PARENT SESSION
PM16 - Probabilistic Ecological Risk Assessment
Monday, 18 November 2002
8:00 AM to 6:30 PM
Exhibit Hall
(P370) Probabilistic Assessment of Non-Target Plants Exposure to the Corn Herbicide Isoxaflutole through Run.
Ramanarayanan, Tharacad*,1, Allen, Richard1, Dobbs, Michael1, Cheplick, J2, Williams, W2, Pugsley, Raymond2, 1 Bayer CropScience (formerly Aventis CropScience), Research Triangle Park, North Carolina, USA2 Waterborne Environmental Inc., Leesburg, Virginia
ABSTRACT- A modeling framework was developed to simulate the fate and transport of isoxaflutole, a corn herbicide to a terrestrial non-target plant receiving area from a treated field. The Pesticide Root Zone Model (PRZM) was used in the modeling framework to simulate the runoff and run-on of water, sediment and pesticides. The treated field and the receiving area are assumed to be equal in area, with the receiving area divided into 3 zones, namely, Zone-1 from 10 to 25 ft from the treated field; Zone-2 from 25 to 50 ft; Zone-3 covering the remainder of the receiving area. Each zone received water and pesticide loading from the preceding section. The probabilistic exposure assessment framework consisted of multiple scenarios of different soil-weather combinations selected across the major corn-growing areas in the US. The soil-weather combinations address the spatial and temporal variability. Multiple combinations of environmental fate properties of isoxaflutole and its primary biologically active metabolite (RPA 202248) were considered for each of the scenario in order to address the uncertainty in the parameters. The modeling framework explained above was utilized to simulate each of the scenarios with various combinations of fate parameters. The exposure output of interest is the daily maximum peak residue (lb a.i./A) of isoxafutole and RPA 202248 in the top 15 cm of the soil profile in the different zones of the receiving area. The median exposure levels in Zones-1, 2 and 3 ranged from 0 to 0.7 % of applied active ingredient and the 95th centile exposure levels range from < 0.00001 to 3.6 % of applied active ingredient. These exposure results were compared to effects data (SSD) and presented through another poster (Dobbs, et al.)
Key words: isoxaflutole, non-target plant, phytoxicity, runoff exposure