Some advances in atmospheric chemistry

In the recent decade, researches have been carried out by our group on some aspects of atmospheric chemistry through field observation, mechanism analysis and model simulation. Here some main results on greenhouse gas (CH4, N2O) emission from Chinese agricultural fields, aerosol, global carbon cycle and ozone variation in surface laver over China are briefly reported.     

Aerosol formation: atmospheric particles from organic vapours

Aerosol particles produced over forested areas may affect climate by acting as nuclei for cloud condensation, but their composition (and hence the chemical species that drive their production) remains an open question. Here we show, to our knowledge for the first time, that these newly formed particles (3-5 nm in diameter) are composed primarily of organic species, such as cis-pinonic acid and pinic acid, produced by oxidation of terpenes in organic vapours released from the canopy.     

Complex organic matter in Titan's atmospheric aerosols from in situ pyrolysis and analysis

Aerosols in Titan's atmosphere play an important role in determining its thermal structure. They also serve as sinks for organic vapours and can act as condensation nuclei for the formation of clouds, where the condensation efficiency will depend on the chemical composition of the aerosols. So far, however, no direct information has been available on the chemical composition of these particles. Here we report an in situ chemical analysis of Titan's aerosols by pyrolysis at 600 degrees C. Ammonia (NH3) and hydrogen cyanide (HCN) have been identified as the main pyrolysis products. This clearly shows that the aerosol particles include a solid organic refractory core. NH3 and HCN are gaseous chemical fingerprints of the complex organics that constitute this core, and their presence demonstrates that carbon and nitrogen are in the aerosols.     

有机化学教学如何面向新世纪--有机化学教学改革探索与实践

结合作者多年的教学实践，探讨了在有机化学教学中如何转变教育观念，改革教学内容及教学方法等问题，探讨了面向新世纪，适应新时代要求的教育规律和教育方法。目的在于全面提高学生能力，培养和造就更多高素质的创造性人才。     

中国大气Ca2+传输和沉降模拟

盐基阳离子(Ca2 ,Mg2 ,K ,Na )在缓解土壤和水体酸化中起着重要作用。为了满足中国酸沉降控制的需要,该研究利用建立的多层动态Euler模型模拟中国大气Ca2 传输和沉降。结果表明:2000年中国的Ca2 总沉降量为5.29 Mt,其中湿沉降1.45 Mt,干沉降3.84 Mt。人为源排放对全国总沉降、湿沉降和干沉降的贡献率分别为67.1%、92.4%和57.6%,对东南部地区的贡献率更大,而自然源仅对西北地区的沉降起重要作用。中国酸沉降较为严重的东南部地区,Ca2 沉降量普遍大于0.10 kmol.hm-2.a-1,甚至超过0.25 kmol.hm-2.a-1,能够中和大部分的SO42-沉降。     

中国大气Ca~(2 )传输和沉降模拟

盐基阳离子(Ca2 ,Mg2 ,K ,Na )在缓解土壤和水体酸化中起着重要作用。为了满足中国酸沉降控制的需要,该研究利用建立的多层动态Euler模型,模拟了中国大气Ca2 传输和沉降。结果表明,2000年中国的Ca2 总沉降量为5.29Mt,其中湿沉降1.45Mt,干沉降3.84Mt。人为源排放对全国总沉降、湿沉降和干沉降的贡献率分别为67.1%、92.4%和57.6%,对东南部地区的贡献率更大;而自然源仅对西北地区的沉降起重要作用。中国酸沉降较为严重的东南部地区,Ca2 沉降量普遍大于0.10kmol.hm-2.a-1,甚至超过0.25kmol.hm-2.a-1,能够中和大部分的SO42-沉降。     

有机化学教学模式改革探讨

从改革教学模式出发,提出了有机化学教学中采用点线式教学法,专题报告会,拟订课题讨论提纲组织专题讨论,学生自选题作课程论文报告及改革成绩考核办法等新的教学模式。以培养学生的阅读文献,收集信息,创造性思维及解决实际问题的能力,并收到了明显的效果。     

