The composition and environmental hazard of copper slags in the context of the Basel Convention

A recent comprehensive review of the characteristics and utilization of copper slags encourages (properly) several applications for this important pyrometallurgical byproduct. However, the review does not include possible environmental effects from these slags. The United Nations Basel Convention on the Transboundary Movement of Hazardous Wastes and Their Disposal characterizes copper compounds that exhibit specified hazard characteristics as hazardous wastes. In 1996, the Convention considered further characterization of these and other compounds and substances. The final characterization of copper slags is as non-hazardous, i.e., exempt from control. This decision was based in part (if not largely) on the data that are presented here. Literature reports were used to accumulate data describing the chemical composition and acid leaching of commercial copper slags from three countries. From these data, average values of chemical composition and their statistical confidence limits (95%) were calculated. The variability of the chemical analyses of three commercial slags produced over 19 or 20 months were statistically analyzed and shown to be small. The concentrations of toxic heavy metals in the slags are low and the frequency distributions of the values are narrow. Most of the data are normally distributed, validating the use of the statistics used and permitting predictions of likely values. The amounts of heavy metals extracted by an aggressive standard acid leach procedure are low and well below the United States. regulatory levels derived from drinking water standards. The results for total composition and leaching illustrate why the U.S. Environmental Protection Agency made a regulatory determination that such slags are not hazardous wastes. Later, in 1996, the Basel Convention Technical Working Group concurred and the Parties to the Convention adopted their recommendation.     

Use of tracer tests to evaluate the impact of enhanced-solubilization flushing on in-situ biodegradation

Tracer tests were conducted to evaluate the effect of a complexing sugar flush (CSF) on in-situ biodegradation potential at a site contaminated by jet fuel, solvents, and other organic compounds. Technical-grade hydroxypropyl-beta-cyclodextrin was used during the CSF study, which was conducted in a hydraulically isolated cell emplaced in a surficial aquifer. In-situ biodegradation potential was assessed with the use of tracer tests, which were conducted prior to and immediately following the CSF study. Ethanol, hexanol, and benzoate were used as the biodegradable tracers, while bromide was used as a nonreactive tracer. The results indicate that the biodegradation of benzoate was similar for both tracer tests. Conversely, the biodegradation of ethanol (23% increase) and hexanol (41% increase) was greater for the post-CSF tracer test. In addition, analysis of core samples collected from within the test cell indicates that the population density of aerobic jet-fuel degraders increased in the vicinity of the injection wells during the CSF. These results indicate that the cyclodextrin flush did not deleteriously affect the indigenous microbial community. This study illustrates that tracer tests can be used to evaluate the impact of remediation activities on in-situ biodegradation potential.     

Analytik sprenstofftypischer Substanzen—Ein Methodenvergleich

Six different extraction methods for the determination of nitroaromatics in soil samples were investigated regarding the comparability of the analytical results as well as the trueness and precision of the results. The analysed soil samples came from the intermediate store of the former Hessian ammunition production site Stadtallendorf near Marburg, Germany. The analysis was carried out using gas chromatography with electron capture detector (ECD), and HPLC with a UV-detector. The statistical evaluation of the analytical results was performed according to DIN 38402 part 42, as an interlaboratory trial. Ten explosive-relevant compounds were the subject of investigation. For most compounds a good or at least sufficient comparability of the six methods was evident. Only the two amino-dinitrotoluenes and RDX demonstrated a great extraction-dependent variation.     

Optimized method for dissolved hydrogen sampling in groundwater

Dissolved hydrogen concentrations are used to characterize redox conditions of contaminated aquifers. The currently accepted and recommended bubble strip method for hydrogen sampling (Wiedemeier et al., 1998) requires relatively long sampling times and immediate field analysis. In this study we present methods for optimized sampling and for sample storage. The bubble strip sampling method was examined for various flow rates, bubble sizes (headspace volume in the sampling bulb) and two different H2 concentrations. The results were compared to a theoretical equilibration model. Turbulent flow in the sampling bulb was optimized for gas transfer by reducing the inlet diameter. Extraction with a 5 mL headspace volume and flow rates higher than 100 mL/min resulted in 95-100% equilibrium within 10-15 min. In order to investigate the storage of samples from the gas sampling bulb gas samples were kept in headspace vials for varying periods. Hydrogen samples (4.5 ppmv, corresponding to 3.5 nM in liquid phase) could be stored up to 48 h and 72 h with a recovery rate of 100.1+/-2.6% and 94.6+/-3.2%, respectively. These results are promising and prove the possibility of storage for 2-3 days before laboratory analysis. The optimized method was tested at a field site contaminated with chlorinated solvents. Duplicate gas samples were stored in headspace vials and analyzed after 24 h. Concentrations were measured in the range of 2.5-8.0 nM corresponding to known concentrations in reduced aquifers.