Browsing by Author "Gulliver, John S"

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    Data for: Internal Loading in Stormwater Ponds as a Phosphorus Source to Downstream Waters
    (2019-04-15) Taguchi, Vinicius J; Olsen, Tyler A; Natarajan, Poornima; Janke, Benjamin D; Gulliver, John S; Finlay, Jacques C; Stefan, Heinz G; ; taguc006@umn.edu; Taguchi, Vinicius J; University of Minnesota - St. Anthony Falls Laboratory - Stormwater Research Group
    Stormwater ponds remove phosphorus through sedimentation before releasing captured water downstream. Internal loading can impair net phosphorus removal but is understudied in these highly modified systems. Using a combination of methods, we assessed the prevalence and potential causes of sediment phosphorus release in urban ponds. In a three-year, 98-pond dataset, nearly 40% of ponds had median water column total phosphorus concentrations exceeding the 95% confidence interval for runoff values (0.38 mg/L), suggesting widespread internal loading. In a subsequent intensive monitoring study of four ponds, strong stratification prevented spring and summer diurnal mixing, resulting in persistent hypolimnion anoxia (<1 mg/L dissolved oxygen). Incubated sediment cores from seven ponds demonstrated high anoxic phosphorus release. Sediment analysis revealed high labile organic and redox-sensitive phosphorus fractions with release potential at anoxia onset. Our analyses suggest phosphorus accumulated in stormwater ponds is highly sensitive to internal loading, reducing net removal and contributing to downstream eutrophication.
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    Detecting phosphorus release from stormwater ponds to guide management and design
    (2021-02-23) Finlay, Jacques C; Gulliver, John S; Janke, Benjamin D; Natarajan, Poornima; Taguchi, Vinicius; Shrestha, Paliza; janke024@umn.edu; Janke, Ben D; University of Minnesota - St. Anthony Falls Laboratory - Stormwater Research Group
    There is growing concern that aging stormwater retention ponds may become net sources of phosphorus (P) to receiving waters. Release of P previously deposited in sediments (i.e. internal loading) is a major contributor to eutrophication in lakes. Stormwater ponds often have high external P loading, and other characteristics that may increase the likelihood of internal loading as ponds age. However, stormwater ponds have received comparatively little research attention, even though they are widely used with the intended goal of permanent immobilization of phosphorus. The ability of these systems to retain phosphorus over their lifespan is essentially unknown. The proposed research will build understanding necessary to assess the capacity of stormwater ponds to retain or release phosphorus in Minnesota’s stormwater pond infrastructure. The projects aim to develop methods for rapid and efficient identification of pond phosphorus release, to guide management of existing ponds, and to reveal factors that underlie poor performance for P removal. The results of this project will be used to inform and improve pond maintenance, pond design and decision making around construction of new ponds, and to ultimately improve the water quality of our lakes, rivers and wetlands.
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    Iron-Enhanced Swale Ditch Checks for Phosphorus Retention
    (Minnesota Department of Transportation, 2019-07) Natarajan, Poornima; Gulliver, John S; Weiss, Peter T
    Iron-enhanced ditch checks in roadside swales were developed specifically for capturing dissolved phosphorus and dissolved metals from roadway runoff in both urban and agricultural environments. One iron-enhanced ditch check constructed along CR 15 (formerly TH 5) in Stillwater, Minnesota, was monitored during 40 storm events from 2016 to 2018. The iron-enhanced sand filter insert generally captured phosphate, yielding lower phosphate concentrations and mass load reductions that varied between 22% and 50% during several events. However, the cumulative phosphate retention in the filter insert decreased from 42% in 2015 to 30% in 2016, 25% in 2017, and 23% in 2018. The filter insert was not an effective retention device for dissolved copper and zinc. The overall ditch check’s performance, although unexceptional in 2016 and 2017, appeared to improve in 2018. Sampling issues likely contributed to the low performance measured until 2017. The 2018 water sample collection method provided a better estimate of the ditch check’s performance and roughly matched that of the filter insert. Synthetic runoff testing supported the level of treatment achieved during storm events. Phosphate load from the degrading topsoil and the overutilization of the bottom filter media most likely affected overall treatment performance. Design improvements and recommended maintenance actions were developed based on the lessons learned from field monitoring. The iron-enhanced ditch check can improve net phosphate retention through roadside swales, as long as the recommended maintenance actions are performed as scheduled.