MERCURY CONTAMINATION IN W-CONNECTICUT AND LONG ISLAND SOUND FROM HISTORIC HAT-MAKING SOURCES

Long Island Sound (LIS) is a large urban estuary that receives effluents from a large section of southern New England and New York. Analyses of marsh sediment cores and LIS surface samples and cores provide insight into the Hg contamination history of this region. The sediment cores were dated with 210-Pb, 137-Cs and 14-C methods. Many Hg profiles from marsh and estuarine sediment cores can be explained as a result of atmospheric Hg deposition in the watersheds followed by sediment focusing into the depositional areas. Background Hg concentrations are 50-100 ppb Hg, whereas maximum concentrations of 400-600 ppb Hg occur in sediments deposited during the 1960-1970's. Modern sediments have lower Hg concentrations of 200-300 ppb Hg. Grain size exerts a strong control on the Hg concentrations. Several sediment cores show a second level of Hg enrichment in sediments from the early 1900's. These Hg anomalies may result from enhanced atmospheric Hg wash-out, because the early 1900's was a very wet period in southern New England. Sediment from the Still River and Housatonic River in western Connecticut have Hg concentrations up to 130,000 ppb Hg and anomalies > 1000 ppb Hg also occur in western LIS sediment. These sediments carry Hg derived from the historic hat-making industries in Connecticut that were found mainly in the towns of Danbury and Norwalk, starting in the early 1800's and disappearing in the mid-20th century. Mercury was used to process animal fur into felt using Hg-nitrate solutions (e.g., the phrase mad-as-a-hatter refers to Hg poisoning). Upland sequences near the old hat-making factories have up to 300,000 ppb Hg. During extreme weather events and large floods, this Hg-rich sediment is washed-out and exported to LIS. Thin Hg-rich layers can be recognized in the outflow delta of the Housatonic River and in cores further west in LIS: e.g., layers deposited during the major 1955 floods in Connecticut have up to 1500 ppb Hg. A Hg mass balance estimate suggests that 25 % of Hg in western LIS is derived from the hat-making industry, 35 % derives from sewage inputs, and the remainder from atmospheric deposition in the watersheds and subsequent transport associated with fine particulate material.