Mobilisation of heavy metals by deicing salts in a roadside environment

The seasonal variations of some selected heavy metals (Cd, Cu, Pb and Zn) and principal anions in soil solutions were monitored as a function of distance from the road at two field sites in Sweden. During the winter, the conductivity, concentrations of dissolved sodium and chloride increased dramatically due to the application of deicing agents (i.e. NaCl). Due to ion exchange, the pH decreased one unit in the soil solutions, whereas the concentrations of total organic carbon decreased due to coagulation and/or sorption to stationary solids. The heavy metal concentrations increased during the winter, but through different mechanisms. Cadmium concentrations in the aqueous phase increased as a response to ion exchange, possibly also enhanced by the formation of chloride complexes. Similarly, the concentrations of zinc increased, due to ion exchange, with calcium and protons. The mechanisms of mobilisation for copper and lead were not that clear probably due to association with coagulated or sorbed organic matter in combination with colloid dispersion.     

Drei Jahre Zeitschrift Grundwasser

Liebe Leserinnen und Leser, die Zeitschrift Grundwasser hat mit dem vorliegenden Heft 4 des Jahrganges 1998 ihr drittes Jahr seit dem ersten Erscheinen vollendet. Zum ersten Mal werden in dieser Ausgabe vier Artikel ver?ffentlicht, die thematisch eng zusammenh?ngen. Alle Beitr?ge sind aus Untersuchungen im Rahmen des DFG-Schwerpunktes “Geochemische Prozesse mit Langzeitfolgen im anthropogen beeinflu?ten Sickerwasser und Grundwasser” hervorgegangen und beleuchten die unterschiedlichen Aspekte der hydrogeologischen, hydrochemischen und bodenkundlichen Untersuchungen im Rahmen von BTEX-Schadensf?llen, von der Charakterisierung des Schadstoffherdes im Boden und im Grundwasser über die Bestimmung der hydraulischen Verh?ltnisse in einem Lockergesteins-Grundwasserleiter bis hin zur Schadstoffemission. Wir sind der überzeugung, damit ein abgerundetes Bild eines praxisorientierten Forschungsprojektes exemplarisch darstellen zu k?nnen, das die aktuelle Forschung an die Anwender heranführen kann. Das vorliegende Heft unterscheidet sich somit grunds?tzlich von den bisherigen Ausgaben, in denen Beitr?ge im Gro?en und Ganzen so abgedruckt wurden, wie sie eingereicht und vom Reviewproze? bewertet wurden. Auch wenn das Bild der Zeitschrift Grundwasser in Zukunft weiter vornehmlich durch eine m?glichst gro?e Vielfalt von Beitr?gen aus Praxis und Forschung bestimmt werden soll, zeigt sich aus der nun eingeleiteten Entwicklung, da? die Anfangsphase der Zeitschrift damit als beendet betrachtet werden kann. In den ersten Jahrg?ngen war die Hauptsorge des wissenschaftlichen Redakteurs der Eingang einer ausreichenden Zahl von qualitativ hochwertigen Fachbeitr?gen. Bei dem noch geringen Bekanntheitsgrad der Fachzeitschrift wurden einige Hefte gedruckt ohne zu wissen, welche Beitr?ge in das n?chste Heft aufgenommen werden. Die Redaktion lebte oft von der Hand in den Mund, und die Arbeit konzentrierte sich immer auf die letzten Wochen vor dem Erscheinen. Auch mu?te sich das Zusammenspiel zwischen der wissenschaftlichen Redaktion und der Redaktionsleitung erst einstellen. Der Eingang an wissenschaftlichen Beitr?gen hat sich in dem letzten Jahr deutlich positiv entwickelt. W?hrend in den Jahren zuvor auf zwei ver?ffentlichte Beitr?ge ein abgelehnter Beitrag kam und damit die der Zeitschrift zur Verfügung stehenden Seiten ausgesch?pft wurden, ist abzusehen, da? in Zukunft mehr gute Manuskripte eingehen, als Platz in der Zeitschrift ist. Aus dieser an sich wünschenswerten Entwicklung wird es m?glich werden, einen thematischen Mix in den einzelnen Heften herzustellen oder fachlich verwandte Artikel gemeinsam zu publizieren. L?ngerfristig ist darüber hinaus zu überlegen, ob die Fachsektion Hydrogeologie mit dem Verlag über eine Ausweitung des j?hrlichen Seitenkontingentes verhandeln sollte. Alles in allem sind dies positive Zeichen, die zeigen, da? die Zeitschrift eine weite Akzeptanz erreicht hat, so da? die Funktion des wissenschaftlichen Editors nunmehr wechseln kann. Ab dem ersten Heft 1999 wird Frau Prof. Dr. Margot Isenbeck-Schr?ter, Heidelberg, für den wissenschaftlichen Teil der Zeitschrift verantwortlich zeichnen. Ich hoffe mit meiner Arbeit der Zeitschrift über die ersten Jahre einen guten Start gegeben zu haben und bin sicher, da? meine Nachfolgerin in dem bisherigen Sinne, aber hoffentlich auch mit eigenen neuen Impulsen diese ehrenamtliche und zeitaufwendige Arbeit fortsetzen wird. Ich m?chte mich an dieser Stelle sehr herzlich bei alen bedanken, die mit dazu beigetragen haben, da?Grundwasser so erfolgreich gestartet ist (eine Aufz?hlung erübrigt sich, denn Sie k?nnen die Namen auf der anschlie?enden Seite nachlesen) und hoffe, mich auch weiterhin für die Zeitschrift engagieren zu dürfen.     

