南昌市PM_(2.5)中硫酸盐、硝酸盐及其气态前体物的分布特征与转化机制

2014年1月至2015年1月,在南昌市3种类型采样点(混合区、主干道旁侧、燃煤电厂附近),对大气PM_(2.5)中SO_4~(2-)和NO_3~-及其气体前体物SO_2、NO_2进行同步采样,通过分析硫氧化速率(SOR)和氮氧化速率(NOR),对PM_(2.5)中硫酸盐和硝酸盐的来源、形成机制和影响因素进行探讨。结果表明,南昌市SO_2浓度18.9~74.8μg/m~3,NO_2浓度29.7~62.6μg/m~3,PM_(2.5)中SO_4~(2-)浓度13.7~28.4μg/m~3,NO_3~-浓度3.9~39.9μg/m~3,SOR值0.28~0.60,NOR值0.09~0.33。SO_2、NO_2、SO_4~(2-)、NO_3~-和SOR、NOR的季节分布和日分布,反映硫酸盐和硝酸盐的二次生成受气象条件、环境条件和排放源的影响。SOR与NOR的季节分布正好相反,日分布也差异较大,反映生成机制不同。SO_2、NO_2、SO_4~(2-)、NO_3~-和SOR、NOR在不同采样点的分布,反映燃煤烟气和机动车尾气增加SO_2、NO_2的浓度,促进SO_4~(2-)、NO_3~-的二次生成。[NO_3~-]/[SO_4~(2-)]春、夏、秋、冬分别为0.86、0.15、0.83、0.70,反映南昌市机动车尾气贡献比例较大;[NO_3~-]/[SO_4~(2-)]受硫酸盐和硝酸盐在不同季节的二次生成机制和速率的影响,也受排放源的影响。     

贵阳市大气PM_(2.5)中水溶性阴离子特征及来源分析

于2017年9月～2018年8月在贵阳市市区某楼顶,利用多功能型空气污染物采样仪每日分昼、夜采集大气PM_(2.5)样品,用离子色谱仪(IC)检测分析PM_(2.5)中3种水溶性阴离子Cl~-,NO_3~-和SO_4~(2-)的浓度并解析其来源。结果表明:贵阳市PM_(2.5)为47.69±21.40μg/m~3,是GB3095-2012一级浓度限值(35μg/m~3)的1.36倍。Cl~-,NO_3~-和SO_4~(2-)年浓度总和为13.50±15.26μg/m~3,占PM_(2.5)的28.3%,其中SO_4~(2-)(11.31±13.08μg/m~3)占PM_(2.5)的23.7%。3种阴离子在冬季的浓度都高于其他3个季节,且白天的浓度均高于夜间,浓度大小顺序为:ρ(SO_4~(2-))ρ(NO_3~-)ρ(Cl~-)。气象参数分析发现,3种阴离子与风向上的污染源有关;根据全年的ρ(NO_3~-)/ρ(SO_4~(2-))为0.14判断大气污染主要来自于煤炭的燃烧;后向轨迹分析结果表明,空气中污染气团主要来自贵州省内及周边毗邻省份,受贵州西北方向的气团影响较小,受西南方向气团影响较大,最长的气团来自于国外。     

交通路口大气气溶胶的污染状况以及多环芳烃的污染特征研究

研究了城市交通路口大气气溶胶污染状况及气溶胶中多环芳烃(PAHs)的污染特征.在福州市主要交通路口之一的五四路和二环路的交叉路口采集大气中PM2.5、PM5、PM10、PM2.5~5.0、PM5~10、PM10~100及TSP.将优化的高效液相色谱编程荧光法用于各切割粒径气溶胶样品中的12种多环芳烃分析.研究结果表明:交通路口颗粒物中的飘尘(PM10)占总悬浮颗粒物(TSP)的70%;PM5占飘尘(PM10)的70%;而细粒子PM2.5占PM5的73%.交通源所产生的PAHs主要存在于细粒子PM2.5中,通过特征标志的多环芳烃的比值识别,交通路口大气颗粒物中的多环芳烃主要来源于机动车尾气排放.     

