Name
Seasonal and interannual coupling of phosphorus and iron in a lanthanum remediated lake
Date & Time
Wednesday, May 10, 2023, 11:00 AM - 11:15 AM
Description
Phosphorus (P) release from lake sediments that leads to eutrophication is a global issue. The internal P load, caused by P fluxes from the sediment to the water column, can impede water quality improvement even after reducing external P loads. We examined seasonal changes in the release of P from the sediment of a small eutrophic lake that underwent lanthanum modified bentonite (LMB) treatment. We used high-frequency sensors to measure dissolved oxygen (DO) and temperature in the epilimnion and hypolimnion for one year, sampled sediment and sediment pore water, and conducted inverse diagenetic modelling to calculate the fluxes of P, Iron (Fe), and Lanthanum (La) across the sediment-water interface (SWI) based pore water concentration profiles. We calculated the net reaction rates (Rnet) of the dissolved constituents to identify reactive zones within the sediment layers. Finally, we dated the core sediments using the PLUM model based in the activity of non-supported 210Pb.The lake had two anoxic periods, in summer and winter, which released redox-sensitive P from sediments. Rnet calculations reveal that the surface sediment serves as a source of P, producing it to the pore water at its highest rates in the summer (4.7 � 10-8 �mol cm-3s-1). In contrast to P, rates of La mobilization do not fluctuate seasonally. Burial rate calculations reveal that the LMB layer is moving away from the sediment surface at a rate of 2 mm/year, suggesting that erosion control on the watershed remains key to maintain efficacy of the LMB for as long as possible.
Location Name
Cedar
Full Address
Banff Park Lodge Resort Hotel & Conference Centre
201 Lynx St
Banff AB T1L 1K5
Canada
Abstract
Phosphorus (P) release from lake sediments that leads to eutrophication is a global issue. The internal P load, caused by P fluxes from the sediment to the water column, can impede water quality improvement even after reducing external P loads. We examined seasonal changes in the release of P from the sediment of a small eutrophic lake that underwent lanthanum modified bentonite (LMB) treatment. We used high-frequency sensors to measure dissolved oxygen (DO) and temperature in the epilimnion and hypolimnion for one year, sampled sediment and sediment pore water, and conducted inverse diagenetic modelling to calculate the fluxes of P, Iron (Fe), and Lanthanum (La) across the sediment-water interface (SWI) based pore water concentration profiles. We calculated the net reaction rates (Rnet) of the dissolved constituents to identify reactive zones within the sediment layers. Finally, we dated the core sediments using the PLUM model based in the activity of non-supported 210Pb.The lake had two anoxic periods, in summer and winter, which released redox-sensitive P from sediments. Rnet calculations reveal that the surface sediment serves as a source of P, producing it to the pore water at its highest rates in the summer (4.7 � 10-8 �mol cm-3s-1). In contrast to P, rates of La mobilization do not fluctuate seasonally. Burial rate calculations reveal that the LMB layer is moving away from the sediment surface at a rate of 2 mm/year, suggesting that erosion control on the watershed remains key to maintain efficacy of the LMB for as long as possible.
Session Type
Breakout Session