Submitted to: Journal of Visual Experiments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2019
Publication Date: 7/22/2019
Citation: Young, E.O., Ross, D.S., Sherman, J.F. 2019. Measuring phosphorus release in laboratory microcosms for water quality assessment. Journal of Visual Experiments. (149) e60072. https://doi.org/10.3791/60072.
Interpretive Summary: Accurate quantification of phosphorus (P) desorption potential in saturated soils and sediments with standing water is important for P modeling and transport mitigation efforts. To better account for in situ soil-water redox dynamics and P mobilization under prolonged saturation, a simple approach was developed based on repeated sampling of laboratory microcosms.
Technical Abstract: Phosphorus (P) is a critical limiting nutrient in agroecosystems requiring careful management to reduce transport risk to aquatic environments. Routine laboratory measures of P bioavailability are based on extracting dried samples under oxidizing conditions. While useful, these tests may be limited with respect to characterizing P release behavior under prolonged saturation and onset of reducing conditions. Changes in soil hydrology strongly influence P release potential. In moderately reducing environments, P bound to ferric iron can desorb to solution upon reduction to ferrous iron, increasing P mobilization risk. To better account for P desorption while simulating in situ redox gradients (microcosms open to ambient laboratory air), the method uses repeated sampling and solution P analysis (microcosm porewater and floodwater are sampled simultaneously) at desired time points to quantify P release. The design is useful for testing hypotheses important to P mitigation efforts (i.e., differing soil/sediment labile P concentrations, soil properties, amendments etc.). Advantages include simulating in situ redox gradients, simplicity, low cost, and flexibility.