北京大气颗粒物污染本地源与外来源的区分--元素比值Mg/Al示踪法估算矿物气溶胶外来源的贡献

提出了一种新的元素示踪法, 用于估算和区分北京大气颗粒物污染的主要组成矿物气溶胶的外来源和本地源. 通过采集、分析具有代表性的、可覆盖北京所有地区的气溶胶、地面扬尘以及外来源代表地区内蒙多伦等地的表层土, 发现气溶胶中元素比值Mg/Al是区分北京地区矿物气溶胶本地源与外来源有效的元素示踪体系. 矿物气溶胶即沙尘、硫酸盐和硝酸盐为主的无机污染气溶胶, 和有机污染气溶胶同是北京大气颗粒物的重要组成部分, 其中矿物气溶胶占总颗粒物(TSP)的32%～67%, 占细粒子(PM2.5)的10%～70%, 在沙尘暴期间分别高达74%和90%. 根据元素示踪法, 首次估算出北京地区矿物气溶胶中本地源与外来源的相对贡献量. 春季外来源占TSP的62% (38%～86%), 占PM10的69% (52%～90%), 占PM2.5的76% (59%～93%); 冬季外来源占TSP的69% (52%～83%), 占PM10的79% (52%～93%), 占PM2.5的45% (7%～79%); 而在夏季和秋季, 外来源仅占～20%. 外来源在冬春季对北京矿物气溶胶的贡献要高于夏季, 这显然与冬春季气候差异有关. 沙尘暴期间外来源贡献最高达97%, 成为北京大气颗粒物的主要来源.     

2019年泰州市某区PM_(2.5)中多环芳烃的污染特征及健康风险评价

了解泰州市某区大气环境中多环芳烃的浓度水平和人群暴露健康风险水平,可为污染防治提供参考依据。2019年每个月连续采集7天PM_(2.5),称重法计算PM_(2.5)的质量浓度,超声萃取-液相色谱法测定PM_(2.5)中16种多环芳烃,特征比值法判断多环芳烃来源,人群终身致癌超额危险度评估经呼吸途径产生的健康暴露风险。结果显示,全年萘、苊烯、苊都未检出。但是,冬季多环芳烃总浓度较高,夏季浓度最低。依据《环境空气质量标准》(GB3095-2012)二级标准来判断,PM_(2.5)年度质量浓度均值超标率为16.7%(14/84),苯并[a]芘24 h日均浓度超标率为10.7%(9/84)。多环芳烃年均浓度为(7.57±0.72) ng/m~3,略低于周边地区的水平。根据特征比值法判断,该区多环芳烃主要源自汽油燃烧为主的混合源燃烧排放。人群暴露危险度值均小于最大可接受危险度值1.0×10~(-6),PM_(2.5)中多环芳烃的人群健康风险处于可接受水平。     

北京大气颗粒物污染本地源与外来源的区分

提出了一种新的元素示踪法, 用于估算和区分北京大气颗粒物污染的主要组成矿物气溶胶的外来源和本地源. 通过采集、分析具有代表性的、可覆盖北京所有地区的气溶胶、地面扬尘以及外来源代表地区内蒙多伦等地的表层土, 发现气溶胶中元素比值Mg/Al是区分北京地区矿物气溶胶本地源与外来源有效的元素示踪体系. 矿物气溶胶即沙尘、硫酸盐和硝酸盐为主的无机污染气溶胶, 和有机污染气溶胶同是北京大气颗粒物的重要组成部分, 其中矿物气溶胶占总颗粒物(TSP)的32%~67%, 占细粒子(PM_2.5)的10%~70%, 在沙尘暴期间分别高达74%和90%. 根据元素示踪法, 首次估算出北京地区矿物气溶胶中本地源与外来源的相对贡献量. 春季外来源占TSP的62% (38%~86%), 占PM₁₀的69% (52%~90%), 占PM_2.5的76% (59%~93%); 冬季外来源占TSP的69% (52%~83%), 占PM₁₀的79% (52%~93%), 占PM_2.5的45% (7%~79%); 而在夏季和秋季, 外来源仅占~20%. 外来源在冬春季对北京矿物气溶胶的贡献要高于夏季, 这显然与冬春季气候差异有关. 沙尘暴期间外来源贡献最高达97%, 成为北京大气颗粒物的主要来源.     

