Sequential fractionation of sediment phosphate

Abstract

By means of sequential extractions with Ca-NTA and EDTA, a separation was performed between Fe(OOH) z P and CaCO 3 z P in a few sediments ; the remaining fraction, considered to be organic phosphate, was quantified as well . We found that with the commonly used method of extraction with NaOH and H2S04, less Fe(OOH) z P and much more CaCO 3 z P was found than with the chelating extractants . The organic phosphate pool in live and dead algal material and in some mud samples was partly hydrolysed and therefore recovered as inorganic phosphates with classical extractions . The difference between chelating extractants and the classical ones is discussed .

Evaluation of a well‐established sequential phosphorus fractionation technique for use in calcite‐rich lake sediments: identification and prevention of artifacts due to apatite formation

“…In sedimentary P speciation, commonly used sequential fractionation techniques have frequently been criticized as giving misleading results due to the generation of new solid phases during the extraction process (Martin et al 1987, Barbanti et al 1994, De Groot and Golterman 1990, Benzing and Richardson 2005. In such cases, one fraction is overestimated at the expense of another.…”

“…Although some authors (Martin et al 1987, Barbanti et al 1994 have argued that the formation of new P phases can be an inherent drawback for the interpretation of some sequential fractionation schemes, systematic investigations of this phenomenon are lacking. Especially, the resorption and/or coprecipitation of phosphate with Ca compounds during alkaline extraction (Hieltjes and Lijklema 1980, De Groot and Golterman 1990, Levy and Schlesinger 1999, Benzing and Richardson 2005 could be important in calcite-rich sediments. Despite this, most studies on hardwater lakes have interpreted high contents of HCl-soluble P in sediment and settling seston as Ca-bound P (e.g., Penn and Auer 1997, Gonsiorczyk et al 1998, Eckert et al 2003.…”

Phosphorus Fractions in Water and Sediment and Their Correlations in Hengshui Lake, China

“…Several extraction techniques have been developed to explicate the chemical nature of sediment phosphates [10,11]. Also, sequential extraction of phosphorus is a very useful tool for characterizing various phosphorus fractions [12][13][14]. In this study, the six-step extraction method proposed by Ruttenberg was adopted [6].…”

Nouvelles connaissances des formes du phosphate : conséquences sur le cycle du phosphate dans les sédiments des eaux douces peu profondes

“…Dans les sédiments, la quantité de Fe(OOH) libre règle la capacité d'adsorption, c'est-à-dire « a » et « b », et par consé-quent « A ». La quantité de Fe(OOH)«P dans les sédiments peut être estimée par extraction au Ca-NTA dans des conditions réductrices (Golterman & Booman 1988, De Groot & Golterman 1990). Nous ne savons pas dans quelle mesure les complexes humiques Fe-P sont impliqués ; les extraits obtenus avec le Ca-NTA sont toujours de couleur brun foncé et des interactions paraissent possibles.…”

“…Les agents chélateurs étant moins agressifs que les produits utilisés classiquement pour les extractions (NaOH et H2SO4), nous pensons que le pool restant est organique, et quantitativement plus important qu'il ne l'a été souvent supposé (de Groot & Golterman 1990). Une grande partie de ce pool restant peut être extraite à l'acide (P-org acidosoluble, POAS) ; cette fraction a été supposée être du CaCC"3 ~ P dans les schémas classiques d'extraction.…”