Chemical Fractionation of Sediment Phosphorus in Residential Urban Stormwater Ponds in Florida, USA

Abstract

Stormwater ponds collect and transform pollutants (including nutrients, such as nitrogen and phosphorus) in urban runoff and are often hydrologically connected to downstream waters, making it important to maximize their pollutant retention efficiency. A key mechanism for phosphorus (P) removal in stormwater ponds is sedimentation. However, sediment P in stormwater ponds may be present in several chemical forms with varying bioavailability and potential to move from sediments into the overlying water column. The purpose of this study was to characterize the chemical fractions of sediment P in residential urban stormwater ponds, with the goal of better understanding expected movement of P from sediments to water. We used a chemical fractionation scheme to separate sediment P into the following pools: loosely adsorbed and readily available P, Fe- and Al-bound P, Ca- and Mg-bound P, NaOH-exchangeable organic P, and refractory P. From six stormwater ponds in the Tampa Bay, Florida urban area, we found the pool of readily available P was less than 3% of total sediment P, and the refractory P pool was 28–40% of Total P. However, both Fe/Al-bound and Ca/Mg-bound P each accounted for about 18% of total sediment P. These latter pools may become available under anoxic or low pH (<6) conditions, respectively, demonstrating that a change in environmental conditions could cause internal P loading from sediments to pond water.

Natural Background and the Anthropogenic Enrichment of Mercury in the Southern Florida Environment: A Review with a Discussion on Public Health

“…Even though it is estimated that there are over 70,000 urban stormwater ponds in Florida, little is known about their sediment accumulation rate and characteristics [198]. Such sediments are net sources of carbon to the atmosphere [199] that are prone to phosphorus internal loading [200] and the collection of microplastics [201].…”

Temporal variation and risk assessment of heavy metals and nutrients from water and sediment in a stormwater pond, Brazil

“…However, these structures require specific maintenance and management, such as dredging and proper waste management. Hence, it is essential to know the qualitative properties, especially the concentrations of heavy metals (German & Svensson 2005) because accumulated sediments can be resuspended during flooding, making the pollutants viable again for entering the receiving body of water (Lusk & Chapman 2021).…”