Contribution of the atmospheric emissions of Spanish ceramics industries

Contaminating industrial emissions produced by the ceramics industries (including frit and enamel production) can be divided into dust emissions and emissions produced in high temperature activities. Processes of accumulation and precipitation on the substratum, of compounds enriched in certain elements used in this type of industry can occur. The objective of the present work was to identify the contribution of the emissions of the ceramics industries to the atmospheric particulate that is susceptible to depositing on vegetation and accumulating in the substratum. Samples obtained from high volume collectors were studied. Two zones were considered: zone A, a high volume collector located in the municipalities adjacent to the companies that were the object of the study; and zone B, a high volume collector further away from the said companies and adjacent to a power station and a refinery. The analysis techniques were X-ray diffraction, scanning electron microscopy (SEM), and ICP-MS. The results obtained by means of the X-ray diffraction technique showed a high percentage of clays in the samples, minerals used as raw materials (K-Ba feldspar, zircon silicate), indications of high temperature phases, as well as a background noise characteristic of material of low crystallinity. The SEM analysis confirmed the presence of vitreous particles, which are crystalline phases at high temperature typical of the production of a large variety of frits. The results obtained in the chemical analysis demonstrate that (a) the influence of the frits and enamel production on the high concentrations of Zr, Cu and Ce obtained in zone type A compared with zone B; (b) the affect of clays used as raw materials in the ceramics industry can be demonstrated by the high concentrations of Fe, Al and Mg. The weekly evolution showed two series of elements, a characteristic group of dust emissions and another group of tracers from high temperature processes.     

Preparation and characterization of micron and submicron-sized vermiculite

 The effect of ultrasounds on natural macroscopic vermiculite flakes has been studied. Conditions for the preparation of submicron vermiculite particles of narrow particle-size distribution by sonochemistry are described. The resulting material is crystalline, as assayed by X-ray diffraction. Effects of ultrasound treatment on the mean particle size, crystal structure, crystallite dimensions in different directions, and specific surface area of the resulting particles are investigated. Under the conditions used in this work, there is a practical limit at 40 h in the sonication time for the preparation of submicron particles; longer treatment times promoted aggregation. Received: 21 March 2000 / Accepted: 21 August 2000     

Air pollution prediction models of particles,As, Cd,Ni and Pb in a highly industrialized area in Castellón (NE,Spain)

The objective of this study was to elaborate a series of mathematical models with the aim of short-term prediction of TSP, PM10, As, Cd, Ni and Pb in ambient air. These pollutants depend on some known variables (meteorological variables). The reason for choosing this pollutant type is that particulate matter may present a much higher potential risk despite its low representativeness as compared with the gas pollutant group. A positive correlation between high particle concentrations and deterioration in public health has been shown in recent studies. The elements As, Cd, Ni and Pb in PM10 were also analyzed to determine the toxicity of these particles. The goal is to provide a useful instrument to alert the population facing possible episodes of high concentrations of atmospheric pollutants. The study was carried out in a highly industrialized area in the ceramic cluster of Castellón for 5 years (2001–2005). The origin of the contamination in this area is both natural and anthropogenic. The natural origin is due to the resuspension of mineral materials from the surrounding mountains and from the long-range transport of materials from North Africa. The anthropogenic contamination sources that stand out include the non-metallic mineral material industries (ceramic production), chemical industries (color, frit and enamel manufacturing), as well as vehicular traffic. Once the particle samples were collected in quartz fiber filters, the concentration levels of TSP and PM10 were determined gravimetrically. The chemical analysis of the filters was carried out by ICP-MS. Predictive models have been constructed by using multiple regression analysis together with time series models (ARIMA). The SPSS 14.0 statistical software has been employed to analyze the obtained experimental data.     

Atmospheric inorganic aerosol of a non-industrial city in the centre of an industrial region of the North of Spain,and its possible influence on the climate on a regional scale

Mineral particles could have influenced on the climate of Oviedo, a non-industrial city situated in the centre of an industrial zone of the North of Spain, increasing the temperature and the precipitations, in spite of the fact that “greenhouse gases” concentrations have diminished in this city in recent years. The directive (1999/30/EC) of the European Commission began to be applied in Oviedo in the year 2003. In agreement with this norm, our first aim was the identification of the inorganic particulate matter of the PM10 and PM2.5 fractions sampled in this city. X-ray diffraction and scanning electron microscopy coupled with X-ray dispersive energy spectrometry were used. The percentages of the different mineral phases of the PM were obtained by a Rietveld refinement of powder X-ray diffraction data. The compositions of the PM10 and PM2.5 fractions of this city are similar. Sulphates are the most abundant particles in the both fractions. Most sulphates, nitrates and sal-ammoniac would have formed by reaction between solid, liquid and/or gas particles and they could be associated with the power stations near to the city and traffic. Wüstite and haematites come from the iron and steel industries of Gijón and Avilés. The main natural sources of halite and carbonates and silicates are sea spray and soil resuspension by the wind, respectively.     

The effect of second-phase particles on stable grain size in regionally metamorphosed polyphase calcite marbles

Samples of the calcite-rich Shelburne Marble collected at the Pfizer Quarry in Adams, Massachusetts, show an order of magnitude variation in grain size. Calcite grain size ranges from 94 to 1101  μm. Because these calcite marbles share the same pressure, temperature and strain histories, some other factor must be responsible for the grain size variation.
Grain size appears to be controlled by the concentration of impurity or second-phase particles. Large calcite grain size occurs where the volume fraction of second-phase particles is low and grain size decreases as second-phase volume fraction increases. The relationship between calcite grain size ( D ), second-phase grain size ( d ) and second-phase volume fraction (  f  ) can be described by the power law D / d =1.4/ f   ^0.36, a result that is consistent with models based upon short-term (hours or days) laboratory experiments with metals and ceramics and computer simulations of grain growth. Grain growth appears to be greatly restricted by as little as a few per cent of second-phase particles, with a transition from highly restricted to almost unrestricted grain growth occurring at ≈5% volume of second-phase particles. These results indicate that second-phase particles exercise an important control on grain size and can effectively inhibit grain growth in metamorphic rocks. The behaviour of second-phases in short-term laboratory experiments may closely approximate the behaviour of second-phases in grain growth lasting several orders of magnitude longer in the metamorphic environment.     

Geochemical characteristics of particulate matter in the atmosphere surrounding a ceramic industrialized area

Total suspended particulate samples (TSP) were collected and concentrations measured during seventeen months in the vicinity of a ceramic industrial area. A method of fractionating was applied to the samples in order to obtain two fractions corresponding to mineral particulate coming from dust emissions (Upper-F fraction) and to amorphous matter (carbon plus small amounts of S, Ca, Fe, etc) coming mainly from traffic and other combustion processes. Also for TSP samples several element concentrations were measured following two previous treatments: extraction of elements mainly associated with the soluble fraction of the samples (B, Fe, P, As, NO^2–, NH⁴⁺, Cl^–, F) and acid digestion for trace metals and elements mainly associated with the non-soluble fractions of the samples (Fe, As, Cd, Ni, Pb, Zn Ca). Seasonal differences and the influence of meteorological parameters (temperature, relative humidity, pressure and wind conditions) on the air pollution levels, particles as well as ions, were studied.Results show different seasonal and weekly evolution for mineral and amorphous carbonaceous particles because of the different origins in dust emissions or combustion processes respectively, and the different physical properties such as size grain. Of the ions analyzed Fe, Ca and Zn were clearly associated to mineral phases and consequently related to dust emissions, and NO^2–, NH4+, P, Cl^– were related to amorphous matter coming from combustion. Ni and Cd show lower levels than those reported as guideline values and the source is mainly related to the enrichment of these elements in clay materials. B and As content result in elevated concentrations, with the tendency to increase during cold months. The emission of these elements was associated with vaporization or volatilization during high temperature ceramic processes. The original gaseous state is influenced by temperature. In the winter the content for B and As is higher due to enhanced condensation of gas-phase boron onto particles, while in the summer the increase of air temperature results in elevated evaporation.     

Sedimentation of particulate matter in the Dona Paula Bay, West Coast of India during November to May 1995–1997

