HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Figures Only Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ahlgren, J. Articles by Waldebäck, M. Search for Related Content PubMed PubMed Citation Articles by Ahlgren, J. Articles by Waldebäck, M. Agricola Articles by Ahlgren, J. Articles by Waldebäck, M. Related Collections Phosphorus Nuclear Magnetic Resonance, NMR

TECHNICAL REPORTS

Wetlands and Aquatic Processes

Sediment Phosphorus Extractants for Phosphorus-31 Nuclear Magnetic Resonance Analysis

A Quantitative Evaluation

^a Dep. of Physical and Analytical Chemistry, Analytical Chemistry, Uppsala Univ., Box 599, 751 24 Uppsala, Sweden
^b Inst. of Biology, Univ. of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
^c Dep. of Biochemistry and Organic Chemistry, Organic Chemistry, Uppsala Univ., Box 599, 751 24 Uppsala, Sweden
^d Dep. of Ecology and Evolution, Limnology, Uppsala Univ., Box 573, 751 23 Uppsala, Sweden

^* Corresponding author (Monica.Waldeback{at}kemi.uu.se)

Received for publication June 20, 2006.

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
The influence of pre-extractant, extractant, and post-extractant on total extracted amounts of P and organic P compound groups measured with ³¹P nuclear magnetic resonance (³¹P-NMR) in lacustrine sediment was examined. The main extractants investigated were sodium hydroxide (NaOH) and sodium hydroxide ethylenediaminetetraacetic acid (NaOH-EDTA) with bicarbonate buffered dithionite (BD) or EDTA as pre-extractants. Post extractions were conducted using either NaOH or NaOH-EDTA, depending on the main extractant. Results showed that the most efficient combination of extractants for total P yield was NaOH with EDTA as pre-extractant, yielding almost 50% more than the second best procedure. The P compound groups varying the most between the different extraction procedures were polyphosphates and pyrophosphates. NaOH with BD as pre-extractant was the most efficient combination for these compound groups.

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
PHOSPHORUS is most often the limiting nutrient in lakes, and production is often heavily dependent on recycling of P, either within the water column (Hupfer and Lewandowski, 2005) or after sedimentation. The availability of different inorganic sediment P forms for recycling to the water column is fairly well understood (Mortimer, 1941; Rydin, 2000), while few publications exist on the identity and diagenesis of organic P forms (e.g., Hupfer et al., 1995, 2004; Ahlgren et al., 2005; Reitzel et al., 2006a). Since organic P forms represent a major pool of potentially available sediment P (e.g., Turner et al., 2005; Ahlgren et al., 2005; Reitzel et al., 2006a), knowledge is needed for understanding P turnover in aquatic systems to predict, for example, sediment and water response to reduced P loading from urban and farmland areas.

Phosphorus-31 nuclear magnetic resonance (³¹P-NMR) spectroscopy is currently the prevalent method for assessing organic P composition in extracts of natural samples. Phosphorus-31 NMR spectroscopy can be used on both solid samples (solid state ³¹P-NMR) and on samples in solution (high resolution ³¹P-NMR), but due to the inherently low sensitivity of NMR and low natural abundance of P, high-resolution NMR is the preferred method because it allows pre-concentration of the sample before analysis. In common for all uses of high resolution ³¹P-NMR spectroscopy is the need for extraction of P from the original solid matrix, a procedure in which no method has been agreed on unanimously. Variations of this practice center on the use of alkaline extractants, and include NaOH (e.g., Newman and Tate, 1980; Hawkes et al., 1984; Ahlgren et al., 2005) and Bu₄NOH (Emsley and Niazi, 1983). In addition to these extractants, combinations such as NaOH and EDTA (e.g., Cade-Menun and Preston, 1996; Hupfer et al., 1995, 2004; Reitzel et al., 2006b; Ahlgren et al., 2006b), NaOH and NaF (Sumann et al., 1998), and NaOH and Chelex (Gressel et al., 1996) have been employed. Chelex, a cation exchange resin in water solution, has been used separately as well (Adams and Byrne, 1989; Condron et al., 1996; Cade-Menun and Preston, 1996). The few investigations made on lacustrine or marine sediment show the same diversity in use of extractants. Ahlgren et al. (2005) used NaOH alone, while Ingall et al. (1990), Carman et al. (2000), and Reitzel et al. (2006a) used a pre-extraction step with buffered dithionite (BD) before extraction with NaOH. A combination of NaOH and EDTA has also been used, with (Hupfer et al., 1995, 2004; McDowell and Stewart, 2005) or without (Sundareshwar et al., 2001; Halls, 2002; Paytan et al., 2003; Reitzel et al., 2006b; Ahlgren et al., 2006b) pre-extraction with EDTA. These different extractants and combinations of extractants are likely to solubilize different amounts and forms of P from the sediment. Well-known problems such as hydrolysis or decomposition of labile P forms caused by alkaline extractants are also of importance because the extent of such reactions might differ depending on the extractant used. Thus, ³¹P-NMR analysis of a sediment sample may yield different results depending on the procedure used for extraction and this should be considered when evaluating results and drawing conclusions with ecological implications.

