Compositional fractionation of polyaromatic hydrocarbons in the karst soils, South China

This study aims to explore the condensation and fractionation trends of persistent organic pollutants (POPs) in the karst soils. The tiankeng is a karst surface expression that can act as a focal point for introduction of contaminants to a karst aquifer, which may serve both as condenser for vapor phase POPs and as barrier/sink for particulate associated less volatile POPs. The fractionation of POPs in soils from the upper rim and floor of tiankeng is of interest in understanding the role of tiankeng in the long-distance transport of POPs. In the present study, polycyclic aromatic hydrocarbons (PAHs) in the surface soils from the upper rim and floor of Dashiwei tiankeng in Southern China were analyzed. The total PAH concentrations in soils were 23.40–190 ng g⁻¹, with phenanthrene being the most abundant. The distribution patterns of PAH compounds in the soil samples matched well with their properties. It indicated the heavy PAHs were susceptible to retention by the floor soils of tiankeng than light PAHs. A plot of Cfloor/Crim against PAH molecular weight gave a good positive relationship in the molecular weight range of 152–276. It is suggested that the floor soils can be focal points of more concentrated PAH and deserve attention. The concentrations of total PAHs in the floor soils (43.40–190 ng g⁻¹, mean 87.76 ng g⁻¹) were higher than those in the upper rim (23.40–88.94 ng g⁻¹, mean 57.74 ng g⁻¹). In addition, there was a shift in compound pattern with an increase in the proportion of light PAHs (2–3 rings), a decrease in heavy PAHs (5–6 rings) and a relatively stable content of 4-ring PAHs. A combination of particulate scavenging and cold condensation is proposed as the major mechanism for the compositional fractionation of PAHs in the soils from the upper rim and floor of tiankeng.     

Sample preparation for isotopic determination of boron in clay sediments

The procedures of sample preparation for isotopic determination of boron in clay sediments is very cumbersome, by far, there haven’t been relevant reports on that. In order to establish an effective method for sample preparation, a series of experiments were carried out. In this paper, boron in clay sediments was extracted with HCl solution and purified by two-step ion exchange method. Extracted HCl solution should be adjusted to alkalescency before passing through the Amberlite IRA 743 resin column due to the fact that Amberlite IRA 743 resin absorbs boron only from alkalescent solution. However, a mass of hydroxides of Al and Fe will be precipitated when the extracted HCl solution becomes alkalescent. Hydroxides of Al and Fe have a strong adsorption capacity for boron, which can cause boron isotope fractionation. To treat precipitated hydroxides of Al and Fe, four procedures, namely direct ion exchange (DRIE), decationizing ion exchange (DCIE), once sedimentation ion exchange (OSIE) and repeated sedimentation ion exchange (RSIE) were used and assessed. The influences of the four procedures on separation and extraction and isotopic composition of boron in experimental solutions and clay sediments were also discussed. According to the results, the DRIE, DCIE and OSIE are improper. The result of sample determination indicates that when extracting boron via RSIE, with the increase of precipitation times, there’s an obvious decrease in boron content in the precipitated hydroxides while a sharp increase in recovery of boron and it is favorable for weakening the influence of boron isotope fractionation. But the process of RSIE is time consuming and it may introduce boron. It needs further research to establish a more effective sample preparation method for isotopic deter- mination of boron in clay sediments.     

Sample preparation for analyzing polycyclic aromatic hydrocarbons and polychlorinated dibenzo-p-dioxins and dibenzofurans in sediment by gas chromatography/mass spectrometry

A sample preparation technique was developed to isolate and separate two classes of combustion-produced pollutants: three- to six-ring polycyclic aromatic hydrocarbons (PAH) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F), from sediment samples for interference-free analyses by gas chromatography/mass spectrometry (GC/MS). The method involves soxhlet extraction with methylene chloride, sulfur removal with activated copper powder, gel filtration chromatography with Sephadex LH-20, polarity separations of PAH and PCDD/F with prepacked silica gel solid-phase extraction columns, and isolation of PCDD/F from polychlorinated biphenyls with microalumina columns. Stringent procedural controls were established to achieve clean isolations and recoveries of 70% or better for each step in the method. The prepared sample extracts were analyzed by capillary GC and GC/MS. Electron impact ionization was used for PAH, and negative chemical ionization with methane as a reagent gas was used for PCDD/F. Reproducible results were obtained. The method is simple and has the advantage of conserving sample consumption since two classes of compounds can be analyzed from the same sample. This can be critical in sediment core analyses where sample size is usually limited.     

