Source Identification of Mercury and Methylmercury using Stable Isotope Analysis in the Fox River, WI

The lower Fox River in Wisconsin is a heavily industrialized system and the major tributary to Green Bay within Lake Michigan. The region has been a listed as Area of Concern by the United States Environmental Protection Agency (USEPA), indicating severe impairment of the ecological health of the system. Remedial action has taken place along the river to remove extensive polychlorinated biphenyl (PCB) contamination. However, it was unknown if mercury (Hg), also derived from industrial activity, remained within sediments and actively bioaccumulated within the food web. Mercury stable isotopes were analyzed in sediments and waters collected below the DePere Dam and upstream at Lake Winnebago to compare if Hg sources within the Fox River and determine the extent of industrial contamination. Speciation, methylmercury (MeHg), and isotope measurements were made within biota (prey fish and invertebrates) below DePere Dam to determine if industrial Hg was bioavailable for methylation and bioaccumulation. The interpretation of these results can be found in a companion journal articles published in Environmental Science and Technology (https://doi.org/10.1021/acsestwater.1c00285)