Browsing by Author "Ogrins, Lucas"

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    Investigating Groundwater Impacts and Sulfur Cycling in Urban Stormwater Ponds
    (2023-04-25) Ogrins, Lucas; Cey, Edwin; Mayer, Bernhard; Tutolo, Benjamin Michael
    Stormwater ponds have been used to manage water quality and quantity during high flow events. Groundwater can potentially impact the operations of stormwater ponds by altering pond water chemistry, although this influence is poorly understood. This study was undertaken to improve understanding of groundwater and surface water interactions and sulfur cycling in a stormwater system. A pair of interconnected stormwater ponds were investigated at an airport in Calgary Alberta where one pond, Pond M, was known to generate noticeable quantities of hydrogen sulfide. A site investigation was carried out to evaluate groundwater flow directions, groundwater and surface water chemical compositions, sulfur sources and fate through stable isotope analysis, and water budgets. At both ponds, groundwater accounted for a minor fraction of the total water budget and surface water flows dominated. While groundwater contributions were low, elevated sulfate was seen in groundwater samples in the study area, which was attributed to evaporative concentration, with concentrations being the highest around Pond M. Sulfate was shown to enter the pond bottom by diffusion at an estimated rate of 8.9 to 17 kg per day and is the main sulfur source for bacterial sulfate reduction. Other possible sulfate inputs into Pond M are groundwater leakages into stormwater pipes above the pond and preferential flow paths in fractured till adjacent to the pond. Groundwater with high dissolved solid content contributes to stratification at Pond M and likely enhances hydrogen sulfide generation by reducing oxygenation of the water column. Hydrogen sulfide generated in Pond M oxidizes into elemental sulfur and contributes to turbidity encountered at the second pond, Pond E. Stormwater at Pond E was found to exit the study area by seeping into the ground, potentially bypassing the outlet control structure. Groundwater interactions with stormwater ponds have the potential to alter pond structure and can contribute to hydrogen sulfide generation by diffusion of sulfate into pond sediments where bacterial sulfur reduction can occur.