ASSESSMENT OF ANTHROPOGENIC ENRICHMENT OF TRACE ELEMENTS ALONG STILL RIVER, DANBURY, CONNECTICUT

The Still River flows through the city of Danbury, Connecticut and is a tributary of the Housatonic River which itself flows into the Long Island Sound. During the 1800’s the city of Danbury used to be known as the “the hat capital of the world”. During this time, several hat factories used a mercury nitrate Hg(NO₃)₂ solution to wash the pelts of animals for use in the hat making process. This continued until around 1941 when mercury was outlawed for this manufacturing purpose. Mercury is an element that bioaccumulates in aquatic ecosystems, possibly leading to contamination of the critical zone environments. This study examined the impact of hat factories on the concentrations, and transport of mercury and sixteen other chemical elements on water and stream sediment along Still River. A total of fourteen (14) stream sediments, and corresponding water samples were collected from the upgradient part of the river, through some residential areas until the water emptied its load to the Housatonic River. Sediment samples were air-dried, thoroughly homogenized, and sieved through a 2-mm sieve size, and analyzed for particle sizes, and organic matter fractions. In addition, samples were digested with aqua regia and analyzed for seventeen (17) chemical elements using an ICP-OES at the CCSU Geochemical laboratory. Results showed a range of 0.03 to 4.9 mg/kg concentrations of mercury in stream sediments, while concentrations in the water column were generally below detection limits. Using a combination of statistical analysis, calculation of enrichment factors, GIS maps with overlays of land use activity, we further relate spatial concentrations of trace elements, and land use activities. Results showed concentrations of elements are log-normally distributed, with high concentrations of Pb, As, Cd, Cr, Cu, Pb, and Zn associated with areas of significant human activities along the river.