The geochemistry of iron in puget sound |
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| Authors: | James W Murray Gary Gill |
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| Institution: | Department of Oceanography, University of Washington, Seattle, WA 98195, U.S.A. |
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| Abstract: | The distribution of dissolved iron, ferrous iron and acid-reducing agent soluble iron has been investigated in the main basin of Puget Sound and its tributaries. Essentially all measurable iron in Puget Sound can be removed by filtration through 0.8 μm membrane filters, thus dissolved iron must be less than about 20 nM (our limit of detection). We could also detect no ferrous iron in Puget Sound. This is due to the rapid kinetics of oxidation of Fe(II). Our measured rate constant for the kinetics of oxidation suggests that strong ferrous-organic matter complexes do not exist in Puget Sound pore waters.The distribution of acid-soluble iron is low at mid-depth and increases toward the air-water and sediment-water interface and appears to be controlled by inputs from the rivers and the sediments. Only a small fraction of the river load appears to make it through the estuaries because the magnitude of the surface concentrations is smaller than predicted based on the calculated river flux. The “dissolved” iron in the rivers appears to be actually fine colloidal particles that coagulate before the salinity exceeds 5%. The increase towards the sediments is probably due to resuspension of botton sediments perhaps augmented by iron diffusing out of the sediments to form new iron oxide particles. |
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