Natürliche Schadstoffrückhalteprozesse für Arsen und Kupfer am Standort einer ehemaligen Buntfarbenfabrik

The sharply confined pattern of arsenic groundwater contamination at the site of a historic dye factory suggests that natural attenuation processes are active and efficient. The supporting data included sequential soil extractions combined with analyses of other soil properties like carbonate content, the loss of ignition and cation exchange capacity and the extraction characteristics of the original dye pigment. The results point to iron oxides and iron hydroxides as the most important adsorbers for copper and arsenic. The attenuation of copper can be estimated to be very efficient mainly due to its pH-controlled low solubility. Besides the specific adsorption to iron oxides, however, arsenic exhibits a rather large, loosely bound and easily exchangeable fraction. The speciation of arsenic in groundwater is dominated by As(V). The oxidation state of the original pigment is As(III). In some parts of the aquifer where suboxic conditions prevail, this oxidation state is conserved. In oxic zones of the aquifer, oxidation to the pentavalent form As(V) takes place.     

Multilayer carbon foils for cyclotron beam extraction

The TRIUMF Applied Technology Group operates high-power industrial cyclotrons for commercial radioisotope production. Two of these cyclotrons, TR30-1 and TR30-2, are capable of accelerating H⁻ ions to an energy of 30 MeV and beam currents in excess of 1000 μA. For many years, amorphous carbon foils of approximately 2.0 μm thickness have been utilized to extract proton beams from these accelerators.Novel multilayer foils consisting of layers of amorphous and diamond-like carbon (DLC) of 2.0±0.2 μm thickness were manufactured in-house by carbon arc and pulsed laser deposition, respectively. In the TR30 cyclotrons, the new composite foils with 25% DLC content show a three times longer lifetime than the purely amorphous foils, while maintaining their excellent physical and mechanical characteristics during irradiation.     

Estimation of the surface normal velocity of high frequency ultrasound transducers

This paper is concerned with the characterization of the true locally resolved surface normal velocity of an assumed piston-type ultrasonic transducer. Instead of involving a very complicated direct pointwise measurement of the velocity distribution, an inverse problem is solved which yields a spatially discretized weighting vector for the surface normal velocity of the transducer. The study deals with a spherically focused high frequency transducer, which is driven in pulse-echo mode. As a means of posing the inverse problem, the active transducer surface is divided into annuli of equal surface so that for each annulus the spatial impulse response can be calculated. An acrylic glass plate acts as a simple structured target. The resulting ill-posed nonlinear inverse problem is solved with an iterative regularized Gauss-Newton algorithm. The solution of the inverse problem yields an estimated weight for the surface normal velocity for each annulus. Experimental results for a thin copper wire target are compared to simulation results for both uniform and estimated surface normal velocities.     

A Theme‐Based Seminar on Environmental Sustainability Improves Participant Satisfaction in an Undergraduate Summer Research Program

We analyzed seven years of pre‐program and post‐program survey data to evaluate the Clarkson University Research Experience for Undergraduates (REU) Site Program in Environmental Science and Engineering, and evaluated whether our program was successful at meeting the intended outcome of increasing participants' likelihood of attending graduate school and pursuing a career in science or engineering research or education. We also evaluated how participant satisfaction in the program changed with the addition of a weekly seminar on environmental sustainability that was intended to improve participants' understanding of the societal value of their research projects. Participant satisfaction in the Clarkson REU Program was high, and increased after the addition of the sustainability seminar. Participants' intention to attend graduate or professional school increased after participating in the program, but their intention to pursue a career in science or engineering research declined. Over 60 percent of participants eventually attended graduate or professional school.     

