Levels of eight different types of organophosphorous pesticides in water samples from different parts of the Shahid Rajaei dam reservoir in north of Iran were monitored. Water samples were collected from different locations of the reservoir in June, July and September of 2015 and in February 2016. Water samples were extracted with dichloromethane solvent and quantified using gas chromatography and mass spectrometry analyses. The results showed that all pesticides were detected for all periods and include dichlorvos, trifluralin, diazinon, methyl parathion, fenitrothion, malathion, profenofos and ethion. The highest concentrations were found in the summer that is related to malathion (on average 0.78 μg L-1). In midwinter, no pesticide residues were detected. The results showed that concentration of single and total pesticides for all stations were greater than the maximum contamination level of the European Economic Commission.
Keywords: Anthropogenic pollutant; Drinking water; Organic pollutant; Organophosphorous pesticides; Surface water.