Environmental assessment of elements and polyaromatic hydrocarbons emitted from a Canadian coal-fired power plant

A detailed assessment of elements was carried out at a power plant rated at approximately 760 MW of electricity using western Canadian subbituminous coal. The concentrations of elements of environmental concern (As, Cd, Cr, Hg, Ni, and Pb) in milled coals, ashes, stack-emitted materials. Speciation of As, Cr, and Ni were determined. The polyaromatic hydrocarbons (PAHs) emitted from the stack were also measured. The rates of input of elemental input for As, Cd, Cr, Hg, Ni, and Pb were 28, 0.94, 230, 0.44, 44, and 88 kg/day, respectively; of which only 0.16, 0.01, 0.40, 0.27, 0.15, and 0.04 kg/day, respectively, were stack emitted. The total stack emission of toxic elements is 1.02 kg/day, with Cr being the highest contributor to this group with 0.4 kg/day. However, Hg at 0.27 kg/day has the highest percentage rate of emission at about 60%, while Cd has the lowest at about 1%. The electrostatic precipitator (ESP) removes a significant portion of the elements indicated by their relative enrichment (RE) ratios greater than 0.7. The results show that most of the elements in milled coal are low compared to world coals and other Canadian milled coals.Mercury is mostly ( 81%) emitted as gaseous elemental mercury (GEM), with 19% as reactive gaseous mercury (RGM). Particulate mercury is very low and averages about 0.1% of the total mercury at this station. Most of the arsenic in the milled coal is primarily associated with pyrite or as arsenate in its less toxic form of As⁺⁵ (> 95%). In both bottom and fly ashes, more than 95% of the total arsenic is present as As⁺⁵. Chromium in the milled coal and bottom ash is mostly non-toxic (Cr⁺³). The more toxic Cr⁺⁶ comprise less than 5% of the total Cr in the ESP fly ash and the stack-emitted ash. Nickel in milled coal and ashes is in the form of non-toxic Ni⁺², predominantly in coordination with oxygen.The emitted PAHs include acenapthene, fluorene, 2-methyl-fluorene, phenathrene, anthracene, fluoanthene, and pyrene; which are emitted from stack at the combined rate of 3.6 g/day. The concentrations of elements of environmental concern (As, Cd, Hg, Ni, and Pb) emitted to the atmosphere by the power plant in the zone of maximum impact at ground level are lower than those listed in the Health Guidelines of the USEPA and Canadian National Air Pollution Surveillance. This is based on stable meteorological conditions, down wind from the power plant for a maximum distance of 3 km.     

砂土微观结构样品制备技术及量化方法研究

土体的微观结构是决定其工程特性的重要内在因素,但对于砂土而言,如何制备适合微观分析的样品以及快速准确量化结构参数一直面临诸多挑战。为此,提出一种真空冷冻干燥?注胶相结合的砂土样品制备技术,该技术可在有效去除土样水分的同时保持样品原状结构不被扰动,并可用于后续加工处理。针对不同粒度的砂土样品,分别使用扫描电子显微镜和光学显微镜对制备的试样进行观察,基于自主研发的土体微观结构定量分析系统SMAS对拍摄的照片进行精细量化分析,提出了由土颗粒数量、颗粒周长、表观孔隙率、形状系数、等效直径、分形维数和形态比等参数构成的量度指标体系对砂土样品微观结构特征进行定量评价。研究结果表明：提出的真空冷冻干燥?注胶相结合的砂土样品制备技术具有操作简单、稳定可靠等特点,能有效维持砂土的原状结构;比较而言,扫描电镜更适用于粉细砂的微观结构分析,而光学显微镜更适用于中粗砂的微观结构分析;SMAS能有效识别微观结构图像中的土颗粒及孔隙,为定量分析砂土或其他土体的微观结构特征提供了高效的工具。     

熔体包裹体分析技术进展

熔体包裹体是岩浆岩中矿物生长或结晶过程中捕获的少量硅酸盐熔体,成为地球深部过程的重要见证者。因此,有效识别其记录的岩浆演化信息显得十分重要。文章在前人对熔体包裹体研究的基础上,系统梳理其研究方法,总结了5步研究过程：① 利用偏光显微镜,开展详细的岩相学观察以识别具有代表性的熔体包裹体类型;② 为加热实验和成分分析制备样品;③ 利用高温热台,对熔体包裹体进行加热实验使其内部均一化,并测得捕获温度;④ 通过电子探针、二次离子探针、LA-ICP-MS、显微激光拉曼等技术对熔体包裹体中的主、微量元素、同位素以及挥发分组成进行分析测试;⑤ 熔体包裹体数据分析,与全岩成分和相关实验得出的流体成分进行对比。虽然熔体包裹体的研究经历了近百年的发展,但有效还原其代表的初始岩浆信息,仍然是当前研究的难点和热点。尤其是地球系统科学发展引发宜居地球深部过程的探讨,使得开展熔体包裹体分析新方法的探讨成为重中之重。     

