Water, Wastewater & Stormwater
403483 - Importance of Diagnostic Studies to Develop Effective Phosphorus Load Reduction Strategies in Lentic Systems
Thursday, June 7
10:30 AM - 12:00 PM
Location: Greenway EF
Anthony Aufdenkampe, Oakdale, MN – LimnoTech; John Bratton, Ann Arbor, MI – LimnoTech; Hans Holmberg, Oakdale, MN – LimnoTech
Excessive external phosphorus loading has led to water quality impairments and severe algal blooms in a concerning number of lakes around the world. Accumulation and retention of phosphorus can lead to substantial internal loading, in which phosphorus is recycled and exchanged between the sediments and overlying water column. Internal loading can persist for years following drastic reductions in external loads, which makes eutrophication recovery efforts incredibly challenging. The dominant mechanisms of internal phosphorus loading include diffusive flux of dissolved phosphorus from sediment porewaters, bioturbation, wind-driven sediment resuspension, macrophyte senescence, and recycling among food web components. The net phosphorus load from each internal source pathway varies with the geomorphology of the lake as well as land use and history of external loading. Determination of the relative magnitude of phosphorus loading through the dominant mechanisms is a critical step in choosing a successful load reduction strategy that will result in water quality improvements. Often, however, reduction strategies focus on addressing diffusive flux of soluble phosphorus from the sediments as a primary management technique (e.g. alum treatment) without consideration of the contribution from other source categories. An effective internal phosphorus load reduction strategy should be based on a diagnostic study that quantifies the mass loading from the dominant source categories in order to define the appropriate treatment and recovery strategy. Our presentation will discuss the various source pathways of internal phosphorus loading and present case studies that exemplify the importance of a diagnostic study to develop an effective phosphorus load reduction strategy.