Présence de Pesticides dans l’Eau Souterraine en Milieu Agricole : Étude Pilote du Bassin Versant de la Rivière Châteauguay

Abstract

The occurrence of pesticides in groundwater of the Chateauguay River watershed was investigated. The Chateauguay River is an important tributary of the St. Lawrence River. In this exploratory project, conducted between August and October 2005, water samples were collected from 57 rural domestic wells. Among them, 15 were located near apple orchards, 22 near vegetables production centres, and 20 near corn or soybean fields. In the Chateauguay River watershed, each type of crop is related to a specific hydrogeologic setting. Apple orchards are grown in sandy and gravelly soils in areas of moderate topography. Vegetables are grown in organic-rich soils, whereas corn and soybean are grown mainly in the clay-rich soils of the St. Lawrence plain. Low concentrations of pesticides were detected in 13 of the 57 wells sampled (23%); seven in clay soils near corn and soybean crops, and six in organic soils near vegetables crops. Surprisingly, no pesticides were detected in the wells situated in the most vulnerable zones near apple orchards. Detected pesticides include the herbicides atrazine, metolachlor, linuron, diuron, and metribuzin; the insecticides chlorpyrifos and diazinon; and the fungicide chlorothalonil. Concentrations for all pesticides detected in the wells are below drinking water guidelines.