Phosphorus loading to nearshore waters from legacy septic system groundwater plumes in a Great Lakes coastal community
Phosphorus loading to nearshore waters from legacy septic system groundwater plumes in a Great Lakes coastal community
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- dc.contributor.author
- Wang, Shuyang
- Robinson, Clare E.
- Spoelstra, John
- Schneidewind, Uwe
- Roy, James W.
- dc.date.accepted
- 2024-09-30
- dc.date.accessioned
- 2026-02-10T20:17:09Z
- dc.date.available
- 2026-02-10T20:17:09Z
- dc.date.issued
- 2024-12-02
- dc.date.submitted
- 2024-07-14
- dc.description - en
- Groundwater impacted by wastewater effluent from household septic systems, common in coastal communities, is a recognized phosphorus (P) source to nearby lakes. However, the long-term impact of neighbourhood-scale septic system decommissioning (i.e., conversion to sewer connections) on this P loading is not well understood or quantified. The objective of this study was to investigate long-term P loading to Nottawasaga Bay from groundwater plumes of decommissioned septic systems in the coastal community of Wasaga Beach. Detailed groundwater sampling characterized a legacy P plume from a septic system decommissioned 35 years ago, revealing elevated soluble reactive phosphorus concentrations extending over 40 m and reaching the shoreline. Sorption and dispersion parameters required for neighbourhood-scale modelling were derived by simulating this persistent, long but thin P plume using a numerical model. Numerical simulations of P plumes from > 800 septic systems, 0.01–1.6 km from the shoreline and active < 65 years before decommissioning, revealed P mass discharge to the lake started after ~30 years and will continue for > 4000 years. Relatedly, the extended P transport meant the annual mass discharge rate to the lake was consistently < 1.3% of the annual mass input rate from septic systems to the aquifer, though it varied over time according to the septic systems’ distance from shore.
- dc.description.abstract - en
- High phosphorus (P) loads to the Laurentian Great Lakes contribute to eutrophication, harmful algal blooms, and hypoxia. Groundwater impacted by wastewater effluent from household septic systems, common in coastal communities, is a recognized P source to nearby lakes. However, the long-term impact of neighbourhood-scale septic system decommissioning (i.e., conversion to sewer connections) on this P loading is not well understood or quantified. The objective of this study was to investigate long-term P loading to Nottawasaga Bay from groundwater plumes of decommissioned septic systems in the coastal community of Wasaga Beach. Detailed groundwater sampling characterized a legacy P plume from a septic system decommissioned 35 years ago, revealing elevated soluble reactive phosphorus concentrations extending over 40 m and reaching the shoreline. Sorption and dispersion parameters required for neighbourhood-scale modeling were derived by simulating this persistent, long but thin P plume using a numerical model. Numerical simulations of P plumes from > 800 septic systems, 0.01–1.6 km from the shoreline and active < 65 years before decommissioning, revealed P mass discharge to the lake started after ∼ 30 years and will continue for > 4000 years. Relatedly, the extended P transport meant the annual mass discharge rate to the lake was consistently < 1.3 % of the annual mass input rate from septic systems to the aquifer, though it varied over time according to the septic systems’ distance from shore. These findings highlight the long-term view required in accounting for decommissioned septic systems in P management strategies to protect lake water quality.
- dc.description.fosrctranslation - fr
- Les eaux souterraines affectées par les effluents des fosses septiques domestiques, courantes dans les communautés côtières, sont une source reconnue de phosphore (P) pour les lacs avoisinants. Cependant, l’impact à long terme de la mise hors service des fosses septiques à l’échelle d’un quartier (c’est-à-dire la conversion aux égouts) sur cette charge de P n’est pas bien compris ou quantifié. L’objectif de cette étude était d’étudier la charge de phosphore à long terme dans la baie de Nottawasaga à partir des panaches d’eaux souterraines de systèmes septiques mis hors service dans la communauté côtière de Wasaga Beach. Un échantillonnage détaillé des eaux souterraines a permis de caractériser un panache de P provenant d’une fosse septique mise hors service il y a 35 ans, révélant des concentrations élevées de phosphore réactif soluble s’étendant sur plus de 40 m et atteignant le littoral. Les paramètres de sorption et de dispersion nécessaires à la modélisation à l’échelle du quartier ont été dérivés en simulant ce panache persistant, long mais mince, à l’aide d’un modèle numérique. Des simulations numériques des panaches de P provenant de plus de 800 fosses septiques, situées à une distance de 0,01 à 1,6 km du littoral et actives pendant moins de 65 ans avant leur mise hors service ont révélé que le rejet massif de phosphore dans le lac a commencé après environ 30 ans et se poursuivront pendant plus de 4 000 ans. De même, le transport prolongé de P signifie que le taux de rejet massif annuel dans le lac était constamment < 1,3 % du taux d’entrée massif annuel des fosses septiques dans l’aquifère, bien qu’il ait varié dans le temps en fonction de la distance des fosses septiques par rapport au rivage.
- dc.identifier.doi
- https://doi.org/10.1016/j.jglr.2024.102453
- dc.identifier.issn
- 2773-0719
- 0380-1330
- dc.identifier.uri
- https://open-science.canada.ca/handle/123456789/4240
- dc.language.iso
- en
- dc.publisher - en
- Elsevier
- dc.publisher - fr
- Elsevier
- dc.rights - en
- Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)
- dc.rights - fr
- Creative Commons Attribution - Pas d'utilisation commerciale - Pas de modification 4.0 International (CC BY-NC-ND 4.0)
- dc.rights.openaccesslevel - en
- Gold
- dc.rights.openaccesslevel - fr
- Or
- dc.rights.uri - en
- https://creativecommons.org/licenses/by-nc-nd/4.0/
- dc.rights.uri - fr
- https://creativecommons.org/licenses/by-nc-nd/4.0/deed.fr
- dc.subject - en
- Surface water
- Groundwater
- Waste water
- dc.subject - fr
- Eau de surface
- Eau souterraine
- Eaux usées
- dc.subject.en - en
- Surface water
- Groundwater
- Waste water
- dc.subject.fr - fr
- Eau de surface
- Eau souterraine
- Eaux usées
- dc.title - en
- Phosphorus loading to nearshore waters from legacy septic system groundwater plumes in a Great Lakes coastal community
- dc.title.alternative - fr
- Charge de phosphore dans les eaux littorales provenant des panaches d’eaux souterraines d’anciennes fosses septiques dans une communauté côtière des Grands Lacs
- dc.type - en
- Article
- dc.type - fr
- Article
- local.acceptedmanuscript.articlenum
- 102453
- local.article.journalissue
- 6
- local.article.journaltitle - en
- Journal of Great Lakes Research
- local.article.journalvolume
- 50
- local.pagination
- 13 pages
- local.peerreview - en
- Yes
- local.peerreview - fr
- Oui
- local.requestdoi - en
- No
- local.requestdoi - fr
- No
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