A large strain analytical solution for cavity contraction in dilatant soils

An infinite dilatant elastic–plastic soil mass contains a single cylindrical or spherical cavity within which a slowly increasing pressure is applied. The removal of the cavity pressure takes place after a partly plastic state of the soil has been reached. Closed form solutions for the stress and displacement fields in the soil during any stage of the unloading process are derived. The non-associated Mohr–Coulomb yield criterion is used to account for dilation of the soil during shearing. Large strains are taken into account by adopting an appropriate strain definition within the plastically deforming region.     

两种标准曲线法测定土壤中10种重金属元素

采用混合酸+王水的湿法消解模式,对土壤和水系沉积物的标准物质进行消解,利用电感耦合等离子体质谱仪测量标准物质中10种重金属元素(Ba、Ce、Co、Cs、Cu、La、Ni、Pb、Sc、Sr)的含量,选用103 Rh、185 Re作为内标元素补偿基体效应和灵敏度漂移.结果表明:测量结果与标准值相符,以标准物质绘制标准曲线所...     

Polycyclic aromatic hydrocarbons in the soils of technogenic landscapes

An integrated study of qualitative and quantitative composition of polycyclic aromatic hydrocarbons (PAH) in the atmospheric precipitation-soil-lysimetric water system of aerotechnogenic polluted landscapes was conducted using high-performance liquid chromatography in a gradient mode. Only low-molecular weight polyarenes (phenanthrene, anthracene, fluoranthene, pyrene, benz(a)anthracene, and chrysene) were found in the atmospheric precipitation and lysimetric waters. The growth of PAHs in soils is provided by the input of phenanthrene, fluoranthene, and pyrene with atmospheric precipitation. The absence of heavy PAHs (benzfluoranthenes, benz(a)pyrene, dibenz(a,h)anthracene, benz(ghi) perylene, and indeno[1,2,3-cd]pyrene) in the atmospheric precipitation and their identification in soil give grounds to state that their accumulation was caused mainly by transformation of organic matter during pedogenesis. The technogenic impact was estimated and criterion of the degree of soil pollution by PAH was proposed.     

Numerical and analytical investigation of compressional wave propagation in saturated soils

In geotechnical earthquake engineering, wave propagation plays a fundamental role in engineering applications related to the dynamic response of geotechnical structures and to site response analysis. However, current engineering practice is primarily concentrated on the investigation of shear wave propagation and the corresponding site response only to the horizontal components of the ground motion. Due to the repeated recent observations of strong vertical ground motions and compressional damage of engineering structures, there is an increasing need to carry out a comprehensive investigation of vertical site response and the associated compressional wave propagation, particularly when performing the seismic design for critical structures (e.g. nuclear power plants and high dams). Therefore, in this paper, the compressional wave propagation mechanism in saturated soils is investigated by employing hydro-mechanically (HM) coupled analytical and numerical methods. A HM analytical solution for compressional wave propagation is first studied based on Biot’s theory, which shows the existence of two types of compressional waves (fast and slow waves) and indicates that their characteristics (i.e. wave dispersion and attenuation) are highly dependent on some key geotechnical and seismic parameters (i.e. the permeability, soil stiffness and loading frequency). The subsequent HM Finite Element (FE) study reproduces the duality of compressional waves and identifies the dominant permeability ranges for the existence of the two waves. In particular the existence of the slow compression wave is observed for a range of permeability and loading frequency that is relevant for geotechnical earthquake engineering applications. In order to account for the effects of soil permeability on compressional dynamic soil behaviour and soil properties (i.e. P-wave velocities and damping ratios), the coupled consolidation analysis is therefore recommended as the only tool capable of accurately simulating the dynamic response of geotechnical structures to vertical ground motion at intermediate transient states between undrained and drained conditions.     

Methodology for determination of osmotic suction of soils

Soil suction constitutes of the matric suction and the osmotic suction. Several studies have been conducted and reported by researchers that reveal the importance of the matric suction on unsaturated soil properties. However, not many efforts have been made to develop methodologies that can be employed for measuring osmotic suction of the soil and to understand its influence on unsaturated soil properties. With this in view, efforts were made to utilize the results of the pressure membrane extractor (PME) and the dewpoint potentiameter (WP4), which measure matric and total suction of the soil, respectively. Details of the methodology developed to achieve this are presented in this technical note.     

