Application of δ¹⁸O, δ¹³C_DIC, and major ions to evaluate micropollutant sources in the Bay of Vidy, Lake Geneva^†

^†Dedicated to Professor Dr Jochen Hoefs on the occasion of his 75th birthday.

Abstract

Waters were sampled monthly from a profile at the wastewater outlet and a reference point in the Bay of Vidy (Lake Geneva) for a year. The samples were analyzed for ¹⁸O/¹⁶O of water, ¹³C/¹²C of dissolved inorganic carbon (DIC), major ions, and selected micropollutant concentrations. δ¹⁸O values, combined with the major ion concentrations, allowed discharged waste and storm-drainage water to be traced within the water column. On the basis of δ¹⁸O values, mole fractions of wastewater (up to 45 %), storm-drainage (up to 16 %), and interflowing Rhône River water (up to 34 %) could be determined. The results suggest that the stormwater fractions do not influence micropollutant concentrations in a measurable way. In contrast, the Rhône River interflow coincides with elevated concentrations of Rhône River-derived micropollutants in some profiles. δ¹³C values of DIC suggest that an increase in micropollutant concentrations at the sediment–water interface could be related to remineralization processes or resuspension.

Keywords:

• carbon-13
• dissolved inorganic carbon
• hydrogen-2
• Lake Geneva
• micropollutants
• oxygen-18
• remineralization
• Switzerland
• wastewater

Acknowledgements

Alexander Bahr's help and technical support with the Rosette sampling system are much appreciated. Philippe Arpagaus and Jean-Luc Loizeau kindly navigated the boat and assisted with the sampling, Luca Rossi for the wastewater sampling. Silwan Daouk, Jean-Claude Lavanchy, and Morgane Tournier helped with the ion analysis. Alexandre Hirzel is acknowledged for software support; Hans-Rudolf Pfeifer, Walter Wildi, Jean-Luc Loizeau, Moritz Lehmann, and Tamar Kohn for scientific discussions. Two anonymous reviewers helped to improve the manuscript and their thorough review is much appreciated. The Institut National de la Recherche Agronomique (INRA) kindly provided chemical and physical data that helped to interpret our data. The Federal Office for the Environment of Switzerland (BAFU) provided long-term isotopic compositions of the Rhône River and precipitation from the Swiss Isotopic Network (ISOT) module of the BAFU. This project was generously funded by the Swiss National Science Foundation [SNF project number PDFMP2-123028 to Vennemann, Kohn, and Arey].

Supplemental data

Supplemental data for this article can be accessed at http://dx.doi.org/10.1080/10256016.2014.971786.

Notes

^† Dedicated to Professor Dr Jochen Hoefs on the occasion of his 75th birthday.