Publication Date:
2022-05-26
Description:
Author Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 72 (2008): 3398-3412, doi:10.1016/j.gca.2008.04.027.
Description:
A two-dimensional (2D) reactive transport model is used to investigate the controls on
nutrient (NO3-, NH4+, PO4) dynamics in a coastal aquifer. The model couples density
dependent flow to a reaction network which includes oxic degradation of organic
matter, denitrification, iron oxide reduction, nitrification, Fe2+ oxidation and sorption of PO4 onto iron oxides. Porewater measurements from a well transect at Waquoit
Bay, MA, USA indicate the presence of a reducing plume with high Fe2+, NH4+, DOC
(dissolved organic carbon) and PO4 concentrations overlying a more oxidizing NO3--rich plume. These two plumes travel nearly conservatively until they start to overlap in the intertidal coastal sediments prior to discharge into the bay. In this zone, the aeration of the surface beach sediments drives nitrification and allows the
precipitation of iron oxide, which leads to the removal of PO4 through sorption. Model
simulations suggest that removal of NO3-
through denitrification is inhibited by the
limited overlap between the two freshwater plumes, as well as by the refractory nature
of terrestrial DOC. Submarine groundwater discharge is a significant source of NO3-
to the bay.
Description:
This research was funded by the Netherlands Organisation for Scientific Research
(NWO) and WHOI Guest Student Program (C. Spiteri), the Royal Netherlands
Academy of Arts and Sciences (KNAW) and the Netherlands Organization for
Scientific Research (NWO VIDI-grant) (C.P. Slomp), the US National Science
Foundation NSF-OCE0095384 and NSF-OCE0425061 (M.A. Charette) and the
Georgia Sea Grant of the National Sea Grant College Program of the U.S. Department
of Commerce’s National Oceanic and Atmospheric Administration under NOAA
Grant #NA04OAR4170033 (C. Meile).
Keywords:
Coastal aquifer
;
Reactive transport modeling
;
Nutrients
;
Submarine groundwater discharge
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
Format:
application/pdf
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