燃烧源PM2.5凝结洗涤脱除实验研究

利用蒸汽在燃烧源PM2.5表面凝结,促使PM2.5凝结长大,建立一套燃烧源PM2.5凝结洗涤的实验台;考察了颗粒粒径分布、蒸汽添加量、液气比等对两种燃烧源PM2.5凝结洗涤脱除效果的影响。采用电称低压冲击器 (ELPI)在线测试分析燃煤和燃油PM2.5凝结洗涤前后的数浓度和粒径分布特性,并用SEM和XPS对两种不同燃烧源的颗粒进行了形貌和元素组分分析。结果表明,燃煤和燃油产生的PM2.5形貌和组分具有较大的差别,燃煤PM2.5主要为硅铝矿物质,而燃油PM2.5主要为含炭物质;相同条件下,燃煤PM2.5相变脱除效果优于燃油PM2.5;随着蒸汽添加量的增加,两者的脱除效率均升高;随粒径的增大,脱除效率提高;蒸汽添加量为0.08kg/m3时,粒径为0.4μm的燃煤和燃油细颗粒的脱除效率分别81％和72％;此外,适当增加液气比有利于凝结长大含尘液滴的脱除。     

现代分析技术在PM_(2.5)组份识别中的应用

以上海市闵行地区的大气细颗粒物PM_(2.5)为研究对象,综合多种分析测试手段对颗粒物的成份进行分析,以识别PM_(2.5)中主要污染物的来源。采用扫描电镜和透射电镜技术观察颗粒物的形貌特征,红外光谱技术识别颗粒物中的特征官能团,再结合碳分析仪,电感耦合等离子体质谱,离子色谱和气相色谱等技术对颗粒物中的元素碳和有机碳、无机金属元素、无机水溶性离子及有机化合物PAHs进行定量分析。结果表明PM_(2.5)是由大量的微米颗粒物及部分超细颗粒物组成,颗粒物主要以烟尘聚集体的形式存在;PM_(2.5)中有无机盐类和有机化合物的官能团共存在,有机官能团主要为羧基和芳烃化合物,无机化合物主要为硫酸盐和氨类化合物;各化学组份的质量分数表明了二次离子(SO_4~(2-),NO_3~-,NH_4~+)和有机碳是PM_(2.5)中的主要污染物,并明确解析了PM_(2.5)中各种污染来源的分担率。     

电感耦合等离子体质谱法-电子稀释EDR技术测定大气PM_(2.5)中22种元素的含量

正PM_(2.5)是指大气中空气动力学当量直径小于等于2.5μm的细颗粒物,是大气污染与疾病负担评估的特征指标~([1])。PM_(2.5)中所含元素几乎涉及到元素周期表中所有金属、非金属及过渡性元素~([2]),且浓度水平分布范围宽,痕量元素(铍、汞、铀、钒、镉等)与高含量元素(钾、钠、钙、镁、铁、锌等)浓度常相差4～5个数量级~([2-4]);其中金属污染物是PM_(2.5)的重要组成部分~([5]),进入人体后蓄积,会导致器官功能性障碍和不可逆性损害~([6])。     

