Residential catchments to coastal waters: Forms, fluxes, and mechanisms of phosphorus transport

Yun-Ya Yang; Sinan Asal; Gurpal S Toor

doi:10.1016/j.scitotenv.2020.142767

Residential catchments to coastal waters: Forms, fluxes, and mechanisms of phosphorus transport

Sci Total Environ. 2021 Apr 15:765:142767. doi: 10.1016/j.scitotenv.2020.142767. Epub 2020 Oct 5.

Authors

Yun-Ya Yang¹, Sinan Asal², Gurpal S Toor³

Affiliations

¹ Department of Environmental Science and Technology, University of Maryland, College Park, MD 20742, United States. Electronic address: yyunya@umd.edu.
² Former Soil and Water Quality Laboratory, Gulf Coast Research and Education Center, University of Florida, Wimauma, FL 33598, United States.
³ Department of Environmental Science and Technology, University of Maryland, College Park, MD 20742, United States. Electronic address: gstoor@umd.edu.

PMID: 33097253
DOI: 10.1016/j.scitotenv.2020.142767

Abstract

Controlling phosphorus (P) loss from land to water bodies is of immense scientific and societal interest and scrutiny. We investigated P forms in a longitudinal gradient in three typical urban junctions: stormwater from a residential catchment, pond discharges from a stormwater retention pond, and 13 coastal waters (rivers and estuary). Concentrations of total P (TP) were 122.7 ± 99.1 μg/L in the stormwater, 89.7 ± 35.8 μg/L in the pond discharges, and 212.1 ± 51.2 μg/L in 13 coastal water sites. Lower P concentrations in pond discharges reflect P attenuation in the stormwater pond, and higher P concentrations in surface waters are likely attributed to the additional contributing P sources in the watershed. Dissolved reactive P (DRP) was 38% of TP load in stormwater and 46% of TP concentrations in surface water sites, whereas particulate unreactive P (PUP) was 52% of TP load in pond discharges. The first-flush strength of P forms in the stormwater indicated the dominance of particulate P over dissolved P. More particulate P was transported in the early stages of storms due to the runoff of P associated with sediment, plant materials, and built up on impervious surfaces. Whereas more dissolved P was transported in the later stages of storms likely due to the flushing of P, as exacerbated by greater runoff amounts, from the landscape sources, i.e., grass clippings, tree leaves, and soil. In the pond discharges, DRP was a minor form suggesting its utilization by bacteria and algae in the pond. The high concentration and proportion of DRP in surface waters suggest an abundance of bioavailable P in urban waters. These results imply that treatment designs in urban areas should consider ways to remove P in urban landscapes focusing on attenuating P before the initiation of runoff and discharge to surface waters to protect downstream water quality.

Keywords: Coastal waters; Dissolved phosphorus; Particulate phosphorus; Pond discharges; Stormwater runoff; Urban water quality.