SMRL: Stanford NMR Facility and Resource

Paytan Group Research at the SMRL

Adina Paytan

Assistant Professor
Dept. of Geological and Environmental Sciences

(650) 724-4073

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(Details Below) Paytan, A; Cade-Menun, BJ; McLaughlin, K; Faul, KL (2003) "Selective phosphorus regeneration of sinking marine particles: evidence from P-31-NMR" MARINE CHEMISTRY, 82 55-70. PDF


Selective phosphorus regeneration of sinking marine particles: evidence from P-31-NMR

Paytan, A; Cade-Menun, BJ; McLaughlin, K; Faul, KL (2003) MARINE CHEMISTRY, 82 55-70. PDF

Abstract: Phosphorus (P) regeneration and transformation in the oceanic water column and in marine sediments depends on the chemical nature of the sinking particulate P pool. For the first time, we have characterized the molecular composition of this pool, in various oceanic settings and water depths, using 31P nuclear magnetic resonance (NMR) spectroscopy. Both inorganic P (orthophosphate, pyrophosphate, and polyphosphate) and organic P compounds (orthophosphate monoesters, orthophosphate diesters, and phosphonates) were identified. The inorganic P is present predominantly as orthophosphate with small amounts ( < 10%) of pyro- and polyphosphates. These inorganic compounds may be at least partially of biological origin. The relatively high abundance of inorganic P suggests that considerable transformation from the organic to the inorganic pool occurs in the water column. Some of this inorganic P may be present in association with mineral phases (apatite, clays, and oxyhydroxides) and thus may not be bioavailable.
The distribution of organic P compounds in the sinking particulate matter pool is generally similar in composition to phytoplankton and significantly different than in the dissolved organic matter (DOM) pool. Results indicate that in most oceanic regions the majority of P regeneration occurs at very shallow depths. However, in the Ross Sea, a significant fraction of organic P is exported to depth below the euphotic zone. Hydrolysis of P compounds continues throughout the water column as indicated by a decrease in total particulate P with depth and a relative decrease in the organic P fraction at some sites. Orthophosphate monoesters dominate the organic P pool at all locations, followed by orthophosphate diesters. Phosphonates are present in a few samples but never contribute more than 6% of total extractable P compared to 25% abundance in the dissolved organic P (DOP) pool. This work shows that considerable spatial and temporal variability in the molecular composition of sinking particulate P exists. A more systematic study is needed to assess the different environmental parameters that affect the composition of particulate P and result in this variability.

Figure Caption. 31P-NMR spectra of sediment trap material. Peaks corresponding to different compounds are labeled. The spectra were acquired at 202.45 MHz on a GE Omega 500 MHz spectrometer equipped with a 10-mm broadband observe probe (see Methods). Chemical shifts were measured relative to an external orthophosphate standard. Peak areas were calculated by integration. The spectra presented are for (a) plankton tow sample M1, 505 Am; (b) Equatorial Pacific Station EP2, 1024 m; (c) Santa Barbara Basin (SBB-8 #7), 540 m, sampling period July 10-24, 1997; and (d) core top sediments TTN013-69. Note that spectra are plotted for best fit and are not to scale.
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