Sequential fractionation of phosphorus in lake sediments of Northern Greece

The amounts and forms of potentially mobile P in surface sediments from two lakes, Volvi and Koronia, located in Northern Greece were evaluated using a sequential chemical extraction. Five sedimentary P reservoirs were separately quantified: loosely sorbed P (NH₄Cl-P); iron associated P (BD-P); calcium bound P (HCl-P); metal oxide bound P (NaOH-P) and residual P (organic and refractory P). Samples were taken in two seasons and the average concentration of the fractions of phosphorus were calculated. The results indicated that the TP content and chemically extractable phosphorus in the sediments of Koronia Lake were higher than those of Volvi Lake. Sediment TP was also strongly and positively correlated with sediment Fe. Fine-sized sediments exhibited significantly higher concentrations for both lakes than the sand fraction. The P in the surface sediment mainly consisted of HCl-P and Res-P, while NH₄Cl-P and BD-P only constituted a minor part. The rank order of the different P extracts was the same for the two lakes and was Residual-P > HCl-P > NaOH-P > BD-P > NH₄Cl-P.