The few studies comparing extractants for high-resolution ³¹P-NMR spectroscopy (Cade-Menun and Preston, 1996; Cade-Menun et al., 2002) were made on soil and litter samples, and, to our knowledge, no thorough comparison regarding extraction efficiency has been made on sediment samples, apart from McDowell and Stewart (2005), who investigated the effects of Ca-EDTA-dithionite as a pre-extractant before NaOH-EDTA extraction. The aim of this article is to compare different extraction procedures used for NMR investigation of sediment by evaluating their respective efficiency on both total extracted amount of P and the relative amount of the extracted individual P compound groups.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Sampling
Twelve sediment cores were collected with a gravity core sampler (Willner sampler) at a depth of 16 m within an accumulation bottom area (50 m²) in the moderately eutrophic Lake Erken (Sweden) in February 2005. The 0- to 2-cm layer of the cores was collected, pooled, and homogenized to obtain a representative sample of sufficient size for extraction. The sediment in this layer has a total P concentration of 1.6 mg g^–1 dry weight, and a water content of 93%. The average total P concentration in the lake water is 27 µg L^–1. The surface area of the lake is 24 km², and mean and maximum depths are 9 and 21 m, respectively. The drainage area (137 km²) is mostly forested and consists of nutrient-rich glacial and post-glacial clay deposits. The lake has been studied extensively, and has been in a stable trophic state since observations began in 1930. During summer stratification, bottom water occasionally becomes anoxic.

Extraction
Two main extractants were used: 0.1 M NaOH solution (p.a., EKA Bohus-Sweden) and a 1:1 mixture of 0.25 M NaOH and 0.05 M EDTA (di-sodium salt, Merck, Switzerland). For pre-extraction a 0.067 M EDTA and a BD solution containing 0.11 M NaHCO₃ (Merck, Switzerland) and 0.11 M Na₂S₂O₄ (Merck, Switzerland) were used. The various extraction procedures are presented in Table 1.

All extractions were made on 15 g of wet sediment. The sediment to extractant ratio was 1:3 w/v. All samples were extracted at room temperature for 16 h in the main and post-extraction steps, and the pre-extractions were performed for 30 min (EDTA) or 1 h (BD). The pre-extractants were removed by centrifugation before the addition of the main extractant. After centrifugation, the main extractant supernatant was concentrated 25 times by rotary evaporation at 35°C. Three replicates were made of each extraction sequence to have a basis for statistical evaluation. The concentrated extracts were frozen until analysis, a procedure proven not to affect the extracted P compounds (Hupfer et al., 2004). Aluminum, Fe, Mn, and total P amounts in the extracts were measured by inductively coupled plasma–atomic emission spectrometry (ICP–AES).

Phosphorus-31 Nuclear Magnetic Resonance Analysis
Before ³¹P-NMR measurement, a small amount of BD solution was added to the extracts in a 10% (v/v) ratio to reduce Fe(III) to Fe(II), as the paramagnetic Fe(III) otherwise could interfere with the NMR runs (Vassallo et al., 1987). The BD and EDTA pre-extractants were not suitable for ³¹P-NMR analysis, due to low concentrations or interfering ions.

