MP5 Agrochemicals and Pesticides
Monday, 14 November 2005: 8:00 AM - 5:30 PM in Exhibit Hall

(MUI-1117-835206) Atmospheric deposition and bioaccumulation of current use pesticides in remote lakes in Ontario, Canada.

Muir, D.¹, Teixeira, C.¹, Wang, X.¹, ¹ National Water Research Institute, Environment Canada, Burlington, ON, Canada

ABSTRACT- The objective of this study was to determine the extent of deposition and bioaccumulation of a wide range of current use pesticides (CUPs) in remote and isolated lakes within or just to the north of the Great Lakes basin. The basin is a major pesticide use area with 160 major products used and over 28 kilotonnes applied for agricultural pest control. CUPs were determined in surface and subsurface waters from 3 small lakes in southwestern Ontario and 7 lakes in north/central Ontario from May to July 2003 and 2004. Precipitation samples and XAD-based passive air samplers (PAS) were collected at 3 southern sites and 2 north/central locations from April the end of August. Zooplankton (>100 um) and phytoplankton (approx 1-100 um) were collected at 3 lakes. Gas chromatography with electron ionization or chemical ionization MS with selected ion monitoring was used for quantification of the CUPs. Of the 51 target CUPs (including degradation products) 23 were detected in lake water, 28 in precipitation, 24 in PAS and 13 in zooplankton. Major compounds in lake water were ametryn, atrazine, desethyl atrazine, chlorothalonil, chlorpyrifos, dacthal, dyfonate, diazinon, endosulfan, metolachlor, metribuzin, and trifluralin. Most of these compounds also were prominent in precipitation and air, along with alachlor and pendamethalin. Water concentrations of two major herbicides, atrazine and metolachlor were similar in lakes from within the agricultural area of southwestern Ontario and in north/central Ontario lakes that were more than 200 km from the nearest intensively farmed area. A low detection frequency of CUPs was found in zooplankton compared to other media and concentrations were generally <1 ng/g wet wt. Major CUPs detected in zooplankton were chlorpyrifos, disulfoton, dyfonate, endosulfan and pendamethalin. Bioaccumulation factors (lipid wt) for these CUPs ranged from 103 -106 and were higher than expected based on their reported laboratory bioconcentration factors.

Key words: current use pesticides, deposition, bioaccumulation, lakes