A New Focus on Groundwater–Seawater Interactions (Proceedings of Symposium HS1001 at IUGG2007, Perugia, July 2007). IAHS Publ. 312, 2007,109-118

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Remaining uncertainties in the use of Rn-222 as a quantitative tracer of submarine groundwater discharge

William c. Burnett¹, isaac R. santos¹, yishai weinstein², peter w. Swarzenski³ & barak herut⁴

1 Department of Oceanography, Florida State University, Tallahassee, Florida 32306, USA

wburnett@mailer.fsu.edu

2 Bar-Ilan University, Ramat-Gan, 52900, Israel

3 US Geological Survey, St Petersburg, Florida 33701, USA

4 Israel Oceanographic and Limnological Research, Haifa, Israel

Abstract Research performed in many locations over the past decade has shown that radon is an effective tracer for quantifying submarine groundwater discharge (SGD). The technique works because both fresh and saline groundwaters acquire radon from the subterranean environment and display activities that are typically orders of magnitude greater than those found in coastal seawaters. However, some uncertainties and unanswered problems remain. We focus here on three components of the mass balance, each of which has some unresolved issues: (1) End-member radon – what to do if groundwater Rn measurements are highly variable? (2) Atmospheric evasion – do the standard gas exchange equations work under high-energy coastal mixing scenarios? And (3) “mixing” losses – are there other significant radon losses (e.g. recharge of coastal waters into the aquifer) besides those attributed to mixing with lower-activity waters offshore? We address these issues using data sets collected from several different types of coastal environment.

Key words radon; submarine groundwater discharge; mass balance model

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