AN INTEGRATED FIELD AND MODELING STUDY OF THE TRANSPORT OF CYANOTOXIN FROM LAKE ERIE TO COASTAL AQUIFERS

Lake Erie’s water quality has been frequently threatened and deteriorated by harmful algal blooms (HABs). During the occurrence of HABs, cyanotoxins are produced and released, causing health related issues and ecological and economic losses. Previous studies on HABs and cyanotoxins were mostly focused on surface water bodies and the knowledge of groundwater contamination caused by cyanotoxin migration from HABs polluted lakes remains notably limited. Following our proof-of-concept, MODFLOW-based study (Abesh et al., 2019), this study takes a step further to tackle and advance our understanding of such a contamination issue with the assistance of HydroGeoSphere (HGS) and field investigation. As the first step, a three-dimensional (3-D) HGS flow model for the entire South Bass Island, Ohio was developed, aiming to simulate the interaction between the Lake Erie and coastal groundwater. The island and its aquifer underneath, along with the surrounding lake (with), were discretized into ten vertical layers, with each layer consisting of 7,543 2-D triangular elements. Results show that pumping (pumpage = 160 m³/d) at a well located ~30 m away from the lake would create a reverse gradient, driving lake water to flow towards the well and coast aquifer. Our next step is to complete the model by coupling the solute transport and calibrate the model against the cyanotoxin concentration data collected from wells on the island. Ultimately, this study is expected to raise the awareness of groundwater contamination due to HABs in the lake and to identify viable strategies for monitoring and prevention of microcystin contamination in groundwater.