Concentration-discharge relations in the critical zone

Trees along the shore of a lake. Photo credit Ivan Forsman (CC BY 2.0, via https://www.flickr.com/photos/123937568@N05/15979883057/).

Last Updated: 7 December 2017

Critical Zone scientists seek to develop mechanistic-predictive theory of critical zone structure, function, and long-term evolution. One postulate is that contemporaneous hydrochemical controls over all three can be related quantitatively to dissipative solute releases measured down-gradient of reactive flow paths.These flow paths have variable lengths, compositions, and residence times, and their mixing is reflected in concentration-discharge (C/Q) relations.It is recognized that contemporaneous measurements are only that, and don’t necessarily reflect C/Q behavior over the course of CZ evolution. Motivation for this special section originates from a U.S. Critical Zone Observatories workshop that was held at the University of New Hampshire, July 20-22, 2015.The workshop focused on resolving mechanistic CZ controls over surface water chemical dynamics across the full range of lithogenic (e.g., non-hydrolyzing and hydrolyzing cations and oxyanions) and bioactive solutes (e.g., organic and inorganic forms of C, N, P, S), including dissolved and colloidal species that may co-occur for a given element. Papers included in this special section utilize information pertaining to internal, integrated catchment function (relations between hydrology, biogeochemistry and landscape structure) to help shed light on controls over observed C/Q relations.
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