Geo-chemical fractionations of phosphorus in sediments of Thuy Trieu lagoon and Cam Ranh Bay, Vietnam

Abstract

The geochemical fractions of phosphorus (P) and its bioavailability in sediments of Thuy Trieu Lagoon and Cam Ranh Bay were investigated. Twenty-four surface sediment samples were collected in the dry season (Jun 2024) and the rainy season (Oct 2024). A sequential extraction procedure was applied to identify the phosphorus (P) fractions in sediments, including Exchangeable P (Ex-P), iron-bound P (Fe-P), aluminum-bound P (Al-P), calcium-bound P (Ca-P), and residual P (Res-P). Total P (TP) ranged from 214.9 to 2365.2 μg·g¡1 , and the Ca-P fraction was the dominant chemical form in sediments. Based on the results of Pearson correlation and principal component analysis, this study suggests that the terrestrial organic matter was the main source for shaping the distribution of P fractions in sediments. Meanwhile, the Ca-P fraction was likely formed through co-precipitation with calcite and other minerals in the sediments. The bioavailable P fraction constituted a small proportion of the total sedimentary P, accounting for 7.6—45.5 % in sediments of Cam Ranh Bay.