利用飞行时间质谱初步分析苯酚水相光化学反应的产物分布特征

近年的实验室模拟和野外观测研究表明,酚类化合物的水相反应(aqueous-phase reaction)对环境二次有机气溶胶(secondary organic aerosol,SOA)的形成具有重要的贡献,因此探讨酚类化合物光化学过程中的演化特征有助于深化二次气溶胶形成的科学认识。本文以苯酚为研究对象,利用大气压喷雾电离(ESI)-飞行时间质谱(TOF-MS),对其在水相光化学反应下的产物分布特征进行了初步探讨。水相光照实验通过直接光解(无添加氧化剂)和光氧化反应(添加H_2O_2)两种情况进行。结果表明,两种方式进行的水相光化学反应均可能生成一系列的低聚物、羟基化化合物以及其他多官能团含氧产物。在m/z 150～400的区间内,添加H_2O_2的光氧化反应产物的分子式种类(150种)明显多于直接光解的形成产物(60种),但直接光解形成的高分子量产物(如低聚物等)离子丰度明显高于光氧化反应,直接光解的产物中可观察到四聚体化合物的生成;同时,水相光反应的产物在紫外-可见光波段内具有明显的光吸收增强特征。由此推断在大气中,以苯酚为代表的酚类化合物进入大气水相环境(云、雾水和气溶胶液态水)中发生的光化学过程对大气吸光性有机物或气溶胶的形成具有贡献作用。     

沉积有机含氮化合物的成因及其分布综述

有机含氮化合物广泛存在于不同沉积环境形成的沉积有机质及其热演化产物中,查明其在石油地质体中的成因和分布,有利于油气二次运移方向和相对运移距离的确定.关于有机含氮化合物的成因和来源主要有以下几种观点:①有机含氮化合物是干酪根深成作用阶段的产物.沉积有机质经生物改造作用后,其中的部分组成如蛋白质和含氮环的物质等进入干酪根中,在深成作用阶段干酪根被降解,有机含氮化合物以芳香多环化合物的形式释放出来;②地质体中的有机含氮化合物如卟啉等与生物体中的某些原始生化组分如叶绿素等在骨架上具有继承性,地质体中的有机含氮化合物是由生物体中的这些原始生化组成演化而来的;③在地质环境中通过环的开启和闭合作用而形成,这一形式机制已被人工合成反应和生物合成反应所证实;④基于地质体中芳香杂环化合物异构体分布的相似性以及自然界无机氮的分布特征,无机氮与有机分子结合而形成有机含氮化合物也是可能的.     

原油不同极性含氮化合物的氮同位素组成特征

氮是原油的重要组成元素,主要赋存在非烃和沥青质中,依据其极性差异分为碱性与非碱性2种类型。相较于其他组成元素,原油氮同位素的研究非常有限,不同极性含氮组分的氮同位素特征研究更是缺乏。本次研究应用杜马斯燃烧法原理,利用EA-IRMS连用技术测定了江汉油田6个原油样品不同极性含氮化合物的δ~(15)N和δ~(13)C。结果表明,不同极性含氮化合物的氮同位素组成具有明显的差异,碱性氮的δ~(15)N为9.7‰~11.8‰,明显轻于非碱性氮(11.4‰~14.5‰),原因可能是2种含氮组分的形成机制不同,碱性氮形成于成岩作用早期,δ~(15)值主要受原始母质的影响,而非碱性氮在热演化过程中的富集,氮同位素值更重,利用氮同位素有益于进一步明确原油中含氮化合物的演化机制及其地球化学意义。     

锰的迁移形式成矿机理新探

通过对锰氢化物、锰羰基化合物、锰羰基氢化物的形成条件和理化性质,现代火山气体化学成分,现代海底喷口热液流体成分,有关矿床矿物流体包裹体气相成分,有代表性锰矿物化学成分及铁锰结核的物质组构,菱锰矿的碳同位素组成、锰矿物的共生、伴生矿物组合的探究,认为锰氢化物、锰羰基化合物、锰羰基氢化物是原生锰矿的主要迁移形式.它们从地球深部强还原富H2、富CO高压环境通过断裂、裂隙随岩浆、热液迁移至地壳浅部,由于压力、温度骤降,氧逸度大增,H2和CO逃逸、氧化,锰氢化物、锰羰基化合物、锰羰基氢化物分解、氧化、硫化成原生锰矿,经氧化淋(浸)滤,形成锰的高价氧化矿物.     

