Interstellar carbon in meteorites

The Murchison and Allende chondrites contain up to 5 parts per million carbon that is enriched in carbon-13 by up to + 1100 per mil (the ratio of carbon-12 to carbon-13 is approximately 42, compared to 88 to 93 for terrestrial carbon). This "heavy" carbon is associated with neon-22 and with anomalous krypton and xenon showing the signature of the s-process (neutron capture on a slow time scale). It apparently represents interstellar grains ejected from late-type stars. A second anomalous xenon component ("CCFXe") is associated with a distinctive, light carbon (depleted in carbon-13 by 38 per mil), which, however, falls within the terrestrial range and hence may be of either local or exotic origin.     

Identification of complex aromatic molecules in individual interplanetary dust particles

Seventeen stratospherically collected particles-eight of which are classified as interplanetary dust particles (IDPs), seven of which are classified as probable terrestrial contaminants, and two of which have uncertain origins-were studied with a microprobe two-step laser mass spectrometer. Many polycyclic aromatic hydrocarbons(PAHs) and their alkylated derivatives were identified in two of the eight IDPs. The PAHs observed include a high-mass envelope not found in meteorites or terrestrial contaminants and prominent odd-mass peaks suggestive of nitrogen-containing functional groups attached to aromatic chromophores. In addition, the complexity of the IDP mass spectra has no precedence in previous studies of meteorite samples or their acid residues. Extensive checks were performed to demonstrate that the PAH signals are not caused by terrestrial contaminants.     

Reports refractory interplanetary dust particles

Criteria are described by which refractory interplanetary dust particles (IDPs) can be differentiated from the products of spacecraft debris. These criteria have been used to discover and characterize IDPs that are composed predominantly of refractory phases. Two of these particles contain hibonite, perovskite, spinel, refractory glass, and a melilite; only hibonite was identified within a third. The grain size for all particles ranges from 0.05 to 1 micrometer, so that they are much finer grained than the refractory calcium- and aluminum-rich inclusions in meteorites. The glass-containing refractory IDPs may be primitive nebular condensates that never completely crystallized and thus have been preserved extant.     

Magnesium isotopic composition of interplanetary dust particles

The magnesium isotopic composition of some extraterrestrial dust particles has been measured. The particles are believed to be samples of interplanetary dust, a significant fraction of which originated from the disaggregation of comets and may contain preserved isotopic anomalies. Improvements in mass spectrometric and sample preparation techniques have made it possible to measure the magnesium isotopic composition of the dust particles, which are typically 10 micrometers in size and contain on the order of 10(-10) gram of magnesium. Of the 13 samples analyzed, nine have the terrestrial magnesium isotopic composition within 2 parts per thousand, and one shows isotopic mass fractionation of 1.1 percent per mass unit. A subset of the particles, described as chondritic aggregates, are very close to normal isotopic composition, but their normalized isotopic ratios appear to show nonlinear effects of 3 to 4 parts per thousand, which is near the present limit of detection for samples of this size. The isotopic composition of calcium was also determined in one particle and found to be normal within 2 percent. It is clear that the isotopic composition of interplanetary dust particles can be determined with good precision. Collection of dust particles during the earth's passage through a comet tail or an intense meteor stream may permit laboratory analysis of material from a known comet.     

An astronomical 2175 angstrom feature in interplanetary dust particles

The 2175 angstrom extinction feature is the strongest (visible-ultraviolet) spectral signature of dust in the interstellar medium. Forty years after its discovery, the origin of the feature and the nature of the carrier(s) remain controversial. Using a transmission electron microscope, we detected a 5.7-electron volt (2175 angstrom) feature in interstellar grains embedded within interplanetary dust particles (IDPs). The carriers are organic carbon and amorphous silicates that are abundant in IDPs and in the interstellar medium. These multiple carriers may explain the enigmatic invariant central wavelength and variable bandwidth of the astronomical 2175 angstrom feature.     

Sedimentary polycyclic aromatic hydrocarbons: the historical record

Polycyclic aromatic hydrocarbons in three sections of a dated sediment core from Buzzards Bay, Massachusetts, have been analyzed by gas chromatographic spectrometry. This historical information suggests that sedimentary polycyclic aromatic hydrocarbons, at least at this location, result primarily from the anthropogenic combustion of fossil fuels.     

