[MCN] Subdivisions and health: Deep fossil groundwater wells may not be clean as assumed

[Lance Olsen]

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 <> <http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2941.html> <http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2946.html>Nature Geoscience Published online 25 April 2017

doi:10.1038/ngeo2943

Global aquifers dominated by fossil groundwaters but wells vulnerable to modern contamination

Scott Jasechko <http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2943.html#auth-1>,	Debra Perrone <http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2943.html#auth-2>,	Kevin M. Befus <http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2943.html#auth-3>,	M. Bayani Cardenas <http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2943.html#auth-4>,	Grant Ferguson <http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2943.html#auth-5>,	Tom Gleeson <http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2943.html#auth-6>,	Elco Luijendijk <http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2943.html#auth-7>,	Jeffrey J. McDonnell <http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2943.html#auth-8>,	Richard G. Taylor <http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2943.html#auth-9>,	Yoshihide Wada <http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2943.html#auth-10>	& James W. Kirchner <http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2943.html#auth-11>
Abstract
The vulnerability of groundwater to contamination is closely related to its age. Groundwaters that infiltrated prior to the Holocene have been documented in many aquifers and are widely assumed to be unaffected by modern contamination. However, the global prevalence of these ‘fossil’ groundwaters and their vulnerability to modern-era pollutants remain unclear. Here we analyse groundwater carbon isotope data (12C, 13C, 14C) from 6,455 wells around the globe. We show that fossil groundwaters comprise a large share (42–85%) of total aquifer storage in the upper 1 km of the crust, and the majority of waters pumped from wells deeper than 250 m. However, half of the wells in our study that are dominated by fossil groundwater also contain detectable levels of tritium, indicating the presence of much younger, decadal-age waters and suggesting that contemporary contaminants may be able to reach deep wells that tap fossil aquifers. We conclude that water quality risk should be considered along with sustainable use when managing fossil groundwater resources.

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“Climate has long been identified as a primary control on the geographic distribution of plants (Forman 1964, Box
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Delcourt and Delcourt 1988, Malanson 1993, Williams et al. 2004). In addition, species are expected to be 
redistributed independently, forming new forest types with unique species combinations (Webb 1992, 
Williams et al. 2004).”

McKenney et al. Potential Impacts of Climate Change on the Distribution of North American Trees. Bioscience  2007
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“Forests are shaped by climate. Along with soils, aspect, inclination, and elevation, climate determines
 what will grow where and how well. Changes in temperature and precipitation regimes therefore have
 the potential to dramatically affect forests nationwide. “
 
Robert W. Malmsheimer, Patrick Heffernan, Steve Brink, Douglas Crandall, Fred Deneke, Christopher Galik, 
Edmund Gee, John A. Helms, Nathan McClure, Michael Mortimer, Steve Ruddell, Matthew Smith, and John 
Stewart. Forest Management Solutions for Mitigating Climate Change in the United States.  Journal of Forestry April/May 2008

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