A combination of liquid chromatography mass spectrometry (LC-MS), solution 31P and solid 13C-NMR spectroscopy was applied to reveal different behavior for soils sharing similar physical properties but differing in the quality of soil carbon. We used hydrofluoric acid (HF) pretreatment to differentiate phosphorus chelated to metals or sorbed to anionic sorption sites from phosphorus incorporated into soil organic matter. Relatively little phosphorus was removed after HF treatment in soils dominated by alkyl and aromatic groups (i.e. humified) compared to soils with abundant by O-alkyl groups. While organic P was the dominant form associated with humified soil carbon, a surprisingly large amount of inorganic P was sequestered as well. These differences support the hypothesis that phosphorus will form stable humic complexes in soils with humified organic matter consisting primarily of alkyl and aromatic functional groups, although the extent to which inorganic P behaves in this way remains a mystery. Conversely, in soils dominated by carbohydrates, phosphorus appears to be predominantly bound to free metals or small molecules. Inositol phosphates (IPs) were specifically targeted in this work using ion chromatography (IC) coupled to high resolution time-of-flight mass spectrometry (TOF-MS). The behavior of IPx congeners containing x = 1-6 phosphate groups could be determined at soil levels well below those that can be observed by 31P NMR. Our data are consistent with previous results that suggest sequestration of phosphorus in wetlands may be tightly linked to soil carbon humification, the process that converts labile biopolymers into stable geopolymers. Once sequestered in this way, release of phosphorus into overlying water would be minimized as long as the soil organic matter was stabilized.

Studies of phosphorus sequestration and carbon humification in wetland soils by LC-MS, <sup>31</sup>P and <sup>13</sup>C NMR

245th National Meeting (2013)

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Studies of phosphorus sequestration and carbon humification in wetland soils by LC-MS, 31P and 13C NMR

Studies of phosphorus sequestration and carbon humification in wetland soils by LC-MS, ³¹P and ¹³C NMR