Phosphate and Iron correlations in an intertidal Georgia saltmarsh By Colin Dean
Fe(hydr)oxide dissolution Abiotic (H2S method) Biological Complicated, difficult to quantify The importance of soluble Fe (III) Likely the greatest source of Fe(II) in the marsh (otherwise all FeS) • 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)
Orthophosphate: PO43- Phosphate salts are (weak) buffers Dominant form at pH 7: HPO4- , H2PO4- • Inorganic form • H3P04, etc. • Pka’s: 2.16, 7.21, 12.32 -Negative charge in solution, and readily adsorbs to metal oxides, mostly aluminum and iron (hydr)oxides (as a bidentate ligand).
Correlate this! • Deborde et al. (2009).
Winter mud flat R=.7942 P=2.9e-5 Slope:.1948 Unvegetated R=.88 P=2.79e-7 Slope:.1935 Vegetated
Summer mud flat R=.8076 P=2.9e-5 Slope:.1326 Unvegetated Vegetated R=.8434 P=5.7e-6 Slope:.1368
Winter Creek Bank R=.7942 P=Slope:.1243 Unvegetated R=.88 P=2.79e-7 Slope:.1935 Vegetated
Summer Creek Bank R=.5540 P=.0138 Slope:.1243 Unvegetated R=.7267 P=.0004 Slope:.1043 Vegetated