METAL CONTAMINATION IN SEDIMENTS FROM THE HOUSATONIC RIVER WATERSHED

The Housatonic River watershed in Connecticut was a prominent brass-making and industrial region from the 1700's until well into the 20th century, and that history is recorded in the river's sediments. Trace metal profiles for Cu, Zn, Cr, Cd, Co, Ni, Pb and major elements were determined for several marsh cores along the lower reaches of the river. Maximum trace metal concentrations were 8,400ppm Cu; 2,200ppm Zn; 2,700ppm Cr; 18ppm Cd; 14ppm Co; 170ppm Ni; 470ppm Pb and15ppm Hg. These metal concentrations are much higher than those found in other marsh deposits in Connecticut. Most metals appear to come from the Naugatuck River valley, except Hg, which came from the hat-making industry in Danbury. Further upstream, (e.g., Kent, CT) the Housatonic River sediments are relatively clean. The metal profiles show a high degree of correlation, which is puzzling given the multiple metal sources from a wide geographic area. The Housatonic River has a steep gradient and is prone to major flood events during wet periods in Southern New England (1890-1905; mid 1950's - notably the flood of 1955; 1970-1980). We surmise that the marsh deposits in the estuarine region of the Housatonic River include sediments deposited during these massive flood events, a conclusion for which there is historical evidence. The metal profiles from the marsh deposits, which were dated with 210Pb, thus do not represent contamination chronologies but sedimentary events involving re-deposition of highly contaminated sediments drawn from a large area of the watershed. Plumes of contaminated sediment exited from the mouth of the Housatonic River into Long Island Sound and contributed pulses of contaminated sediment to the Western Sound. Sediment layers with high metal contaminant loadings and a Housatonic River metal "fingerprint" with ages corresponding to the major flood events (1900's, 1950's) are found in the Sound.