Characterization of Inorganic Phosphate in Noncalcareous Lake Sediments

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Abstract
Inorganic P added with 0.5M NH4F to noncalcareous sediments was recovered in the NH4F and succeeding 0.1N NaOH extractions. Values of NH4F‐P, corrected on the basis of the recovery of P added with the NH4F reagent, underestimated the total amount of inorganic P capable of interacting with NH4F, but by less than the corresponding uncorrected values. The amounts of inorganic P extracted by 0.5M NH4F followed by 0.1N NaOH, by citrate‐dithionite‐bicarbonate, and by 0.3N NaOH were very similar, the means of the three quantities varying by only 11 ppm. Oxalate‐extractable inorganic P exceeded these quantities by an average of 250 ppm but exceeded the sum of NH4F‐P, 1st NaOH‐P, and reductant‐soluble P by an average of 60 ppm, the difference in the latter comparison being ascribed to the partial or complete dissolution of apatite by the oxalate reagent. Although NH4F‐Al was moderately well correlated with oxalate‐Al (r = 0.70) neither variable was related to NH4F‐P. The very high correlations between NH4F‐P, 1st NaOH‐P, and reductant‐soluble P, on the one hand, and between these three fractions and oxalate‐ and citrate‐dithionite‐bicarbonate‐extractable Fe, on the other, indicate a common origin for the inorganic P in the three fractions as part of a short range order Fe‐rich complex. Apatite was low in all sediments.
Funding Information
  • Federal Water Quality Admin. (WP-01470-01)
  • Engineering Exp. Sta
  • Office of Water Resources Res. (14-01-0001-1961, B-022WIS)
  • Univ. of Wisconsin Water Resources Center

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