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Physical Weathering Intensity Controls Bioavailable Primary Iron(II) Silicate Content in Major Global Dust Sources
Author(s) -
Shoenfelt Elizabeth M.,
Winckler Gisela,
Annett Amber L.,
Hendry Katharine R.,
Bostick Benjamin C.
Publication year - 2019
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 - 10.1029/2019gl084180
Subject(s) - weathering , silicate , sediment , environmental chemistry , environmental science , iron fertilization , mineral dust , oceanography , bioavailability , aeolian processes , genetic algorithm , geology , earth science , geochemistry , phytoplankton , chemistry , nutrient , geomorphology , ecology , aerosol , bioinformatics , organic chemistry , biology
The speciation of iron (Fe) reaching the ocean, for instance in wind‐blown dust and coastal sediments, impacts its bioavailability to phytoplankton and its impact on atmospheric carbon dioxide (CO 2 ) and climate. For dust reaching the Southern Ocean, primary Fe(II) silicates that are physically weathered from bedrock are highly bioavailable compared to more chemically weathered, Fe(III)‐rich species, suggesting that weathering in dust source regions impacts the bioavailable Fe supply. However, this phenomenon has not been studied in other important terrestrial Fe sources, where weathering regimes and source geology vary. Here, we use Fe X‐ray absorption spectroscopy on marine sediment cores to show that major global dust and sediment sources impacted by high physical weathering contain abundant primary minerals and thus are overlooked as a source of highly bioavailable Fe globally. Thus, it is important to consider the role of physical versus chemical weathering in Fe fertilization and biotic CO 2 cycling.