Assignment of peaks was done from spectra of sediment extracts spiked with standard solutions (Na₂HPO₄·7H₂O for orthophosphate and Na₂P₂O₇·10H₂O for pyrophosphate), added to one of the sediment extracts, as well as comparisons with literature (e.g., Hupfer et al., 1995; Cade-Menun and Preston, 1996; Makarov et al., 2002; Turner et al., 2003). The ³¹P-NMR spectra were measured at 121.5 MHz on a Varian MercuryPlus NMR spectrometer (Varian, Palo Alto, CA) at ambient temperature. An amount of D₂O sufficient to obtain a stable lock signal was added to the extracts before measurement. Spectra were recorded using a 63° observe pulse, acquisition time 0.4 s, relaxation delay 1.2 s, acquiring around 30 000 transients (12 h). Chemical shifts were indirectly referenced to external 85% H₃PO₄ (at = 0.0) via the lock signal. To obtain peak areas, peaks in the raw spectrum, with a signal to noise ratio exceeding 4, were fitted with Lorentzian line shapes using the deconvolution subroutine of the NMR software (Vnmr 6.1C; Varian Inc., 1998). From these peak areas, the contribution of individual P compound groups was calculated relative to total extracted P.

	RESULTS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Seven P-containing groups were found in total: orthophosphate (Ortho-P); orthophosphate monoesters (Mono-P); three different compound groups within the orthophosphate diester area–most likely deoxyribonucleic acid P (DNA-P), P lipids (Lipid-P), and a signal possibly caused by teichoic acid P (Teichoic-P) but which could also be another form of phospholipids (Makarov et al., 2002), as well as pyrophosphate (Pyro-P) and polyphosphate middle and end groups (Poly-P), which were not found in all extracts (Fig. 1).

View larger version (15K): [in this window] [in a new window]   Fig. 1. Typical spectra from the various extractants of the 0- to 2-cm layer of Lake Erken sediments.

View larger version (9K): [in this window] [in a new window]   Fig. 2. Interaction plot, with standard deviations, of the main extractants and their dependence on pre-extraction procedures (from the top to the bottom, EDTA, BD, and none) for the total extracted amount of P. BD, bicarbonate buffered dithionite.

The other identified compound groups showed less variation between the various extraction procedures, but the relative order of magnitude was the same for most of the extractants (Table 2).

To facilitate interpretation of the relative data regarding the organic P groups in Table 2, a principal components analysis (PCA) was performed (Fig. 3), using The Unscrambler 7.6 (ASA Camo, Oslo, Norway). This confirmed that the extraction procedures differing most from those used were NaOH with BD as pre-extraction and NaOH without pre-extraction (A in Fig. 3), and that what distinguished these extraction procedures was related mainly to Pyro-P and Poly-P. Both procedures gave a higher yield of Pyro-P, and NaOH with BD as pre-extractant gave a higher yield of Poly-P as well (B in Fig. 3).

View larger version (9K): [in this window] [in a new window]   Fig. 3. Principal components analysis (PCA) of the individual organic P groups extracted by the various extractants. In the PCA, the triplicate pre-extraction procedures are labeled: A = None, B = BD, C = EDTA, and the triplicates of the main extraction procedures: 1 = NaOH, 2 = NaOH-EDTA. The scoreplot (to the left) indicates how the main extractants vary from each other, and the loading plot (to the right) indicates on which organic P compounds this depends. BD, bicarbonate buffered dithionite.

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

The different total P sediment extraction efficiency found in this study agrees well with similar investigations made on soil and litter (Cade-Menun and Preston, 1996; Cade-Menun et al., 2002), proving that NaOH in combination with EDTA was more efficient than NaOH alone. However, these studies were done without any pre-extraction step, a procedure shown here to have a substantial impact on P extraction efficiency. While NaOH-EDTA (T3, Table 2) can extract more than NaOH with no pre-extractant used (T1 and T2), the use of a pre-extractant (BD or EDTA) makes NaOH (T4 and T6) more efficient than NaOH-EDTA for the sediment samples. The increased efficiency when using pre-extractants, as well as the difference in efficiency between NaOH-EDTA and NaOH, might be explained by the structure of P compounds in the sediment, in particular the way they are adsorbed to or incorporated in mineral and organic particles. The most common interaction between P compounds and mineral particles in sediment or soil with lower than neutral pH is via adsorption to Fe or Al oxides. This adsorption occurs between phosphate groups of the organic P compounds and the oxide, through ligand exchange between water and hydroxide ion groups on the surface of the mineral particles (Parfitt et al., 1976; Goldberg and Sposito, 1985; Celi and Barberis, 2005). Proof of this is the formation of Fe-O-P bonds from P = O and P-O shown by Fourier-transform infrared spectroscopy (Celi et al., 1999).