钴的迁移形式成矿机理初探

通过对钴有关化合物的形成条件和理化性质,钴矿床矿物流体包裹体的化学成分、代表性钴矿物的化学成分、共、伴生矿物组合的探究,结合钴成矿地质背景和环境研究认为,钴的氢化物、合金氢化物、羰基化合物、羰基氢化物是内生钴的主要迁移形式。它们形成于地球深部高压、高温、富氢、富CO的强还原环境,通过断裂、裂隙随岩浆、热液迁移至地壳浅部,由于压力、温度骤降,氧逸度渐增、H2和CO逃逸、氧化,上述钴的化合物分解、氧化、硫化、砷化,沉淀富集形成内生钴矿床,并在以后地质事件中进一步叠加富集,形成更富更大的钴矿床。     

北京市区冬季颗粒态有机硝酸酯的污染特征与生成

有机硝酸酯是二次有机气溶胶的重要组分,对区域氮循环有重要意义。本次研究于2018年冬季在北京市区采集大气细颗粒物样品并测定5类主要有机硝酸酯的含量。结果显示,5类有机硝酸酯(包括单萜烯羟基硝酸酯、蒎烯羰基硝酸酯、柠檬烯羰基硝酸酯、油酸羰基硝酸酯和油酸羟基硝酸酯)的总浓度范围为127～528 ng/m~3,对二次有机气溶胶的平均贡献为5.6%,昼夜浓度基本相当。其中,单萜烯羟基硝酸酯的含量最高,平均占比高达41%。灰霾期间有机硝酸酯浓度明显升高,相关性分析表明,燃煤和机动车排放的NO_x对有机硝酸酯浓度有显著促进作用。利用基于观测的盒子模型模拟了单萜烯羟基硝酸酯的生成速率,发现OH自由基和NO_3自由基氧化分别是白天和夜间单萜烯羟基硝酸酯的主要生成途径,但模拟值普遍低于计算值,推测模型中的生成机制可能有一定缺失。结果表明,人为活动会影响有机硝酸酯的二次生成,削减NO_x和臭氧有利于降低有机硝酸酯的大气浓度。     

中性含氮化合物的演化及地化意义

通过对生油岩样品中的中性氮系列化合物含量和组成变化的系统研究。指出含氮化合物的热演化规律和形成机制。含氮化合物是沉积有机质成岩演化的产物。其含量和组成明显受控于有机质成熟度；认为1-/4-甲基咔唑，苯并[a]咔唑/苯并[c]咔唑等比值可作为成熟度参数。     

泰山大气棕色碳的光吸收特性、吸光贡献及影响因素

棕色碳是大气气溶胶中重要的吸光性物质,会影响大气光化学过程、改变区域气候。本次研究于2017年冬季和2018年春季在泰山顶采集了大气细颗粒物(PM_(2.5))样品,在实验室测定了样品中棕色碳和黑碳的光吸收系数,并测定了棕色碳成分硝基苯酚类化合物的含量。测定结果表明,泰山冬、春两季PM_(2.5)样品中棕色碳的平均吸收系数Abs_(365)分别为(4.61±2.42)Mm~(-1)和(2.38±0.98)Mm~(-1),质量吸收效率MAE_(365)分别为(0.72±0.12)m~2/g和(0.52±0.24)m~2/g,棕色碳在365 nm处的吸收系数分别占碳质气溶胶总吸收系数的(32±7)%和(20±9)%。通过对比与相关性分析,发现泰山周边地区人为活动对泰山顶上棕色碳的光学特性有重要影响,泰山冬季受邻近区域煤炭燃烧活动影响很大,排放的大量一次有机物增强了棕色碳的吸光能力和吸收系数,导致泰山冬季棕色碳的吸收系数与吸光贡献显著高于春季。根据测定结果,泰山冬、春两季硝基苯酚类化合物在365 nm处对棕色碳吸收系数的贡献分别为(3.5±1.2)%和(2.5±1.0)%,其中在紫外和紫光区域4-硝基酚的吸光贡献最大,而在420～450 nm的蓝光区域4-甲基-2,6二硝基酚的贡献最大。硝基苯酚类化合物的吸光贡献相对较小,说明泰山棕色碳的吸光作用大部分来自于其他有机成分,将来有待进一步的识别和评估。     