Epsilon carbide: a low-temperature component of interplanetary dust particles

Transmission electron microscope study of a chondritic interplanetary dust particle has revealed the presence of epsilon iron-nickel carbide, a low- temperature carbide previously encountered only in metallurgical studies. In these studies in-carbide was synthesized by carburization of iron or nickel grains in a stream of carbon monoxide or carbon monoxide plus hydrogen. Similar carburization of an iron-nickel metal in situ may have produced in-carbide during particle heating on atmospheric entry or in solar orbit. Alternatively, the epsilon-carbide may be a by-product of Fischer-Tropsch reactions in the solar nebula. Such reactions have been proposed as the mechanism of hydrocarbon formation in the early solar system.     

高效液相色谱法检测羊粪水热碳制备中多环芳烃的含量

为探究羊粪水热碳制备过程中多环芳烃的含量变化,在水热法制备羊粪水热碳过程中,采用高效液相色谱法对不同条件下制备的羊粪水热碳中多环芳烃的含量进行检测。结果表明,羊粪：水 = 1：12,反应时间为10 h,温度为200℃条件下制备的水热碳多环芳烃的含量最低。研究为有效控制畜禽粪便水热碳制备中多环芳烃的含量提供了参考。     

多毛类动物对多环芳烃的毒性响应及代谢研究进展

多环芳烃可富集在水生生物体内,进而通过食物链的放大作用危害人类,多毛类动物是已知能够蓄积大量多环芳烃的物种,有关多毛类动物解毒代谢酶与抗氧化酶的活性及其基因表达水平作为多环芳烃监测指标的研究已有大量报道,但有关多毛类动物如何代谢蓄积在体内多环芳烃的基础理论研究目前尚处于初步阶段。本研究中,综述了近年来国内外有关多毛类动物对多环芳烃的毒性响应及代谢研究,多毛类动物对多环芳烃的代谢类似于脊椎动物,分为两个阶段,参与第一阶段代谢的酶主要是细胞色素P450酶家族,而尿苷二磷酸葡萄糖醛酸转移酶和磺基转移酶被认为是第二阶段代谢过程中起主导作用的酶类,针对目前研究中存在的问题,提出今后应加强多毛类动物对复合多环芳烃以及低剂量多环芳烃长期暴露的毒性响应研究,同时增强对不同多环芳烃的代谢研究。     

多毛类动物对多环芳烃的毒性响应及代谢研究进展

多环芳烃可富集在水生生物体内,进而通过食物链的放大作用危害人类,多毛类动物是已知能够蓄积大量多环芳烃的物种,有关多毛类动物解毒代谢酶与抗氧化酶的活性及其基因表达水平作为多环芳烃监测指标的研究已有大量报道,但有关多毛类动物如何代谢蓄积在体内多环芳烃的基础理论研究目前尚处于初步阶段。本研究中,综述了近年来国内外有关多毛类动物对多环芳烃的毒性响应及代谢研究,多毛类动物对多环芳烃的代谢类似于脊椎动物,分为两个阶段,参与第一阶段代谢的酶主要是细胞色素P450酶家族,而尿苷二磷酸葡萄糖醛酸转移酶和磺基转移酶被认为是第二阶段代谢过程中起主导作用的酶类,针对目前研究中存在的问题,提出今后应加强多毛类动物对复合多环芳烃以及低剂量多环芳烃长期暴露的毒性响应研究,同时增强对不同多环芳烃的代谢研究。     

大气降尘样品中多环芳烃采样方法综述

[目的]归纳总结现有大气降尘的采样方法,为今后采集降尘样品的学者提供参考;并在此基础上,提出建立相对统一的降尘采集标准方法与规范我国降尘采集的建议,以提高降尘研究结果的可比性。[方法]本文对大气降尘样品采集中采样点个数及其位置选取的条件和原则、采样时间的选择与周期的确定、采样装置材质及形状的选取和采样器内固定降尘样品介质的类型等现有大气降尘采样方法中的一系列条件与要求进行了综述。[结果]采样点位置的选取要以没有遮挡物且避免周围物质起尘的影响为原则;采样时间与周期的选取因研究目的不同有所差异;采集装置通常使用玻璃漏斗、圆柱形玻璃罐、不锈钢桶、金属平板等;根据集尘容器内固定降尘介质的不同,目前常用的收集方法分为干法、湿法和玻璃球法3种。[结论]合理地选择降尘采样点、采集方法和采样周期是研究大气降尘中多环芳烃的基础,在实际工作中可以根据研究目的及实际情况选择合适的采集方法,并且急需出台一套完整规范的降尘采集标准。     

Acid dissolution experiments: carbonates and the 6.8-micrometer bands in interplanetary dust particles

A chemical dissolution experiment on an interplanetary dust particle (IDP) showed that carbonates, not acid-insoluble organic compounds, were responsible for virtually all the absorption at 6.8 micrometers seen in the infrared spectra of this particle. The IDP examined had an infrared spectrum characteristic of layer-lattice silicates and belongs to a class of IDP's whose spectra resemble those of protostellar objects like W33 A, which also exhibit a band at 6.8 micrometers.     