深圳冬、夏季大气细粒子及其二次组分的污染特征

在2004年夏季和冬季, 分别在深圳宝安中心区进行了大气颗粒物细粒子的加强观测, 共获得30套样品. 通过对样品质量浓度、化学成分分析, 结合采样期间的气象条件, 对深圳当前大气颗粒物的污染特征、季节变化规律(夏季和冬季)及二次污染特征进行了研究. 结果表明, 深圳大气颗粒物污染的季节差异较大, 在夏季加强观测期间, PM_2.5和PM₁₀的日均质量浓度分别为34.9 μg·m^-3和56.9 μg·m^-3; 冬季加强观测期间PM_2.5和PM₁₀的日均质量浓度分别为99.0 μg·m^-3和134.8 μg·m^-3, 分别比夏季增长184%和137%. PM_2.5在夏季和冬季观测期间平均分别占PM₁₀的61%和73%, 细粒子污染严重; 夏、冬季加强观测期间OC和EC的比值平均分别为3.4和1.6, 估算的SOC占OC的比例平均分别为56%和6%, 夏季SOC对OC的贡献显著; 在夏季持续高温期间, 二次颗粒物的浓度及其在PM_2.5中的比重都急剧升高, 本地二次污染严重; 当夏季主导风向来自西南或东南海面时, 大气环境质量较好, 冬季主导风向来自北方内陆时, 大气环境质量较差.     

Generation and detection of levuglandins and isolevuglandins in vitro and in vivo

Levuglandins (LGs) and isolevuglandins (isoLGs), formed by rearrangement of endoperoxide intermediates generated through the cyclooxygenase and free radical induced oxidation of polyunsaturated fatty acids (PUFAs), are extraordinarily reactive, forming covalent adducts incorporating protein lysyl ε-amino groups. Because they accumulate, these adducts provide a dosimeter of oxidative injury. This review provides an updated and comprehensive overview of the generation of LG/isoLG in vitro and in vivo and the detection methods for the adducts of LG/isoLG and biological molecules in vivo.     

Femtosecond electron-transfer reactions in mono- and polynucleotides and in DNA

Quenching of redox active, intercalating dyes by guanine bases in DNA can occur on a femtosecond time scale both in DNA and in nucleotide complexes. Notwithstanding the ultrafast rate coefficients, we find that a classical, nonadiabatic Marcus model for electron transfer explains the experimental observations, which allows us to estimate the electronic coupling (330 cm(-1)) and reorganization (8070 cm(-1)) energies involved for thionine-[poly(dG-dC)](2) complexes. Making the simplifying assumption that other charged, pi-stacked DNA intercalators also have approximately these same values, the electron-transfer rate coefficients as a function of the driving force, DeltaG, are derived for similar molecules. The rate of electron transfer is found to be independent of the speed of molecular reorientation. Electron transfer to the thionine singlet excited state from DNA obtained from calf thymus, salmon testes, and the bacterium, micrococcus luteus (lysodeikticus) containing different fractions of G-C pairs, has also been studied. Using a Monte Carlo model for electron transfer in DNA and allowing for reaction of the dye with the nearest 10 bases in the chain, the distance dependence scaling parameter, beta, is found to be 0.8 +/- 0.1 A(-1). The model also predicts the redox potential for guanine dimers, and we find this to be close to the value for isolated guanine bases. Additionally, we find that the pyrimidine bases are barriers to efficient electron transfer within the superexchange limit, and we also infer from this model that the electrons do not cross between strands on the picosecond time scale; that is, the electronic coupling occurs predominantly through the pi-stack and is not increased substantially by the presence of hydrogen bonding within the duplex. We conclude that long-range electron transfer in DNA is not exceptionally fast as would be expected if DNA behaved as a "molecular wire" but nor is it as slow as is seen in proteins, which do not benefit from pi-stacking.     

