Study on different forms and phosphorus distribution in the coastal surface sediments of Southern Caspian Sea by using UV–Vis spectrophotometery A. Samadi-Maybodi a , H. Taheri Saffar a , S. Khodadoust b,⇑ , H. Nasrollahzadeh Saravi c , S. Najafpour c a Analytical Division, Faculty of Chemistry, University of Mazandaran, Babolsar, Iran b Medicinal Plant Research Center, Yasuj University of Medicinal Science, Yasuj, Iran c Ecology Aquatic Center of the Caspian Sea (EACCS), P.O. Box 961, Sari, Iran highlights  P is one of the vital elements for life and plays an important role in the biological productivity.  Determination of P is an essential part of water quality control.  The concentration of P was determined using UV–Vis spectrophotometery technique. graphical abstract . article info Article history: Received 13 December 2012 Received in revised form 10 April 2013 Accepted 15 April 2013 Available online 6 May 2013 Keywords: Phosphorus Sequential extraction Sediment Caspian Sea abstract This paper presents distribution of phosphorus (total P, organic and inorganic P) in the southern of Cas- pian 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) authi- genic phosphorus, (iv) detrital phosphorus, and (v) organic phosphorus. The total P contents were ranged from 124.5 to 328.2 lgg 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. Ó 2013 Elsevier B.V. All rights reserved. Introduction Phosphorus (P) is one of the vital elements for life on earth and plays an important role in the biological productivity in oceans and on continents. Phosphorus is an element essential for plant growth. In marine ecosystems the magnitude of primary production de- pends on the resources of phosphorus compounds bioavailable to autotrophic organisms. In aquatic environments the phosphorus cycle is markedly affected by processes taking place in the sedi- ments and at the water–sediment interface [1,2]. Therefore, the determination of phosphorus as both dissolved and suspended compounds in ground, surface, and sewage waters is an essential 1386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.saa.2013.04.071 ⇑ Corresponding author. Tel./fax: +98 7443231385. E-mail address: khodadoustsaeid@yahoo.com (S. Khodadoust). Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 113 (2013) 67–71 Contents lists available at SciVerse ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa