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Characterization of Inorganic Phosphate in Noncalcareous Lake Sediments

1971; Wiley; Volume: 35; Issue: 4 Linguagem: Inglês

10.2136/sssaj1971.03615995003500040024x

1435-0661

J. D. H. Williams, J. K. Syers, David E. Armstrong, R. F. Harris,

Soil and Water Nutrient Dynamics

Abstract Inorganic P added with 0.5 M NH 4 F to noncalcareous sediments was recovered in the NH 4 F and succeeding 0.1 N NaOH extractions. Values of NH 4 F‐P, corrected on the basis of the recovery of P added with the NH 4 F reagent, underestimated the total amount of inorganic P capable of interacting with NH 4 F, but by less than the corresponding uncorrected values. The amounts of inorganic P extracted by 0.5 M NH 4 F followed by 0.1 N NaOH, by citrate‐dithionite‐bicarbonate, and by 0.3 N 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 NH 4 F‐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 NH 4 F‐Al was moderately well correlated with oxalate‐Al ( r = 0.70) neither variable was related to NH 4 F‐P. The very high correlations between NH 4 F‐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.