HEAVY METAL CONTAMINATION OF SHALLOW GROUNDWATER, SOUTHEASTERN MICHIGAN

The occurence of dissolved heavy metals in shallow groundwater at concentrations in excess of their Maximum Contaminant Levels (MCLs), were found at 126 sites in the Rouge River drainage basin in southeastern Michigan. A total of 1,140 samples were collected from the first saturated zone in a sequence of glacial drift aquifers. Water samples were analyzed for 11 heavy metals (arsenic, barium, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver and zinc)and the results compared to the mean concentrations of each metal found in the surface soil. The results suggest that current and former land use practices have led to contamination of the shallow groundwater in southeastern Michigan, a potential source of drinking water in several metropolitan Detroit communities. Levels of Cr, 20 to 30 times its MCL along with elevated levels of cadmium and lead (>10 times their MCLs) have been found in the groundwater beneath industrial sites despite the generally clay-rich nature of the unsaturated zone. The high levels of Chromium in the groundwater strongly suggests that the Cr is in a hexavalent form, and therefore represents a potential ecological and public health concern to the Detroit River and the lower Great Lakes.