Step 1:- Acid-soluble fraction-bound to carbonates
Three 0.5 g dry sediment samples were each
placed into a 50 mL polypropylene centrifuge tube to
which 20 ml of 0.11 mol/L of acetic acid was added,
capped and then shaken at 30 rpm for 16 hr at room
temperature. The extract was separated from the solid
phase by centrifugation at 3000 rpm (20 cm rotar
radius) for 20 min. The supernatant was decanted and
stored in a refrigerator at 4 oC prior to analysis. The
residue was washed with 10 mL of deionized water,
shaken again for 15 min and then centrifuged for 20
min at 3,000 rpm (20 cm rotar radius). The
supernatant was then removed leaving the pellet for
the second step extraction.