4.08 - Submarine Groundwater Discharge: A Source of Nutrients, Metals, and Pollutants to the Coastal Ocean

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Abstract

This chapter provides a review of the current state of knowledge on submarine groundwater discharge (SGD) and the associated fluxes of nutrients, trace metals, microbes, pharmaceuticals, and other terrestrial constituents to coastal waters. We review methods of estimating SGD, present flux estimates from different locations worldwide, and discuss how various hydrogeologic features such as topography, aquifer substrate, climate, waves, and tides affect SGD. We discuss the range of nutrient and metal concentrations observed in groundwater and their relationship to land use, and explore the chemical changes that nutrients and metals undergo during their seaward journey through the aquifer. Climate change is likely to affect both the quantity and the quality of SGD, and we investigate these effects, which are only beginning to be studied. The chapter concludes with a discussion of active areas of SGD research, including expanding the geographic scope of SGD studies; characterizing and reducing the uncertainty associated with SGD measurements; understanding the behavior of nutrients, metals, and other pollutants in the subterranean estuary; and modeling SGD on a global scale.

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Karen L. Knee earned a bachelor of science degree with honors in environmental science from Brown University in 2002 and a PhD in geological and environmental science from Stanford University in 2010. She went on to complete a Fulbright project focusing on land use and stream water quality in the Intag cloud forest of northwestern Ecuador, and she is currently a postdoctoral scholar at the Smithsonian Environmental Research Center in Edgewater, Maryland. Her research interests include submarine groundwater discharge and water quality in tropical systems, the effects of land use on water quality, the development of novel wastewater tracers, and the use of radium isotopes to understand coastal mixing processes. Additionally, she has a long-standing interest in science writing and journalism.

Adina Paytan is a research professor at the University of California, Santa Cruz. She earned a bachelor of science degree in biology and geology from the Hebrew University in Jerusalem and went on to earn a master’s degree in oceanography from the same institution, a second master’s degree in science education from the Weizmann Institute of Science in Rehovot (Israel), and a PhD in oceanography from the Scripps Institute of Oceanography in San Diego, CA. Her research focuses on using chemical and isotopic records enclosed in a wide range of Earth materials to study present and past biogeochemical processes. This research spans a wide range of temporal (seasons to millions of years) and spatial (molecular to global) scales, with the overarching goal of understanding the processes and feedbacks operating in the Earth system and how they relate to global changes in climate and tectonics. She is also interested in natural and anthropogenic perturbations that affect biogeochemical processes and their impact on humans and the environment.

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