Dissolved organic phosphorus concentrations

Because the application of NMR spectroscopy to environmental samples is relatively new, we focused our studies on the identification and characterization of DOP by 31P FT-NMR spectroscopy. Ultrafiltration and reverse osmosis concentration techniques were employed to increase the dissolved organic phosphorus concentrations to the detection level of 31P FT-NMR techniques (approximately 10-20 mg of P/L). With these concentration methods a DOP concentration factor of up to 2000 is obtainable. This chapter reports the use of 31P FT-NMR spectroscopy in the analysis of DOP. In... 

Lake-Water Samples. Ten lake-water samples were collected from September 1990 to May 1991. The total soluble phosphorus concentration for the concentrated samples ranged from 23.8 to 60.8 mg of P/L, and the soluble reactive phosphorus concentrations ranged from 1.0 to 18.1 mg of P/L (Table I). Dissolved organic carbon concentration values for the concentrated samples ranged from 5000 to 20,000 mg of C/L. The signal-to-noise ratios from 12-14-h runs achieved for the NMR spectra range from 3.0 to 7.0. The pH of the concentrated samples after the addition of FeEDTA fell between the values of 7.00 and 8.00. Addition of the FeEDTA increased the pH by only a few tenths of a pH unit. 

Organic P also occurs in dissolved forms, particularly in euphoric surface waters, where it may exceed inorganic phosphate concentrations (Smith et al., 1986). The labile fraction of dissolved organic phosphorus may be the most rapidly cycled marine phosphate pool (Orrett and Karl, 1987 Jackson and Williams, 1985). This pool may also provide a "buffer", providing utilizable phosphate to phytoplankton between episodic inputs from other sources (Jackson and Williams, 1985). 

Concentrations of dissolved organic material expressed as dissolved organic carbon (DOC), dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) in mg m (ppb) for surface microlayer (M) and subsurface water (Sub) samples... 

Cooper, W.T. (2002) Electrospray ionization transform ion cyclotron resonance mass spectrometry of dissolved organic phosphorus species in a treatment wetland after selective isolation and concentration. Analytical Chemistry 74, 500-505. 

Dissolved organic matter concentration and isolation of filterable organic phosphorus from surface waters at four sites in the ENR were carried out and the resulting concentrates analysed by ultrahigh-resolution FT-ICR with electrospray ionization. These sites represent a gradation in water residence time within the wetland and include the inflow, the conveyance linking Cells 1 and 3, the output from Cell 4, and the integrated ENR outflow (see Fig. 3.9 for reference). Detailed mass analysis of each peak in these spectra allowed several... 

Fig. 3.20. Electrospray ion cyclotron resonance mass spectra of dissolved organic matter isolated from Experimental Nutrient Removal (ENR) wetland outflow before (top) and after (bottom) selective organic phosphorus concentration. Reprinted from Llewelyn etal. (2002) with permission from the American Chemical Society.

The concentrations of dissolved inorganic phosphorus (DIP) and dissolved organic phosphorus (DOP) in the ECS ranged from 0.05 to 3.01 and from 0.01 to 0.54 imol/L, respectively. The concentrations of DIP and DOP in the inner shelf were significantly higher than those in the middle and the outer shelves. The concentrations of DIP were significantly higher than those... 

Reverse osmosis has been used as a concentration technique for dissolved organic phosphorus in fresh waters [47]. Prefiltered water (100 L) was concentrated to 2.5 L prior to analysis of the >300 Da material that was retained. An intermediate cation exchange step was required to prevent precipitation of Ca and Mg salts. Nanny et al. used a combination of tangential flow filtration with membranes of 30 and 1 kDa cutoff and reverse osmosis to achieve preconcentration of up to 500 to 1.8 L [48,49]. 

Fig. 2.5 Timeseries of daily phytoplankton, zooplankton, dissolved organic carbon, detritus, and phosphorus concentration, and photosyntesis over one model year at two location the shelf seas of the Pacific Ocean, 170 E 65 N and 140 E 10 S.

For these reasons, numerous attempts have been made to identify and characterize DOP, but with little success because it is usually present in very low concentrations. Typical values in lake waters range from 5 to 100 xg of P/L in oligotrophic to eutrophic systems. Colorimetric methods have been used extensively to detect and differentiate between soluble reactive phosphorus (SRP) and soluble unreactive phosphorus (SUP) at concentrations as low as 10 xg of P/L (I). SRP is generally considered to consist of only orthophosphate compounds, whereas SUP is composed of all other phosphorus species, primarily organic phosphorus compounds. The sum of SRP and SUP is equal to the total soluble phosphorus (TSP). These methods were used to study the dynamics of bulk phosphorus fractionation between the sediments, suspended particulate matter, the biota, and the dissolved fraction (2). Despite these studies, very little is known regarding the identity and characteristics of the DOP in the hydrosphere. 

Fig. 2 Vertical distribution of temperature (T), salinity (S), dissolved oxygen (02), hydrogen sulfide (H2S), dissolved manganese (Mn diss), nitrate (NO3), nitrite (NO2), ammonia (NH4), phosphate (P04), silicate (Si), pH (pH), total alkalinity (Aik), methane (CH4), organic phosphorus (Porg), organic nitrogen (Norg), and urea (Urea), at a station near Gelendzhik (St. 2618, September, 2006). Concentrations of chemical parameters are in aM. Distributions are plotted versus depth (m) at the top and versus density (agy kg nr3) at the bottom...

---