Sequentielle Schwermetallextraktion aus Staubniederschl?gen und Stra?ensedimenten Teil I: Sequentielle Schwermetallextraktion von Mikroproben

Für die Anwendung der sequentiellen Schwermetallextraktion auf Proben, die nur im Milligramm-Bereich erhalten werden k?nnen (Mikroproben, wie z. B. Staubniederschl?ge), wurde die Methode vonZeien &Brümmer (1989) weiterentwickelt. Der Extraktionsma?stab wurde um den Faktor 1∶100 verringert und die Reproduzierbarkeit des Verfahrens mit variablen Probenmengen um 20mg und einem Extraktionsvolumen von 500 μl mit Hilfe von Standardb?den nachgewiesen. M?gliche Einflüsse variabler Extraktionsverh?ltnisse (Verh?ltnis von Probenmenge zu Extraktionsvolumen) sowie eine aufwendige Vorbehandlung von Staubproben, die nach der Bergerhoff-Methode (VDI 2119/2, 1972) gesammelt wurden, lagen bei diesen Untersuchungen weitgehend im Variationsbereich des Verfahrens. Die sequentielle Extraktion kann folglich zur Untersuchung der Mobilisierbarkeit von Schwermetallen auch aus Mikroproben mit variablen Probenmengen eingesetzt werden. Mit Hilfe dieses Verfahrens wurden die Mobilisierbarkeiten von Zink, Kupfer und Blei der Schluff- und Tonfraktion von Stra?ensedimenten mit Staubniederschl?gen an zwei urbanen Standorten mit unterschiedlicher, verkehrsbedingter Schwermetallbelastung verglichen. Diese Untersuchungen werden in Teil 2 (“Sequentielle Schwermetallextraktion von st?dtischen St?uben”) vorgestellt.     

Organizational embeddedness,turnover intentions,and voluntary turnover: The moderating effects of employee demographic characteristics and value orientations

To explain why some employees who experience high embeddedness contemplate leaving their organizations and others do not, we examined the moderating effects of employee demographic characteristics (age and gender) and value orientations (individualism and risk aversion) between organizational embeddedness and turnover intentions. Turnover intentions were further expected to increase voluntary turnover. Data were collected from 643 full‐time employees at three points in time over a 12‐month time period in a wide range of organizations in Japan, a relatively low turnover context with little prior embeddedness research. Findings show that gender and risk aversion moderate the relationship between organizational embeddedness and turnover intentions, which in turn predict voluntary turnover. Copyright © 2014 John Wiley & Sons, Ltd.     

Precious metals and rare earth elements in municipal solid waste – Sources and fate in a Swiss incineration plant

In Switzerland many kinds of waste, e.g. paper, metals, electrical and electronic equipment are separately collected and recycled to a large extent. The residual amount of municipal solid waste (MSW) has to be thermally treated before final disposal. Efforts to recover valuable metals from incineration residues have recently increased. However, the resource potential of critical elements in the waste input (sources) and their partitioning into recyclable fractions and residues (fate) is unknown. Therefore, a substance flow analysis (SFA) for 31 elements including precious metals (Au, Ag), platinum metal group elements (Pt, Rh) and rare earth elements (La, Ce, etc.) has been conducted in a solid waste incinerator (SWI) with a state-of-the-art bottom ash treatment according to the Thermo-Re® concept. The SFA allowed the determination of the element partitioning in the SWI, as well as the elemental composition of the MSW by indirect analysis. The results show that the waste-input contains substantial quantities of precious metals, such as 0.4 ± 0.2 mg/kg Au and 5.3 ± 0.7 mg/kg Ag. Many of the valuable substances, such as Au and Ag are enriched in specific outputs (e.g. non-ferrous metal fractions) and are therefore recoverable. As the precious metal content in MSW is expected to rise due to its increasing application in complex consumer products, the results of this study are essential for the improvement of resource recovery in the Thermo-Re® process.     

Freisetzung von Schwermetallen aus dem bodenbildenden Tonmineral Illit durch Aminosäuren

Kaolin W from Lohrheim (51% Illite, 31% Kaolinite, 18% Quarz, no Carbon) was loaded with various amounts of heavy metal ions (0.11–6.0 mmol/100g Cu, Ni, Cd) from their nitrate solutions. In the next step the release of the bound metals was tested with or without aminoacids (penicillamine and histidine) in solutions of weak acidity or alkalinity. It was found an evident influence of the aminoacids to the metal release in dependence of metalcoating, metal-aminoacid-ratio and experimental pH. Especially in alkali environment a multiplication of the copper release (to a factor of 39 (pen) or 27 (his)) was observed. An increased nickel (factor 53) and cadmium release (factor 4.5) was found with histidine. In this cases 80 to 100% of the heavy metals were removed from the clay-mineral-surface.