Carbon chains and rings in the laboratory and in space

Seventy-seven reactive organic molecules of astrophysical interest have been identified in a supersonic molecular beam, 73 in the radio band by Fourier-transform microwave spectroscopy, four in the optical by laser cavity ringdown spectroscopy. Most are linear carbon chains, but six consist of carbon chains attached to the compact, highly polar C3 ring, and two are rhomboidal cyclic configurations of SiC3. The laboratory astrophysics of the radio molecules is complete for the time being, in the sense that essentially all the rotational transitions of current interest to radio astronomy (including hyperfine structure when present) can now be calculated to a small fraction of 1 km s(-1) in equivalent radial velocity; six of the radio molecules have already been detected in space on the basis of the present data. The FTM spectrometer employed in this work is far from fundamental limits of sensitivity, so many more molecules can probably be found by refinements of present techniques. The density of reactive molecules in our supersonic beam is generally high by the standards of laser spectroscopy, and many of the radio molecules probably have detectable optical transitions which we are attempting to find, largely motivated by the long-standing problem of the diffuse interstellar bands. Our most interesting result to date is the detection of a fairly strong molecular band at 443 nm in a benzene discharge, in exact coincidence with the strongest and best known interstellar band. Isotopic shifts measured with partially and totally deuterated benzene suggest that the carrier of the laboratory band is a hydrocarbon molecule with the elemental formula CnH5, with n most likely in the range 3-6.     

Supercomputing and supercomputers for science and engineering in general and for chemistry and biosciences in particular

We start by pointing out relationships between production of information, global simulation, and supercomputing, thus placing our research activities in today's society context. Then we detail the evolution in hardware and software for 1CAP, our experimental supercomputer, which we claim to be especially well suited for supercomputing in science and engineering. A preliminary discussion of 1CAP/3090 (our latest experimental effort) is included. Many examples from different disciplines are provided to verify our assertions. We “prove” our point by presenting an example of global supercomputing. Starting with 3 nuclei and 10 electrons, building up to a single water molecule, then to a few hundred, we learn, for example, about Raman, infrared, and neutron scattering; we then move up to a few hundred thousand molecules to analyze particle flow and obstructions; finally we experiment, but only preliminarily, with a few million particles to learn more on nonequilibrium dynamics as in the Rayleigh-Benard systems. In this way, quantum mechanics is overlapped with statistical mechanics and expanded into microdynamics. The entire paper is finally reanalyzed from a different perspective, presenting rather systematically, even if most briefly, our ideas on “modern” computational chemistry, where quantum mechanics is as much needed as fluid dynamics and graphics. In this section the main computational techniques are analyzed in terms of computer programs and their associated flow diagrams to solve the basic equations using parallel supercomputers.     

钙与人体及临床

钙是宏量元素，是人体中含量较高的元素之一，体内99％的钙构成骨骼和牙齿以及维持骨骼结构，1％的钙调节人体重要生理功能。钙的含量过高或过低都与许多疾病有关，只有保持一种平衡状态，才能使机体处于正常环境。     

Structure Formation and Molecular Mobility in Water and in Aqueous Solutions

The study of the structure of water and of aqueous solutions has recently received new impetus from the efforts at commercial desalineation of sea water and from developments in molecular biology. The current view that, apart from single molecules, water contains only one type of structural element, namely “flickering” network structures with tetrahedrally hydrogen-bonded water molecules (two-states model) is proving inadequate in the interpretation of new experimental data and in the calculation of thermodynamic functions. After a critical discussion of the basis of this model and of the concept of hydrogen bonds, a second kind of structural element, i.e. a third state, is suggested: small aggregates of molecules containing mainly non-tetrahedral hydrogen bonds as well as some tetrahedral ones, and packed more densely than allowed by the lattice-like structure. These aggregates – dimers to hexamers – can be regarded as the primary products of disruption of the network structures, and displace the latter as structural components in water with increasing temperature or concentration of solutes. This “combined” model allows a consistent interpretation of the properties of water and of the various effects of dissolved substances.     

Electrostatic interactions in cations and their importance in biology and chemistry

Electrostatic effects exert strongly stabilizing influences on cations, in many cases controlling the conformational preferences of these cations. The lowest energy conformers are ones where the positive charge is brought closest to substituents bearing partial negative charges. These conformational biases, along with stereoelectronic effects, can control the stereoselectivity of reactions involving carbocationic intermediates.