1. Phosphate and Iron correlations in an intertidal Georgia saltmarsh
By Colin Dean

2. Fe(hydr)oxide dissolution
Abiotic (H2S method)
Biological
Surface controlled by chemisorbed HS- and S2-
≡FeOH + HS-  ≡FeS- + H2O
≡ FeS-  ≡Fe(II)S
Fe(II) is then hydrated and leaves the surface into solution.
(Afonso and Stumm 1991)
Complicated, difficult to quantify
The importance of soluble Fe (III)
Likely the greatest source of Fe(II) in the marsh (otherwise all FeS)

3. Orthophosphate: PO43- Inorganic form H3P04, etc.
Pka’s: 2.16, 7.21, 12.32
Phosphate salts are (weak) buffers
Dominant form at pH 7:
HPO4- , H2PO4-
-Negative charge in solution, and readily adsorbs to metal oxides, mostly aluminum and iron (hydr)oxides (as a bidentate ligand).

4. Correlate this!
Deborde et al. (2009).

5. Winter mud flat R=.7942 P=2.9e-5 Unvegetated Slope:.1948 R=.88

6. Summer mud flat R=.8076 P=2.9e-5 Slope:.1326 Unvegetated Vegetated

7. Winter Creek Bank R=.7942 P=Slope:.1243 Unvegetated R=.88 Vegetated

8. Summer Creek Bank R=.5540 P=.0138 Unvegetated Slope:.1243 R=.7267