Reducing leachable petroleum hydrocarbon concentration in weathered fuel oil contaminated soil by chemical oxidation with hydrogen peroxide

Number 6 fuel oil is one of the most used energy sources for electricity generation. However, leaks can contaminate soil and also groundwater due to leaching. At old sites, the oil may have low toxicity but still contaminate groundwater with foul-tasting compounds even at low concentrations. The purpose of this study was to evaluate the feasibility of applying H₂O₂ to reduce the leaching potential of a fuel oil contaminated soil. A silt-loam soil was collected from a contaminated thermal-electric plant with a hydrocarbon concentration of 3.2% in soil producing 4.3 mg/l in leachate. Hydrogen peroxide was applied (0.1, 0.2, 0.3, 0.6, 1.2% dry weight basis), and petroleum hydrocarbons were measured in soil and leachate pre- and post-treatment (72 h). At first, the soil and leachate concentrations diminished linearly (24.4 and 27.3% in soil and leachate, respectively). This was followed by a phase in which the concentration in leachate diminished greatly (75.8%) although the concentration in soil was reduced only moderately (15.1%). Overall, hydrocarbons in leachates were reduced 82.4% even though concentrations in soil were only reduced 35.8%. Correlation analysis showed that at only 1.0% w/w H₂O₂ a concentration of petroleum hydrocarbons in leachate safe for human consumption (≤ 1 mg/l) could be obtained even with a final hydrocarbon concentration in soil > 2%. Thus, this study presents an alternative strategy for remediation of fuel oil contaminated soils in urban environments that protects water sources by focusing on contamination in leachates, without spending extra financial resources to reduce the hydrocarbon concentration in low-toxicity soil.     

铂族元素在地壳中的富集:以布什维尔德杂岩为例

地幔是地壳铂族元素富集的主要源库。铂族元素迁移主要有两个途径:(1)地幔部分熔融物质侵入地壳;(2)地幔板片就位于俯冲/碰撞带。前一途径比后一途径重要得多。地幔物质进入地壳造成铂族元素富集并成为可供开采的主矿产而非副产品,这一过程可包含许多成矿作用机制:(i)基性侵入体中Ni-Cu硫化物矿浆的发育,岩浆冷却与分离结晶作用导致富含Cu,Pt,Pd的硫化物矿浆的形成;(ii)层状侵入体一定层位形成高品位的铂族元素硫化物层,伴生或不伴生铬铁岩;(iii)富铂族元素及硫化物的岩浆沿着层状侵入体的边缘就位;(iv)直至层状侵入体结晶分异作用晚期的硫化物不混溶滞后分离;(v)不发育硫化物不混溶作用的铬铁矿结晶作用;(vi)低程度硫化物浸染带中的热液作用与铂族元素富集;(vii)乌拉尔-阿拉斯加型侵入体重结晶过程中的铂族元素与铬铁矿的次生富集作用,岩体在风化过程中形成砂矿床;(viii)黑色页岩形成过程中Pt的富集。南非布什维尔德火成杂岩蕴藏世界Pt资源的75%,Pd资源的54%,Rh资源的82%,并具有(ii)、(iii)、(iv)、(v)、(vi)成矿作用的实例。在这些作用中,作用(ii)形成的现有经济储量和资源量占90%,作用(iii)占9%。Merensky矿层(占总资源量30%)是一个铂族元素富集层位,它含1~3铬铁矿薄层,在可采宽度内硫化物平均含量为1%~3%(质量分数)。硫化物一般被认为是铂族元素的主要聚集体。该矿层由两个或两个以上含硫化物的基性热岩浆上升汇聚而成。这些岩浆的汇聚造成超镁铁质堆晶岩的厚度(主要是斜方辉石岩,某些地区包括橄榄岩)变化于50cm至数米之间。开采通常集中在厚度不到1m的地带。矿层的成因至今仍存在争议,一些观点认为铂族元素来自下部上升的热液流体,另一些观点认为铂族元素来自上部岩浆的硫化物沉降作用,并形成了Merensky辉石岩。已经知道矿层上覆的辉石岩、苏长岩和斜长岩中矿物来自两种岩浆类型:一种富含MgO(12%,质量分数)和Cr,而贫Al2O3(12%);另一种含典型的粒玄岩成分。UG-2铬铁岩含有全部经济资源量的58%,由一0.6~1m厚的铬铁岩层(有时见辉石岩夹层)和上覆的1~3层由铬铁矿所构成的薄层。虽然硫化物被认为至少是某些情况下对铂族元素的富集起作用,但UG-2的硫化物含量(0.5%~1.5%)显著低于Merensky矿层。UG-2层之下共有13个铬铁岩层位,所有的都含铂族元素,虽然铂族元素总含量和(Pt+Pd)/(Ru+Ir+Os)比值远低于UG-2。UG-2内所含的辉石岩"夹层"具高的87Sr/86Sr比值,说明与顶部熔融岩石的混合促进了铬铁岩和硫化物的形成。作用(iii)的主要实例是Platreef。目前它占总资源量的9%。不过,沿该带正积极开展找矿勘探工作,这一比例将来还会提高。这一矿层的厚度比Merensky和UG-2都要大,目前开采厚度达50多米。Platreef呈带状,上部为斜方辉石岩的堆晶岩;下部为辉石岩、长石辉石岩和苏长岩,它们与页岩、铁矿层和白云岩强烈相互作用,直接形成了底盘岩石。笔者认为Platreef是不同期次岩浆作用的结果,这些作用形成了不同的单元产物,包括布什维尔德主岩浆房的UG-2和Merensky矿层。新的岩浆进入主岩浆房会造成先存岩浆移位、岩浆错动并会冲破岩浆房的壁。圆筒状、带状岩管中的超镁铁岩含极高的Pt品位,在布什维尔德杂岩的下部切穿堆晶层,被认为是热液再活化的产物。它们现在未被开采,只是构成存封的铂族元素资源,对整个杂岩体资源没有重要的贡献。     

