Influence of Oxidative Treatment on the AOX‐formation Potential of Aromatic Sulfonates

Aromatic sulfonates can be found in drinking water. Thus, they must have passed water treatment and survived ozonation. Degradation of aromatic sulfonates can be achieved by the UV/H2O2‐process. Since drinking water is often treated with chlorine as a disinfectant, the formation of disinfection by‐products has to be considered. Therefore, the production of AOX (on activated carbon adsorbable organic halogens) after chlorination of the sulfonates with and without preoxidation was investigated. Instead of the analysis of the individual degradation products, the determination of the sum parameter AOX was used as a fast screening method. The investigated sulfonates were: anthraquinone‐2‐sulfonate, naphthalene‐2‐sulfonate, 2‐aminonaphthalene‐1‐sulfonate, and 4,4′‐diaminostilbene‐2,2′‐disulfonate. All sulfonates containing amino groups showed high potentials of AOX formation. The preoxidation with ozone increased the potentials of AOX formation in general. Treating the sulfonates by using the UV/H2O2‐process, the formation potentials run to zero after going through a maximum value.     

Metal Distribution in Different Size Fractions of Natural Organic Matter

In this paper, size‐exclusion chromatography (SEC) was used to determine the metal concentration in different size fractions of a bog lake water. Two methods were applied: (a) preparative SEC with off‐line metal concentration analysis and (b) direct coupling of an analytical SEC system on‐line with an inductively‐coupled plasma mass spectrometer (ICP‐MS). In the preparative SEC measurements, maximum concentrations were found for different metal ions in different size fractions of the natural organic matter (NOM). Normalization of metal concentrations to dissolved organic carbon concentration (DOC) yielded two maxima in the high and in the very low molecular‐weight fractions. Whereas good recoveries were found for Al, Fe, and Ni, only 40% were obtained for Pb. This indicates that Pb formed labile complexes with NOM, and hence could strongly interact with the column material. In the experiments with the analytical SEC‐ICP‐MS system, the same trends were observed, but with even lower recoveries than in the preparative system. Sample preconcentration and storage were also investigated with respect to decrease in metal concentration. During the ultrafiltration preconcentration step Al and Fe were removed only to a small extent, whereas about half of the initial Pb was lost. This indicates that Al and Fe were mainly bound to high molecular‐weight fractions of NOM. In contrast to that, Al and in particular Fe were removed from solution more than proportionally with respect to DOC because of aggregation of the NOM during storage, whereas Pb and Ni were concentrated relative to the DOC.     

Rn-generated206Pb in hydrothermal sulphide minerals and bitumen from the Ventersdorp Contact Reef, South Africa

Summary The auriferous conglomerate horizons (reefs) in the Witwatersrand Basin of South Africa are in many places cut by hydrothermal quartz veins that frequently contain sulphide, bitumen, and, less commonly, free gold. New Pb isotopic results for the Ventersdorp Contact Reef which has experienced particularly intense hydrothermal alteration, reaffirm the radiogenically enriched nature of the Pb in this reef and provide additional insight into its origin. This study focuses on analyses of galena, chalcopyrite, pyrrhotite, and bitumen from quartz veins, which presumably formed during the 2.020 Ga Vredefort meteorite impact event. The radiogenic, mainly uranogenic, component of the Pb appears to have been derived almost entirely from uraninite in the surrounding reef rock. Assigning a 2.02 Ga age of mineralization and constructing secondary isochrons for paragenetically early galena and chalcopyrite, ages of the source uraninite are calculated as 2.6–2.4 Ga. No special significance is ascribed to these source ages, which likely reflect extensive radiogenic Pb loss from originally somewhat older detrital uraninite during transport, sedimentation, and post-burial alteration. Analyses of detrital(?), syngenetic, and epigenetic pyrite from a reef conglomerate define a subsidiary linear array with a considerably shallower slope. Interpreted as a secondary isochron, the array gives an implausibly young mineralization and/or source age indicative of a superimposed isotopic disturbance.Five analyses of paragenetically late chalcopyrite and pyrrhotite plot on a²⁰⁷Pb/²⁰⁴pb versus²⁰⁶Pb/²⁰⁴Pb diagram with nearly constant²⁰⁷Pb/²⁰⁴Pb of 24.1–24.6 despite a huge range in²⁰⁶Pb/²⁰⁴Pb from 60–230. This trend is further revealed by Pb with similar²⁰⁷Pb/²⁰⁴Pb but still higher²⁰⁶Pb/²⁰⁴Pb ratios (up to 949) in bitumen globules deposited on quartz crystals lining cavities in the veins. This nearly horizontal array cannot be interpreted as a secondary isochron, and requires the addition of virtually pure²⁰⁶pb to a more normal, radiogenically-enriched Pb. The most plausible explanation for this decoupling of the²³⁸U and²³⁵U decay schemes is that an intermediate daughter isotope, most likely²²²Rn, diffused from uraninite and was selectively captured by the bitumen where it subsequently decayed to²⁰⁶Pb. Whether the 206 Pb was acquired mainly at the time of hydrothermal activity by fluids at elevated temperatures, or more or less continuously until the present remains unresolved.