Data on hydrography, nutrients, suspended particles, and sedimented particles were collected at weekly intervals from November to May during 1995 to 1997 at a station in the coastal waters of Dona Paula Bay, India. Suspended and sedimented particles were analyzed for total suspended matter (SPM), total sedimented particulate matter (TPM), particulate organic carbon (POC), particulate organic nitrogen (PON), chlorophylla (chla), and diatom abundance. Variations in hydrography and nutrients influenced the quantity and composition of sedimented particles. The TPM, POC, PON, and chla fluxes showed small-scale seasonal variations and were higher in the summer (February to May) than in the winter (November to January). Resuspension of carbon accounted for approximately 25% of the gross POC and was highest in April 1997 (45%). The mean net POC flux was 197±90 mg C m⁻² d⁻¹ and accounts for 4.6% of the TPM. The average C∶N (w∶w) ratio of the sedimented material was 13.2±6.6. The POC:chla ratio was relatively higher in the sedimented material as compared to the suspended material. The particulate carbon reaching the bottom sediment was 39% of the primary production. The low organic carbon concentration (approximately 0.1% of dry sediment) in the sediments implies that about 98% of the sedimented carbon was either consumed at the sedimentwater interface or resuspended/advected before it was finally buried into the sediments.     

Magnetic enhancement of urban roadside soils as a proxy of degree of pollution by traffic-related activities

Detailed magnetic and geochemical measurements were performed on urban roadside soils collected from Lishui city, China, to establish a possible link between the enhanced concentration of traffic-related magnetic particles and heavy metals. Relatively higher magnetic susceptibility (mean: 124.1 × 10⁻⁸ m³ kg⁻¹) and concentrations of metals (Cd, Cu, Pb and Zn) were observed for roadside soils. Concentration-dependent magnetic parameters (χ and SIRM) are highly significantly positively correlated to the concentration of metals (Ca, Cr, Ni, Cu, Zn, Cd, Pb, Fe, and V), but not significantly correlated with As, Mn, Co, Mg, and K. The principal component analysis showed that χ and SIRM significantly correspond to elements Ca, Cd, Cu, Pb, and Zn. The χ and SIRM also have significant linear correlation with integrated pollution index, indicating that χ and SIRM can be used as effective proxy indicators for the pollution of heavy metals. Magnetite in the pseudo-single-domain/multidomain (PSD/MD) grain size was identified as the dominant magnetic carrier by temperature-dependent measurements of saturation magnetization (Ms–T curve), XRD and hysteresis loops. Field emission scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS) analysis of the magnetic particles revealed the presence of large traffic-related angular-subangular, blocky, and spherical iron oxide particles. These iron oxide particles are typical for particles produced by traffic-related anthropogenic activities. It is concluded that vehicle emissions may be the major source of elevated heavy metals and magnetic particles in roadside soils. The results proved the applicability of magnetic method in detecting roadside pollution derived from vehicle emissions.     

奥运会及残奥会期间北京市区大气颗粒物污染特征及微观形貌类型

2008年8月和9月,北京市成功举办了第29届奥运会和第13届残奥会,对这段时间在北京市区(中国矿业大学校园综合楼五层,距奥运村3 km)采集的大气颗粒物的质量浓度和微观形貌类型进行了研究。结果表明:奥运会期间,北京市区大气PM10和PM2.5的日均质量浓度分别小于国家PM10二级标准(150μg/m3)和美国EPA的PM2.5二级标准(65μg/m3),12 h的质量浓度范围分别为7.64~81.63μg/m3和1.91~54.59μg/m3;残奥会期间,12 h的PM10质量浓度范围为33.83~106.36μg/m3,没有超标,PM2.5质量浓度变化范围为15.29~88.30μg/m3,其中出现了3 d超标天,分别为9月6日、7日和14日;从奥运期间PM2.5/PM10的比值(0.26~0.86,大部分值大于0.5)可以看出,奥运期间北京大气颗粒物以细粒子为主。与往年相比,颗粒物质量浓度出现大幅下降趋势。场发射扫描电镜观察显示,奥运会和残奥会期间样品的微观形貌类型主要有球形颗粒、烟尘集合体、不规则矿物和未知颗粒,其数量-粒径分布主要呈单峰分布,峰值均在0.1~0.2μm范围,其中球形颗粒明显占多数。各种分析数据均显示,残奥会期间样品比奥运会期间样品污染要严重。     

Dust emission from desertified lands in the Heihe River Basin,Northwest China

The annual and seasonal dust emissions were calculated for eight types of desertified lands at 120 sites in the Heihe River Basin of northwestern China. The results showed that dust emission rates increased from the middle to the lower reaches of the river by a factor of up to 10³. There two strongest areas of dust emission are the dried-up Gaxun Lake with a dust emission rate of 1.6 t ha⁻¹ year⁻¹, and the desertified grassland areas around the abandoned Heicheng City, with a dust emission rate of 0.6–0.7 t ha⁻¹ year⁻¹. The total annual dust emissions with their particle diameters less than 50, 30, and 10 μm were 1.71 × 10⁶, 1.11 × 10⁶, and 0.555 × 10⁶ t, respectively. Dust emission rates showed striking seasonal variations, with the maximum value (45%) occurring in spring and the minimum value (13.5%) in summer. The mineral aerosol-size distributions were also measured and the results showed that the size distributions for dust and non-dust events were both trimodal, in contrast with the widely accepted view that primary particles such as aeolian dust are coarse, whereas particles less than 1 μm in diameter are mainly secondary particulate substances such as ammonium nitrate, ammonium sulfate, and organic matter.     

