Effects of discharge on silver loading and transport in the Quinnipiac River, Connecticut

Silver concentrations were measured in water and sediment samples collected from the Quinnipiac River in Connecticut. This river was chosen for study because of its history of industrialization and high levels of Ag contamination. Sewage treatment plant (STP) effluent accounts for approximately 15% of the total river discharge and approximately 60% of the dissolved Ag in the water column during baseflow conditions. Erosion of contaminated riverbank sediment is the primary source of particulate Ag in the river. Both dissolved and particulate Ag fractions vary as a function of river discharge. Increased discharge due to rain events decreases the relative importance of STP effluent, and thus dilutes the dissolved Ag concentration in the water column. Conversely, increasing discharge results in higher particulate Ag concentrations from increased erosion. The results of this study clearly indicate that both point and non-point sources contribute significantly to Ag loading in this river system, with the level of river discharge determining the relative importance of each.