Three-dimensional photonic metamaterials at optical frequencies

Metamaterials are artificially structured media with unit cells much smaller than the wavelength of light. They have proved to possess novel electromagnetic properties, such as negative magnetic permeability and negative refractive index. This enables applications such as negative refraction, superlensing and invisibility cloaking. Although the physical properties can already be demonstrated in two-dimensional (2D) metamaterials, the practical applications require 3D bulk-like structures. This prerequisite has been achieved in the gigahertz range for microwave applications owing to the ease of fabrication by simply stacking printed circuit boards. In the optical domain, such an elegant method has been the missing building block towards the realization of 3D metamaterials. Here, we present a general method to manufacture 3D optical (infrared) metamaterials using a layer-by-layer technique. Specifically, we introduce a fabrication process involving planarization, lateral alignment and stacking. We demonstrate stacked metamaterials, investigate the interaction between adjacent stacked layers and analyse the optical properties of stacked metamaterials with respect to an increasing number of layers.     

Nanoparticle self-assembly on a DNA-scaffold written by single-molecule cut-and-paste

Self-assembly guided by molecular recognition has in the past been employed to assemble nanoparticle superstructures like hypercrystals or nanoparticle molecules. An alternative approach, the direct molecule-by-molecule assembly of nanoscale superstructures, was demonstrated recently. Here we present a hybrid approach where we first assemble a pattern of binding sites one-by-one at a surface and then allow different nanoparticles to attach by self-assembly. For this approach, biotin bearing DNA oligomers were picked up from a depot using a cDNA strand bound to an AFM tip. These units were deposited in the target area by hybridization, forming a recognition pattern on this surface. Fluorescent semiconductor nanoparticles conjugated with streptavidin were allowed to assemble on this scaffold and to form the final nanoparticle superstructures.     

Selective Intermixing of InAs/InGaAs/InP Quantum Dot Structure With Large Energy Band Gap Tuning

Selective postgrowth band gap tuning of self-assembled InAs/InGaAs/InP quantum dot (QD) structures has been investigated. Very large band gap blueshift of over 158 meV of the InAs QD structure has been received through the intermixing by exposing the sample under argon plasma and followed by thermal annealing at 780 °C. Selective intermixing of the InAs QD structure has been studied by depositing a $hbox{SiO}_{2}$ mask layer on the sample for the intermixing. The largest selective band gap shift between the $hbox{SiO}_{2}$ covered and uncovered regions of the sample reaches 77 meV. This intermixing selectivity decreases when the annealing temperature is increased. This reduction in the intermixing selectivity is attributed to the enhanced QDs intermixing of the $hbox{SiO}_{2}$-masked samples because of the out diffusion of different elements from the InAs/InGaAs/InP QD structure into the $hbox{SiO}_{2}$ cover layer. Three different energy band gap shifts of an InAs/InGaAs/InP QD structure across the wafer have been received by this postgrowth selective intermixing. The selective band gap tuning paves a way for monolithic integration of passive and active optoelectronic devices in QD systems.      

Micro-organism-triggered release of silver nanoparticles from biodegradable oxide carriers allows preparation of self-sterilizing polymer surfaces

The antimicrobial activity of silver has attracted significant research interest and contributes to an exponentially growing use of this noble metal in commodity products. In this investigation, we describe a general approach to increase the antimicrobial activity of a silver-containing surface by two to three orders of magnitude. The use of 1-2-nm silver particles decorating the surface of 20-50-nm carrier particles consisting of a phosphate-based, biodegradable ceramic allows the triggered release of silver in the presence of a growing microorganism. This effect is based on the organism's requirements for mineral uptake during growth creating a flux of calcium, phosphate, and other ions to the organism. The growing micro-organism dissolves the carrier containing these nutrients and thereby releases the silver nanoparticles. Further, we demonstrate the rapid self-sterilization of polymer surfaces containing silver on calcium phosphate nanoparticles using a series of human pathogens. Colony-forming units (viable bacteria or fungi counts) have been routinely reduced below detection limit and suggest application of these self-sterilizing surfaces in hospital environments, food and pharmaceutical processing, and personal care.