稀土元素及钇在东太平洋CC区深海泥中的富集特征与机制

东太平洋CC区深海泥具有高的REY(REE+Y)含量,理解其富集机制对于寻找深海稀土资源具有重要意义。本文对WPC1101站位的沉积物柱状样开展了沉积物类型、粒度、黏土矿物和元素组成分析,结合已有资料探讨研究区深海泥的稀土元素富集特征及其形成机制。研究区深海泥主要以远洋黏土和硅质生物组分为主,其∑REY范围主要为400~1 000 μg/g。深海泥北美页岩标准化后的REY配分模式具有显著的负Ce异常,指示富稀土深海泥中海相自生组分贡献较大。根据统计发现,研究区深海泥的∑REY与Al2O3、MnO、P2O5均具有良好的相关性,黏土组分、铁锰氧化物和磷酸盐对REY都有贡献。通过综合分析,提出研究区富稀土泥中高P含量是高∑REY重要的控制因素。     

大气颗粒物中水溶性有机物的理化性质和污染特征研究进展

水溶性有机物(WSOM)是颗粒物的重要组成部分,来源广泛,组成复杂,对大气能见度、全球气候变化以及人体健康均有影响。本文主要综述了近5年国内外有关WSOM的研究成果,主要结论如下:(1)脂肪族化合物是WSOM的主要化学组分,而芳香族化合物含量相对较低;(2)WSOM相对于水溶性无机离子的占比增加时,气溶胶的吸湿增长因子相对较低;(3)不同来源的WSOM,其吸光性能差异较大,生物质燃烧源对WSOM的吸光贡献最大;(4) WSOM主要来自于生物质燃烧和光化学反应的二次生成,其秋、冬季浓度水平明显高于春、夏季,城区和郊区浓度水平均明显高于地区背景点。     

Single carbon surface reactions of 1-octadecene and 2,3,6-trimethylphenol on activated carbon: Implications for methane formation in sediments

The reactions of a terminal alkene (1-octadecene) and a polymethyl phenol (2,3,6-trimethylphenol) on activated carbon have been investigated in closed system pyrolysis experiments in the temperature range 170-340 °C. The reaction products of 1-octadecene included methane, isomeric octadecenes, methyl substituted alkanes, alkyl aromatics and an homologous series of n-alkanes with carbon numbers indicative of progressive single carbon depletion of the reactant. The reaction products of 2,3,6-trimethylphenol also contained methane, as well as C₁-C₄ methyl phenols produced by demethylation and methyl transfer reactions. A carbon surface reaction involving the formation of a reactive single carbon intermediate (i.e. methylene/carbene) is proposed. This reaction accounts for the products observed from the pyrolysis experiments and also is consistent with liquid hydrocarbon distributions found in petroleum basins. Methane was the dominant (ca. 85% of C₁-C₄) gaseous hydrocarbon product of 2,3,6-trimethylphenol but accounted for only ca. 17% of the C₁-C₄ hydrocarbons from 1-octadecene. These findings suggest that single carbon surface reactions may play an important role in the geochemical formation of crude oil and natural gas and that the composition of the source material and therefore the type of organic compounds undergoing such reactions, influences the hydrocarbon gas composition in sedimentary basins.     

Sulfur isotopic composition of individual organic compounds from Cariaco Basin sediments

Reactions between reduced inorganic sulfur and organic compounds are thought to be important for the preservation of organic matter (OM) in sediments, but the sulfurization process is poorly understood. Sulfur isotopes are potentially useful tracers of sulfurization reactions, which often occur in the presence of a strong porewater isotopic gradient driven by microbial sulfate reduction. Prior studies of bulk sedimentary OM indicate that sulfurized products are ³⁴S-enriched relative to coexisting sulfide, and experiments have produced ³⁴S-enriched organosulfur compounds. However, analytical limitations have prevented the relationship from being tested at the molecular level in natural environments. Here we apply a new method, coupled gas chromatography – inductively coupled plasma mass spectrometry, to measure the compound-specific sulfur isotopic compositions of volatile organosulfur compounds over a 6 m core of anoxic Cariaco Basin sediments. In contrast to current conceptual models, nearly all extractable organosulfur compounds were substantially depleted in ³⁴S relative to coexisting kerogen and porewater sulfide. We hypothesize that this ³⁴S depletion is due to a normal kinetic isotope effect during the initial formation of a carbon–sulfur bond and that the source of sulfur in this relatively irreversible reaction is most likely the bisulfide anion in sedimentary porewater. The ³⁴S-depleted products of irreversible bisulfide addition alone cannot explain the isotopic composition of total extractable or residual OM. Therefore, at least two different sulfurization pathways must operate in the Cariaco Basin, generating isotopically distinct products. Compound-specific sulfur isotope analysis thus provides new insights into the timescales and mechanisms of OM sulfurization.     