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Durch Rn erzeugtes²⁰⁶Pb in hydrothermalen Sulfid-Mineralen und Bittunen vom Ventersdorp Contact Reef, Südafrika

Zusammenfassung Die goldhältigen Konglomeratehorizonte (Reefs) im Witwatersrand Becken von Südafrika werden vielerorts von hydrothermalen Quarzadern durchkreuzt, die verschiedene Sulfide, Bitumen, und Spuren von Gold führen. Neue Pb-Isotopendaten vom Ventersdorp Contact Reef (VCR), welches besonders intensive hydrothermale Veränderung erfahren hat, bestätigen die abnormal radiogene Natur des Pb in diesem speziellen Reef. Darüber hinaus führen sie zu einem neuen Verständnis der Herkunft dieses Pb. Schwerpunkt dieser Studie war die Analyse von Bleiglanz, Kupferkies und Bitumen in Quarzadern, deren Bildung dem 2.020 Ga Vredefort Impaktereignis zugeschrieben wird. Die radiogene, hauptsächlich uranogene Pb-Komponente kann beinahe ausschließlich von Uraninit im umgebenden Reef abgeleitet werden. Von sekundären Isochronen, deren Berechnung auf der Annahme eines Mineralisationsalters von 2.02 Ga beruht, lassen sich Alter von 2.6–2.4 Ga für den Uraninit ableiten. Diesen Altern wird jedoch keine weitere Bedeutung beigemessen, da sie wohl eher erheblichen radiogenen Pb-Verlust eines ursprünglich etwas älteren Uraninit während Transport, Sedimentation und spät- bis post-diagentischer Alteration widerspiegeln. Analysen von detritischem (?), syngenetischem und epigenetischem Pyrit von einem Reef-Horizont folgen einem abweichenden Trend mit erheblich geringerer Neigung in einem²⁰⁶Pb/²⁰⁴Pb versus²⁰⁷Pb/²⁰⁴Pb Diagramm. Als sekundäre Isochrone betrachtet, entspricht dieser Trend entweder einem unwahrscheinlich jungen Alter oder er drückt eine spätere Störung des Isotopensystems aus.Fünf Analysen von paragentisch spätem Kupferkies und Magnetkies haben ein nahezu konstantes²⁰⁷Pb/²⁰⁴Pb Verhältnis von 24.1–24.6 trotz einer enormen Spanne in deren²⁰⁶Pb/²⁰⁴Pb Verhältnissen (60–230). Dieser Trend wird weiters duch Pb mit ähnlichen²⁰⁷Pb/²⁰⁴Pb aber noch höheren²⁰⁶Pb/²⁰⁴Pb Verhältnissen (bis zu 949) in Bitumen-Aggregaten innerhalb von Quarz-Drusen unterstrichen. Diese extrem flache Datenverteilung in einem²⁰⁷Pb/²⁰⁴Pb versus²⁰⁶Pb/²⁰⁴Pb Diagramm kann nicht als sekundäre Isochrone interpretiert werden, sondern verlangt die Zufuhr von praktisch reinem²⁰⁶Pb zu eher normalem, radiogen angereichertem Pb. Diffusion eines intermediären Tochterisotops, höchst wahrscheinlich²²²Rn, und selektiver Einbau desselben in das Bitumen mit anschließendem Zerfall zu²⁰⁶Pb halten wir für die naheliegendste Erklärung dieser Entkoppelung der²³⁸U- und²³⁹U-Zerfallsreihen. Offen bleibt die Frage, ob der Einbau des²⁰⁶Pb hauptsächlich zum Zeitpunkt der hydrothermalen Überprägung oder mehr oder weniger kontinuierlich bis heute stattgefunden hat.