Thorium adsorption in the ocean: reversibility and distribution amongst particle sizes

Experiments have been carried out to determine whether the adsorption of Th by marine suspended particles is a reversible process. The results indicate reversibility on a time scale of hours. The distribution of Th between the ‘dissolved’ state (<0.22 μm particle size) and various particle size fractions has been compared with predictions based on a hyperbolic size distribution of marine particles assuming spherical geometry and surface adsorption. Thorium is present in small particles to a much smaller degree than such a model would predict, so that the use of 1 μm pore size filters to separate ‘dissolved’ and ‘particulate’ Th does not introduce serious errors. The implications of these results on the reversible exchange model of Bacon and Anderson (1982) and on the settling model of Tsunogai and Minagawa (1978) are discussed.     

Evaluation of the ability of an artificial neural network model to simulate the input-output responses of a large karstic aquifer: the La Rochefoucauld aquifer (Charente,France)

The ability of artificial neural networks (ANN) to model the rainfall-discharge relationships of karstic aquifers has been studied in the La Rochefoucauld karst system, south-west France, which supplies water to the city of Angoulême. A neural networks model was developed based on MLP (multi-layer perceptron) networks and the Levenberg-Marquardt optimization algorithm. Raw rainfall data were used without transformation into effective rainfall. This allowed for the elimination of certain non-verifiable simplifying assumptions and their subsequent introduction into the modeling procedure. The raw rainfall and discharge data were divided into three groups for the training, the validation and the prediction test of the ANN model. The training and validation phases led to a very satisfactory calibration of the ANN model. The attempt to predict discharges showed that the ANN model is able to simulate the karstic aquifer discharges. The shape of the simulated hydrographs was found to be similar to that of the actual hydrographs. These encouraging results make it possible to consider interesting and new prospects for the modeling of karstic aquifers, which are highly non-linear systems.

---

Resumen Se ha estudiado la capacidad de las redes artificiales neurales (ANN) para modelizar las relaciones de lluvia-descarga de acuíferos kársticos en el sistema kárstico La Rochefocauld, al suroeste de Francia, el cual abastece de agua a la ciudad de Angoulême. Se desarrolló un modelo de redes neurales en base a redes MLP (Perceptron Multi-Capas) y el algoritmo de optimización Levenberg-Marquardt. Se utilizaron datos de lluvia sin la transformación hacia lluvia efectiva. Esto permitió la eliminación de ciertos supuestos simplificadores no verificables y su subsiguiente introducción en el procedimiento de modelizado. Los datos brutos de descarga y lluvia se dividieron en 3 grupos para la preparación, validación y la prueba de predicción del modelo ANN. Las fases de preparación y validación llevaron a una calibración muy satisfactoria del modelo ANN. El intento por predecir descargas mostró que el modelo ANN es capaz de simular las descargas del acuífero kárstico. Se encontró que la forma de los hidrogramas sintéticos es similar a la de los hidrogramas reales. Estos resultados alentadores hacen posible considerar prospectos nuevos e interesantes para el modelizado de acuíferos kársticos los cuales son sistemas altamente no-lineares.

---

Résumé L’aptitude des réseaux de neurones artificiels (RNA) à modéliser les relations pluie-débit des aquifères karstiques a été évaluée sur le karst de La Rochefoucauld (Sud-Ouest de la France), qui fournit l’eau potable à la capitale régionale Angoulême. Un modèle RNA a été développé à cet effet, basé sur les réseaux PMC (Perceptron Multicouche) et l’algorithme d’optimisation de Levenberg-Marquardt. Les données de pluie utilisées concernent la pluie brute, sans transformation en pluie efficace, ce qui permet de s’affranchir de certaines hypothèses simplificatrices non vérifiables. Les données de pluie brute et de débit ont été réparties en 3 groupes pour l’apprentissage, la validation et le test de prédiction du RNA. Les phases d’apprentissage et de validation ont permis d’aboutir à une calibration très satisfaisante du modèle RNA. La tentative de prédiction a montré que le RNA est apte à simuler les débits de l’aquifère karstique à partir de la pluie brute. La forme des hydrogrammes simulés est semblable à celle des hydrogrammes réels. Les résultats obtenus sont très encourageants et permettent d’envisager des perspectives intéressantes et nouvelles de modélisation des aquifères karstiques, qui sont des systèmes hautement non-linéaires.

