Sequential extraction of different forms of phosphorus in the surface sediments of Chilika Lake

Abstract

Sequential chemical extractions were used to study the spatial and temporal distribution of different forms of phosphorus (P) in the surface sediments of Chilika, the largest brackish water lake in Indian subcontinent. Sediments were analyzed for different forms of phosphorus along with some sedimentary parameters such as sand, mud, and organic carbon. The lake sediments are found to be mostly sandy near outer channel, whereas other parts of the lake are muddy sand type. Among the inorganic phosphorous fractions, calcium-bound P (Ca-P) emerged as the most dominant fraction contributing 55 and 37 % of the total phosphorous (TP) respectively in pre- and post-monsoon seasons, respectively. Contribution of loosely bound phosphorus (Lo-P) to the TP in lake system was the lowest (<1 %) in both the seasons. TP concentration of the lake sediment ranged from 291.9 to 1653.4 mg/kg with an average of 1047.71 mg/kg in pre-monsoon and 243.97–2150.55 mg/kg with an average of 1100.81 mg/kg in post-monsoon seasons. The bioavailable fraction contributes 1.4–26.7 % with average of 23.8 % in pre-monsoon whereas it contributes 32.1–34.32 % with an average of 35.72 % of TP in post-monsoon. The order of abundance of the major forms of P in the surface sediments of Chilika Lake was as follows: Lo-P < Al-P < Fe-P < O-P < Ca-P for both the seasons. Correlation matrix and factor analysis were used for result interpretation.