Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 16, 2001
Publication Date: June 22, 2002
Citation: Liu, B., McConnell, L.L., Torrents, A. 2002. Herbicide and insecticide loadings from the Susquehanna River to the Northern Chesapeake Bay. Journal of Agricultural and Food Chemistry. 50:4385-4392.
Interpretive Summary: The Susquehanna River is the largest source of freshwater to the Chesapeake Bay. It also flows through a large agricultural region in Pennsylvania. Pesticides enter the Susquehanna River primarily during rain events and are transported to the Chesapeake Bay. Since the Susquehanna River may be one of the largest sources of pesticides to the Chesapeake Bay, it is important tto characterize this source and to understand the most important factors influencing the magnitude at different times of the year. This report describes a study whereby water samples were collected every nine days from February 1997 to March 1998 and analyzed for a large number of pesticides used in agriculture, in home gardening, and for residential insect control. Weed control chemicals used in agriculture were found in the highest concentrations overall with the maximum found in the spring planting season. Other chemicals used for insect control were also found consistently but at lower concentrations. Winter storms were also found to cause significant pulses of pesticides to enter the river. This research will be used as a baseline to compare with future studies and to gauge the success of new farming techniques to control pesticide losses from agricultural fields.
The Susquehanna River watershed has a large drainage area containing heavy agricultural land usage. This tributary provides approximately half the total freshwater input to the Chesapeake Bay. Water samples were collected at Conowingo Dam every 9 days from 2/97-3/98. Atrazine, its transformation product CIAT (6-amino-2-chloro-4-isopropylamino-s-triazine), and metolachlor were found in the highest concentrations at a maximum of 500, 150, and 330 ng/L, respectively. The annual mass load for atrazine, CIAT, metolachlor, simazine, and CEAT (6-amino-2-chloro-4-ethylamino-s-triazine) from the Susquehanna River to the Chesapeake Bay were 1600, 1600, 1100, 820, 720 kg/yr, respectively. Annual loadings of insecticides and organochlorine compounds ranged from 2.8 kg/yr for alpha-HCH to 34 kg/yr for diazinon. A strong correlation between loading data from this and previous studies combined with total annual water discharge through the Dam mwas used to estimate total metolachlor and atrazine loads (12400 kg and 9950 kg, respectively) to the northern Chesapeake Bay for 1992-1997.