     

Natural radionuclides in the Arabian Sea and Bay of Bengal: Distribution and evaluation of particle scavenging processes

Vertical and temporal variations in the activities of²³⁴Th,²¹⁰Po and²¹⁰Pb have been measured, in both dissolved and paniculate phases, at several stations in the eastern Arabian Sea and north-central Bay of Bengal. A comparative study allows us to make inferences about the particle associated scavenging processes in these two seas having distinct biogeochemical properties. A common feature of the²³⁴Th profiles, in the Arabian Sea and Bay of Bengal, is that the dissolved as well as total (dissolved + particulate) activity of²³⁴Th is deficient in the surface 200 m with respect to its parent,²³⁸U. This gross deficiency is attributed to the preferential removal of²³⁴Th by adsorption onto settling particles which account for its net loss from the surface waters. The scavenging rates of dissolved²³⁴Th are comparable in these two basins. The temporal variations in the²³⁴Th-²³⁸U disequilibrium are significantly pronounced both in the Arabian Sea and Bay of Bengal indicating that the scavenging rates are more influenced by the increased abundance of particles rather than their chemical make-up. In the mixed layer (0–50 m), the scavenging residence time of²³⁴Th ranges from 30 to 100 days. The surface and deep waters of both the seas show an enhanced deficiency of dissolved²¹⁰Po relative to²¹⁰Pb and that of²¹⁰Pb relative to²²⁶Ra. The deficiencies of both²¹⁰Po and²¹⁰Pb in the dissolved phases are not balanced by their abundance in the particulate form indicating a net loss of both these nuclides from the water column. The scavenging rates of²¹⁰Po and²¹⁰Pb are significantly enhanced in the Bay of Bengal compared to those in the Arabian Sea. The mean dissolved²¹⁰Po/²¹⁰Pb and²¹⁰Pb/²²⁶Ra activity ratios in deep waters of the Bay of Bengal are ∼ 0.7 and 0.1, respectively, representing some of the most pronounced disequilibria observed to date in the deep sea. The Bay of Bengal and the Arabian Sea appear to be the regions of most intense particle moderated scavenging processes in the world oceans. This is evidenced by the gross disequilibria exhibited by the three isotope pairs used in this study.     

Characterization of indoor and outdoor atmospheric pollutants impacting architectural monuments: the case of San Jerónimo Monastery (Granada, Spain)

Indoor and outdoor concentrations of atmospheric gaseous pollutants as well as composition, size, and morphology of particulate matter have been investigated at the monastery of San Jerónimo in Granada (Southern Spain). Complementary micro- and nano-analytical techniques were applied; elemental and mineralogical composition and morphological characteristics of particulate matter were investigated combining electron probe microanalysis at the single particle level, and bulk aerosol samples were analyzed using energy-dispersive X-ray fluorescence, X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray analyzer and transmission electron microscopy (TEM). Microclimatic conditions at the monastery were monitored, and gas concentrations were assessed by means of diffusion tubes subsequently analyzed with ion chromatography. Results revealed high abundances of soil dust particles (aluminosilicates, calcite, dolomite, quartz), salt aerosols (chlorides, sulfates and ammonium-rich salts), and NO₂ and SO₂ both outdoors and indoors. Amorphous black carbon particles had surprisingly high abundances for Granada, a non-industrialized city. The composition of indoor particles corresponds to severe weathering affecting the construction materials and artworks inside the church; moreover their composition promotes a feedback process that intensifies the deterioration. Chemical reactions between chloride-rich salts and pigments from paintings were confirmed by TEM analyses. Indoors, blackening of surface decorative materials is fostered by particle re-suspension due to cleaning habits in the monastery (i.e. dusting). This is the first air quality study performed in a monument in the city of Granada with the aim of developing a strategy for preventive conservation.     

