Gruber's Grove Bay Mercury Site Assessment

Mercury (Hg) concentrations and isotopic compositions were collected in sediments, soils, and suspended particulate matter from Gruber's Grove Bay (GGB) and upstream reference sites to inform future remedial efforts. The highest concentrations and isotopic signatures were observed in soils collected from historic water settling ponds from the Badger Army Ammunition Plant (BAAP). Sediments from the upper portion of GGB showed higher isotopic compositions than sediments from the Wisconsin River. Hg concentrations in sediments were also higher in the upper portion of GGB and decreased towards the river. Sediments collected from the GGB margin (the confluence with the Wisconsin River) were within the concentration and isotopic ranges of Weigand's Bay and further upstream sites. Suspended particulate matter collected from the Wisconsin River and GGB site were isotopically similar to particulate matter from upstream and reference sites.