HISTORIC MERCURY SOURCES IN CONNECTICUT: FROM FASHION TO FACTORIES

Mercury contamination in Connecticut has two unusual sources: a. the hat making industry of Danbury and Norwalk and b. a power plant (HELCO) that used Hg (instead of steam) as its working fluid on Dutch Point in Hartford CT. The former has contaminated much of the Still River, Housatonic River and Norwalk River with Hg at high ppm levels. Spillage and accidents at HELCO may have impacted the Hg concentrations in fine-grained sediment in river coves along the Connecticut River. Wethersfield Cove just south of Dutch Point is a former bend in the Connecticut River (oxbow) that has up to 3 ppm Hg in its sediment and contains > 0.5 ton Hg. The cove sediment is also rich in Cu, Pb, Zn and Cr, which may be partially derived from effluents from the Hartford waste water treatment plant that is situated just north of the cove. River coves further downstream along the Connecticut River (e.g., Chapman Pond) show similar high concentrations of Hg and some other metals (Woodruff and Martini, UMass, Amherst / Amherst College). Sediment of the Still River north of Danbury and its coves have up to 100 ppm Hg. These core records show an increase in concentrations around the early 1800s, coincident with the onset of the local hatting industry. Several islands in the Housatonic River south of the Merritt Parkway all have layers with up to several ppm Hg (as well as excessively high Cu, Zn and Cr concentrations from the metal industries in the Brass Valley). The delta of the Housatonic River in Long Island Sound has a core record with a 1.5 ppm Hg spike at ~1955, a time when two hurricanes hit central Connecticut in two weeks. These floods carried Hg-contaminated upland sediment downstream creating thin Hg-rich layers in the Sound, which may be a sentinel for hurricane-tracing in deeper Sound sediment. The thin sediment layer deposited by hurricane Irene in Wethersfield Cove in 2011 was very low in Hg, indicating that these sediments were not reworked polluted sediment.