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Projekt Druckansicht

Quecksilberisotopenverhältnisse als Werkzeug zur Bestimmung von Speziestransformationsprozessen in kontaminierten Boden-Aquifer-Systemen

Fachliche Zuordnung Hydrogeologie, Hydrologie, Limnologie, Siedlungswasserwirtschaft, Wasserchemie, Integrierte Wasserressourcen-Bewirtschaftung
Mineralogie, Petrologie und Geochemie
Förderung Förderung von 2018 bis 2023
Projektkennung Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 389190907
 
Erstellungsjahr 2023

Zusammenfassung der Projektergebnisse

In this project we investigated the relationship between Hg species and Hg isotope fractionation in soil and groundwater and stream sediments at two sites contaminated by HgCl2 as a result of wood impregnation (kyanisation). Besides comprehensive field investigations we carried out additional laboratory experiments to decipher the retention of HgCl2 by aquifer sediments and related Hg species transformation and Hg isotope fractionation. By combining Hg speciation analyses using pyrolysis-thermodesorption and selective extractions with Hg isotope analyses of total Hg and separated Hg pools of soil and groundwater samples, we were able to trace Hg species transformations at the studied contamination cases. These results are useful not only for future investigations of similar contaminated sites but can also be transferred to uncontaminated systems to better understand Hg isotope fractionation in natural soil and groundwater systems as a function of Hg species transformation reactions. With this novel combination of Hg concentration, Hg speciation, and Hg isotope analysis (using CV-MC-ICP-MS) of liquid and solid samples significant improvements of our capability to predict the behavior and fate of Hg not only for the studied field sites but also for other contaminated and pristine aquifer and soil systems in general were anticipated. The findings of this project provide insights into the applicability of Hg isotope ratios as process tracers and the benefits of combining multiple analytical approaches to assess the geochemical behavior of Hg at contaminated sites which also have implications for the general interpretation of Hg isotope ratios in natural samples. Despite the demonstrated advancements in Hg geochemical interpretations highlighted by the addition of Hg isotope analyses within such a comprehensive study, considerable uncertainties and distinct unknowns remain. System complexity (multiple groundwater bodies, complex terrain, and highly variable redox conditions) observed particularly at the TN site appear to limit our ability to identify processes. A major limiting factor remains our inability to identify all Hg2+ species in environmental solid- or liquid-phase samples, a task that is not advanced by analyses of Hg isotopes. The application of Hg isotopes in Hg geochemistry is still relatively new and many processes that might occur in the natural environment have not been examined in laboratory conditions to determine fractionation factors. This puts a limit on how much we can presently interpret Hg isotope signatures of environmental samples. It is critical that laboratory examination of fractionation factors for MDF and MIF of known and potential biogeochemical processes continue to be pursed and then examined via holistic field studies such as this. Equally as important is the need to continue to assess these processes in field-based studies as we have done here to determine if they are indeed relevant (do occur) and can be identified under environmentally relevant conditions.

Projektbezogene Publikationen (Auswahl)

 
 

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