The principle of using an alkali extractant is that the hydroxide ion will bind to the metal ion and release the phosphorus compound into the extraction solution. In addition, increased pH leads to formation of repulsive forces between the highly negative P compounds and the mineral particle surfaces, which become progressively more negative as pH increases. This leads to decreased adsorption. The addition of EDTA to the extractant should generally give increased extraction efficiency since EDTA will chelate polyvalent metal ions and thus help release more P compounds into solution (e.g., Bowman and Moir, 1993; Cade-Menun and Preston, 1996). This effect is observed in this study, with the combination of NaOH-EDTA extracting almost twice as much P as NaOH alone.

Both of the pre-extractants used in this study will affect the metal ions of the mineral surfaces; EDTA, as mentioned, will chelate them, while the BD solution will reduce Fe and Mn to states more ready to release adsorbed organic P compounds. As shown in Table 2, EDTA seems to be the most efficient pre-extraction solvent of those investigated, in terms of P recovered in the following extraction steps. The reason for this is most likely that the organic P compounds are most commonly adsorbed to mineral particles via Fe ions, and EDTA is more efficient than BD in removing these from the solution (Table 3, T6 and T7 vs. T4 and T5). When Fe and other polyvalent ions functioning as bridges between organic P compounds and mineral surfaces are moved into solution, they are replaced with monovalent ions such as sodium (Turner et al., 2005). These are much less efficient in retaining organic P compounds, which most likely explains the increased extraction yields found with NaOH after the use of pre-extractants. The benefits of pre-extraction with EDTA have been shown before (Hupfer et al., 1995, 2004; McDowell and Stewart, 2005). These studies used it primarily to improve on the quality of the spectra, and the efficiency of the extraction was not prioritized. They used NaOH-EDTA as a main extractant instead of NaOH, which was shown to be more efficient in this study. The fact that NaOH is more efficient than NaOH-EDTA (Table 2) when a pre-extractant is used is interesting and warrants further investigation. The additional P extracted with NaOH after pre-extraction with EDTA is apparently also of organic origin because the additional organic P compounds have a similar composition when compared with the other extraction procedures, and not only an increased share of Ortho-P. This means that NaOH after pre-extraction with EDTA extracts from the same P pool as the other extractants, only more efficient. When comparing with traditional P fractionation (e.g., Psenner et al., 1988), EDTA followed by NaOH seems to extract a larger portion of total sediment P. This indicates that the EDTA-NaOH procedure extracts a part of the total sediment P previously referred to as residual P. It is also very likely that the additional extracted organic P is connected to Al in the sediment, because this is the extraction procedure most efficient in extracting Al (Table 3). This may depend on the clay content of the sediment, as clay minerals adsorb organic P compounds with higher affinity than pure Fe and Al oxides (Celi and Barberis, 2005), which is related to the active Al content of the clay minerals (Anderson and Arlidge, 1962).

The ability of extractants to remove all potentially extractable organic P from the sediment can, to some extent, be surmised by the post-extractions. In the case of NaOH without pre-extraction (T2), a post-extraction with NaOH-EDTA (T2) yields more P than the first step, indicating that NaOH only manages to extract a fraction of what potentially can be extracted from the sediment. When using pre-extractants (T4 and T6), the post-extraction steps yielded much less than the first main step of the extraction, especially in the case of NaOH after EDTA as pre-extraction (T6). The sequential use of NaOH-EDTA after this yielded only a negligible amount of P, indicating that all extractable P had been recovered from the sediment sample.

