、工业区、居住区、清洁区的趋势递减。叶片中硫的质量分数随春、夏、秋季而增长,季节差异显著。植物叶片、降尘中硫质量分数随交通流量的减少而降低。叶片和叶面降尘中硫的质量分数与大气硫酸盐化速率三者显著相关,大叶榕和紫荆与降尘协同生物监测大气SO2的二元数学模型的相关系数分别为R=0.995和R=0.990,明显优于植物与硫酸盐化速率监测SO2的常规一元数学模型。表明大叶榕、紫荆叶片及其叶面降尘均可作为城市区域大气SO2污染的有效指示剂,叶片的长期效益和季节效益显著,降尘则短期效益显著;两者协同监测,可靠性和灵敏度更高,应用前景广阔,可为地方和区域环境监测和评价提供参考。     

Diurnal changes in photosynthesis of Antarctic fast ice algal communities determined by pulse amplitude modulation fluorometry

The aim of this project was to determine both the diurnal changes in photosynthetic activity of Antarctic sea ice algae and also the protective mechanisms they use to mitigate the effects of in situ UV radiation. Changes in the diurnal photosynthetic parameters of fast ice algal communities at McMurdo Sound were measured in situ, using a custom designed monitoring pulse amplitude modulation fluorometer. The sea ice microalgae were able to adapt rapidly to either increasing or decreasing ambient irradiances. ΔF/F_m' values were between 0.2 and 0.51, while E_k varied between 2.1 and 18 μmol photons m^-2 s^-1. ΔF/F_m', E_k, and relative electron transfer rate (rETR) all varied sequentially over the course of a day. rETR and E_k were highest at midday at the highest irradiances, when there was apparent midday down regulation of photosynthesis, while ΔF/F_m' was highest at midnight. The effects of natural UV radiation on sea ice were examined, but it was not possible to detect the effect of either UVB or UVA and UVB on photosynthesis. This was considered to be largely because of the large spatial and temporal heterogeneity of the under ice community, changing irradiances throughout the day and the relatively small change caused by UV.