Occurrence of some pesticides in the dissolved water phase of the Danube River and its three major tributaries

Polar organic contaminants like organophosphate insecticides (fenthion, disulfoton, azinphos-ethyl, azinphos-methyl, dimethoate, omethoate, demeton-s-methyl) and herbicide (bentazone) were analysed in the surface water of Danube River and its tributaries (Arges, Jiu and Olt). Analyses were performed by solid-phase extraction (SPE) followed by triple-quadrupole liquid chromatography mass spectrometry (LC-MS/MS). The surface water samples were found to be contaminated by disulfoton over the admissible value (7.5 - 10.7 ng/l), demeton-s-methyl (4.67-19.8 ng/l), dimethoate (0.21-2.8 ng/l). The pesticides detected with the highest frequency were omethoate and bentazon in concentrations ranging from 6.5ng/l to 16 ng/l and from 0.34ng/l to 18.8 ng/l, respectively. The highest concentrations of pesticides were recorded in Danube River in Calafat sampling point: demeton-s-methyl 19.8 ng/l, omethoate 17 ng/l.