Studying the effect of non‐spherical micro‐particles on Hoek–Brown strength parameter mi using numerical true triaxial compressive tests

The strength parameter m_i in the Hoek–Brown strength criterion is empirical and was developed by trial and error. To better understand the fundamental relationship between m_i and the physical characteristics of intact rock, this paper presents a systematic study of m_i by representing intact rock as a densely packed cemented particle material and simulating its mechanical behavior using particle flow modeling. Specifically, the three‐dimensional particle flow code (PFC3D) was used to conduct numerical true triaxial compression tests on intact rock and to investigate the effect of non‐spherical micro‐particle parameters on m_i. To generate numerical intact rock specimens containing non‐spherical micro‐particles, a new genesis process was proposed, and a specific loop algorithm was used based on the efficiency of the process and the acceptability of generated specimens. Four main parameters—number, aspect ratio, size, and shape—of non‐spherical micro‐particles were studied, and the results indicated that they all have great effect on m_i. The strength parameter m_i increases when the number, aspect ratio, or size is larger or the shape becomes more irregular, mainly as a result of the higher level of interlocking between particles. This confirms the observations from engineering experience and laboratory experiments. To simulate the right strength parameter m_i, it is important to use appropriate non‐spherical micro‐particles by controlling these four parameters. This is further demonstrated by the simulation of two widely studied rocks, Lac du Bonnet granite and Carrara marble. Copyright © 2014 John Wiley & Sons, Ltd.     

Pb on groundwater particles,Door County,Wisconsin

Pb was detected on groundwater particles larger than 0.45m. Pb concentration (micrograms per liter) showed positive correlations with particle concentration (milligrams per liter) at five sampled wells, although the slopes of the best-fit lines were different. X-ray fluorescence scans suggested that the particles primarily consist of K-Al silicate minerals, and that Pb is absorbed onto Fe oxyhydroxide coatings on Mg-rich silicates. Particle compositions varied at wells, but remained consistent at each well through the sampling period of a month. The particulate nature of Pb in groundwater could cause the spatial and temporal variations due to: (1) the unique composition of particles at wells, (2) the irregular pathways for groundwater particles, (3) the unpredictable amount of Pb-carrying particles entering the groundwater system during recharge events, and (4) the irregular sampling of groundwater particles subsequently dispersed along the advective flow path.     

Analytical Electron-Microscopy Fractionation of Fine and Colloidal Particulate-Phosphorus in Riverbed and Suspended Sediments

The impact particulate-phosphorus (particulate-P) has on eutrophication of aquatic systems that greatly depends on its composition. As a result, analysis methods for evaluating particulate-P speciation must be capable of identifying and/or quantifying the wide range of forms particulate-P can take. In the present study, we compare the particulate P speciation of the fine and colloidal fractions of riverbed sediment and suspended matter from two rivers in the Lake Geneva basin (French Alps) as determined with chemical extractions to results of a combined Transmission Electron Microscopy and Energy Dispersive Detection (TEM–EDS) analysis of the same samples. TEM–EDS provides semi-quantitative information about the distribution of P throughout the solid fraction of a sample and on the diversity of carrier phases, which are identified by their morphology and stochiometry. EDS-detectable quantities of phosphorus were found in 15–35% of the particles in the samples analyzed. As expected, particulate-P existed in a wide variety of forms, mostly associated with Al, Fe, Ca and Si. Some types of particles, often well-crystallized phosphate minerals, had high P contents (10–30%), but the dominant carrier phases of P were diffuse matrices of particles with low P contents (<5%). These matrices had a wide range of chemical compositions and included clay minerals, crystallized and amorphous phases of Fe, as well as intermediary components. Classical chemical extractions showed major differences in P content and speciation between the upstream and downstream sediment samples. The downstream samples showed higher frequencies of particles containing P, a larger diversity of carrier phases, a higher contribution of clays as carrier phases of P, and the presence of a new fraction with Al and Fe amorphous minerals. The processes that create and select carrier phases of particulate-P are part of the general dynamics of P within a watershed.     