有机化学实验中自我安全意识的教育

有机化学是一门以实验为基础的学科,学习有机化学必须认真做好有机化学实验。在实验室对学生进行动手能力,研究设计能力,思维表达能力等的培养固然是主要目的,但是基于有机化学实验自身的特点,对学生进行安全知识教育,培养学生的自我安全意识也是至关重要的。从大学有机化学实验安全出发,从几个方面对学生安全意识的培养提出了自己的一些看法及解决途径。     

Export of dissolved organic carbon from peatlands under elevated carbon dioxide levels

Peatlands represent a vast store of global carbon. Observations of rapidly rising dissolved organic carbon concentrations in rivers draining peatlands have created concerns that those stores are beginning to destabilize. Three main factors have been put forward as potential causal mechanisms, but it appears that two alternatives--warming and increased river discharge--cannot offer satisfactory explanations. Here we show that the third proposed mechanism, namely shifting trends in the proportion of annual rainfall arriving in summer, is similarly unable to account for the trend. Instead we infer that a previously unrecognized mechanism--carbon dioxide mediated stimulation of primary productivity--is responsible. Under elevated carbon dioxide levels, the proportion of dissolved organic carbon derived from recently assimilated carbon dioxide was ten times higher than that of the control cases. Concentrations of dissolved organic carbon appear far more sensitive to environmental drivers that affect net primary productivity than those affecting decomposition alone.     

Indication of drier periods on Mars from the chemistry and mineralogy of atmospheric dust

The ubiquitous atmospheric dust on Mars is well mixed by periodic global dust storms, and such dust carries information about the environment in which it once formed and hence about the history of water on Mars. The Mars Exploration Rovers have permanent magnets to collect atmospheric dust for investigation by instruments on the rovers. Here we report results from M?ssbauer spectroscopy and X-ray fluorescence of dust particles captured from the martian atmosphere by the magnets. The dust on the magnets contains magnetite and olivine; this indicates a basaltic origin of the dust and shows that magnetite, not maghemite, is the mineral mainly responsible for the magnetic properties of the dust. Furthermore, the dust on the magnets contains some ferric oxides, probably including nanocrystalline phases, so some alteration or oxidation of the basaltic dust seems to have occurred. The presence of olivine indicates that liquid water did not play a dominant role in the processes that formed the atmospheric dust.     

超声在有机化学中的研究进展

 介绍了1997到2002年间在我国超声有机化学领域内的研究成果.     

在有机化学实验教学中实行双语教学的尝试

随着中国加入世界贸易组织、外语在人们的日常生活中变得越来越重要，一个优秀人才不仅要懂专业，而且更要有较高的外语水平，才能适应当今社会的发展要求，根据西南民族学院化学专业学生的实际情况，为了提高学生的专业英语水平，有机化学实验教学中进行了双语教学的尝式，取得了一定的成效。     

有机化学实验开放式教学改革的探讨

根据有机化学实验的教学特点,对有机化学实验教学内容、授课方式等体系进行了改革,有效地调动学生学习的主动性,培养了学生的创新能力,提高了教育教学质量,促进了学生知识、能力和综合素质的提高.     

有机化学与生命科学的碰撞——2016年生物有机化学热点回眸

 生物有机化学旨在阐明复杂生命体系中的内在化学机制,以及通过理性的设计和改良来创造能够由于有机合成化学的生物大分子催化剂。本文遴选2016年发表于《Science》《Nature》《PNAS》《Nature Chemistry》等期刊的部分重要研究结果,回顾2016年生物有机化学领域取得的突破性进展。     

A 300-million-year record of atmospheric carbon dioxide from fossil plant cuticles

