Identification and characterization of aquatic soluble unreactive phosphorus in the hydrosphere with 31-phosphorus Fourier transform nuclear magnetic resonance spectroscopy and high-performance liquid chromatography
The identity and characteristics of aquatic soluble phosphorus (SUP) present in a small mid-western mesotropic lake were examined with 31-Phosphorus Fourier Transform Nuclear Magnetic Resonance Spectroscopy $\rm (\sp{31}P$ FT-NMR) and High Performance Liquid Chromatography (HPLC). Samples were concentrated and fractionated according to molecular size using a series of ultrafiltration (UF) and reverse osmosis (RO) membranes. The UF membrane pore sizes were 30,000 Da and 1,000 Da while the RO membrane had a 95% NaCl rejection rating. The SUP was analyzed as a function of apparent molecular size and season. In the 30,000 Da retentate, monoester phosphates, diester phosphates, and phophonates were detected. In the 1,000 Da retentate, monoester and diester phosphates were seen, and in the reverse osmosis retentate, orthophosphate and monoester phosphates were detected. Seasonal changes in the monoester phosphates of the 1,000 Da retentate were detected with $\rm\sp{31}P$ FT-NMR and HPLC. Enhancement of the $\rm\sp{31}P$ FT-NMR spectral resolution and sample characterization was achieved with the use of $\rm T\sb1$ relaxation agents and aqueous soluble lanthanide shift reagents. A Mississippi River sample, fractionated into a 1,000K Da retentate and a RO retentate sample, was examined with $\rm\sp{31}P$ FT-NMR and HPLC. The SUP in the 1,000 Da retentate sample was found to be different from the lake samples in that it contained polyphosphates and possibly phosphonates, while the RO retentate was very similar to the lake RO retentate sample. This research has also demonstrated that changes occur with the SUP in the sample during concentration by UF and RO methods. It appears the phosphorus compounds are becoming incorporated into an aggregate structure which forms during the concentration procedure. Possible identities of this aggregate structure were examined using a variety of extraction and degradation methods. Extraction of SUP with ion pairing reagents and hydrophobic resins was started to be examined as a method for further enhancing SUP characterization ability by obtaining samples free from $\rm\sp{31}P$ FT-NMR and HPLC interferents.
Biogeochemistry, Environmental Sciences, Biology, Limnology
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign