Ground Water and Surface Water A Single Resource--USGS Circular
1139 Evolution of Ground-Water Chemistry from Recharge to
Discharge Areas in the Atlantic Coastal Plain Changes in the
chemical composition of ground water in sediments of the
Atlantic Coastal Plain (Figure E-1) provide an example of the
chemical evolution of ground water in a regional flow system. In
the shallow regime, infiltrating water comes in contact with
gases in the unsaturated zone and shallow ground water. As a
result of this contact, localized, short-term, fast reactions
take place that dissolve minerals and degrade organic material.
In the deep regime, long-term, slower chemical reactions, such
as precipitation and dissolution of minerals and ion-exchange,
add or remove solutes. These natural processes and reactions
commonly produce a predictable sequence of hydrochemical facies.
In the Atlantic Coastal Plain, ground water evolves from water
containing abundant bicarbonate ions and small concentrations of
dissolved solids near the poi