To understand better the link between atmospheric CO2 concentrations and climate over geological time, records of past CO2 are reconstructed from geochemical proxies. Although these records have provided us with a broad picture of CO2 variation throughout the Phanerozoic eon (the past 544 Myr), inconsistencies and gaps remain that still need to be resolved. Here I present a continuous 300-Myr record of stomatal abundance from fossil leaves of four genera of plants that are closely related to the present-day Ginkgo tree. Using the known relationship between leaf stomatal abundance and growing season CO2 concentrations, I reconstruct past atmospheric CO2 concentrations. For the past 300 Myr, only two intervals of low CO2 (<1,000 p.p.m.v.) are inferred, both of which coincide with known ice ages in Neogene (1-8 Myr) and early Permian (275-290 Myr) times. But for most of the Mesozoic era (65-250 Myr), CO2 levels were high (1,000-2,000 p.p.m.v.), with transient excursions to even higher CO2 (>2,000 p.p.m.v.) concentrations. These results are consistent with some reconstructions of past CO2 (refs 1, 2) and palaeotemperature records, but suggest that CO2 reconstructions based on carbon isotope proxies may be compromised by episodic outbursts of isotopically light methane. These results support the role of water vapour, methane and CO2 in greenhouse climate warming over the past 300 Myr.     

Glacial/interglacial variations in atmospheric carbon dioxide

Twenty years ago, measurements on ice cores showed that the concentration of carbon dioxide in the atmosphere was lower during ice ages than it is today. As yet, there is no broadly accepted explanation for this difference. Current investigations focus on the ocean's 'biological pump', the sequestration of carbon in the ocean interior by the rain of organic carbon out of the surface ocean, and its effect on the burial of calcium carbonate in marine sediments. Some researchers surmise that the whole-ocean reservoir of algal nutrients was larger during glacial times, strengthening the biological pump at low latitudes, where these nutrients are currently limiting. Others propose that the biological pump was more efficient during glacial times because of more complete utilization of nutrients at high latitudes, where much of the nutrient supply currently goes unused. We present a version of the latter hypothesis that focuses on the open ocean surrounding Antarctica, involving both the biology and physics of that region.     

煤矿区大气降尘中Hg和As的赋存形态及健康风险评价

对宿州煤矿区大气降尘中Hg和As的含量特征及赋存形态进行分析,并利用健康风险评价模型,评估其在多暴露途径下对人体的健康风险。结果表明:宿州煤矿区大气降尘中Hg和As的平均含量分别为土壤背景值的19.91和1.54倍,前者为偏重污染,后者介于无污染至轻度污染;降尘中Hg和As均以残渣态形式为主,生物可利用程度较低,但Hg元素具有较高的潜在生物危害性;As经手口摄入分别是引发大气降尘重金属非致癌健康风险的主要元素和暴露途径,儿童的非致癌风险(0.903)高于成人(0.122),但均低于美国EPA的风险限值1.0;降尘中As通过呼吸吸入途径不具有致癌风险。     

北京市局部大气沉降颗粒表面成分分析

采用X射线光电子能谱（XPS）对大气沉降颗粒表面元素组成和元素的存在形式进行分析,发现其表面含有Al、Ca、Si等地壳元素和C、N、O等轻元素。Al、Si、Ca等地壳元素的原子数分数总和高达16.4%,表明大气颗粒物的沉降过程伴随着地壳元素的累积;元素S与N的原子数分数比值接近1,表明没有足够的碱性物质NH₃中和酸性物质SO₄^2-,沉降颗粒表面呈现酸性。结合高分辨率XPS图谱分析,发现沉降颗粒物表面的含碳物质以有机含碳化合物为主,同时存在少量的无定型碳;而氮元素则主要来源于以NO_x、NH₄⁺为主的无机氮和以吡啶氮为主的有机氮。     

有机化学中立体化学的教学探讨

立体化学是基础有机化学中的重点和难点之一.本文在多年教学的基础上,分析了在立体化学教学过程中存在的几个难点问题,并介绍了解决这几个难点问题的有效方法.