Association Between Stream Impairment by Mercury and Superfund Sites in the Conterminous USA

Mercury is a natural element that can cause harm to the brain, heart, kidneys, lungs, and immune system, especially to fetuses developing in the womb. Many natural and anthropogenic factors contribute to mercury in the environment, such as geologic deposits, landfills, gold and silver mining operations, cement production, and atmospheric deposition. Mercury has been identified as a contaminant of concern at many National Priority List (NPL) sites, however, studies on contamination at NPL sites are often only conducted on a local level. This study was to analyze the potential connection between mercury-contaminated NPL sites and the presence of mercury impaired streams at the Hydrologic Unit Code 12 (HUC-12) level across the conterminous United States. Various regression models were employed to explore this connection relative to other sources that contribute to mercury in the environment. Model results consistently indicated a positive statistical association between current and deleted NPL sites and the presence of mercury stream impairment at the HUC-12 level. It suggests that mercury-contaminated NPL sites need to be looked at with a more comprehensive approach at regional and national levels rather than treated on the individual site basis exclusively.