     

Problems and Solutions in Pesticide Analysis Using Solid‐phase Extraction (SPE) and Gas Chromatography Ion‐trap Mass Spectrometry Detection (GC‐MS)

In the present study an analytical method was tested for the determination of selected pesticides and metabolites using solid‐phase extraction (SPE) and gas chromatography ion‐trap mass spectrometry (GC‐MS). The extraction efficiency of C18, Isolut ENV+, and Lichrolut EN for SPE was compared for trifluralin, fenitrothion, endosulfan, propargite, 2,4‐D, 3‐methyl‐4‐nitrophenol, 2‐(4‐tert‐butylphenoxy)cyclohexanol, endosulfan sulfate, and 2,4‐dichlorophenol. Isolut ENV+ and C18 showed good results as sorbents and acetone as an elution solvent for SPE for the selected pesticides. Recoveries varied between 36% and 176% with a relative standard deviation of 2...18%. Because of coextracts from the SPE materials, recovery values higher than 100% were obtained for fenitrothion, endosulfan sulfate, and 2,4‐D with C18 as well as for endosulfan sulfate and 3‐methyl‐4‐nitrophenol with Isolut ENV+. A standard addition method was used to verify the occurrence of coextracts in the sample after SPE.     

Spectroscopic Characterization of Fulvic Acid Fractions of a Contaminated Groundwater

Two fulvic acid (FA) samples taken from a former gas production facility in the Southwest of Germany were characterized using advanced fluorescence techniques. Steady-state fluorescence (fluorescence excitation, synchronous fluorescence) as well as time-resolved fluorescence were applied. Distinct differences between the sample B22 FA taken within the contamination plume and the sample B53 FA taken downstream were found. Comparison with a model compound for metabolites and humic substances revealed that due to the downstream passage the characteristics of the dissolved organic matter became more humic-like. The assignment of single classes of compounds in the sample B22 FA is discussed in terms of their synchronous fluorescence spectra and fluorescence decay time distribution.     

Metamorphism of the Permo-Triassic Cape Fold Belt and its basement, South Africa

Summary  The Permo-Triassic Cape Fold Belt around the southern tip of Africa consists of a thick sequence of Palaezoic siliciclastic sedimentary and pre-Cape basement rocks believed to be of Pan-African age. Both the basement rocks and the supracrustal rocks of the Cape Supergroup display only low metamorphic grades. Application of chlorite, chlorite-chloritoid Fe-Mg exchange, and calcite-graphite carbon isotope geothermometry to rocks from the unconformable contact between pre-Cape basement and the Cape Supergroup made it possible to distinguish pre-Cape and syn-Cape metamorphic overprints. During Pan-African metamorphism temperatures of up to middle greenschist facies conditions (around 400 °C) were reached, whereas lowermost greenschist facies conditions (around 300 °C) were not exceeded during the 220–290 Ma Cape orogeny. In the past, most if not all of the pre-Cape basement rocks, which form the Pan-African Saldania Belt, were considered to be of Neoproterozoic age. A hiatus of about 100 °C observed between two adjacent limestone horizons that previously had been grouped together into a single formation at the bottom of the allegedly Neoproterozoic Kango Group indicates that almost all of this group is syn- to post-orogenic with respect to the Pan-African orogeny. A revision of the stratigraphy of the Kango Group is therefore suggested. Only its lowermost member is truly Pan-African and probably related to about 620–740 Ma post-Sturtian cap carbonates in other Pan-African belts of southern Africa. The remainder of the Kango Group reflects the successive development of two stages of orogen-related intra-continental basins: The older stage led to a typical syn-orogenic foreland basin related to tectonic loading in the Gariep and Damara orogenic belts further north(west) between 570 and 540 Ma; the younger is believed to have formed either a further foreland basin or an intra-orogen pull-apart basin caused by later tectonic loading in the Ross orogenic belt and its continuation into the southern Saldania Belt between 510 and 480 Ma. Received May 7, 2000;/revised version accepted January 15, 2001     

Zielvorgaben für Pflanzenschutzmittelwirkstoffe und andere Schadstoffe in Oberflächengewässern