In terms of the individual P compound groups, the most notable difference is the lack of Poly-P extracted by NaOH (T1, Table 2). This might indicate degradation of this compound group when using NaOH as an extractant without pre-extraction (e.g., Hupfer et al., 1995). Most likely the Poly-P is degraded into Pyro-P, explaining the higher yield of this P compound group when Poly-P is absent. This process is likely connected to the presence of Ca ions, because these catalyze the hydrolysis of Poly-P (Van Wazer, 1958). The use of a pre-extractant apparently reduces this phenomenon. The most efficient extraction method for Pyro-P and Poly-P is NaOH with BD as a pre-extractant (T4), and this method thus may be preferred in cases, where these compound groups are the main target of the study. It should be noted that if EDTA is to be used, Na-EDTA is preferred if Poly-P is of interest, as Ca-EDTA (McDowell and Stewart 2005) will not chelate Ca in the extract.

Previous investigations have shown that the combination of NaOH-EDTA can give broader peaks and thus spectra are more difficult to interpret than those detected with extraction procedures giving lower total yield (Cade-Menun and Preston, 1996). However, as can be seen in Fig. 1, the spectra from the investigated extractions are all sufficient for quantitative evaluation. Furthermore, as the use of ³¹P-NMR for assessing the P composition of natural samples has been proven with regard to precision and reliability (Ahlgren et al., 2006a), the results presented here must be considered certain enough to make valid comparisons and conclusions. In spite of this, evaluation of the spectra should be made with care, because it is obvious that different extraction methods can give different results due to the potential varying extraction efficiency of the different extractants with respect to individual P compound groups. Hydrolysis or decomposition under the influence of alkaline extractants may also give rise to artifacts in evaluation. While the highest yield is given by NaOH after pre-extraction with EDTA (T6), this extraction procedure might not be ideal for all applications, e.g., if the aim of the investigation would be directed toward Poly-P. In all cases, it is important to be aware of the potentially different results various extraction procedures can produce.

In summary, using NaOH with EDTA as pre-extractant will maximize total extracted organic P, and using NaOH with BD as a pre-extractant will optimize the Poly-P yield.

	ACKNOWLEDGMENTS

 
Kasper Reitzel was supported by a post doctoral grant from the Carlsberg Foundation and by the Danish Lake Restoration Center (CLEAR) funded by the Villum Kann Rasmussen Foundation.

