Phosphorus Fractionation in River Sediments, Hamadan, Western Iran

Abstract

Phosphorus (P) in sediments was fractionated by sequential extraction procedure, in which the P fractions were experimentally defined as exchangeable (KCl-P), Fe- and Al-bound (NaOH-P), Ca-bound (HCl-P), and residual P (Res-P) fractions. In all sediment samples the rank order of P-fractions was HCl-P > Res-P > NaOH-P > KCl-P. The loosely sorbed P (KCl-P) represented 6.7% of sedimentary inorganic P, while Res-P ranged from 27.1–61.2%. The Ca-bound P showed considerable contribution (32.8–52.0%) to the sedimentary inorganic P. Relative NaOH-P in sediments ranged from 6.6 to 13.5%. The dominant P fraction in the sediments generally changed from Res-P at upstream to HCl-P at downstream, suggesting that more P and Ca are added by point and diffuse sources along the river. Multivariate analysis was used to identify the factors which influence the P fractions. The principal component analysis showed that the first four factors explained 82.8% of the overall variation. Carbonate calcium and silt seem to play a significant role in regulating the NaOH-P fraction, while KCl-P and HCl-P are affected by EC.