From micron-sized needle-shaped hydrates to meter-sized shotcrete tunnel shells: micromechanical upscaling of stiffness and strength of hydrating shotcrete

Knowledge on the stresses in shotcrete tunnel shells is of great importance, as to assess their safety against severe cracking or failure. Estimation of these stresses from 3D optical displacement measurements requires shotcrete material models, which may preferentially consider variations in the water–cement and aggregate–cement ratios. Therefore, we employ two representative volume elements within a continuum micromechanics framework: the first one relates to cement paste (with a spherical material phase representing cement clinker grains, needle-shaped hydrate phases with isotropically distributed spatial orientations, a spherical water phase, and a spherical air phase; all being in mutual contact), and the second one relates to shotcrete (with phases representing cement paste and aggregates, whereby aggregate inclusions are embedded into a matrix made up by cement paste). Elasticity homogenization follows self-consistent schemes (at the cement paste level) and Mori–Tanaka estimates (at the shotcrete level), and stress peaks in the hydrates related to quasi-brittle material failure are estimated by second-order phase averages derived from the RVE-related elastic energy. The latter permits upscaling from the hydrate strength to the shotcrete strength. Experimental data from resonant frequency tests, ultrasonics tests, adiabatic tests, uniaxial compression tests, and nanoindentation tests suggest that shotcrete elasticity and strength can be reasonably predicted from mixture- and hydration-independent elastic properties of aggregates, clinker, hydrates, water, and air, and from strength properties of hydrates. At the structural level, the micromechanics model, when combined with 3D displacement measurements, predicts that a decrease of the water–cement ratio increases the safety of the shotcrete tunnel shell.     

辽宁中元古代初期粗碎屑岩中微生物砂质颗粒的发现及古环境意义

微生物席成因构造(microbial induced sedimentary structures, MISS)是由微生物与沉积物相互作用形成的生物沉积构造,表现形式有变余波痕、皱饰构造、微生物席碎片、纺锤状或次圆状收缩裂缝等。首次在华北地台东北部辽宁兴城中元古代初期常州沟组底部粗碎屑岩交错层理面上发现了大量的微生物砂质颗粒,在中元古代底部粗碎屑岩中发现大量微生物砂质碎片。这一发现对于了解华北地台MISS的活跃时代以及恢复中元古代早期粗碎屑岩的形成古环境有重要的科学意义,特别是为华北地台古元古代、中元古代的地层划分与对比提供一定的生物地层学参考。发现的微生物砂质颗粒大小在0.1~0.2 mm,形态以球形为主。这些微生物砂质颗粒形成于静水环境的潮上带或泥坪之中的微生物席底,在剧烈的构造运动以及海侵初期高频的海平面运动中被风暴、海啸等灾难性事件破坏,并随着退潮水流被搬运至发育交错层理的潮道区域,与粗碎屑物质一起沉积。这些被风暴破坏的微生物砂质颗粒在搬运过程中被磨圆并产生一定的分选。     

Geomechanical model for fracture deformation under hydraulic, mechanical and thermal loads

Hydraulic flow and transport (heat and solute) within crystalline rocks is dominated by the fracture systems found within them. In situ stress conditions have a significant impact on the hydraulic, mechanical and thermal coupled processes, and quantification of these processes provides a key to understanding the often transient time-dependent behaviour of crystalline rocks. In this paper, a geomechanical model is presented which describes fracture closure as a function of effective stress and the changes in parameters such as storage, permeability, porosity and aperture. Allowing the fracture closure to be defined by the change in normal effective stress provides a link to the numerical consideration of parametrical changes due to rock stress alterations caused for example by changes in fracture fluid pressure, stress release, tectonic stress, thermal stress, orientation of the natural fracture in the pervasive stress system and local changes in a rock mass due to stress alteration. The model uses geometrical considerations based on a fractal distribution of apertures on the fracture surface, and applies well-established analytical elastic deformation solutions to calculate the deformation response to changes in effective stress. Analysis of the fractal generation method allows a standard normal distribution of fracture apertures to be predicted for all common fractal dimensions relating to a 2D surface. Changes in the fracture aperture are related to hydraulic functions such as permeability, storage and porosity of the fracture. The geomechanical model is experimentally validated against laboratory scale experimental data gained from the closure of a fractured sample recovered at a depth of 3,800 m from the KTB pilot borehole. Parameters for matching the experimental data were established externally, the only fitting parameters applied were the minimum and maximum contact area between the surfaces and the number of allowable contacts. The model provides an insight into the key processes determining the closure of a fracture, and can act as a material input function for numerical models linking the effects of changes in the stress field, hydraulic or thermal conditions, to the flow and transport parameters of a fractured system.

