Characterization of the sediment
Before starting any experiment all sediment samples was air-dried at
room temperature and ground with pestle and mortar to put sediment
through stainless steel 10 mesh sieve. The sediments physical
composition including clay and silt contents were determined by
hydrometer method and then sand and very find sand (Vfs) were weighed
after washing over sieve and 110 C oven drying. Organic matter (OM)
content was determined with the classical Walkley-Balck procedure
(Rowell, 1994). The activity of H3O+,
pH = [-log (H+)] and conductivity (EC) were
measured in a sediment-solution ratio of 1:5. The acid-base titration
method was used for determination of calcium carbonate equivalents (CCE)
(Rowell, 1994). The activity of calcium carbonate (ACCE) was measured in
ground uniform sediment particles with ammonium oxalate method (Loeppert
and Suarez, 1996).
Sediments were extracted using several single extraction methods that
are summarized in Table 1. Olsen-P and Colwell-P extraction method have
been designed for calcareous soils. Mehlich III-P and Bary II-P have
been designed for acidic soil, and both contain HCl acid and ammonium
fluoride for dissolution of Fe/Al-P minerals such as Strengite,
(FePO4·2H2O) and Variscite,
(AlPO4·2H2O). AB-DTPA extraction method
is chelating agent for Fe, Al, Ca, and Mg and has been shown to be a
good extraction method for acidic and calcareous soils. Morgan-P was
designed for soil with a high association of Ca-P pools and usually
dissolve soluble calcium phosphate (Ahmad and Jones, 1967). 0.1 M NaOH
is for soil and sediment with high Fe/Al-P pools. Chemical analysis of P
was done colorimetrically (Murphy and Riley, 1962).