FRACTIONATION OF SEDIMENT PHOSPHATE WITH CHELATING COMPOUNDS - A SIMPLIFICATION, AND COMPARISON WITH OTHER METHODS

The NTA/EDTA fractionation of sediment-bound, inorganic phosphate was improved and made more effective. The iron-bound phosphate is now extr acted with Ca-EDTA plus dithionite and followed by an extraction of ca lcium-bound phosphate by Na-2-EDTA at pH = 4.5. A comparison is made w ith two other sequential extraction procedures: the SEDEX and the Hiel tjes & Lijklema extractions. The EDTA extractions have an advantage ov er the other two methods.