Pesticide multiresidues in waters of the Lower Fraser Valley, British Columbia, Canada. Part I. Surface water.

In the period 2003 to 2005, a study was conducted to determine the occurrence, and spatial and temporal distribution of 78 pesticides in surface waters of the Lower Fraser Valley (LFV) region of British Columbia, Canada. A high resolution gas chromatography/electron impact high resolution mass spectrometry (HRGC/[EI]HRMS) method capable of detecting analytes at the subnanograms per liter level was developed for this study. Samples were collected and analyzed from three reference, five agricultural and two urban sites. Endosulfan sulfate was detected in all samples collected during the study period including the samples from the reference sites. The maximum concentration of a pesticide detected at the reference sites was 0.261 ng L(-1) for beta-endosulfan. Over the study period, the numbers of pesticides detected at the agricultural sites ranged from 22 to 33 of which 20.8 to 40.9% had a 100% detection frequency. At the agricultural sites, the greatest concentration was detected for diazinon (12,500 ng L(-1)), followed by linuron (1050 ng L(-1)) and simazine (896 ng L(-1)). The greatest pesticide concentration observed for the urban sites was 90.4 ng L(-1) for simazine followed by diazinon (5.39 ng L(-1)). With few exceptions, greater concentrations of herbicides were observed for samples collected during spring than for samples collected during fall. Pesticide data presented in this study provide reference levels for future pesticide monitoring programs in the region.