Phosphorous Fractionation in Surface Sediments of the Cauvery Delta Region, Southeast India

Phosphorus is both a nutrient and a key factor responsible for eutrophication of freshwater ecosystem. Knowledge on geochemical forms of phosphorous is one among the proxies to monitor the quality of an aquatic ecosystem. Channel-bed sediment samples were collected from the Cauvery River in delta region, fractionated into five namely, exchangeable P, Fe-P, Al-P, Ca-P and Residual-P and were studied. Total phosphorous concentration of ranged between 360 and 1,070 mg/kg. The mean values of P fractions are: HCl-P (68 %), NaOH-P (12 %) and NH4Cl-P (8 %). Among the phosphorous fractions studied, HCl extractable P recorded as a dominating chemical form. It implies P had a preferential association with Ca. The pH of the river sediments varied from 7.37 to 8.69 implying alkaline nature. Total Organic Carbon (TOC) and Organic Matter (OM) of the sediments showed ranges of 0.04–1.0 % and 0.14–3.45 %, respectively. Total Nitrogen (TN) of the sediment samples was in the range between 0.08 and 0.20 %. The C/P and N/P ratios ranged 1.65–78.67 and 1.33–6.69, respectively.