Effect of Hot Phenomena on Groundwater Derived Nutrients in the Nearshore Aquifer in the Great Lakes
Sabina Rakhimbekova, University of Western Ontario, [email protected]
Denis O'Carroll, University of New South Wales, [email protected]
Clare Robinson, The University of Western Ontario, Civil & Environmental Eng., [email protected]
Abstract
The contribution of direct groundwater discharge as a source of nutrients (phosphorus and nitrogen) to the Great Lakes is unclear. In particular, the role of hot spots and hot moments in controlling the fate of nutrients near the groundwater-lake interface is uncertain. The objective of this study was to evaluate the transport and transformation of septic-derived nutrients through a sandy beach aquifer and assess their ultimate discharge to the lake. Field investigations were conducted in 2014 and 2015 downgradient of a large public septic system near Lake Huron. The sampling was designed to understand the seasonal variability as well as physical and geochemical factors controlling nutrient distribution near the groundwater-lake interface. Elevated nitrate (110 mgNO3-/L) and phosphate (450 µgPO43-/L) were observed between 1-3 m below the ground surface with concentrations decreasing towards the lake. Coupled dissolved and solid phase analysis showed the potential sequestration of PO43- to the aquifer sediments. Artificial sweetener data confirmed anthropogenic origin of the nutrient-rich groundwater plume. Seasonal changes in hydrologic regime and septic system use have direct impact on the nutrient distribution in the beach aquifer. Findings of this study are valuable in improving prediction of groundwater nutrient loading to the lake.
1. Keyword
nutrients
2. Keyword
spatial distribution
3. Keyword
geochemistry
4. Additional Keyword
Groundwater-lake interactions
5. Additional Keyword
Septic system
6. Additional Keyword
artificial sweetener