Abstract
Air concentrations of lindane and pre-emergent herbicides were measured during 2003 and 2010 at Bratt's Lake, Saskatchewan and compared to other Canadian or worldwide sites. The removal of sales and usage of lindane in 2002 in Canada has resulted in a rapid decline in atmospheric concentrations of gamma-hexachlorocyclohexane in the Canadian prairies. Pre-emergent herbicides which are used on grain and oil seed crops in the Canadian prairies show the highest atmospheric concentrations during the spring (May-June) when they are typically applied. Atmospheric concentrations of triallate are much higher than trifluralin or ethalfluralin in 2003. In 2010, there was a shift in time of the spring maximum atmospheric concentration of pre-emergent herbicides attributed to delays in seeding of wheat and canola. There was also a decline in atmospheric concentrations of triallate in 2010 as compared to 2003 which was associated with an increase in production of canola, and decline both locally and regionally in wheat production due to wet weather conditions in 2010. Ethalfluralin or triallate are potential replacement herbicides for use on canola or grain crops, and the long-range atmospheric transport of these pre-emergent herbicides should be considered together with trifluralin in future implications of potential restrictions developed for United Nations Economic Commission of Europe protocol on persistent organic pollutants.