COMBINED CHEMICAL AND P-31-NMR SPECTROSCOPIC ANALYSIS OF PHOSPHORUS IN WETLAND ORGANIC SOILS

The organic P (Po) status of wetland soils has a large influence on th e internal P cycling, and therefore on the biological productivity and water quality, of wetland ecosystems, Chemical extraction and solutio n-state P-31-nuclear magnetic resonance (NMR) spectroscopy were used t o identify and quantify the distribution of the major forms of P in or ganic soils of three created wetland sites-Apopka Marsh, Eustis Muck F arm, and Sunny Hill Farm (SHF), Spectra were obtained on 0.25 M NaOH-0 .05 M EDTA extracts of soils with and without previous chemical remova l of labile soil P, P-31-NMR spectral analysis of the NaOH-EDTA extrac ts revealed the presence of inorganic ortho P (Pi), ortho-P monoesters , and ortho-P diesters, Chemically determined proportions of total P ( TP) as Pi in the NaOH-EDTA. extracts were similar to those obtained by 31P-NMR. P monoester was the predominant P form in Apopka Marsh (51% TP) and SHF (59% TP) soils. The Eustis soil contained a high proportio n of Pi (65% TP), and the SHF soil contained significant (10% TP) P di ester, Chemical removal of labile Pi, using 1 M KCl and 0.5 M NaHCO3, enhanced the quality of all NMR signatures and demonstrated that not a ll P diesters are removed in the NaHCO3 extract. NMR spectra were obta ined with acquisition times ranging from 0.5 to 1.2 h, which represent s a significant reduction in data acquisition times reported in the pr evious P-31 NMR studies of soil extracts.