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Oxidative precipitation of groundwater‐derived ferrous iron in the subterranean estuary of a coastal bay
Author(s) -
Charette Matthew A.,
Sholkovitz Edward R.
Publication year - 2002
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2001gl014512
Subject(s) - bay , ferrous , estuary , groundwater , geology , sediment , environmental chemistry , seawater , intertidal zone , precipitation , oceanography , geochemistry , environmental science , chemistry , geomorphology , geotechnical engineering , organic chemistry , meteorology , physics
Sediment cores from the intertidal zone of Waquoit Bay (Cape Cod, Massachusetts) yielded iron oxide‐coated sands in the subterranean estuary, which underlies the head of the bay. The oxides were dark red, yellow and orange colors and are formed by the oxidation of ferrous iron‐rich groundwater near the groundwater‐seawater interface. Within these iron oxide‐rich sediments, the concentration of the combined amorphous and crystalline forms of iron oxides ranged between 2500 and 4100 ppm of Fe. These concentrations were 4–6 times greater than the surface sands, and 10–15 times more Fe rich than sands collected from an off‐site location. The precipitation of iron oxides in subterranean estuaries could act as a geochemical barrier by retaining and accumulating certain dissolved chemical species carried to the coast by groundwater. Indeed, phosphorus concentrations in the iron oxide‐rich sands of Waquoit Bay were 5–7 times greater than the overlying surface sands.