Mercury has many anthropogenic sources, stemming mainly from industrial activity, including the manufacture of electrical apparatus and computers, the amalgamation of metals, the production of hydrochloric acid and sodium hydroxide, and the production of pesticides. Mercury deposited on a river’s watershed can be much more significant than what is deposited in the river itself, because most watersheds are many times larger than the streams that drain them.

Past studies of urbanized watersheds in the Washington, D.C. area have demonstrated that storm flow is aquatic mercury’s most important transport into urbanized watersheds. These flows can be three to five times higher than base flows. Despite being similarly urbanized watershed, New Haven area watersheds have not been studied in relation to land use and the mercury cycle. This study tested the following hypotheses:

1. Watershed mercury concentrations are positively correlated with the degree of urbanization in the watershed, defined as the percentage of ground covered with impervious surfaces.
2. Mercury concentrations under conditions of storm flow are significantly higher than base flow concentrations, in addition to following the trend outlined in hypothesis 1.
3. Mercury concentrations are positively correlated with Total Suspended Solids under base and storm flow.

The study was conducted on four sites in three major watersheds within the City of New Haven. These sites contained streams of similar order, discharge, and watershed size. The site selection was based on land use and represented a gradient from non-urban (3.20% impervious surface cover) to almost entirely urban (77.29%).

Findings from the analysis of the data show that hypotheses 1 and 3 can be rejected and that hypothesis 2 could not be accepted or rejected without additional data. Further sampling is needed and will continue through the early summer of 2006.