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 

• Adams, M.A., and L.T. Byrne. 1989. ³¹P-NMR analysis of phosphorus compounds in extracts of surface soils from selected Karri (Eucalyptus diversicolor F. Muell.) forests. Soil Biol. Biochem. 21:523–528.[CrossRef]
• Ahlgren, J., K. Reitzel, R. Danielsson, A. Gogoll, and E. Rydin. 2006a. Biogenic phosphorus in oligotrophic mountain lake sediments; differences in composition measured with NMR spectroscopy. Water Res. 40:3705–3712.[Medline]
• Ahlgren, J., K. Reitzel, L. Tranvik, A. Gogoll, and E. Rydin. 2006b. Degradation of organic phosphorus compounds in anoxic Baltic Sea sediments: A ³¹P nuclear magnetic resonance study. Limnol. Oceanogr. 51(5):2341–2348.
• Ahlgren, J., L. Tranvik, A. Gogoll, M. Waldebäck, K. Markides, and E. Rydin. 2005. Sediment depth attenuation of biogenic phosphorus compounds measured by ³¹P NMR. Environ. Sci. Technol. 39:867–872.[Medline]
• Anderson, G., and E.Z. Arlidge. 1962. The adsorption of inositol phosphates and glycerophoshpate by soil clays, clay minerals, and hydrated sesquioxides in acid media. J. Soil Sci. 13:216–224.[CrossRef]
• Bowman, R.A., and J.O. Moir. 1993. Basic EDTA as an extractant for soil organic phosphorus. Soil Sci. Soc. Am. J. 57(6):1516–1518.[Abstract/Free Full Text]
• Cade-Menun, B.J., C.W. Liu, R. Nunlist, and J.G. McColl. 2002. Soil and litter phosphorus-31 nuclear magnetic resonance spectroscopy: Extractants, metals, and phosphorus relaxation times. J. Environ. Qual. 31(2):457–465.[Web of Science]
• Cade-Menun, B.J., and C.M. Preston. 1996. A comparison of soil extraction procedures for ³¹P NMR spectroscopy. Soil Sci. 161:770–785.[CrossRef]
• Carman, R., G. Edlund, and C. Damberg. 2000. Distribution of organic and inorganic phosphorus compounds in marine and lacustrine sediments: A ³¹P NMR study. Chem. Geol. 163:101–114.[CrossRef][Web of Science]
• Celi, L., and E. Barberis. 2005. Abiotic stabilization of organic phosphorus. p. 113–132. In B.L. Turner et al. (ed.) Organic phosphorus in the environment. CABI Publ., Wallingford, UK.
• Celi, L., S. Lamacchia, F.A. Marsan, and E. Barberis. 1999. Interaction of inositol hexaphosphate on clays: Adsorption and charging phenomena. Soil Sci. 164:574–585.[CrossRef]
• Condron, L.M., M.R. Davis, R.H. Newman, and I.S. Cornforth. 1996. Influence of conifers on the forms of phosphorus in selected New Zealand grassland soils. Biol. Fertil. Soils 21:37–42.[CrossRef]
• Emsley, J., and S. Niazi. 1983. The analysis of soil phosphorus by ICP and phosphorus-31 NMR spectroscopy. Phosphorus Sulfur Relat. Elem. 16:303–312.
• Goldberg, S., and G. Sposito. 1985. On the mechanism of specific phosphate adsorption by hydroxylated mineral surfaces: A review. Commun. Soil Sci. Plant Anal. 16:801–821.[Web of Science]
• Gressel, N., J.G. McColl, C.M. Preston, R.H. Newman, and R.F. Powers. 1996. Linkages between phosphorus transformations and carbon decomposition in a forest soil. Biogeochemistry 33:97–123.
• Halls, J.N. 2002. A spatial sensitivity analysis of land use characteristics and phosphorus levels in small tidal creek estuaries of North Carolina, USA. J. Coastal Res. 36:340–351.
• Hawkes, G.E., D.S. Powlson, E.W. Randall, and K.R. Tate. 1984. A phosphorus-31 nuclear magnetic resonance study of the phosphorus species in alkali extracts of soils from long-term field experiments. J. Soil Sci. 35:35–45.[CrossRef]
• Hupfer, M., R. Gachter, and H. Rüegger. 1995. Polyphosphate in lake sediments: ³¹P NMR-spectroscopy as a tool for its identification. Limnol. Oceanogr. 40:610–617.
• Hupfer, M., and J. Lewandowski. 2005. Retention and early diagenetic transformation of phosphorus in Lake Arendsee (Germany)—Consequences for management strategies. Arch. Hydrobiol. 164(2):143–167.[CrossRef]
• Hupfer, M., B. Rube, and P. Schmieder. 2004. Origin and diagenesis of polyphosphate in lake sediments: A ³¹P NMR study. Limnol. Oceanogr. 49:1–10.
• Ingall, E.D., P.A. Schroeder, and R.A. Berner. 1990. The nature of organic phosphorus in marine sediments: New insights from ³¹P NMR. Geochim. Cosmochim. Acta 54:2617–2620.[CrossRef][Web of Science]