The role of labile sulfur compounds in thermochemical sulfate reduction

The reduction of sulfate to sulfide coupled with the oxidation of hydrocarbons to carbon dioxide, commonly referred to as thermochemical sulfate reduction (TSR), is an important abiotic alteration process that most commonly occurs in hot carbonate petroleum reservoirs. In the present study we focus on the role that organic labile sulfur compounds play in increasing the rate of TSR. A series of gold-tube hydrous pyrolysis experiments were conducted with n-octane and CaSO₄ in the presence of reduced sulfur (e.g. H₂S, S°, organic S) at temperatures of 330 and 356 °C under a constant confining pressure. The in-situ pH was buffered to 3.5 (∼6.3 at room temperature) with talc and silica. For comparison, three types of oil with different total S and labile S contents were reacted under similar conditions. The results show that the initial presence of organic or inorganic sulfur compounds increases the rate of TSR. However, organic sulfur compounds, such as 1-pentanethiol or diethyldisulfide, were significantly more effective in increasing the rate of TSR than H₂S or elemental sulfur (on a mole S basis). The increase in rate is achieved at relatively low concentrations of 1-pentanethiol, less than 1 wt% of the total n-octane, which is comparable to the concentration of organic S that is common in many oils (∼0.3 wt%). We examined several potential reaction mechanisms to explain the observed reactivity of organic LSC. First, the release of H₂S from the thermal degradation of thiols was discounted as an important mechanism due to the significantly greater reactivity of thiol compared to an equivalent amount of H₂S. Second, we considered the generation of olefines in association with the elimination of H₂S during thermal degradation of thiols because olefines are much more reactive than n-alkanes during TSR. In our experiments, olefines increased the rate of TSR, but were less effective than 1-pentanethiol and other organic LSC. Third, the thermal decomposition of organic LSC creates free-radicals that in turn might initiate a radical chain-reaction that creates more reactive species. Experiments involving radical initiators, such as diethyldisulfide and benzyldisulfide, did not show an increase in reactivity compared to 1-pentanethiol. Therefore, we conclude that none of these can sufficiently explain our observations of the initial stages of TSR; they may, however, be important in the later stages. In order to gain greater insight into the potential mechanism for the observed reactivity of these organic sulfur compounds during TSR, we applied density functional theory-based molecular modeling techniques to our system. The results of these calculations indicate that 1-pentanethiol or its thermal degradation products may directly react with sulfate and reduce the activation energy required to rupture the first S-O bond through the formation of a sulfate ester. This study demonstrates the importance of labile sulfur compounds in reducing the onset timing and temperature of TSR. It is therefore essential that labile sulfur concentrations are taken into consideration when trying to make accurate predictions of TSR kinetics and the potential for H₂S accumulation in petroleum reservoirs.     

金银铂族元素成矿机理的新探索

通过对金、银、铂族元素的氢化物，羧基化合物理化性质，贵金属矿物主要和次要化学成分，贵金属矿物的共伴生矿物组合，有关矿物流体包裹体化学成分，类地行星概况，生产实验等相关问题的讨论，认为金、银、铂族元素主要呈单质及其合金氢化物，单质羧基化合物，单质羧基氢化物迁移的。它们随岩浆，热液，热气迁至地壳浅部，由于减压，降温，氧逸度显著加大，Eh、Ph值发生变化，H2，CO逃逸，氧化，形成贵金属的单质及合金矿物，有的还能与硫，硫化氢作用形成贵金属的硫化矿物和硫盐矿物。     

Chemistry of alkali extraction of brown coals—I. Kinetics, characterisation and implications to coalification

Three Australian brown coals have been separated into humin and humic acid fractions and studied by high resolution solid state ¹³C NMR spectroscopy and Fourier transform IR spectroscopy. The aromatic rings of the humic acids are highly substituted showing that extensive cross linking must have occurred during formation from wood lignin and tannin. However, the humins contain more aliphatic carbon and hydrogen than the corresponding humic acids. This shows that little cross linking has occurred with other components of the brown coal such as resins, waxes cutin and algal detritus, and cross linking has not rendered the aromatics alkali insoluble. The kinetics of extraction are complex and not simple first order. This is reflected in the chemical composition of the humic acid which is extraction temperature dependent. We also observed that there is a conversion of aromatic carbon to aliphatic carbon and gas during extraction, probably by alkaline oxidation, resulting in ring opening. A range of suitable model compounds have been studied to confirm this finding. Such a mechanism may account for the modification of lignin in oxidising environments such as those occurring in the initial stages of coalification (lignite or brown coal formation) and in soils.     

