Occurrence of pesticide residues in Lebanon's water resources.

Contamination of water sources by pesticides is one of the most critical environmental problems. The present work is designed to address the occurrence of 67 pesticides in the Lebanese waters. Chemical analysis was performed by a solid-phase extraction followed by a gas chromatography-mass spectrometry using programmed temperature vaporization injection. In drinking water and groundwater samples, organochlorine and organophosphate pesticides were frequently detected with a maximal sum concentration of up to 31.8 ng L(-1). High pesticide ecotoxicological risk was noticed in many surface waters, while this risk was driven mainly by diazinon, chlorpyrifos, fenpropathrin and bifenthrin insecticides.