Use of electrophoresis for transporting nano-iron in porous media

Research has been conducted to evaluate if electrophoresis could transport surface stabilized nanoscale zero-valent iron (nZVI) through fine grained sand with the intent of remediating a contaminant in situ. The experimental procedure involved determining the transport rates of polymer modified nZVI and hematite in fine grained sands under an applied electrical gradient under different physical and chemical conditions. Results indicated transport of polymer modified nZVI and hematite can be accomplished by electrophoresis, with rates found to be much higher than diffusion alone and comparable to those predicted by electrokinetic theory. This study indicates there is potential for this method to deliver polymer modified nZVI into contaminated zones within fine grained sands for the purpose of remediation.     

Predicting the tails of breakthrough curves in regional-scale alluvial systems

The late tail of the breakthrough curve (BTC) of a conservative tracer in a regional-scale alluvial system is explored using Monte Carlo simulations. The ensemble numerical BTC, for an instantaneous point source injected into the mobile domain, has a heavy late tail transforming from power law to exponential due to a maximum thickness of clayey material. Haggerty et al.'s (2000) multiple-rate mass transfer (MRMT) method is used to predict the numerical late-time BTCs for solutes in the mobile phase. We use a simple analysis of the thicknesses of fine-grained units noted in boring logs to construct the memory function that describes the slow decline of concentrations at very late time. The good fit between the predictions and the numerical results indicates that the late-time BTC can be approximated by a summation of a small number of exponential functions, and its shape depends primarily on the thicknesses and the associated volume fractions of immobile water in "blocks" of fine-grained material. The prediction of the late-time BTC using the MRMT method relies on an estimate of the average advective residence time, t(ad). The predictions are not sensitive to estimation errors in t(ad), which can be approximated by L/v , where v is the arithmetic mean ground water velocity and L is the transport distance. This is the first example of deriving an analytical MRMT model from measured hydrofacies properties to predict the late-time BTC. The parsimonious model directly and quantitatively relates the observable subsurface heterogeneity to nonlocal transport parameters.     

MBACI sampling of an episodic disturbance: stormwater effects on algal epifauna

Whilst it has been well established that stormwater and associated contaminants negatively impact the quality of recipient waters, the ecological effects of individual stormwater pulses in marine environments are relatively unknown. In this study, the impacts of stormwater outfalls upon water quality and epifaunal invertebrates inhabiting the alga Sargassum linearifolium are assessed through an MBACI sampling program. Water quality and the abundance of mobile algal epifauna were recorded at three control sites and three impact sites every 10-12 weeks during dry weather and opportunistically within 24h of large rain events (>50 ml rainfall in 24h) and again 4d after the rain event. Sampling took place during two periods over two separate years and this included four large rainfall events. Following rainfall, salinity dropped rapidly at impact sites close to stormwater outfalls, whilst turbidity increased. Declines in salinity at control sites were slight and turbidity did not differ to 'before' periods. The abundance of epifaunal gastropods and polychaetes were reduced at impact sites 24h after rain events, but not control sites. The abundance of copepods, amphipods and ostracods, however, were reduced at both control and impact sites for up to 4d following rainfall. Reductions of these taxonomic groups could not be attributed to stormwater outfalls. Whilst short-term impacts of stormwater runoff were identified for some faunal groups, impacts were not identified for the majority. Instead, effects were harbour-wide (i.e. at control and impact sites), probably in response to the physical disturbance of heavy seas associated with large rain events.     

层结流体中具有纬向基本剪切流的Rossby波振幅的mKdV方程

In this paper,modified Korteweg-de Vries (mKdV) equations for the amplitude of solitary Rossby waves in stratified fluids with a zonal shear flow are derived by using a weakly nonlinear method.It is found that the coefficients of mKdV equations depend not only on the β effect and the Visl-Brunt frequency,but also on the basic shear flow.     

