An improved spectral turning-bands algorithm for simulating stationary vector Gaussian random fields

We propose a spectral turning-bands approach for the simulation of second-order stationary vector Gaussian random fields. The approach improves existing spectral methods through coupling with importance sampling techniques. A notable insight is that one can simulate any vector random field whose direct and cross-covariance functions are continuous and absolutely integrable, provided that one knows the analytical expression of their spectral densities, without the need for these spectral densities to have a bounded support. The simulation algorithm is computationally faster than circulant-embedding techniques, lends itself to parallel computing and has a low memory storage requirement. Numerical examples with varied spatial correlation structures are presented to demonstrate the accuracy and versatility of the proposal.     

Polycyclic aromatic hydrocarbon concentrations in urban soils representing different land use categories in Shanghai

An extensive soil survey was carried out in Shanghai to investigate the spatial distribution and possible sources of polycyclic aromatic hydrocarbons (PAHs) in urban soils. Soil samples were collected from highways, iron-smelting plants, steel-smelting plants, shipbuilding yards, coking plants, power plants, chemical plants, urban parks, university campuses and residential areas and were analyzed for 16 PAHs by gas chromatography with mass detection. High PAH concentrations were found in all locations investigated, with mean values of soil total PAH concentrations in the range 3,279–38,868 μg/kg DM, and the PAH concentrations were significantly influenced by soil organic matter content. Soil PAH profiles in all districts were dominated by PAHs with 4–6 rings. Principal components analysis and diagnostic ratios of PAHs indicate that they were mainly derived from coal combustion and petroleum but in soils from highways the PAHs were derived largely from vehicle exhaust emissions. The high concentrations of PAHs found indicate that many urban soils in Shanghai represent a potential hazard to public health.     

Transport in fracture processes: Fragmentation and slip

We present a new development in the asymmetric continuum theory with the shear oscillations (twist motions) and independent spin; these motions (displacement velocities and spin) can be shifted in phase to describe the independent rebound processes. Our approach provides an extension of the asymmetric continuum theory by including the microfragmentation processes with a double transport which may appear in an advanced fracture process under very high load. The related nonlinear equations, leading to soliton solutions, are derived.     

Toward the understanding of the treatment of textile industries’ effluents by clay: adsorption of anionic dye on kaolinite

Clays, particularly kaolinite, are promising adsorbents for the treatment of textile effluents, but there is a need of better understanding the mechanisms of adsorption, especially in the case of anionic dyes. Thus, the removal of RR120 anionic dye was investigated using Tunisian raw clay (TBK) composed of kaolinite and illite, and a standard kaolinite (KGa-2), and conducting batch experiments by varying different parameters (contact time, ionic strength, concentration, temperature). We investigated the clays’ surface charges by electrophoretic mobility measures and the dye-clay interactions during adsorption, by the streaming-induced potentials (SIP). The results showed that KGa-2 has higher adsorption capacity for RR120 dye than TBK clay, moreover enhanced by increasing the ionic strength and/or lowering the pH of the aqueous. The SIP results showed an increase of negative charges for both clays, reflecting the adsorption of the anionic dye on the positive charges of the amphoteric surfaces of the clays. The SIP magnitudes indicated a higher adsorption rate for KGa-2 in accordance with the kinetic study. The Sips model that described the best adsorption isotherms indicates lateral interactions of the dye molecules, stronger in the case of KGa-2 than TBK. Also, the dye molecules form a thinner layer on KGa-2 surfaces. In addition, the dye molecule’s structure was not altered, as verified by mass spectrometry. The adsorption process was feasible and spontaneous and favored at ambient temperature. Thus, kaolinite-rich clays are effective in the removal of anionic dyes in aqueous solution and potential good adsorbents in wastewater treatment.     

<Emphasis Type="Italic">Deepwater Horizon</Emphasis> Oil Spill Impacts on Salt Marsh Fiddler Crabs (<Emphasis Type="Italic">Uca</Emphasis> spp.)

The Deepwater Horizon oil spill was the largest marine oil spill in US waters to date and one of the largest worldwide. Impacts of this spill on salt marsh vegetation have been well documented, although impacts on marsh macroinvertebrates have received less attention. To examine impacts of the oil spill on an important marsh invertebrate and ecosystem engineer, we conducted a meta-analysis on fiddler crabs (Uca spp.) using published sources and newly available Natural Resources Damage Assessment (NRDA) and Gulf of Mexico Research Initiative (GoMRI) data. Fiddler crabs influence marsh ecosystem structure and function through their burrowing and feeding activities and are key prey for a number of marsh and estuarine predators. We tested the hypothesis that the spill affected fiddler crab burrow density (crab abundance), burrow diameter (crab size), and crab species composition. Averaged across multiple studies, sites, and years, our synthesis revealed a negative effect of oiling on all three metrics. Burrow densities were reduced by 39 % in oiled sites, with impacts and incomplete recovery observed over 2010–2014. Burrow diameters were reduced from 2010 to 2011, but appeared to have recovered by 2012. Fiddler crab species composition was altered through at least 2013 and only returned to reference conditions where marsh vegetation recovered, via restoration planting in one case. Given the spatial and temporal extent of data analyzed, this synthesis provides compelling evidence that the Deepwater Horizon spill suppressed populations of fiddler crabs in oiled marshes, likely affecting other ecosystem attributes, including marsh productivity, marsh soil characteristics, and associated predators.     