Temporal trends of aliphatic and polyaromatic hydrocarbons in the Bohai Sea, China: Evidence from the sedimentary record

This work reports the historical trends and sources of aliphatic hydrocarbons (AHs) and polycyclic aromatic hydrocarbons (PAHs) in two ²¹⁰Pb dated sediment cores extracted from the central mud areas of Bohai Sea (Bohai). The TOC/TN ratio of the bulk organic matter (OM) and the composition of the n-alkanes suggest that the sedimentary organic matter was of mixed marine and terrigenous sources. The coarser sediment grain size and decreasing C/N ratios since ∼1976 could be attributed to the relocation of the Yellow River mouth causing a decreased influence of Yellow River derived sediments and associated OM into the central Bohai. The concentration of total 16 PAHs in the two cores ranged from 34.2-202 ng/g (mean, 91.5) for BC1, and from 53.3-186 ng/g (mean, 103) for BC2, with a high abundance of 2-3 ring PAHs. Perylene in the two cores mainly originated from terrigenous sources via riverine discharge and thus could be potentially related to changes in the sediment load from the Yellow River into the Bohai over time. Petroleum inputs could be revealed by ratios of methylphenanthrenes to phenanthrene (MP/P) and the patterns of more stable geochemical biomarkers (hopanes and steranes) along the two cores, in addition to the presence of unresolved complex mixtures (UCM) in the surface layers. Source diagnostic ratios of PAHs indicated a pyrogenic origin from biomass and coal combustion with a minor petroleum contribution. Downcore trends of compositional PAHs profiles were in agreement with the socio-economic development in China in the past decades. This temporal variation of sedimentary PAHs can also reflect a different evolution stage of energy structure in China as compared with those of the western developed countries.     

国际地球化学填图样品分析方法和数据对比

以中国和世界发达国家或地区(欧洲、北美、澳大利亚与日本)过去10年内完成的或目前正在开展的全球性或国家性地球化学填图项目为例,总结了国际地球化学样品分析技术的新进展,并以中国实验室与欧洲实验室的分析数据的对比结果,剖析国际地球化学填图样品分析技术面临的挑战。研究表明:分析组成地壳所有元素的构想已被越来越多国家性、全球性地球化学填图项目所采纳;中国是世界上唯一具有填图样品76元素分析能力的国家;高水平的分析实验室(欧洲与中国)取得的数据大部分可以实现对比,但仍有10余个元素的分析数据存在明显偏差。实现所有分析元素数据的全球可对比,应是今后国际地球化学填图样品分析技术的主要发展方向。     

国际地球化学填图样品分析方法和数据对比

以中国和世界发达国家或地区(欧洲、北美、澳大利亚与日本)过去10年内完成的或目前正在开展的全球性或国家性地球化学填图项目为例,总结了国际地球化学样品分析技术的新进展,并以中国实验室与欧洲实验室的分析数据的对比结果,剖析国际地球化学填图样品分析技术面临的挑战。研究表明:分析组成地壳所有元素的构想已被越来越多国家性、全球性地球化学填图项目所采纳;中国是世界上唯一具有填图样品76元素分析能力的国家;高水平的分析实验室(欧洲与中国)取得的数据大部分可以实现对比,但仍有10余个元素的分析数据存在明显偏差。实现所有分析元素数据的全球可对比,应是今后国际地球化学填图样品分析技术的主要发展方向。     

土体应变局部化现象的理论解析

引起土体失稳的应变局部化现象是在特定应力状态下,土体本构产生的分叉特性。基于有限变形理论推导了应变局部化产生的三维解析解。基于应变局部化的理论解析,分析了轴对称和平面应变条件下应变局部化现象在弹塑性硬化阶段的存在性以及剪切带的方向性。 理论分析表明,在轴对称条件下,土体应变局部化产生于土体应力-应变的软化阶段,而平面应变条件下,土体应变局部化一般出现在应力-应变的硬化阶段,其剪切带方向角的理论预测与Arthur等[1]建议值较为一致。     