Formation of sulfur and nitrogen cross-linked macromolecules under aqueous conditions

Polysulfides and ammonia are abundant in young depositional environments and play an important role in the formation of macromolecular structures such as protokerogen and humics. In this work, we study the co-incorporation of polysulfides and ammonia into simple carbonyl model compounds, octanal and trans 2-octenal, in order to study their effect on the formation of a cross-linked macromolecule and suggest a feasible mechanism. The reactions, performed in aqueous solutions at ambient temperature and pH ∼6 to 9, simulate formation of S and N cross-linked polymers in the natural environment. The complex S and N containing polymer was studied by ¹⁵N enrichment coupled to 2D NMR (¹H, ¹³C, ¹⁵N) techniques and chemical degradation of S-S bonds followed by deuterium labeling and GC-MS analyses. In addition, molecular modeling techniques were used to provide theoretical interpretations and important insights at the molecular level. The results indicate that polysulfide out competes ammonia in the formation of Michael adducts while ammonia is equally competitive with polysulfides when the reaction is addition to the carbonyl position. The co-incorporation of ammonia and polysulfides into carbonyls rapidly forms N and S cross-linked polymers. The effects of ammonia and amines on the polymerization processes are by two means: (i) reaction with carbonyls through an imine functionality to form oligomers and polymers and (ii) catalysis of sulfur nucleophiles onto carbonyls by transfer of a proton which enhances the rate of polymerization. A similar catalytic effect is observed when glycine is used instead of ammonia. This mechanism is especially important under basic to neutral conditions like those that prevail in marine environments. The results show that ammonia and glycine or possibly other amino acids and/or peptides are intimately involved with sulfur nucleophiles throughout the polymerization processes that occur at low temperatures and thus are suggested as key reactants in diagenetic formation of protokerogen and humics.     

煤岩及其主显微组份热解气碳同位素组成的演化

模拟实验是有机地球化学研究的重要组成部分 ,也是油气地球化学研究的重要手段。本文通过煤岩及其主要显微组分的热解成气模拟实验产物的组分和同位素组成分析 ,补充和完善了前人对煤岩热解气同位素组成分布的一些认识。同时 ,对比研究了煤型气与煤岩热解气的碳同位素分馏特征 ,结果表明两者具有良好的一致性 ,认为可以通过精细的热解模拟来提供不同含煤沉积盆地煤型气的判识指标 ,而模拟气与天然气碳同位素组成的对比 ,关键是对同位素分析资料的处理。在模拟系列产物碳同位素分析基础上 ,获得了单一成因来源天然气甲烷、乙烷碳同位素组成与演化程度之间的关系式以及演化过程中甲烷碳同位素之间的关系式 ,这些结果会对混源气的判识有重要意义。     

Chemical mass transfer in the Rio Tanama system,west-central Puerto Rico

Equilibrium relationships are defined between stream waters and weathering products, kaolinite and calcium montmorillonite, for the Rio Tanama system, west-central Puerto Rico. The major element composition of 46 water samples of springs and streams define a reaction path in the system CaO-Na₂O-MgO-Al₂O₃-SiO₂-H₂O between acid waters containing low concentrations of alkali cations and detrital reactant minerals. The principal reactant phases appear to be chlorite, plagioclase and orthoclase and occasionally anhydrite or calcite. Headward erosion by the Rio Tanama supplies the reactant phases to the stream silt load.The chemical denudation rate calculated for the Rio Tanama system is about 30 m/million yr. The chemical stream load appears to be buffered by the product phases in the main river over the 15–20 km river length sampled in this study.The silt and soil mineralogy and water compositions are used to define a log K for the hydrolysis of Ca-montmorillonite at 25°C of 35.0 ± 0.8. This value is in reasonable agreement with the value of 37.1 ± 1.0 defined by Garrels and Mackenzie (1967) in a similar manner for spring waters in the Sierra Nevada.