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Fractionation of phosphate in marine aquaculture sediments: optimization of the ethylenediaminetetraacetic acid method and comparison with other procedures
Author(s) -
Kassila Jawad,
Hussenot Jérôme
Publication year - 2004
Publication title -
aquaculture research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.646
H-Index - 89
eISSN - 1365-2109
pISSN - 1355-557X
DOI - 10.1111/j.1365-2109.2004.01157.x
Subject(s) - ethylenediaminetetraacetic acid , fractionation , phosphate , extraction (chemistry) , dithionite , chromatography , environmental chemistry , nuclear chemistry , chemistry , biology , chelation , inorganic chemistry , biochemistry , enzyme
The ethylenediaminetetraacetic acid (EDTA) method was compared with two other P‐fractionation methods, Sedex and Hieltjes & Lijklema (H. & L.), in order to choose a suitable method that extracts better the inorganic (inorg‐P) and organic (org‐P) phosphate from marine aquaculture sediments. The EDTA method gave reliable results and did not change the P‐composition of the sediments during the analysis. The Sedex method can be improved if the quantity of pre‐extracted org‐P is separately determined after digestion, and the org‐P can thereby corrected. The Sedex method underestimates the org‐P present in the sediments (−59%), whereas the calcium‐bound phosphate (CaCO 3 ≈P) is overestimated (+17%) in comparison with the EDTA method. The NaOH and HCl used in H. & L. method are not specific to extract inorg‐P from the sediments. To provide optimal extractions of inorg‐P in muddy sediments containing 1% org‐C and 15% CaCO 3 , the EDTA method was optimized according to extraction times, dithionite concentration and solute/solid ratio. Five extractions of 2‐h duration each with Ca‐EDTA are required to extract more than 95% of the iron‐bound phosphate (Fe(OOH)≈P) while the extraction of CaCO 3 ≈P with Na‐EDTA takes more than 96 h. The concentration of dithionite up to 1% did not influence the amount of P and Fe extracted ( P =0.098 and 0.174 respectively), whereas a solute/solid ratio of 40:1 was best suitable for the optimal extraction of Fe(OOH)≈P. These conditions can be applied to analyse P composition of other marine pond sediments having similar texture and chemical composition.