Estimating Algal Available Phosphorus in Suspended Sediments by Chemical Extraction1
- R. A. Dorich,
- D. W. Nelson and
- L. E. Sommers2
The availability of sediment inorganic phosphorus (Pi) to algae was determined in 28 suspended stream sediments collected from an agricultural watershed in northeastern Indiana by short- (2-d) and longerterm (14-d) incubations. Unincubated sediment was also analyzed for dissolved molybdate reactive Pi (DMRP) and Pi extracted by: (i) sequential NaOH and HCl, (ii) sequential NH4F, NaOH, and HCl, (iii) nitrilotriacetic acid (NTA), (iv) hydroxy-Al resin, and (v) total P. Available P (Paa) measured in sediments by 2-d and 14-d incubations with algae averaged 21 and 25% of total sediment P, respectively. Extraction of sediments with 0.1 M NaOH, 0.5 M NH4F, sequential 0.5 M NH4F + 0.1 M NaOH, NTA, and hydroxy-Al resin removed an average of 36, 22, 31, 45, and 17% of the total P, respectively. Of the extractants tested, NaOH-extractable Pi was significantly correlated with 2-d and 14-d Paa (r = 0.89*** and 0.95***, respectively) but NaOH extraction removed amounts of Pi that exceeded sediment Paa by a relatively constant amount. The results suggest that a single extraction with 0.1 M NaOH can be used to estimate both short- and longer-term Paa in suspended stream sediments derived from noncalcareous soils in the Northcentral USA.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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