植烟土壤和烟叶中多环芳烃的污染特征及污染源解析

【目的】分析贵州松桃县植烟土壤和烟叶中多环芳烃（PAHs）的含量及污染特征,并解析其污染来源,为烟区土壤 烤烟体系的环境评价、PAHs污染修复提供参考。【方法】2020年7月,分别采集贵州省铜仁市松桃县烤烟成熟期40个土壤样品和40个新鲜烟叶样品,测定了16种PAHs含量,分析土壤和烟叶中PAHs的组成特征,并解析其在土壤 烤烟体系中的污染来源。【结果】贵州松桃县植烟土壤中16种PAHs的总含量为166.74~989.43 μg/kg,平均含量为600.77 μg/kg,其中以3~5环PAHs所占比例较高（78.7%）;致癌性的∑₇PAHs含量为70.97~365.71 μg/kg,平均含量为221.13 μg/kg,占16种PAHs总含量的24.5%~62.7%,其中具有强致癌性的苯并(b)荧蒽（BbF）、苯并(k)荧蒽（BkF）和苯并(a)芘(BaP)的平均占比分别为5.18%,5.32%和6.03%;在松桃县烤烟烟叶中,16种PAHs的含量为502.79~2 217.15 μg/kg,平均值为1 011.23 μg/kg,其中4~5环PAHs占75.1%;致癌性的∑₇PAHs含量为293.53~1 730.72 μg/kg,平均含量为707.03 μg/kg,占16种PAHs总含量的56.0%~85.5%;其中具有强致癌性的BbF、BkF和BaP平均占比分别为10.19%,7.78%和39.96%。烟叶中的PAHs平均含量高于土壤。根据欧洲农业土壤中PAHs的控制标准,本研究有50%的土壤样品处于PAHs中度污染水平,45%的土壤样品处于PAHs轻度污染水平。诊断比例法解析表明,PAHs主要来源于当地工业生产活动、车用石油燃烧及煤炭、秸秆、木材的高温燃烧排放,最终通过大气沉降和叶面吸收进入土壤-烤烟体系;此外,烤烟种植和管理中塑料薄膜及肥料的使用也是土壤PAHs累积的重要来源。【结论】工业活动和农膜及肥料的使用,使贵州松桃县土壤 烤烟体系中PAHs出现累积,可能会对当地生态环境和居民（尤其是烟农）健康造成威胁,应当引起足够重视。     

亚热带地区农业土壤和植物中多环芳烃的分布

以汕头经济特区的农业土壤和蔬菜为例,运用气相色谱-质谱方法对美国EPA优控多环芳烃(PAH)进行定性、定量测定,分析了其在中国亚热带地区农业土壤和植物中的分布特征,讨论了影响其分布的主要因素.结果表明:该区农业土壤中的PAH以3环和4环为主,单个PAH以萘、菲、荧蒽和苯并[b]萤蒽为主;而植物中的PAH以3环为主,单个PAH以萘、菲为主.PAH可在0～100 cm的土层范围内有效移动和传输,其中表层土壤的输入比率要高于移动和传输的比率.影响PAH在土壤和植物中分布的因素除PAH本身的理化性质外,土壤的理化性质、植物种类和环境条件同时起重要的作用.     

Refractory minerals in interplanetary dust

A newly studied interplanetary dust particle contains a unique set of minerals that closely resembles assemblages in the refractory, calcium- and aluminum-rich inclusions in carbonaceous chondrite meteorites. The set of minerals includes diopside, magnesium- aluminum spinel, anorthite, perovskite, and fassaite. Only fassaite has previously been identified in interplanetary dust particles. Diopside and spinel occur in complex symplectic intergrowths that may have formed by a reaction between condensed melilite and the solar nebula gas. The particle represents a new link between interplanetary dust particles and carbonaceous chondrites; however, the compositions of its two most abundant refractory phases, diopside and spinel, differ in detail from corresponding minerals in calcium- and aluminum-rich inclusions.     

