Factors influencing release of phosphorus from sediments in a high productive polymictic lake system

摘要

Phosphorus (P) release rates from bottom sediments are high (20.6mg/m2n/day) in Dal Lake (India),na polymictic hyper-eutrophic lake. These gross release rates occur over a period of 72 daysnduring summer only. Likewise, a net internal load of 11.3 tons was obtained from mass balancenestimates. Significant proportion i.e. , 80% of 287.3 tons/yr of nitrate nitrogen (NO3-N) load isneither eliminated by denitrification or gets entrapped for a short period in high macrophytenbiomass of 3.2 kg/m2nf.w., which eventually get decomposed and nitrogen (N) is released back.nThese processes result in low lake water NO3-N concentrations which potentially influencensediment phosphorus (P) release. Especially, nitrate nitrogen (NO3-N) ,500mg/L in the lakenwaters were associated with high P concentrations. Phosphorus was also observed to increasensignificantly in relation to temperature and pH, and it seems likely that release of phosphorusnand ammonical nitrogen (NH4-N) depend on decomposition of rich reserves of organic matter (893ntons d.w. in superficial 10-cm bottom sediment layer). Lake P concentrations were significantlynpredicted by a multivariate regression model developed for the lake. This study describesnsignificance of various lake water variables in relation to P-release from bottom sediments.