USGS CONN NAWQA

ABSTRACT

Nitrogen and Pesticide Concentrations in an Agricultural Basin in North-Central Connecticut

Water-Resources Investigations Report 97-4076

By John R. Mullaney and Marc J. Zimmerman

Concentrations and yields of selected nitrogen compounds and herbicides fluctuated with changes in river discharge during a stormflow event in samples from three subbasins of the Scantic River in north- central Connecticut during May 31-June 2, 1992. Concentrations of nitrite plus nitrate nitrogen and the herbicide metabolite desethyl atrazine decreased with increasing river discharge, i ndicating that the ground-water runoff component of streamflow contained larger concentrations of these constituents than the surface-water runoff component. Concentrations of ammonia plus organic nitrogen, atrazine, and metolachlor increased with increasing river discharge, indicating that overland runoff from fertilizer and pesticide-treated fields contained larger concentrations of these constituents than baseflow. Analysis of additional water-quality data from Broad Brook at Broad Brook, Connecticut, from 1993 to 1994 showed that concentrations of nitrate nitrogen had an inverse relation with streamflow, indicating that ground water was a major nitrate nitrogen source. Concentrations and yields of ammonia nitrogen and total organic nitrogen in Broad Brook increased when streamflow exceeded 100 cubic feet per second, indicating that large concentrations of these nitrogen constituents are derived primarily from overland runoff from agricultural fields.