Atmospheric Concentrations of Selected Insecticides and Current Use Herbicides in Saskatchewan

Date
2013-05
Authors
Al-Zahrani, Noof Edan
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Faculty of Graduate Studies and Research, University of Regina
Abstract

Atmospheric samples were collected during 2007-2010 at Bratt’s Lake, Saskatchewan. Samples were analyzed by gas chromatography-mass spectrometry in negative ion selected ion monitoring mode. Atmospheric concentrations of three high usage pre-emergent herbicides (triallate, trifluralin, and ethalfluralin) in the Canadian prairies showed increasing atmospheric concentrations in spring-early summer when they were recommended for application for weed control. Atmospheric concentrations of triallate during 2007-2010 remained in a similar concentration range (maximum concentration >5000 pg/m3) to the previous measurements. In 2010 the increase in concentration of triallate was higher during the fall than previous years with a maximum concentration of 3183 pg/m3 on October 29. The higher concentrations of triallate observed in fall 2010 were attributed to additional weed control used on fields that were not seeded with crop due to the wet conditions in 2010. Increases in crop production of specialty crops such as lentils may have also contributed to higher atmospheric concentrations of triallate and ethalfluralin observed in fall 2010. The concentrations of trifluralin ranged from 1259 pg/m3 to 2555 pg/m3 during 2007-2010 showing that trifluralin is still heavily used in the region. Maximum concentrations of ethalfluralin were also >3000 pg/m3 in 2009. These concentrations of trifluralin and other preemergent herbicides should be considered in the evaluation of trifluralin as a potential persistent organic pollutant for the Stockholm Convention. Atmospheric concentrations of chlorpyrifos were highest during the summer 2007-2010, as had previously been observed in 2003 and 2005. Unlike 2003, the higher atmospheric concentrations of chlorpyrifos were associated with years (2007 and 2008) when there were greater insect counts for bertha armyworms and wheat midge in the prairies. Maximum concentration of chlorpyrifos in 2008 was 207300 pg/m3 and was similar to 2003 when there was usage of chlorpyrifos for grasshopper eradication. Concentrations of -HCH, a legacy organochlorine, were the lowest reported on record at Bratt’s Lake in 2010 and attributed to the termination of usage of lindane in Saskatchewan after 2003. The concentrations of endosulfan observed at Bratt’s Lake would be considered in the range of concentrations at background sites influenced by global atmospheric transport.

Description
A Thesis Submitted to the Faculty of Graduate Studies and Research In Partial Fulfillment of the Requirements for the Degree of Master of Science in Chemistry, University of Regina. xi, 123 l.
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