Evaluation of Phosphorus Fractions in Suspended and Bed Sediments of Rozeh-Chay River

Soil erosion causes the accumulation of phosphorus in the river sediments which may increase the phosphorus release to surface waters. Phosphorus release from sediments has been recognized as a key factor responsible for eutrophication of fresh waters and for this reason knowledge of phosphors concentration and its fractions is very important. The aim of this study was evaluation and comparison of phosphorus fractions in suspended and bed sediments of Rozeh-Chay river, Urmia, west Azarbayjan province, Iran. Six Suspended sediment samples and 19 bed sediment samples were collected from the river and some of physicochemical properties were determined. Phosphorus in sediments was fractionated by sequential extraction method, in which the phosphorus fractions were defined as exchangeable (KCl-P), Fe and Al bound (NaOH-P), Ca-bound (HCl-P), and residual phosphorus (Res-P) fractions. Results indicated that, percent of sand in bed sediments was higher than suspended sediments. But, silt fraction was higher in suspended samples than bed sediments. The organic matter content of the bed sediments was also higher than the suspended sediments. In the bed sediment samples order of phosphorus fractions was HCl-P (54.8%) > Res-P (40.8%) > NaOH-P (3.5%) > KCl-P (0.9%), while for suspended sedimentsthe order was Res-P (64.9%) > HCl-P (31.9%) > NaOH-P (2.8%) > KCl-P (0.4%). Multivariate analysis was used to identify factors which influence the phosphorus fractions. Principal component analysis results indicated that the first four components explained 85.4% of overall variation in sediments properties. Silt, sand and organic matter content seem to play significant role in regulating the distribution of phosphorus fractions in the sediment samples.