Pesticide multiresidues in waters of the Lower Fraser Valley, British Columbia, Canada. Part II. Groundwater.

In Part I of this work we presented pesticide levels in the surface waters of the Lower Fraser Valley (LFV) region of British Columbia, Canada. In Part II pesticide levels in the groundwater of the LFV are presented. During the period 2003 to 2005 a study was conducted to determine the occurrence and spatial distribution of 78 pesticides in the groundwater of the LFV. Samples were collected and analyzed from one reference, nine agricultural, one urban, and three urban-agriculture mixed sites. Overall 24 different pesticides were detected in the sites monitored. The maximum single pesticide concentration observed was for simazine (90 ng L(-1)) at one of the agricultural sites. All concentrations of pesticides detected in groundwater samples were below Canadian surface water quality criteria and below available drinking water quality criteria set by World Health Organization (WHO), Health Canada, USEPA, and the European Union (EU). Pesticide levels in surface and groundwater were compared in the Abbotsford area. Generally, a pesticide with a high groundwater concentration tended to also have a high surface water concentration (Simazine 29 ng L(-1) in groundwater and 58 ng L(-1) in surface water, atrazine 5.5 ng L(-1) in groundwater and 14 ng L(-1) in surface water). For pesticides that were detected above 1 ng L(-1) concentration the only exception to this was desethylatrazine that showed greater concentration in groundwater (2.2 ng L(-1)) than surface water (1.5 ng L(-1)). Herbicides were the predominant pesticides detected in the agricultural sites and insecticides were predominant in the urban sites. Pesticide data presented in this study provide reference levels for future pesticide monitoring programs in the region.