Technical hexachlorocyclohexane (HCH) mixtures and Lindane (γ-HCH) have been produced in Bitterfeld-Wolfen, Germany, for about 30 years until 1982. In the vicinity of the former dump sites and production facilities, large plumes of HCHs persist within two aquifer systems. We studied the natural attenuation of HCH in these groundwater systems through a combination of enantiomeric and carbon isotope fractionation to characterize the degradation of α-HCH in the areas downstream of a former disposal and production site in Bitterfeld-Wolfen. The concentration and isotope composition of α-HCH from the Quaternary and Tertiary aquifers were analyzed. The carbon isotope compositions were compared to the source signal of waste deposits for the dumpsite and highly contaminated areas. The average value of δC at dumpsite was -29.7 ± 0.3 ‰ and -29.0 ± 0.1 ‰ for (-) and (+)α-HCH, respectively, while those for the β-, γ-, δ-HCH isomers were -29.0 ± 0.3 ‰, -29.5 ± 0.4 ‰, and -28.2 ± 0.2 ‰, respectively. In the plume, the enantiomer fraction shifted up to 0.35, from 0.50 at source area to 0.15 (well T1), and was found accompanied by a carbon isotope enrichment of 5 ‰ and 2.9 ‰ for (-) and (+)α-HCH, respectively. The established model for interpreting isotope and enantiomer fractionation patterns showed potential for analyzing the degradation process at a field site with a complex history with respect to contamination and fluctuating geochemical conditions.
The spatial and temporal biogeochemical development of a model wetland loaded with cis- and trans-1,2-dichloroethene contaminated groundwater was characterized over 430 days by hydrogeochemical and compound-specific isotope analyses (CSIA). The hydrogeochemistry dramatically changed over time from oxic to strongly reducing conditions as emphasized by increasing concentrations of ferrous iron, sulfide, and methane since day 225. delta(13)C values for trans- and cis-DCE substantially changed over the flow path and correlated over time with DCE removal. The carbon enrichment factor values (epsilon) retrieved from the wetland became progressively larger over the investigation period, ranging from -1.7 +/- 0.3% per hundred to -32.6 +/- 2.2% per hundred. This indicated that less fractionating DCE oxidation was progressively replaced by reductive dechlorination, associated with a more pronounced isotopic effect and further confirmed by the detection of vinyl chloride and ethene since day 250. This study demonstrates the linkage between hydrogeochemical variability and intrinsic degradation processes and highlights the potential of CSIA to trace the temporal and spatial changes of the dominant degradation mechanism of DCE in natural or engineered systems.
EinführungIn Deutschland werden ca. 75 % des Trinkwassers aus Grundwasser gewonnen. Aus diesem Grunde kommt dem Schutz dieser lebenswichtigen Ressource eine ganz besondere Bedeutung zu. Dies bringt der Gesetzgeber in einer sehr strengen Gesetzgebung zum Schutz von Trinkwasserressourcen zum Ausdruck, sodass sich heute wesentliche Teile der Forschung auf den vorsorgenden Grundwasserschutz konzentrieren. KurzfassungZiel des SAFIRA-Projektes (SAnierungs-Forschung In Regional kontaminierten Aquiferen) ist es, innovative Technologien zur In-situ-Sanierung komplex belasteter Grundwässer zu entwickeln. Für die Untersuchungen wurde Bitterfeld als Modellstandort ausgewählt. An den dortigen Altstandorten der Chemieindustrie ist das Grundwasser mit aliphatischen und aromatischen chlorierten Kohlenwasserstoffen (CKW) hohen Konzentrationen kontaminiert. In einer Pilotanlage werden unter kontrollierten Insitu-Bedingungen neue Verfahren für reaktive Wände entwickelt, getestet und optimiert. Um den geeigneten Modellstandort festzulegen, wurden die geologischen und hydrogeologischen Bedingungen untersucht und ver-schiedene Ausbautechnologien für die In-situ-Pilotanlage ausgewertet. Vor der Anwendung der neuen Technologien im Feld wurden kleinskalige Laborstudien und Versuche in einer mobilen Testeinheit (Skale 1 m) durchgeführt. Die Technologien, welche z. Z. in den reaktiven Säulen der Pilotanlage getestet werden, schließen physiko-chemische, mikrobiologische und Kombinationsverfahren ein. AbstractThe SAFIRA-project (remediation research in regionally contaminated aquifers) focuses on innovative in situ remediation technologies to treat complex groundwater contamination. For this purpose, a model site located in Bitterfeld, Germany, was selected. The site is heavily contaminated with aliphatic and aromatic chlorinated hydrocarbons. The goal of the project is to develop, test and optimize new technologies of reactive barriers under controlled in situ conditions in a pilot plant. In order to create the necessary basis for this model project, the hydrogeological and hydrogeochemical conditions at the selected field site were investigated and various technologies for the design of the in situ pilot plant were examined. Smallscale laboratory studies and tests in a mobile test unit (scale 1 m) were carried out in order to test the technologies prior to their application in the field. The technologies now tested in the reactive columns at the pilot plant include physico-chemical, microbial and combined techniques.Abb. 1: Lageskizze des SAFIRA-Modellstandortes Bitterfeld einschließlich der Pilotanlage
While constructed wetlands have become established for the decentralized treatment of wastewater and rainwater, wetland roofs have only been built in isolated cases up to now. The historical development of wetland roofs is described here on the basis of a survey of literature and patents, and the increasing interest in this ecotechnology around the world is presented. In particular, this article describes the potential for using wetland roofs and examines experience with applications in decentralized water management in urban environments and for climate regulation in buildings. Wetland roofs are suitable as a green-blue technology for the future—particularly in cities with an acute shortage of unoccupied ground-level sites—for the decentralized treatment of wastewater streams of various origins. Positive “side effects” such as nearly complete stormwater retention and the improvement of climates in buildings and their surroundings, coupled with an increase in biodiversity, make wetland roofs an ideal multi-functional technology for urban areas.
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