Minimum relative entropy and probabilistic inversion in groundwater hydrology

The similarity between maximum entropy (MaxEnt) and minimum relative entropy (MRE) allows recent advances in probabilistic inversion to obviate some of the shortcomings in the former method. The purpose of this paper is to review and extend the theory and practice of minimum relative entropy. In this regard, we illustrate important philosophies on inversion and the similarly and differences between maximum entropy, minimum relative entropy, classical smallest model (SVD) and Bayesian solutions for inverse problems. MaxEnt is applicable when we are determining a function that can be regarded as a probability distribution. The approach can be extended to the case of the general linear problem and is interpreted as the model which fits all the constraints and is the one model which has the greatest multiplicity or “spreadout” that can be realized in the greatest number of ways. The MRE solution to the inverse problem differs from the maximum entropy viewpoint as noted above. The relative entropy formulation provides the advantage of allowing for non-positive models, a prior bias in the estimated pdf and `hard' bounds if desired. We outline how MRE can be used as a measure of resolution in linear inversion and show that MRE provides us with a method to explore the limits of model space. The Bayesian methodology readily lends itself to the problem of updating prior probabilities based on uncertain field measurements, and whose truth follows from the theorems of total and compound probabilities. In the Bayesian approach information is complete and Bayes' theorem gives a unique posterior pdf. In comparing the results of the classical, MaxEnt, MRE and Bayesian approaches we notice that the approaches produce different results. In␣comparing MaxEnt with MRE for Jayne's die problem we see excellent comparisons between the results. We compare MaxEnt, smallest model and MRE approaches for the density distribution of an equivalent spherically-symmetric earth and for the contaminant plume-source problem. Theoretical comparisons between MRE and Bayesian solutions for the case of the linear model and Gaussian priors may show different results. The Bayesian expected-value solution approaches that of MRE and that of the smallest model as the prior distribution becomes uniform, but the Bayesian maximum aposteriori (MAP) solution may not exist for an underdetermined case with a uniform prior.     

