Groundwater–Surface Water Interaction: Process Understanding, Conceptualization and Modelling (Proceedings of Symposium HS1002 at IUGG2007, Perugia, July 2007). IAHS Publ. 321, 2008, 141-147.

Do downwelling streams have a natural attenuation potential for perfluorinated chemicals?

EDUARD HOEHN¹, MEGAN H. PLUMLEE² & MARTIN REINHARD²

1 Eawag, Swiss Federal Institute of Water Science and Technology, CH-8600 Dübendorf, Switzerland

hoehn@eawag.ch

2 Department of Civil and Environmental Engineering, Stanford University, Stanford, California 94305, USA

Abstract Stream augmentation is increasingly considered as an ecologically beneficial way to utilize tertiary-treated municipal wastewater, i.e. recycled water, especially in the semi-arid regions of the American southwest. There is concern that emerging contaminants, i.e. a variety of unregulated and biologically active organic compounds, may be present in recycled water and will impact the aquatic environment and the groundwater (e.g. pharmaceuticals, endocrine disruptors, and residues of perfluorinated surfactants (PFCs)). This paper presents background data on the occurrence and transport of PFCs in Upper Silver Creek (USC), San Jose, California. The recession-flow constant of this creek shows a lack of water at the end of dry summer seasons. Augmenting the natural flow of USC with recycled water is currently being considered as a means to provide more freshwater to the creek’s ecosystem. Data indicate that some of the PFCs are refractory along this distance and act as groundwater contaminants. Thus for these compounds, downwelling creeks cannot be considered to have a natural attenuation potential.

Key words perfluorinated chemicals; natural attenuation; losing stream; hyporheic zone