1992年加州半德斯地震的前震序列及对地震起始的推断

１９９２年６月２８日加州兰德期地震震前有一个７小时的前震序列，它至少由２８个地震组成，在这次研究中，我们根据附近台站记录的地震波形互相关的高精度定位，对几何条件和时间进程进行了仔细胞调查。在兰德斯地震中，确定出现了这情况，虽然不均匀的尺度很少，以用常规定位技术都无法确定。     

Element Geochemical Characteristics of the Cretaceous Dinosaur Eggshell Fossils and Their Implications for Palaeoenvironment

Dinosaur eggshells from the Cretaceous red beds of southern China were selected for element geochemical study.The concentrations of the major elements indicate that the eggshells did not change much in their chemical composition after they were formed.Variations in the contents of trace elements and REEs imply that a palaeoclimatic anomaly might occur during Late Cretaceous.     

Detection of the 2165 inverse centimeter (4.619 micron) XCN band in the spectrum of L1551 IRS 5

We report the detection of a broad absorption band at 2165 cm-1 (4.619 microns) in the spectrum of L1551 IRS 5. New laboratory results over the 2200-2100 cm-1 wavenumber interval (4.55-4.76 microns), performed with realistic interstellar ice analogs, suggest that this feature is due to a CN-containing compound. We will refer to this compound as XCN. We also confirm the presence of frozen CO (both in nonpolar and polar matrices) through absorption bands at 2140 cm-1 (4.67 microns) and 2135 cm-1 (4.68 microns). The relative abundance of solid-state CO to frozen H2O is approximately 0.13 while the abundance of XCN seems comparable to that of frozen CO.     

Isotope-ratio-monitoring gas chromatography-mass spectrometry: methods for isotopic calibration

In trial analyses of a series of n-alkanes, precise determinations of 13C contents were based on isotopic standards introduced by five different techniques and results were compared. Specifically, organic-compound standards were coinjected with the analytes and carried through chromatography and combustion with them; or CO2 was supplied from a conventional inlet and mixed with the analyte in the ion source, or CO2 was supplied from an auxiliary mixing volume and transmitted to the source without interruption of the analyte stream. Additionally, two techniques were investigated in which the analyte stream was diverted and CO2 standards were placed on a near-zero background. All methods provided accurate results. Where applicable, methods not involving interruption of the analyte stream provided the highest performance (sigma = 0.00006 at.% 13C or 0.06% for 250 pmol C as CO2 reaching the ion source), but great care was required. Techniques involving diversion of the analyte stream were immune to interference from coeluting sample components and still provided high precision (0.0001 < or = sigma < or = 0.0002 at.% or 0.1 < or = sigma < or = 0.2%).     

Petrography and bulk chemistry of Martian orthopyroxenite ALH84001: implications for the origin of secondary carbonates

New petrologic and bulk geochemical data for the SNC-related (Martian) meteorite ALH84001 suggest a relatively simple igneous history overprinted by complex shock and hydrothermal processes. ALH84001 is an igneous orthopyroxene cumulate containing penetrative shock deformation textures and a few percent secondary extraterrestrial carbonates. Rare earth element (REE) patterns for several splits of the meteorite reveal substantial heterogeneity in REE abundances and significant fractionation of the REEs between crushed and uncrushed domains within the meteorite. Complex zoning in carbonates indicates nonequilibrium processes were involved in their formation, suggesting that CO2-rich fluids of variable composition infiltrated the rock while on Mars. We interpret petrographic textures to be consistent with an inorganic origin for the carbonate involving dissolution-replacement reactions between CO2-charged fluids and feldspathic glass in the meteorite. Carbonate formation clearly postdated processes that last redistributed the REE in the meteorite.     

黔中陡山沱期磷块岩成因的系统研究

黔中成磷区是中国南方陡山沱成磷期磷块岩矿床的重要组成部分。包括瓮福、开阳两个大型磷块岩矿床和若干中小型磷矿床。本文从磷的来源、沉积和富集3个方面系统地揭示了该区磷块岩的成因。稀土元素分析表明,磷可能来自同期海底火山喷发物。海洋地球化学、生物化学及磷块岩的组构研究证明,藻类生物的吸收和固定作用是磷质沉积的主要途径。磷的富集的多阶段、多因素的,经历不同的富集阶段(或方式)形成不同的磷块岩类型。