The detoxification of iron cyanide in a soil–plant system was investigated to assess the total cyanide extracted from contaminated soil and allocated in the leaf tissue of willow trees(Salix caprea). They were grown ...The detoxification of iron cyanide in a soil–plant system was investigated to assess the total cyanide extracted from contaminated soil and allocated in the leaf tissue of willow trees(Salix caprea). They were grown in soil containing up to 1000 mg/kg dry weight(dw) of cyanide(CN),added as ^(15)N-labeled potassium ferrocyanide and prepared with a new method for synthesis of labeled iron cyanides. CN content and ^(15)N enrichment were monitored weekly over the exposure in leaf tissue of different age. The ^(15)N enrichment in the young and old leaf tissue reached up to 15.197‰ and 9063‰, respectively; it increased significantly over the exposure and with increasing exposure concentrations(p < 0.05). Although the CN accumulation in the old leaf tissue was higher, compared to the young leaf tissue(p < 0.05), the ^(15)N enrichment in the two tissue types did not differ statistically. This indicates a non-uniform CN accumulation but a uniform ^(15)N allocation throughout the leaf mass. Significant differences were detected between the measured CN content and the C^(15)N content, calculated from the ^(15)N enrichment(p < 0.05), revealing a significant CN fraction within the leaf tissue, which could not be detected as ionic CN. The application of labeled iron CN clearly shows that CN is detoxified during uptake by the willows. However, these results do not exclude other detoxification pathways, not related to the trees. Still, they are strongly indicative of the central role the trees played in CN removal and detoxification under the experimental conditions.展开更多
Iron-cyanide (Fe-CN) complexes have been detected at Manufactured Gas Plant sites (MGP) worldwide. The risk of groundwater contamination depends mainly on the dissolution of ferric ferrocyanide. In order to design eff...Iron-cyanide (Fe-CN) complexes have been detected at Manufactured Gas Plant sites (MGP) worldwide. The risk of groundwater contamination depends mainly on the dissolution of ferric ferrocyanide. In order to design effective remediation strategies, it is relevant to understand the contaminant’s fate and transport in soil, and to quantify and mathematically model a release rate. The release of iron-cyanide complexes from four contaminated soils, originating from the former MGP in Cottbus, has been studied by using a column experiment. Results indicated that long-term cyanide (CN) release is governed by two phases: one readily dissolved and one strongly fixed. Different isotherm and kinetic equations were used to investigate the driving mechanisms for the ferric ferrocyanide release. Applying the isotherm equations assumed an approach by which two phases were separate in time, whereas the multiple first order equation considered simultaneous occurrence of both cyanide pools. Results indicated varying CN release rates according to the phase and soil. According to isotherm and kinetic models, the long-term iron cyanide release from the MGP soils is a complex phenomenon driven by various mechanisms parallely involving desorption, diffusion and transport processes. Phase I (rapid release) is presumably mainly constrained by the transport process of readily dissolved iron-cyanide complexes combined with desorption of CN bound to reactive heterogeneous surfaces that are in direct contact with the aqueous phase (outer-sphere complexation). Phase II (limited rate) is presumably driven by the diffusion controlled processes involving dissolution of precipitated ferric ferrocyanide from the mineral or inner-sphere complexation of ferricyanides. CN release rates in phase I and II were mainly influenced by the pH, organic matter (OM) and the total CN content. The cyanide release rates increased with increasing pH, decreased with low initial CN concentration and were retarded by the increase in OM content.展开更多
基金financed by the project of the German Railways(Deutsche Bahn AG) "Stabilisation of the former manufactured gas plant site "ehemalige Leuchtgasanstalt" in Cottbus through means of bioremediation"
文摘The detoxification of iron cyanide in a soil–plant system was investigated to assess the total cyanide extracted from contaminated soil and allocated in the leaf tissue of willow trees(Salix caprea). They were grown in soil containing up to 1000 mg/kg dry weight(dw) of cyanide(CN),added as ^(15)N-labeled potassium ferrocyanide and prepared with a new method for synthesis of labeled iron cyanides. CN content and ^(15)N enrichment were monitored weekly over the exposure in leaf tissue of different age. The ^(15)N enrichment in the young and old leaf tissue reached up to 15.197‰ and 9063‰, respectively; it increased significantly over the exposure and with increasing exposure concentrations(p < 0.05). Although the CN accumulation in the old leaf tissue was higher, compared to the young leaf tissue(p < 0.05), the ^(15)N enrichment in the two tissue types did not differ statistically. This indicates a non-uniform CN accumulation but a uniform ^(15)N allocation throughout the leaf mass. Significant differences were detected between the measured CN content and the C^(15)N content, calculated from the ^(15)N enrichment(p < 0.05), revealing a significant CN fraction within the leaf tissue, which could not be detected as ionic CN. The application of labeled iron CN clearly shows that CN is detoxified during uptake by the willows. However, these results do not exclude other detoxification pathways, not related to the trees. Still, they are strongly indicative of the central role the trees played in CN removal and detoxification under the experimental conditions.
文摘Iron-cyanide (Fe-CN) complexes have been detected at Manufactured Gas Plant sites (MGP) worldwide. The risk of groundwater contamination depends mainly on the dissolution of ferric ferrocyanide. In order to design effective remediation strategies, it is relevant to understand the contaminant’s fate and transport in soil, and to quantify and mathematically model a release rate. The release of iron-cyanide complexes from four contaminated soils, originating from the former MGP in Cottbus, has been studied by using a column experiment. Results indicated that long-term cyanide (CN) release is governed by two phases: one readily dissolved and one strongly fixed. Different isotherm and kinetic equations were used to investigate the driving mechanisms for the ferric ferrocyanide release. Applying the isotherm equations assumed an approach by which two phases were separate in time, whereas the multiple first order equation considered simultaneous occurrence of both cyanide pools. Results indicated varying CN release rates according to the phase and soil. According to isotherm and kinetic models, the long-term iron cyanide release from the MGP soils is a complex phenomenon driven by various mechanisms parallely involving desorption, diffusion and transport processes. Phase I (rapid release) is presumably mainly constrained by the transport process of readily dissolved iron-cyanide complexes combined with desorption of CN bound to reactive heterogeneous surfaces that are in direct contact with the aqueous phase (outer-sphere complexation). Phase II (limited rate) is presumably driven by the diffusion controlled processes involving dissolution of precipitated ferric ferrocyanide from the mineral or inner-sphere complexation of ferricyanides. CN release rates in phase I and II were mainly influenced by the pH, organic matter (OM) and the total CN content. The cyanide release rates increased with increasing pH, decreased with low initial CN concentration and were retarded by the increase in OM content.
