Submitted to: IUPAC Congress
Publication Type: Abstract Only
Publication Acceptance Date: May 12, 2010
Publication Date: July 15, 2010
Citation: Rice, C., Bialek Kalinski, K.M. 2010. Evidence for atmospheric deposition of herbicides to forests bordering agricultural fields. IUPAC Congress.
The ability of a forested system to intercept herbicides from the air, deliver them directly by rainfall to the forest floor and then to a receiving stream within the forested area was evaluated over a four year period in an agricultural watershed in Maryland. The collected rain included through-fall, stem-flow, and rain collections outside the forested area. Herbicides appear to be deposited onto the leaf canopy, and later washed off during rain events. A later-season application of herbicides, accompanied by high temperature, high humidity and dense foliage, resulted in a very small proportion of rain-delivered herbicides in rain collected downwind of the forested area, i.e., less than 5% of that measured beneath the tree canopy. In contrast, these values were nearly 50% for metolachlor and around 30% for atrazine for early spring applications, when temperature and humidity were low and tree foliage less developed. Therefore, the removal and delivery of pesticides directly into forested regions through atmospheric processes may be an important contributor of pesticides into these regions and one that has received little attention.