Phosphorus fractions in the sediment of a tropical reservoir, India: Implications for pollution source identification and eutrophication

Abstract

Eutrophication level in lakes and reservoirs depends on both internal and external phosphorus (P) load. Characterization of sediment P fractionation and identifying the P pollution sources are important for assessing the bio - availability of P and the dominant P source, for effectively controlling the water pollution. For determining the availability and sources of sediment P and eutrophication status, spatio - temporal variation in different P fractionation of sediment of hyper - eutrophic Krishnagiri reservoir, Tamil Nadu, India, was investigated. Sediment average total P (TP) content ranged from 4.62 to 5.64 g/kg. Main phosphorus form was the inorganic P (IP), and it makes up to 73.4–87.7% of TP. Among the different P fraction, viz. calcium bound (Ca - P), iron bound (Fe– P), aluminium bound (Al - P), exchangeable (Ex - P) and Organic - P (Org - P), Ca - P was the dominating fraction in both IP and TP. Trend of IP fraction was as follows: Ca - P[Fe–P][Al - P][Ex - P] in pre - monsoon season, Fe–P[Ca - P][Al - P][Ex - P] in monsoon and Ca - P[Al - P][Fe–P][Ex - P] in post - monsoon. Overall the trend was as follows Ca - P[Fe–P][Al - P][Org - P][Ex - P]. Bio - available - P (BAP) fractions ranged from 35.2 to 64.0% of TP, indicating its comparative higher value. Pearson’s correlation matrix revealed that there was strong correlation among the different P fractions. Factor analysis indicates that different fractions of P were the dominating factor than the other sediment parameters. The observed variation in sediment P fractionation indicate the differences in source and characterization of P which is very helpful for implementation of effective management practices in controlling pollution that arises due to phosphorus in this hyper - eutrophic reservoir.