Heavy metal contamination in both soil and the shallow groundwater was assessed and monitored over a period of several years to determine its impact on surface water quality in a heavily urbanized southeastern Michigan watershed. A spatially dis- persed set of soil samples were analyzed to capture the inherent variability of soils over a variety historic land uses. The analysis focused on 11 metals, including arsenic (As), bar- ium (Ba), cadmium, (Cd), chromium (Cr), copper (Cu), lead (Pb), mercury (Hg), nickel (Ni), selenium (Se), silver (Ag) and zinc (Zn), that are part of the USEPA’s list of the most common pollutants. Metal concentrations in the soils were measured at three depths: surface/near surface (< 0.5m), shallow subsurface (0.5–10m) and depths greater than 10m across six soil units in glacial terrain. Additional analyses assessed the metal concentrations in each depth profile across three general land use categories: residential, commercial and industrial. Metal concentrations in the shallow groundwater were then obtained and compared to their corresponding mean concentrations within the vadose zone soils. The results suggest that former and current land use activities have resulted in significant adverse impacts on the study region. Metal concentrations in the near-surface soils were the highest with lead present at 15.5 times that of background in industrial ar- eas and approximately 16 times the background in residential areas. Cd, Hg and Zn were also present in near-surface soils at levels several times that of their respective back- ground concentrations. Total Cr levels were found in the shallow groundwater beneath industrial sites at 20 to 30 times the maximum contaminant level (MCL) for drinking wa- ter. More importantly, recent work suggests that the Cr is in a hexavalent form and is spreading across the watershed into residential areas and surface water and sediments of the watershed. Because the Rouge River is a tributary to the Detroit River, these pollut- ants represents a significant source of contamination to the lower Great Lakes.
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