丝瓜络固定化微生物对土壤多环芳烃吸附-降解作用

以假单胞菌(Pseudomonas sp.SDR4,简称S4)、毛霉真菌(Mucormucedo sp.SDR1,简称S1)为研究对象,采用微生物固定化技术,研究了其对土壤多环芳烃的吸附和降解动力学,并探讨了固定化微生物对土壤多环芳烃的吸附机理及吸附降解关系。结果表明:试验60 d,改性丝瓜络(CK)、死体固定化S1(S1-D)、死体固定化S4(S4-D)、死体固定化S1与S4混合菌(S1+S4-D)对菲(Phe)的动态平衡吸附量分别为5.28、6.82、5.73、7.46μg,对芘(Pyr)的动态平衡吸附量分别为4.17、4.72、4.53、5.00μg,死体固定化微生物对Phe与Pyr的吸附过程均服从于准二级动力学;活体真菌S1、细菌S4、混合菌S1+S4对Phe的动态吸附量分别为2.32、2.01、2.76μg,对Pyr的动态吸附量分别为2.79、2.41、3.14μg,活体固定化微生物对土壤中Phe与Pyr的准一级动力学与准二级动力学拟合结果R2相差较小;S1、S4、S1+S4对Phe的降解率分别为54.34%、61.45%、64.23%,对Pyr的降解率分别为38.42%、35.02%、42.43%;经S1、S4、S1+S4处理后,Phe的降解半衰期分别为38.88、29.41、25.63 d,Pyr的降解半衰期分别为64.76、69.02、59.28 d。研究表明,化学作用是控制丝瓜络固定化微生物对多环芳烃吸附速率的主要因素;提高微生物的降解能力能增加对土壤中PAHs迁移的影响;混合菌中真菌与细菌存在协同作用,能提高Phe与Pyr的降解效率。     

瓜类蔬菜体内多环芳烃的分布特征及健康风险评估

【目的】探讨多环芳烃(PAHs)在瓜类蔬菜体内的分布特征和积累规律,并对南宁市不同年龄不同性别人群摄食每种瓜类蔬菜果实的健康风险进行评估。【方法】采集黄瓜Cucumis sativus、苦瓜Momordica charantia、丝瓜Luffa cylindrical和节瓜Benincasa hispida var. chieh-qua根系各30株和果实各20个,并分别称取茎1 kg、叶片1 kg和叶柄1 kg,用超声波提取、固相萃取对蔬菜进行前处理,用高效液相色谱法检测各部位中16种PAHs含量。【结果】16种PAHs在4种瓜类蔬菜中均有检出,PAHs的总质量分数为88.44～1 229.85μg·kg–1,其中各环数PAHs含量顺序为5环6环2环4环3环。南宁市不同人群食用瓜类果实引起的致癌风险值在1.48×10–6～7.84×10–5范围内,仅摄入可食用部分引起的致癌风险值在2.23×10–7～3.35×10–6范围内。【结论】比较同种瓜类不同部位,4种瓜皆是叶片PAHs含量最高,黄瓜果瓤含量最低,苦瓜和丝瓜果肉含量最低,节瓜叶柄含量最低;比较4种瓜类叶片,节瓜叶片PAHs含量最高,苦瓜叶片含量最低。在目前蔬菜消费量下,南宁市民摄食瓜类蔬菜果实存在潜在致癌风险。     

多环芳烃对土壤线虫和微生物生物量的影响

通过向土壤中添加不同浓度的3种多环芳烃(PAHs)蒽、2-甲基蒽和7,12-二甲基苯并[a]蒽,研究PAHs对土壤微生物生物量碳和土壤线虫的影响。结果表明,土壤微生物生物量碳随PAHs浓度增加而呈指数下降,说明PAHs可抑制土壤微生物活性。土壤线虫总数随PAHs浓度不同而变化,低浓度和高浓度条件下土壤线虫总数增加,中等浓度对土壤线虫总数无影响。土壤线虫中食植物线虫和食细菌线虫占总数的81.8%,PAHs加入后此两类线虫仍占绝对优势,占总数的77.0%-92.8%。但线虫营养类群发生变化,食植物线虫和杂食性线虫比例增高,而食细菌线虫和食真菌线虫比例趋于降低,这主要由PAHs对土壤微生物的影响所致。     

Interstellar chemistry recorded in organic matter from primitive meteorites

Organic matter in extraterrestrial materials has isotopic anomalies in hydrogen and nitrogen that suggest an origin in the presolar molecular cloud or perhaps in the protoplanetary disk. Interplanetary dust particles are generally regarded as the most primitive solar system matter available, in part because until recently they exhibited the most extreme isotope anomalies. However, we show that hydrogen and nitrogen isotopic compositions in carbonaceous chondrite organic matter reach and even exceed those found in interplanetary dust particles. Hence, both meteorites (originating from the asteroid belt) and interplanetary dust particles (possibly from comets) preserve primitive organics that were a component of the original building blocks of the solar system.