表层岩溶带土壤中多环芳烃分布特征及来源解析

利用气相色谱-质谱联用仪(GC-MS)对表层岩溶泉域土壤中的16种优控的多环芳烃(Polycyclic Aromatic Hydrocarbons, PAHs)含量进行了分析,并对其组成、污染水平和来源进行了探讨。结果表明,16种优控PAHs在表层岩溶泉域土壤中的检出率为100%,其含量介于439.19~3329.72ng/g之间,平均值为1392.44ng/g,7种致癌性PAHs占总量的26%。PAHs的组成特征受地形的控制,随着海拔升高,低环PAHs所占比例升高,高环PAHs比例降低。同分异构体比值分析表明,研究区土壤中的PAHs主要来自于煤、生物质和石油的燃烧排放。研究区土壤中16种PAHs的TEQcarc值介于18.65~501.13ng/g,平均值为140.57ng/g。7种致癌性PAHs占总TEQcarc的比例达到96.8%。研究区表土中,后沟泉域的污染程度最大,次之是兰花沟泉域和柏树湾泉域,水房泉泉域的污染程度最小,但由于柏树湾泉域松针落叶中BaP、PAHs含量较高,松针落叶中PAHs含量分别高达36.36ng/g和2370.1ng/g,土壤生态风险评价中应考虑松针落叶层的潜在影响。      

地质实体模型的三维交互与分析技术研究

地质实体模型的三维可视化涉及到复杂地质体结构构造和相关地质属性数据的视觉表达与分析,利用科学计算可视化技术来充分、完整、交互式地展示与分析三维地质实体模型一直是三维地质建模领域的研究热点。研发的三维地质建模及可视化系统中可实现通用三维交互操作,包括三维模型的几何变换、三维交互定位与空间属性查询、三维模型的剖切、虚拟钻探、基坑开挖、隧道生成与虚拟漫游等。这些操作采用面向软件的技术,通过对现有的二维设备（如鼠标、键盘等）进行三维仿真,为全方位、多角度的认识和理解地质实体模型提供了强有力的支持。     

Geochemical exploration for hydrocarbons in the soils of southeast of Krishna-Godavari Basin, Andhra Pradesh

Surface adsorbed gas surveys and geo-microbiological surveys are known techniques of petroleum exploration and aim towards risk reduction in exploration by way of identifying the areas warm with hydrocarbons and to establish intense exploration priorities amongst the identified warm areas. The present investigation aims to explore correlation between the adsorbed gas distribution pattern with the distribution of the counts of methane, ethane, propane and butane microbial oxidizers in the sub soil samples to establish the role of the latter in identifying the upward migration of hydrocarbons especially in the known petroliferous Krishna-Godavari Basin, India. A total of 135 soil samples were collected near oil and gas fields of Tatipaka, Pasarlapudi areas of Krishna Godavari Basin, Andhra Pradesh. The soil samples were collected from a depth of 2?C2.5 m. The samples collected, were analyzed for indicator hydrocarbon oxidizing bacteria, adsorbed light gaseous hydrocarbons and carbon isotopes (??¹³C_methane). The microbial prospecting studies showed the presence of high bacterial population for methane (3.94 × 10⁵ cfu/gm), ethane (3.85 × 10⁵ cfu/gm), propane (4.85 × 10⁵ cfu/gm) and butane oxidizing bacteria (3.63 × 10⁵ cfu/gm) in soil samples indicating microseepage of hydrocarbons. The light gaseous hydrocarbon analysis showed 83 ppb, 92 ppb, 134 ppb, 187 ppb and 316 ppb of C₁, C₂, C₃, nC₄ and nC₅, respectively, and the carbon isotopic composition of ??¹³C₁ of the samples ranged between ? 36.6 ?? to ?22.7?? (Pee Dee Belemnite) values, which presents convincing evidence that the adsorbed soil gases collected from these sediments are of thermogenic origin. Geo-microbial prospecting method and adsorbed soil gas and carbon isotope studies have shown good correlation with existing oil/ gas fields of K.G basin. Microbial surveys indicating microseepage of hydrocarbons can, therefore, independently precede other geochemical and geophysical surveys to delineate areas warm with hydrocarbons and mapped microbiological anomalies may provide focus for locales of hydrocarbon accumulation in the K.G basin.     

An analytical technique for rapid determination of surface rock density

Computation of the coefficient of correlation between the Bouguer reduced gravity and the ground relief apparently helps minimize the subjectivity inherent in the Nettleton’s method of surface rock density determination. The ideal density is the one that results in zero correlation between them. The iterative procedure in sweeping the calculations through the range of densities chosen can be avoided by taking advantage of the linear relationship between this coefficient and the density. Linear interpolation is therefore suggested to arrive at the ideal density. The suggested procedure consequently consists of correlation coefficient computations for the two-density extremum values within which the density of the surface rock formations is expected to lie. The computer program for this method is also presented. The procedure involved and the efficacy of the method are illustrated with some practical analyses.