Rain Deposition of Pesticides in Coastal Waters of the South Atlantic Bight

Concentrations of currently used pesticides were measured in surface waters of the South Atlantic Bight immediately after a major storm event that deposited significant rainfall (200−300 mm) in the coastal region. A plume of freshened water (salinity at least 2‰ lower than surrounding 36.2‰ salinity waters) was detected offshore. A concurrent study determined that the freshened plume was the result of rainfall. Concentrations of atrazine, metolachlor, and trifluralin were enriched inside the freshened plume (by a factor of approximately 2−6) as compared to surface waters outside the plume, providing direct evidence of rain deposition of these pesticides. Calculated rain end-member concentrations were higher than local river end-members. Estimated quantities of pesticides deposited in the freshened plume during the 2−3-day event ranged from 130 to 490 kg of atrazine, from 95 to 120 kg of metolachlor, and from 10 to 27 kg of trifluralin. These values represent approximately 4−10%, 3−5%, and 1−3% of the esti...