• Makarov, M.I., L. Haumaier, and W. Zech. 2002. Nature of soil organic phosphorus: An assessment of peak assignments in the diester region of ³¹P NMR spectra. Soil Biol. Biochem. 34:1467–1477.[CrossRef]
• McDowell, R.W., and I. Stewart. 2005. An improved technique for the determination of organic phosphorus in sediments and soils by ³¹P nuclear magnetic resonance spectroscopy. Chem. Ecol. 21(1):11–22.[CrossRef]
• Mortimer, C.H. 1941. The exchange of dissolved substances between mud and water in lakes. J. Ecol. 29:280–329.[CrossRef][Web of Science]
• Newman, R.H., and K.R. Tate. 1980. Soil phosphorus characterization by phosphorus-31 nuclear magnetic resonance. Commun. Soil Sci. Plant Anal. 11:835–842.[Web of Science]
• Parfitt, R.L., J.D. Russel, and V.C. Farmer. 1976. Confirmation of the surface structures of goethite (-FeOOH) and phosphated goethite by infrared spectroscopy. J. Chem. Soc., Faraday Trans. 172:1082–1087.
• Paytan, A., B.J. Cade-Menun, K. McLaughlin, and K.L. Faul. 2003. Selective phosphorus regeneration of sinking marine particles: Evidence from ³¹P NMR. Mar. Chem. 82:55–70.[CrossRef][Web of Science]
• Psenner, R., B. Boström, M. Dinka, K. Pettersson, R. Pucsko, and M. Sager. 1988. Fractionation of phosphorus in suspended matter and sediment. Arch. Hydrobiol. Beih. Ergebn. Limnol. 30:98–110.
• Reitzel, K., J. Ahlgren, H. De Brabandere, M. Waldebäck, A. Gogoll, L. Tranvik, and E. Rydin. 2006a. Degradation rates of organic phosphorus in lake sediments. Biogeochemistry (in press).
• Reitzel, K., J. Ahlgren, A. Gogoll, and E. Rydin. 2006b. Effects of aluminum treatment on phosphorus, carbon, and nitrogen distribution in lake sediment: A ³¹P NMR study. Water Res. 40:647–654.[Medline]
• Rydin, E. 2000. Potentially mobile phosphorus in Lake Erken sediment. Water Res. 34:2037–2042.
• Sumann, M., W. Amelung, L. Haumaier, and W. Zech. 1998. Climatic effects on soil organic phosphorus in the North American Great Plains identified by phosphorus-31 nuclear magnetic resonance. Soil Sci. Soc. Am. J. 62:1580–1586.[Abstract/Free Full Text]
• Sundareshwar, P.V., J.T. Morris, P.J. Pellechia, H.J. Cohen, D.E. Porter, and B.C. Jones. 2001. Occurrence and ecological implications of pyrophosphate in estuaries. Limnol. Oceanogr. 46:1570–1577.
• Turner, B.L., B.J. Cade-Menun, L.M. Condron, and S. Newman. 2005. Extraction of soil organic phosphorus. Talanta 66:294–306.
• Turner, B.L., N. Mahieu, and L.M. Condron. 2003. Phosphorus-31 nuclear magnetic resonance spectral assignments of phosphorus compounds in soil NaOH-EDTA extracts. Soil Sci. Soc. Am. J. 67:497–510.[Abstract/Free Full Text]
• Van Wazer, J.R. 1958. Structure and properties of condensed phosphates. p. 452–459. In J.R. Van Wazer (ed.) Phosphorus and its compounds. Vol. 1. John Wiley & Sons, New York.
• Varian, Inc. 1998. Vnmr ver. 6.1. Varian Inc., Palo Alto, CA.
• Vassallo, A.M., M.A. Wilson, P.J. Collin, J.M. Oades, A.G. Waters, and R.L. Malcolm. 1987. Structural analysis of geochemical samples by solid-state nuclear magnetic resonance spectrometry: Role of paramagnetic material. Anal. Chem. 59:558–562.

This article has been cited by other articles:

				Z. He, C. W. Honeycutt, T. S. Griffin, B. J. Cade-Menun, P. J. Pellechia, and Z. Dou Phosphorus Forms in Conventional and Organic Dairy Manure Identified by Solution and Solid State P-31 NMR Spectroscopy J. Environ. Qual., July 23, 2009; 38(5): 1909 - 1918. [Abstract] [Full Text] [PDF]

				R. Zhang, F. Wu, Z. He, J. Zheng, B. Song, and L. Jin Phosphorus Composition in Sediments from Seven Different Trophic Lakes, China: A Phosphorus-31 NMR Study J. Environ. Qual., January 13, 2009; 38(1): 353 - 359. [Abstract] [Full Text] [PDF]

This Article Abstract Figures Only Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ahlgren, J. Articles by Waldebäck, M. Search for Related Content PubMed PubMed Citation Articles by Ahlgren, J. Articles by Waldebäck, M. Agricola Articles by Ahlgren, J. Articles by Waldebäck, M. Related Collections Phosphorus Nuclear Magnetic Resonance, NMR