A laboratory study on groundwater quality and mass movement occurrence

In this study, soil samples collected from the sides of two streams with high debris flow potential at Shenmu and Fengchiou village in Nantou County, Taiwan, were used for seepage tank tests in the laboratory. While the tests were being conducted, observations were made to investigate the relationships among displacement of the slope, quality of the seepage water and occurrence of mass movement. The results showed that according to the change rate, displacement could be divided into two stages, namely, the initial failure displacement stage and primary failure displacement stage. While the displacement of the slope was in primary failure displacement stages, the probability of slope failure became much higher. Before general slope failure, electrical conductivity (EC) and sulfate ion (SO₄ ²⁻) concentration of the seepage water increased significantly. The time when EC of the seepage water started to increase rapidly was much earlier than that when displacement of the slope started to increase significantly. Therefore, from the hazard mitigation view, there will be a longer time for response if EC of the seepage water was monitored.     

渤海湾盆地垦东凸起北坡馆上段沉积相模式探讨

主要通过岩心观察、粒度分析、参数计算、录测井分析等手段,充分吸收国内外河流研究成果,结合研究区区域地质背景,揭示垦东凸起北坡馆上段沉积相模式。得到以下认识：研究区馆上段地层为河流相沉积,从沉积物特征和平面形态角度可以将研究区馆上段河流沉积理解为介于辫状河及曲流河之间的过渡河型。其平均河道弯曲度大于1.7,垂向层序表现为泥多砂少,具有曲流河的特征;但沉积层序顶部常直接覆盖河漫/洪泛平原沉积,特别是河道内砂坝发育造成河道分汊河,砂坝沉积物粒度特征反映受洪水控制的震荡性特点而与曲流河有重要差别。本文借用在水利学界和地貌学界广为使用的分汊河概念建立了研究区馆上段沉积相模式,包括河床、堤岸、河漫/洪泛平原、废弃河道等4个亚相,组成下粗上细的正旋回。其中,河道砂坝是其主要砂体,顶部常被洪泛平原直接覆盖;决口扇是仅次于河道砂坝的第二大砂体。     

Landslide susceptibility mapping for a landslide-prone area (Findikli,NE of Turkey) by likelihood-frequency ratio and weighted linear combination models

Landslides are very common natural problems in the Black Sea Region of Turkey due to the steep topography, improper use of land cover and adverse climatic conditions for landslides. In the western part of region, many studies have been carried out especially in the last decade for landslide susceptibility mapping using different evaluation methods such as deterministic approach, landslide distribution, qualitative, statistical and distribution-free analyses. The purpose of this study is to produce landslide susceptibility maps of a landslide-prone area (Findikli district, Rize) located at the eastern part of the Black Sea Region of Turkey by likelihood frequency ratio (LRM) model and weighted linear combination (WLC) model and to compare the results obtained. For this purpose, landslide inventory map of the area were prepared for the years of 1983 and 1995 by detailed field surveys and aerial-photography studies. Slope angle, slope aspect, lithology, distance from drainage lines, distance from roads and the land-cover of the study area are considered as the landslide-conditioning parameters. The differences between the susceptibility maps derived by the LRM and the WLC models are relatively minor when broad-based classifications are taken into account. However, the WLC map showed more details but the other map produced by LRM model produced weak results. The reason for this result is considered to be the fact that the majority of pixels in the LRM map have high values than the WLC-derived susceptibility map. In order to validate the two susceptibility maps, both of them were compared with the landslide inventory map. Although the landslides do not exist in the very high susceptibility class of the both maps, 79% of the landslides fall into the high and very high susceptibility zones of the WLC map while this is 49% for the LRM map. This shows that the WLC model exhibited higher performance than the LRM model.     

The distribution, sources and toxicity risks of polycyclic aromatic hydrocarbons and n-alkanes in riverine and estuarine core sediments from the Daliao River watershed

The burial characteristics and toxicity risks associated with n-alkanes and polycyclic aromatic hydrocarbons (PAHs) in the riverine and estuarine sediments of the Daliao River watershed were investigated based on three sediment cores. The sum of the n-alkane and PAH concentrations, normalized to organic carbon (OC), ranged from 0.27 to 63.09 μg g^?1OC^?1 and 6.60 to 366.20 μg g^?1OC^?1, respectively. The features and the history of industrial activities, such as the oil and chemical industries and port activities near the river and estuary, resulted in different distributions and sources of hydrocarbons. The sources of pollution were identified based on n-alkane indexes and on diagnostic ratios of PAHs. The diagnostic ratios indicated that the n-alkanes were derived from both biogenic and petrogenic sources in different proportions and that the PAHs were derived primarily from petrogenic combustion sources. A hierarchical cluster analysis grouped the core samples into two clusters. The first cluster, river sediments, corresponded to industrial activities; the second cluster, estuarine sediments, corresponded to port shipping activities. The toxic potency of the PAHs in the cores was assessed in terms of toxic equivalents (TEQs) of dibenzo[a,h]anthracene and benzo[a]pyrene. The top layer of the sediment in the cores had a relatively high toxicity. The TEQ values for benzo(a)pyrene (TEQ_BaP) and dioxins (TEQ_TCDD) furnished a consistent assessment of the PAHs in the sediment cores.