An analysis of the impact of spatial variability in rainfall on runoff and sediment predictions from a distributed model

This paper investigates the effect of introducing spatially varying rainfall fields to a hydrological model simulating runoff and erosion. Pairs of model simulations were run using either spatially uniform (i.e. spatially averaged) or spatially varying rainfall fields on a 500‐m grid. The hydrological model used was a simplified version of Thales which enabled runoff generation processes to be isolated from hillslope averaging processes. Both saturation excess and infiltration excess generation mechanisms were considered, as simplifications of actual hillslope processes. A 5‐year average recurrence interval synthetic rainfall event typical of temperate climates (Melbourne, Australia) was used. The erosion model was based on the WEPP interrill equation, modified to allow nonlinear terms relating the erosion rate to rainfall or runoff‐squared. The model results were extracted at different scales to investigate whether the effects of spatially varying rainfall were scale dependent. A series of statistical metrics were developed to assess the variability due to introducing the spatially varying rainfall field. At the catchment (approximately 150 km²) scale, it was found that particularly for saturation excess runoff, model predictions of runoff were insensitive to the spatial resolution of the rainfall data. Generally, erosion processes at smaller sub‐catchment scales, particularly when the sediment generation equation had non linearity, were more sensitive to spatial rainfall variability. Introducing runon infiltration reduced the total runoff and sediment yield at all scales, and this process was also most sensitive to the rainfall resolution. Copyright © 2011 John Wiley & Sons, Ltd.     

Anisotropic elastic full‐waveform inversion of walkaway vertical seismic profiling data from the Arabian Gulf

Borehole seismic addresses the need for high‐resolution images and elastic parameters of the subsurface. Full‐waveform inversion of vertical seismic profile data is a promising technology with the potential to recover quantitative information about elastic properties of the medium. Full‐waveform inversion has the capability to process the entire wavefield and to address the wave propagation effects contained in the borehole data—multi‐component measurements; anisotropic effects; compressional and shear waves; and transmitted, converted, and reflected waves and multiples. Full‐waveform inversion, therefore, has the potential to provide a more accurate result compared with conventional processing methods. We present a feasibility study with results of the application of high‐frequency (up to 60 Hz) anisotropic elastic full‐waveform inversion to a walkaway vertical seismic profile data from the Arabian Gulf. Full‐waveform inversion has reproduced the majority of the wave events and recovered a geologically plausible layered model with physically meaningful values of the medium.     

Geophysical Surveys in the Jebel Hamrat Fidan,Jordan

The Jebel (Jebel is mountain in Arabic) Hamrat Fidan marks the “gateway” to the Feinan district of southern Jordan—one of the largest sources of copper during the prehistoric and Early Bronze Ages in the eastern Mediterranean. Preliminary excavations and surveys at sites along the Wadi Fidan have revealed a long history of settled occupation extending from the Pre‐Pottery Neolithic (ca. 6,500 B.C.) to early medieval times. Because of this long history of occupation, and the fact that this area was a regional center for the production of copper, the study of this area is important for understanding early metallurgy, craft specialization, and social evolution. During the summer of 1997, geophysical investigations at a series of Neolithic and Bronze Age sites identified specific areas within Wadi Fidan for future intensive excavations. Three geophysical techniques (electromagnetic induction, ground‐penetrating radar, and magnetometry) were used to help locate buried architectural and industrial features remaining from early mining and metallurgical operations, including copper ore bodies or voids. Geophysics was not used at the actual mining sites because of scheduling constraints; however, geophysics did delineate buried stone walls at three distinct Wadi Fidan sites. Magnetometry and ground penetrating radar provided little useful information. Buried stone walls were apparently “masked” by numerous magnetic stones on the ground surface making magnetometry useless. Reflections from known strata demonstrated that radar penetrated the ground adequately; however, known shallowly buried walls were not recognizable. Electromagnetic induction produced maps of linear and rectilinear features that suggested spatial distribution of widespread buried stone walls suitable for future excavation. A significant and unexpected finding was that electromagnetic induction proved capable of delineating buried stone walls. © 2000 John Wiley & Sons, Inc.