Phenoxy herbicides in Alberta rainfall: cause for concern?

Abstract

A survey for herbicides in air was conducted by analyzing rainfall at eight Lethbridge area locations. Rainfall samples were collected at weekly intervals from May 30 to August 17, 1998 and analyzed for 2,4-D, bromoxynil, dicamba, MCPA, diclofop, fenoxaprop, quinclorac, triallate and trifluralin using a MSD-GC method. With few exceptions, herbicides were detected at every sample date, at every location. 2,4-D was detected most frequently, and in the highest amounts, with bromoxynil and dicamba usually also present. The other herbicides were not detected. On June 12, 2,4-D was detected at two rural locations at 5.1 and 3.6 ppb compared with the Canadian Aquatic Life guideline of 4 ppb. Some high herbicide levels (2.0 and 4.3 ppb) also occurred in early July. Levels at the three city residences (maximum 1.0-1.6 ppb) were lower than at the rural locations. These herbicide detections results raise several concerns.