Study on different forms and phosphorus distribution in the coastal surface sediments of Southern Caspian Sea by using UV-Vis spectrophotometery.

This paper presents distribution of phosphorus (total P, organic and inorganic P) in the southern of Caspian Sea sediments where collected from four sampling stations in the summer 2009. Several forms of the phosphorus in sediment were separated and extracted according to sequential extraction method. Then extracted phosphorus in each fraction was determined by UV-Vis spectrophotometery. Five forms of phosphorus were studied (i) loosely sorbed phosphorus, (ii) ferric-iron-bound phosphorus, (iii) authigenic phosphorus, (iv) detrital phosphorus, and (v) organic phosphorus. The total P contents were ranged from 124.5 to 328.2 μg g(-1). It was found that more than 98% of the total P is inorganic phosphorus (IP). Among the four forms of IP, loosely bound P, P-Fe, P-detrital and P-authigenic distribution ranges were 2.70-17.31%, 10.00-44.79%, 0.40-1.70% and 48.35-83.48%, respectively. Result also showed that the most abundant forms of phosphorus were authigenic phosphorus. Relative abundances of other forms of phosphorus follow the order: P-Fe>loosely bound-P>organic P>detrital P.