SIMULATING THE OCCURRENCE OF CYANOTOXIN CONTAMINATION IN COASTAL AQUIFERS IN THE GREAT LAKES REGION

Previous studies on harmful algal blooms (HABs) and cyanotoxin contamination in Lake Erie were mostly focused on surface water bodies and the knowledge of groundwater contamination caused by cyanotoxins migrated from HABs polluted lakes remains notably limited. This study aimed to fill in the knowledge gap on such an emerging contamination issue with the assistance of a newer generation hydrologic model, i.e., HydroGeoSphere (HGS). Specifically, a 3-D HGS flow and solute transport model for the entire South Bass Island, Ohio was developed to simulate pumping-induced reverse groundwater flow and microcystin transport from Lake Erie to the fractured aquifer underneath the island. The model was applied to explore how different hydrogeologic settings (including fracture configuration, lake levels, well locations, etc.) would impact the movement of microcystins from the lake to pumping wells. Simulation results show that fractures along the longitudinal flow direction and in forms of connected matrix, higher lake levels, and pumping closer to the shore would facilitate such movements and degrade the quality of well water. Therefore, we strongly recommend that drinking wells along the Lake Erie coast should be regularly monitored and tested for the presence of cyanotoxins.