Quality Targets for Pesticides and Other Pollutants in Surface Waters Surface waters are not only adversely affected by industrial and municipal wastewaters but also by diffuse sources. For the control of the ecological water quality, so‐called quality targets are set. The quality targets are threshold concentrations for hazardous substances related to the protected goods like water ecosystems, drinking water supply, sediments, or fishing. In this paper, quality targets for the protection of aquatic life in surface waters were derived on the basis of a concept developed by the International Commission for the Protection of the Rhine (Internationale Kommission zum Schutze des Rheins – IKSR). The quality targets for the selected hazardous substances, which mainly belong to the chemical class of pesticides, were calculated using ecotoxicological results for species of bacteria, algae, fish, and small crustaceans, as the four trophic standards of the water ecosystem. In cooperation with the Federal Environmental Agency (Umweltbundesamt – UBA) the effect data were taken from ecotoxicological data bases. According to the concept of the IKSR, the lowest test result for the most sensitive species was multiplied by an assessment factor. This proceeding concerns the difficulty in describing the complex interactions in water ecosystems with toxicity data of single laboratory experiments for a few organisms. For seven pesticides quality targets below 0.1 μg/L were proposed. These results show that the ecotoxicologically based quality targets might be even lower than the limit values for pesticides in drinking water of 0.1 μg/L. But for most of the substances the determined values are significantly higher. The great concentration range of quality targets demonstrates distinctly that one standard concentration for all pesticides could not be given with regard to the different effects on aquatic organisms.     

Characterization of AOX by Fractionation Analysis and Size‐exclusion Chromatography

A characterization method for AOX in surface water samples was developed and tested. The method involves fractionation using a hydrophobic C18 resin and a weak anionic exchange resin and allows the fractionation of the AOX pool of surface water samples into four fractions: (1) hydrophilic acidic, (2) hydrophilic non‐acidic, (3) hydrophobic acidic, and (4) hydrophobic non‐acidic. The adsorption analysis was verified with AOX‐relevant model compounds and was applied to characterize the AOX pool of a stream sample from the Moskva river (Russia). In addition to the fractionation analysis, size‐exclusion chromatography was used to characterize the AOX pool of the sample studied. Hydrophilic acids made up the major fraction of the AOX pool (55 %). Among this fraction chlorinated high‐molecular acids (humic substances) made up the main fraction (35 %).     

Geometallurgical Approach for Implications of Ore Blending on Cyanide Leaching and Adsorption Behavior of Witwatersrand Gold Ores,South Africa

Gold production in South Africa is projected to continue its decline in future, and prospects for discovery of new high-grade deposits are limited. Many of the mining companies have resorted to mining and processing low-grade and complex gold ores. Such ores are technically challenging to process, which results in low recovery rates, excessive reagent consumption and high operating costs when compared to free-milling gold ores. In the Witwatersrand mines, options of blending low-grade gold ores with high-grade ores exist. Although it is well known that most of the Witwatersrand gold ores are highly amenable to gold cyanidation, not much is known on the leachability of blended ores, especially the effects of mineralogical and metallurgical variability between different gold ores. In this study, we apply a geometallurgical approach to investigate mineralogical and metallurgical factors that influence the leaching of blended ores in a set of bottle shaker and reactor column tests. Three gold-bearing conglomerate units, so-called reefs, i.e., Carbon Leader Reef, Ventersdorp Contact Reef and the Black Reef, all in the Carletonville goldfield, were sampled. The ores were prepared using a terminator jaw crusher followed by vertical spindle pulverizer (20 kg aliquot) and high-pressure grinding rolls (80 kg aliquot). Mineralogical analysis was conducted using a range of complementary tools such as optical microscopy, QEMSCAN and micro–XCT. The results show that Witwatersrand gold ores are amenable to the process of ore blending. Some of the ores, however, contain impervious inert gangue and reactive ore minerals. Leach solution can only access gold locked in impervious gangue minerals through HPGR-induced pores and/or cracks. The optimum ore blending ratio of the bottle shaker experiments (p80?=???75 μm) comprises 60% Carbon Leader Reef, 20% Ventersdorp Contact Reef and 20% Black Reef and yields 92% recovered Au over a leach period of 40 h. Blended ores with high carbonaceous material (>?1 wt% carbonaceous material, (Black Reef?=?36–60%) yield lower recoveries of 60–69% Au). Ore leaching at the mixed-bed reactor column (??75 μm and ??5.6/+?4 mm) yields about 70% over a leach period of two weeks. We therefore suggest that the feasibility of ore blending is strongly controlled by the mineralogy of the constituent ores and that a mixed-bed reactor may be a viable alternative method for leaching of the low-grade Witwatersrand gold ores. Material from certain reefs, such as the Black Reef, has synergistic/antagonistic (nonadditive) blending effects. The overall implication of this study is that ore blending ratios, effects of comminution on mineral liberation, an association of gold with other minerals, and gold adsorption behavior will greatly inform future technology choices in the area of geometallurgy.