---

Résumé L’écoulement et le transport (chaleur et soluté) dans les roches cristallines sont dominés par les systèmes de fracture. Les conditions de stress in-situ ont un impact significatif sur l’hydraulique, les processus couplés de mécanique et thermique et la quantification de ces processus apportent une clé pour comprendre le comportement transitoire des roches cristallines. Dans cet article un modèle géomécanique est présenté, modèle qui décrit la fermeture des fractures comme une fonction de la contrainte effective et des changements de paramètres tels le coefficient d’emmagasinement, la perméabilité, la porosité et l’ouverture. En s’accordant que la fermeture des fractures est définit par les changements de la contrainte effective normale, on apporte le lien avec la considération numérique des changements paramétriques dus aux altérations de la contrainte des roches, causés par exemple par des variations de la pression des fluides dans les fractures, du dégagement de la contrainte, des contraintes tectoniques et thermiques, des orientations des fractures naturelles dans le système de contraintes pénétrantes, et des changements locaux dans un massif de roches dus à l’altération des contraintes. Le modèle utilise des considérations géométriques basées sur une distribution fractale des ouvertures à la surface des fractures, et permet d’établir des solutions analytiques de la déformation élastique pour calculer la réponse de la déformation à la contrainte effective. L’analyse de la méthode par génération fractale permet de prédire une distribution normale standard de l’ouverture des fractures, pour toutes les dimensions fractales en relation avec les surfaces 2D. Les changements dans l’ouverture des fractures sont mis en relation avec les fonctions hydrauliques tels la perméabilité, l’emmagasinement et la porosité de la fracture. Le modèle géoméchanique est expérimentalement validé à l’échelle du laboratoire sur un échantillon fracturé récupéré à une profondeur de 3,800 mètres sur le puits du site pilote KTB. Les paramètres du calibrage des données expérimentales ont été établies extérieurement, les seuls paramètres utilisés étant les surfaces de contact minimum et maximum, et le nombre de contacts permis. Le modèle apporte une connaissance perspicace sur le processus clé déterminant la fermeture des fractures, et peut servir de fonction input dans les modèles numériques reliant les effets des variations de la contrainte du terrain, les conditions hydrauliques ou thermales, les paramètres de l’écoulement et du transport et les systèmes de fracture.

---

Resumen El flujo hidráulico y transporte (de calor y solutos) dentro de rocas cristalinas está dominado por los sistemas de fracturas que se encuentran en ellas. Las condiciones de esfuerzos in-situ tienen un impacto significativo en los procesos aparejados termales, mecánicos e hidráulicos y la cuantificación de estos procesos aporta una clave para entender el frecuente comportamiento transitorio dependiente de las rocas cristalinas. En este artículo se presenta un modelo geomecánico que describe el cierre de fracturas en función del esfuerzo efectivo y los cambios en parámetros tal como almacenamiento, permeabilidad, porosidad y apertura. El definir el cierre de fractura mediante el cambio en esfuerzo normal efectivo aporta un vínculo con la consideración numérica de cambios paramétricos ocasionados por alteraciones de esfuerzos en la roca causadas, por ejemplo, por cambios en presión de fluidos en fractura, liberación de esfuerzo, esfuerzo tectónico, esfuerzo termal, orientación de fracturas naturales en el sistema de esfuerzos penetrante, y cambios locales en una masa rocosa ocasionados por alteración de esfuerzos. El modelo utiliza consideraciones geométricas basadas en la distribución fractal de aperturas en la superficie de fractura y aplica soluciones analíticas bien establecidas de deformación elástica para calcular la respuesta de deformación a cambios en el esfuerzo efectivo. Los análisis del método de generación fractal permiten predecir una distribución normal standard para la distribución de aperturas de fracturas para todas las dimensiones fractales comunes que se relacionan con una superficie 2D. Los cambios en la apertura de fractura se relacionan con funciones hidráulicas tal como permeabilidad, almacenamiento y porosidad de la fractura. El modelo geomecánico se ha validado experimentalmente en contra de datos experimentales a escala de laboratorio obtenidos a partir del cierre de una muestra fracturada recuperada a una profundidad de 3,800 m en el pozo piloto KTB. Se establecieron externamente parámetros que se ajustan a los datos experimentales, con los parámetros de ajuste aplicados que fueron el área máxima y mínima de contacto entre las superficies y el número de contactos permisibles. El modelo arroja luz sobre los procesos clave que determinan el cierre de una fractura y puede actuar como un material de función de entrada para modelos numéricos que vinculan los efectos de cambios en el campo de esfuerzos, condiciones termales o hidráulicas, con los parámetros de flujo y transporte de un sistema fracturado.