Residues of atrazine and N-deethylated atrazine in water from five agricultural watersheds in Québec.

Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) and N-deethylated atrazine (2-chloro-4-amino-6-isopropylamino-s-triazine) were monitored (1974 and 1975) in five rivers which drained agricultural areas in the Yamaska river basin of Québec. Water samples were collected frequently from April to December each year from sites near the outflow of each river. The water samples were extracted with benzene, chloroform, or ethyl acetate and the extracts were analyzed by gas chromatography using a Hall electrolytic conductivity detector and an alkali-flame detector. Atrazine and N-deethylated atrazine residues ranged in concentration from 0.01 to 26.6 microgram/L and less than 0.01 to 1.34 microgram/L, respectively, over the monitoring period. The highest levels of atrazine were observed in July each year and they coincided with the herbicide spraying season in this region and with occasional heavy rainfall events. Discharges (kg/yr) of atrazine from the five rivers were related to corn-growing area in each watershed. Losses of atrazine ranged from 0.1 to 2.9% of the atrazine that was estimated to have been applied in each watershed.