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Total Phosphorus Determination in Colloid‐Containing Soil Solutions by Enhanced Persulfate Digestion
Author(s) -
Pagel Holger,
Ilg Katrin,
Siemens Jan,
Kaupenjohann Martin
Publication year - 2008
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2007.0178n
Subject(s) - persulfate , chemistry , gibbsite , goethite , aqueous solution , digestion (alchemy) , nuclear chemistry , illite , montmorillonite , phosphorus , chromatography , adsorption , inorganic chemistry , mineralogy , kaolinite , clay minerals , biochemistry , organic chemistry , catalysis
It is unclear whether persulfate digestions completely liberate P associated with mineral colloids in soil solutions and aqueous soil extracts. We tested a modified persulfate digestion using aqueous soil extracts and suspensions of goethite, gibbsite, illite, and montmorillonite that were exposed to 24 μmol P L −1 as orthophosphate (ortho‐P) or myo‐inositol hexaphosphate (IHP). Digestion was performed by autoclaving (121°C, 60 min) 5 mL of extract or suspension after the addition of 1 mL of solution, which contained 150 mmol L −1 K 2 O 8 S 2 and 180 mmol L −1 H 2 SO 4 Subsequently, 0.7 mL of 188 mmol L −1 ascorbic acid was added and the sample was heated in a water bath at 95°C for 60 min. For the samples where P was sorbed onto goethite and gibbsite, recoveries of total P were 97.2 ± 3.7% (ortho‐P) and 102 ± 3.7% (IHP). For the samples where P was sorbed onto clay minerals, average total P recoveries were 99.2 ± 5.1% (ortho‐P) and 106 ± 3.0% (IHP). No differences between total P concentrations measured in persulfate‐digested soil extracts or with an additional digestion with HF and HNO 3 were detected.